Method and device for measuring complex impedance of machine element

Abstract

To suppress noise in a wiring when measuring a complex impedance and obtaining a more accurate result of measurement.SOLUTION: The method for measuring the complex impedance of a machine element has a measurement step of measuring a complex impedance by a measurement device connected to the machine element. At least two wires for connecting the machine element and the measurement device to each other are covered by a shield material, and the shield materials of the at least two wires are conducted to each other.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a method and device for measuring the complex impedance of a mechanical element. [Background technology]

[0002] Mechanical devices including rolling devices such as bearings are used in a wide range of industrial fields, such as automobiles and various industrial machines. Understanding the lubrication state inside such mechanical devices is extremely important from the viewpoint of smooth operation of the machine and ensuring its lifespan. Therefore, by properly understanding this, maintenance such as supplying various lubricants (oil, grease, etc.) and replacing the rolling devices can be performed at the optimal time without excess or deficiency. However, since it is difficult to directly observe the lubrication state with the naked eye, methods of monitoring vibration, sound, and oil film state have been proposed as a method of diagnosing the condition of mechanical devices.

[0003] For example, Patent Document 1 discloses a method for diagnosing the lubrication condition inside a rolling device, in which an AC power source is applied to the rolling device, impedance and phase angle are measured, and the lubricant film thickness and metal contact ratio are calculated. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 6380720 Summary of the Invention [Problem to be solved by the invention]

[0005] For example, in a method for diagnosing a lubrication condition using an electrical impedance method, in order to improve the accuracy of diagnosis, it is necessary to consider noise in the wiring between the measurement target and the measurement device. On the other hand, in complex impedance measurement, a certain length is required for the wiring connecting the measurement device and the element of the mechanical device that is the measurement target. In such a configuration, each wiring receives electromagnetic waves from various electronic devices such as motors and controllers for driving the mechanical device as noise, which affects the measurement results. Conventionally, a measure is taken to connect a shielding material that covers the entire wiring to the ground as a noise countermeasure. In this case, for example, if the ground itself is contaminated with electromagnetic waves from the electronic devices or the distance from the shielding material to the ground is large, it may not be possible to take effective noise countermeasures. As a result, there may be cases where the complex impedance measurement value is measured as a value that is not expected in the electrical circuit. For example, the phase angle θ may be measured as a value of -90° or less.

[0006] In view of the above problems, an object of the present invention is to obtain more accurate measurement results by suppressing noise in wiring when measuring complex impedance. [Means for solving the problem]

[0007] In order to solve the above problems, the present invention has the following configuration. That is, a method for measuring a complex impedance of a mechanical element, comprising: A measuring step of measuring a complex impedance by a measuring device connected to the mechanical element, At least two wires for connecting the mechanical element and the measuring device are each covered with a shielding material; The shielding materials of the at least two wirings are electrically connected to each other.

[0008] Another aspect of the present invention has the following configuration: A measuring device for measuring a complex impedance of a mechanical element, comprising: A measuring means is connected to the mechanical element and measures a complex impedance, At least two wires for connecting the mechanical element and the measuring device are each covered with a shielding material; The shielding materials of the at least two wirings are electrically connected to each other. Effect of the Invention

[0009] According to the present invention, when measuring complex impedance, it is possible to suppress noise in wiring and obtain more accurate measurement results. [Brief description of the drawings]

[0010] [Figure 1] 1 is a schematic diagram showing an example of the configuration of a system to which a diagnostic process according to an embodiment of the present invention can be applied; [Diagram 2] 4 is a flowchart of a diagnostic process according to an embodiment of the present invention. [Diagram 3] FIG. 11 is a table showing an example of a measurement result according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, an embodiment 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, and all configurations described in each embodiment are not necessarily essential configurations for solving the problems of the present invention. In addition, in each drawing, the same components are given the same reference numbers to indicate their correspondence.

[0012] <First embodiment> A first embodiment of the present invention will be described below. In the following description of the device configuration, a ball bearing will be taken as an example, but the present invention is not limited to this and can be applied to devices with other configurations. For example, the present invention can be applied to roller bearings in which the rolling elements are rollers (needle-shaped, conical, cylindrical, spherical). The present invention is also not limited to rolling bearings and can be applied to devices in general having a configuration such as a ball screw, linear guide, actuator, sliding bearing, engine piston, etc. Examples of such devices include moving objects such as automobiles, motorcycles, and railroad cars, as well as industrial machines and machine tools.

