JPS61103169A - Image forming device - Google Patents

Abstract

PURPOSE:To make possible the setting of correct image density without generating a wasteful copy even in the case of copying an original having a considerable density difference by detecting the original density and adjusting image forming conditions according to the detected original density then executing copying and displaying the detected original density. CONSTITUTION:A potential sensor 49 measures the surface potential of a photosensitive drum 33. The surface position of the drum is electrostatically charged to VD by corona discharge and is dark-attenuated up to an exposing point A. The original is irradiated by an original illuminating lamp 21 and the light corresponding to the original density generated by the reflection is exposed. The quantity of the reflected light is large and therefore the surface potential decreases down to above VL if the original is light in this stage. The quantity of the reflected light decreases conversely when the original is dark. The varied densities of the original can be identified by reading the surface potential. A control device 100 controls the exposure of the original or developing bias in order to obtain the correct reproduced image by identifying the varied densities of the original.

Description

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

BACKGROUND TECHNOLOGY Conventionally, a copying machine, l! S: There is a place.

In such a copying apparatus, the AE measurement operation is performed prior to or simultaneously with the copy sequence, and
Even if the AE measurement results were inconvenient, a copy would still be made, which could lead to erroneous copies.

Further, the AE measurement is not necessarily all-purpose, and there are some originals (such as originals where only the AE measurement area has an extremely different density than the rest) for which proper measurement cannot be performed.

OBJECTS The present invention has been made in view of the above points, and it is an object of the present invention to provide an image forming apparatus that can prevent the occurrence of copy errors and wasteful consumption of recording materials.

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

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

■ is the main body of the copying machine. 33 is a photosensitive drum that rotates clockwise as indicated by the arrow. 5o is a main motor, which drives all the drives including the photosensitive drum 33, the fixing device 44, the transport unit 41, the paper feed roller 38, and the optical system including the original μs bright lamp 21 using a chain (not shown). This is done through. The drum 33 is simultaneously neutralized by the pre-exposure lamp 32 and the pre-eliminating charger 2, and then corona charged (for example, +) by the negative charger 31. Thereafter, the image irradiated by the illumination lamp 21 is illuminated on the drum 1 at the exposure point A.

At the same time, the secondary charger 4 performs corona charge removal with a polarity opposite to that of AC or - (for example -) to form a high-contrast electrostatic latent image on the drum 33. The electrostatic latent image on the photosensitive drum 33 is then developed by the developing roller 34 of the developing device 29 and visualized as a toner image.

Here, 59 is a blank exposure lamp, which is turned on while the drum is rotating other than when exposing the original, to erase the drum surface charge in the non-image area and prevent excess toner from adhering to the drum. .

In addition, with the same effect, the blank exposure lamp is also turned on during small cassette and reduction copying.

A plurality of blank exposure lamps 59 are provided in the axial direction of the photosensitive drum 33. Then, the toner image is transferred to the transfer paper in the transfer charger 40. Prior to this, the paper 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 , and the paper is sent out by the registration rollers 39 . At this time, the document illumination lamp 2 is used to expose the document.
The optical system including the document illumination lamp 21 scans the document in the direction of the arrow while scanning the document by the reflecting mirror 24.
．． 25, 27 and 28, and the lens 26, the image is formed at point A on the photosensitive drum 33, and exposure is performed over the entire surface of the document. Here, 26 is the zoom lens 1, which moves when changing the magnification and at the same time rotates a zoom ring to make the focal length variable.

Further, a stepping motor (not shown) is used to move and rotate the zoom lens, and it can be moved to a predetermined position corresponding to a set magnification.

Reference numeral 48 denotes a registration sensor, and this sensor causes the registration roller 39 to start rotating, so that the leading edge of the image and the leading edge of the transfer paper are aligned as described above. This sensor also generates a reference signal during AE measurement.

