Modularized camshaft blank assembly and preparation method

Abstract

The invention relates to the technical field of mechanical parts, and discloses a modular camshaft blank assembly and a preparation method, the assembly is of a single-cylinder independent structure, is manufactured by machining after integral casting forming, and comprises a first valve cam, a second valve cam, a journal, a positioning boss and an assembly structure; the first valve cam and the second valve cam are in a blank state with molded lines not machined, and the base circle diameter, the shaft neck diameter, the distance between the first valve cam and the second valve cam and the peach piece width of the first valve cam and the peach piece width of the second valve cam are all locked through machining. According to the technical scheme, after a single-cylinder independent structure is integrally cast and formed, the key size is locked, so that the technical effect of improving the universality and the size precision of the assembly is achieved; the defects that the flexibility of adapting to engines with different cylinder numbers is poor, and the size consistency of all cylinder assemblies is low are overcome.

Description

Technical Field

[0001] This invention relates to the field of mechanical components technology, specifically to a modular camshaft blank assembly and its preparation method. Background Technology

[0002] The camshaft is a core transmission component of the internal combustion engine's valve train system. Its function is to control the opening and closing sequence of valves through the rotational movement of the cam profile, directly affecting the engine's power, fuel economy, and emissions performance. Modular camshaft blanks, serving as the basic raw material for camshaft machining, typically integrate valve cams, journals, locating structures, and assembly connection structures. Their structural integrity, dimensional accuracy, and material uniformity not only determine the ease of subsequent machining but also play a crucial role in the assembly compatibility and long-term service life of the finished camshaft. Currently, most camshaft blanks in the industry require an integral structure designed according to the number of engine cylinders, followed by casting and machining to form a preliminary shape, providing a foundation for subsequent cam profile precision grinding, assembly, and inspection processes.

[0003] In the existing technology, the integral casting solution is to cast all valve cams, journals and connecting structures into a single blank in one go for an engine with a specific number of cylinders;

[0004] The modular assembly method involves casting individual valve cams, journals, and other components separately, and then connecting them by welding or bolting to form a complete blank.

[0005] Among them, the integral casting scheme is prone to casting defects due to the large size and complex structure of the billet. Furthermore, subsequent machining requires the removal of a large amount of redundant material, resulting in low material utilization and long processing cycle. Although the split splicing scheme can reduce the casting difficulty of individual components, weak mechanical properties are easily formed at the splicing points. Moreover, the coaxiality and position of the components are difficult to control precisely, which can easily lead to poor compatibility during subsequent assembly and affect the running stability of the finished camshaft. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides a modular camshaft blank assembly and its preparation method, which solves the problems of poor flexibility in adapting to engines with different numbers of cylinders and low dimensional consistency of cylinder components caused by integral casting or separate splicing assembly of existing technologies.

[0007] To achieve the above objectives, the present invention is implemented through the following technical solution: a modular camshaft blank assembly, wherein the assembly is a single-cylinder independent structure, which is integrally cast and then machined, and includes a first valve cam, a second valve cam, a journal, a positioning boss and an assembly structure;

[0008] The first valve cam and the second valve cam are in a blank state without machined profiles. Their base circle diameter, journal diameter, distance between the first valve cam and the second valve cam, and the width of the cam strips of the first valve cam and the second valve cam are all locked by machining.

[0009] Preferably, the positioning boss includes a first boss at the rear end of the journal, a second boss at the front end of the first valve cam, a third boss at the front end of the journal, and a fourth boss at the rear end of the second valve cam. The first boss, the second boss, the third boss, and the fourth boss are matched in shape and size for positioning and alignment during multi-component assembly.

[0010] Preferably, the assembly structure includes a shaft hole at one end of the journal and a shaft head at the other end, wherein the shaft hole and the shaft head of the adjacent component are connected by an interference fit.

[0011] The interference fit has an interference amount of 0.02-0.04mm. During assembly, the shaft hole needs to be heated to 120-150℃ and fixed with a pressing force of 5-8kN.

[0012] A method for preparing a modular camshaft blank assembly, the method comprising the following steps:

[0013] S1. Integrated casting: The first valve cam, the second valve cam, the journal, the positioning boss and the assembly structure are integrally cast into a single cylinder blank. After casting, aging treatment is performed to eliminate internal stress.

[0014] S2. Standardized machining: The single-cylinder blank is sequentially roughed, heat-treated and fine-machined to lock the base circle diameter of the first valve cam and the second valve cam, the journal diameter, the distance between the two cams and the width of the valve piece, forming a single-cylinder modular blank assembly.

[0015] S3. Multi-component assembly: Select the corresponding number of single-cylinder modular blank components according to the number of cylinders on one side of the engine. Position and align them through the first boss, second boss, third boss and fourth boss. Assemble the shaft head and shaft hole of the adjacent components with interference fit and lock the distance between the two components as the cylinder center distance of the engine.

[0016] S4. Cam profile machining: Based on the valve train requirements of the target model, the cam profile is designed using a 5th order polynomial motion law. The blanks of the first valve cam and the second valve cam are ground to form a matching profile.

[0017] S5. End assembly: Select head and tail end pieces that fit the overall machine boundary and assemble them to both ends of the multi-component assembly described in step S3 to complete the finished camshaft manufacturing. The finished product needs to pass dynamic balance testing and bench reliability testing.

[0018] Preferably, in step S1, the raw materials need to be pretreated before integral casting, including the following steps:

[0019] If ductile iron is used, the original molten iron needs to be spheroidized and inoculated using the pouring method. The spheroidizing agent is FeSiMg8Re3, with an addition amount of 1.2%-1.5%, and the inoculating agent is 75SiFe, with an addition amount of 0.8%-1.0%, to ensure that the spheroidization grade is ≥3 and the graphite size is 6-8.

[0020] If alloy cast iron is used, the temperature of the molten iron must be controlled at 1420-1450℃ to prevent the alloying elements from burning off.

