Built-in electric spindle structure of machine tool

Abstract

The invention relates to the technical field of machine tool motorized spindles, in particular to a machine tool built-in motorized spindle structure which comprises a box body, a permanent magnet motor and a spindle, the permanent magnet motor and the spindle are fixed in the box body, a bearing chamber is arranged at the end of the box body, and an angular contact ball bearing is arranged in the bearing chamber; the main shaft is also provided with a sealing mechanism for sealing the bearing chamber; the sealing mechanism comprises a bearing retainer ring, a sealing ring and a circulation sealing cavity which are arranged on the main shaft in a sleeving manner; the circulation sealing cavity comprises an S-shaped cavity, a wedge-shaped cavity, an L-shaped cavity and a special-shaped cavity which are communicated in sequence, the L-shaped cavity comprises a long cavity and a short cavity, the wedge-shaped cavity is communicated with the middle lower section of the long cavity, the short cavity is located above the long cavity, the end, away from the bearing chamber, of the short cavity is communicated with the special-shaped cavity, and double grooves are formed in the bottom of the special-shaped cavity. The device is suitable for a high-flying-dust machining environment, the main shaft rotates and heats to form temperature difference to drive hot air flow to overflow, a self-driving air curtain is formed for heat removal and dust prevention, and an external air source is not needed; cost is effectively saved, and operation stability and service life of equipment are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of electric spindles for machine tools, in particular to a built-in electric spindle structure for machine tools. Background Art

[0002] In modern machining, as manufacturing demands ever-increasing precision, efficiency, and automation, improving the performance of machine tools, the core processing equipment, is crucial. As the core functional component of CNC machine tools, the electric spindle plays a decisive role in the overall quality, performance, efficiency, and operational stability of the machine tools.

[0003] The motor installation position of the electric spindle is divided into external and internal types. The internal electric spindle combines the motor and the high-precision spindle. The motor rotor is installed on the axis of the spindle, and the motor stator is fixed on the spindle box. The spindle is directly driven by the motor to rotate. Its structural design simplifies the transmission system of the machine tool spindle to the maximum extent. Compared with the traditional mechanical spindle, the electric spindle eliminates the material input such as the pulley set, belt, spindle motor, and motor mounting plate. It shortens the length of the transmission chain to the maximum extent, improves the transmission efficiency, and reduces the transmission noise and vibration, avoids energy loss, and thus improves the dynamic performance and processing efficiency.

[0004] There are various existing designs for built-in electric spindles. For example, in the prior art "A Built-in Permanent Magnet Synchronous Electric Spindle" (Publication No.: CN109434140B), the rotary joint, pull rod, and tool holder are sequentially connected from top to bottom, allowing the rotary joint to be connected to compressed air and coolant. When connected to compressed air, it can provide an airflow to blow away dust from the tool on the tool holder. When connected to coolant, the coolant can be used to directly cool the tool. Another example is the prior art "A CNC Machine Tool with an Air Curtain Protective Device" (Publication No.: CN116352494A). By injecting high-pressure gas into the air cavity of the air curtain protective device, the high-pressure gas in the air cavity is ejected downward through an annular gap, thereby forming an air curtain barrier around the tool, which can prevent dust and debris from flying out during internal processing, thereby preventing dust and debris from contaminating the working environment. However, the prior art still has the following technical problems: The above existing technologies all form airflow at the tool by inflating from the outside, and the technical solution of "a built-in permanent magnet synchronous electric spindle" is to use airflow to blow away the dust and iron chips on the tool, and at the same time achieve the effect of cooling the tool; and the technical solution of "a CNC machine tool with an air curtain protection device" is to form an air curtain around the tool to prevent dust and debris from flying out of the air curtain during workpiece processing, so as to avoid pollution of the working environment. However, due to the high requirements of the electric spindle for the environment, on the one hand, the high temperature generated at high speed inside the motor needs to be discharged to reduce the heat generation of the motor. Therefore, the spindle mounting cavity cannot be completely sealed, and a gap needs to be left for heat dissipation. On the other hand, the bearings at the end of the spindle need to be in a dust-free state, because even a small amount of dust or iron filings entering the spindle will cause irreversible damage to the spindle bearings, or water vapor entering the bearings will easily cause the bearings to rust and become scrapped. Therefore, the sealing structure requirements for the bearings are quite strict. The airflow protection of the above two existing technologies are both set around the tool, but cannot prevent dust from entering the gap of the bearing mounting chamber of the electric spindle, especially in a high-dust working environment, such as when processing graphite and carbon composite materials. A large amount of fine powder and dust will be generated during the processing. After the dust enters the interior of the electric spindle, it will adhere to the surfaces of precision moving parts such as bearings, rotors, and stators. When the electric spindle rotates at high speed, the dust will intensify the friction between the components, resulting in scratches on the bearing raceway, wear on the rotor journal, and even cause bearing jamming, directly affecting the rotation accuracy and stability of the spindle, and reducing the service life of the spindle. Summary of the Invention

