Thermal displacement estimation method for machine tool and machine tool

Abstract

The present application provides a thermal displacement estimation method for a machine tool and a machine tool. A temperature detection step of detecting the temperature of a bearing portion of a spindle and a column and a thermal displacement estimation step of estimating the thermal displacement of the spindle by an estimation model according to the detected temperature are executed, in the thermal displacement estimation step, a coefficient for estimating the thermal displacement according to the detected temperature is decided according to a change in cooling capacity, a change in cooling heat corresponding to the change in cooling capacity is found according to the relationship between the cooling heat of a spindle cooling device and the temperature corresponding to the cooling heat, a change in conversion coefficient corresponding to the change in cooling capacity is found according to the relationship between the cooling heat and the conversion coefficient for estimating the thermal displacement according to the detected temperature, and the thermal displacement of the spindle is estimated according to the temperature after the detected temperature is added with the change in corresponding temperature and the coefficient.

Description

Technical Field

[0001] This disclosure relates to a method for estimating the thermal displacement of a machine tool based on temperature, and a machine tool capable of performing the method. Background Technology

[0002] In machining processes using machine tools such as machining centers, thermal displacement along the axial direction occurs due to frictional heat generated by the bearings during spindle rotation and heat generated by the motor, which degrades machining accuracy. As a preventative measure, mechanical structures employ methods to remove heat by installing a cooling circuit in the spindle housing and circulating cooling oil (hereinafter referred to as "spindle cooling"). Furthermore, electrical control systems utilize methods to estimate and correct for spindle thermal displacement based on machine body temperature information.

[0003] In the former case of spindle cooling, the power consumption of the spindle cooling device, which controls the temperature of the supplied cooling oil to match the machine body temperature, accounts for a relatively high proportion of the power consumption of peripheral equipment. Therefore, measures to reduce power consumption through the operation control of the spindle cooling device are widely implemented. For example, Patent Document 1 discloses an invention that stops the spindle cooling device when the temperature near the spindle, calculated using the spindle temperature rise value based on the machine body temperature, meets any arbitrary threshold during machine downtime. According to this invention, power consumption can be reduced without deteriorating machining accuracy. Furthermore, Patent Document 2 discloses an invention that stops the spindle cooling device when the influence of rotational speed and heat source temperature on machining accuracy below a predetermined threshold is minimal, thereby reducing power consumption.

[0004] In the latter method of estimating thermal displacement, the applicant's patent document 3 proposes a calculation method to estimate the thermal displacement of the spindle by changing the calculation coefficients of the thermal displacement estimation formula based on the rotational speed and time or the number of corrections.

[0005] Existing technical documents

[0006] Patent documents

[0007] Patent Document 1: Japanese Patent No. 6445395

[0008] Patent Document 2: Japanese Patent No. 6349276

[0009] Patent Document 3: Japanese Patent Application Publication No. 9-225781 Summary of the Invention

[0010] The problem that the invention aims to solve

[0011] The preferred method for reducing power consumption is not only to stop the spindle cooling device when the machine is idle, as in the invention of Patent Document 1, but also to stop the spindle cooling device while the machine tool is running, as in the invention of Patent Document 2. However, in the spindle of a machining center, if the cooling device is stopped while the spindle is rotating, even after 1000 minutes... -1 The spindle thermal displacement increases over time with varying rotational speeds, thus its impact on accuracy is limited to short periods. Therefore, to maintain accuracy over a longer period, it is necessary to estimate and correct the spindle thermal displacement as described in Patent Document 3. However, the thermal displacement characteristics differ when the spindle cooling system is running and when it is stopped, making it impossible to accurately estimate the thermal displacement using the method described in Patent Document 3.

[0012] Therefore, the purpose of this disclosure is to provide a method for estimating the thermal displacement of a machine tool and a machine tool that can accurately estimate the thermal displacement even in a transitional state where the operating state of the cooling device changes, thereby reducing power consumption without deteriorating machining accuracy.

