Rocket engine injector thin-wall milling self-positioning clamp and assembling method

Abstract

The invention relates to a rocket engine injector thin-wall milling self-positioning clamp and an assembling method, and the clamp mainly comprises an upper positioning tire body assembly, a conical surface expansion ring, a tire unloading bottom plate, a pressing cover plate, a tire unloading hanging ring, a pressing bolt, an expansion screw, a lower positioning chassis assembly, a locking bolt and a long fixing bolt, the lower positioning bottom plate assembly is fixed to a machine tool workbench for a long time through locking bolts and is not detached all the time. Before a product is milled, the thin wall of the injector and the positioning tire body assembly are positioned, clamped and supported through a conical surface expansion ring, a tire unloading bottom plate, a pressing cover plate, a pressing bolt and an expansion screw, and radial and axial movement of the thin wall of the injector is limited; after the thin wall of the injector and the upper positioning matrix assembly are assembled, the thin wall of the injector and the upper positioning matrix assembly are moved into a machine tool through a hanging ring, and the upper positioning matrix assembly and the lower positioning chassis assembly fixed to a machine tool workbench are rapidly assembled and positioned and are milled. The self-centering quick-change combined clamp is provided with a plurality of upper positioning tire body assemblies used for assembling a plurality of injector thin-wall products for quick production change.

Description

Technical Field

[0001] The invention belongs to the technical field of rocket engine machining, and relates to a self-positioning fixture and an assembly method for thin-wall milling of a rocket engine injector. Background Art

[0002] Liquid rocket engines have long been the focus of development for the power of various heavy rockets due to their high reliability, low cost, and reusable characteristics. The thrust chamber is an important core combustion component, and the injector located inside the thrust chamber is the most core complex structural component in the thrust chamber. 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 them into the combustion component for combustion to generate high-temperature and high-pressure propulsion gas. Since the injector works in harsh conditions of high temperature, high pressure, and high heat flux density for a long time, the injector is designed to consist of two parts, namely the thin-wall of the injector and the outer shell. The outer surface of the thin-wall of the injector is evenly distributed with hundreds of high-precision spiral deep and narrow grooves. After brazing with the outer shell, hundreds of mutually closed spiral inner cavities are formed as a regenerative cooling structure for cooling and heat exchange. To ensure the heat dissipation performance of the thin-wall of the injector, the thin-wall of the injector is made of copper alloy with a total wall thickness of less than 3 mm, and the groove depth and groove width have high dimensional accuracy and consistency requirements. After milling, the remaining wall thickness of the thin-wall of the injector is only 1 mm, and large plastic deformation is easily generated during the product processing. To ensure the brazing gap requirement between the thin-wall of the injector and the outer wall and the consistency of the groove depth dimension, the plastic deformation amount generated by the workpiece needs to be strictly controlled during the processing of the thin-wall of the injector, so as to ensure that the runout of the outer circle and the top plane of the thin-wall of the injector after milling is not greater than 0.02 mm. Therefore, this special self-centering fixture for milling is designed to realize the clamping and positioning and plastic deformation control during the milling process of the copper thin-wall of the injector, and finally ensure the high-precision requirements of product processing. Summary of the Invention

[0003] The technical problem solved by the invention is: overcoming the deficiencies of the prior art, in order to suppress the problems such as easy deformation of the copper alloy thin-wall workpiece of the injector during the machining process due to milling force, uneven cutting amount caused by no surface support, and difficult disassembly and assembly of the workpiece, a self-positioning fixture and an assembly method for thin-wall milling of a rocket engine injector are designed to solve the problems of easy deformation and difficult positioning and clamping during the processing of the thin-wall of the injector, and ensure the machining accuracy requirements of the product.

[0004] The solution of the invention to solve the technical problem is: a self-positioning fixture for thin-wall milling of a rocket engine injector, the positioning fixture includes a tensioning self-centering combined fixture, and the tensioning self-centering combined fixture includes a main positioning body, a conical surface expander, a tire removal bottom plate, a pressing cover plate, a tire removal lifting ring, a pressing bolt, a tensioning screw, a lower positioning chassis assembly, and a locking bolt; wherein:

