Blind hole inner surface polishing device based on cavitation and magnetic control grinding materials and working method of blind hole inner surface polishing device

Abstract

The invention discloses a blind hole inner surface polishing device based on cavitation and magnetic control grinding materials and a working method thereof. The blind hole inner surface polishing device comprises a piston cylinder, and a connecting port is formed in the piston cylinder and connected with a blind hole; cavitation liquid is arranged in the piston cylinder, when a piston in the piston cylinder reciprocates, cavitation bubbles are generated in the cavitation liquid, and the cavitation liquid containing the cavitation bubbles enters and exits from the blind hole through the connecting port; abrasive is arranged in the blind hole and has ferromagnetism, a magnetic control assembly is arranged outside the blind hole, and the abrasive forms a movement track covering the inner surface of the blind hole under the control of the magnetic control assembly. According to the device, the cavitation liquid containing the cavitation bubbles is injected into the blind hole in a reciprocating mode through the piston cylinder, the grinding material with ferromagnetism is loaded into the blind hole, the grinding material forms a movement track covering the inner surface of the blind hole under the control of the magnetic control assembly, and therefore the inner surface of the blind hole can be evenly polished by combining the cavitation grinding material and the magnetic control grinding material.

Description

Technical Field

[0001] This invention relates to the field of hole polishing technology, and more particularly to a blind hole inner surface polishing device and its working method based on cavitation and magnetron abrasives. Background Technology

[0002] With the development of society and science and technology, the requirements for the machining precision of blind holes are increasing. Currently, abrasive jets are commonly used to treat the inner surface of blind holes. However, for small-diameter deep blind holes, traditional machining methods are difficult to achieve uniform and effective inner surface treatment, and there is an urgent need to develop specialized equipment to complete the polishing and strengthening of their inner surfaces. Summary of the Invention

[0003] Purpose of the invention: In order to overcome the shortcomings of the prior art, the present invention provides a blind hole inner surface polishing device and its working method based on cavitation and magnetron abrasive. The piston cylinder reciprocates to inject cavitation liquid containing cavitation bubbles into the blind hole, and ferromagnetic abrasive is loaded into the blind hole. Under the control of the magnetron component, the abrasive forms a motion trajectory covering the inner surface of the blind hole, thereby achieving uniform polishing of the inner surface of the blind hole by combining cavitation and magnetron abrasive.

[0004] After passing through the spiral guide structure, the cavitation fluid enters the blind hole, generating a swirling flow. The swirling flow agitates the abrasive inside the blind hole, and the cavitation bubbles are thrown towards the inner surface of the blind hole with the swirling flow, thereby polishing the inner surface of the blind hole.

[0005] Technical Solution: To achieve the above objectives, the present invention provides a blind hole inner surface polishing device based on cavitation and magnetron abrasive, comprising a piston cylinder with a connection port connected to the blind hole; a cavitation liquid is contained in the piston cylinder, and when the piston reciprocates within the piston cylinder, cavitation bubbles are generated in the cavitation liquid, and the cavitation liquid containing cavitation bubbles enters and exits the blind hole through the connection port; an abrasive is contained within the blind hole, the abrasive being ferromagnetic, and a magnetron abrasive assembly is disposed outside the blind hole, and the abrasive forms a motion trajectory covering the inner surface of the blind hole under the control of the magnetron abrasive assembly.

[0006] Furthermore, the piston cylinder has a connection port at its top, and the inverted blind hole is connected to the connection port; the magnetic control component can apply a magnetic force along the radial direction of the blind hole to the abrasive; the magnetic force along the radial direction of the blind hole is called the magnetic adsorption force, and under the action of the magnetic adsorption force, the abrasive adheres to the inner surface of the blind hole.

