A multi-position long-lasting lubricating automobile limiting bushing formed by single reference single fine machining and a processing method thereof

Abstract

The application discloses a same-reference single-precision-turning-formed multiple-positioning long-acting lubricating automobile limiting bushing and a processing method thereof, and belongs to the field of numerical control machining of automobile precise parts. The existing bushing is subjected to multiple clamping and reference conversion, and the shape and position precision is out of tolerance, single interference positioning is easy to deviate, stress concentration dry grinding of a right-angle oil storage groove occurs, and the cost is high due to the dependence on a special grinding machine. The bushing is integrally formed with a stepped shaft sleeve of a same rotary reference by single clamping of a numerical control lathe, an annular axial positioning step is arranged between a large-diameter section and a small-diameter section, a semicircular tangent transition closed-loop oil storage groove is arranged on the outer wall of the small-diameter section, a spherical bottom blind hole positioning counterbore is arranged on the end face of the large-diameter section, and an axial, circumferential and radial three-dimensional positioning system is formed by cooperating with a through chamfer inner hole; a synchronous limiting undismounting continuous turning method and three kinds of material differentiation post-processing processes are simultaneously limited. The batch size dispersion is 0.15%, the 500,000-time wear is less than or equal to 0.01 mm, and the cost is reduced by 35%.

Description

Technical Field

[0001] This invention relates to the field of automotive precision structural parts manufacturing technology, and is particularly applicable to the batch precision machining of small metal limit bushings on CNC lathes. Specifically, it is a multi-positioning long-lasting lubricated automotive limit bushing formed by single precision machining on the same datum and its CNC integrated machining method. Background Technology

[0002] Metal bushings used in automotive steering limiters, suspension buffer limiters, and door opening and closing limiters are small, precision load-bearing components. They perform four core functions: axial limiting, radial damping, drag reduction of moving parts, and precise assembly positioning. The bushing's machining accuracy, structural positioning capability, and wear resistance directly determine the smoothness of the vehicle's motion mechanism operation.

[0003] Existing commercially available general-purpose limiting bushings suffer from multiple interconnected defects, leading to a chain of failures: First, in terms of processing technology, traditional bushings involve multiple separate processes, including rough turning, secondary clamping and fine turning, and external cylindrical grinding. Each clamping introduces a datum conversion deviation, making it easy for bushing coaxiality, end face perpendicularity, and step flatness to exceed tolerances. The dimensional dispersion of batch products reaches 3% to 5%, resulting in a persistently high defect rate. Improved bushings with oil reservoirs and end face positioning holes require grooving and boring followed by secondary clamping, further amplifying dimensional and positional errors and compromising the structural strength of the bushing substrate. High-precision bushings require dedicated external cylindrical grinding machines, resulting in high equipment investment costs and long single-piece processing cycles, placing significant pressure on small and medium-sized parts manufacturers to achieve mass production. Secondly, regarding structural positioning, existing bushings rely solely on external interference fit for radial positioning, lacking independent axial step constraints and circumferential anti-rotation structures. Under prolonged vehicle vibration and bumpy conditions, the bushings are prone to circumferential deflection and axial movement, leading to a continuous decrease in positioning accuracy. After 100,000 reciprocating cycles, the offset can exceed 0.05mm, ultimately resulting in excessive clearance and loose parts causing abnormal noises. Thirdly, in terms of lubrication and wear resistance, conventional bushings lack an integrated oil reservoir structure, relying solely on pre-applied grease during assembly. During reciprocating motion, the grease is quickly thrown out and lost, leading to dry friction wear over long-term operation. A small number of existing oil groove bushings use rectangular right-angle grooves, which have stress concentration points at the bottom, making them prone to micro-cracks under alternating loads, resulting in rapid wear. After 500,000 fatigue cycles, the clearance wear is 0.03–0.05mm, shortening the replacement cycle of parts. Fourthly, regarding material compatibility, traditional bushings only use carbon steel or brass, lacking differentiated heat treatment and anti-corrosion processes, failing to meet the diverse automotive operating conditions such as heavy loads, lightweighting, and high temperatures.

