Lubrication state diagnosis device, diagnosis method, and program

Abstract

To provide a technique capable of measuring a lubrication state of a rolling device when rotational operation of the rolling device is stopped.SOLUTION: A diagnostic device for diagnosing a rolling device that uses a lubricant comprises: acquisition means for acquiring the impedance and phase of the rolling device using an electrical impedance method when the rolling device starts to rotate and stops after a predetermined number of rotations; derivation means for deriving a thickness of a film derived from the lubricant on the rolling device from the impedance and the phase; and determination means for determining the lubrication state of the rolling device based on the thickness of the film.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a lubrication state diagnostic device, a diagnostic method, and a program.

Background Art

[0002] Conventionally, in rolling devices such as ball screws, a configuration that lubricates its operation using a lubricant has been used. In a device with such a configuration, stable operation is achieved by appropriately grasping and managing the lubrication state.

[0003] As a method for monitoring the lubrication state, there is a method using the electrical impedance method. For example, Patent Document 1 describes a method for deriving the oil film thickness and electrical characteristics using an AC power supply in a device that performs lubrication with a lubricant.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] When measuring the lubrication state of a rolling device using a lubricant, there is also a demand for a method for measuring the lubrication state in a state where the rotational operation of the rolling device has stopped. For example, in a vehicle device or the like, there is a demand to grasp the lubrication state when the operation has stopped.

[0006] In view of the above problems, an object of the present invention is to provide a method capable of measuring the lubrication state of a rolling device in a state where the rotational operation of the rolling device has stopped.

Means for Solving the Problems

[0007] In order to solve the above problems, the present invention has the following configuration. That is, a diagnostic device for diagnosing a rolling device using a lubricant, acquisition means for acquiring the impedance and phase of the rolling device in a state where the rolling device has started rotating and stopped after a predetermined rotation has been performed, using the electrical impedance method; derivation means for deriving the thickness of the film derived from the lubricant in the rolling device from the impedance and the phase; determination means for determining the lubrication state of the rolling device based on the thickness of the film; and a diagnostic device having the same.

[0008] Another aspect of the present invention has the following configuration. That is, a diagnostic method for diagnosing a rolling device using a lubricant, an acquisition step of acquiring the impedance and phase of the rolling device in a state where the rolling device has started rotating and stopped after a predetermined rotation has been performed, using the electrical impedance method; a derivation step of deriving the thickness of the film derived from the lubricant in the rolling device from the impedance and the phase; a determination step of determining the lubrication state of the rolling device based on the thickness of the film; and a diagnostic method having the same.

[0009] Another aspect of the present invention has the following configuration. That is, a program, which causes a computer to, acquire the impedance and phase of a rolling device using a lubricant in a state where the rolling device has started rotating and stopped after a predetermined rotation has been performed, using the electrical impedance method; derive the thickness of the film derived from the lubricant in the rolling device from the impedance and the phase; determine the lubrication state of the rolling device based on the thickness of the film; and a program for causing the same to be executed.

Advantages of the Invention

[0010] According to the present invention, it is possible to measure the lubrication state of a rolling device in a state where the rotational operation thereof has stopped.

Brief Description of the Drawings

[0011]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Modes for Carrying Out the Invention

[0012] Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings and the like. Note that the embodiments described below are merely examples for explaining the present invention, and are not intended to limit the interpretation of the present invention. Also, not all the configurations described in each embodiment are essential for solving the problems of the present invention. In each drawing, the same reference numerals are given to the same components to indicate the correspondence.

[0013] <First Embodiment> Hereinafter, the first embodiment of the present invention will be described. In this embodiment, a ball screw will be used as an example of a rolling device that performs a rotational operation using a lubricant. However, the present invention is not limited thereto, and other rolling devices may be used as long as it is possible to monitor the lubrication state as described later. Also, the mechanical device on which the rolling device is mounted is not particularly limited, and for example, it can be applied to any device such as a vehicle or a machine tool.