[0005] The outer surface of the main positioning carcass and the inner surface of the tapered surface expansion ring are tapered surface structures with the same taper. The tapered surface expansion ring is sleeved outside the main positioning carcass. The outer tapered surface of the main positioning carcass and the inner tapered surface of the tapered surface expansion ring are mutually attached. Dozens of long grooves are machined on both the inner surface and the outer surface of the tapered surface expansion ring. Due to the radial force, the long groove structure causes the tapered surface expansion ring to produce uniform elastic deformation. The tapered surface structure of the main positioning carcass is used to generate a radial force to promote the radial deformation of the tapered surface expansion ring; the tightening screw passes through the through hole at the lower end of the main positioning carcass and is connected to the threaded hole at the bottom end face of the tapered surface expansion ring already installed on the main positioning carcass; a groove is provided on the upper surface of the main positioning carcass, the tire removal bottom plate is placed in the groove, and the thin wall of the injector is sleeved on the tapered surface expansion ring along the axis direction of the main positioning carcass. The inner surface of the thin wall of the injector is attached to the outer surface of the tapered surface expansion ring; the pressing cover plate is placed on the upper surface of the thin wall of the injector, and the pressing bolt passes through the pressing cover plate from top to bottom and is connected to the threaded hole on the main positioning carcass. The axial pressing force generated by the threaded fastening tightly fixes the pressing cover plate, the thin wall of the injector, and the main positioning carcass, restricting the axial movement of the thin wall of the injector.

[0006] Preferably, the groove on the upper surface of the main positioning carcass has a semi-circular protrusion along the radial direction, and the tire removal bottom plate 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 bottom plate and restrict the circumferential rotation of the tire removal bottom plate.

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

[0008] The upper positioning carcass assembly includes a circumferential pre-positioning block, a tapered surface positioning pin, a central guiding tapered hole, a lock washer, a fixing bolt, and a positioning support plate;

[0009] The fixing bolt and the lock washer lock and connect the main positioning carcass and the positioning support plate;

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

[0011] When the upper positioning carcass assembly and the lower positioning chassis assembly are assembled, the circumferential pre-positioning block and the circumferential pre-positioning column are circumferentially pre-positioned through the shaft-hole fit. The central positioning is realized by the tapered surface fit of the central guiding tapered hole and the central guiding tapered column. The circumferential positioning is realized by the tapered surface fit of the tapered surface positioning pin and the tapered hole positioning block. The axial positioning of the upper positioning carcass assembly and the lower positioning chassis assembly is completed through the long fixing bolt.

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

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

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

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

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

[0017] S1. Assemble the thin wall of the injector, the expansion self-centering combined fixture, and the upper positioning carcass assembly to form a whole;

[0018] S2, assembling the lower positioning chassis assembly to form a whole;

[0019] S3, fixing the lower positioning base plate assembly as a whole to the machine tool workbench;

[0020] S4. Move the upper positioning carcass assembly from the operating table outside the machine tool to the inside of the machine tool, and assemble the upper positioning carcass assembly with the lower positioning chassis assembly. During the assembly process, it is necessary to ensure that the circumferential pre-positioning block cooperates with the circumferential pre-positioning column shaft hole for circumferential pre-positioning. The center positioning is achieved by the cooperation between the center guide tapered hole and the tapered surface of the center guide tapered column. The circumferential positioning is achieved by the cooperation between the tapered surface positioning pin and the tapered surface of the tapered hole positioning block. Finally, the upper positioning carcass assembly and the lower positioning chassis assembly are fixed by long fixing bolts. Thus, the assembly of the injector thin-wall and expansion self-centering combined clamp is completed, which is convenient for the injector thin-wall milling processing on the machine tool.

[0021] Preferably, the steps of assembling the thin wall of the injector, the expansion self-centering combined fixture, and the upper positioning carcass assembly are as follows:

[0022] The first step is to install the conical expansion ring into the main positioning tire body, ensure that the outer conical surface of the main positioning tire body and the inner conical surface of the conical expansion ring fit each other, and use a feeler gauge to measure the fitting gap to ensure that the gap value is between 0.1mm and 0.2mm;

[0023] Step 2: Pass the expansion screw through the through hole at the lower end of the main positioning tire body and connect it with the threaded hole on the bottom end surface of the conical expansion ring installed on the main positioning tire body;

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

[0025] Step 4: Install the thin wall of the injector along the axis of the main positioning carcass on the conical surface expansion ring on the main positioning carcass, ensuring that the inner surface of the thin wall of the injector fits the outer surface of the conical surface expansion ring, and the fitting gap is between 0.05 and 0.08 mm;

[0026] Step 5: Place the pressing cover plate on the upper surface of the thin wall of the injector. The pressing bolts pass through the pressing cover plate and are connected to the uniformly distributed threaded holes on the main positioning carcass. The axial pressing force generated by the threaded fastening tightly fixes the pressing cover plate, the thin wall of the injector, and the main positioning carcass;

[0027] Step 6: Rotate and tighten the expansion screw. During this process, the expansion screw generates an axially downward pulling force on the conical surface expansion ring. The conical surface expansion ring moves axially downward along the main positioning carcass. The conical surface expansion ring is deformed by the radial force of the conical surface, resulting in an increase in the outer surface diameter. The outer surface of the conical surface expansion ring fits with the inner surface of the thin wall of the injector to generate a radial supporting force, and thus the assembly of the thin wall of the injector is completed.

