An electric spindle structure for a CNC machining center

Abstract

The present invention discloses an electric spindle structure of a CNC machining center, which relates to the technical field of electric spindles, and comprises a shell installed on a mechanical arm, wherein a rotating shaft is arranged at the inner center of the shell to rotate along its axial direction, at least two bearings are sleeved on the circumferential surface of the rotating shaft, and the bearings are arranged at a position close to the end face of the rotating shaft, and two end covers are slidably assembled on the shell along the axial direction of the shell; in the axial direction of the shell, the two end covers make a linear motion away from the shell until the bearings and the end covers are separated, and at the same time, the end covers make a flipping motion away from the shell in a direction perpendicular to the axis of the shell until the end covers and the bearings are completely staggered in the axial direction of the shell. The present invention drives the end covers to move in a direction away from the shell by setting a rack, and the end covers and the bearings are completely staggered in the axial direction of the shell, which not only improves the efficiency of bearing removal and replacement, but also provides a larger operating space when replacing the bearings, making the work of replacing the bearings more flexible and convenient.

Description

Technical Field

[0001] The invention relates to the technical field of electric spindles, and in particular to an electric spindle structure of a numerical control machining center. Background Art

[0002] In CNC machining centers, the electric spindle is a crucial component responsible for driving the tool to achieve high-speed rotation for various machining operations. The electric spindle is usually composed of a housing, a shaft, a bearing and other components, and the core shaft and bearings are responsible for the high-speed rotation task. Among them, the housing is generally fixed on the robot arm, and the position and angle of the electric spindle are changed by the robot arm.

[0003] Bearings will be subjected to heavy pressure and friction when rotating at high speeds. They will wear and age after long-term use, which may lead to reduced bearing performance, increased friction, noise, and even malfunctions. Replacing the bearings can restore the normal operation of the equipment. In the prior art, the end cover and the housing are connected by bolts, which not only has low disassembly efficiency, but also easily leads to reduced installation accuracy when reinstalling the end cover.

[0004] For the above-mentioned problem, a Chinese patent with announcement number CN116372201B discloses an electric spindle structure for a CNC machining center, which relates to the technical field of CNC machining robot arms. When maintaining the internal bearings of the existing electric spindle structure, the limit assembly between the spindle unit housing and the end cover can be removed simultaneously using a transmission assembly. The significance of this is that the end covers at both ends of the spindle unit housing can be removed simultaneously, which facilitates the disassembly process of the end covers and eliminates the need for staff to use disassembly tools to disassemble them one by one by hand, thereby reducing the labor intensity of the staff.

[0005] Although the above-mentioned prior art improves the efficiency of disassembly of the end cover, the end cover is separated from the shell after disassembly. When reinstalling the end cover, manual positioning is required. If the axial direction of the end cover and the shell cannot completely overlap, it is very easy to cause increased bearing wear, shortening the maintenance cycle of the electric spindle and increasing the maintenance cost. Based on this, the present invention proposes an electric spindle structure for a CNC machining center. Summary of the invention

[0006] The object of the present invention is to provide an electric spindle structure for a numerical control machining center to solve the problems raised in the above background technology.

[0007] To achieve the above object, the technical solution adopted by the present invention is:

[0008] An electric spindle structure of a CNC machining center includes a shell installed on a mechanical arm, a rotating shaft is arranged at the inner center of the shell along its axial direction, at least two bearings are sleeved on the circumferential surface of the rotating shaft, and the bearings are arranged at positions close to the end faces of the rotating shaft, and two end covers are slidably assembled on the shell along the axial direction of the shell; in the axial direction of the shell, the two end covers make a linear motion away from the shell until the bearings and the end covers are separated, and at the same time, the end covers make a flipping motion away from the shell in a direction perpendicular to the axis of the shell until the end covers and the bearings are completely offset in the axial direction of the shell.

[0009] Preferably, a group of racks arranged along the axial direction of the shell are fixedly mounted on the circumferential surfaces of the two end covers, and each group of racks is provided with two racks. A gear is meshed and connected between the two racks on the same side. The gear is rotatably mounted on the circumferential surface of the shell. The two racks on the same side are centrally symmetrically arranged with the gear as the center. A guide plate is installed on the circumferential surface of the shell at the position corresponding to the rack, and the rack is slidably assembled in the guide plate.