[0007] Furthermore, the magnetic control component can also alternately apply upward and downward magnetic forces to the abrasive, with the upward magnetic force referred to as the magnetic lifting force and the downward magnetic force referred to as the magnetic descent force. When the abrasive is subjected to the magnetic lifting force, it overcomes the effect of gravity and moves up along the inner surface of the blind hole. When the abrasive is subjected to the magnetic descent force, it moves down along the inner surface of the blind hole under the combined action of gravity.

[0008] Furthermore, the magnetic control assembly includes a surrounding magnetic unit and a variable magnetic unit; the surrounding magnetic unit is disposed outside the blind hole, and the surrounding magnetic unit is generally in the shape of a cone that is narrower at the top and wider at the bottom. The surrounding magnetic unit can apply a magnetic force along the radial direction of the blind hole and an upward magnetic force to the abrasive; the variable magnetic unit is disposed below the blind hole, and the variable magnetic unit can apply a downward magnetic force to the abrasive, and the magnitude of the magnetic force of the variable magnetic unit is variable.

[0009] Furthermore, the surrounding magnetic unit is composed of several magnetic strips distributed in a ring. The magnetic strips are inclined from top to bottom in the direction away from the blind hole, so that the surrounding magnetic unit is a cone-shaped structure that is narrow at the top and wide at the bottom. The adjacent magnetic strips in the surrounding magnetic unit are spaced apart. The abrasive in the blind hole is attracted to the magnetic strips and concentrated, thereby forming alternating abrasive concentration stripe areas and abrasive dispersion stripe areas in the blind hole. Cavities can directly contact the inner surface of the blind hole through the abrasive dispersion stripe areas. Several magnetic strips are mounted on a rotating frame. When the magnetic strips rotate around the blind hole with the rotating frame, they attract abrasive to sweep across the inner surface of the blind hole in a circumferential direction.

[0010] Furthermore, the variable magnet unit includes an electromagnet disposed at the end of the piston cylinder away from the blind hole; as the current changes, the resultant force of the electromagnet and the surrounding magnet unit forms a magnetic lifting force or a magnetic drooping force.

[0011] Furthermore, a spiral guide structure is provided inside the piston cylinder. After the cavitation liquid passes through the spiral guide structure, it forms a swirling flow, and the cavitation bubbles are thrown towards the inner surface of the blind hole along with the swirling flow.

[0012] Furthermore, a fan blade is provided on the end of the piston facing the connection port, and the rotation axis of the fan blade is consistent with the movement direction of the piston; when the piston reciprocates, the fan blade rotates under the action of the liquid flow.

[0013] Furthermore, the connection port of the piston cylinder is sealed to the opening of the blind hole, and the piston cylinder is provided with an injection port and a discharge port.

[0014] Furthermore, the working method of the blind hole inner surface polishing device based on cavitation and magnetron abrasive involves the following steps: During the polishing process of the inner surface of the blind hole, the piston reciprocates, injecting cavitation liquid containing cavitation bubbles into the blind hole; the magnetic force of the variable magnet unit changes periodically, and the entire magnetron assembly alternately applies magnetic upward and downward forces to the abrasive, causing the abrasive to reciprocate along the inner surface of the blind hole; the magnetic strip rotates around the blind hole with the rotating frame, attracting the abrasive to sweep across the inner surface of the blind hole circumferentially; the abrasive simultaneously performs reciprocating upward and downward motion and circumferential rotation along the inner surface of the blind hole, so that the movement trajectory of the abrasive can completely cover the inner surface of the blind hole.

[0015] Beneficial effects: The blind hole inner surface polishing device and its working method based on cavitation and magnetron abrasive of the present invention have the following beneficial effects:

[0016] 1) After passing through the spiral guide structure, the cavitation fluid enters the blind hole and generates a swirling flow, which throws the cavitation fluid onto the inner wall of the blind hole, so that the cavitation bubbles strengthen the inner surface of the blind hole; the abrasive has ferromagnetism; under the control of the magnetron control component, the abrasive simultaneously performs reciprocating lifting and circumferential rotation along the inner surface of the blind hole, so that the movement trajectory of the abrasive can completely cover the inner surface of the blind hole. Thus, the combination of cavitation and magnetron control abrasive achieves uniform polishing of the inner surface of the blind hole.

