A rotating machinery bearing cooling control system

Abstract

The objective is to provide a bearing cooling control system for a rotating machine that can appropriately estimate the inner ring temperature even if the rotating machine does not have special equipment for measuring the inner ring temperature, and even if the inner ring temperature and outer ring temperature are in a non-steady state, and that can appropriately control the cooling state of the bearing by the cooling device based on the estimation result. [Solution] The inner ring temperature is measured in relation to the load of the motor 9, the rotational speed of the spindle 7, and the elapsed time t after the change in the rotational speed of the spindle 7. N And the elapsed time t after the change in the operating state of the cooling device 14. C And the outer ring temperature T measured by the outer ring temperature measuring unit 6 out Based on this, one or more inner ring temperature estimation models corresponding to the operating state of the cooling device 14 are used to estimate the inner ring temperature T in The estimated inner ring temperature T in The outer ring temperature T is measured as out Based on this, the operating state of the cooling device 14 or the operating state of the spindle 7 is controlled.

Description

[Technical Field]

[0001] This disclosure relates to a bearing cooling control system for a rotating machine having a rotating shaft supported by bearings and cooled by a cooling device, which can appropriately control the spindle operating state and the cooling state even when the operating state of the rotating shaft and the cooling state by the cooling device are frequently changed. [Background technology]

[0002] During machining with machine tools, the spindle temperature rises due to factors such as heat generated by the bearings and motor during spindle rotation. This temperature rise causes thermal displacement in the spindle, leading to a decrease in machining accuracy or spindle seizure. Therefore, spindles have traditionally been equipped with cooling systems. In most cases, a cooling medium is circulated from a cooling device through the outer cylinder of the spindle to cool the heat generated by the motor and bearings. However, the operation of cooling systems, which control the spindle temperature using cooling media, leads to increased power consumption. Furthermore, the power consumption of cooling systems accounts for a high proportion of the total power consumption of the machine tool. Therefore, in order to reduce power consumption from the perspectives of cost reduction and carbon neutrality, it has been proposed to shorten the operating time of cooling systems.

[0003] The bearing preload during spindle rotation is affected by the temperature difference between the inner and outer rings. Generally, the part cooled by the cooling medium of the cooling device is the outer cylinder portion of the spindle, i.e., the outer ring side. On the other hand, the inner ring side is difficult to dissipate heat from and is directly affected by heat from the motor and friction heat of the bearing. Therefore, the temperature of the inner ring tends to be higher than that of the outer ring. Furthermore, the expansion of the inner ring due to heating can lead to excessive preload, which can cause damage to the bearing and reduce its lifespan.

[0004] When the cooling system is switched between stopped and running states, or the spindle operating state is changed, there is a difference in the rate of temperature rise between the inner and outer rings of the bearing. For example, when the spindle rotation speed is increased, the inner ring heats up first and its temperature rises, followed by the outer ring. Therefore, during this temperature transition, the temperature difference between the inner and outer rings can become large. Also, when cooling is started from a stopped state, the outer ring cools first, followed by the inner ring. In this cooling transition, as with increasing the spindle rotation speed, the temperature difference between the inner and outer rings becomes large. In other words, in transient states where the temperature is not constant, as described above, it is necessary to control the cooling state by the cooling system or the spindle operating state, taking into account the changes in the inner and outer ring temperatures. However, while the outer ring temperature can be measured relatively easily by installing a temperature sensor near the outer ring that can measure temperature at all times, measuring the temperature near the inner ring, which is a rotating part, is difficult. For example, it is possible to measure the temperature near the inner ring using a non-contact method by installing an external radiation thermometer. However, in actual processing environments, installing equipment such as infrared thermometers is often difficult. Furthermore, even if the environment allows for installation, it incurs significant costs.

[0005] For example, Patent Document 1 discloses a method for controlling the cooling state, in which the temperature of a part that deforms due to temperature changes is estimated based on the difference in the time response between the temperature change of a nearby area that can be measured and the deformed part, and the cooling device is controlled based on the estimated temperature. Patent Document 2 discloses a method for measuring the inner ring temperature by fixing a heat flow sensor to the housing that secures the bearing, thereby detecting the heat flux from the inner ring side to the outer ring side and measuring the inner ring temperature. Patent Document 3 discloses a method for storing the relationship between the temperature rise of the inner ring, the temperature rise of the outer ring, the rotational speed, and the spindle load in a database, and controlling the flow rate of the cooling fluid so that the temperature rise values ​​of the inner and outer rings when the temperature of the rolling bearing reaches a steady state reach a target value, using the rotational speed and spindle load as input. Patent Document 4 discloses a method for estimating the inner ring temperature based on the temperature information of the aircraft, and switching the estimation model according to the transient state and stable state after a change in the cooling state. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Patent No. 6445395 [Patent Document 2] Japanese Patent Publication No. 2020-133889 [Patent Document 3] Japanese Patent Publication No. 2020-49571 [Patent Document 4] Japanese Patent Publication No. 2024-37534 [Overview of the project] [Problems that the invention aims to solve]

[0007] However, since the inner ring temperature changes in a complex way due to fluctuations in rotational speed and spindle load, it is difficult to estimate the inner ring temperature by measuring only the temperature near the outer ring, as disclosed in Patent Document 1. Furthermore, when controlling the cooling system based solely on the outer ring temperature, it is necessary to take a large safety margin to account for situations where the temperature difference between the inner and outer rings becomes large during transient conditions where the temperature is not constant. This necessitates increasing the time for which the cooling capacity is increased, thus reducing the power consumption reduction effect. Furthermore, the method described in Patent Document 2 is susceptible to influences from the installation location, spindle rotation, and airflow caused by lubricating oil injection, and is not suitable for measuring transient conditions where the temperature is not constant.

[0008] Furthermore, when the spindle rotation speed is changed, when cooling is stopped, and when switching between the stopped and running cooling states, the temperatures of the inner and outer rings change significantly in an unsteady manner. Moreover, heat transfer differs greatly between the stopped and running cooling states. Therefore, in the method described in Patent Document 3, since only the rotation speed and spindle load are inputs, it is difficult to appropriately control the spindle operating state and cooling state, including the stopped cooling state, which takes into account the changes in inner and outer ring temperatures.

