A vibration and hot-pressing integrated forming process for L-shaped slot insulation of a generator rotor

Abstract

The application relates to an oscillation hot-pressing integrated forming process for L-shaped slot insulation of a generator rotor, and specifically comprises the following steps: S1, mold preparation and base layer laying, S2, primary oscillation hot-pressing forming, S3, thickening layer laying and secondary oscillation solidification, wherein when the oscillation hot-pressing head performs pressing, the working surface of the oscillation hot-pressing head applies dynamic pressure to the material in a combined mode of rolling rolling and wave scanning, and S4, post-processing, the application has the following advantages: through the introduction of a dynamic oscillation pressure field, the interlayer fusion and internal stress problems in the twice hot-pressing process of different materials are effectively solved.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of advanced manufacturing technology for core components of new energy power generation equipment, and particularly relates to an oscillation and hot-pressing integrated forming process for L-shaped slot insulation of a generator rotor, which is particularly suitable for manufacturing insulation structures of high-power-density generator rotors. BACKGROUND

[0002] The generator rotor slot insulation usually adopts an L-shaped structure, with the long side attached to the slot wall and the short side (i.e., the spacer part) needing to bear the main compression force of the rotor winding, so the thickness of the short side is usually much greater than that of the long side. The traditional L-shaped slot insulation manufacturing process usually adopts the method of separately forming the base material and the spacer, and then bonding them through an adhesive. This method has problems such as aging of the adhesive layer, uneven adhesive coating leading to adhesive failure or adhesive overflow, and concentration of thermal stress at the interface, which seriously affects the long-term reliability of the insulation system.

[0003] To overcome the defects of the adhesive bonding process, the existing technology proposes the idea of integrated hot-pressing forming of L-shaped slot insulation. However, due to the significant difference in thickness between the long side and the short side of the L-shaped structure, if direct hot-pressing forming is performed using an L-shaped mold, the internal stress distribution will be extremely uneven due to the difference in solidification shrinkage rate and heat transfer speed of the material in thick and thin areas, and the short side part is particularly prone to severe warping deformation, resulting in low product yield.

[0004] Therefore, some schemes propose a process path of first hot-pressing forming a U-shaped slot insulation, and then cutting it into two L-shaped slot insulations. This path has improved the warping deformation problem of directly forming L-shaped parts to some extent, but when a two-step hot-pressing process is used, i.e., first hot-pressing forming a U-shaped base (composed of epoxy glass fiber prepreg and NOMEX paper), and then laying a thickening layer (epoxy glass fiber prepreg) on the bottom for the second hot-pressing, new and more hidden technical defects are introduced:

[0005] Risk of poor interlayer interface fusion: After the first hot-pressing, the U-shaped base material is in a partially solidified or nearly completely solidified state, and its surface chemical activity is significantly reduced. During the second hot-pressing, the newly laid thickening layer prepreg and the already formed U-shaped base interface have difficulty in achieving sufficient molecular-level diffusion and cross-linking. Even under vacuum and pressure, they tend to form a clear physical interface rather than a continuous chemical bond whole. This weak interface is prone to become a delamination starting point under the action of thermal cycling and electromagnetic force during generator operation.

[0006] Complex secondary thermal stress: After the first thermal compression molding, there is an initial solidification stress in the U-shaped substrate. During the second thermal compression process, the bottom area of the U-shaped substrate is locally reheated and solidified, which undergoes thermal expansion and cooling shrinkage again, while the sidewall area is less affected by heat. This uneven thermal history will lead to the formation of a complex and difficult-to-eliminate residual stress system inside the final product, which not only may cause micro-cracks, but also reduces the size stability and fatigue life of the product under long-term dynamic load.

[0007] NOMEX paper performance impairment risk: NOMEX paper as a high-performance insulating material, its excellent dielectric properties depend partly on its porous fiber structure. Under the action of high temperature and high pressure in the second thermal compression, the NOMEX paper in the bottom area is at risk of being excessively compressed, causing its porosity to drop sharply, and may be excessively infiltrated by the secondary molten epoxy resin, resulting in impairment of its inherent flexibility and dielectric strength. SUMMARY

[0008] The purpose of the present application is to overcome the above shortcomings and provide an oscillating thermal compression integrated molding process for the insulation of L-shaped slots of a generator rotor, which effectively solves the interlayer fusion and internal stress problems during the two thermal compression processes of different materials by introducing a dynamic oscillating pressure field.

