Electric spindle, numerical control system and machine tool

Abstract

The invention provides an electric spindle, a numerical control system and a machine tool, and belongs to the field of electric spindles. Wherein the motorized spindle comprises a spindle core; the rotor part rotates synchronously with the shaft core; the stator part does not rotate along with the shaft core; a displacement measurement sensor is arranged on the stator part and used for measuring the thermal displacement generated by the spindle core in the operation process of the electric spindle. The displacement measurement sensor is designed to measure the thermal displacement generated by the spindle core in the operation process of the electric spindle, the displacement can be directly converted into the compensation amount and then transmitted to the numerical control system in real time, and the numerical control system is controlled to compensate the thermal displacement of the spindle core. The step of temperature and displacement conversion in the temperature-thermal displacement prediction model is omitted, conversion errors generated in the step are eliminated, and compensation operation can be completed efficiently and precisely.

Description

Technical Field

[0001] The present application relates to the technical field of electric spindles, and in particular to an electric spindle, a numerical control system and a machine tool. Background Art

[0002] The electric spindle is a core component of CNC machine tools. During operation, it generates a lot of heat, causing thermal displacement of the electric spindle, thus affecting the machining accuracy.

[0003] There are currently two major solutions to this problem: thermal error suppression and thermal error compensation. The thermal error suppression method eliminates or reduces possible thermal error sources through reasonable design to improve the manufacturing accuracy of machine tools. This method will significantly increase the cost of machine tool development. The thermal error compensation method uses a combination of control strategies, sensor perception, computer technology and other technologies to analyze the error sources generated during the machining process and feed them back to the control system in real time without improving the machining accuracy of the machine tool itself. It uses closed-loop control to achieve error correction, thereby improving the accuracy of the machined workpiece. This method has become a research hotspot due to its low application cost and good compensation effect.

[0004] Patents CN118192419A and CN118237969A both propose a method of using a temperature sensor to establish a prediction model between temperature and thermal displacement of an electric spindle, thereby performing real-time compensation for thermal displacement of an electric spindle. Thermal displacement compensation of an electric spindle based on a temperature sensor needs to focus on the arrangement of temperature measurement points. Theoretical analysis and experiments are required from multiple aspects such as the heat source distribution, heat propagation, and heat-sensitive parts of the machine tool to obtain the most economical and effective solution. In addition, the constructed prediction model only considers the temperature factor, and does not consider factors such as humidity and vibration in the environment where the machine tool is located. The model is easily affected by the on-site environment, resulting in a large prediction error. Summary of the invention

[0005] The embodiment of the present application provides an electric spindle, a numerical control system and a machine tool. In the embodiment of the present application, a displacement measurement sensor is designed to measure the thermal displacement of the shaft core during the operation of the electric spindle. The displacement can be directly converted into a compensation amount and then transmitted to the numerical control system in real time, so as to control the numerical control system to compensate for the thermal displacement of the shaft core. The step of converting temperature and displacement in the temperature-thermal displacement prediction model is omitted, and the conversion error generated in this step is eliminated, so that the compensation operation can be completed efficiently and accurately.

[0006] Specific:

[0007] A first aspect of an embodiment of the present application provides an electric spindle, comprising:

[0008] Axis core;

[0009] The rotor part that rotates synchronously with the shaft core and the stator part that does not rotate with the shaft core;

[0010] A displacement measuring sensor is provided on the stator part to measure the thermal displacement of the shaft core during the operation of the electric spindle.

[0011] In the above technical solution, the rotor part includes a front dynamic balancing ring, which is fixedly sleeved on the outer periphery of the shaft core so as to be able to rotate synchronously with the shaft core;

[0012] The stator part includes an annular spray flange, which is sleeved on the outer periphery of the shaft core and the front dynamic balance ring, and the annular spray flange, the shaft core and the front dynamic balance ring are all clearance-fitted together;

[0013] A displacement measuring sensor is fixedly arranged on the annular spray flange, and the displacement measuring sensor is used to detect whether the front dynamic balance ring is displaced relative to the annular spray flange in the axial direction of the shaft core.

[0014] In the above technical solution, the shaft core includes a front end having a handle side, and a rear end opposite to the front end;

[0015] The annular spray flange and the front dynamic balancing ring are arranged close to the front end of the shaft core relative to the rear end of the shaft core.

