JPS6037571A - Control device for copying machine - Google Patents

Abstract

PURPOSE:To maintain always a copied image at adequate density by detecting the quantity of the light reflected from an original and the surface condition of a photosensitive body and controlling or limiting separately copying conditions by the two detection signals. CONSTITUTION:The signal from a potenstial sensor which detects the potential of a photosensitive body is inputted to a terminal P1 and is inverted and amplified by an operational amplifier Q5 via a MIller inregrator consisting of a resistor R8, and operational amplifier Q3 and a capacitor C1. The light reflected from an original is detected via a photodetecting sensor 9 by a Miller integrator consisting of a resistor R4, an operational amplifier Q3 and a capacitor C1. If the output voltage from the Q5 is smaller than the output voltage from the Q2, the exposure of an exposing lamp is controlled by the output voltage from the Q5 and if the output voltage from the Q5 is larger than the output voltage from the Q2, the exposure is limited by the output voltage from the Q2. The controlled and limited voltages are inputted from a terminal P4 to a control circuit for quantity of light. The copied image is thus always maintained at the adequate density.

Description

Detailed Description of the Invention [Technical Field] The present invention is directed to a control device for a copying machine, and in particular, to a control device for a copying machine, and in particular, to constantly check the proper density of a copied image by measuring the density of a document using two types of detection means with different detection characteristics. The present invention relates to a control device that can be obtained.

[Prior art]

Some copying machines are equipped with an original density detection means that detects the density of the original, and based on the signal from this detection means, the amount of exposure to the photoreceptor is controlled, and the # degree of the copied image is automatically adjusted. I
It is adjusted to i1E 6 degrees.

Conventionally, as a control device for a copying machine equipped with this type of document density detection means, for example, the following has been proposed.

That is, the document is irradiated by an exposure lamp for document irradiation, the amount of light reflected from the document is detected by a light receiving element, the density of the document is measured, and the amount of exposure to the photoreceptor is controlled based on this measurement result. An automatic exposure (AE) control device is known.

However, the control device configured in this manner has the disadvantage that it is not always possible to accurately control the amount of exposure to the photoreceptor due to the effects of temperature drift of the light receiving element, temperature characteristics of the photoreceptor, humidity characteristics, etc. .

In addition, the density of the original is measured by detecting the potential of the photoreceptor using a potential sensor, and the amount of exposure to the photoreceptor is controlled based on this measurement result, and the density of the copied image is automatically adjusted. Some devices are known that adjust the density to an appropriate level, but with a control device configured like this, the portion of the photoreceptor where the potential can be detected by the potential sensor is limited, and the density of a portion of the original is limited. This method has disadvantages, such as not being able to obtain an appropriate density depending on the document.

[Purpose of the invention]

The present invention has been made to eliminate the above-mentioned drawbacks of the conventional art. and a second detection means for detecting the surface condition, the copying conditions are controlled based on the detection signal of one of these two detection means, and the copying conditions are limited by the remaining detection signal of the other detection means. It is an object of the present invention to provide a control device for a copying machine that accurately controls the amount of exposure from an exposure lamp and always provides a copy image with an appropriate density.

〔Example〕

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

FIG. 1 is a schematic diagram showing the basic configuration of an electrophotographic copying machine according to the present invention. In the figure, l is a contact glass serving as an original platen on which an original is placed, and an original placed below the double contact glass l is shown. An exposure lamp for irradiation (halogen lamp); 3.4 and 5.6 are mirrors constituting an optical system for projecting the reflected light from the original onto the drum-shaped rotating photoreceptor 7; 8 is an imaging lens; 9 .10 is a light receiving sensor (first detecting means) and a potential sensor (second detecting means) constituting the document density detecting means for detecting the density of the document, and the light receiving sensor 9 is arranged near the optical system. The potential sensor 10 is arranged near the surface of the photoreceptor 10. 11 is the light receiving sensor 9
and a control circuit which inputs a detection signal from the potential sensor IO, and together with a light amount control circuit to be described later, constitutes an adjusting means for adjusting the amount of exposure of the exposure lamp 2. 12 is a developing device installed around the photoreceptor 7, 13 is a transfer electrode, +4
．． 15.16 is a charger.