[0009] The purpose of the present application is achieved by the following technical solution: an oscillating thermal compression integrated molding process for the insulation of L-shaped slots of a generator rotor, characterized in that it specifically comprises the following steps:

[0010] S1, mold preparation and substrate layer laying: positioning a U-shaped thermal compression molding mold, which includes an oscillating thermal compression head assembly composed of a plurality of independent compression head units arranged in parallel along the axial direction, a fixed U-shaped mold core, and a vacuum sealing system; on the platform of the U-shaped mold core, 20-30 layers of epoxy glass fiber prepreg and 2-5 layers of NOMEX paper are sequentially stacked to form a composite substrate layer; S2, primary oscillating thermal compression molding: the oscillating thermal compression head assembly is pressed down to contact the composite substrate layer, and the composite substrate layer is continuously bent into the cavity of the U-shaped mold core under the action of the oscillating thermal compression head assembly, under the condition of a basic pressure of 120-140℃ and 0.5-1.0MPa, the oscillating program is started and lasts for 10-30 minutes, so that the composite substrate layer is uniformly heated and preliminarily shaped into a U-shaped preform under dynamic pressure; S3, laying of thickening layer and secondary oscillating solidification: the U-shaped preform is kept in the mold, and 40-50 layers of epoxy glass fiber prepreg II are laid on the inner side of the bottom of the U-shaped preform to form a gasket thickening layer; the mold is closed, the vacuum system is started, and the gradient pressure solidification program is executed;

[0011] The oscillating hot press head applies dynamic pressure to the material in a rolling and wave scanning combined manner when performing pressing; S4, post-processing: the U-shaped groove insulation is demolded, cut to a fixed length, and then cut along the longitudinal center line to obtain two L-shaped groove insulation finished products.

[0012] Further improvement of the present application is that the gradient pressure curing process comprises:

[0013] The first stage: maintaining at 120-140 DEG C, 1.0-1.5 MPa pressure for 1-2 hours, and simultaneously performing the axial oscillation process;

[0014] The second stage: increasing the temperature to 140-160 DEG C, increasing the pressure to 2.0-3.0 MPa, maintaining for 4-6 hours, stopping oscillation, and performing static pressure maintaining curing;

[0015] The third stage: decreasing the temperature to below 60 DEG C at a controllable speed of 1-2 DEG C / min, and then unloading pressure.

[0016] Further improvement of the present application is that the axial oscillation process is that the control system controls the multiple independent press head units to perform alternating and wave-like additional pressing and micro-lifting actions along the axial direction of the workpiece at a preset order and frequency under the premise of maintaining the basic pressure, so that the dynamic pressure wave propagates along the axial direction.

[0017] Further improvement of the present application is that the resin content of the epoxy glass fiber prepreg I and the epoxy glass fiber prepreg II is 35%-45%, which is made by a process comprising the following steps:

[0018] After the glass fiber cloth is impregnated with the epoxy resin, it is extruded through a preforming die, and then sequentially passes through a preheating zone of 120-140 DEG C, a gelation zone of 140-160 DEG C and a constant temperature zone of 160-180 DEG C to complete curing, and finally is cut by traction.

[0019] Further improvement of the present application is that the U-shaped hot press forming die comprises a die frame, a fixed U-shaped die core arranged on the die frame, and an oscillating hot press head assembly arranged directly above the U-shaped die core, wherein the oscillating hot press head assembly comprises:

[0020] A main press head base connected with the die frame through a main pressure cylinder and driven by the main pressure cylinder to lift integrally;

[0021] A plurality of independent press head units installed on the main press head base in parallel along the axial direction of the U-shaped die core, each independent press head unit being independently controlled by a micro servo drive cylinder to perform a pressing action; the bottom working surface of each independent press head unit is provided with a row of self-rotating press rollers, and the row of press rollers is synchronously self-rotated by a driving motor, and the axial direction of the press rollers is consistent with the radial direction of the U-shaped die core;

[0022] a heating element integrated in the independent pressure head unit for heating the material;

[0023] a vacuum system in communication with the cavity of the U-shaped mold core for vacuumizing during the pressing process;

[0024] a cooling system including a cooling liquid supply unit and a pipeline connected with the cooling pipeline inside the U-shaped mold core;

[0025] a comprehensive control system connected with the main pressure cylinder, the micro servo drive cylinders, the heating element and the vacuum system; the comprehensive control system controls the main pressure cylinder to drive the entire hot head assembly to press down to provide a basic pressure, simultaneously drives each pressure roller to actively rotate to realize rolling compaction, and coordinates the control of the micro servo drive cylinders to make the independent pressure head units driven thereby generate an axially propagating wave-shaped pressure distribution to realize wave-shaped scanning; and controls the cooling system to work in the third stage of the curing process to realize controllable cooling.

