A self-positioning fixture for thin-wall milling of a rocket engine injector and an assembling method thereof

Abstract

The present application relates to a kind of rocket engine injector thin-wall milling self-positioning fixture and assembly method, it mainly includes upper positioning tire body component, conical surface expansion ring, tire unloading bottom plate, pressing cover plate, tire unloading lifting ring, pressing bolt, expansion screw, lower positioning bottom plate component, locking bolt, long fixed bolt, lower positioning bottom plate component is fixed in machine tool workbench by locking bolt long-term, always not disassembled.Product is positioned and clamped and supported by conical surface expansion ring, tire unloading bottom plate, pressing cover plate, pressing bolt, expansion screw before milling injector thin-wall and positioning tire body component, limit the radial and axial movement of injector thin-wall;Injector thin-wall is positioned and clamped and supported by conical surface expansion ring, tire unloading bottom plate, pressing cover plate, pressing bolt, expansion screw before milling injector thin-wall and positioning tire body component, limit the radial and axial movement of injector thin-wall;Injector thin-wall is positioned and clamped and supported by conical surface expansion ring, tire unloading bottom plate, pressing cover plate, pressing bolt, expansion sleeve before milling injector thin-wall and positioning tire body component, limit the radial and axial movement of injector thinn

Description

Technical Field

[0001] This invention belongs to the field of rocket engine mechanical manufacturing technology, and relates to a self-positioning fixture and assembly method for thin-wall milling of rocket engine injectors. Background Technology

[0002] Liquid rocket engines, due to their high reliability, low cost, and reusability, have long been a key focus in the development of various heavy-lift rocket propulsion systems. The thrust chamber is a crucial core combustion component, and the injector, located inside the thrust chamber, is the most complex and critical structural component. Its main function is to atomize and mix the oxidizer and fuel in the propellant according to the required injection pressure and flow rate, and then inject it into the combustion chamber for combustion to generate high-temperature, high-pressure propellant gas. Because the injector operates under harsh conditions of high temperature, high pressure, and high heat flux density for extended periods, it is designed with two parts: a thin-walled injector and an outer shell, which together form the injector. The outer surface of the thin-walled injector has hundreds of high-precision, deep, narrow spiral grooves evenly distributed. After being brazed with the outer shell, these grooves form hundreds of mutually enclosed spiral cavities, serving as a regenerative cooling structure for cooling and heat exchange. To ensure the heat dissipation performance of the thin-walled injector, the injector wall is made of copper alloy with a total wall thickness of less than 3mm. The milling structure requires high precision and consistency in the groove depth and width. After milling, the remaining wall thickness is only 1mm, making the product highly susceptible to large plastic deformation during processing. To ensure the consistency of the brazing gap and groove depth between the thin-walled injector and the outer wall, the amount of plastic deformation generated during the thin-walled injector machining process must be strictly controlled. This ensures that the runout of the outer circle and top plane of the thin-walled injector after milling is no more than 0.02mm. Therefore, a special self-centering fixture for milling is designed to achieve clamping, positioning, and plastic deformation control during the milling process of the copper injector thin-walled injector, ultimately ensuring the high precision requirements of the product. Summary of the Invention

[0003] The technical problem solved by this invention is to overcome the shortcomings of the prior art. In order to suppress the problems of easy deformation of thin-walled workpieces of copper alloy injectors due to milling force, uneven cutting amount due to lack of surface support, and difficulty in disassembling and assembling workpieces, a self-positioning fixture and assembly method for milling thin-walled rocket engine injectors is designed. This solves the problems of easy deformation and difficult positioning and clamping during the thin-walled machining process of injectors, and ensures the machining accuracy requirements of the product.

[0004] The solution to the technical problem of this invention is: a self-positioning fixture for thin-wall milling of rocket engine injectors, the positioning fixture comprising a self-centering expansion assembly, wherein the self-centering expansion assembly comprises a main positioning jig, a conical expansion, a jig removal base plate, a clamping cover plate, a jig removal lifting ring, clamping bolts, expansion screws, a lower positioning chassis assembly, and locking bolts; wherein:

[0005] The outer surface of the main positioning tire and the inner surface of the conical expansion ring are both conical structures with the same taper. The conical expansion ring is fitted onto the outside of the main positioning tire, with the outer conical surface of the main positioning tire and the inner conical surface of the conical expansion ring fitting together. Both the inner and outer surfaces of the conical expansion ring are machined with dozens of long grooves. Due to radial force, the long groove structure causes the conical expansion ring to produce uniform elastic deformation. The conical structure of the main positioning tire is used to generate radial force, causing the conical expansion ring to deform radially. The tightening screw passes through the through hole at the lower end of the main positioning tire and engages with the conical surface already installed on the main positioning tire. The threaded holes on the bottom end face of the expansion ring are connected; the upper surface of the main positioning tire body is provided with a groove, the tire removal base plate is placed in the groove, the thin wall of the injector is fitted on the conical expansion ring along the axis of the main positioning tire body, and the inner surface of the thin wall of the injector is in contact with the outer surface of the conical expansion ring; the clamping cover plate is placed on the upper surface of the thin wall of the injector, and the clamping bolt passes through the clamping cover plate from top to bottom and is connected to the threaded hole on the main positioning tire body. The axial clamping force generated by the threaded fastening tightly fixes the clamping cover plate, the thin wall of the injector and the main positioning tire body, restricting the axial movement of the thin wall of the injector.

