JP2009053329A - Toner density control device and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a toner concentration controller capable of accurately controlling toner concentration without taking much time for initial developer setting and also even when the initial developer setting is not performed in using a developing device for 2PM, that means, the developing device is replaced and used again in another image forming apparatus. <P>SOLUTION: Provided is the toner concentration controller for the image forming apparatus which is equipped with an image carrier, a developing device, a toner concentration sensor, a control means to change and adjust a detection signal Vt from the toner concentration sensor to a control signal value Vcnt, a toner supply device, the toner concentration controller to control toner concentration, a Vcnt adjusting mode on/off storage device, and a Vcnt storage device to store the control signal value Vcnt therein, and stores the adjusted Vcnt in the Vcnt storage device, performs toner concentration control based on the stored Vcnt, and adjusts the Vcnt after changing the developing device when on of a Vcnt adjusting mode is selected. The toner concentration controller is equipped with a sensitivity storage device for storing sensitivity of the toner concentration sensor, and decides a Vcnt value based on the Vcnt value adjusted when the Vcnt adjusting mode is made on and the stored sensitivity of the toner concentration sensor when changing the developing device. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an image forming apparatus such as a copying machine, a facsimile machine, a printer, or a composite machine of these, and more specifically, an image forming apparatus including a developing device using a two-component developer composed of a magnetic carrier and a toner. The present invention relates to a toner density control device for controlling the toner density of the developing device and an image forming apparatus provided with the toner density control device.

2. Description of the Related Art Conventionally, in an image forming apparatus such as an electrophotographic copying apparatus, a two-component developing apparatus that performs development using a two-component developer composed of a magnetic carrier and toner, and a one-component developing apparatus that performs development using only toner Is known.
The two-component developing device usually includes a developing sleeve that is a cylindrical developer carrier that is rotatably supported, and a magnet roller that includes a magnet body having a plurality of magnetic poles arranged inside the developing sleeve. The developing sleeve and the magnet roller may be collectively referred to as a developing roller. In the two-component developing device, the magnetic carrier with the toner attached to the surface of the developing sleeve is carried to the developing area which is opposite to the image carrier, and developed with a magnetic brush made of two-component developer. Is to do.

  In the two-component developing device having such a configuration, charging is performed by stirring and mixing the magnetic carrier and the toner, so that the charging property of the toner is stable and a relatively stable good image can be obtained. However, since the toner density fluctuates due to carrier deterioration and toner in the developer is consumed, there are disadvantages such as fluctuation in the mixing ratio of the toner and the magnetic carrier. Further, in order to suppress fluctuations in the mixing ratio of the toner and the magnetic carrier, it is necessary to provide a toner concentration control device and replenish the toner as necessary to suppress the fluctuations.

  On the other hand, the one-component developing device carries out development by transporting the toner carried on the surface of the developer carrying member to the development area. For this reason, unlike the two-component developing device, it does not have the drawback of having a carrier deterioration or toner concentration control device, but has the disadvantage that the charging property is difficult to stabilize.

When a two-component developing device is used, the triboelectric charge amount of the developer varies depending on the environment, running conditions, mechanical conditions, and sensor variations. If the change in the charge amount is controlled using an optical sensor so that the pattern adhesion amount becomes constant, the toner density fluctuates instead of the charge amount becoming substantially constant.
In particular, if the toner density rises above a certain value due to low-temperature humidity and fluctuations in the charge amount of the carrier, there is a limit to the coverage of the carrier. Toner is generated, causing toner scattering, background dirt, and the like.
On the contrary, when the charge amount of the developer is lowered, if the pattern adhesion amount is controlled to be constant, there is a problem that the toner density is lowered and the image density is insufficient and carrier adhesion occurs in a solid image.

In order to prevent this problem, a method is generally used in which a limiter is provided in the reference value of the output value of the toner density sensor so that the output value falls within a certain value (or above) (for example, Patent Documents). 1, see Patent Document 2).
By this method, it is possible to suppress an increase (decrease) in toner density over time and environment to some extent.
Also, since this method may have different sensitivities for each toner density sensor, the sensitivity variation among the sensors can be canceled by adjusting the control voltage of the toner density sensor when the developer is in the initial stage.