[0026] The further improvement of the present application is that the comprehensive control system includes an oscillating wave form control module which pre-stores a plurality of oscillating wave form modes for sending instructions to the micro servo drive cylinders;

[0027] The oscillating wave form modes at least include a one-way traveling wave mode, in which the control system controls the independent pressure head units to sequentially perform additional pressing down and resetting from one end of the workpiece to the other end to form a continuously traveling pressure wave.

[0028] The further improvement of the present application is that the comprehensive control system further includes:

[0029] a resin flow optimization logic which dynamically adjusts the frequency and amplitude of the wave-shaped pressure distribution according to real-time temperature monitoring values;

[0030] a contact pressure self-adaptive logic which adjusts the output pressure of the independent pressure head units in real time by monitoring the current feedback of the micro servo drive cylinders.

[0031] The further improvement of the present application is that the surface of the pressure roller is coated with a high-temperature-resistant anti-sticking coating.

[0032] The further improvement of the present application is that the comprehensive control system is further configured to independently control the rotating speed of the drive motor in each pressure roller drive mechanism, so that the average rotation speed of the pressure roller at the bottom of each independent pressure head unit changes according to a preset wave form and sequence, specifically, the rotating speed of the pressure roller of the plurality of independent pressure head units experiences a cycle of “acceleration-peak-deceleration” along the axial direction, thereby forming a rolling speed wave propagating along the axial direction.

[0033] The further improvement of the present application is that the bonding strength between the U-shaped prefabricated part and the thickened layer of the mat strip is not less than 15 MPa.

[0034] Compared with the prior art, the present application has the following advantages:

[0035] 1. The present application fundamentally solves the interlayer fusion problem of heterogeneous material in multiple heat pressing. The traditional static secondary heat pressing forms a clear weak interface between the preliminarily solidified base and the newly thickened layer. The dynamic pressure wave generated by the axial oscillation program continuously rubs and shears the bonding interface, which effectively breaks the low-activity layer on the surface of the base, greatly promotes the mutual diffusion and cross-linking reaction of epoxy resin molecules, and forms a strong, continuous and chemically bonded whole at the interface of the two laid materials, thereby increasing the interlayer bonding strength to more than 15 MPa and significantly improving the anti-delamination capability of the insulation structure under long-term thermal cycling and mechanical vibration.

[0036] 2. Due to the inherent thickness difference of the L-shaped structure, the traditional process is prone to cause warping due to uneven cooling shrinkage. However, the oscillating pressure field of the present application makes the material bear dynamic and alternating stress during the solidification process, rather than static directional stress, which is beneficial to the relaxation of molecular chains and the uniform distribution of stress. Combined with the gradient cooling controlled by the program, the internal stress generated by the difference in thermal expansion coefficient and solidification shrinkage of different materials can be effectively released and offset, so that the warping amount of the finally formed L-shaped slot insulation is significantly reduced, and the geometric precision and long-term dimensional stability are fundamentally improved.

[0037] 3. The dynamic oscillating pressure has a self-adaptive compensation effect on the local unevenness of the material (such as slight deviation in the laid layer), which reduces its sensitivity to process parameters. By accurately controlling the frequency and amplitude of oscillation, the sufficient fusion between layers can be ensured while avoiding the application of continuous excessive compression force on the NOMEX paper as a key insulation barrier, thereby preventing the porous structure of the NOMEX paper from being excessively crushed or the resin from being excessively infiltrated, and better preserving the inherent high dielectric strength and toughness of the NOMEX paper. Thus, the product not only has excellent mechanical properties, but also has synchronous guarantee of insulation reliability. BRIEF DESCRIPTION OF DRAWINGS

[0038] Figure 1 The flow chart of the oscillating heat pressing integrated molding process of the L-shaped slot insulation of the generator rotor of the present application.

[0039] Figure 2 The molding schematic diagram of the oscillating heat pressing integrated molding process of the L-shaped slot insulation of the generator rotor of the present application.

