JP2557704B2 - Electrostatic characteristic evaluation device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to an evaluation device for accurately grasping the electrostatic characteristics of a charged body, which is useful for developing an antistatic means for eliminating and suppressing static electricity charged on an object. In particular, the present invention relates to an electrostatic characteristic evaluation device that accurately and simply measures electrostatic characteristics of fabric materials used for automobile seats.

[Prior art]

As an antistatic means for preventing the generation of static electricity on an object, conventionally, a means of giving conductivity to the object to release static electricity charged to the ground side has been generally used. For example, in seat fabrics for cars,
It is known that conductive fibers are mixed or a hydrophilic surfactant or the like is added to impart conductivity. However, the antistatic effect, that is, the static elimination performance greatly changes depending on the structure of the conductive fiber, the mixing ratio thereof, the usage environment, and the like. Therefore, in developing various antistatic means, it is important to evaluate the static elimination performance of static electricity charged on an object.

Conventionally, in order to evaluate the static elimination performance in this antistatic means, after charging the measured object to 5000 V, ground the measured object and measure the time until the surface potential of the measured object becomes 50 V or less. However, if the static electricity decay time is 2 seconds or less, there is a static electricity decay test means for judging that the charge removal performance of the measured object is good and it is difficult to be charged. Furthermore, two surface potential detecting means for scanning the surface of the object to be measured at a desired pitch are provided, and the scanning pitch of the surface potential detecting means is made variable according to the presence or absence of a change in the surface potential to detect the first surface potential. When a potential change is detected on the surface of the object to be measured by the means, there is a surface potential detecting means for measuring the potential distribution by scanning the second surface potential detecting means only at the portion at a fine pitch. (JP-A-62-90565).

[Problems of conventional technology]

The static electricity decay test means measures the discharge time required to drop to a specified voltage when static electricity is discharged after the object to be measured is placed in a measurement holder and charged, and then the measurement holder is grounded. With this means, the electrostatic discharge time from the entire measured object is measured. Therefore, there is a practical problem that it is not possible to evaluate the partial difference in discharge time due to the structure of the object to be measured and the directionality of the discharge path of the charged static electricity.

Further, the surface potential distribution measuring device scans the first surface potential measuring means at a large pitch to detect the surface potential change. For this purpose, one surface potential detecting means sets a time interval. It is necessary to measure the potential twice in advance and obtain the potential change by comparing the previous data and the current data. Therefore, a data storage mechanism is required, and the device becomes complicated. Furthermore, there is a practical inconvenience that the potential difference measurement in real time becomes impossible for the convenience of data comparison and the potential difference measurement of a steep voltage drop such as during electrostatic discharge cannot be performed.

[Problems to be Solved by the Invention]

The present invention solves the above-mentioned problems of the prior art, by connecting an electrode for discharge to one point on the DUT, and by forming a means for discharging the static electricity charged on the DUT to the ground, By changing the position of the discharge electrode, it is possible to detect the difference in the discharge rate of static electricity by the antistatic means and the discharge path. That is, in an antistatic fabric in which conductive fibers are mixed, the discharge rate and discharge path of static electricity are locally different depending on the method of mixing the conductive fibers and the weave.

Therefore, according to the present invention, from an arbitrary position on the DUT,
It is an object of the present invention to provide an apparatus capable of discharging the static electricity and evaluating the charge removal performance of the object to be measured and accurately and efficiently.

Further, according to the present invention, the potential difference can be measured in real time by measuring the potential difference of static electricity between a plurality of surface electrometers which are separated by a predetermined distance from the difference output of the surface electrometer, and at the time of discharging. It is possible to accurately measure even a very short time potential difference that occurs when there is a sharp voltage drop, and it is possible to detect the static electricity movement state between multiple points on the DUT, that is, the charge movement speed, from the period of occurrence of the potential difference between them. It is an object of the present invention to provide a practically extremely effective evaluation device capable of measuring basic data of static elimination performance, such as how to give an optimum conductivity as an antistatic means.