[0006] Preferably, the groove on the upper surface of the main positioning tire has a semi-circular protrusion along the radial direction, and the tire removal base plate has a concave edge. The protrusion and the concave edge cooperate with each other to position the circumferential position of the tire removal base plate and restrict the circumferential rotation of the tire removal base plate.

[0007] Preferably, the above-mentioned self-positioning fixture for thin-wall milling of rocket engine injectors further includes an upper positioning jig assembly and a lower positioning chassis assembly;

[0008] The upper positioning tire assembly includes a circumferential pre-positioning block, a conical positioning pin, a central guide cone hole, an anti-loosening washer, a fixing bolt, and a positioning support plate;

[0009] The fixing bolts and anti-loosening washers lock the positioning main positioning tire and positioning support plate in a secure connection.

[0010] The lower positioning chassis assembly includes a conical hole positioning block, a central guide cone, a circumferential pre-positioning column, and a positioning chassis;

[0011] When assembling the upper positioning tire assembly and the lower positioning chassis assembly, the circumferential pre-positioning block and the circumferential pre-positioning column are pre-positioned circumferentially through the engagement of the shaft hole. The center positioning is achieved by the engagement of the conical surface of the center guide cone hole and the center guide cone column. The circumferential positioning is achieved by the engagement of the conical surface positioning pin and the conical surface positioning block. The upper positioning tire assembly and the lower positioning chassis assembly are axially positioned by the long fixing bolt.

[0012] Preferably, the height of the circumferential pre-positioning block is 10% larger than that of the conical positioning pin.

[0013] Preferably, the bottom surface of the conical locating pin is a high-precision conical surface with a conical angle of 1.5°, a conical surface roughness of Ra0.8, and a conical surface dimensional accuracy error of less than 0.005mm.

[0014] Preferably, the inner hole of the conical positioning block is a high-precision conical surface with a conical angle of 1.5°, a conical surface roughness of Ra0.8, and a conical surface dimensional accuracy error of less than 0.005mm.

[0015] Preferably, the outer surface of the main positioning tire and the inner surface of the conical expansion ring are conical surfaces with an angle of 3.5° and a surface roughness of Ra1.6.

[0016] Another technical solution of the present invention is: a method for thin-wall milling and assembly of a rocket engine injector, the method comprising the following steps:

[0017] S1. Assemble the thin-walled injector, the self-centering expansion clamp, and the upper positioning tire assembly into a single unit;

[0018] S2. Assemble the lower positioning chassis components to form a whole;

[0019] S3. Fix the lower positioning base plate assembly to the machine tool worktable as a whole;

[0020] S4. Move the upper positioning jig assembly from the operating table outside the machine tool to inside the machine tool, and assemble the upper positioning jig assembly with the lower positioning chassis assembly. During the assembly process, it is necessary to ensure that the circumferential pre-positioning block and the circumferential pre-positioning column shaft hole cooperate to perform circumferential pre-positioning. The center positioning is achieved by the cooperation of the central guide cone hole and the conical surface of the central guide cone column. The circumferential positioning is achieved by the cooperation of the conical surface positioning pin and the conical surface positioning block. Finally, fix the upper positioning jig assembly and the lower positioning chassis assembly with long fixing bolts. Thus, the assembly of the injector thin-wall and expansion self-centering combination fixture is completed, which is convenient for the injector thin-wall milling on the machine tool.

[0021] Preferably, the steps for assembling the thin-walled injector, the self-centering expansion clamp, and the upper positioning tire assembly are as follows:

[0022] Step 1: Install the conical expansion ring into the main positioning tire body, ensuring that the outer conical surface of the main positioning tire body and the inner conical surface of the conical expansion ring fit together. Use a feeler gauge to measure the fitting gap, ensuring that the gap value is between 0.1mm and 0.2mm.

[0023] The second step is to pass the expansion screw through the through hole at the lower end of the main positioning tire body and connect it to the threaded hole at the bottom end of the tapered expansion ring that has been installed on the main positioning tire body.

[0024] Step 3: Place the tire removal base plate into the groove on the upper surface of the main positioning tire;

[0025] Step 4: Install the thin-walled injector onto the conical expansion ring on the main positioning body along the axis of the main positioning body, ensuring that the inner surface of the thin-walled injector is in contact with the outer surface of the conical expansion ring, with a contact gap between 0.05 and 0.08 mm.

[0026] Step 5: Place the clamping cover plate on the upper surface of the thin wall of the injector, and connect the clamping bolts through the clamping cover plate and the evenly distributed threaded holes on the main positioning body. The axial clamping force generated by the threaded fastening will tightly fix the clamping cover plate, the thin wall of the injector and the main positioning body.

