A diesel engine connecting rod big end hole coaxial fine boring device and method

Abstract

The present application relates to the technical field of boring device, and disclose a diesel engine connecting rod big and small head hole coaxial fine boring device and method, including fine boring device main part, workbench, big hole boring bar, small hole boring bar, connecting assembly, fixed shaft assembly, adjust shaft assembly and expansion assembly, after big head hole fine boring, expansion assembly and big head hole inner wall abutment, make big hole boring bar stable reflection big head hole actual axis direction, small hole boring bar lower end in small head pre-machining hole axial middle part radial centering forms fulcrum, fixed shaft assembly passes through connecting assembly and will big head hole actual axis direction transmission to adjust shaft assembly, adjust shaft assembly drives small hole boring bar with the fulcrum slight deflection, and by coaxial positioning sleeve continuously guide small hole boring bar completes fine boring, the present application can take into account small head pre-machining hole center position and cutting allowance distribution, and improve big and small head hole axis parallelism and processing stability.

Description

Technical Field

[0001] This invention relates to the field of boring equipment technology, and in particular to a coaxial precision boring device and method for connecting rod large and small end holes of a diesel engine. Background Technology

[0002] Diesel engine connecting rods typically consist of a large end and a small end spaced apart from each other. The large end forms a large end bore, and the small end forms a small end bore. The large end bore connects to the crankshaft, and the small end bore connects to the piston pin. Therefore, the dimensional accuracy, cylindricity, and parallelism between the axes of the large and small end bores directly affect the motion stability of the connecting rod after assembly. A large parallelism error between the axes of the two bores can easily cause uneven loading between the piston pin, connecting rod, and crankshaft, increasing localized wear and affecting the vibration and transmission efficiency of the diesel engine during operation. To ensure the machining accuracy of the two bores, it is usually necessary to perform finish boring on both the large and small end bores after rough machining or semi-finishing.

[0003] Existing connecting rod precision boring devices typically use fixtures to fix the connecting rod to the worktable and employ boring bars corresponding to the large and small end holes respectively for machining. The two boring mechanisms are generally installed according to a preset theoretical orientation, relying primarily on the machine tool guideways, spindle mounting position, and fixture positioning references to ensure the axial orientation of the two boring bars. However, the positioning surface of the connecting rod blank may have dimensional errors, the connecting rod may also tilt slightly within the fixture, and it is also affected by factors such as spindle installation errors, boring bar deflection under stress, and tool wear. Therefore, the actual axis formed after precision boring of the large end hole may deviate from the preset theoretical axis of the equipment. If the small end hole is still machined according to the equipment's theoretical orientation, it is difficult to guarantee that the final axis of the small end hole remains stably parallel to the actual axis of the machined large end hole.

[0004] Furthermore, small-end holes are typically cast, forged, or pre-machined holes before precision boring, and their center position, axial inclination, and wall allowance distribution are prone to deviations. If the small-end boring bar is rigidly constrained to be parallel to the axis of the large-end hole without considering the actual center position of the pre-machined small-end hole, the small-end boring bar may deviate from the center of the pre-machined hole, causing the cutting allowance on one side of the hole wall to be significantly greater than that on the other side. This results in a larger biased cutting force, increasing the risk of boring bar vibration, tool wear, and out-of-tolerance hole diameter. If the small-end boring bar is made to self-center entirely according to the pre-machined small-end hole, it is likely to inherit the original axial inclination of the pre-machined hole, and the parallelism between the axes of the large and small ends still cannot be effectively guaranteed. Summary of the Invention

[0005] The technical problem to be solved by the present invention is that the existing technology has the disadvantage of being difficult to balance the actual center of the small end pre-machined hole and the cutting allowance, and it is difficult to adjust the shaft of the small hole boring bar and continuously guide it according to the actual axis of the large end hole after precision boring, which makes it difficult to guarantee the parallelism of the axes of the large and small ends. To this end, we propose a coaxial precision boring device and method for connecting rods of diesel engines.

[0006] To achieve the above objectives, this application adopts the following technical solution: a coaxial precision boring device and method for connecting rod large and small end holes of a diesel engine, comprising: a precision boring device body, a worktable, and a clamping mechanism mounted on the worktable; the precision boring device body is provided with a large-hole boring bar and a small-hole boring bar; the clamping mechanism holds a connecting rod workpiece, the connecting rod workpiece including a large end hole and a small end hole; the large-hole boring bar is characterized in that: a tensioning component that expands radially along the large end hole after precision boring is installed at its lower end, so that the large-hole boring bar is kept at the actual axial position of the large end hole; the small-hole boring bar is connected to a drive mechanism through a coupling structure that allows slight deflection, and its lower end is provided with a tensioning component that expands radially in the axial middle of the small end hole, so that the small-hole boring bar uses the center of the pre-machined hole as the centering fulcrum;

[0007] The main body of the precision boring device is also provided with a connecting assembly, which includes a rigid telescopic connecting rod. The two ends of the rigid telescopic connecting rod are respectively connected to a fixed axis assembly sleeved on the outside of the large hole boring rod and an adjusting axis assembly sleeved on the outside of the small hole boring rod. The adjusting axis assembly includes a downward positioning cylinder that is parallel to the axis of the fixed axis assembly. A conical sleeve is sleeved inside the downward positioning cylinder. A coaxial positioning sleeve passes through the inside of the conical sleeve. The inner side of the downward positioning cylinder forms a conical inclined surface that cooperates with the conical sleeve.