[0017] 2) Under the control of the magnetron control component, alternating abrasive concentrated stripe areas and abrasive dispersed stripe areas are formed inside the blind hole. Cavitation can directly contact the inner surface of the blind hole through the abrasive dispersed stripe area. The energy released when the cavitation collapses can directly act on the inner surface of the blind hole, enhancing the strengthening effect on the inner surface of the blind hole. Attached Figure Description

[0018] Appendix Figure 1 This is a schematic diagram of the overall polishing device;

[0019] Appendix Figure 2 This is a schematic diagram showing the abrasive material moving up and down along the inner surface of the blind hole;

[0020] Appendix Figure 3 A schematic diagram of the concentrated and dispersed abrasive stripe regions;

[0021] Appendix Figure 4 A schematic diagram of the first embodiment of the spiral flow guide structure;

[0022] Appendix Figure 5 This is a schematic diagram of a second embodiment of the spiral flow guide structure;

[0023] Appendix Figure 6 This is a schematic diagram of the fan blade structure on the piston. Detailed Implementation

[0024] The invention will now be further described with reference to the accompanying drawings.

[0025] As attached Figures 1 to 6 The blind hole inner surface polishing device based on cavitation and magnetron abrasive includes a piston cylinder 1 with a connection port 2 connected to a blind hole 3. When polishing the inner surface of the blind hole 3 on a workpiece 14, the blind hole 3 is connected to the connection port 2, so that the internal space of the blind hole 3 is connected to the internal space of the piston cylinder 1 to form a sealed cavity.

[0026] Piston cylinder 1 contains cavitation fluid, which is generally pure water, but some additives may be added to the water depending on the material of workpiece 14. Blind hole 3 contains abrasive 4. When piston 11 reciprocates in piston cylinder 1, the volume of the sealed cavity changes periodically. The alternation of volume will trigger a cavitation reaction in the liquid, generating a large number of cavitation bubbles 5. The cavitation fluid containing cavitation bubbles 5 enters and exits blind hole 3 through connection port 2.

[0027] The piston cylinder 1's connection port 2 is sealed to the opening of the blind hole 3, thereby combining the piston cylinder 1 and the blind hole 3 into a single unit, forming a sealed processing space. This sealed connection effectively prevents leakage of the working medium inside the device under pressure, and also blocks impurities from the external environment from entering the processing area, thus ensuring that the processing is carried out in a controlled clean environment. In one embodiment, the connection port 2 and the blind hole 3 can be sealed together using a sealing flange.

[0028] The piston cylinder 1 is provided with an injection port 12 and an outlet port 13, which serve as the inlet and outlet of the cavitation fluid. In order to precisely control the flow of the cavitation fluid, control valves are respectively provided on the injection port 12 and the outlet port 13 to control the opening and closing of the injection port 12 and the outlet port 13.

[0029] A spiral guide structure is installed inside the piston cylinder 1. After passing through the spiral guide structure, the cavitation liquid forms a swirling flow, which agitates the abrasive 4 inside the blind hole 3. As the abrasive 4 moves along the inner surface of the blind hole 3, it polishes the blind hole 3. The top of the piston cylinder 1 has a connection port 2, and the inverted blind hole 3 is connected to the connection port 2. The piston 11 rapidly reciprocates, and the cavitation liquid is thrown upward into the blind hole 3 under the action of inertia, and then flung onto the inner wall of the blind hole 3 under the action of the swirling flow. The cavitation bubbles 5 are flung towards the inner surface of the blind hole 3 with the swirling flow. When the cavitation bubbles 5 come into contact with the inner wall of the blind hole 3, they collapse. The micro-jet and shock wave generated when they collapse act on the surface of the hole wall, which can not only remove micro-unevenness, but also cause plastic deformation of the surface layer material to form a reinforcing layer.

