Power transmission mechanism management device and power transmission mechanism management method

Abstract

The present invention relates to a management device for a power transmission mechanism that transmits driving force from an electric motor to a load-side device. The management device acquires the torque current value of the electric motor for each unit step of driving the power transmission mechanism, divides the unit step into arbitrary intervals, classifies the acquired torque current values ​​into torque current values ​​within a reference value and torque current values ​​outside a reference value according to the torque current value in each interval, calculates the average value of the torque current values ​​within the reference value and the torque current values ​​outside the reference value for each interval, and detects abnormalities in the power transmission mechanism based on the torque current values ​​outside the reference value in the interval with the largest difference in the average values.

Description

Technical Field

[0001] This invention relates to a management device and a management method for a power transmission mechanism. Background Technology

[0002] For example, various industrial equipment such as injection molding machines and stamping devices can be listed as devices that supply power from a power source to certain load-side devices via a power transmission mechanism. Taking an injection molding machine as an example, there are known devices that use a rotary electric motor (electric motor) as a power source to inject soft and viscous materials such as resin, metal fibers, or mixtures thereof into a mold that is shaped into a specified mold, thereby obtaining any molded article.

[0003] As an example, let's illustrate the structure and operation of an injection molding machine. An injection molding machine transmits the power of an electric motor (or, in some cases, a horizontal force like a linear motor) as the driving force to the mold through a power transmission mechanism, injecting a soft, viscous part into the mold to obtain the desired molded product. More specifically, it is mechanically connected directly or indirectly to a power conversion mechanism that converts the rotational driving force of the electric motor into linear motion, such as a ball screw. A nut assembly that engages with the linear power of the ball screw, which is part of this power transmission mechanism, is integrated with the nut assembly. However, the injection shaft is configured to press the soft, viscous part into the mold.

[0004] Managing malfunctions in the entire load-side system (including the drive source itself and the workpiece mechanism of the load-side system), particularly injection molding machines and stamping equipment, is a crucial factor that profoundly impacts the quality of the final molded product. Furthermore, malfunctions can lead to environmental issues such as equipment and component overload and energy efficiency problems, as well as business-related issues such as manufacturing stoppages due to equipment damage. Therefore, managing equipment malfunctions is a significant issue with substantial societal implications.

[0005] As a technology related to this anomaly detection, Patent Document 1 discloses a technique for estimating the state of equipment. Specifically, it discloses the following technique: A motor control unit, which includes a drive source and controls the motor, generates an internal motor control value for the motor control unit, and estimating equipment anomalies by comparing this internal motor control value. This technique enables the detection of equipment (load-side device and its associated workpiece components) degradation by monitoring the internal value of the motor control unit.

[0006] Patent Document 2 discloses an anomaly diagnosis device and method for a power transmission mechanism that transmits power from an electric motor as a drive source. More specifically, in Patent Document 2, in a structure that connects the power of the electric motor to a mechanical device as a load via a pulley belt and gear chain, an anomaly diagnosis is made by obtaining a current spectrum waveform based on a value sent from a current detector connected to the electric motor, and by counting the number of sideband waves outside the frequency band of the pulley belt and gear chain generated with the rotational speed based on the spectrum peak value calculated by analysis.

[0007] With injection molding machines and stamping devices as the primary components, power transmission mechanisms function as intermediaries between power sources and molds, which directly generate loads. Therefore, the performance of power transmission mechanisms has a profound impact on the quality (completeness) of the molded product as the final output, making their management crucial.

[0008] Existing technical documents

[0009] Patent documents

[0010] Patent Document 1: WO2018 / 220751A1

[0011] Patent Document 2: WO2018 / 109993A1 Summary of the Invention

[0012] The problem that the invention aims to solve

[0013] Here, we examine the detection of abnormalities (deterioration) in power transmission mechanisms. There are many cases where the load applied to the load-side device varies, and there are also many cases where the load applied to the power transmission mechanism is mixed, with some parts being larger and some smaller. That is, examples of power transmission mechanisms include ball screws, pulleys, belts, or gear chains, but depending on the load conditions of the load-side device, deviations occur in the parts that deteriorate due to these mechanisms.

