A heat treatment positioning device and method for dismounting a large gear of an automobile gearbox

Abstract

The application relates to a heat treatment positioning device and method for dismounting a large gear of an automobile gearbox, which comprises a cross beam provided with a lifting point, a driving assembly arranged in the middle of the cross beam, positioning rods arranged on the two sides of the cross beam, upper parts of the two positioning rods connected to the two sides of the cross beam through first and second pressure sensors respectively, lower parts of the positioning rods provided with connecting parts used for being connected in process holes of the gear, upper and lower heating covers used for buckling annular heating covers at gear hubs, a control unit signal-connected with the first and second pressure sensors, the electric heating assembly and the driving assembly respectively, and used for calculating a pressure difference value of the first and second pressure sensors, adjusting heating power on the two sides according to the pressure difference value, and driving the driving assembly to perform a dismounting action according to a pressure change rate. The application realizes lossless and self-adaptive dismounting of the large gear and the shaft, and effectively avoids shaft neck injury and hub cracking.

Description

Technical Field

[0001] This invention relates to the field of automotive transmission technology, and more specifically to a heat treatment positioning device and method for disassembling the large gear of an automotive transmission. Background Technology

[0002] The large gear inside an automotive transmission is typically assembled with the gear shaft using an interference fit to ensure reliable torque transmission and precise fit. During transmission repair or remanufacturing, it's necessary to remove the large gear from the shaft, for example, when replacing gears, repairing bearings, or remanufacturing the transmission. Because the large gear operates under heavy loads, complex shifting and lubrication conditions, fretting wear, corrosion, or adhesion can easily occur between the gear's inner bore and the shaft journal. This makes disassembling the interference fit far more difficult than the initial assembly.

[0003] The common disassembly method involves opening the gearbox housing, removing the gear along with the shaft, and then using a press or puller to disassemble it. For small gears, a hydraulic puller is typically used for direct pulling. The puller's claws hook onto the gear's rim or spokes, and a central screw holds the shaft end, applying pulling force to pull the gear out. For larger gears or gears with high interference fits, current technology often uses a blowtorch to locally heat the hub surface, utilizing the principle of thermal expansion to reduce disassembly resistance. However, the heat output of the blowtorch is dispersed. Because the heating time, temperature, and location of the flame on the hub surface are closely related to manual operation, heat conduction is highly random. This often results in one side of the gear heating up too quickly while the other side remains at a low temperature, leading to a highly unstable thermal stress gradient inside the hub and causing asymmetric thermal expansion.

[0004] Existing heating methods further exacerbate the morphological distortion of the shaft and gear mating surfaces, resulting in significant elliptical deformation or axial taper deviation. This not only fails to achieve uniform separation of the interference fit but also generates abnormal radial compressive stress at the mating surfaces due to irregular expansion of localized material, exacerbating the locking between the gear's inner bore and the journal surface. When resistance is not effectively released and is extremely unevenly distributed, blindly increasing the axial thrust of the drive assembly can easily cause slight tilting of the gear because the center of force and the center of frictional resistance cannot coincide. This transforms axial slippage into radial cutting, leading to mechanical tearing and metal spalling on the journal surface. Consequently, the large gear, unable to withstand the locally concentrated shear stress, undergoes yielding deformation or even fatigue cracking, rendering the high-value gear spare parts unusable for reuse.

[0005] In summary, the existing technologies that rely on manual experience for extensive heating and mechanical pulling are highly susceptible to journal damage and wheel hub cracking. Therefore, it is necessary to research a heat treatment positioning device and method for disassembling large gears in automotive transmissions. Summary of the Invention

[0006] Therefore, the purpose of this invention is to provide a heat treatment positioning device and method for disassembling the large gear of an automotive transmission, which effectively solves the problem that existing disassembly fixtures cannot overcome the stress imbalance between the shaft and the gear, and are prone to causing journal damage and wheel hub cracking during operation.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is: a heat treatment positioning device for disassembling the large gear of an automotive transmission, comprising, The crossbeam is equipped with lifting points for connecting lifting equipment; The drive assembly, located in the middle of the crossbeam, is used to push the shaft to be disassembled. Positioning rods are set on both sides of the crossbeam. The upper parts of the two positioning rods are connected to both sides of the crossbeam via a first pressure sensor and a second pressure sensor, respectively. The lower part of the positioning rods is provided with a connecting part, which is used to connect to the process hole of the gear. The upper heating cover and the lower heating cover both include a first cover body and a second cover body. Electric heating components are provided in both covers body and are connected together to form an annular heating cover for fastening to the gear hub. The control unit is connected to the first pressure sensor, the second pressure sensor, the electric heating component, and the drive component, respectively. It calculates the pressure difference between the first and second pressure sensors, adjusts the heating power on both sides according to the pressure difference, and drives the component to perform a disassembly action according to the pressure change rate.

[0008] Furthermore, the connecting part includes a limiting sleeve, a connector, and a fixing member. The limiting sleeve is fixed to the lower part of the positioning rod, the connector is fixed to the bottom of the positioning rod, and the fixing member is connected to the connector to fix the positioning rod in the process hole.

[0009] Furthermore, corresponding docking blocks are provided on both sides of the first and second covers, and corresponding docking grooves are provided in the middle of the docking blocks. The two docking grooves are spliced ​​together to form a hollow annular groove. Fasteners are fitted into the annular groove and pass through the process hole to fasten the heating covers on the upper and lower sides to the hub of the gear.

