Lubrication state diagnosis device, diagnosis method, and program

Abstract

Provided is a diagnosis device for diagnosing a rolling device in which a lubricant is used, the diagnosis device including: an acquisition means for acquiring, by using an electric impedance method, the impedance and the phase of the rolling device in a stopped state after the rolling device starts rotating and prescribed rotation is performed; a derivation means for deriving, from the impedance and the phase, the thickness of a film originating from the lubricant in the rolling device; and a determination means for determining the lubrication state of the rolling device on the basis of the thickness of the film.

Description

Lubrication condition diagnostic device, diagnostic method, and program

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

[0002] Conventionally, rolling devices such as ball screws have been configured to use lubricants to lubricate their operation. Devices with such configurations achieve stable operation by properly understanding and managing the lubrication state.

[0003] One method for monitoring the lubrication state is to use an electrical impedance method. For example, Patent Document 1 describes a method for deriving oil film thickness and electrical characteristics using an AC power source in a device that uses lubricant.

[0004] Japanese Patent No. 7057868

[0005] When measuring the lubrication state of a rolling device that uses a lubricant, there is also a need for a method for measuring the lubrication state when the rotation of the rolling device is stopped. For example, there is a demand for knowing the lubrication state of a vehicle device when the device is stopped.

[0006] In view of the above-mentioned problems, an object of the present invention is to provide a method for measuring the lubrication state of a rolling device when the rotation of the rolling device is stopped.

[0007] In order to solve the above problems, the present invention has the following configuration: A diagnostic device for diagnosing a rolling device that uses a lubricant, comprising: acquisition means for acquiring, by an electrical impedance method, the impedance and phase of the rolling device when the rolling device starts to rotate, performs a predetermined number of rotations, and then stops; derivation means for deriving the 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.

[0008] Another aspect of the present invention has the following configuration: A diagnostic method for diagnosing a rolling device that uses a lubricant, comprising: an acquisition step of acquiring, by an electrical impedance method, the impedance and phase of the rolling device when the rolling device starts to rotate, performs a predetermined number of rotations, and then stops; a derivation step of deriving the thickness of a film derived from the lubricant on the rolling device from the impedance and the phase; and a determination step of determining the lubrication state of the rolling device based on the thickness of the film.

[0009] Another aspect of the present invention has the following configuration: a program for causing a computer to execute: acquisition means for acquiring, by an electrical impedance method, the impedance and phase of a rolling device that uses a lubricant when the rolling device starts to rotate, performs a predetermined number of rotations, and then stops; derivation means for deriving the 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.

[0010] According to the present invention, it is possible to measure the lubrication state of a rolling device when the rotation of the rolling device is stopped.

[0011] The present invention relates to a diagnostic system for detecting a temperature difference between a temperature range of a vehicle and a vehicle body, and a diagnostic system for detecting a temperature difference between a vehicle body and a vehicle body.

[0012] Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings. 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. Furthermore, not all of the configurations described in each embodiment are necessarily essential configurations for solving the problems of the present invention. Furthermore, in each drawing, the same components are assigned the same reference numerals to indicate corresponding relationships.

[0013] <First embodiment> A first embodiment of the present invention will be described below. In this embodiment, a ball screw will be used as an example of a rolling device that performs a rotational motion using a lubricant. However, the present invention is not limited to this, and other rolling devices may be used as long as the lubrication state can be monitored as described below. Furthermore, the mechanical device on which the rolling device is mounted is not particularly limited, and the present invention 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. Shown here is a machine 100 including a ball screw (BS) to be diagnosed. The system further includes a diagnosis device 200, an LCR meter 300, and a control device 400. Note that the machine 100 shows an example of a configuration as a test environment for diagnosing the lubrication state according to this embodiment, and may have a different configuration from the actual machine in which the rolling device to be diagnosed is installed.