[0014] Regarding this point, the abnormality diagnosis technology for the power transmission mechanism disclosed in Patent Document 2 detects abnormalities in the power transmission mechanism by monitoring the spectral peaks or their accompanying sideband waves from the current spectrum waveform. However, when the deterioration of the power transmission mechanism is minor or in its initial stage, there is a problem of reduced sensitivity in detecting abnormalities. That is, even if only the current spectrum of the motor is analyzed for the deterioration of the power transmission mechanism, there are many cases where the abnormal values ​​caused by the deterioration of the power transmission mechanism only manifest as extremely small vibrations. It is difficult to distinguish between temporary current noise under normal conditions and vibrations caused by abnormalities. Relying solely on monitoring the state of the current spectrum leaves a problem in terms of the accuracy of abnormality detection.

[0015] A technology for detecting anomalies in power transmission mechanisms with higher precision and accuracy is desired.

[0016] Technical solutions for solving the problem

[0017] To address the aforementioned issues, the present invention provides a management device for a power transmission mechanism that transmits driving force from an electric motor to a load-side device. The management device acquires the torque current value of the electric motor for each unit step of driving the power transmission mechanism, divides the unit step into arbitrary intervals, classifies the acquired torque current values ​​into torque current values ​​within a reference value and torque current values ​​outside a reference value according to the torque current value in each interval, calculates the average value of the torque current values ​​within the reference value and the torque current values ​​outside the reference value for each interval, and detects abnormalities in the power transmission mechanism based on the torque current values ​​outside the reference value in the interval with the largest difference in the average values.

[0018] Alternatively, another approach is a management method for a power transmission mechanism that transmits driving force from an electric motor to a load-side device. This management method includes the following steps: dividing the unit step of driving the power transmission mechanism into arbitrary multiple partitions; obtaining the torque current value of the electric motor for each of the multiple partitions driven by the power transmission mechanism; for each of the multiple partitions, calculating the average value of the torque current values ​​within a reference value and the average value of the torque current values ​​outside the reference value; and detecting abnormalities in the power transmission mechanism based on the average value of the torque current values ​​outside the reference value in the interval where the difference between the average values ​​is large.

[0019] Invention Effects

[0020] According to the present invention, abnormalities (deterioration) in power transmission mechanisms can be detected with higher precision and accuracy. In particular, according to the present invention, even when the abnormality (deterioration) in the power transmission mechanism is minor or in its initial stage, it has the effect of improving the precision and accuracy of detecting it as an abnormality.

[0021] Other aspects, structures, and effects of the present invention will become clear from the following description. Attached Figure Description

[0022] Figure 1 This is a schematic diagram showing the mechanical structure of an injection molding machine as an embodiment of the present invention.

[0023] Figure 2 This is a schematic diagram illustrating the functional structure of the injection molding machine in the embodiment.

[0024] Figure 3This is a schematic diagram showing the functional structure of the motor control unit and the state calculation unit in the embodiment.

[0025] Figure 4 This is a schematic diagram illustrating the functional structure of the control internal value generation unit in the embodiment.

[0026] Figure 5 This is a schematic diagram illustrating the functional structure of the state calculation unit in the embodiment.

[0027] Figure 6 middle, Figure 6 (a) is a schematic diagram showing the operation and deterioration of the ball screw mechanism. Figure 6 (b) is a schematic diagram of the torque current change of the ball screw mechanism from the start position to the end position.

[0028] Figure 7 middle, Figure 7 (a) is a schematic diagram showing the normal and abnormal values ​​of torque current under the condition of degradation judgment processing in the implementation embodiment. Figure 7 (b) is a schematic diagram showing the calculation result of the average of the normal and outlier values ​​of each segmentation when the degradation case processing in the embodiment is performed.

[0029] Figure 8 middle, Figure 8 (a) is a graph showing the distribution of the average values ​​of normal and outlier values ​​for each loop when the degradation case processing of the embodiment is not performed. Figure 8 (b) is a graph showing the distribution of the average values ​​of normal and outlier values ​​for each cycle when the degradation case processing of the embodiment is performed.

[0030] Figure 9 middle, Figure 9 (a) is a graph showing the relationship between torque current and component when the calculated characteristic quantity varies over a range. Figure 9 (b) is a schematic diagram showing the characteristic quantity (average value) of torque current in each interval when the interval of the calculated characteristic quantity is varied. Detailed Implementation

[0031] Hereinafter, embodiments of the present invention will be described using the accompanying drawings.

[0032] Figure 1 The schematic diagram shows a partial outline of an injection molding machine 1 that includes a management device (control unit 30) employing the power transmission mechanism of the present invention. Furthermore, in this embodiment, an injection molding machine is used as an example for explanation, but the present invention is not limited thereto; any device that transmits the driving force of a drive source to the load side via a power transmission mechanism, such as a stamping device or a cutting device, can be used.

