Bent hole inner surface polishing and strengthening treatment device and method

Abstract

The invention discloses a bent hole inner surface polishing and strengthening treatment device and method. External controllable square planar magnetic fields are placed on the front side, the rear side, the left side and the right side of a to-be-ground workpiece with a bent hole, and an external controllable annular magnetic field surrounds the periphery of the to-be-ground workpiece with the bent hole as the center; the soft magnetic grinding head is formed by detachably connecting multiple stages of grinding heads in series front and back through rotary connecting pieces, the innermost part of each stage of grinding head is provided with an air bag, the outer surface of the air bag is tightly attached to an internal framework, the outer surface of the internal framework is tightly attached to a magnetic carrier layer, and an abrasive particle layer is embedded in the outer surface of the magnetic carrier layer. The particles of the abrasive particles on the front-stage grinding head are larger than the particles of the abrasive particles on the rear-stage grinding head; active bending of the grinding head in the stretching-in process and expansion from inside to outside in the grinding process are achieved, rough grinding, accurate grinding and polishing are conducted from front to back, the grinding state is maintained through inflation, the abrasive particle layer is separated from the hole wall through deflation, and controllable adjustment of the grinding area is achieved.

Description

An apparatus and method for polishing and strengthening the inner surface of a curved hole. Technical Field

[0001] This invention belongs to the field of surface treatment technology for parts. Specifically, it is used to polish and strengthen the inner surface of curved holes. It is applicable to curved holes with curved geometric features in fields such as high-end equipment manufacturing, aerospace, precision optical instruments, medical devices and automotive parts. It is widely used in key components such as hydraulic valve bodies, engine fuel injectors, artificial joints, and mold cooling channels. Background Technology

[0002] The common characteristics of curved hole structures are: the hole body exhibits a certain curvature or even multiple bends along the axis, and the inner surface often needs to have high dimensional accuracy, low surface roughness, and uniform machining quality to ensure the reliability and service life of the component under high pressure, high temperature, or high friction environments. However, the machining of the inner surface of curved holes has long been a technical challenge in the field of precision manufacturing. Traditional machining methods mainly rely on rigid grinding heads, flexible brushes, abrasive flow, or manual polishing, but all have obvious limitations. Rigid grinding heads or grinding rods cannot bend and deform within curved channels; forcibly inserting them can easily lead to scratches on the hole wall, tool jamming, or even workpiece scrapping. Even when using small-diameter long-handled tools, their rigid structure is only suitable for straight or small-curvature channels and cannot meet the machining requirements of complex curved holes. For example, patent application CN2024109888515 discloses a grinding tool and a manual internal hole grinding method. It adopts a structure in which the grinding rod and the grinding sleeve are taper-fitted. The workpiece is manually pushed to reciprocate along the axis on the grinding sleeve to achieve graded grinding of straight internal holes. This method can achieve high precision in the machining of straight holes. However, both the grinding rod and the grinding sleeve are rigid metal structures. Relying on the axial linear reciprocating motion trajectory, it is impossible to generate bending deformation in the curved section, and it is difficult to maintain stable contact pressure in the curved channel. Moreover, it cannot achieve precise grinding of selective areas for curved through holes, and the bottom machining capability is obviously insufficient for curved blind holes.

[0003] While ordinary soft abrasives such as sponge wheels and nylon brushes have a certain degree of flexibility, they cannot actively conform to the hole wall in the bending section. The contact pressure between the abrasive grains and the surface to be processed is difficult to control, which can easily lead to local over-grinding or under-grinding, resulting in inconsistent processing quality and surface roughness that is difficult to meet design requirements.

[0004] Most current grinding tools only offer a single abrasive grit size, making it impossible to simultaneously achieve graded grinding, fine grinding, and polishing in a single process. For blind holes with significant depth or high requirements for the bottom, multiple tool changes or repeated processing are often necessary, resulting in lengthy and inconsistent procedures. Furthermore, existing tools struggle to precisely control the grinding depth or position, failing to meet diverse working conditions requiring only processing to a specific depth or focusing on the bottom. While some recent research has attempted to utilize magnetic fields to drive magnetic abrasives for in-hole grinding, most methods employ free-flowing or simple coating of the magnetic abrasive, leading to uneven abrasive distribution, complex magnetic field control, and low processing efficiency. Existing magnetic grinding tools generally lack internal support structures, making them prone to overall collapse or local instability in curved sections, and struggling to maintain stable grinding patterns and pressure distribution in complex paths.

[0005] In summary, existing technologies still have significant shortcomings in meeting the requirements for high-quality, high-efficiency, and high-consistency processing of the inner surface of curved holes. Therefore, there is an urgent need in the field for a new type of grinding device that can adapt to the shape of curved channels, has the ability to perform graded grinding, and can flexibly control the grinding area and grinding pressure. Summary of the Invention

[0006] The purpose of this invention is to provide a device and method for polishing and strengthening the inner surface of a curved hole. The device actively conforms to the hole wall within the curved section, performs efficient grinding on the inner surface of the curved hole with controllable flexibility, and can simultaneously achieve rough grinding, fine grinding and polishing, thus meeting the processing requirements of complex curved holes.

[0007] To achieve the above objectives, the technical solution of the present invention for polishing and strengthening the inner surface of a curved hole is as follows: It includes a flexible magnetic grinding head with an outer diameter that is clearance-fitted to the diameter of the curved hole. An external controllable square planar magnetic field is placed on the front, back, left, and right sides of the workpiece to be ground with the curved hole. An external controllable annular magnetic field surrounds the workpiece around the curved hole. A servo motor, connecting rod, and ultrasonic oscillation device are all connected to the rear end of the flexible magnetic grinding head. The flexible magnetic grinding head is composed of multiple grinding heads that are detachably connected in series via rotating connectors. The external mounting between adjacent grinding heads... There is a rubber sleeve with the same outer diameter as the grinding head. At the innermost part of each grinding head stage is an air bladder. The outer surface of the air bladder is tightly attached to the internal skeleton, and the outer surface of the internal skeleton is tightly attached to a magnetic carrier layer made of soft magnetic material. An abrasive layer with abrasive grains is embedded on the outer surface of the magnetic carrier layer. The internal skeleton and the magnetic carrier layer can expand and contract with the air bladder. The front and rear ends of the rubber sleeve are fixedly connected to the corresponding magnetic carrier layers using a slotted structure. The rubber sleeve has the same sleeve magnetic carrier layer and sleeve abrasive layer as the grinding head. The abrasive grains on the preceding grinding head are larger than those on the following grinding heads.