[0010] Preferably, the rack is composed of a flipping part and a linear motion part, and the flipping part and the linear motion part are hinged at one end close to each other, and the flipping part is fixedly connected to the end cover; a second guide rod is installed on the side of the flipping part, and at least two first guide rods are installed on the side of the linear motion part; a linear guide groove and a flipping guide groove connected end to end are provided on the guide plate, the linear guide groove is parallel to the axial direction of the shell, and the flipping guide groove is arc-shaped.

[0011] Preferably, a reinforcing hook plate is slidably mounted axially on the shell, and the reinforcing hook plate and the rack are symmetrically arranged with the end cover as the center. When a rack applies a tensioning force to the end cover toward the shell, the reinforcing hook plate symmetrical to it also applies a tensioning force to the end cover toward the shell.

[0012] Preferably, a thin tube parallel to the axial direction of the shell is installed at one end of the guide plate close to the linear motion part, and a thick tube is installed at the other end of the thin tube, and the thick tube and the thin tube are arranged in parallel. A first piston is slidably connected in the thin tube, and a second piston is slidably connected in the thick tube. The second piston and the first piston are filled with liquid, and a second push rod is installed at the end of the second piston away from the liquid. The second push rod movably passes through the thick tube and extends to the outside of the thick tube. A reinforcement hook plate is installed at the other end of the second push rod, and the reinforcement hook plate is a hook-shaped structure; a first push rod is installed at one end of the linear motion part away from the flipping part, and the first push rod movably passes through the guide plate and extends to the inside of the thin tube.

[0013] Preferably, the diameter of the thin tube is smaller than the diameter of the thick tube.

[0014] Preferably, the reinforcement hook plate is rotatably connected to the second push rod.

[0015] Preferably, a rotating shaft is installed at the center of the end face of the gear away from the shell; a spiral groove is engraved on the circumferential surface of the rotating shaft, a sleeve is slidably sleeved on the outside of the rotating shaft along its axial direction, and a guide block slidably connected to the spiral groove is fixedly installed on the inside of the sleeve; a U-shaped mounting seat is fixedly sleeved on the circumferential surface of the sleeve, and the mounting seat is slidably connected to the guide plate; a base is provided on the robotic arm, linear modules are installed at both ends of the base, a splint is installed on the movable end of the linear module, and the splint and the mounting seat are fixedly connected by bolts.

[0016] Preferably, a positioning block is installed at the lower part of the circumferential surface of the shell, and a positioning groove matching the positioning block is opened on the base.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] (1) The present invention provides a rack to drive the end cover to move in a direction away from the shell. During the entire process of disassembling the end cover, the end cover and the rack are always connected, and the rack and the shell are always connected. This ensures that when the end cover is reinstalled, the end cover and the shell can be perfectly spliced ​​together, greatly improving the sealing degree between the end cover and the shell.

[0019] (2) The present invention realizes the disassembly and connection of the end cover and the shell by providing a rack and a reinforcing hook plate. When the gear rotates counterclockwise, the end cover and the shell are tightly connected together. When the gear rotates clockwise, the end cover and the shell are separated, which effectively improves the efficiency of bearing disassembly and replacement, making the work of bearing replacement more flexible and convenient.

[0020] (3) In the present invention, the robot arm clamps and fixes the shell by two clamping plates making relative linear motion. At the same time, the linear motion of the clamping plates is used to drive the gear to rotate. When the shell is firmly fixed on the robot arm, the end cover and the shell are tightly connected together. When the clamping plates move in a direction away from the shell, the end cover moves away from the shell along the axial direction of the shell. The connection between the end cover and the shell, and the connection between the shell and the robot arm are realized by using one driving source, which not only saves manufacturing costs but also simplifies the volume of the entire electric spindle.