[0016] In the above technical solution, in the axial direction of the shaft core, the annular spray flange has a first annular surface facing one side of the front dynamic balance ring, and the front dynamic balance ring has a second annular surface facing one side of the annular spray flange;

[0017] The first annular surface is provided with a displacement measurement sensor installation groove, the displacement measurement sensor is arranged in the displacement measurement sensor installation groove, and the displacement measurement sensor is used to detect whether the second annular surface is displaced relative to the first annular surface in the axial direction of the shaft core.

[0018] In the above technical solution, the displacement measurement sensor is used to detect and output a displacement parameter value representing the displacement of the front dynamic balancing ring relative to the ring spray flange in the axial direction of the shaft core.

[0019] In the above technical solution, the second ring surface of the front dynamic balance ring is used as the detection surface of the displacement measurement sensor;

[0020] The structural parameters of the displacement measuring sensor are determined according to the size of the second annular surface and the size of the installation groove of the displacement measuring sensor.

[0021] In the above technical solution, the electric spindle also includes a control panel, which is used to convert the parameter value output by the displacement measurement sensor into a pulse signal of the numerical control system, so that the numerical control system equipped with the electric spindle can directly use the pulse signal to adjust the electric spindle axially to compensate for the thermal displacement generated by the shaft core.

[0022] In the above technical solution, the displacement measurement sensor is used to detect and output an inductance signal representing the thermal displacement of the shaft core;

[0023] The control panel is used to determine the output voltage value of the displacement measurement sensor according to the inductance signal, determine the thermal displacement of the shaft core according to the voltage value, and convert the thermal displacement into a pulse signal of the numerical control system.

[0024] In the above technical solution, the electric spindle also includes:

[0025] The electric spindle housing is sleeved on the outer periphery of the stator part and fixedly connected to the stator part;

[0026] A circuit board placement compartment is provided with a control panel, and the circuit board placement compartment is attached to the outer surface of the electric spindle housing;

[0027] A lead-in port is also provided on the annular spray flange serving as the stator part, and an electrical connection line passing through the lead-in port is connected between the control panel and the displacement measurement sensor.

[0028] In the above technical solution, the stator part also includes a gas sealing ring and a front gland fixed on the ring spray flange;

[0029] An air flow channel for exhausting air to the outside of the electric spindle is defined between the air sealing ring, the front pressure cover, the ring spray flange as the stator part and the front dynamic balance ring as the rotor part and the shaft core, and the air flow channel is connected to the installation groove of the displacement measurement sensor.

[0030] In the above technical solution, the above displacement sensor is preferably an eddy current displacement sensor.

[0031] A second aspect of an embodiment of the present application provides a numerical control system, which includes the electric spindle provided by the first aspect of an embodiment of the present application.

[0032] In the above technical solution, the numerical control system includes a z-axis for driving the electric spindle as a whole to move along the axial direction of the shaft core;

[0033] The numerical control system is used to control the z-axis to drive the electric spindle to move according to the pulse signal representing the thermal displacement of the shaft core, so as to compensate for the thermal displacement of the shaft core.

[0034] A third aspect of the embodiments of the present application provides a machine tool, which includes the numerical control system provided in the second aspect of the embodiments of the present application.

[0035] After adopting the above technical solution, the present invention has the following beneficial effects compared with the prior art:

[0036] In the embodiment of the present application, a displacement measurement sensor is designed to measure the thermal displacement of the shaft core during the operation of the electric spindle. The displacement can be directly converted into a compensation amount and transmitted to the numerical control system in real time, so as to control the numerical control system to compensate for the thermal displacement of the shaft core. The step of converting temperature to displacement in the temperature-thermal displacement prediction model is omitted, and the conversion error generated in this step is eliminated, so that the compensation operation can be completed efficiently and accurately. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 It is a schematic diagram of the explosion structure of the front dynamic balance ring, the ring spray flange and the gas sealing ring during assembly in the embodiment of the present application;

[0038] Figure 2 It is a schematic diagram of the cross-sectional structure of the front dynamic balance ring, the ring spray flange, the gas seal and the front gland after assembly in the embodiment of the present application;

[0039] Figure 3 This is a schematic diagram of the connection structure between the displacement measurement sensor and the circuit board in the embodiment of the present application;

[0040] Figure 4 This is a flow chart of the real-time compensation method for thermal displacement of an electric spindle of a CNC machine tool in an embodiment of the present application;

[0041] Figure 5 It is a schematic diagram of the optimization simulation and results of the structure parameters of the built-in coil of the electric spindle in the embodiment of the present application;

[0042] Figure 6 This is a schematic diagram of the fitting relationship between the output voltage and displacement of the displacement measurement sensor in the embodiment of the present application;

[0043] Figure 7 This is a hardware framework diagram of the electric spindle thermal displacement compensation system in the embodiment of the present application.