[0010] Furthermore, both the first and second covers have a central hole at their interior center, and a heat insulation cover extends from the edge of the central hole into the cover body to maintain the radial temperature gradient between the shaft to be disassembled and the gear hub during the heating process.

[0011] Furthermore, the first pressure value of the first pressure sensor and the second pressure value of the second pressure sensor are acquired in real time. When the pressure difference between the two exceeds a preset threshold, the control unit increases the heating power of the cover with the larger pressure value or decreases the heating power of the cover with the smaller pressure value.

[0012] Furthermore, the pressure drop slope of the two pressure sensors is monitored in real time; when the pressure drop slope reaches a preset threshold, the control unit determines that the interference surface is loose and sends a command to allow pressure increase.

[0013] Furthermore, a top seat is fitted to the end of the shaft to be disassembled, and ear plates are provided on both sides of the top seat. A first displacement sensor and a second displacement sensor corresponding to the ear plates are respectively provided on both sides of the crossbeam. The first displacement sensor and the second displacement sensor are used to obtain the displacement of the two sides of the shaft to be disassembled relative to the crossbeam.

[0014] Furthermore, the first and second displacements of the lugs on both sides of the shaft to be disassembled relative to the crossbeam are obtained, and the displacement deviation between the first and second displacements is calculated. Combined with the pressure deviation and displacement deviation, an imbalance coefficient is generated. When the imbalance coefficient is less than or equal to the first balance threshold, the power output of each electric heating component is maintained. When the imbalance coefficient is greater than the first balance threshold and less than or equal to the second balance threshold, the heating power of the side with the larger pressure value or the smaller displacement value is increased. When the imbalance coefficient is greater than the second balance threshold, the drive component is controlled to stop pressurizing and perform pressure relief, while simultaneously shutting down heating and issuing an alarm signal.

[0015] Furthermore, the average displacement values ​​of the first and second displacement sensors, and the average pressure values ​​of the first and second pressure sensors are obtained; the stress reduction rate is obtained based on the ratio of the rate of change of the average pressure over time to the initial pre-tightening pressure, and the slip growth rate is obtained based on the ratio of the rate of change of the average displacement over time to the preset speed reference value; the reciprocal of the product of the stress reduction rate and the slip growth rate is calculated to obtain the loosening coefficient; when the loosening coefficient is greater than the first loosening threshold, the drive component is controlled to maintain the current pressure; when the loosening coefficient is less than or equal to the first loosening threshold and greater than the second loosening threshold, the drive component is controlled to perform pre-pressurization; when the loosening coefficient is less than or equal to the second loosening threshold, the drive component is controlled to switch to the high-frequency pulse pressurization mode.

[0016] A heat treatment positioning method for disassembling the large gear of an automotive transmission, applied to the aforementioned device, includes the following steps: Step 1: Connect the lifting ring of the crossbeam using the lifting equipment, fix the lower part of the positioning rod to the process hole of the gear, and fasten the upper heating cover and lower heating cover to the hub of the gear. Step 2: The drive assembly applies axial thrust to the shaft to be disassembled and establishes an initial preload state through feedback from the first pressure sensor and the second pressure sensor. Step 3: Maintain the pre-tightening pressure and start the electric heating assembly to heat the upper heating cover and the lower heating cover respectively, while collecting the pressure values ​​of the first pressure sensor and the second pressure sensor in real time. Step 4: Calculate the pressure deviation between the two pressure sensors. When the pressure deviation exceeds the preset threshold, adjust the heating power on both sides to reduce the pressure deviation to within the threshold range. Step 5: Calculate the pressure drop slope in real time. When the pressure drop slope reaches the preset loosening threshold, it is determined that the interference fit surface has loosened, and a pressure increase command is sent to the drive component. Step 6: The drive component performs the action of pushing the shaft to be disassembled.

[0017] The beneficial effects of the above technical solution are as follows: Addressing the difficulty of disassembling the large gear and gear shaft of an automotive transmission under interference fit conditions, especially the non-uniform adhesion caused by microscopic welding, corrosion, and heat load accumulation on the mating surfaces after long-term service, as well as the asymmetric thermal expansion and local jamming problems of the wheel hub caused by blind heating in existing technologies, this invention connects the crossbeam and the process holes on the gear end face with positioning rods on both sides to form a force-bearing frame. Split-type annular heating covers are arranged on the upper and lower sides of the wheel hub to achieve uniform and controllable heating. The control unit actively adjusts the heating power of the corresponding side heating cover according to the pressure deviation, and automatically identifies the loose state of the interference fit surface based on the pressure change rate, thereby achieving smooth separation of the shaft and gear mating surfaces.

[0018] During the actual operation, the lifting equipment suspends the device above the gear to be disassembled via the crossbeam lifting points. The connecting part at the lower part of the positioning rod is fixedly connected to the gear's process hole. The upper and lower heating covers are fastened to the outer surface of the wheel hub and secured with fasteners. The control unit activates the electric heating assembly to heat the wheel hub, while simultaneously reading the pressure values ​​from the pressure sensors on both sides in real time. When the pressure deviation exceeds a preset threshold, the control unit increases the power of the heating cover on the side with higher pressure, causing the wheel hub on that side to further expand and release the jamming stress. At the same time, the control unit monitors the pressure drop slope. Once it detects loosening of the interference fit, it issues a pressure increase command, driving the assembly to perform a pushing action to complete the separation.