[0005] The present invention provides a built-in electric spindle structure for machine tools, which can solve the problem that the spindle structure in the prior art cannot effectively prevent dust and water vapor from entering the installation chamber of the spindle and bearings when applied to a high-dust environment, thereby causing spindle wear and bearing rust and damage, resulting in reduced spindle rotation accuracy and stability, and shortening the spindle service life.

[0006] The present application provides the following technical solution: a machine tool built-in electric spindle structure, comprising a housing, a permanent magnet motor fixed inside the housing, and a spindle rotatably connected to the housing, wherein a bearing chamber is provided at an end of the housing, and an angular contact ball bearing is provided in the bearing chamber; The main shaft is also provided with a sealing mechanism for sealing the bearing chamber, the sealing mechanism comprising a bearing retaining ring sleeved on the main shaft, a sealing ring sleeved outside the bearing retaining ring and fixed to the end face of the housing, and a circulating sealing cavity opened between the bearing retaining ring and the sealing ring; The circulating sealing cavity includes an S-shaped cavity, a wedge-shaped cavity, an L-shaped cavity and a special-shaped cavity which are connected in sequence from the direction away from the bearing chamber. The wedge-shaped surface of the wedge-shaped cavity is inclined toward the direction away from the bearing chamber. The L-shaped cavity includes a long cavity and a short cavity. The wedge-shaped cavity is connected in the middle and lower section of the long cavity. The short cavity is located above the long cavity. One end of the short cavity away from the bearing chamber is connected to the special-shaped cavity. A double groove is provided at the bottom of the special-shaped cavity. One end of the special-shaped cavity away from the short cavity is connected to the outside world.

[0007] Beneficial effects: 1. Multi-stage sealing is used to ensure sealing performance and improve the working accuracy and service life of the main shaft and bearings. The circulating seal chamber between the bearing retaining ring and the sealing ring utilizes a multi-stage structure consisting of S-shaped, wedge-shaped, L-shaped, and irregularly shaped cavities connected in sequence, forming a progressive dust barrier. The spindle instantly heats up when it rotates, causing the air inside the motor to expand. Due to the temperature difference, the hot air overflows from the bearing chamber and is discharged outward through the circulating seal chamber. The high-speed rotation of the spindle ensures that the hot air remains in a circular shape, thus preventing external impurities such as dust and moisture from entering the spindle and bearing mounting chambers. This sealing method relies entirely on the heat generated by the spindle's rotation to raise the temperature inside the spindle and bearing chambers, creating a temperature difference with the outside world. This allows the hot air to spontaneously overflow and be discharged through the circulating seal chamber, forming an air curtain. This neither hinders the dissipation of heat from the bearing chamber nor prevents external dust from entering the bearing chamber and spindle, thus maintaining a clean working environment for the spindle and bearing chambers. This effectively improves the operating stability, precision, and service life of the spindle bearings. Compared to existing technologies, this method eliminates the need for external compressed air, reduces internal structure, and saves manufacturing costs.

[0008] 2. The special-shaped cavity adopts a double-groove structure to enhance the dust blocking effect. When external impurities try to invade the bearing chamber with the airflow, the special-shaped cavity first acts as a barrier. The special-shaped cavity has double grooves at the bottom, which can block dust and water vapor and settle them in the grooves. The double grooves form a double protection, improving the blocking effect.

