A preload control device for high-speed spindle bearings and its CNC machine tool

Abstract

This invention discloses a preload control device for a high-speed spindle bearing and its CNC machine tool. In this invention, a hydraulic cylinder unit is installed on the outer ring side of the bearing. When the CNC machine tool system outputs a command to control the spindle speed, it simultaneously outputs a hydraulic control command to the controller. After receiving the control command, the controller controls the hydraulic control unit to operate via a cable. The hydraulic control unit adjusts the thrust of the hydraulic cylinder unit according to the control command transmitted from the controller. This invention applies preload to the outer ring of the bearing by setting up a hydraulically controlled hydraulic cylinder unit and controls the thrust of the hydraulic cylinder unit through the hydraulic control unit. The CNC machine tool system adjusts the bearing preload according to the spindle speed, thus achieving an optimal balance between bearing heat generation, spindle system rigidity, and bearing life under different spindle speed conditions. This provides better dynamic performance for the spindle and significantly extends bearing life.

Description

Technical Field

[0001] This invention belongs to the field of CNC machine tool technology, and in particular relates to a preload control device for a high-speed spindle bearing and a CNC machine tool thereof. Background Technology

[0002] The manufacturing and development of CNC machine tools is one of the important indicators for measuring a country's industrial level. Modern CNC machine tools are increasingly developing towards higher speeds, higher feed rates, higher accelerations, and higher precision. Among these, the design, development, and practical application of high-speed electric spindles have become key issues. In the design of high-speed electric spindle units, the preload design of high-speed precision rolling bearings is related to the accuracy and rigidity of the bearings, and has a significant impact on the dynamic characteristics of the high-speed precision CNC machine tool spindle, thus affecting the smoothness of the entire system operation.

[0003] To improve the rigidity and radial and axial accuracy of CNC machine tool spindle systems, and to prevent abnormal noises caused by axial vibration and resonance, a certain preload is usually applied to the spindle bearings during design and installation. Currently, there are two main preload design methods for spindle bearings: positioning preload and constant pressure preload. Generally, positioning preload is used for low-to-medium speed spindle bearings, while constant pressure preload is used for high-speed spindle bearings. Under positioning preload, the heat generated at high spindle speeds causes the spindle to extend and retract. However, the change in spring load caused by spindle extension and retraction is extremely small. Therefore, theoretically, the constant pressure preload is considered to remain constant at different speeds, representing a constant value.

[0004] Therefore, constant-pressure preload high-speed spindle bearings maintain a constant preload under both low-speed, high-torque and high-speed, low-torque conditions. However, in the low-speed range of the spindle, a larger preload is desired to achieve systemic stiffness, reduce systemic vibration, and improve bearing life; conversely, in the high-speed range of the spindle, a smaller preload is desired to reduce bearing heat generation, reduce frictional torque, and improve bearing fatigue life. To achieve these goals and overcome the shortcomings of constant-pressure preload, this application proposes a method for controllable preload of high-speed spindle bearings, based on market demand and application perspectives, to achieve preload that varies with spindle speed. This not only promises high-quality dynamic performance but also significantly extends bearing life. Summary of the Invention

[0005] The purpose of this invention is to provide a preload control device for high-speed spindle bearings and a CNC machine tool thereof. By setting up a hydraulic control hydraulic cylinder unit to apply preload to the outer ring of the bearing, and by controlling the thrust of the hydraulic cylinder unit through a hydraulic control unit, the CNC machine tool system adjusts the preload of the bearing according to the spindle speed. This ensures that the bearing heat generation, the rigidity of the spindle system, and the bearing life are in an optimal balance under different spindle speed conditions, improving the dynamic performance of the spindle and significantly extending the bearing life.

