A differential boring mechanism for the wide and deep tapered bore of ultra-large ship rudder blades

Abstract

This invention discloses a differential boring mechanism for ultra-large ship rudder blades with wide and deep tapered holes, belonging to the technical field of boring machining of ship rudder blades with wide and deep tapered holes. It includes a spindle drive unit for providing the main rotary cutting motion of the tool; a feed drive unit for providing the axial feed power of the tool; a hollow spindle connected to the spindle drive unit and fixed to the tool table for driving the tool on the tool table to rotate; a feed shaft coaxially passing through the hollow spindle and rotating independently of it, one end of which is connected to the power output end of the feed drive unit; a motion conversion unit connected to the other end of the feed shaft for converting the rotational motion of the feed shaft into the axial feed motion of the tool; a speed difference is formed between the hollow spindle and the feed shaft, which is converted into the axial feed amount of the tool by the motion conversion unit. This invention can solve the tool runout problem caused by radial cutting force imbalance during single-edge boring.

Description

Technical Field

[0001] This invention belongs to the field of boring technology for the wide and deep tapered holes of ship rudder blades, specifically relating to a differential boring mechanism for the wide and deep tapered holes of ultra-large ship rudder blades. Background Technology

[0002] In the field of large shipbuilding and maintenance, rudder blades, as key components for controlling course, typically have internally machined large-scale tapered bore structures for mounting rudder pins, bearings, and sealing components. For ultra-large ships, the external dimensions of rudder blades often reach several meters or even more than ten meters, and their tapered bores are characterized by large diameters and small tapers. The geometric accuracy and surface quality of these deep and wide tapered bores directly determine the assembly clearance between the rudder stock and the rudder blade, as well as the uniformity of the rudder turning torque, thus affecting the overall ship's maneuverability. However, due to the rudder blade's bulky structure, uneven rigidity, and the fact that it is usually made of high-strength hull steel or corrosion-resistant duplex stainless steel, its machinability is poor, making traditional boring methods face serious technical bottlenecks when machining rudder blades for ultra-large ships.

[0003] To address the core issue of uneven tool stress and difficulty in balancing radial cutting forces when machining ultra-large ship rudder blades, existing single-edge, intermittent feed boring methods can only improve machining stability by adding auxiliary support structures. However, most of these solutions are still passive force suppression measures, i.e., reducing the impact of tool deformation by increasing tool stiffness or reducing cutting parameters, failing to solve the tool runout problem caused by unilateral cutting forces. Furthermore, differential boring bars or differential continuously variable feed mechanisms, due to their complex structure and manufacturing limitations, have not yet been successfully applied in the machining of wide and deep tapered holes for large ship rudder blades, both domestically and internationally.

[0004] To address the unique machining characteristics of the deep-broad tapered bore in ultra-large ship rudder blades, a deep integration of the differential principle with the boring mechanism, resulting in a boring device with the differential mechanism as the core of motion conversion, could solve problems in existing technologies such as strong dependence on forming tools, difficulty in suppressing tool deformation, and tool runout caused by unilateral cutting forces. Based on the above analysis, a differential boring mechanism for the deep-broad tapered bore in ultra-large ship rudder blades has been developed, which is of significant engineering importance for improving the independent machining capabilities of core components of large ships. Summary of the Invention

[0005] This invention addresses the aforementioned problems and overcomes the shortcomings of existing technologies by providing a differential boring mechanism for the wide and deep tapered holes of ultra-large ship rudder blades. This invention can overcome the defects of high machining difficulty and poor machining accuracy in the machining of wide and deep tapered holes of ultra-large ship rudder blades, and in particular, it can solve the problem of tool runout caused by radial cutting force imbalance during single-edge boring.

[0006] To achieve the above objectives, the present invention adopts the following technical solution.

