Machining center lead screw with cooling structure

Abstract

The invention provides a machining center lead screw with a cooling structure, and relates to the technical field of lead screws, the machining center lead screw comprises a driving assembly and a hollow lead screw, an axial through cooling hole channel is formed in the hollow lead screw, and the driving end of the hollow lead screw is connected with an output shaft of a motor through a coupler and is supported by a first bearing assembly installed in a motor base; the rotary sealing unit is arranged in the oil cooling sleeve and used for sealing a gap between the outer circle of the tail end of the hollow lead screw and an inner hole of the oil cooling sleeve, and the liquid inlet and the liquid outlet are formed in a gland of the oil cooling sleeve. Starting from the internal structure of the lead screw, active and direct management of a heat source of the lead screw is achieved through the innovative internal cooling circulation design, and the core problems that thermal error control of a traditional solid lead screw is passive and low in efficiency are effectively solved.

Description

Technical Field

[0001] This invention relates to the field of lead screw technology, and more particularly to a machining center lead screw with a cooling structure. Background Technology

[0002] In CNC machine tools, especially machining centers, the ball screw pair is the core transmission and positioning component of the linear feed system. Its accuracy, rigidity and thermal stability directly determine the positioning accuracy, repeatability and quality of the machine tool and the workpiece. With the increasing demands for processing efficiency and precision in the manufacturing industry, machine tools are developing towards high speed, high load, and high precision. However, when the lead screw operates at high speed and bears a load, the friction between the balls and the lead screw raceway, and between the balls and the nut, generates a large amount of heat. At the same time, the motor drive and bearing operation also generate additional heat. Since the lead screw is usually made of metal materials such as steel, its inherent thermal expansion characteristics will cause the lead screw to produce significant axial elongation and radial expansion, i.e., thermal deformation. This thermal deformation will bring a series of serious problems: First, the axial thermal elongation of the lead screw will directly translate into the positioning error of the worktable, resulting in machining dimensions exceeding tolerances; second, thermal deformation may change the lead screw's lead accuracy and pitch, affecting the smoothness of motion; third, radial expansion may affect the fit clearance and preload of the lead screw, nut, and bearing, reducing transmission stiffness, and even causing vibration and noise. Therefore, the thermal error of the lead screw has become one of the key bottlenecks restricting the performance improvement of machine tools, especially precision machine tools.

[0003] In existing technologies, the thermal management methods for traditional lead screws with non-hollow (solid) structures are relatively passive and limited: Natural heat dissipation and limited design optimization: It mainly relies on the heat conduction of the lead screw itself, surface air convection and heat dissipation of the surrounding structure. The heat dissipation efficiency is low and the thermal equilibrium time is long. After the machine tool is turned on, it often needs to be "warmed up" for 30 minutes to several hours. Only after the temperature of each component slowly rises and tends to stabilize can the accuracy reach a working state, which seriously affects the equipment utilization rate and production cycle.

[0004] Performance compromises: To avoid excessive thermal deformation, conservative strategies are often necessary in design and use. For example, reducing the preload of the lead screw to reduce frictional heat generation, but this sacrifices the rigidity and dynamic response of the transmission system. Alternatively, strictly limiting the maximum speed of the lead screw and the feed rate of the machine tool directly restricts the improvement of processing efficiency. In essence, speed is sacrificed when pursuing high precision, and precision is difficult to guarantee when pursuing high speed.

[0005] Limitations of software compensation: Post-hoc thermal error software compensation via CNC system is a common auxiliary method. This method requires the pre-establishment of a complex thermal error model, monitoring the temperature of key points through temperature sensors and predicting the amount of deformation for offset compensation. However, this method is a "post-hoc correction", and the compensation accuracy depends on the accuracy of the model and the representativeness of the temperature measurement points. It is difficult to achieve completely real-time and accurate compensation for complex and transient thermal fields, and it cannot fundamentally eliminate the adverse effects of thermal deformation on the mechanical system itself (such as pre-tightened state).

[0006] In summary, traditional solid lead screws and their associated thermal management solutions are insufficient to fundamentally meet the integrated requirements of modern high-performance machining centers for high speed, high precision, high stability, and high equipment utilization. How to actively, in real-time, and efficiently manage heat from the heat source to suppress the temperature rise of the lead screw body has become a key technical problem that urgently needs to be solved in this field. Summary of the Invention

[0007] The purpose of this invention is to overcome the shortcomings of the existing technology. Against this background, this invention proposes an active thermal error control scheme that starts from the internal structure of the lead screw and uses forced circulation coolant for direct cooling.