[0006] To solve the above-mentioned technical problems, the present invention is achieved through the following technical solution:

[0007] This invention relates to a preload control device for a high-speed spindle bearing, comprising an actuator, which includes a hydraulic cylinder unit for applying thrust to the bearing; the hydraulic cylinder unit is mounted on the outer ring side of the bearing; a CNC unit for controlling the operation of the device, the CNC unit including a CNC machine tool system and a controller; the CNC machine tool system outputs a spindle speed control command and simultaneously outputs a hydraulic control command to the controller; the controller receives the control command and controls the operation of the hydraulic control unit via a cable; the hydraulic control unit drives the actuator, and adjusts the thrust of the hydraulic cylinder unit according to the control command transmitted from the controller; the hydraulic control unit includes a variable hydraulic pump group, an oil filter unit, a pilot-operated pressure reducing valve, a pilot-operated relief valve, a hydraulically controlled check valve, and a CNC relief valve; the input end of the variable hydraulic pump group is connected to an oil tank, and the variable hydraulic pump group... The output hydraulic power source enters the pilot-operated pressure reducing valve through the oil filter unit; after the pilot-operated pressure reducing valve reduces the pressure of the hydraulic power source, it enters the hydraulic cylinder unit through the hydraulically controlled check valve to generate thrust; the hydraulically controlled check valve is also connected to the oil inlet of the pilot-operated relief valve and the oil tank respectively, and the oil outlet of the pilot-operated relief valve is connected to the oil tank to recover hydraulic oil; the oil inlet of the CNC relief valve is connected to the oil outlet of the oil filter unit through the speed regulating valve, and the oil inlet of the CNC relief valve is also connected to the hydraulic control port of the pilot-operated pressure reducing valve and the pilot-operated relief valve respectively; the oil outlet of the CNC relief valve is connected to the oil tank through the check valve; the control terminal of the CNC relief valve is connected to the controller, and the controller sends pulse commands to the stepper motor in the CNC relief valve and controls and changes the hydraulic value at the oil inlet of the CNC relief valve, thereby controlling and changing the pressure reduction setting value of the pilot-operated pressure reducing valve and the relief setting value of the pilot-operated relief valve.

[0008] Furthermore, the bearing is axially positioned and fixed to the main shaft by anti-loosening washers and locking nuts; the bearing is a pair, and the two bearings are assembled on the main shaft in a back-to-back combination.

[0009] Furthermore, the inner rings of the two bearings are positioned together by an inner positioning bushing; the hydraulic cylinder unit is installed outside the inner positioning bushing to position the outer ring of the bearing.

[0010] Furthermore, a throttle valve is installed at the pilot hydraulic control port of both the pilot-operated pressure reducing valve and the pilot-operated relief valve.

[0011] Furthermore, a pressure relay and a pressure gauge are installed at the oil outlet of the hydraulic control check valve, and the pressure relay is used to control the power supply to the hydraulic control unit.

[0012] Furthermore, the CNC machine tool system interacts with the controller through a signal input / output module, which uses an I / O port.

[0013] Furthermore, the controller is also connected to a 100V AC power supply and a 24V DC power supply; the 100V AC power supply is used to power the controller; and the 24V DC power supply is used to power the stepper motor in the CNC overflow valve.

[0014] A CNC machine tool, wherein the control device is applied.

[0015] The present invention has the following beneficial effects:

[0016] This invention applies preload to the outer ring of the bearing by setting up a hydraulically controlled hydraulic cylinder unit, and controls the thrust of the hydraulic cylinder unit through a hydraulic control unit. The CNC machine tool system adjusts the preload of the bearing according to the spindle speed. This ensures that the bearing heat generation, the rigidity of the spindle system, and the bearing life are in an optimal balance under different spindle speed conditions, improving the dynamic performance of the spindle and significantly extending the bearing life.

[0017] Of course, any product implementing this invention does not necessarily need to achieve all of the advantages described above at the same time. Attached Figure Description

[0018] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 This is a schematic diagram of a preload control device for a high-speed spindle bearing.