[0021] (4) When the end cover moves away from the housing, it also flips in a direction perpendicular to the axial direction of the housing, so that the end cover and the bearing are completely offset in the axial direction of the housing, providing a larger operating space when replacing the bearing. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the present invention and do not constitute a limitation of the present invention. In the accompanying drawings:

[0023] Figure 1 It is a structural schematic diagram of the entire electric spindle structure proposed in an embodiment of the present invention;

[0024] Figure 2 Schematic diagram of the tightly connected state of the housing and the end cover in an embodiment of the present invention;

[0025] Figure 3 This is a schematic diagram of the first step of disassembling the shell and the end cover in an embodiment of the present invention;

[0026] Figure 4 This is a schematic diagram of the second step disassembly state of the shell and the end cover in an embodiment of the present invention;

[0027] Figure 5 is a schematic diagram of the cross-sectional structure of a housing in an embodiment of the present invention;

[0028] Figure 6 Schematic diagram of the installation structure of the rack and the gear in the embodiment of the present invention;

[0029] Figure 7 A schematic diagram of the structure of a rack in an embodiment of the present invention;

[0030] Figure 8 A schematic diagram of the structure of a guide plate in an embodiment of the present invention;

[0031] Fig. 9 for Figure 8 Schematic diagram of the structure of the middle part;

[0032] Fig.10 Schematic diagram of the installation structure of the reinforcement hook plate in an embodiment of the present invention;

[0033] Fig.11 is a schematic cross-sectional structure diagram of a sleeve and a mounting seat in an embodiment of the present invention;

[0034] Fig.12 Schematic diagram of the installation structure of the gear and the rotating shaft in the embodiment of the present invention;

[0035] Fig.13 Schematic diagram of the installation structure of the guide block in an embodiment of the present invention;

[0036] Fig.14 Schematic diagram of the local structure of the robotic arm in an embodiment of the present invention.

[0037] In the figure: 1. Robotic arm; 11. Base; 12. Positioning slot; 13. Linear module; 14. Clamp;

[0038] 2. housing; 21. rotating shaft; 22. bearing; 23. positioning block;

[0039] 3. End cover; 31. Rack; 311. Flipping part; 312. Linear motion part; 313. First guide rod; 314. Second guide rod; 32. Gear; 321. Baffle; 322. Rotating shaft; 323. Spiral groove; 324. Guide block; 325. Sleeve; 326. Mounting seat; 33. Reinforcement hook plate; 331. Thin tube; 332. Thick tube; 333. First push rod; 334. First piston; 335. Second push rod; 336. Second piston; 34. Guide plate; 341. Linear guide groove; 342. Flipping guide groove. DETAILED DESCRIPTION

[0040] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. The components of the embodiments of the present invention generally described and shown in the drawings here can be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the drawings is not intended to limit the scope of the claimed invention, but merely represents the selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without making creative work belong to the scope of protection of the present invention.

[0041] See also Figure 1-Figure 14The present embodiment proposes an electric spindle structure for a CNC machining center, including a shell 2 mounted on a mechanical arm 1, a rotating shaft 21 is arranged at the inner center of the shell 2 along its axial direction, at least two bearings 22 are sleeved on the circumferential surface of the rotating shaft 21, and the bearings 22 are arranged at a position close to the end surface of the rotating shaft 21. In practical applications, the bearings 22 may cause wear or even damage due to friction and heavy loads during operation. Timely replacement of worn bearings 22 helps to ensure the normal operation of the electric spindle and improve the reliability and life of the electric spindle. In order to reduce the difficulty of removing and replacing the bearings 22, removable end covers 3 are installed at both ends of the shell 2, and the bearings 22 are completely sealed inside the shell 2 by the end covers 3. In order to facilitate the removal and replacement of the bearings 22, bolted connection is generally adopted between the end covers 3 and the shell 2, but this method has the following disadvantages: on the one hand, due to the large number of bolts, it takes a long time to remove the bolts and the efficiency is low. On the other hand, When reinstalling the end cover 3, it is necessary to manually align the end cover 3 and the shell 2, and in the process of tightening the bolts, the end cover 3 is prone to slight displacement, which may cause the axis of the end cover 3 and the shell 2 to not completely overlap, thereby reducing the service life of the bearing 22. Therefore, in order to ensure that the connection between the end cover 3 and the shell 2 can be smoother and more reliable during disassembly and reinstallation, in the present invention, the two end covers 3 are both slidably assembled on the shell 2 along the axial direction of the shell 2. When the bearing 22 needs to be replaced, the two end covers 3 make a linear motion away from the shell 2 along the axial direction of the shell 2 until the bearing 22 and the end cover 3 are separated. On the basis of the above scheme, since the end cover 3 and the bearing 22 are located on the same straight line, the space between the end cover 3 and the bearing 22 is small, which affects the replacement operation of the bearing 22. Therefore, in the process of the end cover 3 moving linearly along the axial direction of the housing 2 to separate from the bearing 22, the end cover 3 makes a flipping movement away from the housing 2 in a direction perpendicular to the axis of the housing 2, so that the end cover 3 and the bearing 22 are completely staggered in the axial direction of the housing 2, which is conducive to improving the efficiency of replacing the bearing 22. In this embodiment, the flipping directions of the two end covers 3 are opposite, which can avoid collision between the two end covers 3 during the flipping process.

