A spindle system with adaptive stiffness for CNC machine tools

Abstract

The present invention provides a spindle system with self-adaptive stiffness for a numerically controlled machine tool, which includes a spindle housing, a spindle disposed in the spindle housing, a power unit for driving the spindle, a control system and a control method. A set of support bearings is sleeved on each of the upper and lower ends of the spindle. The outer rings of the support bearings are fixedly connected to the spindle housing. The spindle is axially fixed to the inner ring of the lower support bearing, and the spindle is not axially fixed to the inner ring of the upper support bearing. The spindle and the two sets of support bearings form a basic spindle unit. A spindle structure transformation unit I and a spindle structure transformation unit II are sleeved on the outer wall of the spindle located in the spindle housing. Through the transformation of the basic spindle unit and the spindle structure transformation unit, the drive of the electromagnetic static component and the electromagnetic dynamic component, and the adaptive control, the present invention realizes a spindle system with self-adaptive stiffness for a numerically controlled machine tool, enabling the numerically controlled machine tool to integrate high precision, high speed and heavy load, laying a foundation for the development of high-grade numerically controlled machine tools.

Description

Technical Field

[0001] The present invention relates to the technical field of CNC machine tool spindle systems, and particularly to a spindle system with self-adaptive stiffness for CNC machine tools. Background Art

[0002] With the rapid development of modern industrial technology, people have higher and higher requirements for high-grade CNC machine tools. The most concentrated concerns are the accuracy, speed, and load problems of the machine tools. So far, there is no high-grade CNC machine tool that combines high precision, high speed, and heavy load. The core problem is that the spindle system of the CNC machine tool cannot meet the above requirements. The accuracy and speed of the machine tool spindle system and the load-bearing capacity of the machine tool spindle system are mainly determined by the structure of the spindle system. The core component that affects the performance of the spindle system in the spindle system structure is the bearing, that is, the accuracy, speed, and load-bearing capacity of the spindle system are mainly affected by the structural performance of the bearing. At present, the bearings used in the machine tool spindle system are divided into high-speed precision bearings and low-speed heavy-duty bearings. The shape and size of the rolling elements in the bearing determine the accuracy, limiting speed, and load-bearing capacity of the bearing. For example, smaller spherical rolling elements can be made into high-speed and high-precision bearings. The load-bearing capacity of such high-speed and high-precision bearings is relatively small, while larger non-spherical rolling elements can be made into high-rigidity bearings, and the limiting speed of such high-rigidity bearings is relatively low. Although the material, self-manufacturing accuracy, cooling, lubrication, and clearance of the bearing also have a certain impact on the accuracy, speed, and load of the bearing, these impacts are universal and are only the common conditions of the bearing. That is to say, at present, spherical rolling elements cannot be made into heavy-duty bearings, and non-spherical rolling elements cannot be made into high-speed bearings. Therefore, for the machine tool spindle system supported by rolling bearings, there are two bearing structures, namely, the application of high-speed bearings and the application of heavy-duty bearings. As long as high-speed bearings are used, the heavy-load requirements cannot be met, and as long as heavy-duty bearings are used, the high-speed requirements cannot be met. It is impossible to achieve high precision, high speed, and heavy load in one. Summary of the Invention

[0003] To solve the problem that the bearings used in the existing machine tool spindle system cannot meet the heavy-load and high-speed requirements at the same time, which affects the spindle system structure and makes the existing machine tools unable to achieve high precision, high speed, and heavy load in one, the present invention proposes a spindle system with self-adaptive stiffness for CNC machine tools, including a spindle housing, a spindle passing through the spindle housing, a power unit for driving the spindle, a control system, and a control method. A set of support bearings is sleeved on each of the upper and lower ends of the spindle. The outer ring of the support bearing is fixedly connected to the spindle housing. The spindle is axially fixed to the inner ring of the lower support bearing, and the spindle is not axially fixed to the inner ring of the upper support bearing. The spindle and the two sets of support bearings form a basic spindle unit. A spindle structure transformation unit I and a spindle structure transformation unit II are sleeved on the outer wall of the spindle located inside the spindle housing.

[0004] The main shaft structure transformation unit I includes a tapered roller bearing I with an upward opening, a bearing sleeve I, an electromagnetic moving component I, an electromagnetic static component I, and an elastic plate I. The inner ring of the tapered roller bearing I is fixedly installed on the outer wall of the main shaft, the outer ring of the tapered roller bearing I is fixedly installed in the inner ring of the bearing sleeve I, the outer ring of the bearing sleeve I is fixedly connected to the inner ring of the electromagnetic moving component I and the inner ring of the elastic plate I respectively. The elastic plate I is located below the electromagnetic moving component I and the electromagnetic static component I. The inner ring of the electromagnetic static component I is sleeved on the outer ring of the electromagnetic moving component I, and there is a gap between the electromagnetic static component I and the electromagnetic moving component I. The outer ring of the electromagnetic static component I and the outer ring of the elastic plate are both fixedly connected to the main shaft housing. One end of the bearing sleeve I extends to the bottom end surface of the outer ring of the tapered roller bearing I, and a sensor I is provided between the bottom end surface of the outer ring of the tapered roller bearing I and the bearing sleeve I;

[0005] The main shaft structure transformation unit II includes a tapered roller bearing II with an upward opening, a bearing sleeve II, an electromagnetic moving component II, an electromagnetic static component II, and an elastic plate II. The inner ring of the tapered roller bearing II is sleeved on the outer wall of the main shaft, the outer ring of the tapered roller bearing II is fixedly installed in the inner ring of the bearing sleeve II, the outer ring of the bearing sleeve II is fixedly connected to the inner ring of the electromagnetic moving component II and the inner ring of the elastic plate II respectively. The inner ring of the electromagnetic static component II is sleeved on the outer ring of the electromagnetic moving component II, and there is a gap between the electromagnetic static component II and the electromagnetic moving component II. The outer ring of the electromagnetic static component II and the outer ring of the elastic plate are both fixedly connected to the main shaft housing. The elastic plate II is located below the electromagnetic moving component II and the electromagnetic static component II. A bearing cover II is provided below the tapered roller bearing II, and a sensor II is provided between the bottom end surface of the outer ring of the tapered roller bearing II and the bearing cover II. A disc spring is provided at the bottom of the tapered roller bearing II. One end of the disc spring is connected to the bottom surface of the inner ring of the tapered roller bearing II, and the other end of the disc spring is closely attached to the shaft shoulder of the main shaft;

[0006] Both the sensor I and the sensor II are connected to the control system.

