JP5261916B2 - Electrophotographic printing device - Google Patents

Description

  The present invention relates to an electrophotographic printing apparatus such as a copying machine, a facsimile machine, and a printer.

  The background art will be described with reference to the block diagram of the developing machine in FIG. 1 and the toner density control program flowchart in FIG.

  The electrophotographic printing apparatus has a developing method called a two-component magnetic brush developing method. An image of the photoreceptor 2 is developed using a toner that is powder ink in the developer container 1 and a developer composed of carrier beads that are magnetic particles. In this system, toner on a developing roll 3 that forms a magnetic brush made of a developer is attached to an electrostatic latent image formed on the surface of the carrier, and this is developed as a toner image. In such a development system, the toner concentration, which is the mixing ratio of the developer toner and carrier beads, is an important factor in print quality.

  Therefore, in order to obtain a good printing result, a toner density sensor 4 for monitoring the toner density of the developer in the developer container 1 is provided, and a toner density reference in which the toner density VTsns output from the toner density sensor 4 is a target value. It is necessary to control the value VTref.

  Specifically, the toner density VTsns output from the toner density sensor 4 and its rate of change, and the toner replenishment amount per specified time are monitored, and the developer toner in the developer container 1 is consumed by the printing operation. However, the toner replenishing motor 7 that rotates the toner replenishing roller 6 for rotating the toner from the toner hopper 5 to the developer container 1 is appropriately driven and stopped so that the toner concentration VTsns output from the toner concentration sensor 4 does not decrease. A toner density control program 8 for executing toner supply or stopping toner supply is executed.

  The contents of the toner density control program 8 are as shown in the flowchart of FIG. 2, which is a flowchart for keeping the toner density constant.

  During printing, when the value VTsns output from the toner density sensor 4 is higher than the value for recognizing that the toner density is high (Yes in Step 1), the toner supply motor 7 is stopped and the toner supply is stopped (Step 2). On the other hand, when the value VTsns output from the toner density sensor 4 is lower than the value for recognizing that the toner density is high (No in Step 1), the value for recognizing that the change rate to the next higher toner density is higher. It is determined whether or not it is high (Step 3).

  When the change rate to the higher toner density is higher than the value for recognizing that it is higher (Yes in Step 3), the toner supply motor 7 is stopped and the toner supply is stopped (Step 4). On the other hand, when it is lower than the value for recognizing that the rate of change to the higher toner concentration is higher (No in Step 3), the value VTsns output from the toner concentration sensor 4 next is the value for recognizing that the toner concentration is low. It is determined whether or not it is low (Step 5).

  When the value VTsns output from the toner density sensor 4 is lower than the value for recognizing that the toner density is low (Yes in Step 5), the toner supply motor 7 is driven to perform toner supply (Step 6). On the other hand, when the value VTsns output from the toner density sensor 4 is higher than the value for recognizing that the toner density is low (No in Step 5), the value for recognizing that the rate of change to the next lower toner density is higher. It is determined whether or not it is high (Step 7).

  When the toner density is higher than the value for recognizing that the rate of change to the lower one is higher (Yes in Step 7), the toner replenishing motor 7 is driven to perform toner replenishment (Step 8). On the other hand, when the toner density is lower than the value for recognizing that the rate of change to the lower one is higher (No in Step 7), the toner replenishment time per specified time by the toner replenishment motor 7 is larger than the toner replenishment amount. It is determined whether or not there are more than the recognized values (Step 9).

  When the toner replenishment time per specified time by the toner replenishment motor 7 is longer than a value for recognizing that the toner replenishment amount is large (Yes in Step 9), the toner replenishment motor 7 is stopped and the toner replenishment is stopped (Step 10). On the other hand, when the toner replenishing time per specified time by the toner replenishing motor 7 is less than the value for recognizing that the toner replenishing amount is large (No in Step 9), the toner replenishing time per specified time by the toner replenishing motor 7 is It is determined whether or not the replenishment amount is smaller than a value for recognizing that it is small (Step 11).

  When the toner replenishment time per specified time by the toner replenishment motor 7 is less than the value for recognizing that the toner replenishment amount is small (Yes in Step 11), the toner replenishment motor 7 is driven to perform toner replenishment (Step 12).

  According to the above flowchart, the toner density VTsns output from the toner density sensor 4 is controlled to be within an appropriate range centered on the toner density reference value VTref.

JP-A-8-76583 JP 2003-195622 A JP-A-8-110700 JP 2001-281979 A

  In this type of electrophotographic printing apparatus, even when the developer toner density VTsns output from the toner density sensor 4 is within an appropriate range, printing at a high print density results in a lower image density VTdns of the print result. There is. Specifically, as shown in FIG.

  This is because the developer used has a characteristic of being charged by performing printing with a high print density.

