JP2686358B2 - Charge amount distribution / particle size measuring device for charged particles - Google Patents

Description

The present invention relates to a charge amount distribution / particle size measuring device for charged particles, and more specifically to a laser beam generator and a laser beam generated from this laser beam generator. , A beam splitting mechanism which is connected to the acoustic modulator for splitting the laser beam into two, and a laser beam split by the beam splitting mechanism is introduced from a particle inlet for measurement. A chamber provided with a sound wave vibration generating mechanism for irradiating particles and applying vibration to the particles, and an electrode for generating an electric field,
The present invention relates to a charge amount distribution / particle size measuring device for charged particles, which comprises a detection device for detecting a laser beam scattered by the particles and an arithmetic device for calculating the charge amount and particle size from the detection device.

[Conventional technology]

Conventionally, as a charge amount distribution / particle size measuring device of this kind of charged particles, there is one based on a so-called laser Doppler method as described in JP-A-63-118634. In other words, this device drops particles between electrodes that vibrate with sound waves at a certain frequency, and irradiates the particles with a laser beam from one end. The size of is measured at the same time. In other words, the falling particles fall while oscillating following the air vibration caused by the sound waves, but the larger the particle size, the later the particles vibrate due to the inertia of the particles,
On the other hand, when an appropriate voltage is applied between the electrodes, the particles vibrate according to the particle size, the magnitude of the amount of charge and the strength of the electric field, and as a whole, they are biased and fall. The phase delay and the degree of deviation of the falling particles at this time are measured by the laser Doppler method.

[Problems to be solved by the invention]

However, even when the applied voltage is set to 0 (V = 0) in the above-mentioned conventional charged amount distribution / particle size measuring device for charged amount distribution / particle size measuring device, the distribution is positively or negatively charged. There was a problem that the result was obtained. It must be said that it is extremely doubtful whether or not the charge amount of the particles can be truly accurately measured. Therefore, as a result of diligent efforts by the present inventors to investigate the cause, the self-oscillation frequency of the Bragg cell at the time of dividing a falling particle into two beams by an acoustic modulator (Bragg cell) when irradiating a laser beam, and It has been clarified that an error inevitably intervenes in the self-oscillation frequency of the mixer used for frequency conversion after receiving this beam, and this is the main cause of the zero-point bias of the charge amount distribution.

That is, the calculation of the charge amount q in the frequency characteristic is expressed by the following equation.

Here, V: Applied voltage d: Distance between electrodes θ: Half angle of laser beam crossing angle (2θ is crossing angle) η: Air viscosity Cc: Cunningham's correction coefficient λ: Laser wavelength.

In the case of He-Ne laser λ = 0.6328 × 10 ^-4 [cm] D: Aerodynamic diameter of particle Δf: Beat frequency due to laser Doppler effect By the way, in the above-mentioned conventional apparatus, this beat frequency Δf
Was counted (so to speak, the moving speed of particles between the electrodes was measured) to obtain the charge amount q. That is, the laser light is divided into two beams at a predetermined self-oscillation frequency (for example, 41 MHz) by a Bragg cell, and this beam is received by a photodetector such as a photomultiplier, and then at a predetermined self-oscillation frequency (for example, 39 MHz). Since the frequency conversion is performed by the mixer, then the signal processing is performed, and counting is performed, the accuracy of the self-oscillation frequency of the Bragg cell and the mixer has an important influence on the measurement of the beat frequency. The self-oscillation frequency of was not always a predetermined value.

For example, the self-oscillation frequency of the Bragg cell above is 41 MHz.
When set to z, it is actually 40.9957798 × 10 ⁶ Hz, 0.01
There is an error of 03%, and the self-oscillation frequency of the mixer is 39 MHz.
z is actually 38.9987316 × 10 ⁶ Hz, which is 0.0032%
There was an error. These errors are not negligible, and they are directly brought to the measurement of the charge amount, and even when the applied voltage is set to 0, the charge amount does not become 0. In the end, the reliability of the measured value of the charge amount itself is high. The sex was suspicious.