[0008] The technical solution of the polishing and strengthening treatment method for the inner surface of a curved hole of the present invention includes the following steps:

[0009] Step 1): The ultrasonic oscillation device is turned off, the servo motor and connecting rod are working, and the external controllable square planar magnetic field is working. It applies a unidirectional magnetic field force to the magnetic carrier layer in the same direction as the bending hole, causing it to bend and guiding the soft magnetic grinding head to follow the bending path of the bending hole and extend into the bending hole.

[0010] Step 2): When the front of the first-stage grinding head reaches the preset position A, the first-stage grinding head and its rear rubber sleeve are completely inserted into the curved hole. The servo motor, connecting rod and external controllable square planar magnetic field stop working, and the external controllable annular magnetic field works to generate a radial magnetic force from the inside out. The magnetic carrier layer expands uniformly from the inside out, driving the internal skeleton and abrasive layer, so that the abrasive layer is tightly attached to the inner surface of the curved hole. The ultrasonic oscillation device is turned on, driving the abrasive to perform rough grinding on the hole wall behind position A.

[0011] Step 3): After rough grinding is completed, the ultrasonic oscillation device is turned off, the servo motor and connecting rod are restarted, and the external controllable square planar magnetic field works again. The first-stage grinding head advances deeper into the curved hole to the preset position B, and the front end of the second-stage grinding head reaches position A, replacing the initial position of the first-stage grinding head and its rear rubber sleeve. The external controllable annular magnetic field works, and the ultrasonic oscillation device is turned on to grind again. The first-stage grinding head performs rough grinding on the new area inside the curved hole, while the second-stage grinding head and its rear rubber sleeve perform fine grinding on the rough-ground area.

[0012] Step 4): Repeat steps 1)-3), each grinding head will proceed from coarse grinding to fine grinding and then to polishing in a progressive manner until the rubber sleeve at the rear end of the first grinding head crosses the set grinding boundary line, the air bladder of the first grinding head will be deflated, the abrasive layer will be separated from the inner surface of the curved hole and the grinding of the first grinding head will be terminated, and the remaining grinding heads that have not yet crossed the grinding boundary line will complete the grinding of their respective areas.

[0013] Step 5): After each grinding head is pushed to the grinding boundary line and completes the grinding work, the grinding is stopped by deflating the corresponding air bladder until the air bladder of the last grinding head is deflated, and the entire polishing and strengthening process ends.

[0014] Compared with the prior art, the present invention has the following advantages:

[0015] 1. Coordinated control of flexible adaptive structure and magnetic field

[0016] This invention employs a flexible magnetic grinding head with an inflatable, segmented flexible tube as its inner core. Combined with an external controllable magnetic field, it enables the grinding head to actively bend during insertion and expand from the inside out during grinding. Compared to traditional rigid or passively flexible tools, this structure can precisely match the internal shape of curved holes, significantly improving the fit between the grinding head and the surface to be processed, and avoiding problems such as jamming, wear, and uneven grinding.

[0017] 2. The dual driving mechanism of ultrasonic oscillation and magnetic field action

[0018] The grinding head in this invention is subjected to high-frequency vibration generated by an ultrasonic oscillation device and the force of an external controllable magnetic field during the grinding process. The ultrasonic oscillation provides the main grinding energy, which significantly improves the grinding efficiency; the magnetic field causes the magnetic carrier layer to expand outward, which enhances the contact pressure between the abrasive grains and the hole wall, making the grinding more thorough. The two work together to improve the processing quality and shorten the processing time.

[0019] 3. Multi-stage detachable grinding head and graded abrasive grain design

[0020] The grinding head in this invention adopts a multi-stage series structure, with each stage independently embedded with abrasive grains of different sizes, progressing from coarse to fine from front to back, realizing a processing flow from coarse grinding to fine grinding and then to polishing; the grinding heads at each stage are detachably connected by rotating connectors, and the number of stages can be selected according to the processing accuracy requirements, reducing the cost of use and improving the flexibility of the device during use.

[0021] 4. Controllable grinding mechanism based on airbag inflation and deflation

[0022] Each grinding head in this invention has an independent air bladder inside. Inflating the air bladder maintains the grinding shape, while deflating it allows the abrasive layer to detach from the hole wall. This design allows for flexible selection of which stages to participate in the grinding process, making it particularly suitable for curved through-holes that only need to be processed to a specific depth. Compared to traditional integral grinding tools, this invention enables controllable adjustment of the grinding area, avoiding over-processing or ineffective processing.

[0023] 5. Optimized structural design ensures uniform processing.

[0024] Each grinding head in this invention features a convex-rear-concave interface shape, coupled with a centrally located rotating connector, ensuring a tight connection between stages during bending and minimizing inter-stage gaps. This design effectively avoids grinding blind spots caused by gaps, ensuring the continuity and uniformity of machining along the axial direction of the hole's inner surface. Attached Figure Description

[0025] Figure 1 is a schematic diagram of the overall structure of the device for polishing and strengthening the inner surface of a curved hole according to the present invention.

