Integral oil seal track positioning directional sand blasting-thermal expansion preheating coupled forming method

Abstract

The application discloses an integrated oil seal track positioning directional sand blasting-thermal expansion preheating coupling forming method and belongs to the technical field of precise forming of rubber sealing elements; directional pretreatment is performed on a stamping steel plate framework through track positioning directional sand blasting, and deformation and corrosion of the framework in the pretreatment process are reduced; a thermal deformation amount is calculated based on a thermal expansion coefficient and a characteristic size of the framework material, a thermal expansion compensation preheating positioning tool and a temperature control curve are designed, the framework is uniformly preheated under the constraint of controlled transient temperature rise, warping and interface defects after vulcanization cooling are inhibited, and the shape-position consistency of the positioning pin and the sealing lip is ensured. On the basis, combined with multi-cavity injection balanced runner design, rubber formula reconstruction, injection parameter precise control and one-time vulcanization forming, quantitative acceptance of the positioning pin position, the lip roundness and the flatness is realized through lip fixed-length cutting and three-coordinate detection. The method is suitable for the manufacturing scene of the integrated oil seal with high assembly positioning accuracy and sealing reliability.

Description

Technical Field

[0001] This invention relates to the field of oil seal manufacturing technology, and more particularly to a method for pretreatment and preheating molding of the skeleton for an integrated oil seal. More specifically, it relates to the coupling control of track positioning directional sandblasting with preheating positioning fixtures based on thermal expansion compensation and temperature control curves to improve the shape and position consistency between the positioning structure and the sealing lip. Background Technology

[0002] After automotive oil seals and crankshafts are installed on the engine, a high degree of coaxiality and dimensional consistency is required. Current mass production of engine skeletons often uses a roller-turning method for sandblasting, which easily leads to secondary deformation and corrosion during the turning and impact process, affecting the dimensional consistency of the subsequent locating pins and sealing lips. The lack of consistent control between the dimensional state of the sandblasted skeleton and the preheating / injection vulcanization process means that the "precision gains from front-end pretreatment" are offset by subsequent thermal shock. Furthermore, even when preheating the skeleton in existing technologies, it is often based on an empirical window of "given temperature / time," lacking calculations of deformation based on thermal expansion differences and tooling constraint design. This easily leads to excessive transient thermal strain during the heating phase, causing warping or bonding interface defects after cooling.

[0003] The specific patent comparison documents are as follows: 1) "A Sealing Device for Automotive Oil Seals", Patent No. CN116044993B. This invention patent discloses a sealing device for automotive oil seals, including an oil seal sleeved and mounted on the surface of a shaft and a sealing mounting mechanism disposed on the outer surface of the oil seal. The shaft is mounted on the front surface of a bearing seat, and the rear end of the oil seal is fitted to the bearing seat. The sealing mounting mechanism includes two oil seal mounting seats and a splicing assembly, with the two oil seal mounting seats connected by the splicing assembly. A mounting side block is fixed to the outer surface of each oil seal mounting seat, and a clamping assembly is provided between the mounting side block and the bearing seat. The splicing assembly enables rapid assembly between the two oil seal mounting seats, and the clamping assembly enables rapid connection between the mounting side block and the bearing seat, thereby improving the ease of installation and assembly of the entire sealing mounting mechanism. This facilitates the installation and sealing of the oil seal for operators and also makes subsequent disassembly and replacement of the oil seal easier. However, it relies on multiple external mounting and connecting components, increasing the number of parts, assembly steps, and potential leakage points. Its split design is prone to loosening of connections and positioning misalignment under long-term high temperature and vibration conditions, and its sealing reliability and accuracy are weaker than those of integrated oil seals that do not require assembly.

[0004] 2) "An Engine Oil Seal", Patent No. CN120984698A. This invention provides an engine oil seal, assembled on the crankshaft of an engine. It includes: a support frame, 30 having a horizontal section extending laterally along the engine casing, and a vertical section extending longitudinally towards the crankshaft along the tail of the horizontal section. The horizontal section is divided into a first step and a second step. The support frame is divided into an outer frame and an inner frame; the first step of the horizontal section is the outer frame, and the second step and the vertical section are the inner frame. A rubber body made of modified fluororubber is wrapped around the outer surface of the inner frame. The rubber body wraps around the outer surface of the second step and connects and is flush with the outer surface of the outer frame. However, due to its reliance on multi-component assembly and step overlap, under long-term high and low temperature alternation and vibration conditions, fretting wear and stress concentration easily occur at the joint surfaces, affecting the long-term stability and positional accuracy of the sealing interface.