FIG. 2 is a block diagram showing the basic configuration of the control device of the copying machine, and numeral 11 in the figure is a light amount control circuit that controls the amount of exposure of the exposure lamp 2 in accordance with a signal from the control circuit 11 described above.

Based on the above configuration, the operation will be explained below. Note that since the normal copying process is well known, detailed explanation will be omitted.

The surface of the photoreceptor 10 is uniformly charged by corona discharge by chargers 14, 15, 16, and then an electrostatic latent image corresponding to the original is formed by light reflected from the original. This latent image is
Next, a developer is applied in the developing device 12 to visualize the image. Then, although not shown, the image is transferred onto copy paper wrapped around a transfer drum by the transfer electrode 13, and the toner is fixed by a fixing device (not shown), thereby making it possible to obtain a copy of the original. .

Here, the process of forming an electrostatic latent image of a document on the photoreceptor 7 will be explained in detail.

The electrophotographic copying machine shown in FIGS. 1 and 2 is equipped with an original density detection means for detecting the density of the original.
An automatic density setting mode is provided in which the density of the copied image is automatically adjusted to an appropriate density based on a detection signal from the detection means. That is, a light receiving sensor 9 that detects the amount of light reflected from the original and a potential sensor 10 that detects the surface condition of the photoreceptor 7 are provided, and these two sensors 9, 1
Based on the detection signal from one of the sensors 0, for example, the potential sensor 10, copying conditions such as the amount of exposure from the exposure lamp 2 are controlled to make the copied image have an appropriate density. The detection signal from the remaining light receiving sensor 9 is the potential sensor! When the difference between the detection signal from 0 and the detection signal exceeds a predetermined value, the copying conditions are limited. (2) By using 0, an AE control device is configured that corrects errors in document density detection and optimally controls the exposure amount of the exposure lamp 2.

FIG. 3 shows the input/output voltage characteristics of the light amount control circuit 17 shown in FIG. The amount is controlled. Further, FIG. 4 is a diagram showing the relationship between the amount of exposure to the photoreceptor 1, the surface pattern of the photoreceptor 7, and the density of the original. For example, if the voltage applied to the exposure lamp 2 that illuminates the original is 60V, and the density of the original is 0.07 (same density as a standard white plate), the potential on the surface of the photoreceptor 7 will be OV, and the density of the original will be OV. If it is 0.3 (gray), the potential on the surface of the photoreceptor 7 is 300.

FIG. 5 is a diagram showing the positions of the document whose density is detected by the sensors 9 and 10. A potential sensor 10 detects a portion of the width of the document placed on a contact glass 1 serving as a document table, and a light receiving section 9 detects a portion of a width of 8.
The potential sensor 1 is configured to detect
This indicates that the range detected by the light receiving sensor 9 is wider than the range detected by 0.

FIG. 6 is a circuit diagram showing a specific example of the control circuit 11 shown in FIG. 2. In the figure, gx to TL14 are resistors, C1
and 02 are capacitors, Dl is a diode, Ql to Q6 are OPAMPs (operational amplifiers), and 'I'r1 to Tr4 are FETs) transistors.

A detection signal from the potential sensor 10 is inputted from a terminal P, and the potential of the photoreceptor 7 is measured by a first mirror integrator 118 constituted by a resistor R8, an OPAMPQ3, and a capacitor C1.

The amount of reflected light from the original is measured by a light receiving sensor 9 such as a photodiode.
a second Miller integrator 1, which is detected by a resistor R,4, OPAMPQ2 and a capacitor C2.
1b.

Before measuring the density of the original, a reset signal is input from the terminal P2, and is reset by the first integrator 118 FET transistors Tr4 and the resistor R1. Then, when the density of the original is measured based on the detection signal from the potential sensor 10, the original is scanned with the amount of light from the exposure lamp 2 according to the measurement result, and a copied image with an appropriate density is formed.

Miller integrators +1a and Ilb are connected to FET transistors Tr and Tr, respectively, and only when measuring the density of a document, the gate potential of each is set to H (Hi) by a measurement timing signal from terminal P3.
g h ) level, the resistance between the drain and the source becomes smaller. And the respective resistance aS, 几4 and conduit? Integration is performed using an integration constant determined by the values of 0+ and 02.