22 and 23 are reversal sensors, and 22B is an optical system reversal position where the cassette 37 is a small size (for example, B5° A4 size, etc.). On the other hand, 23 is an optical system reversal position for 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 directed downward by the suction fan 42. Fixing a-ra 44 with built-in fixing motor 77
The completed copy paper is then ejected to a paper ejection tray 47 by a paper ejection roller 46. 45 is a web motor that winds up a web for cleaning the fixing roller 44. 43 is a power transformer, and 30 is a heat exhaust fan that releases the heat of the illumination lamp 21. 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 Vo by corona discharge. Then, dark decay occurs until the exposure point A is reached. At the 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 document is light, the amount of reflected light is large and the surface potential drops to near VL shown in FIG. On the other hand, if the manuscript is dense,
The amount of reflected light is reduced, and by reading the surface potential, it becomes possible to determine whether the original is one shade or another.

Note that the process of determining the density of the original and controlling the exposure amount or developing bias of the original in order to obtain a properly reproduced image is hereinafter referred to as AE.

Alternatively, the same thing can be done not only by measuring the surface potential but also by directly measuring the amount of light reflected from the document using a photosensor to determine the amount of light reflected from the original, which is also called AE.

FIG. 3 is a plan view showing the operation section of the copying machine 1. In FIG. 6, 201 is a magnification selection key, and this key is used to set the desired magnification, and the set magnification is displayed on the magnification display LED 206. be done. Also, if the magnification setting value is changed from the original magnification, the stenting motor will
The lens 26 is moved to a predetermined position and the focal length is also changed. Note that when the magnification is changed while the lens is being moved by the stamping motor, the movement is immediately stopped and the lens is moved from the reference point to a predetermined position again. 202
is the cassette ID selection key, allowing you to select two types of cassettes. A cassette size display LED 224 displays the cassette size of the selected cassette. 203 is the AE selection key, which sets the AE mode and also controls the A of 221.
E mode display I, E D Ka, 6. Light up. 205+
1DOWN+-+.

204 is the UP key, and from this, copy-1 density is set to 1.
You can change it step by step. Also, by operating the key 204 or 205, the manual mode is selected at the same time,
The manual mode display LED of 222 lights up. 21
Reference numeral 5 denotes a magnification indicator, which is composed of 17 LEDs with light intensity intervals corresponding to 0.5 aperture between Fl and F9. The DOWN key 205 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 is completed, or when the AE key 203 is turned on, normally the L button is pressed at the F5 position.
Display the ED.

207 is a sheet number setting key, and the set number of sheets is displayed on a sheet number display 208. 209 is a copy key, and by pressing this, a copy operation is started. 210 is a clear/stop key for clearing set numbers and stopping copying. Reference numeral 214 is an interrupt key, and when turned on, an interrupt mode is selected and an interrupt indicator lamp 213 lights up. Furthermore, when the interrupt key is pressed again, the interrupt mode is canceled.

217 is a toner lamp indicating that the toner is running out;
218 is a paper fish lamp indicating that paper is running out, 219
indicates that manual feed mode is selected,
220 is a JAM display lamp, and 221 is a counter warning lamp that indicates that there is no counter. 223 key is AE
Pressing this monitor key during standby causes only the AE bliscan to be executed, which is used to measure the document quality. Note that you cannot copy using this key.

Next, referring to FIG. 4, a hardware configuration for performing AE control of the present invention will be explained.

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 measurement position 522.

100 is a control circuit including ROM, RAM, and A/D.

1-chip microcomputer with built-in converter 10
0-a, and D/A converter equipment 0-a.

101 is a group of keys included in the operation section of FIG.
2 is a display circuit also included in the operation section. Key group 1
The input of 01 is inputted to the control circuit 100 using the usual key matrix method, and the display circuit 102 is capable of arbitrarily lighting up LEDs using a dynamic lighting circuit and lighting lamps using a lamp lighting circuit. 104 is an optical system position sensor, which is a reversal sensor (
22A, 22B, 23).