[0009] 3. Increase the volume of the annular seal chamber and avoid hot air retention. The short chamber of the special-shaped chamber and the L-shaped chamber both have a certain volume. When the high-speed rotation of the main shaft causes the gas temperature inside the bearing chamber to be too high, the hot air flow may not be able to be quickly discharged from the annular seal chamber. The special-shaped chamber and the short chamber increase the overall volume of the annular seal chamber, allowing the hot air flow to be temporarily stored in the special-shaped chamber and the short chamber, thereby preventing the hot air flow with excessive temperature from being retained in the bearing chamber due to slow discharge speed, preventing the bearing from being damaged prematurely due to being in an overly high working environment, and effectively improving the service life of the bearing.

[0010] 4. Optimize the shape of the annular sealing cavity to improve the reliability of the sealing mechanism. If the special-shaped cavity fails to block dust and impurities and causes impurities to enter the short cavity, the wedge-shaped cavity is connected to the middle and lower section of the long cavity of the L-shaped cavity. At this time, there is a space below the connection between the long cavity and the wedge-shaped cavity, allowing impurities to fall into this space without being blocked at the connection between the long cavity and the wedge-shaped cavity. This ensures the smooth flow of the entire annular sealing cavity, maintains the stable discharge of hot air flow, and improves the reliability of the sealing mechanism.

[0011] 5. Optimize the structural layout of the wedge-shaped cavity and increase the strength of the airflow seal. The wedge-shaped surface of the wedge-shaped cavity is tilted away from the bearing chamber, so that when the hot air flows through the wedge-shaped cavity, it will flow from the wide opening to the narrow opening. According to the Bernoulli principle, the airflow velocity in the wedge-shaped cavity channel is increased, which is more conducive to the discharge of hot air, thereby increasing the strength of the airflow seal. At the same time, the wedge-shaped surface of the wedge-shaped cavity also has the effect of accommodating dust and impurities, which can prevent the circulation seal cavity from being blocked and improve reliability.

[0012] 6. The S-shaped cavity is closest to the bearing chamber. As the final protective sealing cavity, its tortuous path can consume the kinetic energy of dust and water vapor, thereby improving the success rate of intercepting dust and water vapor. Moreover, after being blocked by the previous cavities, the dust and impurities that finally enter the S-shaped cavity are already very small. The tortuous path of the S-shaped cavity also prolongs the time for water vapor to enter the bearing chamber, prompting water vapor to condense into droplets on the inner wall of the S-shaped cavity. These droplets can absorb dust, further improving the ability to capture dust and water vapor and improving sealing performance. Furthermore, the double grooves are wedge-shaped grooves, and the wedge-shaped surfaces of the double grooves are inclined in a direction away from the bearing chamber.

[0013] Beneficial effect: Since the end of the special-shaped cavity away from the short cavity is directly connected to the outside world, the inclination angle of the wedge surface is set in the direction away from the bearing chamber, which can form an "outward diversion" trend for the dust and impurities entering the special-shaped cavity from the outside world. When the impurities settle into the double grooves with the airflow or their own gravity, the hot air flow discharged from the bearing chamber can guide the dust and impurities to the outside world along the wedge surface, avoiding the accumulation and blockage of dust and impurities in the groove, and ensuring the patency of the circulating sealing cavity.

[0014] Furthermore, a retaining ring is provided at one end of the bearing chamber away from the bearing retaining ring, and a locking ring is provided at one end of the retaining ring away from the bearing. The locking ring is threadedly connected to the main shaft rod, and a gap is provided between the outer cylindrical surface of the retaining ring and the inner wall surface of the bearing chamber.

[0015] Beneficial effect: The locking ring is connected to the main shaft rod through a thread. After tightening, the retaining ring can be pushed toward the bearing end face, thereby applying axial preload force to the bearing. By adjusting the tightening degree of the locking ring, the preload amount of the bearing can be accurately controlled, the rotation accuracy and rigidity of the main shaft are optimized, and the axial movement of the bearing is reduced.

[0016] Furthermore, a motor installation chamber is opened in the box body on the side of the locking ring away from the retaining ring, and the permanent magnet motor is located in the installation chamber. The motor installation chamber is connected to the bearing chamber through the gap formed by the outer cylindrical surface of the retaining ring and the inner wall surface of the bearing chamber.

