Evaluation device

Abstract

To provide an evaluation device capable of evaluating the electrical characteristics of grease with high accuracy.SOLUTION: An evaluation device according to the present disclosure includes a bearing into which grease to be evaluated is sealed, a shaft to which the bearing is attached, a motor for rotating the shaft, a power supply circuit for generating and supplying voltage to the bearing. an evaluation circuit that evaluates the electrical characteristics of the grease based on the current flowing from the power supply circuit to the bearing, a metal casing that contains the bearing, shaft, and motor, a conductive sheet that covers the inner surface of the casing and is grounded, and a supply port that supplies dry air into the casing.SELECTED DRAWING: Figure 1

Description

Technical Field

[0007] ,

[0001] The present disclosure relates to an evaluation device.

Background Art

[0002] In recent years, it has been required to accurately evaluate the electrical properties of grease encapsulated in a rotating bearing. Related technologies are disclosed, for example, in Patent Document 1.

[0003] The bearing test device disclosed in Patent Document 1 rotates a rotating shaft while flowing a current through a bearing, thereby forcibly generating hydrogen by electrolysis from the grease encapsulated in the bearing, and evaluating a decrease in the bearing life due to brittle peeling considered to be caused by hydrogen embrittlement.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In related technologies, an evaluation of the bearing life has been performed, but a detailed evaluation of the electrical properties of the grease has not been performed. Here, the measurement environment of the electrical properties of the grease is likely to become unstable under the influence of disturbances. Therefore, there has been a problem in related technologies that it is impossible to accurately evaluate the electrical properties of the grease under the influence of disturbances.

[0006] The present disclosure has been made in view of the above background, and an object thereof is to provide an evaluation device capable of accurately evaluating the electrical properties of grease.

Means for Solving the Problems

[0007] The evaluation apparatus according to this disclosure comprises a bearing in which the grease to be evaluated is sealed, a shaft to which the bearing is attached, a motor for rotating the shaft, a power supply circuit for generating and supplying a voltage to the bearing, an evaluation circuit for evaluating the electrical properties of the grease based on the current flowing from the power supply circuit to the bearing, a metal housing enclosing the bearing, the shaft, and the motor, a conductive sheet covering the inner surface of the housing and grounded, and a supply port for supplying dry air into the housing. This evaluation apparatus can accurately evaluate the electrical properties of the grease while suppressing the influence of external disturbances. [Effects of the Invention]

[0008] This disclosure provides an evaluation apparatus capable of accurately evaluating the electrical properties of grease. [Brief explanation of the drawing]

[0009] [Figure 1] This is a schematic diagram showing an example of the configuration of the evaluation device according to Embodiment 1. [Figure 2] This figure shows the details of the tests conducted using the evaluation device shown in Figure 1. [Figure 3] This figure shows some of the results of tests conducted using the evaluation device shown in Figure 1. [Figure 4] This figure shows some of the results of tests conducted using the evaluation device shown in Figure 1. [Figure 5] This figure shows the final results of the tests conducted using the evaluation device shown in Figure 1. [Modes for carrying out the invention]

[0010] The following describes specific embodiments to which the present invention is applied, with reference to the drawings. However, the present invention is not limited to the following embodiments. Also, for clarity of explanation, the following description and drawings have been simplified as appropriate.

[0011] <Embodiment 1> Figure 1 is a schematic diagram showing an example of the configuration of the evaluation device 1 according to Embodiment 1. The evaluation device 1 according to this embodiment is a device for evaluating the electrical characteristics of grease sealed in a rotating bearing. In other words, the evaluation device 1 according to this embodiment is a device for evaluating the energized state, charged state, etc., of a rotating bearing that is sealed with grease when a voltage is applied to the bearing. Here, the evaluation device 1 according to this embodiment can accurately evaluate the electrical characteristics of the grease by suppressing the influence of disturbances. This will be explained in detail below.