[0015] The mechanical device 100 is composed of a motor 101, a coupling 102, a bearing housing 103, a support bearing 104, a BS shaft 106, a BS nut 107, an anti-rotation jig 108, an anti-rotation guide 109, a joint 110, a spring load jig 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 support the support bearings 104 and 114. The rolling elements 105 and 115 provided in the support bearings 104 and 114 are made of ceramic balls and are electrically insulated from the bearing housings 103 and 113. The BS nut 107 is insulated by using a joint that serves as an insulator (e.g., resin) between the anti-rotation jig 108 and the anti-rotation guide 109.

[0017] Diagnostic device 200 is an information processing device for executing the condition diagnosis process according to this embodiment. Diagnostic device 200 is configured to include a control unit, a storage unit, an IF (Interface) unit, a UI (User Interface) unit, and a communication unit, all of which are not shown. Diagnostic device 200 may be configured as 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 diagnostic device 200 may be composed of a CPU (Central Processing Unit), an MPU (Micro Processing Unit), a DSP (Digital Single Processor), 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), or a RAM (Random Access Memory), and is capable of inputting and outputting various information in response to instructions from the control unit.

[0019] The IF unit is an interface for connecting to an external device, and in this embodiment, is configured to be able to send and receive data to and from the LCR meter 300. The UI unit accepts operations from the user and displays various information such as measurement results. For example, the UI unit is composed of a speaker, a light, or a display device such as an LCD display, and outputs information to the user in response to instructions from the control unit. The output method by the UI unit is not particularly limited, and may be, for example, visual output via screen output or auditory output via voice. The communication unit is a network interface for communicating with external devices.

[0020] The LCR meter 300 is electrically connected to the ball screw via the BS nut 107 and the slip ring 116. The LCR meter 300 applies AC power to these components and measures the impedance Z and phase θ. The LCR meter 300 provides the measurement results to the diagnostic device 200 as appropriate. 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 also be integrated.

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

[0023] [Diagnostic Processing] In the method for diagnosing the lubrication state according to this embodiment, the rolling device is operated for a certain period of time, and then the rotational movement is stopped, and then the lubrication state is diagnosed. FIG. 2 is a flowchart of the diagnostic processing according to this embodiment. This processing is executed by the diagnostic device 200, and may be realized, for example, by a control unit included in the diagnostic device 200 reading out from a storage unit and executing a program for implementing the processing according to this embodiment. Furthermore, this processing flow may be executed at any timing based on a user instruction.

[0024] In S201, the diagnostic device 200 executes the rotational operation of the ball screw under predetermined conditions. The rotational operation of the ball screw may be controlled by the diagnostic device 200 in cooperation with the control device 400.

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

[0026] In S203, diagnostic device 200 performs measurements using LCR meter 300 to obtain information on impedance Z and phase θ.

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

[0028] In S205, diagnostic device 200 determines the state based on the film thickness calculated in S204. A specific example of the state determination will be described later using the test results shown in FIGS.

[0029] In S206, diagnostic device 200 outputs the result of the state determination made in S205 as the diagnostic result, and then ends this processing flow.

[0030] 3 to 5 show test examples for verifying the lubrication state diagnosis method according to this 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 retainer piece Lubricant: Grease (lithium soap type), initially filled only (no intermediate grease) Nut outer diameter temperature [℃]: 80 (temperature adjusted 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, the ball screw is stopped at the stroke start position for a certain period of time, and then the ball screw is rotated at each rotation speed to travel. Then, the rotation is stopped at the timing of an arbitrary travel distance (0 min). －１ ) and then the impedance Z and phase θ were measured by the electrical impedance method. Then, the impedance Z and phase θ were used to derive the film thickness h and metal contact ratio α derived from the lubricant by a known method. In addition, vibration, torque, and temperature were measured by known means to detect seizure, and the presence or absence and progression of flaking on the rolling surface of the screw shaft were periodically visually inspected.

[0033] Figures 3 to 5 show example test results. In Figures 3(a), 4(a), and 5(a), the vertical axis represents the lubricant-derived film thickness h [nm], and the horizontal axis represents the travel distance [km]. In Figures 3(b), 4(b), and 5(b), the vertical axis represents the metal contact ratio α [-] in logarithm, and the horizontal axis represents the travel distance [km]. In the graphs, the plots indicate the timing when rotation was stopped and measurements were taken.

