Thermal displacement estimating method for machine tool and machine tool

Abstract

To be able to accurately estimate thermal displacement without deteriorating processing accuracy, even in a transient state where an operation status of a cooling device is changed.SOLUTION: A thermal displacement estimating method for a machine tool executes: a temperature detecting step S2 of detecting temperatures of a bearing part of a main spindle and of a column; and thermal displacement estimating steps (S3-S12) of estimating thermal displacement of the main spindle using an estimation model on the basis of the detected temperatures. The thermal displacement estimating steps includes: determining a coefficient for estimating thermal displacement from the detected temperatures in accordance with change of a cooling capacity (S6 and S7); determining, from a relation between the amount of heat of cooling of a main spindle cooling device 12 and a temperature corresponding to the amount of heat of cooling, a temperature-change amount corresponding to an amount of heat of cooling that is corresponding to an amount of change of heat determined after and before the cooling capacity changes, and, from a relation between a temperature for estimating the thermal displacement from the amount of heat of cooling and the detected temperatures and the conversion coefficient during the displacement, a temperature-change amount corresponding to a conversion coefficient that is corresponding to an amount of change of the conversion coefficient determined after and before the cooling capacity changes (S8); and estimating thermal displacement of the main spindle, on the basis of a temperature determined by adding the corresponding temperature change amount to the detected temperatures and the coefficient (S12).SELECTED DRAWING: Figure 2

Description

[Technical field]

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

[0002] In machining with machine tools such as machining centers, thermal displacement in the axial direction occurs due to heat generated by friction in the bearings during spindle rotation and heat generated by the motor, resulting in a deterioration in machining accuracy. As a preventative measure, in terms of mechanical structure, there is a method of removing heat by running cooling oil through a cooling circuit in the spindle housing (hereinafter referred to as "spindle cooling"). In addition, in terms of electrical control, there is a method of estimating and correcting the spindle thermal displacement from machine temperature information. In the former spindle cooling, the power consumption of the spindle cooling device for controlling the temperature of the cooling oil supplied to the machine body temperature accounts for a large proportion of the power consumption of the peripheral devices, and measures to reduce power consumption by controlling the operation of the spindle cooling device are widely used. For example, Patent Document 1 discloses an invention in which the spindle cooling device is stopped when the temperature near the spindle calculated using the spindle temperature rise value based on the machine body temperature during machine downtime meets an arbitrary threshold. According to this invention, power consumption can be reduced in a situation in which the machining accuracy does not deteriorate. In addition, Patent Document 2 discloses an invention in which power consumption is reduced by stopping the spindle cooling device in a situation in which the impact on the machining accuracy is small, such as when the rotation speed and heat source temperature are below a preset threshold. In the latter thermal displacement estimation method, Patent Document 3 by the present applicant proposes a calculation method for estimating the spindle thermal displacement by changing the calculation coefficient of the thermal displacement estimation equation according to the rotation speed and time or the number of corrections. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 6445395 [Patent Document 2] Patent No. 6349276 [Patent Document 3] Japanese Patent Application Publication No. 9-225781 Summary of the Invention [Problem to be solved by the invention]

[0004] It is desirable to reduce power consumption not only by stopping the spindle cooling device when the machine is idle as in the invention of Patent Document 1, but also by stopping the spindle cooling device when the machine is in operation as in the invention of Patent Document 2. However, in the case of the spindle of a machining center, stopping the cooling device while the spindle is rotating can result in a loss of power over 1000 min. -1 Even at rotation speeds of this order, the amount of spindle thermal displacement increases over time, so the period during which the effect on accuracy is small is limited to a short period of time. Therefore, in order to maintain accuracy for a longer period of time, it is necessary to estimate and correct the spindle thermal displacement as in the invention of Patent Document 3. However, because the thermal displacement characteristics differ between when the spindle cooling device is operating and when it is stopped, the method of Patent Document 3 cannot accurately estimate the thermal displacement.