[Structure of Invention]

The apparatus for evaluating electrostatic characteristics of a charged body of the present invention measures the discharge state when static electricity charged on a measured object is forcibly discharged by a plurality of surface electrometers, and measures the discharge rate (time constant) of the static electricity. It is configured to easily and accurately evaluate the electrostatic characteristics such as the charge removal performance of the object to be measured from the magnitude and the magnitude of the potential difference obtained from the output differences of the surface electrometers. That is, the electrostatic characteristic evaluation apparatus of the present invention includes a surface potential detecting unit including a plurality of surface electrometers facing each other at a predetermined distance from the object to be measured, and an electrode connected to a surface end of the object to be measured. And a discharge means composed of a switch connected between the electrode and the ground, and from the respective surface potentials measured by the plurality of surface electrometers at the time of discharging the static electricity charged on the object to be measured by the discharge means to the ground. A potential difference duration detection circuit that detects a potential difference between each other and calculates the duration, and a discharge time constant detection circuit that measures a discharge time constant from an electrostatic decay signal output from one of the surface electrometers,
And a measuring circuit comprising a display circuit for judging the magnitude of the potential difference duration and the discharge time constant and displaying the static characteristic of the object to be measured. More specifically, as shown in FIG. 1, the device of the present invention is configured such that the static electricity charged on the DUT 3 can be discharged by the discharge means 1 including the discharge electrode 10 and the switch 11. The discharge electrode is composed of a conductive member having an electrode surface of a fixed area, and is configured to be settable at an arbitrary position on the object to be measured. Also, if the object to be measured is turned over, static electricity can be discharged from the back surface.

[Functions and effects of the invention]

The electrostatic characteristic evaluation apparatus of the present invention is capable of measuring the discharge time constant of static electricity, and setting the discharge electrode connected to the surface of the object to be measured at any position. It has the effect of discharging the charged static electricity.

As a result, there is an effect that it is possible to accurately measure a change in discharge time constant caused by a local static electricity distribution due to the structure of the object to be measured, a discharge path in which electric charges easily flow, or the like. Also, by arranging multiple surface electrometers at multiple positions on the surface of the object to be measured, it is possible to measure in real time the potential difference between the surface potentials of the multiple objects when the electrostatic charge on the object to be measured is discharged. To do. This makes it possible to accurately detect a plurality of potential differences even in the case of a sharp potential drop during discharge, and to know the moving speed of charges moving on the surface or inside of the DUT from the duration of the potential difference. A significant effect that cannot be obtained conventionally is obtained in that effective information indicating the static elimination performance of is obtained.

That is, in the electrostatic characteristic evaluation apparatus of the present invention having the above configuration, the surface potential detecting means 2 is set on the object to be measured 3, the object to be measured 3 is charged, and then the static electricity is discharged to the ground by the discharging means 1. Let The state of decay of the static electricity is
The measurement is performed by the surface potential detecting means 2, and the discharge time constant of the static electricity is measured by the measuring device 5 from the attenuation characteristic of the output signal of the surface potential detecting means 2.

In this configuration, as a method of charging the DUT 3, a corona charging method, a friction charging method, a peeling charging method, or the like can be applied.

According to the electrostatic discharge time constant measuring means including the discharging means 1, the surface potential detecting means 2 and the determining device 5, the setting position of the discharging means 1 on the DUT 3 can be arbitrarily changed. It is possible to measure the difference in the discharge time constants from all angles based on the structure of the object 3, the non-uniformity of the material, and the like, and a particularly remarkable operation effect that cannot be obtained by the conventional technique is exhibited. Next, the surface potential detecting means 2 measures the static electricity charged on the object 3 to be measured set on the insulating table 4, and therefore, the first surface of the object 3 to be measured is separated by an arbitrary distance to a plurality of, for example, two points. A surface electrometer 20 and a second surface electrometer 21 are installed. The surface potential signals measured by the surface potential meters 20 and 21 are input to the measuring device 5 and the difference between the two signals is calculated to calculate the potential difference between the two points on the surface of the object 3 to be measured (point A in FIG. 1). Measure point B).

According to this structure, when the static electricity charged on the DUT 3 is discharged to the ground by the discharging means 1, the charges on the DUT 3 move toward the discharge electrode side (from A point to B point). Therefore, the potential difference generated between the two points A and B is detected. This operation will be described with reference to FIG. In FIG. 2, (A), (B), and (C) show the types of the DUT 3 to be evaluated. The voltage signal I is the output of the first surface electrometer 20, the voltage signal II is the output of the second surface electrometer 21, and the voltage signal III is the first surface electrometer 20 and the first surface electrometer 20 measured by the measuring device 5. 2 shows the output difference with the surface electrometer 21.