[0020] Figure 2 A schematic diagram of the main spindle and bearings;

[0021] Figure 3This is a system block diagram of the hydraulic control unit;

[0022] Figure 4 This is a system block diagram of a preload control device for a high-speed spindle bearing;

[0023] Figure 5 A schematic diagram of the structure of a high-speed electric spindle unit for a CNC machine tool equipped with a preload control device;

[0024] Figure 6 for Figure 5 A schematic diagram of the hydraulic cylinder at point I;

[0025] Figure 7 for Figure 6 Cross-sectional view at point AA. Detailed Implementation

[0026] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0027] Please see Figure 1-5 As shown, the present invention is a preload control device for a high-speed spindle bearing, comprising an actuator and a CNC unit for controlling the operation of the device. The actuator includes a hydraulic cylinder unit 100 for applying thrust to the bearing 102. The bearing 102 is a high-speed angular contact ball bearing. The hydraulic cylinder unit 100 is mounted on the outer ring side of the bearing 102. The bearing 102 is axially positioned and integrally fixed on the spindle 101 by anti-loosening washers 104 and locking nuts 105. There is a pair of bearings 102, which are assembled on the spindle 101 in a back-to-back configuration. The inner rings of the two bearings 102 are positioned by an inner positioning bushing 103. The hydraulic cylinder unit 100 is mounted on the outside of the inner positioning bushing 103 to position the outer ring of the bearing 102.

[0028] When the spindle is in the low-speed range, the oil pressure entering the hydraulic cylinder unit 100 is relatively high, which generates a large thrust and acts on the outer ring end face of the bearing. This increases the preload of the bearing and improves the overall rigidity of the spindle system. As the spindle speed increases, the oil pressure entering the hydraulic cylinder unit 100 gradually decreases, which means the thrust acting on the outer ring end face of the bearing gradually decreases. As a result, the preload of the bearing gradually decreases with the decrease in thrust, and the rigidity of the spindle system decreases relatively. However, the heat generation of the bearing can be controlled and kept within a stable range.

[0029] Therefore, the preload of bearing 102 is determined by the thrust generated by hydraulic cylinder unit 100. A greater thrust results in a greater preload, relatively greater spindle stiffness, and a lower spindle speed; conversely, a smaller thrust results in a smaller preload, relatively smaller spindle stiffness, and a higher spindle speed. The source and magnitude of the thrust of hydraulic cylinder unit 100 are controlled by the hydraulic control unit.

[0030] like Figure 3-4 As shown, the CNC unit includes a CNC machine tool system 200 and a controller 202; the CNC machine tool system 200 is a CNC; when the CNC machine tool system 200 outputs a speed control command to the spindle 101 of the CNC machine tool, it simultaneously outputs a hydraulic control command to the controller 202; after receiving the control command, the controller 202 controls the operation of the hydraulic control unit through cable 203; the CNC machine tool system 200 interacts with the controller 202 through a signal input / output module 201, which uses an I / O port; the controller 202 is also connected to a 100V AC power supply and a 24V DC power supply; the 100V AC power supply is used to power the controller 202; the 24V DC power supply is used to power the stepper motor in the CNC relief valve 10;

[0031] The hydraulic control unit is used to drive the actuator to operate. The hydraulic control unit adjusts the thrust of the hydraulic cylinder unit 100 according to the control command transmitted by the controller 202.

[0032] The hydraulic control unit includes a variable hydraulic pump assembly 1, an oil filter unit 2, a pilot-operated pressure reducing valve 3, a pilot-operated relief valve 4, a hydraulically controlled check valve 5, and a numerically controlled relief valve 10. The input end of the variable hydraulic pump assembly 1 is connected to the oil tank 12, and the output end of the variable hydraulic pump assembly 1 outputs a hydraulic power source with a certain pressure, which enters the pilot-operated pressure reducing valve 3 through the oil filter unit 2. The pilot-operated pressure reducing valve 3 reduces the pressure of the hydraulic power source to the required pressure, and then enters the hydraulic cylinder unit 100 through the hydraulically controlled check valve 5, thereby causing the hydraulic cylinder unit 100 to generate a corresponding thrust. The hydraulically controlled check valve 5 is also connected to the oil inlet of the pilot-operated relief valve 4 and the oil tank 12, respectively. The oil outlet of the pilot-operated relief valve 4 is connected to the oil tank 12 to recover hydraulic oil. When the required oil pressure in the hydraulic cylinder unit 100 decreases, the oil inside it passes through the hydraulically controlled check valve 5 and directly enters the pilot-operated relief valve 4, where a portion of the hydraulic pressure is unloaded, thereby reducing the thrust of the hydraulic cylinder unit 100 to the required value.

