Crankshaft lightening hole machining auxiliary tool
By designing auxiliary tooling for crankshaft weight reduction hole machining, and utilizing the multi-point contact structure of nylon guide sleeves and wedge-shaped parts, the problems of low precision, low efficiency, and high cost in traditional machining methods were solved, achieving efficient and stable crankshaft weight reduction hole machining.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- SICHUAN ZHONGYU HEAVY IND TECH CO LTD
- Filing Date
- 2025-04-29
- Publication Date
- 2026-04-17
AI Technical Summary
Traditional crankshaft weight reduction hole machining methods suffer from problems such as numerous burrs, low hole diameter accuracy, low efficiency, high cost, and difficulty in adapting to mass production. Furthermore, the boring bar is susceptible to deviation and vibration due to chip force during the feed process.
A crankshaft weight reduction hole machining auxiliary tooling is designed. A nylon guide sleeve is used in an interference fit on the boring bar head. Through the design of the guide section, transition section and fixed section, dynamic guidance of the boring bar is achieved. Combined with the multi-point contact and lubrication structure of the wedge and boss, the cutting vibration energy is dispersed, and the machining accuracy and stability are improved.
It achieves high-precision and stable machining of crankshaft weight reduction holes, reduces overall costs, and improves machining efficiency and boring bar service life.
Smart Images
Figure CN224128672U_ABST
Abstract
Description
Technical Field
[0001] This utility model relates to the field of crankshaft weight reduction hole processing technology, and in particular to an auxiliary tooling for crankshaft weight reduction hole processing. Background Technology
[0002] As a core component of the engine, the crankshaft must maintain dynamic balance when rotating at high speeds. Weight removal holes (also known as balance holes) are drilled in specific locations on the crankshaft (such as counterweights) to remove material, adjust the mass distribution, counteract the centrifugal force caused by structural asymmetry or uneven material distribution, and reduce vibration and wear.
[0003] Traditional machining methods have limitations. Ordinary drilling is prone to producing burrs and low hole diameter accuracy, requiring subsequent processing. Milling or grinding is inefficient and costly, making it difficult to meet the requirements of deep holes or complex angles. Manual operation relies on worker experience, resulting in poor consistency and making it difficult to adapt to mass production.
[0004] Boring bars offer significant advantages. When used with precision boring tools, they can achieve hole diameter tolerances of IT7 or higher (e.g., ±0.01mm) and surface roughness Ra≤1.6μm, meeting the micron-level requirements for dynamic balancing correction. Using carbide or vibration-damping boring bars (e.g., damped boring bars) reduces deflection when the length-to-diameter ratio is too large, ensuring the straightness of the hole axis. Modern CNC boring bars integrate a probe feedback system, allowing real-time adjustment of cutting parameters (e.g., speed 2000-5000rpm, feed 0.05-0.2mm / r) to adapt to different materials (cast iron, forged steel, etc.).
[0005] First, a pre-drilled hole is made on the crankshaft using a drill bit, and then the pre-drilled hole is precision machined using a boring bar. The length-to-diameter ratio (L / D) of the boring bar is usually relatively large, and excessive overhang can easily cause cutting vibration, resulting in chatter marks on the hole wall, tool chipping, or out-of-tolerance hole diameter. Ordinary boring bars are easily affected by chip forces during the feed process, causing deviations and resulting in misalignment of the hollow axis and failure of coaxiality in multi-step holes. Utility Model Content
[0006] This utility model provides an auxiliary tooling for machining crankshaft weight reduction holes. A guide bushing is set at the head of the boring bar, and the boring bar is dynamically guided by inserting it into the pre-drilled hole of the crankshaft, so as to ensure the machining accuracy and stability of the crankshaft weight reduction hole and improve efficiency.
[0007] An auxiliary tooling for machining crankshaft weight reduction holes includes an integrally formed guide section, transition section, and fixing section on its main body. A bend is formed between the fixing section and the outer side of the transition section. This bend serves to abut against a pre-drilled hole in the crankshaft workpiece, maintaining the auxiliary tooling in a relative position to the crankshaft workpiece. The guide section has a ring-shaped array of radially protruding wedge-shaped members on its outer wall. A groove is formed between adjacent wedge-shaped members. The bottom of the groove extends radially inward along the guide section to form a boss. The wedge-shaped members extend radially outward along the transition section to form a wedge-shaped extension. The radial plane of the fixing section is perpendicular to the outer wall of the wedge-shaped extension.