[0034] Figure 3 shows an example where no delamination occurred during the test. Figure 4 shows an example where delamination occurred during the test, resulting in temperature abnormalities. Figure 5 shows an example where delamination occurred during the test, resulting in locking (inoperability).

[0035] Referring to the results of Figures 3 to 5, as an overall trend, the value of the film thickness h is 0 at the start of the test (travel distance: 0 km), but the value gradually increases as the travel distance increases. Then, after a certain travel distance, the value of the film thickness h becomes stable. In the example of Figures 3 to 5, the film thickness h becomes stable after the fifth measurement indicated by A (fifth plot from the left). In this embodiment, when the rotation is stopped (rotation speed: 0 min), the film thickness h becomes stable. －１ ) was measured. As shown in Figures 3 to 5, the formation of a film derived from the lubricant (grease) was confirmed even when the rotation was stopped. This film is thought to be caused by additives such as thickeners contained in the lubricant.

[0036] Let us consider the case where no peeling or its rapid progression occurs, as shown in Figure 3. In this state, even if the rotation is stopped and the film thickness h is measured, the value remains stable within a certain range.

[0037] On the other hand, let us consider the cases where flaking has occurred or has progressed rapidly, as shown in Figures 4 and 5. In these cases, when the film thickness h is measured after flaking has occurred, the value of the film thickness h remains stable within a certain range. However, when flaking progresses rapidly, the film thickness h decreases. Furthermore, an abnormality (e.g., temperature abnormality or locking) occurs after the film thickness h reaches 0. Therefore, by detecting a decrease in the film thickness h after the film thickness h has stabilized, it is possible to diagnose the lubrication condition even when rotation is stopped. In other words, detecting a decrease in the film thickness makes it possible to diagnose it as a sign of an abnormality.

[0038] 4 and 5, the film thickness h decreases not immediately after the flakes have occurred, but after the flakes have progressed to a certain extent. Furthermore, even if the film thickness h becomes 0, an abnormality does not immediately occur. Therefore, the lubrication condition may be diagnosed based on the degree of decrease in the film thickness h or the elapsed time. Furthermore, based on the change in the film thickness h from an increase in the film thickness h after 0 km of travel to a stable state, it may be possible to diagnose whether initial wear and lubricant penetration have progressed well in the early stages of operation.

[0039] For example, when the state determination is performed in S205 of FIG. 2 , a diagnosis of an abnormality may be performed if the thickness h falls below a predetermined threshold value. Alternatively, the rotation may be periodically stopped and measurements may be performed multiple times, and the thickness h that shows a stable value may be used as a reference. Here, a stable value may mean, for example, a state in which the fluctuation (increase or decrease) of the thickness h is within a predetermined range over multiple consecutive measurements. In this state, the most recent thickness h may be used as a reference. Then, when a newly measured thickness falls below a predetermined percentage of the reference value, a diagnosis of an abnormality may be performed. Furthermore, the urgency of the abnormality may be diagnosed based on the rate of decrease of the thickness h value or the time elapsed since it reached zero.

[0040] As described above, the configuration of this embodiment makes it possible to measure the lubrication state of the rolling device when the rotational motion of the rolling device is stopped.

[0041] <Other Embodiments> 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 using a network or a storage medium, etc., and one or more processors in a computer of the system or device can read and execute the program.

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

[0043] 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.

[0044] As described above, this specification discloses the following: (1) A diagnostic device (e.g., 200) for diagnosing a rolling device (e.g., 100) that uses a lubricant, the diagnostic device comprising: acquisition means (e.g., 200, 300) that acquires the impedance and phase of the rolling device using an electrical impedance method when the rolling device starts rotating, performs a predetermined number of rotations, and then stops; derivation means (e.g., 200) that derives the thickness of a film derived from the lubricant on the rolling device from the impedance and the phase; and determination means (e.g., 200) that determines the lubrication state of the rolling device based on the film thickness. This configuration makes it possible to measure the lubrication state of the rolling device when the rotation of the rolling device is stopped.