[0033] First, the mechanical structure and operation of the injection molding machine 1 will be explained. The injection molding machine 1 converts the rotation of multiple electric motors into linear motion to drive a single linear moving part, thereby synchronizing the operation of the multiple electric motors in a manner that aligns their travel positions. Furthermore, the structure to which this invention can be applied can also be a structure that uses a single electric motor to supply driving force to multiple power transmission mechanisms via gears, or a structure that uses a single electric motor to supply driving force to a single power transmission mechanism.

[0034] The injection molding machine 1 can make molten resin flow into the hole 11 of the fixed mold 12B provided in the mold 12, and make a resin molded article corresponding to the shape of the gap existing between the movable mold 12A and the fixed mold 12B.

[0035] The mold includes a fixed mold 12B fixed to the housing and a movable mold 12A capable of moving forward and backward. It includes a motor 13, a drive pulley 14 fixed to the output shaft of the motor 13, a driven pulley 15, a synchronous belt 16 that transmits the rotation of the drive pulley 14 to the driven pulley 15, a ball screw mechanism 20 that converts the rotation of the pulley 15 into linear motion and transmits it to the movable mold 12A, and a control unit 30.

[0036] The electric motor 13 includes an encoder (not shown) that outputs a motor position signal S2 indicating its travel position (equivalent to the travel position of the ball screw mechanism 20). In the injection molding machine 1, the control unit 30 receives the original speed command signal S0 from the upstream device (not shown) and thereby performs drive control on the electric motor 13.

[0037] When the motor 13 is driven, its rotation is transmitted to the screw shaft 17 of the ball screw mechanism 20 via the drive pulley 14, the synchronous belt 16, and the driven pulley 15. The rotational force is converted into linear motion via the balls and the nut portion 18 that engages with these grooves. The movable mold 12A is integrally or mechanically coupled to the nut portion 18, and the movable mold 12A also moves linearly according to the linear movement of the nut portion 18. As a result, the movable mold 12A approaches or moves away from the fixed mold 12B. After the movable mold 12A contacts the fixed mold 12B, resin is flowed in and formed. After cooling and solidification of the molded article, the movable mold 12A is removed from the fixed mold 12B, thereby removing the molded article.

[0038] The control unit 30 is configured, for example, as a microcomputer with built-in devices, including a CPU, ROM, RAM, EEPROM, various I / O interfaces, etc., which performs various functions in cooperation with the program. The control unit 30 performs control of the injection molding machine 1, such as controlling the overall molding process, including plasticizing, injection, mold opening and closing, and ejection. Furthermore, the present invention is not limited to this embodiment; a portion of it may also be constructed using analog circuitry.

[0039] Next, the control unit 30 will be described as a functional structure. Figure 2 A schematic diagram of the functional block diagram of the control unit 30.

[0040] The inverter 40 is controlled by a motor control unit 41 that employs a so-called vector control method. The motor control unit 41 obtains information such as motor current, motor voltage, rotor position information, and speed from the inverter 40 or the motor 13. Based on this information, it generates a voltage command value for driving the motor 13 according to instructions from the upper-level controller. Then, the motor control unit 41 provides the generated voltage command value to the inverter 40.

[0041] The external data acquisition unit 47 consists of sensors and other components installed in addition to the motor 13 and inverter 40, and acquires the equipment temperature, external air temperature, and upper-level command values ​​of the equipment.

[0042] The state calculation unit 42 includes: a control internal value generation unit 43 that generates internal values ​​for motor control; and a state calculation unit 44 that calculates characteristic quantities or state quantities of the injection molding machine 1 based on the internal values ​​for motor control generated by the control internal value generation unit 43.

[0043] The internal value generation unit 43, for the input or output of the motor 13, generates internal values ​​for motor control that are associated with the state of the injection molding machine 1, based on time series data acquired by the current sensor, voltage sensor and position sensor which are separately installed from the motor control unit 41, and data acquired by the external data acquisition unit 47.

[0044] The state calculation unit 44 has a state estimation model. Using the state estimation model, it calculates the state of the equipment system, that is, the state of the equipment itself or the state (quality, etc.) of the manufactured product produced by the equipment, based on the motor control internal value generated by the motor control internal value generation unit. Specifically, the state estimation unit 42 takes into account data acquired by the aforementioned sensors and the external data acquisition unit 47, generates motor control internal values ​​based on the input data, and outputs a state quantity calculated based on the generated motor control internal values ​​or information related to the state of the injection molding machine 1 represented by that state quantity (hereinafter referred to as "estimated state"). The estimated state output from the state estimation unit 42 is transmitted to the information transmission unit 45 and the motor control update unit 46, described later.