[0013] Methods for solving problems

[0014] To achieve the above objectives, the first structure of this disclosure is characterized in that, in a machine tool having a cooling device and a temperature measuring device, the following steps are performed:

[0015] The temperature detection step involves using the temperature measuring device to detect the temperatures of a specified heating element and a specified main structural element, respectively; and

[0016] The thermal displacement estimation step involves estimating the thermal displacement of the heating element based on the detected temperature using an estimation model.

[0017] The method for estimating the thermal displacement of the machine tool is characterized by the following:

[0018] In the thermal displacement estimation step, the following processing is performed:

[0019] Based on the change in cooling capacity caused by the operation control of the cooling device during machine tool operation, a time-response related coefficient for estimating thermal displacement based on the detected temperature is determined.

[0020] Based on the relationship between the pre-set cooling heat of the cooling device and the conversion coefficient between temperature and displacement used to estimate the thermal displacement based on the detected temperature, a temperature change equivalent to the change in the conversion coefficient before and after the change in cooling capacity is calculated; and / or, based on the pre-set relationship between the cooling heat and the temperature equivalent to the cooling heat, a temperature change equivalent to the change in cooling heat before and after the change in cooling capacity is calculated.

[0021] The thermal displacement of the heating element is estimated based on the temperature and the coefficient obtained by adding the conversion coefficient to the detected temperature and / or the cooling heat to the temperature change.

[0022] Another aspect of the first structure is characterized in that, in the above structure, the change in the cooling capacity of the cooling device is due to any one or both of the operation and shutdown of the cooling device and the increase and decrease of the amount of cooling oil used for cooling.

[0023] Another aspect of the first structure is characterized in that, in the above structure, the heating element is a rotating shaft, and the conversion coefficient is calculated based on the rotational speed of the rotating shaft and the time after the cooling capacity of the cooling device changes.

[0024] Another aspect of the first structure is characterized in that, in the above structure, the amount of temperature change equivalent to the cooling heat is calculated based on the temperature time constant before the change in cooling capacity, the temperature time constant after the change in cooling capacity, and the time after the change in cooling capacity.

[0025] Another aspect of the first structure is characterized in that, in the above structure, the cooling capacity of the cooling device changes under the following conditions: using a preset upper limit and lower limit as thresholds, the cooling capacity is reduced when the temperature rise of the detected temperature is below the lower limit, and the cooling capacity is increased when the temperature rise of the detected temperature is above the upper limit.

[0026] Another feature of the first structure is that, in the above structure, the heating element is a rotating shaft, and the temperature rise of the bearing portion of the rotating shaft or near the bearing portion, based on the temperature of the main structure portion, is used for thermal displacement estimation.

[0027] To achieve the above objectives, the second structure disclosed herein is a machine tool having a cooling device and a temperature measuring device, characterized in that the machine tool comprises:

[0028] The temperature detection unit detects the temperatures of a specified heating element and a specified main structural element using a temperature measuring device; and

[0029] The thermal displacement estimation unit estimates the thermal displacement of the heating element based on the detected temperature and using an estimation model.

[0030] The thermal displacement estimation unit performs the following processing:

[0031] Based on the change in cooling capacity caused by the operation control of the cooling device during machine tool operation, a time-response related coefficient for estimating thermal displacement based on the detected temperature is determined.

[0032] Based on the relationship between the pre-set cooling heat of the cooling device and the conversion coefficient between temperature and displacement used to estimate the thermal displacement based on the detected temperature, a temperature change equivalent to the change in the conversion coefficient before and after the change in cooling capacity is calculated; and / or, based on the pre-set relationship between the cooling heat and the temperature equivalent to the cooling heat, a temperature change equivalent to the change in cooling heat before and after the change in cooling capacity is calculated.

[0033] The thermal displacement of the heating element is estimated based on the temperature obtained by adding the temperature change equivalent to the conversion coefficient and / or the temperature change equivalent to the cooling heat to the detected temperature, and the coefficient.

[0034] Furthermore, the "presumed model" in this disclosure refers to a series of pre-modeled processes for presuming thermal displacement. For example, a decision process consisting of one or more mathematical formulas containing coefficients can be cited.