[0017] Beneficial effect: By connecting the motor installation room with the bearing room, the hot air generated by the high-speed rotation of the main shaft, the hot air generated by the permanent magnet motor and the hot air in the bearing room can be discharged from the circulating seal chamber. The main shaft rotates continuously, so that the hot air always maintains a circular overflow state, thereby reducing the temperature of the main shaft and the permanent magnet motor, avoiding heat, and improving operation stability.

[0018] Furthermore, the main shaft is a hollow shaft, and a positioning portion is integrally formed at the end of the main shaft. The diameter of the positioning portion is larger than the diameter of the rod of the main shaft, and a chuck is fixed to the end of the positioning portion away from the bearing chamber.

[0019] Beneficial effect: The hollow setting of the spindle facilitates the installation of the pull rod, which controls the movement of the chuck's claws through the pull rod. It also facilitates the discharge of heat inside the spindle from the center of the spindle along the axial direction to the outside, thereby improving the heat dissipation effect.

[0020] Furthermore, a first sealing ring is provided at the contact point between the sealing ring and the end surface of the box body, and a second sealing ring is provided at the contact point between the bearing retaining ring and the rod portion of the main shaft.

[0021] Beneficial effect: Through the first sealing ring and the second sealing ring, the hot air flow discharge end of the bearing chamber can only be connected to the S-shaped cavity of the circulating sealing cavity, so as to realize the directional guidance of the hot air flow, avoid the disordered leakage of the hot air flow causing the heat dissipation path to be chaotic, and prevent the hot air flow from being diverted when discharged, thereby ensuring the air flow strength of the circulating sealing cavity and improving the sealing effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is the structural front view of the present invention.

[0023] Figure 2 for Figure 1 Magnified view of center A. DETAILED DESCRIPTION

[0024] The following is further described in detail through specific implementation methods: The marks in the drawings of the specification include: hydraulic rotary tensioning cylinder 1, brake disc 2, connecting part 201, hydraulic brake 3, bracket 4, rotor 5, stator 6, cooling jacket 7, housing 8, bearing 9, main shaft 10, positioning part 101, gap 11, chuck 12, pull rod 13, double groove 14, connecting gap 15, special-shaped cavity 16, short cavity 17, long cavity 171, wedge-shaped cavity 18, S-shaped cavity 19, sealing ring 20, second sealing ring 21, bearing retaining ring 22, first sealing ring 23, locking ring 24, retaining ring 25, encoder 26, bearing chamber 27, cylindrical roller bearing 28, bearing seat 29, end cover 30, locking nut 31.

[0025] Example 1 like Figure 1 and Figure 2 As shown, a machine tool built-in electric spindle structure includes a box body 8, a permanent magnet motor fixed inside the box body 8 and a spindle 10 rotatably connected to the box body 8, as shown in FIG. Figure 1 As shown, a motor mounting cavity is provided within the housing 8, within which the permanent magnet motor is located. A cooling jacket 7 is provided on the exterior of the permanent magnet motor's stator 6 for heat dissipation. The permanent magnet motor's rotor 5 is interference-fitted onto the shaft of the main shaft 10. A bearing seat 29 is provided at the left end of the motor mounting cavity, within which a cylindrical roller bearing 28 is mounted. An end cap 30 is provided at the left end of the bearing seat 29, which is screwed to the end of the housing 8. A bearing chamber 27 is provided at the right end of the housing 8, within which multiple angular contact ball bearings 9 are mounted. The main shaft 10 is rotatably connected between the cylindrical roller bearing 28 and the angular contact ball bearings 9.