[0045] The information transmission unit 45, based on the calculated status output from the status calculation unit 42, notifies the operator using the equipment system or the manager of the equipment system of information about the status of the injection molding machine 1, such as characteristic quantities of the equipment itself (deterioration judgment of the threaded shaft 17, etc., described later) or the quality and changes of the manufactured product, through displays, sounds, lights, vibrations, etc. This reduces the workload in monitoring equipment maintenance periods, understanding the status of quality changes, and adjusting equipment.

[0046] The motor control update unit 46 modifies the motor control unit 41, i.e., the control commands, control parameters, or control software, based on the calculated state output from the state calculation unit 42. For example, if the quality of the manufactured product changes, the motor control update unit 46 modifies the motor control unit 41 to suppress the quality change. As a result, the adjustment operation of the injection molding machine 1 can be automated, thus reducing the workload.

[0047] Next, the motor control unit 41 and the state calculation unit 42 will be explained in more detail. Figure 3 This is a block diagram schematically representing the functional structure of the motor control unit 41.

[0048] exist Figure 3 In this diagram, the command from the upper-level controller is a position command θ*, but it can also be a speed (rotational speed) command ω* or a torque command Trq*. Furthermore, when the command from the upper-level controller is a speed (rotational speed) command ω* or a torque command Trq*, the block diagram of the motor control unit 41 becomes... Figure 3 The diagrams shown are located to the right of boundary line A and to the right of boundary line B.

[0049] like Figure 3 As shown, when a position command θ* is input from the upper-level controller to the motor control unit 41, the speed command generation unit 101 generates a speed command based on the position feedback value θ measured by the sensor. mThe velocity command ω* is generated and output based on the difference between the position command value θ* and the position command value θ*.

[0050] If a speed command ω* is input, the torque command generation unit 102 will generate a torque command based on the speed (rotational speed) feedback value ω measured by the sensor. m The torque command Trq* is generated and output based on the difference between the speed command ω* and the torque command ω*.

[0051] If a torque command Trq* is input, the current command generation unit 103 generates and outputs current commands on the dq axis of the rotating coordinate system, namely the d-axis current command Id* and the q-axis current command Iq*, based on the torque command Trq*.

[0052] If the voltage command generation unit 104 inputs the d-axis current command Id* and the q-axis current command Iq*, it generates and outputs the voltage commands on the d and q axes, namely the d-axis voltage command Vd* and the q-axis voltage command Vq*, based on the difference between the d-axis current feedback value Id and the d-axis current command Id*, and the difference between the q-axis current feedback value Iq and the q-axis current command Iq*.

[0053] Here, the d-axis current feedback value Id and the q-axis current feedback value Iq are obtained by converting the U-phase current feedback value Iu, V-phase current feedback value Iv and W-phase current feedback value Iw of the motor measured by the sensor into 3-phase / 2-phase values ​​through the 3-phase / 2-phase conversion unit 106.

[0054] When the 2-phase / 3-phase conversion unit 105 receives the d-axis voltage command Vd* and the q-axis voltage command Vq*, it converts the d-axis voltage command Vd* and the q-axis voltage command Vq* into the U-phase voltage command Vu*, the V-phase voltage command Vv* and the W-phase voltage command Vw*, and outputs these voltage commands to the inverter 40.

[0055] Next, the state calculation unit 42 will be explained.

[0056] As described above (refer to) Figure 2 The state estimation unit 42 includes a control internal value generation unit 43 and a state calculation unit 44. These will be described below using the accompanying drawings.

[0057] Figure 4 This schematically illustrates the functional structure of the internal value generation unit 43. For example... Figure 4 As shown, the internal value generation unit 43 can be described as... Figure 3 The inverse model of the motor control unit 41 shown. That is, the control internal value generation unit 43 and the motor control unit 41 (refer to...) Figure 3The speed command generation unit 101, torque command generation unit 102, current command generation unit 103, voltage command generation unit 104, 2-phase / 3-phase conversion unit 105, and 3-phase / 2-phase conversion unit 106 in the ) have corresponding speed command generation unit inverse model 111, torque command generation unit inverse model 112, current command generation unit inverse model 113, voltage command generation unit inverse model 114, 3-phase / 2-phase conversion unit 115, and 3-phase / 2-phase conversion unit 116, respectively.