[0007] This invention provides a differential boring mechanism for the wide and deep tapered bore of ultra-large ship rudder blades, comprising: The spindle drive unit is used to provide the main motion for the tool to rotate and cut. The feed drive unit is used to provide power for the axial feed of the tool; A hollow spindle is connected to the spindle drive unit and fixed to the tool table to drive the tool on the tool table to rotate. The feed shaft is coaxially inserted in the hollow main shaft and rotates independently of the hollow main shaft. One end of the feed shaft is connected to the power output end of the feed drive unit. A motion conversion unit is connected to the other end of the feed axis for converting the rotational motion of the feed axis into the axial feed motion of the tool. A speed difference is formed between the hollow spindle and the feed axis, and the speed difference is converted into the axial feed amount of the tool by the motion conversion unit.

[0008] In a preferred embodiment of the present invention, both the spindle drive unit and the feed drive unit are servo motors. The servo motors are connected to a servo control system for independently setting the speed of the hollow spindle and the speed of the feed shaft, so as to adjust the speed difference between the two.

[0009] As another preferred embodiment of the present invention, the power output end of the spindle drive unit is connected to a first belt drive mechanism, and the spindle drive unit and the hollow spindle are connected by the first belt drive mechanism; the other end of the feed shaft is connected to a second belt drive mechanism, and the other end of the feed shaft is connected to the motion conversion unit by the second belt drive mechanism; the second belt drive mechanism is used to transmit the rotational motion of the feed shaft to the motion conversion unit and realize the deceleration or acceleration of a predetermined transmission ratio.

[0010] As another preferred embodiment of the present invention, the motion conversion unit includes an output shaft and a ball screw, the output shaft being drivenly connected to the feed shaft, and the ball screw being connected to the output shaft, for converting rotary motion into axial linear motion of the tool.

[0011] As another preferred embodiment of the present invention, at least two cutting tools are mounted on the tool table, and each cutting tool is distributed circumferentially, wherein at least one cutting tool is used as a roughing tool and at least one cutting tool is used as a finishing tool; the roughing tool and the finishing tool have a phase difference in the circumferential direction, and their axial positions maintain a preset misalignment during the machining process.

[0012] As another preferred embodiment of the present invention, the servo control system includes a first encoder for detecting the rotational speed of the hollow spindle and a second encoder for detecting the rotational speed of the feed axis. Both the first encoder and the second encoder are signal-connected to the servo controller to form a closed-loop speed control.

[0013] As another preferred embodiment of the present invention, both the first belt drive mechanism and the second belt drive mechanism are transmission mechanisms composed of a synchronous belt and a pulley, wherein the synchronous belt is used to filter the torque pulsation of the servo motor.

[0014] As another preferred embodiment of the present invention, the tool table and the hollow spindle are an integral structure, and the tool has no axial feed motion when the tool table rotates synchronously with the hollow spindle.

[0015] As another preferred embodiment of the present invention, the roughing tool and the finishing tool are arranged 180° apart in the circumferential direction to make the radial cutting forces generated by the two tools cancel each other out; the roughing tool and the finishing tool have a preset misalignment in the axial direction to form an axial misalignment layout in which roughing comes first and finishing comes later, so that roughing and finishing are completed in one pass.

[0016] As another preferred embodiment of the present invention, a sliding bearing or a rolling bearing is provided between the hollow spindle and the feed shaft to support the feed shaft to rotate in the hollow spindle and keep the two coaxial.

[0017] Beneficial effects of this invention: 1. The present invention provides a differential boring mechanism for the wide and deep tapered hole of a super-large ship rudder blade. Through the structural design of the hollow spindle and the feed axis being coaxially mounted, the center of rotational mass coincides with the geometric center, eliminating radial vibration caused by the eccentricity of the rotating mass. The present invention combines multiple means such as synchronous belt flexible buffering to filter torque pulsation, using the speed difference between the hollow spindle and the feed axis to drive axial feed (i.e., differential principle) and using its deceleration and force amplification characteristics to improve radial feed rigidity, dual-blade collaborative cutting to cancel out radial forces, and servo closed-loop real-time correction, thereby solving the tool runout problem of traditional single-blade boring.