  However, in the above-described conventional technology, for example, when the cleaning device and the developing device are used as an integrated cartridge, the developing device is once removed at the end of the cleaning device's life, and then reinserted into another image forming apparatus main body to be used again. (Hereinafter referred to as “use of 2PM of the development unit”), etc., if the initial agent setting is performed when the developer has a different toner density over time, the limiter of the toner density sensor to be originally applied is set. There is a problem that the position is shifted.

JP 2003-57939 A Japanese Patent No. 3451470

  In order to prevent the above-described problems of the prior art, the present inventors have stated that “the image carrier and a two-component developer that is detachably provided from the main body device and holds toner and a carrier and holds the latent image on the image carrier. A developing device that develops an image with the developer toner to make a visible image, a toner concentration sensor that is provided in the developing device and detects the toner concentration of the developer, and a detection signal Vt of the toner concentration sensor is used as the toner. Control means that can be adjusted by changing a control signal value Vcnt input to the density sensor, a toner replenishing device that replenishes the toner to the developing device, and a toner concentration control device that controls the toner concentration of the developer A Vcnt adjustment mode on / off storage device provided in the developing device or the toner concentration sensor, and the control signal value Vcnt provided in the developing device or the toner concentration sensor are stored. the Vcnt storage device, the adjusted Vcnt is stored in the Vcnt storage device, the toner density control is performed based on the stored Vcnt, and when the Vcnt adjustment mode on is selected, the development The present inventors have invented a “toner density control device for an image forming apparatus” that performs Vcnt adjustment after replacing the device.

  In the toner density control device of this image forming apparatus, if the Vcnt adjustment is performed after the main power supply is turned on only when the Vcnt adjustment mode on is selected, only the cartridge cleaning device is replaced, and the developing device is not replaced. In this case, the Vcnt adjustment mode (hereinafter referred to as “initial agent setting”) off is selected, and Vcnt can be determined regardless of the toner concentration of the developer in the developing device.

  However, once Vcnt is stored in the toner density sensor as described above, if a developing device in which Vcnt is stored in a machine with a different linear speed, such as a series machine of an image forming apparatus, is reused, the toner density (TC) There is a problem that the relationship of the output Vt of the toner density sensor (HST sensor) is shifted. FIG. 9 shows an example, and # 27 and # 28 are Vcnt adjusted with a machine with a linear speed of 150 mm / sec. When this is used with a machine with a linear speed of # 26 and 200 mm / sec, , TC-Vt relationship is shifted.

Therefore, in such a case, the Vcnt value determination method used when the linear speed of the machine that uses the developing device for the second PM is different from the linear speed of the machine that originally set the initial agent (used for the first PM) is used. Is
(1) Perform initial agent setting at multiple linear speeds when setting the initial agent of the original machine.
(2) The Vcnt shift amount for each linear velocity is determined in advance as a fixed value, and the value is corrected.
There is a method.

However, in the above method (1), since the initial agent is set for each linear speed, accurate initial agent setting can be performed. On the other hand, when the initial agent is set in the machine using the first developing device 1PM, the initial agent is set at a plurality of linear speeds. Since the agent setting must be performed, there is a problem in that it takes too much time to set the initial agent. For example, as shown in FIG. 10, in the case of a series machine of image forming apparatuses, when each machine of machine a, machine b and machine c has a plurality of linear speeds, a considerable time is required.
In the method (2), the initial agent setting is performed only at a certain linear speed, so the initial agent setting time does not take. However, since it is a constant value, it includes variations in sensor sensitivity. There is a problem.

  The present invention has been made in view of the above circumstances, and it is possible to control the toner concentration with high accuracy even when the initial agent setting time is not required and the initial agent setting is not performed for the second use of the developing device. An object of the present invention is to provide a control device and an image forming device that includes the toner density control device and can perform good image formation.