[0021] Three Φ50×100mm test blocks are taken from each batch of raw materials to test tensile strength and hardness. The hardness range is HB180-220. Batches that fail to meet the requirements are prohibited from use.

[0022] Preferably, in step S1, the integral casting is performed using a resin sand mold, wherein the amount of resin added to the mold is 1.2%-1.5%, the amount of curing agent added is 0.4%-0.6%, the surface roughness of the cavity Ra is ≤1.6μm, and two Φ15mm vent holes are provided at the corresponding positions of the cam tip.

[0023] The mold parting surface is set horizontally along the journal axis. The upper mold is equipped with a Φ30mm sprue cup, the lower mold is equipped with a Φ20mm straight sprue, the cross-sectional area of ​​the horizontal sprue is 300mm2, the ingate is directly opposite the thick part of the journal, and the molten metal filling time is ≤8s.

[0024] In step S1, the casting and post-treatment parameters include:

[0025] The pouring temperature for ductile iron is 1300-1350℃, and the pouring temperature for alloy cast iron is 1350-1400℃. An automatic pouring machine is used, with a pouring speed of 5-8 kg / s.

[0026] After unpacking, shot blasting is used for cleaning. The diameter of the steel shot is Φ1.5mm and the shot blasting time is 5min. Visual inspection is performed on the surface for defects. The depth of pores and sand holes is ≤1mm and the area is ≤5mm2. Components with defects exceeding the tolerance are repaired by welding with welding rods. The welding current is 90-110A.

[0027] The aging treatment involves heating at a rate of 50℃ / h to 200-250℃, holding at that temperature for 4-6 hours, and then cooling in the furnace to below 100℃ before being removed from the furnace. The residual stress is ≤80MPa.

[0028] Preferably, in step S2, rough machining is performed using a CNC lathe with a spindle speed of 800-1200 r / min. A carbide turning tool is used for rough turning the outer diameter, and a boring tool is used for rough turning the inner diameter. The depth of cut is 2-3 mm, and the feed rate is 0.2-0.3 mm / r. After rough machining, the allowance for the journal, shaft head, and shaft hole is controlled to be 0.5-0.8 mm.

[0029] In step S2, heat treatment and flaw detection include:

[0030] Tempering: Heat to 850-880℃ and hold for 1.5h, then oil cool to below 200℃ at a rate of ≥30℃ / s, then heat to 550-600℃ and hold for 2h for tempering, then air cool after removal from the furnace;

[0031] After heat treatment, three samples were taken to test the hardness and metallographic structure. The hardness range was HB220-250, and the sorbite content was ≥80%. An ultrasonic flaw detector was used to detect internal defects.

[0032] In step S2, finishing and surface treatment include:

[0033] The outer diameter of the journal is ground using an external cylindrical grinding machine at a speed of 1500 r / min and a feed rate of 0.01-0.02 mm / r, with a surface roughness Ra≤0.8μm. The shaft hole is ground using an internal cylindrical grinding machine at a speed of 2000 r / min.

[0034] The positioning boss is machined using a vertical machining center with a carbide end mill, 4 teeth, a milling speed of 80-100 m / min, a feed rate of 0.1-0.15 mm / r, a dimensional tolerance of ±0.01 mm, and a perpendicularity of ≤0.005 mm.

[0035] After finishing, use KD-120 hydrocarbon cleaner for ultrasonic cleaning for 10 minutes at a temperature of 40-50℃, then soak in RP-308 rust inhibitor for 5 minutes at a concentration of 5%, and air dry before sealing and packaging.

[0036] Preferably, in step S3, the multi-component assembly adopts an assembly platform made of cast iron with a flatness of ≤0.01mm / m. The platform is equipped with 4 positioning pins that match the positioning bosses. The pressing equipment is a CNC press with an accuracy of ±0.1kN and is equipped with a displacement sensor with an accuracy of ±0.001mm.

[0037] In step S3, the assembly process parameters include:

[0038] Clean the shaft head with an alkaline degreaser for 10-15 minutes. The degreaser consists of 5% sodium hydroxide, 3% sodium carbonate, and 2% surfactant. The cleaning temperature is 50-60℃. Then dry it with 0.6MPa oil-free and water-free compressed air.

[0039] During pressing, the press speed is 0.5 mm / s, and after pressing, the pressure is held for 30 seconds, and the natural cooling time is ≥2 hours.

[0040] After assembly, use a dial indicator to check the coaxiality. The dial indicator accuracy is 0.001mm, and the coaxiality is ≤0.03mm. For unqualified parts, heat the shaft hole to 180-200℃, disassemble, and reassemble.

[0041] Preferably, in step S4, the cam profile machining includes:

[0042] The lift of the profile buffer section is 0-1mm, and the acceleration is ≤500mm / s2. The lift of the working section is 1-15mm, and the speed is ≤1.2m / s. Through simulation verification using AGLEXCITE software, the valve seat force is ≤800N and the valve runout is ≤0.1mm at a speed of 6000r / min.

[0043] Different grinding wheels are selected for grinding depending on the material being processed.

[0044] Dual-nozzle cooling is used, with a distance of 5-10 mm from the grinding zone. The coolant is a mixture of 7%-9% emulsified oil, 2%-4% rust inhibitor, and 87%-91% water, with a flow rate ≥15L / min and a pressure ≥0.3MPa.

[0045] For every 10 pieces processed, the profile error is checked using a cam profiler, and the profile error is ≤0.01mm. The surface roughness is checked using a roughness tester, and Ra≤0.4μm.

[0046] Preferably, in step S5, the end-component assembly and finished product inspection include:

[0047] The head end is assembled with an interference fit, heated to 120-140℃, with a pressing force of 7-9kN. The tail end is assembled with argon arc welding, with a welding current of 120-150A, an arc voltage of 18-20V, an Ar gas flow rate of 8-10L / min, and stress relief annealing at 300-350℃ for 2 hours after welding. The residual stress in the welded area is ≤60MPa.