[0004] While existing technologies disclose individual stepped bushings, individual bushings with oil reservoirs, and individual end-face positioning holes, there is no complete technical solution that simultaneously integrates a triple spatial positioning system with a full-circle stress-free oil reservoir and adopts a single-clamping integrated forming process based on the same CNC datum. This makes it impossible to simultaneously solve the four interconnected technical defects of machining accuracy, assembly offset, wear resistance life, and mass production cost, and the industry has a long-term need for improvement. Summary of the Invention Technical issues

[0005] The technical problems to be solved by this invention are: overcoming the process defects of excessive tolerance in coaxiality, perpendicularity, and flatness accuracy of bushings and poor batch dimensional consistency caused by multiple clamping reference conversions; solving the structural defects of bushing circumferential deflection, axial movement, and long-term operation limit failure caused by a single interference positioning method; eliminating the wear-resistant defects of dry grinding noise and short wear life caused by stress concentration in right-angle oil reservoirs and easy grease loss; solving the industrialization defects of high-precision bushings relying on special grinding machines, high threshold of mass production equipment, and high overall processing cost; and providing a CNC integrated non-disassembly machining process adapted to this bushing, with all structures formed synchronously on the same reference, avoiding cumulative accuracy errors from the source of the process. Technical solution

[0006] To solve the above technical problems, the present invention provides a multi-positioning long-lasting lubrication automotive limiting bushing formed by a single precision turning based on the same datum, including a stepped bushing body. The stepped bushing body is continuously and integrally precision turned by a single clamping and rotation datum on a CNC lathe, and the whole has a continuous smooth turning texture formed by a unified machining datum. The stepped bushing body includes a large diameter section (1) and a small diameter section (2) that are coaxially arranged and integrally formed. The outer diameter of the large diameter section (1) is larger than the outer diameter of the small diameter section (2). The two are integrally formed with an annular axial positioning step surface (3). The outer cylindrical wall of the small diameter section (2) is provided with a closed-loop annular oil reservoir (4) with a complete semi-circular arc cross section. The bottom of the reservoir, the wall of the reservoir and the transition of the outer circle are all connected by tangent arcs, without right-angle stress concentration structure, and the cross section radius R = 0.4~0. 6mm, groove depth equal to cross-sectional radius, inner wall surface roughness Ra≤0.8μm; large diameter section (1) has several spherical bottom blind hole positioning countersunk holes (5) evenly opened along the circumference on the outer end face away from the step surface. The bottom of the hole is a smooth spherical structure, which is fitted with the positioning protrusion of the mating part to form a circumferential anti-rotation constraint; a through smooth precision machined inner hole (6) is opened inside the stepped bushing body. The two ends of the inner hole (6) are provided with a 30°~45° smooth arc chamfer (7); the four sets of structures, namely the annular axial positioning step surface (3), the closed-loop annular oil storage groove (4), the spherical bottom positioning countersunk hole (5), and the through precision machined inner hole (6), are formed synchronously based on the same CNC clamping reference, and work together to form a triple spatial constraint positioning system of axial limit, circumferential anti-rotation, and radial guidance, and simultaneously realize long-term oil storage lubrication of the moving pair.

[0007] The number of the spherical bottom blind hole positioning countersunk holes (5) is 3 to 6, and they are distributed in a ring array at equal angles along the center of the end face of the large diameter section (1); the depth of a single hole is 0.2 to 0.4 mm, the hole diameter is 1.5 to 2.0 mm, and the radius of the spherical bottom of the hole is equal to 1 / 2 of the hole diameter.

[0008] The ratio of the outer diameter of the large diameter section (1) to the outer diameter of the small diameter section (2) is 1.2:1 to 1.5:1; the axial width of the annular axial positioning step surface (3) is 8% to 15% of the total length of the bushing body, and the flatness tolerance of the step surface is ≤0.002mm.

[0009] The stepped bushing body is made of any one of the following materials: 45# high-quality carbon structural steel, H62 brass, or GCr15 bearing steel. When 45# steel is used, low-temperature galvanizing and passivation are applied for rust prevention. When GCr15 bearing steel is used, it is subjected to oil quenching at 840℃ and low-temperature tempering at 180℃, with a surface hardness of HRC 58~62. When H62 brass is used, only fine machining and polishing are performed.