In order to achieve the above object, the present invention employs the following solutions.
According to a first aspect of the present invention, an image carrier and a two-component developer that is detachably provided from the main body device and holds a toner and a carrier, and a latent image on the image carrier is transferred with the toner of the developer. A developing device that develops a visible image, a toner concentration sensor that is provided in the developing device and detects the toner concentration of the developer, and a control signal that is input to the toner concentration sensor as a detection signal Vt of the toner concentration sensor Control means that can be adjusted by changing the value Vcnt, a toner replenishing device that replenishes the toner to the developing device, a toner concentration control device that controls the toner concentration of the developer, and the developing device or the toner concentration A Vcnt adjustment mode on / off storage device provided in the sensor, and a Vcnt storage device that stores the control signal value Vcnt provided in the developing device or the toner density sensor. The adjusted Vcnt is stored in the Vcnt storage device, the toner density control is performed based on the stored Vcnt, and when the Vcnt adjustment mode on is selected, the Vcnt adjustment is performed after replacing the developing device. The toner density control device of the forming apparatus includes a sensitivity storage device of the toner density sensor, and when the developing device is replaced, based on the Vcnt value adjusted when the Vcnt adjustment mode is on and the stored sensitivity of the toner density sensor. And determining the Vcnt value.

  According to a second means of the present invention, in the toner density control device according to the first means, the toner density sensor has a Vcnt correction value storage device, and when the developing device is replaced, the adjustment is performed when the Vcnt adjustment mode is on. Based on the measured Vcnt value and the stored Vcnt value of the toner density sensor, a Vcnt value used for toner density control after replacement of the developing device is determined.

  According to a third means of the present invention, in the toner density control device of the first means, a Vref upper / lower limit correction value storage device for the toner density sensor is provided, and when the developing device is replaced, the stored toner density sensor is provided. The Vref upper / lower limit value used for toner density control after replacement of the developing device is determined based on the Vref upper / lower limit correction value.

  According to a fourth aspect of the present invention, there is provided an image forming apparatus including the toner concentration control apparatus according to any one of the first to third means.

  The toner density control device of the first means includes a toner density sensor sensitivity storage device, and when the developing device is replaced, based on the Vcnt value adjusted when the Vcnt adjustment mode is on and the stored sensitivity of the toner density sensor. Since the Vcnt value is determined in this way, it is possible to accurately control the toner density even when the initial agent setting time is not spent and the initial agent setting is not performed for the second use of the developing device.

  The toner density control device of the second means includes the Vcnt value storage device of the toner density sensor in addition to the configuration and effect of the first means, and when the developing device is replaced, the Vcnt value adjusted when the Vcnt adjustment mode is on Since the Vcnt value used for toner density control after replacement of the developing device is determined based on the stored Vcnt value of the toner concentration sensor, the time required for setting the initial agent is not increased, and the second PM of the developing device is used. Even when the initial agent is not set for use, accurate toner density control can be performed.

  The toner density control device of the third means includes a Vref upper / lower limit correction value storage device for the toner density sensor in addition to the configuration and effect of the first means, and the stored toner density sensor when the developing device is replaced. Since the Vref upper and lower limit values used for toner density control after replacement of the developing device are determined based on the Vref upper and lower limit correction values, the initial setting time of the initial agent is not required, and the development device is initially used for the second PM. Even when the agent setting is not performed, the toner density can be accurately controlled.

  In the image forming apparatus of the fourth means, the toner density control device described in any one of the first to third means is provided, so that the toner density control can be performed with high accuracy, and good and high image quality can be achieved. Image formation can be performed.

  The best mode for carrying out the present invention will be described below with reference to the drawings. However, these are merely embodiments and do not limit the present invention.

FIG. 1 is a diagram illustrating a configuration example of an image forming apparatus according to an embodiment of the present invention. The image forming apparatus 100 includes a photoconductor 5 as an image carrier, a photoconductor unit 1 including a charging device and a cleaning device, an exposure device 104 such as a laser scanning method, and a two-component developer composed of toner and a carrier. A developing unit 2 that is a developing device to be used, a transfer device 105 that conveys the transfer paper P and transfers the toner image on the photosensitive member 5 to the transfer paper P, and a paper feeder that feeds and conveys the transfer paper P from the paper feed tray 109. A paper conveying device and a fixing device 106 for fixing the toner image to the transfer paper P after the transfer paper P to which the toner image has been transferred are separated from the photoreceptor are provided. The image forming apparatus 100 includes a configuration example of a so-called tandem color printer in which four image forming units each including the photosensitive unit 1 and the developing unit 2 are arranged along the transfer belt 105a of the transfer device 105. It has become. Although the configuration of the four image forming units is the same, the toner colors of the developers used in the developing device are different. For example, yellow and magenta are used in the four image forming units. Cyan and black images are formed.
If only one image forming unit including the photosensitive unit 1 and the developing unit 2 is provided, a single color image forming apparatus is obtained. If a document reading unit (scanner), an automatic document feeder (ADF), or the like is installed on the upper part of the image forming apparatus 100 shown in FIG. 1, a digital copier is constructed, and an image processing function and a communication function are added. If it is connected to an external communication line, LAN, etc., it can function as a facsimile or a digital multi-function peripheral.