[0009] Furthermore, the method described in Patent Document 4 only deals with the transient and stable states when switching cooling states. On the other hand, the characteristics of heat generation and heat transfer differ depending on the transient and stable states after changing the spindle rotation speed, the spindle rotation speed, and the spindle load (cutting load). Therefore, for example, when performing machining in a machine tool where the spindle rotation speed is frequently changed and the cutting load also changes, it is difficult to estimate the appropriate inner ring temperature due to the influence of the transient and stable states after changing the spindle rotation speed, the spindle rotation speed, and the changes in the cutting load.

[0010] Therefore, the present disclosure aims to provide a bearing cooling control system for a rotating machine that can appropriately estimate the inner ring temperature even if the rotating machine does not have a special device for measuring the inner ring temperature, and even if the temperatures of the inner ring and the outer ring are in a non-steady state, and that can appropriately control the cooling state of the bearing by the cooling device based on the estimation result. [Means for solving the problem]

[0011] To solve the above problems, a first aspect of the present disclosure is a bearing cooling control system for a rotating machine, comprising: a rolling bearing supporting the rotating shaft of the rotating machine; a cooling device that supplies a cooling medium to the rotating machine to cool the rolling bearing; a cooling control device that controls the cooling state of the rolling bearing by the cooling device; a motor that drives the rotating shaft; and an operation control device that controls the operating state of the rotating shaft, the system comprising: an outer ring temperature measuring unit that measures the temperature of the outer ring side of the rolling bearing; an inner ring temperature estimation unit that estimates the inner ring temperature using one or more inner ring temperature estimation models corresponding to the cooling state of the rolling bearing, based on the load of the motor, the rotational speed of the rotating shaft, the elapsed time after a change in the rotational speed of the rotating shaft, the elapsed time after a change in the cooling state of the rolling bearing, and the outer ring temperature measured by the outer ring temperature measuring unit; and a control command unit that issues at least one of a command to control the cooling device to the cooling control device and a command to control the rotating machine to the operation control device, based on the inner ring temperature estimated by the inner ring temperature estimation unit. Another aspect of the first configuration of the present disclosure is characterized in that, in the above configuration, the inner ring temperature estimation model includes a first coefficient that depends on the motor load, a second coefficient that depends on the rotational speed of the rotating shaft and the elapsed time after a change in the rotational speed of the rotating shaft, and a third coefficient that depends on the rotational speed of the rotating shaft, the elapsed time after a change in the cooling state of the rolling bearing and the cooling state of the rolling bearing. Another aspect of the first configuration of this disclosure is characterized in that, in the above configuration, the inner ring temperature estimation model includes an interpolation temperature term that complements the temperature difference between the estimated inner ring temperature before the change in cooling state and the estimated inner ring temperature after the change in cooling state when the rotational speed or the cooling state of the rolling bearing is changed, in a transient state of the cooling state of a rolling bearing where the temperature difference between the inner ring and the outer ring is transient, and the first coefficient, the second coefficient, and the third coefficient are not constant. Another aspect of the first configuration of the present disclosure further comprises a bearing condition index determination unit that derives and determines a bearing condition index and an allowable value of the bearing condition index based on the inner ring temperature estimated by the inner ring temperature estimation unit, and the control command unit issues at least one of a command to control the cooling device and a command to control the rotating machine based on the determination result relating to the bearing condition index and the allowable value of the bearing condition index calculated by the bearing index calculation unit. Another aspect of the first configuration of the present disclosure is characterized in that, in the above configuration, the bearing condition index determination unit uses at least one of the following as a bearing condition index: the inner-outer ring temperature difference, which is the difference between the inner ring temperature estimated by the inner ring temperature estimation unit and the outer ring temperature measured by the outer ring temperature measurement unit; the measured outer ring temperature; and the estimated inner ring temperature; and sets an allowable value for the bearing condition index according to the cooling state of the rolling bearing or the operating state of the rotating shaft. Another aspect of the first configuration of the present disclosure is characterized in that, in the above configuration, the control command unit determines the cooling state of the rolling bearing based on at least one of the operation and stop of the cooling device, the amount of cooling medium supplied, and the temperature of the cooling medium, and issues a command to control the cooling device according to the cooling state of the rolling bearing. Another aspect of the first configuration of the present disclosure is characterized in that, in the above configuration, the control command unit determines the operating state of the rotating machine based on at least one of the rotational speed of the rotating shaft and the load of the motor, and issues a command to control the rotating machine according to the operating state. Another aspect of the first configuration of the present disclosure is characterized in that, in the above configuration, the control command unit determines the cooling state of the rolling bearing based on at least one of the operation and stop of the cooling device, the amount of cooling medium supplied, and the temperature of the cooling medium, issues a command to control the cooling device according to the cooling state of the rolling bearing, and even when cooling is performed by the cooling device, if the decrease in the inner ring temperature difference, which is the difference between the inner ring temperature estimated by the inner ring temperature estimation unit and the outer ring temperature measured by the outer ring temperature measurement unit, the measured outer ring temperature, and the estimated inner ring temperature is insufficient, the control command unit determines the operating state of the rotating machine based on at least one of the rotational speed of the rotating shaft and the load of the motor, and issues a command to control the rotating machine according to the operating state. [Effects of the Invention]