[0027] Step 6: Tighten the expansion screw by rotating it. During this process, the expansion screw generates an axial downward pulling force on the conical expansion ring. The conical expansion ring moves axially downward along the main positioning body. The conical expansion ring is deformed by the radial force of the conical surface, which causes its outer surface diameter to increase. The conical expansion ring and the inner surface of the thin wall of the injector fit together to generate a radial support force. Thus, the assembly of the thin wall of the injector is completed.

[0028] Preferably, after the fourth step is performed, the gap between the inner surface of the thin wall of the injector and the outer surface of the conical expansion ring is between 0.05 and 0.08 mm.

[0029] The advantages of this invention compared to the prior art are:

[0030] (1) The fixture provided by the present invention is convenient for disassembling and assembling workpieces and has a quick production change function, which facilitates the batch, standardization and high-precision processing of workpieces. Moreover, the various parts of the fixture are easy to disassemble and assemble, the structural accessories are easy to replace and easy to maintain, which can completely solve the problems of easy deformation and difficult positioning and clamping in the product processing process, and ensure the processing accuracy requirements of the product.

[0031] (2) The self-positioning fixture for thin-wall milling of the injector of the present invention adopts a modular design structure, which is composed of multiple parts. The important structural features of the upper positioning jig assembly and the lower positioning chassis assembly are modular parts, which facilitates the disassembly, replacement and maintenance of the fixture's vulnerable structure, thereby reducing the fixture's operating cost and increasing its service life.

[0032] (3) The present invention locks the positioning main positioning body and positioning support plate 107 together with fixing bolts and anti-loosening washers, which can prevent the threads from loosening due to mechanical vibration and cause the fixture to become unstable.

[0033] (4) The main positioning tire body of the present invention adopts a conical structure with a conical angle of 3.5° and a surface roughness of Ra1.6. The conical structure is used to generate radial force to cause the conical expansion ring to deform radially.

[0034] (5) The main positioning tire body of the present invention has a groove on the upper surface of the groove, and four semi-circular protrusions along the radial direction of the groove, which are used to restrict the circumferential rotation of the tire removal base plate.

[0035] (6) The inner surface of the conical expansion ring of the present invention is a conical surface with an angle of 3.5° and the outer surface is a cylindrical surface. Dozens of long grooves are machined on the inner and outer surfaces. During use, the conical expansion ring 2 is subjected to radial force. The long groove structure is conducive to expansion and generates large elastic deformation.

[0036] (7) The outer circle of the tire removal base plate of the present invention has four semi-circular concave edges for circumferential positioning and to prevent circumferential rotation;

[0037] (8) The circumferential prepositioning post and circumferential prepositioning block of the present invention can realize the circumferential prepositioning function through the shaft hole cooperation. The height of the circumferential prepositioning block is higher than that of the conical positioning pin, so as to prevent the conical positioning pin from being bumped during assembly, resulting in loss of accuracy and loss of self-centering function.

[0038] (9) This invention is applicable to batch rapid production changeover processing of product milling process. After the lower positioning chassis assembly 8 is assembled, it is fixed to the machine tool worktable for a long time without disassembly. Before milling, multiple thin-walled injectors are loaded into the corresponding number of upper positioning jig assemblies and stored for later use. During processing, the upper positioning jig assembly with the product is moved into the machine tool and quickly assembled with the lower positioning chassis assembly and milled. After processing, the upper positioning jig assembly and product are removed from the machine tool, and the unprocessed upper positioning jig assembly 1 with the product is loaded for milling. This realizes rapid production changeover and clamping processing of thin-walled injector products, which can greatly improve the processing efficiency of such products, reduce machine tool waiting time, and improve equipment utilization. Attached Figure Description

[0039] Figure 1 This is a cross-sectional view of the assembly of the thin-walled injector and the upper positioning tire body assembly according to an embodiment of the present invention;

[0040] Figure 2 This is a three-dimensional view of the assembly of the thin-walled injector and the upper positioning tire body assembly according to an embodiment of the present invention;

[0041] Figure 3 The positioning chassis assembly is fixed to the machine tool in a three-dimensional view according to an embodiment of the present invention;

[0042] Figure 4 This is a front view of the self-centering assembly fixture for milling according to an embodiment of the present invention;

[0043] Figure 5 This is an isometric view of a milling self-centering assembly fixture according to an embodiment of the present invention;

[0044] Figure 6 This is a structural diagram of the main positioning tire body in an embodiment of the present invention. Detailed Implementation

[0045] The present invention will be further described below with reference to the embodiments.

[0046] like Figure 1 and Figure 2 As shown, this invention provides a self-positioning fixture for thin-wall milling of rocket engine injectors, mainly comprising an upper positioning jig assembly 1, a self-centering expansion jig assembly, and a lower positioning chassis assembly 8. Each part is assembled using a split, modular structure.