  FIG. 2 is an enlarged view of the transfer device of the image forming apparatus shown in FIG. The transfer device 105 is configured such that an endless transfer belt 105a is stretched over a support roller and pressed against the support roller via the transfer belt 105a. The reference density pattern sensor (P sensor) 121 detects the density of the reference pattern formed on the transfer belt 105a.

  In the image forming apparatus 100 configured as described above, the surface of the rotating photoconductor 5 is uniformly charged by the charging device and then irradiated with the laser beam or the like of the exposure device 104 based on the image information. An electrostatic latent image is formed on the surface. A toner image is formed by attaching a toner charged by a developing device to the electrostatic latent image formed on the photoreceptor 5 to form a visible image. On the other hand, the transfer paper P is fed from a paper feed tray 109 by a paper feed / conveyance device, and then conveyed to a transfer portion where the photoconductor 5 and the transfer device 105 face each other. Then, the toner image formed on the photoconductor 5 is transferred to the transfer paper P by applying a charge having a polarity opposite to that of the toner image on the photoconductor 5 to the transfer paper P by the transfer device 105. Next, the transfer paper P is separated from the photoconductor 5 and sent to the fixing device 106, and the fixing device 106 fixes the toner on the transfer paper P to obtain an image. Thereafter, the transfer paper P on which the toner image is fixed is discharged by a paper discharge roller 111 to a paper discharge tray 112 at the top of the image forming apparatus.

FIG. 3 is an enlarged view of the photosensitive unit and the developing unit of the image forming apparatus according to the present embodiment. A charging device 4, a cleaning device 3, a developing unit 2 as a developing device, and the like are sequentially arranged around the photoconductor 5 as an image carrier.
The photoconductor unit 1 has a configuration common to the image forming units of the respective colors, in which the charging / cleaning process is housed in one unit. The photosensitive member 5 is charged by the charging roller 4A. The charging cleaning roller 4B attached to the upper part of the charging roller 4A cleans the charging roller 4A. Untransferred toner on the photoconductor 5 is collected by the cleaning blade 3C and the cleaning brush 3A, and sent to the waste toner conveying coil 3B side. The waste toner is transported from the waste toner transport coil 3B to the waste toner discharge port and collected by a waste toner bottle (not shown).

The development unit 2 has a new configuration common to the image forming units of the respective colors, and after being mounted on the image forming apparatus 100, from the toner cartridge 6 separately provided in the main body of the image forming apparatus 100 via the toner supply port. When each color toner is replenished and mixed with the carrier, each color developing unit becomes independent. Therefore, the developing unit 2 after the toner is replenished becomes incompatible and cannot be replaced between the colors. Each photoconductor unit 1 and each developing unit 2 are configured such that they can be replaced as needed by releasing their stoppers when necessary.
In the image forming apparatus according to the present embodiment, a process cartridge in which the photoconductor unit 1 and the developing unit 2 are integrated can be used for each color image forming unit. And is detachably installed.

  The toner density of the developing unit 2 is detected by the toner density sensor 2C and the reference density pattern sensor (P sensor) 121 shown in FIG. The toner concentration sensor 2C is an inductance sensor, and detects the toner concentration from the ratio of the toner and the carrier by measuring the magnetic permeability of the developer mixed with the toner and the carrier. When the toner density is equal to or lower than a predetermined value, toner is supplied to the developing unit 2 from the toner cartridge 6.

