JPH0478885A - Toner concentration control system for electrostatic printer - Google Patents

Abstract

PURPOSE:To prevent toner concentration from lowering and to prevent the excessive adhesion of toner caused by faulty mixing by executing ATC in a test printing mode. CONSTITUTION:In the test printing mode, a photosensitive drum is rotated, electrostatic charging, exposure and development are performed to generate an unfixed plate on the drum. Then, a drum speed is adjusted to a fixing device and transfer is performed by rotating the drum at a high speed, while a developing machine is stopped. When the transfer is finished, the drum speed is restored to the speed of a developing process and a developing machine motor, an erasing corotron 10a and an erasing lamp 12 are turned on to clean the surface of the drum. At the first half of this stage, the toner concentration in the developing machine is detected by a concentration sensor 31. When it is low, the toner is supplied and mixed at the latter half of the stage, so that the excessive adhesion of the toner caused by the faulty mixing is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a toner density control method in an electrostatic printing device having a test print mode and a print mode.

[Conventional technology]

A conventional electrostatic printing device will be described with reference to FIGS. 7 and 8.

As shown in FIG. 7, a photosensitive member 2, an exposure optical system 3, a paper feed mechanism 4, a fixing device 5, and the like are arranged within the electrostatic printing apparatus main body 1. As shown in FIG. 8, the photosensitive member 2 is provided with a roll-shaped master 7 and a take-up roll 8 in a scroll drum 6, and the master 7 is inserted into the surface of the scroll tram 6 through a slit-shaped opening 9 of the scroll drum 6. The master 7 is wound on the scroll drum 6, and the master 7 is wound on the take-up roll 8 through the slit opening 9, and the master 7 is unwound by rotating the take-up roll 8, and a new master 7 is wound on the surface of the scroll drum 6. ing. Around this photosensitive member 2 is a charging corotron 10. Static elimination lamp 11. A flash fixing device 12, a developing device 13, a transfer corotron 14, a paper peeling section 15, etc. are arranged in this order, and the exposure optical system 3 includes a lamp 16, a lens 17, and a mirror 18.
The original image on the platen glass 19 is exposed to light onto a photosensitive member to form an electrostatic latent image.

The paper feeding mechanism 4 includes an upper tray 20 and a lower tray 21,
The paper is sent from one of these trays through the paper transport path 22 onto the photosensitive member 2, and the paper transport path 22
As shown in FIG. 8, a feed roll 23 is provided,
The paper 24 sent by this feed roll 23 is
It passes between the chute 25 and the second chute 26, and is sent between the photosensitive member 2 and the transfer corotron 14 via the upper chute 28 by the feed roll 27.

This paper is charged by corona discharge from the transfer corotron 14, and is electrostatically attracted to the surface of the photosensitive member 2.

The paper peeling unit 15 includes a peeling belt 15a, and the photosensitive member 2
Peel off the paper adsorbed to the surface of the paper conveyor belt 2.
9, and the sheet conveying belt 29 sends the sheet to the fixing device 5.

In such an electrostatic printing device, when performing a copying operation, the surface of the photosensitive member 2 is charged with a charging corotron 10, and then an original image is irradiated with an exposure optical system 3, as in a normal electrophotographic copying machine. An electrostatic latent image is formed by exposure, and this electrostatic latent image is developed with toner by a developing device 13, and then the toner image is transferred to a sheet of paper 24 by a transfer corotron 14, and the sheet of paper 24 is sent to a fixing device 5 to be fixed. Afterwards, the paper is discharged to the paper receiver 30.

In the print mode, the toner image formed as described above is flash-fixed by the flash fixing device 12, and the toner image is fixed on the photosensitive member to form a print master, and then the print master is charged with an electrostatic corotron. Then, the entire surface is exposed using a static elimination lamp 11 to leave a charge only on the toner image portion, and the developing device 13 is used to develop the image again to form an unfixed toner image.
This unfixed toner image is transferred to the paper 24 by the transfer corotron 14.
After the paper 24 is transferred to the fixing device 5, the paper 24 is transferred to the fixing device 5 and fixed. Thereafter, by repeating this operation, a large number of copies can be obtained using the toner image as a printing master.

