JP2008129359A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To accurately detect toner concentration according to a quantity of developer in a developing unit, which changes accompanying the supply of developer. <P>SOLUTION: The image forming apparatus (U) comprises: the developing unit (G) having a developer discharge port (7) for discharging developer in a developing container (V), and used to develop an electrostatic latent image into a toner image with the developer; a cumulative drive quantity measuring means (C5) for measuring the cumulative quantity (tr) by which developer supply units (11 to 17+G5) have been driven is measured; a toner concentration detecting member (SN2) for detecting the toner concentration; a concentration correcting means (C7) for correcting a target toner concentration (TCO) based on the cumulative quantity (tr) by which the developer supply units have been driven; and a supply unit driving means (C9B) by which, based on the corrected target concentration obtained by the concentration correcting means, the developer supply units (11 to 17+G5) are driven so that the toner concentration reaches the target toner concentration. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an image forming apparatus that forms an image with a developer including toner and a carrier.

2. Description of the Related Art Conventionally, in an image forming apparatus such as an electrophotographic copying machine or printer, a developing unit having a developer carrying member is disposed opposite to a photoreceptor on which a latent image is formed, and is carried on the surface of the developer carrying member. The latent image is developed with the developed developer to form an image.
As the developer, a two-component developer containing a toner and a carrier may be used, and the toner and the carrier are contained in a predetermined ratio, stirred and frictionally charged, and used for development. The toner density, which is the ratio between the toner and the carrier, is detected by a toner density sensor and controlled to a predetermined density.
As such an image forming apparatus, techniques described in Patent Documents 1 to 3 below are known.

  In Patent Document 1 (Japanese Patent Laid-Open No. 6-348345), in a developing device that discharges deteriorated developer little by little while replenishing toner and carrier separately, a toner concentration sensor (25) The toner concentration is detected, the discharged developer amount is calculated based on the value of the magnetic permeability sensor (24), a target sensor value is set based on the discharged developer amount and a predetermined toner concentration, and the toner A technique for supplying toner by rotating the toner supply roller (21) when the value of the density sensor (25) is larger than the target sensor value is described. In addition, a technique for changing the replenishment time by the carrier developer replenishment roller (22) according to the cumulative number of copies is also described.

Patent Document 2 (Japanese Patent Laid-Open No. 2000-75617) discloses an L detection sensor (40) that detects toner density based on a characteristic recovery time calculated from an operation stop time and an operation time of a developing device (DV). A technique for correcting toner output and controlling toner supply is described.
Patent Document 3 (Japanese Patent Application Laid-Open No. 2005-92059) discloses an excessive developer that has a regulating member (58Y) disposed in front of the discharge port (57Y) of the developing device (DY) and exceeds the regulating member (58Y). A position where only a relatively large amount of developer (DY) exists in front of the regulating member (58Y) in the toner density sensor (8Y) in which only (DY) is discharged and the output value is likely to fluctuate according to the amount of developer. And a technique for stabilizing the output value of the toner density.

JP-A-6-3481345 (“0019” to “0023”, “0028” to “0042”) JP 2000-75617 A ("0016" to "0036") JP-A-2005-92059 ("0003" to "0007", "0037" to "0048")

  It is a technical object of the present invention to accurately detect the toner concentration according to the amount of developer in the developing device that varies with developer replenishment.

In order to solve the technical problem, an image forming apparatus according to claim 1,
A developer container containing a developer containing toner and a carrier; and a developer discharge port for discharging the developer in the developer container when the developer amount in the developer container exceeds a predetermined stable developer amount; A developing device for developing an electrostatic latent image into a toner image by the developer;
A developer replenisher for replenishing the developer with a new developer containing toner and a carrier;
Cumulative driving amount measuring means for measuring the cumulative driving amount of the developer replenisher;
A toner concentration detecting member for detecting a toner concentration which is a ratio of toner and carrier contained in the developing container;
A target toner density storage means for storing a preset target toner density which is a target density of the toner density in the developing container;
Density correction means for correcting at least one of the detected toner density detected by the toner density detection member and the target toner density based on the cumulative drive amount;
Based on at least one of the detected toner density and the target toner density corrected by the density correction means, a replenisher driving means for driving the developer replenisher so that the toner density becomes the target toner density. When,
It is provided with.

The image forming apparatus according to claim 2 is the image forming apparatus according to claim 1,
The target toner density has an upper limit value and a lower limit value, and the density correction unit corrects at least one of the upper limit value and the lower limit value based on the cumulative driving amount;
The replenisher drive means for driving the developer replenisher so that the toner density is within a target density range between the upper limit value and the lower limit value after being corrected by the density correction means;
It is provided with.