[0047] The self-centering expansion clamp includes a main positioning tire body 108, a conical expansion 2, a tire removal base plate 3, a pressure cover plate 4, a tire removal lifting ring 5, a pressure bolt 6, an expansion screw 7, a lower positioning chassis assembly 8, and a locking bolt 9.

[0048] like Figure 6 As shown, the outer surface of the main positioning tire body 108 and the inner surface of the conical expansion ring 2 are conical structures with the same taper. The conical expansion ring 2 is fitted onto the outside of the main positioning tire body 108. The outer conical surface of the main positioning tire body 108 and the inner conical surface of the conical expansion ring 2 fit together. Dozens of long grooves are machined on both the inner and outer surfaces of the conical expansion ring 2. Due to radial force, the long groove structure causes the conical expansion ring 2 to produce uniform elastic deformation. The conical structure of the main positioning tire body 108 is used to generate radial force to cause the conical expansion ring 2 to produce radial deformation. The tightening screw 7 passes through the through hole at the lower end of the main positioning tire body 108 and is installed on the main positioning tire body 108. The conical expansion ring 2 is connected to the threaded hole at the bottom end; the upper surface of the main positioning tire body 108 is provided with a groove, the tire removal base plate 3 is placed in the groove, the thin wall of the injector is sleeved on the conical expansion ring 2 along the axial direction of the main positioning tire body 108, and the inner surface of the thin wall of the injector is in contact with the outer surface of the conical expansion ring 2; the pressure cover plate 4 is placed on the upper surface of the thin wall of the injector, and the pressure bolt 6 passes through the pressure cover plate 4 from top to bottom and is connected to the threaded hole on the main positioning tire body 108. The axial pressure force generated by the threaded fastening tightly fixes the pressure cover plate 4, the thin wall of the injector and the main positioning tire body 108, restricting the axial movement of the thin wall of the injector.

[0049] Before milling, the thin wall of the injector is positioned and clamped to the upper positioning jig assembly 1 using the conical expansion ring 2, the jig removal base plate 3, the clamping cover plate 4, the clamping bolt 6, and the expansion screw 7. After the thin wall of the injector is assembled with the upper positioning jig assembly 1, it is moved to the machine tool by the lifting ring 101. The upper positioning jig assembly 1 is then quickly assembled and positioned with the lower positioning chassis assembly 8, which is fixed to the machine tool worktable, and then milled.

[0050] A set of self-centering tensioning combination fixtures is equipped with only one lower positioning chassis component 8, but can be equipped with multiple upper positioning tire body components 1.

[0051] The upper positioning tire assembly 1 is mainly composed of seven parts, including a lifting ring 101, a circumferential pre-positioning block 102, a conical positioning pin 103, a central guide cone hole 104, an anti-loosening washer 105, a fixing bolt 106, and a positioning support plate 107.

[0052] The fixing bolts 106 and the anti-loosening washers 105 lock the positioning main positioning jig 108 and the positioning tray 107 together to prevent the threads from loosening due to mechanical vibration and causing the fixture to become unstable; the flatness of the upper surface of the positioning tray is not greater than 0.005mm.

[0053] like Figure 3 As shown, the lower positioning chassis assembly 8 is mainly composed of five parts, including a lifting ring 101, a conical hole positioning block 801, a central guide cone 802, a circumferential pre-positioning column 803, and a positioning chassis 804.

[0054] like Figure 4 and Figure 5 As shown, when the upper positioning tire assembly 1 and the lower positioning chassis assembly 8 are assembled, the circumferential pre-positioning block 102 and the circumferential pre-positioning post 803 are pre-positioned circumferentially through the shaft hole cooperation. The center positioning is achieved by the conical surface cooperation of the center guide cone hole 104 and the center guide cone post 802. The circumferential positioning is achieved by the conical surface positioning pin 103 and the conical surface cooperation of the cone hole positioning block 801. The upper positioning tire assembly 1 and the lower positioning chassis assembly 8 are axially positioned by the long fixing bolt 10.

[0055] The height of the circumferential pre-positioning block 102 is 10% larger than that of the conical positioning pin 103 to prevent the high-precision conical surface of the conical positioning pin 103 from directly colliding with the lower positioning chassis assembly 8 during the assembly of the upper positioning tire assembly 1 and the lower positioning chassis assembly 8, which would result in loss of precision and loss of self-centering function.

[0056] The bottom outer circle of the conical locating pin 103 is a high-precision conical surface with a conical angle of 1.5°, a surface roughness of Ra0.8, and a dimensional accuracy error of less than 0.005mm.

[0057] The inner hole of the tapered hole positioning block 801 is a high-precision tapered surface with a tapered angle of 1.5°, a tapered surface roughness of Ra0.8, and a tapered surface dimensional accuracy error of less than 0.005mm.

[0058] The upper surface of the main positioning tire body 108 has a groove with four semi-circular protrusions along the radial direction of the groove, which are used to restrict the 3-dimensional rotation of the tire removal base plate.