[0019] Meanwhile, the displacement sensor monitors the slippage on both sides of the shaft end in real time. The control unit weights and fuses the pressure deviation and displacement deviation to generate an imbalance coefficient, thereby achieving a comprehensive judgment of off-center load and skew. Then, the loosening coefficient is calculated by the stress reduction rate and slippage growth rate. The disassembly process is divided into three stages: heating, pre-pressurization and pulse pressurization, for graded control.

[0020] Compared with existing technologies, this invention uses a pressure sensor to sense force deviation in real time and actively adjusts the heating power on the stuck side. By monitoring the pressure drop slope, it automatically identifies the moment of loosening of the interference surface, ensuring that the pressure application is synchronized with the state of the mating surfaces, thus avoiding journal scoring or gear cracking caused by blind pressure application. By introducing a displacement sensor and a pressure sensor to form a dual discrimination, it effectively prevents radial cutting and stress concentration caused by gear tilting, balancing disassembly efficiency and safety.

[0021] This invention uses pressure sensors to monitor the force deviation of the positioning rods on both sides in real time, and adjusts the heating power of the corresponding heating cover according to the deviation to correct the unevenness of the wheel hub's thermal expansion. At the same time, it automatically identifies the loose state of the interference surface based on the pressure change rate and triggers the drive component to operate, thereby achieving non-destructive and adaptive disassembly of the large gear and shaft. This effectively solves the problems of journal scoring and wheel hub cracking in the prior art, significantly improves the safety, controllability and workpiece integrity of the disassembly process, and provides reliable technical equipment support for gearbox maintenance. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of an embodiment of the present invention; Figure 2 This is a schematic diagram of another implementation of the structure of the present invention; Figure 3 for Figure 1 Front view structural diagram; Figure 4 for Figure 1 A schematic diagram of the structure viewed from below; Figure 5 for Figure 1 A top-view structural diagram; Figure 6 This is a schematic diagram of the implementation structure of the heating cover; Figure 7 This is a schematic diagram of the mating structure of the first and second covers; Figure 8 This is a schematic diagram of the mating structure of the upper heating cover and the lower heating cover; Figure 9 This is a schematic diagram of the implementation structure of the fastener; Figure 10 This is a schematic diagram of the assembly structure of the displacement sensor.

[0023] Reference numerals: 1. Crossbeam; 2. Drive assembly; 3. Positioning rod; 31. End cap; 32. Limiting sleeve; 33. Connector; 34. Fixing component; 4. First pressure sensor; 5. Second pressure sensor; 6. Upper heating cover; 7. Lower heating cover; 8. First cover body; 9. Second cover body; 10. Electric heating assembly; 11. Connecting block; 12. Heat insulation cover; 13. Connecting groove; 14. Annular groove; 15. Fastener; 16. Gear; 17. Shaft to be disassembled; 18. Lifting ring; 19. Top seat; 20. Ear plate; 21. First displacement sensor; 22. Second displacement sensor. Detailed Implementation

[0024] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments: Example 1: This example aims to provide a heat treatment positioning device and method for disassembling the large gear of an automotive transmission. It is a fixture used for positioning and heat treatment of gear 16 and shaft during the disassembly and maintenance process of an automotive transmission. Given the extremely high precision of the interference fit between gear 16 and shaft in an automotive transmission, under long-term high temperature and load, the mating surfaces often experience adhesion resistance due to microscopic welding and corrosion. Existing technologies mainly rely on hydraulic pullers combined with conventional heating for disassembly. However, in actual operation, due to the varying contact strength at different points on the mating surfaces, blindly heating simultaneously can lead to asymmetrical thermal expansion of the hub, not only failing to relieve the interference force but also easily causing localized jamming. Therefore, this example provides a heat treatment positioning device for disassembling the large gear 16 of an automotive transmission.

[0025] like Figure 1 As shown, a heat treatment positioning device for disassembling the large gear 16 of an automotive gearbox includes a crossbeam 1, a drive assembly 2, positioning rods 3 arranged on both sides of the crossbeam 1, an upper heating cover 6, a lower heating cover 7, and a control unit. The device uses a pressure sensor to monitor the force deviation during the disassembly process in real time, and adjusts the heating power on both sides through the control unit. While ensuring the radial temperature difference of the gear shaft, it corrects the thermal deformation distortion of the wheel hub, thereby guiding the drive assembly 2 to achieve precise, non-destructive, and stable separation.

[0026] During implementation, the crossbeam 1 is equipped with lifting points for connecting to lifting equipment. Specifically, crossbeam 1 is a box-shaped beam structure made of high-strength steel with internal reinforcing ribs, capable of withstanding significant stress without deformation or breakage. In actual operation, the lifting points are connected to lifting equipment (such as an overhead crane) within the plant, allowing the entire device to be suspended and precisely positioned above the gearbox assembly to be disassembled. The lifting device includes a lifting ring 18 and two steel wire ropes of equal length. The lifting ring 18 is fixed to crossbeam 1 to suspend the entire device from the overhead crane, ensuring that crossbeam 1 remains horizontal during lifting.