Resist sensor (48)! It is made up of.

105 is a switch provided for service personnel, and 17 LEDs (Fig. 3, 21
5) is used to display check data other than the aperture value.

60 is a temperature sensor provided in the fixing unit; 10
8 is a volume group for adjusting AE and potential control.

Further, 533 is a control circuit for controlling the lighting of the illumination lamp 21, 103 is an optical rigid device, 106 is a stepping motor for moving the lens, and 107 is a blank exposure lamp group (first
[corresponding to 59 of J] and is connected to the control circuit 100.

The microcomputer lO〇-a described in this example includes:
An 8-bit A/D converter is built-in, and it is possible to directly input an analog potential and digitize the pressure between the analog GND terminal and the power supply terminal with an accuracy of 256 steps (8 bits). It also has eight analog input terminals and converts them into A/D in a time-division manner.

Using this function, in the present invention, the surface potential of the drum, AE,
The microcomputer 100-a directly converts the adjustment volume value of potential control and the temperature sensor value of the fixing device into analog values.
is being entered.

The surface potential of the tram 33 is detected by a potential sensor 49 and further attenuated or level-shifted to an appropriate analog value by a surface potential measuring device 522.

Further, the temperature of the fixing device 44 is directly input in analog form to the control circuit as a potential change based on a change in resistance value of a temperature sensor 60 provided nearby.

On the other hand, the output of the microcomputer too-a is D/A
It is connected to converter 100-b, the analog output of which is supplied to lamp control circuit 533. Lamp control circuit 533
is the power corresponding to the input analog voltage to the lighting lamp 2.
1.

Therefore, the microcomputer Zoo-a can arbitrarily set the power supplied to the illumination lamp 21, and can also set the amount of light for image exposure.

Further, the blank exposure lamp group 107 is composed of five lamps, and a cross section thereof is shown in FIG. 59-a is a B-size blank, which is for B-size paper smaller than AI size; 59-b is an R1 blank, which is lit when R1 is reduced; 59-C is an R2 blank, which is lit when R2 is reduced. , 59-d, and 59-e are standard blanks and are turned on during non-copying to prevent wasteful consumption of toner. Note that here, in both cases, lamps are used in combination.

Further, the optical system driving device 103 can drive the optical system freely forward/backward. Further, the position sensor 104 of the optical system connected to the control circuit 100 is configured to output an output according to the position and movement of the optical system, and the control circuit 100 outputs an output according to the position and movement of the optical system. , drives the optical system drive circuit IO3, registration rollers, etc.

Further, when the stepping motor 106 accepts a change in magnification using the key 101, the stepping motor 106 moves the lens to a predetermined position using a two-phase excitation force method according to instructions from the control circuit 100. In order to increase the accuracy of the stopping position difference by the stepping motor, when stopping, the motor is controlled so that it always stops from the same direction with respect to a predetermined position, and when it moves to enlargement or when the power is turned on, it is controlled so that it always moves through the reference point. There is.

Furthermore, in response to a request to change the magnification while the lens is moving, the movement is immediately stopped and the lens is repositioned via the reference point.

The microcomputer equipped with the AE sub-control of the present invention is
Not only the AE sub-control, but also the copying operation and potential control function.
Processed within the chip.

Hereinafter, the copying procedure will be explained with reference to the flowcharts of FIGS. 13 to 16.

FIG. 1O is a time chart showing the operation when the main switch is turned on, and will be described below with reference to FIG. 10.

When the main switch is turned on, power is started to be applied to the fixing heater 77, and after a predetermined time (50 seconds), the main motor 5 is turned on.
At the same time as the drum 33 and fixing roller 44 begin to rotate, high pressure is applied to the primary charger 31 and secondary charger 4, and the pre-exposure lamp 32 and blank exposure lamp 5 are turned on.
Turn on 9. This eliminates the residual charge on the drum 33. Thereafter, when the fixing port 44 reaches the first set temperature (165° C.), controlled rotation begins. Thereafter, the temperature of the fixing roller 44 is constantly adjusted to the second set temperature (200''C).

