JPS5915265A - Moving speed measuring device of photosensitive drum - Google Patents

Abstract

PURPOSE:To detect an exact moving speed of the surface of a photosensitive drum, by measuring a displacement quantity of charge induced by a detecting electrode in accordance with an electrostatic charge distribution provided to the photosensitive drum. CONSTITUTION:Picture information is not exposed on a recording body 3 of a photosensitive drum 10, exposure is given through an image forming lens 12 from a detecting light source 11, and also a detecting electrode 13 is placed on the recording body 3 being distance at a prescribed distance from an exposure position, so that an output of the detecting light source 11 can be compared with an output of the detecting electrode 13. The detecting light source 11 flickers at an eqeal period, and a periodical charge distribution is formed on the recording body 3, but in case when a moving speed V is uneven, the formed charge distribution does not become an equal period, and also a current i(t) flowing to the detecting electrode 13 does not become an equal period. Accordingly, unevenness of the moving speed V can be detected by detecting a phase difference of a signal applied to the detecting light source 11 and the current i(t). when raising the accuracy, it can be attained by shifiting slightly the detecting electrode 13 in the direction of the speed V and arraying plural pieces.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a photoconductor that detects time-series information and spatial image information given to a photoconductor drum of a copying machine as an electric signal 5 and measures the moving speed of the photoconductor drum. This invention relates to a drum movement speed measuring device.

In a copying apparatus such as a laser beam printer, if there is unevenness in the moving speed of a photosensitive drum, which is a scanned medium, the resulting image will have irregular pitch intervals between scanning lines, resulting in an unsightly image. Several means are known for detecting this rotational unevenness, but each has its advantages and disadvantages.

For example, although it is possible to detect the rotational angular velocity using a rotary encoder, if the photosensitive drum has eccentricity, it is impossible to accurately detect the moving velocity of the surface.

An object of the present invention is to accurately detect the moving speed of the surface of the photoreceptor drum by measuring the amount of charge displacement induced on the detection electrode by the electrostatic charge distribution applied to the photoreceptor drum. It is an object of the present invention to provide a photoconductor drum movement speed measuring device, the gist of which is to provide a photoconductor tram consisting of an insulator and a conductor in close contact with the insulator, and a photoconductor tram that measures the photoconductor drum according to given information. means for forming an electrostatic charge distribution on the photoreceptor drum; an electrode arranged to face the insulating surface of the photoreceptor drum for detecting the electrostatic charge; and means for comparing given information with the detected electrostatic charge. It is characterized by comprising the following.

FIG. 1 shows a detailed explanatory diagram of the present invention, in which given information is transferred to a recording body 3 consisting of a film of an insulator 1 and a conductor 2 in close contact with each other.
This is an example of giving an electrostatic charge distribution to the electrostatic charge distribution, and is known as an electrophotographic process. Here, the insulator 1, including the photoconductive material, is one that can maintain a given electrostatic charge distribution for a non-zero time under the following conditions. The insulator 1 is a photoconductive material such as cadmium sulfide (CdS), and when the recording medium 3 is in a dark area as shown in FIG. A static charge distribution is given. A given electrostatic charge distribution is maintained in the form of capacitance by charges of opposite polarity flowing into the interface 2a between the insulator l and the conductor 2 by the conductor 2. Next, (b
), bright and dark exposure is applied to the recording medium 3 according to the information provided by the exposure section 5. As a result of this exposure, the resistance of the insulator 1 decreases and the static charge disappears in the portions where the light is pushed open. Therefore, an electrostatic charge distribution corresponding to the given information is formed on the surface 1a of the insulator 1. If the input information at this time is a time-series signal, the information is stored in the recording medium 3 by modulating the exposure with the time-series signal, and if it is spatial image information, the information is stored in the recording body 3 by the reflected light that illuminates the image. Ru.

Here, as shown in FIG. 2, the recording body 3 is moved to the electrode 6 at a speed V.
move below. At this time, if no exposure is given, the insulator 1 is considered to be an electrical insulator, and the electrode 6 is the insulator 1.
The electrostatic charge distribution on the surface 1a is not changed by the electrode 6 because it does not directly contact the recording medium 3 via the air layer or the insulating layer with the surface 1a of the electrode 6.
is grounded through a minute resistance R between it and the conductor 2, but for convenience of explanation, it will be assumed that R=O.

In this way, since the potentials of the conductor 2 and the electrode 6 are both O, the total amount of charge on the surface 1a of the insulator l in the area of the electrode 6ρ is Qs', and the charge induced in the electrode 6 is If q, then q --(Ct/Ci) ・Qs ・・
・There is the relationship (1). Here, C1 is surface 1a and surface 2
a ■ j Glue 1st area capacitance, Ca to electrode 6
Assuming the capacitance per unit area between and surface 1a, C
t is the combined capacity of these 1/(1/C:i+1/
It is represented by Ca).

First, if the electrode 6 is infinitely continuous in the V direction shown in FIG. vb
-(2). Here, Q(X) is the charge distribution in the X-axis direction on the surface 1a in a coordinate system with the V direction as the X-axis, so-called surface density. b is the length of the electrode 6 in the direction perpendicular to the V direction, and if the origin of the The current i (t) flowing from is 1(t)
= (Ct/C:i) v b ・Q(x = −
v t )=-Ctvb-V(x=-vt)-(3
). Here, V(X) = Q(X)/Ci is the surface 1aJj7).