[0042] Among them, a group of racks 31 arranged along the axial direction of the shell 2 are fixedly installed on the circumferential surfaces of the two end covers 3, and each group of racks 31 is provided with two, and the two racks 31 located on the same side are meshed and connected with a gear 32, and the gear 32 is rotatably installed on the circumferential surface of the shell 2. The two racks 31 on the same side are centrally symmetrically arranged with the gear 32 as the center, and a guide plate 34 is installed on the circumferential surface of the shell 2 at the position corresponding to the rack 31, and the rack 31 is slidably assembled in the guide plate 34. When the bearing 22 needs to be replaced, the clockwise rotation of the gear 32 drives the two racks 31 on the same side to make a linear motion away from each other, thereby driving the two end covers 3 to make a linear motion away from the shell 2 along the axial direction of the shell 2.

[0043] When the end cover 3 makes a linear motion along the axial direction of the shell 2 and just misses the bearing 22, the end cover 3 needs to make a flipping motion away from the shell 2 in a direction perpendicular to the axial direction of the shell 2. Therefore, in this embodiment, the rack 31 is composed of a flipping part 311 and a linear motion part 312, and the flipping part 311 and the linear motion part 312 are hinged at one end close to each other, and the flipping part 311 is fixedly connected to the end cover 3; a second guide rod 314 is installed on the side of the flipping part 311, and at least two first guide rods 313 are installed on the side of the linear motion part 312. Through the at least two first guide rods 313, the linear motion part 312 is kept parallel to the axial direction of the shell 2 during the sliding process in the guide plate 34, ensuring the stable meshing of the rack 31 and the gear 32; the guide plate 34 is provided with a linear guide groove 341 and a flipping guide groove 342 connected end to end, the linear guide groove 341 is arranged parallel to the axial direction of the shell 2, and the flipping guide groove 342 is arc-shaped. When the end cover 3 and the shell 2 are in a tightly connected state, the first guide rod 313 and the second guide rod 314 are both in the linear guide groove 341, and the two racks 31 on the same side maintain a relative movement trend, so that the end cover 3 and the shell 2 maintain a tightly connected state; when the bearing 22 needs to be replaced, the gear 32 rotates clockwise, and the flipping part 311 and the linear motion part 312 move synchronously along the linear guide groove 341 toward the flipping guide groove 342. When the second guide rod 314 moves to the linear guide groove 341 and the flipping guide groove 342, When the end cover 3 and the bearing 22 meet at the intersection of the groove 342, the end cover 3 and the bearing 22 are completely offset in the axial direction of the shell 2. As the gear 32 continues to rotate, the second guide rod 314 enters the flipping guide groove 342, so that the flipping part 311 flips around the hinge axis between the flipping part 311 and the linear motion part 312. At the same time, the linear motion part 312 continues to move along the linear guide groove 341 and pushes the flipping part 311 to continue flipping along the flipping guide groove 342 until the end cover 3 and the bearing 22 are completely offset in the axial direction of the shell 2.