[0026] Figure 2 is an enlarged cross-sectional view of the layered structure of the magnetic grinding head in Figure 1;

[0027] Figure 3 is an enlarged view of the front and rear two-stage grinding head structure of the magnetic grinding head in Figure 1;

[0028] Figure 4 is a partial enlarged view of the layered structure of the magnetic grinding head in Figure 3;

[0029] Figure 5 is a magnified view of part of the three-dimensional structure of the rubber sleeve in Figure 3;

[0030] Figure 6 is an enlarged cross-sectional view of the internal skeleton of each level of the grinding head in Figure 2;

[0031] Figure 7 is an enlarged view of the internal skeleton structure of each level of the grinding head in Figure 2;

[0032] Figure 8 is a schematic diagram of the structure of the abrasive particles of each level of the grinding head in Figure 1 under the air-filled state;

[0033] Figure 9 is a schematic diagram of the first-stage grinding head in the vented state in Figure 8;

[0034] Figure 10 is a schematic diagram of the state when the first-stage grinding head shown in Figure 1 enters the curved hole;

[0035] Figure 11 is a schematic diagram of the state when the first-stage grinding head in Figure 10 grinds the curved hole;

[0036] Figure 12 is a schematic diagram of the propulsion state after the first-stage grinding head in Figure 11 has finished grinding;

[0037] Figure 13 is a schematic diagram of the state when the second-stage grinding head in Figure 12 is grinding the curved hole;

[0038] Figure 14 is a schematic diagram of the propulsion state of the second-stage grinding head after grinding in Figure 13;

[0039] Figure 15 is a schematic diagram of the state when the third-stage grinding head in Figure 14 is grinding the curved hole;

[0040] Figure 16 is a schematic diagram of the propulsion state of the third-stage grinding head after grinding in Figure 15;

[0041] Figure 17 is a schematic diagram of the first-stage grinding head in Figure 16 in the venting state and the fourth-stage grinding head grinding the curved hole.

[0042] Figure 18 is a schematic diagram of the state of grinding the bottom of the blind hole when the first-stage grinding head shown in Figure 1 enters the curved blind hole;

[0043] Figure 19 is a schematic diagram of the state of the second-stage grinding head grinding the bottom of the blind hole shown in Figure 18;

[0044] Figure 20 is a schematic diagram of the state of the third-stage grinding head grinding the bottom of the blind hole as shown in Figure 19;

[0045] Figure 21 is a schematic diagram of the state of the fourth-stage grinding head grinding the bottom of the blind hole as shown in Figure 20.

[0046] In the diagram: 1. Bending hole; 2. Flexible magnetic grinding head; 3. External controllable square planar magnetic field; 4. External controllable annular magnetic field; 5. Servo motor and connecting rod; 6. Ultrasonic oscillation device; 7. Airbag; 8. Internal skeleton; 9. Magnetic carrier layer; 10. Abrasive layer; 11. Grinding fluid delivery pipe; 12. Rotating connector; 13. Rubber sleeve; 14. Block shell; 15. Spring; 16. Slot; 17. First-stage grinding head; 18. Second-stage grinding head; 19. Third-stage grinding head; 20. First-stage abrasive; 21. Second-stage abrasive; 22. Third-stage abrasive; 23. Air tube; 24. Direction of the magnetic field generated by the square planar magnetic field in the pushing state; 25. Pushing direction of the servo motor; 26. Fourth-stage grinding head; 27. Grinding boundary line; 28. Direction of the magnetic field generated by the annular magnetic field in the grinding state. Detailed Implementation

[0047] As shown in Figure 1, the position of the first-stage grinding head, where the flexible magnetic grinding head 2 extends to the deepest part of the curved hole 1, is defined as "front," and the position of the ultrasonic oscillation device 6 is defined as "rear." This invention provides a device for polishing and strengthening the inner surface of a curved hole, comprising a flexible magnetic grinding head 2, an external controllable square planar magnetic field 3, an external controllable annular magnetic field 4, a servo motor, and a connecting rod 5. The outer diameter of the flexible magnetic grinding head 2 is the same as the diameter of the curved hole 1 to be ground, with a clearance fit, allowing it to extend into the curved hole 1 and move back and forth within it.

[0048] The external controllable square planar magnetic field 3 has four planar magnetic fields, which are placed on the front, back, left, and right sides of the workpiece to be ground with the curved hole 1, respectively. During operation, it provides a unidirectional controllable magnetic field to the soft magnetic grinding head 2 in the curved hole 1. The external controllable annular magnetic field 4 surrounds the workpiece to be ground with the curved hole 1 as the center, and is used to provide a magnetic field that radiates from the inside to the outside.

[0049] The soft magnetic grinding head 2 has a magnetic carrier layer inside, which can bend and deform under the intervention of an external magnetic field, so as to smoothly extend into the inside of the curved hole and complete the grinding operation, especially suitable for curved holes with irregular internal shapes.

[0050] In the inflated state, each stage of the soft magnetic grinding head 2 has the same shape, which is a cylindrical shape with a convex front end and a concave rear end. Except for the convex and concave parts, the radius of the rest is the same.

[0051] Both the external controllable square planar magnetic field 3 and the external controllable ring magnetic field 4 are connected to a controller. The controller can start and stop the magnetic field in real time and change its direction and magnitude according to different working processes. These two controllable magnetic fields and their controllers are important auxiliary devices to ensure the grinding fit.

[0052] The ultrasonic oscillation device 6 is connected to the rear end of the flexible magnetic grinding head 2. It is activated after the flexible magnetic grinding head 2 enters the predetermined position and directly transmits the high-frequency oscillation it generates to the flexible magnetic grinding head 2, causing the abrasive grains embedded on the surface of the flexible magnetic grinding head 2 to generate high-frequency micro-vibration, thereby achieving efficient grinding of the inner surface of the curved hole 1. It is the energy source for the entire grinding process.

[0053] The servo motor and connecting rod 5 are connected to the rear end of the flexible magnetic grinding head 2, which slowly and precisely feeds the flexible magnetic grinding head 2 into the interior of the curved hole 1 to be processed, ensuring that the speed and position of the flexible magnetic grinding head 2 are controllable during the advancement process, and providing precise displacement guarantee for graded grinding and layer-by-layer processing.

