Temperature estimation device and thermal displacement compensation device

Abstract

A temperature estimation device comprising: a target temperature acquisition unit that acquires a target temperature, which is the detection value of a main temperature sensor arranged in a target portion of a machine tool; an active temperature estimation unit that estimates an active temperature, which is the temperature of the target portion when there is no change in the thermal environment of the machine tool, based on at least one of operation information of the machine tool and the detection value of an auxiliary temperature sensor arranged in a reference portion that is not affected by changes in the thermal environment of the machine tool; and a passive temperature estimation unit that estimates a passive temperature, which is the temperature change of the target portion due to changes in the thermal environment, based on the target temperature and the active temperature.

Description

[Technical Field]

[0001] The present disclosure relates to a temperature estimation device and a thermal displacement correction device. [Background technology]

[0002] In machine tools, a technique is known in which the temperature of components in a drive mechanism is measured and the drive amount is corrected to compensate for positioning errors caused by thermal displacement. Accurately determining the temperature of each component requires the installation of a temperature sensor in each component. However, there may be components for which a temperature sensor cannot be installed. For this reason, it has been proposed to estimate the temperature of a component where a temperature sensor cannot be installed based on the detected value of a temperature sensor installed in another component (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2018-103274 Summary of the Invention [Problem to be solved by the invention]

[0004] Patent Document 1 discloses a method for estimating the temperature of a portion of a machine tool where no temperature sensor is installed, based on the temperature of the machine tool's structure or machining space, the coolant temperature, and information on whether the coolant is being discharged or stopped. However, the temperature estimation method of Patent Document 1 does not take into account heat generated by friction and the like associated with the operation of the machine tool. Therefore, a technology is desired that can accurately estimate the temperature by taking into account the heat generated by the operation of the machine tool and heat transfer with the outside. [Means for solving the problem]

[0005] A temperature estimation device according to one aspect of the present disclosure includes a target temperature acquisition unit that acquires a target temperature, which is the detection value of a main temperature sensor arranged in a target portion of a machine tool; an active temperature estimation unit that estimates an active temperature, which is the temperature of the target portion when there is no change in the thermal environment of the machine tool, based on at least one of operation information of the machine tool and the detection value of an auxiliary temperature sensor arranged in a reference portion that is not affected by changes in the thermal environment of the machine tool; and a passive temperature estimation unit that estimates a passive temperature, which is the temperature change of the target portion due to changes in the thermal environment, based on the target temperature and the active temperature. [Brief explanation of the drawings]

[0006] [Figure 1] 1 is a block diagram illustrating a configuration of a thermal displacement correction device according to an embodiment of the present disclosure. [Figure 2] 1 is a graph illustrating an example of a temperature change in a machine tool. DETAILED DESCRIPTION OF THE INVENTION

[0007] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. Fig. 1 is a block diagram showing the configuration of a thermal displacement correction device 100 according to one embodiment of the present disclosure. The thermal displacement correction device 100 includes a temperature estimation device 1 which is itself an embodiment of the temperature estimation device according to the present invention, and corrects the thermal displacement of a machine tool 200.

[0008] The temperature estimation device 1 estimates the temperature of a target portion of the machine tool 200. The temperature estimation device 1 may be realized by one or more computers having, for example, a memory, a processor, an input / output interface, etc., and executing an appropriate control program. The temperature estimation device 1 may also be integrated with a control device for the machine tool or the like. In other words, the temperature estimation device 1 may be provided as one function of a numerical control device.

[0009] The temperature estimation device 1 includes a target temperature acquisition unit 11, an active temperature estimation unit 12, a passive temperature estimation unit 13, a relationship recording unit 14, and an alternative temperature estimation unit 15. Note that these components categorize the functions of the temperature estimation device 1, and do not necessarily have to be clearly distinguishable in terms of physical configuration and program configuration.

[0010] The target temperature acquisition unit 11 acquires the target temperature, which is the detection value of the main temperature sensor 201 disposed in the target portion of the machine tool 200. The target portion is a portion whose temperature changes due to mechanical heat generated during the machining operation of the machine tool 200 and which may also be affected by changes in the thermal environment. Examples of changes in the thermal environment include changes in the ambient temperature, whether or not a coolant is used, and whether or not a blower is used. The target portion may typically be a portion that holds a tool, such as a chuck at the tip of the spindle. The temperature of the portion that holds the tool is likely to differ depending on whether or not a coolant is used, as the tool may be cooled by coolant (cutting oil).

