JPS6025788B2 - image forming device - Google Patents

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, from US Pat. No. 2,956,487.

When such control is performed, a situation may arise where an appropriate image cannot be obtained for some reason. If image formation is continued while such a situation occurs, not only will the recording material and the like be wasted, but in some cases, there is a risk that the apparatus will be damaged. The present invention has been made in view of the above points, and includes means for photoelectrically detecting the density corresponding to a grayscale image, means for forming a static silkworm latent image based on the grayscale image, means for developing a static exposure latent image,
A means for transferring a developed image onto a sheet, a procedure for determining at least one of a latent image potential when forming the electrostatic latent image or a developing bias potential when developing is programmed in advance in a memory, and the detection means is detected by the detecting means. and control means for executing a program based on the output, and the control means sets a limit value for the concentration detected by the detection means, and sets the limit value to the bright area,
It is characterized by being provided in both dark areas. This makes it possible to prevent recording at inappropriate densities and to cope with abnormal densities in both bright and dark areas. Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 1 shows a schematic diagram of an electrostatic printing machine using a master. A master 110 having an image developed in advance by a master creating machine (not shown) is sent to the drum 109 by a pickup roller 111 and a feed roller 112. The drum grips the master with clippers 124 and fixes it on the drum. A charger 107 uniformly corona charges the master fixed on the drum.
A static latent image appears on the master depending on the image density on the master. If the high voltage transformer (HVTI) 108 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 toner will adhere to the master due to the positive charge on the master and a toner image will appear. On the other hand, printing paper 101 is fed by a pickup roller 102 and sent to a transfer section by a feed roller 103. The printing paper is HV from the back side.
Since the drum is uniformly positively charged by the TI, 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 paper output tray 106. Figure 2 shows the charger applied voltage of 1
FIG. 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.

As a result, when the applied voltage increases, the contrast potential (
It can be seen that the surface potential in the dark area (surface potential in the dark area - surface potential in the bright area) increases and the surface potential in the bright area also increases. Therefore, when developing, so-called fog occurs. The disadvantage is that the printing paper gets stained all over. If a bias voltage is applied to the developing device along the Magosen curve at the center point in the figure, toner will adhere to the master side at the surface potential of the bright and dark areas, but toner will adhere to the developing unit at the surface potential of the floor area. It will not stick 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 with respect to the contrast potential on the master. As described above, in an electrostatic printing machine that uses a master, depending on the quality of the master, the finished product may be foggy after printing, or there may not be enough toner on the surface.

The present invention automatically corrects these.

First, as shown in Fig. 5, a reference tension zone (hereinafter referred to as a check zone) is provided on the master. That is, a bright area (black area 2) and a dark area (white area 5) are created on the check zone using a fixed pattern provided on the master creating machine. The master image portion produced by this check zone is the result of including all variable factors such as the exposure amount of the master producing machine, the temperature of the thermal developing machine, and the material properties of the master. 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 printing condition of the master, if the reflection density in the dark becomes less than a predetermined value or if the reflection density in the light becomes more than the predetermined value, the bright contrast may be too low and the master may not be able to be printed even if it is run on a printing machine. A sufficiently good image cannot be obtained. In such cases, an interlock is placed to prevent the printing process from entering. The automatic setting of the voltage applied to the charger and the developing bias fin pressure will be described in detail below with reference to the drawings.

In FIG. 1, numeral 119 is an automatic voltage setting control section including a microprocessor, the internal details of which are shown in FIG.

120 is a printing press control section (hereinafter referred to as a panel section), and a printing press start signal STR and a printing stop signal STP are sent from the panel section 120 to the control section 119.

On the other hand, from the control unit 1 19 to the panel unit 120, the current start command signal CPY, master contrast density abnormality A (floor is too bright - NM town 1), master contrast density abnormality B
(The bright place is too dark - MM2) signals are sent. In response to these abnormal signals, a warning lamp is lit on the panel to notify the operator of the abnormality, and at the same time an interlock is established to prevent the printing process from proceeding. Reference numerals 121 and 122 are setters SET1 and SET2 for setting the abnormality limit of the aforementioned master concentration.

SETI is a digital switch for setting an abnormal concentration limit value for floors, and SET2 is a digital switch for setting an abnormal concentration limit value for a bright place. 1
23 is an IJ set switch REST used by the operator to release the interlock that removes the abnormal mass when the master concentration is abnormal.

1 13 is a photoelectric converter for measuring the reflection density at the master check part, 114 PH-A, 115
PH-B detects the positions of the dark and bright areas of the master's check zone (FIG. 5).

The resulting signal is a reference signal for creating a sample signal for sampling the reflection density value of each bright and dark portion of the master. An example of control by the microcomputer will be explained below with reference to the flowchart of FIG.

When the printing machine and the automatic voltage setting control unit 119 are powered on, first, master density limit values SET1 and SET2 are stored in the memory 212. The memory is sequentially revised to the latest setting values set by SET1 and SET2 until the STR signal is sent from the panel 120. 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 master check zone detectors 114, 115 located between the roller 112 and the drum 109
This notifies the control unit 119 that a check position has been created below the reflection density detector 113. If success and failure 3 and 4 are provided in the mass concentration check zone, PH-A and PH-B are output signals as shown in FIG. When PH-A is "H" level and PH-B is "L" level, the master is in the bright part of the concentration check zone, and when PH-A is "L", PH-B is
When is “H”, the floor part of the master is the reflection density detector 1.
13 indicates that it is below. These signals are read by the CPU 208 via input port 2. Therefore, PH-A is “
When PH-B is “H” and PH-B is “L”, the CPU 208 holds the A/○ converter 206 and outputs the detector 1 of the master Akatsuki part.
The reflection density data value XI by 13 is converted into a digital quantity and stored in the memory section 119. In addition, master 11 in Figure 2
0 is a heat-developable photosensitive sheet member comprising a support 202 and a photosensitive layer 2.
It is made up of 03. 113 is a master reflection density detection photoelectric element consisting of a lamp and a light receiving element, and 205 is an amplifier.