[0005] 3) "A Rubber Sealing Component for Automotive Oil Seals", Patent No. CN223469712U. This utility model relates to the field of sealing technology and discloses a rubber sealing component for automotive oil seals, including a rubber outer ring and a rubber inner ring fixedly installed on the inner wall of the rubber outer ring. The rubber outer ring and the rubber inner ring are integrally formed. An embedded groove is formed inside the rubber outer ring, and a support component is set inside the embedded groove. Multiple annular buffer grooves are formed on the outer wall of the rubber outer ring. Maintenance personnel can tilt a screwdriver to move its end into the arc-shaped groove. The screwdriver forms a lever to pry out one of the support brackets. After all the support brackets are removed, the maintenance personnel can easily remove the rubber outer ring and the rubber inner ring from their installation position. However, it lacks the positioning pin and integral vulcanized sealing rib structure inherent in integrated oil seals. During installation, it relies on manual alignment, making it difficult to achieve integrated protection of high-precision positioning and static sealing.

[0006] As can be seen from the technical information provided in the aforementioned comparative documents, none of the comparative documents involve pretreatment methods to reduce skeleton deformation through posture constraints during sandblasting.

[0007] Existing integrated oil seals still face problems in mass production, such as skeleton deformation and corrosion caused by sandblasting, as well as thermal strain and cooling warping caused by experience preheating. Summary of the Invention

[0008] To address the problems of deformation and corrosion caused by sandblasting of the skeleton in mass production, as well as thermal strain and cooling warping due to empirical preheating, this invention provides a high-precision forming process for integrated oil seals, which couples track-positioning directional sandblasting with a thermal expansion compensation preheating positioning fixture and temperature control curve. This improves the skeleton's ability to maintain its shape and position during pretreatment and heating, thereby enhancing the shape and position consistency between the positioning structure and the sealing lip. The core of this invention lies in the coupled control of "track-positioning directional sandblasting + thermal expansion compensation preheating positioning fixture and curve." Other mold flow / formula / control strategies are preferred embodiments.

[0009] The objective of this invention is achieved through the following technical solution: The integrated oil seal track positioning and directional sandblasting-thermal expansion preheating coupling molding method includes the following steps: Step S1: Position the skeleton made of stamped steel plate through a ring conveyor track and perform directional sandblasting pretreatment to form a directional rough texture on the surface of the skeleton. Step S2: Based on the thermal expansion coefficient and vulcanization temperature of the skeleton material, calculate the thermal deformation during the vulcanization process, design a thermal expansion compensation preheating positioning fixture based on the deformation data, and optimize the temperature control curve; preheat the skeleton so that it reaches the preset preheating temperature before vulcanization. Step S3: Place the preheated skeleton into a multi-cavity injection mold, and use a balanced flow channel system for rubber injection and vulcanization molding. The rubber injection process is dynamically closed-loop controlled based on real-time feedback of cavity inlet pressure to achieve uniform filling of each cavity at equal pressure. Step S4: Trim the edges of the vulcanized semi-finished product and cut the sealing lip to a fixed length to obtain an integrated oil seal.

[0010] Furthermore, in step S1: The stamped steel plate is SPCC-SD or DC04 cold-rolled steel plate with a yield strength ≥280MPa and a thickness of 1.0~2.0mm; the skeleton is provided with 2~4 circumferentially distributed positioning pins and sealing rib grooves; the diameter tolerance of the through hole of the positioning pin is controlled within ±0.04mm, and the position tolerance of the positioning pin is controlled within ±0.05mm. The sealing rib groove includes a first end face stamping groove for accommodating the sealing rib and a second end face circular hole for forming a sealing lip; the flatness of the first end face of the sealing rib is ≤0.08mm, and the roundness of the second end face is ≤0.03mm.

[0011] Further, in step S1, the directional sandblasting pretreatment includes: The axial and circumferential positions of the skeleton are fixed by positioning brackets on the circular conveying track. 8 to 12 positioning brackets are evenly arranged on the circumference of the track, and the distance between adjacent brackets is 200 to 300 mm. The sandblasting pressure is 0.3–0.5 MPa, the sandblasting angle is 30°–60°, the sand particle size is 80–120 mesh corundum sand, and the skeleton traveling speed is 0.5–1.2 m / min; the sandblasting angle is the angle between the sand jet and the tangent of the skeleton surface. The directional rough texture is uniformly distributed along the circumference of the skeleton, and the surface roughness Ra is 3.2 to 6.3 μm.

[0012] Further, in step S2, the thermal expansion compensation preheating positioning fixture includes: The positioning base plate has positioning holes on its surface that mate with the positioning pins of the skeleton, with a positional tolerance of ±0.02mm. The positioning base plate is provided with circulating cooling water channels. The circumferential clamping mechanism includes 3 to 4 sets of pneumatic grippers. The inner side of the pneumatic grippers is provided with an arc-shaped clamping surface that matches the outer circle of the skeleton. The clamping air pressure is 0.3 to 0.6 MPa. The axial clamping device adopts a spring-cylinder combination structure to provide an axial clamping force of 50 to 100 N; The induction heating coil uses medium-frequency induction heating with a frequency of 1 to 10 kHz and a power density of 5 to 15 kW / m².