[0010] The overall shape and position accuracy control standard for bushings is as follows: the coaxiality of the large diameter section (1) and the small diameter section (2) is ≤0.005mm, the perpendicularity of the end face of the axial positioning step surface (3) is ≤0.003mm, and the roundness of the through inner hole (6) is ≤0.003mm.

[0011] This invention also provides a CNC integrated machining method for a multi-positioning long-lasting lubrication automotive limiting bushing formed by a single precision turning of the same datum. The entire process uses a three-jaw chuck to clamp the blank with the same outer diameter datum in a single operation. The process is continuous without disassembly or secondary positioning correction. The method includes the following steps: S1, Blank clamping and rough machining: The bar blank is clamped and fixed in a single operation. The outer diameter of the large diameter section (1), the outer diameter of the small diameter section (2), and the through inner hole (6) are rough turned, with a precision turning allowance of 0.2 to 0.3 mm reserved on each side; S2, Step integrated precision turning: The annular axial positioning step surface (3) is precision turned under the same rotation datum, and the flatness and end face perpendicularity of the step are controlled to the design tolerance simultaneously; S3, Closed-loop oil reservoir arc forming: Using G02 / G03 The small diameter section (2) is machined in one go by the circular interpolation program. The outer wall of the semi-circular closed-loop oil reservoir (4) is machined with a circular arc transition of the tangent of the reservoir wall without a right angle structure. S4, end face countersinking: the spindle rotation reference remains unchanged, and the large diameter section (1) end face spherical bottom blind hole positioning countersinking (5) is machined. The bottom of the hole is formed by spherical interpolation tooling. S5, inner hole chamfering and polishing: the inner hole (6) is precision machined to the final size, and the two ends are machined with 30°~45° circular arc chamfers (7). The inner hole (6), the inner wall of the oil reservoir (4), and the step surface (3) are CNC precision machined and polished. S6, material processing after blanking: 45# steel is subjected to low temperature galvanizing passivation; GCr15 bearing steel is subjected to oil quenching + low temperature tempering; H62 brass is directly inspected for finished product dimensions.

[0012] In step S3, the feed rate of the oil reservoir (4) is controlled at 0.08 to 0.12 mm / r to suppress the vibration marks and tool marks at the bottom of the reservoir; the spindle speed is 1200 to 1800 r / min and the feed rate is 0.06 to 0.10 mm / r throughout the process. All geometric tolerances are naturally guaranteed by the single clamping reference, eliminating the need for subsequent grinding machine calibration. Beneficial effects

[0013] The beneficial effects of this invention are as follows:

[0014] First, machining accuracy and batch consistency are significantly improved. All structures are formed using the same clamping datum, eliminating the cumulative error of datum conversion in multiple processes; the dimensional dispersion of 500 continuously processed products is only 0.15%, far lower than the 3% to 5% of traditional processes; coaxiality is ≤0.005mm and step end face perpendicularity is ≤0.003mm, eliminating the need for external cylindrical grinding machines for precision machining, reducing fixed asset investment in equipment by more than 60%, and shortening the processing time per piece by 40%.

[0015] Second, the triple spatial positioning system eliminates assembly misalignment. The annular step (3) restricts axial movement, the spherical countersunk hole (5) restricts circumferential rotation, and the through inner hole (6) constrains radial displacement. The three work together to form a complete spatial constraint. After 100,000 simulated vehicle vibration tests, the bushing's circumferential deflection is close to 0, and the axial displacement is ≤0.002mm. Compared with the traditional bushing's offset of 0.05~0.08mm, the anti-misalignment performance is improved by more than 25 times.

[0016] Third, the fully circular arc closed-loop oil reservoir extends wear resistance and eliminates metallic noise. The semi-circular arc groove eliminates stress concentration, avoiding the risk of cracking under alternating loads; the grease storage capacity is increased by 40%, and after 500,000 cycles of reciprocating fatigue testing, the wear amount is ≤0.01mm, which is only 1 / 3 to 1 / 5 of the wear amount of traditional right-angle groove bushings; there is no dry grinding metallic noise throughout the process, and the overall service life of the components is increased by 2 to 3 times.