  When the developer is charged, the toner density sensor 4 outputs the toner density VTsns higher than the actual toner density VTdev of the developer. In the toner density control program 8, the control is continued so that the toner density VTsns output from the toner density sensor 4 becomes the target toner density reference value VTref. Since the density VTsns is output higher than actual, the actual developer toner density VTdev is controlled to be lower.

  It is an object of the present invention to prevent the actual developer toner density VTdev from being lowered by executing printing at a high print density, and to maintain a constant image density VTdns of the printing result. Is to provide.

  In order to achieve the above object, the first means of the present invention comprises a developer accommodating portion that accommodates a developer composed of two components of toner and carrier beads, and is rotatably supported by the developer accommodating portion. A developer roll that forms a magnetic brush with a developer, a toner concentration sensor that monitors the toner concentration of the developer provided in the developer container, and an upper part of the developer container, the developer container A toner hopper that contains toner for replenishing the toner, a toner replenishing roller that is provided in the lower part of the toner hopper and rotates to replenish the toner in the toner hopper to the developer accommodating portion, and rotates the toner replenishing roller Therefore, the toner replenishing motor to be driven and the output value VTsns of the toner concentration sensor are set to the toner concentration reference value VTref which is a target value. -In an electrophotographic printing apparatus having a toner density control program for instructing driving and stopping of a replenishment motor, when printing at a high printing density is executed, the phenomenon that the image density VTdns of the printing result is lowered due to the characteristics of the developer As a result of recognizing that printing at a printing density is being executed and printing at a high printing density, the image density VTdns of the printing result is lowered, so that the toner density reference value VTref is set higher, and the printing result image The density VTdns is kept constant.

  According to a second means of the present invention, in the first means, the fact that printing with a high print density is being executed, the command from the host device is not used, and the toner in the toner hopper is transferred to the developer container. It is characterized by recognizing from the rotation rate of the toner replenishing motor driven to replenish the toner.

  In the electrophotographic printing apparatus configured as described above, the toner density reference value VTref is set high when printing at a high printing density, so that even if printing at a high printing density is executed, the actual developer It is possible to prevent the toner density VTdev from being lowered and to output a printing result with a stable image density VTdns.

  In addition, as shown in FIG. 4, the electrophotographic printing apparatus is configured to determine that printing with a high print density is being performed based on the rotation rate per specified time of the toner replenishment motor 7 that is driven to replenish toner. It becomes possible to judge by.

  When high density printing is being performed, the toner density reference value VTref, which is the target value of the toner density, which has been a fixed value in the past, is corrected by the amount ΔVTdev by which the actual toner density VTdev of the developer decreases. Set to a high value (VTref = VTref + ΔVTdev).

  Means for recognizing that high-density printing is being performed is as follows.

  In the electrophotographic printing apparatus, the toner supply motor 7 is driven to supply toner from the toner hopper 5 to the developer accommodating portion 1 so that the toner density does not decrease even when printing is performed and the developer toner is consumed. ing. Since the developer toner is consumed as the printing density increases, the rotation rate of the toner supply motor 7 also increases. Using this relationship between the print density and the rotation rate of the toner replenishing motor 7, it is recognized that printing with a high print density is being executed.

  The purpose of preventing a decrease in the image density VTdns of the print result when printing at a high print density is performed, a change to a developer that does not decrease the image density, addition of a sensor for detecting a decrease in the image density, etc. This is realized only by changing the control method of changing the setting of the toner density reference value.

  In the electrophotographic printing apparatus, as shown in FIG. 5, the print data is printed from the controller, which is the host apparatus, only through hardware. Since the software executes printing control but has no means of grasping print data, high-density printing is performed by a controller that is a host device of an electrophotographic printing apparatus that processes print data. Can be recognized relatively easily.

  As shown in FIG. 6, a print density determination program for determining that high-density printing is being executed from print data in the controller, and whether or not high-density printing is being executed are sent to the electrophotographic printing apparatus. If a command to be transmitted is added to the interface processing of both the controller and the electrophotographic printing apparatus, the electrophotographic printing apparatus can recognize that printing of high print density is being executed by the command.

  However, if one function is provided in combination with the host device, the versatility of the host device decreases. There is a problem in upgrading the program of only one of the host apparatus and the electrophotographic printing apparatus. The fact that the relationship between the host device and the electrophotographic printing device becomes deep causes the creation of defects, and so the fact that high-density printing is being performed is confirmed from the host device of the electrophotographic printing device. It was realized by judgment using an electrophotographic printer without requiring instructions.

  The toner density reference value VTref, which is a target value of the toner density, which has been a fixed value in the past, is corrected as shown in FIG. 7 by reducing the image density VTdns of the printing result by performing printing at a high printing density, A toner density reference value setting control program for setting a high value is added.