The controlled rotation consists of a potential control section and a light amount control section, and the potential control section measures the drum surface potential (referred to as VSL) with a potential sensor 49 while the blank exposure lamp is lit.
Next, the drum surface potential (referred to as VD) is measured with the blank exposure lamp turned off. The high voltage current flowing through the primary charger 31 and the secondary charger 4 is controlled based on the values of VSL and VD so that it approaches predetermined VD and VSL. This control is repeated four times here so that stable contrast can always be obtained.

Next, the light amount control is started, and the document illumination lamp 21 is turned on.
A standard white plate 61 corresponding to the reflectance of the white background of the original is irradiated, and the potential (referred to as VLI) on the drum 33 is detected by the potential sensor 4.
Measure according to 9. Then, the light amount of the original illumination lamp 21 is shifted to the lamp control circuit 533 so that VLI becomes Ov. This vL measurement control is performed three times to optimally control the light amount of the document illumination lamp 21.

The amount of halogen light such that the surface potential obtained by controlling the amount of light becomes Ov is called the standard amount of light, that is, the amount of light usually called F5 is sometimes variable in this device by controlling the amount of light.

The standard light amount can be interpreted as the specific reference value plus the light amount control correction voltage.

Finally, VL is measured and this value is set as VL2 to end the controlled rotation. Note that this value of VL2 is used in the AE sub-control described later.

Next, the post-rotation starts, the primary charger 31 is turned off, and then,
The high voltage output of the secondary charger 4 is weakened, and the secondary charger 4 is turned off after a predetermined rotation. This is to eliminate unevenness in the surface potential of the drum before stopping. Thereafter, everything except the power supply to the fixing heater 77 is stopped, and the copy key enters a standby state waiting for human power.
1. Also, if the fixing roller 44 reaches the first set temperature (165° C.) within a predetermined time (50 seconds) after the main switch is turned on, the controlled rotation starts immediately. The fixing temperature of the toner is about 180°C, and if the controlled rotation starts at 165°C as described above, the fixing roller 44 will reach 180°C at the end of the controlled rotation.
The temperature is supposed to have reached 80°C, and we are trying to shorten the wait time.

It should be noted that the lens position is not limited to the same magnification position when controlling the light quantity, so the lens is fixed at an arbitrary magnification position selected before starting the control rotation, and the light quantity control is performed.

It is possible to change the magnification using the keys during controlled rotation, but
Actual lens movement occurs after light amount control.

Next, a series of (movements) from AE measurement to AE copy by the copy key 209 when the AE mode is selected by the AE selection key will be explained with reference to the time chart of FIG.

When AE copying is started by the copy start key 209, the lens is set at the set magnification position, and then the drum 33 is rotated and the optical system is advanced to a predetermined position at the same time.

Also, at this time, the illumination lamp 21 is turned on at a voltage of a standard value that provides a standard amount of light.

Next, the optical system starts moving backward (prescanning), and the microcomputer 100-a starts sampling the surface potential VDR of the drum 33 at a predetermined timing based on a signal from the optical system position sensor 104.

VDR is sampled multiple times based on the signal from the optical system position sensor 104, and the average value VDM is calculated. This sampling is performed when the latent image on the drum corresponding to a predetermined position on the original reaches the surface potential sensor, so the average value V corresponding to the density at a predetermined position on the original is
DM is now available.

After the optical system returns to the home position, the illumination lamp 21 is turned on with a lighting voltage whose standard value is corrected according to the value of VDM, and the optical system is advanced to perform image exposure. At this time, the concentration is displayed according to the lighting voltage.