[0007] Preferably, a spacer sleeve I is provided between the tapered roller bearing I and the lower support bearing. A retaining ring I is provided at the bottom of the inner ring of the lower support bearing. The spacer sleeve I and the retaining ring I are both sleeved on the outer wall of the main shaft. The inner ring of the lower support bearing is fastened by the spacer sleeve I and the retaining ring I. A retaining ring II is provided at the top of the tapered roller bearing I. The retaining ring II is sleeved on the outer wall of the main shaft. The inner ring of the tapered roller bearing I is fastened by the retaining ring II and the spacer sleeve;

[0008] The top of the bearing sleeve I is connected to a bearing cover I. The inner ring side of the bearing cover I is located at the bottom end of the outer ring of the tapered roller bearing I. The outer ring of the tapered roller bearing I is fastened by the inner ring side of the bearing cover I and the bearing sleeve I. The outer ring side of the bearing cover I is located at the top of the inner ring of the elastic plate I. The inner ring side of the elastic plate I is fastened by the bearing cover I and the bearing sleeve I;

[0009] A spacer sleeve II is provided between the tapered roller bearing II and the upper support bearing. The spacer sleeve II is sleeved on the outer wall of the main shaft. The top end of the spacer sleeve II is in close contact with the bottom end face of the inner ring of the upper support bearing. The top end of the inner ring of the tapered roller bearing II is in close contact with the bottom end of the spacer sleeve II under the elastic force of the disc spring. One end of the inner ring of the bearing sleeve II extends to the top end face of the outer ring of the tapered roller bearing II. The inner ring of the tapered roller bearing II is fastened through the bearing cover II and the extended end of the inner ring of the bearing sleeve II;

[0010] The outer ring side of the bearing cover II is located at the top end of the inner ring of the elastic plate II. The inner ring side of the elastic plate II is fastened through the bearing cover II and the bearing sleeve II.

[0011] Preferably, the elastic plate I includes elastic webs I and the first spacer. There are multiple elastic webs I. The multiple elastic webs I are arranged at intervals through the first spacer. The first spacer includes an inner spacer I and an outer spacer I. The inner spacer I is located on the inner ring side of the elastic web I, and the outer spacer I is located on the outer ring side of the elastic web I;

[0012] The elastic plate II includes elastic webs II and the second spacer. There are multiple elastic webs II. The multiple elastic webs II are arranged at intervals through the second spacer. The second spacer includes an inner spacer II and an outer spacer II. The inner spacer II is located on the inner ring side of the elastic web II, and the outer spacer II is located on the outer ring side of the elastic web II.

[0013] Preferably, long slots and drilled holes are provided on both the elastic web I and the elastic web II.

[0014] Preferably, there are multiple long slots and drilled holes. The length direction of the long slots is arranged along the radial direction of the elastic web I. The long slots and the drilled holes are arranged in the distribution form of long slot - drilled hole - long slot along the circumferential direction of the elastic web I. There are two drilled holes between adjacent two long slots. The two drilled holes are arranged in sequence along the radial direction of the elastic web I. The structure of the elastic web II is the same as that of the elastic web I.

[0015] Preferably, the main shaft housing includes a main shaft shell, a main shaft upper cover, a main shaft lower cover, an upper bearing end cover, and a lower bearing end cover. The main shaft upper cover and the main shaft lower cover are respectively installed at the upper end and the lower end of the main shaft shell. The electromagnetic static assembly I and the outer ring of the support bearing are both connected to the main shaft lower cover. An outer pressure ring I is provided at the bottom end of the outer ring of the elastic plate I. The outer ring of the elastic plate I is fastened through the outer pressure ring I and the lower bearing end cover. The electromagnetic static assembly II and the outer ring of the support bearing are both connected to the main shaft upper cover. An outer pressure ring II is provided at the bottom end of the outer ring of the elastic plate II. The outer ring of the elastic plate II is fastened through the outer pressure ring II and the upper bearing cover;

[0016] The upper bearing end cover is installed at the top end of the main shaft upper cover, and the lower bearing end cover is installed at the bottom end of the main shaft lower cover. The outer ring of the upper support bearing is fastened through the upper bearing end cover and the main shaft upper cover, and the outer ring of the lower support bearing is fastened through the lower bearing end cover and the main shaft lower cover.

[0017] Preferably, the lower support bearings of the spindle basic unit include bearing one, bearing two, and bearing three that are sequentially and fittingly arranged from bottom to top, and the upper support bearings include bearing four, bearing five, and bearing six that are sequentially and fittingly arranged from bottom to top;

[0018] The support bearings one, two, and three are angular contact bearings. Bearing one and bearing two have openings facing downward, and bearing three has an opening facing upward. Bearing one, bearing two, and bearing three form a preloaded bearing assembly;

[0019] The support bearings four, five, and six are angular contact bearings. Bearing four and bearing five have openings facing downward, and bearing six has an opening facing upward. Bearing four, bearing five, and bearing six form a preloaded bearing assembly.