[0027] Drive assembly 2, located in the middle of crossbeam 1, is used to push the shaft 17 to be disassembled. In practice, drive assembly 2 is a hydraulic jack. The cylinder of the hydraulic jack is fixed to the middle of crossbeam 1 by bolts via a mounting base. Its ejector rod abuts against the end of the shaft 16 to be disassembled via an ejector block. The ejector block protects the end face of the shaft 16 and ensures even force transmission from the jack. An electric oil pump is connected to the hydraulic jack via a high-pressure hose. A pressure gauge and control valve assembly are mounted on the electric oil pump. The pressure gauge displays the oil pressure in real time to precisely control the pulling force of the hydraulic jack, and the control valve assembly controls the supply, holding, and release of pressure to the hydraulic jack.

[0028] Positioning rods 3 are set on both sides of the crossbeam 1. The upper parts of the two positioning rods 3 are connected to both sides of the crossbeam 1 via the first pressure sensor 4 and the second pressure sensor 5, respectively. The lower part of the positioning rods 3 is provided with a connecting part, which is used to connect to the process hole of the gear 16.

[0029] This implementation example Figure 5 As shown, cylindrical pressure sensors are symmetrically fixed on both sides of the crossbeam 1. The pressure sensors on both sides are the first pressure sensor 4 and the second pressure sensor 5, respectively. The pressure sensors are fixed on the mounting base, which is fixed on the crossbeam 1. An end cap 31 is provided at the end of the positioning rod 3. The end cap 31 is adapted to press against the detection end of the sensor. Furthermore, a limiting rod can be provided on the end cap 31. The limiting rod is positioned and fitted on the crossbeam 1 or the mounting base of the pressure sensor to ensure the detection effect.

[0030] In a further implementation, two elongated holes can be provided on the crossbeam 1, and the mounting seat can be fitted into the elongated holes and locked by nuts and washers on both sides to fix the position of the mounting seat. This allows for adjustment of the installation spacing of the positioning rod 3 to accommodate large gears 16 of different diameters and improve its applicability.

[0031] In specific implementation, in order to establish a connection between the lower part of the positioning rod 3 and the gear 16, the connecting part in this embodiment includes a limiting sleeve 32, a connecting head 33, and a fixing member 34. The limiting sleeve 32 is fixed to the lower part of the positioning rod 3, and the specific connection method can be welding or threaded connection. Its function is to form a limiting blocking part on the positioning rod 3, which is used to press against the upper surface of the gear 16 and to allow the main body of the positioning rod 3 to pass through the process hole of the gear 16. The connecting head 33 is fixed to the bottom of the positioning rod 3, and the specific fixing method of the connecting head 33 is welding. The fixing member 34 is connected to the connecting head 33 to fix the positioning rod 3 in the process hole. In implementation, the fixing member 34 is a nut and a washer. The bottom of the positioning rod 3 passes through the process hole, and the fixing member 34 is fixed from the lower part of the gear 16. It is fixed to the gear 16 by clamping. At the same time, the washer and the limiting sleeve 32 are used to expand the contact area and improve the stress strength.

[0032] The upper heating cover 6 and the lower heating cover 7 both include a first cover body 8 and a second cover body 9. Electric heating components 10 are provided in both covers, and they are joined together to form an annular heating cover for fastening to the hub of the gear 16. In this embodiment, the heating cover has four half pieces, which are arranged in pairs to form a heating cover. In this embodiment, the heating cover is connected to the upper and lower surfaces of the gear 16 in a combined manner to facilitate assembly and ensure that the hub of the large gear 16 can be sealed in all directions.

[0033] The interior of the heating cover is hollow, and an electric heating component 10 is arranged on the inner wall. The electric heating component, such as an electric heating wire, is fixed to the inner wall of the cover in a serpentine arrangement to ensure that heat radiation can be evenly projected onto the surface of the wheel hub.

[0034] Both the first cover 8 and the second cover 9 have a central hole at their interior center. The diameter of the central hole is slightly larger than the diameter of the shaft 17 to be disassembled, allowing the shaft 17 to pass through. A heat insulation cover 12 extends from the edge of the central hole toward the interior of the cover. The heat insulation cover 12 is made of high-temperature resistant ceramic fiber or aerogel material, has a cylindrical structure, and covers the surface of the shaft 17 to be disassembled. Its function is to prevent heat from being conducted toward the shaft center during heating, thereby increasing the radial temperature difference between the gear 16 and the shaft, improving the thermal expansion difference, and reducing the external force required for disassembly.

[0035] Both sides of the first cover 8 and the second cover 9 are provided with corresponding docking blocks 11, which are arranged in a cross shape with the positioning rod 3. A groove 13 is opened in the middle of the docking block 11, and when the first cover 8 and the second cover 9 are docked, the two docking grooves 13 are joined to form a hollow T-shaped annular groove 14. The shape of the fastener 15 is adapted to the annular groove, and the caps at both ends of the fastener are fitted into the annular groove 14. The main body of the fastener passes through the process hole on the end face of the gear 16, simultaneously pressing and fixing the upper heating cover 6 and the lower heating cover 7 onto the outer circumferential surface of the gear 16 hub. The nuts at the ends of the fastener 15 are tightened to ensure a tight fit between the heating cover and the gear 16 hub, reducing heat loss and ensuring that the heating cover will not shift due to vibration or external force during disassembly.

[0036] The control unit is connected to the first pressure sensor 4, the second pressure sensor 5, the electric heating component 10 and the drive component 2 respectively, and calculates the pressure difference between the first pressure sensor 4 and the second pressure sensor 5. The control unit adjusts the heating power on both sides according to the pressure difference and drives the component 2 to perform disassembly action according to the pressure change rate.

