Method for parking and heating of an electric spindle based on end face grinding of the stator coils of the drive motor

Abstract

The method based on the stator coil of driving motor to heat the end face grinding electric spindle, when the end face grinding electric spindle is stopped in the process of machining, the stator coil of driving motor is changed into an electric heating coil to heat the end face grinding electric spindle, the end face grinding electric spindle is heated by induction and / or heat radiation, and the electric power parameter of the stator coil of driving motor is controlled to ensure that the shaft temperature of the end face grinding electric spindle is kept above the shaft temperature in the process of operation when the end face grinding electric spindle is stopped in the process of machining, the end face grinding electric spindle is prevented from being cooled after the operation is stopped, and the axial machining precision of the end face grinding electric spindle is affected when the end face grinding electric spindle is started again. The stator coil of driving motor is used to heat the end face grinding electric spindle when the end face grinding electric spindle is stopped in the process of machining, the shaft temperature of the end face grinding electric spindle after the operation is stopped is consistent with the shaft temperature when the end face grinding electric spindle is operated, and the machining precision error of the end face grinding electric spindle in the axial direction caused by temperature change is effectively prevented.

Description

TECHNICAL FIELD

[0001] The application relates to a method for improving machining precision, in particular to a method for stopping and heating an end face grinding motorized spindle based on a driving motor stator coil, which is mainly used for improving grinding machining precision and belongs to the technical field of precision machining. BACKGROUND

[0002] Grinding machining is a kind of conventional high-precision machining, and grinding machining mainly grinds the plane or inner and outer circle of a machined part. With the progress of modern machining technology, the precision requirement of grinding machining is higher and higher, especially the precision requirement of numerical control grinding machining is higher and higher. Since numerical control grinding machining has the characteristics of high precision, high efficiency, strong flexibility and high intelligentization, the application of numerical control grinding machining is developing in a wider and wider range. At present, numerical control grinding machines include numerical control surface grinding machines, numerical control centerless grinding machines, numerical control internal and external grinding machines, numerical control vertical universal grinding machines, numerical control coordinate grinding machines and numerical control profile grinding machines, and the application range is wider and wider. However, since the numerical control grinding machine often needs to complete the grinding machining of multiple surfaces at one time, multiple grinding tools (also called grinding heads) are needed to complete the grinding machining, and the grinding tools are different in direction and mode. However, the limited space in the numerical control machine tool needs to install multiple grinding machining tools, which not only needs to occupy a large space, but also needs to lengthen the grinding spindle of the grinding head in order to avoid the interference between the multiple grinding tools. Generally, the length of the machining spindle of the numerical control grinding machine from the fixed end to the machining surface is more than 300 mm.

[0003] It is found through research that the long grinding spindle in the numerical control grinding machine will change the structure size due to the temperature change of the grinding spindle in the grinding machining, and the change in the axial direction is particularly obvious because the axial size is relatively long. The change of the length direction size of the grinding machining spindle has little influence on the grinding machining in the circular rear angle machining mode (the outer diameter surface of the circular grinding wheel is used for grinding machining), but has great influence on the grinding machining in the plane rear angle machining mode (the end surface of the grinding wheel is used for grinding machining). Figure 1It can be seen that for the grinding processing of the plane relief angle, because the processing surface of the grinding processing is perpendicular to the axis of the grinding processing spindle, the stress direction is parallel to the axis of the grinding processing spindle, thus the axial dimension change of the grinding processing spindle directly affects the processing precision. It is also found in the research that the grinding processing spindle of the plane relief angle grinding processing is affected by the temperature change of about 1 meter length, and the length changes about 0.01 mm when the temperature of the grinding processing spindle rises 1℃. Thus for the grinding processing spindle whose length from the fixed end to the processing surface is greater than 300 mm, the length changes about 0.003 mm when the temperature of the grinding processing spindle rises 1℃. The length change seems very limited, but when the temperature change reaches 5℃ or above, the length change will reach 0.015 mm or above, that is, the processing precision will be affected by 0.015 mm. Moreover, if the processed workpiece is a circular workpiece, such as the external cylindrical plane relief angle grinding processing of a tool, the influence on the external cylindrical precision of the processed workpiece will be doubled to 0.03 mm. Such a large precision error is acceptable for ordinary grinding processing, but for high-precision numerical control grinding processing, the precision of the numerical control grinding will be greatly reduced. Therefore, for high-precision numerical control grinding machines, if the external cylindrical plane relief angle grinding processing of a tool is adopted, the temperature change of the grinding processing spindle will be controlled within 3℃. In order to achieve this, foreign countries generally adopt a mechanical grinding processing spindle, that is, the grinding processing spindle and the driving motor are two separate shafts, and the driving motor drives the grinding processing spindle through a belt. The temperature change of the grinding processing spindle can be controlled within 3℃, but this will increase the structure size of the whole grinding head, which is not conducive to high-precision numerical control grinding machines.

[0004] On the other hand, most grinding processing machines now generally adopt an end face grinding electric spindle, that is, the grinding processing spindle and the rotor of the driving motor are made together, which can greatly reduce the space size of the whole grinding head and is convenient for realizing variable frequency driving control. However, because the rotor of the driving motor is easy to generate heat under the driving of the driving current, the axial dimension change of the grinding processing spindle of the general end face grinding electric spindle generally exceeds 3℃ or above, and most of the variable frequency motor driving will be above 6℃. Thus the precision affected by the shaft temperature of the end face grinding electric spindle will reach 0.009-0.018 mm or above, and if the end face grinding electric spindle is used for processing the external cylindrical surface in the numerical control grinding machine, the influence on the external cylindrical precision of the processed workpiece will increase by 0.018-0.036 mm or above based on the original mechanical spindle. If the thermal deformation of the grinding processing spindle itself is added, the error will reach 0.003-0.045 mm or above, which is unacceptable for the numerical control grinding machine.

[0005] In order to change this situation, there is currently proposed to use the pre-judgment spindle changes, in the processing of the spindle axial elongation in advance to pre-judgment, through the calculation of the spindle budget in advance because of temperature changes, and then through the control system to adjust the processing quantity to carry out temperature compensation; but this method has the disadvantages of difficult to predict, many influencing factors, and difficult to accurately estimate. In addition, there is also proposed the concept of constant temperature spindle, mainly through the input of the processing spindle heat preservation medium, so that the processing spindle constant temperature in a certain range, so as to avoid the influence of the spindle temperature change on the processing.

[0006] But in the study also found that, for grinding processing is continuous processing, or intermittent processing, but not stop, heat preservation medium is not stop to keep the processing spindle; so the face grinding electric spindle in the working process, the size of the workpiece will not have too much change; but the face grinding electric spindle in the process of machining will stop for a period of time, change the other grinding head processing, after a period of time, start the original face grinding electric spindle machining same parts, the machining accuracy of the parts will also have a big change. Through careful study found that, why will be like this, the fundamental reason is that the face grinding electric spindle stop running, because there is no heating medium to keep the spindle, and lack of heat preservation measures, will make the face grinding electric spindle temperature will decrease rapidly, start again, will appear from the cold shaft to normal operation of the shaft temperature thermal expansion and cold shrinkage problem; after testing, if stop running 10 minutes, will again produce temperature difference in 5 ℃ above, so as to further expand the face grinding electric spindle precision error, on the basis of increasing 0.015 mm above, the outer circle machining error increases 0.036 mm above, because of the grinding spindle axial size change lead to the whole machining precision error reaches 0.06 mm above, so it is necessary to improve.

