Ball screw offset load detection device, offset load detection method, and program

Abstract

To easily detect an offset load in a ball screw mechanism.SOLUTION: A ball screw offset load detection device includes an acquisition unit that acquires vibration information during operation of a ball screw, a division unit that divides the vibration information into a plurality of sections, a calculation unit that calculates an evaluation value for each of the plurality of sections, and a determination unit that determines the presence or absence of an offset load in the ball screw on the basis of a degree of change in the evaluation values.SELECTED DRAWING: Figure 7

Description

[Technical Field]

[0001] The present invention relates to a device for detecting an unbalanced load on a ball screw, a method for detecting an unbalanced load, and a program. [Background technology]

[0002] Conventionally, a ball screw mechanism has been known that includes a screw shaft that rotates around a rotation axis and a nut that moves in the axial direction of the rotation axis as the screw shaft rotates. Ball screw mechanisms are used in a variety of devices, and to ensure their operation with precision, it is necessary to properly install supports that support both ends of the screw shaft of the ball screw mechanism. When a ball screw mechanism is operated in an improperly installed state, such as when it is installed unevenly, an offset load is generated in one part of the mechanism, which can interfere with the operation of the ball screw mechanism and may also cause malfunctions.

[0003] For example, Patent Document 1 discloses a configuration for measuring the installation error of a ball screw using the results of a fast Fourier transform (FFT) of rotational periodic vibration. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2020-20425 Summary of the Invention [Problem to be solved by the invention]

[0005] For example, in the method disclosed in Patent Document 1, it is necessary to set a threshold value for a signal value in order to determine an installation error of a ball screw mechanism. However, the appropriate threshold value used in the method disclosed in Patent Document 1 may vary depending on the specifications, type, and usage conditions of the device. Therefore, it is difficult to specify in advance an individual threshold value for determining an installation error, taking into account the various conditions of the ball screw mechanism.

[0006] Therefore, there is a need to detect unbalanced loads during installation and use of a ball screw mechanism without needing to set individual threshold values ​​according to the type or application of the ball screw mechanism.

[0007] In view of the above-mentioned problems, an object of the present invention is to easily detect an unbalanced load in a ball screw mechanism. [Means for solving the problem]

[0008] In order to solve the above problems, the present invention has the following configuration: an acquisition unit that acquires vibration information during operation of the ball screw; a division unit that divides the vibration information into a plurality of sections; a calculation unit that calculates an evaluation value for each of the plurality of sections; a determination unit that determines whether or not there is an unbalanced load in the ball screw based on the degree of change in the evaluation value; It has.

[0009] Another aspect of the present invention has the following configuration: A method for detecting an unbalanced load on a ball screw includes: an acquisition step of acquiring vibration information during operation of the ball screw; a dividing step of dividing the vibration information into a plurality of sections; a calculation step of calculating an evaluation value for each of the plurality of sections; a determination step of determining whether or not there is an unbalanced load in the ball screw based on the degree of change in the evaluation value; It has.

[0010] Another aspect of the present invention has the following configuration: On the computer, an acquisition step of acquiring vibration information during operation of the ball screw; a dividing step of dividing the vibration information into a plurality of sections; a calculation step of calculating an evaluation value for each of the plurality of sections; a determination step of determining whether or not there is an unbalanced load in the ball screw based on the degree of change in the evaluation value; Execute the following. [Effects of the Invention]

[0011] According to the present invention, it is possible to easily detect an unbalanced load in a ball screw mechanism. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a block diagram showing an example of the configuration of a system according to a first embodiment of the present invention. [Figure 2] FIG. 2 is a schematic view illustrating an offset load of the ball screw according to the first embodiment of the present invention. [Figure 3] FIG. 3 is a graph illustrating a change in vibration due to an unbalanced load of the ball screw according to the first embodiment of the present invention. [Figure 4] FIG. 4 is a graph illustrating a change in evaluation value due to an unbalanced load according to the first embodiment of the present invention. [Figure 5] FIG. 4 is a graph illustrating a change in evaluation value due to an unbalanced load according to the first embodiment of the present invention. [Figure 6] 1 is a schematic view showing an example of the configuration of a ball screw according to a first embodiment of the present invention. [Figure 7] 4 is a flowchart of an installation error determination process according to the first embodiment of the present invention. [Figure 8] FIG. 5 is a schematic view showing an example of the configuration of a ball screw according to a second embodiment of the present invention. [Figure 9] FIG. 10 is a graph illustrating a change in vibration due to an unbalanced load in a ball screw according to a second embodiment of the present invention. [Figure 10] FIG. 6 is a schematic view illustrating an offset load of a ball screw according to a second embodiment of the present invention. [Figure 11] FIG. 10 is a graph illustrating a change in vibration due to an unbalanced load in a ball screw according to a second embodiment of the present invention. [Figure 12] FIG. 10 is a graph illustrating a change in vibration due to an unbalanced load in the ball screw according to the second embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0013] Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings, etc. Note that the embodiment described below is one embodiment for explaining the present invention, and is not intended to be interpreted as limiting the present invention, and all of the configurations described in each embodiment are not necessarily essential configurations for solving the problems of the present invention.