FIG. 2 (A) shows a case where the discharge time constant is gentle, FIG. 2 (C) shows a case where the discharge time constant is steep, and FIG. 2 (B) shows a case where the discharge time constant is intermediate between the two. Shown respectively.

In FIGS. 2A and 2B, when the static electricity charged on the DUT 3 is discharged to the ground by the discharging means 1, the charge on the surface of the DUT 3 moves toward the discharge electrode 10. , The potential at point B decays faster than at point A (discharge electrode
Because it is close to 10.) Therefore, a potential difference (III in FIGS. 2 (A), (B), and (C)) occurs between points A and B,
The time when this potential difference occurs, the greater the discharge time constant,
Lasts a long time. In the case of a steep discharge as shown in FIG. 2 (C), the potential difference also appears for a very short time.

Therefore, the longer the duration of this potential difference, the slower the movement of the charges on the DUT 3. This is because from the experimental fact that the duration of the potential difference becomes longer as the surface resistance and volume resistance of the measurement object 3 become larger, the measurement object 3 (in the case of FIG. 2 (A)) having a long duration of the potential difference becomes Since the movement of the charged electric charge is delayed due to its high resistance, it can be determined that the electric charge is hardly removed. That is, if the duration of the potential difference is long, it can be determined that the static elimination performance is poor. On the contrary, when the DUT 3 is discharged, the electric potentials at the points A and B sharply decrease almost simultaneously (FIG. 2 (C)), the electric charge of the DUT 3 quickly flows to the discharge electrode 10. This is because the surface resistance and volume resistance of the DUT 3 become smaller as the surface resistance and volume resistance of the DUT 3 become smaller. Therefore, in this case, since the appearance time of the potential difference becomes extremely short, if the duration of the potential difference is short, it is a phenomenon that the charged charge is instantly discharged,
It can be judged that the static elimination performance is good. As described above, the static electricity charged on the object to be measured 3 is discharged by the discharging means 1, the decay state of the static electricity is measured between two points on the surface of the object to be measured, the electrode difference between the two points is measured, and the continuation is maintained. By discriminating the time, there is a great effect that cannot be expected in the conventional technology that the static elimination performance of the DUT 3, for example, the antistatic fabric can be measured with high accuracy.

〔Example〕

A typical embodiment of the present invention will be described below with reference to FIGS. 3 and 4.

The apparatus for evaluating electrostatic characteristics of a charged body according to this embodiment includes a discharging unit 1, a surface potential detecting unit 2 and a measuring unit 5. The discharge means 1 is a discharge electrode 10 having a certain area made of a conductive material, which is in contact with and connected to one end of the surface of the DUT 3 set on an insulating base 4 made of an insulating material such as acrylic, and one end of the discharge electrode 10. It is connected to the electrode 10 and the other end is connected to the ground, and comprises a switch 11 having a high withstand voltage so as to be operated by an energizing signal from the measuring device 5. The discharging means 1 is
The discharge electrode 10 can be set at any position on the DUT 3, and the static electricity charged on the DUT 3 can be discharged from any position to the ground.

Further, the switch 11 uses a highly insulating relay having a sufficiently high contact breakdown voltage, so that the static electricity of the DUT 3 can be stably held for a long period of time without leaking from the switch 11, and the measuring device 5 can be used. A static electricity can be automatically discharged at an arbitrary timing by an energizing signal from.

Next, the surface potential detecting means 2 is composed of a first surface potential meter 20 and a second surface potential meter 21, and is arranged at two points on the surface space of the DUT 3 at arbitrary distances. . Therefore, the first surface electrometer 20 is around the point A on the surface of the DUT 3,
The second surface potential meter 21 can measure the surface potential around the point B.