The developing device 13 in such an electrostatic printing device has a ninth
As shown in Figure (al), the housing 13 has an open top surface.
The housing includes a stirring roll 13e that supplies toner supplied from a toner supply section (not shown) to each of the developing rolls 13c and 13d, and stirs the toner in the housing. It is provided. The toner that has been completely developed on the photosensitive member 2 is scraped off from the outer peripheral surface of the developing roll 13c by a scraping blade 33 provided in contact with the developing roll 13c, and also by a cross provided below the scraping plate 33. Mixing is performed by a mixer 34. This mixing is similarly performed for the supplied toner.

Then, the toner supplied to the developing roll 13d by the stirring roll 13e is scraped off by the spike regulating plate 32 installed near the developing roll 13d.
The height of the spikes of the magnetic brush formed on the outer peripheral surface of the magnetic brush is regulated to be constant, and the toner flows into a toner concentration detector 31 provided below the spike regulation plate 32. As shown in FIG. 9 (bl), this concentration detector 3I has a hopper 31a with a wide opening on the top surface, and a sensor 31b on the side of the hopper that measures the concentration of toner passing through the hopper by magnetic permeability. Based on the output of this density sensor, a controller (not shown) determines whether the toner density is lower or higher than the standard, and if the toner density is low, a dispense motor (not shown) that supplies an ON signal or toner is provided. The dispense motor is not driven when the toner concentration is low.

In this way, concentration control (hereinafter referred to as ATC) is performed.

[Problem to be solved by the invention]

By the way, conventional electrostatic printing devices have two process speeds: for example, 150 mm/sec in order to move the optical system in the copy mode, and 437 mm/sec in the print mode. The speed of the fixing device is approximately the same as the process speed in the printing mode, for example, 440 mm/see.

In addition, in the flash fixing of the plate-making process, the toner images are fixed one after another in a fixed width, so at that time, the speed of 23 mm/sec is
It is said that

In this way, in copy mode, the process speed is
Because the speed is as slow as 50 mm/sec, if the leading edge of the paper reaches the fuser while the paper is wrapped around the drum, the paper will be pulled by the fuser and the paper will rub against the drum, resulting in image distortion. Therefore, as shown in FIG. 7, the gap between the fixing device and the drum is made larger than the maximum paper size to prevent the paper from being pulled by the fixing device. Therefore,
If the size of the device is increased, or if the master is unsatisfied with the test print after creating a plate-making master to check whether the original position, magnification, etc. are set correctly before printing, the master must be rolled up. First, there is a problem that the master is wasted, and furthermore, when creating the master for plate making, there is a problem that it takes a very long time because flash fixing is performed.

In order to solve these shortcomings of the conventional electrostatic printing device, the present applicant has developed a test printing mode in which copying is performed by changing the speed of the development process and the transfer process, and a print mode. After creating an unfixed plate-making master by charging, exposing, and developing, the speed of the main motor is changed to match the speed of the fixing device, and the drum is rotated and paper is fed at high speed to transfer and fix the master. We have separately proposed an electrostatic printing device that prevents image disturbances even if the distance between the drum and the fixing device is shortened.

This type of electrostatic printing device is mainly used for printing many copies of one document, and it is unlikely that the test printing mode will be used that often, so ATC should not be performed. ing. However, depending on the user, even if the electrostatic device is mainly used for printing, it may be possible to use it in place of a copying machine for only trial printing, and if ATC is not performed during that time, the toner density may decrease.

The present invention is intended to solve the above-mentioned problems, and provides an electrostatic printing apparatus that performs ATC in a test printing mode to prevent a decrease in toner density and prevent excessive toner from adhering due to poor mixing. The purpose is to provide a toner density control method.