[0020] Preferably, the power unit includes a stator assembly, a rotor assembly, a lower sleeve, an upper sleeve, and a nut. The lower sleeve and the upper sleeve are sleeved on the outer wall at the middle position of the spindle. The rotor assembly is sleeved on the outer walls of the lower sleeve and the upper sleeve. The inner ring of the rotor assembly is fastened by the lower sleeve and the upper sleeve. The stator assembly is sleeved on the outer ring side of the rotor assembly, and the outer ring of the stator assembly is fixedly connected to the inner wall of the spindle housing.

[0021] Preferably, the control system includes a numerical control system and an in-built control module connected to the numerical control system. Both sensor one and sensor two include a force sensor and a displacement sensor. A torque sensor, a temperature sensor, and a vibration frequency sensor are also installed in the spindle housing. The control system is respectively connected to the torque sensor, the temperature sensor, and the vibration frequency sensor.

[0022] Preferably, the control method has an adaptive control ability. The numerical control system and the in-built control module cooperate to calculate the information collected in real time by the force, torque, displacement, temperature, and vibration frequency sensors, the information of the pre-read program for part processing, and a large amount of empirical data stored in the machine tool, and perform closed-loop control on the electromagnetic static component one, the electromagnetic dynamic component one, the electromagnetic static component two, and the electromagnetic dynamic component two to achieve the adaptive transformation of the spindle system stiffness.

[0023] The beneficial effects of the present invention are as follows: The spindle basic unit of the present invention can operate independently. When the spindle basic unit operates independently, it is in the high-speed and precision state of the spindle system. The spindle basic unit can also operate together with any group of spindle structure transformation units or simultaneously with two groups of spindle structure transformation units. When the spindle basic unit operates together with the spindle structure transformation unit, it is in the heavy-load state of the spindle system and also in the state of load transformation of the spindle system. The working state of the spindle structure transformation unit is controlled by the electromagnetic static component and the electromagnetic dynamic component. The electromagnetic static component and the electromagnetic dynamic component are controlled by voltage and current, and can instantaneously change the load-bearing state of the spindle system to achieve rapid conversion of the performance of the spindle system. Through the transformation of the spindle basic unit and the spindle structure transformation unit, the drive of the electromagnetic static component and the electromagnetic dynamic component, and adaptive control, the present invention realizes a spindle system with adaptive stiffness for CNC machine tools, enabling the CNC machine tools to integrate high precision, high speed, and heavy load, laying a foundation for the development of high-grade CNC machine tools. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 is a schematic diagram of the overall structure of the present invention;

[0025] Figure 2 is Figure 1 an enlarged schematic diagram at position A in

[0026] Figure 3 is Figure 1 an enlarged schematic diagram at position B in

[0027] Figure 4 is a schematic diagram of the elastic web structure in the present invention.

[0028] Reference numerals in the figures: 1 - spindle housing, 2 - stator assembly, 3 - rotor assembly, 4 - lower spindle cover, 5 - lower bearing end cover, 6 - spindle, 7 - retaining ring 1, 8 - bearing 1, 9 - bearing 2, 10 - bearing 3, 11 - spacer sleeve 1, 12 - sensor 1, 13 - bearing sleeve 1, 14 - electromagnetic static component 1, 15 - electromagnetic dynamic component 1, 16 - tapered roller bearing 1, 17 - outer spacer 1, 18 - elastic web 1, 19 - inner spacer 1, 20 - outer pressure ring, 21 - bearing cover 1, 22 - retaining ring 2, 23 - lower sleeve, 24 - upper sleeve, 25 - nut, 26 - sensor 2, 27 - bearing cover 2, 28 - disc spring, 29 - elastic web 2, 30 - tapered roller bearing 2, 31 - electromagnetic static component 2, 32 - electromagnetic dynamic component 2, 33 - bearing sleeve 2, 34 - spacer sleeve 2, 35 - bearing 4, 36 - bearing 5, 37 - upper bearing end cover, 38 - bearing 6, 39 - upper spindle cover, 40 - inner spacer 2, 41 - outer spacer 2, 42 - outer pressure ring 2. DETAILED DESCRIPTION OF THE INVENTION

[0029] To make the present invention clearer and more understandable, the following further elaborates on the technical solution of the present invention in conjunction with the accompanying drawings and embodiments. It should be understood that the given embodiments are only one of the implementation manners and do not represent all embodiments.

[0030] In this article, terms such as "left, right, up, down" are established based on the positional relationship shown in the accompanying drawings. Depending on the different accompanying drawings, the corresponding positional relationship may also change accordingly. Therefore, it cannot be understood as an absolute limitation of the protection scope.

[0031] Combined with the attached Figures 1-4 , a spindle system with self-adaptive stiffness for a numerically controlled machine tool, including a spindle housing, a spindle 6 inserted in the spindle housing, a power unit for driving the spindle 6, a control system, and a control method. A set of support bearings is sleeved on each of the upper and lower ends of the spindle 6. The outer ring of the support bearing is fixedly connected to the spindle housing. The spindle 6 is axially fixed to the inner ring of the lower support bearing, and the spindle 6 is not axially fixed to the inner ring of the upper support bearing. The spindle 6 and the two sets of support bearings form a basic spindle unit. A spindle structure transformation unit I and a spindle structure transformation unit II are sleeved on the outer wall of the spindle 6 located inside the spindle housing. The basic spindle unit can operate independently, and the basic spindle unit can also operate together with at least one set of spindle structure transformation units. When the basic spindle unit of the spindle system operates together with at least one set of spindle structure transformation units, the stiffness of the spindle system can be continuously transformed, enhanced, or restored;