[0014] First Embodiment A first embodiment of the present invention will be described below. A ball screw unbalanced load detection device according to one embodiment of the present invention acquires vibration information indicating vibrations that occur with the operation of a ball screw, which will be described later, and detects unbalanced loads on the ball screw. The configuration, specifications, and uses of the ball screw are not particularly limited, and are not particularly limited as long as the processing described later can be applied.

[0015] [Control system] FIG. 1 shows an example of a system configuration including an unbalanced load detection device 100 that can realize the unbalanced load detection method for a ball screw according to this embodiment.

[0016] The unbalanced load detection device 100 is configured to be able to acquire vibration information generated during operation of the ball screw 200 via the acceleration sensor 300. The unbalanced load detection device 100 may be configured as a general-purpose information processing device such as a PC (Personal Computer), or may be configured as a dedicated device. The unbalanced load detection device 100 includes a processing unit 101, a storage unit 102, a UI (User Interface) unit 103, an external interface 104, and a communication unit 105.

[0017] The processing unit 101 may be configured with a CPU (Central Processing Unit), an MPU (Micro Processing Unit), a DSP (Digital Single Processor), a dedicated circuit, etc. The storage unit 102 is configured with volatile and non-volatile storage media such as an HDD (Hard Disk Drive), a ROM (Read Only Memory), and a RAM (Random Access Memory), and is capable of inputting and outputting various types of information in response to instructions from the processing unit 101.

[0018] The UI unit 103 receives operations from the user and displays various information such as detection results. For example, the UI unit 103 is composed of a speaker, a light, a display device such as a liquid crystal display, and the like, and outputs to the user in response to instructions from the control unit. The output method by the UI unit 103 is not particularly limited, and may be, for example, visual output via screen output or auditory output via voice. The external IF 104 is an interface for connection to an external device, and in this embodiment, is configured to be able to send and receive data to and from the acceleration sensor 300. The communication unit 105 is a network interface for communicating with external devices.

[0019] The ball screw 200 is a target for detecting an attachment error, i.e., an unbalanced load, according to this embodiment. A configuration example of the ball screw 200 will be described later using FIG. 2 etc. The operation of the ball screw 200 may be controlled by the processing unit 101 of the unbalanced load detection device 100, or may be controlled by a separate control device (not shown) that can operate in cooperation with the unbalanced load detection device 100.

[0020] The acceleration sensor 300 is installed on the ball screw 200, acquires vibration information while the ball screw 200 is operating, and provides the information to the unbalanced load detection device 100. An example of the installation of the acceleration sensor 300 will be described later. The vibration information acquired by the acceleration sensor 300 is managed and stored in the memory unit 102 of the unbalanced load detection device 100 as appropriate.

[0021] [Unbalanced load] 2 is a schematic diagram for explaining the unbalanced load of a ball screw 200 according to this embodiment. A motor 201 is connected to a screw shaft 203 via a coupling portion 202. When the motor 201 rotates, the screw shaft 203 rotates, and a nut 205 provided on the screw shaft 203 moves along the axial direction (rotational axis direction) of the screw shaft 203. The screw shaft 203 is rotatably supported by rolling bearings 204 and 206. The range of movement of the nut 205 is defined between the rolling bearing 204 and the rolling bearing 206. Note that grease and the like are also used when the ball screw 200 rotates, but this is not described here.

[0022] Here, it is assumed that distortion occurs in the screw shaft 203 due to an installation error of the rolling bearings 204 and 206. The rolling bearings 204 and 206 are fixed to a bed or the like of a machine tool (not shown). The nut 205 is fixed to a table or the like (not shown) that moves in the longitudinal direction of the screw shaft 203 relative to the bed or the like. As described above, because there is an installation error such as misalignment between the rolling bearings 204 and 206, distortion occurs in the screw shaft 203, and the moving direction of the nut 205 and the axial direction of the screw shaft 203 do not strictly coincide. Under such circumstances, an offset load occurs in the ball screw 200, and the offset load changes depending on the position of the nut 205 on the screw shaft 203.

[0023] In this example, the area between the rolling bearing 204 and the rolling bearing 206 will be divided into three regions 210a to 210c for explanation. When the nut 205 performs a reciprocating motion due to the operation of the ball screw 200, an offset load occurs between the nut 205 and the screw shaft 203 in region 210a on the motor 201 side, but the offset load is the smallest among the three regions. The offset load increases toward region 210c on the rolling bearing 206 side. The offset load occurring between the screw shaft 203 and the nut 205 due to installation errors appears, for example, at the edges of the region where the screw shaft 203 and the nut 205 contact each other.