[0044] in:

[0045] 100-shaft core; 101-tool handle;

[0046] 200-front dynamic balance ring; 201-second ring surface;

[0047] 300-ring spray flange; 301-first ring surface; 3011-displacement measurement sensor installation groove; 302-lead port;

[0048] 400-Electric spindle housing;

[0049] 500-Circuit board placement compartment;

[0050] 600-electrical connecting wire;

[0051] 700-gas sealing ring;

[0052] 800-front gland;

[0053] 900 - Airflow channel. DETAILED DESCRIPTION

[0054] Embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present invention, and should not be construed as limiting the present invention.

[0055] Throughout the specification and claims, the following terms have at least the meanings explicitly associated herein, unless the context dictates otherwise. The meanings identified below do not necessarily limit the terms, but merely provide illustrative examples of the terms.

[0056] In the description of the present invention, the phrase "in one embodiment" does not necessarily refer to the same embodiment, although it may refer to the same embodiment. Similarly, the phrase "in some embodiments" as used herein, when used multiple times, does not necessarily refer to the same embodiment, although it may refer to the same embodiment. As used herein, the term "or" is an inclusive "or" operator and is equivalent to the term "and / or", unless the context clearly dictates otherwise. The term "based on" is not exclusive and allows for additional factors not described, unless the context clearly dictates otherwise. The word "exemplary" means "used as an example, instance or illustration" in this article. Any embodiment described herein as "exemplary" is not necessarily interpreted as being superior or superior to other embodiments. The scope of the present invention is limited only by the scope of the appended claims, and any examples set forth in this specification are not intended to be limiting, but only to set forth some of the many possible embodiments of the claimed invention. The various embodiments provided by the present invention should not be interpreted as limiting the scope of protection of the present invention.

[0057] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0058] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0059] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0060] In the present invention, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may include that the first and second features are in direct contact, or may include that the first and second features are not in direct contact but are in contact through another feature between them. Moreover, a first feature being "above", "above" and "above" a second feature includes that the first feature is directly above and obliquely above the second feature, or simply indicates that the first feature is higher in level than the second feature. A first feature being "below", "below" and "below" a second feature includes that the first feature is directly below and obliquely below the second feature, or simply indicates that the first feature is lower in level than the second feature.

[0061] Background

[0062] Patents CN118192419A and CN118237969A both propose a method of using a temperature sensor to establish a prediction model between temperature and thermal displacement of an electric spindle, thereby performing real-time compensation for thermal displacement of an electric spindle. Thermal displacement compensation of an electric spindle based on a temperature sensor needs to focus on the arrangement of temperature measurement points. Theoretical analysis and experiments are required from multiple aspects such as the heat source distribution, heat propagation, and heat-sensitive parts of the machine tool to obtain the most economical and effective solution. In addition, the constructed prediction model only considers the temperature factor, and does not consider factors such as humidity and vibration in the environment where the machine tool is located. The model is easily affected by the on-site environment, resulting in a large prediction error.

[0063] Based on this, Figure 1-Figure 7 As shown, the first aspect of the embodiment of the present application provides an electric spindle, comprising:

[0064] Axis core 100;

[0065] A rotor part that rotates synchronously with the shaft core 100 and a stator part that does not rotate with the shaft core 100;

[0066] A displacement measuring sensor is provided on the stator part for measuring the thermal displacement of the shaft core 100 during the operation of the electric spindle.

[0067] In the embodiment of the present application, a displacement measurement sensor is designed to measure the thermal displacement of the shaft core 100 during the operation of the electric spindle, and the displacement can be directly converted into a compensation amount and transmitted to the numerical control system in real time, so as to control the numerical control system to compensate for the thermal displacement of the shaft core 100. The step of converting temperature and displacement in the temperature-thermal displacement prediction model is omitted, and the conversion error generated in this step is eliminated, so that the compensation operation can be completed efficiently and accurately.