[0007] Through patent retrieval, it is found that some technical solutions about spindle temperature control are proposed, mainly to control the spindle temperature, and to ensure the axial stability of the spindle by temperature compensation. This axial temperature compensation method almost detects the spindle temperature through a temperature detector, then calculates the required temperature compensation through a computer model, and then manually compensates through manual intervention, but this way is complicated, many factors need to be considered, the model error is also large, and the manual intervention makes it difficult to ensure accurate temperature compensation, thereby affecting the machining precision. At present, another method is to use a water circulation system to keep the temperature of the spindle in a constant range through the flow of water, but this method is too complex and not suitable for most end face grinding electric spindle axial temperature compensation. Moreover, the current spindle temperature compensation or water circulation constant temperature emphasizes the heat preservation or constant temperature of the spindle during processing, and there is no information about the spindle temperature control during parking and restarting. The existing technical solutions are only suitable for heat preservation or constant temperature during processing, but once the machine is stopped, these heat preservation or constant temperature systems will stop, so they cannot solve the temperature change of the machining spindle caused by parking and restarting. There is no patent document reporting the same technology as the present invention. The patents related to the present invention mainly include the following:

[0008] 1. Patent No. CN113695970A, entitled "Method for compensating thermal elongation caused by temperature rise of milling machine spindle", the patent application discloses a method for compensating thermal elongation caused by temperature rise of milling machine spindle, comprising the following steps: first, run a process from the cold state of the machine tool, and collect temperature data and thermal elongation data, use a temperature sensor to detect the temperature data at the current milling machine spindle speed in real time, at the same time, detect the thermal elongation data of the spindle at the current temperature data through the tool detector; then, the controller captures the temperature data and spindle thermal elongation data during the running process to establish a relationship model between them; finally, through the established relationship model, the current thermal elongation is calculated according to the real-time temperature data of the machine tool to compensate. Through careful analysis of the patent, it can be found that this method uses temperature detection, then uses a computer to establish a relationship model between the spindle and the temperature, and then manually intervenes to compensate the temperature in advance, which is the current conventional technical means, but this method has errors in the algorithm model, and the reaction needs to be supplemented by manual intervention, which has the disadvantages of slow reaction and large error.

[0009] 2. Patent No. CN207637017U, entitled "A constant temperature main shaft with an internal circulation loop", which discloses a constant temperature main shaft with an internal circulation loop, comprising a single-head sliding bottom plate, a main shaft, a main shaft clamping sleeve and a temperature sensor. The single-head sliding bottom plate is U-shaped, the main shaft is fixed in the single-head sliding bottom plate through the main shaft clamping sleeve, the single-head sliding bottom plate is provided with a U-shaped pipeline, an input hole and an output hole, the U-shaped pipeline surrounds the axis of the main shaft, the input hole and the output hole are parallel to the axis of the main shaft, the input hole, the U-shaped pipeline and the output hole are sequentially connected, and the temperature sensor is in contact with the surface of the main shaft. This method controls the shaft temperature by setting a circulation loop outside the main shaft and controlling the flow of water. Although it is theoretically feasible, the reaction effect is slow in actual effect, and the water circulation system can only be operated continuously without stopping. Moreover, the structure is very complex and completely unsuitable for grinding spindle applications.

[0010] 3. Patent No. CN114571284A, entitled "A precision machine tool electric spindle thermal elongation error testing and active control method", which discloses a precision machine tool electric spindle thermal elongation error testing and active control method, comprising the following steps: first, through experimental testing, the relationship between different spindle speeds and the processing spindle thermal elongation at thermal equilibrium is established; second, the processing spindle is supplied with constant temperature water, and the relationship between the processing spindle elongation after thermal equilibrium and the constant temperature water temperature is tested; third, after the spindle stops, the corresponding thermal elongation temperature of the constant temperature water is switched according to the thermal elongation of the spindle at the corresponding speed after thermal equilibrium, so that the spindle elongation remains unchanged; fourth, when the spindle runs again at the speed before stopping, the water cooling system switches to a 20-degree water cooling machine. The patent proposes to conduct tests in a constant temperature environment with the same temperature as the first step, and the spindle water cooling machine is set to the same constant temperature as the room temperature. After the spindle stops, the thermal elongation at the corresponding speed is obtained by the first step test, and the water temperature corresponding to the processing spindle thermal elongation is obtained by the second step test. The numerical control system switches the constant temperature water of the corresponding temperature to maintain the spindle temperature, and the thermal elongation of the spindle can remain unchanged. Although the patent proposes to use constant temperature water to maintain the temperature of the spindle unchanged, the supply of constant temperature water will also stop after the machine stops during processing. Therefore, the spindle temperature difference between stopping and running will still occur, which will also cause the spindle length error during the process of stopping running and starting running again, thereby affecting the processing precision.

[0011] 4. Patent application for invention patent application with publication number CN107861470A and title "Real-time compensation method for spindle thermal elongation error of numerical control machine tool based on PMC control", which discloses a real-time compensation method for spindle thermal elongation error of numerical control machine tool based on PMC control. Firstly, the temperature sensor is used to measure the thermal key point temperature under the current spindle speed in real time, and the spindle thermal elongation error compensation amount under the current thermal state is calculated by using the pre-established thermal error model, and the error compensation amount is used to update the machine tool coordinate system offset function system variable. The numerical control system of the machine tool corrects the error compensation amount to the numerical control system through the PMC data processing function, and updates the machine tool coordinate system offset function system variable. The machine tool coordinate system offset system variable is executed, and the real-time compensation of the spindle thermal elongation error is completed. Only the key temperature point is measured, and the temperature field is simplified. The built-in PMC function of the numerical control machine tool is used to realize the real-time compensation function of the spindle thermal error, solve the technical problem of machine tool thermal deformation error compensation, and ensure the real-time of the compensation. The axial thermal error of the spindle of the numerical control machine tool is effectively reduced, and the machining precision is improved. Although the patent also proposes to compensate the thermal elongation of the spindle of the numerical control machine tool, it only proposes to compensate based on PMC. In actual application, it is difficult to compensate the length change of the spindle during running and stopping through simple PMC function.

[0012] Through careful analysis of these patent documents, it is found that although these patent documents all involve detecting and compensating the length change of the spindle caused by different temperatures of the spindle, through careful analysis of these patent documents, it is found that the technical solutions disclosed in these patent documents are only limited to the length change of the spindle caused by different temperatures during running of the spindle, thereby affecting the machining precision. The size change in the axial direction caused by the stop of the spindle is not considered. When the machine is stopped during machining and then started again, the axial error caused by the length change of the cold spindle to the stable thermal spindle during running is caused, and the existing technical solutions are not suitable for solving this problem. Therefore, the problems described above still exist and need to be further improved. SUMMARY

[0013] The present application aims to solve the problem of the influence of the axial temperature change of the end face grinding electric spindle during machining on the machining precision. A method for eliminating the influence of the axial temperature deformation of the end face grinding electric spindle during machining on the machining precision is provided. The method can effectively and reliably eliminate the axial temperature deformation of the end face grinding electric spindle during machining, and improve the machining precision.

[0014] In order to achieve this purpose, the application provides a method for heating the end face grinding electric spindle by converting the driving motor stator coil into an electric heating coil. When the end face grinding electric spindle is stopped during processing, the end face grinding electric spindle is heated by converting the driving motor stator coil into an electric heating coil. The heating method is to heat the end face grinding electric spindle by induction and / or thermal radiation heating method, and to ensure that the shaft temperature of the end face grinding electric spindle during the stop is above the shaft temperature during operation by controlling the electric power parameters of the driving motor stator coil, so as to prevent the end face grinding electric spindle from being cooled after the operation is stopped, and to prevent the end face grinding electric spindle from being deformed due to cooling when the processing is started again, thereby affecting the axial processing precision.