[0040] Figure 3 The structural schematic diagram of the U-shaped heat pressing molding die of the present application.

[0041] Figure 4Figure 1 is a perspective view of the oscillating hot-pressing head assembly of the present application. Figure 3 Figure 2 is a side view of the oscillating hot-pressing head assembly of the present application.

[0042] Figure 5 Figure 4 is a comparison of the interlayer interface structure of the shaped part of the present application and the prior art oscillating secondary hot-pressing shaped part.

[0043] Figure 6 Figure 5 is a comparison of the internal stress distribution and warping of the shaped part of the present application and the prior art shaped part.

[0044] Reference numerals in the drawings:

[0045] 1-oscillating hot-pressing head assembly, 2-U-shaped mold core, 3-epoxy glass fiber prepreg 1, 4-NOMEX paper, 5-base layer, 6-pad strip thickening layer, 7-U-shaped prefabricated part, 8-L-shaped groove insulation, 9-epoxy glass fiber prepreg 2, 10-U-shaped groove insulation, 11-mold frame, 12-main press head base, 13-actuating cylinder, 14-independent press head unit, 15-micro servo drive cylinder, 16-press roller. DETAILED DESCRIPTION

[0046] In order to deepen the understanding of the present application, the present application will be further described below in combination with examples and drawings, which are only used to explain the present application and do not constitute a limitation on the protection scope of the present application.

[0047] In the description of the present application, it should be understood that the terms indicating the orientation or positional relationship, such as the orientation or positional relationship based on the drawings, are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the structure or unit referred to must have a specific orientation, and therefore cannot be understood as a limitation on the present application.

[0048] In the present application, unless otherwise explicitly specified and limited, the terms such as “connection”, “provided with”, “have” and the like should be understood in a broad sense, for example, it can be fixedly connected, it can be detachably connected, or it can be integrally connected, it can be mechanically connected, it can be directly connected, or it can be connected through an intermediate medium, and for those skilled in the art, the basic meaning of the above terms in the present application can be understood according to the specific circumstances.

[0049] An oscillating hot-pressing integrated forming process for a generator rotor L-shaped groove insulation, referring to Figure 1 、 Figure 2 , an oscillating hot-pressing integrated forming process for a generator rotor L-shaped groove insulation, characterized in that it specifically comprises the following steps:

[0050] S1, mold preparation and substrate layer laying: position a set of U-shaped hot press forming mold, which includes an oscillating hot press head assembly 1 composed of a plurality of independent press head units 13 arranged in parallel along the axial direction, a fixed U-shaped mold core 2, and a vacuum sealing system; on the platform of the U-shaped mold core 2, 20-30 layers of epoxy glass fiber prepreg 3 and 2-5 layers of NOMEX paper 4 are sequentially stacked to form a composite substrate layer 5; S2, primary oscillation hot press forming: the oscillating hot press head assembly 1 is pressed as a whole to contact the composite substrate layer 5, and the composite substrate layer 5 is continuously pressed to bend into the cavity of the U-shaped mold core 2; under the basic pressure of 120-140 DEG C, 0.5-1.0 MPa, the oscillation program is started for 10-30 minutes, so that the composite substrate layer 5 is uniformly heated and preliminarily shaped into a U-shaped preform 7 under dynamic pressure; S3, thickening layer laying and secondary oscillation curing: the U-shaped preform 7 is kept in the mold, and 40-50 layers of epoxy glass fiber prepreg 2 9 are laid on the inner side of the bottom to form a gasket thickening layer 6; the mold is closed, the vacuum system is started, and the gradient pressure curing program is executed.

[0051] Wherein, the working surface of the oscillating hot press head applies dynamic pressure to the material in the form of rolling and rolling and wave scanning when performing pressing; S4, post-processing: the U-shaped groove insulation 10 is demolded, and after being cut to a fixed length, it is cut along the longitudinal center line to obtain two L-shaped groove insulations 8.

[0052] The application fundamentally solves the problem of interlayer fusion of heterogeneous materials in multiple hot pressing. The traditional static secondary hot pressing forms a clear weak interface between the preliminarily cured substrate and the newly added thick layer, while the dynamic pressure wave generated by the axial oscillation program continuously rubs and shears the bonding interface, which effectively breaks the low activity layer on the surface of the substrate, greatly promotes the mutual diffusion and crosslinking reaction of epoxy resin molecules, and forms a strong, continuous and chemical bonding whole at the interface of the two laid materials, thereby increasing the interlayer bonding strength to more than 15 MPa, and significantly improving the anti-delamination ability of the insulation structure under long-term thermal cycling and mechanical vibration.