[0014] [System Configuration] FIG. 1 is a schematic diagram of a system configuration to which the lubrication state diagnosis method according to this embodiment can be applied. Here, a mechanical device 100 including a ball screw (BS) to be diagnosed is shown. The system further includes a diagnostic device 200, an LCR meter 300, and a control device 400. Note that the mechanical device 100 shows an example when configured as a test environment for diagnosing the lubrication state according to this embodiment, and may be different from the configuration of an actual mechanical device equipped with a rolling device to be diagnosed.

[0015] The mechanical device 100 includes a motor 101, a coupling 102, a bearing housing 103, a support bearing 104, a BS shaft 106, a BS nut 107, a detent fixture 108, a detent guide 109, a joint 110, a spring load fixture 111, a BS nut 112, a bearing housing 113, a support bearing 114, and a slip ring 116.

[0016] The bearing housings 103 and 113 respectively indicate the support bearings 104 and 114. The rolling elements 105 and 115 provided in the support bearings 104 and 114 are each composed of ceramic balls and are electrically insulated from the bearing housings 103 and 113. The BS nut 107 is in an insulated state by using a joint that becomes an insulator (for example, resin) between the detent fixture 108 and the detent guide 109.

[0017] The diagnostic device 200 is an information processing device for executing the state diagnosis process according to this embodiment. The diagnostic device 200 includes a control unit, a storage unit, an IF (Interface) unit, a UI (User Interface) unit, and a communication unit (not shown). The diagnostic device 200 may be configured by a general-purpose information processing device such as a PC (Personal Computer), or may be configured as a dedicated device.

[0018] The control unit of the diagnostic device 200 may be composed of a CPU (Central Processing Unit), an MPU (Micro Processing Unit), a DSP (Digital Single Processor), or a dedicated circuit, etc. The storage unit is composed of 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 can input and output various information according to instructions from the control unit.

[0019] The IF unit is an interface for connecting to an external device. In this embodiment, it is configured to be able to transmit and receive data with the LCR meter 300. The UI unit receives operations from the user and displays various information such as measurement results. For example, the UI unit is composed of a display device such as a speaker, a light, or a liquid crystal display, etc., and outputs to the user according to instructions from the control unit. The output method by the UI unit is not particularly limited. For example, it may be a visual output by screen output or an auditory output by sound. The communication unit is a network interface for communicating with an external device.

[0020] The LCR meter 300 is electrically connected to the ball screw via the BS nut 107 and the slip ring 116. Then, the LCR meter 300 applies an AC power supply to these to measure the impedance Z and the phase θ. The LCR meter 300 appropriately provides the measurement results to the diagnostic device 200. The measurement results by the LCR meter 300 are managed by the information processing device 20.

[0021] The control device 400 generates a control signal for the motor 101 and controls the rotational operation of the ball screw. In this embodiment, the control device 400 is configured separately from the diagnostic device 200, but they may be integrated.

[0022] In the present embodiment, a lubricant is used to lubricate the rotational movement of the ball screw. The lubricant is enclosed around rolling elements (not shown) provided inside the BS nut 107 and the BS nut 112. In the present embodiment, grease is used as the lubricant for explanation.

[0023] [Diagnosis Process] In the method for diagnosing the lubrication state according to the present embodiment, after operating the rolling device to a certain extent, the rotational movement is stopped, and then the lubrication state is diagnosed. FIG. 2 is a flowchart of the diagnosis process according to the present embodiment. This process is executed by the diagnosis device 200. For example, it may be realized by the control unit included in the diagnosis device 200 reading a program for realizing the process according to the present embodiment from the storage unit and executing it. Further, this process flow may be executed at an arbitrary timing based on a user's instruction.

[0024] In S201, the diagnosis device 200 causes the rotational movement of the ball screw to be executed under predetermined conditions. Note that the rotational movement of the ball screw may be controlled by the diagnosis device 200 in cooperation with the control device 400.

[0025] In S202, the diagnosis device 200 stops the rotational movement of the ball screw. The rotational movement of the ball screw may be controlled by the diagnosis device 200 in cooperation with the control device 400.

[0026] In S203, the diagnosis device 200 performs measurement using the LCR meter 300 and acquires information on the impedance Z and the phase θ.