[0030] As attached Figure 4 In one embodiment shown, the piston cylinder 1 is provided with a conical portion, and the connection port 2 is located at the tip of the conical portion. The spiral guide structure includes a spiral guide plate 9 disposed on the inner surface of the conical portion. When the cavitation liquid flows through the spiral guide plate 9, the spiral guide plate 9 can guide the liquid flow to form a regular rotating flow field. In addition, a large number of irregular protrusions are distributed on the surface of the spiral guide plate 9. When the high-speed cavitation liquid passes through these protrusions, eddies and strong local disturbances are generated. This continuous disturbance effect significantly reduces the local pressure of the flow field. When the local pressure is lower than the saturated vapor pressure corresponding to the working water temperature, a large number of cavitation bubbles 5 are generated. These newly generated cavitation bubbles 5 are then carried downstream by the main flow, replenishing the number of cavitation bubbles 5 in the flow field, further improving the overall processing efficiency from the perspective of the number of cavitation bubble groups 5.

[0031] As attached Figure 5 In another embodiment shown, the spiral flow guiding structure includes an annular inclined plate array 17 disposed at the connection port 2. The annular inclined plate array 17 can be used in conjunction with the spiral flow guiding plate 9 to enhance the spiral effect of the liquid flow.

[0032] The piston 11 maintains a close fit with the inner wall of the piston cylinder 1, forming an effective dynamic seal that prevents cavitation fluid from leaking through the gap during piston 1's movement. A fan blade 10 is mounted on the end of the piston 11 facing the connection port 2 via a bearing, allowing the fan blade 10 to rotate freely in the cavitation fluid. The rotation axis of the fan blade 10 is aligned with the direction of piston 11's movement. During the reciprocating motion of the piston 11, the fan blade 10 rotates under the influence of the fluid flow. As the piston 11 moves, the cavitation fluid impacts the surface of the fan blade 10, generating a hydrodynamic torque that drives the fan blade 10 to rotate around its axis. The rotational motion of the fan blade 10 exerts a tangential force on the surrounding fluid; this force, combined with the axial thrust of the piston 1, further enhances the spiral forward effect of the water flow. Numerous irregular protrusions are also distributed on the surface of the fan blade 10 to increase the number of generated cavitation bubbles 5.

[0033] When the cavitation fluid enters the blind hole 3 in a spiral motion, the centrifugal force generated by the spiral motion throws the cavitation bubbles 5 carried in the water towards the periphery of the flow field. This physical process forces the cavitation bubbles 5 to move closer to the inner surface of the blind hole 3 after entering it. The reduced distance between the cavitation bubbles 5 and the inner surface of the blind hole 3 increases the probability of the cavitation bubbles 5 collapsing near the inner surface, making the energy released when the cavitation bubbles 5 collapse more concentrated on the surface of the workpiece material. This directly improves the efficiency of polishing and strengthening. At the same time, due to the symmetry and stability of the flow field, the distribution of cavitation bubbles 5 along the circumference of the blind hole 3 is more uniform, thereby improving the uniformity of the processing effect on the inner surface of the hole and avoiding local under-processing or over-processing.

[0034] The abrasive 4 is ferromagnetic, allowing it to be attracted by a magnet. In one embodiment, the abrasive 4 is ferromagnetic powder. A magnetocontrol assembly is provided outside the blind hole 3, and the abrasive 4 forms a movement trajectory covering the inner surface of the blind hole 3 under the control of the magnetocontrol assembly.

[0035] Specifically, the magnetron sputtering assembly can apply a magnetic force along the radial direction of the blind hole 3 to the abrasive 4. This magnetic force along the radial direction of the blind hole 3 is called the magnetic attraction force. Under the action of the magnetic attraction force, the abrasive 4 adheres to the inner surface of the blind hole 3 and will not fall directly into the piston cylinder 1 under the action of gravity.