[0048] The finished product is tested for coaxiality, cam phase angle error and journal roundness using a coordinate measuring machine. The coaxiality is ≤0.05mm, the cam phase angle error is ≤0.5° and the journal roundness is ≤0.005mm. It is tested with a dynamic balancing machine at a speed of 6000r / min. The allowable unbalance is ≤15g・mm.

[0049] Bench reliability test: Assembled into the engine cylinder head, a 1000-hour cyclic operating condition test is conducted at a speed of 1000-6000 r / min and an oil temperature of 80-100℃. After the test, the cam wear is ≤0.008mm and the journal wear is ≤0.005mm.

[0050] Laser marking is applied to the head end of the component, and the marking includes the product model, batch number, production date, and QR code. Each batch is accompanied by a material, size, and performance test report.

[0051] The above solution achieves the following beneficial technical effects:

[0052] 1. This invention achieves the technical effect of improving the versatility and dimensional accuracy of components by adopting a single-cylinder independent structure integral casting and locking key dimensions. Compared with the existing technology of integral casting of camshaft or separate splicing assembly, it solves the shortcomings of poor flexibility in adapting to engines with different numbers of cylinders and low consistency of the dimensions of each cylinder component.

[0053] 2. This invention adopts a full-process collaborative technology solution that combines resin sand mold casting with aging treatment, standardized machining sequence, and boss positioning assembly. This achieves the technical effects of reducing billet deformation, ensuring assembly accuracy, and reducing machining losses. Compared with the existing technology that omits aging treatment, disrupts the machining sequence, or lacks a dedicated positioning structure, this invention solves the shortcomings of billet machining resulting in dimensional deviations, low coaxiality of component assembly, and high scrap rate of finished products.

[0054] 3. This invention adopts a 5th-order polynomial motion law design for cam profiles, combined with a special cooling and precise detection technology, which achieves the technical effect of optimizing the operational stability of the valve train system and extending the service life of the camshaft. Compared with the existing technology that uses traditional involute profiles or simplifies cooling and detection processes, it solves the shortcomings of large valve movement impact, rapid cam wear, and high noise in the valve train system. Attached Figure Description

[0055] Figure 1 This is a cross-sectional view of a modular camshaft blank assembly provided in one or more embodiments of the present invention.

[0056] Figure 2 This is a schematic diagram of another component of a modular camshaft blank assembly provided in one or more embodiments of the present invention.

[0057] Figure 3 This is a schematic flowchart illustrating a method for preparing a modular camshaft blank assembly according to a specific embodiment of the present invention.

[0058] Among them, 1. First valve cam; 2. Second valve cam; 3. Journal; 4. First boss; 5. Shaft hole; 6. Shaft head; 7. Second boss; 8. Third boss; 9. Fourth boss. Detailed Implementation

[0059] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. 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.

[0060] Please see the appendix Figure 1 -Appendix Figure 2This invention provides a modular camshaft blank assembly, which is a single-cylinder independent structure. It is manufactured by integral casting and then machining, and includes a first valve cam 1, a second valve cam 2, a journal 3, a positioning boss and an assembly structure.

[0061] The first valve cam 1 and the second valve cam 2 are in a blank state without machined profiles. Their base circle diameter, journal 3 diameter, distance between the first valve cam 1 and the second valve cam 2, and the width of the leaflets of the first valve cam 1 and the second valve cam 2 are all locked by machining.

[0062] The positioning bosses include a first boss 4 at the rear end of the journal 3, a second boss 7 at the front end of the first valve cam 1, a third boss 8 at the front end of the journal 3, and a fourth boss 9 at the rear end of the second valve cam 2. The shapes and sizes of the first boss 4, the second boss 7, the third boss 8, and the fourth boss 9 are matched for positioning and alignment during multi-component assembly.

[0063] The assembly structure includes a shaft hole 5 at one end of the journal 3 and a shaft head 6 at the other end. The shaft hole 5 and the shaft head 6 of the adjacent component are connected by an interference fit.

[0064] The interference fit has an interference amount of 0.02-0.04mm. During assembly, the shaft hole 5 needs to be heated to 120-150℃ and fixed with a pressing force of 5-8kN.

[0065] Please see the appendix Figure 3 A method for preparing a modular camshaft blank assembly, the method comprising the following steps:

[0066] S1. Integrated casting: The first valve cam 1, the second valve cam 2, the journal 3, the positioning boss and the assembly structure are integrally cast into a single cylinder blank. After casting, aging treatment is performed to eliminate internal stress.

[0067] Before integral casting, raw material pretreatment is required, including the following steps:

[0068] If ductile iron is used, the original molten iron needs to be spheroidized and inoculated using the pouring method. The spheroidizing agent is FeSiMg8Re3, with an addition amount of 1.2%-1.5%, and the inoculating agent is 75SiFe, with an addition amount of 0.8%-1.0%, to ensure that the spheroidization grade is ≥3 and the graphite size is 6-8.

[0069] If alloy cast iron is used, the temperature of the molten iron must be controlled at 1420-1450℃ to prevent the alloying elements from burning off.

[0070] Three Φ50×100mm test blocks are taken from each batch of raw materials to test tensile strength and hardness. The hardness range is HB180-220. Batches that fail to meet the requirements are prohibited from use.

[0071] The integral casting process uses a resin sand mold with a resin addition of 1.2%-1.5% and a curing agent addition of 0.4%-0.6%. The surface roughness of the cavity is Ra≤1.6μm, and two Φ15mm vent holes are set at the corresponding positions of the cam tip.

[0072] The mold parting surface is set horizontally along the axis of journal 3. The upper mold is equipped with a Φ30mm sprue cup, the lower mold is equipped with a Φ20mm straight sprue, the cross-sectional area of ​​the horizontal sprue is 300mm2, the inner sprue is directly opposite the thick part of journal 3, and the molten metal filling time is ≤8s.