[0044] Since the two racks 31 located on the same side are symmetrically arranged with the gear 32 as the center, the connecting line between the two racks 31 in a group does not pass through the center of the end cover 3, that is, the rack 31 is biased toward one side of the end cover 3, resulting in a smaller tensioning force on the side away from the rack 31 and a larger tensioning force on the side close to the rack 31, which in turn causes the end cover 3 to be subjected to uneven force, affecting the sealing effect between the end cover 3 and the shell 2. Therefore, in this embodiment, a reinforcing hook plate 33 is slidably assembled in the axial direction of the shell 2, and the reinforcing hook plate 33 and the rack 31 are symmetrically arranged with the end cover 3 as the center. When a rack 31 applies a tensioning force to the end cover 3 in the direction close to the shell 2, the reinforced hook plate 33 symmetrical to it also applies a tensioning force to the end cover 3 in the direction close to the shell 2, so that the end cover 3 is subjected to balanced force, thereby improving the sealing degree between the end cover 3 and the shell 2.

[0045] Specifically, a thin tube 331 is installed at one end of the guide plate 34 close to the linear motion part 312 and is parallel to the axial direction of the shell 2. The other end of the thin tube 331 is connected to a thick tube 332, and the thick tube 332 and the thin tube 331 are arranged in parallel. A first piston 334 is slidably connected in the thin tube 331, and a second piston 336 is slidably connected in the thick tube 332. The space between the second piston 336 and the first piston 334 is filled with liquid. The liquid filled in this embodiment is hydraulic oil. A second push rod 335 is installed at the end of the second piston 336 away from the liquid. The second push rod 335 movably penetrates the thick tube 332 and extends to the outside of the thick tube 332. A reinforcing hook plate 33 is installed at the other end of the second push rod 335. The reinforcing hook plate 33 is a hook-shaped structure. A first push rod 333 is installed at one end of the linear motion part 312 away from the flipping part 311. The first push rod 333 movably penetrates the guide plate 34 and extends to the inside of the thin tube 331. When one rack 31 applies a tensioning force toward the shell 2 to the end cover 3, the linear motion portion 312 in the other rack 31 on the same side drives the first push rod 333 to move toward the first piston 334, thereby pushing the first piston 334 to move in a direction away from the guide plate 34, so that the hydraulic oil squeezes the second piston 336, and the second piston 336 drives the second push rod 335 to make a linear motion toward the shell 2. The second push rod 335 applies a tensioning force toward the shell 2 to the end cover 3 through the reinforcing hook plate 33.

[0046] On the basis of the above scheme, since the contact area between the reinforcing hook plate 33 and the end cover 3 is much smaller than the contact area between the rack 31 and the end cover 3, the tension applied by the reinforcing hook plate 33 to the end cover 3 is smaller when acting on the entire end cover 3. Therefore, in order to increase the tension applied by the reinforcing hook plate 33 to the entire end cover 3, in this embodiment, the diameter of the thin tube 331 is smaller than the diameter of the thick tube 332; according to Pascal's law, applying a certain pressure on a piston in a liquid system will inevitably produce the same pressure increment on the other piston. If the area of ​​the second piston is ten times that of the first piston, the force acting on the second piston will increase to ten times that of the first piston. In this embodiment, the diameter of the thick tube 332 is twice the diameter of the thin tube 331, and the thrust applied by the hydraulic oil to the second piston 336 is twice the thrust applied by the first piston 334 to the hydraulic oil, thereby increasing the tension applied by the reinforcing hook plate 33 to the entire end cover 3.

[0047] Since the end cover 3 needs to move in a direction away from the housing 2 when replacing the bearing 22, the reinforcing hook plate 33 will block the movement of the end cover 3. Therefore, in this embodiment, a rotational connection is adopted between the reinforcing hook plate 33 and the second push rod 335. When the bearing 22 needs to be replaced, the reinforcing hook plate 33 is manually rotated so that the reinforcing hook plate 33 and the end cover 3 are staggered, which does not affect the subsequent movement of the end cover 3.