[0015] Further, the driving motor stator coil is used as a heating coil, and the driving motor stator coil is controlled by an auxiliary electric heating control system. After the driving motor is stopped during processing, the control mode of the driving motor stator coil is switched to a heating control mode by the auxiliary electric heating control system, and a heating electric heating parameter value is provided to the driving motor stator coil to form a heating current. The heating current passes through the driving motor stator coil, and the driving motor stator coil is used as a heating device. The driving motor rotor shaft is heated by induction and / or thermal radiation heating method, and the entire end face grinding electric spindle is heated by heat conduction. The entire end face grinding electric spindle maintains the shaft temperature during operation when the operation is stopped, and prevents the axial deformation of the entire end face grinding electric spindle due to the cooling of the entire end face grinding electric spindle after the stop, thereby affecting the processing precision. It is found in the research that the driving motor stator coil is converted into a heating coil after the stop, and the electric parameters of the driving motor stator coil are controlled to convert the driving motor stator coil into a heating coil. The end face grinding electric spindle is not rotated by electromagnetic or radiation heating method, but only generates heat. This electric auxiliary heating method can not change the entire end face grinding electric spindle, and only needs to slightly change the control system of the driving motor stator coil. Therefore, the change is very convenient, and the cost is very low.

[0016] Further, the heating electric parameter value provided to the driving motor stator coil is an auxiliary electric heating control system in the driving motor control system for providing heating current to the driving motor stator coil; after the end face grinding electric spindle stops rotating in the processing, the driving control system of the driving motor stator coil is switched by the switching device of the auxiliary electric heating control system, the driving motor stator coil is provided with an inductive or radiative heating heating electric parameter value by the auxiliary electric heating control system, so that the driving motor stator coil becomes an inductive or radiative heating coil; in the case of not driving the driving motor to rotate normally, the driving motor rotor shaft is heated in an inductive or radiative heating mode, and the entire end face grinding electric spindle is heated through heat conduction, so that the entire end face grinding electric spindle maintains the shaft temperature above the shaft temperature during operation after stopping rotating in the processing.

[0017] Further, the heating electric parameter value includes frequency, voltage and current, and the current supplied to the driving motor stator coil becomes heating current by adjusting the frequency, voltage and current of the auxiliary electric heating control system. The frequency heating includes medium frequency or low frequency heating; preferably low frequency heating, so that the shaft temperature can be more uniformly and stably maintained on the basis of small energy. Through experimental verification, the heating energy required to maintain the shaft temperature during stopping is actually not large, and is different according to the size of the end face grinding electric spindle. According to the experiment, the existing end face grinding electric spindle heating energy can be controlled at about 20-60 joules / hour.

[0018] Further, the driving motor rotor shaft is heated in an inductive or radiative heating mode by setting a heating frequency converter and its heating frequency converter control system in the driving motor control system, changing the control mode of the driving motor stator coil through the heating frequency converter control system after the driving motor stops rotating in the processing, starting the heating frequency converter by the heating frequency converter control system, supplying heating electric parameters to the driving motor stator coil in a frequency heating mode to form heating current, and heating the driving motor rotor shaft through inductive and / or thermal radiation heating.

[0019] Further, the frequency heating includes the following steps:

[0020] 1) The driving motor control system presses the stop key, the end face grinding electric spindle loses power, and the end face grinding electric spindle gradually stops rotating;

[0021] 2) After determining that the end face grinding electric spindle stops rotating, the control mode of the driving motor stator coil is switched by the switching device of the auxiliary electric heating control system, so that the control of the driving motor stator coil is switched from driving control to heating frequency converter control system control;

[0022] 3) The heating inverter is started by the heating inverter control system, the required electric heating power is determined according to the resistance value of the face grinding motor spindle, the heating electric parameters, including frequency, voltage and current, are calculated to supply the driving motor stator coil in the heating mode of frequency conversion heating, so that the driving motor stator coil becomes an induction heating coil;

[0023] 4) The heating inverter supplies the driving motor stator coil with heating electric parameters to form a heating current, and the driving motor rotor shaft is inductively heated, including intermittent heating and continuous heating;

[0024] 5) When the driving motor control system presses the start key again, the driving motor control system will first convert the control mode of the driving motor stator coil, cut off the heating inverter control system control of the driving motor stator coil, and restore the normal driving control of the driving motor control system.

[0025] Further, the driving motor rotor shaft is heated in an induction heating mode. A heating semiconductor switch control component is provided in the driving motor control system, and at least one heating semiconductor switch control component has an electric parameter value adjusting device with adjustable voltage or adjustable current. After the driving motor stops driving the face grinding motor spindle, the driving motor control system automatically switches the control of the driving motor stator coil to the heating semiconductor switch control component. The electric parameter value adjusting device of the heating semiconductor switch control component adjusts the voltage and / or current to apply a heating current to the driving motor stator coil. The driving motor stator coil becomes an electric heating coil through the heating current, and the driving motor rotor shaft is heated through induction and / or thermal radiation. The entire face grinding motor spindle is heated through heat conduction in a non-rotating or low-speed state, so that the shaft temperature of the face grinding motor spindle after stopping operation is maintained above the shaft temperature during operation, preventing the shaft deformation in the axial direction caused by the cooling of the face grinding motor spindle.

[0026] Further, the driving motor control system automatically switches the control of the driving motor stator coil to the heating semiconductor switch control component, which uses power semiconductor devices to provide heating electric parameters to the driving motor stator coil. The driving motor stator coil heats the driving motor rotor shaft in an induction heating mode, and the entire face grinding motor spindle is heated through heat conduction in a non-rotating or low-speed state, so that the shaft temperature of the face grinding motor spindle after stopping operation is maintained above the shaft temperature during operation. The power semiconductor devices include insulated gate bipolar transistors (IGBT), metal oxide semiconductor field effect transistors (MOSFET) and silicon carbide (SiC) MOSFET.

[0027] Further, the heating electric parameter value provided by the auxiliary electric heating control system to the driving motor stator coil is an inductive or radiative heating value, and a constant voltage or constant current device is additionally arranged in the driving motor control system, and when the grinding spindle stops running, the original driving motor control system is switched to the control mode of the constant voltage or constant current device for heating and keeping warm of the end face grinding electric spindle, the heating current is provided to the driving motor stator coil by the constant voltage or constant current device, and the end face grinding electric spindle is heated through heat radiation, so that the shaft temperature of the end face grinding electric spindle when stopping running is consistent with the shaft temperature when running.

[0028] Further, the size of the heating current is determined according to the power required for heating the driving motor rotor shaft, and the heating current controlled by the frequency converter or the heating semiconductor switch control assembly and the constant voltage or constant current device can only keep the shaft temperature of the end face grinding electric spindle after stopping running in the machining process within the temperature range of 2-8℃ above the shaft temperature when running.

[0029] Further, when the driving motor drives the end face grinding electric spindle to run normally again, the driving motor stator coil stops heating the end face grinding electric spindle, and at this time, it is necessary to ensure that the shaft temperature of the end face grinding electric spindle is 3-8℃ higher than the shaft temperature when running when the driving motor stator coil stops providing the heating current, so as to prevent the end face grinding electric spindle from having an error in the axial dimension during the period of stable heating shaft when the end face grinding electric spindle is started again to normal running.