[0053] Due to the inherent thickness difference of the L-shaped structure, the traditional process is prone to cause uneven cooling shrinkage and warping, while the oscillating pressure field of the application makes the material bear dynamic and alternating stress during the curing process, rather than static directional stress, which is beneficial to the relaxation of molecular chains and the uniform distribution of stress. Combined with the gradient cooling controlled by the program, the internal stress generated by the difference in thermal expansion coefficient and curing shrinkage of different materials can be effectively released and offset, so that the warping amount of the finally formed L-shaped groove insulation is significantly reduced, and the geometric precision and long-term dimensional stability are fundamentally improved.

[0054] The dynamic oscillation pressure has self-adaptive compensation effect on local non-uniformity of the material (such as slight deviation of the layer), and reduces the sensitivity to the process parameters. By precisely controlling the frequency and amplitude of the oscillation, the continuous excessive compression force applied to the NOMEX paper as a key insulation barrier can be avoided, so that the porous structure of the NOMEX paper is prevented from being excessively crushed or excessively infiltrated with resin, the inherent high dielectric strength and toughness of the NOMEX paper are well reserved, and the product can obtain excellent mechanical properties and synchronous guarantee of insulation reliability.

[0055] The gradient pressure curing procedure comprises:

[0056] The first stage: maintaining at 120-140 DEG C and 1.0-1.5 MPa pressure for 1-2 hours, and simultaneously performing the axial oscillation procedure;

[0057] The second stage: increasing the temperature to 140-160 DEG C and the pressure to 2.0-3.0 MPa, maintaining for 4-6 hours, stopping the oscillation, and performing static pressure maintaining curing;

[0058] The third stage: decreasing the temperature to below 60 DEG C at a controllable rate of 1-2 DEG C / min, and then unloading the pressure.

[0059] The design of the gradient pressure curing procedure is the key to realize high-quality interlaminar composite and optimized internal structure. The effects are embodied in the following aspects: in the first stage, the medium temperature and pressure are maintained with simultaneous axial oscillation, which mainly aims to promote the resin to flow, infiltrate and diffuse in the interlaminar under the condition of suitable viscosity of the epoxy resin, effectively remove the bubbles, and lay a foundation for forming a dense and uniform interface transition layer. In the second stage, the temperature and pressure are increased to a higher level and static pressure maintaining is performed, which aims to make the resin system complete the crosslinking and curing reaction, build a high-strength three-dimensional network structure, and ensure the final mechanical properties and thermal stability of the product. The controllable temperature decreasing in the third stage has the core effect of releasing and homogenizing the internal stress generated in the curing process by slow and uniform cooling rate, so as to effectively inhibit the warping deformation of the product, and ensure the dimensional accuracy and dimensional stability during long-term use.

[0060] The axial oscillation procedure comprises: the control system controls multiple independent pressure head units to perform alternating and wave-like additional pressing and micro-lifting actions along the axial direction of the workpiece under the premise of maintaining the basic pressure according to the preset sequence and frequency, and forms dynamic pressure waves propagating along the axial direction.

[0061] The resin content of the epoxy glass fiber prepreg 3 and the epoxy glass fiber prepreg 2 is 35%-45%, which is made by the process comprising the following steps:

[0062] The glass fiber cloth is impregnated with epoxy resin, extruded through a preforming mold, and then cured by passing through a preheating zone of 120-140 DEG C, a gelation zone of 140-160 DEG C, and a constant temperature zone of 160-180 DEG C, and finally cut by traction.