[0008] When the connecting assembly moves down, the fixed axis assembly obtains the actual axis direction of the large end hole based on the large hole boring bar. The tapered inclined surface pushes the tapered sleeve and the coaxial positioning sleeve to drive the small hole boring bar to deflect around the centering fulcrum until the axis of the small hole boring bar is parallel to the actual axis of the large end hole. After the shaft adjustment assembly locks, the coaxial positioning sleeve limits and guides the fine boring movement of the small hole boring bar.

[0009] Preferably, the coupling structure is a diaphragm coupling, which is used to transmit the torque output by the drive mechanism to the small hole boring bar and allows the small hole boring bar to produce radial offset and angular deflection relative to the drive mechanism.

[0010] Preferably, the connecting assembly further includes a downward push rod installed on the main body of the precision boring device. The output end of the downward push rod is connected to the middle of the rigid telescopic connecting rod through a flexible connecting block, which is used to drive the fixed axis assembly and the adjusting axis assembly to move up and down synchronously.

[0011] Preferably, the fixed-axis assembly includes a fixed-axis cylinder connected to a rigid telescopic connecting rod. The fixed-axis cylinder has multiple sets of eccentric pressure rollers spaced circumferentially inside. Each eccentric pressure roller has an eccentric shaft passing through it eccentrically, and the eccentric pressure roller is fixedly connected to the corresponding eccentric shaft.

[0012] Preferably, each of the eccentric shafts is fixedly connected to a bevel gear at its end, and the bevel gears on adjacent eccentric shafts mesh with each other; a fixed shaft part is fixedly connected to the outer wall of the large hole boring bar, the outer diameter of the fixed shaft part is larger than the outer diameter of the large hole boring bar, and its outer circumferential surface is a rough surface that can drive the eccentric pressure roller to rotate synchronously.

[0013] Preferably, the upper and lower edges of the tapered sleeve are respectively provided with multiple sets of balls along the circumference, the coaxial positioning sleeve is slidably sleeved on the outside of the small hole boring bar, and a support block located below the coaxial positioning sleeve is fixedly connected to the small hole boring bar.

[0014] Preferably, the conical inclined surface and the opposite surface of the conical sleeve are provided with an electromagnetic locking mechanism, which is used to lock the conical sleeve into the pressing positioning cylinder after the axis of the coaxial positioning sleeve is adjusted.

[0015] Preferably, the tensioning assembly includes a mounting cylinder installed at the lower end of the corresponding boring bar, a miniature push rod is provided inside the mounting cylinder, and an inverted conical push block is fixedly connected to the output end of the miniature push rod; multiple sets of synchronous push rods that radially penetrate the mounting cylinder are provided on the outer periphery of the inverted conical push block, the inner end of the synchronous push rod slides against the conical surface of the inverted conical push block, and a return spring is sleeved on the part of the synchronous push rod that extends out of the mounting cylinder.

[0016] Preferably, the outer ends of the synchronous push rods at the lower end of the large-hole boring bar are fixedly connected to tension blocks, and the outer ends of the synchronous push rods at the lower end of the small-hole boring bar are rotatably connected to spherical blocks; the worktable is provided with clearance holes corresponding to the large-end hole and the small-end hole respectively, for the tensioning components in the retracted state to enter.

[0017] Preferably, the steps include:

[0018] S1. Clamp the connecting rod workpiece on the worktable, aligning the large end hole and small end hole with the large-hole boring bar and small-hole boring bar, respectively; S2. Use the large-hole boring bar to precision bore the large end hole, and radially expand the expansion block at its lower end to abut against the inner wall of the large end hole to establish the actual axis reference of the large end hole; S3. Radially expand the spherical block at the lower end of the small-hole boring bar in the axial middle of the small end hole to form the centering fulcrum of the small-hole boring bar; S4. Drive the connecting assembly to descend, so that the fixed axis assembly determines the axis direction based on the large-hole boring bar, and the shaft adjusting assembly drives the small-hole boring bar to deflect around the centering fulcrum until the axis of the small-hole boring bar is parallel to the actual axis of the large end hole, and then lock the shaft adjusting assembly; S5. Retract the spherical block and drive the small-hole boring bar to rotate and feed along the coaxial positioning sleeve to complete the precision boring of the small end hole.