[0058] exist Figure 4 In this process, the command from the upper-level controller to the motor control unit 41 is a position command θ*, but it can also be a torque command Trq* or a speed command ω*. Furthermore, when the command from the upper-level controller is a torque command Trq*, a speed command ω*, or a position command θ*, the block diagram of the motor control internal value generation unit 6 becomes respectively... Figure 4 The block diagrams to the right of boundary line C, boundary line D, and boundary line E are shown in the diagram.

[0059] according to Figure 4 The structure shown describes a control internal value generation unit 43 that calculates one or more of the following based on time-series data acquired by the motor control unit 41 in the input or output section of the motor 13 using independently installed current sensors, voltage sensors, and position sensors: motor three-phase voltage feedback values ​​Vu, Vv, Vw; motor three-phase current feedback values ​​Iu, Iv, Iw; speed feedback value ωm; and position feedback value θm. These control internal values ​​include d-axis current feedback values ​​Id and Iq, d-axis voltage commands Vd* and Vq*, d-axis current commands Id* and Iq*, torque command Trq*, speed command ω*, and position command θ*.

[0060] Furthermore, in this embodiment, the state variables θ*, θm, ω*, ωm, Trq*, Id*, Iq*, Id, Iq, Vd*, Vq*, Vu*, Vv*, Vw*, Vu, Vv, Vw, Iu, Iv, Iw, the difference between the command value and the measured value, and the output values ​​of the proportional, integrator, and differentiator units constituting the controller are internal values ​​for motor control. That is, any one or more of these internal values ​​for motor control in the motor control unit 41 are generated by the internal control value generation unit 43.

[0061] Furthermore, in this embodiment, through Figure 4The control internal value generation unit 43 shown can also generate state variables (e.g., Id*, Iq*, Id, Iq, Vd*, Vq*) that are generated and used during the processing of the motor control unit 41 but are not output from the motor control unit 41. Therefore, this embodiment can be applied to the calculation of various states of a wide variety of injection molding machines 1.

[0062] Figure 5 This is a block diagram schematically representing the functional structure of the state calculation unit 44. As described above, the state calculation unit 44 (refer to...) Figure 2 Based on the internal values ​​controlled by at least one motor generated by the internal value generation unit 43, a state quantity representing the state of the injection molding machine 1, i.e., the state of the equipment itself or the state (quality, etc.) of the manufactured product produced by the equipment, is calculated. Furthermore, the state calculation unit 44 may also base its calculation on internal values ​​controlled by the motor, in addition to those generated by the internal values ​​controlled by the motor, on values ​​obtained from the external data acquisition unit 47 (see reference 47). Figure 2 The state variables are calculated using data obtained from the equipment (such as temperature). Therefore, in Figure 5 and Figure 6 In this process, the internal values ​​of motor control (X1 to Xn) and the data (Z1 to Zn) acquired by the external data acquisition unit 47 are input to the state calculation unit 44.

[0063] Figure 5 In this context, X1 to Xn represent internal values ​​for motor control, and Z1 to Zn represent information acquired by the external data acquisition unit 47. The state calculation unit 44 is input with at least one internal value for motor control. Furthermore, the presence or absence of information acquired by the external data acquisition unit 47 relative to the input to the state calculation unit 44, and the number of inputs, are arbitrary.

[0064] The types and number of internal values ​​for motor control input to the state calculation unit 44 and information acquired by the external data acquisition unit 47 are set according to the structure of the state calculation unit 44 (e.g., the statistical model described later).

[0065] In addition, Figure 5 For convenience, the subscripts of Xn, Zn, and Cn (described later) are set to the same "n". However, this "n" indicates that each number of Xn, Zn, and Cn is arbitrary, and does not mean that the number of Xn, Zn, and Cn is the same.

[0066] exist Figure 5In the structural example, the state calculation unit 44 consists of a feature quantity calculation unit 121 that calculates characteristic quantities for diagnosis based on internal motor control values ​​X1 to Xn and external data Z1 to Zn, and a diagnosis unit 122 that diagnoses the deterioration state of the equipment, product quality, and other states based on characteristic quantities C1 to Cn. In the diagnosis unit 122, statistical models and machine learning models are used to diagnose the state. The feature quantity calculation unit 121 does not process the instantaneous data of Xn and Zn but directly outputs them as characteristic quantities Cn, or outputs the results of frequency analysis (amplitude, phase, etc.) of the instantaneous data of Xn and Zn within a specified time interval, the effective value, average value, standard deviation, maximum or minimum value, overshoot, and peak value within the specified time interval. The number of characteristic quantities Cn can be single or multiple.