[0030] The advantages of the present application are:

[0031] Compared with the prior art, the present application heats the end face grinding electric spindle through the auxiliary electric heating device when the driving motor stops running in the machining process, provides a heating current for keeping warm, so that the temperature of the end face grinding electric spindle can be maintained even when the end face grinding electric spindle does not run, so that the end face grinding electric spindle will not be in a cooling state when the end face grinding electric spindle is started again to run, which can effectively eliminate the problem that the axial deformation of the end face grinding electric spindle affects the machining precision during the process of stopping running to starting again; and the present application has the following advantages:

[0032] 1. The present invention addresses the problem that when the end face grinding electric spindle stops running, the axial change caused by the end face grinding electric spindle becoming cold will affect the processing accuracy when it is restarted. The present invention proposes a method for heating and keeping the end face grinding electric spindle warm when it stops running, so that the end face grinding electric spindle can still maintain its original temperature when it stops running, preventing the axial direction change caused by the end face grinding electric spindle becoming cold, thereby effectively improving the axial processing accuracy of the end face grinding electric spindle. Through actual tests, the technical solution of the present invention can effectively eliminate the grinding accuracy error of the plane back angle by more than 0.03mm, so that the overall grinding accuracy of the plane back angle is controlled within 0.05mm, thereby meeting the accuracy requirements of high-precision CNC grinding machines.

[0033] 2. The auxiliary heating proposed in the present invention is electric auxiliary heating, which changes the traditional water constant temperature spindle insulation method. After the electric auxiliary heating is started, the stopped end face grinding electric spindle can be kept warm and heated, thereby effectively preventing the end face grinding electric spindle from stopping and restarting due to the change in shaft temperature, which affects the processing accuracy. This electric heating method not only responds quickly but is also simpler and easier to control;

[0034] 3. The present invention adopts electric auxiliary heating to control the shaft temperature of the end face grinding electric spindle, so that the shaft temperature of the end face grinding electric spindle can be kept stable, thereby allowing the end face grinding electric spindle to be applied to high-precision CNC grinding machines, replacing the current foreign method of using a mechanical spindle to improve the precision of plane back angle grinding. This can significantly reduce the space occupied by the entire grinding head, which is more conducive to increasing the application space of the CNC grinding machine and reducing the volume of the entire machine tool;

[0035] 4. The present invention cleverly adopts the method of directly changing the stator coil of the driving motor into a heating coil, and taking the driving motor rotor as the heated body. Through the driving motor stator coil control system, after the driving motor stops running during processing, the driving motor stator coil is used as the heating coil, and a heating current is provided to it. The driving motor rotor shaft is heated by induction and / or thermal radiation heating, and then the entire end face grinding electric spindle is heated by heat conduction in a non-rotating or low-speed state. In this way, there is no need to modify the original end face grinding electric spindle integral grinding head, so the implementation method is simple and easy. The principle of heating the end face grinding electric spindle is to make full use of the principle that the driving motor is prone to heating when the driving electrical parameters are abnormal.

[0036] 5、The application controls and drives motor stator coil through frequency converter or semiconductor switching device or constant voltage or constant current device, provides a heating current to heat end face grinding electric spindle, and the heating principle is that end face grinding electric spindle has coil resistance, according to the physical formula P=UI=l x l x R (in the formula: P is power, U is voltage, I is current, and R is resistance), through the formula, it can be seen that the coil is given appropriate current (equivalent to I in the formula), so that the end face grinding electric spindle (equivalent to R in the formula) can be heated; the heating principle only needs simple calculation control to ensure that the end face grinding electric spindle is constant temperature at a certain temperature value, and is easy to realize.

[0037] 6、The application adopts intermediate frequency or low frequency heating mode to heat the end face grinding electric spindle, heating speed is fast: because eddy current is generated in the metal, heating speed is fast, and efficiency is high.

[0038] 7、The application adopts auxiliary electric heating mode to heat the end face grinding electric spindle, and temperature is convenient to control accurately: various electric parameter values can be adjusted to realize accurate temperature control, including adjusting current, voltage and frequency.

[0039] 8、The application adopts electric heating mode to heat the end face grinding electric spindle, compared with the original water constant temperature system, the application is more environmentally friendly and energy-saving, and has no water pollution problem: induction heating has no open fire, safety is high, and energy efficiency ratio is high. BRIEF DESCRIPTION OF DRAWINGS

[0040] Figure 1 is a schematic diagram of conventional grinding plane rear angle processing;

[0041] Figure 2 is a schematic diagram of the electric auxiliary heating system principle of the application;

[0042] Figure 3 is a schematic diagram of the electric auxiliary heating principle of the first embodiment of the application;

[0043] Figure 4 is a schematic diagram of the electric auxiliary heating principle of the second embodiment of the application;

[0044] Figure 5 is a schematic diagram of the electric auxiliary heating principle of the third embodiment of the application.

[0045] In the figure, 1, end face grinding electric spindle; 2, auxiliary electric heating device; 3, auxiliary electric heating control system; 101, grinding spindle; 102, heating frequency converter; 103, heating frequency converter control system; 104, driving motor stator coil; 105, driving motor rotor shaft; 202, heating semiconductor switch control assembly; 203, driving motor control system; 205, contactor; 206, power module (DC or AC); 207, semiconductor switch; 302, constant voltage or constant current device; 303, contactor control system; 305, original driving motor control system. DETAILED DESCRIPTION

[0046] The present application is further illustrated below in conjunction with the accompanying drawings and specific examples.

[0047] ATTACHMENT Figure 2 The basic principle of the present application is shown in the figure, and the auxiliary electric heating device 2 is combined with the driving motor stator coil and its control system to form an auxiliary heating device, which cleverly utilizes the principle that the driving motor will heat up when the electric parameters do not match, to achieve the heating and temperature maintenance of the end face grinding electric spindle 1. The following are several specific examples. Figure 2 It can be seen that the present application is mainly used to prevent the end face grinding electric spindle 1 from becoming cold and affecting the axial machining precision when it stops running; through an auxiliary electric heating device 2, under the control of an auxiliary electric heating control system 3, in the form of electromagnetic induction, eddy current effect or heat radiation conduction, the end face grinding electric spindle 1 is heated and temperature maintained, thereby avoiding the end face grinding electric spindle 1 from shrinking in axial size due to the decrease in shaft temperature caused by stopping running, and causing the end face grinding electric spindle 1 to stretch out when it resumes running and the shaft temperature is restored, thereby affecting the axial machining precision. Only the auxiliary electric heating device 2 proposed by the present application is an auxiliary heating device formed by the combination of the driving motor stator coil and its control system, which cleverly utilizes the principle that the driving motor will heat up when the electric parameters do not match, to achieve the heating and temperature maintenance of the end face grinding electric spindle 1. The following are several specific examples.

[0048] Example one: as shown in the figure, the auxiliary electric heating device 2 is combined with the driving motor stator coil and its control system to form an auxiliary heating device. Figure 3The application discloses an end face grinding motor spindle axial deformation influence machining precision preventing end face grinding motor spindle axial temperature control method of a numerical control tool grinder, the numerical control tool grinder adopts a driving motor driven end face grinding spindle 101, a heating frequency converter 102 is arranged in a driving motor control system of the numerical control tool grinder, and the heating frequency converter 102 is controlled by a heating frequency converter control system 103; when the end face grinding spindle 101 of the tool grinder stops running, the control mode of a driving motor stator coil 104 is switched by the heating frequency converter control system 103, the driving motor stator coil 104 is converted into a heating control mode, and the heating frequency converter 102 is started; under the control of the heating frequency converter control system 103, the end face grinding spindle 101 of the tool grinder is heated and kept warm in a frequency heating mode, so that the axial temperature of the end face grinding spindle 101 of the tool grinder is consistent with the axial temperature during running or is 2-8 DEG C higher than the axial temperature during running when the end face grinding spindle 101 of the tool grinder stops running, the change of slowly stretching is avoided when the end face grinding spindle 101 of the tool grinder is started again, the axial dimension of the end face grinding spindle 101 of the tool grinder is changed, and therefore the machining precision of the end face grinding spindle 101 of the tool grinder is influenced. Wherein, the end face grinding spindle 101 of the tool grinder is heated and kept warm by connecting the end face grinding spindle 101 of the tool grinder and a driving motor rotor shaft 105 into one, forming an end face grinding motor spindle 1, and taking the driving motor rotor shaft 105 as a heated resistor and taking the driving motor stator coil 104 as a heating coil; when the driving motor stops driving the end face grinding spindle 101 to run, a heating current is provided for the driving motor stator coil 104 by the heating frequency converter 102 analog quantity control, the driving motor stator coil 104 provides a heating current, the driving motor rotor shaft 105 is heated by induction and / or heat radiation heating, and then the end face grinding spindle 101 is heated by heat conduction, so that the axial temperature of the whole end face grinding spindle 101 is maintained at the axial temperature during running or is 2-8 DEG C higher than the axial temperature during running when the end face grinding spindle 101 stops running, so that the axial dimension is stable when the end face grinding spindle 101 is started again, the axial deformation of the end face grinding spindle 101 caused by cooling is prevented, and the machining precision is influenced.