[0027] In S204, the diagnosis device 200 derives the thickness of the film on the ball screw using the impedance Z and the phase θ acquired in S204. The film here is a film formed on the rolling surface of the ball screw due to the lubricant. As a method for calculating the film thickness using the impedance Z and the phase θ, for example, a known method such as Patent No. 7099551 by the applicant of the present application may be used.

[0028] In S205, the diagnostic device 200 performs a state determination based on the film thickness derived in S204. Specific examples of the state determination here will be described later using the test results in FIGS. 3 to 5.

[0029] In S206, the diagnostic device 200 outputs the result of the state determination performed in S205 as a diagnostic result. Then, this processing flow ends.

[0030] [Test Example] FIGS. 3 to 5 show test examples for verifying the lubrication state diagnosis method according to the present embodiment. Each test uses the system configuration example shown in FIG. 1. The test conditions were as follows.

[0031] Diagnosis target: Ball screw (double nut type), with ball retaining piece Lubricant: Grease (lithium soap type), only initial filling (no intermediate lubrication supply) Nut outer diameter temperature [°C]: 80 (temperature adjustment by external device) Stroke [mm]: 60 Rotation speed [min -1 : 1500 Applied AC frequency [MHz]: 1 Applied AC voltage [V]: 1.5

[0032] In this test example, during measurement, after stopping for a certain period of time at the stroke start position of the ball screw, the ball screw is run by rotating it at each rotation speed. Then, rotation is stopped (0 min -1 ) and then, the impedance Z and the phase θ are measured by the electrical impedance method. Then, using the impedance Z and the phase θ, the film thickness h and the metal contact ratio α derived from the lubricant are obtained by a known method. In addition, vibration, torque, and temperature for seizure detection are measured by known means, and the presence or absence and progress of peeling of the rolling surface of the screw shaft are visually judged periodically.

[0033] Figures 3 to 5 are examples of test results. In Figs. 3(a), 4(a), and 5(a), the vertical axis represents the film thickness h [nm] derived from the lubricant, and the horizontal axis represents the running distance [km]. Also, in Figs. 3(b), 4(b), and 5(b), the vertical axis represents the logarithm of the metal contact ratio α [-], and the horizontal axis represents the running distance [km]. In the graph figures, the plots indicate the timing when the rotation was stopped for measurement.

[0034] Figure 3 shows an example where no peeling occurred during the test. Figure 4 shows an example where peeling occurred during the test, and as a result, an abnormal temperature occurred. Figure 5 shows an example where peeling occurred during the test and locking (inoperability) occurred.

[0035] Referring to the results of Figs. 3 to 5, as a general trend, those with a film thickness h value of 0 at the start of the test (running distance: 0 km) gradually increase in value as the running distance increases. And after a predetermined running distance, the value of the film thickness h is stable. In the case of the examples in Figs. 3 to 5, the film thickness h has been stable since the 5th measurement shown at A (the fifth plot from the left). In the present embodiment, the measurement is being performed with the rotation stopped (rotation speed: 0 min -1 ). At this time, as shown in Figs. 3 to 5, the formation of a film derived from the lubricant (grease) can be confirmed even in the state where the rotation is stopped. Such a film is considered to be due to additives such as thickeners contained in the lubricant, for example.

[0036] Referring to the case where no peeling or its rapid progression occurred as shown in Fig. 3. In this state, even when the rotation is stopped and the film thickness h is measured, the value is stable within a certain range.

[0037] On the one hand, refer to the case where peeling occurs and its rapid progression occurs as shown in FIGS. 4 and 5. In these states, when measuring the film thickness h in the state where peeling has occurred, the value of the film thickness h remains stable within a certain range. However, when the peeling progresses rapidly, the film thickness h decreases. Further, abnormalities (for example, temperature abnormalities or lock) occur after the film thickness h becomes 0. Therefore, by detecting the decrease in the film thickness h after the film thickness h reaches a stable state, it is possible to diagnose the lubrication state even in the state where rotation has stopped. In other words, by detecting the decrease in the film thickness, it becomes possible to diagnose it as a sign of the occurrence of an abnormality.