[0028] Preferably, after the execution of Step 4, the fitting gap between the inner surface of the thin wall of the injector and the outer surface of the conical surface expansion ring is between 0.05 and 0.08 mm.

[0029] The beneficial effects of the present invention compared with the prior art are as follows:

[0030] (1) The fixture provided by the present invention is convenient for disassembling and assembling workpieces, has the function of quickly changing production, is convenient for batch, standardized, and high-precision processing of workpieces, and the disassembly and assembly of each part of the fixture are convenient, the structural parts are easy to replace, and it is convenient for maintenance. It can completely solve the problems of easy deformation and difficult positioning and clamping during the product processing process, and ensure the processing accuracy requirements of the product.

[0031] (2) The self-positioning fixture for milling the thin wall of the injector of the present invention adopts a modular design structure and is composed of multiple parts. The important structural features of the upper positioning carcass assembly and the lower positioning chassis assembly are modular parts, which are convenient for the disassembly, replacement, and maintenance of the vulnerable structures of the fixture, so as to reduce the use cost of the fixture and improve the service life of the fixture;

[0032] (3) The present invention locks and connects the main positioning carcass and the positioning support plate 107 through fixing bolts and anti-loosening washers, which can prevent the loosening of the threads caused by mechanical vibration and cause the fixture to become unstable;

[0033] (4) The main positioning carcass of the present invention adopts a conical surface structure, the conical surface angle is 3.5°, and the surface roughness is Ra1.6. The conical surface structure is used to generate a radial force to cause the conical surface expansion ring to generate radial deformation;

[0034] (5) The upper surface of the main positioning carcass of the present invention has a groove, and there are four semi-circular protrusions along the radial direction of the groove, which are used to limit the circumferential rotation of the tire removal bottom 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 radially stressed, and the long groove structure is conducive to generating large elastic deformation during expansion;

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

[0037] (8) The circumferential pre-positioning column and circumferential pre-positioning block of the present invention can achieve the circumferential pre-positioning function through shaft-hole cooperation. The height of the circumferential pre-positioning block is higher than that of the conical positioning pin, preventing the conical positioning pin from being knocked during assembly, resulting in accuracy loss and the loss of the self-centering function.

[0038] (9) The present invention is applicable to batch rapid changeover processing in the milling processing operation of products. After the lower positioning chassis assembly 8 is assembled, it is fixedly installed on the machine tool workbench for a long time without disassembly. Before milling processing, a plurality of thin-walled injectors are loaded into the corresponding number of upper positioning tire body assemblies and stored in the warehouse for use. During processing, the upper positioning tire body assembly equipped with the product is moved into the machine tool and quickly assembled with the lower positioning chassis assembly for milling processing. After processing, the upper positioning tire body assembly and the product in the machine tool are removed, and the unprocessed upper positioning tire body assembly 1 equipped with the product is loaded for milling processing. Thus, rapid changeover clamping processing of thin-walled injector products is realized, which can greatly improve the processing efficiency of such products, reduce the waiting time of the machine tool, and improve the equipment utilization rate. Description of the Drawings

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

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

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

[0042] Figure 4 It is a front view of the self-centering combined fixture for milling processing according to the embodiment of the present invention;

[0043] Figure 5 It is an axonometric view of the self-centering combined fixture for milling processing according to the embodiment of the present invention;

[0044] Figure 6 It is a structural diagram of the main positioning tire body according to the embodiment of the present invention. Detailed Embodiments

[0045] The present invention will be further described below in conjunction with the embodiments.

[0046] As Figure 1 and Figure 2 shown, the present invention provides a self - positioning fixture for thin - wall milling of a rocket engine injector, mainly including an upper positioning matrix assembly 1, a tensioning self - centering combined fixture, and a lower positioning chassis assembly 8. Each part is assembled by a split - type and modular structure.