[0054] As shown in Figure 2, the flexible magnetic grinding head 2 is composed of multiple grinding heads connected in series. Each grinding head has the same layered structure: the innermost part is the internal air bladder 7, which can support each grinding head by the pressure generated by inflation, maintaining its working shape; closely attached to the outer surface of the internal air bladder 7 is the internal skeleton 8, which can protect the internal air bladder 7 from damage and also provide a reliable attachment site for the magnetic carrier layer 9; the outer surface of the internal skeleton 8 is closely attached to the magnetic carrier layer 9, which is made of flexible magnetic material, such as magnetic rubber or flexible neodymium iron boron magnetic sheets, which has good flexibility and high magnetic permeability. It can produce stable and uniform deformation and displacement under the action of the external controllable square planar magnetic field 3 and the external controllable annular magnetic field 4, while ensuring that it maintains its original magnetic properties and structural integrity after multiple bends. Under the influence of an external controllable magnetic field, the magnetic carrier layer 9 can bend the entire flexible magnetic grinding head 2. Due to its flexibility, it can achieve better fit during each grinding head pushing and grinding stage through bending. An abrasive layer 10 is embedded on the outer surface of the magnetic carrier layer 9. The abrasive layer 10 is the outermost layer, containing abrasive grains that perform the actual grinding work. The abrasive grains can be made of superhard materials such as diamond, cubic boron nitride, or alumina. Different abrasive grain sizes are selected according to different grinding processes and are firmly attached to the surface of the magnetic carrier layer 8 through electroplating or brazing, ensuring that they do not easily fall off under ultrasonic high-frequency vibration and magnetic field forces, guaranteeing the stability and durability of the grinding process. Small micropores are left between the abrasive grains as gaps to facilitate the seepage of grinding fluid.

[0055] As shown in Figure 3, two adjacent grinding heads are connected by a detachable rotating connector 12. Except for the first-stage grinding head at the front end, each of the other grinding heads has a rotating connector 12 installed in the middle of its front and rear ends. This ensures that the two grinding heads can be bent and rotated. The rotating connector 12 not only enhances the bending ability of the grinding head but also ensures that the flexible magnetic grinding head 2 will not break during bending.

[0056] Both the internal skeleton 8 and the internal airbag 7 adopt a shape with a protruding front end and a concave rear end. The protrusion and concavity structures match, ensuring that the ends of adjacent grinding heads fit together. Along the grinding direction, the protrusion of each grinding head is in front of the concave part. The rotating connector 12 is located in the middle of the protrusion and concavity between adjacent grinding heads, minimizing the inter-stage gap caused by the installation of the rotating connector 12 and avoiding uneven grinding caused by excessive gaps during the grinding process. At the same time, to completely avoid the problem of gaps in grinding, a rubber sleeve 13 is also installed on the outside between adjacent grinding heads. The outer diameter of the rubber sleeve 13 is the same as the outer diameter of the grinding head.

[0057] As shown in Figures 4 and 5, the front and rear ends of the rubber sleeve 13 are fixedly connected to the corresponding magnetic carrier layer 9 of the grinding head using a slot 16 structure. Inside the rubber sleeve 13, a layer of the same material as the magnetic carrier layer 9 is also fixedly attached, allowing it to be subjected to the magnetic field. Furthermore, an abrasive layer is also installed on the outer surface of the magnetic carrier layer 9. The size of the abrasive grains on each rubber sleeve 13 is the same as the size of the abrasive grains embedded in the adjacent preceding grinding head, thus solving the problem of grinding the gap between the two stages.

[0058] A small-aperture grinding fluid delivery pipe 11 is provided in the magnetic carrier layer 9 of each grinding head and rubber sleeve 13. The grinding fluid delivery pipe 11 passes through each grinding head and rubber sleeve 13 in the front-to-back direction. Several branch tubes are provided on the wall of the grinding fluid delivery pipe 11. These branch tubes connect to the abrasive layer 10 and eventually reach the abrasive layer 10, allowing the grinding fluid in the grinding fluid delivery pipe 11 to flow out through the small gaps between the abrasive grains. This grinding fluid can both lubricate and cool, reducing the temperature rise caused by ultrasonic oscillation and friction, avoiding thermal damage to the surface of the workpiece, and promptly flushing away the chips and abrasive shavings generated during grinding, preventing abrasive grain blockage, maintaining the cutting ability of the abrasive layer, thereby further improving the stability of the grinding process and the consistency of the processed surface. Each grinding fluid delivery pipe 11 is composed of detachably connected segmented delivery pipes connected in series. The front-to-back length of each segmented delivery pipe is consistent with the front-to-back length of the corresponding first-stage grinding head.

[0059] Each grinding head is equipped with an air tube 23, meaning each air bladder 7 is connected to an air tube 23 for inflation and deflation. As shown in Figure 4, the air tube 23, like the grinding fluid delivery tube 11, is also installed within the magnetic carrier layer 9. The air tube 23 extends from the magnetic carrier layer 9 and passes through the gap between the arc-shaped block shell 14 of the internal skeleton 8 to connect with the air bladder 7. This prevents the air tube 23 from affecting the inflation of the air bladder 7 due to part of the tube being between the air bladder 7 and the internal skeleton 8. Each air tube 23 is composed of detachably connected segmented tubes connected in series, with the front-to-back length of each segmented tube matching the front-to-back length of the corresponding grinding head. Starting from the first-stage grinding head at the very front, the air tube 23 of each grinding head extends from its connection with the air bladder 7 towards the rear of the grinding head, until it extends from the rear of the entire grinding head and connects to the air valve. Therefore, the air tube 23 corresponding to the first-stage grinding head at the very front will enter the magnetic carrier layer 9 of all the remaining grinding heads. Similarly, one air tube 23 of the next stage grinding head will also enter the magnetic carrier layer 9 of all subsequent grinding heads. The number of air tube segments corresponds to the number of grinding head stages. All air tubes 23 will be installed in the magnetic carrier layer 9 of the last stage grinding head. Since the thickness of the magnetic carrier layer 9 is limited, the air tubes 23 of each stage grinding head can be staggered from the air tubes 23 of other grinding heads within the magnetic carrier layer 9.

[0060] Each stage of the grinding head is detachable. By removing the rotating connector 12 and rubber sleeve 13, a single grinding head can be separated into its own units. The grinding fluid delivery pipe 11 and air pipe 23, connecting the preceding and following grinding heads, also need to be disassembled. To achieve this, several through holes are made between the abrasive grains at the front of each grinding head, the number corresponding to the number of pipes connecting the preceding and following grinding heads. Using these through holes as boundaries, the grinding fluid delivery pipe 11 and air pipe 23 are segmented. Each segment has threaded connections at both ends, and each air pipe 23 is composed of segmented pipes with detachable threaded connections. The pipe extending from the magnetic carrier layer 9 of the preceding grinding head is threadedly connected to the front of the following grinding head. This allows for complete disassembly by disconnecting the threaded connections, thus breaking the connection between the preceding and following stages. The air valve connected to the disconnected air pipe 23 will no longer operate, preventing air from being released into the grinding hole and affecting the grinding process.

