Combined machining and manufacturing method for turbine pump shafting speed measurement sleeve

Abstract

The invention relates to a combined machining and manufacturing method for a turbine pump shafting speed measuring sleeve, which comprises the following steps of: a rough machining process: performing rough machining before heat treatment, finishing machining of the inner shape and the outer shape of a workpiece by adopting numerical control lathe machining, and removing most of allowance before heat treatment of the workpiece to obtain a speed measuring sleeve semi-finished product; the semi-finished speed measuring sleeve is of a structure with a disc protruding from the middle of cylinders at two ends; in the strengthening heat treatment process, heat treatment is conducted on the speed measuring sleeve semi-finished product in a quenching, tempering and cold treatment mode, and the hardness of the speed measuring sleeve is improved; in the finish machining process, the two end faces of the speed measuring sleeve semi-finished product are ground in a plane grinding mode, and deformation generated by the speed measuring sleeve semi-finished product after heat treatment is eliminated; after plane grinding, low-speed wire cut electrical discharge machining is adopted to machine speed measuring teeth and an inner hole of the speed measuring sleeve; and the outer circle of the speed measuring sleeve is ground, and the speed measuring sleeve is demagnetized after grinding is completed.

Description

Technical Field

[0001] The present invention relates to a composite processing and manufacturing method for a speed measurement sleeve of a turbopump shaft system, belonging to the field of aerospace manufacturing, and specifically a high-precision processing and manufacturing method combining mechanical processing and slow wire electrical discharge machining. Background Art

[0002] In order to improve the reliability of liquid rocket engines, more and more new materials with high hardness and high strength are being used. When processing such parts using traditional mechanical processing methods, tool wear is serious and the processing accuracy is low. In order to meet the processing requirements of such products, special processing methods are often used. Electrical discharge wire cutting is a type of electrical discharge machining. It uses a thin metal wire as the electrode and relies on the instantaneous high temperature generated during the pulsed spark discharge between the electrode wire and the workpiece to achieve the erosion processing of the workpiece material. Electrical discharge wire cutting can be divided into three types according to the wire running speed: slow wire, medium wire, and fast wire. Among them, slow wire electrical discharge wire cutting uses a zinc-plated brass wire as the tool electrode, and the electrode wire runs unidirectionally, enabling multiple machining of the workpiece. Using slow wire electrical discharge wire cutting can achieve the processing of high-hardness products without being affected by the mechanical properties of the material.

[0003] The turbopump is the heart of a liquid rocket engine. During the operation of the engine, the shaft system parts in the turbopump rotate at high speed to provide power for the entire engine. The rotational speed is one of the important parameters of the entire turbopump. In order to achieve dynamic monitoring of the turbopump rotational speed, a speed measurement sleeve is installed on the turbopump shaft system, and a rotational speed sensor is installed on the pump housing to measure the pump rotational speed. The speed measurement sleeve is evenly distributed with multiple speed measurement teeth in the circumferential direction. When the turbopump is operating, the speed measurement teeth cut the magnetic induction lines of the permanent magnet inside the rotational speed sensor, generating an electrical signal. By calculating and processing the electrical signal, the actual rotational speed of the turbopump can be obtained. In addition, the speed measurement sleeve is also an important sealing part. The outer circle of the speed measurement sleeve cooperates with the floating ring, which can separate the high-temperature gas and liquid oxygen, playing a good sealing role. In order to improve the sealing effect of the speed measurement sleeve, it is required that the speed measurement sleeve has high hardness and wear resistance, and at the same time, the machining accuracy requirements for the inner hole and outer circle of the speed measurement sleeve are relatively high. Using traditional and single processing methods can no longer meet the processing requirements for such products. Summary of the Invention

[0004] The technical problem solved by the present invention is: overcoming the deficiencies of the prior art, the present invention provides a composite processing and manufacturing method for a speed measurement sleeve of a turbopump shaft system. By combining slow wire electrical discharge machining and numerical control grinding, the problem of out-of-tolerance caused by high product hardness after heat treatment of speed measurement sleeve products is solved, and the qualification rate of such products is improved.