[0018] 2. This invention uses two independently driven servo motors to control the rotational speeds of the hollow spindle and the feed axis respectively, thereby achieving independent control and precise adjustment of the cutting main motion and the axial feed motion, without interference between them.

[0019] 3. The coaxial design of the hollow spindle and feed axis makes the overall radial dimension of the boring mechanism of the present invention small, which can extend into the inner cavity of the ultra-large rudder blade for deep hole machining; the dual-blade collaborative cutting completes roughing and finishing in one pass, improving machining efficiency and improving the surface quality of the machined tapered hole.

[0020] 4. By utilizing the speed difference between the hollow spindle and the feed axis and the synergistic effect of servo control, the present invention can realize efficient, high-precision and low-cost boring of the wide and deep tapered hole of ultra-large ship rudder blades on machine tools. Attached Figure Description

[0021] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the description of the embodiments of this application will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 This is a schematic diagram of the overall structure of a differential boring mechanism for the wide and deep tapered bore of a super-large ship rudder blade, provided as an embodiment of the present invention.

[0023] Figure 2 This is a front view structural schematic diagram of a differential boring mechanism for a wide and deep tapered hole of a super-large ship rudder blade, provided as an embodiment of the present invention.

[0024] Figure 3 This is a left-side structural schematic diagram of a differential boring mechanism for a wide and deep tapered hole of a super-large ship rudder blade, provided as an embodiment of the present invention.

[0025] Figure 4 This is a right-side structural schematic diagram of a differential boring mechanism for a wide and deep tapered hole of a super-large ship rudder blade, provided in an embodiment of the present invention.

[0026] Figure 5 This is a top view schematic diagram of a differential boring mechanism for the wide and deep tapered bore of a super-large ship rudder blade, provided as an embodiment of the present invention.

[0027] In the diagram, the markings are as follows: 1 is the main spindle drive unit; 2 is the feed drive unit; 3 is the first pulley; 4 is the first synchronous belt; 5 is the second pulley; 6 is the hollow spindle; 7 is the feed shaft; 8 is the third pulley; 9 is the second synchronous belt; 10 is the output shaft; 11 is the fourth pulley; 12 is the first belt drive mechanism; and 13 is the second belt drive mechanism. Detailed Implementation

[0028] To make the technical problems solved, the technical solutions, and the beneficial effects of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0029] like Figures 1 to 5As shown in the figure, an embodiment of the present invention provides a differential boring mechanism for a wide and deep tapered hole of a super-large ship rudder blade, mainly comprising a spindle drive unit 1, a feed drive unit 2, a hollow spindle 6, a feed shaft 7, a first belt drive mechanism 12, a second belt drive mechanism 13, and a motion conversion unit. Both the spindle drive unit 1 and the feed drive unit 2 employ servo motors, which are connected to a servo control system for independently setting the rotational speed of the hollow spindle 6 and the rotational speed of the feed shaft 7 to adjust the speed difference between them. The motion conversion unit includes an output shaft 10 and a ball screw. The output shaft 10 is drive-connected to the feed shaft 7, and the ball screw is connected to the output shaft 10, for converting rotary motion into axial linear motion of the tool. The first belt drive mechanism 12 consists of a first pulley 3, a first synchronous belt 4, and a second pulley 5. The first pulley 3 is fixedly sleeved on the motor shaft of the main shaft drive unit 1, and the second pulley 5 is fixedly sleeved on the hollow main shaft 6. The first synchronous belt 4 connects the first pulley 3 and the second pulley 5. The second belt drive mechanism 13 consists of a third pulley 8, a second synchronous belt 9, and a fourth pulley 11. The third pulley 8 is fixedly sleeved on the feed shaft 7, and the fourth pulley 11 is fixedly sleeved on the output shaft 10 of the motion conversion unit. The second synchronous belt 9 connects the third pulley 8 and the fourth pulley 11. That is, both the first belt drive mechanism 12 and the second belt drive mechanism 13 adopt a transmission mechanism composed of a synchronous belt and a pulley. The synchronous belt is used to filter the torque pulsation of the servo motor.