[0024] In the configuration example shown in FIG. 2, the nut 205 moves back and forth from side to side along the screw shaft 203. Here, the movement of the nut 205 along the screw shaft 203 toward the left in the drawing is referred to as "forward." Furthermore, the movement of the nut 205 along the screw shaft 203 toward the right in the drawing is referred to as "return." Note that, although an example in which the ball screw 200 is installed horizontally will be described here, the same applies to installation errors that occur when the ball screw 200 is installed vertically, for example.

[0025] Fig. 3 is a graph showing an example of vibration information obtained when the ball screw 200 operates in the installation state shown in Fig. 2. In Fig. 3, the vertical axis represents acceleration and the horizontal axis represents time. Here, the vibration information obtained during one reciprocating movement (one stroke) of the nut 205 is shown. Note that the numerical values ​​in the graphs in this specification are not numerical values ​​obtained by experiment, but numerical values ​​created as an example to explain this embodiment.

[0026] Each waveform is divided into sections of a predetermined time width, and each section is evaluated. As shown in FIG. 2, if an unbalanced load occurs, the evaluation value for the vibration information obtained when the nut 205 moves changes. In other words, if no unbalanced load occurs, the change in the evaluation value for the vibration information becomes small. In other words, an unbalanced load can be detected by capturing the relative change in the evaluation value as shown in FIG. 3.

[0027] In this embodiment, the occurrence of an unbalanced load due to an installation error is determined by an evaluation value based on at least one of the following three criteria. (i) The first component of the rotation frequency in the FFT spectrum, fr (ii) The characteristic frequency Zfc of the nut in the envelope FFT spectrum (iii) Effective value

[0028] First, we will explain the first-order component fr of the rotation frequency. As shown in Figure 3, FFT processing is applied to each section of the divided vibration information to derive the first-order component fr of the rotation frequency. This fr is a whirling vibration, and increases as the unbalanced load increases.

[0029] Figure 4 is a graph illustrating changes in fr, showing the results of applying FFT processing to each section without averaging. The vertical axis represents signal strength, and the horizontal axis represents frequency. Here, evaluation values ​​1, 2, and n are shown as examples for the "going" section shown in Figure 3. Focusing on the primary component fr of the rotation frequency, the signal strength gradually increases from A1, A2, ..., An as we move from evaluation value 1 to evaluation value n. The occurrence of unbalanced loads can be detected based on these changes in fr, i.e., the transition in the amplitude of fr.

[0030] In this embodiment, the evaluation values ​​based on fr are expressed in chronological order as A1, A2, . . . , A n Then, the ratio is calculated using the following formulas (1) and (2).

[0031]

number

[0032] If the ratio calculated by the above formula exceeds a predetermined threshold, it is determined that an unbalanced load exists. The threshold here is not particularly limited and may vary depending on the configuration, specifications, and application of the ball screw. For example, the threshold may be set to 10%. Furthermore, multiple thresholds may be set for each criterion. For example, multiple thresholds may be set corresponding to the degree of unbalanced load (e.g., large unbalanced load, medium unbalanced load, small unbalanced load), and the degree of occurrence of unbalanced load may be identified.

[0033] Next, the characteristic frequency Zfc of the nut 205 will be described. The nut 205 includes multiple rolling elements (not shown) that move on the rolling surface (loaded portion) of the screw shaft 203 as the screw shaft 203 rotates. These rolling elements are located either on the rolling surface or in a tube (not shown) that serves as a circulation path within the nut 205, and move as the nut rotates. When an unbalanced load occurs, the area near the entrance where the tube enters the rolling surface becomes narrower, resulting in collision vibration. In other words, as the unbalanced load increases, the collision vibration also increases. In this embodiment, this collision vibration is captured using the characteristic frequency Zfc of the nut 205. The characteristic frequency Zfc is derived by applying envelope FFT processing to each divided section as shown in FIG. 3. Note that the ball screw to which this embodiment is applied is not limited to one that uses a tube as the circulation path. For example, the present embodiment can be applied to a ball screw that uses an end deflector, end plate, top, or end cap instead of a tube as the circulation path. In either case, the occurrence of an unbalanced load changes the degree of collision vibration.

[0034] FIG. 5 is a graph illustrating the change in Zfc, showing the results of applying envelope FFT processing to each divided region without averaging. The vertical axis represents signal strength, and the horizontal axis represents frequency. Here, evaluation values ​​1, 2, and n are shown as examples for the "go" shown in FIG. 3. Focusing on the characteristic frequency Zfc of nut 205, the signal strength gradually increases from evaluation value 1 to evaluation value n. The occurrence of an unbalanced load can be detected based on this change in Zfc, i.e., the transition in the amplitude of Zfc.

[0035] The determination of the unbalanced load using the evaluation value based on Zfc may be made using a ratio, similar to the determination of the evaluation value based on fr. The threshold value for the evaluation value based on Zfc is also set in advance.