  FIG. 4 is a schematic configuration diagram of the developing device of the image forming apparatus according to the present embodiment. This developing device is provided as a developing unit 2 on the side of the photoreceptor 5 and serves as a developer carrying member that carries a two-component developer (hereinafter referred to as “developer”) containing toner and a magnetic carrier on the surface. A developing roller 2D made of a non-magnetic developing sleeve is provided. The developing roller 2D is attached so as to be partially exposed from an opening formed on the photosensitive member side of the developing casing, and is rotated by a driving device (not shown). Further, a magnet roller (not shown) composed of a fixed magnet group as a magnetic field generating means is fixedly arranged inside the developing sleeve of the developing roller 2D. Further, the developing device includes a doctor blade 2E as a developer regulating member made of a rigid body that regulates the amount of developer carried on the developing sleeve of the developing roller 2D. A developer accommodating portion for accommodating the developer is formed on the upstream side of the rotation direction of the developing roller 2D with respect to the doctor blade 2E, and a conveying screw (left) 2A for agitating and mixing the developer in the developer accommodating portion, conveying A screw (right) 2B is provided. A toner replenishing port disposed above the developer accommodating portion; a toner cartridge 6 filled with toner to be replenished to the developer accommodating portion; and a toner feeding device that connects the toner replenishing port and the toner cartridge 6. Is provided.

  In the developing device having the above-described configuration, the developer in the developer container is agitated by rotating the transport screw (left) 2A and the transport screw (right) 2B, and the toner and the magnetic carrier are triboelectrically charged in opposite polarities. Is done. The developer is supplied to the peripheral surface of the developing sleeve of the developing roller 2D that is rotationally driven, and the supplied developer is carried on the peripheral surface of the developing sleeve, and is conveyed in the rotation direction by the rotation of the developing sleeve. Next, the amount of the conveyed developer is regulated by the doctor blade 2E, and the regulated developer is conveyed to a development area where the photoconductor 5 and the developing roller 2D face each other. In this developing region, the toner in the developer is electrostatically transferred to the electrostatic latent image on the surface of the photoconductor 5, and the electrostatic latent image is visualized as a toner image.

  In an image forming apparatus such as a copying machine or a printer, in order to maintain the image density, a toner test pattern is created outside the printing area of the photosensitive member 5 or the transfer belt 105a, and the amount of pattern adhesion is measured using a reference density pattern sensor ( It is necessary to control the image forming conditions so that the adhesion amount is optimized by detecting with the P sensor 121), and particularly in a full color machine as shown in FIG. 1, the density gradation and color reproducibility are maintained. Therefore, it is necessary to detect from the high density part to the low density part.

  Further, when detecting from a high density part to a low density part, it is necessary to create a plurality of toner image patterns in order to obtain gradation. As a method of creating a plurality of toner image patterns, a toner image pattern is formed by varying a developing bias and exposure energy in the rotation direction on the photosensitive member, and the toner image pattern is transferred to a transfer belt, and a reference density pattern sensor When the toner image pattern reaches a position such as (P sensor) 121, the density is generally detected sequentially. In this case, since the detection time becomes long, frequent detection cannot be performed, and the detection is performed at a predetermined time or at a predetermined print number interval.

Next, specific examples of the toner concentration control apparatus of the present invention will be described.
The actual machine configuration of the machine main body of the present embodiment is the same as that of the image forming apparatus described with reference to FIGS.
FIG. 5 shows a block diagram of the toner concentration control apparatus of this embodiment. A storage device such as a CPU, ROM, or RAM serving as a main control unit is installed in the machine main body, and controls each driving means such as a main motor and a developing motor via various drivers. Vcnt storage device, Vcnt adjustment on / off mode storage device, Vpnt adjustment Vp storage device, HST sensor sensitivity storage device, HST sensor Vcnt storage device, HST Sen Vref upper and lower limit storage device, toner of developing device It is provided in the concentration sensor (name in this embodiment is “HST sensor”).