[0047] The tensioning self - centering combined fixture includes a main positioning matrix 108, a tapered surface expansion ring 2, a tire - removing bottom plate 3, a pressing cover plate 4, a tire - removing lifting ring 5, a pressing bolt 6, a tensioning screw 7, a lower positioning chassis assembly 8, and a locking bolt 9;

[0048] As Figure 6 shown, the outer surface of the main positioning matrix 108 and the inner surface of the tapered surface expansion ring 2 are tapered surface structures with the same taper. The tapered surface expansion ring 2 is sleeved outside the main positioning matrix 108, and the outer tapered surface of the main positioning matrix 108 and the inner tapered surface of the tapered surface expansion ring 2 are mutually attached. Dozens of long grooves are processed on both the inner surface and the outer surface of the tapered surface expansion ring 2. Due to the radial force, the long - groove structure makes the tapered surface expansion ring 2 produce uniform elastic deformation. The tapered surface structure of the main positioning matrix 108 is used to generate a radial force to cause the tapered surface expansion ring 2 to produce radial deformation; the tensioning screw 7 passes through the through - hole at the lower end of the main positioning matrix 108 and is connected to the threaded hole at the bottom end surface of the tapered surface expansion ring 2 already installed on the main positioning matrix 108; a groove is provided on the upper surface of the main positioning matrix 108, and the tire - removing bottom plate 3 is placed in the groove. The thin - wall of the injector is sleeved on the tapered surface expansion ring 2 along the axis direction of the main positioning matrix 108, and the inner surface of the thin - wall of the injector is attached to the outer surface of the tapered surface expansion ring 2; the pressing cover plate 4 is placed on the upper surface of the thin - wall of the injector, and the pressing bolt 6 passes through the pressing cover plate 4 from top to bottom and is connected to the threaded hole on the main positioning matrix 108. The axial pressing force generated by thread tightening tightly fixes the three parts of the pressing cover plate 4, the thin - wall of the injector, and the main positioning matrix 108, restricting the axial movement of the thin - wall of the injector.

[0049] Before milling the product, the thin - wall of the injector is positioned and clamped with the upper positioning matrix assembly 1 through the tapered surface expansion ring 2, the tire - removing bottom plate 3, the pressing cover plate 4, the pressing bolt 6, and the tensioning screw 7; after the assembly of the thin - wall of the injector and the upper positioning matrix assembly 1 is completed, it is moved into the machine tool through the lifting ring 101, and the upper positioning matrix assembly 1 is quickly assembled and positioned with the lower positioning chassis assembly 8 already fixed on the machine - tool workbench for milling processing.

[0050] A set of tensioning self - centering combined fixture is only equipped with one lower positioning chassis assembly 8 and can be equipped with multiple upper positioning matrix assemblies 1.

[0051] The upper positioning matrix assembly 1 is mainly composed of seven parts, including a lifting ring 101, a circumferential pre - positioning block 102, a tapered surface positioning pin 103, a central guiding tapered hole 104, a lock - preventing gasket 105, a fixing bolt 106, and a positioning support plate 107;

[0052] The fixing bolt 106 and the lock washer 105 lock and connect the positioning main positioning carcass 108 and the positioning support plate 107 to prevent thread loosening caused by mechanical vibration and fixture instability; the flatness of the upper surface of the positioning support plate is not greater than 0.005 mm.

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

[0054] As Figure 4 and Figure 5 shown, when the upper positioning carcass assembly 1 and the lower positioning chassis assembly 8 are assembled, the circumferential pre-positioning block 102 and the circumferential pre-positioning column 803 are circumferentially pre-positioned through shaft-hole fit. The central positioning is achieved by the conical surface fit of the central guiding conical hole 104 and the central guiding cone column 802. The circumferential positioning is achieved by the conical surface fit of the conical surface positioning pin 103 and the tapered hole positioning block 801. The axial positioning of the upper positioning carcass assembly 1 and the lower positioning chassis assembly 8 is completed through the long fixing bolt 10.

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

[0056] The outer circle of the bottom surface of the conical surface 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 dimension accuracy error of less than 0.005 mm.

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

[0058] There are grooves on the upper surface of the main positioning carcass 108, and there are four semi-circular protrusions along the radial direction of the grooves, which are used to limit the circumferential rotation of the tire unloading bottom plate 3;

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

[0060] Hundreds of spiral deep and narrow grooves with a depth greater than 6 mm, a width less than 1 mm, and a spiral lift angle of 18° are evenly distributed on the outer surface of the injector thin wall. The accuracy requirements for the groove depth and groove width are extremely high, and the machining error is required to be not greater than 0.03 mm.

[0061] Before the batch milling of the thin wall of the injector, the upper positioning matrix assembly 1 needs to be assembled by combining its seven parts first. After the assembly is completed, it can be regarded as a whole and will not be disassembled during the production process unless for tooling maintenance. Five parts need to be assembled to form the lower positioning chassis assembly 8. The positioning bottom plate assembly 8 can be regarded as a whole and is always fixed to the machine tool workbench by the locking bolt 9 and generally will not be disassembled.