[0033] The inlet of the CNC relief valve 10 is connected to the outlet of the oil filter unit 2 through the speed control valve 8. The inlet of the CNC relief valve 10 is also connected to the hydraulic control ports of the pilot-operated pressure reducing valve 3 and the pilot-operated relief valve 4, respectively. The outlet of the CNC relief valve 10 is connected to the oil tank 12 through the check valve 11. A throttle valve 9 is installed on the pilot hydraulic control ports of the pilot-operated pressure reducing valve 3 and the pilot-operated relief valve 4. The speed control valve 8 and the fixed throttle valve 9 can ensure the pressure stability of the hydraulic control circuit and avoid oil pressure fluctuations in the hydraulic control circuit.

[0034] The pressure reduction setting value of the pilot-operated hydraulic pressure reducing valve 3 and the overflow setting value of the pilot-operated relief valve 4 are not fixed, but change with the spindle speed. The working principle is as follows: The control terminal of the CNC relief valve 10 is connected to the controller 202. The controller 202 sends pulse commands to the stepper motor in the CNC relief valve 10 and controls and changes the hydraulic pressure value at the oil inlet of the CNC relief valve 10, thereby controlling and changing the pressure value at the pilot hydraulic control port of the pilot-operated hydraulic pressure reducing valve 3 and the pilot-operated relief valve 4, and finally controlling and changing the pressure reduction setting value of the pilot-operated hydraulic pressure reducing valve 3 and the overflow setting value of the pilot-operated relief valve 4.

[0035] The hydraulic check valve 5 is equipped with a pressure relay 6 and a pressure gauge 7 at its outlet. The pressure relay 6 is used to control the power supply of the hydraulic control unit and plays the role of maintaining pressure after power failure. The pressure gauge 7 monitors whether the oil pressure inside the hydraulic cylinder unit 100 is normal.

[0036] A CNC machine tool that uses the aforementioned preload control device.

[0037] Example 1:

[0038] like Figure 5-7 As shown, this embodiment illustrates the bearing preload design for a high-speed electric spindle unit of a CNC machine tool. The spindle bearing of the high-speed electric spindle unit is designed with one end fixed and the other end floating. The fixed end consists of a set of high-speed angular contact ball bearings mounted back-to-back, while the floating end is designed with a single-row cylindrical roller bearing. An inner positioning bushing is installed between the inner rings of the back-to-back angular contact bearings, and a hydraulic cylinder unit for preload control is installed between the outer rings.

[0039] When the spindle operates at low speed, the angular contact ball bearing generates relatively little heat. At this time, the spindle speed signal is input to the hydraulic control unit via the CNC, which then outputs a certain pressure of oil. This oil pressure flows through the oil passages of the electric spindle unit into the hydraulic cylinder body 301 of the preload-controlled hydraulic cylinder unit, pushing the hydraulic cylinder piston 302 to move axially with a certain axial force. Ultimately, this applies force to the outer ring end face of the angular contact ball bearing, increasing the preload and improving the overall rigidity of the spindle system. When the spindle operates at high speed, the angular contact ball bearing generates more heat. At this time, the spindle speed signal is input to the hydraulic control unit via the CNC, which then outputs a certain pressure of oil. This oil pressure is lower than that at low spindle speeds, so a portion of the oil pressure in the hydraulic cylinder body 301 needs to be unloaded until it reaches the required pressure value. During this pressure reduction process, due to the unloading of oil pressure and the thermal expansion of the outer ring of the angular contact bearing, the two pistons 302 of the hydraulic cylinder will undergo a slight displacement towards each other. In this way, the preload of the angular contact ball bearing is reduced to adapt to high-speed operation, the heat generation is stabilized, the overall rigidity of the spindle system is relatively reduced, and the service life of the bearing is improved.