[0035] Invention Effects

[0036] According to this disclosure, by calculating the temperature change corresponding to the difference between the temperature and displacement before and after a pre-set change in the conversion coefficient between the detected temperature of the heating element or its vicinity and the conversion coefficient between the temperature and displacement before and after the change in the operation control of the cooling device, and / or the temperature change corresponding to the difference in the cooling heat, the deterioration of thermal displacement estimation accuracy during the cooling transition state when the cooling device is under operation control during machine tool operation can be addressed. Therefore, even in the transition state where the operation state of the cooling device changes, thermal displacement can be accurately estimated, reducing power consumption without deteriorating machining accuracy.

[0037] According to another aspect of this disclosure, in addition to the effects described above, since the change in the cooling capacity of the cooling device is set as either or both of the operation and shutdown of the cooling device and the increase and decrease of the amount of cooling oil used for cooling, it is possible not only to operate and stop the cooling device, but also to estimate the thermal displacement corresponding to the increase and decrease of the amount of cooling oil.

[0038] According to another aspect of this disclosure, in addition to the effects described above, since the conversion coefficient is calculated based on the time following the change in the rotational speed of the rotating shaft and the change in cooling capacity, the thermal displacement can be estimated with high precision in correspondence to the change in cooling capacity corresponding to the rotational speed.

[0039] According to another aspect of this disclosure, in addition to the effects described above, the amount of temperature change equivalent to cooling heat is calculated based on a pre-set temperature time constant before the change in cooling capacity of the cooling device, a pre-set temperature time constant after the change in cooling capacity of the cooling device, and the time after the change in cooling capacity. Therefore, setting the amount of temperature change equivalent to cooling heat becomes easy.

[0040] According to another aspect of this disclosure, in addition to the effects described above, as a condition for changing the cooling capacity of the cooling device, an upper limit and a lower limit for the temperature rise are preset. When the temperature rise is above the upper limit, the cooling capacity is increased, thereby avoiding the risk of abnormal heating such as bearing sintering caused by reducing the cooling capacity. On the other hand, when the temperature rise is below the lower limit, reducing the cooling capacity can reduce power consumption.

[0041] According to other methods of this disclosure, in addition to the effects described above, when the rotating shaft is the object to be cooled, the thermal displacement can be estimated with high accuracy by using the temperature rise value of the rotating shaft bearing portion or the vicinity of the bearing portion based on the temperature of the main structure. Attached Figure Description

[0042] Figure 1 It is a block diagram representing the structure of a machining center.

[0043] Figure 2 This is a flowchart of the thermal displacement estimation method.

[0044] Explanation of reference numerals in the attached figures

[0045] 1. Bed, 2. Column, 3. Spindle head, 4. Spindle unit, 5. Worktable, 6. Cooling oil inlet, 7. Cooling oil outlet, 8, 9. Temperature sensor, 1. Temperature measuring device, 11. NC device, 12. Spindle cooling device, 13. Calibration calculation device, M. Machining center. Detailed Implementation

[0046] Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings.

[0047] Figure 1 This is a block diagram showing the structure of a machining center M, which is an example of a machine tool with a second structure.

[0048] Machining center M comprises a bed 1, a column 2, a spindle head 3, a spindle unit 4, and a worktable 5. Additionally, machining center M includes a temperature measuring device 10, an NC unit 11, a spindle cooling device 12, and a calibration calculation device 13. The NC unit 11 includes a central processing unit (CPU) and a memory connected to the CPU, ensuring reliable operation.

[0049] The temperature measuring device 10 uses a temperature sensor 8 installed on the spindle unit 4 to detect the temperature rise of the bearing part of the spindle, and uses a temperature sensor 9 installed on the column 2 to detect the body temperature, which becomes the reference temperature.

[0050] The spindle cooling device 12 has a cooling circuit that supplies cooling oil to the cooling oil inlet 6 of the outer cylinder of the spindle housing and returns it from the cooling oil outlet 7.