[0049] The heating inverter 102 is separately provided in the control system of the whole driving motor for controlling the heating inverter 102 of the driving motor stator coil, and the heating inverter 102 is controlled by the heating inverter control system 103; when the driving motor stops the end face grinding spindle 101 from running, the control mode of the driving motor stator coil is switched (which can be realized by a conventional contactor control), the heating inverter 102 is started, the heating inverter control system 103 provides the heating inverter 102 with appropriate electrical parameter values, so that the heating inverter 102 provides the driving motor stator coil 104 with a heating current different from the normal driving motor running, at this time the driving motor stator coil 104 becomes a heating coil, and the driving motor stator coil 104 heats the driving motor rotor shaft 105 through inductive and / or thermal radiation heating; because the end face grinding spindle 101 and the driving motor rotor shaft 105 are an integrated shaft, the driving motor rotor shaft 105 will heat the end face grinding spindle 101 through heat conduction, so as to heat and keep warm the end face grinding spindle 101, and keep the shaft temperature of the end face grinding spindle 101 consistent or 2-8℃ higher than that in normal running when the end face grinding spindle 101 stops running.

[0050] Of course, the heating inverter 102 can be additionally provided in the original control system of the driving motor to provide the driving motor stator coil with a heating current required for keeping warm the spindle; when the end face grinding spindle 1 stops running, the additionally provided heating inverter 102 is started, the heating inverter control system 103 adjusts the electrical parameter values of the heating inverter 102, so that the heating current provided to the driving motor stator coil 104 can keep the shaft temperature of the end face grinding spindle 101. In addition, if the control system of the driving motor originally has a frequency conversion control device, such as the control system of a frequency conversion motor, the original frequency conversion control system can be directly used as the heating inverter control system 103 for heating, and after the machining is stopped, the output electrical parameter values of the original frequency conversion device, such as the frequency, voltage and current, are changed, and the driving motor stator coil 104 continues to be powered for heating; only the output electrical parameter values of the original frequency conversion device, such as the frequency, voltage and current, are adjusted by the control system, so that the driving motor stator coil 104 continues to be powered after the machining is stopped, but because the electrical parameter values of the driving motor stator coil 104 continue to be powered are different from the original normal driving electrical parameter values, the driving motor cannot run normally, but becomes a heating coil, that is, the driving motor rotor shaft 105 is heated by the inductive or thermal radiation conduction heating of the driving motor stator coil 104, and then the end face grinding spindle 101 is heated by the driving motor rotor shaft 105 through heat conduction, so as to keep the shaft temperature of the whole end face grinding spindle 1 after the machining is stopped.

[0051] It is worth noting that the size of the heating current is calculated according to the power required to heat and keep the rotor shaft 105 of the motor, which can be calculated according to the following formulas (1) and (2):

[0052] Wherein:

[0053] The heating power is determined according to formula (1):

[0054] P=(C×G×T) / (0.24×t×∮) (1)

[0055] Wherein:

[0056] P: heating power (kW);

[0057] C: specific heat of metal (steel is 0.17-0.168);

[0058] G: workpiece weight (kg);

[0059] T: heating temperature (℃);

[0060] t: working rhythm (seconds);

[0061] ∮: comprehensive thermal efficiency of equipment (0.4-0.7).

[0062] The relationship between heating power and heating current can be determined according to formula (2):

[0063] I=P / U=U / R (2)

[0064] In the formula, P is the power, U is the voltage, I is the current, and R is the resistance;

[0065] As can be seen from the formula, passing appropriate current (equivalent to I in the formula) to the coil can make the end face grinding electric spindle 1 (equivalent to R in the formula) heat, but it is necessary to ensure that the heating current provided by the induction heating control system does not always make the shaft temperature of the end face grinding spindle 101 rise, so as to ensure that the shaft temperature of the end face grinding spindle 101 after parking in the processing process can continue to keep consistent with the shaft temperature during operation, or within the range of 2-8℃ above the shaft temperature during operation.

[0066] The magnitude of the heating current is controlled by adjusting the power supply frequency or voltage of the heating inverter 102. The power supply frequency of the heating current is controlled within the low-frequency (less than 1kHz) or medium-frequency (1kHz-20kHz) heating frequency range. This ensures that the stator coil 104 of the drive motor heats the drive motor rotor shaft 105 more gently and evenly, preventing structural deformation of the drive motor rotor shaft 105 itself. The power of the heating current is determined by the resistance of the drive motor rotor shaft 105 and the power required to heat the drive motor rotor shaft 105 using induction heating. The resistance value is primarily calculated based on the size and material of the drive motor rotor shaft 105. Actual test calculations show that the power required to maintain the drive motor rotor shaft 105 temperature in current CNC tool grinders to prevent end face grinding of the electric spindle 1 is approximately 40-50 watts / second.

[0067] At the same time, when the drive motor drives the end face grinding spindle 101 to operate again, the drive motor stator coil 104 must stop inputting heating current to the end face grinding electric spindle 1. At this time, it is necessary to ensure that when the drive motor stator coil 104 stops providing heating current, the shaft temperature of the end face grinding spindle 101 is still 3-6°C higher than the shaft temperature during operation, so as to prevent the axial dimension of the end face grinding electric spindle 1 from having expansion and contraction errors during the stable hot shaft period from the end face grinding electric spindle 1 to normal operation, causing changes in the axial dimension.

[0068] The specific implementation steps of the variable frequency heating are as follows:

[0069] 1) When the stop button of the drive motor control system is pressed, the end face grinding electric spindle 1 loses power and the end face grinding electric spindle 1 gradually stops rotating under the action of the braking device;

[0070] 2) A speed sensor is provided next to the end face grinding electric spindle 1. When the speed sensor detects that the end face grinding electric spindle 1 has stopped rotating, the switching device of the heating inverter control system 103 switches the control mode of the drive motor stator coil 104, so that the control of the drive motor stator coil 104 is transferred to the control of the heating inverter control system 103;

[0071] 3) The heating inverter control system 103 starts the heating inverter 102 and determines the required electric heating power based on the resistance value and temperature of the end face grinding electric spindle 1. It then calculates the heating electrical parameters supplied to the stator coil 104 of the driving motor in a heating mode of electromagnetic induction heating or thermal radiation heating. The heating electrical parameters include frequency and voltage to ensure that the shaft temperature of the end face grinding spindle 101 is maintained at a consistent temperature during normal operation or 2-8°C higher than the operating temperature. The heating frequency includes medium frequency and low frequency. Preferably, a low frequency of 500Hz to 800Hz is used for heating, which makes heating more uniform and stable and consumes less energy.

[0072] 4) The heating inverter 102 supplies heating electrical parameters to the drive motor stator coil 104, generating a heating current that performs variable-frequency induction heating on the drive motor rotor shaft 105. This heating can be either intermittent or continuous. Continuous heating requires accurate calculation of the heating power required to achieve a thermal balance between heating and heat loss. Intermittent heating requires a temperature sensor installed on the drive motor rotor shaft 105, which is used for real-time control based on the temperature value of the temperature sensor.