The image forming apparatus according to claim 3 is the image forming apparatus according to claim 1 or 2,
A developer discriminating means in the developing device for discriminating whether or not the developer in the developing device is a new developer;
The cumulative drive amount measuring means for initializing the cumulative drive amount when the developer in the developing device is new;
It is provided with.

An image forming apparatus according to claim 4 is the image forming apparatus according to any one of claims 1 to 3,
The developing device in which the amount of the new developer accommodated in the developing container is set to be smaller than the amount of the stable developer;
It is provided with.

The image forming apparatus according to claim 5 is the image forming apparatus according to claim 4,
The toner concentration detecting member for detecting the toner concentration by detecting a magnetic permeability of a developer including a non-magnetic toner and a magnetic carrier;
In a state in which the cumulative drive amount is initialized, the target toner density is corrected to a corrected target density that is higher by a preset target toner density correction value, and the target drive density increases as the cumulative drive amount increases. The density for reducing the corrected target density so as to approach the toner density, and for making the corrected target density coincide with the target toner density when the cumulative drive amount reaches a preset correction end amount Correction means;
It is provided with.

The image forming apparatus according to claim 6 is the image forming apparatus according to claim 2,
The density correction means for correcting the target toner density by correcting the target density width of the target toner density;
It is provided with.

The image forming apparatus according to claim 7 is the image forming apparatus according to claim 6,
The toner concentration detecting member for detecting the toner concentration by detecting a magnetic permeability of a developer including a non-magnetic toner and a magnetic carrier;
In the state where the cumulative drive amount is initialized, the target toner density is corrected to the corrected target density obtained by expanding the target density range by a preset density width correction value, and the cumulative drive amount increases. Accordingly, correction is performed to reduce the density range of the corrected target density so as to approach the target density range, and the density of the corrected target density is reached when the cumulative drive amount reaches a preset correction end amount. The density correction means for matching a width with the target density width;
It is provided with.

The image forming apparatus according to claim 8 is the image forming apparatus according to claim 5 or 7,
The correction end amount set so that the amount of developer accommodated in the developer container reaches the stable developer amount when the developer supply device is driven by the correction end amount;
It is provided with.

According to the first aspect of the present invention, the deviation between the detected toner density and the true toner density in which the developer amount in the developing device fluctuates in accordance with the cumulative driving amount is corrected, and compared with the case where the present invention is not adopted. Thus, the toner density can be detected with high accuracy, and the true toner density, which is the toner density in the developing device, can be accurately maintained at the target toner density.
According to the second aspect of the present invention, the supply of the developer can be stopped when the toner density is within the target density range of the target toner density. The frequency can be reduced.
According to the third aspect of the present invention, the cumulative driving amount can be initialized each time the developer in the developing device is replaced with a new developer, and compared to the case where the present invention is not adopted, the product is not shipped. Even if the developer is replaced, the toner concentration can be detected with high accuracy.

According to the fourth aspect of the present invention, it is possible to reduce discharge of a new developer with little deterioration, and it is possible to reduce wasteful discharge of the developer that does not need to be discharged.
According to the fifth aspect of the present invention, the target toner concentration can be appropriately corrected according to the relationship between the output value of the toner concentration detecting member using the magnetic permeability, the developer amount, and the true toner concentration.
According to the sixth aspect of the invention, by correcting the target density range, both the dark side and the light side can be corrected, and the toner density can be more accurately compared with the case where the present invention is not adopted. It can be detected.

According to the seventh aspect of the present invention, the target density range can be appropriately corrected in accordance with the relationship between the output value of the toner density detecting member using the magnetic permeability, the developer amount, and the true toner density.
According to the eighth aspect of the present invention, the correction can be terminated when the stable developer amount is reached and the correction is no longer necessary.

Next, specific examples of embodiments of the present invention (hereinafter referred to as examples) will be described with reference to the drawings, but the present invention is not limited to the following examples.
In order to facilitate understanding of the following description, in the drawings, the front-rear direction is the X-axis direction, the left-right direction is the Y-axis direction, the up-down direction is the Z-axis direction, and arrows X, -X, Y, -Y, The direction indicated by Z and -Z or the indicated side is defined as front, rear, right, left, upper, lower, or front, rear, right, left, upper, and lower, respectively.
In the figure, “•” in “○” means an arrow heading from the back of the page to the front, and “×” in “○” is the front of the page. It means an arrow pointing from the back to the back.
In the following description using the drawings, illustrations other than members necessary for the description are omitted as appropriate for easy understanding.