[0062] Therefore, based on the above fixture, the present invention provides a method for assembling the thin wall milling of a rocket engine injector, and the method includes the following steps:

[0063] S1. Assemble the injector thin wall, the expansion self-centering combined fixture, and the upper positioning matrix assembly 1 to form a whole;

[0064] S2. Assemble the lower positioning chassis assembly 8 to form a whole;

[0065] S3. Fix the whole lower positioning bottom plate assembly 8 to the machine tool workbench;

[0066] S4. Move the upper positioning matrix assembly 1 from the operating table outside the machine tool into the machine tool, and assemble the upper positioning matrix 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 axially and radially aligned for circumferential pre-positioning. The central positioning is achieved by the conical surface fit of the central guiding conical hole 104 and the central guiding conical column 802, and the circumferential positioning is achieved by the conical surface fit of the conical surface positioning pin 103 and the conical hole positioning block 801. Finally, the upper positioning matrix assembly 1 and the lower positioning chassis assembly 8 are fixed by the long fixing bolt 10, and thus the thin wall and the expansion self-centering combined fixture are assembled, which is convenient for the milling of the injector thin wall on the machine tool.

[0067] The specific steps are as follows:

[0068] Assemble the injector thin wall, the expansion self-centering combined fixture, and the upper positioning matrix assembly 1. In the first step, two circumferential pre-positioning blocks 102, four high-precision positioning pins 103, a central guiding taper hole 104 and the positioning tray 107 need to be fixedly connected. The fixing method is to use high-strength socket head cap screws with the same M8 thread specification for threaded connection. Among them, 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 socket head cap screws are tightened with a torque wrench, and the tightening torque is set to a fixed value of 20.5 Nm. This torque can ensure the reliability of the part connection and the assembly accuracy. In the second step, the positioning main positioning matrix 108 and the positioning tray 107 need to be locked and connected through the fixing bolts 106 and the lock washers 105 to prevent the loosening of the threads caused by mechanical vibration. In the third step, the large lifting ring 101 with threads is inserted into the threaded hole of the positioning plate 107 for fixation. This lifting ring 101 can be used for the loading, unloading, hoisting and moving of the upper positioning matrix assembly 1. After the upper positioning matrix assembly 1 is assembled, it can be regarded as a whole and will not be disassembled during the production process unless for tooling maintenance. A set of self-centering quick-change fixtures can be equipped with multiple upper positioning matrix assemblies 1.

[0069] Assemble 5 parts to form the lower positioning chassis assembly 8. Fix the taper hole positioning block 801, the central guiding taper column 802, the circumferential pre-positioning column 803 and the positioning chassis 804 through high-strength socket head cap screws. The four taper hole positioning blocks 801 are evenly arranged on the upper surface of the positioning chassis 804 away from the center along the circumferential direction. The central guiding taper column 802 is installed at the center position of the chassis 804. The two circumferential pre-positioning columns 803 are symmetrically installed at the edge of the positioning chassis 804. All socket head cap screws are tightened with a torque wrench. When assembling the central guiding taper column 802, use socket head cap screws with a thread specification of M6, and the tightening torque is set to 15.5 Nm; when assembling the taper hole positioning block 801 and the circumferential pre-positioning column 803, use socket head cap screws with a thread specification of M8, and the tightening torque is set to 20.5 Nm. After the lower positioning chassis assembly 8 is assembled, place it on the machine tool workbench, align the outer circle and the upper surface of the lower positioning chassis assembly 8 to ensure that it is flush with the workbench, and ensure that the runout of the outer circle and the upper surface is not greater than 0.008 mm; the lower positioning chassis assembly 8 is in close contact with the surface of the machine tool workbench, and the fitting gap is not greater than 0.005 mm; fix the positioning bottom plate assembly 8 and the machine tool workbench together through the locking bolts 9. The locking bolts 9 with a thread specification of M15 are evenly distributed on the upper surface of the lower positioning chassis assembly 8 near the outer circle edge side and the center. The tightening torque of the locking bolts 9 is 125 Nm. During the mass production process of the product, the positioning bottom plate assembly 8 is always fixed on the machine tool workbench and will not be disassembled unless there is a fault.