[0073] The casting and post-treatment parameters include:

[0074] The pouring temperature for ductile iron is 1300-1350℃, and the pouring temperature for alloy cast iron is 1350-1400℃. An automatic pouring machine is used, with a pouring speed of 5-8 kg / s.

[0075] After unpacking, shot blasting is used for cleaning. The diameter of the steel shot is Φ1.5mm and the shot blasting time is 5min. Visual inspection is performed on the surface for defects. The depth of pores and sand holes is ≤1mm and the area is ≤5mm2. Components with defects exceeding the tolerance are repaired by welding with welding rods. The welding current is 90-110A.

[0076] The aging treatment involves heating at a rate of 50℃ / h to 200-250℃, holding at that temperature for 4-6 hours, and then cooling in the furnace to below 100℃ before being removed from the furnace. The residual stress is ≤80MPa.

[0077] S2. Standardized machining: The single-cylinder blank is subjected to rough machining, heat treatment and fine machining in sequence to lock the base circle diameter of the first valve cam 1 and the second valve cam 2, the diameter of the journal 3, the distance between the two cams and the width of the cam strip, forming a single-cylinder modular blank assembly.

[0078] The roughing process uses a CNC lathe with a spindle speed of 800-1200 r / min. The outer diameter is roughed with a carbide turning tool, and the inner diameter is roughed with a boring tool. The depth of cut is 2-3 mm, and the feed rate is 0.2-0.3 mm / r. After roughing, the allowance of journal 3, shaft head 6, and shaft hole 5 is controlled to be 0.5-0.8 mm.

[0079] In step S2, heat treatment and flaw detection include:

[0080] Tempering: Heat to 850-880℃ and hold for 1.5h, then oil cool to below 200℃ at a rate of ≥30℃ / s, then heat to 550-600℃ and hold for 2h for tempering, then air cool after removal from the furnace;

[0081] After heat treatment, three samples were taken to test the hardness and metallographic structure. The hardness range was HB220-250, and the sorbite content was ≥80%. An ultrasonic flaw detector was used to detect internal defects.

[0082] Finishing and surface treatment include:

[0083] The outer diameter of journal 3 is ground using an external cylindrical grinder at a speed of 1500 r / min and a feed rate of 0.01-0.02 mm / r, with a surface roughness Ra≤0.8 μm. The shaft hole 5 is ground using an internal cylindrical grinder at a speed of 2000 r / min.

[0084] The positioning boss is machined using a vertical machining center with a carbide end mill, 4 teeth, a milling speed of 80-100 m / min, a feed rate of 0.1-0.15 mm / r, a dimensional tolerance of ±0.01 mm, and a perpendicularity of ≤0.005 mm.

[0085] After finishing, use KD-120 hydrocarbon cleaner for ultrasonic cleaning for 10 minutes at a temperature of 40-50℃, then soak in RP-308 rust inhibitor for 5 minutes at a concentration of 5%, and air dry before sealing and packaging.

[0086] S3. Multi-component assembly: Select the corresponding number of single-cylinder modular blank components according to the number of cylinders on one side of the engine. Position and align them through the first boss 4, the second boss 7, the third boss 8 and the fourth boss 9. Then, assemble the shaft head 6 and shaft hole 5 of the adjacent components with an interference fit and lock the distance between the two components as the cylinder center distance of the engine.

[0087] Among them, the multi-component assembly adopts an assembly platform made of cast iron with a flatness of ≤0.01mm / m. The platform is equipped with 4 positioning pins that match the positioning bosses. The pressing equipment is a CNC press with an accuracy of ±0.1kN and is equipped with a displacement sensor with an accuracy of ±0.001mm.

[0088] Assembly process parameters include:

[0089] Clean the shaft head 6 with an alkaline degreaser for 10-15 minutes. The degreaser consists of 5% sodium hydroxide, 3% sodium carbonate, and 2% surfactant. The cleaning temperature is 50-60℃. Then dry it with 0.6MPa oil-free and water-free compressed air.

[0090] During pressing, the press speed is 0.5 mm / s, and after pressing, the pressure is held for 30 seconds, and the natural cooling time is ≥2 hours.

[0091] After assembly, use a dial indicator to check the coaxiality. The dial indicator accuracy is 0.001mm, and the coaxiality is ≤0.03mm. For unqualified parts, heat the shaft hole to 5 to 180-200℃, disassemble, and reassemble.

[0092] S4. Cam profile machining: Based on the valve train requirements of the target model, the cam profile is designed using a 5th order polynomial motion law. The blanks of the first valve cam 1 and the second valve cam 2 are ground to form a matching profile.

[0093] Cam profile machining includes:

[0094] The lift of the profile buffer section is 0-1mm, and the acceleration is ≤500mm / s2. The lift of the working section is 1-15mm, and the speed is ≤1.2m / s. Through simulation verification using AGLEXCITE software, the valve seat force is ≤800N and the valve runout is ≤0.1mm at a speed of 6000r / min.

[0095] Different grinding wheels are selected for grinding depending on the material being processed.

[0096] Dual-nozzle cooling is used, with a distance of 5-10 mm from the grinding zone. The coolant is a mixture of 7%-9% emulsified oil, 2%-4% rust inhibitor, and 87%-91% water, with a flow rate ≥15L / min and a pressure ≥0.3MPa.

[0097] For every 10 pieces processed, the profile error is checked using a cam profiler, and the profile error is ≤0.01mm. The surface roughness is checked using a roughness tester, and Ra≤0.4μm.

[0098] S5. End component assembly: Select head and tail end components that are compatible with the boundaries of the whole machine, assemble them to both ends of the multi-component assembly in step S3, and complete the preparation of the finished camshaft. The finished product needs to pass dynamic balance test and bench reliability test.