[0059] The outer surface of the main positioning tire body 108 and the inner surface of the conical expansion ring 2 are conical surfaces with an angle of 3.5° and a surface roughness of Ra1.6.

[0060] The thin-walled outer surface of the injector is uniformly distributed with hundreds of spiral deep and narrow grooves with a depth greater than 6mm, a width less than 1mm, and a helix angle of 18°. The groove depth and width have extremely high precision requirements, and the machining error is required to be no greater than 0.03mm.

[0061] Before the thin-walled batch milling of the injector, the upper positioning body assembly 1, consisting of seven parts, must first be assembled. After assembly, it can be regarded as a whole and will not be disassembled during production unless tooling maintenance is required. The lower positioning chassis assembly 8, consisting of five parts, must be assembled. The positioning base plate assembly 8 can be regarded as a whole and is always fixed to the machine tool worktable by locking bolts 9. It is generally not disassembled.

[0062] Therefore, based on the above-mentioned fixture, the present invention provides a method for thin-wall milling and assembly of rocket engine injectors, the method comprising the following steps:

[0063] S1. Assemble the thin-walled injector, the self-centering expansion clamp, and the upper positioning tire assembly 1 into a whole;

[0064] S2. Assemble the lower positioning chassis component 8 into a whole;

[0065] S3. Fix the lower positioning base plate assembly 8 to the machine tool worktable as a whole;

[0066] S4. Move the upper positioning jig assembly 1 from the operating table outside the machine tool to inside the machine tool, and assemble the upper positioning jig assembly 1 with the lower positioning chassis assembly 8. During the assembly process, it is necessary to ensure that the circumferential pre-positioning block 102 and the circumferential pre-positioning column 803 are engaged in the shaft hole for circumferential pre-positioning. The center positioning is achieved by the engagement of the central guide cone hole 104 and the conical surface of the central guide cone column 802. The circumferential positioning is achieved by the engagement of the conical surface positioning pin 103 and the conical surface of the cone hole positioning block 801. Finally, the upper positioning jig assembly 1 and the lower positioning chassis assembly 8 are fixed by the long fixing bolt 10. Thus, the thin-walled and expansion self-centering combination fixture is assembled, which is convenient for the thin-walled milling of the injector on the machine tool.

[0067] The specific steps are as follows:

[0068] The thin-walled injector, the self-centering expansion clamp, and the upper positioning jig assembly 1 are assembled. The first step involves fixing two circumferential pre-positioning blocks 102, four high-precision positioning pins 103, and one central guide cone hole 104 to the positioning tray 107. All fixing methods utilize high-strength internal hex bolts with the same M8 thread specification for threaded connection. The four high-precision positioning pins 14 are evenly distributed along the circumference of the bottom surface of the positioning tray 1, and the two pre-positioning blocks 12 are symmetrically distributed along the bottom surface of the positioning tray 1. All internal hex bolts... The threads are tightened using a torque wrench, with the tightening torque set to a fixed value of 20.5 Nm. This torque ensures the reliability of the part connection and the assembly accuracy. The second step involves locking the positioning main positioning jig 108 and positioning tray 107 together using fixing bolts 106 and anti-loosening washers 105 to prevent loosening of the threads due to mechanical vibration. The third step involves inserting a large threaded lifting eye 101 into the threaded hole of the positioning tray 107 for fixation. This lifting eye 101 can be used for loading, unloading, lifting, and moving the upper positioning jig assembly 1. Once assembled, the upper positioning jig assembly 1 can be considered a single unit and is not disassembled during production except for tooling maintenance. One set of self-centering quick-change fixtures can be equipped with multiple upper positioning jig assemblies 1.

[0069] Five parts are assembled to form the lower positioning chassis assembly 8. The tapered hole positioning block 801, the central guide tapered column 802, and the circumferential pre-positioning column 803 are fixedly connected to the positioning chassis 804 using high-strength hexagonal socket head cap screws. The four tapered hole positioning blocks 801 are evenly distributed along the circumference on the upper surface of the positioning chassis 804 away from the center. The central guide tapered column 802 is installed at the center of the chassis 804, and the two circumferential pre-positioning columns 803 are symmetrically installed on the edges of the positioning chassis 804. All the hexagonal socket head cap screws are tightened using a torque wrench. When assembling the central guide tapered column 802, M6 threaded hexagonal socket head cap screws are used, with a tightening torque of 15.5 Nm; when assembling the tapered hole positioning block 801 and the circumferential pre-positioning column 803, M8 threaded hexagonal socket head cap screws are used, with a tightening torque of 20.5 Nm. After the lower positioning base assembly 8 is assembled, it is placed on the machine tool worktable. The outer circle and upper surface of the lower positioning base assembly 8 are aligned to ensure that it is flush with the worktable, and the runout of the outer circle and upper surface is no greater than 0.008mm. The lower positioning base assembly 8 is tightly fitted to the surface of the machine tool worktable, with a fitting gap of no more than 0.005mm. The positioning base assembly 8 and the machine tool worktable are fixed together by locking bolts 9. The M15 threaded locking bolts 9 are evenly distributed on the upper surface of the lower positioning base assembly 8 near the outer edge and center, and the tightening torque of the locking bolts 9 is 125NM. During the batch processing of products, the positioning base assembly 8 is always fixed to the machine tool worktable and is not disassembled unless there is a fault.