FIG. 1 is an overall explanatory view of an image forming apparatus according to Embodiment 1 of the present invention.
In FIG. 1, the image forming apparatus U has an image forming apparatus main body U1 and an automatic document feeder U2 placed on a transparent document reading surface PG on the upper surface of the image forming apparatus main body U1. The automatic document feeder U2 has a document storage portion TG1 in which a plurality of documents Gi to be copied are stored. Each of the plurality of documents Gi stored in the document storage unit TG1 sequentially passes through the copy position on the document reading surface PG and is discharged to the document discharge unit TG2. The automatic document feeder U2 can be rotated with respect to the image forming apparatus main body U1 by a hinge shaft (not shown) which is an example of a rotation shaft provided in the rear end portion and extending in the left-right direction. When placed on the original reading surface PG by hand, it is rotated upward.

The image forming apparatus main body U1 has an operation unit UI for a user to input an operation command signal for starting copying.
The document reading device IIT arranged below the transparent document reading surface PG on the upper surface of the copying machine main body U1 has an exposure optical system A.
At the time of an automatic document conveyance operation in which the automatic document conveyance device U2 automatically conveys and reads and copies a document, the exposure optical system A is stopped on the document reading position and is on the document reading surface PG. Each document Gi that sequentially passes through the document reading position is exposed.
At the time of manual placement where the operator manually places the document Gi on the document reading surface PG for copying, the exposure optical system A exposes and scans the document on the document reading surface PG while moving. The reflected light from the original document Gi exposed by the light source device of the exposure optical system A passes through the exposure optical system A and is converged on the solid-state image sensor CCD. The solid-state imaging device CCD outputs an electrical signal corresponding to the amount of reflected document light converged on the imaging surface.

The controller C as an example of the control unit controls the operation timing of the image processing unit IPS, the power supply circuit (power supply circuits such as a developing device, a transfer roll, and a fixing device) E, the image writing light driving circuit DL, and the like. The image processing unit IPS converts the electrical signal input from the solid-state imaging device CCD into image information and temporarily stores it, and the image data is stored as image information for forming a latent image at a predetermined time. Output to the IOT image writing light drive circuit DL.
The image writing light driving circuit DL outputs an image writing light driving signal to the latent image forming device ROS according to the input image information.

  The photoconductor PR as an example of the image carrier rotates in the direction of the arrow Ya, and the surface of the photoconductor PR is uniformly charged by the charger CR in the charging area Q0 and then the latent image is written at the latent image writing position Q1. Exposure scanning is performed with a laser beam L as an example of image writing light of the forming apparatus ROS to form an electrostatic latent image. The electrostatic latent image on the rotating photoconductor PR is developed into a toner image by the developing device G in the developing area Q2. The voltage applied to the charger CR and the developing device G, the intensity of the laser beam L, and the like are based on the detection value of the image density sensor SN1 that detects the density of the density detection image formed on the photoconductor PR. And controlled by the controller C.

  The surface of the photoconductor PR on which the toner image is formed moves to the transfer region Q3. Below the transfer region Q3, a slide as an example of a transfer device support frame that can be slid back and forth (in a direction perpendicular to the paper surface of FIG. 1) by slide rails SR, SR as an example of a pair of left and right guide members. The frame Fs is detachably supported on the image forming apparatus main body U1. The slide frame Fs includes a transfer roll T as an example of a transfer device, a transfer roll cleaner CLt as an example of a transfer device cleaner, a roll support lever Lr as an example of a transfer device support member, and a post-transfer medium guide member. A post-transfer sheet guide SG2 as an example and a sheet conveying belt BH as an example of a medium conveying member are supported.

The roll support lever Lr is a rotatable lever that supports the transfer roll T and the transfer roll cleaner CLt. The roll support lever Lr is rotated by a motor (not shown) as an example of a drive source, and moves the transfer roll T between a transfer position in contact with the photoconductor PR and a paper jam processing position away from the photoconductor PR. Let
The post-transfer sheet guide SG2 guides a recording sheet S as an example of a medium that has passed through a transfer area Q3, which is a contact area between the transfer roll T and the photoconductor PR, to a downstream sheet conveyance belt BH.