[0005] Therefore, the present disclosure aims to provide a thermal displacement estimation method and a machine tool that can accurately estimate thermal displacement even in a transient state where the operating state of the cooling device changes, thereby reducing power consumption without degrading machining accuracy. [Means for solving the problem]

[0006] In order to achieve the above object, a first configuration of the present disclosure provides a machine tool having a cooling device and a temperature measuring device, comprising: a temperature detection step of detecting temperatures of a predetermined heat generating portion and a predetermined main body structural portion by the temperature measuring device; A thermal displacement estimation step of estimating thermal displacement of the heat generating part by an estimation model based on a detected temperature, In the thermal displacement estimation step, determining a coefficient related to a time response for estimating a thermal displacement from the detected temperature in response to a change in cooling capacity caused by an operation control of the cooling device during operation of a machine; determining a temperature change amount equivalent to a conversion coefficient corresponding to a change in the conversion coefficient before and after a change in cooling capacity from a relationship between a preset amount of cooling heat of the cooling device and a conversion coefficient between temperature and displacement for estimating thermal displacement from the detected temperature, and / or determining a temperature change amount equivalent to a cooling heat amount corresponding to a change in the amount of heat before and after a change in cooling capacity from a relationship between the preset amount of cooling heat and a temperature equivalent to the amount of cooling heat, The thermal displacement of the heat generating portion is estimated based on the temperature obtained by adding the detected temperature to the temperature change amount equivalent to the conversion coefficient and / or the temperature change amount equivalent to the amount of heat cooled, and on the coefficient. Another aspect of the first configuration is characterized in that, in the above configuration, the change in the cooling capacity of the cooling device is either or both of operating and stopping the cooling device, or increasing and decreasing the amount of cooling oil used for cooling. Another aspect of the first configuration is characterized in that, in the above configuration, the heat-generating part is a rotating shaft, and the temperature change amount equivalent to the conversion coefficient is calculated based on the rotational speed of the rotating shaft and the time after the cooling capacity changes. Another aspect of the first configuration is characterized in that, in the above configuration, the temperature change equivalent to the cooling heat quantity is calculated based on a temperature time constant before the change in cooling capacity, a temperature time constant after the change in cooling capacity, and a time after the change in cooling capacity. Another aspect of the first configuration is characterized in that, in the above configuration, the condition for changing the cooling capacity of the cooling device is to set preset upper and lower limit values ​​as threshold values, and when the temperature rise value of the detected temperature becomes equal to or lower than the lower limit value, the cooling capacity is reduced, and when the temperature rise value becomes equal to or higher than the upper limit value, the cooling capacity is increased. Another aspect of the first configuration is characterized in that, in the above configuration, the heat-generating part is a rotating shaft, and the temperature rise value of the bearing part of the rotating shaft or near the bearing part based on the temperature of the main body structure part is used for estimating thermal displacement. In order to achieve the above object, a second configuration of the present disclosure is a machine tool having a cooling device and a temperature measuring device, a temperature detection means for detecting the temperatures of a predetermined heat generating portion and a predetermined main body structure portion by a temperature measuring device; a thermal displacement estimation means for estimating a thermal displacement of the heat generating portion by an estimation model based on a detected temperature, The thermal displacement estimation means determining a coefficient related to a time response for estimating a thermal displacement from the detected temperature in response to a change in cooling capacity caused by an operation control of the cooling device during operation of a machine; determining a temperature change amount equivalent to a conversion coefficient corresponding to a change in the conversion coefficient before and after a change in cooling capacity from a relationship between a preset amount of cooling heat of the cooling device and a conversion coefficient between temperature and displacement for estimating thermal displacement from the detected temperature, and / or determining a temperature change amount equivalent to a cooling heat amount corresponding to a change in the amount of heat before and after a change in cooling capacity from a relationship between the preset amount of cooling heat and a temperature equivalent to the amount of cooling heat, The thermal displacement of the heat generating portion is estimated based on the temperature obtained by adding the detected temperature to the temperature change amount equivalent to the conversion coefficient and / or the temperature change amount equivalent to the amount of heat cooled, and on the coefficient. In addition, the "estimation model" in this disclosure refers to a series of processes patterned in advance for estimating thermal displacement, such as a determination process or one or more mathematical expressions including coefficients. Effect of the Invention