[0073] 5) When the drive motor control system presses the start button again, the drive motor control system will first convert the control mode of the drive motor stator coil 104, cut off the heating inverter control system 103 from controlling the drive motor stator coil 104, and restore the normal drive control of the drive motor control system.

[0074] The control methods of electromagnetic induction heating mainly include the following:

[0075] Switch control: This is the simplest control method, which uses a switch signal to control the start and stop of the electromagnetic heater. Its advantages are simplicity and resistance to interference, but the temperature control accuracy is poor, generally within a temperature range of plus or minus 2 degrees.

[0076] Analog Control: Controls the power of the electromagnetic heater via a 0-5V voltage signal or a 0-20mA (4-20mA) current signal. This allows for more precise temperature control, with a temperature control accuracy of ±0.5°C.

[0077] PID Control: The PID controller adjusts the power output based on the deviation of the temperature from the set point. When the temperature approaches the set point, the power is automatically reduced, allowing for more precise temperature control.

[0078] ‌485 communication control‌: Through the RS485 communication interface, the working status of the electromagnetic heater can be remotely controlled, including start and stop control and power adjustment, and the operating parameters of the electromagnetic heater can also be read;‌

[0079] PWM Control: Pulse Width Modulation (PWM) controls the heating temperature by varying the heater's supply voltage and duration by adjusting the pulse width. This method allows for precise temperature control and is suitable for applications requiring high-precision temperature control.

[0080] The embodiment adopts an induction heating control system to supply a heating current to the end face grinding motor shaft 1 after the end face grinding motor shaft 101 is stopped. This method using the stator coil 104 of the driving motor is very simple to change; without any improvement to the main body of the end face grinding motor shaft 101, the heating and temperature maintaining after the end face grinding motor shaft 1 is stopped can be realized by changing the driving mode of the driving motor, which can effectively improve the axial machining accuracy of the end face grinding motor shaft 1 and is simple and easy to implement. Through comparative tests, it is found that the machining accuracy of the end face grinding motor shaft 1 during the machining of the flat clearance angle can be effectively improved.

[0081] Through test tests, it is found that the machining accuracy of the end face grinding motor shaft 1 during the machining of the flat clearance angle can be effectively improved by using the method, and the specific test data is as follows:

[0082] 1. Measurement data of ordinary end face grinding motor shaft grinding machining

[0083] Test equipment: QD560 numerical control tool grinder;

[0084] Test conditions: The diameter of the ground tool is 4 mm; the driving motor shaft is an 11 kW motor shaft;

[0085] Test purpose: To trace back test the unstable diameter size during cold machining and the large size change during stoppage; to detect the degree of the influence of the key shafts (Y axis and grinding motor shaft) of the QD560 machine on the diameter size of the linear clearance angle machining tool.

[0086] A total of 49 tools were tested, and the size balance size during cold machining was 0.051 mm. After the motor shaft was stopped for half an hour, the tool size became smaller by 0.01 mm, which was understood as excessive thermal elongation of the motor shaft. The test data of the subsequent two stoppages were basically the same, and the conclusion was that the thermal elongation size of this motor shaft was about 0.025 mm (the influence on the tool diameter was about 0.05 mm), and the stoppage for half an hour was about 0.018-0.02 mm (the influence on the tool diameter was about 0.036-0.04 mm);

[0087] 2. Measurement data of end face grinding motor shaft grinding machining with auxiliary heating and temperature maintaining

[0088] Test equipment: QD560 numerical control tool grinder;

[0089] Test conditions: The diameter of the ground tool is 4 mm; the driving motor shaft is an 11 kW motor shaft, and the auxiliary induction heating control system is used for heating when stopped, and the heating electrical parameter value is: frequency 50 Hz, and the electrical power required for heating is selected according to the resistance R of the 11 kW motor shaft of the QD560 numerical control tool grinder, and is controlled at about 40-50 watts per second;

[0090] Test purpose: To test the effect of auxiliary electric heating on the temperature preservation of the end face grinding electric spindle after parking.

[0091] The total number of test tools is 50. Starting from cold, the change in tool size when the spindle is not rotating is -0.03 mm (understood as the thermal elongation of the spindle being 0.015 mm). After the spindle is rotated at 3000 RPM, the change in tool size is within 0.01 mm. Therefore, the thermal elongation of the spindle after auxiliary heating is significantly controlled, which is 0.015 mm lower than the cold elongation of the ordinary end face grinding electric spindle (the impact on tool diameter is reduced by 0.03 mm).

[0092] Example two: The auxiliary electric heating method of the end face grinding electric spindle of the numerical control tool grinder for preventing the axial deformation of the end face grinding electric spindle from affecting the machining precision, as shown in FIG. 2, comprises the following steps: Figure 4 As shown in FIG. 2, a heating semiconductor switch control component 202 is added in the driving motor control system 203 of the tool grinder. When the end face grinding electric spindle 1 of the tool grinder stops running, the end face grinding electric spindle 1 of the tool grinder is heated and preserved by the heating semiconductor switch control component 202 under the control of the driving motor control system 203, so that the shaft temperature of the end face grinding electric spindle 1 of the tool grinder when it stops running is consistent with the shaft temperature when it runs, avoiding the rapid cooling of the end face grinding electric spindle 1 of the tool grinder after it stops running, which leads to the change of the axial size of the end face grinding electric spindle 1 of the tool grinder, thereby affecting the machining precision of the end face grinding electric spindle 1 of the tool grinder.

[0093] The auxiliary heating device of this embodiment still uses the drive motor stator coil 104 as the auxiliary electric heating element, but the drive motor stator coil 104 is controlled by a heating semiconductor switch control component 202 arranged outside the drive motor control system of the end face grinding electric spindle 1; the heating semiconductor switch control component 202 is powered by a power module (DC or AC) 206, and the heating semiconductor switch control component 202 includes a semiconductor switch 207 and a contactor 205, and at least one contactor 205 or semiconductor switch 207 is provided with an electrical parameter value adjustment device with adjustable voltage or adjustable current; after the drive motor stops driving the end face grinding electric spindle 1 to operate, the drive motor control system 203 automatically switches to supplying The driving motor stator coil 104 provides a control mode of heating current, and adjusts the voltage and / or current provided to the driving motor stator coil 104 through the electrical parameter value adjustment device of the contactor 205 or the semiconductor switch 207, so that a heating current is applied to the driving motor stator coil 104. The driving motor stator coil 104 is converted into an electric heating coil by the heating current, and the driving motor rotor shaft is heated by induction and / or thermal radiation heating. Then, the entire end face grinding electric spindle 1 is heated by heat conduction in a non-rotating or low-speed state, so that the shaft temperature of the end face grinding electric spindle 1 after stopping is maintained above the shaft temperature during operation, thereby preventing axial deformation caused by cooling of the end face grinding electric spindle 1.

[0094] The size of the heating current is calculated and determined based on the power required to heat the rotor shaft of the drive motor, ensuring that the heating current controlled by the frequency converter or the heating semiconductor switch control component will not continuously increase the shaft temperature of the end face grinding electric spindle 1, so as to ensure that the shaft temperature of the end face grinding electric spindle 1 after it stops during processing can continue to be maintained at 2-8°C higher than the shaft temperature during operation.

[0095] The magnitude of the heating current is controlled by adjusting the power supply frequency or voltage of the induction heating control system; the power supply frequency of the heating current is controlled within the frequency range of low-frequency or medium-frequency heating, so that the heating current provided to the stator coil 104 of the drive motor is a low-frequency or medium-frequency heating current; the power of the heating current is determined according to the resistance value of the rotor shaft of the drive motor and the power required to heat the rotor shaft of the drive motor according to the induction heating method.

