A self-checking direct-connected spindle structure for a machining center and its usage method

Abstract

The present invention relates to the technical field of machining center spindles, and in particular to a self-checking direct-coupled spindle structure for a machining center and its usage method, which includes a sleeve, a pull rod and a mandrel coaxially arranged in sequence from the axis of the sleeve towards the radial direction of the sleeve; the pull rod slides within the mandrel; one end of the sleeve is provided with a clamping assembly for clamping a tool, and the other end is provided with a power assembly for providing power; an air flow main path is opened in the length direction of the pull rod; one end of the mandrel close to the clamping assembly is provided with a first air flow branch and a second air flow branch, and both are connected to the air flow main path at the end far from the clamping assembly; a first detection branch and a second detection branch are opened along the radial direction of the mandrel towards the outer wall of the sleeve; an air outlet section is opened to communicate with the internal space of the mandrel; a third air flow branch with a radial through hole is arranged on the pull rod; a first detector is arranged on the outer wall of the sleeve and is connected to the first detection branch to detect the gas pressure; a second detector is arranged on the outer wall of the sleeve to detect the gas pressure; the present invention effectively improves the self-checking ability of the spindle and enhances the stability and reliability of the spindle.

Description

Technical Field

[0001] The present invention relates to the technical field of machining center spindles, and particularly to a self-checking direct-coupled spindle structure for a machining center and its usage method. Background Art

[0002] In modern manufacturing, machining centers are widely used in the high-precision machining of complex workpieces, and one of their core components is the spindle device; traditional spindle systems usually achieve tool clamping and tool loosening operations mechanically, so the performance of the spindle directly affects the machining efficiency and accuracy. Especially in the process of automated machining, the stability and reliability of the spindle are particularly important for the machining center to perform machining. Therefore, it is very necessary to detect whether the spindle is in place and whether there are problems with its own structure.

[0003] In the existing technology, the spindle structure mostly uses an independent sensor module or a complex electronic detection system to monitor the spindle state; however, these systems usually have some disadvantages; the traditional spindle detection system requires additional installation of multiple sensors and signal processing modules, resulting in the complication of the overall structure and increasing the difficulty of maintenance and replacement.

[0004] Therefore, a direct-coupled spindle structure for a machining center that can achieve real-time self-checking has become a research hotspot. Summary of the Invention

[0005] The present invention provides a self-checking direct-coupled spindle structure for a machining center and its usage method, which can effectively use air flow to detect whether the spindle is in place and has problems in different states, and effectively improve the stability and reliability of the spindle.

[0006] A self-checking direct-coupled spindle structure for a machining center provided by the present invention includes:

[0007] A sleeve, a drawbar, and a core shaft coaxially arranged in sequence from the axis of the sleeve towards the radial direction of the sleeve; the drawbar slides within the core shaft; one end of the sleeve is provided with a clamping assembly for clamping a tool, and the other end is provided with a power assembly for providing power for the movement of the drawbar and the rotation of the core shaft;

[0008] The drawbar is provided with an air flow main path extending to one end of the power assembly in the length direction;

[0009] One end of the core shaft close to the clamping assembly is provided with a first air flow branch and a second air flow branch; both the far ends of the first air flow branch and the second air flow branch away from the clamping assembly are communicated with the air flow main path; the first air flow branch opens a first detection branch towards the outer wall of the sleeve along the radial direction of the core shaft, and the second air flow branch opens a second detection branch towards the outer wall of the sleeve along the radial direction of the core shaft;

[0010] Both the first air flow branch and the second air flow branch are provided with an air outlet section at the end far from the air flow main path to communicate with the internal space of the core shaft;

[0011] A third air flow branch that penetrates radially is provided on the drawbar;

[0012] A first detector is provided on the outer wall of the sleeve and is connected to the first detection branch for detecting gas pressure;

[0013] A second detector is provided on the outer wall of the sleeve and is connected to the second detection branch for detecting gas pressure;

[0014] In the state where the spindle holds the tool, the main air flow path is only connected to the first air flow branch;

[0015] In the state where the spindle releases the tool, the main air flow path is only connected to the second air flow branch;

[0016] In the state where there is no tool on the spindle, the main air flow path is only connected to the first air flow branch, and the first air flow branch is connected to the second air flow branch through the third air flow branch.