[0007] According to the present disclosure, by adding a temperature change amount equivalent to a conversion coefficient corresponding to the difference between the temperature and displacement before and after a preset operation control change of the cooling device, and / or a temperature change amount equivalent to a cooling heat amount corresponding to the difference in the amount of cooling heat, to the detected temperature of the heat generating part or near the heat generating part, it is possible to deal with the deterioration of the thermal displacement estimation accuracy that occurs in a cooling transient state when the operation control of the cooling device is performed during the operation of the machine. Therefore, it is possible to accurately estimate the thermal displacement even in a transient state in which the operation state of the cooling device changes, and it is possible to reduce power consumption without deteriorating the machining accuracy. According to another aspect of the present disclosure, in addition to the above effects, a change in the cooling capacity of the cooling device is determined as either operation or shutdown of the cooling device, or an increase or decrease in the amount of cooling oil used for cooling, or both, so that thermal displacement estimation can be performed in response not only to operation and shutdown of the cooling device, but also to an increase or decrease in the amount of cooling oil. According to another aspect of the present disclosure, in addition to the above effects, the conversion coefficient equivalent temperature change amount is calculated based on the rotational speed of the rotating shaft and the time after the cooling capacity change, so that the thermal displacement can be estimated with high accuracy in response to the change in cooling capacity depending on the rotational speed. According to another aspect of the present disclosure, in addition to the above effects, the temperature change equivalent to the cooling heat quantity is calculated based on the temperature time constant before the cooling capacity of the cooling device is changed in advance, the temperature time constant after the cooling capacity of the cooling device is changed in advance, and the time after the cooling capacity is changed, making it easy to set the temperature change equivalent to the cooling heat quantity. According to another aspect of the present disclosure, in addition to the above effects, an upper limit and a lower limit of the rise value are preset as conditions for changing the cooling capacity of the cooling device, and when the temperature rise value is equal to or greater than the upper limit, the cooling capacity is increased, thereby avoiding the risk of abnormal heat generation, such as bearing seizure, caused by a decrease in the cooling capacity. On the other hand, when the temperature rise value is equal to or less than the lower limit, the cooling capacity is decreased, thereby reducing power consumption. According to another aspect of the present disclosure, in addition to the above effects, when a 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 body structure. [Brief description of the drawings]

[0008] [Figure 1] FIG. 2 is a block diagram showing the configuration of a machining center. [Diagram 2] 1 is a flowchart of a thermal displacement estimation method. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, an embodiment of the present disclosure will be described with reference to the drawings. FIG. 1 is a block diagram showing the configuration of a machining center M, which is an example of a machine tool of the second configuration. The machining center M includes a bed 1, a column 2, a spindle head 3, a spindle unit 4, and a table 5. The machining center M also includes a temperature measuring device 10, an NC device 11, a spindle cooling device 12, and a correction amount calculation device 13. The temperature measuring device 10 detects a temperature rise in the bearing portion of the spindle with a temperature sensor 8 provided on the spindle unit 4, and detects the body temperature, which serves as a reference temperature, with a temperature sensor 9 provided on the column 2. The spindle cooling device 12 has a cooling circuit that supplies cooling oil to a cooling oil inlet 6 in the outer tubular portion of the spindle housing and returns it from a cooling oil outlet 7 .