[0032] The spindle structure transformation unit I includes a tapered roller bearing 16 with an upward opening, a bearing sleeve 13, an electromagnetic moving component 15, an electromagnetic static component 14, and an elastic plate 1. The inner ring of the tapered roller bearing 16 is fixedly installed on the outer wall of the spindle 6. The outer ring of the tapered roller bearing 16 is fixedly installed in the inner ring of the bearing sleeve 13. The outer ring of the bearing sleeve 13 is fixedly connected to the inner ring of the electromagnetic moving component 15 and the inner ring of the elastic plate 1 respectively. The elastic plate 1 is located below the electromagnetic moving component 15 and the electromagnetic static component 14. The inner ring of the electromagnetic static component 14 is sleeved on the outer ring of the electromagnetic moving component 15, and there is a gap between the electromagnetic static component 14 and the electromagnetic moving component 15. The outer ring of the electromagnetic static component 14 and the outer ring of the elastic plate are both fixedly connected to the spindle housing. One end of the bearing sleeve 13 extends to the bottom end surface of the outer ring of the tapered roller bearing 16. A sensor 12 is provided between the bottom end surface of the outer ring of the tapered roller bearing 16 and the bearing sleeve 13. When the spindle structure transformation unit I does not work, there is a gap between the outer ring of the tapered roller bearing 16 and its rollers and they do not contact;

[0033] The main shaft structure transformation unit II includes a tapered roller bearing II 30 with an upward opening, a bearing sleeve II 27, an electromagnetic moving component II 32, an electromagnetic static component II 31, and an elastic plate II. The inner ring of the tapered roller bearing II 30 is sleeved on the outer wall of the main shaft 6, and the outer ring of the tapered roller bearing II 30 is fixedly installed in the inner ring of the bearing sleeve II 33. The outer ring of the bearing sleeve II 33 is fixedly connected to the inner ring of the electromagnetic moving component II 32 and the inner ring of the elastic plate II respectively. The inner ring of the electromagnetic static component II 31 is sleeved on the outer ring of the electromagnetic moving component II 32, and there is a gap between the electromagnetic static component II 31 and the electromagnetic moving component II 32. The outer ring of the electromagnetic static component II 31 and the outer ring of the elastic plate are both fixedly connected to the main shaft housing. The elastic plate II is located below the electromagnetic moving component II 32 and the electromagnetic static component II 31. A bearing cover II 27 is provided below the tapered roller bearing II 30, and a sensor II 26 is provided between the bottom end surface of the outer ring of the tapered roller bearing II 30 and the bearing cover II 27. A disc spring 28 is provided at the bottom of the tapered roller bearing II 30. One end of the disc spring 28 is connected to the bottom surface of the inner ring of the tapered roller bearing II 30, and the other end of the disc spring 28 is closely attached to the shoulder of the main shaft 6. When the main shaft structure transformation unit II is not working, there is a gap and no contact between the outer ring of the tapered roller bearing II 30 and its rollers;

[0034] Both the sensor I 12 and the sensor II 26 are connected to the control system.

[0035] Specifically, the electromagnetic moving and static components are electromagnetic force driving devices. The electromagnetic moving component is driven to move relative to the electromagnetic static component by electromagnetic force, and the magnitude of the electromagnetic force is controlled by current and voltage. The electromagnetic moving component I 15 and the electromagnetic static component I 14 are a pair of components, and the electromagnetic moving component II 32 and the electromagnetic static component II 31 are a pair of components; the electromagnetic moving component I 15 drives the bearing sleeve I 13 to move axially, and at the same time the elastic plate I undergoes elastic deformation, thereby driving the tapered roller bearing I 16 to move axially. Similarly, the electromagnetic moving component II 32 drives the tapered roller bearing II 30 to move axially.

[0036] Specifically, a spacer sleeve I 11 is provided between the tapered roller bearing I 16 and the lower support bearing. A retaining ring I 7 is provided at the bottom of the inner ring of the lower support bearing. Both the spacer sleeve I 11 and the retaining ring I 7 are sleeved on the outer wall of the main shaft 6. The inner ring of the lower support bearing is fastened by the spacer sleeve I 11 and the retaining ring I 7. A retaining ring II 22 is provided at the top of the tapered roller bearing I 16. The retaining ring II 22 is sleeved on the outer wall of the main shaft 6. The inner ring of the tapered roller bearing I 16 is fastened by the retaining ring II 22 and the spacer 11;

[0037] The top of the bearing sleeve I 13 is connected to a bearing cover I 21. The inner ring side of the bearing cover I 21 is located at the bottom end of the outer ring of the tapered roller bearing I 16. The outer ring of the tapered roller bearing I 16 is fastened by the inner ring side of the bearing cover I 21 and the bearing sleeve I 13. The outer ring side of the bearing cover I 21 is located at the top of the inner ring of the elastic plate I. The inner ring side of the elastic plate I is fastened by the bearing cover I 21 and the bearing sleeve I 13;

[0038] A spacer two 34 is provided between the tapered roller bearing two 30 and the upper support bearing. The spacer two 34 is sleeved on the outer wall of the main shaft 6. The top end of the spacer two 34 is in close contact with the bottom end face of the inner ring of the upper support bearing. The top end of the inner ring of the tapered roller bearing two 30 is in close contact with the bottom end of the spacer two 34 under the elastic action of the disc spring 28. One end of the inner ring of the bearing sleeve two 33 extends to the top end face of the outer ring of the tapered roller bearing two 30. The inner ring of the tapered roller bearing two 30 is fastened by the bearing cover two 27 and the extended end of the inner ring of the bearing sleeve two 33;

[0039] The outer ring side of the bearing cover two 21 is located at the top end of the inner ring of the elastic plate member two. The inner ring side of the elastic plate member two is fastened by the bearing cover two 21 and the bearing sleeve two 13.