[0068] Preferably, the displacement measurement sensor is an eddy current displacement sensor or a laser displacement sensor, but relatively speaking, it is preferred that the detection effect is better by building an eddy current displacement sensor inside the electric spindle. The reason why the detection effect is better when the eddy current displacement sensor is built inside the electric spindle is that the laser sensor is more sensitive to environmental interference. For example, the water jet and cutting debris during processing will interfere with the laser beam emitted by the laser sensor, thereby affecting the accuracy of displacement measurement and being interfered by noise. Compared with the laser displacement sensor, the eddy current displacement sensor has stronger anti-interference ability. The water jet and cutting debris will not affect the eddy current signal, and the anti-noise interference ability is stronger. In summary, in this application scenario, the displacement measurement stability of the eddy current sensor is higher than that of the laser sensor. And the price of the laser sensor is much higher than that of the eddy current sensor, and it is more delicate than the eddy current sensor. The laser sensor is more suitable for laboratory scenarios, not suitable for processing scenarios with harsh environments, and it has more stringent requirements on the use environment.

[0069] Further, in some possible implementations, the rotor portion includes a front dynamic balance ring 200, and the front dynamic balance ring 200 is fixedly sleeved on the outer periphery of the shaft core 100 so as to be able to rotate synchronously with the shaft core 100;

[0070] The stator part includes an annular spray flange 300, which is sleeved on the outer periphery of the shaft core 100 and the front dynamic balance ring 200, and the annular spray flange 300, the shaft core 100 and the front dynamic balance ring 200 are all clearance-fitted together;

[0071] A displacement measuring sensor is fixedly arranged on the annular spray flange 300 , and the displacement measuring sensor is used to detect whether the front dynamic balance ring 200 is displaced relative to the annular spray flange 300 in the axial direction of the shaft core 100 .

[0072] That is, in the embodiment of the present application, a displacement measurement sensor is designed to detect the displacement of the front dynamic balance ring 200 relative to the annular spray flange 300 in the axial direction of the shaft core 100, which can directly reflect the thermal displacement of the shaft core 100, and can convert the thermal displacement into a compensation amount and transmit it to the numerical control system in real time, so as to control the numerical control system to compensate for the thermal displacement generated by the shaft core 100.

[0073] Further, in some possible implementations, such as Figure 1-Figure 3 As shown, the shaft core 100 includes a front end having a side of the tool handle 101, and a rear end opposite to the front end;

[0074] The annular spray flange 300 and the front dynamic balance ring 200 are arranged close to the front end of the shaft core 100 relative to the rear end of the shaft core 100 .

[0075] The reason why a displacement measurement sensor is provided on the annular spray flange 300 at the position of the tool handle 101 in the embodiment of the present application to detect whether the front dynamic balance ring 200 is displaced relative to the annular spray flange 300 in the axial direction of the shaft core 100 is because this part of the structure is closer to the tool handle 101 and can better reflect the thermal expansion of the shaft core 100. The thermal expansion of the electric spindle shaft core 100 is mainly reflected at the front end of the tool handle 101. The change in the vertical distance between the displacement measurement sensor and the front dynamic balance ring 200 is approximately equivalent to the change in the displacement of the front end of the tool handle 101, that is, the thermal displacement of the electric spindle shaft core 100. The displacement measurement sensor is fixed on the annular spray flange 300. The displacement measurement sensor is stationary. The component that moves due to thermal displacement is the front dynamic balance ring 200. Therefore, by providing a displacement measurement sensor on the annular spray flange 300, the thermal expansion of the shaft core 100 of the electric spindle can be accurately detected.

[0076] Specifically, in some possible implementations, such as Figure 1-Figure 3 As shown, in the axial direction of the shaft core 100, the annular spray flange 300 has a first annular surface 301 facing one side of the front dynamic balance ring 200, and the front dynamic balance ring 200 has a second annular surface 201 facing one side of the annular spray flange 300;

[0077] The first annular surface 301 is provided with a displacement measurement sensor installation groove 3011 , and the displacement measurement sensor is arranged in the displacement measurement sensor installation groove 3011 for detecting whether the second annular surface 201 is displaced relative to the first annular surface 301 in the axial direction of the shaft core 100 .

[0078] That is, by detecting the change in the distance between the second annular surface 201 of the front dynamic balancing ring 200 and the displacement measurement sensor, it can be reflected whether the second annular surface 201 is displaced in the axial direction of the shaft core 100 relative to the first annular surface 301, that is, it can be reflected whether the shaft core 100 of the electric spindle has undergone thermal expansion.