[0010] The NC device 11 controls the rotation of the spindle and the movement of the feed axis, as well as the operation of the spindle cooling device 12. This operation control is performed based on upper and lower limits of the temperature difference (hereinafter referred to as "temperature rise value") between the temperature sensors 8 and 9 that are set in advance. Specifically, when the temperature rise value becomes equal to or lower than the lower limit value, the operation of the spindle cooling device 12 is stopped, and when the temperature rise value becomes equal to or higher than the upper limit value, the operation of the spindle cooling device 12 is resumed. The temperatures detected by the temperature sensors 8 and 9 are converted from analog signals to digital signals at a preset cycle by a known method in the temperature measuring device 10, digitized, and sent to the correction amount calculation device 13. The temperature sensors 8 and 9 and the temperature measuring device 10 are an example of the temperature detection means of the present disclosure. In the correction amount calculation device 13, the spindle thermal displacement is estimated based on an estimation model including an estimated spindle temperature calculated from the digitized temperature data and a thermal displacement estimation formula that uses a preset conversion coefficient from the spindle temperature to the spindle thermal displacement. A correction amount based on the estimated thermal displacement is output to the NC device 11. The correction amount calculation device 13 is an example of a thermal displacement estimation means of the present disclosure. The NC device 11 corrects the movement amount of each feed axis based on the correction amount.

[0011] The estimation of the spindle thermal displacement in the correction amount calculation device 13 will be described below. First, in Equation 1, the temperature θ1 measured by the temperature sensor 8 n and the temperature θ2 measured by the temperature sensor 9 nAs a result, the temperature rise value θ n The calculated temperature rise value θ n The temperature θ shown in Equation 2 corresponds to the change in the amount of heat before and after the change in the cooling capacity of the spindle cooling device 12. Equn (Temperature change amount equivalent to the amount of cooling heat) and the temperature θ shown in Equation 3-1 and Equation 3-2, which corresponds to the difference in the conversion coefficient between the temperature and displacement before and after the change in the cooling capacity of the spindle cooling device 12 Gn (Conversion coefficient equivalent temperature change amount) is added (Equation 4), and the obtained temperature θ CORn Based on this, the estimated spindle temperature θ ESTn Calculate.

[0012] θ n =θ1 n -θ2 n ·Formula 1 θ1 n The temperature of the bearing of the spindle detected by the temperature sensor 8 at the nth time θ2 n : Aircraft temperature detected by temperature sensor 9 for the nth time θ n : nth temperature rise value θ Equn =β1×exp(Δt×n / T1)-β2×exp(Δt×n / T2) ···Equation 2 Δt: Time interval for estimation calculation processing β1:θ Equ Calculation factor 1 β2:θ Equ Calculation factor 2 T1: Temperature time constant related to the amount of heat cooled before the cooling capacity changes T2: Temperature time constant related to the amount of heat cooled after the cooling capacity change θ Equn : Temperature change equivalent to the nth cooling heat amount G n =G n-1 +(G0-G n-1 ) × [Δt / (Δt+T3)] Equation 3-1 θ Gn =(θ n +θ Equn )×G n ·Formula 3-2 G n :nth θG Calculation coefficient G0:θ G Convergence value of the calculated coefficient Δt: Time interval for estimation calculation processing T3: Time constant for the conversion coefficient between temperature and displacement after a change in cooling capacity θ Gn : Temperature change equivalent to the nth conversion coefficient θ CORn =θ n +θ Equn +θ Gn ·Formula 4 θ CORn : The temperature obtained by adding the temperature equivalent to the change in heat quantity before and after the change in cooling capacity to the nth temperature rise value and the temperature equivalent to the difference in the conversion coefficient between the temperature before and after the change in cooling capacity and the change in temperature θ ESTn =θ ESTn-1 +(θ CORn -θ ESTn-1 ) × [Δt / (Δt+α)] Formula 5 Δt: Time interval for estimation calculation processing α: Time response factor θ ESTn :nth estimated spindle temperature

[0013] Next, in Equation 6, the estimated spindle temperature θ ESTn and the temperature displacement conversion coefficient γ, the spindle thermal displacement Z n The coefficient γ is a temperature displacement conversion coefficient that is preset in accordance with the operating state of the spindle cooling device 12. Z n =θ ESTn ×γ ···Equation 6 γ: Temperature displacement conversion coefficient Z n :nth spindle thermal displacement