[0051] In addition to controlling the spindle rotation and the feed axis movement, the NC device 11 also controls the operation of the spindle cooling device 12. This operation control is based on a preset upper and lower limit of the temperature difference between temperature sensor 8 and temperature sensor 9 (hereinafter referred to as the "temperature rise value"). Specifically, when the temperature rise value falls below the lower limit, the operation of the spindle cooling device 12 is stopped; when the temperature rise value rises above the upper limit, the operation of the spindle cooling device 12 is restarted.

[0052] The temperatures detected by each temperature sensor 8 and 9 are converted from analog signals to digital signals using a known method according to a pre-set period by the temperature measuring device 10, and then sent to the calibration calculation device 13 after being quantified. Each temperature sensor 8 and 9 and the temperature measuring device 10 are examples of the temperature detection unit of this disclosure.

[0053] In the correction calculation device 13, the spindle thermal displacement is estimated based on an estimation model, which includes an estimated spindle temperature calculated from quantified temperature data and a pre-set thermal displacement estimation formula using a conversion coefficient from spindle temperature to spindle thermal displacement. The correction amount based on the estimated thermal displacement is output to the NC device 11. The correction calculation device 13 is an example of the thermal displacement estimation unit of this disclosure.

[0054] The NC device 11 corrects the movement of each feed axis based on the correction amount.

[0055] The following explains the estimation of the spindle thermal displacement in the calibration calculation device 13.

[0056] First, in Equation 1, the temperature θ1 measured by temperature sensor 8 is used... n and the temperature θ2 measured by temperature sensor 9 n Calculate the temperature rise θ n The calculated temperature rise θ n Above, add the temperature θ shown in Equation 2, which is equivalent to the change in heat before and after the change in the cooling capacity of the spindle cooling device 12. Equn The temperature θ, represented by Equations 3-1 and 3-2, is equivalent to the temperature change (equivalent to the amount of cooling heat) and the difference between the conversion coefficients between temperature and displacement before and after the change in the cooling capacity of the spindle cooling device 12. Gn (The conversion coefficient corresponds to the temperature change) (Equation 4), based on the obtained temperature θ CORn The spindle temperature θ is estimated by calculating using Equation 5. ESTn .

[0057] θ n =θ1 n -θ2 n …Formula 1

[0058] θ1 n The temperature of the spindle bearing section detected by temperature sensor 8 for the nth time.

[0059] θ2 n The nth time the body temperature is detected by temperature sensor 9

[0060] θ n The temperature rise value at the nth time

[0061] θ Equn =β1×exp(Δt×n / T1)-β2×exp(Δt×n / T2)…Equation 2

[0062] Δt: Estimated time interval for computation and processing

[0063] β1:θ Equ Calculation coefficient 1

[0064] β2:θ Equ Calculation coefficient 2

[0065] T1: Temperature time constant related to the cooling heat before the change in cooling capacity

[0066] T2: Temperature time constant related to the amount of heat dissipated after the change in cooling capacity.

[0067] θ Equn The amount of heat generated during the nth cooling event corresponds to the temperature change.

[0068] G n =G n-1 +(G0-G n-1 )×〔Δt / (Δt+T3)〕…Equation 3-1

[0069] θ Gn =(θ n +θ Equn )×G n …Formula 3-2

[0070] G n θ of the nth time G Calculation coefficients

[0071] G0: θ G The convergence value of the calculated coefficients

[0072] Δt: Estimated time interval for computation and processing

[0073] T3: Time constant for the conversion coefficient between temperature and displacement after a change in cooling capacity

[0074] θ Gn The conversion coefficient for the nth time corresponds to the temperature change.

[0075] θ CORn =θ n +θ Equn +θ Gn …Form 4

[0076] θ CORn The temperature at the nth temperature rise, plus the temperature equivalent to the change in heat before and after the change in cooling capacity, and the temperature equivalent to the difference between the temperature and displacement before and after the change in cooling capacity.