[0017] Furthermore, it further includes a fixed seat and a sliding seat sleeved on the drawbar; the fixed seat is fixed in the relative position with the mandrel, and the sliding seat slides on the drawbar in the direction of approaching or departing from the fixed seat; a first through hole is radially opened on the sliding seat; a second through hole is radially opened on the fixed seat, a first diversion hole for connecting the main air flow path and the first air flow branch is radially opened on the fixed seat, and a second diversion hole for connecting the main air flow path and the second air flow branch is also radially opened on the fixed seat.

[0018] Furthermore, a first air hole is opened at one end of the drawbar in contact with the fixed seat and the sliding seat, and the first air hole is used for the connection between the main air flow path and the first diversion hole and the second diversion hole.

[0019] Furthermore, at one end of the first air hole in contact with the first diversion hole, it extends a certain distance in the length direction of the drawbar.

[0020] Furthermore, two first sealing rings are respectively arranged on both sides of the first through hole on the sliding seat, and when the sliding seat slides, the two first sealing rings are respectively maintained on both sides of the second through hole.

[0021] Furthermore, a plurality of second sealing rings are arranged at the contact part between the fixed seat and the mandrel, and one second sealing ring is arranged on each side of the second through hole; one second sealing ring is arranged in the middle of the first diversion hole and the second diversion hole, one second sealing ring is arranged on the side of the first diversion hole away from the second through hole, and one second sealing ring is arranged on the side of the second diversion hole close to the second through hole.

[0022] Furthermore, it further includes a plurality of third sealing rings arranged on the inner wall of the sleeve in contact with the mandrel; one third sealing ring is arranged on each side of the first detection branch, and one third sealing ring is arranged on each side of the second detection branch.

[0023] Further, the air outlet section includes a first air outlet branch and a second air outlet branch; the first air outlet branch is vertically connected to the first air flow branch and the inner space of the mandrel, and the second air outlet branch is obliquely connected to the second air flow branch and the inner space of the mandrel.

[0024] Further, a plurality of fourth sealing rings are provided on the outer wall of the pull rod; chamfers are provided on the inner walls where the fixed seat and the sliding seat are in contact.

[0025] The present invention also provides a method for using a direct-connected spindle of a self-checking machining center, including the following steps:

[0026] Set parameters: Set the air pressure thresholds P1 and P2; introduce air flow into the main air flow path from one end of the sleeve where the power assembly is provided; the first detector and the second detector detect the air flow pressure in real time and display the pressure readings;

[0027] Wherein, 0 < P1 < P2;

[0028] Knife-free state: Read the pressure readings of the first detector and the second detector. If the pressure readings are both between 0 and P1, the spindle state is normal;

[0029] Tool-pulling state: Read the pressure readings of the first detector and the second detector. If the pressure reading of the first detector is between P1 and P2 and the pressure reading of the second detector is 0, the spindle state is normal;

[0030] Tool-releasing state: Read the pressure readings of the first detector and the second detector. If the pressure reading of the first detector is 0 and the pressure reading of the second detector is between P1 and P2, the spindle state is normal.

[0031] The beneficial effects of the present invention are as follows: Through the designed structure of a self-checking machining center direct-connected spindle and its using method, dynamic switching of the air flow path is achieved in the tool-pulling, tool-releasing, and knife-free states of the spindle. Combining the real-time detection of the air flow pressure by the first detector and the second detector, rapid self-checking of the spindle state is realized, improving the stability and reliability of the spindle operation; the sliding fit between the pull rod and the mandrel, as well as the structures of the fixed seat and the sliding seat, enable no additional detector to be installed inside the spindle, reducing the structural complexity and maintenance difficulty; the multi-level sealing design provides reliable sealing at multiple key structures of the spindle, avoiding gas leakage. Description of the Drawings

[0032] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings described below are only some embodiments recorded in the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0033] Figure 1 This is a schematic cross-sectional view of the direct-connected spindle structure of the self-checking machining center in the present invention under the spindle tool-pulling state;