[0012] According to this disclosure, the bearing cooling control system estimates the inner ring temperature using one or more inner ring temperature estimation models corresponding to the cooling state of the cooling device, based on the motor load, the rotational speed of the rotating shaft, the elapsed time after a change in the rotational speed of the rotating shaft, the elapsed time after a change in the cooling state of the cooling device, and the outer ring temperature measured by the outer ring temperature measuring unit. Therefore, even when the inner ring temperature and outer ring temperature are in a non-steady state when switching the spindle operation state of the rotating machine and the cooling state of the rolling bearing, the inner ring temperature can be appropriately estimated without using a special device to measure the inner ring temperature. Furthermore, the estimated inner ring temperature can be used to control the spindle operation and the stopping and operating states of the cooling device. This makes it possible to properly manage the temperature of the rolling bearing even when the operating state of the rotating shaft and the cooling state of the cooling device are frequently changed. As a result, it is possible to avoid the generation of excessive preload due to expansion of the inner ring side due to heating and prevent damage to the rolling bearing. In addition, when performing cooling control, it becomes possible to perform efficient cooling control with reduced power consumption. [Brief explanation of the drawing]

[0013] [Figure 1] This is a schematic diagram of an example of a bearing cooling control system that performs operation control and cooling control of a rotating machine in this disclosure. [Figure 2] This diagram shows the inner and outer ring temperatures when the cooling system is switched on and off. [Figure 3] This diagram shows the temperature difference between the inner and outer rings when the cooling system is switched on and off. [Figure 4] This is a flowchart illustrating the process of collecting input information and estimating the internal temperature. [Figure 5] This is a flowchart illustrating the process of collecting input information and estimating the internal temperature. [Figure 6] This flowchart shows the bearing condition index determination process and the control commands issued based on the bearing condition index determination results. [Modes for carrying out the invention]

[0014] The embodiments of this disclosure will be described below with reference to the drawings. Figure 1 is a schematic diagram of an example of a bearing cooling control system that performs spindle operation control and cooling control of a machining center in this disclosure. A machining center, as a machine tool, is equipped with a spindle unit 1, which is a rotating machine. The machining center is also fitted with a cooling device 14 capable of cooling the spindle unit 1. The spindle unit 1 comprises, inside an outer housing 1a, a housing 8, rolling bearings 2 installed in the housing 8, a spindle 7 supported by the rolling bearings 2, and a motor 9 that rotates the spindle 7. The rolling bearings 2 support the rotation of the spindle 7 with rolling elements 2a located between the outer ring 3 on the housing 8 side and the inner ring 4 on the spindle 7 side. A tool 18 is attached to the spindle 7. The machining center can machine a workpiece fixed to a table (not shown) by rotating the tool 18 via the spindle 7. Various operations in the machining center, including spindle rotation control, i.e., control of the motor 9's operating state, are performed by an operation control device 12. In this embodiment, the operating state of the spindle unit 1 is defined as the state in which the rotational speed of the spindle 7 and the load of the motor 9 are commanded by the operation control device 12. The spindle unit 1 is equipped with measuring instruments capable of measuring the rotational speed of at least one of the spindle 7 and the motor 9, and measuring instruments capable of measuring the load.

[0015] The cooling device 14 is capable of supplying a cooling medium to a cooling passage 5 located outside the housing 8 of the spindle unit 1. The cooling medium supplied to the cooling passage 5 cools the spindle unit 1, and more specifically, the rolling bearing 2 via the housing 8. The operation of the cooling device 14 is controlled by the cooling control device 13. The cooling control device 13 can switch between an operating state in which the cooling device 14 supplies a cooling medium to the spindle unit 1 and a stopped state in which it does not supply a cooling medium. In other words, the cooling control device 13 can switch the ON and OFF of a pump (not shown) of the cooling device 14. In this embodiment, the operating state of the cooling device 14 and the cooling state of the rolling bearing 2 are determined by whether the cooling device 14 is in an operating state or a stopped state. Furthermore, the cooling control device 13 may be capable of controlling the cooling medium to a predetermined temperature. Also, the cooling control device 13 may be capable of controlling the amount of cooling medium supplied to the spindle unit 1 by the cooling device 14. If the cooling control device 13 has these functions, the operating state of the cooling device 14 and the cooling state of the rolling bearing 2 may be determined based on whether the temperature of the cooling medium is below a predetermined value and whether the amount of cooling medium supplied to the spindle unit 1 is above a predetermined amount.

[0016] The bearing cooling control system, which includes a machining center and a cooling device 14, is equipped with a control command unit 11 that is responsible for controlling the entire system. Based on commands issued from the control command unit 11, the operation control device 12 controls the operation of the spindle unit 1 and the cooling control device 13 controls the operation of the cooling device 14. The control command unit 11, the operation control device 12, and the cooling control device 13 include a CPU and memory connected to the CPU, and various processes are realized by utilizing them. Furthermore, the control command unit 11, the operation control device 12, and the cooling control device 13 may each be independent devices, or they may be integrated into a single device as long as they can perform their respective functions.

[0017] The bearing cooling control system further comprises a temperature sensor 10, an outer ring temperature measurement unit 6, a bearing condition index determination unit 15, an inner ring temperature estimation unit 16, and a data recording unit 17. The outer ring temperature measurement unit 6, the bearing condition index determination unit 15, the inner ring temperature estimation unit 16, and the data recording unit 17 include a CPU and memory connected to the CPU, and various processes are realized by utilizing them. Furthermore, the outer ring temperature measurement unit 6, the bearing condition index determination unit 15, the inner ring temperature estimation unit 16, and the data recording unit 17 may each be independent devices, or they may be integrated into a single device as long as they can perform their respective functions. In addition, the outer ring temperature measurement unit 6, the bearing condition index determination unit 15, the inner ring temperature estimation unit 16, and the data recording unit 17 may be integrated into any combination of the control command unit 11, the operation control device 12, and the cooling control device 13, or all of them may be integrated into a single device.

[0018] The temperature sensor 10 is installed near the outer ring 3 of the housing 8. The temperature sensor 10 is electrically connected to the outer ring temperature measuring unit 6. The outer ring temperature measuring unit 6 measures the outer ring temperature from the output of the temperature sensor 10.