[0037] The heating power is regulated by a power regulation module connected to the electric heating assembly 10. This module is either located inside the control unit or arranged independently. Its input receives the power regulation signal from the control unit, and its output is connected to the electric heating assemblies 10 within each enclosure via high-temperature resistant wires. The power regulation module uses a silicon controlled rectifier (SCR) or a solid-state relay to adjust the effective voltage applied across the resistance wire using phase-shift triggering or zero-crossing triggering, thereby regulating the heating power. The power regulation module uses independent channels to control the four enclosure units. Specifically, the first enclosure 8 of the upper heating enclosure 6, the second enclosure 9 of the upper heating enclosure 6, the first enclosure 8 of the lower heating enclosure 7, and the second enclosure 9 of the lower heating enclosure 7 each correspond to an independent power regulation channel. These four channels are independent of each other. In a further preferred embodiment, each side can be controlled as a separate group. The control unit sends different power regulation commands to the four channels based on the pressure deviation between the first pressure sensor 4 and the second pressure sensor 5, achieving differentiated heating for the left and right sides. When the pressure on the left side is greater than that on the right side, the control unit sends a command to increase the power to the power adjustment channel of the left heating cover. The heating power of the left heating cover increases, the left wheel hub receives more heat and expands further, releasing the stuck stress on that side.

[0038] The control unit acquires the first pressure value from the first pressure sensor 4 and the second pressure value from the second pressure sensor 5 in real time. When the pressure difference between the two exceeds a preset threshold, the control unit increases the heating power of the cover with the larger pressure value or decreases the heating power of the cover with the smaller pressure value. The control unit is connected to the first pressure sensor 4, the second pressure sensor 5, the electric heating assembly 10, and the drive assembly 2. The control unit uses a programmable logic controller or an embedded microprocessor, with a built-in analog-to-digital conversion module and a power regulation module. The control unit reads the pressure values ​​of the first pressure sensor 4 and the second pressure sensor 5 in real time and calculates the pressure difference between them. When the pressure difference exceeds a preset balance threshold, the control unit determines that the device is in an off-center load state. At this time, it adjusts the heating power of the heating covers on both sides according to the direction and magnitude of the pressure difference: if the value of the first pressure sensor 4 is greater than that of the second pressure sensor 5, the control unit increases the power supply of the heating cover on the side where the first pressure sensor 4 is located, so that the hub on that side receives more heat and expands further, releasing the jamming stress on that side, while maintaining or appropriately reducing the power of the heating cover on the other side until the pressure difference between the two sides falls back to within the balance threshold.

[0039] The control unit monitors the pressure drop slope of the two pressure sensors in real time. When the pressure drop slope reaches a preset threshold, the control unit determines that the interference fit is loose and sends a pressurization command. The control unit also monitors the rate of change of the pressure sensor values ​​over time and calculates the pressure drop slope. During heating and pressurization, when the interference fit begins to loosen, the static friction between gear 16 and the shaft transforms into dynamic friction, causing a sudden decrease in the required thrust, and a significant downward trend in the pressure sensor readings. When the control unit detects that the pressure drop slope exceeds the preset loosening threshold, it determines that the interference fit is loose and immediately sends a pressurization command to drive assembly 2. Drive assembly 2 can then perform the disassembly action at a faster speed or with a greater thrust. If, during pressurization, the pressure drop slope does not reach the loosening threshold but the pressure difference continues to expand and exceeds the safety limit threshold, the control unit determines that gear 16 has irreversibly tilted and jammed, immediately issues an alarm signal, and stops the pressurization action of drive assembly 2.

[0040] This embodiment also provides a heat treatment positioning method for disassembling the large gear of an automotive transmission, including the following steps: Step 1: Connect the lifting ring 18 of the crossbeam 1 using the lifting equipment, fix the lower part of the positioning rod 3 to the process hole of the gear 16, and fasten the upper heating cover 6 and the lower heating cover 7 to the hub of the gear 16. Step 2: The drive assembly 2 applies axial thrust to the shaft 17 to be disassembled and establishes an initial pre-tightening state through feedback from the first pressure sensor 4 and the second pressure sensor 5. Step 3: Maintain the pre-tightening pressure and start the electric heating assembly 10 to heat the upper heating cover 6 and the lower heating cover 7 respectively, while collecting the pressure values ​​of the first pressure sensor 4 and the second pressure sensor 5 in real time. Step 4: Calculate the pressure deviation between the two pressure sensors. When the pressure deviation exceeds the preset threshold, adjust the heating power on both sides to reduce the pressure deviation to within the threshold range. Step 5: Calculate the pressure drop slope in real time. When the pressure drop slope reaches the preset loosening threshold, it is determined that the interference fit surface has loosened, and a pressure increase command is sent to the drive component 2. Step 6: Drive component 2 performs the action of pushing the shaft 17 to be disassembled.

[0041] Example 2 This embodiment further increases the displacement detection quantity based on Embodiment 1 to solve the problem that the misalignment state of gear 16 is difficult to directly perceive during disassembly. In the actual operation of disassembling the large gear 16, although the pressure sensor can reflect the force difference of the positioning rods 3 on both sides, when gear 16 tilts slightly, the pressure deviation may be delayed or insensitive due to the high contact stiffness of the interference fit surface. At the same time, relying solely on the pressure signal cannot determine how much actual displacement gear 16 has generated, nor can it distinguish whether the shaft and gear 16 are in a static friction lock state or are sliding smoothly. This embodiment introduces displacement detection, incorporating the axial sliding amount and the sliding deviation on both sides into the control decision, further improving the safety and adaptability of the disassembly process.