[Means and effects for solving the problem] The present invention is configured to charge, expose, and develop an unfixed plate-making master, then change the speed of the main motor to match the speed of the fixing device, and rotate the drum at high speed. In the test printing mode in which paper is fed, transferred and fixed, ATC is performed when creating an unfixed plate-making master and the supplied toner is mixed during the cleaning period, or ATC is performed by leaving a mixing period within the cleaning period. It is characterized by the fact that it has been implemented. By adopting such an ATC method, ATC can be performed even in the trial printing mode to prevent a decrease in toner density, and mixing can also be performed, which can prevent excessive adhesion of toner due to poor mixing. It becomes possible.

〔Example〕

Examples will be described below with reference to the drawings.

First, prior to a detailed description of the present invention, an electrostatic printing apparatus having a test printing mode, which was separately proposed by the applicant, will be described.

FIG. 4 is a diagram for explaining the concept of an electrostatic printing device having a trial printing mode, FIG. 5 is a diagram for explaining the characteristics of an electrostatic printing device having a trial printing mode, and FIG. FIG. 3 is a diagram showing a sequence. In the figure, 100 is a speed switching means, and 101 is a main motor.

In this electrostatic printing apparatus, when a test print is performed prior to printing, the speeds of the development process and the transfer process are made to be different. That is, when an unfixed plate is created by charging the photoreceptor, exposing it to light, and developing it, as shown in FIG.
As shown in FIG. 4(b), the speed switching means 100 switches the speed of the main motor 101 to a high speed side to make the photosensitive drum speed almost the same as that of the fixing device, and the paper conveyance speed is also the same. Transfer at high speed. As a result, as shown in FIG. 5, even if the distance between the drum 2 and the fuser 5 is about 300 or less, the speeds of the drum and the fuser are the same, so there is no paper between the drum and the fuser. Since the paper will not be pulled even if it straddles the paper, there will be no image disturbance, and the fruiting device can be made smaller.

FIG. 6 is a diagram showing the sequence in the trial printing mode of the present invention, where the horizontal axis shows the number of drum rotations (clock count value).
It represents.

To explain the outline of the sequence, first, when the switch is turned on, the main motor rotates, and at the home position, the exposure lamp and 15IL (lamp for erasing unnecessary image areas) are activated.
, the developing bias, and the developing motor are turned on. Then, at the specified timing, charge corotron (CC) is turned on.
to charge the photoconductor, and the carriage motor is turned off.
N, the optical system is driven, and exposure is performed. The figure shows the timings of the exposure lamp, fixing lamp, carriage motor, transfer corotron (TC), and erase corotron (EC) depending on the paper size. When the development is completed, the development motor is reversely rotated to eliminate spikes of toner and prevent the unfixed toner image from being disturbed. Then, at the same time as turning off the developing machine, the speed of the main motor was increased from +50 rrm/sec to a high speed of 437 mm/sec.
Switch to e and set it to almost the same speed as the fixing device. Then, the registration roll is turned ON to feed the paper at a timing such that the paper is aligned with the leading edge of the toner image, and the TC is turned ON at the same time as the paper to perform transfer.

After the transfer is completed, switch the main motor to PV-2 and start the EC
is turned on to make it easier to remove the toner remaining on the photoreceptor, and the developing motor is rotated to scrape off the toner with its bristles to perform cleaning. In this case, by turning on the erase lamp, the potential of the photoreceptor is set to approximately 0, and the developing bias is increased to attract the toner, thereby making it easier to scrape off the toner.

Next, the ATC method of the present invention will be explained.

In FIG. 1, in the test printing mode, the photosensitive drum is driven to rotate, and charging, exposure, and development are performed, and a toner image is formed on the photosensitive drum to create an unfixed plate. At the same time, the developer motor is rotated in the reverse direction to eliminate the bristles of the magnetic brush so that the unfixed toner image will not be disturbed by the bristles in subsequent processes, and then the developer motor is stopped.

When the unfixed plate-making process is completed, the tram speed is set to approximately match the speed of the fixing device and transfer is performed at high speed, while the developing device is stopped during this time. When the transfer process is completed, the drum speed is returned to the speed of the development process, and at the same time, the developer motor is turned on, the photosensitive drum is rotated for about two revolutions, and the erase corotron 10a shown in FIG. 2 is turned on to erase the toner. Set the charge to (+),
The erase lamp 12 is turned ON to lower the potential of the drum to make it easier for the toner to fall off, and cleaning is performed by writing off the residual toner on the drum surface with the buffing of the developing machine.