[0036] In this example, the effective value is the root mean square (RMS) value of the acceleration. The occurrence of an unbalanced load causes vibration to increase over a wide frequency range. In other words, the effective value increases as the unbalanced load increases. The effective value can be obtained by calculating it for each divided section as shown in Figure 3.

[0037] The determination of unbalanced load using the evaluation value based on the effective value may be made using a ratio, similar to the determination of the evaluation value based on the fr. The threshold value for the evaluation value based on the effective value is also assumed to be specified in advance. Note that the FFT processing, envelope FFT processing, and calculation processing of the effective value may be performed using known methods, and detailed description thereof will be omitted here.

[0038] [Sensor installation] FIG. 6 is a schematic diagram showing an example of installation of an acceleration sensor 300 on a ball screw according to this embodiment. The configuration of the ball screw 200 is the same as that shown in FIG. 2. In this example, one acceleration sensor 300 is used and is attached to the nut 205. The acceleration sensor 300 may be configured as a wireless sensor or as a wired sensor. The acceleration sensor 300 may be attached using a magnet, adhesive, a dedicated clip, or the like. Therefore, the acceleration sensor 300 may be configured to be detachable from the nut 205, or may be fixed.

[0039] Of the vibration information obtained when the acceleration sensor 300 is installed as shown in Figure 6, the vibration information in the direction in which an external load is applied in the axial direction is used. The section in which the external load is applied is based on this, as the amplitude of the signal component increases and the S / N ratio increases. For example, in the example shown in Figure 6, if an external load is applied to the nut 205 in the axial direction toward the left in the figure, only the vibration information obtained in the forward direction, i.e., while the nut is moving from right to left, is used for diagnosis. On the other hand, if the direction of the external load is reversed, only the vibration information obtained in the return direction is used for diagnosis.

[0040] [Processing flow] 7 is a flowchart of the unbalanced load detection process according to this embodiment. This process flow may be implemented by the processing unit 101 of the unbalanced load detection device 100 reading and executing a program and various data stored in the storage unit 102. This process flow may be started based on a user's instruction, or may be configured to be executed at a predetermined timing. For example, the process may be configured to start execution when the ball screw 200 is installed to detect an installation error, or may be configured to determine whether an installation error has occurred while the ball screw 200 is being used continuously.

[0041] In S701, the unbalanced load detection device 100 starts obtaining vibration information by the acceleration sensor 300.

[0042] In S702, the unbalanced load detection device 100 starts the operation of the ball screw 200. At this time, if the unbalanced load detection device 100 and a control device that controls the rotational operation of the ball screw 200 are separate devices, the unbalanced load detection device 100 instructs the control device when to start the rotational operation. The operating conditions of the ball screw 200 when detecting an unbalanced load may be specified in advance, or may be arbitrarily specified by the user.

[0043] In S703, the unbalanced load detection device 100 determines whether or not the reciprocating motion of the ball screw 200 has been completed. If the reciprocating motion has been completed (YES in S703), the processing of the unbalanced load detection device 100 proceeds to S704. On the other hand, if the reciprocating motion has not been completed (NO in S703), the unbalanced load detection device 100 continues the rotational motion and detection of vibration information.

[0044] In S704, the unbalanced load detection device 100 stops acquiring vibration information by the acceleration sensor 300. At the same time, the unbalanced load detection device 100 may also stop the operation of the ball screw 200.

[0045] In S705, the unbalanced load detection device 100 extracts data to be used for diagnosis from the acquired vibration information. As explained with reference to FIG. 6, vibration information for only either the outbound or return movement of the nut 205 during one reciprocating motion is extracted based on the external load. Note that when vibration information collection starts in S701, there may be cases where the nut 205 is located in the middle rather than at the end of its range of movement. Taking such cases into consideration, it is desirable to acquire vibration information as a result of the nut 205 having traveled back and forth over the entire range of movement.

[0046] In S706, the unbalanced load detection device 100 divides the vibration information extracted in S705 into a plurality of sections with a predetermined time width. The time width here is assumed to be predetermined and may vary depending on the configuration, size, etc. of the ball screw 200.

[0047] In S707, the unbalanced load detection device 100 calculates an evaluation value based on the three criteria described above for each of the sections divided in S706. In the case of the first-order component fr of the rotation frequency in the FFT spectrum, FFT processing is applied to the vibration information of each section to calculate the value of fr. In addition, in the case of the characteristic frequency Zfc of the nut in the envelope FFT spectrum, envelope FFT processing is applied to the vibration information of each section to calculate the value of Zfc. In the case of the effective value, the effective value of the acceleration in the vibration information of each section is calculated. Note that it is not necessary to perform all three of the above methods to calculate the evaluation value; at least one of them can be used.