[0070] After completing the assembly preparation of the upper positioning jig assembly 1 and the lower positioning chassis assembly 8, assemble the injector thin-walled part and the upper positioning jig assembly 1. Place the upper positioning jig assembly 1 on the operating table outside the machine tool. First, install the conical expansion ring 2 into the main positioning jig 108 of the upper positioning jig assembly 1. When installing, ensure that the outer conical surface of the main positioning jig 108 and the inner conical surface of the conical expansion ring 2 are in contact with each other. Use a feeler gauge to measure the contact gap and ensure that the gap value is between 0.1mm and 0.2mm. Second, pass the six tightening screws 7 through the six through holes at the lower end of the main positioning jig 108 and connect them with the six screws on the bottom end face of the conical expansion ring 2 already installed on the main positioning jig 108. The threaded holes are connected; the third step is to place the tire removal base plate 3 in the groove on the upper surface of the main positioning tire body 108. There is a 1mm gap between the outer surface of the tire removal base plate 3 and the main positioning tire body 108 for easy removal and placement. The tire removal cover plate 3 has four semi-circular concave edges evenly distributed around its circumference, and the inner surface of the groove of the main positioning tire body 108 has four semi-circular protrusions evenly distributed around its circumference. The main function of these semi-circular concave edges and protrusions is to position the tire removal base plate 3 around its circumference and prevent it from rotating around its circumference; the fourth step is to place the thin wall of the injector along the axis of the main positioning tire body 108. The conical expansion ring 2, installed on the main positioning jig 108, ensures that the inner surface of the thin wall of the injector is in contact with the outer surface of the conical expansion ring 2, with a contact gap between 0.05 and 0.08 mm. In the fifth step, the clamping cover plate 4 is placed on the upper surface of the thin wall of the injector. Four clamping bolts 6 pass through the clamping cover plate 4 and connect to four evenly distributed threaded holes on the main positioning jig 108. The axial clamping force generated by the threaded fastening tightly fixes the clamping cover plate 4, the thin wall of the injector, and the main positioning jig 108, restricting the thin wall of the injector. The sixth step involves rotating and tightening the six expansion screws 7. During this process, the expansion screws 7 exert an axial downward pulling force on the conical expansion ring 2. The conical expansion ring 2 moves axially downward along the main positioning body 108. The conical expansion ring 2 is deformed by the radial force of the conical surface, causing its outer surface diameter to increase. The conical expansion ring 2 and the inner surface of the injector thin wall are in contact with each other to generate radial support force, which can prevent the injector thin wall from being deformed by radial cutting force during product processing. Thus, the injector thin wall assembly is completed. A set of self-centering quick-change fixtures can be equipped with multiple upper positioning body components 1, and multiple injector thin wall products can be assembled with multiple upper positioning body components 1 for standby at the same time, so as to facilitate the quick loading, unloading and positioning of fixtures in actual production, and to prepare for mass production.

[0071] After the thin-walled injector is assembled, the upper positioning jig assembly 1 is moved from the operating table outside the machine tool to the machine tool by a crane using the lifting ring 101. The upper positioning jig assembly 1 is then assembled with the lower positioning chassis assembly 8. During the assembly process, it is necessary to ensure that the circumferential pre-positioning block 102 and the circumferential pre-positioning column 803 are engaged in circumferential pre-positioning. The center positioning is achieved by the engagement of the central guide cone hole 104 and the conical surface of the central guide cone column 802. The circumferential positioning is achieved by the engagement of the conical surface positioning pin 103 and the conical surface of the cone hole positioning block 801. Finally, the upper positioning jig assembly 1 and the lower positioning chassis assembly 8 are fixed by the long fixing bolt 10. Thus, the thin-walled injector product and the self-centering expansion combination fixture are assembled and can be machined on the machine tool for thin-walled injector milling.

[0072] After processing, the four long fixing bolts 10 are quickly removed. The crane uses the lifting ring 101 to move the upper positioning jig assembly 1 from inside the machine tool to the operating table outside the machine tool. At the same time, the spare positioning jig assembly 1 of the assembled product is moved into the machine tool and assembled with the lower positioning chassis assembly 8 and quickly positioned for the next injection nozzle thin-wall milling process. This reduces the machine tool waiting time and realizes batch quick change positioning processing of products. The pre-machined thin-walled sprayer, moved to the machine tool's external operating table, is disassembled. First, a torque wrench is used to loosen the six expansion screws 7. During this process, the conical expansion ring 2, which is in contact with the thin-walled sprayer, loses its radial force, causing its diameter to return to its original size and decrease. At this point, a gap is created between the thin-walled sprayer and the conical expansion ring 2, and the thin-walled sprayer is no longer radially constrained. Second, the four clamping bolts 6 are removed, and four circumferentially distributed tire-removing rings 5 ​​are passed through the product clamping cover plate 4 and the thin-walled sprayer, and connected and tightened to the four threaded holes in the tire-removing base plate 3 within the groove on the upper surface of the main positioning tire 108. This ensures that the tire-removing base plate 3, the thin-walled sprayer, and the clamping cover plate 4 are connected as a single unit. After the milling of the thin-walled sprayer is completed, the four clamping bolts 6 are removed. The hook of the gantry crane is then passed through the four tire-removing rings 5, and by moving the hook, the pre-machined thin-walled sprayer can be separated from the fixture, completing the tire removal process.