FIG. 6 shows the relationship between VDM and illumination lamp correction value, and FIG. 7 shows the relationship between halogen correction voltage and density display value.

For example, when VDM=75V, that is, for a standard original, the correction value is 0, and the illumination lamp is turned on with the standard light amount during exposure of the original.

Also, at this time, the aperture display shows F5.

In addition, in the case of manuscripts with blurred texture such as newspapers, VDM is 3.
00V, and as shown in Figure 6, AE correction of about 9.6V is required, and the standard value +9.6 (V
) is lit with the amount of light.

By increasing the amount of light, the ground yellowtail will fly away and a proper image will be obtained.

The aperture display value at this time is F8.5 from FIG. 7. The flow of control for determining the amount of light is shown in FIG. 14.

The AE correction curve shown in FIG. 6 is often required to be adjusted depending on the machine condition or on the user's side.

Here, it is possible to input the curve adjustment amount directly into the microcomputer 100-a as an analog amount.

Specifically, it is possible to move the AE left curve in parallel (sufficient to change the standard light amount value) or change the AE left curve inclination using the volume.

This situation is shown in Figures 8 and 9. Further, FIG. 15 shows the flow of control for correcting the AE value.

In addition, the calculation of the light amount based on these AE left curves is performed by the microcomputer Z based on external input data.
It is calculated in oo-a and output as an analog output for /\logen light amount control.

Further, the aperture value is calculated internally from the halogen light amount value and output and displayed on the aperture display 215. In addition, in the AE correction, if the standard light intensity is deviated by l,% (if IVL2 does not become 0 even after the predetermined number of light control operations described above), the corresponding correction will be added to the AE correction. For example, if VL2=5V, the AE correction value is determined by taking into account the error 5V of the AE left curve VL2 mentioned above in VDM.

The factors determining these AE correction values are summarized as follows.

As mentioned above, by measuring the surface potential VDM corresponding to the density of the original through pre-scanning and controlling the lighting voltage of the illumination lamp based on that value, it is possible to obtain an appropriate copy image regardless of the type of original. I can do it. In addition, a display corresponding to the darkness of the original is made once.

Also, when the AE mode is not selected, the drum starts rotating at the same time as the copy start key 209 is pressed.
The illumination lamp 21 is turned on with a standard light amount plus a manual correction value selected by the density adjustment means. after that,
The optical system starts moving forward and moves to image exposure scanning.

When variable size copying is selected using the key, light amount control is performed before entering the forward copying sequence. That is, when the copy start key 209 is pressed, if the magnification is different from the previous copy, the optical system is returned to the home position, and then the light amount control described above is performed to compensate for changes in the standard light amount due to zooming. do.

If it is in the rough AE mode, the AE left curve inclination is changed in order to adjust the AE correction amount for each magnification. This change in the AE left curve slope is done in parallel with the tilt adjustment volume described above, and the slope is actually a function of the adjustment volume and the copy magnification.

As described above, in the copying apparatus according to the present invention, potential control and AE sub-control are all executed in one microcomputer-100-a, input data is input from a predetermined port at a specific timing, and halogen is output as an output. The amount of light etc. is given. Therefore, a means is needed to show the state of data processing to the outside.

In this copying apparatus, the information data taken in by the microcomputer 100-a is transferred to the microcomputer 100-a.
It is possible to output to the aperture display LED using the display selection means of the ditub switch that 0-a inputs, and depending on the setting, the drum display potential, drum surface potential VDM during AE measurement, bright area potential during potential control VSL, dark potential VD,
Displays VL2, etc. during light amount control in binary digitization. This selection means is not installed on the operation panel in this embodiment because it is intended for general users.

FIG. 12 shows an aperture display as a data display function.

Further, FIG. 16 shows a control flow for data display.

00 by using the 8 LEDs on the right side of the 17 LEDs for aperture.
- shows the binary value of 256 steps up to fFFH, and in Fig. I2, it is oioo.