[Example 1]
FIG. 6 is a flowchart showing an embodiment of the control operation of the toner density control device of the first means described above. Hereinafter, description will be made along the embodiment of FIG.
(1) Turn on the main power.
(2) Motor start-up: The photosensitive member and the developing device are rotated to stabilize the fluidity of the developer. (T sensor output Vt is stabilized.)
・ Vcnt = Vcnt1
(3) Vcnt adjustment mode on: When the Vcnt adjustment off / on signal Vcnt (off / on) stored in the storage device provided in the toner density sensor of the developing device is 1 (on), the Vcnt adjustment procedure is performed. Proceed.
(4) Vcnt1 = 5.0V: Vcnt1 is set to the upper limit value Vcnt of 5.0V.
(5) Vcnt = Vcnt1-0.1V
(6) Vt1 detection: Toner density sensor output Vt1 at Vcnt1 is detected.
(7) Vt1 storage: Vt1 is stored in the RAM of the main body.
(8) Vt1 = 3.0 ± 0.2V: It is determined whether Vt1 is within the target value of 3.0V. If not, decrease Vcnt1 by 0.1V.
(9) Vcnt0 = Vcnt1: When Vt1 enters the target value, it is determined that Vcnt adjustment is completed, and Vcnt1 is stored as Vcnt0 in a memory (Vcnt storage device) provided in the HST sensor.
The toner density control during normal linear speed printing is performed using this Vcnt0 value.
(10) Vcnt adjustment The signal Vcnt (off / on) of the off / on mode storage device is set to “0” (off).
(11) “Initial agent setting Vp” of the machine for which the initial agent setting has been performed is stored as Vp1.
(12) Stop motors: End Vcnt adjustment, stop motors, and end Vcnt adjustment.

(13) When Vcnt (off / on) is 0 (off) in (3) above, the cartridge is replaced, but it is determined that only the cleaning device is new and the developing device is used for the second PM. There is no drug setting.
(14) When the linear speed “main body Vp” of the machine body in which the replaced developing device is used for the second PM is the same as the linear speed “initial agent setting Vp” of the machine body in which the initial agent is set when the first PM is used Then, Vcnt0 used for toner density control during normal linear speed printing is set to Vcnt0 = Vcnt1, and the initial agent setting mode is terminated.
Thereafter, the above operations (10) to (12) are performed.

(15) In the above (14), the linear speed “main body Vp” of the machine main body in which the replaced developing device is used for the second PM is the initial speed setting of the main body of the machine main body when the first PM is used. If it is different from “Vp”, the flow goes to a flow for correcting the linear velocity of Vcnt.
(16) The sensitivity (Vt / toner concentration TC) of the HST sensor varies somewhat from sensor to sensor (see FIG. 9). The sensitivity of each sensor is measured by the toner density sensor sensitivity measurement jig in the mass production process and stored in a storage device provided in the HST sensor. (Sensitivity measurement jig: In the present invention, Vt / TC linearity at 5 points is measured using a developer with a varying toner concentration as a sample piece.)
In the embodiment of the present invention, Vt / TC is used, but a method of storing Vcnt / TC is naturally conceivable.
(17) Read Vt / TC stored in the HST sensor.
(18) The value “Vcnt0” determined by the initial agent setting used for the first PM is Vcnt0 used for toner density control during normal linear speed printing.
The value “Vcnt / Vp” determined from the relationship between the mechanical linear velocity Vp and Vcnt when measured with the HST sensor fixed,
"Vt / TC", a value obtained by measuring the mass production variation of HST sensor sensitivity for each sensor
A value “Vcnt / Vt” determined from the relationship between the sensitivity of the HST sensor and Vcnt,
To Vcnt0.
Thereafter, the above operations (10) to (12) are performed.

  As described above, the toner density control device according to the present embodiment includes the sensitivity storage device of the toner density sensor. When the developing device is replaced, the Vcnt value adjusted when the Vcnt adjustment mode is on and the stored toner density sensor Since the Vcnt value is determined based on the sensitivity of the toner, accurate toner concentration control can be performed even when the initial agent setting is not performed for the second use of the developing device without taking the time for setting the initial agent. Can do.

  In this embodiment, since the developing device is used only up to the second PM, Vcnt0 is stored in the storage device of the HST sensor in any flow. Of course, it is only necessary to store only the initial agent set value at the time of using the first PM.