A detection signal from the potential sensor 10 that detects the potential of the photoreceptor 1 is integrated by a first mirror integrator 118, and is output to the OP.
It is inverted and amplified by AMPQs.

This inverted and amplified output voltage of OPAMPQ5 is
If the output voltage of OPAMPQ2 is smaller than the output voltage of OPAMPQ2 corresponding to the amount of reflected light from the original measured by the mirror integrator 11b, the exposure amount of the exposure lamp 2 is controlled by the output voltage of the integrator +18, and the output voltage of the integrator +18 is Integrator 11
When the output voltage of the integrator 11b is larger than the output voltage of the integrator 11b, the exposure amount of the exposure lamp 2 controlled by the output voltage of the integrator 118 is limited by the output voltage of the integrator 11b. That is, the exposure amount of the exposure lamp 2 is controlled based on the detection signal from the city's No. 1 sensor 10, and the exposure amount is limited based on the detection signal from the light receiving sensor 9. A control signal is then output to the light amount control circuit 11 from the terminal P4. Note that the exposure amount of the exposure tube 2 is controlled based on the detection signal from the light receiving sensor 9, and when the difference between the density of the original and the density detected by the potential sensor 10 exceeds a predetermined value, the potential sensor lO The exposure amount of the exposure lamp 2 may be limited based on the detection signal from the exposure lamp 2.

FIG. 7 is a diagram showing the relationship between the density integration amount (voltage) corresponding to the density of the original, which is subjected to the fine integration by the integrators 11a and 1 lb, and the density of the original. When the density of the original detected by the potential sensor 10 and the light receiving sensor 9 is the same value, the integration constants of j are set so that the output of the integrator 11b is 0 and the output of the integrator +18 is D. This is set in advance, and the exposure amount of the exposure lamp 2 is always controlled based on the detection signal of the potential sensor 10 when documents of the same density are detected. Further, as shown in FIG. 5, although the detection position of the document that can be detected by the potential sensor 10 has a small area, if the density of the detected document is significantly different from the density of the document detected by the light receiving sensor 9, By limiting the exposure amount of the exposure lamp 2 based on the detection signal from the light-receiving sensor 9, errors in document density measurement can be corrected, and accurate exposure control can be performed to always obtain a copied image with an appropriate density.

〔Effect of the invention〕

As described above, according to the present invention, the document density detection means for detecting the density of the document is divided into the first detection means for detecting the amount of reflected light from the document and the second detection means for detecting the surface condition of the photoreceptor. The copying conditions are controlled based on the detection signal of one of these two detection means, and the copying conditions are limited by the detection signal of the other one, so that the density of the original can be controlled. It is possible to correct errors in measuring , and therefore, it is possible to accurately control copying conditions such as the exposure amount of an exposure lamp, and there is an effect that a copied image with an appropriate density can always be obtained.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the basic configuration of an electrophotographic copying machine according to the present invention, FIG. 2 is a block diagram showing the basic configuration of a control device according to an embodiment of the present invention, and FIG. 3 is an input/output diagram of a light amount control circuit. Figure 4 is a diagram showing the voltage characteristics, Figure 4 is a diagram showing the relationship between the amount of exposure to the photoreceptor, the surface potential of the photoreceptor, and the density of the original, and Figure 5 is a diagram showing the position of the original where the density is detected by each sensor. ,
FIG. 6 is a circuit diagram showing a specific example of the control circuit, and FIG. 7 is a diagram showing the relationship between the density integral amount depending on the density of the original and the density of the original. 2...Exposure lamp...Photoreceptor 9...Light receiving sensor (first detection means) lO...
... Potential sensor (second detection means) 11 ...
- Control circuit 11...Light amount control circuit Note that the same reference numerals in the drawings indicate the same or equivalent parts. wise calyx

Claims (1)

[Claims] In a control device for a copying machine equipped with an automatic density setting mode that automatically adjusts the density of a copy image to an appropriate density based on a detection signal from an original density detection means for detecting the density of the original, the original density detection means comprises: It is composed of a first detection means for detecting the amount of reflected light from the document and a second detection means for detecting the surface condition of the photoreceptor, and the detection method is configured based on the detection signal of one of these two detection means. A control device for a copying machine, characterized in that the copying condition is controlled and the copying condition is limited by the remaining detection signal of the other side.