[0048] In addition, when replacing the bearing 22, the gear 32 needs to rotate clockwise. In order to realize the driving of the gear 32 and reduce the manufacturing cost, in this embodiment, the disassembly of the end cover 3 and the shell 2 is associated with the disassembly of the mechanical arm 1 and the shell 2. Two relatively arranged clamping plates 14 are provided on the mechanical arm 1. The two clamping plates 14 move towards each other to realize the fixed connection between the mechanical arm 1 and the shell 2, and the movement of the clamping plates 14 is used to drive the rotation of the gear 32. Specifically, a rotating shaft 322 is installed at the end center of the gear 32 away from the shell 2. In this embodiment, in order to avoid the separation between the gear 32 and the rack 31, baffles 321 are installed at both ends of the gear 32. The limiting effect of the baffles 321 keeps the gear 32 and the rack 31 in a tight meshing state; the circumferential surface of the rotating shaft 322 is engraved with a spiral spiral groove 323, and the outer part of the rotating shaft 322 is slidably sleeved with a sleeve 325 along its axial direction, and the inner part of the sleeve 325 A guide block 324 is fixedly installed and slidably connected to the spiral groove 323; when the bearing 22 needs to be replaced, the sleeve 325 makes a linear motion away from the rotating shaft 322 along the axial direction of the rotating shaft 322 and moves through the guide block 324. The movement of the guide block 324 in the spiral groove 323 causes the rotating shaft 322 to rotate clockwise; it should be noted that in order to prevent the sleeve 325 from rotating on its own during the linear motion, the circumferential surface of the sleeve 325 is fixedly sleeved with a U-shaped mounting seat 326, and the mounting seat 326 is slidably connected to the guide plate 34. The guiding effect of the mounting seat 326 prevents the sleeve 325 from rotating on its own; a base 11 is provided on the robot arm 1, and linear modules 13 are installed at both ends of the base 11, and a splint 14 is installed at the movable end of the linear module 13. The splint 14 and the mounting seat 326 are fixedly connected by bolts. When the bearing 22 does not need to be replaced, the bolts between the splint 14 and the mounting seat 326 are removed. When the bearing 22 needs to be replaced, the linear module 13 drives the clamp plate 14 to make a linear motion away from the mounting seat 326, and the clamp plate 14 drives the mounting seat 326 to move, and the mounting seat 326 drives the sleeve 325 to make a linear motion away from the rotating shaft 322, and the sleeve 325 causes the rotating shaft 322 to rotate clockwise through the guide block 324, and the rotating shaft 322 drives the gear 32 to rotate clockwise, and the gear 32 drives the two racks 31 on the same side to make a linear motion away from each other. At the same time, the reinforcing hook plate 33 is manually rotated to separate it from the end cover 3, and the two racks 31 on the same side drive the two end covers 3 to make a linear motion away from the shell 2, and finally completely staggered with the bearing 22 in the axial direction of the shell 2.

[0049] On the basis of the above scheme, in order to prevent the shell 2 from rotating when the clamp 14 moves away from the shell 2, in this embodiment, a positioning block 23 is installed on the lower part of the circumferential surface of the shell 2, and a positioning groove 12 matching the positioning block 23 is opened on the base 11.

[0050] It should be noted that the robot arm 1 and the linear module 13 in the present invention both adopt currently known equipment. Since they are not the focus of the technical solution to be protected by this application, they will not be described in detail.

[0051] In the description of the present invention, the terms "first", "second", "another", and "yet another" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, the features defined as "first" or "second" may explicitly or implicitly include one or more features. In the description of the embodiments of the present invention, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0052] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "connected" and "connection" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances. In addition, in the description of the present invention, unless otherwise specified, "plurality" means two or more.

[0053] Although the embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the claims and their equivalents.

Claims

1. An electric spindle structure for a numerical control machining center, comprising a housing (2) mounted on a mechanical arm (1), a rotating shaft (21) being arranged at the center of the housing (2) so as to rotate along its axial direction, at least two bearings (22) being sleeved on the circumferential surface of the rotating shaft (21), and the bearings (22) being arranged at positions close to the end surfaces of the rotating shaft (21), characterized in that: The two end covers (3) are both slidably assembled on the housing (2) along the axial direction of the housing (2); in the axial direction of the housing (2), the two end covers (3) perform linear motion away from the housing (2) until the bearing (22) and the end covers (3) are separated; at the same time, the end covers (3) perform a flipping motion away from the housing (2) in a direction perpendicular to the axis of the housing (2) until the end covers (3) and the bearing (22) are completely offset in the axial direction of the housing (2); A group of racks (31) arranged along the axial direction of the housing (2) are fixedly mounted on the circumferential surfaces of the two end covers (3), each group of racks (31) is provided with two racks, and a gear (32) is meshed and connected between the two racks (31) located on the same side, and the gear (32) is rotatably mounted on the circumferential surface of the housing (2), and a guide plate (34) is mounted on the circumferential surface of the housing (2) at a position corresponding to the racks (31), and the racks (31) are slidably assembled in the guide plate (34); The rack (31) is composed of a flipping portion (311) and a linear motion portion (312) spliced ​​together, and the flipping portion (311) and the linear motion portion (312) are hingedly arranged at one end close to each other, and the flipping portion (311) is fixedly connected to the end cover (3); a second guide rod (314) is installed on the side of the flipping portion (311), and at least two first guide rods (313) are installed on the side of the linear motion portion (312); and the guide plate (34) is provided with a linear guide groove (341) and a flipping guide groove (342) connected end to end.