[0096] At the same time, when the drive motor drives the end face grinding electric spindle 1 to operate normally again, the drive motor stator coil must stop heating the end face grinding electric spindle 1. At this time, it is necessary to ensure that when the drive motor stator coil stops providing heating current, the shaft temperature of the end face grinding electric spindle 1 is 6-10°C higher than the shaft temperature during operation, so as to prevent the axial size of the end face grinding electric spindle 1 from having errors during the stable hot shaft period from the end face grinding electric spindle 1 being started again to normal operation.

[0097] The embodiment is characterized in that a heating semiconductor switch control assembly 202 is adopted, and the switching and control of the driving motor are driven to make the driving motor stator coil 104 obtain a heating current after parking, so that the required effect can be achieved although the structure is relatively complex to adjust.

[0098] The basic principle of the third embodiment is also the same as that of the second embodiment, which is an auxiliary electric heating method for preventing the axial deformation of the end face grinding electric spindle from affecting the machining precision of the multi-functional tool grinder, as shown in the accompanying drawings. Figure 5 As shown in the accompanying drawings, a constant voltage or constant current device 302 is added to the driving motor control system of the multi-functional tool grinder, and when the end face grinding electric spindle 1 of the multi-functional tool grinder stops running, the original driving motor control system 305 is switched to the control mode of the constant voltage or constant current device 302 for heating and keeping warm the end face grinding electric spindle 1 of the multi-functional tool grinder under the control of the contactor control system 303, the heating current is provided to the driving stator coil 104 by the constant voltage or constant current device 302, and the end face grinding electric spindle 1 is heated and kept warm through heat radiation and heat conduction, so that the shaft temperature of the end face grinding electric spindle 1 of the multi-functional tool grinder when stopping running is basically the same as that when running, the rapid cooling of the end face grinding electric spindle 1 of the multi-functional tool grinder after stopping running is avoided, the axial dimension of the end face grinding electric spindle 1 of the multi-functional tool grinder changes, and the axial machining precision of the end face grinding electric spindle 1 of the multi-functional tool grinder is affected.

[0099] The auxiliary heating device of the embodiment still takes the driving motor stator coil 104 as the auxiliary electric heating element, but the driving motor stator coil 104 is controlled by the constant voltage or constant current device 302 arranged outside the end face grinding electric spindle 1; at least one constant voltage or constant current device 302 is provided with an electric parameter value adjusting device with adjustable voltage or adjustable current; after the driving motor stops driving the end face grinding electric spindle 1 to run, the electric parameter value adjusting device of the constant voltage or constant current device 302 adjusts the size of the voltage or / and current to apply a heating current to the driving motor stator coil 104, the driving motor stator coil 104 becomes an electric heating coil through the heating current, the driving motor stator coil 104 is heated, the driving motor rotor shaft is heated through direct heat radiation and heat conduction, and the entire end face grinding electric spindle 1 is heated in the state of not rotating or rotating at low speed, so that the shaft temperature of the end face grinding electric spindle 1 after stopping running is maintained above the shaft temperature when running, and the deformation in the axial direction of the end face grinding electric spindle 1 caused by the cooling is prevented.

[0100] The other parts are the same as those of the second embodiment.

[0101] The embodiment is characterized in that a constant voltage or constant current device 302 is used to provide a heating current for the stator coil 104 of the driving motor after the driving motor is stopped during the machining process, and the power supply mode can be intermittent or continuous.

[0102] The above-listed embodiments are only used to clearly and completely describe the technical solutions of the present application in combination with the drawings; obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the protection scope of the present application.

[0103] The present application has the following advantages:

[0104] Compared with the prior art, the present application can heat, keep warm and supply a keeping-warm current to the end face grinding electric spindle when the end face grinding electric spindle is stopped, so that the temperature of the end face grinding electric spindle can be kept when the end face grinding electric spindle is not running, and the end face grinding electric spindle will not be in a cooling state when the end face grinding electric spindle is started again, which can effectively eliminate the problem of axial deformation of the end face grinding electric spindle caused by the cooling of the end face grinding electric spindle when the end face grinding electric spindle is stopped, and has the following advantages:

[0105] 1. The present application can heat and keep warm the end face grinding electric spindle when the end face grinding electric spindle is stopped, so that the original temperature of the end face grinding electric spindle can be kept when the end face grinding electric spindle is stopped, and the axial change caused by the cooling of the end face grinding electric spindle can be prevented, which can effectively improve the axial machining precision of the end face grinding electric spindle. Through actual test, the grinding precision error of the plane relief angle can be effectively eliminated to be more than 0.03 mm, the overall grinding precision of the plane relief angle can be controlled to be within 0.05 mm, and the precision requirement of the high-precision numerical control grinding machine is met.

[0106] 2. The auxiliary heating proposed in the present application is electric auxiliary heating, which changes the traditional water constant temperature spindle keeping-warm mode. After the electric auxiliary heating is started, the stopped end face grinding electric spindle can be kept warm, so that the axial temperature change of the end face grinding electric spindle from stopping to starting machining again is effectively prevented, and the machining precision is affected. This electric heating mode not only has fast response, but also is simple and easy to control.

[0107] 3、The application adopts electric auxiliary heating to control the shaft temperature of the end face grinding electric spindle, so that the shaft temperature of the end face grinding electric spindle can be kept stable, so that the end face grinding electric spindle can be applied to high-precision numerical control grinding machine, replacing the current foreign mechanical spindle method to improve the plane rear angle grinding precision, which can greatly reduce the occupied space of the whole grinding head, and is more conducive to improving the application space of the numerical control grinding machine and reducing the volume of the whole machine tool;

[0108] 4、The application ingeniously adopts the method of directly changing the driving motor stator coil into a heating coil, taking the driving motor rotor as the heated body, and providing a heating current to the driving motor stator coil as the heating coil through the driving motor stator coil control system after the driving motor stops running during processing, so as to heat the driving motor rotor shaft through induction and / or thermal radiation heating, and then heat the whole end face grinding electric spindle at a non-rotating or low speed state through heat conduction, so that the original end face grinding electric spindle whole grinding head does not need to be changed, and the implementation is simple and easy to implement;

[0109] 5、The end face grinding electric spindle is heated by the frequency converter or contactor or semiconductor switch, and the heating principle is that the end face grinding electric spindle itself has a coil with resistance, according to the formula P=UI=lxlR (in the formula: P is power, U is voltage, I is current, and R is resistance), through the formula, it can be seen that the end face grinding electric spindle (equivalent to the formula R) can be heated by passing appropriate current (equivalent to the formula I) to the coil; this heating principle only needs simple calculation control to ensure that the end face grinding electric spindle is kept at a certain temperature, and is easy to implement;

[0110] 6、The end face grinding electric spindle is heated by the intermediate frequency heating method, and the heating speed is fast: the eddy current is generated in the metal, the heating speed is fast, and the efficiency is high;

[0111] 7、The end face grinding electric spindle is heated by the auxiliary electric heating method, and the temperature can be accurately controlled: various electric parameters can be adjusted to realize accurate temperature control, including adjusting current, voltage and frequency;

[0112] 8、The end face grinding electric spindle is heated by the induction heating method, compared with the original water constant temperature system, it is more environmentally friendly and energy-saving, and there is no water pollution problem: the induction heating has no open flame, high safety, and high energy efficiency ratio.