[0061] As shown in Figures 6 and 7, the internal skeleton 7 of each grinding head is a shell shape formed by connecting several block-shaped shells 14 with springs 15. The internal skeleton 7 has multiple layers in the front-to-back direction, each layer being circular as shown in Figure 6, designed to fit and maintain the shape of the grinding head. Each layer has four arc-shaped block-shaped shells 14, which are connected to each other by springs 15. The springs have excellent plasticity; the connection with springs 15 prevents excessive compression of the internal airbag 7 during inflation. More importantly, when the external controllable annular magnetic field 4 is applied, the skeleton can expand along with the magnetic carrier layer 9 fixed to it, and simultaneously contract with the airbag 7 when it deflates, achieving a free-flowing effect. This also causes the magnetic carrier layer 9 to contract and expand with the airbag 7. As shown in Figure 7, each layer of the skeleton is also connected by springs, so the entire skeleton can not only contract and expand, but also bend thanks to the springs 15 connecting each layer, preventing the magnetic carrier layer 9 from colliding with the internal skeleton 7 and causing damage when bending.

[0062] Figure 8 shows the grinding heads in the inflated state, and Figure 9 shows the first-stage grinding head in the deflated state. Figures 8 and 9 only show three stages of grinding heads. Following the grinding direction, the first-stage grinding head 17 is located at the front of the entire grinding head, followed by the second-stage grinding head 18 and the third-stage grinding head 19. The last stage grinding head has the longest front-to-back length, approximately equal to the sum of the length of a set of grinding heads plus the length of the rubber sleeve 13. The number of grinding stages determines their order of participation in grinding. Furthermore, the abrasive grains embedded in each stage grinding head are different; the grain size varies with the stage, and each stage is embedded in its corresponding grinding head. The abrasive grains in the preceding stage grinding head are larger than those in the following stage grinding head. The abrasive grain size decreases sequentially from the first to the third stage. The first-stage abrasive grain 20 has the largest grain size and is mounted on the first-stage grinding head 17. It participates in grinding first, mainly performing coarse grinding on the inner surface of the curved hole 1, removing the most obvious protrusions and creating conditions for subsequent grinding. The second-stage abrasive grain 21 has a moderate grain size and performs more detailed grinding on the coarsely ground area. The third-stage abrasive grain 22 has the smallest grain size and is responsible for the final polishing and fine grinding. The grinding head in this invention can freely select the required number of stages according to the processing accuracy requirements. In addition, the grinding head can flexibly control whether each stage participates in grinding. The internal air bladder 7 of the grinding head expands by inflating to open the internal skeleton 8 and its external structure, maintaining the working shape of the grinding head. When the air bladder 7 is deflated manually, the air bladder 7 shrinks, and the pressure that originally opened the internal skeleton 8 disappears. As shown in Figure 9, after the first-stage grinding head 17 is degassed, the air bladder 7 shrinks and the internal skeleton 8 loses its supporting force and contracts inward. This contraction will cause the outermost first-stage abrasive grains 20 to no longer adhere tightly to the inner surface of the curved hole 1, thus losing their grinding effect. Through such inflation and deflation control, it is possible to flexibly select whether each stage grinding head participates in grinding, significantly increasing the controllability of the grinding process and adapting to more diverse working conditions.

[0063] The following are the basic working processes of grinding heads under various operating conditions:

[0064] Taking the process of grinding a curved hole 1 to a designated position using a four-stage grinding head as an example, as shown in Figure 10, the ultrasonic oscillation device 6 is turned off, the servo motor and connecting rod 5 are activated, and the head is pushed forward in the direction 25 of the servo motor. The flexible magnetic grinding head 2 slowly extends into the interior of the curved hole 1 under the delivery of the servo motor and connecting rod 5. When the curved hole 1 does not need to be fully ground, but only needs to be ground to a designated position, although the flexible magnetic grinding head 2 can achieve a certain degree of bending by rotating the connecting part 12, during the direct insertion process, the abrasive layer 10 on its surface will come into contact with the inner surface of the curved hole 1, which can easily lead to uneven grinding due to uneven local contact pressure, forming unnecessary pits on the inner surface. On the other hand, it will accelerate the wear of the grinding head and affect its service life. During the pushing stage of the flexible magnetic grinding head 2, the external controllable square planar magnetic field 3 is activated. The external controllable square planar magnetic field 3 can cause the flexible magnetic grinding head 2 to bend actively by acting on the magnetic carrier layer 9 on the flexible magnetic grinding head 2, as shown in the direction 24 of the magnetic field generated by the square planar magnetic field in the pushing state, guiding the flexible magnetic grinding head 2 to follow the bending path of the curved hole 1. Meanwhile, the magnetic carrier layer 9 itself has flexible properties and undergoes slight deformation under the action of the magnetic field, further improving the conformity between the grinding head and the hole wall. Thus, the flexible magnetic grinding head 2 can smoothly bend along the shape of the curved hole 1 when inserted, ensuring smooth entry and effectively reducing friction and impact. This is the pushing stage of the grinding process. During this stage, the external controllable square planar magnetic field 3 applies a unidirectional direction 24 to the magnetic carrier layer 9, as shown in Figure 10, which is consistent with the bending direction of the curved hole 1. When the front of the first-stage grinding head 17 reaches the preset position A as shown in Figure 10, the first-stage grinding head 17 and its rear rubber sleeve 13 are completely inside the curved hole 1.