[0038] Referring to FIGS. 4 and 5, the film thickness h causes a decrease not immediately after peeling occurs, but after peeling has progressed to a certain extent. Also, even when the film thickness h becomes 0, an abnormality does not occur immediately. Therefore, the lubrication state may be diagnosed based on the degree of decrease in the film thickness h, the elapsed time, etc. Further, based on the change from the increase in the film thickness h from 0 km of the running distance to stability, it may be diagnosed whether the initial wear and the bedding-in of the lubricant have progressed favorably in the initial stage of operation.

[0039] For example, when performing state determination at S205 in FIG. 2, it may be diagnosed that an abnormality occurs when the value falls below a threshold value for the film thickness h specified in advance. Alternatively, rotation is stopped periodically and measured multiple times, and a stable value of the film thickness h is used as a reference for derivation. The stable value here may mean, for example, a state where the variation (increase or decrease) of the film thickness h is within a predetermined range in a plurality of consecutive measurements. In this state, the most recent film thickness h may be used as a reference. Then, when the newly measured film thickness falls below a predetermined ratio with respect to the reference, it may be diagnosed that an abnormality has occurred or that an abnormality may occur. Also, the urgency of the occurrence of an abnormality may be diagnosed based on the rate of decrease of the value of the film thickness h and the elapsed time after it becomes 0.

[0040] As described above, with the configuration of the present embodiment, it becomes possible to measure the lubrication state in the state where the rotational operation of the rolling device has stopped.

[0041] <Other Embodiments> In the present invention, a program or application for realizing the functions of one or more of the above-described embodiments is supplied to a system or device using a network, a storage medium, or the like, and one or more processors in a computer of the system or device read and execute the program. This process can also achieve the same result.

[0042] Alternatively, it may be realized by a circuit (for example, an ASIC (Application Specific Integrated Circuit) or an FPGA (Field Programmable Gate Array)) that realizes one or more functions.

[0043] As described above, the present invention is not limited to the above embodiments. Combinations of the components of the embodiments, as well as modifications and applications made by those skilled in the art based on the description in the specification and well-known techniques, are also within the scope contemplated by the present invention and are included in the scope for which protection is sought.

[0044] As described above, the following matters are disclosed in this specification. (1) A diagnostic device (for example, 200) for diagnosing a rolling device (for example, 100) using a lubricant, acquisition means (for example, 200, 300) for acquiring the impedance and phase of the rolling device in a state where the rolling device has started rotating and then stopped after a predetermined rotation is performed, using the electrical impedance method; derivation means (for example, 200) for deriving the thickness of a film derived from the lubricant in the rolling device from the impedance and the phase; determination means (for example, 200) for determining the lubrication state of the rolling device based on the thickness of the film; A diagnostic device having the above. According to this configuration, it is possible to measure the lubrication state of the rolling device in a state where the rotational operation of the rolling device has stopped.

[0045] (2) The diagnostic apparatus according to (1), wherein the determination means determines that there is a sign of an abnormality when the thickness of the film is less than a predetermined threshold value. According to this configuration, it becomes possible to detect a sign of an abnormality based on the detected thickness of the film.

[0046] (3) The determination means identifies a reference thickness based on the thicknesses of the film obtained by a plurality of derivations by the derivation means, and determines that there is a sign of an abnormality when the newly derived thickness of the film is less than a predetermined ratio with respect to the reference. The diagnostic apparatus according to (1). According to this configuration, it becomes possible to detect a sign of an abnormality by detecting a decreasing change in the thickness of the film that has been stable.

[0047] (4) The reference is the most recent thickness of the film in a state where the variation in the thickness of the film obtained by a plurality of derivations by the derivation means is within a predetermined range. The diagnostic apparatus according to (3). According to this configuration, it becomes possible to detect a sign of an abnormality by detecting a decreasing change in the thickness of the film with respect to the reference obtained from the results of a plurality of measurements.

[0048] (5) The lubricant is grease containing an additive. The diagnostic apparatus according to any one of (1) to (4). According to this configuration, it becomes possible to detect a sign of an abnormality based on the variation in the thickness of the film derived from the additive contained in the grease.

[0049] (6) The rolling device is a ball screw. The diagnostic apparatus according to any one of (1) to (4). According to this configuration, it becomes possible to perform a condition diagnosis on a ball screw using a lubricant.