[0079] Further, in some possible embodiments, the displacement measurement sensor includes a displacement measurement sensor disposed on the annular spray flange 300, and the displacement measurement sensor is used to detect and output a displacement parameter value representing the front dynamic balance ring 200 relative to the annular spray flange 300 in the axial direction of the shaft core 100.

[0080] Further, in some possible implementations, the second annular surface 201 of the front dynamic balance ring 200 is used as a detection surface of a displacement measurement sensor;

[0081] The structural parameters of the displacement measurement sensor are determined according to the size of the second annular surface 201 and the size of the displacement measurement sensor installation groove 3011 .

[0082] In the embodiment of the present application, by designing the structural dimension parameters of the displacement measurement sensor according to the size of the second annular surface 201 and the size of the displacement measurement sensor installation groove 3011, the resolution of the eddy current sensor can be higher, the detection accuracy can be improved, the displacement measurement result can be more accurate, and the thermal displacement detection effect can be improved. By optimizing the structural parameters of the displacement measurement sensor, the outer diameter, height, number of turns and other structural parameters of the displacement measurement sensor that are most suitable for the application scenario can be obtained.

[0083] Specifically, Figure 1 As shown, the front dynamic balance ring 200 is a stepped ring structure, which is composed of an outer ring and an inner ring, wherein the size of the second ring surface 201 of the front dynamic balance ring 200 refers to the outer ring radius size minus the inner ring radius size, that is, the outer ring radius size minus the inner ring radius size is the above-mentioned detection surface size.

[0084] That is, in the embodiment of the present application, the size of the displacement measurement sensor is limited by the size of the detection surface of the front dynamic balance ring 200 and the size of the displacement measurement sensor installation groove 3011, and the outer diameter and height of the displacement measurement sensor are constrained by these two sizes. And the sensor coil size obtained by the simulation model is the actual sensor coil size.

[0085] Furthermore, in some possible embodiments, the electric spindle also includes a control panel, which is used to convert the parameter values ​​output by the displacement measurement sensor into pulse signals of the numerical control system, so that the numerical control system equipped with the electric spindle can directly use the pulse signal to adjust the electric spindle axially to compensate for the thermal displacement generated by the shaft core 100.

[0086] In the embodiment of the present application, the thermal displacement of the shaft core 100 is converted into a compensation amount and then transmitted to the numerical control system in real time, so that the electric spindle can be directly controlled by the numerical control system to perform compensation operations.

[0087] Specifically, in some possible implementations, the displacement measurement sensor is used to detect and output an inductance signal representing the axial displacement of the front dynamic balance ring 200 relative to the ring spray flange 300;

[0088] The control panel is used to determine the output voltage value of the displacement measurement sensor according to the inductance signal, determine the thermal displacement of the shaft core 100 according to the voltage value, and convert the thermal displacement into a pulse signal of the numerical control system.

[0089] That is, in the embodiment of the present application, the thermal displacement of the shaft core 100 is converted into a compensation amount and then transmitted to the CNC system in real time, and the thermal displacement of the shaft core 100 is compensated directly by the CNC system. The step of converting temperature and displacement in the temperature-thermal displacement prediction model can be omitted, the conversion error generated in this step is eliminated, and the compensation operation can be completed efficiently and accurately.

[0090] Specifically, in order to more clearly understand the automatic detection and automatic compensation operations of the electric spindle in the embodiment of the present application, the following is combined with Figure 1-Figure 7 To explain in detail:

[0091] First, if Figure 1-Figure 3 As shown, the enameled coil of the electric displacement measurement sensor {the sensor is not shown in the figure, only the text description} is installed in the displacement measurement sensor installation groove 3011 of the annular spray flange 300, and the enameled coil of the electric displacement measurement sensor is fixed in the displacement measurement sensor installation groove 3011 by using epoxy resin. This not only isolates the influence of the other metal materials inside the electric spindle on the sensor coil signal, but also protects the coil from damage caused by the harsh internal environment of the electric spindle when the electric spindle is running, thereby extending the service life of the sensor coil. The detection surface directly facing the sensor coil is the front dynamic balance ring 200. By measuring the change in the vertical distance between the coil and the front dynamic balance ring 200, the thermal displacement compensation amount of the electric spindle is finally obtained, and the compensation amount is transmitted to the numerical control system to complete the thermal displacement compensation operation in the Z-axis direction of the electric spindle. The complete electric spindle thermal displacement compensation process is the following steps S1-S4, as shown Figure 4 shown.