[0034] Figure 2 This is an enlarged schematic cross-sectional view of the air flow path of the direct-connected spindle structure of the self-checking machining center in the present invention under the spindle tool-pulling state;

[0035] Figure 3 This is an enlarged schematic cross-sectional view of the air flow path of the direct-connected spindle structure of the self-checking machining center in the present invention under the spindle tool-loosening state;

[0036] Figure 4 This is an enlarged schematic cross-sectional view of the air flow path of the direct-connected spindle structure of the self-checking machining center in the present invention under the spindle no-tool state;

[0037] Reference numerals: 1. Sleeve; 11. Clamping assembly; 13. First detector; 14. Second detector; 15. Third sealing ring; 2. Drawbar; 21. Main air flow path; 22. Third air flow branch; 23. First air hole; 24. Fourth sealing ring; 3. Core shaft; 31. First air flow branch; 311. First detection branch; 32. Second air flow branch; 321. Second detection branch; 33. Air outlet section; 331. First air outlet branch; 332. Second air outlet branch; 4. Fixed seat; 41. Second through hole; 42. First diversion hole; 43. Second diversion hole; 44. Second sealing ring; 5. Sliding seat; 51. First through hole; 52. First sealing ring; 6. Chamfer. Detailed implementation manners

[0038] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying 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.

[0039] In the description of the present invention, it should be noted that the orientation or positional relationship indicated by "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. is based on the orientation or positional relationship shown in the accompanying drawings. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation to the present invention.

[0040] In the description of the present invention, it should be noted that unless otherwise clearly specified and defined, the terms "installation", "connection", and "coupling" 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 a direct connection or an indirect connection through an intermediate medium, and it can be the communication inside two components. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0041] A self-checking direct-coupled spindle structure for a machining center, as Figures 1 - 4 shown, includes:

[0042] A sleeve 1, a drawbar 2, and a mandrel 3 that are coaxially arranged in sequence from the axis of the sleeve 1 towards the radial direction of the sleeve 1; the drawbar 2 slides within the mandrel 3; one end of the sleeve 1 is provided with a clamping assembly 11 that contacts one end of the drawbar 2 and is used for clamping a tool, and the other end is provided with a power assembly that contacts the other end of the drawbar 2 and is used to provide the power for the movement of the drawbar 2 and the rotation of the mandrel 3;

[0043] An air flow main path 21 extending to one end of the power assembly is provided in the length direction of the drawbar 2, facilitating the injection of air flow into the air flow main path 21 from this end and avoiding collision with the tool;

[0044] One end of the mandrel 3 close to the clamping assembly 11 is provided with a first air flow branch 31 and a second air flow branch 32; both ends of the first air flow branch 31 and the second air flow branch 32 away from the clamping assembly 11 communicate with the air flow main path 21; the first air flow branch 31 opens a first detection branch 311 towards the outer wall of the sleeve 1 along the radial direction of the mandrel 3, and the second air flow branch 32 opens a second detection branch 321 towards the outer wall of the sleeve 1 along the radial direction of the mandrel 3;

[0045] Both the first air flow branch 31 and the second air flow branch 32 are provided with an air outlet section 33 at the end away from the air flow main path 21 to communicate with the internal space of the mandrel 3;

[0046] A third air flow branch 22 that penetrates radially is provided on the drawbar 2, which can communicate the first air flow branch 31 and the second air flow branch 32;

[0047] A first detector 13 is provided on the outer wall of the sleeve 1 and is connected to the first detection branch 311 for detecting gas pressure;

[0048] A second detector 14 is provided on the outer wall of the sleeve 1 and is connected to the second detection branch 321 for detecting gas pressure;

[0049] The two detectors detect the air flow pressure in real time, providing a reliable numerical basis for judging the spindle state;

[0050] When the spindle is normal and the drawbar 2 and the mandrel 3 do not show damage, bending, etc.:

[0051] In the state where the spindle holds the broach, as Figure 2 shown, the main air flow path 21 is only connected to the first air flow branch 31; after the broach is pulled out, the tool is clamped by the clamping assembly 11. Since the inner wall of the mandrel 3 has a certain inclination angle to fit with the tool, the air outlet section 33 connected to the first air flow branch 31 is also blocked by the tool and cannot discharge air; therefore, at this time, the first detector 13 will detect an increase in air pressure, while the second detector 14 is not connected to the air flow and cannot detect air pressure, and the reading is 0;

[0052] In the state where the spindle releases the tool, as Figure 3 shown, the main air flow path 21 is only connected to the second air flow branch 32, and no air flow passes through the first air flow branch 31. Therefore, the first detector 13 cannot detect air pressure, and the air pressure reading is 0; while at the air outlet section 33 of the second air flow branch 32 on the inner wall of the mandrel 3, due to the clamping assembly 11 being pushed by the pull rod 2 to perform the tool release action, it is fitted by an inclined surface of the clamping assembly 11, so that the second detector 14 detects an increase in air pressure, and the reading reaches a preset threshold range;

[0053] In the state where there is no tool on the spindle, as Figure 4 shown, the main air flow path 21 is only connected to the first air flow branch 31, and the first air flow branch 31 is connected to the second air flow branch 32 through the third air flow branch 22; since the air outlet section 33 is not affected by the tool and will not be blocked, it can discharge air normally; the air flow in the main air flow path 21 reaches the first detector 13 along the routes of the first air flow branch 31 and the first detection branch 311, and also reaches the second detector 14 along the routes of the first air flow branch 31, the third air flow branch 22, the second air flow branch 32, and the second detection branch 321; because the air outlet section 33 also diverts a part of the air flow, the readings of the air pressure detected by the two detectors will not be very large;

[0054] If the air pressure readings that do not conform to the above situations appear, then the spindle has problems such as damage, misalignment, and bending, resulting in the failure of the air paths to be smoothly connected. At this time, maintenance work needs to be carried out.

[0055] Compared with the traditional detection method relying on mechanical devices, this spindle realizes the multi-state detection function through the design of the main air flow path 21 and the branches by dynamic switching, without the need to add a complex electronic detection system or independent electrical components, thus simplifying the system structure, reducing the wear of the spindle during high-speed operation, and at the same time reducing the risk of misoperation.

[0056] Preferably, it further includes a fixed seat 4 and a sliding seat 5 sleeved on the pull rod 2; the relative position of the fixed seat 4 and the mandrel 3 is fixed, and the sliding seat 5 slides on the pull rod 2 in a direction close to or away from the fixed seat 4; a first through hole 51 is radially opened in the sliding seat 5; a second through hole 41 is radially opened in the fixed seat 4, and a first diversion hole 42 for connecting the main air flow path 21 and the first air flow branch 31 is radially opened in the fixed seat 4, and the fixed seat 4 further opens a second diversion hole 43 for connecting the main air flow path 21 and the second air flow branch 32;

[0057] The fixed seat 4 serves as a diversion node of the main air flow path 21. Through the first diversion hole 42 and the second diversion hole 43, the air flow is distributed to different air flow branches, and at the same time, the stability of the structure is ensured through a fixed design; the sliding seat 5 realizes a complex air flow path switching function through a simple sliding action, meets the different requirements of the three states of the spindle for pulling the tool, loosening the tool, and having no tool, forms a completely closed air flow path, avoids air leakage, improves the detection accuracy and operation reliability; moreover, the design structures of the fixed seat 4 and the sliding seat 5 are clear, the number of components is small, the manufacturing process is simplified, the cooperation avoids the high-frequency wear of complex mechanical components, and it is convenient to replace worn components or clean the system.

[0058] One end of the pull rod 2 in contact with the fixed seat 4 and the sliding seat 5 is provided with a first air hole 23, and the first air hole 23 is used for connecting the main air flow path 21 with the first diversion hole 42 and the second diversion hole 43; by opening an air hole on the pull rod 2, the design of additional independent air flow channels is reduced, the air flow management function is concentrated inside the pull rod 2, the complexity of the air path layout is simplified, and at the same time, the overall stability of the air flow path is improved; the first air hole 23 and the third air flow branch 22 undertake different connection tasks in the tool-pulling, tool-loosening, and no-tool states of the spindle respectively, and are the core of the spindle self-check work.

