A spiral wedge sliding bearing and a method of manufacturing the same

Abstract

This invention discloses a transformer oil pump technology, aiming to provide a helical wedge-shaped sliding bearing and its manufacturing method. The key technical points include a bearing bush housed within a bearing housing and a journal housed within the bearing bush and connected to a motor rotor and impeller assembly, used to reduce vibration and noise during transformer oil pump operation through hydraulic suspension. The inner surface of the bearing bush has a helical wedge-shaped groove extending axially along the bearing bush, with the helical direction matching the rotation direction of the motor rotor. The inner surface of the bearing bush also has several guide grooves arranged in a ring array along the central axis. The groove depth H and groove width W of the helical wedge-shaped groove are gradually varied axially, forming a converging wedge-shaped space with an inlet end larger than the outlet end, allowing transformer oil to form a dynamic pressure oil film within the wedge-shaped space during bearing operation. This invention is applicable to the field of transformer oil pump technology.

Description

Technical Field

[0001] This invention relates to a transformer oil pump technology, and more specifically, to a spiral wedge-shaped sliding bearing and its manufacturing method. Background Technology

[0002] The transformer oil pump is a key component of the transformer cooling system. Its function is to drive the circulation of transformer oil, ensuring stable operation of the transformer at a suitable temperature. During the operation of the transformer oil pump, the support and lubrication of the motor rotor and impeller assembly are crucial.

[0003] Traditional transformer oil pumps typically use rolling bearings to support the motor rotor and impeller assembly. However, rolling bearings suffer from high friction, easy wear, and severe heat generation, which not only increases pump vibration and noise but also shortens the service life of both the bearings and the pump. Furthermore, during high-speed operation, the contact stress between the internal balls and raceways of rolling bearings is significant, making them prone to fatigue damage and further impacting pump reliability.

[0004] While existing sliding bearings can reduce friction and wear to some extent, they still fall short in achieving hydraulic suspension and reducing vibration and noise. Therefore, a new type of sliding bearing is urgently needed to solve the problems existing in the bearings of current transformer oil pumps. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a spiral wedge-shaped sliding bearing for transformer oil pumps and its manufacturing method.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a spiral wedge-shaped sliding bearing, comprising a bearing bush disposed within a bearing housing and a journal disposed within the bearing bush and connected to a motor rotor and impeller assembly, used to reduce vibration and noise through hydraulic suspension during transformer oil pump operation;

[0007] The inner surface of the bearing bush is provided with a spiral wedge-shaped groove, which extends along the axial direction of the bearing bush and the spiral direction matches the rotation direction of the motor rotor; the inner surface of the bearing bush is also provided with a number of guide grooves arranged in a ring array along the central axis.

[0008] The spiral wedge groove has a gradually changing groove depth H and groove width W along the axial direction, forming a converging wedge space with the inlet end larger than the outlet end, so that the transformer oil forms a dynamic pressure oil film in the wedge space when the bearing is working.

[0009] The radial clearance δ between the journal and the bearing is configured such that when the journal speed reaches the rated threshold, the hydraulic pressure generated by the hydrodynamic oil film drives the motor rotor and impeller assembly to achieve hydrodynamic suspension.

[0010] The present invention is further configured such that the helix angle α of the spiral wedge groove satisfies tanα=pitch / (π×bearing inner diameter), and the value of α is in the range of 6°-8°.

[0011] The present invention is further configured such that the ratio of the inlet end groove depth H1 to the outlet end groove depth H2 of the spiral wedge groove is 1.8-2.2:1.

[0012] The present invention is further configured such that the ratio of the radial clearance δ to the journal diameter is 0.0008-0.0012.

[0013] The present invention is further configured such that the total cross-sectional area of ​​the oil inlet of the bearing housing is 1.5-2 times the cross-sectional area of ​​the inlet end of the spiral wedge groove.

[0014] A method for manufacturing a helical wedge-shaped sliding bearing, characterized by comprising the following steps:

[0015] S1. Pre-treatment and preparation of bearing blanks:

[0016] Select copper-based alloy billets for stress-relief annealing, and control the annealing temperature at 30-50°C above the material recrystallization temperature; at the same time, prepare the testing equipment required for the manufacturing process.