[0092] S1: The electric displacement measuring sensor is installed on the ring spray flange 300, and the detection surface is the front dynamic balance ring 200. The coil is connected to the circuit board through the signal line, and the circuit board is placed in the circuit board placement bin, which is fixed to the surface of the electric spindle housing 400, such as Figure 3 As shown. The vertical initial distance between the sensor coil and the detection surface is d1, and the thermal displacement caused by the heating of the electric spindle is △d. According to the size limit of the detection surface and the maximum size limit of the installation slot where the coil is placed, the COMSOL software is used to construct a two-dimensional axisymmetric electromagnetic simulation model for displacement detection of eddy current sensors. The purpose of optimizing the structural parameters of the sensor coil is to improve the resolution and accuracy of displacement detection. The most suitable coil structural parameters are selected according to the simulation results, as shown in Figure 5 shown.

[0093] S2: Connect the coil with optimized structural parameters in S1 to the signal processing circuit, and convert the inductance signal collected by the coil into a voltage signal output with an output range of 0-10V. Since the maximum thermal displacement of the electric spindle does not exceed 100 microns, within the small displacement range, the inductance and displacement show a good linear relationship. The sensor is calibrated using the Z-axis stepping function of the machine tool electric spindle. The coil is pasted on the front end of the tool handle, and the dynamic balance ring is fixed on the workbench. The step is made in 10 microns, so that the coil pasted on the tool handle is constantly approaching the thermal displacement detection surface on the dynamic balance ring from the far end. The displacement and the corresponding voltage output by the sensor are recorded. The larger the voltage, the larger the distance between the coil and the detection surface, and the smaller the voltage, the smaller the distance between the coil and the detection surface. The relationship between the sensor output voltage and V and the displacement d is fitted using the cftool toolbox {i.e., curve fitting toolbox} in Matlab. The fitting relationship between the two is linear, and the fitting degree is 0.999. The fitting diagram is shown as follows Figure 6 shown.

[0094] S3: When the electric spindle is running, the displacement measurement sensor measures the initial thermal displacement d1 at time t1, the thermal displacement d2 at time t2, the thermal displacement d3 at time t3..., and the thermal displacement dn at time tn. The displacement compensation amounts transmitted to the CNC system are d2-d1, d3-d1, ..., dn-d1. Each compensation amount needs to be compared with the initial displacement d1. If the displacement compensation amount is smaller than the initial displacement amount, it means that the electric spindle has thermally displaced downward, and the electric spindle needs to be controlled to lift up. If the displacement compensation amount is larger than the initial displacement amount, it means that the electric spindle has thermally displaced upward, and the electric spindle needs to be controlled to move downward. It should be noted that the upward and downward mentioned in step S3 refer to Figure 2 The direction is explained.

[0095] S4: The signal circuit hardware uses STM32F103 as the main control MCU {i.e., using ARM microcontroller as the main control MCU}, controls LDC1614 to collect coil inductance signals {i.e., controls the inductance digital converter to collect coil inductance signals}, and synchronously performs displacement calculation, signal filtering, inter-chip communication, etc. in the MCU. AD5686 converts the displacement into a voltage signal {i.e., using a digital-to-analog converter to convert the displacement into a voltage signal}, and the optical coupler ELM453 converts the displacement into a pulse signal, communicates with the CNC system, and controls the electric spindle to perform thermal displacement compensation operations. The hardware system framework is as follows Figure 7 At the same time, the voltage signal output by the sensor can also be transmitted to the Labview host computer voltage acquisition platform through the serial port, and the voltage data generated in the experiment can be saved to facilitate further data processing later.

[0096] Furthermore, in some possible implementations, the electric spindle further includes:

[0097] The electric spindle housing 400 is sleeved on the outer periphery of the stator part and fixedly connected to the stator part;

[0098] A circuit board placement compartment 500, the circuit board placement compartment 500 is provided with a control panel, and the circuit board placement compartment 500 is attached to the outer surface of the electric spindle housing 400;

[0099] The annular spray flange 300 serving as the stator part is also provided with a lead-in port 302 , and an electrical connection line 600 passing through the lead-in port 302 is connected between the control panel and the displacement measurement sensor.

[0100] Further, in some possible implementations, the stator part further includes a gas sealing ring 700 and a front gland 800 fixed on the ring spray flange 300;

[0101] An air flow channel 900 for exhausting air to the outside of the electric spindle is defined between the air sealing ring 700, the front pressure cover 800, the annular spray flange 300 as the stator part and the front dynamic balance ring 200 as the rotor part and the shaft core 100, and the air flow channel 900 is connected to the displacement measurement sensor installation groove 3011.