[0019] The technical effects and advantages of this invention are as follows:

[0020] After the large-end bore is precision bored, this invention utilizes multiple sets of expansion blocks with a certain contact height along the axial direction at the lower end of the large-end boring bar to synchronously abut against the inner wall of the large-end bore, so that the large-end boring bar stably reflects the actual axial direction of the large-end bore. At the same time, a spherical block is used for adaptive centering in the axial middle of the small-end pre-machined hole to retain a more reasonable actual center position of the small-end bore. Then, the fixed-axis assembly, rigid telescopic connecting rod and adjusting-axis assembly transmit the actual axial direction of the large-end bore to one side of the small-end boring bar. Through the cooperation of the tapered inclined surface and the tapered sleeve, the small-end boring bar is slightly deflected with the middle centering position as the fulcrum. Finally, the coaxial positioning sleeve continuously limits and guides its precision boring process. This can correct the original axis inclination of the small end pre-machined hole, reduce the excessive unilateral cutting allowance and biased cutting force caused by the small hole boring bar deviating from the center of the pre-machined hole, reduce boring bar vibration, tool wear and hole diameter deviation, and improve the parallelism, machining stability and batch machining consistency of the connecting rod large and small end holes of the diesel engine. Attached Figure Description

[0021] The disclosure of this invention is illustrated with reference to the accompanying drawings. It should be understood that the drawings are for illustrative purposes only and are not intended to limit the scope of protection of this invention. In the drawings, the same reference numerals are used to refer to the same parts:

[0022] Figure 1 This is a schematic cross-sectional view of the overall structure of the present invention;

[0023] Figure 2 This is a three-dimensional structural diagram of the entire invention;

[0024] Figure 3 This is a schematic cross-sectional view of the fixed-axis assembly of the present invention;

[0025] Figure 4 This is a three-dimensional structural diagram of the eccentric pressure roller portion of the present invention;

[0026] Figure 5 This is a cross-sectional structural diagram of the shaft adjusting assembly of the present invention;

[0027] Figure 6 This is a three-dimensional structural diagram of the connecting component portion of the present invention;

[0028] Figure 7 This is a three-dimensional structural diagram of the bottom end tightening component of the large-hole boring bar of the present invention;

[0029] Figure 8 This is a three-dimensional structural diagram of the bottom end tightening component of the small hole boring bar of the present invention.

[0030] Legend: 1. Main body of the precision boring device; 2. Worktable; 3. Large hole boring bar; 4. Small hole boring bar; 5. Connecting assembly; 51. Downward push rod; 52. Flexible connecting block; 53. Rigid telescopic connecting rod; 6. Fixed shaft assembly; 61. Fixed shaft cylinder; 62. Eccentric pressure roller; 63. Eccentric shaft; 64. Bevel gear; 7. Adjusting shaft assembly; 71. Downward positioning cylinder; 72. Conical inclined surface; 73. Conical sleeve; 74. Ball bearing; 75. Coaxial positioning sleeve; 76. Support block; 77. Electromagnetic locking mechanism; 8. Expansion assembly; 81. Mounting cylinder; 82. Miniature push rod; 83. Inverted conical push block; 84. Synchronous push rod; 85. Return spring; 9. Connecting rod workpiece; 10. Clamping mechanism; 11. Clearance hole; 12. Expansion block; 13. Spherical block. Detailed Implementation

[0031] It is readily understood that, based on the technical solution of this invention, those skilled in the art can propose various interchangeable structural methods and implementations without altering the essential spirit of the invention. Therefore, the following detailed embodiments and accompanying drawings are merely illustrative examples of the technical solution of this invention and should not be considered as the entirety of the invention or as limitations or restrictions on the technical solution of this invention.

[0032] Reference Figures 1 to 8 As shown, this embodiment provides a coaxial precision boring device for the large and small end holes of a diesel engine connecting rod, including a main body 1 and a worktable 2 disposed in the middle of the main body 1. A clamping mechanism 10 for clamping the connecting rod workpiece 9 is installed on the worktable 2. The connecting rod workpiece 9 includes a large end hole 91 and a small end hole 92 respectively disposed at both ends. The clamping mechanism 10 can press the connecting rod workpiece 9 from the outside, so that the large end hole 91 and the small end hole 92 are respectively located in the corresponding machining positions. The worktable 2 is provided with clearance holes 11 respectively located below the large end hole 91 and the small end hole 92, so that the tensioning components 8 at the lower ends of the large end boring bar 3 and the small end boring bar 4 can extend downwards to avoid interference between the tensioning components 8 and the worktable 2.

[0033] The main body 1 of the precision boring device is equipped with an independent large-hole boring bar 3 and a small-hole boring bar 4. The large-hole boring bar 3 corresponds to the large-end hole 91, and the small-hole boring bar 4 corresponds to the small-end hole 92. The large-hole boring bar 3 and the small-hole boring bar 4 are driven to rotate and feed axially by corresponding drive mechanisms. The large-hole boring bar 3 is used to perform precision boring on the large-end hole 91. After the precision boring of the large-end hole 91 is completed, the large-hole boring bar 3 continues to maintain the axial constraint between itself and its drive end. The radial clearance between the large-hole boring bar 3 and the machined large-end hole 91 is eliminated by the expansion assembly 8 set at its lower end, so that the large-hole boring bar 3 is stably maintained at the actual axial position of the large-end hole 91.

[0034] The small-hole boring bar 4 is connected to the corresponding drive mechanism via a diaphragm coupling. The diaphragm coupling allows the small-hole boring bar 4 to produce limited radial displacement and angular deflection relative to the drive mechanism while transmitting rotational power. Therefore, when adjusting the axis of the small-hole boring bar 4, it can deflect slightly while maintaining its power transmission capability, reducing the limitations imposed by the rigid transmission structure on the axis adjustment action. After the axis adjustment is completed, the diaphragm coupling can still transmit the torque of the drive mechanism to the small-hole boring bar 4, enabling it to complete the precision boring operation of the small-end hole 92.