[0030] Specifically, the spindle drive unit 1 is a servo motor for the hollow spindle 6, used to drive the cutting tool to rotate and cut. After the operator sets the speed of the spindle drive unit 1, the spindle drive unit 1 is started. The motor shaft of the spindle drive unit 1 outputs power to the first pulley 3 of the first belt drive mechanism 12 through a coupling. The first pulley 3 transmits power to the second pulley 5 through the first synchronous belt 4. The second pulley 5 drives the hollow spindle 6 to rotate. The hollow spindle 6 is integrally connected to the tool table. When the tool table rotates with the hollow spindle 6, it rotates in a fixed position, and the tool has no axial feed motion (the tool table and the tool are not shown in the figure).

[0031] Specifically, the feed drive unit 2 is a servo motor for the feed shaft 7, used to provide power for the axial feed of the tool. The motor shaft of the feed drive unit 2 is connected to the feed shaft 7 via a coupling, thus outputting power to the feed shaft 7. The feed shaft 7 is coaxially mounted in the hollow spindle 6, and the two rotate independently without interference. When the feed shaft 7 rotates, it drives the third pulley 8 of the second belt drive mechanism 13 to rotate. The third pulley 8 transmits power to the fourth pulley 11 via the second synchronous belt 9. The fourth pulley 11 drives the output shaft 10 of the motion conversion unit to rotate. The end of the output shaft 10 is connected to a ball screw (not shown in the figure), which acts on the ball screw through the second belt drive mechanism 13 to convert the rotational motion into the axial linear motion of the tool, thereby realizing the axial feed of the tool.

[0032] The present invention addresses the solution mechanism for tool runout from multiple levels, systematically resolving the problem, as detailed below: (1) Structural level – Coaxial assembly eliminates radial vibration. The hollow spindle 6 is a hollow shaft, and the feed shaft 7 is coaxially inserted into the hollow spindle 6, and the two rotate coaxially. This coaxial assembly structure makes the center of the rotating mass coincide with the geometric center, eliminating the centrifugal force caused by the eccentricity of the rotating mass from a physical structure point of view, and thus eliminating the radial vibration caused by it. This is the fundamental structural guarantee for suppressing tool runout. At the same time, sliding bearings or rolling bearings can be installed between the hollow spindle 6 and the feed shaft 7 to further ensure their coaxiality and support the feed shaft 7 to rotate smoothly in the hollow spindle 6.

[0033] (2) Transmission Level – Synchronous Belt Flexible Buffer Filtering of Torque Pulse. Power transmission adopts a belt drive mechanism. The first synchronous belt 4 of the first belt drive mechanism 12 and the second synchronous belt 9 of the second belt drive mechanism 13 have good flexible buffering effect, which can effectively filter the torque pulsation generated during the operation of the servo motor, making the rotational motion transmitted to the hollow spindle 6 and the feed shaft 7 more stable and avoiding instantaneous sway caused by torque fluctuations. Compared with traditional gear transmission, belt transmission does not generate meshing impact, further reducing vibration sources.

[0034] (3) Feed Level – Speed ​​Difference Drives Feed and Improves Radial Feed Rigidity. When there is a speed difference between the feed shaft 7 and the hollow spindle 6, this speed difference is transmitted to the output shaft 10 of the motion conversion unit via the second belt drive mechanism 13, and further converted into the axial feed of the tool via the ball screw. Since the difference between the speed of the feed shaft 7 and the speed of the hollow spindle 6 is converted into a small displacement of the tool via the transmission chain, the tool can obtain extremely high resolution axial feed. More importantly, the feed transmission chain driven by the speed difference (i.e., feed shaft 7 → second belt drive mechanism 13 → output shaft 10 → ball screw) improves the overall rigidity of the radial feed system due to its deceleration and force amplification characteristics, which significantly enhances its ability to resist radial force fluctuations during cutting and effectively reduces the tool effect. It should be noted that in this invention, "differential" refers to the "speed difference" between the hollow spindle 6 and the feed shaft 7 and the axial feed motion relationship driven by it.