[0048] In S708, the unbalanced load detection device 100 determines the installation error based on the transition of each evaluation value calculated in S707. Specifically, the unbalanced load detection device 100 identifies the presence or absence of an unbalanced load by comparing the transition of the evaluation value as shown in the above formula (1) and formula (2) with a predetermined threshold value. In this example, the transition of the evaluation value is captured using three criteria. At this time, it may be determined that an unbalanced load exists if the transition of the evaluation value based on at least one criterion exceeds a threshold value, or it may be determined that an unbalanced load exists if the transition of the evaluation value based on all criteria exceeds a threshold value. Furthermore, if multiple threshold values ​​are set for each criterion, the degree of unbalanced load may be determined by comparing with the multiple threshold values.

[0049] In S709, the unbalanced load detection device 100 outputs the determination result of S708. The output method here may be, for example, audible output by voice, or visual output via a screen or the like. Furthermore, in the step of S708, the determination results based on each of the three criteria may be output separately, or the presence or absence of unbalanced load may be output in an integrated manner. Furthermore, if the degree of unbalanced load is determined in addition to the presence or absence of unbalanced load in the step of S708, the result may also be output together. Then, this processing flow ends.

[0050] As described above, this embodiment makes it possible to easily detect an unbalanced load in a ball screw. In particular, it is possible to detect an unbalanced load when the ball screw is installed or used, without the need to set individual threshold values ​​according to the type or application of the ball screw. Note that, based on the detection result, the mounting positions of the rolling bearing 204 and the rolling bearing 206 may be fine-tuned. Furthermore, based on the detection result, the operation of the ball screw 200 by the motor 201 may be limited.

[0051] <Second embodiment> A second embodiment of the present invention will be described below. Note that the description of the same configuration as the first embodiment will be omitted and the description will focus on the differences.

[0052] [Sensor installation] FIG. 8 is a schematic diagram showing an example of how acceleration sensors 300 are installed on a ball screw 200 according to this embodiment. The configuration of the ball screw 200 is the same as that shown in FIG. 2 of the first embodiment. In this embodiment, two acceleration sensors 300 are used. Acceleration sensor 300a is installed on a rolling bearing 204 located on the motor 201 side and supporting a screw shaft 203. Acceleration sensor 300b is installed on a rolling bearing 206 located on the opposite side of the motor 201 and supporting the screw shaft 203. The configurations of acceleration sensors 300a and 300b may be the same as that of acceleration sensor 300 shown in the first embodiment.

[0053] When acceleration sensors 300a and 300b are installed as shown in Figure 8, for example, it is assumed that the distribution of the installation error in ball screw 200 is as shown in Figure 2. In this case, the magnitude of the detected vibration increases as the distance between each of acceleration sensors 300a and 300b and the oscillation source (i.e., nut 205) decreases.

[0054] Fig. 9 is a graph showing an example of vibration information detected by each of acceleration sensors 300a and 300b. In Fig. 9, the vertical axis represents acceleration, and the vertical axis represents time. In this example, in Fig. 9, the nut 205 moves along screw shaft 203 from the rolling bearing 204 side to the rolling bearing 206 side (forward), and then moves from the rolling bearing 206 side to the rolling bearing 204 side (return).

[0055] Figure 9(a) shows vibration information detected by acceleration sensor 300a installed on rolling bearing 204 while nut 205 is reciprocating. Figure 9(b) shows vibration information detected by acceleration sensor 300b installed on rolling bearing 206 while nut 205 is reciprocating. In this way, when multiple acceleration sensors 300 are used, the vibration information obtained differs.

[0056] In this embodiment, the evaluation value is calculated and used by further limiting the range of vibration information in one direction (for example, "forward") of the vibration information. More specifically, as shown in FIG. 10, attention is paid to the vibration information when the nut 205 is located in a range 1000 where the unbalanced load is assumed to be the largest and a range 1001 where the unbalanced load is assumed to be the smallest. That is, as shown in FIG. 11, the vibration information in a range 1100 and a range 1101 is extracted and used. In this embodiment, since the vibration information is detected by each of the two acceleration sensors 300a and 300b, the relevant portion is detected from each vibration information.

[0057] Here, among the vibration information detected by the acceleration sensor 300a, the evaluation value corresponding to the area 1001 at the beginning of the forward movement is defined as A1, and the evaluation value corresponding to the area 1000 at the end of the forward movement is defined as A2. n In addition, among the vibration information detected by the acceleration sensor 300b, the evaluation value corresponding to the area 1001 at the beginning of the forward movement is defined as B1, and the evaluation value corresponding to the area 1000 at the end of the forward movement is defined as B n Let's say.

[0058] In this case, the following values ​​are calculated based on the above formulas (1) and (2).

[0059]

number

[0060]

number

[0061] Furthermore, the following values ​​are calculated:

[0062]

number

[0063] If the value obtained by formula (7) or formula (8) exceeds a predetermined threshold, it is determined that an unbalanced load exists, i.e., that there is an installation error. These determinations may be made for each of the three criteria, as in the first embodiment.

[0064] In the above example, the determination of the installation error is performed by focusing on two regions (sections), but this is not limited to this. For example, the determination of the installation error may be performed by focusing on three or more regions (sections).