[0067] Furthermore, the characteristic quantity calculation unit 121 can also output specified quantities, such as active power and reactive power, calculated based on the internal values ​​of the motor control as characteristic quantities. Additionally, disturbance torque calculated by a so-called observer can also be output as a characteristic quantity. Moreover, these characteristic quantities can be output after further frequency analysis, statistical calculation (averaging), etc.

[0068] The diagnostic unit 122 inputs the feature quantities C1 to Cn output from the feature quantity calculation unit 121, and calculates the state quantity estimation values ​​Y1 to Yn based on the feature quantities C1 to Cn.

[0069] Here, the calculation of characteristic quantities related to the power transmission mechanism (especially the threaded shaft 17 of the ball screw mechanism 20) of the injection molding machine 1, which is one of the features of this embodiment, and the method for judging equipment anomalies will be explained.

[0070] Figure 6 (a) schematically shows the operation and deterioration points of the ball screw mechanism 20 of the injection molding machine 1. Through long-term use, the ball screw mechanism 20 experiences wear on the grooves of the screw shaft 17. While it's possible for all grooves of the screw shaft 17 to deteriorate, there are more cases where deterioration occurs sequentially from specific locations due to variations in usage frequency. For example, in… Figure 6 In case (a), it indicates that the nut portion 18, which is a component, has deteriorated by Z in the portion further back from the middle point of the threaded shaft 17. Since this deterioration causes instability in the mold opening and closing operation, it is preferable to perform high-precision detection in advance.

[0071] Figure 6(b) schematically illustrates the change in torque current (q-axis current) of the ball screw mechanism 20 from the starting position to the ending position. First, as the nut 18 moves from the starting position towards the injection direction via the rotation of the threaded shaft 17, the torque current increases with the injection stress. Then, in the stage where the nut 18 reaches position X, the torque current rises in a convex shape (dashed line). This is because, due to the deteriorated portion Z of the threaded shaft 17, more friction is generated than normal, correspondingly increasing the torque of the motor used to drive the ball screw mechanism 20.

[0072] In this way, the characteristic quantity calculation unit 121 can detect the deterioration of the threaded shaft 17 by monitoring the change in torque current value from the start position to the end position.

[0073] However, in situations such as the initial stage of degradation, fluctuations in torque current values, such as noise, often present challenges in significantly judging changes in torque current. This is because the difference between these fluctuations and normal torque current values ​​is very small.

[0074] Therefore, in this embodiment, the ball screw mechanism 20 divides the steps from the start point to the end point into several defined regions, and calculates the average value of the torque current value (q-axis current feedback value Iq) in each region. The difference between the average torque current value under normal conditions and the average torque current value under diagnostic conditions is calculated for each region. Then, the maximum value of the calculated difference between each region is extracted as a feature quantity. By comparing this feature quantity with a predetermined threshold, it is determined whether the threaded shaft 17 has deteriorated and the degree of deterioration.

[0075] Figure 7 (a) and Figure 7 (b) schematically illustrates the region segmentation and feature-based degradation judgment of this embodiment. Figure 7 Figure (a) is a diagram showing the relationship between the torque current and the position of the nut part 18. For example... Figure 7 As shown in (a), the interval of one injection-related step from the start point to the end point is divided into an arbitrary number of regions. For example, as in this embodiment, in the case of injection molding machine 1, the position of the nut portion 18 on the threaded shaft 17 can be detected based on the rotational speed of the motor 13. For example, if the rotational speed of the motor in one step is 30 revolutions per minute, it is divided into three intervals 1 to 3, each lasting 10 revolutions. Furthermore, the division method is not limited to equal division and can also be unequal. For example, if the deterioration portion is predicted to some extent in advance based on empirical rules or experiments, the interval where the deterioration is predicted can be divided into intervals that are larger (or smaller) than other intervals.

[0076] The feature quantity calculation unit 121 measures the torque current values ​​and quantities below the threshold (normal values) detected at predetermined time intervals in each interval, and calculates their average value. Similarly, the feature quantity calculation unit 121 measures the torque current values ​​and quantities above the threshold (abnormal values) detected at predetermined time intervals in each interval, and calculates their average value. Then, the feature quantity calculation unit 121 calculates the difference between the average value of normal torque current values ​​and the average value of abnormal torque current values ​​in each region, and extracts the maximum value of the difference for each region as a feature quantity. These results are output to the diagnostic unit 122 of the state estimation unit 42.

