JPS59204772A - Surface potential meter - Google Patents

Abstract

PURPOSE:To set the condition of forming the optimum image by arranging a first electrode with the length almost the same as the width of an object to be measured in parallel near the body being measured to measure the potential with respect to a second electrode connected electrically to the first electrode. CONSTITUTION:A linear electrode 8 is arranged entirely on the length of a photosensitive body 6, namely, on almost the entire width of a manuscript. An electrode 9 is arranged immediate before a vibrator 2 on the side of the photosensitive body 6 while a measuring electrode 10 opposite to the electrode 9 sandwitching flat plate sections 2a and 2a of the vibrator. Fine parts composing the linear electrode 8 is given a potential directivity characteristic having such a gaus distribution as to maximize the surface potential detected at position where it is in front of the fine part in the surface of the photosensitive body 6 with respect to angle or distance and a only a potential thereof is measured facing the fine part of the photosensitive body. The entire electrode 8 provides the sum or the integration of the measured potentials at fine parts. Connecting the linear electrode 8 and the electrode 9, the electrode 9 is given a potential measured with the linear electrode 8.

Description

DETAILED DESCRIPTION OF THE INVENTION TECHNICAL FIELD The present invention relates to a surface electrometer, and more particularly to a surface electrometer for measuring the potential of an object to be measured, such as the surface of a photoreceptor in a copying machine or the like.

2. Description of the Related Art Generally, photoreceptors using photoconductive materials, such as those used in electronic copying machines, are susceptible to sensitivity shifts due to changes over time. Therefore, in order to compensate for this sensitivity shift, a method is known in which a means for controlling the surface potential of the photoreceptor is added so that the surface potential is always set within a certain range.

For this purpose, a surface electrometer is used to measure the potential on the surface of the photoreceptor.

As a surface electrometer, by intermittently shielding the electric field generated between the object to be measured and the potential measurement electrode placed opposite it, it is possible to generate an amplitude proportional to the voltage difference between the surface of the object to be measured and the measurement electrode. A structure has been proposed in which the surface potential is determined by inducing an alternating current signal in the measuring electrode.

Such a surface electrometer consists of a potential measuring electrode circuit and a chopping means that intermittently shields between the measuring electrode and the object to be measured, and both are covered with a metal shield to prevent external electric fields and noise. covered by.

This metal shield is formed with an ff1ll constant window for potential measurement, which is placed opposite to the portion to be measured of the photoreceptor, and the potential of the photoreceptor is measured through this measurement window.

Although it has been proposed to use a DC motor as the chopping means, it has been proposed to use a piezoelectric element because it is small and easy to manufacture.

Such chopping means is constructed as shown in FIGS. 1 and 2.

In each figure, the reference numeral '1 indicates a mounting board, and a tuning fork-shaped vibrator 2 is fixed to the side surface of this board 1. The vibrator 2 has a tuning fork shape, and a flat plate part 2a is formed on the free end side of the U-shape, and this flat plate part 2a faces the object to be measured of a measurement electrode (not shown). It is placed parallel to the front side of the end face. This vibrator 2
Piezoelectric elements 3, 3 are fixed to the upper and lower surfaces of the U-shaped bent portion. A pin 3 is attached to the end of the U-shaped bent part of the vibrator 2.
a protrudes toward the mounting board 1 side, and this pin 3
A is embedded in the mounting board 1, bent downward, exposed from the bottom end of the mounting board 1, and connected to the printed circuit board (not shown).This pin 3a is for grounding. be.

Additionally, lead pins 4.5 are provided on the mounting board 1 side, and each is connected to the piezoelectric elements 3, 3. These lead pins 4 and 5 guide signals for driving the piezoelectric element 3, and are connected to a printed circuit board (not shown) similarly to the pin 3a.

The chopping means having such a structure includes a piezoelectric element 3.
3, when a voltage is applied in the vertical direction in FIG. 1, the piezoelectric elements 3, 3 produce distortion in the plane direction, and due to this distortion, each side of the bifurcated vibrator 5 vibrates in the vertical direction in FIG. arise.

When such vibration occurs, the total area of the electric field applied to the measurement electrode (not shown) changes, and an amplitude proportional to the potential difference between the object to be measured and the measurement electrode is generated at the same frequency as the vibration frequency of the vibrator 2. An alternating current signal with this voltage is induced on the measurement electrode side.

By the way, FIG. 3 explains the arrangement relationship between a photoreceptor of a copying machine, which is an object to be measured, and a surface electrometer. Reference numeral 6 indicates the photoreceptor, and reference numeral 7 indicates a surface electrometer.