[0019] The data recording unit 17 records various information related to the machining center. For example, the data recording unit 17 records the current rotational speed command obtained from the operation control device 12, the measured rotational speed, the spindle load of the motor 9, and information regarding the elapsed time after the rotational speed command was changed. The data recording unit 17 also records the current operating status of the cooling device 14 obtained from the cooling control device 13, and information regarding the elapsed time after the operating status of the cooling device 14 was changed, such as the operating time and stop time. Furthermore, the data recording unit 17 also records information on the outer ring temperature measured by the temperature sensor 10 obtained from the outer ring temperature measurement unit 6, and information on the inner ring temperature estimated earlier. The information recorded in the data recording unit 17 is input to the inner ring temperature estimation unit 16, and the inner ring temperature is estimated using a pre-set model equation. The inner ring temperature estimation unit 16 outputs the estimated inner ring temperature. The information regarding the outputted inner ring temperature is recorded in the data recording unit 17.

[0020] The bearing condition index determination unit 15 determines the state of the rolling bearing 2 based on the bearing condition index recorded in the data recording unit 17. As described later, in this embodiment, the bearing condition index is at least one of the following: the measured outer ring temperature, the estimated inner ring temperature, the current inner and outer ring temperature difference, the maximum value of the inner and outer ring temperature difference estimated when the operating state of the spindle 7 is changed or the cooling state of the rolling bearing 2 is changed, and the allowable value of the inner ring temperature that can be allowed from the current outer ring temperature and spindle load.

[0021] As described above, the cooling medium supplied from the cooling device 14 to the spindle unit 1 cools the spindle unit 1 and, consequently, the rolling bearing 2, through the cooling passage 5 provided in the housing 8. Therefore, the outer ring 3 on the housing 8 side is cooled first, and the inner ring 4 is cooled later. In addition, the inner ring 4 that supports the spindle 7 is easily heated by bearing friction heat and generates a large amount of heat. Furthermore, if a built-in motor is used as the motor 9, it is also heated by the motor 9. Due to these factors, a temperature difference occurs between the inner ring 4 and the outer ring 3.

[0022] Figure 2 shows the inner and outer ring temperatures when the cooling system is switched on and off. Figure 3 shows the temperature difference between the inner and outer rings when the cooling system is switched on and off. For example, suppose that after 200 minutes, the cooling device 14 is stopped, and the cooling of the spindle unit 1 is halted. Then, as can be seen during the cooling device shutdown period from 200 min to 240 min, the rolling bearing 2 no longer receives cooling from the outer ring side, and as time passes, the temperature difference between the outer ring 3 and the inner ring 4, which generates a lot of heat, decreases. However, while the cooling device is shut down, the temperature of the rolling bearing 2 continues to rise due to the influence of the spindle 7 and the motor 9. Therefore, in order to prevent damage to the rolling bearing 2, cooling needs to be restarted at some point.

[0023] Therefore, if cooling is resumed at 240 mins, as described above, the temperature of the outer ring 3 will decrease first, and the temperature of the inner ring 4 will decrease later. As a result, the temperature difference between the inner ring 4 and the outer ring 3 will be larger than in the steady state up to 200 mins. In other words, in order to prevent damage to the rolling bearing 2, cooling must be resumed at a timing when the temperature difference between the inner ring 4 and the outer ring 3 after cooling is within a predetermined allowable value. Accordingly, in order to perform appropriate bearing cooling when the temperatures of the inner ring 4 and the outer ring 3 are in a transient state, information on the outer ring temperature and the inner ring temperature estimation unit 16 can appropriately estimate the inner ring temperature. Therefore, if the outer ring temperature measurement unit 6 measures the outer ring temperature and the inner ring temperature estimation unit 16 can appropriately estimate the inner ring temperature when the temperatures of the inner ring 4 and the outer ring 3 are in a transient state, the appropriate timing for resuming cooling can be determined by using the measured outer ring temperature and the estimated inner ring temperature.

[0024] The spindle operation control of the spindle unit 1 and the operation control of the cooling device 14 by the bearing cooling control system of this disclosure will be described in detail below based on the flowcharts shown in Figures 4 to 6. Figures 4 and 5 are flowcharts showing the input information collection and inner ring temperature estimation performed by the data recording unit 17 and the inner ring temperature estimation unit 16. The enclosed text in Figures 4 and 5 indicates the next step in the flow that spans across the figures.

[0025] The following is an example of a method for estimating the inner ring temperature in this disclosure, using the outer ring temperature T, which can be measured at any time. out This section explains a method for estimating the inner ring temperature by multiplying it by a coefficient. As part of the input information collection process, a series of processes related to step A below will be executed as appropriate. In step A1, the spindle load L observed from the motor 9 is acquired, and the value of the spindle load L recorded in the data recording area of ​​the data recording unit 17 is updated. In step A2, the rotational speed N of the spindle 7 is acquired, and the value of rotational speed N recorded in the data recording area of ​​the data recording unit 17 is updated. Step A3 involves measuring the outer ring temperature T using the temperature sensor 10 with the outer ring temperature measuring unit 6.out is acquired, and the value of the outer ring temperature T recorded in the data recording area of the data recording unit 17 out is updated.

[0026] Next, the inner ring temperature estimation by the inner ring temperature estimation unit 16 is executed. Hereinafter, the series of processes related to step B are executed by the inner ring temperature estimation unit 16. As step B1, when the operating state of the main shaft 7 and the cooling state of the rolling bearing 2 are steady, according to the main shaft load L recorded in the data recording area of the data recording unit 17 in step A1, the outer ring temperature T measured by the outer ring temperature measurement unit 6 out from the inner ring temperature T in is calculated as the first coefficient for the inner ring temperature estimation model formula for estimating the inner ring temperature T. The coefficient F is the outer ring temperature T corresponding to the main shaft load L derived from the data obtained in the test run performed in advance out and the inner ring temperature T in is set based on the relationship therebetween. Subsequently, as step B2, it is determined whether there is a change in the rotational speed N of the main shaft 7 from the value of the rotational speed N recorded in the data recording area of the data recording unit 17. In step B2, if it is determined that there is a change in the rotational speed N of the main shaft 7, step B3 described later is executed. On the other hand, if it is determined that there is no change in the rotational speed N of the main shaft 7, step B5 described later is executed.