[0073] The self-positioning fixture for milling thin-walled injectors designed in this invention is suitable for batch rapid production changeover processing of product milling processes. After the lower positioning chassis assembly 8 is assembled, it is fixed to the machine tool worktable for a long time without disassembly. Before milling, multiple thin-walled injectors are loaded into the corresponding number of upper positioning jig assemblies 1 and stored for later use. During processing, the upper positioning jig assemblies 1 with the products are moved into the machine tool and quickly assembled with the lower positioning chassis assembly 8 and milled. After processing, the upper positioning jig assemblies 1 and the products are removed from the machine tool, and unprocessed upper positioning jig assemblies 1 with the products are loaded for milling. This realizes rapid production changeover and clamping processing of thin-walled injector products, which can significantly improve the processing efficiency of such products, reduce machine tool waiting time, and improve equipment utilization.

[0074] In summary, the self-centering combination fixture for milling thin-walled injectors described in this invention is mainly used for supporting and clamping, limiting deformation, batch processing, and rapid production changeover in the milling of thin-walled copper injectors. It features a split design, modularity, easy disassembly, and stable processing, facilitating the batch, standardization, and high-precision milling of thin-walled injectors.

[0075] Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make possible changes and modifications to the technical solutions of the present invention by utilizing the methods and techniques disclosed above without departing from the spirit and scope of the present invention. Therefore, any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solutions of the present invention shall fall within the protection scope of the technical solutions of the present invention.

Claims

1. A self-positioning fixture for thin-walled milling of rocket engine injectors, characterized in that... The system includes a self-centering tensioning assembly, comprising a main positioning tire body (108), a conical expansion ring (2), a tire removal base plate (3), a clamping cover plate (4), a tire removal lifting ring (5), a clamping bolt (6), a tensioning screw (7), a locking bolt (9), an upper positioning tire body assembly (1), and a lower positioning chassis assembly (8); wherein: The outer surface of the main positioning tire body (108) and the inner surface of the conical expansion ring (2) are conical structures with the same taper. The conical expansion ring (2) is fitted on the outside of the main positioning body (108). The outer conical surface of the main positioning body (108) and the inner conical surface of the conical expansion ring (2) fit together. The inner and outer surfaces of the conical expansion ring (2) are machined with dozens of long grooves. Due to the radial force, the long groove structure causes the conical expansion ring (2) to produce uniform elastic deformation. The conical structure of the main positioning body (108) is used to generate radial force to cause the conical expansion ring (2) to produce radial deformation. The tightening screw (7) passes through the through hole at the lower end of the main positioning body (108) and is connected to the threaded hole at the bottom end of the conical expansion ring (2) that has been installed on the main positioning body (108). Connection; The upper surface of the main positioning tire (108) is provided with a groove, the tire removal base plate (3) is placed in the groove, the thin wall of the injector is sleeved on the conical expansion ring (2) along the axial direction of the main positioning tire (108), and the inner surface of the thin wall of the injector is in contact with the outer surface of the conical expansion ring (2); the clamping cover plate (4) is placed on the upper surface of the thin wall of the injector, and the clamping bolt (6) passes through the clamping cover plate (4) from top to bottom and connects with the threaded hole on the main positioning tire (108). The axial clamping force generated by the threaded fastening tightly fixes the clamping cover plate (4), the thin wall of the injector and the main positioning tire (108), restricting the axial movement of the thin wall of the injector; The groove on the upper surface of the main positioning tire body (108) has a semi-circular protrusion along the radial direction, and the tire removal base plate (3) is provided with a concave edge. The protrusion and the concave edge cooperate with each other to position the circumferential position of the tire removal base plate (3) and restrict the circumferential rotation of the tire removal base plate (3); The upper positioning tire assembly (1) includes a circumferential prepositioning block (102), a conical positioning pin (103), a central guide cone hole (104), an anti-loosening washer (105), a fixing bolt (106), and a positioning support plate (107). The fixing bolts (106) and the anti-loosening washers (105) lock the positioning main positioning tire body (108) and the positioning bracket (107) in a locked connection; The lower positioning chassis assembly (8) includes a cone hole positioning block (801), a central guide cone column (802), a circumferential pre-positioning column (803), and a positioning chassis (804). When assembling the upper positioning tire assembly (1) and the lower positioning chassis assembly (8), the circumferential prepositioning block (102) and the circumferential prepositioning column (803) are prepositioned circumferentially through the shaft hole. The center positioning is achieved by the conical surface of the center guide cone hole (104) and the center guide cone column (802). The circumferential positioning is achieved by the conical surface positioning pin (103) and the conical hole positioning block (801). The upper positioning tire assembly (1) and the lower positioning chassis assembly (8) are axially positioned by the long fixing bolt (10).