In the present invention, in the first half of this cleaning process, the density sensor 31 shown in FIG. 2 detects the toner density inside the developing machine, and if the toner density is low, a dispense motor (not shown) is driven to remove the toner inside the developing machine. Toner is supplied and the dispense motor is not driven when the toner concentration is high. Then, as shown in FIG. 1, in the latter half of the cleaning process, the supplied toner is mixed to prevent excessive adhesion of toner due to poor mixing, so-called fogging.

In the above explanation, ATC is performed at least at a timing when a mixing period is included in the cleaning period, for example, in the first half of the cleaning period, or when the developing machine motor is rotating before the cleaning period. If there is, even if toner is supplied, the supplied toner can be mixed within the cleaning period. Therefore, ATC may be performed in the unfixed plate-making process, toner may be supplied if the toner concentration has decreased, and mixing may be performed during the cleaning period.

Such ATC, for example, constantly monitors toner concentration,
The dispensing motor may be driven during the unfixed master making period or the first half of the cleaning period when the toner concentration decreases.

FIG. 3 is a diagram showing a flow in the case of constantly monitoring the density sensor and controlling ○N/○FF of the dispense motor in the trial printing mode.

First, check whether the concentration sensor is ON or OFF (step ■)
If it is ON, determine whether it is within the unfixed plate making process period (Step ■). If it is within that period, turn on the dispensing motor to supply toner (Step ■), and wait until the unfixed plate making process period has passed. For example, if the transfer process has been completed and the cleaning period is within the period of one cleaning cycle (step ①), the dispense motor is turned on. In this way, toner supply continues until the density sensor turns off, and when the density sensor turns off, the dispensing motor is stopped. Mixing is then performed in a subsequent cleaning period. Also, if the density sensor is OFF and the toner density is above a certain value, if the density sensor turns ON during the second round of the cleaning period, the mixing period cannot be taken, so the dispense motor will not turn ON in the same way. .

Note that the ATC method does not constantly monitor the toner density, but detects the density at the timing of a predetermined rotation of the photoreceptor drum, and if it is an unfixed plate-making process or the first half of the cleaning period, the toner density is detected during one rotation of the drum at that time. This may also be done by driving a dispense motor.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to perform ATC in the test printing mode to prevent a decrease in toner concentration and also to prevent excessive toner from adhering due to poor mixing.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a sequence for explaining the present invention in detail, FIG. 2 is a diagram showing the configuration of a developing machine, and FIG. 3 is a diagram showing an ATC
FIG. 4 is a diagram for explaining the concept of an electrostatic printing device having a trial printing mode. FIG.
The figure is a diagram for explaining the characteristics of an electrostatic printing device having a test print mode, FIG. 6 is a diagram for explaining the test print sequence, and FIGS. 7 and 8 show a conventional electrostatic printing device. 9 are diagrams showing the configuration of the developing machine. 31...Toner concentration detector, 31a...Hotsunoku,
31b...Sensor, 100...Speed switching means, 10
1... Main motor. Figure 1 Applicant Fuji Xerox Co., Ltd. Agent Patent Attorney Masanobu Hirukawa (7 others) Figure 2 Figure 1515a 〆

Claims (1)

[Claims] (1) Trial printing in which an unfixed plate-making master created by charging, exposing, and developing a photoreceptor that is wound in a roll inside a scroll drum and fed out along the outer circumferential surface of the drum is transferred and fixed by switching to the high speed side. mode and charging the photoreceptor;
The electrostatic printing device is capable of selecting a printing mode in which a plate-making master created by flash fixing after exposure and development is charged, exposed, developed, transferred, and fixed, and in the test printing mode, an unfixed plate-making master is selected. A toner density control method for an electrostatic printing device, characterized in that toner density control is performed during a master creation period or a cleaning period that leaves a toner mixing period.