[0045] (2) The diagnostic device according to (1), wherein the determining means determines that a film thickness falling below a predetermined threshold is a sign of an abnormality. With this configuration, it is possible to detect an abnormality sign based on the detected film thickness.

[0046] (3) The diagnostic device according to (1), wherein the determining means identifies a reference thickness based on the film thickness obtained by multiple derivings by the deriving means, and determines that a newly derived film thickness is a sign of an abnormality when the newly derived film thickness is reduced by more than a predetermined percentage relative to the reference thickness. With this configuration, it is possible to detect a sign of an abnormality by detecting a decrease in the film thickness that had been stable.

[0047] (4) The diagnostic device according to (3), wherein the reference value is the most recent film thickness when the variation in film thickness obtained by multiple measurements by the deriving means falls within a predetermined range. With this configuration, it is possible to detect signs of abnormality by detecting a decrease in film thickness relative to the reference value obtained from the results of multiple measurements.

[0048] (5) The diagnostic device according to any one of (1) to (4), wherein the lubricant is grease containing an additive. With this configuration, it is possible to detect signs of abnormalities based on fluctuations in the thickness of a film derived from the additive contained in the grease.

[0049] (6) The diagnostic device according to any one of (1) to (4), wherein the rolling device is a ball screw. With this configuration, it is possible to perform a condition diagnosis on a ball screw that uses a lubricant.

[0050] (7) A diagnostic method for diagnosing a rolling device (e.g., 100) that uses a lubricant, comprising: an acquisition step of acquiring, by an electrical impedance method, the impedance and phase of the rolling device when the rolling device starts rotating, performs a predetermined number of rotations, and then stops; a derivation step of deriving the thickness of a film derived from the lubricant on the rolling device from the impedance and the phase; and a determination step of determining the lubrication state of the rolling device based on the thickness of the film. With this configuration, it is possible to measure the lubrication state of the rolling device when the rotation of the rolling device is stopped.

[0051] (8) A program for causing a computer (e.g., 200) to execute: an acquisition means (e.g., 200) that acquires the impedance and phase of the rolling device using an electrical impedance method when the rolling device starts rotating, completes a predetermined number of rotations, and then stops; a derivation means (e.g., 200) that derives the thickness of the film derived from the lubricant on the rolling device from the impedance and the phase; and a determination means (e.g., 200) that determines the lubrication state of the rolling device based on the thickness of the film. With this configuration, it is possible to measure the lubrication state of the rolling device when the rotation of the rolling device is stopped.

[0052] Although various embodiments have been described above with reference to the drawings, it goes without saying that the present invention is not limited to such examples. It is clear that a person skilled in the art can conceive of various modifications or alterations within the scope of the claims, and it is understood that these also naturally fall within the technical scope of the present invention. Furthermore, the components of the above-described embodiments may be combined in any manner without departing from the spirit of the invention.

[0053] This application is based on a Japanese patent application (Patent Application No. 2023-223379) filed on December 28, 2023, the contents of which are incorporated herein by reference.

[0054] DESCRIPTION OF SYMBOLS 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... Coupling 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, the diagnostic device 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 then stopped after a predetermined rotation is performed, using an electrical impedance method; a derivation means for deriving the thickness of a film derived from the lubricant in the rolling device from the impedance and the phase; and a determination means for determining the lubrication state of the rolling device based on the thickness of the film.

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 according to claim 1, wherein: a reference thickness is specified based on the thickness of the film obtained by a plurality of derivations by the derivation means; and 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 closest to the current state in which 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, the diagnostic method 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 then stopped after a predetermined rotation is performed, using an electrical impedance method; a derivation step of deriving the thickness of a film derived from the lubricant in the rolling device from the impedance and the phase; and a determination step of determining the lubrication state of the rolling device based on the thickness of the film.

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

Images