[0011] The active temperature estimator 12 estimates the active temperature, which is the temperature of the target location when there is no change in the thermal environment of the machine tool, i.e., when the thermal environment is constant under standard conditions. The active temperature estimator 12 may estimate the active temperature based on operation information of the machine tool 200, or may estimate the active temperature based on a reference temperature, which is a detection value of an auxiliary temperature sensor 202 disposed in a reference location that is not affected by changes in the thermal environment of the machine tool 200, or may estimate the active temperature based on both the operation information and the reference temperature. The active temperature estimator 12 may be configured to calculate the active temperature using a conversion formula that expresses the active temperature as a function of at least one of the operation information and the reference temperature. Depending on the selection of the reference location, the active temperature estimator 12 may also estimate the reference temperature as the active temperature. Note that "not affected" means that the influence is sufficiently small, meaning that the maximum temperature difference between the target temperature and the temperature when there is no change in the thermal environment is less than 1 / 10 of the maximum temperature difference due to the operation of the machine tool 200.

[0012] The operation information of the machine tool 200 may be the drive amount of the drive unit, the cutting amount, etc., but more simply, it can be the number of times the machining program of the machine tool 200 is executed. For this reason, the active temperature estimator 12 may be configured to count the number of times the machining program is executed based on the machining program execution information of the program execution unit 203 of the machine tool 200. The reference portion is a portion whose temperature does not easily fluctuate due to changes in the thermal environment, that is, a portion that has a relatively large thermal resistance between it and a portion that is affected by changes in the thermal environment. As a specific example, the reference portion may be the inside of the housing of the machine tool 200, etc.

[0013] The passive temperature estimator 13 estimates the passive temperature, which is the temperature change due to a change in the thermal environment of the target part, based on the target temperature and the active temperature. That is, the passive temperature estimator 13 calculates the passive temperature by subtracting the active temperature from the target temperature.

[0014] The relationship recording unit 14 records the relationship between the active temperature estimated by the active temperature estimating unit 12 and the passive temperature estimated by the passive temperature estimating unit 13. When the machine tool 200 repeatedly executes the same machining program, the active temperature and the passive temperature often repeat the same changes. For this reason, the relationship between the active temperature and the passive temperature has a relatively high repeatability for each cycle of the machining program.

[0015] When the target temperature acquisition unit 11 cannot acquire the detection value of the main temperature sensor 201, the alternative temperature estimation unit 15 estimates the passive temperature from the active temperature estimated by the active temperature estimation unit 12 based on the relationship recorded in the relationship recording unit 14. This makes it possible to estimate the passive temperature even if the detection value of the main temperature sensor 201 cannot be acquired temporarily.

[0016] Figure 2 shows the changes in the target temperature, which is the measured temperature at the tip of the spindle; the active temperature, calculated from the spindle rotational speed as operational information; and the passive temperature, calculated as the difference between the target temperature and the active temperature, as deviations from the start. The spindle was driven only within the range of spindle speeds shown at the bottom of the graph, and coolant was supplied only within the range marked "Coolant ON" at the top of the graph. As shown, when no coolant was used, the target temperature and active temperature were nearly identical, and the passive temperature was nearly zero with only small fluctuations that could be considered noise. Therefore, the passive temperature in the area where coolant was supplied can be said to be the contribution of the coolant, i.e., the temperature change caused by changes in the thermal environment, excluding noise components.

[0017] As described above, temperature estimation device 1 can separate the actually measured target temperature into an active temperature, which is a temperature change component due to the machining operation of machine tool 200, and a passive temperature caused by changes in the thermal environment. This makes it possible to accurately estimate the temperatures of a large number of locations using a relatively small number of temperature sensors.