[0013] Further, in step S2, the temperature control curve is determined based on the calculation result of the heat deformation; the heat deformation is calculated based on the theory of thermal expansion, specifically the heat deformation of the skeleton at the vulcanization temperature; the formula for calculating the heat deformation is: (1) in, The coefficient of thermal expansion of the skeleton material is... For skeleton feature dimensions, vulcanization temperature, The ambient temperature.

[0014] Furthermore, in step S2, the temperature control curve includes: The first stage of heating: the skeleton is heated from room temperature to 80°C at a rate of 2-3°C / min; The second stage is the homogenization zone: heating from 80°C to the preset preheating temperature of 130-150°C at a rate of 1-2°C / min. The third stage of heat preservation: heat preservation at a preheating temperature of 130-150℃, with temperature fluctuations controlled within ±2℃. The fourth stage is the transfer section: the preheated skeleton is transferred to the injection mold within 30 seconds, and the temperature drop of the skeleton during the transfer process does not exceed 10℃.

[0015] Furthermore, based on the calculation results of thermal deformation, a preheating fixture is designed to uniformly preheat the skeleton to the target temperature. ,make satisfy: (2) in, Here, ln represents the process coefficient, and ln is the natural logarithm symbol, with a value range of 1.2 to 1.5. This represents the maximum allowable transient temperature rise of the skeleton.

[0016] Furthermore, in step S3, the balanced runner system adopts an H-shaped symmetrical layout, including a main runner with a diameter of 8-12mm, a branch runner with a diameter of 6-8mm, and a gate with a thickness of 0.8-1.2mm. The runner lengths and cross-sectional areas from each cavity to the main runner are equal. The injection point position and runner cross-sectional dimensions are optimized through mold flow analysis to ensure that the filling imbalance rate of each cavity is ≤5%.

[0017] Furthermore, the model flow analysis includes: Establish the flow equations for Hele-Shaw fluids that are non-isothermal and non-Newtonian; Model flow analysis was performed based on the Hele-Shaw flow equations for non-isothermal, non-Newtonian fluids to determine the weld line location and filling equilibrium. The Hele-Shaw flow equations are as follows: (3) in, For the density of the rubber compound, For cavity clearance, The average flow velocity, For time.

[0018] Furthermore, in step S3, the injection pressure algorithm for dynamic closed-loop control is based on the cavity inlet pressure. Real-time feedback, t Injection pressure at all times P inj ( t The algorithm formula is: (4) in, For pressure deviation, , K p This is the proportional gain coefficient. K i This is the integral gain coefficient. τ Let be the time constant for the change in the specific volume of the material. To set pressure, This is the feedforward pressure predicted based on the flow model.

[0019] Furthermore, after the rubber injection, a variable holding pressure control strategy based on the pressure-volume-temperature characteristic curve is adopted, and the holding pressure decreases exponentially with time: (5) in, To maintain pressure, P hold This is the initial holding pressure. Let be the time constant for the change in the specific volume of the material. This is the final holding pressure.

[0020] Tackifier FPA: 0.3–0.8 parts by weight; Bisphenol AF vulcanizing agent: 1.5–2.5 parts by weight; Accelerator BPP 0.5-1 parts by weight; Magnesium oxide, an acid absorber, 3-5 parts by weight; 10-20 parts by weight of calcium sulfate whiskers as filler.

[0021] Furthermore, in step S4, the sealing lip cutting is performed using a CNC laser cutting machine or a die-cutting machine, with a cutting accuracy of ±0.02mm.

[0022] Compared with the prior art, one or more embodiments of the present invention may have the following advantages: 1) Achieved a systematic leap in form and position accuracy and structural reliability: Achieved stable and controllable key form and position accuracy: The collision deformation and corrosion of the sandblasting process were suppressed by track positioning and directional sandblasting, and the transient thermal strain during the heating stage was reduced by combining thermal expansion compensation preheating positioning tooling and temperature control curve, thereby suppressing warping and interface defects after vulcanization cooling and improving the form and position consistency of the positioning structure and sealing lip. 2) Significantly improved product quality and adaptability to operating conditions: The rubber formulation, reconstructed based on the principles of polymer rheology and interfacial chemistry, effectively eliminates weld lines and sulfur marks by controlling the dosage of release agents and tackifiers, and by using a combination of high and low Mooney raw rubber. This enhances the strength of the rubber itself and its interfacial adhesion to the metal skeleton. Combined with precise vulcanization process control, the oil seal exhibits excellent anti-aging, anti-fatigue, and sealing stability under harsh engine conditions such as high temperature, media corrosion, and continuous vibration. 3) A quantifiable and replicable high-quality production process has been established: This process transforms procedures that originally relied on worker experience into a precision control process based on physical models and real-time feedback. From track sandblasting to prevent deformation, to flow channel balance optimization, and then to quantitative detection of form and position tolerances, key parameters throughout the entire process are measurable, controllable, and optimizable, greatly improving the stability of the production process and the consistency between product batches, providing a solid technical foundation for the large-scale, high-quality manufacturing of high-performance oil seals. Attached Figure Description