[0102] The gas sealing ring 700 is interference fit with the ring spray flange 300, and a large number of fine holes are evenly distributed along the circumference. The high-speed gas passes through the gas sealing ring and is ejected from the gap at its lower end to form an air curtain, which is used for the sealing function of the front end of the electric spindle.

[0103] In the embodiment of the present application, a displacement measurement sensor mounting groove 3011 for accommodating the displacement measurement sensor is provided inside the electric spindle, and the mounting groove is arranged to be connected to the air flow channel 900, so as to prevent cutting fluid or impurities outside the electric spindle from contacting the displacement measurement sensor, thereby improving the service life of the displacement measurement sensor.

[0104] Of course, in some possible implementations, the displacement measuring sensor may also be arranged on the outside of the annular spray flange, but the service life of the displacement measuring sensor in this arrangement is not as long as that of the above-mentioned built-in arrangement.

[0105] Furthermore, the second aspect of the embodiment of the present application also provides a numerical control system, which includes the electric spindle provided by the first aspect of the embodiment of the present application.

[0106] Further, in some possible implementations, the numerical control system includes a z-axis for driving the entire electric spindle to move along the axial direction of the shaft core 100;

[0107] The numerical control system is used to control the z-axis to drive the electric spindle to move according to the pulse signal representing the thermal displacement of the shaft core 100, so as to compensate for the thermal displacement of the shaft core 100.

[0108] Furthermore, the third aspect of the embodiment of the present application also provides a machine tool, which includes the numerical control system provided in the second aspect of the embodiment of the present application.

[0109] In summary, in the embodiment of the present application, a high-precision electric displacement measurement sensor is used to directly measure the thermal displacement amount that occurs during the operation of the electric spindle, and the thermal displacement amount is converted into a compensation amount and transmitted to the numerical control system in real time, so as to control the numerical control system to perform compensation operations on the electric spindle in real time. The step of converting temperature and displacement amount in the temperature-thermal displacement prediction model is omitted, and the conversion error generated in this step is eliminated, so that the compensation operation can be completed efficiently and accurately.

[0110] At the same time, in the embodiment of the present application, the structural parameters of the eddy current sensor coil are optimized through electromagnetic simulation, and it is placed inside the electric spindle. There is no need to make large-scale changes to the internal structure of the electric spindle, and it can be directly put into production and use, which reduces the implementation cost while greatly improving the machining accuracy of the electric spindle, reducing the influence of the thermal displacement of the electric spindle on the machining, and providing strong support for the practical application of thermal displacement compensation of the electric spindle. It is worth noting that the thermal displacement of the electric spindle occurs not only in the specimen processing stage, but also in the cold start-up stage of the machine tool. Through the analysis of the experimental data, it can be concluded that the CNC system provided in the embodiment of the present application can also shorten the warm-up time of the machine tool, so that the machine tool can enter the production link faster.

[0111] In the above-mentioned embodiments of the present application, the description of each embodiment has its own emphasis. For parts that are not described in detail in a certain embodiment, please refer to the relevant description of other embodiments. The steps shown in the relevant flow chart can be executed in a computer system such as a set of computer executable instructions, and although the logical order is shown in the flow chart, in some cases, the steps shown or described can be executed in an order different from that here. In other words, the order of steps described in the foregoing embodiments is only an example, and it is also within the scope of protection of the embodiments of the present application to reasonably adjust the order of steps based on the content of the embodiments of the present application.

[0112] The sequence of serial numbers or introduction of the embodiments of the present application is for description only and does not represent the superiority or inferiority of the embodiments.

[0113] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine different embodiments or examples described in this specification.

[0114] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations of the present invention. A person skilled in the art may change, modify, replace and vary the above embodiments within the scope of the present invention.

Claims

1. An electric spindle, characterized in that: include: A shaft core (100); A rotor part that rotates synchronously with the shaft core (100) and a stator part that does not rotate with the shaft core (100); A displacement measuring sensor is provided on the stator part, which is used to measure the thermal displacement of the shaft core (100) during the operation of the electric spindle.