[0013] Fig. 1 is a schematic diagram showing an example of the overall configuration when diagnosis is performed by a condition diagnosis device 300 that executes the condition diagnosis method according to the present embodiment. In Fig. 1, a bearing device including a rolling bearing 100 to which the diagnosis method according to the present embodiment is applied, and condition diagnosis device 300 that performs the diagnosis are provided. Note that the configuration shown in Fig. 1 is just one example, and a different configuration may be used depending on the configuration of rolling bearing 100, etc.

[0014] The rolling bearing 100 includes an outer ring 101, a plurality of rolling elements 102 (balls in this example), an inner ring 103, and a cage 104 that holds the rolling elements 102 so that they can roll freely. Each part that constitutes the rolling bearing 100 is a mechanical element. Here, the outer ring 101 is a fixed ring, and the inner ring 103 is a rotating ring. The shape of the cage 104 is not particularly limited, and may be changed according to the shape of the rolling elements 102, for example. In addition, the peripheral members of the rolling elements 102, such as the outer ring 101 and the inner ring 103, may have different shapes and rolling surface configurations according to the configuration of the bearing device. Inside the rolling bearing 100, friction between the outer ring 101 and the rolling elements 102, and between the inner ring 103 and the rolling elements 102 is reduced by a predetermined lubrication method. The lubrication method is not particularly limited, but for example, grease lubrication or oil lubrication is used and is supplied to the inside of the rolling bearing 100. The type of lubricant is also not particularly limited.

[0015] A rotating shaft 105 is connected to the inner ring 103, which is a rotating ring, and the inner ring 103 rotates integrally with the rotating shaft 105. Although not shown in FIG. 1, a driving motor is connected to the rotating shaft 105 and supplies power for rotation to the rotating shaft 105. The rotating shaft 105 is electrically connected to the LCR meter 200 via a wiring 106. In addition, the outer ring 101 is electrically connected to the LCR meter 200 via a wiring 107. A rotary connector (not shown) such as a carbon brush or a slip ring may be provided to the wiring 106 at a connection portion with the rotating shaft 105.

[0016] The LCR meter 200 is electrically connected to the rolling bearing 100, and measures the impedance Z and phase angle θ associated with the operation of the rolling bearing 100. The LCR meter 200 then provides the measurement results to the condition diagnostic device 300. The LCR meter 200 also functions as an AC power source for the rolling bearing 100.

[0017] When diagnosing the condition of rolling bearing 100, condition diagnosis device 300 instructs LCR meter 200 to input the angular frequency ω of the AC power supply and AC voltage V. Then, as a corresponding output, condition diagnosis device 300 obtains impedance |Z| (|Z| indicates the absolute value of Z) and phase angle θ of rolling bearing 100 from LCR meter 200. Then, condition diagnosis device 300 performs condition diagnosis of rolling bearing 100 using these values.

[0018] The condition diagnosis device 300 may be realized by, for example, an information processing device including a control device, a storage device, and an output device (not shown). The control device may be composed of a central processing unit (CPU), a micro processing unit (MPU), a digital single processor (DSP), or a dedicated circuit. The storage device is composed of volatile and non-volatile storage media such as a hard disk drive (HDD), a read only memory (ROM), or a random access memory (RAM), and is capable of inputting and outputting various information in response to an instruction from the control device. The output device is composed of a speaker, a light, or a display device such as a liquid crystal display, and notifies the operator in response to an instruction from the control device. The notification method by the output device is not particularly limited, and may be, for example, an auditory notification by voice or a visual notification by screen output. The output device may be a network interface equipped with a communication function, and may perform a notification operation by transmitting data to an external device (not shown) via a network (not shown). The content of the notification here is not limited to a notification when an abnormality is detected as a result of performing the diagnosis, but may also include a notification that the rolling bearing 100 is normal.

[0019] In this embodiment, wiring 106, 107 are provided for electrically connecting the rolling bearing 100 and the LCR meter 200. Each of the wiring 106, 107 is partially covered with a shielding material 106a, 107a. Furthermore, the shielding material 106a and the shielding material 107a are electrically connected by a conductor 108. By providing the shielding materials 106a, 107a for each of the wiring 106, 107, noise emitted by each wiring itself is prevented from affecting the pair of wiring. In addition, the influence of noise caused by electronic devices located around the wiring 106, 107 can also be suppressed. Furthermore, by electrically connecting each shielding material with the conductor 108, it is possible to make the potentials generated in each shielding material due to noise from one or both of the two wirings uniform. This suppresses the influence on each wiring. In addition, in order to reduce noise, the conductor 108 is preferably connected near the center of the shielding materials 106a, 107a as shown in FIG. 1, and does not have to be connected to the ground.

