JPS5993463A - Image forming device - Google Patents

Abstract

PURPOSE:To discriminate density values of the black part and while part of a master by operating a means which converts the analog output of a density detecting means into a digital value only at a specific point of time in an electrostatic printing machine which detects the density values of the black and white parts respectively and controls picture quality. CONSTITUTION:Check zone detecting means 114 and 115 detect a black-part out and a white-part cut of the master respectively to generate pulses. Then, the time when the black part and white part pass is known by the master density detecting means 13 from combinations (1.0 and 0.1) of those two pulses, and the means which converts the density value into the digital value only at the point of time and stores it in a CPU119 is operated. Then, an electrostatically charge potential is controlled corresponding to the density of the black part and a development bias is controlled corresponding to the density of the white part to correct variation in the picture density of the master, performing electrostatic printing with excellent picture quality.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an image forming apparatus that detects image forming power and controls image forming based on its output.

2. Description of the Related Art Conventionally, a technique for detecting image forming power and controlling image forming using its output is known, for example, in TJ SP 295 (based on S487). Such control is performed by digital processing using a processor such as a digital computer, and the detected image forming force is then transferred to an A/D converter.
It is conceivable to convert the signal into D and input it to the control means.

In this case, errors may occur in digital processing due to the relationship between the processing time of the processor and the processing time of the A/D converter.

The present invention has been made in view of the above points, and includes a detection means for detecting image forming power, an A/D conversion means for converting the detection output of the detection means into a digital signal, and an output of the A/D conversion means. and control means for controlling image formation accordingly, and the control means performs hold control on the A/D conversion means when the detection output is read by the control means.

This makes it possible to accurately and quickly perform digital processing for controlling image formation.

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

Reprint of the specification (no changes to the contents) Figure 1 shows a schematic diagram of an electrostatic printing machine for master use. The master 110, which has been developed as a mask in advance by a mask making machine (not shown) and has a mental image, is picked up.
Ra111. It is sent to the drum 109 by the feeder 90-ler 112. The drum grips the mask with a gripper 124 and secures it on the drum. A charger 107 uniformly charges the master fixed on the drum with cycorona.

An electrostatic latent image is formed on the master according to the image density on the master. If the high voltage transformer (HVTl) 10B has a positive output, a latent image with a positive charge is formed on the master. If negative toner is contained in the developing device 116, the positive charge on the master causes the toner to adhere to the master, forming an image using the toner. On the other hand, printing paper 101
The paper is fed by the Fi pickup roller 102K and sent to the transfer section by the paper feed roller 103. Since the printing paper is uniformly positively charged from the back side by the HVT 1, the negative toner is transferred to the printing paper, and at the same time, the drum is again positively charged. The transferred printed paper passes through the fixing device 104 and enters the tray 106 for engraving the discharge specification (no change in content).

Figure 2 shows the characteristics of the reflection density versus surface potential of the master when the voltage applied to the charger is set to 10 and Figure 3 shows the relationship between the voltage applied to the charger and the surface potential of the master in the dark and in the light. shows. This shows that as the applied voltage increases, the contrast potential (surface potential in the dark - surface potential in the light) increases and the surface potential in the light also increases. Therefore 1Jla+
When this occurs, a so-called capri occurs. The disadvantage is that the printing paper gets stained all over. When a voltage along the dotted line curve in the figure is applied as a bias voltage to the developer, the toner adheres to the master side in the surface potential of the bright and dark areas, but the toner remains attached to the developer side in the dark areas. It does not adhere to the master side. This shows that the above drawbacks can be compensated for by applying an appropriate bias to the developing device. FIG. 4 shows the reflection density of the printed paper after printing versus the contrast potential on the master.

From the above, in electrostatic printing machines that use masters, the finished product after printing depends on the quality of the master (
No change in content] Capri occurs or not enough toner is applied to dark areas.

The present invention automatically corrects these. First, a reference tension area (hereinafter referred to as check zone) is provided on the master as shown in FIG. That is, a bright area (dot area 2) and a dark area (white area 5) are created on the check zone using a fixed pattern provided on the mask making machine. The mask image area formed by this check zone is the result of including all variable factors such as the exposure amount of the mask making machine, the temperature of the thermal developing machine, and the material properties of the mask. 0 By detecting the reflection density of the bright area 2, the developer bias voltage is determined, and by detecting the reflection density of the dark area S, the voltage applied to the charger is determined. Also, depending on the quality of the mask, if the reflection density in dark areas falls below a predetermined value or the reflection density in bright areas exceeds a predetermined value, the bright area contrast may be too low and the mask may need to be printed on the printing machine. However, a sufficiently good image cannot be obtained. In such cases, an intermediary is applied to prevent the printing process from proceeding.