The surface electrometer 7 is placed with respect to the photoreceptor 6 with its measurement electrode and measurement window accurately positioned, and is placed so as to face a specific portion of the photoreceptor 6.

As a result, as is clear from FIG. 3, the surface potential meter 7 only measured the surface potential of a small portion of the photoreceptor 6 to be measured.

Therefore, when scanning the entire document once to form a latent image on the photoreceptor 6, and determining the optimal image forming conditions by measuring the surface potential of this latent image, it is necessary to Optimum image forming conditions have not always been determined for special objects to be copied, such as originals or photographs, which have a large contrast in the axial direction.

Purpose The present invention has been made in order to eliminate the above-mentioned drawbacks of the conventional art, and to make it possible to determine effective image forming conditions even when a document has a large contrast in the width direction. The object of the present invention is to provide a surface electrometer configured according to the present invention.

Embodiment FIGS. 4(a) and 4(b) illustrate an embodiment of the present invention. In the figures, the same parts as in FIGS. 1 to 3 are denoted by the same reference numerals, and the explanation thereof will be omitted. .

In the figure, the reference numeral 8 indicates a linear electrode, which is arranged over almost the entire length of the photoreceptor 6 in the longitudinal direction, that is, in the width direction of the document.

On the other hand, an electrode 9 is disposed immediately in front of the photoreceptor 6 side of the vibrator 2, and a measurement electrode 10 is disposed on the opposite side of the electrode 9 across the flat plate portions 2a, 2a of the vibrator 2. . An amplifier circuit 11 is connected to the measurement electrode 10.

Based on the structure described above, the surface potential of the entire surface of the photoreceptor 6 is detected by the linear electrode 8.

The minute portion constituting the linear electrode 8 has a potential directivity characteristic having a strong Gaussian distribution such that the detected surface potential has a maximum value at a position facing the minute portion on the surface of the photoreceptor 6 with respect to the angle or distance. It is given.

Therefore, the linear type fl! The minute portion 8 measures only the potential of the minute portion of the photoreceptor that faces it.

Since the linear electrode 8 is considered to be a collection of such minute portions, the potential of the linear electrode 8 as a whole is the sum or integral of the potentials measured at each minute portion.

If this linear electrode 8 is connected to an electrode 9 located on the front side of the vibrator 2, which is a chopping means, the linear electrode 8
A potential measured by is applied to the electrode 9.

The measurement electrode IO is grounded, so it is Ov, and the vibrator 2 is also grounded, as described above, so it is Ov.

As a result, the linear electrode 8 and the electrode 9 have a potential corresponding to the surface potential of the photoreceptor 6.

As a result, an electric field is generated between the electrode 9 and the measurement electrode 10, and the vibrator 2 chops this electric field, so that the measurement potential 1
The total area of the electric field applied to the oscillator 2 changes, and an alternating current signal having the same frequency as the vibration frequency of the vibrator 2 and an amplitude proportional to the potential difference between the electrode 9 and the measurement electrode 10 is induced in the measurement electrode 10.

Since the electrode 9 has the same potential as the linear electrode 8, and the linear electrode 8 has a potential proportional to the surface potential of the photoreceptor, which is the object to be measured, the amplitude of the AC signal induced in the measurement electrode 10 is It is proportional to the surface potential of the measuring object.

As a result, the surface potential having a special contrast can be measured over the entire surface of the object to be measured, the surface potential of latent images of all kinds of objects to be copied can be measured, and the optimum image forming conditions can be set.

Effects As is clear from the above explanation, according to the present invention, a first electrode λ having a length comparable to the width of the measured object is arranged near the measured object, and the first electrode λ is arranged in parallel with the measured object. Since it uses a structure in which the potential is measured with respect to a second electrode that is electrically connected to the electrode, it can be used for all kinds of copies, including special copies that have a large contrast in the measurement direction. The surface potential of the latent image can be measured, and the optimal image forming conditions can be set.

[Brief explanation of drawings]

1 and 2 are a front view and a plan view of a chopping means applied to the present invention, and FIG. 3(A). (B) is a side view and a front view illustrating the arrangement relationship between the surface potential of the conventional structure and the measured object, and FIGS. 4 (A) and (B)
1 is a side view and a front view illustrating an embodiment of the present invention. FIG.

Claims (1)

[Claims] In a surface electrometer that measures the potential of a measured object, a first electrode having a length comparable to the width of the measured object is arranged in parallel near the measured object, and the first electrode and the electrical potential are arranged in parallel. 1. A surface electrometer, characterized in that the potential is measured with respect to a second electrode connected to the surface.