[0014] Hereinafter, based on the flowchart in FIG. 2, a thermal displacement estimating method according to the first configuration in the case where the operation of the spindle cooling device 12 is controlled at an arbitrary spindle rotation speed will be described. The estimation calculation process is performed at time intervals Δt, and in S1, a counter for the number of times the process is performed is started. In S2, the bearing temperature is measured by the temperature sensor 8 and the machine temperature is measured by the temperature sensor 9, and these are converted into numerical values ​​to obtain the current temperature data. The temperature rise value θ n Calculate. In S3, it is determined whether or not the thermal displacement compensation process is being performed for the first time. If it is the first time, the process proceeds to S7, and if it is the second or subsequent time, the process proceeds to S4. In S4, it is determined whether or not the timing condition for changing the operation control of the spindle cooling device 12 is satisfied. The timing condition here is whether or not the temperature rise value reaches either an upper limit value or a lower limit value set in advance. When the temperature rise value becomes equal to or less than the lower limit value, the operation of the spindle cooling device 12 is stopped, and when the temperature rise value becomes equal to or more than the upper limit value, the operation of the spindle cooling device 12 is resumed. For the upper and lower limits, for example, the temperature rise value when the spindle cooling device 12 is in an operating state and is operated at the maximum rotation speed is set as the upper limit value, and the temperature rise value when the spindle cooling device 12 is in an operating state and is operated at a rotation speed that is half the maximum rotation speed is set as the lower limit value.

[0015] When the timing condition is satisfied in S4 and the operation of the spindle cooling device 12 changes, the count number is reset in S5 and the counter starts again. In S6 and S7, the coefficients β1, β2, T1, T2, G0, T3, and α used in the formulas 2, 3, and 5 are changed or set to preset optimum coefficients according to the operating state or the stopped state of the spindle cooling device 12. These coefficients may be fixed values, may be different depending on whether the spindle cooling device 12 is in the operating state or the stopped state, or may be functions of the temperature according to whether the spindle cooling device 12 is in the operating state or the stopped state. In addition, θ G The convergence value G0 of the calculation coefficient can be a function of the spindle rotation speed. In this case, the thermal displacement can be estimated with high accuracy in response to the change in cooling capacity according to the rotation speed. In S8, the temperature change equivalent to the amount of cooling heat θ Equn From equations 3-1 and 3-2, the conversion coefficient equivalent temperature change θ Gn are calculated respectively. In S9, the temperature change equivalent to the amount of cooling heat θ Equ and the conversion coefficient equivalent temperature change θ GnThe process judges whether to add the count number. The judgment condition is, for example, whether the equivalent temperature change amount to be added is larger than a preset threshold value, or whether the count number is larger than a threshold value. In the former case, if the equivalent temperature change amount to be added is equal to or larger than the threshold value, the process proceeds to S10, and if it is smaller than the threshold value, the process proceeds to S11. In the latter case, if the count number is equal to or smaller than the threshold value, the process proceeds to S10, and if it is larger than the threshold value, the process proceeds to S11.

[0016] In S10, the temperature rise value θ calculated in S2 is calculated using Equation 4. n The temperature change equivalent to the cooling heat calculated in S8, θ Equn and the conversion coefficient equivalent temperature change θ Gn Add. In S11, the estimated spindle temperature θ ESTn Calculate. In S12, the estimated spindle temperature θ calculated in S11 is ESTn Based on this, the thermal displacement of the spindle Z is calculated from Equation 6. n and calculate the correction amount. In S13, it is determined whether or not to continue the thermal displacement compensation. If it is to be continued, the process returns to S2 and executes the process from the temperature measurement.