[0005] The solution to the technical problem of the present invention is: a composite processing and manufacturing method for a speed measurement sleeve of a turbopump shaft system, which includes the following steps:

[0006] Rough machining process: It is carried out before heat treatment. The numerical control turning is used to complete the machining of the inner and outer shapes of the workpiece. Most of the surplus is removed before the workpiece is heat-treated to obtain a semi-finished product of the speed measurement sleeve. The semi-finished product of the speed measurement sleeve has a structure with two cylindrical ends and a protruding disc in the middle;

[0007] Strengthening heat treatment process: The semi-finished product of the speed measurement sleeve is heat-treated by using the method of quenching + tempering + cryogenic treatment to improve the hardness of the speed measurement sleeve;

[0008] Finishing process: The two end faces of the semi-finished product of the speed measurement sleeve are ground by using surface grinding to eliminate the deformation generated by the semi-finished product of the speed measurement sleeve after heat treatment; After surface grinding, the slow wire electrical discharge machining is used to machine the speed measurement teeth and the inner hole of the speed measurement sleeve; The outer circle of the speed measurement sleeve is ground, and after the grinding process is completed, the speed measurement sleeve is demagnetized.

[0009] Preferably, the surplus left on each side of the semi-finished product of the speed measurement sleeve after rough machining should be greater than or equal to 0.2 mm.

[0010] Preferably, after heat treatment, the hardness of the semi-finished product of the speed measurement sleeve is between HRC56 and HRC62.

[0011] Preferably, the inner hole and the speed measurement teeth of the speed measurement sleeve are machined by slow wire electrical discharge machining. The inner hole is cut 5 times, and the speed measurement teeth are cut 3 times.

[0012] Preferably, after the speed measurement sleeve is machined, the roundness of the inner hole of the speed measurement sleeve is less than or equal to 0.01 mm, and the diameter tolerance is less than or equal to 0.008 mm.

[0013] Preferably, when the slow wire electrical discharge machining is carried out, a special fixture is used for clamping. The overall structure of the special fixture is a hollow cylindrical barrel. Four rib plates are evenly distributed in its inner hole. The rib plates extend inward from the hollow cylindrical barrel structure and are aligned with the central axis of the cylindrical barrel structure. A space is left in the middle of the four rib plates for inserting the cylindrical body of the semi-finished product of the speed measurement sleeve. The end face of one side of the rib plate close to the axis is a stepped surface. The cylindrical body at one end of the semi-finished product of the speed measurement sleeve is inserted into the space left in the middle of the four rib plates. One side of the protruding disc structure in the middle of the semi-finished product of the speed measurement sleeve is placed on the step of the rib plate, and the other side is aligned with the end face of the special fixture and the hollow cylindrical barrel structure. The workpiece is fixed by using a pressing plate and the threaded holes on the end face of the fixture to realize the clamping of the semi-finished product of the speed measurement sleeve.

[0014] Preferably, when the outer circle is finish-ground, the inner hole is clamped by using a mandrel, and the mandrel is aligned. The coaxiality between the mandrel and the rotating shaft of the machine tool is within 0.005 mm.

[0015] Preferably, after finish-grinding, the coaxiality between the outer circle and the inner hole of the speed measurement sleeve is within 0.01 mm.

[0016] Preferably, the tolerance of the outer diameter is less than or equal to 0.008 mm.

[0017] Preferably, during the demagnetization process, the magnetic induction intensity is not greater than 2 mT.

[0018] The beneficial effects of the present invention compared with the prior art are as follows:

[0019] (1) Since the present invention adopts the machining method of slow wire electrical discharge machining, it realizes the precision machining of high-hardness materials after heat treatment. Compared with the traditional internal grinding machining method, while ensuring the machining efficiency, it improves the machining accuracy and product qualification rate of the inner holes of speed measurement sleeve products.

[0020] (2) By designing a special clamping fixture, the present invention realizes the combined machining of the speed measurement teeth and the inner hole of the speed measurement sleeve. While improving the machining accuracy of the product, it reduces the number of clamping and alignment times, and realizes the efficient and precision machining of speed measurement sleeve products. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] FIG. 1(a) is a sectional view of the speed measurement sleeve according to the embodiment of the present invention;

[0022] FIG. 1(b) is a left view of the embodiment of the present invention;

[0023] FIG. 2(a) is a sectional view of the special fixture for slow wire electrical discharge machining of the speed measurement sleeve according to the embodiment of the present invention;

[0024] FIG. 2(b) is a sectional view taken along line A-A of FIG. 2(a) of the present invention;

[0025] FIG. 2(c) is an overall view of the special fixture for slow wire electrical discharge machining of the speed measurement sleeve according to the embodiment of the present invention;

[0026] Figure 3 is a special mandrel for outer circle grinding of the speed measurement sleeve according to the embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0027] The working principle of the present invention will be described in detail with reference to the accompanying drawings: This embodiment is implemented on the premise of the technical solution of the present invention, and the detailed implementation manner and specific operation process are given, but the protection scope of the present invention is not limited to the following embodiments.