[0012] As shown in Figure 1, the evaluation device 1 comprises at least a bearing 101, a shaft 102, a motor 103, a housing 104, a conductive sheet 105, a supply port 106, a power supply circuit 121, and an evaluation circuit 131.

[0013] The bearing 101 has an inner ring 101a fixed to the shaft 102, an outer ring 101b provided outside the inner ring 101a, and a plurality of balls 101c provided in the gap region between the inner ring 101a and the outer ring 101b. The gap region between the inner ring 101a and the outer ring 101b is filled with grease 200, which is evaluated for, for example, its volume resistivity, one of its electrical properties. The motor 103 rotates the shaft 102.

[0014] The power supply circuit 121 generates a voltage and supplies it to the bearing 101. For example, the power supply circuit 121 includes a high-voltage power supply 122 and a function generator 123. The high-voltage power supply 122 generates a voltage. The function generator 123 controls the waveform of the voltage generated by the high-voltage power supply 122 so that it has a frequency and fluctuation range according to the evaluation conditions.

[0015] The evaluation circuit 131 evaluates the volume resistivity and pseudo capacitance, which are electrical characteristics of the grease 200, based on the current flowing from the power supply circuit 121 to the bearing 101. For example, the evaluation circuit 131 includes at least a resistive element 132 provided on the wire connecting the power supply circuit 121 and the bearing 101, and a data logger 133 that detects and records the potential difference across the resistive element 132. More specifically, the evaluation circuit 131 can calculate the volume resistivity of the grease 200 sealed in the rotating bearing 101 from the potential difference across the resistive element 132 recorded in the data logger 133, or from the current flowing through the resistive element 132, which is obtained from the potential difference across the resistive element 132 recorded in the data logger 133 and the resistance value of the resistive element 132. It can also evaluate the pseudo capacitance of the grease 200 sealed in the rotating bearing 101 from the phase difference between the voltage fluctuation of the power supply circuit 121 and the fluctuation of the potential difference across the resistive element 132 recorded in the data logger 133.

[0016] Here, the bearing 101, shaft 102, and motor 103 are housed inside a metal housing 104. The housing 104 is made of, for example, aluminum or an aluminum-containing alloy. This makes the evaluation environment for the electrical properties of the grease 200 housed inside the housing 104 less susceptible to the influence of the electric field outside the housing 104. In other words, the housing 104 prevents the evaluation environment for the electrical properties of the grease 200 housed inside the housing 104 from becoming unstable due to the influence of the electric field outside the housing 104.

[0017] Furthermore, a conductive sheet 105 is provided inside the housing 104, covering the inner surface of the housing 104. The conductive sheet 105 is connected to ground GND. In other words, the conductive sheet 105 is grounded. As a result, the conductive sheet 105 can absorb and remove the charge discharged inside the housing 104. In other words, the conductive sheet 105 can prevent the evaluation environment for the electrical properties of the grease 200 provided inside the housing 104 from becoming unstable due to the influence of the charge discharged inside the housing 104.

[0018] Furthermore, the housing 104 is provided with a supply port 106 for supplying dry air to the inside of the housing 104. Thereby, since the inside of the housing 104 is kept at low humidity, the discharge of electric charges inside the housing 104 is suppressed.

[0019] As described above, since the evaluation apparatus 1 according to the present embodiment can suppress the influence of disturbances, the electrical characteristics of the grease can be accurately evaluated.

[0020] In the present embodiment, a resin housing (first member) 108 is provided so as to cover the bearing 101. Also, between the shaft 102 and the motor 103, a resin joint (second member) 107 for insulating the shaft 102 and the motor 103 is provided. Further, the bearing 101, the shaft 102, and the motor 103 are installed on a resin pedestal (third member) 109 installed on the bottom surface in the housing 104. Thereby, leakage of electricity is suppressed.