[0035] Reference Figure 1 and Figure 6 As shown, a connecting assembly 5 is provided on the main body 1 of the precision boring device. The connecting assembly 5 includes a downward push rod 51, a flexible connecting block 52, and a rigid telescopic connecting rod 53. The downward push rod 51 is fixedly installed on the main body 1 of the precision boring device, with its output end facing downward and fixedly connected to the flexible connecting block 52. The lower end of the flexible connecting block 52 is connected to the middle of the rigid telescopic connecting rod 53. When the downward push rod 51 extends or retracts, it can drive the rigid telescopic connecting rod 53 to descend or rise as a whole through the flexible connecting block 52.

[0036] One end of the rigid telescopic link 53 is connected to a fixed-axis assembly 6 sleeved on the outside of the large-hole boring bar 3, and the other end is connected to an adjusting-axis assembly 7 sleeved on the outside of the small-hole boring bar 4. The fixed-axis assembly 6 is used to determine the actual axial direction of the large-end hole 91 after precision boring based on the large-hole boring bar 3, and the adjusting-axis assembly 7 is used to adjust the axial orientation of the small-hole boring bar 4 according to the actual axial direction. Since the fixed-axis assembly 6 and the adjusting-axis assembly 7 are installed at both ends of the same rigid telescopic link 53, the axis of the fixed-axis assembly 6 is parallel to the axis of the lower positioning cylinder 71 in the adjusting-axis assembly 7, thereby enabling the actual axial direction of the large-end hole 91 to be transmitted to the position of the small-hole boring bar 4.

[0037] Reference Figure 3 and Figure 4 As shown, the fixed-axis assembly 6 includes a fixed-axis cylinder 61 fixedly connected to the rigid telescopic connecting rod 53, and the fixed-axis cylinder 61 is sleeved on the outside of the large-hole boring bar 3. Four sets of eccentric pressure rollers 62 are circumferentially spaced inside the fixed-axis cylinder 61. Each set of eccentric pressure rollers 62 has an eccentric shaft 63 eccentrically passing through it. The eccentric pressure rollers 62 are fixedly connected to the corresponding eccentric shafts 63, and the eccentric shafts 63 are rotatably connected to the fixed-axis cylinder 61. Because the eccentric shafts 63 are offset from the geometric center of the eccentric pressure rollers 62, the eccentric pressure rollers 62 form smaller and larger portions with different radial dimensions relative to the eccentric shafts 63.

[0038] Each eccentric shaft 63 is fixedly connected to a bevel gear 64 at its end, and the bevel gears 64 at the ends of adjacent eccentric shafts 63 mesh with each other. When one set of eccentric shafts 63 rotates, the meshing bevel gears 64 can drive the other eccentric shafts 63 to rotate synchronously, so that each eccentric pressure roller 62 maintains the same rotation angle, avoiding uneven radial force applied to the large hole boring bar 3 due to asynchronous rotation of multiple sets of eccentric pressure rollers 62.

[0039] A fixed shaft portion 65 is fixedly connected to the outer wall of the large-hole boring bar 3. The fixed shaft portion 65 is located below the fixed shaft cylinder 61. The outer diameter of the fixed shaft portion 65 is larger than the outer diameter of the adjacent part of the large-hole boring bar 3, and the outer peripheral surface of the fixed shaft portion 65 is set as a rough surface. When the fixed shaft assembly 6 is in the initial position, the smaller part of each eccentric pressure roller 62 faces the large-hole boring bar 3, so that a gap is maintained between the eccentric pressure roller 62 and the large-hole boring bar 3, and the large-hole boring bar 3 can rotate and move axially relative to the fixed shaft cylinder 61.

[0040] As the connecting assembly 5 lowers the fixed-axis cylinder 61, the eccentric pressure roller 62 gradually moves to the outside of the fixed-axis portion 65. After the eccentric pressure roller 62 contacts the rough surface of the fixed-axis portion 65, the friction between them drives the eccentric pressure roller 62 and the eccentric shaft 63 to rotate, and through the bevel gears 64, the four sets of eccentric pressure rollers 62 rotate synchronously. Each eccentric pressure roller 62 gradually changes from having its smaller portion facing the fixed-axis portion 65 to having its larger portion facing the fixed-axis portion 65, so that the four sets of eccentric pressure rollers 62 simultaneously press the fixed-axis portion 65 from different radial directions. As a result, the axis of the fixed-axis cylinder 61 gradually coincides with the axis of the large-hole boring bar 3, and the downward positioning cylinder 71 connected to the other end of the rigid telescopic connecting rod 53 achieves an axial direction parallel to the large-hole boring bar 3.