[0017] S2, Rough machining and forming:

[0018] The outer diameter and inner hole of the bearing bush are machined on a CNC lathe, with a 0.5mm finishing allowance for the inner hole. Then, the roundness error of the inner hole is checked by a laser diameter gauge. If the error is >0.05mm, return to S1 for re-annealing; if it is ≤0.05mm, go to S3.

[0019] S3, Precision milling of spiral grooves:

[0020] Using CNC machine tools, the guide groove is first machined, and then the helical interpolation program is generated based on the pitch in the design requirements.

[0021] Use an R-angle ball end mill to mill a spiral wedge groove along the inner surface of the bearing bush. The groove depth decreases linearly from the inlet depth H1 to the outlet depth H2, and the groove width converges linearly from the inlet width W1 to the outlet width W2.

[0022] The online surface profiler is activated to collect groove depth and width data in real time and compare them with the theoretical gradient curve. If the deviation at any measurement point is greater than 8% of the theoretical value, the tool compensation module is triggered. If the deviation still exceeds the tolerance after compensation, the blank is scrapped. If the deviation is ≤8% throughout the process, the process switches to S4.

[0023] S4. Hydraulic polishing treatment:

[0024] The bearing bush was immersed in transformer oil containing nano-abrasives and polished by rotating at 200 r / min for 40 min.

[0025] S5, Heat Treatment Strengthening:

[0026] Surface sulfurizing treatment is carried out in a protective atmosphere furnace, and the sulfurized layer depth is 15-20μm.

[0027] The depth of the sulfur-permeable layer is detected by glow discharge spectroscopy. If the depth of the sulfur-permeable layer is <15μm, return to S5 to extend the processing time; if the depth of the sulfur-permeable layer is >20μm, perform plasma thinning treatment to the acceptable range; if 15μm≤sulfur-permeable layer depth≤20μm, proceed to S6.

[0028] S6. Fine grinding of the inner hole:

[0029] The inner hole of the bearing bush is ground to the final dimensional accuracy using a CBN grinding wheel, with a surface roughness Ra≤0.2μm;

[0030] S7. Dynamic pressure performance simulation verification:

[0031] Import the 3D model of the bearing bush into the fluid dynamics simulation software, set the transformer oil viscosity to 40-50 cSt and the journal speed to 1500-3000 r / min; calculate the oil film pressure distribution and load-bearing capacity curves under different operating conditions.

[0032] If the simulation shows that the minimum oil film thickness is <5μm or the maximum pressure is >50MPa, then return to S3 to adjust the convergence ratio of the spiral wedge groove; if the critical speed of hydraulic suspension is >120% of the rated speed, then scrap it; if it meets the standard, then go to S8.

[0033] S8, journal machining and overall assembly:

[0034] The journal is machined according to the design requirements. Then the journal and the bearing bush are assembled into a bearing. Next, the bearing is pressed into the inner hole of the bearing housing. The interference fit is controlled at 0.03%-0.05% of the outer diameter of the bearing bush.

[0035] S9, Dynamic Grinding and Finishing:

[0036] The installed bearing is tested on a dedicated test bench. It is run at 2000 rpm without load. Transformer oil at 40℃ is injected into the oil inlet of the bearing housing, and the oil outlet flow rate Q is measured. If the measured flow rate Q > 1.2Q0, the bearing is marked as unqualified. If 0.8Q0 ≤ Q ≤ 1.2Q0, turn to S10.

[0037] S10, Running-in Test:

[0038] The test bench was operated in a stepped speed-increasing manner, with each speed increment maintained for 10 minutes. Vibration acceleration values ​​were monitored throughout the process. If the vibration value was >4.5 mm / s at 80% of the rated speed, the spiral wedge groove surface defects were inspected. If the oil temperature rise was >35 K at 100% of the rated speed, the test bench was returned to S4 to increase the polishing time. If no abnormalities were found throughout the test, the test bench was moved to S11.

[0039] S11. Finished product inspection and packaging:

[0040] The key dimensions are re-measured using a coordinate measuring machine, and after passing the inspection, they are coated with anti-rust oil and sealed.

[0041] The present invention is further configured such that, in step S3, the gradient change rate K1 of the linearly decreasing groove depth satisfies: K1=(H1-H2) / L, where L is the bearing length, and the value range of K1 is 0.15-0.25mm / 100mm.

[0042] The present invention is further configured such that, in step S7, the spiral groove convergence ratio adjustment is specifically as follows: when the minimum oil film thickness is insufficient, the H1 / H2 ratio is increased to the upper limit of 2.2; when the pressure exceeds the limit, the W1 / W2 ratio is reduced to 1.5.