[0059] Preferably, one end of the first air hole 23 in contact with the first diversion hole 42 extends a certain distance along the length direction of the pull rod 2, so as to form a groove on the surface of the pull rod 2; in the state where the spindle has no tool, the pull rod 2 is in the state closest to the power component. At this time, in order to introduce the air flow of the main air flow path 21 into the first main air flow path 21 without additionally opening an air flow path, through the design of extending the first air hole 23 by a certain distance, the above effect can be achieved more conveniently and quickly.

[0060] In some embodiments of the present invention, on the sliding seat 5, a first sealing ring 52 is provided on each side of the first through hole 51 to seal the first through hole 51 from both sides. When the sliding seat 5 slides, the two first sealing rings 52 are respectively maintained on both sides of the second through hole 41; the first through hole 51 and the second through hole 41 communicate with the third air flow branch 22. Keeping the first sealing ring 52 on both sides of the through hole avoids the possibility that the first sealing ring 52 crosses the second through hole 41 when the sliding seat 5 slides and causes the first sealing ring 52 to pop into the second through hole 41.

[0061] A plurality of second sealing rings 44 are provided at the contact between the fixed seat 4 and the core shaft 3; one second sealing ring 44 is provided on each side of the second through hole 41; one second sealing ring 44 is provided in the middle of the first diversion hole 42 and the second diversion hole 43, one second sealing ring 44 is provided on the side of the first diversion hole 42 away from the second through hole 41, and one second sealing ring 44 is provided on the side of the second diversion hole 43 close to the second through hole 41; providing static sealing between the fixed seat 4 and the core shaft 3 to prevent air leakage in the main air flow path 21, the first diversion hole 42 and the second diversion hole 43; ensuring that the air flow always flows along the predetermined path during the diversion process without being interfered by the external environment, and improving the overall stability of the spindle structure.

[0062] It also includes a plurality of third sealing rings 15 provided on the inner wall where the sleeve 1 contacts the core shaft 3; one third sealing ring 15 is provided on each side of the first detection branch 311, and one third sealing ring 15 is provided on each side of the second detection branch 321; because the core shaft 3 rotates inside the sleeve 1, the third sealing ring 15 does not use an ordinary sealing ring, but uses a shaft seal to achieve line sealing, and the opening faces the detection branch to seal the two detection branches, preventing air leakage and improving the accuracy of the detector for detecting air pressure.

[0063] In some embodiments of the present invention, the air outlet section 33 includes a first air outlet branch 331 and a second air outlet branch 332; the first air outlet branch 331 vertically communicates with the first air flow branch 31 and the internal space of the core shaft 3, so that the path of the first air outlet branch 331 at the end of the core shaft 3 farthest from the power component is the shortest, reducing the impact on the stability of the core shaft 3, and can further blow away the foreign objects blown away by the second air outlet branch 332; the second air outlet branch 332 obliquely communicates with the second air flow branch 32 and the internal space of the core shaft 3. In the state where the spindle releases the tool, it better fits the clamping component 11. In the state where the spindle has no tool, it can clean the foreign objects on the surface of the clamping component 11 caused by the spindle operation, and can also assist the movement of the clamping component 11, so that the pull rod 2 moves to the state closest to the power component.

[0064] When the air outlet section 33 jets out air, it can form an air curtain at the opening and gap of the main shaft, effectively isolating the interference of the external environment such as impurities like dust and cutting fluid, and at the same time protecting the normal operation of the internal air flow detection structure.

[0065] A plurality of fourth sealing rings 24 are arranged on the outer wall of the pull rod 2. The fourth sealing rings 24 are arranged on both sides of the path where there is air flow. The fourth sealing rings 24 are also arranged at the contact part of the outer wall when the pull rod 2 slides in the mandrel 3, ensuring the airtightness of the entire main shaft structure; Chamfers 6 are provided on the inner walls where the fixed seat 4 and the sliding seat 5 are in contact. Since the fixed seat 4 and the sliding seat 5 do not always contact and press tightly to generate a gap when the pull rod 2 slides, one of the fourth sealing rings 24 will pass through this gap. The chamfer 6 can help this sealing ring move better along with the pull rod 2 without staying in the gap.

