JP2001116786A - Electric characteristics measuring apparatus for particle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To simply measure electric characteristics of particles such as toner particles or the like. SOLUTION: The electric characteristics measuring apparatus comprises a first electrode 12, a second electrode 14 disposed oppositely to the electrode 12, a power source 28 for applying a predetermined voltage between the opposed electrodes 12 and 14, a piezoelectric element 18 for discharging particles to be detected and its drive circuit 22 in a space between the opposed electrodes, an amplifier for detecting a signal present at the electrode 14, an analyzer for measuring peak values of the signal waveform present in the case of discharging the particles by changing the applied voltage between the opposed electrodes and calculating information regarding electric characteristics of the particles to be detected from a difference of the peak values of the measured respective signal waveforms, and a controller for controlling these means.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for measuring electric characteristics such as the amount of electric charge held by particles.

[0002]

2. Description of the Related Art Toner particles are used in copiers. The characteristic of the charge amount of the toner particles affects the quality of printing. Therefore, it is necessary to measure the charge amount of the toner particles.

For example, Japanese Patent Application Laid-Open No. 09-113559 discloses that a lower electrode is vibrated by a vibrator at a predetermined cycle to fly particles on the lower electrode, and a voltage is applied between both electrodes to reach the upper electrode. It is disclosed that by measuring the amount of current generated at the time of measurement, the total charge amount of the particles at the applied voltage is measured. It is also disclosed that the distribution of the charge amount q of a group of particles is obtained by measuring the total charge amount at each applied voltage. In addition, it is disclosed that the number of particles is calculated by counting a pulse signal generated when the particles reach the upper voltage, and the total charge is divided by the number of particles to obtain a charge q per particle. Have been. In addition, various methods for measuring particle characteristics such as the total charge amount Σq and the total mass Σm are known.

[0004]

However, in these prior arts, the charge-to-mass ratio (Charge-to-M
ass Ratio) The distribution of q / m is not easily measured with a simple configuration. An object of the present invention is to provide an apparatus that can more easily measure the electrical properties of particles.

[0005]

According to the present invention, there is provided an apparatus for measuring electrical properties of a particle, comprising: a first electrode; a second electrode disposed opposite to the first electrode; A voltage applying means for applying the voltage; an input means for discharging the test particles into the space between the opposed electrodes; a signal detecting means for detecting a signal appearing at the second electrode; Analysis means for measuring the peak values of the signal waveforms appearing at the time of emission of the particle, and calculating information on the electrical characteristics of the particles to be measured from the difference between the peak values of the measured signal waveforms; Control means for controlling
It is characterized by having.

[0006] Adhesion acts on particles on the electrode (adhesion consists of image and van der Waals forces). Since this adhesive force is a force (such as 100 times or more) larger than the gravity applied to the particles, the particles remain attached to the electrode unless a large force against them is applied to the particles. An object of the present invention is to solve the above-mentioned problem concerning the adhesive force by releasing the test particles into the space between the opposed electrodes by the test particle input means, and to measure the electrical characteristics of the test particles.

The first electrode is connected to the second
A device that includes a driving unit that vibrates in the direction of the electrode can be used. In this case, the first electrode is oscillated by the driving means so that the test particles on the first electrode can fly into the space between the opposing electrodes.

Further, as the means for introducing particles to be tested, a means comprising an electrode sheet arranged in proximity to the counter electrode and having a polyphase electrode formed on the surface thereof and a driving means for applying a polyphase voltage to the polyphase electrode is used. can do. In this case, the test particles on the multi-phase electrode sheet can be conveyed to the vicinity of the counter electrode by the driving means and can be introduced into the space between the counter electrodes from the end of the multi-phase electrode sheet, and the supply of the test particles can be automated. Is preferred.

The behavior of the test particles released between the opposing electrodes to which a voltage is applied is different due to the difference in charging characteristics. Particles having a large charge amount reach the upper electrode by Coulomb force greater than gravity against gravity. Particles whose Coulomb force is smaller than gravity do not reach the upper electrode and return to the lower electrode.

If the amount of charged particles reaching the upper electrode changes, it appears as a difference in the measurement signal (the behavior of particles returning to the lower electrode without reaching the upper electrode has a relatively small effect on the measurement signal. Is). Thus, the signal is measured each time the voltage applied between the electrodes is changed little by little from zero, and the information on the electrical characteristics of the particles can be calculated by determining the difference between the measured signals.