[0042] like Figure 10 As shown, in this embodiment, structurally, a top seat 19 is fitted to the end of the shaft 17 to be disassembled. The top seat 19 is cylindrical, and its inner hole is fitted to the end of the shaft 17 to be disassembled. The upper end face of the top seat 19 is in direct contact with the top block of the drive assembly 2, which is used to uniformly transmit the thrust of the drive assembly 2 to the axis of the shaft 17 to be disassembled. Symmetrical ear plates 20 are arranged on both sides of the top seat 19. The ear plates 20 extend horizontally outward, and the upper surface of the ear plates 20 is polished to form a smooth reflective surface or is covered with a highly reflective film, providing a stable measurement reference for the displacement sensor.

[0043] On both sides of the crossbeam 1, a first displacement sensor 21 and a second displacement sensor 22 corresponding to the two ear plates 20 are respectively provided. The displacement sensors are laser displacement sensors or high-precision wire-type displacement sensors, with their measuring ends vertically downward aligned with the upper surface of the ear plate 20, used to obtain the vertical displacement of the ear plate 20 relative to the crossbeam 1 in real time. Since the ear plate 20 is fixedly connected to the shaft 17 to be disassembled through the top seat 19, and there is no relative movement between the top seat 19 and the shaft 17 to be disassembled, the displacement of the ear plate 20 is the actual displacement of the shaft 17 to be disassembled on that side. By comparing the difference in readings of the first displacement sensor 21 and the second displacement sensor 22, it can be accurately determined whether the gear 16 has tilted during the disassembly process: if the displacement on the left side is greater than the displacement on the right side, it means that the left shaft end extends more, the gear 16 has loosened faster on that side, and there may still be local jamming on the right side; the opposite is also true.

[0044] The control unit acquires the first and second displacements of the lugs 20 on both sides of the shaft to be disassembled relative to the crossbeam 1, calculates the displacement deviation between the first and second displacements, and generates an imbalance coefficient by combining the pressure deviation and displacement deviation. The control unit also acquires the displacement values ​​of the first displacement sensor 21 and the second displacement sensor 22 in real time, calculates the displacement deviation, and simultaneously acquires the pressure values ​​of the first pressure sensor 4 and the second pressure sensor 5, calculates the pressure deviation. The control unit weights and fuses the displacement deviation and pressure deviation to generate an imbalance coefficient, which comprehensively characterizes the current degree of off-center loading and skewness of the gear 16.

[0045] Unbalance coefficient The specific calculation formula is as follows: In the formula, and The pressure values ​​of the first pressure sensor 4 and the second pressure sensor 5 are respectively. The average of the two. and These are the displacement values ​​of the first displacement sensor 21 and the second displacement sensor 22, respectively. The preset displacement deviation reference value, and This is a weighting coefficient, which can be determined based on the actual working conditions.

[0046] When the imbalance coefficient is less than or equal to the first balance threshold, the determination device is in a basically aligned state, the gear 16 has no obvious skew or off-center load, the control unit maintains the current power output of each electric heating component 10, maintains the stability of the heating state, and allows the heat to be continuously and evenly conducted to the entire wheel hub mating surface.

[0047] When the imbalance coefficient is greater than the first balance threshold and less than or equal to the second balance threshold, the device is determined to have a moderate degree of off-center loading or skewness. The control unit determines the direction of skewness based on the signs of the pressure deviation and displacement deviation: if the pressure on the left side is greater than the pressure on the right side, or the displacement on the left side is less than the displacement on the right side (indicating that the left side is more tightly stuck), the control unit increases the heating power of the left heating cover to release the stuck stress on that side; at the same time, it maintains or appropriately reduces the power of the right heating cover until the imbalance coefficient falls back to within the first balance threshold.

[0048] When the imbalance coefficient exceeds the second balance threshold, the device is deemed to have experienced severe off-center loading or skewness. Continuing to apply pressure at this point could potentially cause the inner bore of gear 16 to become rough, gear 16 to crack, or the journal to be damaged. The control unit immediately issues a stop command, halting the pressurization of drive assembly 2 and performing pressure relief. Simultaneously, it shuts off the output of all electric heating components 10 and issues an alarm signal via an audible and visual alarm device, prompting the operator to intervene manually.

[0049] This embodiment further introduces the concept of a loosening coefficient, which is used to determine the loosening state of the interference surface and control the pressure application strategy of the drive assembly 2. The control unit acquires the average displacement values ​​of the first displacement sensor 21 and the second displacement sensor 22, as well as the average pressure values ​​of the first pressure sensor 4 and the second pressure sensor 5.

[0050] Obtain the average displacement values ​​of the first and second displacement sensors 22, and the average pressure values ​​of the first and second pressure sensors 5; based on the ratio of the rate of change of the average pressure over time to the initial preload pressure, obtain the stress reduction rate, calculated using the following formula: In the formula, This is the average pressure value from both pressure sensors. This is the initial preload pressure, i.e., the initial pressure value when drive assembly 2 begins to apply thrust. The stress drop rate reflects the rate at which stress is released on the interference fit surface; a higher stress drop rate indicates that the locking state of the mating surface is being rapidly released.

