JPH0466031B2 - - Google Patents

Description

Detailed Description of the Invention Technical Field The present invention relates to an image forming apparatus such as a copying machine, and in particular has an image density automatic adjustment function that measures the density of a document and determines appropriate image forming conditions during image formation based on the density. It is related to the device.

BACKGROUND OF THE INVENTION In the past, density adjustment in copying machines was generally performed by a manually variable aperture lever, e.g., from F1 to F9, or by a step-like selection means, e.g., selecting "dark,""normal," and "light." was.

However, in the case of these manual density adjustments, if the original has a dark background color, such as newspaper, diazo copy paper, color paper, etc., if the density adjustment is set to the standard state and it is copied, the development of the copying device will be delayed. In the case of a single color (for example, black), a phenomenon called "fogging" occurs in which the background color of the document is the same color as the text and the entire surface of the copy paper appears uniformly smudged. On the contrary, in the case of an original with extremely low character density, for example, characters written lightly with a pencil, a phenomenon occurs in which the characters are skipped.

To avoid this, in the former case, generally, the concentration setting volume is adjusted based on a certain degree of anticipation.
Set to F8-F9 (F3-F4 in the latter case) position, or "light" (in the latter case "dark")
I was setting up a copy.

However, even in this case, in order to obtain an optimal copy, the user must rely on the experience gained from copying the same type of document multiple times, which may lead to the occurrence of copy errors.

In order to solve these problems, copying machines with an automatic density adjustment function have been developed in recent years. This type of apparatus generally automatically adjusts the density by reading the density of the original and automatically adjusting the exposure amount or the development level of the developing means.

In this case, if the background color of the original is detected perfectly, the density adjustment will be appropriate.
It is very difficult to detect the background color of various types of originals, and the average density of the originals is generally detected. Therefore, even when automatic density adjustment is performed, it is difficult to cover all types of documents, and there is a possibility that copy errors may occur. Furthermore, the appropriate density level set by the copying device may be different from the level desired by the user. For these reasons, even in copying machines with automatic density adjustment, there are still cases where manual density adjustment must be performed.

Purpose The present invention has been made in view of the above points, and an object of the present invention is to provide a copying apparatus with improved operability of the density adjustment function during interrupt copying.

Embodiments Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 shows a sectional view of a copying apparatus to which the present invention is applicable.

1 is the main body of the copying machine. 33 is a photosensitive drum that rotates clockwise as indicated by the arrow. 50 is the main motor, including 33, 44 fuser, and 41
A chain (not shown) performs all driving including the transport section, 38 paper feed rollers, etc., and the optical system drive including 21 document illumination lamps. Further, 31 is a high voltage charger. As a result, charges are charged on the photosensitive drum 33. Then, after being exposed to light at point A and forming an electrostatic latent image, toner is attached to the developing roller 34 in the developing device 29 to form a visible image. Then, the toner image is transferred to the transfer paper in the transfer charger 40. Prior to this, the toner image is transferred from the cassette 37 to the paper feed roller 38 at a timing such that the leading edge of the toner image and the leading edge of the transfer paper coincide. The paper is fed by the rotation of the register rollers 39, and the paper is sent out by the registration rollers 39. At this time, the original is exposed to light by the original illumination lamp 21, and the optical system including 21 scans the original in the direction of the arrow and passes through the reflecting mirrors 24, 25, 27, and 28, and the lens 26 to expose the 33 light. An image is formed at point A on the drum, and exposure is performed over the entire surface of the document.
Reference numeral 48 denotes a registration sensor, and this sensor causes the registration roller 39 to start rotating so that the leading edges of the images are aligned as described above, and the AE leading edge is also aligned, and the AE It also generates a reference signal during measurement.
22 and 23 are reversal sensors, and 22B is
Cassette 37 gas mall size (e.g. B5, A
4 size, etc.) is the optical system inversion position. On the other hand 23
is the optical system inversion position of a large size (for example, A3 size, etc.).