[0041] Multiple sets of synchronously rotating eccentric pressure rollers 62 are used to tighten the fixed shaft part 65, which can automatically complete radial centering during the descent of the fixed shaft assembly 6, reducing the possibility of the fixed shaft cylinder 61 deviating from the axis of the large hole boring bar 3 due to unilateral clamping. At the same time, the fixed shaft assembly 6 obtains the actual axial direction of the large end hole 91 after precision boring through the large hole boring bar 3, which can reduce the error caused by determining the machining direction of the small end hole 92 solely based on the theoretical installation direction of the precision boring device body 1.

[0042] Reference Figure 5 As shown, the shaft adjusting assembly 7 includes a pressing positioning cylinder 71 fixedly connected to the other end of the rigid telescopic connecting rod 53. The pressing positioning cylinder 71 has an internally formed conical inclined surface 72, smaller at the top and larger at the bottom. A conical sleeve 73 is disposed inside the conical inclined surface 72, and the outer circumference taper of the conical sleeve 73 matches that of the conical inclined surface 72. A coaxial positioning sleeve 75 is disposed through the middle of the conical sleeve 73. The coaxial positioning sleeve 75 is slidably sleeved on the outside of the small hole boring bar 4, allowing the small hole boring bar 4 to be axially fed and rotated relative to the coaxial positioning sleeve 75.

[0043] Multiple sets of balls 74 are circumferentially arranged on the upper and lower edges of the tapered sleeve 73, located between the tapered sleeve 73 and the tapered inclined surface 72. When the pressing positioning cylinder 71 descends relative to the tapered sleeve 73, the balls 74 convert some of the sliding friction between the tapered sleeve 73 and the tapered inclined surface 72 into rolling friction. When there is a deviation between the initial axis of the tapered sleeve 73 and the axis of the pressing positioning cylinder 71, the tapered inclined surface 72 first contacts the balls 74 on the side of the deviation direction, and applies radial and angular adjustment to the tapered sleeve 73 through the balls 74, thereby reducing the possibility of the tapered sleeve 73 getting stuck or scraping on one side.

[0044] A support block 76 is fixedly connected to the small-hole boring bar 4, located below the coaxial positioning sleeve 75. The support block 76 is used to provide axial support for the coaxial positioning sleeve 75 and the tapered sleeve 73 when the pressing positioning cylinder 71 descends, preventing the tapered sleeve 73 from moving downwards only synchronously with the pressing positioning cylinder 71. As the pressing positioning cylinder 71 continues to descend, the tapered inclined surface 72 gradually fits against the outer circumferential surface of the tapered sleeve 73, causing the tapered sleeve 73 and the coaxial positioning sleeve 75 to move radially and adjust angularly under the support of the support block 76, until the tapered sleeve 73 and the pressing positioning cylinder 71 form a coaxial fit.

[0045] An electromagnetic locking mechanism 77 is provided on the opposing surfaces of the tapered inclined surface 72 and the tapered sleeve 73. After the tapered sleeve 73 completes the axial adjustment, the electromagnetic locking mechanism 77 is energized, locking the tapered sleeve 73 inside the pressing positioning cylinder 71, restricting the tapered sleeve 73 from further movement or deflection relative to the pressing positioning cylinder 71. This keeps the axis of the coaxial positioning sleeve 75 aligned with the axis of the pressing positioning cylinder 71, and keeps the axis of the small hole boring bar 4 defined by the coaxial positioning sleeve 75 parallel to the actual axis of the large end hole 91 reflected by the large hole boring bar 3.

[0046] The tapered inclined surface 72 and the tapered sleeve 73 cooperate to convert the axial movement of the pressing positioning cylinder 71 into radial and angular adjustment of the coaxial positioning sleeve 75, and improve the axial stability after adjustment by utilizing the circumferential limiting characteristics of the tapered surface. The ball bearing 74 can reduce the movement resistance of the tapered sleeve 73 during adjustment, and the electromagnetic locking mechanism 77 can maintain the adjustment result after adjustment, preventing the coaxial positioning sleeve 75 from loosening due to the rotation of the small hole boring bar 4 and the cutting force.

[0047] Reference Figure 7 and Figure 8As shown, a set of tensioning components 8 are respectively installed at the lower ends of the large-hole boring bar 3 and the small-hole boring bar 4. The tensioning component 8 includes a mounting cylinder 81 installed at the lower end of the corresponding boring bar. A miniature push rod 82 is fixedly installed inside the mounting cylinder 81. The output end of the miniature push rod 82 is set downward and fixedly connected to an inverted conical push block 83. Multiple sets of synchronous push rods 84 are arranged circumferentially at intervals on the outer periphery of the inverted conical push block 83. Each synchronous push rod 84 passes through the side wall of the mounting cylinder 81 radially and is slidably connected to the mounting cylinder 81.

[0048] The inner end of the synchronous push rod 84 forms an inclined contact surface that mates with the outer conical surface of the inverted conical push block 83, and slides against the inverted conical push block 83. A return spring 85 is fitted onto the portion of the synchronous push rod 84 extending out of the mounting cylinder 81. One end of the return spring 85 abuts against the mounting cylinder 81, and the other end applies a return force towards the interior of the mounting cylinder 81 to the synchronous push rod 84. When the miniature push rod 82 pushes the inverted conical push block 83 downwards, the inverted conical push block 83 uses its outer conical surface to synchronously push each synchronous push rod 84 outwards, causing each synchronous push rod 84 to unfold radially. When the miniature push rod 82 drives the inverted conical push block 83 upwards, each synchronous push rod 84 retracts synchronously inwards under the action of the return spring 85.