[0077] The obtained temperature

[0078] θ ESTn =θ ESTn-1 +(θ CORn -θ ESTn-1 )×〔Δt / (Δt+α)〕

[0079] …Form 5

[0080] Δt: Estimated time interval for computation and processing

[0081] α: Time response coefficient

[0082] θ ESTn Estimated spindle temperature for the nth time

[0083] Next, in Equation 6, based on the estimated spindle temperature θ ESTn The thermal displacement Z of the spindle is estimated using the temperature displacement conversion coefficient γ. n The coefficient γ is a temperature displacement conversion coefficient preset under the operating conditions of the spindle cooling device 12.

[0084] Z n =θ ESTn ×γ…Formula 6

[0085] γ: Temperature displacement conversion coefficient

[0086] Z n The nth spindle thermal displacement

[0087] The following is based on Figure 2 The flowchart describes the method for estimating thermal displacement involved in the first structure when controlling the operation of the spindle cooling device 12 at any spindle speed.

[0088] The estimated operation is performed at time intervals Δt. In S1, a counter for the number of operations is started.

[0089] In S2, the bearing temperature is measured by temperature sensor 8, and the mechanical temperature is measured and quantified by temperature sensor 9 to obtain the current temperature data. The temperature rise θ is then calculated using Equation 1. n .

[0090] In step S3, it is determined whether the thermal displacement correction process is being performed for the first time. If it is the first time, the process proceeds to step S7; otherwise, it proceeds to step S4.

[0091] In step S4, it is determined whether the timing conditions for changing the operation control of the spindle cooling device 12 are met. These timing conditions are as follows: depending on whether either a preset upper or lower limit for temperature rise is reached, if the temperature rise falls below the lower limit, the operation of the spindle cooling device 12 is stopped; if the temperature rise exceeds the upper limit, the operation of the spindle cooling device 12 is restarted. For example, the upper limit is set to the temperature rise when the spindle cooling device 12 is operating at its maximum speed, and the lower limit is set to the temperature rise when the spindle cooling device 12 is operating at half its maximum speed.

[0092] When the timing condition is met in S4 and the operation of the spindle cooling device 12 changes, the count is reset in S5, and the counter is restarted.

[0093] In S6 and S7, corresponding to the operating or stopped state of the spindle cooling device 12, the coefficients β1, β2, T1, T2, G0, T3, and α used in Equations 2, 3, and 5 are changed or set to preset optimal coefficients. These coefficients can be fixed values, can differ in the operating or stopped state, or can be functions of the temperature corresponding to the operating or stopped state.

[0094] In addition, θ G The convergence value G0 of the calculation coefficients can also be set as a function of the spindle speed. In this case, the thermal displacement can be estimated with high accuracy in correspondence with the change in cooling capacity corresponding to the speed.

[0095] In S8, the equivalent temperature change θ of the cooling heat is calculated according to Equation 2. Equn The conversion coefficient equivalent temperature change θ is calculated according to equations 3-1 and 3-2. Gn .

[0096] In S9, it is determined whether to perform the cooling heat equivalent to the temperature change θ. Equn And the conversion coefficient equivalent to the temperature change θ GnThe summation is performed. The determination condition is, for example, the relationship between the summed equivalent temperature change and a pre-set threshold, or the relationship between the number of counts and a threshold. In the former case, if the summed equivalent temperature change is above the threshold, the process proceeds to S10; if it is below the threshold, the process proceeds to S11. In the latter case, if the number of counts is below the threshold, the process proceeds to S10; if it is above the threshold, the process proceeds to S11.

[0097] In S10, according to Equation 4, the temperature rise θ calculated in S2 is... n Add the cooling heat equivalent to the temperature change θ calculated in S8 Equn and the conversion coefficient equivalent to the temperature change θ Gn .

[0098] In S11, the estimated spindle temperature θ is calculated according to Equation 5. ESTn .

[0099] In S12, based on the estimated spindle temperature θ calculated in S11... ESTn Based on Equation 6, the thermal displacement Z of the main shaft is estimated. n And calculate the correction amount.

[0100] In S13, determine whether to continue thermal displacement correction. If to continue, return to S2 and execute the process starting from the temperature measurement.