[0008] To achieve the above objectives, the present invention adopts the following technical solution: A hollow ball screw device with an internal cooling structure for use in machining centers, comprising: The drive assembly includes a motor and a fixed motor mount; A hollow lead screw with an axially penetrating cooling channel inside. The drive end of the hollow lead screw is connected to the output shaft of the motor via a coupling and is supported by a first bearing assembly installed in the motor housing. Tail end seat, the tail end of the hollow screw extends into the tail end seat and is rotatably supported by the second bearing assembly; The coolant circulation assembly includes an oil cooling jacket fixed to the tail end seat, an oil cooling jacket cover fixed to the end of the oil cooling jacket, a rotary sealing unit disposed inside the oil cooling jacket for sealing the gap between the outer circle of the tail end of the hollow screw and the inner hole of the oil cooling jacket, and an inlet and an outlet disposed on the oil cooling jacket cover. A liquid collection cavity is formed between the oil cooling jacket and the tail end of the hollow screw; The liquid inlet is connected to the cooling channel through a guide pipe that extends into the internal cooling channel of the hollow screw; The liquid outlet is connected to the liquid collection chamber.

[0009] Furthermore, the rotary sealing unit includes an oil seal and an elastic retaining ring for axially limiting the oil seal, wherein the inner ring of the oil seal contacts and seals with the outer circular surface of the hollow screw tail end.

[0010] Furthermore, the area on the outer circular surface of the tail end of the hollow screw that contacts the oil seal undergoes local surface hardening treatment.

[0011] Furthermore, the first bearing assembly includes a pair of angular contact bearings, one end of which is limited by a short spacer and the other end is pressed by a front end cap, which is fixed to the thread of the hollow lead screw drive end by a lock nut.

[0012] Furthermore, the second bearing assembly includes two ball bearings, which are axially separated and positioned by long spacers on both sides. One end of the long spacer is close to the shoulder of the hollow lead screw tail end, and the other end of the long spacer is pressed and fixed by another locking nut.

[0013] Furthermore, the end of the tailstock is provided with a rear end cap, and the oil cooling sleeve is fixed to the rear end cap.

[0014] Furthermore, a dust cover is provided inside the tail end seat on the outside of the second bearing assembly, and a gap is left between the dust cover and the hollow lead screw.

[0015] Furthermore, the guide tube is a quick-connect hose, which is connected to the liquid inlet of the oil cooling jacket cap via a quick-connect direct connector.

[0016] Furthermore, quick-connect fittings are installed at the liquid inlet and liquid outlet.

[0017] Furthermore, an O-ring is provided at the mating surface between the oil cooling jacket cover and the oil cooling jacket.

[0018] The beneficial effect of this invention lies in that it directly addresses the three core limitations of traditional solid lead screw thermal management as pointed out in the background art, and provides a fundamental solution, with the specific effects as follows: 1. Achieve proactive, efficient, and real-time heat management to fundamentally suppress temperature rise and thermal deformation: By setting axial cooling channels inside the hollow screw and introducing forced circulation coolant for direct internal cooling, the cooling medium is directed to the core area where heat is generated (the screw body), transforming the traditional passive and slow natural heat dissipation into proactive and efficient internal forced heat exchange. This can quickly remove the frictional and conductive heat generated by the screw during high-speed and high-load operation, significantly reducing its temperature rise rate and steady-state temperature, thereby effectively suppressing the axial elongation and radial expansion (thermal deformation) of the screw from the source.

[0019] 2. Improve equipment utilization and production cycle time, and solve the problem of warm-up waiting time: Since the active cooling system can quickly establish and maintain the temperature stability of the lead screw, the temperature of the key parts of the lead screw can reach equilibrium in a short time after the machine tool is turned on, without the long "warm-up" waiting time of tens of minutes or even hours in the traditional solution; This allows the machine tool to enter the high-precision working state more quickly, greatly improving the utilization rate of the equipment and the response speed of the production line.