[Example 2]
Next, FIG. 7 is a flowchart showing an embodiment of the control operation of the toner density control device of the second means described above, and shows only a part of the control operation. This control operation is executed in place of the operations (16) to (18) in the first embodiment, and the control operations in (1) to (15) are the same as those in the first embodiment, and are therefore omitted here. To do. Hereinafter, description will be made along the embodiment of FIG.

(16) The sensitivity (Vt / toner concentration TC) of the HST sensor varies slightly from sensor to sensor. Using a sensitivity measurement jig for the toner concentration sensor, Vcnt values such that Vt takes a constant value (for example, 3.0 V) are measured in the mass production process for each sensor, and stored in a storage device provided in the HST sensor. It is remembered.
(17) Read Vcnt / TC stored in the HST sensor.
(18) The value “Vcnt0” determined by the initial agent setting at the time of using the first PM is Vcnt0 used for toner density control at normal linear speed printing.
The value “Vcnt / Vp” determined from the relationship between the mechanical linear velocity Vp and Vcnt when measured with the HST sensor fixed,
The value “Vcnt / TC” obtained by measuring the variation in mass production of the HST sensor Vcnt for each sensor,
To Vcnt0.
Thereafter, the operations (10) to (12) of the first embodiment are performed.

  As described above, the toner density control apparatus of the present embodiment includes the Vcnt value storage device of the toner density sensor. When the developing device is replaced, the Vcnt value adjusted when the Vcnt adjustment mode is on and the stored toner density Since the Vcnt value used for toner density control after replacement of the developing device is determined based on the Vcnt value of the sensor, the initial agent setting is performed for the second use of the developing device without taking the time for setting the initial agent. Even when the toner density is not present, the toner density can be accurately controlled.

[Example 3]
FIG. 8 is a flowchart showing an embodiment of the control operation of the toner density control apparatus of the third means described above, and shows only a part of the control operation. This control operation is executed in place of the operations (16) to (18) in the first embodiment, and the control operations in (1) to (15) are the same as those in the first embodiment, and are therefore omitted here. To do. Hereinafter, description will be made along the embodiment of FIG.

(16) In the toner density control of this embodiment, Vt does not fall below the target value of Vt (Vref lower limit (the toner density and Vt are in a half proportional relationship with the HST sensor)) so that the toner density does not increase excessively. Thus, when Vref lower limit> Vt, toner is not replenished.
However, the sensitivity (Vt / toner concentration TC) of the HST sensor varies somewhat from sensor to sensor.
The sensitivity measurement jig of the toner density sensor, the sensitivity of each sensor is 100% measured by the sensitivity measurement jig of the toner density sensor in the mass production process, the Vref lower limit correction value is determined based on the measured value, and the HST sensor Is stored in the Vref lower limit storage device.
The Vref lower limit value is used in the embodiment of the present invention, but the same applies to the Vref upper limit value.
(17) Read Vcnt's linear velocity shift amount Vcnt / Vp.
(18) The value “Vcnt0” determined by the initial agent setting at the time of using the first PM is Vcnt0 used for toner density control at normal linear speed printing.
The value “Vcnt / Vp” determined from the relationship between the mechanical linear velocity Vp and Vcnt when measured with the HST sensor fixed,
To Vcnt0.
(19) Read the Vref lower limit correction value stored in the storage device equipped with the HST sensor.
(20) From the Vref lower limit correction value, the value of the Vref lower limit value 1 (fixed value (for example, 1.5 V)) when the machine linear velocity is fixed is corrected to determine the Vref lower limit value for normal linear velocity printing. To do.
Thereafter, the operations (10) to (12) of the first embodiment are performed.

  As described above, the toner density control device of this embodiment includes the Vref upper / lower limit correction value storage device of the toner density sensor, and when the developing device is replaced, the stored Vref upper / lower limit correction value of the toner density sensor is set. Based on the above, the upper and lower limits of Vref used for toner density control after replacement of the developing device are determined. Therefore, when the initial agent setting is not performed for the second use of the developing device without taking the time for setting the initial agent. In addition, the toner density can be accurately controlled.