[0043] The present invention is further configured such that, in step S6, the ratio of the feed rate F of the fine grinding inner hole to the linear velocity V of the grinding wheel satisfies: F / V=0.08-0.12μm / (m·min).

[0044] The present invention is further configured such that: in S10, the step difference of the step speed increase is 15% of the rated speed, and the oil temperature rise threshold at each speed level is calculated according to ΔT=0.8n×35K, where n is the current level.

[0045] The beneficial effects of this invention are:

[0046] 1. Compared with existing technologies, the spiral wedge sliding bearing of this invention solves the vibration and noise problems of transformer oil pump operation by designing a spiral wedge groove and its gradual change along the axial direction. The spiral wedge groove and guide groove opened on the inner surface of the bearing not only help to improve the formation of oil film, but also effectively reduce mechanical friction and vibration. The gradual convergence structure of the spiral wedge groove forces the formation of a unidirectional oil film pressurization effect, so that the transformer oil is squeezed and pressurized along the rotation direction, significantly improving the dynamic pressure oil film bearing capacity. Through the hydraulic suspension effect, the bearing achieves lower energy consumption and longer service life during operation, effectively reducing solid contact friction and significantly reducing vibration and noise during oil pump operation. Compared with traditional bearings, this design can effectively reduce maintenance costs and extend the service life of the bearing, thereby improving the working efficiency and stability of the transformer oil pump.

[0047] 2. In the spiral wedge sliding bearing of the present invention, the spiral helix angle α is limited to 6°-8°, which is the optimal balance point between lubrication efficiency and load-bearing capacity. When α < 6°, the oil guiding capacity of the spiral wedge groove is weakened, the oil film formation is delayed, and boundary friction is prone to occur during the start-up stage, accelerating the wear of the bearing. When α > 8°, the axial leakage of transformer oil is aggravated, the dynamic pressure effect is weakened, resulting in insufficient suspension force and excessive temperature rise. Therefore, a spiral helix angle of 6°-8° is preferred so that the transformer oil can form a stable laminar flow under the action of centrifugal force and viscous drag force, shortening the oil film establishment time and avoiding collapse in the high-voltage area.

[0048] 3. In this invention, the manufacturing method precisely controls the linear decreasing gradient change rate K1 of the spiral wedge groove depth, which helps to ensure the uniformity and stability of the oil film in the bearing. By adjusting the gradient change rate, the bearing's load-bearing capacity and friction performance can be optimized according to different working conditions, thereby achieving the best hydraulic suspension effect. This control method effectively improves the service life of the bearing and optimizes the working efficiency of the transformer oil pump, and has significant engineering application value.

[0049] 4. The present invention has a simple and reasonable structure, is easy to manufacture and operate, avoids the defects of the prior art, and is suitable for promotion and application. Attached Figure Description

[0050] Figure 1 This is a structural diagram of the spiral wedge-shaped sliding bearing of the present invention.

[0051] Figure 2 This is a structural diagram of the bearing bush in the spiral wedge-shaped sliding bearing of the present invention.

[0052] Figure 3 This is a structural diagram of the journal in the spiral wedge-shaped sliding bearing of the present invention.

[0053] Figure 1-3 Reference numerals: 1. Bearing bush; 2. Journal; 3. Spiral wedge groove; 4. Guide groove. Detailed Implementation

[0054] Reference Figure 1-3 The embodiments of the spiral structure wedge sliding bearing and its manufacturing method of the present invention are further described below.

[0055] For ease of explanation, spatial relative terms such as “up,” “down,” “left,” and “right” are used in the embodiments to describe the relationship of one element or feature shown in the figures relative to another element or feature. It should be understood that, in addition to the orientations shown in the figures, spatial terms are intended to include different orientations of the device in use or operation. For example, if the device in the figures is inverted, an element described as being “down” of other elements or features would be positioned “up” of those other elements or features. Therefore, the exemplary term “down” can encompass both up and down orientations. The device may be positioned in other ways (rotated 90 degrees or in other orientations), and the spatial relative descriptions used herein will be interpreted accordingly.

[0056] Moreover, relational terms such as “first” and “second” are used merely to distinguish one component from another that has the same name, without necessarily requiring or implying any such actual relationship or order between the components.