It is a potential distribution. Therefore, by knowing this current 1(t), it is possible to detect the potential distribution V(X) on the surfaces 1aJ,H.

Next, when the electrode 6 has a finite length a in the V direction,
Considering the charge flowing out from under the electrode 6, 1(t) = Ctv b [V(x = −v t )
−V(x = −v t + a)] ・”(
4) is obtained. That is, the current 1(t) has a potential distribution V(x
). When l/a is larger than the spatial frequency of the potential distribution V(X) on the surface 1a of the insulator 1, 1(t)=Ctv a b ・((dV/dx)(x = −v t))
-(5), and the given information Q(x) = C
The differential value of 1-V(X) can be detected.

When the resistor RNO is used, a time constant Ct-R is required to charge and discharge the electrode 6. Therefore, the conditions for detecting the current 1(t) in equations (4) and (5) are Ct-R≦a/
v-(6). In addition, even if the current is 3, if the reverse current is bypassed by one diode D'4 as shown in Fig.
) has the form of an expression.

゛Therefore, in unimplemented examples, the moving speed V can be determined from the charge distribution Q(x) itself or from the differential value d Q(x)/d
Direct detection is also possible from x. Also, (3), (5
) As is clear from the equation, since the relative velocity V between the electrode 6 and the surface 1a is proportional to the current 1(t), a large current 1(t) can be extracted by increasing the velocity V. One possible method is to rotate the electrode 6 as shown in FIG.

FIG. 5 shows an embodiment of the present invention, in which the moving speed V of the photosensitive drum 10 in a normal electrophotographic process is measured. When recording information on the photoreceptor drum 10 by slint exposure or scanning exposure, the photoreceptor drum 10
If there is any unevenness in the moving speed (2), unevenness will occur in the scanning line pitch of the recorded image. To measure this moving speed V, the recording medium 3 at the edge of the photosensitive drum IO can be used. “Edge record 3”
Second, the image information is not exposed to light, but can be exposed from the detection light source 11 through the imaging lens 12. Also, on the recording body 3 separated by a predetermined distance from the exposure position,
A detection electrode 13 is arranged. The output of the detection light source 11 and the detection electrode 13 are controlled by a circuit configuration not shown.
The output can be compared with the output of

The detection light source 11 blinks at regular intervals to form a periodic charge distribution on the recording medium 3. However, if the moving speed V is uneven, the charge distribution that is formed does not have equal periods, and the current 1(t) flowing through the detection electrode 13 also does not have equal periods. Therefore, the signal given to the detection light source 11 and the current 1 (
By detecting the phase difference of t), it is possible to detect the unevenness of the moving speed (2). In order to accurately detect this moving speed V, as shown in FIG.
It is good to arrange multiple pieces slightly shifted in the direction of .

In the embodiment shown in FIG. 5, since the moving speed V of the photoreceptor drums 10 and 10 can be directly detected, it is also possible to detect irregularities in the moving speed V caused by eccentricity of the rotating shaft of the photoreceptor drum 10, errors in the drum radius, etc. . The moving speed V can be kept constant by foot-banking the detected unevenness to the drive mechanism of the photosensitive drum 10. Note that i (as is clear from the explanation in j), a photoconductive material is used instead of the conductor 2, the detection electrode 13 and the insulator 1 are made transparent, and the detection electrode 13 is used in a bright place. You can also get the same effect.

As explained above, according to the photoreceptor drum movement speed measuring device according to the present invention, it is possible to extract the differential signal of the given information, and it is also possible to directly read out the electrostatic charge distribution given to the recording medium. The moving speed can be measured from these detections, and this measuring device can be effectively used to detect unevenness in the moving speed of the photoreceptor drum of an electrophotographic device.

[Brief explanation of drawings]

1(a), (b), 2, 3, and 4 are principle explanatory diagrams of the photosensitive drum movement speed measuring device according to the present invention, and FIG. 5 is a configuration diagram of an embodiment thereof. It is. Symbol l is an insulator, 1a is a surface, 2 is a conductor, 3 is a recording body, 4 is a corona electrode, 5 is an exposure part, 6 is an electrode, 10 is a photosensitive drum, 11 is a detection light source, 12 is an image forming lens, 13
is a detection electrode. Patent applicant Canon Co., Ltd.

Claims (1)

[Claims] 1. A photoreceptor drum made of an insulator and a conductor in close contact with the insulator, and means for forming an electrostatic charge distribution on the photoreceptor drum according to given information. , comprising an electrode arranged to face the insulating surface of the photoreceptor drum and detecting the electrostatic charge, and means for comparing the given information and the detected electrostatic charge. 2. A photosensitive drum moving speed measuring device according to claim 1, wherein the means for forming an electrostatic charge distribution on the photosensitive drum is performed by exposing optical information. Measuring device. 3. The photosensitive drum movement speed measuring device according to claim 1, wherein the electrostatic charge detected by the electrode is detected in the form of a differential value. 4. The given information and detection 2. The photosensitive drum moving speed measuring device according to claim 1, wherein the means for comparing the electrostatic charge generated by the electrostatic charge is carried out by detecting a phase difference.