[0026] A retaining ring 25 is provided at the left end of the bearing chamber 27. A locking ring 24 is provided at the end of the retaining ring 25 away from the bearing chamber 27. The locking ring 24 is threadedly connected to the rod of the main shaft 10. After the locking ring 24 is tightened, the retaining ring 25 and the angular contact ball bearing 9 are locked in the bearing chamber 27. A gap 11 is provided between the outer surface of the retaining ring 25 and the inner wall of the bearing chamber 27, so that the motor installation cavity can be connected to the bearing chamber 27. A sealing mechanism is provided at the end of the main shaft 10 to seal the bearing chamber 27, such as Figure 2As shown, the sealing mechanism includes a bearing retaining ring 22 mounted on the main shaft 10, a sealing ring 20 mounted on the outside of the bearing retaining ring 22 and fixed to the end face of the housing 8 by screws, and a circulating sealing chamber opened between the bearing retaining ring 22 and the sealing ring 20; the circulating sealing chamber is an annular chamber formed by the surface shapes of the bearing retaining ring 22 and the sealing ring 20 after they are installed, and the circulating sealing chamber includes an S-shaped chamber 19, a wedge-shaped chamber 18, an L-shaped chamber and a special-shaped chamber 16 which are sequentially connected from the direction away from the bearing 9, and the S-shaped chamber 19, the wedge-shaped chamber 18, the L-shaped chamber and the special-shaped chamber 16 are all connected to each other through a connecting gap 15. The left end of the S-shaped cavity 19 communicates with the bearing chamber 27, and the right end of the S-shaped cavity 19 communicates with the wedge-shaped cavity 18. The wedge-shaped surface of the wedge-shaped cavity 18 is tilted away from the bearing chamber 27. The right end of the wedge-shaped cavity 18 communicates with the L-shaped cavity. The L-shaped cavity includes a long cavity 171 and a short cavity 17. The wedge-shaped cavity 18 communicates with the middle and lower section of the long cavity 171, and the short cavity 17 is located above the long cavity 171. The right end of the short cavity 17 communicates with the special-shaped cavity 16, and the right end of the special-shaped cavity 16 communicates with the outside of the housing 8. The bottom of the special-shaped cavity 16 is provided with a double groove 14. The double groove 14 is a wedge-shaped groove, and the wedge-shaped surface of the double groove 14 is tilted away from the bearing chamber 27. A first sealing ring 23 is provided at the contact point between the sealing ring 20 and the end face of the housing 8, and a second sealing ring 21 is provided at the contact point between the bearing retaining ring 22 and the rod of the main shaft 10.

[0027] The main shaft 10 is provided with an integrally formed positioning portion 101 at the right end of the bearing retaining ring 22. The diameter of the positioning portion 101 is larger than the diameter of the rod of the main shaft 10. Figure 1As shown, the right end of the positioning portion 101 is fixed with a chuck 12 by screws. The main shaft 10 is a hollow shaft, and the center of the main shaft 10 is slidably connected to a hollow pull rod 13. The right end of the pull rod 13 is connected to the chuck 12, and the chuck 12 is also a hydraulic chuck 12. The left end of the pull rod 13 is threadedly connected to the oil hydraulic rotary tensioning cylinder 1. By driving the pull rod 13 to slide axially by the oil hydraulic rotary tensioning cylinder 1, the clamping jaws of the chuck 12 can be controlled to achieve clamping and loosening. The structure of the pull rod 13, the chuck 12 and the oil hydraulic rotary tensioning cylinder 1 and their connection method are all prior art and will not be repeated here. The right end of the hydraulic rotary tensioning cylinder 1 is provided with a connector 201, which is keyed to the rod of the main shaft 10. The right end of the connector 201 is provided with an encoder 26, the right end of which is tightly abutted against the bearing seat 29. The encoder 26 is keyed to the main shaft 10. A locking nut 31 is also provided at the left end of the connector 201. The locking nut 31 is used to axially limit the connector 201 and the encoder 26 to prevent axial movement of the connector 201 and the encoder 26. A brake disc 2 is fixed to the outer periphery of the connector 201, and a hydraulic brake 3 is provided above the brake disc 2. The hydraulic brake 3 is fixed to the top of the housing 8 by a bracket 4. The hydraulic brake 3 brakes the brake disc 2, thereby braking the connector 201 and its main shaft 10. The structure of the hydraulic brake 3 on the brake disc 2 and its braking principle are both prior art and will not be described here.

[0028] The sealing method of the annular seal chamber is as follows: Figure 1 The high-speed rotation of the permanent magnet motor drives the main shaft 10, which increases the air temperature in the motor mounting cavity of the permanent magnet motor, forming a hot air flow. The hot air flow will enter the bearing chamber 27 through the gap 11. Due to the temperature difference, the hot air flow will pass through the S-shaped cavity 19, the wedge-shaped cavity 18, the long cavity 171, the short cavity 17 and the special-shaped cavity 16 in sequence to discharge the hot air flow. The continuous rotation of the main shaft 10 causes the hot air flow to continuously overflow, thereby preventing external dust and water vapor from entering the bearing chamber 27, achieving a sealing effect.