[0057] Figures 1 to 3 The spiral wedge sliding bearing shown includes a bearing shell 1 disposed in a bearing housing and a journal 2 disposed in the bearing shell 1 and connected to the motor rotor and impeller assembly, which is used to reduce vibration and noise by hydraulic suspension during the operation of the transformer oil pump.

[0058] The inner surface of the bearing bush 1 is provided with a spiral wedge-shaped groove 3, which extends along the axial direction of the bearing bush 1 and the spiral direction matches the rotation direction of the motor rotor; the inner surface of the bearing bush 1 is also provided with a number of guide grooves 4 arranged in a ring array along the central axis; wherein, the number of guide grooves 4 is 6-8.

[0059] The spiral wedge groove 3 has a groove depth H and groove width W that are gradually changed along the axial direction, forming a converging wedge space with the inlet end larger than the outlet end, so that when the bearing is working, the transformer oil forms a dynamic pressure oil film in the wedge space.

[0060] The radial clearance δ between the journal 2 and the bearing 1 is configured such that when the journal 2 reaches the rated threshold speed, the hydraulic pressure generated by the hydrodynamic oil film pushes the motor rotor and impeller assembly to achieve hydraulic suspension; the pitch of the spiral wedge groove 3 is 17mm, which is configured to generate an axial pressure gradient through the viscous resistance of the transformer oil during oil pump operation; this pitch value has been theoretically calculated and experimentally verified, and can reduce oil leakage and improve the bearing's load-bearing capacity and lubrication effect while ensuring oil film formation;

[0061] The bearing housing is provided with an oil inlet and an oil outlet that connect to the spiral wedge groove 3. The oil inlet is connected to the oil supply system of the transformer oil pump to ensure that the spiral wedge groove 3 is always full of transformer oil. The oil outlet is used to discharge the transformer oil after use, forming a circulating lubrication system. During the circulation process, the lubricating oil can also carry away the heat generated by the bearing, play a cooling role, and extend the service life of the bearing.

[0062] By designing the spiral wedge groove 3 and its axial gradient design, the vibration and noise problems during transformer oil pump operation are solved. The spiral wedge groove 3 and guide groove 4 opened on the inner surface of the bearing bush 1 not only help improve the formation of oil film, but also effectively reduce mechanical friction and vibration. The gradient convergent structure of the spiral wedge groove 3 forces the formation of a unidirectional oil film pressurization effect, so that the transformer oil is squeezed and pressurized along the rotation direction, significantly improving the dynamic pressure oil film bearing capacity. Through the hydraulic suspension effect, the bearing achieves lower energy consumption and longer service life during operation, effectively reducing solid contact friction and significantly reducing vibration and noise during oil pump operation. Compared with traditional bearings, this design can effectively reduce maintenance costs and extend the service life of bearings, thereby improving the working efficiency and stability of transformer oil pump. In addition, the function of the guide groove 4 is: 1. It can relieve pressure. When the pressure of the spiral wedge groove 3 is too high, the transformer oil can flow out through the guide groove 4 to relieve pressure; 2. When the bearing is not rotating, the transformer oil can enter to form a partial oil film.

[0063] The helix angle α of the spiral wedge groove 3 satisfies tanα=pitch / (π×inner diameter of bearing 1), and the value of α is in the range of 6°-8°;

[0064] A helix angle α of 6°-8° represents the optimal balance between lubrication efficiency and load-bearing capacity. When α < 6°, the oil guiding capacity of the helical wedge groove 3 weakens, oil film formation is delayed, boundary friction is prone to occur during the start-up phase, and the wear of the bearing 1 is accelerated. When α > 8°, axial leakage of transformer oil intensifies, the dynamic pressure effect weakens, resulting in insufficient levitation force and excessive temperature rise. Therefore, a helix angle of 6°-8° is preferred to enable transformer oil to form a stable laminar flow under the action of centrifugal force and viscous drag force, shorten the oil film establishment time, and avoid collapse in the high-voltage area.