207 is an input port INI which reads data from the A/D converter.

21 1 is the input port IN2, PH-A, PH-B, S
This is a board for TR, STP, SET1, SET2, and REST signals, and each input terminal is designated by a designated signal from the CPU.

212 is a group of memory elements such as a fixed program memory and a readable/writable memory.

Each memory and address within the memory is specified by an address designation signal from the CPU, and is negotiated by a control signal from the CPU.
Writing is done. Reference numeral 209 indicates output ports 1 to 3, and OUTI and OUTI are each connected to a D/A converter, and output digital data is converted to analog data.

Since the analog output is input to the high voltage transformer, the output voltage can be changed according to the input voltage. HVTI
is applied to the charger, and HVT2 is applied to the developer. From output boat 3, CPY, MM1, MMS signal panels 1
Sent out to 20.

Since this signal can be "H", it can be output without converting it to analog data. Each output port is also selected by a designated signal from the CPU. When the detected reflection density XI in a bright place enters the memory through the A/D converter, the hold of the A/D converter is released in the next step and the momentary detection data is transferred to the A/D converter.
○The converter outputs. PH-A from input boat 2
, PH-B, and then PH-A="L",
When PH-B becomes "H", the A/D converter is held again, and this time, the reflection density of the master floor is passed through the A/○ converter and inputted from the input port 1 via the CPU 208 to the terminal module. Let the data at this time be X2. After writing the data in the clear place, release the A/D computer hold using the program. This means that the measurement of the master density check part is completed. In the next step, x2=SETI is checked.

That is, if the reflection density value - of the floor is greater than or equal to the density limit value SETI, the process proceeds to the next step. However, when x2 is set, an MMI signal is output from OUT3 to notify the master density abnormality, and the machine is interlocked so as not to enter the printing process. When the average is normal, in the next step, the CPU checks whether x, SSET2, and if >SET2, MM2
is output and the machine is interlocked as described above. If it is normal, calculate the optimum voltage applied to the charger at that time using the CP peak. This is the master reflection density x and the optimum charger applied voltage y. , or the relationship with the optimum bias voltage ground as y,=f
(x), y2=g(x). This calculation procedure is stored in memory 212 in advance. FIG. 7 is an example showing the relationship between the bias voltage and the charger applied voltage with respect to the master reflection density obtained from experiments. Optimal voltage 3,=f(x2
), seal = (x,) are calculated respectively for each output port OUT1
and 2 are output. The digital data output from the output boats OUTI and OUT2 is converted into voltage from the D/A converter 21 and then sent to the high voltage transformers HVT1 and HV, respectively.
The optimum charger applied voltage and developer bias voltage according to the master density contrast are input to T2, HVT1, H
Issued from VT2. Next, after the stabilization period ↑2 has elapsed, when the printing process step is entered, the master is not changed, so a predetermined number of sheets are printed using the optimal charger applied voltage and developer bias voltage that have been set once. When printing is completed, the main body 120 detects the ejection of the last sheet and outputs STP, and the CPU outputs MM1,
All output signals except MM2 are reset. After that, it returns to the starting state 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.

It should be noted that a person skilled in the art can operate a general-purpose microcomputer to carry out the desired compensation control using the program steps described above, so a detailed explanation of the more detailed steps using command words will be omitted. It is also possible to control HTV1 and HTV2 to appropriate values from the density of the visible image obtained in the printing process in the same manner as in the case of the master. Therefore, in not only printing machines but also so-called copying machines, it is possible to control HVT1 and HVT2 from the density of the original first visible image or the second visible image after development to achieve the appropriate density. Become.

[Brief explanation of drawings]

Figure 1 is an electrostatic printing process diagram to which the present invention is applied, Figure 2 is a master concentration-surface potential characteristic diagram, and Figure 3 is an applied voltage-
Surface potential characteristic diagram, Figure 4 is a master contrast position-concentration characteristic diagram, Figure 5 is a master plan view, Figure 6 is a block diagram of the control section in Figure 1, and Figure 7 is a concentration-charger voltage/bias voltage diagram. 8 is a check zone detection signal diagram, and FIG. 9 is a flowchart for executing FIG. 6. In FIG. 1, 113 is a master concentration detector, 114, 11
5 is a check zone detector, 119 is a control unit, HVTI
is a charged voltage source, and HTV2 is a bias voltage source. Kotobuki 〆Fig. 5 Fig. 2 younger brother Fig. 3 Fig. 4 younger brother Fig. 6 Fig. 7 Fig. 8 Fig.

Claims (1)

[Claims] 1 means for photoelectrically detecting the density corresponding to the grayscale image;
means for forming an electrostatic latent image based on the grayscale image; means for developing the electrostatic latent image; means for transferring the developed image onto a sheet;
A control means for preprogramming in a memory a procedure for determining at least one of a latent image potential when forming the electrostatic latent image or a developing bias potential when developing the electrostatic latent image, and executing the program based on the detection output of the detection means. A transfer image forming apparatus, characterized in that the control means sets a limit value for the density detected by the detection means, and the limit value is set for both bright areas and dark areas.