[0050] (7) A diagnostic method for diagnosing a rolling device (for example, 100) using a lubricant, An acquisition step of acquiring the impedance and phase of the rolling device in a state where the rolling device has started rotating and then stopped after a predetermined rotation is performed, using the electrical impedance method; A derivation step of deriving the thickness of the film derived from the lubricant in the rolling device from the impedance and the phase; A determination step of determining the lubrication state of the rolling device based on the thickness of the film; A diagnostic method having the above. According to this configuration, it is possible to measure the lubrication state of the rolling device in a state where the rotational operation of the rolling device has stopped.

[0051] (8) A computer (for example, 200) is provided with An acquisition means (for example, 200) for acquiring the impedance and phase of the rolling device in a state where the rolling device has started rotating and then stopped after a predetermined rotation is performed, using the electrical impedance method; A derivation means (for example, 200) for deriving the thickness of the film derived from the lubricant in the rolling device from the impedance and the phase; A determination means (for example, 200) for determining the lubrication state of the rolling device based on the thickness of the film; A program for causing the above to be executed. According to this configuration, it is possible to measure the lubrication state of the rolling device in a state where the rotational operation of the rolling device has stopped.

[0052] As described above, various embodiments have been described with reference to the drawings, but it goes without saying that the present invention is not limited to such examples. It is obvious that those skilled in the art can conceive of various modification examples or correction examples within the scope described in the claims, and it is naturally understood that those also belong to the technical scope of the present invention. Also, within the scope not departing from the gist of the invention, the respective components in the above embodiments may be arbitrarily combined.

Description of Reference Numerals

[0053] 100... Mechanical device 101... Motor 102…Coupling 103…Bearing housing 104…Support bearing 105…Rolling element 106…BS shaft 107…BS nut 108…Anti-rotation jig 109…Anti-rotation guide 110…Joint 111…Spring load jig 112…BS nut 113…Bearing housing 114…Support bearing 115…Rolling element 116…Slip ring 200…Diagnostic device 300…LCR meter 400…Control device

Claims

1. A diagnostic device for diagnosing a rolling device using a lubricant, comprising: an acquisition means for acquiring the impedance and phase of the rolling device in a state where the rolling device has started rotating and stopped after a predetermined rotation has been performed, using the electrical impedance method; a derivation means for deriving the thickness of the film derived from the lubricant in the rolling device from the impedance and the phase; a determination means for determining the lubrication state of the rolling device based on the thickness of the film; A diagnostic device having the above.

2. The diagnostic device according to claim 1, wherein the determination means determines that there is a sign of an abnormality when the thickness of the film is less than a predetermined threshold value.

3. The determination means: specifies a reference thickness based on the thickness of the film obtained by a plurality of derivations by the derivation means; The diagnostic device according to claim 1, wherein when the newly derived thickness of the film is reduced by more than a predetermined ratio with respect to the reference, it is determined that there is a sign of an abnormality.

4. The diagnostic device according to claim 3, wherein the reference is the thickness of the film most recently obtained when the variation in the thickness of the film obtained by a plurality of derivations by the derivation means is within a predetermined range.

5. The diagnostic device according to claim 1, wherein the lubricant is grease containing an additive.

6. The diagnostic device according to claim 1, wherein the rolling device is a ball screw.

7. A diagnostic method for diagnosing a rolling device using a lubricant, comprising: an acquisition step of acquiring the impedance and phase of the rolling device in a state where the rolling device has started rotating and stopped after a predetermined rotation has been performed, using the electrical impedance method; a derivation step of deriving the thickness of the film derived from the lubricant in the rolling device from the impedance and the phase; a determination step of determining the lubrication state of the rolling device based on the thickness of the film; A diagnostic method having the above.

8. A program for causing a computer to execute: an acquisition means for acquiring the impedance and phase of the rolling device in a state where the rolling device using a lubricant has started rotating and stopped after a predetermined rotation has been performed, using the electrical impedance method; a derivation means for deriving the thickness of the film derived from the lubricant in the rolling device from the impedance and the phase; a determination means for determining the lubrication state of the rolling device based on the thickness of the film. ​

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