[0021] Also, in the present embodiment, a slip ring 110 is attached to the shaft 102. The slip ring 110 and the ground GND are connected by a ground wire 111. A switch 112 is provided on the ground wire 111. By turning on the switch 112, the electric charges charged on the shaft 102 are removed.

[0022] (Explanation of the test performed using the evaluation apparatus 1) Subsequently, the content and results of the test performed using the evaluation apparatus 1 will be described with reference to FIGS. 2 to 5. FIG. 2 is a diagram showing the content of the test performed using the evaluation apparatus 1. FIGS. 3 and 4 are diagrams showing a part of the results of the test performed using the evaluation apparatus 1. Note that in FIG. 3, the test results at time zones N1 and N3 of test condition No. 1 described later are shown. In FIG. 4, the test results at time zones N1 and N3 of test condition No. 4 described later are shown. FIG. 5 is a diagram showing the final result of the test performed using the evaluation apparatus 1.

[0023] As shown in Figure 2, tests were conducted under seven different test conditions, No. 1 to No. 7. In Figure 2, "Grease A" means that type A grease 200 was used, and "Grease B" means that type B grease 200, which is different from type A, was used. "Grounding present" means that switch 112 is ON and shaft 102 is grounded, and "Grounding absent" means that switch 112 is OFF and shaft 102 is not grounded. "Housing closed" means that the door of housing 104 is closed, and "Housing open" means that the door of housing 104 is open (i.e., housing 104 is effectively absent). "Dry air present" means that dry air is supplied into housing 104, and "dry air absent" means that dry air is not supplied into housing 104. When dry air is supplied into housing 104, for example, the humidity inside housing 104 is maintained at 5% or less. "Conductive sheet present" means that the conductive sheet 105 is attached to the inner surface of the housing 104, and "conductive sheet absent" means that the conductive sheet 105 has been removed from the inner surface of the housing 104.

[0024] The rotational speed refers to the rotational speed of shaft 102. The rotational speed is 400 rpm in all cases. The applied voltage refers to the voltage applied from the power supply circuit 121 to bearing 101. The applied voltage is -250V in all cases. Voltage fluctuation refers to the amplitude of the applied voltage fluctuation. The voltage fluctuation is between -250V and +250V in all cases. Voltage fluctuation frequency refers to the frequency of the waveform of the applied voltage. The voltage fluctuation frequency is 10Hz in all cases.

[0025] The tests under each condition were conducted a total of four times: during time slots N1 and N2 on the first day, and during time slots N3 and N4 on the second day. In each test, the evaluation device 1 first rotated the bearing 101 at a specified rotational speed (400 rpm). In this state, the evaluation device 1 applied a fixed voltage (-250V) to the bearing 101 for 5 seconds (times t1 to t2 in Figures 3 and 4). Subsequently, the evaluation device 1 varied the applied voltage at a specified frequency (10 Hz) and within a specified fluctuation range (-250V to +250V) for 5 seconds (times t2 to t3). After that, the evaluation device 1 applied the fixed voltage (-250V) to the bearing 101 again for 5 seconds (times t3 to t4). The evaluation device 1 acquires the potential difference across a total of 3000 resistor elements 132 at a sampling rate of 1000 points / second during the 3 seconds of the second application of the fixed voltage (times t3 to t4), and calculates the average value. The evaluation device 1 then outputs the difference between the maximum and minimum average values ​​for each of the four tests under each test condition as the final result (see Figure 5).

[0026] In test condition No. 1, the grease level is "A", the ground connection is "present", the enclosure is "closed", dry air is "present", and the conductive sheet is "present".

[0027] In test condition No. 2, the grease is type "B", the ground connection is "present", the enclosure is "closed", dry air is "present", and the conductive sheet is "present". In other words, in test condition No. 2, the type of grease 200 is different compared to test condition No. 1.

[0028] In test condition No. 3, the grease is set to "A", the ground connection is "absent", the enclosure is "closed", dry air is "present", and the conductive sheet is "present". In other words, test condition No. 3 differs from test condition No. 1 in that the ground connection is "absent".