[0023] Figure 1This is a flowchart of the integrated oil seal track positioning and directional sandblasting-thermal expansion preheating coupling molding method; Figure 2 This is a schematic diagram of the temperature control curve; Figure 3 This is a layout diagram of a multi-cavity injection balanced flow channel; Figure 4 This is a structural diagram of a stamped steel plate integral forming product. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be described in further detail below with reference to the embodiments and accompanying drawings.

[0025] like Figure 1 The image shows a method for integrated oil seal track positioning and orientation sandblasting-thermal expansion preheating coupling molding, including: Step S1. The skeleton made of stamped steel plate is pre-treated by directional sandblasting through track positioning to form a directional rough texture on the surface of the skeleton; Cold-rolled steel sheets with a yield strength ≥280MPa (such as SPCC-SD or DC04) are selected and integrally formed by precision stamping. During the stamping process, 2 to 4 circumferentially distributed locating pins and sealing rib grooves are formed simultaneously. The sealing rib grooves include a first end face stamping groove for accommodating the sealing rib 1 and a second end face circular hole for forming the sealing lip 3; the flatness of the sealing rib end face is ≤0.08mm, and the roundness of the sealing lip is ≤0.03mm. After forming, the diameter tolerance of the through hole of the locating pin 2 is controlled within ±0.04mm, and the position tolerance of the locating pin is controlled within ±0.05mm, providing a reference for subsequent forming (such as...). Figure 4 (As shown).

[0026] The directional sandblasting pretreatment includes: a track-positioned directional sandblasting device, which comprises a conveyor track, a circumferential positioning mechanism, a directional sandblasting gun assembly, and a dust collection and recovery system. The conveyor track is made of stainless steel with a surface hardness of HRC45-50 and has V-shaped positioning grooves with a depth of 1 / 3 to 1 / 4 of the skeleton diameter to constrain the axial position of the skeleton. The circumferential positioning mechanism includes symmetrically arranged elastic pressure rollers made of polyurethane, with a clamping force controlled at 5-10N to constrain the circumferential rotation of the skeleton. The directional sandblasting gun assembly contains 4-6 sandblasting guns evenly distributed in a ring, with the angle between the gun axis and the tangent to the skeleton surface being 30°-60°, and the distance between the guns and the skeleton surface being 100-150mm. The dust collection and recovery system is connected to the sandblasting chamber, with negative pressure controlled at -2000 to -3000Pa.

[0027] The track adopts a ring-shaped conveyor track. The skeleton is fixed in axial and circumferential positions by positioning brackets on the conveyor track. 8-12 positioning brackets are evenly arranged around the track circumference, with a spacing of 200-300 mm between adjacent brackets. The process parameters for sandblasting are shown in Table 1. Table 1

[0028] Compared to the roller-tumbling type, the track-positioned directional sandblasting reduces the skeleton deformation rate from 8-12% to below 1%, controls the surface roughness Ra to 3.2-6.3μm, improves roughness uniformity by 40%, and eliminates hidden cracks caused by tumbling collisions.

[0029] Step S2: Based on the thermal expansion coefficient and vulcanization temperature of the skeleton material, calculate the thermal deformation during vulcanization; design a thermal expansion compensation preheating positioning fixture based on the deformation data, and optimize the temperature control curve; preheat the skeleton to ensure it reaches the preset preheating temperature before vulcanization; specifically: The main purpose of preheating is to minimize the thermal stress caused by the difference in the coefficient of thermal expansion between the metal skeleton and the vulcanized rubber, and to promote the full wetting and chemical bonding of the rubber on the metal surface. This significantly reduces the instantaneous thermal strain of the skeleton from room temperature to vulcanization temperature, thereby avoiding defects such as skeleton warping, peeling of the rubber-metal bonding interface, or misalignment of the sealing rib dimensions caused by uneven shrinkage during the subsequent cooling stage.

[0030] To achieve shape and position retention and thermal expansion compensation during the preheating process, the designed thermal expansion compensation preheating positioning fixture includes: The positioning base plate is made of heat-resistant alloy steel with a thermal expansion coefficient that matches the frame. The surface is provided with positioning holes that mate with the positioning pins of the frame (the hole diameter is 0.02 to 0.03 mm larger than the positioning pin to account for thermal expansion gaps). The hole position accuracy is ±0.02 mm. The positioning base plate is provided with circulating cooling water channels to prevent the base plate from overheating and deforming.