In order to oscillate the self-oscillation frequency of the Bragg cell and the mixer with high accuracy, it is necessary to use an expensive stabilizing device, and such a device is not economically economically feasible.

Therefore, in order to solve the problems of the above-described conventional technology, the present invention solves the above-mentioned drawbacks of the conventional technology, and charges charged particles with high accuracy even if there is an error in each self-oscillation frequency of the Bragg cell and the mixer. An object is to provide an apparatus capable of measuring a quantity distribution.

[Means for solving the problem]

In order to achieve the above object, the characteristic configuration of the charge amount distribution / particle size measuring device for charged particles of the present invention is the “charge amount distribution / particle size measuring device for charged particles” at the beginning, in which the arithmetic unit is the acoustic Detects the frequency by the modulator and the frequency used in the frequency conversion mixer provided in the detection device,
A point is provided with a correction unit that calculates a correction frequency from both values and calculates / calculates the charge amount.

[Action / Effect]

Next, the operation and effect of the charge amount distribution / particle size measuring device for charged particles according to the present invention will be described.

Since the measuring device of the present invention has the above-mentioned configuration, even if there is an error in the self-oscillation frequency of the Bragg cell and the mixer, the difference between these and the frequency after the target conversion is detected and the error is automatically detected. Only the difference is corrected, and it is not affected by the error. That is,
Even when the applied voltage is set to 0, the distribution does not deviate to either polarity side, and therefore the charge amount distribution of the charged particles can always be measured with high accuracy. Moreover, it does not require any specially expensive equipment.

As described above, according to the present invention, it is possible to provide an inexpensive and accurate charge amount distribution / particle size measuring device for charged particles.

〔Example〕

An embodiment of a charge amount distribution / particle size measuring device for charged particles according to the present invention will be described in detail with reference to the drawings.

1 and 2 show one embodiment of the device of the present invention. That is,
This charge amount distribution / particle size measuring device for charged particles is composed of a laser beam generator (1) and a beam generated by the laser beam generator (1) which is divided into two by giving a certain frequency deviation. An acoustic modulator (2) having a split mechanism, a chamber (7) for introducing a laser beam split by the beam split mechanism and irradiating a particle (9) to be measured with a beam at a measurement point (10), Focusing device (11) for focusing the laser beam scattered by the particles (9) emitted from the chamber (7)
A detection device (4) for detecting the condensed beam, and a calculation device (12) for calculating the charge amount and the particle size from the detection device (4).

Then, the chamber (7) irradiates the laser beam (5) to the measured particles (9) flowing downward from the measured particle introduction port (6), and at the same time, vibrates the particles (9) with sound wave vibration. It comprises a generating mechanism (3) and an electrode (8) for generating an electric field. Further, the detection device (4) is a photomultiplier tube (photomultiplier) that receives the focused beam.
(14), a mixer (15) connected to this Photomul for frequency conversion to reduce noise, and this mixer (1
It consists of a signal processing mechanism that processes the signal from 5) and a counter (16) that counts the frequency.

On the other hand, the arithmetic unit (12) includes a central processing unit (CPU) (17) that calculates the particle size and charge amount of the measured particles from the frequency counted by the detection unit (4), and a printer that outputs the result. An error detection circuit (19) including an output device (18) and the like, and an arithmetic unit (12) for detecting an error of each self-oscillation frequency of the Bragg cell and the mixer.
And a correction means (13) for correcting the charge amount by calculating a correction frequency from the detected error.

 Next, the operation of the device of the present invention will be described.