[0020] 3. Design compromise between precision, speed, and rigidity unlocks the machine tool's performance potential: Because temperature rise is effectively controlled, designers and users do not need to deliberately reduce the lead screw's preload or limit its operating speed to suppress thermal errors; this invention allows the lead screw to achieve higher rotational speed and feed rate while maintaining a high preload (ensuring transmission rigidity and dynamic response); thus enabling the machine tool to balance high precision, high rigidity, and high speed, breaking the dilemma of forced performance trade-offs in traditional solutions.

[0021] 5. It creates favorable conditions for thermal error compensation and improves the accuracy and stability of the system: Active temperature control makes the temperature field distribution of the lead screw body more uniform, the change more gradual and easier to predict; this greatly simplifies the complexity of the temperature-deformation model that the CNC system relies on when performing thermal error software compensation, and improves the accuracy of the model and the real-time performance and reliability of the compensation; in essence, starting from "suppressing error sources" and complementing "post-event software compensation", a more precise and reliable thermal error control system is jointly constructed.

[0022] In summary, this invention starts with the internal structure of the lead screw and achieves active and direct management of the lead screw heat source through an innovative internal cooling circulation design, effectively solving the core problem of passive and inefficient thermal error control in traditional solid lead screws. Attached Figure Description

[0023] Figure 1 A schematic diagram of the overall mounting structure of the machining center lead screw with a cooling structure provided by the present invention; Figure 2 A schematic diagram of the overall disassembled structure of the machining center lead screw with a cooling structure provided by the present invention; Figure 3 A schematic diagram of the overall anatomical structure of a machining center lead screw with a cooling structure provided by the present invention; Figure 4 A partial structural diagram of a machining center lead screw with a cooling structure provided by the present invention; Figure 5 A schematic diagram of the B-part structure of the machining center lead screw with a cooling structure provided by the present invention; Figure 6 A schematic diagram of a hollow lead screw structure with a cooling structure for a machining center, provided by the present invention.

[0024] Legend: 1. Motor; 2. Coupling; 3. Lock nut; 4. Front end cap; 5. Long spacer; 6. Angular contact bearing; 7. Short spacer; 8. Motor mount; 9. Hollow lead screw; 10. Dust cover; 11. Ball bearing; 12. Tail end seat; 13. Rear end cap; 14. Elastic retaining ring; 15. Oil seal; 16. Oil cooling jacket; 17. Guide tube; 18. O-ring; 19. Quick-connect fitting; 20. Oil cooling jacket cap; 21. Quick-tight connector. Detailed Implementation

[0025] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0026] To facilitate understanding of the present invention, a more comprehensive description of the invention will be provided below with reference to relevant embodiments. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided so that the disclosure of the present invention will be more thorough and complete.

[0027] It should be noted that when an element is referred to as being "fixed to" another element, it can be directly on the other element or there may be an intervening element. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or there may be an intervening element. The terms "vertical," "horizontal," "left," "right," and similar expressions used in this document are for illustrative purposes only.

[0028] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the specification of this invention is for the purpose of describing particular embodiments only and is not intended to limit the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0029] Example 1 like Figure 1-5 As shown, the present invention provides a machining center lead screw with a cooling structure, which realizes both cooling and stable driving functions. The specific structure is as follows: Drive assembly: includes motor 1 and fixed motor mount 8. Motor 1 serves as the power source, providing torque for the operation of the entire lead screw.

[0030] Hollow lead screw 9: It has an axially through cooling channel inside, and this hollow design provides a channel for the flow of coolant; the drive end of the hollow lead screw 9 is connected to the output shaft of the motor 1 through the coupling 2. The coupling 2 plays the role of transmitting torque and allows for a certain installation error; the hollow lead screw 9 is supported by the first bearing assembly installed in the motor base 8 to ensure the stable rotation of the lead screw at the drive end.

[0031] Tail end seat 12: The tail end of the hollow lead screw 9 extends into the tail end seat 12 and is rotated and supported by the second bearing assembly. The tail end seat 12 provides a stable support structure for the tail end of the lead screw.

[0032] Coolant circulation assembly: includes an oil cooling jacket 16 fixed to the end of the tail end seat 12, an oil cooling jacket cover 20 fixed to the end of the oil cooling jacket 16, a rotary sealing unit disposed inside the oil cooling jacket 16 to seal the gap between the outer circle of the tail end of the hollow screw 9 and the inner hole of the oil cooling jacket 16, and an inlet and an outlet disposed on the oil cooling jacket cover 20; a liquid collecting chamber is formed between the oil cooling jacket 16 and the tail end of the hollow screw 9 for collecting coolant; the inlet is connected to the cooling channel through a guide pipe 17 extending into the internal cooling channel of the hollow screw 9, and the outlet is connected to the liquid collecting chamber, thereby forming a complete coolant circulation path.