[0036] Under the influence of gravity, the abrasive 4 tends to slide down along the inner surface of the blind hole 3. The abrasive 4 is concentrated in the opening area of ​​the blind hole 3. Too much abrasive 4 in the opening area of ​​the blind hole 3 and insufficient abrasive 4 in the bottom area will result in inconsistent polishing effects in different sections of the blind hole 3.

[0037] Therefore, the magnetron sputtering assembly alternately applies upward and downward magnetic forces to the abrasive 4. The upward magnetic force is called the magnetic lifting force, and the downward magnetic force is called the magnetic descent force. When the abrasive 4 is subjected to the magnetic lifting force, it overcomes gravity and moves upward along the inner surface of the blind hole 3. When the abrasive 4 is subjected to the magnetic descent force, it moves downward along the inner surface of the blind hole 3 under the combined action of gravity. (See attached diagram) Figure 2 As shown, the abrasive 4 can move up and down along the inner surface of the blind hole 3, thereby dynamically and uniformly distributing the abrasive 4 along the length of the blind hole 3, so as to improve the consistency of the polishing effect in each section of the blind hole 3.

[0038] The magnetocontrol assembly includes a surrounding magnetic unit and a variable magnetic unit. The surrounding magnetic unit surrounds the blind hole 3 and is generally cone-shaped, narrower at the top and wider at the bottom. This results in a stronger magnetic field at the upper part of the blind hole 3 than at the lower part, allowing the surrounding magnetic unit to apply a radial magnetic force and an upward magnetic force to the abrasive 4. The variable magnetic unit is located below the blind hole 3 and applies a downward magnetic force to the abrasive 4. The magnitude of the magnetic force applied by the variable magnetic unit is variable.

[0039] By employing a surrounding magnetic unit and a variable magnetic unit, polishing and strengthening of the inner surface can be achieved solely from one side of the blind hole 3 opening. This design eliminates the accessibility requirement for the other side of the blind hole 3, thus overcoming the limitations imposed by the overall shape of the blind hole 3. Even if the bottom of the blind hole 3 has a complex curved surface, a stepped shape, or an asymmetrical structure, the device can still effectively control the movement path of the abrasive 4 using a magnetic field and achieve complete coverage by utilizing the flow of cavitation bubbles 5 within the blind hole 3. This allows for uniform processing of the inner surface without requiring operation from the other end of the blind hole 3.

[0040] As attached Figure 1 As shown, the surrounding magnetic unit consists of several magnetic strips 6 arranged in a ring. The magnetic strips 6 are inclined from top to bottom in a direction away from the blind hole 3, so that the surrounding magnetic unit is generally conical in shape, narrow at the top and wide at the bottom. In one embodiment, six magnetic strips 6 are distributed at equal angles outside the blind hole 3, and the central axis of the ring array formed by the six magnetic strips 6 is collinear with the blind hole 3.

[0041] The adjacent magnetic strips 6 within the surrounding magnetic unit are spaced apart, and the abrasive 4 within the blind hole 3 is attracted to concentrate towards the magnetic strips 6, as shown in the attached figure. Figure 3 As shown, since the abrasive 4 will concentrate towards the magnetic stripe 6, alternating abrasive concentration stripe areas 15 and abrasive dispersion stripe areas 16 will be formed in the blind hole 3. The cavitation bubble 5 can directly contact the inner surface of the blind hole 3 through the abrasive dispersion stripe area 16.

[0042] Assuming that the abrasive 4 is uniformly distributed circumferentially within the blind hole 3, then all areas of the inner surface of the blind hole 3 are covered by the abrasive 4. Under the obstruction of the abrasive 4, the cavitation bubble 5 cannot directly contact the inner surface of the blind hole 3. The micro-jet and shock wave generated when the cavitation bubble 5 collapses will also be blocked by the abrasive 4, thereby weakening the reinforcing effect of the cavitation bubble 5 on the inner surface of the blind hole 3.