First, in FIG. 1, the particles to be measured (9) conveyed to the air flow of nitrogen gas or the like are introduced from the particles to be measured introduction port (6) of the chamber (7) using an appropriate supply means. The charged particles fall according to the magnitude of the charge amount and the vibration due to the vibration of the sound wave from the sound wave vibration generating mechanism (3) and the electric field from the electrode (8) to which a predetermined voltage is applied,
The measurement point (10) is irradiated with the laser beam divided into two. In this case, the particles vibrate later than the reference sound wave according to their size, and at the same time, they fall with a certain bias depending on the charge amount. The beam will scatter reflecting such information from the particles. This scattered beam is once condensed and introduced into Photomaru (14),
Here, it undergoes frequency conversion by the mixer (15). Further, the converted signal is output through the filter (20), the waveform shaping circuit (21), the frequency counter (16) and the error detection circuit (19) and then output to the printer (18). ing.

Next, correction of the charge amount distribution will be described with reference to the flowchart of FIG.

(A) First, the actual conversion frequency is detected from the self-oscillation frequency f ₁ of the Bragg cell and the self-oscillation frequency f _{2 of the} mixer, and the difference Δfc (correction value) between this and the desired conversion frequency.
Is read.

(B) All frequency data counted by the frequency counter is divided into channels within a certain range by copying the working area of the computer for each positive charge or negative charge.

(C) Correct the representative frequency Δfi (representative frequency of the i channel) for each channel.

 That is, Δfi ′ = Δfi ± Δfc.

(D) If the corrected Δfi ′ is smaller than 0, Δfi ′ is adopted instead of Δf in the equation (1) regarding the charge amount, and the charge amount is calculated.

(E) If the corrected .DELTA.fi 'is larger than 0, the data contained in this channel is moved to the opposite polarity side and the charge amount is calculated in the same manner as in (D).

By using the above correction means, even if charged particles such as toner used in a copying machine are used and the applied voltage is measured as 0, the amount of charge correctly indicates 0 point, and the charge amount deviates from 0 point. I had nothing to do.

A He—Ne laser generator is generally used as the laser beam generator (1), but the laser beam generator (1) is not limited to this. As the beam splitting mechanism, it is common to separate the laser beam by a prism and then use a mirror to send the beam in a predetermined direction.
Other methods may be used.

INDUSTRIAL APPLICABILITY The apparatus of the present invention can be applied not only to the quality control and quality improvement of toner of copying machines, but also to the quality control, quality improvement, research and development of powders for various paints, resin powders, cosmetic powders and the like.

In the claims, reference numerals are provided for convenience of comparison with the drawings, but the present invention is not limited to the structure shown in the attached drawings.

[Brief description of the drawings]

FIG. 1 is an overall conceptual diagram showing an embodiment of a charge amount distribution / particle size measuring device for charged particles according to the present invention, FIG. 2 is a flow chart relating to a detection device and a computing device, and FIG. 3 is for correcting the charge amount distribution. It is a flowchart. (1) ... Laser beam generator, (2) ... Acoustic modulator, (3) ... Sound wave vibration generating mechanism, (4) ... Laser beam detector, (5) ... Laser beam, (6)
...... Measured particle inlet, (7) …… Chamber, (8) ……
… Electrodes, (9) …… Particles to be measured, (12) …… Computers,
(13) …… Correction means.

Claims (1)

(57) [Claims] 1. A laser beam generator (1) and a beam splitting mechanism for dividing a laser beam (5) generated from the laser beam generator (1) into two laser beams by giving a certain frequency deviation. An acoustic modulator (2) having the same and a laser beam divided by the beam splitting mechanism are applied to a particle (9) to be measured which is introduced from an inlet (6) of the particle to be measured, and vibration is imparted to the particle (9). A chamber (7) equipped with a sound wave vibration generating mechanism (3) and an electrode (8) for generating an electric field, a detection device (4) for detecting the laser beam scattered by the particles (9), and this detection A charged particle charge amount distribution / particle size measuring device comprising a calculation device (12) for calculating a charge amount and a particle size from a device (4), wherein the calculation device (12) comprises the acoustic modulator (2). Frequency and detection device (4)
Is equipped with a correction means (13) for detecting the frequency used in the frequency conversion mixer (15) provided in the device, calculating the correction frequency from the values of both, and calculating / calculating the charge amount. Charge amount distribution / particle size measuring device for charged particles.