[0031] The circumferential clamping mechanism includes 3 to 4 sets of pneumatic grippers. The inner side of the grippers is provided with an arc-shaped clamping surface that matches the outer circle of the skeleton (the radius of curvature is consistent with the outer diameter of the skeleton). The clamping force is controlled by air pressure at 0.3 to 0.6 MPa. This pressure range ensures that there is no relative displacement of the skeleton during the preheating process and avoids clamping deformation. The grippers are coated with a high-temperature resistant ceramic coating (0.1 mm thick) to reduce local overcooling caused by heat conduction.

[0032] The axial clamping device adopts a spring-cylinder combination structure. The cylinder provides the initial clamping force, and the spring adaptively adjusts when the skeleton thermally expands, providing an axial clamping force of 50-100N to prevent axial warping of the skeleton during thermal expansion and maintain axial positioning accuracy. The induction heating coil adopts medium-frequency induction heating with a frequency of 1 to 10 kHz, preferably 3 to 5 kHz, and a power density of 5 to 15 kW / m². The gap between the coil and the frame is controlled at 3 to 5 mm to ensure uniform heating.

[0033] To avoid transient thermal strain, a four-segment temperature control curve and corresponding thermal strain control targets are adopted, such as... Figure 2 As shown in Table 2: Table 2

[0034] After adopting the above tooling and temperature control curve, the flatness retention rate of the skeleton after preheating is ≥95%, the thermal deformation during the transfer to the mold is ≤0.01mm, and the warpage after vulcanization and cooling is ≤0.03mm.

[0035] The temperature control curve is determined based on the calculation results of thermal deformation, which is based on the theory of thermal expansion. The thermal deformation of the skeleton at the vulcanization temperature is calculated. : (1) in, The coefficient of thermal expansion of the skeleton material is... For skeleton feature dimensions, vulcanization temperature, The ambient temperature.

[0036] Based on the calculation results of thermal deformation, a special preheating fixture was designed to uniformly preheat the skeleton to the target temperature. , satisfy: (2) in, This is the process coefficient, with a value ranging from 1.2 to 1.5; The target preheating temperature and preheating time are calculated based on the thermal deformation amount, process coefficients, and the maximum allowable transient temperature rise of the skeleton. It was jointly determined that, preferably, the preheating temperature is 130–150°C and the preheating time is 540 s. The above is one implementation method; equivalent calculation or fitting methods can also be used to achieve the same boundary constraint and control effect.

[0037] like Figure 3 As shown, the balanced runner system adopts an H-shaped symmetrical layout. The injection point position and runner cross-sectional dimensions are optimized through mold flow analysis. The filling time difference of each cavity is ≤0.1s, so that the filling imbalance rate of each cavity is ≤5%. Among them, the main runner diameter is 8-12mm, the branch runner diameter is 6-8mm, and the gate thickness is 0.8-1.2mm (fan-shaped gate), ensuring that the melt fills each cavity uniformly in a laminar flow state.

[0038] The model flow analysis includes: Establish the flow equations for Hele-Shaw fluids that are non-isothermal and non-Newtonian; Model flow analysis was performed based on the Hele-Shaw flow equation for non-isothermal, non-Newtonian fluids to determine the weld line location and filling balance. The Hele-Shaw flow equation is as follows: (3) in, For the density of the rubber compound, For cavity clearance, The average flow velocity, For time.

[0039] The injection pressure dynamic closed-loop control algorithm is based on the cavity inlet pressure Real-time feedback, t Injection pressure at all times P inj ( t The algorithm formula is: (4) in, For pressure deviation, K p This is the proportional gain coefficient. K i This is the integral gain coefficient. τ The time constant of the specific volume change of a material To set pressure, Forward pressure is predicted based on a flow model; The injection pressure is controlled at 230±10 bar, the vulcanization temperature is 160~180℃, preferably 170℃, and the vulcanization time is 120~180s.

[0040] After the rubber injection filling is completed, a method based on... Variable holding pressure control strategy for (pressure-volume-temperature) characteristic curve, holding pressure Decays according to the following function: (5) in, To maintain pressure, P hold This is the initial holding pressure. Let be the time constant for the change in the specific volume of the material. The final holding pressure is used to compensate for the shrinkage of the rubber compound.