[0018] More specifically, the temperature change of each part of the machine tool 200 is affected differently by the distance and thermal resistance between the internal heat source, such as the motor, and the part affected by the thermal environment, such as the coolant. For this reason, conventional methods require multiple temperature sensors to estimate the temperature of one part, and an even larger number of temperature sensors are required to estimate the temperatures of multiple parts. However, the temperature estimation device 1 separates the target temperature into active temperatures and passive temperatures, so that the temperatures of multiple parts can be estimated using only the main temperature sensor 201 or only the main temperature sensor 201 and the auxiliary temperature sensor 202.

[0019] Furthermore, in order to define a function for estimating the amount of temperature change using conventional methods, it is necessary to accurately grasp the relationship between the detected values ​​of the temperature sensors and the amount of temperature change. However, as the number of temperature sensors increases, grasping the relationship becomes more difficult. In reality, it is difficult for a human to identify this relationship, so a model representing the relationship between the detected values ​​of the temperature sensors and temperature change can be generated using machine learning. However, even when using machine learning, it is difficult to select effective training data, and many conditions must be tested to generate the model, which is a time-consuming process. In contrast, the temperature estimation device 1 distinguishes between temperature changes due to the operation of the machine tool 200 and temperature changes due to changes in the thermal environment, making it relatively easy to model temperature changes. As a result, the temperature estimation device 1 can be constructed relatively easily and estimates temperature changes relatively accurately.

[0020] In addition to the above-described temperature estimation device 1, the thermal displacement correction device 100 includes an active thermal displacement estimation unit 101, a passive thermal displacement estimation unit 102, and a correction value calculation unit 103. These components may be configured by the same computer device as the temperature estimation device 1 or a different computer device.

[0021] The active thermal displacement estimation unit 101 estimates the component of the thermal displacement of the machine tool 200 that is caused by the active temperature based on the estimated value of the active temperature by the active temperature estimation unit 12. Because the active thermal displacement estimation unit 101 does not take into account temperature changes caused by changes in the thermal environment in which heat is conducted through different paths, it is easy to model the thermal displacement and can estimate the thermal displacement caused by the machining operation of the machine tool 200 with relatively high accuracy.

[0022] The passive thermal displacement estimation unit 102 estimates the component of thermal displacement caused by passive temperature based on the estimated value of passive temperature by the passive temperature estimation unit 13 or the alternative temperature estimation unit 15. Because the passive thermal displacement estimation unit 102 does not take into account temperature changes caused by the machining operation of the machine tool 200, it is easy to model thermal displacement and can estimate thermal displacement caused by changes in the thermal environment with relatively high accuracy.

[0023] Correction value calculation unit 103 calculates a correction value for correcting the command value of machine tool 200 so as to offset the thermal displacement, based on the component of thermal displacement caused by the active temperature and the component caused by the passive temperature. The thermal displacement of machine tool 200 can be calculated as the sum of the component caused by the active temperature and the component caused by the passive temperature, which are each estimated with high accuracy. Therefore, correction value calculation unit 103 can calculate a correction value that offsets the thermal displacement of machine tool 200 relatively accurately.

[0024] The following additional notes are provided regarding the above-described embodiment and modifications. (Appendix 1) The temperature estimation device (1) includes a target temperature acquisition unit (11) that acquires a target temperature, which is a detected value of a main temperature sensor (201) arranged in a target location of the machine tool (200); an active temperature estimation unit (12) that estimates an active temperature, which is the temperature of the target location when there is no change in the thermal environment of the machine tool (200), based on at least one of operation information of the machine tool (200) and a detected value of an auxiliary temperature sensor (202) arranged in a reference location that is not affected by changes in the thermal environment of the machine tool (200); and a passive temperature estimation unit (13) that estimates a passive temperature, which is the temperature change due to changes in the thermal environment of the target location, based on the target temperature and the active temperature.

[0025] (Appendix 2) In the temperature estimation device (1) of Supplementary Note 1, the operation information may be the number of times the machining program of the machine tool (200) has been executed.

[0026] (Appendix 3) In the temperature estimation device (1) of Supplementary Notes 1 and 2, the target portion may be a portion that holds a tool.

[0027] (Appendix 4) In the temperature estimation device (1) according to Supplementary Notes 1 to 3, the change in the thermal environment may be the presence or absence of use of a coolant.