After the transfer, the photosensitive drum 33 is cleaned by the cleaner brush 36 of the cleaner section 35 and then electrostatically cleaned by the eraser 32 in preparation for the next charging. On the other hand, the transfer paper on which the toner image has been transferred is separated from the photosensitive drum and is transported by a paper transport section 41 toward a fixing device. At this time, the conveyance continues while being drawn downward by the suction fan 42. After being fixed by the fixing roller 44, the completed copy paper is eventually discharged to a paper discharge tray 47 by a paper discharge roller 46. 45 is a web motor that winds up a web for cleaning the fixing roller 44. 43 is a power transformer; 30
is a heat exhaust fan that releases heat from the 21 lighting lamp. By the way, 49 is a potential sensor for measuring the surface potential of the photosensitive drum 33. Generally, the surface potential of a photosensitive drum is as shown in FIG.
The drum surface potential is charged to V ₀ by corona discharge. Then, dark decay occurs until the exposure point A is reached. At exposure point A, the original is illuminated by the original illumination lamp 21 and exposed to light that is generated by reflection and corresponds to the density of the original. At this time, if the original is light, the amount of reflected light is large and the second
The surface potential decreases to around _VL shown in the figure. On the other hand, when the original is dark, the amount of reflected light is reduced, and it becomes possible to determine the darkness of the original by reading the surface potential.

The following describes how to determine the density of the original and control the original light intensity or developing bias in order to obtain a properly reproduced image.
It is called AE. The same thing can be done by directly measuring the amount of reflected light from the original with a photo sensor and determining the lightness and darkness.
This is also called AE.

FIG. 3 is a plan view showing the operation section of the copying machine 1. FIG. In the figure, 201 is a magnification selection key, which is used to set a desired magnification, and the set magnification is displayed on a magnification display LED 206. Reference numeral 202 is a cassette selection key that allows selection of two types of cassettes. A cassette size display LED 220 displays the cassette size of the selected cassette. 203 sets the AE mode with the AE selection key, and also displays the AE mode of 221.
The LED lights up. 221 is the DOWN key, 204
is the UP key, which allows you to change the copy density by a predetermined amount, one step at a time. At the same time, the manual mode is selected, and the manual mode display LED 222 lights up. 215 is the concentration display
174 light intensity intervals corresponding to 0.5 aperture between F1 and F9
Consists of LEDs. The DOWN key 221 shifts 0.5 to the left, and the UP key 204 shifts 0.5 to the right. When the power is turned on, after copying, or AE
When the key 203 is turned on, the LED is normally displayed at the F5 position.

207 is the number of sheets set with the number of sheets setting key is 20
8 is displayed on the number display. 209 is a copy key, and by pressing this, a copy operation is started. 210 is a clear/stop key for clearing the set number and stopping copying. 214
is an interrupt key, and when turned on, the interrupt mode is selected and the interrupt indicator lamp 213 lights up. Furthermore, when the interrupt key is pressed again, the interrupt mode is canceled.

217 indicates that the toner has run out. The toner lamp 218 indicates that the paper is out, and the no-paper lamp 219 indicates that the manual feed mode has been selected. Manual feed lamp, 220 is JAM indicator lamp,
221 indicates that there is no counter. This is a counter warning lamp.

Next, control of A of the present invention will be explained with reference to FIG. 4 and subsequent figures.

In FIG. 4, 33 is a drum, 49 is a potential sensor provided near the drum 33, and its output is connected to a potential measuring device 522. 100 is a control circuit including a one-chip microcomputer 100-b built in ROM and RAM, and an A/D
Conversion device 100-a D/A conversion device 100-c
including. 533 is a lamp control circuit, and 21 is an illumination lamp connected thereto.

Reference numeral 101 indicates a key group 102 included in the operating section shown in FIG. 3 described above, and a display circuit included in the operating section shown in FIG. 3 described above. Inputs from the key group 101 are input to the control circuit 100 using a normal key matrix method, and the display circuit uses a dynamic lighting circuit.
The LEDs and lamps can be turned on at will using the lamp lighting circuit.

103 is an optical system driving device, and 104 is an optical system position sensor, both of which are connected to the control circuit 100.

The surface potential of the drum 33 is detected by a potential sensor 49 and further converted into an appropriate analog value output VA by a surface potential measuring device 522.

This analog value is digitized by the A/D conversion value 100-a connected thereto, and the microcomputer 100-b can take in the digital value. That is, the microcomputer 100-b is configured to be able to take in the surface potential of the drum 33 at any timing. On the other hand, microcomputer 100
The output of -b is connected to D/A converter 100-c, and its analog output voltage V _A ' is supplied to lamp control circuit 533. The lamp control circuit 533 applies a voltage corresponding to the analog voltage V _A ' to the illumination lamp 2.
1. Therefore, the microcomputer 100-b arbitrarily sets the voltage to be supplied to the illumination lamp 21. In other words, the amount of light for image exposure can be set.

