Ball screw

Abstract

The utility model provides a ball screw. The ball screw comprises a screw assembly, a driving motor and a liquid cooling machine, the lead screw assembly comprises a lead screw and a lead screw nut rotationally connected to the outer side of the lead screw in a sleeving mode, and a lead screw through hole is formed in the lead screw in the axis direction. The driving motor comprises a motor rotating shaft, the motor rotating shaft penetrates through the driving motor, and a rotating shaft through hole is formed in the motor rotating shaft in the axis direction; the screw rod is in sealed connection with the rotating shaft of the motor; the screw rod through hole is communicated with the rotating shaft through hole; and the liquid cooling machine is used for enabling cooling liquid to flow through the screw rod through hole and the rotating shaft through hole. The liquid cooling machine can enable cooling liquid to flow through the lead screw through hole and the rotating shaft through hole to take away heat generated by high-speed rotation of the motor and heat generated by friction between the lead screw nut and the lead screw, so that the lead screw is kept in a constant-temperature state. The influence of thermal expansion and cold contraction of the lead screw on the machining precision of the numerical control machine tool is reduced.

Description

Technical Field

[0001] The utility model relates to the field of mechanical transmission, in particular to a ball screw. Background Art

[0002] The screw is an ideal product for converting rotary motion into linear motion, or converting linear motion into rotary motion. The screw is the most commonly used transmission element in tool machinery and precision machinery. Its main function is to convert rotary motion into linear motion, or torque into axial repetitive force, while having the characteristics of high precision, reversibility and high efficiency. Due to its small friction resistance, the screw is widely used in various industrial equipment and precision instruments.

[0003] The screw rod is a key transmission and positioning component of CNC machine tools. It belongs to the category of slender shaft parts. Due to the frictional heat generated during movement and the influence of factors such as the surrounding heat source during use, it is easy to produce thermal expansion and deformation, which will cause the precision of CNC equipment to decrease. When the screw rod expands and contracts due to heat and cold, if no corresponding treatment measures are taken, it may have an adverse effect on the mechanical equipment where it is located, and the processing accuracy of the equipment will be affected. It will directly affect the accuracy and stability of the mechanical equipment, and in severe cases, it may even cause the equipment to not work properly.

[0004] Commonly used methods for processing screw hot extension include the following:

[0005] 1. Use temperature compensation structure

[0006] Temperature compensation structure refers to adding some structures and sensing devices to mechanical equipment to monitor temperature changes and then use complex simulation calculations to compensate for the effects of temperature changes. The design principle of this structure is to minimize the thermal effect on the screw rod, thereby reducing the impact on the accuracy of the machine tool caused by the thermal extension of the screw rod. The disadvantage of this method is that the cost is too high. A set of thermal compensation equipment usually costs tens of thousands to hundreds of thousands.

[0007] 2. Environmental Control

[0008] Controlling the temperature in the environment where the mechanical equipment is located is an effective treatment method. For example, in a constant temperature workshop, by controlling the ambient temperature of the workshop, the thermal expansion of the screw can be reduced, thereby reducing the impact of the thermal extension of the screw. This method is usually suitable for large enterprises, and the cost of construction for small private enterprises is too high. Moreover, even in a constant temperature workshop, it is impossible to avoid the frictional thermal deformation of the screw during the transmission process.

[0009] 3. Pre-stretching of screw rod

[0010] Screw pre-stretching is a common practice in the current CNC machine tool industry. It is to calculate the thermal stress of elongation generated in this temperature rise based on the temperature increase of the screw when it is working, and then pre-stretch the screw to produce prestress. The size of this prestress is roughly equal to the stress of thermal elongation, but the direction is opposite. When the screw is working, the thermal stress of elongation generated after the temperature rise is offset by the prestress. In fact, the screw does not elongate at this time, so the original accuracy is maintained. However, this increased temperature cannot exceed the original design temperature. If it exceeds the design temperature, the prestress cannot completely offset the thermal elongation stress, and the screw will produce elongation error. This is very difficult to implement. The amount of pre-stretching is obtained by experience and cannot be unified. That is, the same stretching data acts on the same type of mechanical equipment, but the accuracy results are inconsistent. Utility Model Content

[0011] In order to solve the above technical problems, the utility model provides a ball screw, which can keep the screw at a constant temperature and reduce the influence of thermal expansion and contraction of the screw on the screw precision.

[0012] The specific technical solution is as follows: a ball screw, including a screw assembly, a drive motor and a liquid cooler;

[0013] The screw assembly comprises a screw and a screw nut rotatably sleeved on the outside of the screw, and the screw is provided with a screw through hole along the axial direction;

[0014] The driving motor comprises a motor shaft, the motor shaft passes through the driving motor, and the motor shaft is provided with a shaft through hole along the axial direction;

[0015] The screw rod is sealed and connected to the motor shaft, and the screw rod through hole is connected to the shaft through hole;

[0016] The liquid cooler is used to allow the cooling liquid to flow through the screw rod through hole and the shaft through hole.