[0029] In test condition No. 4, the grease is set to "A", the ground connection is "present", the housing is "open", dry air is "present", and the conductive sheet is "present". In other words, test condition No. 4 differs from test condition No. 1 in that the housing is "open". To put it another way, in test condition No. 4, the test is conducted with the housing 104, one of the features of evaluation device 1, virtually absent.

[0030] In test condition No. 5, the grease is set to "A", the ground connection is "present", the housing is "closed", dry air is "absent", and the conductive sheet is "present". In other words, test condition No. 5 differs from test condition No. 1 in that dry air is "absent". To put it another way, in test condition No. 5, the test is conducted without the supply of dry air to the inside of the housing 104, which is one of the features of evaluation device 1.

[0031] In test condition No. 6, the grease is set to "A", the ground connection is "present", the enclosure is "closed", dry air is "present", and the conductive sheet is "absent". In other words, test condition No. 6 differs from test condition No. 1 in that the conductive sheet is "absent". To put it another way, in test condition No. 6, the test is conducted without the conductive sheet 105, which is one of the features of evaluation device 1.

[0032] In test condition No. 7, the grease is set to "A", the ground connection is "present", the housing is "open", dry air is "absent", and the conductive sheet is "absent". In other words, test condition No. 7 differs from test condition No. 1 in that the housing is "open", dry air is "absent", and the conductive sheet is "absent". To put it another way, in test condition No. 7, the test is conducted with the housing, supply of dry air, and conductive sheet, which are characteristic features of evaluation device 1, all virtually absent.

[0033] As shown in Figure 5, under test conditions No. 1 to No. 3, the difference between the maximum and minimum values ​​of the average values ​​for each of the four tests (variation in test results) is small, while under test conditions No. 4 to No. 7, the difference between the maximum and minimum values ​​of the average values ​​for each of the four tests (variation in test results) is large. From this, it can be seen that the evaluation device 1 can effectively suppress the effects of disturbances and accurately evaluate the electrical characteristics of the grease 200 when the door of the housing 104 is closed, the conductive sheet 105 is attached to the inner surface of the housing 104, and dry air is supplied to the inside of the housing 104.

[0034] As described above, the evaluation device 1 according to this embodiment can accurately evaluate the electrical characteristics of grease by suppressing the influence of disturbances. [Explanation of symbols]

[0035] 1. Evaluation device 101 bearings 101a Inner ring 101b Outer ring 101c ball 102 Shaft 103 Motor 104 cabinets 105 Conductive Sheet 106 Supply port 107 Joint 108 Housing 109 Pedestal 110 Slip Rings 111 Ground wire 112 switches 121 Power supply circuit 122 High-voltage power supply 123 Function Generator 131 Evaluation Circuit 132 Resistor elements 133 Data Logger 200 Grease

Claims

1. The bearing into which the grease to be evaluated is sealed, The shaft to which the bearing is attached, A motor that rotates the aforementioned shaft, A power supply circuit that generates voltage and supplies it to the bearing, An evaluation circuit that evaluates the electrical characteristics of the grease based on the current flowing from the power supply circuit to the bearing, The bearing, the shaft, and the metal housing enclosing the motor, A conductive sheet covers the inner surface of the housing and is grounded, The enclosure includes a supply port for supplying dry air, An evaluation device equipped with the following features.

2. A first resin member provided to cover the bearing, A second resin member is provided between the shaft and the motor to insulate the shaft and the motor, A third resin member is provided between the motor and the housing to insulate the motor and the housing, Furthermore, The evaluation apparatus according to claim 1.

3. The housing is formed of aluminum or an alloy containing aluminum. The evaluation apparatus according to claim 1.

4. An earth wire is provided between the shaft and the ground, A switch provided on the aforementioned ground wire and configured to be switchable on and off, It also has, The evaluation apparatus according to claim 1.

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