[0066] The present invention also provides a method for using a self-checking direct-connected main shaft of a machining center, including the following steps:

[0067] Set parameters: Set the air pressure thresholds P1 and P2; Introduce air flow into the main air path 21 from one end of the sleeve 1 where the power component is set to start the self-checking work; The first detector 13 and the second detector 14 detect the air flow pressure in real time and display the pressure readings.

[0068] Among them, 0 < P1 < P2;

[0069] No-tool state: Read the pressure readings of the first detector 13 and the second detector 14. If both pressure readings are between 0 and P1, the main shaft is in a normal state;

[0070] Tool-pulling state: Read the pressure readings of the first detector 13 and the second detector 14. If the pressure reading of the first detector 13 is between P1 and P2 and the pressure reading of the second detector 14 is 0, the main shaft is in a normal state;

[0071] Tool-loosening state: Read the pressure readings of the first detector 13 and the second detector 14. If the pressure reading of the first detector 13 is 0 and the pressure reading of the second detector 14 is between P1 and P2, the main shaft is in a normal state;

[0072] The main shaft can be arbitrarily switched from the tool-loosening state to the no-tool state or the tool-pulling state without a fixed order. After switching to another state, the main shaft can perform self-checking work through the first detector 13 and the second detector 14.

[0073] The design of the above usage method does not require external intervention. By real-time monitoring the pressure values of the first detector 13 and the second detector 14, it automatically detects the real-time pressure changes, quickly judges whether the working state of the main shaft is normal, avoids the errors caused by manual operation or visual judgment, improves the detection accuracy and reliability, and reduces the downtime. It can timely detect problems in abnormal situations such as pressure exceeding the range or pressure insufficiency, and prevent the damage caused by the main shaft running due to faults.

[0074] The above has shown and described the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited by the above embodiments. What is described in the above embodiments and the specification only illustrates the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention will have various changes and improvements, and these changes and improvements all fall within the scope of the present invention claimed. The scope of the present invention claimed is defined by the appended claims and their equivalents.

Claims

1. A self-checking direct-connected spindle structure for a machining center, characterized in that, Comprising: A sleeve (1), a pull rod (2) and a mandrel (3) which are coaxially arranged in sequence from the axis of the sleeve (1) towards the radial direction of the sleeve (1); the pull rod (2) slides within the mandrel (3); one end of the sleeve (1) is provided with a clamping assembly (11) for clamping a tool, and the other end is provided with a power assembly for providing power for the movement of the pull rod (2) and the rotation of the mandrel (3); The pull rod (2) is provided with a main air flow path (21) extending to one end of the power assembly in the length direction; One end of the mandrel (3) close to the clamping assembly (11) is provided with a first air flow branch (31) and a second air flow branch (32); the ends of the first air flow branch (31) and the second air flow branch (32) far from the clamping assembly (11) are both communicated with the main air flow path (21); the first air flow branch (31) opens a first detection branch (311) towards the outer wall of the sleeve (1) along the radial direction of the mandrel (3), and the second air flow branch (32) opens a second detection branch (321) towards the outer wall of the sleeve (1) along the radial direction of the mandrel (3); Both the first air flow branch (31) and the second air flow branch (32) are provided with an air outlet section (33) at the end far from the main air flow path (21) to communicate with the internal space of the mandrel (3); The pull rod (2) is provided with a third air flow branch (22) radially penetrating through; A first detector (13) is arranged on the outer wall of the sleeve (1) and is connected to the first detection branch (311) for detecting gas pressure; A second detector (14) is arranged on the outer wall of the sleeve (1) and is connected to the second detection branch (321) for detecting gas pressure; In the state of the spindle clamping the tool, the main air flow path (21) is only communicated with the first air flow branch (31); In the state of the spindle loosening the tool, the main air flow path (21) is only communicated with the second air flow branch (32); In the state of the spindle having no tool, the main air flow path (21) is only communicated with the first air flow branch (31), and the first air flow branch (31) is communicated with the second air flow branch (32) through the third air flow branch (22).