[0017] Through the above technical solution, the liquid cooler can make the coolant flow through the screw rod through hole and the shaft through hole, taking away the heat generated by the high-speed rotation of the motor and the heat generated by the friction between the screw nut and the screw rod, so that the screw rod can maintain a constant temperature state, thereby reducing the influence of the thermal expansion and contraction of the screw rod on the processing accuracy of the CNC machine tool.

[0018] Preferably, the screw rod is connected to the motor shaft through a coupling, the coupling is provided with a through hole, the through hole is respectively connected to the screw rod through hole and the shaft through hole, a first sealing ring is provided between the coupling and the screw rod, and a second sealing ring is provided between the coupling and the motor shaft.

[0019] Through the above technical solution, a through hole is provided on the coupling, which can realize transmission between the motor shaft and the screw rod, and at the same time, the screw rod through hole and the shaft through hole are connected in series, so that the coolant can pass through the screw rod through hole and the shaft through hole in sequence, thereby realizing cooling of the motor shaft and the screw rod. The first sealing ring and the second sealing ring are provided to prevent the coolant from leaking at the coupling.

[0020] Preferably, one end of the screw rod is connected to the first rotary joint, and the other end is connected to one end of the motor shaft, the other end of the motor shaft is connected to the second rotary joint, and the first rotary joint and the second rotary joint are respectively connected to the liquid cooler.

[0021] Through the above technical solution, the first rotary joint and the second rotary joint can adopt existing finished products on the market without special design, and the flow rate of the coolant during operation can be guaranteed.

[0022] Preferably, the driving motor comprises a rotary encoder, and the rotary encoder is sleeved on the motor shaft.

[0023] Through the above technical solution, the motor shaft can penetrate the drive motor while ensuring the operating accuracy of the drive motor.

[0024] The beneficial effects of the utility model are:

[0025] 1. Coolant is passed through the screw hole to achieve constant temperature cooling of the screw;

[0026] 2. The coolant in the motor shaft can achieve constant temperature cooling of the drive motor; BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the technical solutions of the embodiments of the present utility model, the following briefly introduces the drawings required for the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present utility model. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative labor. Among them:

[0028] Figure 1 This is a structural schematic diagram of Example 1;

[0029] Figure 2 for Figure 1 AA section view;

[0030] Figure 3 It is a stereogram of embodiment 1;

[0031] Figure 4 It is a schematic diagram of the coupling structure;

[0032] 1. Screw, 11. Screw nut, 12. Screw through hole, 13. First rotary joint, 2. Drive motor, 21. Motor shaft, 22. Shaft through hole, 23. Second rotary joint, 24. Rotary encoder, 3. Coupling, 31. Through hole, 32. First sealing ring, 33. Second sealing ring. DETAILED DESCRIPTION

[0033] In order to make the above-mentioned purposes, features and advantages of the utility model more obvious and easy to understand, the specific implementation methods of the utility model are described in detail below in conjunction with the drawings of the specification. In the following description, many specific details are set forth to facilitate a full understanding of the utility model, but the utility model can also be implemented in other ways different from those described herein, and those skilled in the art can make similar generalizations without violating the connotation of the utility model, so the utility model is not limited by the specific embodiments disclosed below.

[0034] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure or characteristic that may be included in at least one implementation of the present invention. The term "in one embodiment" that appears in different places in this specification does not necessarily refer to the same embodiment, nor does it refer to a separate or selective embodiment that is mutually exclusive with other embodiments.

[0035] Example 1

[0036] like Figure 1-4 As shown, a ball screw includes a screw assembly (a ball screw is selected in this embodiment), a drive motor 2 (a servo motor is selected in this embodiment) and a liquid cooler (the original liquid cooler of the CNC machine tool is used in this embodiment);

[0037] The screw assembly includes a screw 1 and a screw nut 11 rotatably sleeved on the outside of the screw. The screw 1 is fixed to the machine tool through a support bearing 14. The screw 1 is provided with a screw through hole 12 along the axial direction. The drive motor 2 includes a motor shaft 21, which passes through the drive motor 2. The motor shaft 21 is provided with a shaft through hole 22 along the axial direction.

[0038] One end of the screw rod 1 is connected to the first rotary joint 13, and the other end is connected to one end of the motor shaft 21 through the coupling 3. The other end of the motor shaft 21 is connected to the second rotary joint 23. The first rotary joint 13 and the second rotary joint 23 are respectively connected to the liquid cooler.