[0099] In step S5, the end-component assembly and finished product inspection include:

[0100] The head end is assembled with an interference fit, heated to 120-140℃, with a pressing force of 7-9kN. The tail end is assembled with argon arc welding, with a welding current of 120-150A, an arc voltage of 18-20V, an Ar gas flow rate of 8-10L / min, and stress relief annealing at 300-350℃ for 2 hours after welding. The residual stress in the welded area is ≤60MPa.

[0101] The finished product is tested for coaxiality, cam phase angle error and journal roundness using a coordinate measuring machine. The coaxiality is ≤0.05mm, the cam phase angle error is ≤0.5° and the journal roundness is ≤0.005mm. It is tested with a dynamic balancing machine at a speed of 6000r / min. The allowable unbalance is ≤15g・mm.

[0102] Bench reliability test: Assembled into the engine cylinder head, a 1000-hour cyclic operating condition test is conducted at a speed of 1000-6000 r / min and an oil temperature of 80-100℃. After the test, the cam wear is ≤0.008mm and the journal wear is ≤0.005mm.

[0103] Laser marking is applied to the head end of the component, and the marking includes the product model, batch number, production date, and QR code. Each batch is accompanied by a material, size, and performance test report.

[0104] The following is a description with reference to specific embodiments:

[0105] Example 1

[0106] S1. Integral casting: During raw material pretreatment, the amount of spheroidizing agent FeSiMg8Re3 added is 1.2%, the amount of inoculant 75SiFe added is 0.8%, the amount of resin added in the resin sand mold is 1.2%, the amount of curing agent added is 0.4%, the pouring temperature is 1300℃, the pouring speed is 5kg / s, the aging treatment temperature is raised to 200℃ and held for 4h.

[0107] S2, Standardized Machining: Roughing spindle speed 800r / min, depth of cut 2mm, feed rate 0.2mm / r, roughing allowance 0.5mm, journal outer diameter grinding feed rate 0.01mm / r, positioning boss milling speed 80m / min, feed rate 0.1mm / r, cleaning agent temperature 40℃;

[0108] S3, Multi-component assembly: Shaft head cleaning time 10min, cleaning temperature 50℃, natural cooling time 2h;

[0109] S4, Cam profile machining: Dual nozzles 5mm from the grinding zone, coolant contains 7% emulsified oil, 2% rust inhibitor, and 91% water, with a flow rate of 15L / min;

[0110] S5. End assembly: The head end is heated to 120℃ and the pressing force is 7kN; the tail end is welded with a current of 120A, an arc voltage of 18V, an Ar gas flow rate of 8L / min, and a stress-relieving annealing temperature of 300℃ after welding.

[0111] Example 2

[0112] S1. Integral casting: During raw material pretreatment, the amount of spheroidizing agent FeSiMg8Re3 added is 1.35%, the amount of inoculant 75SiFe added is 0.9%, the amount of resin added in the resin sand mold is 1.35%, the amount of curing agent added is 0.5%, the pouring temperature is 1325℃, the pouring speed is 6.5kg / s, the aging treatment temperature is raised to 225℃ and held for 5h;

[0113] S2, Standardized Machining: Roughing spindle speed 1000r / min, depth of cut 2.5mm, feed rate 0.25mm / r, roughing allowance 0.65mm, journal outer diameter grinding feed rate 0.015mm / r, positioning boss milling speed 90m / min, feed rate 0.125mm / r, cleaning agent temperature 45℃;

[0114] S3, Multi-component assembly: Shaft head cleaning time 12.5 min, cleaning temperature 55℃, natural cooling time 2.5 h;

[0115] S4, Cam profile machining: Dual nozzles 7.5mm from the grinding zone, coolant contains 8% emulsified oil, 3% rust inhibitor, and 89% water, with a flow rate of 18L / min;

[0116] S5. End assembly: The head end is heated to 130℃ and the pressing force is 8kN; the tail end is welded with a current of 135A, an arc voltage of 19V, an Ar gas flow rate of 9L / min, and a stress-relieving annealing temperature of 325℃ after welding.

[0117] Example 3

[0118] S1. Integral casting: During raw material pretreatment, the amount of spheroidizing agent FeSiMg8Re3 added is 1.5%, the amount of inoculant 75SiFe added is 1.0%, the amount of resin added in the resin sand mold is 1.5%, the amount of curing agent added is 0.6%, the pouring temperature is 1350℃, the pouring speed is 8kg / s, the aging treatment temperature is raised to 250℃ and held for 6h.

[0119] S2, Standardized Machining: Roughing spindle speed 1200r / min, depth of cut 3mm, feed rate 0.3mm / r, roughing allowance 0.8mm, journal outer diameter grinding feed rate 0.02mm / r, positioning boss milling speed 100m / min, feed rate 0.15mm / r, cleaning agent temperature 50℃;

[0120] S3, Multi-component assembly: Shaft head cleaning time 15min, cleaning temperature 60℃, natural cooling time 3h;

[0121] S4, Cam profile machining: Dual nozzles 10mm from the grinding zone, coolant contains 9% emulsified oil, 4% rust inhibitor, and 87% water, with a flow rate of 20L / min;

[0122] S5. End assembly: The head end is heated to 140℃, the pressing force is 9kN, the tail end is welded with a current of 150A, an arc voltage of 20V, an Ar gas flow rate of 10L / min, and a stress-relieving annealing temperature of 350℃ after welding.

[0123] Comparative Example 1

[0124] Unlike Example 2, step S1 does not use the first valve cam, second valve cam, journal, positioning boss and assembly structure to be cast as a whole. Instead, each component is cast separately and then assembled into a single cylinder blank by arc welding. The remaining steps are the same as in Example 2.

[0125] Comparative Example 2

[0126] Unlike Example 2, after the integral casting is completed in step S1, the aging treatment of heating at a rate of 50°C / h to 225°C and holding for 5 hours is omitted, and the process proceeds directly to rough machining in step S2. The remaining steps are the same as in Example 2.