[0065] As shown in Figure 11, when the top of the first-stage grinding head 17 reaches the preset position A, the servo motor and connecting rod 5 stop working, the external controllable square planar magnetic field 3 is turned off, and the grinding stage begins. The external controllable annular magnetic field 4 operates, and the magnetic field direction 28 generated by the annular magnetic field in the grinding state is a radial direction from the inside to the outside. Under the action of the magnetic field at this time, the magnetic carrier layer 9, which was originally slightly bent in a single direction, changes to a state of uniform expansion from the inside to the outside, like a balloon being inflated. This change in the shape of the magnetic carrier layer 9 simultaneously drives the internal skeleton 8 and the outermost abrasive layer 10, so that the abrasive layer 10 is tightly attached to the inner surface of the curved hole 1, ensuring that the abrasive can fully exert its grinding effect. At the same time, the ultrasonic oscillation device 6, which was originally in the off state, is turned on, generating high-frequency vibration and transmitting it to the grinding head, driving the abrasive to perform efficient grinding on the hole wall. The first-stage grinding head 17 and the sleeve behind it have the same first-stage abrasive 20, and they work together to grind the area behind the preset position A.

[0066] As shown in Figure 12, after grinding is completed behind position A, the ultrasonic oscillation device 6 is turned off, and the servo motor and connecting rod 5 are restarted for conveying. The external controllable square planar magnetic field 3 is activated again, and the magnetic field is controlled by the external controllable square planar magnetic field 3, with the direction changing back to a single direction, namely direction 24. Driven by the servo motor and connecting rod 5, the first-stage grinding head 17 advances deeper into the curved hole 1. The servo motor and connecting rod 5 convey a preset distance, so that the front end of the first-stage grinding head 17 reaches the preset position B, and the front end of the second-stage grinding head 18 reaches position A. At this time, the second-stage grinding head 18 and its rear sleeve are completely inside the curved hole 1, as shown in Figure 13, replacing the initial position of the first-stage grinding head 17 and its rear sleeve. At this time, the external controllable annular magnetic field 4 is activated, and the magnetic field direction is switched back to a radial magnetic field direction 28 from the inside out. The shape of the grinding head changes accordingly, and the ultrasonic oscillation device 6 is activated again, resuming the grinding stage. At this time, the first-stage grinding head 17 performs coarse grinding on a new area inside the curved hole 1, while the second-stage grinding head 18 and its rear sleeve perform more detailed fine grinding on the area that the first-stage grinding head 17 and its rear sleeve had previously coarsened.

[0067] As shown in Figure 14, the above-mentioned pushing, rough grinding, and fine grinding steps are repeated. The ultrasonic oscillation device 6 is then turned off, the external controllable square planar magnetic field 3 resumes operation, and the servo motor and connecting rod 5 continue pushing. Under the guidance of the external controllable square planar magnetic field 3 and the combined action of the servo motor and connecting rod 5, the third-stage grinding head 19 and its rear sleeve are completely conveyed into the curved hole 1, as shown in Figure 15. At this time, the front of the first-stage grinding head 17 reaches position C, which is also the location of the grinding boundary line 27. The second-stage grinding head 18 and the third-stage grinding head 19 then take over the positions of the previous-stage grinding head. At this point, the servo motor and connecting rod 5 stop pushing, the external controllable annular magnetic field 4 resumes operation, with the magnetic field direction being radial. The grinding head expands again and approaches the inner surface of the curved hole 1, and the ultrasonic oscillation device 6 is activated for grinding. This allows each level of grinding head and its rear sleeve containing the abrasive particles to complete the processing of the corresponding area in a tightly fitted state.

[0068] As shown in Figure 16, the front part of the first-stage grinding head 17 is almost touching the grinding boundary line 27 set for the curved hole 1. Then, the servo motor and connecting rod 5 push the head further, continuing to advance the entire grinding head until the end of the rear rubber sleeve 13 of the first-stage grinding head 17 just crosses the set grinding boundary line 27 and reaches position D, as shown in Figure 17. For this curved hole 1, the area forward of the grinding boundary line 27 no longer needs grinding. At this point, the internal air bladder 7 of the first-stage grinding head 17 is deflated. The internal skeleton 8, which was originally stretched open by the air bladder 7, contracts inward after losing its support, causing the abrasive layer 10 to detach from the inner surface of the curved hole 1, terminating the grinding function of the first-stage grinding head 17. Simultaneously, the magnetic field at the location of the first-stage grinding head 17 and its rear sleeve is shut off, preventing the rear sleeve from continuing to grind the unnecessarily ground area. Subsequently, the external controllable annular magnetic field 4 operates radially and activates the ultrasonic oscillation device 6 for grinding. This allows the remaining second- and third-stage grinding heads, which have not yet crossed the grinding boundary line 27, and the fourth-stage grinding head 26, which has just entered the curved hole 1, to complete the grinding work in their respective areas. Due to its longer length, the fourth-stage grinding head 26 avoids the problem of not being able to fully process the ground areas during the final grinding work due to the lack of a rear sleeve.

[0069] The second, third, and fourth grinding heads repeat the above process, pushing the servo motor and connecting rod forward a set distance again, and then venting the second-stage grinding head 12. Each grinding head stops its grinding function by venting after being pushed to the grinding boundary line 27 and completing the grinding work. This process continues until the last grinding head, the fourth-stage grinding head 26, finishes venting, at which point the entire grinding process is complete. This staged, step-by-step control method achieves precise control of the grinding position and depth, ensuring grinding quality while avoiding unnecessary over-processing.

[0070] As shown in Figure 18, when the curved hole 1 to be processed is a curved blind hole, the bottom of the curved blind hole needs to be ground. For curved blind holes that require bottom grinding, the grinding process is similar to that of blind holes that only need grinding to a specific position, but the details differ. The grinding head also adopts a "push-grind" stage transition grinding method. After the previous grinding head completes grinding, the next grinding head takes over its position to continue processing, layer by layer, until the bottom of the blind hole is completely processed. As shown in Figure 19, the rotating connector 10 between the grinding heads can be completely disassembled, allowing each grinding head to be separated independently to form a separate grinding unit. This design provides flexible operation for the special processing requirements of bottom blind holes.

[0071] Under these conditions, the entire process no longer requires venting. The first-stage grinding head 17 will initially undertake the task of grinding the bottom. Driven by the servo motor and connecting rod 5, it advances forward and cooperates with the external controllable magnetic field, repeating the "push-grind-push" process until it reaches the bottom of the blind hole. When the first-stage grinding head 17 reaches the bottom of the blind hole, its front part contacts the bottom of the blind hole, and grinding is then performed to process the bottom flat or curved area, ensuring that the bottom area achieves sufficient grinding effect.