Engraving of the specification (no changes to the contents) Follow the drawings in order for ¥51! The automatic setting of the device applied voltage and the developing bias voltage will be explained in detail. In FIG. 1, reference numeral 119 is an automatic voltage setting control section including a microprocessor, the internal details of which are shown in FIG. 12
0 is a printing press control unit (hereinafter referred to as the panel unit), and the panel unit 120 sends a printing press start signal (
STR) and a print stop signal (STP) are sent. On the other hand, a print start command signal (
cpy), mask contrast density abnormality A (dark place is too bright - MM1), mask contrast density abnormality B (
The bright place is too dark - MM2) Send each signal. In response to these abnormal signals, the panel unit (f:f) is turned on to notify the operator of the abnormality and at the same time interlooks to prevent the printing process from starting. Reference numerals 121 and 122 are setters 5ET1 and 5ET2 for setting the abnormal limit of the mask density. 5ET1 is for setting abnormal density limit value in dark place, 5ET
2 is a digital switch for setting the concentration abnormality limit value in the bright area. 0126 is a reset switch that allows the operator to print out the abnormality statement (no change in content) when the master concentration is abnormal. It is REST. 113 is a photoelectric converter for measuring the reflection density at the master check part;
114 (PH-A) and 115 (PH-B) detect the positions of the dark and bright areas of the check zone (FIG. 5) of the mask. The resulting signal is a reference signal for creating sample signals for sampling the reflection density values of the bright and dark portions of the master.

An example of control by a microcomputer will be described below with reference to the flowchart of FIG. 9. When power is turned on to the printing press and the automatic voltage setting control section 119, master density limit values 5ET1 and 5ET2 are first read into the memory 212. 5ET until STR signal is sent from panel 120
The memory is sequentially revised to the latest setting value according to 1.5ET2.

When the printing press is started, an STR signal is sent and the master 110 is fed by the pickup roller 111.
When the master passes the feed roller 112, the roller 112
The mask check zone detectors 114 and 115 K arranged between the mask check zone detector 114 and the drum 109 engrave the reflection density data value (no change in content).
Let 19 know.

When notches 6 and 4 are provided in the mask concentration check zone, the PH
-A, PH-B are 0P output signals as shown in E8 diagram.
If H-A is at @HIT level and PH-B is at L'' level, the mask is in the bright part of the concentration check zone, and the PH
-A, d; “L” r PH-B is “H” (2)
To @ it, the dark part of mass fi is reflective V degree inspection t
Indicates that it is under B unit 113.

These signals are sent via input port 2 (EPo 20B
will be read more. Therefore, PH-A is "H" and PH-B is
When L#, CPU 2 (H3 is A/D converter 206
is held, and the reflection density data value (Xl) obtained by the detector 11'5 in the bright area of the mask is converted into a digital quantity.
into a part of the memory. The master 110 in FIG. 2 is a heat-developable photosensitive sheet member, and is composed of a support 202 and a photosensitive layer 203. Reference numeral 113 denotes a master reflection density detection photoelectric cable consisting of a rung and a light receiving element, and 205 an amplifier. Reference numeral 207 is a port for reading data from the A/D converter with an input port (IN1). 211 is input boat I
PH-A, PH-B with N2.

Reprint of specification (no change in content) STR, STP, 5ET1, 5ET2. Reference numeral 0212, which is a read port for the RKST signal and each input terminal is designated by a designation signal from the CPU, is a group of memory elements such as a fixed program memory and a narrowing/writable memory. Each memory and memory address is designated by an address designation signal from C1PU, and 0209 is output port 1, which is read and written by a control signal from CPU.
~3, and OUT 1 and 2 are each connected to a D/A converter, and the output digital data is converted into analog data.

Since the analog output is input to the high voltage transformer, the output voltage can be changed according to the input voltage.

) ('/T 1 is applied to the charger, HVT 2 is applied to the developer, and CPY, MMl, MMS are applied from the output port 3.
are sent to the panel 120. This signal quality of 1H" is sufficient, so it can be output without converting to analog data.