[0127] Comparative Example 3

[0128] Unlike Example 2, step S2 does not involve roughing, tempering, and finishing. Instead, it involves roughing first, then finishing, and finally tempering. The remaining steps are the same as in Example 2.

[0129] Comparative Example 4

[0130] Unlike Embodiment 2, step S3 does not use the first boss, second boss, third boss, and fourth boss for positioning and alignment. Instead, it directly aligns the shaft head and shaft hole of the adjacent components and then presses them in place. The remaining steps are the same as in Embodiment 2.

[0131] Comparative Example 5

[0132] Unlike Example 2, step S4 does not use a 5th-order polynomial motion law to design the cam profile, but instead uses a traditional involute profile design. The remaining steps are the same as in Example 2.

[0133] Comparative Example 6

[0134] Unlike Example 2, after the argon arc welding assembly of the tail end parts is completed in step S5, stress relief annealing is omitted, and the finished product is directly inspected. The remaining steps are the same as in Example 2.

[0135] Table 1, Performance Test Data for Examples 1-3

[0136] Example 1 Example 2 Example 3 Tensile strength of a single-cylinder blank (MPa) 580-600 ≥600 600-620 Coaxiality of multi-component assembly (mm) ≤0.035 ≤0.03 ≤0.032 Journal roughness Ra (μm) ≤0.85 ≤0.8 ≤0.82 Cam base circle diameter deviation (mm) ≤0.012 ≤0.01 ≤0.011 Valve seat force (N) at 6000 r / min 780-820 ≤800 790-810 Residual stress in the weld zone (MPa) ≤65 ≤60 ≤58 Fatigue life (h) of finished camshaft 4800-5000 ≥5000 5000-5200

[0137] Table 2, Performance Test Data for Comparative Examples 1-6

[0138] Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Comparative Example 5 Comparative Example 6 Tensile strength of single cylinder blank 480-520 ≥600 ≥600 ≥600 ≥600 ≥600 Multi-component assembly coaxiality 0.12-0.18 0.08-0.12 ≤0.03 0.15-0.22 ≤0.03 ≤0.03 Journal roughness Ra ≤0.8 ≤0.8 1.5-2.0 ≤0.8 ≤0.8 ≤0.8 Cam base circle diameter deviation ≤0.01 0.03-0.05 0.03-0.04 0.08-0.12 ≤0.01 ≤0.01 Valve seat force at 6000 r / min ≤800 ≤800 ≤800 820-850 1200-1500 ≤800 Residual stress in the weld zone ≤60 ≤60 ≤60 ≤60 ≤60 280-350 Fatigue life of finished camshafts 2200-2800 4700-4900 ≥5000 4500-4700 3800-4200 2500-3000

[0139] Based on Examples 1-3, Comparative Examples 1-6, and the performance test data table, it can be seen that the key processes in this invention, such as integral casting, aging treatment, rough machining, tempering and finishing sequence, boss positioning, five-order polynomial profile design, and post-weld stress-relief annealing, as well as the adaptability of parameters in each step, have a significant impact on the strength, accuracy, lifespan, and pass rate of the modular camshaft blank assembly, and there is a synergistic enhancement effect between the processes.

[0140] Comparative Example 1, due to the change to split casting and welding, saw its single-cylinder blank tensile strength drop to 480-520 MPa, with a finished product qualification rate of only 65%, a significant deterioration compared to Example 2, where the tensile strength was ≥600 MPa and the qualification rate was 98%. Comparative Example 2, by omitting the aging treatment, saw its machining scrap rate rise to 28%, an increase of 26 percentage points compared to Example 2's 2%. Comparative Example 3, by reversing the machining sequence, saw its journal roughness reach 1.5-2.0 μm, far exceeding Example 2's ≤0.8 μm. Comparative Example 4, by eliminating the boss positioning, saw its assembly coaxiality exceed 0.15 mm, resulting in a finished product qualification rate of only 55%. Comparative Example 5, by using an involute profile, saw its valve seat force reach 1200-1500 N, with noise exceeding 85 dB. Comparative Example 6, by omitting post-weld stress-relief annealing, saw its residual stress in the welded area rise to 280-350 MPa, and its fatigue life shorten to 2500-3000 h, all confirming that key processes are irreplaceable.

[0141] Examples 1-3 all meet industrial requirements: construction period of 8.0-10.0 hours, steel loss rate of 0.8%-1.2%, journal roughness ≤0.85μm, and finished product qualification rate of 95%-98%. Among them, Example 2 is the best overall, with suitable parameters such as spheroidizing agent addition of 1.35% and casting temperature of 1325℃, tensile strength ≥600MPa, assembly coaxiality ≤0.03mm, no weld defects and rework, and the highest cost performance; Examples 1-3 have a reasonable parameter gradient, covering the needs of different scenarios.

[0142] In summary, this invention solves the problems of low strength, poor precision, short life and low yield in traditional manufacturing by synergistic key processes, significantly improving product performance and production efficiency. Example 2 can be scaled up and provides a standardized solution for modular camshaft manufacturing.

[0143] Table 3, GB testing standards in Tables 1 and 2

[0144] GB Standard Tensile strength of single cylinder blank GB / T1348-2009 Ductile Iron Castings Multi-component assembly coaxiality GB / T1184-2018 "Geometric and Positional Tolerances - Unspecified Tolerance Values" Journal roughness Ra GB / T1031-2009 Surface Roughness Parameters and Their Values ​​by Surface Structure Profiling Method Cam base circle diameter deviation GB / T1804-2000 - General Tolerances - Tolerances for Linear and Angular Dimensions Without Specified Tolerances Valve seat force at 6000 r / min GB / T12797-2019 Technical Requirements for Camshafts of Internal Combustion Engines Residual stress in the weld zone GB / T24179-2023 Determination of Residual Stress in Metallic Materials - Indentation Strain Method Fatigue life of finished camshafts GB / T12797-2019 Technical Requirements for Camshafts of Internal Combustion Engines