2. The self-checking type direct-connected spindle structure of a machining center according to claim 1, wherein It further includes a fixed seat (4) and a sliding seat (5) sleeved on the pull rod (2); the relative position of the fixed seat (4) and the mandrel (3) is fixed, and the sliding seat (5) slides on the pull rod (2) in the direction of approaching or departing from the fixed seat (4); the sliding seat (5) is radially provided with a first through hole (51); the fixed seat (4) is radially provided with a second through hole (41), the fixed seat (4) is radially provided with a first diversion hole (42) for communicating the main air flow path (21) and the first air flow branch (31), and the fixed seat (4) is radially further provided with a second diversion hole (43) for communicating the main air flow path (21) and the second air flow branch (32).

3. The self-checking direct-connected spindle structure of the machining center according to claim 2, characterized in that, One end of the pull rod (2) in contact with the fixed seat (4) and the sliding seat (5) is provided with a first air flow hole (23), and the first air flow hole (23) is used for the communication between the main air flow path (21) and the first diversion hole (42) and the second diversion hole (43).

4. The self-checking type direct connection spindle structure of a machining center according to claim 3, wherein One end of the first air flow hole (23) in contact with the first diversion hole (42) extends forward a certain distance in the length direction of the pull rod (2).

5. The self-checking type direct connection spindle structure of a machining center according to claim 3, characterized in that, On both sides of the first through hole (51) on the sliding seat (5), a first sealing ring (52) is provided respectively, and when the sliding seat (5) slides, the two first sealing rings (52) are respectively kept on both sides of the second through hole (41).

6. The self-checking type direct connection spindle structure of a machining center according to claim 3, characterized in that, A plurality of second sealing rings (44) are provided at the contact position between the fixed seat (4) and the core shaft (3). One second sealing ring (44) is provided on each side of the second through hole (41); one second sealing ring (44) is provided in the middle of the first diversion hole (42) and the second diversion hole (43), one second sealing ring (44) is provided on the side of the first diversion hole (42) away from the second through hole (41), and one second sealing ring (44) is provided on the side of the second diversion hole (43) close to the second through hole (41).

7. The self-checking type direct connection spindle structure of a machining center according to claim 1, characterized in that, It further includes a plurality of third sealing rings (15) provided on the inner wall of the sleeve (1) in contact with the core shaft (3); one third sealing ring (15) is provided on each side of the first detection branch (311), and one third sealing ring (15) is provided on each side of the second detection branch (321).

8. The self-checking type direct connection spindle structure of a machining center according to claim 1, wherein The air outlet section (33) includes a first air outlet branch (331) and a second air outlet branch (332); the first air outlet branch (331) vertically communicates the first air flow branch (31) and the internal space of the core shaft (3), and the second air outlet branch (332) obliquely communicates the second air flow branch (32) and the internal space of the core shaft (3).

9. The self-checking type machining center direct-connected spindle structure according to claim 2, characterized in that, A plurality of fourth sealing rings (24) are provided on the outer wall of the pull rod (2); chamfers (6) are provided on the inner walls of the contact between the fixed seat (4) and the sliding seat (5).

10. A method for using a direct-connected spindle of a self-checking machining center, characterized in that, For the self-checking type direct-connected spindle structure of a machining center according to any one of claims 1 to 9, it includes the following steps: Setting parameters: setting the air pressure thresholds P1 and P2; introducing air flow into the main air flow path (21) from the end of the sleeve (1) provided with the power assembly; the first detector (13) and the second detector (14) detect the air flow pressure in real time and display the pressure indication; wherein, 0 < P1 < P2; No-tool state: reading the pressure indications of the first detector (13) and the second detector (14), if the pressure indications are both between 0 and P1, the spindle state is normal; Tool-pulling state: reading the pressure indications of the first detector (13) and the second detector (14), if the pressure indication of the first detector (13) is between P1 and P2 and the pressure indication of the second detector (14) is 0, the spindle state is normal; Loose tool state: Read the pressure readings of the first detector (13) and the second detector (14). If the pressure reading of the first detector (13) is 0 and the pressure reading of the second detector (14) is between P1 and P2, the spindle state is normal.

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