[0017] Fourth, the multi-material matching process is suitable for all operating conditions. 45# steel is suitable for the limit mechanism of conventional passenger cars, and the passivation and rust prevention meet the requirements of wet chassis conditions; GCr15 quenched bearing steel is suitable for heavy-duty off-road and high-frequency impact conditions of new energy vehicles, with high hardness and wear resistance; H62 brass is suitable for the low-noise conditions of lightweight car doors, and has self-lubricating properties. One set of structures is compatible with three mainstream automotive application scenarios.

[0018] Fifth, the dual protection of both the product and processing method creates a high barrier to infringement avoidance. The independent product claims protect the physical structure of the bushing, while the independent processing method claims protect the proprietary, single-clamp integrated process. If competitors imitate a similar stepped bushing using a secondary clamping processing method, it falls within the scope of the method rights protection, making the protection far stronger than that of a single product structure patent.

[0019] Sixth, the barriers to industrialization are low. No special molds or external cylindrical grinding machines are required; all processing can be completed on a general-purpose economical CNC lathe. Small and medium-sized parts enterprises can directly establish operations there, and the overall manufacturing cost of large-scale mass production will decrease by 35%. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the longitudinal half-section structure of the bushing of the present invention;

[0021] Figure 2 This is a frontal view of the end face of the large-diameter section, showing the annular uniform array distribution structure of the positioning countersunk holes;

[0022] Figure 3 This is a partial enlarged view of the cross-section of the oil storage tank, showing a semi-circular arc cross-section and a structure with rounded transitions of the tangent lines of the tank wall and no right angles.

[0023] Figure 4 This is a flowchart of the CNC integrated machining process of the present invention. Detailed Implementation

[0024] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0025] Example 1:

[0026] like Figure 1 As shown, this embodiment provides a 45# steel conventional passenger car limiting bushing. The bushing body has an overall length of 12mm, an outer diameter of 8mm for the large diameter section (1), an outer diameter of 6mm for the small diameter section (2), and an outer diameter ratio of 1.33:1; a through inner hole (6) with a diameter of 4mm; an axial width of 1mm for the annular positioning step surface (3), accounting for 8.3% of the total bushing length; a closed-loop annular oil reservoir (4) with a cross-sectional radius of 0.5mm and a groove depth of 0.5mm; four positioning countersunk holes (5) are evenly distributed on the end face of the large diameter section (1), with a hole diameter of 1.8mm, a hole depth of 0.3mm, and a spherical radius of 0.9mm at the bottom of the hole; and 45° rounded chamfers (7) at both ends of the inner hole (6), with an axial width of 0.4mm for the chamfer.

[0027] Machining process: 45# steel round bar is clamped once, spindle speed is 1500r / min, feed is 0.08mm / r, and it is processed in continuous process from S1 to S6. The oil reservoir (4) adopts G03 circular interpolation tool with a feed speed of 0.10mm / r. The finished product is subjected to low temperature galvanizing passivation treatment. Detection of geometric tolerances: coaxiality of the large diameter section (1) and the small diameter section (2) is 0.003mm, perpendicularity of the end face of the annular positioning step surface (3) is 0.002mm, and roundness of the through inner hole (6) is 0.002mm; surface roughness of the inner wall of the inner hole (6) and the oil reservoir (4) is Ra=0.6μm, and surface roughness of the outer working surface is Ra=1.2μm. Performance test data: 500,000 cycles of reciprocating wear amount is 0.008mm, 100,000 cycles of vibration test with no circumferential deflection, and batch size deviation is 0.12%.

[0028] Example 2:

[0029] This embodiment is basically the same as Embodiment 1 in terms of structural dimensions and processing steps, except for the material and post-processing. In this embodiment, the bushing body material is replaced with GCr15 bearing steel. After processing, it is quenched in oil at 840℃ for 30 minutes and then tempered at 180℃ for 2 hours. The surface hardness is stably controlled at HRC60. No passivation coating treatment is required. The dimensional accuracy standards of the oil reservoir (4) and the positioning countersunk hole (5) are consistent with those of Embodiment 1. Performance test data: No deformation or cracking after 100 cycles of high and low temperature (-40℃~120℃), and only 0.01mm of wear after 800,000 cycles of heavy load reciprocating wear, which is suitable for high temperature and high frequency impact conditions of new energy off-road vehicles.