Reference numeral 103 denotes an optical system drive device connected to the control circuit 100, which can drive the optical system forward/backward. Further, 104 is a position sensor of the optical system connected to the control circuit 100, which outputs a predetermined output according to the position of the optical system.
0 allows the optical system to stop at a predetermined position or return to the home position. Also, it is possible to sense when the optical system has arrived at a predetermined position.

An embodiment of the AE control of the present invention will be described below. First, a case will be described in which the AE key 203 is pressed and the AE mode is selected.

When the copy button is pressed, the drum 33 is rotated and at the same time the optical system is advanced to a predetermined position. Also, at this time, the illumination lamp 21 is turned on at a standard voltage.

Next, the optical system begins to move backwards (bliss scan), and at a predetermined timing, the microcomputer 10
0-b starts sampling the surface potential Vp of the drum 33.

Multiple days depending on the signal from the optical system position sensor 104
Sample VD and calculate the average value _VDM . This sampling is performed when the latent image on the drum corresponding to a predetermined position on the document reaches the surface potential sensor, so that the average value V _Dn corresponding to the density at a predetermined position on the document is It is becoming possible to obtain it.

After the optical system returns to the home position, the illumination lamp 21 is turned on at a lighting voltage whose standard value is corrected according to the value of V _DM , and the optical system is advanced to perform image exposure. At this time, the concentration is displayed according to the lighting voltage.
FIG. 5 shows the relationship between V _DM and the illumination lamp correction value, and FIG. 6 shows the relationship between the lighting voltage and the density display value in FIG.

For example, when V _DM =75V, that is, for a standard original, the correction value=0 and the illumination lamp is lit at the initial setting value during exposure of the original.

Also, at this time, the display becomes "F5".

In addition, in the case of manuscripts with background fog such as newspapers,
V _DM is about 400V, and the illumination lamp during exposure is turned on at the standard value +5V, increasing the light intensity and eliminating background fog, allowing a proper image to be obtained.

As described above, by measuring the surface potential corresponding to the density of the original using Briscan and controlling the lighting voltage of the illumination lamp based on the value, an appropriate copy image can be obtained regardless of the type of original.
Also, a density display corresponding to the density of the original is displayed.

On the other hand, when the AE mode is not selected, the drum begins to rotate at the same time as the copy key is pressed, and the illumination lamp 21 is turned on at the voltage set by the density adjustment means.Then, the optical system begins to move forward and exposes the image. Move on to Sukyan.

FIG. 7 is a flowchart regarding the light amount setting display among the operations of the subject apparatus.

Sections () show how to set the appropriate light intensity using AE measurements, sections () show correction methods using two types of shift keys, sections () show how to switch to AE, and sections () show how to set the light intensity using the interrupt key. The method is shown in parentheses, and the light amount setting method using auto clear (return to standard mode) is shown in parentheses.

The flow will be explained step by step below.

() shows the aperture settings for the appropriate light intensity based on AE measurements.

When AE copy is executed using the copy start key, an AE correction value is calculated by measuring the drum potential a predetermined number of times during AE measurement, and then the document is irradiated with the corrected light intensity (referred to as AE light intensity) and AE copy is performed. Start.

At the same time, the aperture value is converted from the correction value and displayed on the copy density display section 215 in FIG.

() shows the light amount setting operation using the shift key.

When the shift key is pressed during copying, the AE mode is immediately canceled, and the exposure light amount is changed by reshifting after 0.5 in the correction direction.

During standby, if it is in AE mode, the AE flag is set and the mode shifts to manual mode, and the aperture value does not change.

Furthermore, if the mode is already in manual mode, shifts are executed at predetermined time intervals.

Here, the backward timer is a timer for shifting the backward value at predetermined time intervals when the shift key 204 or 205 is held down, and the basic step time is set by the shift key 204 or 205.
If the button is not pressed, the corresponding timer is set to the end value and is configured to shift each time the button is pressed. Also, in step e, shift key 20
This prevents the aperture value from shifting when 4 or 205 are pressed at the same time. Also, both ends of the aperture value are regulated by limiters and must be within the range of F1 to F9.