[0027] In step B2, if it is determined that there is a change in the rotational speed N of the main shaft 7, then, as step B3, the elapsed time t N is reset. That is, the elapsed time t N is set to t N = 0. And, as step B4, the rotational speed N recorded in the data recording area of the data recording unit 17 before the rotational speed change is updated as N0.

[0028] On the other hand, in step B2, if it is determined that there is no change in the rotational speed N of the main shaft 7, as step B5, the elapsed time t NThe count continues. That is, elapsed time t N is, t N =t N It is given as +Δt. Here, the t on the right side N Δt is the elapsed time in step B2 from the previous change in rotational speed to the timing at which it was determined that there was no change in the rotational speed N of the spindle 7.

[0029] Then, after step B4 or step B5, as step B6, the rotational speed N0 of the spindle 7 before the rotational speed change, the current rotational speed N of the spindle 7, and the elapsed time t after the rotational speed change are determined. N A coefficient G is determined as a second coefficient for the inner ring temperature estimation model equation, which depends on the other factors. In this embodiment, the following equation (1) is used as the model equation for the coefficient G used to estimate the inner ring temperature.

[0030]

number

[0031] Here, γ(N0) is a coefficient that corresponds to the rotational speed N0 in a steady state, where the temperatures of the inner ring 4 and the outer ring 3 are constants. Also, γ(N) is a coefficient that corresponds to the rotational speed N in a steady state, where the temperatures of the inner ring 4 and the outer ring 3 are constants. τ(N) is an index of the transient response speed during which the temperature difference between the inner and outer rings reaches a steady state, depending on the rotational speed N. T G is the elapsed time t N As a result of this process, the coefficient G is a function that represents the time change of the coefficient as it transitions from the steady-state coefficient γ(N0) at rotational speed N0 to the steady-state coefficient γ(N) at rotational speed N. G This is the elapsed time t after the rotation speed has been changed. N Through this process, it converges from 0 to 1. In this embodiment, T G As such, the following equation (2), which is a function that converges from 0 to 1, is used.

[0032]

number

[0033] T G This is the elapsed time t after the rotation speed N has changed. N Outer ring temperature T out Inner ring temperature T in response to changes in If the change in is measured and set accordingly, it is not limited to equation (2) and may be expressed by other functions.

[0034] Next, in step B7, it is determined whether or not there has been a change in the cooling state of the rolling bearing 2. In this embodiment, in step B7, it is determined whether the operating state of the cooling device 14 has switched from stopped to running, or from running to stopped. If it is determined in step B7 that there has been a change in the operating state of the cooling device 14, then in step B8, the elapsed time t after the switch in the operating state of the cooling device 14 is determined. C It is reset. That is, elapsed time t C is, t C This is considered to be equal to 0. On the other hand, if it is determined in step B7 that there is no change in the operating state of the cooling device 14, then step B9 is performed, and the elapsed time t after the switch in the operating state of the cooling device 14 is determined. C The count continues. That is, elapsed time t C is, t C =t C It is given as +Δt. Here, the t on the right side C Δt is the elapsed time in step B7 from the previous change in operating state to the time when it was determined that there was no change in the operating state of the cooling device 14.

[0035] Following step B8 or step B9, step B10 determines whether the cooling device 14 is operational or stopped. If step B10 determines that the cooling device 14 is operational, step B11, described below, is executed. On the other hand, if it determines that the cooling device 14 is stopped, step B12, described below, is executed. Steps B11 and B12 involve changing the operating state of the cooling device 14 to determine the outer ring temperature T. out and inner ring temperature T in A coefficient H, which is a third coefficient for the inner ring temperature estimation model equation showing the relationship, is calculated using a model equation that matches the operating state of the cooling device 14. In this embodiment, as the model equation for the coefficient H for inner ring temperature estimation, H is calculated according to the operating state of the cooling device 14. ON and H OFF A device that switches between these two states is used. Specifically, as step B11, a coefficient H for estimating the inner ring temperature in the operating state of the cooling device 14 is used. ON However, this is calculated using the following equation (3). On the other hand, as step B12, the coefficient H for estimating the inner ring temperature when the cooling device 14 is stopped is used. OFF However, it is calculated using the following formula (4). Note that the coefficient H is used to estimate the inner ring temperature. ON and H OFF This refers to the rotational speed N, the elapsed time after the cooling device started operating, or the elapsed time after the cooling device stopped operating t. C and depends on the operating status of the cooling device 14.

[0036]

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[0037] Here, β ON (N) is a function that depends on the rotational speed N of the cooling device 14 when it is in operation, and β OFF (N) is a function of the rotational speed N of the cooling device 14 when it is stopped. H is the elapsed time t C This is a function that represents the time change of the coefficient H as the process progresses. In this embodiment, T H As such, the following equations (5) and (6) are used, which are functions that represent the effect of the difference in response speed to temperature changes between the inner ring 4 and the outer ring 3 when the cooling state is changed from stopped to running, or from running to stopped.

[0038]

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[0039] Here, the τ in equation (5) used when the cooling device 14 is in operation 1ON ,τ 2ON And, when the cooling device 14 is stopped, the τ in equation (6) is used. 1OFF ,τ 2OFF These are the time constants related to the response speed of the inner ring 4 and the outer ring 3, respectively.

[0040] Next, after step B11 or step B12, step B13 determines whether there has been a change in the rotational speed N or the cooling state of the rolling bearing 2. In step B13, if it is determined that there is a change in the rotational speed N or the cooling state of the rolling bearing 2, step B14 is performed, and the value of the step difference d recorded in the data recording area of ​​the data recording unit 17 is updated. The step difference d is calculated using the following equation (7) based on the coefficients F, G, and H calculated so far. In equation (7), the coefficient H is determined according to the operating state of the cooling device 14. ON and H OFF It can be switched between and .

[0041]

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[0042] Here, the step difference d in this disclosure refers to the outer ring temperature T immediately before a change in rotational speed N or a change in the cooling state of the rolling bearing 2 occurs, when the rotational speed N or the cooling state of the rolling bearing 2 is steady. out The inner ring temperature T is estimated from this. in And the inner ring temperature T that was actually calculated in the previous estimation and recorded in the data recording area of ​​the data recording unit 17. in This is the difference.