[0040] Specifically, the elastic plate member one includes elastic webs one 18 and first spacers. There are multiple elastic webs one 18. The multiple elastic webs one 18 are arranged at intervals through the first spacers. The first spacers include inner spacers one 19 and outer spacers one 17. The inner spacer one 19 is located on the inner ring side of the elastic web one 18, and the outer spacer one 17 is located on the outer ring side of the elastic web one 18;

[0041] The elastic plate member two includes elastic webs two 29 and second spacers. There are multiple elastic webs two 29. The multiple elastic webs two 29 are arranged at intervals through the second spacers. The second spacers include inner spacers two 40 and outer spacers two 41. The inner spacer two 40 is located on the inner ring side of the elastic web two 29, and the outer spacer two 41 is located on the outer ring side of the elastic web two 29. The elastic plate member one may also only include one elastic web one 18, that is, the elastic plate member one may include at least one elastic web one 18. When only one elastic web one 18 is provided, there is no need to provide a second spacer. Similarly, the elastic plate member two may also only include one elastic web two 29.

[0042] Specifically, long grooves and drill holes are formed in both the elastic webs one 18 and the elastic webs two 29 to increase the elasticity of the elastic webs and avoid noise.

[0043] Specifically, there are multiple long grooves and drill holes. The length direction of the long grooves is arranged along the radial direction of the elastic web one 18. The long grooves and drill holes are arranged in a distribution form of long groove - drill hole - long groove along the circumferential direction of the elastic web one 18. There are two drill holes between two adjacent long grooves. The two drill holes are arranged in sequence along the radial direction of the elastic web one 18. The structure of the elastic web two 29 is the same as that of the elastic web one 18.

[0044] Specifically, the main shaft housing includes a main shaft shell 1, an upper main shaft cover 39, a lower main shaft cover 4, an upper bearing end cover 37, and a lower bearing end cover 5. The upper main shaft cover 39 and the lower main shaft cover 4 are respectively installed at the upper and lower ends of the main shaft shell 1. The first electromagnetic static assembly 14 and the outer ring of the support bearing are both connected to the lower main shaft cover 4. The bottom end of the outer ring of the first elastic plate member is provided with an outer retaining ring 20. The outer ring of the first elastic plate member is fastened by the outer retaining ring 20 and the lower bearing end cover 5. The second electromagnetic static assembly 31 and the outer ring of the support bearing are both connected to the upper main shaft cover 37. The bottom end of the outer ring of the second elastic plate member is provided with an outer retaining ring 42. The outer ring of the second elastic plate member is fastened by the outer retaining ring 42 and the upper bearing cover 39. Compared with the traditional sliding sleeve clearance structure, the axial movement of the elastic plate member relies on elastic deformation and is gapless, enabling absolute accuracy retention. More specifically, the inner ring side of the first elastic spoke plate 18 is fastened to the bearing sleeve 13 through the inner spacer 19 and the first bearing cover 21. The outer ring side of the first elastic spoke plate 18 is fastened to the lower main shaft cover 4 through the outer spacer 17 and the outer retaining ring 20. The inner ring side of the second elastic spoke plate 29 is fastened to the bearing sleeve 33 through the inner spacer 40 and the second bearing cover 27. The outer ring side of the second elastic spoke plate 29 is fastened to the upper main shaft cover 39 through the outer spacer 41 and the outer retaining ring 42;

[0045] The upper bearing end cover 37 is installed at the top end of the upper main shaft cover 39, and the lower bearing end cover 5 is installed at the bottom end of the lower main shaft cover 39. The outer ring of the upper support bearing is fastened by the upper bearing end cover 37 and the upper main shaft cover 39, and the outer ring of the lower support bearing is fastened by the lower bearing end cover 5 and the lower main shaft cover 4.

[0046] Specifically, the lower support bearing of the main shaft basic unit includes a bearing one 8, a bearing two 9, and a bearing three 10 that are sequentially attached from bottom to top. The upper support bearing includes a bearing four 35, a bearing five 36, and a bearing six 38 that are sequentially attached from bottom to top;

[0047] The support bearings one 8, two 9, and three 10 are angular contact bearings. The bearings one 8 and two 9 have openings downward, and the bearing three 10 has an opening upward, that is, the bearing two 9 and the bearing three 10 are assembled back-to-back. The bearings one 8, two 9, and three 10 form a preloaded bearing assembly;

[0048] The support bearings four 35, five 36, and six 38 are angular contact bearings. The bearings four 35 and five 36 have openings downward, and the bearing six 38 has an opening upward, that is, the bearing five 36 and the bearing six 38 are assembled back-to-back. The bearings four 35, five 36, and six 38 form a preloaded bearing assembly; Preloading forces are respectively applied to the two groups of support bearings. The bearings one 8, two 9, and three 10 support the radial direction of the main shaft 6 and simultaneously limit the axial direction of the main shaft 6. The inner rings of the bearings four 35, five 36, and six 38 are not axially fixed to the main shaft 6.

[0049] Specifically, the power unit includes a stator assembly 2, a rotor assembly 3, a lower sleeve 23, an upper sleeve 24, and a nut 25. The lower sleeve 23 and the upper sleeve 24 are sleeved on the outer wall of the middle position of the main shaft 6. The rotor assembly 3 is sleeved on the outer walls of the lower sleeve 23 and the upper sleeve 24. The inner ring of the rotor assembly 3 is fastened by the lower sleeve 23 and the upper sleeve 24. The stator assembly 2 is sleeved on the outer ring side of the rotor assembly 3. The outer ring of the stator assembly 2 is fixedly connected to the inner wall of the main shaft housing. A nut 25 for fastening the lower sleeve 23 and the upper sleeve 24 is also provided on the outer wall of the main shaft 6. The power unit can also be an independent external motor system, which can be directly connected to the main shaft 6 or connected to the main shaft 6 through a belt or a gear.