[0040] In the description of this specification, references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0041] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to the specific implementations described. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. The invention is limited only by the claims and their full scope and equivalents.

Claims

1. A preload control device for a high-speed spindle bearing, characterized in that, include An actuator, comprising a hydraulic cylinder unit (100) for applying thrust to a bearing (102); the hydraulic cylinder unit (100) is mounted on the outer ring side of the bearing (102); A numerical control unit for controlling the operation of a control device, the numerical control unit includes a numerical control machine tool system (200) and a controller (202); when the numerical control machine tool system (200) outputs a speed control command for the spindle (101) of the numerical control machine tool, it simultaneously outputs a hydraulic control command to the controller (202); after receiving the control command, the controller (202) controls the operation of the hydraulic control unit through a cable (203); The hydraulic control unit is used to drive the actuator to operate. The hydraulic control unit adjusts the thrust of the hydraulic cylinder unit (100) according to the control command transmitted by the controller (202). The hydraulic control unit includes a variable hydraulic pump group (1), an oil filter unit (2), a pilot-operated pressure reducing valve (3), a pilot-operated relief valve (4), a hydraulically controlled check valve (5), and a numerically controlled relief valve (10). The input end of the variable hydraulic pump group (1) is connected to the oil tank (12). The output end of the variable hydraulic pump group (1) outputs hydraulic power source through the oil filter unit (2) and enters the pilot-operated pressure reducing valve (3). After the pilot-operated pressure reducing valve (3) reduces the pressure of the hydraulic power source, it enters the hydraulic cylinder unit (100) through the hydraulically controlled check valve (5) to generate thrust. The hydraulic control check valve (5) is also connected to the oil inlet of the pilot-operated relief valve (4) and the oil tank (12) respectively. The oil outlet of the pilot-operated relief valve (4) is connected to the oil tank (12) to recover hydraulic oil. The oil inlet of the numerically controlled overflow valve (10) is connected to the oil outlet of the oil filter unit (2) through the speed control valve (8). The oil inlet of the numerically controlled overflow valve (10) is also connected to the hydraulic ports of the pilot-operated pressure reducing valve (3) and the pilot-operated overflow valve (4). The oil outlet of the numerically controlled overflow valve (10) is connected to the oil tank (12) through the check valve (11). The control terminal of the numerical control relief valve (10) is connected to the controller (202). The controller (202) sends pulse commands to the stepper motor in the numerical control relief valve (10) and controls and changes the hydraulic value at the oil inlet of the numerical control relief valve (10), thereby controlling and changing the pressure reduction setting value of the pilot pressure reducing valve (3) and the relief setting value of the pilot relief valve (4). Both the pilot-operated pressure reducing valve (3) and the pilot-operated relief valve (4) are equipped with a throttle valve (9) at their pilot hydraulic control ports; The outlet of the hydraulic control check valve (5) is equipped with a pressure relay (6) and a pressure gauge (7). The pressure relay (6) is used to control the power supply of the hydraulic control unit. The CNC machine tool system (200) interacts with the controller (202) through a signal input / output module (201), and the signal input / output module (201) uses an I / O port; The controller (202) is also connected to a 100V AC power supply and a 24V DC power supply; the 100V AC power supply is used to power the controller (202); the 24V DC power supply is used to power the stepper motor in the numerically controlled overflow valve (10).

2. The preload control device for a high-speed spindle bearing according to claim 1, characterized in that, The bearing (102) is axially positioned and fixed to the main shaft (101) by means of anti-loosening washers (104) and locking nuts (105); The number of bearings (102) is one pair, and the two bearings (102) are assembled on the main shaft (101) in a back-to-back combination.

3. The preload control device for a high-speed spindle bearing according to claim 2, characterized in that, The inner rings of the two bearings (102) are positioned by an inner positioning bushing (103); the hydraulic cylinder unit (100) is installed on the outside of the inner positioning bushing (103) to position the outer ring of the bearing (102).

4. A CNC machine tool, characterized in that, The CNC machine tool uses the control device described in any one of claims 1-3.

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