[0008] The auxiliary tooling for machining crankshaft weight-reducing holes in this invention is a nylon guide sleeve, which is fitted onto the head of the boring bar and has an interference fit with it. The nylon guide sleeve includes a guide section for guiding, a transition section for deformation buffering, and a fixing section for confining the nylon guide sleeve between the pre-drilled hole and the boring bar. The ring-shaped array of wedges forms multi-point contact, dispersing and absorbing the energy of cutting vibrations. The ring-shaped wedges are divided by grooves to form independent elastic units, allowing for radial deformation compensation. The elasticity of the nylon material allows the wedges to maintain contact pressure even after wear. When one side wears 0.1 mm, the remaining wedges can still provide more than 70% of the support force. The wedge angle is 15–30°, preferably 20°, and the height is 1.2–1.5 times the wall thickness. Adding a polytetrafluoroethylene (PTFE) coating to the surface of the wedges can reduce the coefficient of friction.
[0009] The guide section and transition section of the nylon guide sleeve advance as the boring bar moves within the pre-drilled hole. Once the guide section and transition section are inserted into the pre-drilled hole and form an interference fit, the fixed section and the perpendicular portion of the wedge-shaped extension restrict the fixed section to the crankshaft surface outside the pre-drilled hole. This confines the nylon guide sleeve between the boring bar and the pre-drilled hole, thus achieving the guiding effect of the nylon guide sleeve on the boring bar. When the number of pre-drilled holes (n≥2) for crankshaft weight reduction holes, one, two, or more nylon guide sleeves can be provided. This utility model's auxiliary tooling for crankshaft weight reduction hole machining achieves dynamic guidance of the boring bar by inserting it into the crankshaft pre-drilled hole, ensuring machining accuracy and stability, and improving efficiency.
[0010] Furthermore, the guide section has a cylindrical structure, the boss has a height of 0.3 to 0.5 cm, and multiple bosses are arranged in a circular array along the axis of the guide section.
[0011] A groove is formed between two adjacent bosses. The groove can guide the flow of grease in a specific direction and avoid local dry friction.
[0012] Furthermore, the boss shown has a storage cavity inside, which is used to store cutting fluid or grease.
[0013] Furthermore, micro-holes are provided on both sides of the boss, the micro-holes are connected to the interior of the storage cavity, and the micro-holes are provided with elastic plugs, the elastic plugs being interference-fitted with the micro-holes.
[0014] The micropores have a diameter of 0.2–0.4 mm. The storage cavity within the boss continuously releases cutting fluid or grease through these micropores, forming a boundary lubrication film and reducing frictional torque. Guide sleeves with lubricated bosses can significantly improve their lifespan. The elastic plug can be made of polyurethane or fluororubber. The lubricant deep within the micropores can remove more than 50% of the heat, stabilizing the operating temperature below 80°C. The boss has a storage cavity with micropores, which, together with the elastic plug, allow for the on-demand release of grease and cutting fluid.
[0015] Furthermore, the transition section is flared, and the outer diameter of the smaller opening end of the transition section is the same as the inner diameter of the guide section, and the guide section is connected to the smaller opening end of the transition section.
[0016] Furthermore, the smaller opening end of the transition section is connected to the guide section via a first rounded corner, the central angle of which is 30° to 60°.
[0017] The connection is made by a first rounded corner to avoid stress concentration at sharp corners, improve the crack resistance of the nylon guide sleeve under vibration load, guide the axial force of the boring bar to be smoothly transmitted to the guide section, and reduce the risk of local plastic deformation.
[0018] Furthermore, the fixed section is a ring structure, and the inner diameter of the fixed section is the same as the size of the larger opening end of the transition section. The fixed section is connected to the larger opening end of the transition section.
[0019] Furthermore, the fixed section and the larger opening end of the transition section are connected by a second rounded corner, the central angle of which is 20° to 45°.
[0020] The second rounded corner connection reduces the stress peak at the root of the fixed section, facilitating material flow during injection molding and preventing shrinkage cavities.
[0021] Beneficial effects of utility model
[0022] 1. The auxiliary tooling for machining crankshaft weight reduction holes of this utility model achieves dynamic guidance of the boring bar by inserting it into the pre-drilled crankshaft hole, ensuring machining accuracy and stability and improving efficiency; through the lubrication of the elastic wedge and the boss, it achieves the three-in-one effect of self-adaptation, noise reduction and service life extension, which significantly reduces the overall cost.
[0023] 2. The outer wall of the guide section of this utility model is arranged with multiple wedge-shaped elements in a ring array. The inclined surface design of the wedge-shaped elements (such as an inclination angle of 15° to 30°) allows them to adapt to small positional deviations when inserted into the pre-drilled hole. Through elastic deformation, they guide the boring bar to align with the hole axis, reducing the dependence on the positioning accuracy of the machine tool. The boss significantly reduces the actual contact area between the nylon guide sleeve and the boring bar, thereby concentrating the contact pressure on the top of the boss and avoiding large-area creep of the nylon guide sleeve.