[0050] Specifically, the control system includes a numerical control system and an in-built control module connected to the numerical control system. Both the first sensor 12 and the second sensor 26 include a force sensor and a displacement sensor. A torque sensor, a temperature sensor, and a vibration frequency sensor are also installed in the main shaft housing. The control system is respectively connected to the torque sensor, the temperature sensor, and the vibration frequency sensor.

[0051] Specifically, the control method has an adaptive control ability. The numerical control system and the in-built control module cooperate to calculate the information collected in real time by the force, torque, displacement, temperature, and vibration frequency sensors, the pre-read program information for part processing, and a large amount of empirical data stored in the machine tool, and perform closed-loop control on the first electromagnetic static component 14, the first electromagnetic moving component 15, the second electromagnetic static component 31, and the second electromagnetic moving component 32 to achieve adaptive transformation of the stiffness of the main shaft system. The first electromagnetic moving component 15 can drive the outer ring of the bearing sleeve 13 and the first tapered roller bearing 16 to move downward or upward. When the outer ring of the first tapered roller bearing 16 moves downward, it can reach the lower limit position, and when it moves upward, the force can be gradually increased. The second electromagnetic moving component 32 can drive the outer ring of the bearing sleeve 33 and the second tapered roller bearing 30 to move downward or upward. When the outer ring of the second tapered roller bearing 30 moves downward, it can reach the lower limit position, and when it moves upward, the force can be gradually increased. The lower limit position is the limit position that the outer ring of the tapered roller bearing can reach when moving downward, and the increased force means increasing the acting force of the outer ring of the tapered roller bearing on the bearing rollers.

[0052] The spindle system realizes its stiffness self - adaptation function through three motion states, which are the independent operation of the spindle basic unit, the operation of the spindle basic unit together with the spindle structure transformation unit I, and the simultaneous operation of the spindle basic unit, the spindle structure transformation unit I and the spindle structure transformation unit II. When the electromagnetic moving component 1 drives the outer ring of the tapered roller bearing 16 downward, the electromagnetic moving component 2 drives the outer ring of the tapered roller bearing 30 downward, and reaches the lower limit position, the outer rings of the two tapered roller bearings are disengaged from their respective inner rings and rollers. The two tapered roller bearings do not support the spindle 6. At this time, the spindle basic unit operates independently. Since the angular contact bearings are high - speed and high - precision series bearings, the spindle system during the independent operation of the spindle basic unit can meet the requirements of high speed and high precision.

[0053] When the electromagnetic moving component 1 drives the outer ring of the tapered roller bearing 16 upward, the outer ring of the tapered roller bearing 16 contacts its roller and gradually increases the force, so that the tapered roller bearing 16 supports the spindle 6, and the pre - tightening force gradually increases. The rigidity of the spindle 6 and its load - bearing capacity increase accordingly. When the spindle structure transformation unit I participates in the work and at the same time the electromagnetic moving component 2 drives the outer ring of the tapered roller bearing 30 upward, the rigidity and load - bearing capacity of the spindle 6 will be further enhanced. For the machine tool spindle system, the two tapered roller bearings belong to the heavy - duty series bearings. At this time, the structure of the spindle system when the spindle structure transformation unit and the spindle basic unit work simultaneously is a heavy - duty structure, and the spindle system can meet the requirements of heavy load and large torque.

[0054] Specifically, the control method is as follows: The numerical control system and the built - in control module cooperate to pre - read the part processing program and calculate the machine tool program and the self - stored empirical data, determine whether the spindle basic unit operates independently or whether the two groups of spindle structure transformation units participate, and determine how much the pre - tightening force required should be when the spindle structure transformation unit participates. The built - in control module controls the electromagnetic static component and the electromagnetic moving component by controlling the current and voltage. At the same time, the force, torque, displacement, temperature, and vibration frequency sensors collect information in real time and transmit it to the control system. The numerical control system and the built - in control module use the feedback information as input to recalculate the machine tool program information and the self - stored empirical data. The numerical control system and the built - in control module continuously adjust the control of the electromagnetic static component and the electromagnetic moving component according to the calculation results, and repeat the cycle, so that the machine tool spindle system can adapt to the changes in the processing requirements.

[0055] More specifically, for example: If the machine tool is used to machine high-precision small holes, the numerical control system and the control module control the electromagnetic static component and the electromagnetic dynamic component, and there is no need for the two sets of spindle structure transformation units to participate. Only the basic spindle unit operates independently. At this time, the outer rings of the tapered roller bearings of the two sets of spindle structure transformation units do not contact their rollers. If the machine tool encounters heavy-duty cutting machining again, the numerical control system and the control module control the electromagnetic static component and the electromagnetic dynamic component, and require the two sets of spindle structure transformation units to participate at the same time. At this time, the outer rings of the bearings of the two sets of spindle structure transformation units move upward to contact their rollers and participate in the work, and the preload is appropriately increased, enhancing the stiffness of the machine tool spindle system and meeting the machining requirements.

[0056] More specifically, when the basic spindle unit operates independently, the stiffness of the spindle system with stiffness self-adaptation of the numerically controlled machine tool is the smallest and the rotational speed can be the highest. When the basic spindle unit operates together with the two sets of spindle structure transformation units, the stiffness of the spindle system with stiffness self-adaptation of the numerically controlled machine tool can be enhanced. When the basic spindle unit operates together with the two sets of spindle structure transformation units and the preload of the outer ring of the spindle structure transformation unit reaches the maximum, the stiffness of the spindle system with stiffness self-adaptation of the numerically controlled machine tool can reach the maximum, and the preload adjustment process can be steplessly changed.

[0057] In high-grade numerically controlled machine tools, large machine tools are also practical for machining smaller parts. When machining large parts, there are also times when smaller structures need to be machined on the parts. Therefore, the spindle system with stiffness self-adaptation of the numerically controlled machine tool has a wide range of application prospects.