[0033] The rotary sealing unit includes an oil seal 15 and an elastic retaining ring 14 for axially limiting the oil seal 15. The inner ring of the oil seal 15 contacts and seals with the outer circular surface of the end of the hollow screw 9 to prevent coolant leakage. The area of ​​the outer circular surface of the end of the hollow screw 9 that contacts the oil seal 15 is locally surface hardened by a local high-frequency quenching process to increase the surface hardness of the screw, improve wear resistance, and extend the service life of the oil seal.

[0034] The first bearing assembly includes a pair of angular contact bearings 6, which can withstand combined axial and radial loads. One end of the angular contact bearing 6 is limited by a short spacer 7, and the other end is pressed by a front end cap 4. The front end cap 4 is fixed to the thread on the drive end of the hollow screw 9 by a lock nut 3, ensuring that the angular contact bearing 6 is firmly installed and stably supports the drive end of the hollow screw 9.

[0035] The second bearing assembly includes two ball bearings 11. The two ball bearings 11 are axially separated and positioned by long spacers 5 on both sides to ensure accurate relative positioning between them. One end of the long spacer 5 is close to the shoulder of the hollow screw 9, and the other end of the long spacer 5 is pressed and fixed by another locking nut 3 to achieve stable support for the tail end of the hollow screw 9.

[0036] Specifically, the tail end seat structure includes: a rear end cap 13 at the end of the tail end seat 12, and an oil cooling sleeve 16 fixed to the rear end cap 13 for easy installation and removal; a dust cover 10 is provided inside the tail end seat 12 on the outside of the second bearing assembly, and a gap is left between the dust cover 10 and the hollow lead screw 9. This small gap can effectively prevent grease on the lead screw from entering the bearing and extend the service life of the bearing.

[0037] It should be noted that the guide tube 17 is a quick-connect hose, which is connected to the inlet of the oil cooling jacket cap 20 through a quick-connect straight connector 19, which facilitates installation and disassembly and improves assembly efficiency; quick-tight connectors 21 are installed at the inlet and outlet to facilitate the entry and exit of coolant; an O-ring 18 is provided at the mating surface between the oil cooling jacket cap 20 and the oil cooling jacket 16 to provide a seal and prevent coolant leakage from the mating surface.

[0038] The workflow and technical parameters for achieving the desired functions are as follows when using a machining center lead screw with a cooling structure: 1) Coolant inflow: The constant temperature coolant (the temperature can be set according to the actual processing requirements, generally controlled at 20-40℃ to ensure good cooling effect and prevent excessive internal stress of the lead screw due to low temperature) flows in from the quick-connect fitting 21 connected to the oil cooling jacket cover 20, and enters the cooling channel inside the lead screw through the quick-connect fitting 19 and quick-connect hose 17; the inner diameter of the quick-connect hose 17 is designed according to the coolant flow requirements, generally selected at 5-10mm, to ensure smooth flow of coolant, and the flow rate can be controlled at 0.5-2L / min to meet the cooling requirements of the lead screw.

[0039] 2) Coolant collection and sealing: The coolant entering the screw will eventually collect in the end cavity of the oil cooling jacket 16; one end of the cavity is sealed by an O-ring 18 to prevent leakage. The O-ring 18 is made of oil-resistant and wear-resistant rubber material to ensure reliable sealing and prevent coolant leakage from affecting the normal operation of the equipment; the other end is limited by the elastic retaining ring 14 to restrict the axial movement of the oil seal 15. The inner ring of the oil seal 15 is locked in the corresponding position at the end of the screw to seal. The oil seal 15 is made of high-performance rubber material, which has good sealing and wear resistance and can effectively prevent coolant from leaking from the end of the screw.

[0040] 3) Coolant discharge: The end cavity of the oil cooling jacket 16 is provided with a threaded hole along the axial direction. The coolant is discharged from the inside of the screw through the locking quick-connect fitting 21. The discharge pressure can be adjusted according to the design requirements of the cooling system, generally controlled at 0.1-0.3MPa, to ensure that the coolant can be discharged smoothly and complete the cooling cycle.