[0070] After the assembly preparation of the upper positioning carcass assembly 1 and the lower positioning chassis assembly 8 is completed, the injector thin wall and the upper positioning carcass assembly 1 are assembled. Place the upper positioning carcass assembly 1 on the operating table outside the machine tool. First step, install the tapered surface expansion ring 2 into the main positioning carcass 108 of the upper positioning carcass assembly 1. When installing, ensure that the outer tapered surface of the main positioning carcass 108 and the inner tapered surface of the tapered surface expansion ring 2 are in mutual contact. Use a feeler gauge to measure the contact gap and ensure that the gap value is between 0.1 mm and 0.2 mm. Second step, pass six tightening screws 7 through the six through holes at the lower end of the main positioning carcass 108 and connect them to the six threaded holes on the bottom end surface of the tapered surface expansion ring 2 already installed on the main positioning carcass 108. Third step, place the tire removal bottom plate 3 in the groove on the upper surface of the main positioning carcass 108. There is a 1 mm gap between the outer surface of the tire removal bottom plate 3 and the main positioning carcass 108 for easy picking and placing. The tire removal cover plate 3 is circumferentially evenly distributed with four semi-circular concave edges, and the inner surface of the groove of the main positioning carcass 108 is circumferentially evenly distributed with four semi-circular protrusions. The main function of these semi-circular concave edges and protrusions is to position the circumferential position of the tire removal bottom plate 3 and prevent it from rotating circumferentially. Fourth step, install the injector thin wall along the axis direction of the main positioning carcass 108 on the tapered surface expansion ring 2 on the main positioning carcass 108, and ensure that the inner surface of the injector thin wall is in contact with the outer surface of the tapered surface expansion ring 2, and the contact gap is between 0.05 and 0.08 mm. Fifth step, place the pressing cover plate 4 on the upper surface of the injector thin wall. Four pressing bolts 6 pass through the pressing cover plate 4 and are connected to the four threaded holes evenly distributed on the main positioning carcass 108. Through the axial pressing force generated by the threaded fastening, the pressing cover plate 4, the injector thin wall and the main positioning carcass 108 are tightly fixed together, restricting the axial movement of the injector thin wall. Sixth step, rotate and tighten the six tightening screws 7. During this process, the tightening screws 7 generate an axially downward pulling force on the tapered surface expansion ring 2, and the tapered surface expansion ring 2 moves axially downward along the main positioning carcass 108. The tapered surface expansion ring 2 is deformed by the radial force of the tapered surface, resulting in an increase in the outer surface diameter. The tapered surface expansion ring 2 is in contact with the inner surface of the injector thin wall to generate a radial supporting force, which can prevent the injector thin wall from being deformed by the radial cutting force during the product processing. Thus, the assembly of the injector thin wall is completed. A set of self-centering quick-change fixtures can be equipped with multiple upper positioning carcass assemblies 1, and multiple injector thin wall products can be respectively assembled and reserved with multiple upper positioning carcass assemblies 1 at the same time, so as to facilitate the rapid loading and unloading and positioning of the fixtures during the actual production process and prepare for batch production.

[0071] After the thin-wall injector assembly is completed, the crane uses the lifting ring 101 to move the upper positioning carcass assembly 1 from the operating platform outside the machine tool to the inside of the machine tool, and assemble the upper positioning carcass 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 axially and radially mated for circumferential pre-positioning. The central positioning is achieved by the conical surface mating of the central guiding conical hole 104 and the central guiding conical column 802. The circumferential positioning is achieved by the conical surface mating of the conical surface positioning pin 103 and the conical hole positioning block 801. Finally, the upper positioning carcass assembly 1 and the lower positioning chassis assembly 8 are fixed by the long fixing bolts 10. Thus, the thin-wall injector product and the expansion self-centering combined fixture are assembled, and the thin-wall milling process of the injector can be carried out on the machine tool.

[0072] After the processing is completed, quickly remove the 4 long fixing bolts 10. The crane uses the lifting ring 101 to move the upper positioning carcass assembly 1 from the inside of the machine tool to the operating platform outside the machine tool. At the same time, move the spare positioning carcass assembly 1 of the assembled product into the machine tool to be assembled and quickly positioned with the lower positioning chassis assembly 8 for the milling process of the next thin-wall injector. Thus, the waiting time of the machine tool can be reduced, and the batch quick-change positioning processing of the product can be realized. Disassemble the processed thin-wall injector on the operating platform outside the machine tool. First step, use a torque wrench to loosen the six expansion screws 7. During this process, the conical expansion ring 2 that fits with the thin-wall injector returns to its original diameter and becomes smaller due to the disappearance of the radial force. At this time, a gap is generated between the thin-wall injector and the conical expansion ring 2, and the thin-wall injector is not radially constrained. Second step, remove the four compression bolts 6, pass the four circumferentially distributed tire-removing lifting rings 5 through the product pressing cover 4 and the thin-wall injector, and connect and tighten them with the four threaded holes of the tire-removing bottom plate 3 in the upper surface groove of the main positioning carcass 108. Thus, it can be ensured that the tire-removing bottom plate 3, the thin-wall injector, and the pressing cover 4 are connected as a whole. After the milling process of the thin-wall injector product is completed, remove the four compression bolts 6, pass the hook of the hoisting equipment through the 4 tire-removing lifting rings 5, and separate the processed thin-wall injector from the fixture by moving the hook to complete the product tire removal.