[0043] Therefore, in this application, the abrasive 4 is not uniformly distributed circumferentially within the blind hole 3. Instead, alternating abrasive concentration stripe areas 15 and abrasive dispersion stripe areas 16 are formed within the blind hole 3 by several circumferentially distributed and spaced magnetic stripes 6, allowing the cavitation bubble 5 to directly contact the inner surface of the blind hole 3 through the abrasive dispersion stripe areas 16. A rotating frame 7 is provided outside the blind hole 3, and the rotating frame 7 can rotate relative to the blind hole 3 under the drive of an external driving mechanism. In one embodiment, a gear mechanism is provided on the outer side of the rotating frame 7 for meshing and transmission with the external driving mechanism. When the rotating frame 7 receives rotational power, the rotating frame 7 and the magnetic stripes 6 rotate around the blind hole 3.

[0044] Several magnetic strips 6 are mounted on a rotating frame 7. When the magnetic strips 6 rotate around the blind hole 3 with the rotating frame 7, they attract the abrasive 4 to sweep across the inner surface of the blind hole 3 in the circumferential direction, so that the abrasive concentration stripe area 15 and the abrasive dispersion stripe area 16 continuously rotate along the circumferential direction of the blind hole 3. As the abrasive dispersion stripe area 16 rotates, the cavitation bubble 5 can directly contact all areas of the inner surface of the blind hole 3 through the abrasive dispersion stripe area 16.

[0045] The variable magnet unit includes an electromagnet 8 positioned below the blind hole 3. The electromagnet 8 is located at the end of the piston cylinder 1 furthest from the blind hole 3, and its installation position ensures that the central axis of the electromagnet 8's electromagnetic coil, the central axis of the piston cylinder 1, and the central axis of the blind hole 3 are collinear. As the current changes, the attraction force of the electromagnet 8 also changes, thereby creating a magnetic upward or downward force from the combined force of the electromagnet 8 and the surrounding magnetic unit, which attracts the abrasive 4 to rise or fall along the inner wall of the blind hole 3.

[0046] The present invention also provides a working method for a blind hole inner surface polishing device based on cavitation and magnetron abrasive. First, the blind hole 3 is opened upward, and a certain amount of ferromagnetic abrasive 4 is added into the blind hole 3. Then, the abrasive 4 is attracted to the inner surface of the blind hole 3 by magnetic force. After that, the blind hole 3 is inverted and the connection port 2 between the blind hole 3 and the piston cylinder 1 is sealed. Then, cavitation liquid is added into the piston cylinder 1 through the liquid injection port 12, and then the liquid injection port 12 is closed.

[0047] During the polishing process of the inner surface of the blind hole 3, the piston 11 moves up and down repeatedly. When the piston 11 moves down, cavitation occurs due to the increase in volume, generating a large number of cavitation bubbles 5 in the fluid. When the piston 11 moves up, the cavitation liquid containing the cavitation bubbles 5 is injected into the blind hole 3. The cavitation liquid passes through the spiral guide structure to form a spiral flow state, so that the cavitation bubbles 5 move close to the inner surface of the blind hole 3 with the cavitation liquid, thereby enhancing the strengthening effect of the cavitation bubbles 5 on the inner surface of the blind hole 3.

[0048] The magnitude of the magnetic force of the variable magnet unit changes periodically. After the electromagnet 8 is energized, the magnitude of the downward attraction generated by the electromagnet 8 changes continuously. The resultant force generated by the electromagnet 8 and several magnets alternates upward and downward, so that the entire magnetic control assembly alternately applies magnetic upward force and magnetic downward force to the abrasive 4, thereby causing the abrasive 4 to move up and down along the inner surface of the blind hole 3. Thus, the abrasive 4 is dynamically and uniformly distributed along the length of the blind hole 3.