[0077] Figure 7 (b) schematically shows the characteristic quantity (average value) of the torque current in each interval and the position of the nut. In this figure, it can be seen that in interval 3, the average value of the abnormal value (deterioration value) is larger than the average value of the normal value, and the difference in the average value of interval 3 is the largest when compared with other intervals 1 and 2. The diagnostic unit 122 of the state estimation unit 42 compares the characteristic quantity in interval 3 with the deterioration threshold to determine that the threaded shaft 17 has deteriorated. Then, the diagnostic unit 122 outputs the deterioration state quantity estimation value, such as the average value of the torque current of the abnormal value in interval 3, and the state quantity estimation value of the deterioration position (interval 3) to the motor control update unit 46 and the information transmission unit 45.

[0078] use Figure 8 (a) and Figure 8 Figure (b) schematically illustrates an example comparing the results of implementing a degradation judgment based on the characteristic quantity of torque current and not implementing a degradation judgment. In this figure, the horizontal axis represents the number of measurement samples, and the vertical axis represents the characteristic quantity (the difference in the average value of torque current) in each sample.

[0079] Figure 8 Example (a) is an example where only the torque current values ​​are compared without performing the aforementioned degradation judgment process. That is, the difference between the average torque current under normal conditions (in this verification, the average torque current of N samples of normal data) and the average torque current of each sample is calculated as a feature quantity and represented for each cycle. As shown in the figure, there are cases where the difference D between the average values ​​of normal and abnormal values ​​is very small.

[0080] In contrast, it can be seen that after implementation Figure 8In the case of the degradation judgment process shown in (b), the difference D between the normal torque current value group and the abnormal torque current value group increases, and the difference between normal and deteriorated values ​​widens (i.e., the detection sensitivity of degradation increases). That is, in the above degradation judgment, one step is first divided into multiple regions, and the average of the normal and abnormal values ​​in each region is calculated. Therefore, the sample size for calculating the average is small, and the degree to which prominent values ​​affect the average is greater than in the case where the average is calculated without performing degradation judgment processing. Figure 8 (a) way) high.

[0081] Furthermore, from each segmented region that is easily affected by prominent values, the average value of the interval with the higher average value of the outlier is treated as the outlier in that loop (step). Therefore, the difference between the average value of the most abnormal torque current value and the normal average value is manifested as a relatively large difference in current value. That is, even when the amplitude of the torque current value is extremely small, it is possible to clearly distinguish between normal and abnormal values, resulting in a significant improvement in the accuracy of degradation detection and the ability to detect degradation in its early stages.

[0082] As described above, according to this embodiment, one step is divided into multiple steps, and the average value of normal and abnormal values ​​in each interval is calculated. The value with the highest average of the abnormal values ​​is used as the object of deterioration judgment. Therefore, the deterioration detection of the power transmission mechanism can be performed with higher precision and accuracy. In particular, according to the present invention, even when the deterioration of the power transmission mechanism is small or in the initial stage, an improved precision and accuracy in detecting abnormalities can be expected.

[0083] in addition, Figure 9 (a) is a graph showing the relationship between the torque current and the position of the nut part 18 when the range of the calculated characteristic quantity is varied. Figure 9 (b) is a diagram schematically showing the characteristic quantity (average value) of the torque current in each interval and the position of the nut part 18 when the interval of the calculated characteristic quantity is varied.

[0084] like Figure 9 As shown in (a), the sensitivity of anomaly detection can also be improved by varying the intervals of the calculated characteristic quantities. By subdividing the intervals of the calculated characteristic quantities (the time width of one interval and the amount of movement of one interval), the difference between the torque current under normal and deteriorated conditions increases, thus improving the sensitivity of diagnosis.

[0085] Conversely, if the range of the calculated characteristic quantities is expanded, the difference between the torque current under normal and deteriorated conditions becomes smaller, but it is less affected by deviations such as measurement noise, resulting in stable diagnostic results. By applying the methods described above, the detection accuracy and sensitivity can be adjusted according to the deterioration state of the object being diagnosed and its driving conditions (the moving speed and amount of movement of the component, etc.).

[0086] Furthermore, the present invention is not limited to the various structures and functions described above, and various modifications and substitutions can be made without departing from its spirit. For example, in the above embodiments, the injection molding machine 1 is used as an application example, but as already described, it can be applied to devices such as stamping devices and cutting devices that transmit the power of an electric motor, which serves as a drive source, to the load-side equipment via a power transmission mechanism.