[0058] The above embodiments only illustrate the basic principles and characteristics of the present invention, but are not limited by the above embodiments. It should be understood that for those of ordinary skill in the art, various changes and modifications can be made to the present invention without departing from the spirit and scope of the present invention, and these changes and modifications all fall within the scope of the present invention claimed. The scope of protection claimed by the present invention is defined by the appended claims and their equivalents.

Claims

1. A spindle system with self - adapting stiffness for a numerically controlled machine tool, comprising a spindle housing, a spindle (6) disposed in the spindle housing, a power unit for driving the spindle (6), a control system, and a control method. It is characterized in that: A set of support bearings is sleeved on each of the upper and lower ends of the spindle (6). The outer ring of the support bearing is fixedly connected to the spindle housing. The spindle (6) is axially fixed to the inner ring of the lower support bearing, and the spindle (6) is not axially fixed to the inner ring of the upper support bearing. The spindle and the two sets of support bearings form a basic spindle unit. A spindle structure transformation unit I and a spindle structure transformation unit II are sleeved on the outer wall of the spindle (6) located in the spindle housing. The spindle structure transformation unit I includes a tapered roller bearing I (16) with an upward opening, a bearing sleeve I (13), an electromagnetic moving component I (15), an electromagnetic static component I (14), and an elastic plate I. The inner ring of the tapered roller bearing I (16) is fixedly installed on the outer wall of the spindle (6). The outer ring of the tapered roller bearing I (16) is fixedly installed in the inner ring of the bearing sleeve I (13). The outer ring of the bearing sleeve I (13) is fixedly connected to the inner ring of the electromagnetic moving component I (15) and the inner ring of the elastic plate I respectively. The elastic plate I is located below the electromagnetic moving component I (15) and the electromagnetic static component I (14). The inner ring of the electromagnetic static component I (14) is sleeved on the outer ring of the electromagnetic moving component I (15), and there is a gap between the electromagnetic static component I (14) and the electromagnetic moving component I (15). The outer ring of the electromagnetic static component I (14) and the outer ring of the elastic plate are fixedly connected to the spindle housing. One end of the bearing sleeve I (13) extends to the bottom end surface of the outer ring of the tapered roller bearing I (16), and a sensor I (12) is provided between the bottom end surface of the outer ring of the tapered roller bearing I (16) and the bearing sleeve I (13). The spindle structure transformation unit II includes a tapered roller bearing II (30) with an upward opening, a bearing sleeve II (27), an electromagnetic moving component II (32), an electromagnetic static component II (31), and an elastic plate II. The inner ring of the tapered roller bearing II (30) is sleeved on the outer wall of the spindle (6). The outer ring of the tapered roller bearing II (30) is fixedly installed in the inner ring of the bearing sleeve II (33). The outer ring of the bearing sleeve II (33) is fixedly connected to the inner ring of the electromagnetic moving component II (32) and the inner ring of the elastic plate II respectively. The inner ring of the electromagnetic static component II (31) is sleeved on the outer ring of the electromagnetic moving component II (32), and there is a gap between the electromagnetic static component II (31) and the electromagnetic moving component II (32). The outer ring of the electromagnetic static component II (31) and the outer ring of the elastic plate are fixedly connected to the spindle housing. The elastic plate II is located below the electromagnetic moving component II (32) and the electromagnetic static component II (31). A bearing cover II (27) is provided below the tapered roller bearing II (30), and a sensor II (26) is provided between the bottom end surface of the outer ring of the tapered roller bearing II (30) and the bearing cover II (27). A disc spring (28) is provided at the bottom of the tapered roller bearing II (30). One end of the disc spring (28) is connected to the bottom surface of the inner ring of the tapered roller bearing II (30), and the other end of the disc spring (28) is tightly attached to the shoulder of the spindle (6). The first sensor (12) and the second sensor (26) are both connected to the control system.

2. The spindle system with adaptive stiffness for a numerically controlled machine tool according to claim 1, characterized in that: A spacer one (11) is provided between the first tapered roller bearing (16) and the lower support bearing, and a retaining ring one (7) is provided at the bottom of the inner ring of the lower support bearing. Both the spacer one (11) and the retaining ring one (7) are sleeved on the outer wall of the spindle (6). The inner ring of the lower support bearing is fastened through the spacer one (11) and the retaining ring one (7). A retaining ring two (22) is provided at the top of the first tapered roller bearing (16), and the retaining ring two (22) is sleeved on the outer wall of the spindle (6). The inner ring of the first tapered roller bearing (16) is fastened through the retaining ring two (22) and the spacer one (11); The top of the bearing sleeve one (13) is connected to a bearing cover one (21). The inner ring side of the bearing cover one (21) is located at the bottom end of the outer ring of the first tapered roller bearing (16). The outer ring of the first tapered roller bearing (16) is fastened through the inner ring side of the bearing cover one (21) and the bearing sleeve one (13). The outer ring side of the bearing cover one (21) is located at the top end of the inner ring of the first elastic plate member. The inner ring side of the first elastic plate member is fastened through the bearing cover one (21) and the bearing sleeve one (13); A spacer two (34) is provided between the second tapered roller bearing (30) and the upper support bearing. The spacer two (34) is sleeved on the outer wall of the spindle (6). The top end of the spacer two (34) is in close contact with the bottom end face of the inner ring of the upper support bearing. The top end of the inner ring of the second tapered roller bearing (30) is in close contact with the bottom end of the spacer two (34) under the elastic action of the disc spring (28). One end of the inner ring of the bearing sleeve two (33) extends to the top end face of the outer ring of the second tapered roller bearing (30). The inner ring of the second tapered roller bearing (30) is fastened through the bearing cover two (27) and the extended end of the inner ring of the bearing sleeve two (33); The outer ring side of the bearing cover two (21) is located at the top end of the inner ring of the second elastic plate member. The inner ring side of the second elastic plate member is fastened through the bearing cover two (21) and the bearing sleeve two (13).