[0063] Preferably, referring to Figure 3 、 Figure 4 The U-shaped hot-pressing mold comprises a mold frame 11, a fixed U-shaped mold core 2 arranged on the mold frame 11, and an oscillating hot-pressing head assembly 1 arranged above the U-shaped mold core 2, wherein the oscillating hot-pressing head assembly 1 comprises:

[0064] a main pressing head base 12 connected to the mold frame 11 by a main pressing cylinder 13 and driven by the main pressing cylinder 13 to move up and down as a whole;

[0065] a plurality of independent pressing head units 14 arranged on the main pressing head base 12 in parallel along the axial direction of the U-shaped mold core 2, each independent pressing head unit 14 being independently controlled by a micro servo driving cylinder 15 to move downward, and each independent pressing head unit 14 being provided with a row of self-rotating pressing rollers 16 on the bottom working surface thereof, the row of pressing rollers 16 being synchronously self-rotated by a driving motor, and the axial direction of the pressing rollers 16 being consistent with the radial direction of the U-shaped mold core 2;

[0066] a heating element integrated in the independent pressing head unit 14 for heating the material;

[0067] a vacuum system in communication with the cavity of the U-shaped mold core 2 for vacuumizing during the pressing process;

[0068] a cooling system comprising a cooling liquid supply unit and a pipeline connected to the cooling pipeline inside the U-shaped mold core 2;

[0069] a comprehensive control system in signal connection with the main pressing cylinder 13, the micro servo driving cylinders 15, the heating element, and the vacuum system, wherein the comprehensive control system controls the main pressing cylinder to drive the entire hot-pressing head assembly to move downward to provide a basic pressure, synchronously drives the pressing rollers to actively rotate to realize rolling and pressing, and coordinately controls the micro servo driving cylinders to make the independent pressing head units 14 driven thereby generate a wave-shaped pressure distribution propagating along the axial direction to realize wave-shaped scanning, and controls the cooling system to work in the third stage of the curing process to realize controllable cooling.

[0070] It should be noted that, in order to ensure that the working surface of the pressing roller directly contacts the pre-pressed workpiece, the driving motor is designed in a compact and embedded manner and can be transversely arranged inside the independent pressing head unit instead of being arranged directly below or laterally, and the power is transmitted by the built-in gear set, so that the driving motor and other components do not interfere with the pressing of the multiple pressing rollers, and the pressure can be effectively and uniformly applied to the workpiece.

[0071] Preferably, the integrated control system comprises an oscillating waveform control module, which pre-stores a plurality of oscillating waveform modes for sending instructions to each micro servo drive cylinder 15.

[0072] The oscillating waveform mode at least comprises a unidirectional traveling wave mode, in which the control system controls each independent pressure head unit to sequentially perform additional pressing and resetting from one end of the workpiece to the other end, forming a continuous traveling pressure wave.

[0073] Preferably, the integrated control system further comprises:

[0074] Resin flow optimization logic, which dynamically adjusts the frequency and amplitude of the wave-shaped pressure distribution according to real-time temperature monitoring values;

[0075] Contact pressure adaptive logic, which adjusts the output pressure of the corresponding independent pressure head unit in real time by monitoring the current feedback of each micro servo drive cylinder.

[0076] Preferably, the surface of the compression roller is coated with a high-temperature-resistant anti-sticking coating.

[0077] Preferably, the integrated control system is further configured to independently control the rotation speed of the drive motor in each compression roller drive mechanism, so that the average rotation speed of the compression roller at the bottom of each independent pressure head unit changes according to a pre-set waveform and sequence, specifically: the rotation speed of the compression roller of each independent pressure head unit experiences a cycle of “acceleration-peak-deceleration” along the axial direction, thereby forming a rolling speed wave that propagates along the axial direction.

[0078] The present application has essential differences from traditional pressing. In traditional hot pressing of glass fiber pre-preg and NOMEX paper, a whole and flat pressing plate is used, which can only achieve static and uniform pressure, and the effect of solving the problems of interlayer fusion and stress distribution is limited. In the present application, an array of compression rollers is used instead of a whole pressing plate, which is the key to realizing “oscillating hot pressing”. The specific manifestations are as follows: 1. Each compression roller actively rotates under the drive, forming a continuous linear compaction on the material in its rolling track; 2. Multiple compression roller units are coordinated by the control system to generate a wave-shaped pressure distribution (wave-shaped scanning) that propagates along the axial direction of the workpiece, which means that any point on the surface of the workpiece will be subjected to the rolling and pressure wave of different compression rollers in sequence in time, thereby achieving a dynamic and non-missing pressing effect on the whole. This design not only is feasible, but also actively generates a rubbing and shearing action that is beneficial to the interlayer interface, effectively expels bubbles, and promotes resin flow and molecular diffusion, which is not achievable by static flat pressing. This effectively solves the problems of interlayer fusion and stress distribution of heterogeneous materials during hot pressing.