[0028] The speed measurement sleeve of the turbine pump shafting has the characteristics of high hardness, thin wall, and deep and long holes, and cannot be machined by traditional machining methods. The present invention provides a composite machining and manufacturing method for the speed measurement sleeve of the turbine pump shafting, which mainly includes mechanical machining, heat treatment, slow wire electrical discharge machining, etc. The method includes the following steps:

[0029] Rough machining process: It is carried out before heat treatment. The inner and outer shapes of the workpiece are machined by CNC turning. Most of the surplus is removed before the workpiece undergoes heat treatment to obtain a semi-finished speed measuring sleeve. The semi-finished speed measuring sleeve has a structure with cylindrical bodies at both ends and a protruding disc in the middle.

[0030] Strong heat treatment process: The semi-finished speed measuring sleeve is heat-treated by quenching + tempering + cold treatment to improve the hardness of the speed measuring sleeve.

[0031] Fine machining process: The two end faces of the semi-finished speed measuring sleeve are ground by surface grinding to eliminate the deformation generated after heat treatment. After surface grinding, slow wire electrical discharge machining is used to machine the speed measuring teeth and inner hole of the speed measuring sleeve. The outer circle of the speed measuring sleeve is machined by CNC grinding. After the grinding process, the speed measuring sleeve is demagnetized.

[0032] Preferably, the surplus left on each side of the semi-finished speed measuring sleeve after rough machining should be greater than or equal to 0.2 mm.

[0033] After heat treatment, the hardness of the semi-finished speed measuring sleeve is between HRC56 and HRC62.

[0034] The inner hole and speed measuring teeth of the speed measuring sleeve are machined by slow wire electrical discharge machining. The inner hole is cut 5 times, and the speed measuring teeth are cut 3 times.

[0035] After machining the speed measuring sleeve, the roundness of the inner hole of the speed measuring sleeve is less than or equal to 0.01 mm, and the diameter tolerance is less than or equal to 0.008 mm.

[0036] As shown in Figures 2(a), 2(b) and 2(c), when machining by slow wire electrical discharge machining, a special fixture is used for clamping. The overall structure of the special fixture is a hollow cylindrical barrel. Four rib plates are evenly distributed in its inner hole. The rib plates extend inward from the hollow cylindrical barrel structure and are aligned with the central axis of the cylindrical barrel structure. A space is left between the four rib plates for inserting the cylindrical body of the semi-finished speed measuring sleeve. One side end face of the rib plate close to the axis is a stepped surface. The cylindrical body at one end of the semi-finished speed measuring sleeve is inserted into the space left between the four rib plates. One side of the protruding disc structure in the middle of the semi-finished speed measuring sleeve is placed on the step of the rib plate, and the other side is aligned with the end face of the special fixture and the hollow cylindrical barrel structure. The workpiece is fixed using a pressing plate and the threaded holes on the fixture end face to achieve the clamping of the semi-finished speed measuring sleeve.

[0037] As Figure 3 shown, when finely machining and grinding the outer circle, the inner hole is clamped by a mandrel, and the mandrel is aligned. The coaxiality between the mandrel and the rotating shaft of the machine tool is within 0.005 mm.

[0038] After fine machining and grinding, the coaxiality between the outer circle and the inner hole of the speed measuring sleeve is within 0.01 mm.

[0039] Preferably, the outer diameter tolerance of the speed measurement sleeve after finish grinding is less than or equal to 0.008 mm.

[0040] Preferably, during the demagnetization process, the magnetic induction intensity is not greater than 2 mT.

[0041] The present invention solves the out-of-tolerance problem caused by the high hardness of the speed measurement sleeve products after heat treatment by combining slow wire electrical discharge machining and CNC grinding, and improves the qualified rate of such products.