  The contents of the toner density reference value setting control program will be described with reference to the flowchart of FIG. The toner density reference value setting control program is executed during printing.

  When printing is not performed at a high printing density (No in Step 1), the toner density reference value VTref is set to 2.0 V ((a) in FIG. 7) (Step 2).

  On the other hand, when printing at a high print density (Yes in Step 1), the toner density reference value VTref is set to 2.375 V ((b) in FIG. 7) (Step 3).

  As described above, the toner density reference value setting control program corrects the amount of decrease in the actual toner density VTdev, and the toner density control program 8 is executed with the toner density reference value set higher (VTref = VTref + ΔVTdev). As a result, it is possible to prevent a decrease in the image density of the printed result.

The following three elements are used by the electrophotographic printing apparatus to determine that high-density printing is being performed.
(1) When continuous printing with a print density of 8% or more is continuously performed, a phenomenon occurs in which the image density of the printed result is lowered.
(2) The rotation rate of the toner replenishing motor is 18% during printing with a printing density of 8%.
(3) The time from when the developer starts to be charged until the image density of the printing result decreases is after 3 minutes or more have elapsed.

  The conditions for stably recognizing whether or not printing with a higher printing density is being performed are as follows.

  When the rotation rate per minute of the toner replenishing motor 7 is 18% or more continuously for 3 times (3 minutes), it is recognized that high-density printing is being performed, and conversely, 18 times for 3 times (3 minutes) continuously. Add a high print density printing judgment control program that recognizes printing that is not at high print density when it is less than%.

  The contents of the high printing density printing determination control program will be described with reference to the flowchart of FIG.

  First, at Steps 1 to 4, the rotation time of the toner replenishing motor 7 per minute is calculated.

  When the rotation time of the toner replenishing motor 7 per minute is detected continuously three times that is 10.8 sec (18% of one minute) or more (Yes in Step 5), it is assumed that printing with high print density is being executed. Recognize (Step 6). On the other hand, when the rotation time of the toner replenishing motor 7 per minute is not detected three times continuously at 10.8 sec (18% of one minute) or more (Step 5 No), the toner replenishing motor per minute is next. It is determined whether or not the rotation time of 7 is less than 10.8 sec three times continuously (Step 7).

  When the rotation time of the toner replenishing motor 7 per minute is detected three times continuously less than 10.8 sec (Yes in Step 7), it is recognized that printing with a high print density is being executed (Step 8).

  As described above, the high print density printing determination control program can recognize that high-density printing is being performed in the electrophotographic printing apparatus without requiring the intervention of a controller which is a host device.

It is explanatory drawing which showed the structure of the developing machine. FIG. 6 is an explanatory diagram showing a flowchart of a toner density control program. It is explanatory drawing which showed the image density fall when printing of high printing density was performed. It is explanatory drawing which showed the method of recognizing high printing density printing with an electrophotographic printing apparatus. It is explanatory drawing which showed the flow of the printing data in an electrophotographic printing apparatus. It is explanatory drawing which showed the method of recognizing high printing density printing by the instruction | indication from a controller. FIG. 6 is an explanatory diagram showing toner density reference value setting based on printing density. FIG. 6 is an explanatory diagram showing a flowchart of a toner density reference value setting control program. It is explanatory drawing which showed the flowchart of the high printing density printing judgment control program.

Explanation of symbols

Reference numeral 1 denotes a developer container, 2 denotes a photosensitive member, 3 denotes a developing roll, 4 denotes a toner density sensor, 5 denotes a toner hopper, 6 denotes a toner supply roller, 7 denotes a toner supply motor, and 8 denotes a toner density control program.

Claims (1)

A developer accommodating portion for accommodating a developer comprising two components of toner and carrier beads, provided in said developer accommodating portion, and a developing roller to form a magnetic brush by the developer, the toner concentration before Symbol developer A toner density sensor to be monitored; a toner hopper provided in an upper portion of the developer accommodating portion; for accommodating toner for replenishing the developer accommodating portion; and provided in a lower portion in the toner hopper; A toner concentration reference value in which a toner supply roller that rotates to replenish the developer container, a toner supply motor that drives to rotate the toner supply roller, and an output value VTsns of the toner concentration sensor is a target value. An electrophotographic printing apparatus having a toner density control program for instructing to drive and stop the toner replenishing motor so as to become VTref. There are, the electrophotographic printing apparatus, recognizing Then the toner concentration being executed recognizing high print density printing determination control program and executing the printing of high printing density by turnover, the printing of high printing density of the toner supply motor electrophotographic printing apparatus characterized by having a toner concentration reference value setting control program to maintain the image concentration of the printed result by setting a high reference value constant.

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