[0065] The ratio of the inlet end groove depth H1 to the outlet end groove depth H2 of the spiral wedge groove 3 is 1.8-2.2:1;

[0066] When the ratio is <1.8, the continuity of the oil film is easily disrupted under high-speed conditions, leading to cavitation vibration. When the ratio is >2.2, the outlet throttling effect is too strong, the shear heat of the oil film increases dramatically, resulting in viscosity deterioration and the risk of galling. This ratio makes the oil film pressure increase linearly from the inlet to the outlet, with the maximum pressure gradient located in the middle of the bearing, perfectly matching the rotor load distribution, improving the uniformity of the load-bearing capacity, avoiding micro-pitting caused by edge stress concentration, and enabling the bearing to provide better hydraulic suspension effect under different operating conditions, reducing the risk of oil film rupture, and maintaining stable load-bearing capacity at higher speeds.

[0067] The ratio of the radial clearance δ to the diameter of the journal 2 is 0.0008-0.0012;

[0068] When the ratio is less than 0.0008, the thermal expansion tolerance is insufficient, the gap disappears during high-temperature operation, and a bearing seizure accident occurs. When the ratio is greater than 0.0012, the transformer oil leakage exceeds the standard, the dynamic pressure effect is difficult to establish, and the suspension failure speed increases. This ratio range ensures that the pressure distribution of the oil film formation is uniform, which can effectively reduce friction loss without causing insufficient hydraulic suspension due to excessive gap. It achieves the effect of both ensuring hydraulic suspension and effectively preventing transformer oil leakage.

[0069] The total cross-sectional area of ​​the oil inlet of the bearing housing is 1.5-2 times the cross-sectional area of ​​the inlet end of the spiral wedge groove 3;

[0070] It can ensure sufficient supply of transformer oil flow and guarantee the stability of the oil film; with a larger inlet cross-sectional area design, the bearing can more effectively maintain the uniformity of the oil film, reduce friction and wear caused by oil film instability, and thus extend the service life of the equipment; this design plays an important role in improving the overall performance of transformer oil pump, increasing load-bearing capacity and preventing failures.

[0071] A method for manufacturing a helical wedge-shaped sliding bearing, characterized by comprising the following steps:

[0072] S1. Pre-treatment and preparation of bearing shell 1 blank:

[0073] Select copper-based alloy billets for stress-relief annealing, and control the annealing temperature at 30-50°C above the material recrystallization temperature; at the same time, prepare the testing equipment required for the manufacturing process.

[0074] S2, Rough machining and forming:

[0075] The outer diameter and inner hole of the bearing bush 1 are machined on a CNC lathe, with a 0.5mm finishing allowance for the inner hole. Then, the roundness error of the inner hole is checked by a laser diameter gauge. If the error is >0.05mm, return to S1 for re-annealing; if it is ≤0.05mm, go to S3.

[0076] S3, Precision milling of spiral grooves:

[0077] Using a CNC machine tool, the guide groove 4 is first machined, and then the helical interpolation program is generated based on the pitch in the design requirements.

[0078] Using an R-angle ball end mill, a spiral wedge groove 3 is milled along the inner surface of the bearing bush 1. The groove depth decreases linearly from the inlet depth H1 to the outlet depth H2, and the groove width converges linearly from the inlet width W1 to the outlet width W2.

[0079] The online surface profiler is activated to collect groove depth and width data in real time and compare them with the theoretical gradient curve. If the deviation at any measurement point is greater than 8% of the theoretical value, the tool compensation module is triggered. If the deviation still exceeds the tolerance after compensation, the blank is scrapped. If the deviation is ≤8% throughout the process, the process switches to S4.

[0080] S4. Hydraulic polishing treatment:

[0081] The bearing bush 1 was immersed in transformer oil containing nano-abrasives and polished by rotating at 200 r / min for 40 min.

[0082] S5, Heat Treatment Strengthening:

[0083] Surface sulfurizing treatment is carried out in a protective atmosphere furnace, and the sulfurized layer depth is 15-20μm.

[0084] The depth of the sulfur-permeable layer is detected by glow discharge spectroscopy. If the depth of the sulfur-permeable layer is <15μm, return to S5 to extend the processing time; if the depth of the sulfur-permeable layer is >20μm, perform plasma thinning treatment to the acceptable range; if 15μm≤sulfur-permeable layer depth≤20μm, proceed to S6.