[0017] In this manner, the thermal displacement estimation method of the above embodiment executes, in a machining center M having a spindle cooling device 12 (an example of a cooling device) and a temperature measuring device 10, a temperature detection step S2 in which the temperature measuring device 10 detects the temperatures of the spindle bearing portion (an example of a predetermined heat generating portion) and the column 2 (an example of a predetermined main body structural portion), and thermal displacement estimation steps (S3 to S12) in which the thermal displacement of the spindle is estimated based on the detected temperatures using an estimation model consisting of equations 1 to 6. Then, in the thermal displacement estimation step, a coefficient for estimating thermal displacement from the detected temperature is determined according to a change in cooling capacity due to operation control of the spindle cooling device 12 while the machine is in operation (S6, S7). From the relationship between the preset cooling heat amount of the spindle cooling device 12 and the temperature equivalent to that cooling heat amount, a temperature change equivalent to the cooling heat amount equivalent to the change in heat amount before and after the change in cooling capacity is determined, and from the relationship between the cooling heat amount of the cooling device 12 and a conversion coefficient between temperature and displacement for estimating thermal displacement from the detected temperature, a temperature change equivalent to the conversion coefficient before and after the change in cooling capacity is determined (S8). The thermal displacement of the spindle is estimated based on the temperature obtained by adding the equivalent temperature change amount to the detected temperature and the coefficient (S12). This configuration makes it possible to deal with deterioration in thermal displacement estimation accuracy that occurs in a cooling transient state when the operation control of the spindle cooling device 12 is performed during machine operation. Therefore, even in a transient state in which the operation state of the spindle cooling device 12 changes, it is possible to accurately estimate the thermal displacement, and it is possible to reduce power consumption without deteriorating the machining accuracy.

[0018] In particular, the change in the cooling capacity of the spindle cooling device 12 is determined by either operating or stopping the spindle cooling device 12 or increasing or decreasing the amount of cooling oil used for cooling, or both. Therefore, it is possible to perform thermal displacement estimation that corresponds not only to the operation and stoppage of the spindle cooling device 12 but also to an increase and decrease in the amount of cooling oil. The amount of temperature change equivalent to the amount of cooled 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. This makes it easy to set the amount of temperature change equivalent to the amount of cooled heat.

[0019] The conditions for changing the cooling capacity of the spindle cooling device 12 are such that, with preset upper and lower limit values ​​as thresholds, when the temperature rise value of the detected temperature falls below the lower limit value, the cooling capacity is reduced, and when it exceeds the upper limit value, the cooling capacity is increased. This makes it possible to avoid the risk of abnormal heat generation, such as bearing seizure, caused by a reduction in cooling capacity. On the other hand, when the temperature rise falls below the lower limit, the cooling capacity is reduced, thereby reducing power consumption. The heat generating part is the main shaft (an example of a rotating shaft), and the temperature rise value in the vicinity of the bearing part of the main shaft, based on the temperature of the column 2, is used for estimating the thermal displacement. Therefore, the thermal displacement can be estimated with high accuracy.

[0020] In the above embodiment, both the amount of temperature change equivalent to the amount of cooling heat and the amount of temperature change equivalent to the conversion coefficient are used. However, for a spindle or the like with small thermal displacement, the accuracy of estimating thermal displacement can be improved by using only one of the amount of temperature change equivalent to the amount of cooling heat or the amount of temperature change equivalent to the conversion coefficient, so only one of them may be used. In the above embodiment, in S9, it is determined based on the determination condition whether or not to add the equivalent temperature change amount to the measured temperature data, but this determination may be eliminated and the equivalent temperature change amount may always be added. In the above embodiment, the change of the coefficient in S6 is executed depending on the operating state and the stopped state of the spindle cooling device. However, this is not limited to ON / OFF of the spindle cooling device, and the change of the coefficient may be executed, for example, even in the ON state, at the timing when the amount of cooling oil is changed or at the timing when the cooling capacity is changed (for example, a state in which only the refrigerator is stopped and the pump is operating). The rotating shaft for which the thermal displacement is estimated is not limited to the main shaft. The temperature of a part other than the bearing may be detected. A plurality of temperature sensors may be provided in each of the heat generating part and the main body structure, and the average of the measured values ​​may be used. The cooling device of the present disclosure is not limited to a spindle, and the machine tool to which the present disclosure is applied is not limited to a machining center. [Explanation of symbols]

[0021] 1··Bed, 2··Column, 3··Spindle head, 4··Spindle unit, 5··Table, 6··Cooling oil inlet, 7··Cooling oil outlet, 8, 9··Temperature sensor, 10··Temperature measuring device, 11··NC device, 12··Spindle cooling device, 13··Correction value calculation device, M··Machining center.

