JP3096162B2 - Surface electrometer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface voltmeter, and more particularly to a surface voltmeter used in an electrophotographic copying machine, a printer and the like.

[0002]

2. Description of the Related Art Conventionally, in an electrophotographic copying apparatus, a photosensitive drum is first uniformly charged (primary charged) on a photosensitive drum surface in an image forming process.
On the other hand, the reflected light of the document is applied to cause a discharge in accordance with the brightness of the static charge, thereby forming an electrostatic latent image on the drum. Therefore, in order to further improve the image quality, it is essential to control the primary charging to a predetermined value, and it is necessary to control the surface potential using a surface voltmeter.

[0003] The example of a conventional surface potential meter will be described with reference to FIG.

FIG. 7 is a perspective view of a conventional surface voltmeter.

In FIG. 7 , 1 is a counter electrode (measurement electrode), 2 is a sound, 3 is a piezoelectric element, 4 is a sound mount,
5 is a chopping blade, 6 is a sensor substrate, and 101 is a photosensitive drum.

[0006] will be described with reference to FIG. 7 the operation of the conventional example.

In FIG. 7 , first, when the drum 101 is charged and has a potential, the electric field lines S are transmitted from the drum 101 to the counter electrode 1 through a window of a shield case (not shown) covering the sensor substrate 6. Is incident.

On the other hand, the piezoelectric element 3 attached to the pitch 2
, A pulse voltage of about 20 Vpp and 500 Hz is applied, and vibration occurs in the entire pitch 2. Thereby, the pitch 2
Since the tip blade 5 also vibrates similarly, the drum 10
1 is chopped from the line of electric force incident on the counter electrode 1, the amount of the line of electric force S incident on the counter electrode 1 is fluctuated, and a minute AC voltage is induced on the counter electrode 1 grounded to ground at about several tens MΩ. . In principle, the potential on the drum 101 is measured based on the magnitude of this signal.

In this case, the swing width of the blade 5 is sufficiently large,
Also, if the size of the measuring electrode 1 is sufficiently large, the amount of the electric flux lines S to be chopped increases accordingly, and a signal having a sufficient S / N ratio that can ignore signal mixing from other than the object to be measured is output. It is possible to

[0010]

However, with the progress of miniaturization of the entire apparatus, the demand for miniaturization of the surface voltmeter has been increasing in recent years. For example, copying using a photoreceptor drum having a small diameter of about 40.phi. When the conventional electrophotographic basic unit is arranged around the drum, there is a problem that the space for installing the conventional surface electrometer having a thickness of about 1 cm no longer exists .

[0011] Also, the accuracy required for this surface voltmeter
Increases with the demand for higher image quality,
The size reduction of the surface voltmeter with the downsizing of the main unit
Requirements are increasing, and these are generally trade-offs.
If the size is simply reduced, the deterioration of the S / N ratio will be maintained.
There is a problem that leads to deterioration of accuracy
Was.

[0012] For example, in FIG. 7, the object to be measured 101
The ratio of the amount of the signal incident on the electrode 1 from the electrode to the amount of the mixed electrode of the signal for driving the piezoelectric element 3 for vibrating the pitch 2 is reduced by the downsizing of the electrode 1, while the difficulty in shielding measures is increased. since the latter is increased from, there is a challenge that will be significantly degraded.

[0013] The present invention has been made to solve the above problems, the miniaturization of the front surface electrometer, a purpose to realize a high precision.

[0014]

[SUMMARY OF To this end, the measurement electrode facing the surface of the Target object, a conductive shield case having a window portion between the measuring electrode and the object, said shield from said object Chopping means for cutting and opening lines of electric force passing through the window of the case and entering the measurement electrode;
A surface voltmeter for inducing an AC voltage having an amplitude corresponding to a surface potential of the target object on the measurement electrode, wherein the chopping means has a pitch provided with chopping blades, and the surface potential meter, characterized by comprising engagement is matched in the face of the blade to the outer wall surface position of the shield case window, it is intended to achieve the above purposes.

[0015]

Embodiments of the present invention will be described below with reference to the drawings .

[0016] First, the first surface potential meter is an embodiment of the present invention will be described with reference to FIGS.

FIG. 1 is a diagram of a surface voltmeter according to a first embodiment of the present invention, in which (a) is a side sectional view and (b) is a plan view. Figure 2 is a diagram of a conventional example corresponding to the first embodiment of FIG. 1, (a) is a side sectional view, (b) is a plan view.

The contrast to FIG. 1 and FIG. 2 will be the description of the first embodiment.

In the drawing, the same reference numerals as those in the conventional example denote the same or corresponding parts, and the description will be partially repeated.

1 and 2 , reference numeral 1 denotes a measuring electrode which receives a line of electric force S from an object, 2 denotes a sound for chopping electric lines of force incident on the measuring electrode 1 from the object, and 3 denotes a sound 2 Is a piezoelectric vibrator for mechanically vibrating the sound, 4 is a pitch fixing base for fixing the pitch 2 to the substrate 6, 5 is a chopping blade attached to the tip of the pitch, and 6 is a detection signal. A substrate on which a circuit to be processed is mounted, 7 is a shield case for blocking unnecessary external noise, 8 is a window opened in the shield case 7, and the lines of electric force S enter the electrode 1 from an object. Reference numeral 9 denotes an incident direction of the electric force lines S, and reference numeral 10 denotes a blade vibration direction. The feature of the fourth embodiment in comparison with the conventional example (FIG. 2 ) is that the window of the shield case is widened and the blades of the pitch 2 are mounted in accordance with the position of the outer wall surface of the shield case.