[0041] To address the issues of weld lines and sulfur marks that are prone to occur in traditional formulations, the rubber formulation has been reconstructed as shown in Table 3 (parts by weight): Table 3

[0042] High and low Mooney ratios are used together: low Mooney (ML(1+4) 100℃=20-40) and high Mooney (ML(1+4) 100℃=60-90) raw rubber are used together in a ratio of 3:7 to 5:5 to balance flowability and anti-collapse properties and effectively eliminate sulfur marks at the weld joint. Internal release agent is reduced: palm wax is reduced from 2 parts to 0.5-1 part, combined with external spray release agent, to ensure release properties while preventing the internal release agent from migrating to the bonding interface and forming a weak boundary layer; tackifying system: WS280 (silane coupling agent) and FPA (phenolic resin) are used together at 0.5 parts each to form a chemical bond with the skeleton surface, increasing the bond strength by more than 30%. Step S4: Trim the edges of the vulcanized semi-finished product and cut the sealing lip to a fixed length to obtain an integrated oil seal; The trimming is performed using precision punching or cryogenic trimming to remove gates and flash, with a residual height of ≤0.05mm after trimming. Cutting is performed using a CNC laser cutting machine or a precision die-cutting machine, with a lip surface roughness Ra≤0.8μm and a cutting accuracy of ±0.02mm after cutting.

[0043] Finally, the key geometric tolerances are checked by a coordinate measuring machine (CMM) using a Hexagon or Zeiss: locating pin position tolerance: ≤0.05mm, sealing lip roundness: ≤0.03mm, and sealing rib flatness: ≤0.08mm. If all three indicators are met and the bonding strength is ≥4.0MPa, the product is considered qualified.

[0044] Specific Implementation Example 1: Front oil seal of crankshaft for a certain type of engine (outer diameter 85mm) This product is an integrated oil seal with an outer diameter of 85mm, an inner diameter of 35mm, three evenly distributed locating pins, a sealing rib width of 3mm, and a lip thickness of 0.5mm.

[0045] Process steps: It is made of DC04 cold-rolled steel sheet (yield strength 280MPa) and precision stamped; the diameter of the locating pin through hole is 6mm with a tolerance of ±0.04mm; the flatness of the skeleton is 0.04mm.

[0046] Oriented sandblasting with track positioning; V-shaped positioning groove depth 25mm, polyurethane pressure roller clamping force 8N, 4 sandblasting guns arranged at 45°, sandblasting pressure 0.4MPa, 100-mesh corundum abrasive, traveling speed 0.8m / min. After treatment, the surface roughness Ra is 4.5μm, with no deformation and no corrosion.

[0047] Thermal expansion compensation preheating; characteristic dimension L0 = 85mm, calculated thermal deformation ΔL = 0.14mm. Design preheating temperature 140℃, process coefficient k = 1.33. Temperature control curve: room temperature → 80℃ (25min, 2.4℃ / min) → 140℃ (30min, 2℃ / min) → hold for 540s. Pneumatic gripper air pressure 0.5MPa, axial clamping force 80N. Flatness of the skeleton after preheating 0.05mm (retention rate 87.5%).

[0048] Mold flow analysis and optimization were performed using Moldflow analysis. The design features an H-type 4-cavity layout with a main runner of φ10mm, branch runners of φ7mm, and a fan-shaped gate thickness of 1.0mm. The filling time difference between each cavity is 0.08s, and the imbalance rate is 4.2%.

[0049] Injection vulcanization; the skeleton is preheated to 140℃ and then poured into the mold within 30 seconds, with the mold temperature at 170℃. The injection pressure is set to a closed-loop control of 230 bar, but actually ranges from 228 to 235 bar. Variable holding pressure: P0 = 190 bar, τ = 20 s, P∞ = 50 bar. Vulcanization time is 150 seconds.

[0050] Rubber compound formulation (parts by weight): Fluororubber 100 (40 parts low Mooney + 60 parts high Mooney), palm wax 0.8, WS280 0.5, FPA 0.5, bisphenol AF 2.0, BPP 0.8, magnesium oxide 4, calcium sulfate whiskers 15.

[0051] Laser cutting of the lip at a speed of 500 mm / min; coordinate measuring machine (CMM) inspection: locating pin position accuracy 0.032 mm, lip roundness 0.018 mm, sealing rib flatness 0.042 mm. Bond strength 4.5 MPa.

[0052] Compared to traditional processes (roller blasting + experience preheating), the positioning pin position accuracy is improved by 78%, the lip roundness by 75%, the flatness by 72%, and the bonding strength by 50%.

[0053] Specific Implementation Example 2: Oil seal for the output shaft of a certain type of gearbox (outer diameter 120mm) The product has an outer diameter of 120mm, an inner diameter of 50mm, four evenly distributed locating pins, and a double-lip structure. Based on Example 1, the process parameters were adjusted to 6 sandblasting guns with a travel speed of 1.0 m / min (the speed was appropriately increased for large-diameter skeletons). Feature dimensions L0=120mm, ΔL=0.20mm, preheating temperature 145℃, holding time 600s; Vulcanization time 180s (with increased wall thickness).

[0054] Test results: Positioning pin accuracy 0.028mm, lip roundness 0.022mm, sealing rib flatness 0.038mm. No leakage was observed during the high-temperature, high-speed life test (150℃, 8000r / min) for 1200 hours.