[0020] The material of the shielding material is not particularly limited, and may be, for example, a conductive material such as aluminum or copper (for example, metal foil such as aluminum foil or copper foil, or a braided tube of thin aluminum wire or thin copper wire). The configuration of the shielding material 106a for the wiring 106 and the shielding material 107a for the wiring 107 may be the same or different. In this embodiment, it is sufficient that the potentials of these are made uniform via the conductor 108. In order to reduce noise, it is preferable that the shielding materials 106a and 107a do not come into contact with other devices (for example, a stand), and an insulating material such as a polyethylene sheet may be placed between the shielding materials 106a and 107a and the other devices.

[0021] In addition, in the configuration example of Fig. 1, the shielding material 106a and the shielding material 107a are shown to be electrically connected by one conductor 108, but this is not limited to this. A plurality of conductors may be provided to electrically connect the shielding material 106a and the shielding material 107a. Furthermore, in the configuration of Fig. 1, an example is shown in which two paired wires 106, 107 are used to connect the rolling bearing 100 and the LCR meter 200, but this is not limited to this. For example, three or more wires may be provided between the rolling bearing 100 and the LCR meter 200.

[0022] The condition diagnosis method according to the present embodiment is not particularly limited, and for example, the method described in Patent Document 1 may be used. More specifically, the phase angle, the angular frequency of the AC voltage, the impedance, and the specifications of the rolling bearing are used to calculate the lubricant film thickness around the lubricant in the rolling bearing and the metal contact ratio. In this case, the calculation is performed using the measured values ​​obtained by the configuration according to the present embodiment, and the condition of the rolling bearing is diagnosed based on the calculation results.

[0023] [Processing flow] 2 is a flowchart of the diagnosis process according to this embodiment. This process is executed by the condition diagnosis device 300, and may be realized, for example, by a control device (not shown) included in the condition diagnosis device 300 reading out a program for implementing the process according to this embodiment from a storage device (not shown) and executing the program.

[0024] In S201, condition diagnosis device 300 controls so that a load is applied in a predetermined direction to rolling bearing 100. Here, control is performed so that a radial load is applied to rolling bearing 100. Note that the control of applying a load to rolling bearing 100 may be performed by a device other than condition diagnosis device 300.

[0025] In S202, the condition diagnosis device 300 controls the LCR meter 200 to apply an AC voltage V of angular frequency ω to the rolling bearing 100 using an AC power source (not shown) included in the LCR meter 200. As a result, the AC voltage V of angular frequency ω is applied to the rolling bearing 100.

[0026] In S203, the condition diagnosis device 300 starts the rotation of the rotating shaft 105 by a motor (not shown). As a result, the rotation of the rotating shaft 105 also starts the rotational operation of the rolling bearing 100. Note that the motor may be controlled by a device separate from the condition diagnosis device 300.

[0027] In S204, the condition diagnostic device 300 acquires the impedance Z and the phase angle θ from the LCR meter 200 as outputs in response to the input in S203. That is, the LCR meter 200 outputs the impedance Z and the phase angle θ to the condition diagnostic device 300 as detection results of the rolling bearing 100 in response to the input AC voltage V and the angular frequency ω of the AC voltage. The impedance Z and the phase angle θ acquired here are values ​​in which noise is suppressed due to the configuration described using Fig. 1. Specific measurement results will be described later using Fig. 3.

[0028] In S205, the condition diagnosis device 300 derives the lubricant film thickness and the metal contact ratio using the impedance Z and phase angle θ acquired in S204, the angular frequency ω of the AC voltage used in S202, and the specifications of the rolling bearing 100 to be diagnosed.

[0029] In S206, condition diagnosis device 300 diagnoses the lubrication state of rolling bearing 100 using the lubricant film thickness and metal contact ratio derived in S606. Note that the diagnosis method here may, for example, involve setting threshold values ​​in advance for the lubricant film thickness and metal contact ratio, and diagnosing the lubrication state by comparing with the threshold values. Then, this processing flow ends.

[0030] [Comparison of measurement results] 3 is a table for explaining the measurement results using the configuration according to this embodiment and the measurement results using a conventional configuration. Here, the measurement results for complex impedance are shown for the case where 10,000 points are continuously measured, and the results obtained for the detection of unexpected values ​​are shown. An unexpected value is defined as a value in which the phase difference θ between the voltage (voltage waveform) and the current (current waveform) is -90° or less. The other measurement conditions are the same.

[0031] First, in the measurement results using the conventional configuration, the number of points where θ≦−90° was 59 out of 10,000 points, which was 0.59%.