[0021] Thus, the distance of the drum surface and the electrode is a conventional example Figure 2 the object in (a) is the distance a of the drum surface 101 and the shield case 7, the plate thickness b of the shield case 7,
In this embodiment, the distance c between the shield case 7 and the pitch 2 blade, the plate thickness d of the pitch 2 blade 5, and the distance e between the pitch 2 blade 5 and the electrode are sums in this embodiment. The distance a of the shield case 7, the thickness d of the blade 5 having the pitch 2 and the blade 5 having the pitch 2
And the distance e between the electrode 1 and (b + c)
As a result, the electric field between the object and the electrode 1 is strengthened, the chopping efficiency is improved, and the signal S is increased. Therefore, by taking advantage of this effect, further miniaturization and higher accuracy of the surface electrometer can be realized.

Next, FIG. 3 for the second embodiment of the present invention
And it will be described with reference to FIG.

FIG. 3 is a diagram showing the surface potential meter of a second embodiment of the present invention, (a) shows the plan view, (b) is a side sectional view. Figure 4 is a diagram showing a conventional example corresponding to FIG. 3 of the second embodiment, (a) shows the plan view, (b) is a side sectional view.

In FIGS. 3 and 4 , the basic structure of this embodiment is thinner than that shown in the first embodiment.
4 (b) (thickness indicated by h) is created, and the content is explained in Japanese Patent Application No. 3-71388 filed by the present applicant (the schematic diagram is shown in FIG. 8 ). .

Therefore, when such a basic structure is adopted, the thickness f of the blade is designed to be considerably small, and the signal incident on the electrode from the object is inevitably reduced considerably. Was particularly desired. As in the first embodiment, the second embodiment is characterized in that the window of the shield case 7 is widened and the surface of the blade 5 of the pitch 2 is attached to the position of the outer wall surface of the shield case 7. With the above configuration, the fifth embodiment has the same operation and effect as the first embodiment.

Next will be explained with reference to FIGS. 5 and 6 a third embodiment of the present invention.

FIG. 5 is a diagram showing a third surface potential meter of an embodiment of the present invention, (a) shows the plan view, (b) is a side sectional view. Figure 6 is a diagram of a conventional example surface potential meter corresponding to FIG. 5, (a) plan view, (b) is a side sectional view.

In FIG. 5 , the pitch 2 used in the third embodiment differs from the fourth and fifth embodiments in the plane of the pitch, and is parallel to the plane in which the two plates of the pitch 2 are arranged. It has become. The plane of the blade 5 at the tip is perpendicular to this. Since the piezoelectric element 3 is mounted on the plane of the pitch 2 as shown in FIG. In the third embodiment, similarly to the first and second embodiments, the window of the shield case 7 is widened, and the surface of the blade 5 of the pitch 2 is mounted in accordance with the position of the outer wall surface of the shield case 7. There is a similar effect.

[0029]

As described above , according to the present invention,
Shortening the distance between the target object and the electrode by using a pitcher with chopping blades as chopping means, and matching the surface of the pitcher blade with the position of the outer wall of the shield case at the window part of the shield case Becomes possible,
The signal component induced in the electrode increases, and the miniaturization and high accuracy of the surface voltmeter can be realized.

[Brief description of the drawings]

FIG. 1 is a diagram of a surface voltmeter according to a first embodiment of the present invention.

FIG. 2 is a conventional diagram corresponding to the first embodiment of FIG. 1 ;

FIG. 3 is a diagram showing a surface voltmeter according to a second embodiment of the present invention;

FIG. 4 is a diagram showing a conventional example corresponding to FIG. 3 of the second embodiment.

FIG. 5 is a diagram showing a surface voltmeter according to a third embodiment of the present invention.

6 is a diagram of a conventional example surface potential meter corresponding to FIG. 5

FIG. 7 is a perspective view of a conventional surface electrometer.

FIG. 8 is a cross-sectional view of the surface voltmeter described in Japanese Patent Application No. 3-71388.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 electrode 2 pitch 3 piezoelectric element 4 pitch fixing stand 5 blade 6 sensor substrate 7 shield case 8 window 10 blade vibration direction S electric flux line 101 drum

Claims (1)

(57) [Claims] 1. A measurement electrode facing a surface of a target object, a conductive shield case having a window between the target object and the measurement electrode, and the measurement from the target object through a window of the shield case. A chopping means for cutting and opening lines of electric force incident on the electrode, wherein the chopping means comprises: a chopping means, wherein the measuring electrode induces an AC voltage having an amplitude corresponding to a surface potential of the target object. A surface voltmeter having a pitch provided with a blade for adjusting the pitch of the sound, wherein the surface of the pitched blade is aligned with and engaged with the position of the outer wall surface of the shield case window.