[0055] Comparative experiment: Traditional process vs. the process of this invention One hundred skeletons from the same batch were randomly divided into two groups. One group was treated using the traditional process (roller blasting + oven preheating at 150℃ for 10 min + empirical injection), and the other group was treated using the process of this invention. The comparison results are shown in Table 4. Table 4

[0056] As can be seen from the table above, the process of the present invention is significantly superior to the traditional process in terms of dimensional accuracy, bonding strength, and product qualification rate.

[0057] While the embodiments disclosed in this invention are as described above, the content is merely for the purpose of facilitating understanding of the invention and is not intended to limit the invention. Any person skilled in the art to which this invention pertains may make any modifications and variations in form and detail of the implementation without departing from the spirit and scope disclosed herein; however, the scope of patent protection for this invention shall still be determined by the scope defined in the appended claims.

Claims

1. A method for integrated oil seal track positioning and orientation sandblasting-thermal expansion preheating coupling molding, characterized in that, Includes the following steps: Step S1: Position the skeleton made of stamped steel plate through a ring conveyor track and perform directional sandblasting pretreatment to form a directional rough texture on the surface of the skeleton. Step S2: Based on the thermal expansion coefficient and vulcanization temperature of the skeleton material, calculate the thermal deformation during the vulcanization process, design a thermal expansion compensation preheating positioning fixture based on the thermal deformation data, and optimize the temperature control curve. The skeleton is preheated to reach the preset preheating temperature before vulcanization. Step S3: Place the preheated skeleton into a multi-cavity injection mold, and use a balanced flow channel system for rubber injection and vulcanization molding. The rubber injection process is dynamically closed-loop controlled based on real-time feedback of cavity inlet pressure to achieve uniform filling of each cavity at equal pressure. Step S4: Trim the edges of the vulcanized semi-finished product and cut the sealing lip to a fixed length to obtain an integrated oil seal.

2. The integrated oil seal track positioning and orientation sandblasting-thermal expansion preheating coupling molding method according to claim 1, characterized in that, In step S1: The stamped steel plate is SPCC-SD or DC04 cold-rolled steel plate with a yield strength ≥280MPa and a thickness of 1.0~2.0mm; the skeleton is provided with 2~4 circumferentially distributed positioning pins and sealing rib grooves; the diameter tolerance of the through hole of the positioning pin is controlled within ±0.04mm, and the position tolerance of the positioning pin is controlled within ±0.05mm. The sealing rib groove includes a first end face stamping groove for accommodating the sealing rib and a second end face circular hole for forming a sealing lip; the sealing rib has a first end face that mates with the first end face stamping groove and a second end face that corresponds to the second end face circular hole, wherein the flatness of the first end face is ≤0.08mm and the roundness of the second end face is ≤0.03mm.

3. The integrated oil seal track positioning and orientation sandblasting-thermal expansion preheating coupling molding method according to claim 1, characterized in that, In step S1, the directional sandblasting pretreatment includes: The skeleton is positioned axially and circumferentially by positioning brackets set on the circular conveying track. The positioning brackets are evenly arranged along the circumference of the track, with a spacing of 200-300mm between adjacent brackets, and 8-12 brackets are set accordingly. The sandblasting pressure is 0.3–0.5 MPa, the sandblasting angle is 30°–60°, the sand particle size is 80–120 mesh corundum sand, and the skeleton traveling speed is 0.5–1.2 m / min; the sandblasting angle is the angle between the sand jet and the tangent of the skeleton surface. After directional sandblasting, the skeleton surface forms a directional rough texture that is uniformly distributed along the circumference, with a surface roughness Ra of 3.2–6.3 μm.

4. The integrated oil seal track positioning and orientation sandblasting-thermal expansion preheating coupling molding method according to claim 2, characterized in that, In step S2, the thermal expansion compensation preheating positioning fixture includes: The integrated oil seal track positioning and directional sandblasting-thermal expansion preheating coupling molding method according to claim 2 is characterized in that, in step S2, the thermal expansion compensation preheating positioning fixture includes: The positioning base plate has positioning holes on its surface that mate with the positioning pins of the skeleton, with a positional tolerance of 0.02mm. The positioning base plate is provided with circulating cooling water channels. The circumferential clamping mechanism includes 3 to 4 sets of pneumatic grippers. The inner side of the pneumatic grippers is provided with an arc-shaped clamping surface that is adapted to the outer circle of the skeleton. The clamping air pressure of each pneumatic gripper is 0.3 to 0.6 MPa. An axial clamping device, including a spring and a cylinder, provides an axial clamping force of 50–100 N; The induction heating coil operates at a frequency of 1–10 kHz and has a power density of 5–15 kW / m². The gap between the induction heating coil and the frame is 3–5 mm.