110B (=46H) Show 1. T-8S, conversion table (
(not shown) indicates that the surface potential is ov.

In this embodiment, the aperture display is used to display the surface potential of the drum sampled at a specific timing, but the temperature of the fixing heater etc. obtained from the temperature sensor can also be displayed in the same way. It can also be used for

In addition to direct data, maintenance information (number of jams, number of drum replacements, etc.) can also be displayed here.

In addition, in this embodiment, one display device uses 17 LEDs, but it is not limited to this, and 7 segment LEDs can be used directly.
It can also be applied to a display device that numerically displays the aperture using D.

Further, although the display data selection means is not provided with a dedicated switch, it is also possible to use an input means using a combination of the existing 10 key, magnification 1 key, etc.

Further, in this embodiment, the AE monitor key 223 merely performs AE measurement and displays the result on the concentration display section, but in order to further improve operability, this key can be used to
It is also possible to automatically shift to manual mode after measurement, lock the light intensity, and then press the copy key to ensure that copies are made with the appropriate light intensity.

This function is useful when you want to perform AE copying of originals with extremely different densities on the A E 1+11 legs.
Increase the amount of light with this function.

Next, when you set the original correctly and try to make a copy with the proper exposure manually, you can definitely get a copy with the proper amount of light by simplifying the operating procedure.

As described above, since an image is formed by calculating predetermined data on the original density, it is possible to always obtain an optimal reproduced image.

In addition, in a copying machine equipped with an automatic density adjustment device, AE
By providing a function to perform measurements, the scope of use can be freed from limitations imposed by originals (originals with extreme density differences, etc.), and A
It becomes possible to use E effectively.

In addition, in terms of serviceability, there is no unnecessary copying,
AE sub-adjustment can be made.

In addition, in a copying machine that has the function of displaying the copy density, by also having the function of displaying processing data of other displays such as a microcomputer, not only does a dedicated display become unnecessary, but it also becomes easier to maintain. This can contribute to early detection of failures in potential sensors, etc., which can provide high-quality copying devices.

In this embodiment, the density of the original is read through the potential on the drum, but the density of the original may be read by detecting reflected or transmitted light from the original using an optical sensor or the like.

Effects As described above, according to the present invention, it is possible to measure the density of the original and display the copying operation, thereby eliminating unnecessary copying even when copying originals with extreme density differences. It becomes possible to set an appropriate image density without causing any problems.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a copying device to which the present invention can be applied, FIG. 2 is a diagram showing characteristics of surface potential, FIG. 3 is a plan view of the operation section of the copying device, and FIG. 4 is a control section of the copying device. Block Diagram,
Figure 5 shows the arrangement of five blank exposure lamps.
Figure 6 is a diagram showing the relationship between the drum surface potential average value and halogen lighting voltage correction value during AE measurement, Figure 7 is a diagram showing the relationship between halogen lighting voltage correction value and aperture value display, and Figure 8 is a diagram showing the relationship between the halogen lighting voltage correction value and the aperture value display.
Figure 9 shows the horizontal shift of the AE correction curve by the adjustment volume, Figure 9 shows the change in the slope of the AE correction curve by the AEall adjustment volume, and Figure 1O shows each operation of the control rotation after turning on the main switch. Fig. 11 is a time chart showing each operation of AE measurement, Fig. 12 is a plan view of an aperture display capable of displaying various internal data, Fig. 13 is a general brooch yard for copying operations, Fig. 14 is a flowchart showing the control flow for determining the amount of halogen light, and Fig. 15 is a flowchart showing the flow of control for determining the amount of halogen light.
A flowchart showing the flow of control for correcting values,
FIG. 16 is a flowchart showing one control flow for display. Figure 75

Claims (1)

[Claims] An image forming device that can operate in a mode that detects the original density and performs copying after adjusting image forming conditions according to the detected original density, and a mode that detects the original density and displays the detected original density. .