In the present invention, when analyzing, the peak value of the signal waveform is measured, and the information on the electrical characteristics of the particle is calculated from the difference between the peak values of the measured signal waveforms by a simple method. Calculates information about the statistical characteristics.

[0012]

FIG. 1 is a diagram showing the overall structure of a measuring apparatus according to a tenth embodiment of the present invention.
Is to measure the distribution of

The first electrode 12 functions as a lower electrode.
The second electrode 14 is disposed above the first electrode 12 so as to face the first electrode 12, and functions as a sensing electrode. Further, the third electrode 16 is positioned above the first electrode 12 in FIG.
It is arranged to the left of the second electrode 14 by about 0 mm. This electrode 16 functions as a dummy electrode. Here, the gap between the lower electrode 12 and the upper electrode 14 was 500 μm. A predetermined amount of toner particles 20 as test particles are placed on the first electrode portion 12a below the second electrode 14. No toner particles are placed on the first electrode portion 12b below the third electrode 16.

The lower electrode 12 is provided with a piezo element 18. Reference numeral 22 denotes a drive circuit for driving the piezo element 18. These piezo elements 18 and their driving circuits 2
By 2, at least the portion of the first electrode on which the test particles are placed is moved at high speed in the direction of the second electrode. High speed means that the test particles can help to fly. When the start signal St is supplied to the drive circuit 22,
The drive circuit 22 emits a rectangular pulse 24, and the piezo element 18 is driven by the rectangular pulse 24. The lower electrode 12 moves at a very small distance in the vertical direction with respect to the upper electrode 14 at a high speed.

Numeral 30 denotes a differential amplifier having an amplification factor A of about 10 to the third power.
4 is amplified. FIG. 9 shows a circuit diagram of the differential amplifier 30, and a resistor Rc is a variable resistor for fine gain adjustment. The operational amplifier uses C4082C, and the resistors Rf, R1, R
2 was 33 kΩ, 3.3 kΩ, and 180 kΩ, respectively.

The differential amplifier 3 is driven by the movement of the toner particles 20.
Let us analyze what signals are output from 0 with reference to FIG. FIG. 2 is a model diagram for explaining the movement of the toner particles when the lower electrode 12 is driven. It is assumed that the toner particles are positively charged. FIG. 3 shows a waveform of the drive pulse signal 24 for driving the piezo element.
The drive pulse signal 24 has a pulse width of 16 ms and an amplitude of 140 V
Is a rectangular pulse signal. At the rising edge A of the pulse signal, the lower electrode 12 swings downward, that is, in the direction of x1 in FIG. Then, it swings upward at the falling B toward the original position x0. At that time, the lower electrode 12 attenuates while vibrating and returns to the original position.

It is assumed that there is a toner particle 26 having a charge amount q at a point x above the origin x0 of the lower electrode 12. The upper electrode 1 separated upward by d from the origin x0 by the particles 26
The potential Vu induced at 4 is expressed by the equation (1). d is the distance between the electrodes, and ε0 is the dielectric constant of the space between the electrodes.

Vu = q / 4πε0 (d−x) = q / (4πε0d) · 1 / (1-x / d)

By the way, the displacement x of the lower electrode 12 at the time t after passing through the origin x0 is described by the following equation (2). K, α, and ω are constants.

X = K · exp (−αt) · sinωt

Assuming that the charged toner particles having the total charge amount Σq on the lower electrode 12 make the above-mentioned oscillating motion, the potential Vd induced at the upper electrode 14 at that time is expressed by the following equation (3).

Vd = Σq / (4πε0d) · 1 / (1-x / d) = Σq / (4πε0d) · 1 / (1-K / d · exp (−αt) · sinωt) ≒ Σq / ( 4πε0d) · (1 + G · exp (−αt) · sinωt) where G is K / d.

On the other hand, the upper electrode 1 by the toner particle group 28 (total charge 電荷 q) at the initial position, that is, x = 0.
4 is represented by Σq / (4πε0d). Based on the potential Vi, a toner particle group (charge amount Σq) that adheres to the lower electrode 12 and vibrates with the lower electrode 12 to move. potential induced in the upper electrode 14 is expressed as Expression 4 as the potential V _0.