2. The electric spindle structure of a CNC machining center according to claim 1, characterized in that: The two racks (31) on the same side are centrally symmetrically arranged with the gear (32) as the center.

3. The electric spindle structure of a CNC machining center according to claim 1, characterized in that: The linear guide groove (341) is arranged parallel to the axial direction of the housing (2), and the flip guide groove (342) is arc-shaped.

4. The electric spindle structure of a CNC machining center according to claim 1, characterized in that: A reinforcing hook plate (33) is slidably mounted in the axial direction of the housing (2), and the reinforcing hook plate (33) and the rack (31) are symmetrically arranged with the end cover (3) as the center. When one rack (31) applies a tensioning force to the end cover (3) in a direction close to the housing (2), the reinforcing hook plate (33) symmetrical thereto also applies a tensioning force to the end cover (3) in a direction close to the housing (2).

5. The electric spindle structure of a CNC machining center according to claim 4, characterized in that: A thin tube (331) is installed at one end of the guide plate (34) close to the linear motion portion (312) and arranged parallel to the axial direction of the housing (2); a thick tube (332) is installed at the other end of the thin tube (331), and the thick tube (332) and the thin tube (331) are arranged parallel to each other; a first piston (334) is slidably connected in the thin tube (331); a second piston (336) is slidably connected in the thick tube (332); a space between the second piston (336) and the first piston (334) is filled with liquid; and a space between the second piston (336) and the first piston (334) is filled with liquid. A second push rod (335) is mounted on one end of the piston (336) away from the liquid. The second push rod (335) movably penetrates the thick tube (332) and extends to the outside of the thick tube (332). A reinforcing hook plate (33) is mounted on the other end of the second push rod (335). The reinforcing hook plate (33) is in a hook-shaped structure. A first push rod (333) is mounted on one end of the linear motion portion (312) away from the flipping portion (311). The first push rod (333) movably penetrates the guide plate (34) and extends to the inside of the thin tube (331).

6. The electric spindle structure of a CNC machining center according to claim 5, characterized in that: The diameter of the thin tube (331) is smaller than the diameter of the thick tube (332).

7. The electric spindle structure of a CNC machining center according to claim 5, characterized in that: The reinforcement hook plate (33) and the second push rod (335) are rotatably connected.

8. The electric spindle structure of a CNC machining center according to claim 2, characterized in that: A rotating shaft (322) is installed at the center of the end surface of the gear (32) away from the housing (2); a spiral groove (323) is engraved on the circumferential surface of the rotating shaft (322); a sleeve (325) is slidably sleeved on the outside of the rotating shaft (322) along its axial direction; a guide block (324) slidably connected to the spiral groove (323) is fixedly installed inside the sleeve (325); a U-shaped mounting seat (326) is fixedly sleeved on the circumferential surface of the sleeve (325); the mounting seat (326) is slidably connected to the guide plate (34); a base (11) is provided on the mechanical arm (1), linear modules (13) are installed at both ends of the base (11), a clamping plate (14) is installed on the movable end of the linear module (13), and the clamping plate (14) and the mounting seat (326) are fixedly connected by bolts.

9. The electric spindle structure of a CNC machining center according to claim 8, characterized in that: A positioning block (23) is installed at the lower part of the circumferential surface of the housing (2), and a positioning groove (12) matching the positioning block (23) is provided on the base (11).

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