[0035] (4) Cutting Surface – Dynamic Force Balance Achieved Through Dual-Tool Collaboration. At least two tools are mounted on the tool table, distributed circumferentially. One tool serves as the roughing tool, and the other as the finishing tool. The two tools have a phase difference in the circumferential direction and maintain a preset misalignment in their axial positions. When the hollow spindle 6 drives the tool table to rotate, the two tools cut the workpiece surface sequentially – the roughing tool removes most of the excess material first, and the finishing tool then finishes the surface. Because the two tools are offset by a certain angle in the circumferential direction, the radial cutting forces they generate are also offset in direction, resulting in a more uniform and symmetrical distribution of the overall radial force, avoiding tool wobble caused by the continuous action of unidirectional radial force during single-edge cutting. This dual-tool collaborative cutting mechanism achieves the dispersion and balance of radial force from the source of the cutting force.

[0036] (5) Control Level – Servo Closed-Loop Real-Time Correction. Both the spindle drive unit 1 and the feed drive unit 2 use servo motors and are equipped with encoders (not shown in the figure) to detect the rotational speeds of the hollow spindle 6 and the feed axis 7 in real time, and feed the detection signals back to the servo controller to form a closed-loop speed control. If a slight yaw tendency is caused by abnormal force, the speed fluctuation can be sensed through the encoder feedback, and the control parameters can be dynamically corrected to achieve “suppression before yaw” rather than “compensation after yaw”. In addition, the servo control system allows the operator to independently set the rotational speeds of the hollow spindle 6 and the feed axis 7 according to the machining requirements. The mapping relationship between the two can be precisely controlled, thereby realizing continuous boring of any taper.

[0037] The differential working principle of this invention is as follows: Since the hollow spindle 6 and feed axis 7 are independent and driven by spindle drive unit 1 and feed drive unit 2 respectively, a speed difference exists between the two when their speeds differ. This speed difference is converted into the axial feed of the tool through the transmission chain of feed axis 7 → second belt drive mechanism 13 → output shaft 10 of motion conversion unit → ball screw. Specifically, the difference between the speed of feed drive unit 2 and the speed of spindle drive unit 1 determines the speed of the tool's axial feed; a constant speed difference results in a constant taper; a continuously changing speed difference enables variable taper machining. The operator can accurately control the taper parameters of the taper hole by independently setting the speeds of spindle drive unit 1 and feed drive unit 2 through the control panel, without replacing any mechanical parts, thus realizing the digitalization and flexibility of taper machining.

[0038] A preferred embodiment of the dual-tool collaborative machining of the present invention: In this embodiment, two tools are arranged on the tool table, with the two tools positioned 180° apart circumferentially. During machining, the axial position of the roughing tool protrudes a predetermined distance relative to the finishing tool, preferably 0.5-2mm, so that the two tools form a "roughing first, finishing second" layout axially. During one revolution of the hollow spindle 6, the roughing tool first contacts the workpiece surface to remove most of the excess material, and then the finishing tool trims and finishes the machined surface, completing both roughing and finishing processes in a single pass. Because the two tools are symmetrically arranged circumferentially, the radial cutting forces they generate are opposite in direction and similar in magnitude, achieving mutual cancellation of radial forces, thereby avoiding tool wobble during single-edge cutting.

[0039] It will be apparent to those skilled in the art that the present invention is not limited to the specific details of the exemplary embodiments described above, and that other forms may be used to implement it without departing from the spirit or essential characteristics of the invention. Therefore, the above embodiments should be considered exemplary rather than restrictive, and the scope of protection of the present invention should be determined by the appended claims, not by the foregoing description, and should cover all technical solutions falling within the scope of equivalent substitutions of the claims.