[0024] 3. The first and second fillets of this utility model can significantly reduce stress concentration at the connection, prevent cracks from forming at sharp corners, and improve the durability of the auxiliary tooling. Attached Figure Description
[0025] Figure 1 This is a cross-sectional structural diagram of the auxiliary tooling of this utility model;
[0026] Figure 2 This is a cross-sectional structural diagram of the guide section of this utility model;
[0027] Figure 3 This is an enlarged view of section A of this utility model.
[0028] Reference numerals: 1-guide section, 2-transition section, 3-fixed section, 4-wedge-shaped piece, 5-bore, 6-wedge-shaped extension, 7-first fillet, 8-second fillet, 9-groove, 10-storage cavity, 11-strip groove, 12-elastic plug. Detailed Implementation
[0029] Example 1
[0030] like Figure 1-3 As shown, an auxiliary tooling for machining crankshaft weight reduction holes is provided on the main body of the auxiliary tooling, which has an integrally formed guide section 1, transition section 2 and fixing section 3. The fixing section 3 and the outer side of the transition section 2 form a bend, which is used to abut against the pre-drilled hole of the crankshaft workpiece, so that the auxiliary tooling and the crankshaft workpiece are kept in relative position. The outer wall of the guide section 1 is provided with a plurality of radially protruding wedge-shaped members 4 arranged in a ring array. A groove 9 is formed between two adjacent wedge-shaped members 4. The bottom of the groove 9 extends radially inward along the guide section 1 to form a boss 5. The wedge-shaped members 4 extend along the outer side of the transition section 2 to form a wedge-shaped extension 6. The radial plane of the fixing section 3 is perpendicular to the outer wall of the wedge-shaped extension 6.
[0031] The auxiliary tooling for machining crankshaft weight-reducing holes of this utility model is a nylon guide sleeve, which is fitted onto the head of the boring bar and has an interference fit with it. The nylon guide sleeve is integrally molded and includes a guide section 1, a transition section 2, and a fixing section 3. Wedge-shaped elements 4 are set on the periphery of the guide section 1, with an angle of 15-30°. The wedge-shaped elements 4 are distributed in a ring array along the periphery of the guide section 1 to form multi-point contact and disperse and absorb the energy of cutting vibration. Multiple bosses 5 are set on the inner wall of the guide section 1. The bosses 5 significantly reduce the actual contact area between the nylon guide sleeve and the boring bar, thereby concentrating the contact pressure on the top of the bosses 5 to prevent large-area creep of the nylon guide sleeve. The wedge-shaped elements 4 and the wedge-shaped extensions 6 are integrally molded, which enhances the overall integrity of the connection between the guide section 1 and the transition section 2. The fixing section 3 restricts the nylon guide sleeve between the boring bar and the pre-drilled hole, realizing the guiding function of the nylon guide sleeve on the boring bar.
[0032] An auxiliary tooling for machining crankshaft weight-reducing holes, interference-fitted to the head of a boring bar, includes an integrally formed guide section 1, transition section 2, and fixing section 3. Six wedge-shaped members with an angle of 20° are arranged on the periphery of the guide section 1. Six bosses 5 are provided on the inner wall of the guide section 1. In use, the guide section 1 and transition section 2 of the nylon guide sleeve advance with the boring bar head within the pre-drilled hole. After the guide section 1 and transition section 2 are inserted into the pre-drilled hole and form an interference fit, the perpendicular portion of the fixing section 3 and the wedge-shaped extension 6 restricts the fixing section 3 to the crankshaft surface outside the pre-drilled hole, thereby confining the nylon guide sleeve between the boring bar and the pre-drilled hole, achieving the guiding function of the nylon guide sleeve for the boring bar.
[0033] Example 2
[0034] Based on Example 1, Figure 2-3 As shown, the guide section 1 has a cylindrical structure, and the height of the boss 5 is 0.3-0.5 cm. Multiple bosses 5 are arranged in a circular array along the axis of the guide section 1. A storage cavity 10 is provided inside the boss 5, which is used to store cutting fluid or grease. Microholes are provided on both sides of the boss 5, and these microholes communicate with the interior of the storage cavity 10. Elastic plugs 12 are provided in the microholes, and the elastic plugs 12 are interference-fitted with the microholes.
[0035] The guide section 1 has a cylindrical structure. The boss 5 has a height of 0.4 cm and consists of six bosses arranged in a circular array along the axis of the guide section 1. A strip groove 11 is formed between two adjacent bosses 5, which can guide the flow of grease and avoid local dry friction. A storage cavity 10 is provided inside the boss 5, which stores grease. Three microholes with a diameter of 0.3 mm are provided on each side of the boss 5. The microholes are connected to the inside of the storage cavity 10 and are fitted with elastic plugs 12 made of polyurethane. The elastic plugs 12 are interference-fitted with the microholes. When the guide section 1 and the transition section 2 are inserted into the pre-drilled hole and form an interference fit with the pre-drilled hole, the boring bar and the inner wall of the pre-drilled hole press against the boss 5, which in turn presses against the storage cavity 10 in the boss 5. The grease in the storage cavity 10 is compressed, breaks through the restriction of the elastic plug 12, and is sprayed out from the micro-hole, flows along the strip groove 11, and forms a lubricating film on the surface of the boring bar, reducing the friction torque.