If the shift key 204 or 205 is not pressed, the aperture value is held. () indicates the light amount setting using the automatic density adjustment key.

During copying, changing to AE mode using AE is prohibited.

Also, when not copying, the AE flag is reset and the AE
mode and the rear display becomes F5.

Note that after copying starts and before the first paper feeding, changing to AE mode is allowed.

Furthermore, at the end of copying, a change to the AE mode is permitted when the optical system starts to move back for the final copy of the preset number of sheets.

() indicates the light intensity setting using the interrupt key,
When the interrupt key is input, it is determined whether the interrupt mode is already set, and if it is the normal mode (non-interrupt mode), the mode shifts to the interrupt mode, and the mode classification of AE/manual and the aperture value are changed to the microcomputer 100-. It is stored on the RAM of b.

Also, AE mode is defined as a new mode (AE flag reset), and the aperture display is F5 (standard light intensity).
is selected.

On the other hand, if it is in interrupt mode, this key input cancels interrupt mode and returns to the aperture value of the mode specified before the interrupt (AE/manual).

() shows the light amount setting means by auto-clear operation. The auto-clear timer counts up at a predetermined speed in a flow section (not shown), and when a predetermined time elapses after the last copy is reversed, auto-clear (standard mode return) is performed. At this time, the AE flag is reset, the camera enters AE mode, and the aperture display value shifts to F5 (standard exposure).

As shown in each part of the flow, this auto-clear timer is configured so that it returns to the initial value and restarts the count-up at the end of various key inputs and copying.

Also, if it is in interrupt mode when this auto clear function is executed, it will return to normal mode and then return to AE/F5 mode.

If you turn on the AE key and the UP or DOWN key at the same time, the UP or DOWN key will be given priority for key entry.

Therefore, even if the AE key is malfunctioning, manual operation is possible.

Also, if you turn on the up key and down key at the same time, no key entry will be made.

Effects As explained above, according to the present invention, the AE mode is automatically selected by an interrupt input and the concentration becomes the standard concentration, so that, for example, when you want to select the AE mode, you do not have to press the AE mode selection key. It will be omitted. Furthermore, even if manual mode is desired, the standard density will be set regardless of the density before selecting interrupt mode, so when using a standard original (usually used often), A desired concentration can be easily set.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a copying apparatus to which the present invention can be applied, FIG. 2 is a diagram showing surface potential characteristics, FIG. 3 is a plan view of the operation section of the copying apparatus, and FIG. 4 is a diagram of the copying apparatus. A block diagram showing the control unit. Figure 5 is a diagram showing the relationship between the surface potential average value in AE mode and the lighting lamp lighting voltage correction value. Figure 6 is a diagram showing the relationship between the lighting lamp lighting voltage and display. , FIG. 7 is a flowchart showing the flow of control according to the present invention. In the figure, 1 is the main body of the copying machine, 21 is an illumination lamp, 33 is a photosensitive drum, 44 is a potential sensor, 10
0 is a control circuit.

Claims (1)

[Scope of Claims] 1. Manual density adjustment means for adjusting the copy density by manually selecting one of a plurality of predetermined densities; density detection means for detecting the density of the original; and the density detection means. an automatic density adjustment means for automatically adjusting the density so as to obtain an image with an appropriate density based on a density signal output from the automatic density adjustment means; a first mode for adjusting copy density using the manual density adjustment means; a switching means for switching between a second mode in which the copy density is adjusted using the density adjustment means; a display means for displaying the copy density adjusted in the first mode or the second mode; means for selecting, when the mode is switched to the first mode, the density displayed by the display means in the second mode as an initial value of the copy density to be adjusted by the manual density adjustment means; and a copying operation by interruption. an interrupt means for selecting; and a method for selecting a copy operation using the interrupt so that when the interrupt means is operated to select the copy operation using the interrupt, the copy operation using the interrupt is performed in a second mode regardless of the previous mode. a first control means for selecting the second mode and controlling the display means to display a standard specific density; a canceling means for canceling the selection of the copying operation by the interruption; and the canceling means. If the mode before the interrupt means is operated is the first mode, the first mode is selected and the manual density is set before the interrupt means is operated. a second mode for resetting the density selected by the adjusting means and selecting the second mode if the mode before the interrupting means was operated was the second mode;
A copying apparatus comprising a control means.