[0079] Figure 5For the contrast of the interlayer interface structure of the shaped part of the present application and the prior art oscillating secondary hot pressing shaped part: the structure characteristics in the figure clearly show that the oscillating hot pressing integrated forming process of the present application is significantly better than the traditional static secondary hot pressing method in the interlayer bonding quality. The shear interface formed by the traditional static secondary hot pressing has the problem of poor bonding, and interlayer peeling or shear failure easily occurs; and the present application promotes resin flow and recombination under the action of high-frequency micro-vibration and thermal-mechanical coupling through the oscillating hot pressing process, forms a strong interfacial interpenetrating structure, effectively enhances the interlayer bonding strength and interface toughness, and thus improves the overall mechanical properties and insulation reliability of the generator rotor L-shaped slot insulation part. The bonding strength between the U-shaped preform 7 and the gasket thickening layer 6 in the present application is not less than 15MPa.

[0080] Figure 6 For the contrast of the internal stress distribution and warping of the shaped part of the present application and the existing shaped part, the stress distribution state and structural deformation result in the figure clearly show that the oscillating hot pressing integrated forming process of the present application is significantly better than the traditional static hot pressing method in inhibiting residual stress and structural deformation. The existing technology static hot pressing causes uneven thermal-mechanical field and inconsistent resin curing shrinkage, resulting in internal residual stress concentration, causing the L-shaped slot insulation part to have obvious warping deformation; and the present application promotes uniform resin flow and stress release through high-frequency micro-oscillation and gradient pressure regulation, realizes uniform distribution of internal stress, and finally the shaped part has no visible warping deformation, the dimensional stability is significantly improved, and meets the requirements of high-precision assembly and long-term reliability of the generator rotor slot insulation.

[0081] Those skilled in the art should understand that the present application is not limited to the above embodiments, and the above embodiments and descriptions in the specification are only to illustrate the principles of the present application, and various changes and improvements can be made without departing from the spirit and scope of the present application, and these changes and improvements all fall within the scope of the claimed present application. The scope of protection of the present application is defined by the appended claims and their equivalents.

Claims

1. A process for oscillating hot press integration of L-shaped slot insulation for a generator rotor, characterized by, Specifically comprising the following steps: S1, mold preparation and substrate layer laying: positioning a set of U-shaped hot press forming mold, which includes an oscillating hot press head assembly composed of a plurality of independent press head units arranged in parallel along the axial direction, a fixed U-shaped mold core, and a vacuum sealing system; On the platform of the U-shaped mold core, 20-30 layers of epoxy glass fiber prepreg and 2-5 layers of NOMEX paper are stacked in turn to form a composite substrate layer; S2, primary oscillation hot press forming: the oscillating hot press head assembly is pressed as a whole to contact the composite substrate layer, and the composite substrate layer is continuously pressed to bend into the cavity of the U-shaped mold core, under the basic pressure of 120-140℃ and 0.5-1.0MPa, for 10-15min, and the axial oscillation program is started, which lasts for 10-30min, so that the composite substrate layer is uniformly heated and preliminarily shaped into a U-shaped preform under dynamic pressure; S3, laying of thickening layer and secondary oscillation curing: the U-shaped preform is kept in the mold, and 40-50 layers of epoxy glass fiber prepreg II are laid on the inner side of the bottom to form a gasket thickening layer; close the mold, start the vacuum system, and perform a gradient pressure curing program; Wherein, when performing pressing, the working surface of the oscillating hot press head applies dynamic pressure to the material in a combination of rolling and undulating scanning; S4, post-processing: the U-shaped slot insulation is demolded, cut to a fixed length, and cut along the longitudinal center line to obtain two L-shaped slot insulation finished products.

2. The process for oscillating heat pressing of L-shaped slot insulation of a generator rotor as claimed in claim 1 wherein, The gradient pressure curing program includes: First stage: keep at 120-140℃ and 1.0-1.5MPa for 1-2 hours, and the axial oscillation program is performed synchronously; Second stage: increase the temperature to 140-160℃, increase the pressure to 2.0-3.0MPa, keep for 4-6 hours, stop oscillation, and perform static pressure holding curing; Third stage: reduce the temperature to below 60℃ at a controllable rate of 1-2℃ / min, and then release the pressure.