[0043] If, in step B13, it is determined that there is no change in the rotational speed N or the cooling state of the rolling bearing 2, or if step B14 is performed, then step B15 is performed. As step B15, the inner ring temperature T is estimated from the inner ring temperature estimation model equation according to the cooling state of the rolling bearing 2, i.e., the operating state of the cooling device 14. in This is calculated. Inner ring temperature T in The estimation is based on the measured outer ring temperature T out Based on this, the inner ring temperature estimation model equation, which takes into account the spindle load, rotational speed changes, and cooling state changes, is performed by the following equation (8). In equation (8), the coefficient H is determined according to the operating state of the cooling device 14. ON and H OFF It can be switched between and .

[0044]

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[0045] Here, D is the interpolated temperature term. That is, D is the estimated inner ring temperature T before the change when the rotational speed N or the cooling state of the rolling bearing 2 is changed during a transient cooling state of the rolling bearing 2 where the coefficients F, G, and H in equation (8) are not constant and the inner and outer ring temperature difference is transient. in And the estimated inner ring temperature T after the change in This compensates for the temperature difference. As a result, the inner ring temperature can be accurately estimated even during the transient cooling state of the rolling bearing 2. The interpolated temperature term D converges from the step difference d to 0 depending on the rotational speed N or the time t after the change in the cooling state of the cooling device 14. In this embodiment, the following equation (9), which is a function that converges from the step difference d to 0, is used as the interpolated temperature term D.

[0046]

number

[0047] Here, T D This is a function that represents the time change in which the interpolated temperature term D transitions from a step difference d to 0 as time t elapses after a change in rotational speed N or the cooling state of the rolling bearing 2. T D As an example, in this embodiment, TD The following equation (10) is used as the formula.

[0048]

number

[0049] Here, τ3 is the convergence time constant. τ3 may be changed depending on the cooling state of the rolling bearing 2. Also, T D This is not limited to equation (10) and may be expressed by other functions, as long as it is set in accordance with the convergence of the step difference d that has been measured in advance.

[0050] Subsequently, as step B16, the inner ring temperature T recorded in the data recording area of ​​the data recording unit 17 is recorded. in However, the calculated estimated inner ring temperature T in It will be updated.

[0051] The various coefficients in equations 1 to 10 above are the spindle load L, rotational speed N, and the inner ring temperature T when the cooling state of the rolling bearing 2 or the operating state of the cooling device 14 is changed. in and outer ring temperature T out A test run is conducted in advance to measure the relationship, and the setting is determined based on the data obtained during the test run.

[0052] The following describes the bearing condition index determination performed by the bearing condition index determination unit 15 and the control commands issued by the control command unit 11 based on the bearing condition index determination results. Figure 6 is a flowchart showing the bearing condition index determination performed by the bearing condition index determination unit 15 and the control commands issued by the control command unit 11 based on the determination results of the bearing condition index. In this embodiment, it is assumed that the flow shown in Figure 6 is repeated each time the value recorded in the data recording unit 17 is updated.

[0053] The bearing condition index determination unit 15 performs a bearing condition index determination. The series of processes related to step C are then performed by the bearing condition index determination unit 15. First, in step C1, the estimated inner ring temperature T recorded in the data recording area of ​​the data recording unit 17 is recorded. in and the measured outer ring temperature T out Therefore, the difference is the inner and outer ring temperature difference ΔT diff This is calculated. Next, in step C2, it is determined whether the cooling device 14 is in operation or stopped. If it is determined in step C2 that the cooling device 14 is in operation, step C3, described below, is executed. On the other hand, if it is determined that the cooling device 14 is stopped, step C6, described below, is executed. If cooling control is not performed and the cooling device 14 is kept in operation at all times, step C2, as well as steps C5, C6, C7, D2, and D3 described later, are omitted.

[0054] Steps C3, C4, and C5 will be described in detail as processes performed while the cooling device 14 is in operation. If it is determined in step C2 that the cooling device 14 is operating, then in step C3, the temperature difference ΔT between the inner and outer rings of the cooling device 14 in operation is determined. diff The permissible limit is the threshold ΔT for the temperature difference between the inner and outer rings during cooling operation. on It is set as follows: Cooling operation inner and outer ring temperature difference threshold ΔT on For example, outer ring temperature T out , and for each rotational speed N, the temperature difference between the inner and outer rings ΔT after cooling has started. diff The maximum value, i.e., the tolerance limit, is determined in advance by testing or modeling, and the setting is based on that maximum value. Then, as step C4, the inner and outer ring temperature difference ΔT diff However, the threshold ΔT for the temperature difference between the inner and outer rings during cooling operation on It is determined whether or not it exceeds the specified value. Note that the determination in step C4 is made based on the inner and outer ring temperature difference ΔT over a certain period of time. diff The threshold ΔT for the temperature difference between the inner and outer rings during cooling operation. on The determination may also be made based on whether or not it continued to exceed the limit. In step C4, the inner and outer ring temperature difference ΔT diff However, it is used as an indicator of bearing condition.

[0055] In step C4, the temperature difference ΔT between the inner and outer rings diff is determined to exceed the threshold value ΔT of the temperature difference between the inner and outer rings during the cooling operation on If it is so determined, in step D1, assuming that the main shaft load L in step B1 shown in FIG. 5 is reduced, the inner ring temperature T in is estimated based on the virtual coefficient F, or assuming that the rotational speed N in step B6 is changed, the inner ring temperature T in Based on the inverse calculation based on the virtual coefficient G for estimating, the spindle load L or the rotational speed N at which the temperature difference ΔT between the inner and outer rings diff becomes an appropriate value is calculated. Subsequently, based on the calculated spindle load L or rotational speed N, a command for controlling the spindle operating state is issued from the control command unit 11 to the operation control device 12 so as to reduce the spindle load L or change the rotational speed N on the spindle 7. If the control of the spindle operating state is not performed, steps C3, C4, and D1 are omitted.