The output of the surface potential detecting means 2 is input to the measuring device 5, and the static electricity discharge time constant and the point A are calculated from the static electricity decay state when the static electricity charged on the DUT 3 is discharged by the discharging means 1. And the potential difference between point B is measured. The measuring device 5 receives the outputs of the first surface electrometer 20 and the second surface electrometer 21 and receives a differential operation circuit 51 for calculating the difference between them and an output of the differential operation circuit 51. , Is measured as a potential difference between points A and B on the DUT 3,
A potential difference duration detection circuit 52 for detecting the duration of the potential difference signal, and a comparator 53 for receiving the output of the surface electrometer 20 or 21 and determining whether the static electricity of the DUT 3 has become a certain potential or less. A discharge time constant detection circuit 54 that receives the signal output from the comparator 53 and detects the discharge time constant of the static electricity, and the potential difference duration detection circuit
A display circuit 55 that receives and outputs signals output from the discharge time constant detection circuit 54 and the discharge time constant detection circuit 54 to judge and display the result in order to evaluate the static elimination performance of the DUT 3;
Control circuit 56 for energizing the switch 11 constituting the above and controlling the signal processing timing of the discharge time constant detection circuit 54.
It is composed of

The operation and effect of the measuring device 5 having the above configuration will be described with reference to the time charts shown in FIGS.

The decay state of the surface potential of the DUT 3 when the static electricity charged on the DUT 3 is discharged to the ground by the discharging means 1 is measured by the surface potential detecting means 2. The potential signal V ₁ (FIG. 4 (A)) detected by the first surface electrometer 20 of the detecting means 2 is input to one input terminal of the differential operation circuit 51, and further the second surface electrometer. The potential signal V ₂ (FIG. 4 (B)) detected by 21 is input to the other input terminal of the differential operation circuit 51, and the potential difference between both signals is calculated. The difference signal [Delta] V (FIG. 4 (F)) is then input to the potential difference duration detection circuit 52, by determining the difference signal [Delta] V by the reference value e _t, proportional to the duration t of the potential difference signal It is converted into the time signal t (FIG. 4 (G)). The duration signal t is displayed by the display circuit 55.
Then, the magnitude of the duration signal t of the potential difference ΔV is determined and displayed as an amount indicating the static elimination performance of the DUT 3 against static electricity.

Next, the potential signal detected by the second surface electrometer 21
V ₂ (FIG. 4 (B)) is input to the comparator 53. The comparator 53 determines the time when the potential signal V ₂ decays below a certain reference, and when the V ₂ reaches a reference value e ₁ or below, the comparator 53 operates and a determination signal (see FIG. )) Is output. The judgment signal is a discharge time constant proportional to the discharge time constant τ of the potential signal V ₂ by the action of the start signal (FIG. 4 (C)) output from the control circuit 56 to operate the discharge means 1. Signal (FIG. 4 (E)). The discharge time constant signal is input to the display circuit 55, displayed as a discharge time constant, and its magnitude is determined and displayed as a value representing the static elimination performance of the DUT 3 against static electricity.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing an outline of the electrostatic characteristic evaluation device of the present invention, FIGS. 2 (A) to (C) are diagrams showing the operation contents of the device of the present invention, and FIG. FIG. 4A is a diagram showing an apparatus according to the embodiment, and FIGS. 4A to 4G are diagrams showing the operation contents of the apparatus according to the embodiment of the present invention. In the figure 1 ... Discharging means 2 ... Surface potential detecting means 3 ... Object to be measured 4 ... Insulation stand 5 ... Measuring device 20 ... First surface electrometer 21 ... Second surface electrometer

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yoshiro Umemoto 1 Toyota Town, Toyota City, Aichi Prefecture, Toyota Motor Co., Ltd. (72) Inventor Hideki Ohno 1 Toyota Town, Aichi Prefecture, Toyota Motor Company, Ltd. Hiroshi Ogawa

Claims (1)

(57) [Claims] 1. A surface potential detecting means composed of a plurality of surface electrometers facing each other at a predetermined distance from an object to be measured, an electrode connected to a surface end of the object to be measured, and a gap between the electrode and the ground. And a discharge means composed of a switch connected to the discharge means, and a potential difference between the respective surface potentials measured by the plurality of surface electrometers at the time of discharging the static electricity charged on the object to be measured by the discharge means to the ground. A potential difference duration detection circuit that detects and calculates the duration, a discharge time constant detection circuit that measures a discharge time constant from an electrostatic decay signal output from one of the surface electrometers, the potential difference duration and discharge An electrostatic characteristic evaluation apparatus comprising: a measuring circuit including a display circuit that determines the magnitude of a time constant and displays the electrostatic characteristic of an object to be measured.