[0065] In the above example, the first section 1101 and the last section 1100 on the way forward are shown as examples, but the present invention is not limited to this. For example, any of the sections that are separated by a predetermined distance in one stroke of the reciprocating movement of the nut 205 may be used. In other words, the evaluation values ​​of two sections that are separated enough to determine the installation error may be used.

[0066] As described above, this embodiment not only provides the same effects as the first embodiment, but also makes it possible to detect the unbalanced load of the ball screw using vibration information from a certain section, thereby reducing the processing load during diagnosis.

[0067] <Third embodiment> A third embodiment of the present invention will be described below. Note that the description of the same configuration as the first or second embodiment will be omitted, and the description will focus on the differences.

[0068] In the second embodiment, an example configuration using two acceleration sensors 300a, 300b was described. In this configuration, an embodiment in which unbalanced load is detected using yet another criterion will be described. In this embodiment, peak hold processing is applied to vibration information divided into multiple sections. Here, an example of the characteristic frequency of the nut 205 will be described. Envelope FFT processing is applied to each section of the vibration information to calculate the characteristic frequency Zfc of the nut 205. Furthermore, the maximum value component of the characteristic frequency Zfc of the nut 205 in the multiple sections is captured.

[0069] Fig. 12 is a graph illustrating the maximum value component of the evaluation value of the feature frequency Zfc of the nut 205 obtained by each of the acceleration sensors 300a and 300b when the nut 205 is located in a certain region. In Fig. 12, the vertical axis represents the evaluation value, and the horizontal axis represents the frequency. As shown in Fig. 12, the maximum value component of the evaluation value of the feature frequency Zfc based on the vibration information detected by each of the acceleration sensors 300a and 300b is different.

[0070] Here, the maximum value component of the evaluation value calculated based on the vibration information detected by the acceleration sensor 300a is denoted as A a The maximum component of the evaluation value calculated based on the vibration information detected by the acceleration sensor 300b is defined as A b In this case, the ratio is calculated using the following formula:

[0071]

number

[0072] If the value obtained by formula (9) or formula (10) exceeds a predetermined threshold, it is determined that an unbalanced load exists, i.e., that there is an installation error. These determinations may be made based on the primary component fr of the rotation frequency or the characteristic frequency Zfc of the nut 205, respectively.

[0073] As described above, this embodiment can provide the same effects as the first embodiment.

[0074] <Other embodiments> In the above embodiment, an example has been shown in which the acquisition of vibration information and the detection of unbalanced load are performed in a single sequence, but this is not limiting. For example, vibration information of the ball screw that is the target of unbalanced load detection may be acquired in advance, and the unbalanced load may be detected separately using this vibration information. In this case, too, it is desirable that the vibration information include vibration information for the reciprocating movement of the nut that accompanies the operation of the ball screw.

[0075] Furthermore, in the present invention, a program or application for realizing the functions of one or more of the above-described embodiments can be supplied to a system or device via a network or a storage medium, etc., and one or more processors in the computer of the system or device can read and execute the program.

[0076] Furthermore, in this specification, the terms "first" and "second" are used merely for convenience to distinguish from other components, and are not intended to limit interpretation to specific components. Therefore, it will be understood that the components indicated by these terms can be appropriately interpreted and applied depending on the configuration to which the present invention is applied.

[0077] As such, the present invention is not limited to the above-described embodiments, and the present invention also contemplates the mutual combination of the various components of the embodiments, as well as modifications and applications by those skilled in the art based on the description in the specification and well-known techniques, and these modifications and applications are included in the scope of protection sought.

[0078] As described above, the present specification discloses the following: (1) an acquisition unit (e.g., 101, 104) that acquires vibration information during operation of a ball screw (e.g., 200); a division unit (e.g., 101) that divides the vibration information into a plurality of sections; A calculation unit (e.g., 101) that calculates an evaluation value for each of the plurality of sections; a determination unit (for example, 101) that determines whether or not an unbalanced load exists in the ball screw based on the degree of change in the evaluation value; A ball screw unbalanced load detection device having the above structure. This configuration makes it possible to easily detect unbalanced loads in a ball screw. In particular, it is possible to detect unbalanced loads during installation and use of a ball screw without the need to set individual threshold values ​​according to the type or application of the ball screw.

[0079] (2) The ball screw unbalanced load detection device described in (1), wherein the calculation unit calculates at least one of the primary component of the rotational frequency obtained by FFT (Fast Fourier Transform) processing, the characteristic frequency component of the nut (e.g., 205) provided on the ball screw obtained by envelope FFT processing, and the effective value as the evaluation value for each of the plurality of sections. With this configuration, it is possible to detect the presence or absence of an unbalanced load using at least one of the primary component of the rotational frequency of the ball screw, the characteristic frequency component of the nut of the ball screw, and the effective value.