V ₀ = Vd−Vi = Σq / (4πε0d) G · exp (−αt) · sinωt This is because the toner particles (charge amount Σq) correspond to the lower electrode 12.
Can be considered as a signal output from the differential amplifier 30 when the actuator is vibrating with the lower electrode 12.

FIGS. 4 and 5 show the measured output signal waveforms of the differential amplifier 30. FIG. FIG. 4 shows the output signal V ₀ (t) when there is no toner particle on the lower electrode 12, which is almost zero. FIG. 5 shows an output signal waveform when toner particles are placed on the lower electrode 12, and a portion indicated by a broken line in the latter half is a signal waveform measured when the lower electrode 12 swings upward from the position x1 in FIG. But the above equation (Equation 4)
The signal waveform of the vibration damping type shown by.

FIG. 6 is an enlarged view of the dashed line portion in FIG. FIG. 6A is a signal waveform when the voltage Ve applied between the upper electrode 14 and the lower electrode 12 and between the dummy electrode 16 and the lower electrode 12 by the power supply 28 is 0V. At this time, the toner particles remain attached to the lower electrode 12 and are not lifted up (this was confirmed by observation).

On the other hand, FIG. 6B shows that the inter-electrode voltage Ve is 1 V
Is the waveform of the output signal V ₀ (t) when if,
If there is a difference between the signal of FIG. 6A and the signal of FIG. 6B, this is because the behavior of the toner particles is different. In fact, the peak value Vp of the signal in the case of FIG.
At 59 μV, the peak value Vp of the signal in the case of FIG. 6B was 187 μV. It was also observed that some toner particles were lifted up to the upper electrode 14 in the case of FIG. The particles lifted up to the upper electrode 14 have qVe / d> m, where q is the charge amount.
g, wherein at least gd / V
e has a charge-to-weight ratio of q / m. m is the mass of the particle,
g is the gravitational acceleration. On the other hand, particles satisfying qVe / d <mg are not lifted up by the upper electrode 14, ie,
The particles return to the lower electrode 12 immediately after being separated from the lower electrode 12. It can be seen that the rise of the signal V ₀ (t) is substantially caused by the particles satisfying the former condition of qVe / d> mg reaching the upper electrode 14.

For this reason, a fixed amount of toner particles is placed on the lower electrode 12 and the voltage Ve applied between the electrodes is reduced.
Are supplied to Ve1 and Ve2 (Ve1 <Ve2), the peak values Vp1 and Vp2 of the output signal of the differential amplifier 30 are measured, and the difference is obtained, whereby q / m becomes dg / Ve2 to dg / Ve2.
g / Ve1 of toner particle content P12 = (Vp2
−Vp1) / Max. Max is the voltage Vp when all the toner particles reach the second electrode 14, and the voltage Vp that appears when the voltage Ve is extremely increased.
p.

In FIG. 1, reference numeral 32 denotes an analyzer, which simply analyzes the output signal V ₀ (t) of the differential amplifier 30 and calculates the charge-to-weight ratio q / m of the toner particles to be measured. Numeral 34 denotes a control device which plays a role of totally controlling the system. An output device 36 outputs a measurement result and the like. In the present invention, necessary information is obtained by simply measuring and analyzing the peak value Vp of the signal V ₀ (t). FIG. 7 shows the result of actually measuring the peak value Vp by supplying a fixed amount of toner particles to the lower electrode 12 every time and changing the applied voltage Ve little by little. The vertical axis Vp reflects the cumulative number of toner particles that have reached the second electrode. The abscissa Ve has a reciprocal relationship to q / m of the toner particles, and the higher the Ve, the more the q / m is lifted up.

FIG. 7 shows the overall characteristics of the toner particles. In the case of the present toner particles, in order to know a detailed distribution diagram of q / m, it is necessary to measure the portion where the voltage Ve is 0 to 1 V more finely, for example, every 0.1 V. FIG. 8 shows such detailed measurement again, and the charge-to-mass ratio q / m of the toner particles obtained from the result (not shown).
FIG. The distribution map was subjected to a smoothing process to smooth the distribution curve.