Each output port is also selected by a designated signal from the CPU. When the detected reflection density X1 in the bright place is entered into the memory through the A/D converter, the hold of the A/D converter is released in the next step and the detection data statement is updated from time to time (no change in content). The D converter outputs. Check the status of PH-A and PH-B from input port 2, then PH-A=
When it becomes “L” and PH-8 = “H”, the A/D converter is held again, and this time the reflection density of the master in the dark is set to A.
The data enters the memory via the CPU 208 from the input port 1 through the /D converter. Let the data at this time be X2. After reading the data in the dark, release the A/D converter hold using the program 0 This means that the measurement of the horizontal master concentration check part is completed 0 The next step is to check x, = sE'r1.

That is, if the reflection density value x2 in the dark is greater than or equal to the density limit value SET1, the process proceeds to the next step. But xg (SET
When it is 1, the MM1 signal is output from 0UT3 to notify the master density abnormality and interlock the machine in case it is in danger of entering the printing process. X! When is normal, x1≦5 in the next step
Check ET2 from CPUK and find "1>5ET2"
If so, output MM2 and interlock the machine as described above. If it is normal, the optimal charger applied voltage at that time is C.
The calculation will be done in PU and the specification will be reprinted (no changes to the contents). this is! Star reflection density X and optimal charger applied voltage y
1, or the relationship with the optimum bias voltage Yx! ＝'
() p yx = g ('') This is calculated using the experimental formula. This calculation procedure is stored in advance in the memory 212. FIG. This is an example showing the relationship between the voltage applied to the device.
= ("zL 7z=g(Xs) i) '0 output capo which is calculated and output from each output boat 0UT1 and 2.
) The digital data output from OUTj and 2 is D/
The A converter 210 converts the voltage into a high voltage transformer HVT.1. The optimum charger applied voltage and developer bias voltage according to the i-star density contrast are input to HVT1 and HVT2. Next, after the stabilization period has elapsed, when entering the printing process step, the master is changed, so a predetermined number of sheets are printed using the optimal charger applied voltage and developer bias voltage that have been set. When printing is completed, the main body 120 outputs STP by detecting the ejection of the last sheet, and the CPU causes all output signals other than MM1 and MM2 to be used to write a reset specification (no change in content). After that, the race returns to the starting BVC again.

As described above, various fluctuation factors during master creation are automatically corrected during the printing process by controlling the voltage applied to the charger and the developing bias voltage, which has a great advantage in improving the stability of printed images. According to the program steps described above, a person of ordinary skill in the art can operate a general-purpose microcomputer to perform the desired compensation control, so a detailed explanation of the more detailed steps using command words will be omitted. Also, from the density of the visible image obtained in the printing process, HVTl and HVT2 are determined in the same way as in the case of a mask.
It is also possible to control to an appropriate value. Therefore, in a so-called copying machine, HvTl,
It is also possible to control HVT2 to achieve an appropriate concentration.

[Brief explanation of drawings]

Fig. 1 is a diagram of the electrostatic printing process to which the present invention is applied, Fig. 2 is a mask concentration-surface potential characteristic diagram, and Fig. 3 is a diagram of applied voltage-
Surface potential characteristic diagram, Figure 4 is an engraving of the ore master taco specification (no changes to the content), contrast potential-concentration characteristic diagram, Figure 5 is a mask plan view,
Fig. 6 is a block diagram of the control section in Fig. 1, Fig. 7 is a concentration-charger voltage/bias voltage characteristic diagram, Fig. 8 is a check zone detection signal diagram, and Fig. 9 is a block diagram of the control unit in Fig. 6. 1, 113 is a mask concentration detector, 114 and 115 are check zone detectors, and 11 is a flowchart.
9 is a control unit, HVT f is a charging voltage source, and HVT 2 is a bias voltage source. Applicant: Canon Co., Ltd. Kukai-d (Kuta → Mu) 1) - Upstream meal - Keibakuichi (Kabunjo) Ding Continuation Amendment (Method) January 1982? 2nd, 1982 Patent Application No. 121904 2 Name of the invention Image forming device 3 Relationship with the person making the amendment f1 Patent applicant address Tokyo Metropolitan University [3-30-2 Shimomaruko, 11th Ward Address 1
48 3-30-25 Shimomaruko, Ota-ku, Tokyo Date of amendment order: November 29, 1982 (shipment date) 6. Specification subject to amendment and drawing 7, Pages 12 to 24 of the statement of contents of amendment and engraving of drawings (no changes in content)

Claims (1)

[Scope of Claims] A detection means for detecting image forming power, an A/D conversion means for converting the detection output of the detection means into a digital signal, and controlling image formation according to the output of the A/D conversion means. an image forming apparatus, wherein the control means holds the A/D conversion means during a reading operation of the detection output by the control means.