[0041] 4) Power transmission: Motor 1 transmits torque to hollow lead screw 9 through coupling 2. The power of motor 1 is selected according to the load requirements of the machining center, generally 1-5kW, and the speed is 1000-3000r / min. It can rotate together with the parts directly connected to the lead screw to realize the lead screw transmission function of the machining center.

[0042] 5) Advantages of lead screw surface treatment: The surface of the hollow lead screw 9 tail end (where it connects with the oil seal 15) adopts a local high-frequency quenching process to increase the surface hardness of the lead screw, which can reach HRC50-55, improve wear resistance, reduce wear caused by friction with the oil seal 15, and extend the service life of the lead screw and the oil seal.

[0043] 6) Dustproof function: The dust cover 10 at the tail end, through a small gap (the gap is controlled at 0.1-0.3mm), can effectively prevent grease on the screw from entering the bearing, reduce the contamination inside the bearing, extend the service life of the bearing, ensure the normal operation of the bearing, and thus ensure the stability and reliability of the entire screw drive system.

[0044] Through the above workflow and the coordinated work of each component, the machining center lead screw with cooling structure of the present invention can effectively reduce the temperature of the lead screw during operation, improve the service life and machining accuracy of the lead screw, and at the same time ensure the stability and reliability of power transmission.

[0045] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A hollow ball screw device with an internal cooling structure for use in machining centers, characterized in that, include: The drive assembly includes a motor (1) and a fixed motor mount (8); The hollow screw (9) has an axially penetrating cooling channel inside. The drive end of the hollow screw (9) is connected to the output shaft of the motor (1) through a coupling (2) and is supported by a first bearing assembly installed in the motor base (8). Tail end seat (12), the tail end of the hollow screw (9) extends into the tail end seat (12) and is rotated and supported by the second bearing assembly; The coolant circulation assembly includes an oil cooling jacket (16) fixed to the end of the tail end seat (12), an oil cooling jacket cover (20) fixed to the end of the oil cooling jacket (16), a rotary sealing unit disposed in the oil cooling jacket (16) for sealing the gap between the outer circle of the tail end of the hollow screw (9) and the inner hole of the oil cooling jacket (16), and an inlet and an outlet disposed on the oil cooling jacket cover (20); A liquid collection cavity is formed between the oil cooling jacket (16) and the tail end of the hollow screw (9); The liquid inlet is connected to the cooling channel through a guide pipe (17) that extends into the internal cooling channel of the hollow screw (9); The liquid outlet is connected to the liquid collection chamber.

2. The apparatus according to claim 1, characterized in that, The rotary sealing unit includes an oil seal (15) and an elastic retaining ring (14) for axially limiting the oil seal (15). The inner ring of the oil seal (15) contacts and seals with the outer circular surface of the end of the hollow screw (9).

3. The apparatus according to claim 2, characterized in that, The area on the outer circular surface of the tail end of the hollow screw (9) that contacts the oil seal (15) has undergone local surface hardening treatment.

4. The apparatus according to claim 1, characterized in that, The first bearing assembly includes a pair of angular contact bearings (6), one end of which is limited by a short spacer (7) and the other end is pressed by a front end cap (4), which is fixed to the thread of the drive end of the hollow screw (9) by a lock nut (3).

5. The apparatus according to claim 4, characterized in that, The second bearing assembly includes two ball bearings (11), which are axially separated and positioned by long spacers (5) on both sides and on the outside. One end of the long spacer (5) is close to the shoulder of the hollow screw (9), and the other end of the long spacer (5) is pressed and fixed by another locking nut (3).

6. The apparatus according to claim 1, characterized in that, The tail end seat (12) is provided with a rear end cap (13) at its end, and the oil cooling sleeve (16) is fixed on the rear end cap (13).

7. The apparatus according to claim 1, characterized in that, A dust cover (10) is provided inside the tail end seat (12) on the outside of the second bearing assembly, and a gap is left between the dust cover (10) and the hollow screw (9).

8. The apparatus according to claim 1, characterized in that, The guide tube (17) is a quick-connect hose, which is connected to the inlet of the oil cooling jacket cap (20) through a quick-connect direct connector (19).

9. The apparatus according to claim 1, characterized in that, Quick-connect fittings (21) are installed at the inlet and outlet.

10. The apparatus according to claim 1, characterized in that, An O-ring (18) is provided at the mating surface between the oil cooling jacket cover (20) and the oil cooling jacket (16).

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