[0042] Example:

[0043] In the example, the processing principle of the present invention is illustrated by taking the processing of the speed measurement sleeve on a certain type of liquid oxygen-kerosene engine as an example:

[0044] As shown in Figures 1(a) and 1(b), four speed measurement teeth are evenly distributed in the circumferential direction of the speed measurement sleeve. The speed measurement sleeve includes two stepped holes. During assembly, the stepped holes are mated with the shaft. It is required that the clearance between the inner hole of the speed measurement sleeve and the shaft is within 0.02 mm. The outer circle is mated with the inner hole of the sealing component. It is required that the coaxiality of the outer circle of the speed measurement sleeve relative to the two stepped holes is within 0.01 mm, and the outer diameter tolerance in the diameter direction is within 0.008 mm. The processing of the speed measurement sleeve can be roughly divided into three parts: rough machining, heat treatment, and finish machining. The present invention is mainly applied to the finish machining of the inner hole, outer circle, and speed measurement teeth, aiming to improve the machining accuracy of the speed measurement sleeve and the qualified rate of the products.

[0045] Rough machining process: The rough machining is carried out before the heat treatment. The CNC turning is used to complete the machining of the inner and outer shapes of the workpiece, mainly to remove most of the surplus before the strengthening heat treatment of the workpiece. The surplus left on each side of the workpiece after rough machining should be greater than or equal to 0.2 mm to eliminate the deformation generated by the workpiece during the heat treatment during the finish machining.

[0046] Heat treatment process: Since the speed measurement sleeve rotates at a high speed during operation, friction will occur between its outer circle and the inner hole of the sealing component. In order to reduce the wear amount of the speed measurement sleeve during operation and ensure the sealing performance with the sealing component during normal operation, the matrix material of the speed measurement sleeve needs to maintain a high hardness. The heat treatment selects the method of quenching + tempering + cold treatment to improve the hardness of the speed measurement sleeve, so that its hardness is between HRC56 and HRC62.

[0047] Finish machining process:

[0048] Grinding both end faces by surface grinding: The finish machining is carried out after the heat treatment. The product has a high hardness. In order to eliminate the deformation generated by the product after the heat treatment, the machining surplus is large, and there is no machining reference for the whole workpiece due to the deformation after the heat treatment. In the finish machining of the present invention, the machining method of surface grinding is first used to grind both end faces of the workpiece to ensure that the parallelism of both end faces is within 0.02 mm.

[0049] Inner hole machining by slow wire electrical discharge wire cutting: After surface grinding, slow wire electrical discharge wire cutting is used to machine the speed measurement teeth and inner hole of the speed measurement sleeve. When machining by slow wire electrical discharge wire cutting, the workpiece is clamped using the fixture shown in Figure 2. During clamping, the workpiece is fixed through the threaded holes on the fixture and the pressure plate. After fixing, the parallelism between the end face of the workpiece and the machine tool is aligned within 0.01 mm. The electrode wire is inserted into the inner hole of the workpiece. After centering in the inner hole, the program is executed to cut the inner hole 5 times to complete the machining of the inner hole. After the inner hole machining is completed, the electrode wire is threaded outside and the four speed measurement teeth are cut 3 times. Machining the inner hole by slow wire electrical discharge wire cutting can be unaffected by the workpiece allowance and hardness after heat treatment, and can avoid the inner hole out-of-tolerance caused by the large tool withdrawal amount of the grinding wheel during traditional internal circle grinding, improving the qualified rate of the product.

[0050] Grinding the outer circle of the workpiece: When grinding the outer circle of the workpiece, the mandrel shown in Figure 3 is used for clamping. The outer circle of the mandrel 1 is matched with the two stepped holes of the speed measurement sleeve 2. The outer circle of the mandrel 1 needs to be matched and ground according to the inner hole of the speed measurement sleeve to ensure that the clearance between the two is less than or equal to 0.005 mm. The left end of the speed measurement sleeve 2 is positioned by the shoulder of the mandrel. The gasket 3 and nut 4 are matched with the thread on the right side of the mandrel 1 to fix the speed measurement sleeve 2. When grinding the outer circle, the mandrel is fixed on the grinding machine using two centers, and the outer circle of the workpiece is ground. After the grinding process is completed, the part is demagnetized to ensure that the maximum residual magnetic flux of the entire speed measurement sleeve part does not exceed 2 mT.

[0051] In this specific embodiment, the hardness of the semi-finished speed measurement sleeve after heat treatment is greater than or equal to HRC56, the depth of the inner hole of the final speed measurement sleeve is greater than or equal to 65 mm, and the wall thickness is less than or equal to 3.5 mm.