[0085] S6. Fine grinding of the inner hole:

[0086] The inner hole of bearing bush 1 was ground to the final dimensional accuracy using a CBN grinding wheel, with a surface roughness Ra≤0.2μm;

[0087] S7. Dynamic pressure performance simulation verification:

[0088] Import the 3D model of bearing bush 1 into the fluid dynamics simulation software, set the transformer oil viscosity to 40-50 cSt and the journal 2 rotation speed to 1500-3000 r / min; calculate the oil film pressure distribution and load-bearing capacity curves under different operating conditions;

[0089] If the simulation shows that the minimum oil film thickness is <5μm or the maximum pressure is >50MPa, then return to S3 to adjust the convergence ratio of the spiral wedge groove 3; if the critical speed of hydraulic suspension is >120% of the rated speed, then scrap it; if it meets the standard, then go to S8.

[0090] Machining of S8 and journal 2, and overall assembly:

[0091] The journal 2 is machined according to the design requirements. Then the journal 2 and the bearing shell 1 are assembled into a bearing. Next, the bearing is pressed into the inner hole of the bearing housing. The interference fit is controlled at 0.03%-0.05% of the outer diameter of the bearing shell 1.

[0092] S9, Dynamic Grinding and Finishing:

[0093] The installed bearing is tested on a dedicated test bench. It is run at 2000 rpm without load. Transformer oil at 40℃ is injected into the oil inlet of the bearing housing, and the oil outlet flow rate Q is measured. If the measured flow rate Q > 1.2Q0, the bearing is marked as unqualified. If 0.8Q0 ≤ Q ≤ 1.2Q0, turn to S10.

[0094] S10, Running-in Test:

[0095] The test bench was operated in a stepped speed-increasing manner, with each speed increment maintained for 10 minutes. Vibration acceleration values ​​were monitored throughout the process. If the vibration value was >4.5 mm / s at 80% of the rated speed, the spiral wedge groove 3 was disassembled and inspected for surface defects. If the oil temperature rise was >35 K at 100% of the rated speed, the test bench was returned to S4 to increase the polishing time. If no abnormalities were found throughout the test, the test bench was moved to S11.

[0096] S11. Finished product inspection and packaging:

[0097] Key dimensions were re-measured using a coordinate measuring machine, and after passing the inspection, anti-rust oil was applied and the parts were sealed.

[0098] By employing precise CNC turning, laser inspection, and spiral groove precision milling techniques, the accuracy and quality of bearing bush 1 are ensured. During the manufacturing process, real-time online detection and adjustment are used to avoid deviations in production, ensuring product consistency and stability. This highly precise manufacturing method not only improves production efficiency but also guarantees the high quality of each product, reduces rework and losses caused by production errors, and enhances the company's production efficiency and profitability.

[0099] In S3, the gradient change rate K1 of the linearly decreasing groove depth satisfies: K1=(H1-H2) / L, where L is the length of bearing 1, and the value range of K1 is 0.15-0.25mm / 100mm;

[0100] This method precisely controls the linear decreasing gradient change rate K1 of the spiral wedge groove depth 3, which helps to ensure the uniformity and stability of the oil film in the bearing. By adjusting the gradient change rate, the bearing's load-bearing capacity and friction performance can be optimized according to different operating conditions, thereby achieving the best hydraulic suspension effect. This control method effectively improves the service life of the bearing and optimizes the working efficiency of the transformer oil pump, and has significant engineering application value.

[0101] In step S7, the adjustment of the spiral groove convergence ratio is specifically as follows: when the minimum oil film thickness is insufficient, the H1 / H2 ratio is increased to the upper limit of 2.2; when the pressure exceeds the limit, the W1 / W2 ratio is reduced to 1.5.

[0102] By adjusting the convergence ratio of the spiral groove, it is ensured that different oil film thicknesses and oil film pressure distributions can be addressed in actual operation. By adjusting according to actual working conditions, the formation of the oil film can be optimized without affecting the stability of the bearing, ensuring that the bearing achieves the best hydraulic suspension effect during operation. This adjustable design greatly enhances the adaptability of the bearing in complex environments and improves the reliability and operating efficiency of the equipment.

[0103] In S6, the ratio of the feed rate F of the fine grinding inner hole to the linear velocity V of the grinding wheel satisfies: F / V=0.08-0.12μm / (m·min);

[0104] The precise control of the feed rate and grinding wheel speed in the fine grinding of the inner hole helps to achieve high-precision machining of the inner hole, ensuring that the inner surface of the bearing bush 1 reaches the optimal surface roughness; the fine inner hole machining ensures the maximization of the hydraulic suspension effect and reduces friction and vibration caused by surface unevenness; this finishing process can effectively improve the performance of the bearing, reduce bearing wear, and extend the service life of the transformer oil pump.