Claims

1. a temperature detection step of detecting temperatures of a predetermined heat generating portion and a predetermined main body structural portion by the temperature measurement device in a machine tool having a cooling device and a temperature measurement device; A thermal displacement estimation step of estimating thermal displacement of the heat generating part by an estimation model based on a detected temperature, In the thermal displacement estimation step, determining a coefficient related to a time response for estimating a thermal displacement from the detected temperature in response to a change in cooling capacity caused by an operation control of the cooling device during operation of a machine; determining a temperature change amount equivalent to a conversion coefficient corresponding to a change in the conversion coefficient before and after a change in cooling capacity from a relationship between a preset amount of cooling heat of the cooling device and a conversion coefficient between temperature and displacement for estimating thermal displacement from the detected temperature, and / or determining a temperature change amount equivalent to a cooling heat amount corresponding to a change in the amount of heat before and after a change in cooling capacity from a relationship between the preset amount of cooling heat and a temperature equivalent to the amount of cooling heat, A method for estimating thermal displacement of a machine tool, characterized in that the thermal displacement of the heat-generating part is estimated based on the temperature obtained by adding the detected temperature to the temperature change equivalent to the conversion coefficient and / or the temperature change equivalent to the cooling heat amount, and based on the coefficient.

2. 2. A method for estimating thermal displacement of a machine tool according to claim 1, wherein the change in the cooling capacity of the cooling device is either operation or stopping of the cooling device, or an increase or decrease in the amount of cooling oil used for cooling, or both.

3. 3. The method for estimating thermal displacement of a machine tool according to claim 1, wherein the heat-generating portion is a rotating shaft, and the temperature change amount equivalent to 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.

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

5. The method for estimating thermal displacement of a machine tool as described in claim 1 or 2, characterized in that the conditions for changing the cooling capacity of the cooling device are set to predetermined upper and lower limit values ​​as threshold values, and when the temperature rise value of the detected temperature becomes equal to or lower than the lower limit value, the cooling capacity is reduced, and when the temperature rise value becomes equal to or higher than the upper limit value, the cooling capacity is increased.

6. The thermal displacement estimation method for a machine tool according to claim 5, characterized in that the heat-generating part is a rotating shaft, and the temperature rise value of the bearing part of the rotating shaft or the vicinity of the bearing part based on the temperature of the main body structural part is used to estimate the thermal displacement.

7. A machine tool having a cooling device and a temperature measuring device, a temperature detection means for detecting the temperatures of a predetermined heat generating portion and a predetermined main body structure portion by a temperature measuring device; a thermal displacement estimation means for estimating a thermal displacement of the heat generating portion by an estimation model based on a detected temperature, The thermal displacement estimation means determining a coefficient related to a time response for estimating a thermal displacement from the detected temperature in response to a change in cooling capacity caused by an operation control of the cooling device during operation of a machine; determining a temperature change amount equivalent to a conversion coefficient corresponding to a change in the conversion coefficient before and after a change in cooling capacity from a relationship between a preset amount of cooling heat of the cooling device and a conversion coefficient between temperature and displacement for estimating thermal displacement from the detected temperature, and / or determining a temperature change amount equivalent to a cooling heat amount corresponding to a change in the amount of heat before and after a change in cooling capacity from a relationship between the preset amount of cooling heat and a temperature equivalent to the amount of cooling heat, A machine tool characterized in that the thermal displacement of the heat-generating portion is estimated based on the temperature obtained by adding the detected temperature to the temperature change amount equivalent to the conversion coefficient and / or the temperature change amount equivalent to the cooling heat amount, and on the coefficient.

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