[0029] The advantages of this solution are: 1. Multi-stage sealing is adopted to ensure sealing performance and improve the working accuracy and service life of the main shaft 10 and bearing 9. The annular seal chamber adopts a multi-stage sealing structure in which the S-shaped chamber 19, the wedge-shaped chamber 18, the L-shaped chamber and the special-shaped chamber 16 are connected in sequence to form a progressive dust barrier. When the main shaft 10 rotates, it will instantly heat up, causing the air in the motor to expand due to the heat. Due to the influence of the temperature difference, the hot air will overflow from the bearing chamber 27 and be discharged outward from the annular seal chamber. The high-speed rotation of the main shaft 10 will keep the hot air in a ring-shaped state. This prevents external dust, water vapor and other impurities from entering the installation chamber of the main shaft 10 and the bearing 9. This sealing method relies entirely on the heat generated by the rotation of the main shaft 10. The temperature inside the main shaft 10 and the bearing chamber 27 is increased, and a temperature difference is formed with the outside world, so that the hot air flow can overflow spontaneously and be discharged through the circulating sealing chamber, thereby forming an air curtain protection, which will not hinder the heat discharge in the bearing chamber 27, and can also prevent external dust from invading the bearing chamber 27 and the main shaft 10, so that the working environment of the main shaft 10 and the bearing chamber 27 is not polluted, and the working stability, working accuracy and service life of the bearing 9 of the main shaft 10 are effectively improved. Moreover, compared with the existing technology, there is no need to connect compressed air from the outside, which reduces the internal structure and saves manufacturing costs.

[0030] 2. The special-shaped cavity 16 uses a double groove 14 structure to enhance dust blocking. When foreign matter attempts to enter the bearing chamber 27 with the airflow, the special-shaped cavity 16 first acts as a barrier. The double grooves 14 at the bottom of the special-shaped cavity 16 can block dust and water vapor and allow them to settle within the grooves. The double grooves 14 form a double protection, enhancing the blocking effect.

[0031] 3. Increase the volume of the annular seal chamber and avoid hot air retention. The special-shaped chamber 16 and the short chamber 17 of the L-shaped chamber both have a certain volume. When the high-speed rotation of the main shaft 10 causes the gas temperature inside the bearing chamber 27 to be too high, the hot air flow may not be able to be quickly discharged from the annular seal chamber. The special-shaped chamber 16 and the short chamber 17 increase the overall volume of the annular seal chamber, allowing the hot air flow to be temporarily stored in the special-shaped chamber 16 and the short chamber 17, thereby preventing the hot air flow with excessive temperature from being retained in the bearing chamber 27 due to slow discharge speed, preventing the angular contact ball bearing 9 from being in an overly high working environment and being damaged prematurely, and effectively extending the service life of the bearing 9.

[0032] 4. Optimize the shape of the annular sealing cavity to improve the reliability of the sealing mechanism. If the special-shaped cavity 16 fails to successfully block dust impurities and causes impurities to enter the short cavity 17, and the wedge-shaped cavity 18 is connected to the middle and lower section of the long cavity 171 of the L-shaped cavity, there is still a space below the connection between the long cavity 171 and the wedge-shaped cavity 18, allowing impurities to fall into this space without being blocked at the connection between the long cavity and the wedge-shaped cavity 18. This ensures the unobstructed flow of the entire annular sealing cavity, maintains the stable discharge of hot air flow, and improves the reliability of the sealing mechanism.

[0033] 5. Optimize the structural layout of the wedge-shaped cavity 18 and increase the strength of the airflow seal. The wedge-shaped surface of the wedge-shaped cavity 18 is tilted away from the bearing chamber 27, so that when the hot air flows through the wedge-shaped cavity 18, it will flow from the wide opening to the narrow opening. According to Bernoulli's principle, the airflow velocity in the wedge-shaped cavity 18 channel increases, which is more conducive to the discharge of the hot air flow, thereby increasing the strength of the airflow seal. At the same time, the wedge-shaped surface of the wedge-shaped cavity 18 also has the effect of accommodating dust and impurities, which can prevent the circulation seal cavity from being blocked and improve reliability.