[0049] In practical applications, when the piston 11 moves upward, the abrasive 4 also moves upward along the inner surface of the blind hole 3 accordingly, and when the piston 11 moves downward, the abrasive 4 also moves downward along the inner surface of the blind hole 3 accordingly, and the two are consistent.

[0050] Several magnetic strips 6 rotate around the blind hole 3 along with the rotating frame 7. The magnetic strips 6 attract the abrasive 4 to sweep along the inner surface of the blind hole 3 in the circumferential direction. Since the abrasive 4 simultaneously performs reciprocating lifting and circumferential rotation along the inner surface of the blind hole 3, the movement trajectory of the abrasive 4 can completely cover the inner surface of the blind hole 3, thereby improving the uniformity of polishing the inner surface of the blind hole 3.

[0051] In addition, the magnetic stripe 6 will form alternating abrasive concentrated stripe areas 15 and abrasive dispersed stripe areas 16 in the blind hole 3. The cavitation bubble 5 can directly contact the inner surface of the blind hole 3 through the abrasive dispersed stripe area 16 to improve the polishing effect of the cavitation bubble 5 on the inner surface of the blind hole 3.

[0052] The aforementioned composite machining cycle, consisting of the reciprocating motion of piston 11, the periodic changes in the attraction force of electromagnet 8, and the rotation of magnetic strip 6, is repeated multiple times. Each complete cycle causes the ferromagnetic abrasive 4 to comprehensively machine the inner surface of blind hole 3 in both axial and circumferential dimensions. After a preset number of machining cycles, the system enters the chip removal and renewal stage. The valve on drain port 13 opens, and under the push of piston 11, waste working medium containing polishing debris and wear products detached from the inner wall of blind hole 3 is discharged from the system through this outlet. After waste removal, new, clean working medium water is injected again through injection port 12 to prepare for the next batch of machining cycles. This process continues to repeat until the polishing and strengthening treatment of the inner surface of blind hole 3 meets the preset process requirements and quality standards, marking the completion of the entire machining task.

[0053] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. An apparatus for polishing the interior surface of a blind hole based on cavitation and magnetically controlled abrasives, characterized by: The application relates to a piston cylinder (1) with a connecting port (2) and a blind hole (3) connected with the connecting port (2); the piston cylinder (1) contains cavitation liquid; when a piston (11) in the piston cylinder (1) reciprocates, cavities (5) are generated in the cavitation liquid; the cavitation liquid containing the cavities (5) enters and exits the blind hole (3) through the connecting port (2); the blind hole (3) contains abrasive (4) with ferromagnetism; a magnetic control assembly is arranged outside the blind hole (3); the abrasive (4) forms a moving track covering the inner surface of the blind hole (3) under the control of the magnetic control assembly.

2. The cavitation and magnetically controlled abrasive based blind hole inner surface polishing apparatus of claim 1, wherein: The top end of the piston cylinder (1) is provided with the connecting port (2); the inverted blind hole (3) is connected with the connecting port (2); the magnetic control assembly can exert a magnetic force along the radial direction of the blind hole (3) on the abrasive (4); the magnetic force along the radial direction of the blind hole (3) is called magnetic adsorption force; under the action of the magnetic adsorption force, the abrasive (4) adheres to the inner surface of the blind hole (3).

3. The cavitation and magnetically controlled abrasive based blind hole inner surface polishing apparatus of claim 2, wherein: The magnetic control assembly can also alternately exert upward and downward magnetic forces on the abrasive (4); the upward magnetic force is called magnetic upward force, and the downward magnetic force is called magnetic downward force. When the abrasive (4) is subjected to the magnetic upward force, the abrasive (4) overcomes the action of gravity and moves upwards along the inner surface of the blind hole (3). When the abrasive (4) is subjected to the magnetic downward force, the abrasive (4) moves downwards along the inner surface of the blind hole (3) under the joint action of gravity.