[0049] Each of the synchronous push rods 84 at the lower end of the large-hole boring bar 3 has a tensioning block 12 fixedly connected to its outer end. After moving outward with the synchronous push rods 84, the tensioning block 12 abuts against the inner wall of the precision-bored large-end hole 91. Multiple sets of tensioning blocks 12 support the large-end hole 91 from different circumferential positions, ensuring that the radial center of the large-hole boring bar 3 is aligned with the actual center of the large-end hole 91. During this process, the large-hole boring bar 3 maintains its original axial posture through its drive end. Therefore, the tensioning block 12 is mainly used to eliminate the radial clearance between the large-hole boring bar 3 and the large-end hole 91, and to stabilize the actual axis of the large-end hole 91 reflected by the large-hole boring bar 3.

[0050] Each of the synchronous push rods 84 at the lower end of the small-hole boring bar 4 is rotatably connected to a spherical block 13. After the small-hole boring bar 4 descends to the axial center of the small-end hole 92, each spherical block 13 synchronously unfolds outward and abuts against the pre-machined hole wall of the small-end hole 92. The spherical block 13 forms a point-like or small-area contact with the hole wall, and the spherical block 13 can rotate relative to the synchronous push rod 84. Therefore, when there is a center offset, irregular hole wall, or local allowance difference in the pre-machined hole of the small-end hole 92, each spherical block 13 can perform slight rolling and posture adaptation, reducing the degree of inheritance of the local shape of the pre-machined hole by the rigid expansion block.

[0051] After the spherical blocks 13 unfold synchronously, the lower end of the small-hole boring bar 4 forms a centering fulcrum with the center of the small-end hole 92 in the axial direction. Subsequently, the coaxial positioning sleeve 75 adjusts the axial direction of the small-hole boring bar 4 from the upper part, allowing the small-hole boring bar 4 to deflect to a limited extent around this centering fulcrum. This structure, on the one hand, retains the actual center position of the pre-machined hole of the small-end hole 92, reducing the possibility of excessive machining allowance on one side due to forced changes in the center position; on the other hand, it uses the actual axial direction of the large-end hole 91 to correct the original axial tilt of the pre-machined hole of the small-end hole 92, thus taking into account both the allowance distribution of the small-end hole 92 and the parallelism of the axes of the large and small ends.

[0052] Working principle: Before the device operates, the connecting rod workpiece 9 is placed on the worktable 2, so that the large end hole 91 and the small end hole 92 correspond to the large hole boring bar 3 and the small hole boring bar 4, respectively. Then, the clamping mechanism 10 is used to clamp and fix the connecting rod workpiece 9. At this time, the synchronous push rod 84 of the lower end tensioning assembly 8 of the large hole boring bar 3 and the small hole boring bar 4 are both in the retracted state, and the tensioning block 12 and the spherical block 13 are both located in the contracted position on the outer periphery of the mounting cylinder 81.

[0053] First, the drive mechanism corresponding to the large-hole boring bar 3 is activated, causing the large-hole boring bar 3 to rotate and feed downwards to perform fine boring of the large-end hole 91. The expansion assembly 8 at the lower end of the large-hole boring bar 3, which is in a retracted state, passes through the large-end hole 91 and enters the corresponding clearance hole 11 to prevent the expansion assembly 8 from affecting the boring process of the large-end hole 91. After the large-end hole 91 is finished, the large-hole boring bar 3 stops cutting and moves upwards along the axial direction, so that the expansion block 12 at its lower end is located inside the large-end hole 91.

[0054] The miniature push rod 82 at the lower end of the large-hole boring bar 3 pushes the inverted conical push block 83 downward. The inverted conical push block 83 simultaneously pushes each synchronous push rod 84 outward, causing multiple sets of expansion blocks 12 to expand radially and abut against the inner wall of the large-end hole 91 after precision boring. Through the circumferential support of multiple sets of expansion blocks 12, the large-hole boring bar 3 is stably maintained at the actual center position of the large-end hole 91. Combined with the axial constraint of the drive end of the large-hole boring bar 3, the large-hole boring bar 3 can serve as a reference component reflecting the actual axial direction of the large-end hole 91.

[0055] Subsequently, the small-hole boring bar 4 moves downward under the drive of its driving mechanism, causing its lower end tensioning assembly 8 to enter the small-end hole 92, and positioning the spherical block 13 at the axial center of the small-end hole 92. The miniature push rod 82 at the lower end of the small-hole boring bar 4 pushes the inverted conical push block 83 downward, causing each synchronous push rod 84 to drive the spherical block 13 to unfold outward synchronously. After each spherical block 13 contacts the pre-machined hole wall of the small-end hole 92, the actual center of the axial center of the small-end hole 92 is determined by rotation and radial adaptation, so that the small-hole boring bar 4 forms a centering fulcrum at this position.