[0105] In S10, the step difference of the speed increase is 15% of the rated speed, and the oil temperature rise threshold at each speed level is calculated as ΔT = 0.8n × 35K, where n is the current level.

[0106] The stepped speed-increase test method simulates the vibration and oil temperature changes of a transformer oil pump under different operating conditions, ensuring the stability and reliability of the bearings in actual operation. By monitoring vibration acceleration and oil temperature changes, potential problems can be identified and adjusted in a timely manner, thereby ensuring that each bearing can operate stably under high load and high speed. This test method effectively prevents potential failures and improves the safety of bearing use and the overall performance of the transformer oil pump.

[0107] The bearing principle:

[0108] In the lubrication mechanism of the sliding bearing, transformer oil with a certain pressure is delivered to the friction pair surfaces (i.e., between the bearing bush 1 and the journal 2) to form an oil film with a specific thickness and rigidity, which completely separates the two surfaces and achieves a liquid friction state; the rotation of the journal 2 drives the transformer oil to flow in the spiral wedge groove 3.

[0109] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any ordinary changes and substitutions made by those skilled in the art within the scope of the technical solution of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for manufacturing a helical wedge-shaped sliding bearing, characterized in that: Includes a bearing shell (1) disposed in the bearing housing and a journal (2) disposed in the bearing shell (1) and connected to the motor rotor and impeller assembly, used to reduce vibration and noise by hydraulic suspension during the operation of the transformer oil pump; The inner surface of the bearing bush (1) is provided with a spiral wedge groove (3), which extends along the axial direction of the bearing bush (1) and the spiral direction matches the rotation direction of the motor rotor; the inner surface of the bearing bush (1) is also provided with a number of guide grooves (4) arranged in a ring array along the central axis. The groove depth H and groove width W of the spiral wedge groove (3) are gradually designed along the axial direction to form a converging wedge space with the inlet end larger than the outlet end, so that the transformer oil forms a dynamic pressure oil film in the wedge space when the bearing is working. The radial clearance δ between the journal (2) and the bearing (1) is configured such that when the journal (2) reaches the rated threshold speed, the hydraulic pressure generated by the hydrodynamic oil film drives the motor rotor and impeller assembly to achieve hydraulic suspension. Its manufacturing method includes the following steps: S1. Pre-treatment and preparation of bearing bush (1) blank: Select copper-based alloy billets for stress-relief annealing, and control the annealing temperature at 30-50°C above the material recrystallization temperature; at the same time, prepare the testing equipment required for the manufacturing process. S2, Rough machining and forming: The outer diameter and inner hole of the bearing shell (1) are machined on a CNC lathe, with a 0.5mm finishing allowance reserved for the inner hole; then the roundness error of the inner hole is checked by a laser diameter gauge. If the error is >0.05mm, return to S1 for re-annealing; if it is ≤0.05mm, go to S3. S3, Precision milling of spiral grooves: Using a CNC machine tool, the guide groove (4) is first machined, and then the helical interpolation program is generated based on the pitch in the design requirements. Using an R-angle ball end mill, a spiral wedge groove (3) is milled along the inner surface of the bearing shell (1). The groove depth decreases linearly from the inlet depth H1 to the outlet depth H2, and the groove width converges linearly from the inlet width W1 to the outlet width W2. The online surface profiler is activated to collect groove depth and width data in real time and compare them with the theoretical gradient curve. If the deviation at any measurement point is greater than 8% of the theoretical value, the tool compensation module is triggered. If the deviation still exceeds the tolerance after compensation, the blank is scrapped. If the deviation is ≤8% throughout the process, the process switches to S4. S4. Hydraulic polishing treatment: The bearing bush (1) was immersed in transformer oil containing nano-abrasives and polished by rotating at 200 r / min for 40 min; S5, Heat Treatment Strengthening: Surface sulfurizing treatment is carried out in a protective atmosphere furnace, and the sulfurized layer depth is 15-20μm. The depth of the sulfur-permeable layer is detected by glow discharge spectroscopy. If the depth of the sulfur-permeable layer is <15μm, return to S5 to extend the processing time; if the depth of the sulfur-permeable layer is >20μm, perform plasma thinning treatment to the acceptable range; if 15μm≤sulfur-permeable layer depth≤20μm, proceed to S6. S6. Fine grinding of the inner hole: The inner hole of the bearing bush (1) was ground to the final dimensional accuracy using a CBN grinding wheel, with a surface roughness Ra≤0.2μm; S7. Dynamic pressure performance simulation verification: Import the three-dimensional model of the bearing bush (1) into the fluid dynamics simulation software, set the transformer oil viscosity to 40-50 cSt and the journal (2) rotation speed to 1500-3000 r / min; calculate the oil film pressure distribution and load-bearing capacity curves under different working conditions; If the simulation shows that the minimum oil film thickness is <5μm or the maximum pressure is >50MPa, then return to S3 to adjust the convergence ratio of the spiral wedge groove (3); if the critical speed of hydraulic suspension is >120% of the rated speed, then scrap it; if it meets the standard, then go to S8. S8, machining of journal (2) and overall assembly: The journal (2) is machined according to the design requirements. Then the journal (2) and the bearing shell (1) are assembled into a bearing. The bearing is then pressed into the inner hole of the bearing housing. The interference fit is controlled at 0.03%-0.05% of the outer diameter of the bearing shell (1). S9, Dynamic Grinding and Dressing: The installed bearing is tested on a dedicated test bench. It is run at 2000 rpm without load. Transformer oil at 40℃ is injected into the oil inlet of the bearing housing, and the oil outlet flow rate Q is measured. If the measured flow rate Q > 1.2Q0, the bearing is marked as unqualified. If 0.8Q0 ≤ Q ≤ 1.2Q0, turn to S10. S10, Running-in Test: The test bench is operated in a stepped speed-up manner, with each speed level maintained for 10 minutes. Vibration acceleration values ​​are monitored throughout the process: if the vibration value is >4.5 mm / s at 80% of the rated speed, the spiral wedge groove (3) is disassembled and inspected for surface defects; if the oil temperature rise is >35 K at 100% of the rated speed, the test bench is returned to S4 to increase the polishing time; if there are no abnormalities throughout the process, the test bench is switched to S11. S11. Finished product inspection and packaging: The key dimensions are re-measured using a coordinate measuring machine, and after passing the inspection, they are coated with anti-rust oil and sealed.