[0052] Although the present invention has been disclosed above with 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 solution of the present invention without departing from the spirit and scope of the present invention. Therefore, any simple modification, equivalent change, and modification made to the above embodiments based on the technical essence of the present invention without departing from the technical solution of the present invention shall fall within the protection scope of the technical solution of the present invention.

Claims

1. A composite processing and manufacturing method for a turbine pump shaft speed measuring sleeve, characterized in that The steps include: Rough machining process: It is carried out before heat treatment. CNC lathe is used to complete the machining of the inner and outer shapes of the workpiece. Most of the excess is removed before the workpiece is heat treated to obtain a semi-finished speed measuring sleeve. The semi-finished speed measuring sleeve has a structure with a disc protruding in the middle of the cylinders at both ends. Strengthen the heat treatment process: Use the method of quenching + tempering + cold treatment to heat treat the semi-finished speed measuring sleeve to improve the hardness of the speed measuring sleeve; Finishing process: The two end surfaces of the semi-finished speed measuring sleeve are ground by plane grinding to eliminate the deformation of the semi-finished speed measuring sleeve after heat treatment; after plane grinding, the speed measuring teeth and inner hole of the speed measuring sleeve are processed by slow wire electric spark wire cutting; the outer circle of the speed measuring sleeve is ground, and the speed measuring sleeve is demagnetized after the grinding process is completed.

2. The method for composite processing and manufacturing a turbine pump shaft speed measuring sleeve according to claim 1, characterized in that: After rough machining, the remaining margin on one side of the semi-finished speed measuring sleeve must be greater than or equal to 0.2mm.

3. The composite processing and manufacturing method of a turbine pump shaft speed measuring sleeve according to claim 1 is characterized in that: After heat treatment, the hardness of the semi-finished speed measuring sleeve is between HRC56 and HRC62.

4. The method for composite processing and manufacturing a turbine pump shaft speed measuring sleeve according to claim 1, characterized in that: The inner hole of the speed measuring sleeve and the speed measuring teeth are processed by slow-feeding electric spark wire cutting, the inner hole is cut 5 times, and the speed measuring teeth are cut 3 times.

5. The method for composite processing and manufacturing a turbine pump shaft speed measuring sleeve according to claim 4, characterized in that: After the speed sleeve is processed, the roundness of the inner hole of the speed measuring sleeve is less than or equal to 0.01mm, and the diameter tolerance is less than or equal to 0.008mm.

6. The method for composite processing and manufacturing a turbine pump shaft speed measuring sleeve according to claim 4, characterized in that: Special tooling is used for clamping during slow-feed wire electro-spark wire cutting processing. The special tooling is a hollow cylindrical tube structure as a whole, and four ribs are evenly distributed in its inner hole. The ribs extend inward from the hollow cylindrical tube structure and are aligned with the central axis of the cylindrical tube structure. Space is left among the four ribs for inserting the cylinder of the semi-finished speed measuring sleeve. The end face of the rib plate close to the axis is a step surface. The cylinder at one end of the semi-finished speed measuring sleeve is inserted into the space left among the four ribs. One side of the protruding disc structure in the middle of the semi-finished speed measuring sleeve is placed on the step of the rib plate, and the other side is aligned with the end face of the special tooling and the hollow cylindrical tube structure. The workpiece is fixed using a pressure plate and threaded holes on the end face of the tooling to achieve clamping of the semi-finished speed measuring sleeve.

7. The method for composite processing and manufacturing a turbine pump shaft speed measuring sleeve according to claim 1, characterized in that: When finishing and grinding the outer circle, use a spindle to clamp the inner hole, align the spindle, and ensure that the coaxiality between the spindle and the rotating axis of the machine tool is within 0.005mm.

8. The method for composite processing and manufacturing a turbine pump shaft speed measuring sleeve according to claim 1, characterized in that: After fine grinding, the coaxiality of the outer circle of the speed measuring sleeve relative to the inner hole is within 0.01mm.

9. The method for composite processing and manufacturing a turbine pump shaft speed measuring sleeve according to claim 1, characterized in that: The outer diameter tolerance is less than or equal to 0.008 mm.

10. The method for composite processing and manufacturing a turbine pump shaft speed measuring sleeve according to claim 1, characterized in that: During the demagnetization process, the magnetic induction intensity is no more than 2 mT.

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