[0028] (Appendix 5) The temperature estimation device (1) of Supplementary Notes 1 to 4 may further include a relationship recording unit (14) that records the relationship between the active temperature and the passive temperature, and an alternative temperature estimation unit (15) that estimates the passive temperature from the active temperature based on the relationship recorded in the relationship recording unit (14) when the target temperature acquisition unit (11) cannot acquire the detected value of the main temperature sensor (201).

[0029] (Appendix 6) The thermal displacement correction device (100) includes the temperature estimation device (1) of Supplementary Notes 1 to 5, an active thermal displacement estimation unit (101) that estimates a component of the thermal displacement of the machine tool (200) that is caused by the active temperature based on an estimated value of the active temperature, a passive thermal displacement estimation unit (102) that estimates a component of the thermal displacement that is caused by the passive temperature based on an estimated value of the passive temperature, and a correction value calculation unit (103) that calculates a correction value to correct a command value of the machine tool (200) to offset the thermal displacement based on the component of the thermal displacement that is caused by the active temperature and the component of the thermal displacement that is caused by the passive temperature.

[0030] Although the present disclosure has been described in detail above, the present disclosure is not limited to the individual embodiments described above. Various additions, substitutions, modifications, partial deletions, etc. are possible within the scope of the gist of the present disclosure, or the spirit of the present disclosure derived from the content of the claims and their equivalents. These embodiments can also be implemented in combination. For example, the order of each operation and each process in the above-described embodiments is shown as an example and is not limited to these. The same applies when numerical values ​​or mathematical formulas are used in the description of the above-described embodiments. As a specific example, in the temperature estimation device according to the present disclosure, the relationship recording unit and the alternative temperature estimation unit can be omitted. [Explanation of symbols]

[0031] 1 Temperature estimation device 11 Target temperature acquisition unit 12 Active temperature estimation section 13 Passive temperature estimation unit 14. Related Records Section 15 Alternative temperature estimation section 100 Thermal displacement compensation device 101 Active thermal displacement estimation unit 102 Passive thermal displacement estimation unit 103 Correction value calculation unit 200 Machine tools 201 Main temperature sensor 202 Auxiliary Temperature Sensor 203 Program Execution Department

Claims

1. a target temperature acquisition unit that acquires a target temperature, which is a detected value of a main temperature sensor disposed in a target portion whose temperature changes due to mechanical heat generated by a machining operation of the machine tool and which may be affected by a thermal environmental change that is a temperature change factor other than the mechanical heat generated by the machining operation; an active temperature estimation unit that estimates an active temperature, which is the temperature of the target portion when there is no change in the thermal environment of the machine tool, based on at least one of operation information of the machine tool and a detection value of an auxiliary temperature sensor disposed in a reference portion where the maximum value of the temperature change due to the change in the thermal environment of the machine tool is 1 / 10 or less of the maximum value of the temperature change due to mechanical heat generation accompanying the machining operation; a passive temperature estimation unit that estimates a passive temperature, which is a temperature change due to a change in the thermal environment of the target part, based on the target temperature and the active temperature; A temperature estimation device comprising:

2. The temperature estimation device according to claim 1 , wherein the operation information is the number of times a machining program of the machine tool is executed.

3. The temperature estimation device according to claim 1 , wherein the target portion is a portion that holds a tool.

4. The temperature estimation device according to claim 1 , wherein the change in the thermal environment is the presence or absence of use of a coolant.

5. a relationship recording unit that records the relationship between the active temperature and the passive temperature; an alternative temperature estimation unit that estimates the passive temperature from the active temperature based on the relationship recorded in the relationship recording unit when the target temperature acquisition unit cannot acquire the detected value of the main temperature sensor; The temperature estimation device according to claim 1 or 2, further comprising:

6. The temperature estimation device according to claim 1 or 2; an active thermal displacement estimation unit that estimates a component of thermal displacement of the machine tool that is caused by the active temperature based on the estimated value of the active temperature; a passive thermal displacement estimation unit that estimates a component of the thermal displacement caused by the passive temperature based on the estimated value of the passive temperature; a correction value calculation unit that calculates a correction value for correcting a command value of the machine tool so as to offset the thermal displacement, based on a component of the thermal displacement caused by the active temperature and a component of the thermal displacement caused by the passive temperature; A thermal displacement correction device comprising:

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