[0034] 6. The S-shaped cavity 19 is closest to the bearing chamber 27. As the final protective sealing cavity, its tortuous path can consume the kinetic energy of dust and water vapor, thereby improving the success rate of intercepting dust and water vapor. Moreover, after being blocked by the previous S-shaped cavities 19, the dust impurities that finally enter the S-shaped cavity 19 are already very small. The tortuous path of the S-shaped cavity 19 also prolongs the time for water vapor to enter the bearing chamber 27, prompting the water vapor to condense into droplets on the inner wall of the S-shaped cavity 19. These droplets can absorb dust, further improving the ability to capture dust and water vapor and improving the sealing performance.

[0035] The above are only embodiments of the present invention. The invention is not limited to the fields involved in this implementation case. Common knowledge such as the specific structure and characteristics of the scheme are not described in detail here. It should be pointed out that for those skilled in the art, without departing from the structure of the present invention, several modifications and improvements can be made, which should also be regarded as the scope of protection of the present invention. These will not affect the effect of the implementation of the present invention and the practicality of the patent. The scope of protection required by this application shall be based on the content of its claims, and the specific implementation methods and other records in the specification can be used to interpret the content of the claims.

Claims

1. A machine tool built-in electric spindle structure, characterized by: It includes a box body, a permanent magnet motor fixed inside the box body, and a main shaft rotatably connected to the box body, wherein a bearing chamber is provided at the end of the box body, and an angular contact ball bearing is provided in the bearing chamber; The main shaft is also provided with a sealing mechanism for sealing the bearing chamber, the sealing mechanism comprising a bearing retaining ring sleeved on the main shaft, a sealing ring sleeved outside the bearing retaining ring and fixed to the end face of the housing, and a circulating sealing cavity opened between the bearing retaining ring and the sealing ring; The circulating sealing cavity includes an S-shaped cavity, a wedge-shaped cavity, an L-shaped cavity and a special-shaped cavity which are connected in sequence from the direction away from the bearing chamber. The wedge-shaped surface of the wedge-shaped cavity is inclined toward the direction away from the bearing chamber. The L-shaped cavity includes a long cavity and a short cavity. The wedge-shaped cavity is connected in the middle and lower section of the long cavity. The short cavity is located above the long cavity. One end of the short cavity away from the bearing chamber is connected to the special-shaped cavity. A double groove is provided at the bottom of the special-shaped cavity. One end of the special-shaped cavity away from the short cavity is connected to the outside world.

2. The machine tool built-in electric spindle structure according to claim 1, characterized in that: The double grooves are wedge-shaped grooves, and the wedge surfaces of the double grooves are inclined in a direction away from the bearing chamber.

3. The machine tool built-in electric spindle structure according to claim 2, characterized in that: A retaining ring is provided at one end of the bearing chamber away from the bearing retaining ring, and a locking ring is provided at one end of the retaining ring away from the bearing. The locking ring is threadedly connected to the main shaft rod, and a gap is provided between the outer circumference of the retaining ring and the inner wall of the bearing chamber.

4. The machine tool built-in electric spindle structure according to claim 3, characterized in that: A motor installation chamber is provided in the box body on a side of the locking ring away from the retaining ring. The permanent magnet motor is located in the installation chamber. The motor installation chamber is connected to the bearing chamber through a gap formed by the outer cylindrical surface of the retaining ring and the inner wall surface of the bearing chamber.

5. The machine tool built-in electric spindle structure according to claim 4, characterized in that: The main shaft is a hollow shaft, and a positioning portion is integrally formed at the end of the main shaft. The diameter of the positioning portion is larger than the diameter of the rod of the main shaft, and a chuck is fixed to the end of the positioning portion away from the bearing chamber.

6. The machine tool built-in electric spindle structure according to claim 5, characterized in that: A first sealing ring is provided at the contact point between the sealing ring and the end surface of the box body, and a second sealing ring is provided at the contact point between the bearing retaining ring and the rod portion of the main shaft.

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