3. The process for oscillating heat pressing of L-shaped slot insulation of a generator rotor as claimed in claim 2 wherein, The axial oscillation program is: the control system controls the plurality of independent press head units to perform alternating and undulating additional pressing and micro-lifting actions along the axial direction of the workpiece under the premise of maintaining the basic pressure according to the preset sequence and frequency, forming dynamic pressure waves propagating along the axial direction.

4. The process for oscillating heat pressing of L-shaped slot insulation of a generator rotor as claimed in claim 3 wherein, The resin content of the epoxy glass fiber prepreg I and the epoxy glass fiber prepreg II is 35%-45%, which is made by the process comprising the following steps: After the glass fiber cloth is impregnated with epoxy resin, it is extruded through a preforming mold, and then passes through a preheating zone of 120-140℃, a gelation zone of 140-160℃, and a constant temperature zone of 160-180℃ to complete curing, and finally is cut and drawn.

5. The process for oscillating heat pressing of L-shaped slot insulation of a generator rotor as claimed in claim 4 wherein, The U-shaped hot press forming mold includes a mold frame, a fixed U-shaped mold core placed on the mold frame, and an oscillating hot press head assembly placed directly above the U-shaped mold core, and the oscillating hot press head assembly includes: The main press head base is connected with the mold frame through the main pressure cylinder and is driven by the main pressure cylinder to lift as a whole; a plurality of independent pressure head units are installed on the main pressure head base along the axial direction of the U-shaped mold core, each independent pressure head unit is independently controlled by a micro servo drive cylinder to perform a pressing action; the bottom working surface of each independent pressure head unit is provided with a row of self-rotating pressure rollers, and a row of pressure rollers are synchronously self-rotated by a drive motor, and the axial direction of the pressure rollers is consistent with the radial direction of the U-shaped mold core; a heating element integrated in the independent pressure head unit for heating the material; a vacuum system in communication with the cavity of the U-shaped mold core for vacuumizing during the pressing process; a cooling system including a cooling liquid supply unit and a pipeline connected with the cooling pipeline inside the U-shaped mold core; an integrated control system in signal connection with the main pressure cylinder, each micro servo drive cylinder, the heating element and the vacuum system; the integrated control system controls the main pressure cylinder to drive the entire hot head assembly to press down to provide a basic pressure, simultaneously drives each pressure roller to actively rotate to realize rolling and rolling, and coordinates the control of each micro servo drive cylinder to make the independent pressure head unit driven by the micro servo drive cylinder generate an axial wave-shaped pressure distribution to realize wave-shaped scanning, and controls the cooling system to work in the third stage of the curing process to realize controllable cooling.

6. The process for oscillating heat pressing of L-shaped slot insulation of a generator rotor as claimed in claim 5 wherein, The integrated control system includes an oscillation waveform control module, which pre-stores a plurality of oscillation waveform modes for sending instructions to each micro servo drive cylinder. The oscillation waveform mode at least includes a one-way traveling wave mode, in which the control system controls each independent pressure head unit to sequentially perform additional pressing and resetting from one end of the workpiece to the other end to form a continuous traveling pressure wave.

7. The process for oscillating heat pressing of L-shaped slot insulation of a generator rotor as claimed in claim 6 wherein, The integrated control system further includes: resin flow optimization logic for dynamically adjusting the frequency and amplitude of the wave-shaped pressure distribution according to real-time temperature monitoring values; contact pressure self-adaptive logic for adjusting the output pressure of the corresponding independent pressure head unit in real time by monitoring the current feedback of each micro servo drive cylinder.

8. The process for oscillating heat pressing of L-shaped slot insulation of a generator rotor as claimed in claim 7 wherein, The surface of the pressure roller is coated with a high-temperature-resistant anti-sticking coating.

9. The process for oscillating heat pressing of L-shaped slot insulation of a generator rotor as claimed in claim 8 wherein, The integrated control system is further configured to independently control the rotation speed of the drive motor in each pressure roller drive mechanism, so that the average self-rotation speed of the pressure roller at the bottom of each independent pressure head unit changes according to a preset waveform and sequence, specifically: the rotation speed of the pressure roller of the plurality of independent pressure head units experiences a cycle of "acceleration-peak-deceleration" along the axial direction in sequence, thereby forming a rolling speed wave propagating along the axial direction.

10. The process of claim 9, wherein the process is a process of oscillating hot-pressing integrated molding of L-shaped slot insulation of a generator rotor. The bonding strength between the U-shaped preform and the thickened layer of the gasket strip is not less than 15 MPa.

Images