[0080] (3) A ball screw unbalanced load detection device as described in (1) or (2), wherein the dividing unit extracts and divides vibration information obtained during one-way movement of a nut (e.g., 205) provided on the ball screw in a reciprocating movement along the screw axis from the vibration information acquired by the acquiring unit. This configuration makes it possible to detect the presence or absence of an unbalanced load using vibration information from only one direction of the reciprocating motion of the ball screw.

[0081] (4) The device for detecting an unbalanced load on a ball screw according to (3), wherein the one direction is a direction in which an external load is applied to the nut. This configuration makes it possible to detect the presence or absence of an unbalanced load using vibration information only in the direction in which the external load of the reciprocating motion of the ball screw is applied.

[0082] (5) A ball screw unbalanced load detection device described in any one of (1) to (4), wherein the judgment unit judges that an unbalanced load exists in the ball screw when the ratio of the largest evaluation value to the smallest evaluation value among the evaluation values ​​calculated for each of the plurality of sections is greater than a predetermined threshold value. With this configuration, it is possible to determine the occurrence of an unbalanced load by capturing the transition of the evaluation value based on the maximum evaluation value and the minimum evaluation value for each of the multiple sections into which the vibration information is divided.

[0083] (6) A ball screw unbalanced load detection device described in any one of (1) to (5), wherein the vibration information is acquired by a sensor (e.g., 300) attached to a nut (e.g., 205) provided on the ball screw. This configuration makes it possible to detect the occurrence of an unbalanced load using only one sensor provided on the nut.

[0084] (7) A ball screw unbalanced load detection device according to any one of (1) to (5), wherein the vibration information is acquired by a first sensor (e.g., 300a) and a second sensor (e.g., 300b) attached to each of a plurality of rolling bearings (e.g., 204, 206) supporting a screw shaft (e.g., 203) of the ball screw. This configuration makes it possible to detect the occurrence of an unbalanced load using only two sensors provided on the two support parts that support the ball screw.

[0085] (8) The calculation unit Among the multiple sections included in the vibration information acquired by the first sensor, a first evaluation value for a first section (e.g., 1101) and a second evaluation value for a second section (e.g., 1100) obtained when a nut (e.g., 205) of the ball screw moves to a first position (e.g., 1001) and a second position (e.g., 1000), respectively, are calculated; calculating a third evaluation value for a third section and a fourth evaluation value for a fourth section obtained when the nut moves between the first position and the second position, among a plurality of sections included in the vibration information acquired by the second sensor; The determination unit calculating a first value that is a ratio of the larger of the first evaluation value and the second evaluation value to the smaller of the larger of the first evaluation value and the second evaluation value; calculating a second value that is a ratio of the larger of the third evaluation value and the fourth evaluation value to the smaller of the larger of the third evaluation value and the fourth evaluation value; calculating a third value that is a ratio of the larger of the first value and the second value to the smaller of the first value and the second value; The device for detecting an unbalanced load on a ball screw according to (7), wherein it is determined that an unbalanced load exists in the ball screw when the third value is greater than a predetermined threshold value. With this configuration, it is possible to determine the occurrence of an unbalanced load by capturing the transition of the evaluation value based on the relationship between the vibration information detected by the two sensors.

[0086] (9) The determination unit Identifying a first maximum value, which is the maximum evaluation value in a plurality of sections included in the vibration information acquired by the first sensor, and a second maximum value, which is the maximum evaluation value in a plurality of sections included in the vibration information acquired by the second sensor; The device for detecting unbalanced loads on a ball screw according to (7), wherein the device determines that an unbalanced load exists in the ball screw when the ratio of the larger of the first maximum value and the second maximum value to the smaller of the two is greater than a predetermined threshold value. With this configuration, it is possible to determine the occurrence of an unbalanced load by capturing the transition of the evaluation value based on the relationship between the maximum and minimum values ​​among the evaluation values ​​in each of multiple sections of the vibration information detected by the two sensors.

[0087] (10) The ball screw unbalanced load detection device according to (9), wherein the evaluation value is either a primary component of a rotational frequency obtained by FFT processing or a characteristic frequency component of a nut provided on the ball screw obtained by envelope FFT processing. With this configuration, it is possible to detect the presence or absence of an unbalanced load using at least one of the primary component of the rotational frequency of the ball screw and the characteristic frequency component of the nut of the ball screw.

[0088] (11) an acquisition step of acquiring vibration information during operation of the ball screw (e.g., 200); a dividing step of dividing the vibration information into a plurality of sections; a calculation step of calculating an evaluation value for each of the plurality of sections; a determination step of determining whether or not there is an unbalanced load in the ball screw based on the degree of change in the evaluation value; A method for detecting an unbalanced load on a ball screw, comprising: This configuration makes it possible to easily detect unbalanced loads in a ball screw. In particular, it is possible to detect unbalanced loads during installation and use of a ball screw without the need to set individual threshold values ​​according to the type or application of the ball screw.