3. The spindle system with adaptive stiffness for a numerically controlled machine tool according to claim 1 or 2, characterized in that: The first elastic plate member includes elastic web plates one (18) and first spacers. There are multiple elastic web plates one (18). The multiple elastic web plates one (18) are arranged at intervals through the first spacers. The first spacers include inner spacers one (19) and outer spacers one (17). The inner spacers one (19) are located on the inner ring side of the elastic web plates one (18), and the outer spacers one (17) are located on the outer ring side of the elastic web plates one (18); The second elastic plate member includes elastic web plates two (29) and second spacers. There are multiple elastic web plates two (29). The multiple elastic web plates two (29) are arranged at intervals through the second spacers. The second spacers include inner spacers two (40) and outer spacers two (41). The inner spacers two (40) are located on the inner ring side of the elastic web plates two (29), and the outer spacers two (41) are located on the outer ring side of the elastic web plates two (29).

4. The spindle system with adaptive stiffness for a numerically controlled machine tool according to claim 3, characterized in that: Both the first elastic web (18) and the second elastic web (29) are provided with long slots and drilled holes.

5. A stiffness adaptive spindle system for a numerically controlled machine tool according to claim 4, wherein: A plurality of said long slots and drilled holes are provided. The length direction of the long slots is arranged along the radial direction of the first elastic web (18). The long slots and the drilled holes are arranged in a distribution form of long slot - drilled hole - long slot along the circumferential direction of the first elastic web (18). There are two drilled holes between two adjacent long slots, and the two drilled holes are arranged in sequence along the radial direction of the first elastic web (18). The structure of the second elastic web (29) is the same as that of the first elastic web (18).

6. A spindle system for a numerically controlled machine tool with stiffness adaptability according to claim 1, wherein: The spindle housing includes a spindle housing (1), a spindle upper cover (39), a spindle lower cover (4), an upper bearing end cover (37) and a lower bearing end cover (5). The spindle upper cover (39) and the spindle lower cover (4) are respectively installed at the upper end and the lower end of the spindle housing (1). The first electromagnetic static component (14) and the outer ring of the support bearing are both connected to the spindle lower cover (4). An outer pressure ring one (20) is provided at the bottom end of the outer ring of the first elastic plate member. The outer ring of the first elastic plate member is fastened to the spindle lower cover (4) through the outer pressure ring one (20). The second electromagnetic static component (31) and the outer ring of the support bearing are both connected to the spindle upper cover (39). An outer pressure ring two (42) is provided at the bottom end of the outer ring of the second elastic plate member. The outer ring of the second elastic plate member is fastened to the spindle upper cover (39) through the outer pressure ring two (42); The upper bearing end cover (37) is installed at the top of the spindle upper cover (39), and the lower bearing end cover (5) is installed at the bottom of the spindle lower cover (4). The outer ring of the upper support bearing is fastened to the spindle upper cover (39) through the upper bearing end cover (37), and the outer ring of the lower support bearing is fastened to the spindle lower cover (4) through the lower bearing end cover (5).

7. A spindle system for a numerically controlled machine tool with stiffness adaptability according to claim 1, wherein: The lower support bearing of the basic spindle unit includes a bearing one (8), a bearing two (9) and a bearing three (10) which are sequentially attached from bottom to top. The upper support bearing includes a bearing four (35), a bearing five (36) and a bearing six (38) which are sequentially attached from bottom to top; The support bearings one (8), two (9) and three (10) are angular contact bearings. The bearings one (8) and two (9) have openings downward, and the bearing three (10) has an opening upward. The bearings one (8), two (9) and three (10) form a preloaded bearing assembly; The support bearings four (35), five (36) and six (38) are angular contact bearings. The bearings four (35) and five (36) have openings downward, and the bearing six (38) has an opening upward. The bearings four (35), five (36) and six (38) form a preloaded bearing assembly.

8. A spindle system for a numerically controlled machine tool with stiffness adaptability according to claim 1, wherein: The power unit includes a stator assembly (2), a rotor assembly (3), a lower sleeve (23), an upper sleeve (24) and a nut (25). The lower sleeve (23) and the upper sleeve (24) are sleeved on the outer wall of the middle position of the main shaft (6). The rotor assembly (3) is sleeved on the outer walls of the lower sleeve (23) and the upper sleeve (24). The inner ring of the rotor assembly (3) is fastened by the lower sleeve (23) and the upper sleeve (24). The stator assembly (2) is sleeved on the outer ring side of the rotor assembly (3), and the outer ring of the stator assembly (2) is fixedly connected to the inner wall of the main shaft housing.

9. A spindle system with self - adaptive stiffness for a numerically controlled machine tool according to claim 1, characterized in that: the control system includes a numerical control system and a built - in control module connected to the numerical control system. Both the first sensor (12) and the second sensor (26) include a force sensor and a displacement sensor. A torque sensor, a temperature sensor and a vibration frequency sensor are also installed in the main shaft housing. The control system is respectively connected to the torque sensor, the temperature sensor and the vibration frequency sensor.

10. A spindle system with self - adaptive stiffness for a numerically controlled machine tool according to claim 9, characterized in that: the control method has an adaptive control ability. The numerical control system and the built - in control module cooperate to calculate the information collected in real time by the force, torque, displacement, temperature, and vibration frequency sensors, the information of the part processing preview program, and a large amount of empirical data stored in the machine tool, and perform closed - loop control on the first electromagnetic static component (14), the first electromagnetic moving component (15), the second electromagnetic static component (31) and the second electromagnetic moving component (32) to realize the self - adaptive transformation of the stiffness of the spindle system.

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