[0030] Example 3:

[0031] This embodiment is basically the same as the embodiment 1 in terms of structure, size and processing flow, the difference being in the material. This embodiment uses H62 brass material, and after processing, it is only polished, without heat treatment or anti-corrosion coating; the self-lubricating properties of brass combined with the oil reservoir (4) structure reduce the operating noise by 4dB compared to the steel bushing; the weight is reduced by 8% compared to the steel bushing, making it suitable for lightweight vehicle body supporting projects.

[0032] Comparative Example: Using a commercially available integrated straight-through cylindrical bushing, with secondary clamping and machining, without an oil reservoir or end-face positioning countersunk hole, three sets of parallel comparative tests were conducted simultaneously. Batch Accuracy Test: The comparative example showed a dimensional dispersion of 4.2%, while the present invention showed 0.15%; 500,000-cycle friction and wear test: The comparative example showed a wear amount of 0.045 mm, while the present invention showed 0.008 mm; 100,000-cycle vibration offset test: The comparative example showed a circumferential deflection of 0.8° and an axial displacement of 0.06 mm, while the present invention showed 0° circumferentially and 0.002 mm axially. These three sets of test data directly demonstrate that the present invention possesses significant and quantifiable technological advancements compared to existing technologies.

[0033] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A multi-positioning, long-lasting lubricating automotive limiting bushing formed by a single precision machining process using the same reference, comprising a stepped bushing body, characterized in that: (a) The stepped bushing body is continuously precision machined from a single clamping rotation reference on a CNC lathe, and the whole body has a continuous smooth turning texture formed by a unified machining reference; the stepped bushing body includes a large diameter section (1) and a small diameter section (2) that are coaxially arranged and integrally formed, and the outer diameter of the large diameter section (1) is larger than the outer diameter of the small diameter section (2); (b) The connection between the large diameter section (1) and the small diameter section (2) is integrally formed with an annular axial positioning step surface (3), and the annular axial positioning step surface (3) is used to fit the end face of the mating part during assembly to achieve axial displacement constraint; (c) A closed-loop annular oil storage groove (4) is provided on the outer cylindrical wall of the small diameter section (2). The cross section of the closed-loop annular oil storage groove (4) is a complete semi-circular arc. The bottom of the groove, the groove wall and the transition of the outer circle of the small diameter section (2) are all connected by tangent arcs, without right angle stress concentration structure. The cross section radius of the closed-loop annular oil storage groove (4) is R=0.4~0.6mm, the groove depth is equal to the cross section radius, and the surface roughness of the inner wall of the oil storage groove Ra≤0.8μm. (d) Several spherical bottom blind hole positioning countersunk holes (5) are evenly opened along the circumference on the outer end face of the large diameter section (1) away from the annular axial positioning step surface (3). The bottom of the positioning countersunk hole (5) is a smooth spherical structure. When assembled, it is fitted with the positioning protrusion of the mating part to form a circumferential anti-rotation constraint. (e) A through smooth precision machined inner hole (6) is provided inside the stepped bushing body. The two ends of the inner hole (6) are provided with a 30°~45° smooth arc chamfer (7). The four sets of structures, namely the annular axial positioning step surface (3), the closed-loop annular oil reservoir (4), the spherical bottom positioning countersunk hole (5), and the through precision machined inner hole (6), are formed synchronously based on the same CNC clamping datum. They work together to form a triple spatial constraint positioning system of axial limit, circumferential anti-rotation, and radial guidance, and simultaneously achieve long-term oil storage and lubrication of the moving parts.