[0145] Table 4. Test methods according to GB testing standards

[0146] Detection methods Tensile strength of single cylinder blank Prepare Φ50×100mm single-cast specimens, perform tensile tests using a universal testing machine, and calculate the tensile strength according to the standard. Multi-component assembly coaxiality Using the journal axis as a reference, a coordinate measuring machine is used to sample three evenly distributed sections of the assembly, fit the measured axis, and calculate the maximum distance from the reference axis. Journal roughness Ra A stylus-type roughness tester was used, with a sampling length of 0.8 mm and an evaluation length of 5 × sampling length. The measurement was taken along the machining texture direction in the middle of the journal. Cam base circle diameter deviation Data from three cross-sections of the base circle were collected using a coordinate measuring machine. The diameter of the fitted circle was compared with the design value, and the deviation was calculated. Valve seat force at 6000 r / min A test bench for the valve train was built to simulate a 6000 r / min operating condition, and the impact force at the moment the valves came to rest was collected in real time using pressure sensors. Residual stress in the weld zone Indentation strain gauges were used to mark points on the surface of the welding area, and data were collected by strain gauges. The residual stress was calculated according to the standard formula. Fatigue life of finished camshafts Apply cyclic loads at a frequency of 10-50Hz using an MTS fatigue testing machine, record the number of cycles until failure, and determine the fatigue life.

[0147] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A modular camshaft blank assembly, characterized by: The assembly is a single-cylinder independent structure, which is manufactured by machining after being integrally cast, and comprises a first valve cam (1), a second valve cam (2), a journal (3), a positioning boss and an assembly structure; The first valve cam (1) and the second valve cam (2) are in a blank state of an unprocessed profile line, the base circle diameter, the diameter of the journal (3), the distance between the first valve cam (1) and the second valve cam (2) and the peach slice width of the first valve cam (1) and the second valve cam (2) are locked by machining.

2. A modular camshaft blank assembly according to claim 1, characterized in that: The positioning boss comprises a first boss (4) at the rear end of the journal (3), a second boss (7) at the front end of the first valve cam (1), a third boss (8) at the front end of the journal (3) and a fourth boss (9) at the rear end of the second valve cam (2), the shapes and sizes of the first boss (4), the second boss (7), the third boss (8) and the fourth boss (9) are matched, and are used for positioning and alignment during assembly of multiple components.

3. A modular camshaft blank assembly according to claim 1, wherein: The assembly structure comprises a shaft hole (5) at one end of the journal (3) and a shaft head (6) at the other end, and the shaft hole (5) is connected with the shaft head (6) of the adjacent component in an interference fit; The interference amount of the interference fit is 0.02-0.04mm, the shaft hole (5) needs to be heated to 120-150℃ during assembly, and a pressing force of 5-8kN is used to realize fixation.

4. A method of making a modular camshaft blank assembly, characterized by, A modular camshaft blank assembly for any one of claims 1-3, the preparation method comprising the following steps: S1, integrally casting: integrally casting a first valve cam (1), a second valve cam (2), a journal (3), a positioning boss and an assembly structure into a single-cylinder blank body, and performing aging treatment after casting to eliminate internal stress; S2, standardized machining: sequentially performing rough machining, heat treatment and finishing on the single-cylinder blank body to lock the base circle diameter of the first valve cam (1) and the second valve cam (2), the diameter of the journal (3), the distance between the two cams and the peach slice width, and form a single-cylinder modular blank assembly; S3, multi-component assembly: selecting a corresponding number of single-cylinder modular blank assemblies according to the number of single-side cylinders of the engine, positioning and aligning through the first boss (4), the second boss (7), the third boss (8) and the fourth boss (9), and assembling the shaft head (6) of the adjacent component with the shaft hole (5) in an interference fit to lock the distance between the two components as the cylinder center distance of the engine; S4, cam profile machining: designing the cam profile according to the gas distribution requirements of the target model using a 5th order polynomial motion law, and performing grinding machining on the first valve cam (1) and the second valve cam (2) blank to form an adaptive profile; S5, end piece assembly: selecting head end pieces and tail end pieces that are adaptive to the boundaries of the whole machine, and assembling them to both ends of the multi-component assembly body of step S3 to complete the preparation of the finished camshaft, and the finished product needs to pass dynamic balance detection and bench reliability test.

5. A method of making a modular camshaft blank assembly according to claim 4, characterized in that: In step S1, raw material pretreatment is required before integrally casting, comprising the following steps: If adopting nodular cast iron, the original molten iron needs to be treated by pouring method for spheroidizing and inoculation, the spheroidizing agent is FeSiMg8Re3, the adding amount is 1.2%-1.5%, the inoculant is 75SiFe, the adding amount is 0.8%-1.0%, and the spheroidizing grade is ensured to be greater than or equal to 3, and the graphite size is 6-8; If adopting alloy cast iron, the original molten iron temperature needs to be controlled to 1420-1450℃ to prevent the burning loss of alloy elements; Three Φ50*100mm test blocks are taken from each batch of raw materials to detect the tensile strength and hardness, and the hardness range is HB180-220, and the unqualified batch is prohibited to use.

6. A method of making a modular camshaft blank assembly according to claim 4, characterized in that: In the step S1, the integral casting is formed by using a resin sand mold, the resin adding amount of the mold is 1.2%-1.5%, the curing agent adding amount is 0.4%-0.6%, the surface roughness of the cavity is Ra≤1.6μm, and two Φ15mm exhaust holes are arranged at the positions corresponding to the cam peach tips; The mold parting surface is arranged horizontally along the axis of the shaft neck (3), the upper mold is provided with a Φ30mm pouring cup, the lower mold is provided with a Φ20mm direct sprue, and the cross sprue has a cross-sectional area of 300mm 2 The inner gate is opposite to the thick part of the shaft neck (3), and the metal liquid filling time is ≤8s; In the step S1, the pouring and post-processing parameters include: The nodular cast iron pouring temperature is 1300-1350℃, the alloy cast iron pouring temperature is 1350-1400℃, and the automatic pouring machine is adopted, and the pouring speed is 5-8kg / s; After opening the box, the shot blasting is adopted, the steel shot diameter is Φ1.5mm, the shot blasting time is 5min, the surface defects are visually inspected, the pore and blowhole depth is less than or equal to 1mm, the area is less than or equal to 5mm2, the defect exceeds the piece is welded with a welding rod, and the welding current is 90-110A; The aging treatment adopts the heating rate of 50℃ / h to 200-250℃, the holding time is 4-6h, the furnace is cooled to below 100℃, and the residual stress is less than or equal to 80MPa.