4. The blind hole inner surface polishing device based on cavitation and magnetically controlled abrasive of claim 3, wherein: The magnetic control assembly comprises a magnetic surrounding unit and a magnetic variable unit; the magnetic surrounding unit is arranged outside the blind hole (3) and has a taper cylinder shape with a narrow top and a wide bottom; the magnetic surrounding unit can exert a magnetic force along the radial direction of the blind hole (3) and an upward magnetic force on the abrasive (4); the magnetic variable unit is arranged below the blind hole (3); the magnetic variable unit can exert a downward magnetic force on the abrasive (4); and the magnetic force of the magnetic variable unit is variable.

5. The cavitation and magnetically controlled abrasive based blind hole inner surface polishing apparatus of claim 4, wherein: The magnetic surrounding unit is composed of a plurality of magnetic strips (6) distributed in a ring shape; the magnetic strips (6) are inclined from top to bottom towards the direction away from the blind hole (3), so that the magnetic surrounding unit has a taper cylinder shape with a narrow top and a wide bottom. The adjacent magnetic strips (6) in the magnetic surrounding unit are spaced apart; the abrasive (4) in the blind hole (3) is attracted to the magnetic strips (6), so that alternating abrasive concentration stripe areas (15) and abrasive dispersion stripe areas (16) are formed in the blind hole (3); the cavities (5) can directly contact the inner surface of the blind hole (3) through the abrasive dispersion stripe areas (16); the magnetic strips (6) are installed on a rotating frame (7); when the magnetic strips (6) rotate around the blind hole (3) with the rotating frame (7), the abrasive (4) is attracted to sweep the inner surface of the blind hole (3) in a circumferential direction.

6. The blind hole inner surface polishing device based on cavitation and magnetically controlled abrasive of claim 4, wherein: The magnetic variable unit comprises an electromagnet (8) arranged at the end of the piston cylinder (1) away from the blind hole (3); with the change of current, the resultant force of the electromagnet (8) and the magnetic surrounding unit forms the magnetic upward force or the magnetic downward force.

7. The cavitation and magnetically controlled abrasive based blind hole inner surface polishing apparatus of claim 1, wherein: The piston cylinder (1) is provided with a spiral flow guide structure; after the cavitation liquid passes through the spiral flow guide structure, a spiral flow is formed; the cavities (5) are thrown to the inner surface of the blind hole (3) along the spiral flow.

8. The cavitation and magnetically controlled abrasive based blind hole inner surface polishing apparatus of claim 1, wherein: The end of the piston (11) towards the connecting port (2) is provided with a fan blade (10); the rotation axis of the fan blade (10) is consistent with the movement direction of the piston (11); when the piston (11) reciprocates, the fan blade (10) rotates under the action of the liquid flow.

9. The cavitation and magnetically controlled abrasive based blind hole inner surface polishing apparatus of claim 1, wherein: The connecting port (2) of the piston cylinder (1) is in sealed connection with the aperture of the blind hole (3), and the piston cylinder (1) is further provided with a liquid injection port (12) and a liquid discharge port (13).

10. A method of working a blind hole inner surface polishing device based on cavitation and magnetically controlled abrasives according to claim 5, characterized in that: In the process of polishing the inner surface of the blind hole (3), the piston (11) reciprocates to inject the cavitation liquid containing the cavitation bubbles (5) into the blind hole (3); the magnetic force of the variable magnetic unit periodically changes, and the whole magnetic control assembly alternately applies magnetic upward force and magnetic downward force to the abrasive (4), so that the abrasive (4) reciprocates along the inner surface of the blind hole (3); the magnetic strip (6) rotates around the blind hole (3) with the rotating frame (7), and attracts the abrasive (4) to sweep the inner surface of the blind hole (3) in the circumferential direction; the abrasive (4) simultaneously performs reciprocating movement and circumferential rotation along the inner surface of the blind hole (3), so that the movement track of the abrasive (4) can completely cover the inner surface of the blind hole (3).

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