[0051] The slip growth rate is obtained by comparing the rate of change of the mean displacement over time with a preset velocity baseline value; the specific calculation formula is as follows: In the formula, This represents the average displacement value from both displacement sensors. This is a preset standard slip speed reference value. The slip rate increase reflects the axial movement speed of gear 16 relative to the shaft; a higher slip rate increase indicates that gear 16 is exiting rapidly.

[0052] In this embodiment, the loosening coefficient is calculated under the condition that pre-tightening pressure has been established, heating has begun, and displacement has begun to occur. In the initial state before heating and pressure application, the system will not enter the loosening coefficient judgment logic. If the system is completely unresponsive (no stress change, no displacement), it indicates possible incorrect installation, sensor malfunction, or workpiece jamming. In this case, the control unit will directly trigger an alarm through timeout protection or signal anomaly detection, and will not enter the loosening judgment. Based on this, before calculating the loosening coefficient, the control unit first determines whether the following conditions are simultaneously met: stress reduction rate is greater than or equal to the minimum stress reduction rate threshold, slip growth rate is greater than or equal to the minimum slip growth rate threshold, average displacement is greater than or equal to the minimum displacement threshold, and average pressure is greater than or equal to the minimum pressure threshold. Only when all the above conditions are met will the control unit calculate the loosening coefficient and use it for judgment during the disassembly stage; otherwise, the control unit will not use the loosening coefficient for control and may trigger an alarm signal based on the duration. In this embodiment, the minimum stress decrease rate threshold and the minimum slip growth rate threshold are both set to be less than or equal to the instantaneous noise filtering threshold when the sensor just begins to experience micro-loosening and slippage in the system. These thresholds are used to filter out absolutely static states, sensor disconnections, and dead metal jamming conditions.

[0053] The loosening coefficient is obtained by calculating the reciprocal of the product of the stress drop rate and the slip growth rate; the calculation formula is: ε is a very small positive number used to prevent division by zero errors. From this formula, it can be seen that when the stress reduction rate is high and the slip growth rate is low, meaning the pressure is rapidly decreasing while gear 16 has not yet moved significantly, the loosening coefficient is relatively large, indicating that the interference fit is at a critical breakthrough stage of transitioning from static friction to dynamic friction. When both the stress reduction rate and the slip growth rate are at a moderate level, the loosening coefficient is in the middle range. When the slip growth rate is high, meaning gear 16 is rapidly sliding out, the loosening coefficient is relatively small, indicating that the interference fit has been basically released.

[0054] When the loosening coefficient exceeds the first loosening threshold, the interference surface is determined to be in a critical breakthrough state. The control unit controls the drive assembly 2 to maintain the current pressure for heating, keeping the heating power and pushing force constant, allowing the heat to be fully conducted to the entire mating surface, so that the stress is released naturally.

[0055] When the loosening coefficient is less than or equal to the first loosening threshold and greater than the second loosening threshold, it is determined that the interference surface has initially loosened and entered the stable sliding stage. The control unit controls the drive component 2 to perform pre-pressurization, that is, to increase the thrust in a slow and incremental manner, so that the gear 16 slides out at a smooth and controllable speed, avoiding impact caused by sudden speed changes.

[0056] When the loosening coefficient is less than or equal to the second loosening threshold, it is determined that the interference fit has been basically released, and gear 16 is in a free sliding state. The control unit controls the drive component 2 to switch to high-frequency pulse boosting mode, that is, to apply a series of small-amplitude, high-frequency pulse thrusts in a short period of time. The amplitude of each pulse is about 20% to 30% of the rated thrust, and the frequency is 2Hz to 5Hz. High-frequency pulse boosting can effectively overcome the stick-slip phenomenon during the sliding process, allowing gear 16 to complete the final separation with a lower peak thrust, while avoiding sudden bouncing of gear 16 at the moment of separation from the shaft end.

[0057] By introducing displacement detection and implementing a graded control strategy for imbalance coefficient and loosening coefficient, this embodiment further enhances the safety and adaptability of the disassembly process based on Embodiment 1.

[0058] The embodiments of the present invention described above do not constitute a limitation on the scope of protection of the present invention. The basic concept of the present invention is to monitor the force deviation of the positioning rods 3 on both sides in real time through pressure sensors, and adjust the heating power of the heating cover on the corresponding side according to the deviation to correct the unevenness of the thermal expansion of the wheel hub. At the same time, it automatically identifies the loose state of the interference surface according to the pressure change rate and triggers the drive component 2 to act, thereby realizing the non-destructive and adaptive disassembly of the large gear 16 and the shaft. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A heat treatment positioning device for disassembling the large gear of an automotive transmission, characterized in that: include, The crossbeam is equipped with lifting points for connecting lifting equipment; The drive assembly, located in the middle of the crossbeam, is used to push the shaft to be disassembled. Positioning rods are set on both sides of the crossbeam. The upper parts of the two positioning rods are connected to both sides of the crossbeam via a first pressure sensor and a second pressure sensor, respectively. The lower part of the positioning rods is provided with a connecting part, which is used to connect to the process hole of the gear. The upper heating cover and the lower heating cover both include a first cover body and a second cover body. Electric heating components are provided in both covers body and are connected together to form an annular heating cover for fastening to the gear hub. The control unit is connected to the first pressure sensor, the second pressure sensor, the electric heating component, and the drive component, respectively. It calculates the pressure difference between the first and second pressure sensors, adjusts the heating power on both sides according to the pressure difference, and drives the component to perform a disassembly action according to the pressure change rate.