[0087] In addition, in the above embodiment, the threaded shaft 17 of the ball screw mechanism 20 was subjected to a degradation judgment based on characteristic quantities as a power transmission mechanism, but it can also be applied to the degradation judgment of the synchronous belt 16 or the chain that replaces the synchronous belt as a power transmission mechanism.

[0088] In addition, in the above embodiment, a ball screw mechanism 20 was used as the power transmission mechanism, but the present invention can also be applied to a screw mechanism consisting of a screw bolt and nut that does not pass through balls.

[0089] Explanation of reference numerals in the attached figures

[0090] 1…Injection molding machine, 12…Mold, 13…Motor, 14…Drive pulley, 15…Passive pulley, 16…Synchronous belt, 17…Threaded shaft, 18…Nut section, 20…Ball screw mechanism, 30…Control section (management device), 40…Inverter, 41…Motor control section, 42…State calculation section, 43…Control internal value generation section, 44…State calculation section, 45…Information transmission section, 46…Motor control update section, 47…External data acquisition section, 101…Speed ​​command generation section 102… Torque command generation unit, 103… Current command generation unit, 104… Voltage command generation unit, 105… 2-phase / 3-phase conversion unit, 106… 3-phase / 2-phase conversion unit, 111… Speed ​​command generation unit inverse model, 112… Torque command generation unit inverse model, 113… Current command generation unit inverse model, 114… Voltage command generation unit inverse model, 115… 3-phase / 2-phase conversion unit, 116… 3-phase / 2-phase conversion unit, 121… Characteristic quantity calculation unit, 122… Diagnostic unit.

Claims

1. A management device for a power transmission mechanism that transmits driving force from an electric motor to a load-side device, characterized in that: The management device, Obtain the torque current value of the motor for each unit step of driving the power transmission mechanism. The unit step is divided into multiple defined intervals from the start point to the end point. The obtained torque current values ​​are classified into torque current values ​​within the reference value as normal values ​​and torque current values ​​outside the reference value as abnormal values, based on the torque current value of each interval. For each of the aforementioned intervals, calculate the average value of the torque current within the reference value and the average value of the torque current outside the reference value. An anomaly in the power transmission mechanism is detected by the maximum difference between the average of the normal values ​​and the average of the abnormal values ​​in each interval.

2. The management device for the power transmission mechanism as described in claim 1, characterized in that: The management device divides the unit step equally into multiple intervals.

3. The management device for the power transmission mechanism as described in claim 1, characterized in that: The management device divides the unit step into multiple intervals unequally.

4. The management device for the power transmission mechanism as described in claim 1, characterized in that: The management device notifies the outside of any detected abnormalities in the power transmission mechanism.

5. The management device for the power transmission mechanism as described in claim 1, characterized in that: The power transmission mechanism transmits the driving force of the electric motor to the load-side device as linear motion.

6. The management device for the power transmission mechanism as described in claim 1, characterized in that: The power transmission mechanism includes a threaded component and a bolt that engages with the threaded component.

7. The management device for the power transmission mechanism as described in claim 1, characterized in that: The power transmission mechanism is a ball screw mechanism.

8. The management device for the power transmission mechanism as described in claim 1, characterized in that: The load-side device is any one of an injection molding machine, a stamping device, and a cutting device.

9. A method for managing a power transmission mechanism, the power transmission mechanism transmitting driving force from an electric motor to a load-side device, the method being characterized by comprising the following processing: The unit step of driving the power transmission mechanism is divided into several defined intervals from the start point to the end point. The torque current value of the motor is obtained for each of the plurality of intervals driven by the power transmission mechanism. For the torque current values ​​obtained in each of the plurality of intervals, calculate the average value of the torque current values ​​within the reference value range (as normal values) and the average value of the torque current values ​​outside the reference value range (as abnormal values). An anomaly in the power transmission mechanism is detected by the maximum difference between the average of the normal values ​​and the average of the abnormal values ​​in each interval.

10. The management method for the power transmission mechanism as described in claim 9, characterized in that: This includes the process of equally dividing the unit step into multiple intervals.

11. The management method for the power transmission mechanism as described in claim 9, characterized in that: This includes the process of unevenly dividing the unit step into multiple intervals.

12. The management method for the power transmission mechanism as described in claim 9, characterized in that: This includes the processing of external notifications for any detected anomalies in the power transmission mechanism.

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