[0089] (12) To a computer (e.g., 100), An acquisition step of acquiring vibration information during operation of the ball screw (e.g., 200); a dividing step of dividing the vibration information into a plurality of sections; a calculation step of calculating an evaluation value for each of the plurality of sections; a determination step of determining whether or not there is an unbalanced load in the ball screw based on the degree of change in the evaluation value; A program to execute. This configuration makes it possible to easily detect unbalanced loads in a ball screw. In particular, it is possible to detect unbalanced loads during installation and use of a ball screw without the need to set individual threshold values ​​according to the type or application of the ball screw. [Explanation of symbols]

[0090] 100...Unbalanced load detection device 101...Processing section 102...Storage section 103...UI (User Interface) section 104...External interface 105…Communications Department 200...ball screw 201...Motor 202...Connection part 203...Screw shaft 204, 206... Rolling bearings 205...Nut 300...Acceleration sensor

Claims

1. an acquisition unit that acquires vibration information during operation of the ball screw; a division unit that divides the vibration information into a plurality of sections; a calculation unit that calculates an evaluation value for each of the plurality of sections; a determination unit that determines whether or not there is an unbalanced load in the ball screw based on the degree of change in the evaluation value; A ball screw unbalanced load detection device having the above structure.

2. 2. The ball screw unbalanced load detection device according to claim 1, wherein the calculation unit calculates, as the evaluation value for each of the plurality of sections, at least one of a first-order component of a rotational frequency obtained by FFT (Fast Fourier Transform) processing, a characteristic frequency component of a nut provided in the ball screw obtained by envelope FFT processing, and an effective value.

3. 2. The ball screw unbalanced load detection device according to claim 1, wherein the dividing unit extracts and divides vibration information obtained during one-way movement of a nut provided on the ball screw in a reciprocating movement along a screw shaft of the nut from the vibration information acquired by the acquisition unit.

4. 4. The device for detecting an unbalanced load on a ball screw according to claim 3, wherein the one direction is a direction in which an external load is applied to the nut.

5. 2. The ball screw unbalanced load detection device according to claim 1, wherein the determination unit determines that an unbalanced load exists in the ball screw when a ratio of a largest evaluation value to a smallest evaluation value among the evaluation values ​​calculated for each of the plurality of sections is greater than a predetermined threshold value.

6. 2. The device for detecting an unbalanced load on a ball screw according to claim 1, wherein the vibration information is acquired by a sensor attached to a nut of the ball screw.

7. 2. The device for detecting an unbalanced load on a ball screw according to claim 1, wherein the vibration information is acquired by a first sensor and a second sensor attached to each of a plurality of rolling bearings that support a screw shaft of the ball screw.

8. The calculation unit calculating a first evaluation value for a first section and a second evaluation value for a second section obtained when a nut provided on the ball screw moves between a first position and a second position, among a plurality of sections included in the vibration information acquired by the first sensor; calculating a third evaluation value for a third section and a fourth evaluation value for a fourth section obtained when the nut moves between the first position and the second position, among a plurality of sections included in the vibration information acquired by the second sensor; The determination unit calculating a first value that is a ratio of the larger of the first evaluation value and the second evaluation value to the smaller of the first evaluation value and the second evaluation value; calculating a second value that is a ratio of the larger of the third evaluation value and the fourth evaluation value to the smaller of the larger of the third evaluation value and the fourth evaluation value; calculating a third value that is a ratio of the greater of the first value and the second value to the lesser of the greater of the first value and the second value; 8. The device for detecting an unbalanced load on a ball screw according to claim 7, wherein it is determined that an unbalanced load exists in the ball screw when the third value is greater than a predetermined threshold value.

9. The determination unit Identifying a first maximum value, which is the maximum evaluation value in a plurality of sections included in the vibration information acquired by the first sensor, and a second maximum value, which is the maximum evaluation value in a plurality of sections included in the vibration information acquired by the second sensor; 8. The device for detecting unbalanced loads on a ball screw according to claim 7, wherein the device determines that an unbalanced load exists in the ball screw when a ratio of the larger of the first maximum value and the second maximum value to the smaller of the first maximum value and the second maximum value is greater than a predetermined threshold value.

10. 10. The ball screw unbalanced load detection device according to claim 9, wherein the evaluation value is either a first-order component of a rotational frequency obtained by FFT processing, or a characteristic frequency component of a nut provided on the ball screw obtained by envelope FFT processing.

11. an acquisition step of acquiring vibration information during operation of the ball screw; a dividing step of dividing the vibration information into a plurality of sections; a calculation step of calculating an evaluation value for each of the plurality of sections; a determination step of determining whether or not there is an unbalanced load in the ball screw based on the degree of change in the evaluation value; A method for detecting an unbalanced load on a ball screw, comprising:

12. On the computer, an acquisition step of acquiring vibration information during operation of the ball screw; a dividing step of dividing the vibration information into a plurality of sections; a calculation step of calculating an evaluation value for each of the plurality of sections; a determination step of determining whether or not there is an unbalanced load in the ball screw based on the degree of change in the evaluation value; A program to execute.

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