Claims

1. A method for heating the end face grinding electric spindle when it is parked based on the stator coil of the driving motor, characterized in that: When the end face grinding electric spindle stops running during processing, the stator coil of the driving motor is converted into an electric heating coil to heat the end face grinding electric spindle. The end face grinding electric spindle is heated by induction and / or thermal radiation heating, and the electric power parameters of the stator coil of the driving motor are controlled to ensure that the shaft temperature of the end face grinding electric spindle when it stops midway continues to be maintained above the shaft temperature during operation; the heating of the end face grinding electric spindle by converting the stator coil of the driving motor into an electric heating coil uses the stator coil of the driving motor as the heating coil, and the stator coil of the driving motor is controlled by the auxiliary electric heating control system. After the driving motor stops running during processing, the control mode of the stator coil of the driving motor is switched through the auxiliary electric heating control system, and the driving control mode of the stator coil of the driving motor is converted into the heating control mode, The motor stator coil provides a heating electric heating parameter value to form a heating current, the magnitude of which is controlled by adjusting the power supply frequency or voltage of the induction heating control system; the power supply frequency of the heating current is controlled within the frequency range of low-frequency or medium-frequency heating, so that the heating current provided to the stator coil of the drive motor is a low-frequency or medium-frequency heating current; the power of the heating current is determined according to the resistance value of the rotor shaft of the drive motor and the power required to heat the rotor shaft of the drive motor in accordance with the induction heating method; the heating current passes through the stator coil of the drive motor, and the stator coil of the drive motor is used as a heating device to heat the rotor shaft of the drive motor through induction and / or thermal radiation heating, and then the entire end face grinding electric spindle is heated through heat conduction, so that the entire end face grinding electric spindle maintains the shaft temperature during operation when it stops.

2. The method for heating the end face grinding electric spindle while it is parked based on the stator coil of the driving motor according to claim 1, characterized in that: The provision of an electric heating parameter value for heating the stator coil of the drive motor is achieved by setting an auxiliary electric heating control system in the drive motor control system to provide a heating current to the stator coil of the drive motor; after the end face grinding electric spindle stops rotating during processing, the drive control system of the stator coil of the drive motor is switched by the switching device of the auxiliary electric heating control system, and the auxiliary electric heating control system provides a heating electric parameter value for induction or radiation heating to the stator coil of the drive motor, so that the stator coil of the drive motor becomes an induction or radiation heating coil; without driving the normal rotation of the drive motor, the rotor shaft of the drive motor is heated by induction or radiation heating, and then the entire end face grinding electric spindle is heated by heat conduction, so that the shaft temperature of the entire end face grinding electric spindle is maintained above the shaft temperature during operation after the operation stops during processing.

3. The method for heating the end face grinding electric spindle while it is parked based on the stator coil of the driving motor according to claim 2, characterized in that: The heating electrical parameter values ​​include frequency, voltage and current. By adjusting the frequency, voltage and current of the auxiliary electric heating control system, the current supplied to the stator coil of the drive motor becomes the heating current.

4. The method for heating the end face grinding electric spindle while it is parked based on the stator coil of the driving motor according to claim 2, characterized in that: The method of heating the rotor shaft of the drive motor by induction or radiation heating is to provide a heating inverter and its heating inverter control system in the drive motor control system. After the drive motor stops running during processing, the control method of the stator coil of the drive motor is changed by the heating inverter control system, and the heating inverter control system starts the heating inverter to supply heating electrical parameters to the stator coil of the drive motor in a variable frequency heating mode to form a heating current, and then heat the rotor shaft of the drive motor by induction and / or thermal radiation heating.

5. The method for heating the end face grinding electric spindle while it is parked based on the stator coil of the driving motor according to claim 4, characterized in that: The variable frequency heating comprises the following steps: 1) Press the stop button of the drive motor control system, the end face grinding electric spindle loses power, and the end face grinding electric spindle gradually stops rotating; 2) After determining that the end face grinding electric spindle has stopped rotating, the control mode of the drive motor stator coil is switched through the switching device of the auxiliary electric heating control system, so that the control of the drive motor stator coil is switched from drive control to heating inverter control system control; 3) The heating inverter control system starts the heating inverter, determines the required electric heating power according to the resistance value of the end grinding electric spindle, and calculates the heating electrical parameters supplied to the stator coil of the drive motor in the variable frequency heating mode; 4) The heating inverter supplies heating electrical parameters to the stator coil of the drive motor to form a heating current, and performs variable frequency induction heating on the rotor shaft of the drive motor. The heating includes intermittent heating and continuous heating; 5) When the drive motor control system presses the start button again, the drive motor control system will first convert the control mode of the drive motor stator coil, cut off the heating inverter control system from controlling the drive motor stator coil, and restore the normal drive control of the drive motor control system.

6. The method for heating the end face grinding electric spindle while it is parked based on the stator coil of the driving motor according to claim 2, characterized in that: The method of heating the rotor shaft of the drive motor by induction or radiation heating is to set a heating semiconductor switch control component in the control system of the drive motor, and at least one heating semiconductor switch control component is provided with an electrical parameter value adjustment device with adjustable voltage or adjustable current; after the drive motor stops driving the end face grinding electric spindle to operate, the control system of the drive motor automatically switches the control of the drive motor stator coil to the control of the heating semiconductor switch control component, and the electrical parameter value adjustment device of the heating semiconductor switch control component applies a heating current to the stator coil of the drive motor by adjusting the voltage and / or current. The heating current turns the stator coil of the drive motor into an electric heating coil, and heats the rotor shaft of the drive motor by induction and / or thermal radiation heating. Then, the entire end face grinding electric spindle is heated by heat conduction in a non-rotating or low-speed state, so that the shaft temperature of the end face grinding electric spindle after stopping is maintained above the shaft temperature during operation.

7. The method for heating the end face grinding electric spindle while it is parked based on the stator coil of the driving motor according to claim 6, characterized in that: The control system of the drive motor automatically switches the control of the drive motor stator coil to the heating semiconductor switch control component which is controlled by a power semiconductor device. The power semiconductor device provides heating electrical parameters to the drive motor stator coil. The drive motor stator coil heats the drive motor rotor shaft by induction heating, and then heats the entire end face grinding electric spindle in a non-rotating or low-speed state through heat conduction, so that the shaft temperature of the end face grinding electric spindle after stopping is maintained above the shaft temperature during operation.

8. The method for heating the end face grinding electric spindle while it is parked based on the stator coil of the driving motor according to claim 2, characterized in that: The auxiliary electric heating control system provides a heating electrical parameter value for induction or radiation heating to the stator coil of the drive motor. A constant voltage or constant current device is added to the drive motor control system. When the grinding spindle stops running, the constant voltage or constant current device is used, under the control of the contactor control system, to switch the original drive motor control system to a control mode in which the constant voltage or constant current device is used to heat and keep the end face grinding electric spindle warm. The constant voltage or constant current device provides heating current to the stator coil of the drive motor, and then heats the end face grinding electric spindle through thermal radiation, so that the shaft temperature of the end face grinding electric spindle when it stops running is consistent with the shaft temperature when it is running.

9. The method for heating the end face grinding electric spindle when stopped based on the stator coil of the driving motor according to claim 2, 6 or 8, characterized in that: The size of the heating current is calculated and determined based on the power required to heat the rotor shaft of the drive motor, ensuring that the heating current controlled by the frequency converter or heating semiconductor switch control component and the constant voltage or constant current device can only keep the shaft temperature of the end face grinding electric spindle within a temperature range of 2-8°C higher than the shaft temperature during operation after it stops during processing.

10. The method for heating the end face grinding electric spindle while it is parked based on the stator coil of the driving motor according to claim 1, characterized in that: When the drive motor drives the end face grinding electric spindle to operate normally again, the drive motor stator coil stops heating the end face grinding electric spindle. At this time, it is necessary to ensure that when the drive motor stator coil stops providing heating current, the shaft temperature of the end face grinding electric spindle is 3-8℃ higher than the shaft temperature during operation.

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