2. The heat treatment positioning device for disassembling the large gear of an automotive transmission according to claim 1, characterized in that: The connecting part includes a limiting sleeve, a connector, and a fixing member. The limiting sleeve is fixed to the lower part of the positioning rod, the connector is fixed to the bottom of the positioning rod, and the fixing member is connected to the connector to fix the positioning rod in the process hole.

3. The heat treatment positioning device for disassembling the large gear of an automotive transmission according to claim 1, characterized in that: Both sides of the first and second covers are provided with corresponding docking blocks, and the middle of the docking blocks is provided with corresponding docking grooves. The two docking grooves are spliced ​​together to form a hollow annular groove. Fasteners are fitted into the annular groove and pass through the process hole to fasten the heating covers on the upper and lower sides to the hub of the gear.

4. The heat treatment positioning device for disassembling the large gear of an automotive transmission according to claim 1, characterized in that: Both the first and second covers have a central hole at their interior center, and a heat insulation cover extends from the edge of the central hole into the cover body to maintain the radial temperature gradient between the shaft to be disassembled and the gear hub during the heating process.

5. The heat treatment positioning device for disassembling the large gear of an automotive transmission according to claim 1, characterized in that: The first pressure value of the first pressure sensor and the second pressure value of the second pressure sensor are acquired in real time. When the pressure difference between the two exceeds a preset threshold, the control unit increases the heating power of the cover with the larger pressure value or decreases the heating power of the cover with the smaller pressure value.

6. The heat treatment positioning device for disassembling the large gear of an automotive transmission according to claim 5, characterized in that: The pressure drop slope of the two pressure sensors is monitored in real time; when the pressure drop slope reaches the preset threshold, the control unit determines that the interference surface is loose and sends a command to allow pressure increase.

7. The heat treatment positioning device for disassembling the large gear of an automotive transmission according to claim 1, characterized in that: A top seat is fitted to the end of the shaft to be disassembled, and ear plates are provided on both sides of the top seat. A first displacement sensor and a second displacement sensor corresponding to the ear plates are respectively provided on both sides of the crossbeam. The first displacement sensor and the second displacement sensor are used to obtain the displacement of the two sides of the shaft to be disassembled relative to the crossbeam.

8. The heat treatment positioning device for disassembling the large gear of an automotive transmission according to claim 7, characterized in that: The first and second displacements of the lugs on both sides of the shaft to be disassembled relative to the crossbeam are obtained. The displacement deviation between the first and second displacements is calculated. Combined with the pressure deviation and displacement deviation, an imbalance coefficient is generated. When the imbalance coefficient is less than or equal to the first balance threshold, the power output of each electric heating component is maintained. When the imbalance coefficient is greater than the first balance threshold and less than or equal to the second balance threshold, the heating power of the side with the larger pressure value or the smaller displacement value is increased. When the imbalance coefficient is greater than the second balance threshold, the drive component is controlled to stop pressurizing and perform pressure relief, while the heating is turned off and an alarm signal is issued.

9. The heat treatment positioning device for disassembling the large gear of an automotive transmission according to claim 8, characterized in that: Obtain the average displacement values ​​of the first and second displacement sensors, and the average pressure values ​​of the first and second pressure sensors; obtain the stress reduction rate based on the ratio of the rate of change of the average pressure over time to the initial preload pressure; obtain the slip growth rate based on the ratio of the rate of change of the average displacement over time to the preset speed reference value. The loosening coefficient is obtained by calculating the reciprocal of the product of the stress reduction rate and the slip growth rate. When the loosening coefficient is greater than the first loosening threshold, the drive component is controlled to maintain the current pressure. When the loosening coefficient is less than or equal to the first loosening threshold and greater than the second loosening threshold, the drive component is controlled to perform pre-pressurization. When the loosening coefficient is less than or equal to the second loosening threshold, the drive component is controlled to switch to high-frequency pulse pressurization mode.

10. A heat treatment positioning method for disassembling the large gear of an automotive transmission, applied to the apparatus described in any one of claims 1 to 9, characterized in that, Includes the following steps: Step 1: Connect the lifting ring of the crossbeam using the lifting equipment, fix the lower part of the positioning rod to the process hole of the gear, and fasten the upper heating cover and lower heating cover to the hub of the gear. Step 2: The drive assembly applies axial thrust to the shaft to be disassembled and establishes an initial preload state through feedback from the first pressure sensor and the second pressure sensor. Step 3: Maintain the pre-tightening pressure and start the electric heating assembly to heat the upper heating cover and the lower heating cover respectively, while collecting the pressure values ​​of the first pressure sensor and the second pressure sensor in real time. Step 4: Calculate the pressure deviation between the two pressure sensors. When the pressure deviation exceeds the preset threshold, adjust the heating power on both sides to reduce the pressure deviation to within the threshold range. Step 5: Calculate the pressure drop slope in real time. When the pressure drop slope reaches the preset loosening threshold, it is determined that the interference fit surface has loosened, and a pressure increase command is sent to the drive component. Step 6: The drive component performs the action of pushing the shaft to be disassembled.

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