2. The electric spindle according to claim 1, characterized in that: The rotor part comprises a front dynamic balance ring (200), wherein the front dynamic balance ring (200) is fixedly sleeved on the outer periphery of the shaft core (100) so as to be able to rotate synchronously with the shaft core (100); The stator part comprises an annular spray flange (300), the annular spray flange (300) is sleeved on the outer circumference of the shaft core (100) and the front dynamic balance ring (200), and the annular spray flange (300) and the shaft core (100) and the front dynamic balance ring (200) are all clearance-fitted together; The displacement measuring sensor is fixedly arranged on the annular spray flange (300), and the displacement measuring sensor is used to detect whether the front dynamic balance ring (200) is displaced relative to the annular spray flange (300) in the axial direction of the shaft core (100).

3. The electric spindle according to claim 2, characterized in that: The shaft core (100) comprises a front end having a side of the tool handle (101), and a rear end opposite to the front end; The annular spray flange (300) and the front dynamic balance ring (200) are arranged close to the front end of the shaft core (100) relative to the rear end of the shaft core (100).

4. The electric spindle according to claim 2, characterized in that: In the axial direction of the shaft core (100), the annular spray flange (300) has a first annular surface (301) facing one side of the front dynamic balance ring (200), and the front dynamic balance ring (200) has a second annular surface (201) facing one side of the annular spray flange (300); A displacement measurement sensor installation groove (3011) is provided on the first annular surface (301), the displacement measurement sensor is arranged in the displacement measurement sensor installation groove (3011), and the displacement measurement sensor is used to detect whether the second annular surface (201) is displaced in the axial direction of the shaft core (100) relative to the first annular surface (301).

5. The electric spindle according to claim 4, characterized in that: The displacement measurement sensor is used to detect and output a displacement parameter value representing the displacement of the front dynamic balance ring (200) relative to the annular spray flange (300) in the axial direction of the shaft core (100).

6. The electric spindle according to claim 5, characterized in that: The second ring surface (201) of the front dynamic balancing ring (200) serves as a detection surface of a displacement measurement sensor; The structural parameters of the displacement measurement sensor are determined according to the size of the second annular surface (201) and the size of the displacement measurement sensor installation groove (3011).

7. The electric spindle according to any one of claims 4 to 6, characterized in that: The electric spindle also includes a control panel, which is used to convert the parameter value output by the displacement measurement sensor into a pulse signal of a numerical control system, so that the numerical control system equipped with the electric spindle can directly use the pulse signal to adjust the electric spindle in the axial direction to compensate for the thermal displacement generated by the shaft core (100).

8. The electric spindle according to claim 7, characterized in that: The displacement measurement sensor is used to detect and output an inductance signal representing the thermal displacement of the shaft core (100); The control panel is used to determine the output voltage value of the displacement measurement sensor according to the inductance signal, determine the thermal displacement of the shaft core (100) according to the voltage value, and convert the thermal displacement into a pulse signal of a numerical control system.

9. The electric spindle according to claim 7, characterized in that: The electric spindle also includes: An electric spindle housing (400), the electric spindle housing (400) being sleeved on the outer periphery of the stator part and fixedly connected to the stator part; A circuit board placement chamber (500), wherein the circuit board placement chamber (500) is provided with the control panel, and the circuit board placement chamber (500) is attached to the outer surface of the electric spindle housing (400); The annular spray flange (300) serving as the stator part is also provided with a lead-in port (302), and an electrical connection line (600) passing through the lead-in port (302) is connected between the control panel and the displacement measurement sensor.

10. The electric spindle according to any one of claims 4 to 6, characterized in that: The stator part also includes a gas sealing ring (700) and a front gland (800) fixed on the annular spray flange (300); An air flow channel (900) for exhausting air to the outside of the electric spindle is defined between the air sealing ring (700) as the stator part, the front pressure cover (800), the annular spray flange (300), the front dynamic balance ring (200) as the rotor part, and the shaft core (100), and the air flow channel (900) is connected to the displacement measurement sensor installation groove (3011).

11. The electric spindle according to claim 10, characterized in that: The displacement measuring sensor is an eddy current displacement sensor.

12. A numerical control system, characterized in that: The invention comprises the electric spindle according to any one of claims 1 to 11.

13. The numerical control system according to claim 12, characterized in that: The numerical control system comprises a z-axis for driving the electric spindle as a whole to move in the axial direction of the shaft core (100); The numerical control system is used to control the z-axis to drive the electric spindle to move according to a pulse signal representing the thermal displacement of the shaft core (100), so as to compensate for the thermal displacement generated by the shaft core (100).

14. A machine tool, characterized in that: Includes the numerical control system described in claim 12 or 13.

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