[0032] In contrast, in the measurement results for the configuration according to this embodiment, the number of points where θ≦-90° was 3 out of 10,000 points, which was 0.03%. In addition, the median value of impedance Z was 139Ω higher in the conventional configuration than in the configuration according to this embodiment, and the median value of phase difference θ was 0.056° lower in the conventional configuration than in the configuration according to this embodiment.

[0033] According to the measurement results shown in the table in Fig. 3, by measuring the complex impedance using the configuration according to this embodiment, it is possible to suppress the occurrence of unexpected values ​​and their ratio. In the example of Fig. 3, the occurrence of values ​​where θ≦-90° can be reduced to about 1 / 20. In addition, the median value of the impedance Z and the median value of the phase difference θ shift. This is considered to be because the potential generated in the wiring 106, 107 due to noise from electrical equipment, etc. is reduced by the shielding materials 106a, 107a that are mutually conductive, and as a result, the measurement accuracy is improved.

[0034] In this way, it is possible to obtain more accurate measurement results by suppressing noise in the wiring when measuring the complex impedance. By diagnosing the condition of the rolling bearing 100 based on the measurement results of the LCR meter 200 in which the effects of noise have been suppressed, it is possible to perform more accurate condition diagnosis.

[0035] <Other embodiments> In addition, in the present invention, a program or application for realizing the functions of one or more of the above-mentioned embodiments can be supplied to a system or device via 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, thereby making it possible to realize the present invention.

[0036] Moreover, it may be realized by a circuit that realizes one or more functions (for example, an application specific integrated circuit (ASIC) or a field programmable gate array (FPGA)).

[0037] As such, the present invention is not limited to the above-described embodiments, and the present invention also contemplates mutual combinations of the various components of the embodiments, as well as modifications and applications by those skilled in the art based on the descriptions in the specification and well-known technologies, and these are included in the scope of protection sought.

[0038] As described above, the present specification discloses the following: (1) A method for measuring the complex impedance of a mechanical element (e.g., 100), comprising: A measuring step of measuring a complex impedance by a measuring device (e.g., 200) connected to the mechanical element, At least two wirings (e.g., 106, 107) for connecting the mechanical element and the measuring device are each covered with a shielding material (e.g., 106a, 107a); A measuring method, wherein the shielding material of each of the at least two wirings is conductive to each other. According to this configuration, when measuring the complex impedance, it is possible to suppress noise in the wiring and obtain more accurate measurement results.

[0039] (2) The measurement method according to (1), wherein the shielding material is made of aluminum. According to this configuration, the shielding material can be made of aluminum (for example, aluminum foil).

[0040] (3) A condition diagnosis method comprising a diagnosis step of diagnosing the condition of the mechanical element by using a complex impedance value measured by the measurement method according to (1) or (2). According to this configuration, it is possible to diagnose the lubrication condition inside the device more accurately than ever before, using measurement results with reduced noise.

[0041] (4) A measuring device (e.g., 200) for measuring the complex impedance of a mechanical element (e.g., 100), A measuring means (e.g., 200) connected to the mechanical element for measuring a complex impedance, At least two wirings (e.g., 106, 107) for connecting the mechanical element and the measuring device are each covered with a shielding material (e.g., 106a, 107a); A measuring device, wherein the shielding material of each of the at least two wirings is conductive with each other. According to this configuration, when measuring the complex impedance, it is possible to suppress noise in the wiring and obtain more accurate measurement results. [Explanation of symbols]

[0042] 100 Rolling bearings 101 Outer ring 102 Rolling element 103 Inner Circle 104 Retainer 105 Rotational Axis 106,107 Wiring 106a, 107a Shielding material 108 Conductor 200 LCR Meters 300 Condition diagnostic device

Claims

1. A method for measuring a complex impedance of a mechanical element, comprising the steps of: A measuring step of measuring a complex impedance by a measuring device connected to the mechanical element, At least two wires for connecting the mechanical element and the measuring device are each covered with a shielding material; A measuring method, wherein the shielding materials of the at least two wirings are electrically conductive to each other.

2. The measurement method according to claim 1 , wherein the shielding material is made of aluminum.

3. 3. A condition diagnosis method comprising a diagnosis step of diagnosing a condition of the mechanical element by using a value of complex impedance measured by the measurement method according to claim 1 or 2.

4. An apparatus for measuring a complex impedance of a mechanical element, comprising: A measuring means is connected to the mechanical element and measures a complex impedance, At least two wires for connecting the mechanical element and the measuring device are each covered with a shielding material; A measuring device, wherein the shielding material of each of the at least two wires is conductive with each other.

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