[0056] After establishing the axial reference of the large end bore 91 and centering the middle of the small end bore 92, the downward push rod 51 extends and drives the rigid telescopic connecting rod 53 to descend via the flexible connecting block 52. The rigid telescopic connecting rod 53 drives the fixed shaft assembly 6 and the adjusting shaft assembly 7 to descend synchronously. After the fixed shaft cylinder 61 descends to the outside of the fixed shaft part 65, each eccentric pressure roller 62 contacts the rough outer circumferential surface of the fixed shaft part 65 and rotates. Each eccentric shaft 63 maintains synchronous rotation through the meshing bevel gears 64, causing the eccentric portions of each eccentric pressure roller 62 to synchronously turn towards the fixed shaft part 65 and press against the fixed shaft part 65 from different circumferential positions. The fixed shaft cylinder 61 thus remains coaxial with the large hole boring bar 3, so that the downward positioning cylinder 71 connected to it via the rigid telescopic connecting rod 53 takes a direction parallel to the actual axis of the large end bore 91.

[0057] As the lowering positioning cylinder 71 continues to descend, its internal tapered inclined surface 72 gradually contacts the balls 74 on the upper and lower edges of the tapered sleeve 73. If the initial axis of the tapered sleeve 73 and the coaxial positioning sleeve 75 deviates from the axis of the lowering positioning cylinder 71, the tapered inclined surface 72 first applies an adjustment to the tapered sleeve 73 through the balls 74 on the side of the deviation. Since the coaxial positioning sleeve 75 is fitted outside the small-hole boring bar 4, the small-hole boring bar 4 can be slightly deflected within the compensation range allowed by the diaphragm coupling, using the centering fulcrum established by the spherical block 13.

[0058] As the tapered inclined surface 72 gradually comes into contact with the tapered sleeve 73, the axes of the tapered sleeve 73 and the coaxial positioning sleeve 75 are gradually adjusted to be consistent with the axis of the pressing positioning cylinder 71, thereby adjusting the axis of the small hole boring bar 4 to be parallel to the actual axis of the large end hole 91. After the axis adjustment is completed, the electromagnetic locking mechanism 77 is energized to lock the tapered sleeve 73 inside the pressing positioning cylinder 71, so that the coaxial positioning sleeve 75 maintains the adjusted axis position.

[0059] After the shaft adjustment assembly 7 is locked, the miniature push rod 82 at the lower end of the small hole boring bar 4 drives the inverted tapered push block 83 to return to its original position. Each synchronous push rod 84 retracts into the mounting cylinder 81 under the action of the return spring 85, separating the spherical block 13 from the wall of the small end hole 92. Then, the drive mechanism corresponding to the small hole boring bar 4 is activated, causing the small hole boring bar 4 to rotate and feed downwards along the coaxial positioning sleeve 75, performing precision boring on the small end hole 92. During the rotation and feeding of the small hole boring bar 4, the coaxial positioning sleeve 75 continuously restricts its radial and angular deviation, ensuring that the small hole boring bar 4 maintains its adjusted machining direction.

[0060] After the small-end hole 92 is precision bored, the small-end boring bar 4 stops rotating and retracts upward. The electromagnetic locking mechanism 77 is de-energized and released, and the downward push rod 51 retracts, driving the fixed axis assembly 6 and the adjusting axis assembly 7 to rise. After the fixed axis assembly 6 disengages from the fixed axis part 65, each eccentric pressure roller 62 returns to the released state; the miniature push rod 82 at the lower end of the large-end boring bar 3 drives the inverted tapered push block 83 to reset, causing the expansion block 12 to retract under the action of the return spring 85. Finally, the clamping mechanism 10 releases its grip on the connecting rod workpiece 9, and the connecting rod workpiece 9, which has completed the precision boring of the small and large end holes, can be taken out and enter the next machining cycle.

[0061] The technical scope of this invention is not limited to the content described above. Those skilled in the art can make various modifications and variations to the above embodiments without departing from the technical concept of this invention, and all such modifications and variations should fall within the protection scope of this invention.

Claims

1. A coaxial precision boring device for the large and small end bores of a diesel engine connecting rod, characterized in that, The device includes a precision boring unit, a worktable, and a clamping mechanism mounted on the worktable. The precision boring unit has a large-hole boring bar and a small-hole boring bar. The clamping mechanism holds a connecting rod workpiece, which includes a large-end hole and a small-end hole. The lower end of the large-hole boring bar is equipped with a tensioning component that expands radially along the large-end hole after precision boring, so that the large-hole boring bar is kept in the actual axial position of the large-end hole. The small-hole boring bar is connected to the drive mechanism through a coupling structure that allows slight deflection. Its lower end is equipped with a tensioning component that expands radially in the axial middle of the small-end hole, so that the small-hole boring bar uses the center of the pre-machined hole as the centering fulcrum. The main body of the precision boring device is also provided with a connecting assembly, which includes a rigid telescopic connecting rod. The two ends of the rigid telescopic connecting rod are respectively connected to a fixed axis assembly sleeved on the outside of the large hole boring rod and an adjusting axis assembly sleeved on the outside of the small hole boring rod. The adjusting axis assembly includes a downward positioning cylinder that is parallel to the axis of the fixed axis assembly. A conical sleeve is sleeved inside the downward positioning cylinder. A coaxial positioning sleeve passes through the inside of the conical sleeve. The inner side of the downward positioning cylinder forms a conical inclined surface that cooperates with the conical sleeve. When the connecting assembly moves down, the fixed axis assembly obtains the actual axis direction of the large end hole based on the large hole boring bar. The tapered inclined surface pushes the tapered sleeve and the coaxial positioning sleeve to drive the small hole boring bar to deflect around the centering fulcrum until the axis of the small hole boring bar is parallel to the actual axis of the large end hole. After the shaft adjustment assembly locks, the coaxial positioning sleeve limits and guides the fine boring movement of the small hole boring bar.