[0073] The self-positioning fixture for thin-wall milling of the injector designed by the present invention is suitable for batch rapid change production processing of the product milling process. After the lower positioning chassis assembly 8 is assembled, it is permanently fixed on the machine tool workbench without disassembly. Before the milling process, load multiple thin-wall injectors into the corresponding number of upper positioning carcass assemblies 1 for storage. During processing, move the upper positioning carcass assembly 1 equipped with the product into the machine tool for quick assembly with the lower positioning chassis assembly 8 and carry out the milling process. After processing, remove the upper positioning carcass assembly 1 and the product inside the machine tool, and load the unprocessed upper positioning carcass assembly 1 equipped with the product for the milling process. Thus, the rapid change production and clamping processing of the thin-wall injector product can be realized, which can greatly improve the processing efficiency of such products, reduce the waiting time of the machine tool, and improve the equipment utilization rate.

[0074] In summary, the self - centering combined fixture with expansion for milling the thin - wall of the injector of the present invention is mainly used for the milling processing, support clamping, deformation restriction, batch processing and rapid production change of the copper thin - wall of the injector. It has the characteristics of being split - type, modular, easy to disassemble and stable in processing, which is convenient for the batch, standardized and high - precision milling processing of the thin - wall of the injector.

[0075] Although the present invention has been disclosed above with preferred embodiments, it is not used to limit the present invention. Any person skilled in the art can make possible changes and modifications to the technical solution of the present invention by using the methods and technical contents disclosed above without departing from the spirit and scope of the present invention. Therefore, any simple modification, equivalent change and decoration made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention all belong to the protection scope of the technical solution of the present invention.

Claims

1. A self-positioning fixture for thin-wall milling of rocket engine injectors, characterized in that The invention comprises an expansion self-centering combined clamp, which comprises a main positioning tire body (108), a conical expansion (2), a tire unloading bottom plate (3), a clamping cover plate (4), a tire unloading lifting ring (5), a clamping bolt (6), an expansion screw (7), a lower positioning chassis assembly (8), and a locking bolt (9); wherein: The outer surface of the main positioning carcass (108) and the inner surface of the conical expansion ring (2) are conical structures with the same taper. The conical expansion ring (2) is sleeved on the outer side of the main positioning carcass (108). The outer conical surface of the main positioning carcass (108) and the inner conical surface of the conical expansion ring (2) fit each other. The inner and outer surfaces of the conical expansion ring (2) are processed with dozens of long grooves. Due to the radial force on the conical expansion ring (2), the long groove structure causes the conical expansion ring (2) to produce uniform elastic deformation. The conical structure of the main positioning carcass (108) is used to generate radial force to cause the conical expansion ring (2) to produce radial deformation. The expansion screw (7) passes through the through hole at the lower end of the main positioning carcass (108) and is installed on the main positioning carcass (108). ) is connected to the threaded hole on the bottom end face of the conical expansion ring (2) on the main positioning tire body (108); a groove is provided on the upper surface of the main positioning tire body (108), and the tire unloading bottom 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); a clamping cover plate (4) is placed on the upper surface of the thin wall of the injector, and a clamping bolt (6) passes through the clamping cover plate (4) from top to bottom and is connected to the threaded hole on the main positioning tire body (108). The axial clamping force generated by the threaded tightening tightly fixes the clamping cover plate (4), the thin wall of the injector and the main positioning tire body (108) tightly, thereby limiting the axial movement of the thin wall of the injector.

2. A rocket engine injector thin-wall milling self-positioning fixture according to claim 1, characterized in that: The groove on the upper surface of the main positioning tire body (108) has a semicircular protrusion along the radial direction, and the tire unloading base plate (3) is provided with a concave edge. The protrusion and the concave edge cooperate with each other to locate the circumferential position of the tire unloading base plate (3) and limit the circumferential rotation of the tire unloading base plate (3).