[0072] After the first-stage grinding head 17 completes the bottom grinding, the ultrasonic oscillation device 6 is turned off, and the external controllable square planar magnetic field 3 is turned on for control. The magnetic field is adjusted to a single direction, assisting the entire magnetic grinding head 2 to be slowly pulled out of the blind hole as a whole under the retraction action of the servo motor and connecting rod 5. Since the rotating connecting piece 12 can be completely disassembled, the first-stage grinding head 17, which has completed its work, is removed from the entire grinding head, allowing it to detach from the entire grinding head. At this time, the second-stage grinding head 18, which was originally located after the first stage, becomes the new head of the entire magnetic grinding head 2. The second-stage abrasive grains 21 embedded on its surface have a moderate particle size, which can perform more detailed grinding on the bottom area, as shown in Figure 19.

[0073] Subsequently, the servo motor and connecting rod 5 are restarted for pushing. At this time, the external controllable square planar magnetic field 3 operates, controlling the magnetic field to maintain a single direction during the pushing process, ensuring that the soft magnetic grinding head 2 smoothly enters the blind hole. The ultrasonic oscillation device 6 remains closed to avoid unnecessary grinding during the transport process. When the second-stage grinding head 18 contacts the bottom of the blind hole again, the servo motor connecting rod 5 stops, and the external controllable annular magnetic field 4 controls the magnetic field to switch back to a radial direction, so that the abrasive layer of the second-stage grinding head 18 is tightly attached to the bottom and the adjacent side wall area. At the same time, the ultrasonic oscillation device 6 is activated to perform the second stage of fine grinding on the bottom area. Since the particle size of the second-stage abrasive 21 is finer than that of the first stage, this grinding can effectively remove the scratches and micro-protrusions left by the first stage of coarse grinding, further reducing the surface roughness of the bottom and surrounding areas. In this working condition, the blind hole cannot be ground except at the bottom. The area near the bottom cannot be further advanced because the grinding head is blocked by the bottom, and it cannot be ground by the next level or several levels of abrasive grains. After replacing the first level with the second level grinding head, the high-grade abrasive grains that could not be advanced before can continue to advance. With the grinding of the bottom, the areas that could not be reached before are also ground.

[0074] After grinding is completed, repeat the above operation: turn off the ultrasonic oscillation device 6, remove the grinding head as a whole under the assistance of a magnetic field, remove the second-stage grinding head 18, and make the third-stage grinding head 19 the new head, as shown in Figure 20. After being inserted into the blind hole again, the third-stage grinding head 19 grinds the bottom and connected areas again to make the surface smoother. This process continues until the fourth-stage grinding head 26 performs the grinding, as shown in Figure 21. The air tube 23 of the detached grinding head will no longer be inflated by the connected air valve. From Figure 18 to Figure 21, the number of tubes extending from the rear of the grinding head indicates the number of air tubes 23 and their corresponding air valves still in operation. If the grinding head has more stages, this process continues to repeat. Each stage of the grinding head sequentially undertakes the progressive processing tasks from rough grinding to fine grinding to polishing, until the last stage of the grinding head contacts the bottom of the blind hole and completes the grinding.

[0075] This step-by-step disassembly and repeated insertion processing method, while seemingly involving numerous steps, offers the advantage of allowing each grinding head to target the bottom area with optimal abrasive grit. This avoids the problem of insufficient grinding of the bottom due to space constraints when multiple grinding heads enter the blind hole simultaneously. Furthermore, since each grinding head is disassembled and removed after processing, subsequent grinding heads are not affected by the abrasive grit of the previous stage, allowing for full contact with the bottom area with a completely new abrasive surface, ensuring that each process achieves the desired processing effect. This method achieves graded fine grinding of the bottom of blind holes, guaranteeing the processing quality of the bottom area while fully leveraging the progressive grinding advantage of multi-stage abrasive grit from coarse to fine, meeting the stringent requirements of high-precision blind hole bottom processing.

[0076] Besides holes with unidirectional bending, this invention also demonstrates excellent adaptability to more complex bending paths, such as "S"-shaped bending holes. Specifically, during the grinding head insertion stage, an external controllable annular magnetic field 4 adjusts its direction in real time according to the actual bending path of the "S"-shaped bending hole, and segments the magnetic field. Each segment guides the magnetic grinding head sequentially along its corresponding bending direction. Because the grinding head employs a segmented skeleton and rotating connectors, it possesses multi-degree-of-freedom bending capabilities, allowing it to smoothly enter along an "S"-shaped trajectory under the influence of the magnetic field, avoiding jamming or excessive friction with the hole wall. The multi-stage grinding head, with its coarse-to-fine abrasive grain configuration and independent airbag inflation / deflation control, is also suitable for the graded processing of "S"-shaped bending holes, enabling selective grinding of different bending segments or layer-by-layer fine processing.

Claims

1. A device for polishing and strengthening the inner surface of a curved hole, characterized in that: The soft magnetic grinding head (2) has an outer diameter that is clearance-fitted with the diameter of the curved hole. An external controllable square planar magnetic field (3) is placed on the front, back, left and right sides of the workpiece to be ground with the curved hole. An external controllable annular magnetic field (4) surrounds the workpiece to be ground with the curved hole as the center. The servo motor, connecting rod (5), and ultrasonic oscillation device (6) are all connected to the rear end of the soft magnetic grinding head (2). The soft magnetic grinding head (2) is composed of multiple grinding heads that are detachably connected in series front and back through a rotating connector (12). A rubber sleeve (13) is installed on the outside between two adjacent grinding heads. The outer diameter of the rubber sleeve (13) is the same as the outer diameter of the grinding head. The innermost part of each grinding head is an air bladder (7). The outer surface of the air bladder (7) is tightly attached to the inner skeleton (8). The outer surface of the inner skeleton (8) is tightly attached to a magnetic carrier layer (9) made of soft magnetic material. The outer surface of the magnetic carrier layer (9) is inlaid with an abrasive layer (10). The abrasive layer (10) has abrasive grains. The inner skeleton (8) and the magnetic carrier layer (9) can contract and expand with the air bladder (7). The front and rear ends of the rubber sleeve (13) are fixedly connected to the corresponding magnetic carrier layer (9) by a slot structure. The rubber sleeve (13) has the same sleeve magnetic carrier layer and sleeve abrasive layer as the grinding head. The abrasive grains on the front grinding head are larger than the abrasive grains on the rear grinding head.