5. The integrated oil seal track positioning and orientation sandblasting-thermal expansion preheating coupling molding method according to claim 1, characterized in that, In step S2, the temperature control curve is determined based on the calculated thermal deformation of the skeleton at the vulcanization temperature; the thermal deformation is calculated based on the theory of thermal expansion, and the calculation formula is: (1) in, The coefficient of thermal expansion of the skeleton material is... For skeleton feature dimensions, vulcanization temperature, The ambient temperature.

6. The integrated oil seal track positioning and orientation sandblasting-thermal expansion preheating coupling molding method according to claim 5, characterized in that, In step S2, the temperature control curve includes a first stage, a second stage, a third stage, and a fourth stage. The first stage is the heating stage, in which the skeleton is heated from 20°C to 80°C at a rate of 2-3°C / min; The second stage is the heat equalization zone, where the temperature is heated from 80°C to the preset preheating temperature of 130°C to 150°C at a rate of 1 to 2°C / min. The third stage is the heat preservation stage, in which heat preservation is carried out at the preset preheating temperature, and the heat preservation temperature fluctuation range is ±2℃. The fourth stage is the transfer stage, in which the preheated skeleton is transferred to the injection mold within 30 seconds, and the temperature drop of the skeleton during the transfer process does not exceed 10°C.

7. The integrated oil seal track positioning and orientation sandblasting-thermal expansion preheating coupling molding method according to claim 5, characterized in that, Based on the calculation results of thermal deformation, a preheating fixture is designed to uniformly preheat the skeleton to the target temperature. And target temperature satisfy: (2) in, Here, ln represents the process coefficient, and ln is the natural logarithm symbol, with a value range of 1.2 to 1.

5. This represents the maximum allowable transient temperature rise of the skeleton.

8. The integrated oil seal track positioning and orientation sandblasting-thermal expansion preheating coupling molding method according to claim 1, characterized in that, In step S3, the balanced runner system adopts an H-shaped symmetrical layout, including a main runner with a diameter of 8-12mm, a branch runner with a diameter of 6-8mm, and a gate with a thickness of 0.8-1.2mm. The branch runners corresponding to each cavity have equal lengths and equal cross-sectional areas. The injection point position and runner cross-sectional dimensions are optimized through mold flow analysis to ensure that the filling imbalance rate of each cavity is ≤5%.

9. The integrated oil seal track positioning and orientation sandblasting-thermal expansion preheating coupling molding method according to claim 8, characterized in that, The model flow analysis includes: Establish the Hele-Shaw flow equation for non-isothermal, non-Newtonian fluids; Model flow analysis was performed based on the Hele-Shaw flow equation for non-isothermal, non-Newtonian fluids to determine the weld line location and filling balance. The Hele-Shaw flow equation is as follows: (3) in, For the density of the rubber compound, For cavity clearance, The average flow velocity, For time.

10. The integrated oil seal track positioning and orientation sandblasting-thermal expansion preheating coupling molding method according to claim 1, characterized in that, In step S3, the injection pressure algorithm for dynamic closed-loop control is based on the cavity inlet pressure. Real-time feedback, t Injection pressure at all times P inj ( t The algorithm formula is: (4) in, For pressure deviation, , K p This is the proportional gain coefficient. K i Here, τ is the integral gain coefficient, and τ is the time constant for the change in the material's specific volume. To set pressure, This is the feedforward pressure predicted based on the flow model.

11. The integrated oil seal track positioning and orientation sandblasting-thermal expansion preheating coupling molding method according to claim 1, characterized in that, After the rubber injection is completed, a variable holding pressure control strategy based on the pressure-volume-temperature characteristic curve is adopted, and the holding pressure decreases exponentially with time: (5) in, To maintain pressure, P hold This is the initial holding pressure. Let be the time constant for the change in the specific volume of the material. This is the final holding pressure.

12. The integrated oil seal track positioning and orientation sandblasting-thermal expansion preheating coupling molding method according to claim 1, characterized in that, The rubber injected in step S3 is formulated in the following proportions by weight: 100 parts by weight of fluororubber raw rubber consists of low Mooney raw rubber and high Mooney raw rubber, of which low Mooney raw rubber accounts for 30 to 50 parts by weight and high Mooney raw rubber is made up to 100 parts by weight. Carnauba wax, an internal release agent, is added in the form of 0.5 to 1 part by weight. Tackifier WS280: 0.3–0.8 parts by weight; Tackifier FPA: 0.3–0.8 parts by weight; Bisphenol AF vulcanizing agent: 1.5–2.5 parts by weight; Accelerator BPP 0.5-1 parts by weight; Magnesium oxide, an acid absorber, 3-5 parts by weight; 10-20 parts by weight of calcium sulfate whiskers as filler.

13. The integrated oil seal track positioning and orientation sandblasting-thermal expansion preheating coupling molding method according to claim 1, characterized in that, In step S4, the sealing lip is cut using a CNC laser cutting machine or a die-cutting machine, with a cutting dimensional tolerance of ±0.02mm.

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