[0036] Example 3
[0037] Based on Example 1, such as Figure 1 As shown, the transition section 2 is flared, with the outer diameter of the smaller opening end of the transition section 2 matching the inner diameter of the guide section 1. The guide section 1 is connected to the smaller opening end of the transition section 2. The smaller opening end of the transition section 2 is connected to the guide section 1 via a first fillet 7, the central angle of which is 30°–60°. The fixing section 3 is an annular structure, with the inner diameter matching the size of the larger opening end of the transition section 2. The fixing section 3 is connected to the larger opening end of the transition section 2. The fixing section 3 is connected to the larger opening end of the transition section 2 via a second fillet 8, the central angle of which is 20°–45°.
[0038] The smaller opening end of the transition section 2 is connected to the guide section 1. The central angle of the first fillet 7 is 45°. The larger opening end of the transition section 2 is connected to the inner diameter of the fixed section 3. The connection is made through the second fillet 8. The central angle of the second fillet 8 is 30°.
[0039] In use, the guide section 1 and transition section 2 of the nylon guide sleeve advance with the boring bar head in the pre-drilled hole. When the guide section 1 and transition section 2 are inserted into the pre-drilled hole and form an interference fit with the pre-drilled hole, the first rounded corner 7 at the connection between the guide section 1 and the transition section 2 and the second rounded corner 8 at the connection between the transition section 2 and the fixed section 3 slowly approach the boring bar and fit with it under the squeezing action between the boring bar and the inner wall of the pre-drilled hole. The vertical part of the fixed section 3 and the wedge-shaped extension 6 restricts the fixed section 3 on the crankshaft surface outside the pre-drilled hole, thereby restricting the nylon guide sleeve between the boring bar and the pre-drilled hole, realizing the guiding function of the nylon guide sleeve on the boring bar.
Claims
1. A crankshaft lightening hole machining auxiliary tool characterized by, The auxiliary tooling body is provided with an integrally formed guide section (1), transition section (2) and fixing section (3). The fixing section (3) and the transition section (2) form a bend, which is used to abut against the pre-drilled hole of the crankshaft workpiece, so that the auxiliary tooling and the crankshaft workpiece maintain a relative position. The outer wall of the guide section (1) is provided with a ring array of multiple radially protruding wedge-shaped members (4), and a groove (9) is formed between two adjacent wedge-shaped members (4). The bottom of the groove (9) extends radially inward along the guide section (1) to form a boss (5). The wedge-shaped members (4) extend along the outside of the transition section (2) to form a wedge-shaped extension (6). The radial plane of the fixed section (3) is perpendicular to the outer wall of the wedge-shaped extension (6).
2. The crankshaft lightening hole machining auxiliary tool according to claim 1, characterized in that, The guide section (1) is a cylindrical structure, and the boss (5) is provided in a plurality of circular arrays arranged along the axis of the guide section (1).
3. The crankshaft lightening hole machining auxiliary tool according to claim 2, characterized in that, The boss (5) shown has a storage cavity (10) inside, which is used to store cutting fluid or grease.
4. The crankshaft lightening hole machining auxiliary tool according to claim 3, characterized in that, Multiple microholes are provided on both sides of the boss (5). The microholes are connected to the inside of the storage cavity (10). Each microhole is provided with an elastic plug (12), and the elastic plug (12) is interference-fitted with the microhole.
5. The crankshaft lightening hole machining auxiliary tool according to claim 1, characterized in that, The transition section (2) is flared, and the outer diameter of the smaller opening end of the transition section (2) is consistent with the inner diameter of the guide section (1). The guide section (1) is connected to the smaller opening end of the transition section (2).
6. The crankshaft lightening hole machining auxiliary tool according to claim 5, characterized in that, The smaller opening end of the transition section (2) is connected to the guide section (1) through a first fillet (7), the central angle of the first fillet (7) being 30° to 60°.
7. The crankshaft lightening hole machining auxiliary tool according to claim 5, characterized in that, The fixed section (3) is a ring structure. The inner diameter of the fixed section (3) is the same as the size of the larger opening end of the transition section (2). The fixed section (3) is connected to the larger opening end of the transition section (2).
8. The auxiliary tooling for machining crankshaft weight reduction holes according to claim 7, characterized in that, The fixed section (3) and the larger opening end of the transition section (2) are connected by a second rounded corner (8), the central angle of which is 20° to 45°.