7. A method of making a modular camshaft blank assembly according to claim 4, characterized in that: In the step S2, the rough machining adopts a numerical control lathe, the spindle speed is 800-1200r / min, the hard alloy turning tool is used for rough turning the outer circle, the boring tool is used for rough turning the inner hole, the back engagement amount is 2-3mm, and the feed amount is 0.2-0.3mm / r, and the residual amount of the shaft neck (3), the shaft head (6) and the shaft hole (5) is controlled to be 0.5-0.8mm after the rough machining; In the step S2, the heat treatment and flaw detection include: The quenching and tempering treatment: the temperature is raised to 850-880℃, the holding time is 1.5h, the oil cooling is to below 200℃, the cooling speed is greater than or equal to 30℃ / s, the temperature is raised to 550-600℃ again, the holding time is 2h, the tempering is carried out, and the furnace is discharged and air cooled; After the heat treatment, three test samples are taken to detect the hardness and metallographic structure, the hardness range is HB220-250, the sorbite content is greater than or equal to 80%, and the internal defects are detected by using an ultrasonic flaw detector; In the step S2, the finishing and surface treatment include: The shaft neck (3) outer circle is ground by using an outer circle grinding machine, the speed is 1500r / min, the feed amount is 0.01-0.02mm / r, the roughness Ra is less than or equal to 0.8μm, and the shaft hole (5) is ground by using an inner circle grinding machine, the speed is 2000r / min; The positioning boss is machined by using a vertical machining center, the tool is a hard alloy end mill, the number of teeth is 4, the milling speed is 80-100m / min, the feed amount is 0.1-0.15mm / r, the dimensional tolerance is ±0.01mm, and the perpendicularity is less than or equal to 0.005mm. After finishing, ultrasonic cleaning with KD-120 carbon hydrogen cleaning agent for 10 minutes, cleaning agent temperature 40-50℃, then immerse in RP-308 anti-rust agent for 5 minutes, anti-rust agent concentration 5%, dry and seal after drying.

8. A method of making a modular camshaft blank assembly according to claim 4, characterized in that: In the step S3, the multi-component assembly adopts an assembly platform made of cast iron, with a flatness of ≤0.01mm / m, and the platform is provided with four positioning pins matched with the positioning bosses. The press-fitting equipment is a numerical control press, with an accuracy of ±0.1kN, and is equipped with a displacement sensor with an accuracy of ±0.001mm. In the step S3, the assembly process parameters include: The shaft head (6) is cleaned with alkaline degreasing agent for 10-15 minutes, the degreasing agent includes sodium hydroxide 5%, sodium carbonate 3%, and surfactant 2%, and the cleaning temperature is 50-60℃. The shaft head is dried with 0.6MPa oil-free and water-free compressed air. The press-fitting speed of the press is 0.5mm / s, and the pressure is maintained for 30s after the press-fitting is in place. The natural cooling time is ≥2h. After assembly, the coaxiality is detected with a dial gauge with an accuracy of 0.001mm, and the coaxiality is ≤0.03mm. The unqualified parts are disassembled after heating the shaft hole (5) to 180-200℃ and reassembled.

9. A method of making a modular camshaft blank assembly according to claim 4, characterized in that: In the step S4, the cam profile processing includes: The lift of the profile buffer section is 0-1mm, and the acceleration is ≤500mm / s2. The lift of the working section is 1-15mm, and the speed is ≤1.2m / s. Through AVLEX CITE software simulation verification, the valve seating force is ≤800N at a speed of 6000r / min, and the valve bounce is ≤0.1mm. Different grinding wheels are selected according to the material of the grinding wheel; Double-nozzle cooling is adopted, which is 5-10mm away from the grinding area. The coolant is a mixture of 7%-9% emulsified oil, 2%-4% anti-rust agent, and 87%-91% water, with a flow rate of ≥15L / min and a pressure of ≥0.3MPa. Every 10 pieces are detected for profile error with a cam contour instrument, and the profile error is ≤0.01mm. The surface roughness is detected with a roughness instrument, and the Ra is ≤0.4μm.

10. A method of making a modular camshaft blank assembly according to claim 4, characterized in that: In the step S5, the end piece assembly and finished product detection include: The head end piece is assembled by interference fit, heated to 120-140℃, and press-fitted with a force of 7-9kN. The tail end piece is assembled by argon arc welding, with a welding current of 120-150A, an arc voltage of 18-20V, an Ar gas flow rate of 8-10L / min, and a post-welding stress relief annealing at 300-350℃ for 2h to remove residual stress, and the residual stress in the welding area is ≤60MPa. The finished product is detected for coaxiality, cam phase angle error, and shaft neck roundness with a three-coordinate measuring machine, with a coaxiality of ≤0.05mm, a cam phase angle error of ≤0.5°, and a shaft neck roundness of ≤0.005mm. The dynamic balance machine is used for detection, with a speed of 6000r / min and a permissible unbalance of ≤15g・mm. Bench reliability test: assembled to the engine cylinder head, 1000-hour cycle test under working conditions, speed 1000-6000r / min, oil temperature 80-100℃, cam wear ≤0.008mm, shaft neck wear ≤0.005mm after test. The head end piece is laser marked with product model, batch, production date, and two-dimensional code. Each batch is accompanied by material, size, and performance test report.

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