2. The multi-positioning long-life lubrication automotive limiting bushing formed by a single precision machining process based on the same datum as described in claim 1, characterized in that: The number of the spherical bottom blind hole positioning countersunk holes (5) is 3 to 6, and they are distributed in a ring array at equal angles along the center of the end face of the large diameter section (1); the depth of a single hole is 0.2 to 0.4 mm, the hole diameter is 1.5 to 2.0 mm, and the radius of the spherical bottom of the hole is equal to 1 / 2 of the hole diameter.

3. The multi-positioning long-life lubrication automotive limiting bushing formed by a single precision machining process based on the same datum as described in claim 1, characterized in that: The ratio of the outer diameter of the large diameter section (1) to the outer diameter of the small diameter section (2) is 1.2:1 to 1.5:1; the axial width of the annular axial positioning step surface (3) is 8% to 15% of the total length of the bushing body, and the flatness tolerance of the step surface is ≤0.002mm.

4. The multi-positioning long-life lubrication automotive limiting bushing formed by a single precision machining process based on the same datum as described in claim 1, characterized in that: The stepped bushing body is made of any one of the following materials: 45# high-quality carbon structural steel, H62 brass, or GCr15 bearing steel. When 45# steel is selected, the bushing is subjected to low-temperature galvanizing passivation and rust prevention treatment after forming. When GCr15 bearing steel is selected, the bushing is subjected to oil quenching at 840℃ and low-temperature tempering at 180℃, and the surface hardness is controlled to HRC 58~62. When H62 brass is selected, only fine turning and polishing are performed after processing, and no plating strengthening treatment is required.

5. The multi-positioning long-life lubrication automotive limiting bushing formed by a single precision machining process based on the same datum as described in claim 1, characterized in that: The overall shape and position accuracy control standard for bushings is as follows: the coaxiality of the large diameter section (1) and the small diameter section (2) is ≤0.005mm, the perpendicularity of the end face of the axial positioning step surface (3) is ≤0.003mm, and the roundness of the through inner hole (6) is ≤0.003mm.

6. A CNC integrated machining method for a multi-positioning long-life lubrication automotive limiting bushing formed by a single precision turning on the same datum as described in any one of claims 1 to 5, characterized in that, The entire process uses a three-jaw chuck to clamp the blank at the same outer diameter reference in a single operation. The process is continuous without disassembly or secondary positioning and correction. The process includes the following steps: S1, Blank clamping and rough machining: The bar blank is clamped and fixed at one time. The outer diameter of the large diameter section (1), the outer diameter of the small diameter section (2), and the through inner hole (6) are rough machined. A 0.2-0.3mm allowance for finishing machining is reserved on each side; S2, Step-integrated finishing machining: The annular axial positioning step surface (3) is finished machined under the same rotation reference. The flatness of the step and the perpendicularity of the end face are controlled to the design tolerance simultaneously; S3. Closed-loop oil reservoir arc forming: The small diameter section (2) outer wall semi-circular closed-loop oil reservoir (4) is machined in one go using the G02 / G03 arc interpolation program. The tangent arc transition of the reservoir wall has no right angle structure. S4. End face countersunk hole precision boring: The spindle rotation reference remains unchanged. The large diameter section (1) end face spherical bottom blind hole positioning countersunk hole (5) is precision bored. The bottom of the hole is formed in one piece using spherical interpolation tooling. S5. Inner hole chamfering and polishing: The inner hole (6) is precision machined to the final size. The two ends are machined with 30°~45° arc chamfers (7). The inner hole (6), the inner wall of the oil reservoir (4), and the step surface (3) are CNC precision machined and polished. S6. Material sorting and post-processing: 45# steel is subjected to low temperature galvanizing passivation; GCr15 bearing steel is subjected to oil quenching + low temperature tempering; H62 brass is directly inspected for finished product dimensions.

7. The CNC integrated machining method according to claim 6, characterized in that: In step S3, the feed rate of the oil storage tank (4) is controlled to be 0.08-0.12 mm / r to suppress the vibration marks and tool marks at the bottom of the tank.

8. The CNC integrated machining method according to claim 6, characterized in that: The entire machining process uses a spindle speed of 1200-1800 r / min and a feed rate of 0.06-0.10 mm / r. All geometric tolerances are naturally guaranteed by the single clamping datum, eliminating the need for subsequent grinding machine calibration.

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