[0101] Thus, the thermal displacement estimation method described above is performed in a machining center M equipped with a spindle cooling device 12 (an example of a cooling device) and a temperature measuring device 10, by performing the following steps: temperature detection step S2, in which the temperature of the bearing portion (an example of a defined heat-generating portion) and the column 2 (an example of a defined main structure portion) of the spindle are detected by the temperature measuring device 10; and thermal displacement estimation steps (S3 to S12), in which the thermal displacement of the spindle is estimated based on the detected temperature by using an estimation model composed of equations 1 to 6.

[0102] Then, in the thermal displacement estimation step, based on the change in cooling capacity controlled by the spindle cooling device 12 during machine tool operation, a coefficient for estimating the thermal displacement based on the detected temperature is determined (S6, S7). Based on the relationship between the pre-set cooling heat of the spindle cooling device 12 and the temperature equivalent to the cooling heat, the temperature change equivalent to the change in cooling heat before and after the change in cooling capacity is calculated. Based on the relationship between the cooling heat of the spindle cooling device 12 and the conversion coefficient between temperature and displacement used to estimate the thermal displacement based on the detected temperature, the temperature change equivalent to the conversion coefficient before and after the change in cooling capacity is calculated (S8). Based on the temperature and coefficient obtained by adding the equivalent temperature change to the detected temperature, the thermal displacement of the spindle is estimated (S12).

[0103] According to this structure, the deterioration of thermal displacement estimation accuracy during the cooling transition state when the spindle cooling device 12 is controlled during machine tool operation can be addressed. Therefore, even in the transition state where the operating state of the spindle cooling device 12 changes, thermal displacement can be accurately estimated, reducing power consumption without deteriorating machining accuracy.

[0104] In particular, the cooling capacity variation of the spindle cooling device 12 is set to either or both of the operation and shutdown of the spindle cooling device 12 and the increase and decrease of the amount of cooling oil used for cooling.

[0105] Therefore, it can not only operate and stop the spindle cooling device 12, but also estimate the thermal displacement corresponding to the increase or decrease of the amount of cooling oil.

[0106] Based on the temperature-time constant before the change in cooling capacity, the temperature-time constant after the change in cooling capacity, and the time after the change in cooling capacity, calculate the temperature change equivalent to the cooling heat.

[0107] Therefore, setting the amount of cooling heat equivalent to the temperature change becomes easy.

[0108] The conditions for the change in cooling capacity of the spindle cooling device 12 are as follows: using the preset upper and lower limits as thresholds, the cooling capacity is reduced when the temperature rise of the detected temperature is below the lower limit, and increased when it is above the upper limit.

[0109] Therefore, the risk of abnormal heating, such as bearing sintering, caused by reduced cooling capacity can be avoided. On the other hand, when the temperature rise is below the lower limit, reducing the cooling capacity can reduce power consumption.

[0110] The heating element is the spindle (an example of a rotating shaft), and the temperature rise near the bearing of the spindle, based on the temperature of column 2, is used to estimate the thermal displacement.

[0111] Therefore, it is possible to estimate thermal displacement with high accuracy.

[0112] Furthermore, in the above method, the cases of using both the temperature change equivalent to cooling heat and the temperature change equivalent to the conversion coefficient were explained. However, for spindles with small thermal displacement, even if either the temperature change equivalent to cooling heat or the temperature change equivalent to the conversion coefficient is used, the accuracy of the thermal displacement estimation can be predicted. Therefore, either one can be used.

[0113] In the above method, in S9, it is determined whether to add the equivalent temperature change to the measured temperature data based on the determination condition, but it is also possible to not perform this determination and always add the equivalent temperature change.

[0114] In the above method, the change of coefficient in S6 is performed according to the operating state and the stop state of the spindle cooling device, but it is not limited to the start / stop (ON / OFF) of the spindle cooling device. For example, the change of coefficient can also be performed when the amount of cooling oil is changed even when the spindle cooling device is in the start state, or when the cooling capacity is changed (e.g., when only the refrigeration unit is stopped and the pump is working).

[0115] The rotating shaft used to estimate thermal displacement is not limited to the main shaft. Temperatures outside the bearing section can also be detected. Multiple temperature sensors can also be installed in the heating element and the main structure, and the measured values ​​can be averaged.