2. The manufacturing method of a helical wedge-shaped sliding bearing according to claim 1, characterized in that, The helix angle α of the spiral wedge groove (3) satisfies tanα=pitch / (π×inner diameter of bearing (1)), and the value of α is in the range of 6°-8°.

3. The manufacturing method of a helical wedge-shaped sliding bearing according to claim 1, characterized in that, The ratio of the inlet end groove depth H1 to the outlet end groove depth H2 of the spiral wedge groove (3) is 1.8-2.2:

1.

4. The manufacturing method of a spiral wedge-shaped sliding bearing according to claim 1, characterized in that, The ratio of the radial clearance δ to the diameter of the journal (2) is 0.0008-0.0012.

5. The manufacturing method of a helical wedge-shaped sliding bearing according to claim 1, characterized in that, The total cross-sectional area of ​​the oil inlet of the bearing housing is 1.5-2 times the cross-sectional area of ​​the inlet end of the spiral wedge groove (3).

6. The manufacturing method of a helical wedge-shaped sliding bearing according to claim 1, characterized in that, In S3, the gradient change rate K1 of the linearly decreasing groove depth satisfies: K1=(H1-H2) / L, where L is the length of the bearing (1), and the value range of K1 is 0.15-0.25mm / 100mm.

7. The manufacturing method of a helical wedge-shaped sliding bearing according to claim 1, characterized in that, In S7, the convergence ratio adjustment of the spiral wedge groove (3) is specifically as follows: when the minimum oil film thickness is insufficient, the H1 / H2 ratio is increased to the upper limit of 2.2; when the pressure exceeds the limit, the W1 / W2 ratio is reduced to 1.

5.

8. The manufacturing method of a helical wedge-shaped sliding bearing according to claim 1, characterized in that, In S6, the ratio of the feed rate F of the fine grinding inner hole to the linear velocity V of the grinding wheel satisfies: F / V = 0.08-0.12 μm / (m / min).

9. The manufacturing method of a helical wedge-shaped sliding bearing according to claim 1, characterized in that, In step S10, the speed increase increment is 15% of the rated speed, and the oil temperature rise threshold at each speed increment is set at ΔT=0.

8. n The calculation is performed using the formula ×35K, where n is the current level.

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