2. The device for polishing and strengthening the inner surface of a curved hole according to claim 1, characterized in that: The internal skeleton (7) is a shell shape formed by connecting several block shells (14) with springs (15). The internal skeleton (7) has multiple layers in the front and back direction. Each layer of the skeleton is formed by connecting four arc-shaped block shells (14) with each other with springs (15). Each layer of the skeleton is connected with each other with springs (15).

3. The device for polishing and strengthening the inner surface of a curved hole according to claim 1, characterized in that: The last stage of the grinding head has the longest front-to-back length, which is equal to the sum of the length of a set of grinding heads and the length of the rubber sleeve (13).

4. The device for polishing and strengthening the inner surface of a curved hole according to claim 1, characterized in that: The internal skeleton (8) and the internal airbag (7) are both convex at the front and concave at the rear. The convex and concave structures match each other. The rotating connector (12) is connected at the middle position of the convex and concave at the front and rear of the two adjacent grinding heads.

5. The device for polishing and strengthening the inner surface of a curved hole according to claim 1, characterized in that: The grinding fluid delivery pipe (11) passes through the magnetic carrier layer 9 of each grinding head and rubber sleeve (13) in the front-to-back direction. Several branch tubes are provided on the pipe wall of the grinding fluid delivery pipe (11). The branch tubes are connected to the abrasive layer (10), so that the grinding fluid in the grinding fluid delivery pipe (11) flows out in the gap between the abrasive grains. Each grinding fluid delivery pipe (11) is composed of detachable segmented delivery pipes connected in series. The front-to-back length of each segmented delivery pipe is consistent with the front-to-back length of the corresponding first-level grinding head.

6. The device for polishing and strengthening the inner surface of a curved hole according to claim 1, characterized in that: The external controllable square planar magnetic field (3) and the external controllable ring magnetic field (4) are respectively connected to the controller. The controller starts and stops in real time according to different working processes and changes the direction and magnitude of the magnetic field.

7. The device for polishing and strengthening the inner surface of a curved hole according to claim 1, characterized in that: The abrasive grains on each rubber sleeve (13) are the same size as those embedded in the adjacent previous stage grinding head.

8. The device for polishing and strengthening the inner surface of a curved hole according to claim 2, characterized in that: The trachea (23) extends from the magnetic carrier layer (9) and passes through the gap between the block shell (14) to communicate with the airbag (7). Each airbag (7) is connected to a trachea (23). Each trachea (23) is composed of detachable segmented tubing connected in series. The front and back length of each segmented tubing is consistent with the front and back length of the corresponding first-stage grinding head.

9. A polishing and strengthening method for the polishing and strengthening apparatus for the inner surface of a curved hole as described in any one of claims 1-8, characterized in that... Includes the following steps: Step 1): The ultrasonic oscillation device (6) is turned off, the servo motor and connecting rod (5) are working, and the external controllable square plane magnetic field (3) is working. It applies a unidirectional magnetic field force to the magnetic carrier layer (9) in the same direction as the bending hole, causing it to bend and guiding the soft magnetic grinding head (2) to follow the bending path of the bending hole and extend into the bending hole; Step 2): When the front part of the first-stage grinding head reaches the preset position A, the first-stage grinding head and its rear rubber sleeve (13) are exactly fully inserted into the bending hole, and the servo motor and connecting rod (5) and the external controllable square plane The magnetic field (3) stops working, and the external controllable annular magnetic field (4) works, generating a radial magnetic force from the inside out. The magnetic carrier layer (9) expands uniformly from the inside out, driving the internal skeleton (8) and the abrasive layer (10) to tightly adhere to the inner surface of the curved hole. The ultrasonic oscillation device (6) is turned on, driving the abrasive to perform rough grinding on the hole wall behind position A. Step 3): After the rough grinding is completed, the ultrasonic oscillation device (6) is turned off, the servo motor and connecting rod (5) are restarted, and the external controllable square planar magnetic field (3) works again. The first-stage grinding head moves towards the curved hole. The second-stage grinding head advances deeper into the curved hole to the preset position B, and the front end of the second-stage grinding head reaches position A, replacing the initial position of the first-stage grinding head and its rear rubber sleeve (13); the external controllable annular magnetic field (4) operates, and the ultrasonic oscillation device (6) is turned on to perform grinding again; the first-stage grinding head performs rough grinding on the new area inside the curved hole, and the second-stage grinding head and its rear rubber sleeve (13) perform fine grinding on the rough-ground area; Step 4): Repeat steps 1)-3), each grinding head proceeds from rough grinding to fine grinding and then to polishing in a progressive manner. Processing continues until the rubber sleeve (13) at the rear end of the first-stage grinding head crosses the set grinding boundary line. The air bladder (7) of the first-stage grinding head is deflated, causing the abrasive layer (10) to detach from the inner surface of the curved hole, thus terminating the grinding of the first-stage grinding head. The remaining grinding heads that have not yet crossed the grinding boundary line complete the grinding of their respective areas. Step 5): After each grinding head is pushed to the grinding boundary line and completes the grinding work, its grinding is stopped by deflating the corresponding air bladder (7) until the air bladder (7) of the last grinding head is deflated, and the entire polishing and strengthening process ends.

10. The polishing and strengthening method according to claim 9, characterized in that: When the curved hole to be processed is a curved blind hole, the servo motor and connecting rod (5) push the first-stage grinding head to the bottom of the blind hole. The front part of the first-stage grinding head contacts the bottom of the blind hole for grinding. Then the ultrasonic oscillation device (6) is turned off, and the external controllable square planar magnetic field (3) is turned on. The soft magnetic grinding head (2) is pulled out of the blind hole as a whole under the retraction action of the servo motor and connecting rod (5). The first-stage grinding head is removed, and the second-stage grinding head is pushed to the bottom of the blind hole for fine grinding. This process is repeated until the last-stage grinding head completes the grinding.

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