[0056] On the other hand, in step C4, if the temperature difference ΔT between the inner and outer rings diff is determined not to exceed the threshold value ΔT of the temperature difference between the inner and outer rings during the cooling operation on In step C5, it is determined whether the estimated inner ring temperature T in and the measured outer ring temperature T out are each below a preset temperature. Here, a temperature is set at which it is determined that seizure does not occur on the spindle 7 even when the cooling device 14 is stopped for a certain period of time. The temperature is set based on data obtained in a preliminary test run by performing a preliminary test run. In step C5, the estimated inner ring temperature T in and the measured outer ring temperature T out are used as bearing state indicators.

[0057] In step C5, the estimated inner ring temperature T in and the measured outer ring temperature T outIf it is determined that the temperature is below a preset temperature, it can be determined that it is acceptable to stop the cooling device 14 for a certain period of time. Therefore, in step D2, the control command unit 11 issues a command to the cooling control device 13 to stop the operation of the cooling device 14. On the other hand, in step C5, the estimated inner ring temperature T in and the measured outer ring temperature T out If it is determined that the temperature is not below a preset temperature, and if all control commands issued by the control command unit 11 based on the bearing condition index determination result have been executed, the sequence related to the bearing condition index determination and the control commands issued based on the bearing condition index determination result is terminated.

[0058] Furthermore, if it is determined in step C2 that the cooling device 14 is in a stopped state, then in step C6, the temperature difference between the inner and outer rings ΔT in the stopped state of the cooling device 14 is determined. diff The permissible limit is the threshold ΔT for the temperature difference between the inner and outer rings when cooling stops. off It is set as follows: Inner and outer ring temperature difference threshold ΔT when cooling stops. off This refers to the difference in temperature change between the inner ring 4 and the outer ring 3 during cooling, resulting in an inner-outer ring temperature difference ΔT. diff It is set taking into account the rise in temperature. Therefore, the threshold value ΔT for the inner and outer ring temperature difference when cooling is stopped. off The threshold value ΔT is the temperature difference between the inner and outer rings during cooling operation. on It becomes smaller than the threshold ΔT for the inner and outer ring temperature difference when cooling stops. off For example, outer ring temperature T out For each rotational speed N, the temperature difference between the inner and outer rings after cooling begins ΔT diff The maximum value, i.e., the tolerance limit, is determined in advance by testing or modeling, and the setting is based on that maximum value.

[0059] Next, as step C7, the inner and outer ring temperature difference ΔT diff However, the threshold temperature difference between the inner and outer rings when cooling stops is ΔT off It is determined whether or not it exceeds a certain value. Alternatively, the measured outer ring temperature T is used as an indicator of bearing condition. out However, it is determined whether the temperature is above the set temperature. In step C7, the inner and outer ring temperature difference ΔT diff, and the measured outer ring temperature T out However, it is used as an indicator of bearing condition.

[0060] Then, in step C7, the temperature difference between the inner and outer rings ΔT diff The threshold ΔT for the temperature difference between the inner and outer rings when cooling stops. off If it is determined that it exceeds the measured outer ring temperature T out However, if it is determined that the temperature is above the set temperature, it is determined that it is time to start cooling. Therefore, in step D3, the control command unit 11 issues a command to the cooling device 14 to restart operation. On the other hand, in step C7, the temperature difference between the inner and outer rings ΔT diff The threshold ΔT for the temperature difference between the inner and outer rings when cooling stops. off If it is determined that the value does not exceed the threshold, and if all control commands issued by the control command unit 11 based on the bearing condition index determination result have been executed, the sequence related to the bearing condition index determination and the control commands issued based on the bearing condition index determination result is terminated.

[0061] However, if, for a predetermined reason, no new command is issued by the control command unit 11 during the process related to step D, the spindle operating state and the operating state of the cooling device 14 will be maintained as they are.

[0062] The bearing cooling control system with the above configuration comprises a rolling bearing 2 that supports the spindle 7 of the spindle unit 1, a cooling device 14 that supplies a cooling medium to the spindle unit 1 to cool the rolling bearing 2, a cooling control device 13 that controls the cooling state of the rolling bearing 2 by the cooling device 14, a motor 9 that drives the spindle 7, and an operation control device 12 that controls the operating state of the spindle 7, and includes an outer ring temperature measuring unit 6 that measures the temperature on the outer ring 3 side of the rolling bearing 2, the load of the motor 9, the rotational speed of the spindle 7, and the elapsed time t after the change in the rotational speed of the spindle 7. N And the elapsed time t after the change in the cooling state of the rolling bearing 2. C And the outer ring temperature T measured by the outer ring temperature measurement unit out Based on this, one or more inner ring temperature estimation models corresponding to the cooling state of the rolling bearing 2 are used to estimate the inner ring temperature T inAn inner ring temperature estimation unit 16 estimates the inner ring temperature T, and the inner ring temperature T estimated by the inner ring temperature estimation unit 16 in The system includes a control command unit 11 that issues at least one of the following commands to control the cooling device 14 to the cooling control device 13, and a command to control the spindle unit 1 to the operation control device 12.

[0063] Therefore, the inner ring temperature T in Without using special equipment to measure it, the inner ring temperature T can be measured when switching the spindle operating state of the spindle unit 1 and the cooling state of the rolling bearing 2. in and outer ring temperature T out Even in a non-steady state, the inner ring temperature T is appropriately maintained. in It is possible to estimate the inner ring temperature T. in This allows for the control of spindle operation and the stopping and operating states of the cooling device 14. This enables appropriate temperature control of the rolling bearing 2 even when the operating state of the spindle 7 and the cooling state of the cooling device 14 are frequently changed. As a result, it is possible to avoid the generation of excessive preload due to expansion of the inner ring 4 side due to heating, and prevent damage to the rolling bearing 2. Furthermore, when performing cooling control, it becomes possible to perform efficient cooling control with reduced power consumption.