2. The self-positioning fixture for thin-wall milling of rocket engine injectors according to claim 1, characterized in that, The height dimension of the circumferential pre-positioning block (102) is 10% larger than that of the conical positioning pin (103).

3. The self-positioning fixture for thin-walled milling of rocket engine injectors according to claim 1, characterized in that, The bottom surface of the conical positioning pin (103) is a high-precision conical surface with a conical angle of 1.5°, a conical surface roughness of Ra0.8, and a conical surface dimensional accuracy error of less than 0.005mm.

4. A self-positioning fixture for thin-wall milling of rocket engine injectors according to claim 1, characterized in that, The inner hole of the tapered hole positioning block (801) is a high-precision tapered surface with a tapered angle of 1.5°, a tapered surface roughness of Ra0.8, and a tapered surface dimensional accuracy error of less than 0.005mm.

5. A self-positioning fixture for thin-walled milling of rocket engine injectors according to claim 1, characterized in that, The outer surface of the main positioning tire body (108) and the inner surface of the conical expansion ring (2) are conical surfaces with an angle of 3.5° and a surface roughness of Ra1.

6.

6. A method for assembling a rocket engine injector thin-wall milling machine based on the self-positioning fixture for thin-wall milling of a rocket engine injector as described in claim 1, characterized in that, Includes the following steps: S1. Assemble the thin-walled injector, the self-centering clamping fixture, and the upper positioning tire assembly (1) into a whole. S2. Assemble the lower positioning chassis component (8) into a whole; S3. Fix the lower positioning chassis assembly (8) to the machine tool worktable as a whole; S4. Move the upper positioning jig assembly (1) from the operating table outside the machine tool to inside the machine tool, and assemble the upper positioning jig assembly (1) with the lower positioning chassis assembly (8). During the assembly process, it is necessary to ensure that the circumferential prepositioning block (102) and the circumferential prepositioning column (803) shaft hole cooperate for circumferential prepositioning. The center positioning is achieved by the cooperation of the conical surface of the center guide cone hole (104) and the center guide cone column (802). The circumferential positioning is achieved by the cooperation of the conical surface positioning pin (103) and the conical hole positioning block (801). Finally, the upper positioning jig assembly (1) and the lower positioning chassis assembly (8) are fixed by the long fixing bolt (10). Thus, the thin-walled and expansion self-centering combination fixture is assembled, which is convenient for the thin-walled milling of the injector on the machine tool.

7. A method for thin-walled milling and assembly of a rocket engine injector according to claim 6, characterized in that, The steps for assembling the thin-walled injector, the self-centering expansion jig, and the upper positioning tire assembly (1) are as follows: Step 1: Install the conical expansion ring (2) into the main positioning tire body (108) to ensure that the outer conical surface of the main positioning tire body (108) and the inner conical surface of the conical expansion ring (2) fit together. Use a feeler gauge to measure the fit gap and ensure that the gap value is between 0.1mm and 0.2mm. The second step is to pass the expansion screw (7) through the through hole at the lower end of the main positioning body (108) and connect it to the threaded hole at the bottom end of the conical expansion ring (2) that has been installed on the main positioning body (108). Third step: Place the tire removal base plate (3) into the groove on the upper surface of the main positioning tire (108); Step 4: Install the thin wall of the injector onto the conical expansion ring (2) on the main positioning body (108) along the axial direction of the main positioning body (108), ensuring that the inner surface of the thin wall of the injector is in contact with the outer surface of the conical expansion ring (2), with a contact gap between 0.05 and 0.08 mm. Step 5: Place the clamping cover plate (4) on the upper surface of the thin wall of the injector, and connect the clamping bolt (6) through the clamping cover plate (4) to the threaded holes evenly distributed on the main positioning body (108). The clamping cover plate (4), the thin wall of the injector and the main positioning body (108) are tightly fixed by the axial clamping force generated by the thread fastening. Step 6: Tighten the expansion screw (7) by rotating it. During this process, the expansion screw (7) generates an axial downward pulling force on the conical expansion ring (2). The conical expansion ring (2) moves axially downward along the main positioning body (108). The conical expansion ring (2) is deformed by the radial force of the conical surface, which causes its outer surface diameter to increase. The conical expansion ring (2) and the inner surface of the thin wall of the injector are in contact with each other to generate a radial support force. Thus, the assembly of the thin wall of the injector is completed.

8. The method for thin-wall milling and assembly of a rocket engine injector according to claim 7, characterized in that, After the fourth step is performed, the gap between the inner surface of the thin wall of the injector and the outer surface of the conical expansion ring (2) is between 0.05 and 0.08 mm.

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