3. A rocket engine injector thin-wall milling self-positioning fixture according to claim 1, characterized in that: It also includes an upper positioning carcass assembly (1) and a lower positioning chassis assembly (8); The upper positioning carcass assembly (1) comprises a circumferential pre-positioning block (102), a conical positioning pin (103), a central guide conical hole (104), an anti-loosening gasket (105), a fixing bolt (106), and a positioning support plate (107); The fixing bolts (106) and the anti-loosening washers (105) lock and connect the main positioning carcass (108) and the positioning support plate (107); The lower positioning chassis assembly (8) comprises a tapered hole positioning block (801), a central guide tapered column (802), a circumferential pre-positioning column (803), and a positioning chassis (804); When the upper positioning carcass assembly (1) and the lower positioning chassis assembly (8) are assembled, the circumferential pre-positioning block (102) and the circumferential pre-positioning column (803) are matched through the axial hole to perform circumferential pre-positioning, the center positioning is achieved by the matching of the conical surface of the center guide conical hole (104) and the center guide conical column (802), the circumferential positioning is achieved by the matching of the conical surface positioning pin (103) and the conical surface of the conical hole positioning block (801), and the upper positioning carcass assembly (1) and the lower positioning chassis assembly (8) are axially positioned by the long fixing bolt (10).

4. A rocket engine injector thin-wall milling self-positioning fixture according to claim 3, characterized in that: The height dimension of the circumferential pre-positioning block (102) is 10% greater than that of the conical surface positioning pin (103).

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

6. A rocket engine injector thin-wall milling self-positioning fixture according to claim 3, characterized in that: The inner hole of the tapered hole positioning block (801) is a high-precision tapered surface, the tapered surface angle is 1.5°, the tapered surface roughness is Ra0.8, and the tapered surface size accuracy error is less than 0.005mm.

7. A rocket engine injector thin-wall milling self-positioning fixture according to claim 3, characterized in that: The outer surface of the main positioning carcass (108) and the inner surface of the conical expansion ring (2) are conical surfaces with an angle of 3.5°, and the roughness of the conical surfaces is Ra1.

6.

8. The rocket engine injector thin-wall milling processing and assembly method according to claim 3 is characterized in that: The steps include: S1, assembling the thin wall of the injector, the expansion self-centering combined fixture, and the upper positioning carcass assembly (1) to form a whole; S2, assembling the lower positioning chassis assembly (8) to form a whole; S3, fixing the lower positioning base plate assembly (8) as a whole to the machine tool workbench; S4, move the upper positioning carcass assembly (1) from the operating table outside the machine tool to the inside of the machine tool, and assemble the upper positioning carcass assembly (1) and 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) axial hole cooperate to perform circumferential pre-positioning, and the center positioning is achieved by the cooperation of the conical surface of the center guide tapered hole (104) and the center guide tapered column (802), and the circumferential positioning is achieved by the cooperation of the conical surface positioning pin (103) and the conical surface of the tapered hole positioning block (801). Finally, the upper positioning carcass assembly (1) and the lower positioning chassis assembly (8) are fixed by the long fixing bolts (10). Thus, the assembly of the thin-wall and expansion self-centering combined clamp is completed, which is convenient for thin-wall milling of the injector on the machine tool.

9. A rocket engine injector thin-wall milling processing and assembly method according to claim 8, characterized in that: The steps of assembling the thin wall of the injector, the expansion self-centering combined fixture, and the upper positioning carcass assembly (1) are as follows: The first step is to install the conical expansion ring (2) into the main positioning carcass (108), ensure that the outer conical surface of the main positioning carcass (108) and the inner conical surface of the conical expansion ring (2) fit each other, and use a feeler gauge to measure the fitting gap to ensure that the gap value is between 0.1 mm and 0.2 mm; Step 2: Pass the expansion screw (7) through the through hole at the lower end of the main positioning carcass (108) and connect it to the threaded hole at the bottom end surface of the conical expansion ring (2) installed on the main positioning carcass (108); Step 3: placing the tire removal base plate (3) in the groove on the upper surface of the main positioning tire body (108); Step 4: Install the thin wall of the injector on the conical expansion ring (2) on the main positioning carcass (108) along the axial direction of the main positioning carcass (108), ensuring that the inner surface of the thin wall of the injector fits with the outer surface of the conical expansion ring (2), and the fitting gap is 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 bolts (6) through the evenly distributed threaded holes on the clamping cover plate (4) and the main positioning carcass (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 carcass (108). Step 6. Rotate and tighten the expansion screw (7). 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 tire body (108). The conical expansion ring (2) is deformed by the radial force of the conical surface, causing the diameter of its outer surface to increase. The conical expansion ring (2) fits with the inner surface of the thin wall of the injector to generate a radial supporting force, thereby completing the assembly of the thin wall of the injector.

10. A rocket engine injector thin-wall milling machining and assembly method according to claim 9, characterized in that: After the fourth step is performed, the gap between the thin-walled inner surface 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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