FIG. 10 shows another embodiment 5 of the measuring apparatus of the present invention.
0 is a main part configuration diagram, and is different from Example 10 in that a multi-phase electrode sheet 52 is arranged adjacent to the first electrode 12. Numeral 54 denotes a drive circuit for supplying different-phase rectangular waves to the respective electrodes of the multi-phase electrode sheet. FIG. 11 is a plan view of a multi-phase electrode sheet. A copper linear electrode 60i branched from four (four-phase) address lines 58i is formed on the surface of a sheet 56 made of an insulating thin film such as a polyimide film.
Are formed in parallel with each other. Here, the electrode width is 15 μm, and the distance between the electrodes is 100 μm. These electrode patterns can be produced by a vacuum deposition method.
In FIG. 11, a shaded central portion is a region that is not covered with the insulating film and the toner particles are transported in the direction of the arrow.

FIG. 12 shows a four-phase rectangular wave applied to each phase electrode of the multiphase electrode sheet. Each amplitude was about 100 V, and the frequency was about 100 Hz. The toner particles 62 ride on the rectangular waves of each phase and are conveyed so as to fly on the sheet in the order of V 1 → V 2 → V 3 → V 4 →... And are injected between the electrodes 12 and 14 from the end of the sheet. In this embodiment, the distance between the electrodes is 1000
μm.

In this embodiment, analysis can be performed by the same method as in the previous embodiment. FIG. 13 is a graph showing a change in the peak value of the output waveform of the differential amplifier when the inter-electrode voltage obtained for a certain toner particle is changed. FIG. 14 is a distribution diagram of the charge-to-mass ratio q / m of the toner particles obtained based on the data of FIG.

[0030]

As described above, according to the apparatus of the present invention,
The electrical characteristics of the particles can be easily measured with a simple configuration without requiring a complicated analysis.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram of the present invention.

FIG. 2 is a model diagram for explaining movement of particles.

FIG. 3 is a driving pulse signal waveform of a piezo element.

FIG. 4 is an actually measured output signal waveform of the differential amplifier (when there is no particle).

FIG. 5 is a measured output signal waveform of a differential amplifier (when particles are present).

FIG. 6 is an enlarged view of a broken line portion in FIG.

FIG. 7 is a graph showing a change in a peak value of an output signal waveform of a differential amplifier when an applied voltage between electrodes is changed.

FIG. 8 is a distribution diagram of the calculated charge to mass ratio q / m of the particles.

FIG. 9 is a circuit diagram of a differential amplifier.

FIG. 10 is a configuration diagram of a main part of another embodiment of the present invention.

FIG. 11 is a plan view of a multi-phase electrode sheet.

FIG. 12 shows 4 provided to each phase electrode of the multiphase electrode sheet.
It is a phase rectangular wave.

FIG. 13 is a graph showing a change in a peak value of an output signal waveform of a differential amplifier when a voltage applied between electrodes is changed.

FIG. 14 is a distribution diagram of the calculated charge-to-mass ratio q / m of the particles.

DESCRIPTION OF SYMBOLS 12 1st electrode 14 2nd electrode 16 3rd electrode 18 Piezo element 20, 22, 26, 28, 62 Toner particles 22 Drive circuit 28 Power supply 30 Differential amplifier 32 Analysis device 34 Control device 36 Output device 52 Polyphase electrode sheet 54 Drive circuit

Claims (3)

[Claims] A first electrode; a second electrode disposed to face the first electrode; voltage applying means for applying a predetermined voltage between the counter electrodes; and a test particle in the space between the counter electrodes. Means for emitting test particles, signal detecting means for detecting a signal appearing on the second electrode, and measuring the peak value of the signal waveform appearing when the test particles are emitted by changing the voltage applied between the counter electrodes. Then, an analysis unit that calculates information on the electrical characteristics of the test particles from the difference between the peak values of these measured signal waveforms, and a control unit that controls these units,
An apparatus for measuring electrical properties of particles, comprising: 2. The method according to claim 1, wherein the test particle input means includes a driving means for vibrating the first electrode in the direction of the second electrode, and the test particles on the first electrode are caused to vibrate by the vibration of the first electrode by the driving means. 2. The apparatus for measuring electrical properties of particles according to claim 1, wherein the apparatus is exposed to an interspace. 3. The method according to claim 1, wherein the test particle input means includes a polyphase electrode sheet having a polyphase electrode formed on a surface portion of the multiphase electrode sheet and a driving means for supplying a multiphase voltage to the polyphase electrode. 2. An apparatus for measuring electrical characteristics of particles according to claim 1, wherein the test particles on the multi-phase electrode sheet are conveyed to the vicinity of the counter electrode by means and released from the end of the multi-phase electrode sheet to the space between the electrodes. .