[0039] The coupling 3 is provided with a through hole 31 , which is respectively connected with the screw through hole 11 and the shaft through hole 22 . A first sealing ring 32 is provided between the coupling 3 and the screw 1 , and a second sealing ring 33 is provided between the coupling 3 and the motor shaft 21 .

[0040] The motor 2 includes a rotary encoder 24 , and the rotary encoder 24 is hollow and sleeved on the motor shaft 21 .

[0041] Basic principle: In the transmission parts of machine tools, it is not only the friction of the screw guide rail that heats up. There is also the heat of the servo motor and the heat of the bearings at both ends. The current design solutions on the market only solve the cooling and heating of part of the screw, but cannot solve the heat generated by the servo motor, which is the largest heat source. The heat of the servo motor will be transferred through the shaft, especially when running at high speed. The temperature of the servo motor is basically over 40 degrees. If the servo motor is in a sealed environment, the temperature will be higher, even reaching 5-60 degrees.

[0042] Without internal cooling, the bearing will generate about 0.01-0.015mm thermal expansion due to frictional heat when rotating at 3000 rpm for one hour. Therefore, the thermal expansion of the support bearings at both ends must also be dealt with.

[0043] The present application provides a motor with a shaft through hole, the shaft of the motor runs through the entire motor, and the encoder 23 is hollow and sleeved on the motor shaft 21. The coolant can pass through the motor shaft 21 to take away the heat generated by the motor operation, thereby reducing the influence of the motor heat on the screw rod accuracy.

[0044] The heat generated by the friction between the high-speed rotation of the screw and the supporting bearing is transferred to the hollow screw through the inner diameter of the bearing and completely removed by the coolant (cooling oil is used in this embodiment). At a high-speed rotation of 3000 rpm for one hour, the thermal elongation is about 0.002 mm.

[0045] At the same time, a sealed coupling is provided, in which a through hole is provided for the circulation of coolant, and the coupling is sealed by a first sealing ring 32 and a second sealing ring 33 to prevent leakage of coolant. In this embodiment, the first sealing ring 32 and the second sealing ring 33 are both O-rings. After the through hole 31 is connected to the screw rod through hole 11 through the coupling, the screw rod and the motor are connected in series, so that the coolant can be directly supplied.

[0046] Rotary joints are set at the coolant inlet and recovery points at both ends. The rotation speed can give full play to the high-speed rotation of the servo motor without affecting the flow and pressure of the cooling oil. It is measured that when the machine tool runs at a moving speed of 30M (servo motor 3000 revolutions), the flow and pressure of the cooling oil are not affected at all. Because the pressure is high and the flow is large, the heat is taken away quickly.

[0047] It should be noted that the above embodiments are only used to illustrate the technical solution of the utility model rather than to limit it. Although the utility model has been described in detail with reference to the preferred embodiments, ordinary technicians in the field should understand that the technical solution of the utility model can be modified or replaced by equivalents without departing from the spirit and scope of the technical solution of the utility model, which should be included in the scope of the claims of the utility model.

Claims

1. A ball screw, characterized in that: It comprises a screw assembly, a drive motor (2) and a liquid cooler; The screw assembly comprises a screw (1) and a screw nut (11) rotatably sleeved on the outside of the screw, the screw (1) is fixed to the machine tool via a support bearing, and the screw (1) is provided with a screw through hole (12) along the axial direction; The driving motor (2) comprises a motor shaft (21), the motor shaft (21) passes through the driving motor (2), and the motor shaft (21) is provided with a shaft through hole (22) along the axial direction; The screw rod (1) is sealedly connected to the motor shaft (21), and the screw rod through hole (12) is connected to the shaft through hole (22); The liquid cooler is used to allow cooling liquid to flow through the screw rod through hole (12) and the rotating shaft through hole (22).

2. A ball screw according to claim 1, characterized in that: The screw rod (1) is connected to the motor shaft (21) via a coupling (3); a through hole (31) is provided on the coupling (3); the through hole (31) is respectively connected to the screw rod through hole (12) and the shaft through hole (22); a first sealing ring (32) is provided between the coupling (3) and the screw rod (1); and a second sealing ring (33) is provided between the coupling (3) and the motor shaft (21).

3. A ball screw according to claim 1, characterized in that: One end of the screw rod (1) is connected to the first rotary joint (13), and the other end is connected to one end of the motor shaft (21). The other end of the motor shaft (21) is connected to the second rotary joint (23). The first rotary joint (13) and the second rotary joint (23) are respectively connected to a liquid cooler.

4. A ball screw according to claim 1, characterized in that: The driving motor (2) is a servo motor, and the servo motor comprises a rotary encoder (24). The rotary encoder (24) is sleeved on the motor shaft (21).

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