Claims

1. A differential boring mechanism for the wide and deep tapered bore of a super-large ship rudder blade, characterized in that, include: The spindle drive unit is used to provide the main motion for the tool to rotate and cut. The feed drive unit is used to provide power for the axial feed of the tool; A hollow spindle is connected to the spindle drive unit and fixed to the tool table to drive the tool on the tool table to rotate. The feed shaft is coaxially inserted in the hollow main shaft and rotates independently of the hollow main shaft. One end of the feed shaft is connected to the power output end of the feed drive unit. A motion conversion unit is connected to the other end of the feed axis for converting the rotational motion of the feed axis into the axial feed motion of the tool. A speed difference is formed between the hollow spindle and the feed axis, and the speed difference is converted into the axial feed amount of the tool by the motion conversion unit.

2. The differential boring mechanism for the wide and deep tapered bore of a super-large ship rudder blade according to claim 1, characterized in that: Both the spindle drive unit and the feed drive unit are servo motors. The servo motors are connected to a servo control system, which is used to independently set the speed of the hollow spindle and the speed of the feed axis to adjust the speed difference between the two.

3. The differential boring mechanism for the wide and deep tapered bore of a super-large ship rudder blade according to claim 2, characterized in that: The power output end of the main spindle drive unit is connected to a first belt drive mechanism, and the main spindle drive unit and the hollow main spindle are connected by the first belt drive mechanism; the other end of the feed shaft is connected to a second belt drive mechanism, and the other end of the feed shaft is connected to the motion conversion unit by the second belt drive mechanism; the second belt drive mechanism is used to transmit the rotational motion of the feed shaft to the motion conversion unit and realize the deceleration or acceleration of a predetermined transmission ratio.

4. The differential boring mechanism for the wide and deep tapered bore of a super-large ship rudder blade according to claim 1, characterized in that: The motion conversion unit includes an output shaft and a ball screw. The output shaft is connected to the feed shaft, and the ball screw is connected to the output shaft to convert rotary motion into axial linear motion of the tool.

5. The differential boring mechanism for the wide and deep tapered bore of a super-large ship rudder blade according to claim 1, characterized in that: At least two cutting tools are mounted on the tool table, and each cutting tool is distributed circumferentially. At least one cutting tool is used as a roughing tool and at least one cutting tool is used as a finishing tool. The roughing tool and the finishing tool have a phase difference in the circumferential direction, and their axial positions maintain a preset misalignment during the machining process.

6. The differential boring mechanism for the wide and deep tapered bore of a super-large ship rudder blade according to claim 2, characterized in that: The servo control system includes a first encoder for detecting the rotational speed of the hollow spindle and a second encoder for detecting the rotational speed of the feed axis. Both the first encoder and the second encoder are connected to the servo controller to form a closed-loop speed control.

7. The differential boring mechanism for the wide and deep tapered bore of a super-large ship rudder blade according to claim 3, characterized in that: Both the first belt drive mechanism and the second belt drive mechanism are transmission mechanisms composed of a synchronous belt and a pulley. The synchronous belt is used to filter the torque pulsation of the servo motor.

8. The differential boring mechanism for the wide and deep tapered bore of a super-large ship rudder blade according to claim 1, characterized in that: The tool table and the hollow spindle are an integral structure. When the tool table rotates synchronously with the hollow spindle, the tool has no axial feed motion.

9. The differential boring mechanism for the wide and deep tapered bore of a super-large ship rudder blade according to claim 5, characterized in that: The roughing tool and the finishing tool are arranged 180° apart in the circumferential direction to cancel out the radial cutting forces generated by the two tools. The roughing tool and the finishing tool have a preset misalignment in the axial direction, forming an axial misalignment layout with roughing in front and finishing behind, so that roughing and finishing are completed in one pass.

10. The differential boring mechanism for the wide and deep tapered bore of a super-large ship rudder blade according to claim 1, characterized in that: A sliding bearing or rolling bearing is provided between the hollow spindle and the feed shaft to support the feed shaft to rotate within the hollow spindle and to keep the two coaxial.

Images