[0116] The cooling device disclosed herein is not limited to a spindle. The machine tool to which this disclosure pertains is also not limited to a machining center.

Claims

1. A method for estimating the thermal displacement of a machine tool, comprising the following steps in a machine tool equipped with a cooling device and a temperature measuring device: The temperature detection step involves using the temperature measuring device to detect the temperatures of a specified heating element and a specified main structural element, respectively; and The thermal displacement estimation step involves estimating the thermal displacement of the heating element based on the detected temperature using an estimation model. The method for estimating the thermal displacement of the machine tool is characterized by the following: In the thermal displacement estimation step, the following processing is performed: Based on the change in cooling capacity caused by the operation control of the cooling device during machine tool operation, a time-response related coefficient for estimating thermal displacement based on the detected temperature is determined. Based on the relationship between the pre-set cooling heat of the cooling device and the conversion coefficient between temperature and displacement used to estimate the thermal displacement based on the detected temperature, a temperature change equivalent to the change in the conversion coefficient before and after the change in cooling capacity is calculated; and / or, based on the pre-set relationship between the cooling heat and the temperature equivalent to the cooling heat, a temperature change equivalent to the change in cooling heat before and after the change in cooling capacity is calculated. The thermal displacement of the heating element is estimated based on the temperature and the coefficient obtained by adding the conversion coefficient to the detected temperature and / or the cooling heat to the temperature change.

2. The method for estimating the thermal displacement of a machine tool according to claim 1, characterized in that, The change in the cooling capacity of the cooling device is due to any one or both of the operation and shutdown of the cooling device and the increase and decrease of the amount of cooling oil used for cooling.

3. The method for estimating the thermal displacement of a machine tool according to claim 1 or 2, characterized in that, The heating element is a rotating shaft. The conversion coefficient is calculated based on the rotational speed of the rotating shaft and the time elapsed after the cooling capacity of the cooling device changes.

4. The method for estimating the thermal displacement of a machine tool according to claim 1 or 2, characterized in that, Based on the temperature-time constant before the change in cooling capacity, the temperature-time constant after the change in cooling capacity, and the time after the change in cooling capacity, the amount of temperature change equivalent to the cooling heat is calculated.

5. The method for estimating the thermal displacement of a machine tool according to claim 1 or 2, characterized in that, The cooling capacity of the cooling device changes under the following conditions: using a preset upper and lower limit as thresholds, the cooling capacity is reduced when the temperature rise of the detected temperature is below the lower limit, and the cooling capacity is increased when the temperature rise of the detected temperature is above the upper limit.

6. The method for estimating the thermal displacement of a machine tool according to claim 5, characterized in that, The heating element is a rotating shaft. The temperature rise of the bearing portion of the rotating shaft or the vicinity of the bearing portion, based on the temperature of the main structural portion, is used for thermal displacement estimation.

7. A machine tool comprising a cooling device and a temperature measuring device, characterized in that, This machine tool has the following features: The temperature detection unit detects the temperatures of a specified heating element and a specified main structural element using a temperature measuring device; and The thermal displacement estimation unit estimates the thermal displacement of the heating element based on the detected temperature and using an estimation model. The thermal displacement estimation unit performs the following processing: Based on the change in cooling capacity caused by the operation control of the cooling device during machine tool operation, a time-response related coefficient for estimating thermal displacement based on the detected temperature is determined. Based on the relationship between the pre-set cooling heat of the cooling device and the conversion coefficient between temperature and displacement used to estimate the thermal displacement based on the detected temperature, a temperature change equivalent to the change in the conversion coefficient before and after the change in cooling capacity is calculated; and / or, based on the pre-set relationship between the cooling heat and the temperature equivalent to the cooling heat, a temperature change equivalent to the change in cooling heat before and after the change in cooling capacity is calculated. The thermal displacement of the heating element is estimated based on the temperature obtained by adding the temperature change equivalent to the conversion coefficient and / or the temperature change equivalent to the cooling heat to the detected temperature, and the coefficient.

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