1 is a schematic configuration diagram of an image forming apparatus showing an embodiment of the present invention. FIG. 2 is a schematic cross-sectional view illustrating an enlarged transfer device of the image forming apparatus illustrated in FIG. 1. FIG. 2 is an enlarged schematic cross-sectional view showing a photosensitive unit and a developing unit of the image forming apparatus shown in FIG. 1. FIG. 2 is a configuration explanatory diagram of a developing device of the image forming apparatus illustrated in FIG. 1. 1 is a block diagram of a toner concentration control device showing an embodiment of the present invention. FIG. 6 is a flowchart showing an embodiment of a control operation of the toner density control device of the first means. It is a flowchart which shows one Example of control operation | movement of the toner density control apparatus of a 2nd means, and is the figure which showed only a part of control operation | movement. It is a flowchart which shows one Example of control operation | movement of the toner density control apparatus of a 3rd means, and is the figure which showed only a part of control operation | movement. It is a graph which shows the relationship between toner density TC and HST sensor output Vt. It is a figure which shows the example when a linear speed differs with the series machine (a machine, b machine, c machine) of an image forming apparatus. It is a graph which shows the relationship between a linear velocity and Vt shift amount.

Explanation of symbols

1: Photosensitive unit 2: Developing unit 2A: Conveying screw (left)
2B: Conveying screw (right)
2C: Toner density sensor (HST sensor)
2D: Development roller 2E: Doctor blade 3: Cleaning device 3A: Cleaning brush 3B: Waste toner conveying coil 3C: Cleaning blade 4: Charging device 4A: Charging roller 4B: Charging cleaning roller 5: Photoconductor (image) Carrier)
6: Toner cartridge 100: Image forming device 103: Manual feed tray 104: Exposure device 105: Transfer device 105a: Transfer belt 105b: Belt drive roller 106: Fixing device 107: Duplex unit 108: Reversing unit 109: Paper feed tray 109a: Separation Paper feed unit 109b: Registration roller pair 111: Paper discharge roller pair 118: Waste toner storage unit 121: Reference density pattern sensor (P sensor)
122: Cleaning blade 123: Cleaning bias roller 124: Waste toner collecting coil 125: Bias member (each color)
126: Conveyance backup roller (each color)
127: Slide rail 128: Paper adsorption roller P: Transfer paper

Claims (4)

An image carrier;
A developing device that is detachably provided from the main body device, holds a two-component developer composed of toner and carrier, and develops the latent image on the image carrier with the toner of the developer to make a visible image;
A toner concentration sensor that is provided in the developing device and detects a toner concentration of the developer;
Control means capable of adjusting the detection signal Vt of the toner density sensor by changing a control signal value Vcnt input to the toner density sensor;
A toner replenishing device for replenishing the developing device with the toner;
A toner concentration control device for controlling the toner concentration of the developer;
A Vcnt adjustment mode on / off storage device provided in the developing device or the toner density sensor;
A Vcnt storage device for storing the control signal value Vcnt included in the developing device or the toner density sensor;
Comprising
Storing the adjusted Vcnt in the Vcnt storage device;
The toner density control is performed based on the stored Vcnt,
When the Vcnt adjustment mode on is selected, in the toner density control device of the image forming apparatus that performs Vcnt adjustment after replacing the developing device,
A sensitivity storage device for the toner density sensor;
A toner concentration control device, wherein when the developing device is replaced, a Vcnt value is determined based on a Vcnt value adjusted when the Vcnt adjustment mode is on and the stored sensitivity of the toner concentration sensor. The toner concentration control apparatus according to claim 1,
A Vcnt correction value storage device for the toner density sensor;
When the developing device is replaced, a Vcnt value used for toner density control after replacement of the developing device is determined based on the Vcnt value adjusted when the Vcnt adjustment mode is on and the stored Vcnt value of the toner concentration sensor. A toner concentration control device. The toner concentration control apparatus according to claim 1,
Vref upper and lower limit correction value storage device of the toner density sensor,
When the developing device is replaced, the toner concentration control is characterized in that a Vref upper / lower limit value used for toner density control after replacement of the developing device is determined based on the stored Vref upper / lower limit correction value of the toner concentration sensor. apparatus.   An image forming apparatus comprising the toner concentration control apparatus according to claim 1.

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