[0064] Furthermore, the configuration of the bearing cooling control system for rotating machinery described herein is not limited in any way to the embodiments described above, and can be modified as necessary without departing from the spirit of the invention. For example, in the above embodiment, the rolling bearing 2 is cooled by the cooling medium supplied from the cooling device 14 through the cooling passage 5 provided in the housing 8, which cools the spindle unit 1. However, the rolling bearing 2 may also be cooled by axial cooling by providing a cooling passage 5 on the spindle 7 side. In this case, the cooling effect on the inner ring 4 and outer ring 3 is reversed compared to the above embodiment. Furthermore, the rotating machinery relating to this disclosure is not limited to the spindle unit 1 of a machining center, but may also include machine tools such as lathes, or other rotating machinery besides machine tools. Furthermore, equations (1) to (10) above are merely examples of inner ring temperature estimation models, and the inner ring temperature T inTo estimate the inner ring temperature T in and outer ring temperature T out The model equation showing the relationship can be set using, for example, well-known machine learning based on data obtained from test runs, as long as the inner ring temperature can be estimated from information obtained from existing instruments that can be easily attached to the rotating device, such as outer ring temperature, rotating shaft rotation speed, and motor load. [Explanation of Symbols]

[0065] 1. Main spindle unit (rotating machine), 2. Rolling bearing, 3. Outer ring, 4. Inner ring, 6. Outer ring temperature measurement unit, 7. Main spindle (rotating shaft), 9. Motor, 11. Control command unit, 12. Operation control device, 13. Cooling control device, 14. Cooling device, 15. Bearing condition index determination unit, 16. Inner ring temperature estimation unit.

Claims

1. A bearing cooling control system for a rotating machine comprising: a rolling bearing that supports the rotating shaft of the rotating machine; a cooling device that supplies a cooling medium to the rotating machine to cool the rolling bearing; a cooling control device that controls the cooling state of the rolling bearing by the cooling device; a motor that drives the rotating shaft; and an operation control device that controls the operating state of the rotating shaft, The outer ring temperature measuring unit measures the temperature of the outer ring side of the rolling bearing, An inner ring temperature estimation unit estimates the inner ring temperature using one or more inner ring temperature estimation models corresponding to the cooling state of the rolling bearing, based on the load of the motor, the rotational speed of the rotating shaft, the elapsed time after a change in the rotational speed of the rotating shaft, the elapsed time after a change in the cooling state of the rolling bearing, and the outer ring temperature measured by the outer ring temperature measurement unit. A bearing cooling control system for a rotating machine, comprising: a control command unit that issues at least one of the following based on the inner ring temperature estimated by the inner ring temperature estimation unit: a command to control the cooling device to the cooling control device, and a command to control the rotating machine to the operation control unit.

2. The bearing cooling control system for a rotating machine according to claim 1, characterized in that the inner ring temperature estimation model includes a first coefficient that depends on the load of the motor, a second coefficient that depends on the rotational speed of the rotating shaft and the elapsed time after a change in the rotational speed of the rotating shaft, and a third coefficient that depends on the rotational speed of the rotating shaft, the elapsed time after a change in the cooling state of the rolling bearing and the cooling state of the rolling bearing.

3. The bearing cooling control system for a rotating machine according to claim 2, characterized in that the inner ring temperature estimation model includes an interpolation temperature term that compensates for the temperature difference between the estimated inner ring temperature before the cooling state change and the estimated inner ring temperature after the cooling state change when the rotational speed or the cooling state of the rolling bearing is changed in a transient state of the cooling state of the rolling bearing in which the temperature difference between the inner ring and the outer ring is not constant, where the first coefficient, the second coefficient, and the third coefficient are not constant.

4. The system further includes a bearing condition index determination unit that derives and determines a bearing condition index and an allowable value for the bearing condition index based on the inner ring temperature estimated by the inner ring temperature estimation unit, The bearing cooling control system for a rotating machine according to any one of claims 1 to 3, characterized in that the control command unit issues at least one of a command to control the cooling device and a command to control the rotating machine based on a determination result relating to the bearing condition index calculated by the bearing condition index determination unit and the allowable value of the bearing condition index.

5. The bearing condition index determination unit uses at least one of the following as the bearing condition index: the inner-outer ring temperature difference, which is the difference between the inner ring temperature estimated by the inner ring temperature estimation unit and the outer ring temperature measured by the outer ring temperature measurement unit; the measured outer ring temperature; and the estimated inner ring temperature. The bearing cooling control system for a rotating machine according to claim 4, characterized in that the allowable value of the bearing condition index is set according to the cooling state of the rolling bearing or the operating state of the rotating shaft.

6. The bearing cooling control system for a rotating machine according to any one of claims 1 to 3, characterized in that the control command unit determines the cooling state of the rolling bearing based on at least one of the operation and stopping of the cooling device, the amount of the cooling medium supplied, and the temperature of the cooling medium, and issues a command to control the cooling device according to the cooling state of the rolling bearing.

7. The bearing cooling control system for a rotating machine according to any one of claims 1 to 3, characterized in that the control command unit determines the operating state of the rotating machine based on at least one of the rotational speed of the rotating shaft and the load of the motor, and issues a command to control the rotating machine according to the operating state.

8. The control command unit determines the cooling state of the rolling bearing based on at least one of the operation and stop of the cooling device, the amount of the cooling medium supplied, and the temperature of the cooling medium, and issues a command to control the cooling device according to the cooling state of the rolling bearing. Even when cooling is performed by the cooling device, if the decrease in the inner ring temperature estimated by the inner ring temperature estimation unit, the difference between the inner ring temperature and the outer ring temperature measured by the outer ring temperature measurement unit, the measured outer ring temperature, and the estimated inner ring temperature is insufficient, the control command unit determines the operating state of the rotating machine based on at least one of the rotational speed of the rotating shaft and the load of the motor, and issues a command to control the rotating machine according to the operating state, characterized in that a bearing cooling control system for a rotating machine according to any one of claims 1 to 3.

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