2. The coaxial precision boring device for connecting rod large and small end holes of a diesel engine according to claim 1, characterized in that: The coupling structure is a diaphragm coupling, which is used to transmit the torque output by the drive mechanism to the small hole boring bar and allows the small hole boring bar to produce radial offset and angular deflection relative to the drive mechanism.

3. The coaxial precision boring device for the connecting rod large and small end holes of a diesel engine according to claim 1, characterized in that: The connecting assembly also includes a downward push rod installed on the main body of the precision boring device. The output end of the downward push rod is connected to the middle of the rigid telescopic connecting rod through a flexible connecting block, which is used to drive the fixed axis assembly and the adjusting axis assembly to move up and down synchronously.

4. The coaxial precision boring device for connecting rod large and small end holes of a diesel engine according to claim 1, characterized in that: The fixed-axis assembly includes a fixed-axis cylinder connected to a rigid telescopic connecting rod. Multiple sets of eccentric pressure rollers are arranged circumferentially inside the fixed-axis cylinder. Each eccentric pressure roller has an eccentric shaft passing through it eccentrically, and the eccentric pressure roller is fixedly connected to the corresponding eccentric shaft.

5. A coaxial precision boring device for connecting rod large and small end holes of a diesel engine according to claim 4, characterized in that: Each eccentric shaft is fixedly connected to a bevel gear at its end, and the bevel gears on adjacent eccentric shafts mesh with each other; a fixed shaft part is fixedly connected to the outer wall of the large hole boring bar, the outer diameter of the fixed shaft part is larger than the outer diameter of the large hole boring bar, and its outer circumferential surface is a rough surface that can drive the eccentric pressure roller to rotate synchronously.

6. The coaxial precision boring device for connecting rod large and small end holes of a diesel engine according to claim 1, characterized in that: The tapered sleeve has multiple sets of balls arranged circumferentially on its upper and lower edges. The coaxial positioning sleeve is slidably sleeved on the outside of the small hole boring bar. A support block located below the coaxial positioning sleeve is fixedly connected to the small hole boring bar.

7. A coaxial precision boring device for connecting rod large and small end holes of a diesel engine according to claim 1, characterized in that: An electromagnetic locking mechanism is provided on the opposite surface of the conical inclined surface and the conical sleeve. The electromagnetic locking mechanism is used to lock the conical sleeve into the pressing positioning cylinder after the axis of the coaxial positioning sleeve is adjusted.

8. A coaxial precision boring device for connecting rod large and small end holes of a diesel engine according to claim 1, characterized in that: The tensioning assembly includes a mounting cylinder installed at the lower end of the corresponding boring bar. A miniature push rod is installed inside the mounting cylinder, and the output end of the miniature push rod is fixedly connected to an inverted conical push block. Multiple sets of synchronous push rods that radially penetrate the mounting cylinder are arranged on the outer periphery of the inverted conical push block. The inner end of the synchronous push rod slides against the conical surface of the inverted conical push block, and a return spring is sleeved on the part of the push rod that extends out of the mounting cylinder.

9. A coaxial precision boring device for connecting rod large and small end holes of a diesel engine according to claim 1, characterized in that: The outer ends of the synchronous push rods at the lower end of the large-hole boring bar are fixedly connected to tension blocks, and the outer ends of the synchronous push rods at the lower end of the small-hole boring bar are rotatably connected to spherical blocks; the worktable is provided with clearance holes corresponding to the large-end hole and the small-end hole respectively, for the tensioning components in the retracted state to enter.

10. A method for coaxial precision boring of the large and small end bores of a diesel engine connecting rod according to claim 1, characterized in that: The steps include the following: S1. Clamp the connecting rod workpiece on the worktable so that the large end hole and the small end hole correspond to the large hole boring bar and the small hole boring bar, respectively; S2. Use a large-hole boring bar to precision bore the large end hole, and make the expansion block at its lower end radially expand to abut against the inner wall of the large end hole to establish the actual axis reference of the large end hole; S3. Make the spherical block at the lower end of the small hole boring bar expand radially in the middle of the small end hole to form the centering fulcrum of the small hole boring bar; S4. Drive the connecting assembly to descend, so that the fixed axis assembly determines the axis direction based on the large hole boring bar, and the adjusting axis assembly drives the small hole boring bar to deflect around the centering fulcrum until the axis of the small hole boring bar is parallel to the actual axis of the large end hole, and then lock the adjusting axis assembly; S5. Retract the spherical block and drive the small hole boring bar to rotate and feed along the coaxial positioning sleeve to complete the fine boring of the small end hole.

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