Below the slide frame Fs, a first paper feed tray TR1, a second paper feed tray TR2, and a third paper feed tray TR3, which are examples of a medium container that contains the recording sheet S, are used for double-sided copying and the like. An intermediate tray TR0 as an example of the intermediate medium storage container to be used is detachably stored. The intermediate tray TR0 is a tray that is used when the recording sheet S that has been copied for the first time is reversed and resent to the transfer area Q3 during duplex copying or the like.
A manual feed tray TRt is provided at an upper right position of the first paper feed tray TR1. Each recording sheet S sent out from the manual feed tray TRt or each of the paper feed trays TR0 to TR3 is transported to the transfer area Q3 through the medium transport path SH1.

The recording sheets S accommodated in the paper feed trays TR0 to TR3 are taken out at a predetermined timing by a pickup roll Rp which is an example of a medium takeout member, and separated one by one by a separating roll Rs which is an example of a medium separating member. It is transported by a transport roll Ra which is an example of a plurality of double-end transport members, and is transported to a registration roll Rr which is an example of a transport timing adjusting member. The recording sheet S conveyed to the registration roll Rr is conveyed from the pre-transfer sheet guide SG1 to the transfer area Q3 in time with the toner image on the photoconductor PR moving to the transfer area Q3.
In the transfer area Q3, the transfer roll T electrostatically transfers the toner image on the photoreceptor PR to the recording sheet S. Residual toner is removed from the surface of the photoreceptor PR after the transfer by the photoreceptor cleaner CLp. The transfer roll T collects surface-adhered toner by a transfer roll cleaner CLt.

The recording sheet S to which the toner image has been transferred is conveyed to the fixing region Q4 by the post-transfer sheet guide SG2 and the sheet conveying belt BH, and when passing through the fixing region Q4, a heating roll Fh and an additional heating roller as an example of a heat fixing member are transferred. Heat fixing is performed by a fixing device F having a fixing roll as an example of a fixing member constituted by a pressure roll Fp as an example of a pressure fixing member. The recording sheet S on which the toner image is fixed is conveyed to the medium discharge path SH2 or the medium reversal path SH3 by a conveyance path switching gate GT1 as an example of a conveyance path switching member. The recording sheet S conveyed to the medium discharge path SH2 is discharged to a discharge tray TRh as an example of a medium discharge portion by a discharge roll Rh as an example of a conveyance roll Ra and a medium discharge member, and is transferred to a medium reversal path SH3. The sheet S is reversed and then conveyed to the intermediate tray TR0.
A medium transport device SH is constituted by the medium transport path SH1, the medium discharge path SH2, the medium reversing path SH3, and the elements indicated by the symbols Rp, Rs, Rr, SG1, SG2, BH, Ra and the like.

(Developer G)
FIG. 2 is an enlarged explanatory view of the developing device which is a main part of FIG.
FIG. 3 is a perspective view of a developing device as a main part of the developing device.
4 is an enlarged explanatory view of the developer replenishing port portion of the developing device shown in FIG. 3, and is a partial cross-sectional view seen from the direction of arrow IV in FIG.
5 is an explanatory view of the developing device, FIG. 5A is a sectional view taken along the line VA-VA of FIG. 4, FIG. 5B is a sectional view taken along the line VB-VB of FIG. 4, and FIG. It is.
2 to 5, a developing device G disposed in the developing region Q2 so as to face the photoreceptor PR has a developing container V that contains a two-component developer composed of a negatively chargeable toner and a positively chargeable magnetic carrier. have.

In FIG. 3, the developing container V includes a developing container main body 1 and a front connection member 2 connected to a front end (X end) and a rear end (−X end) of the developing container main body 1 (see FIGS. 3 and 5A). And a rear connection member 3. The front connection member 2 has a front upper connection member 2a and a front lower connection member 2b, and the rear connection member 3 has a rear upper connection member 3a and a rear lower connection member 3b.
In FIG. 3, a pair of supported portions 1 a and 1 a are provided on the upper portions of the front end and the rear end of the developing container main body 1, respectively, and the developing container V is mounted inside the image forming apparatus U. At this time, each supported portion 1a is supported by a frame (not shown) of the image forming apparatus U.

In FIG. 5, inside the developing container V formed by the developing container main body 1, the front connecting member 2 and the rear connecting member 3, a developing roll R0 as an example of a developer holder, an agitating and conveying member R1, R2 and a stagnant developer stirring member R3, the developing roll R0 is an example of a magnet roll R0a as an example of a magnet body, and an example of a rotatable developer holding and rotating member that covers the outer surface of the magnet roll R0a And a developing sleeve R0b.
As shown in FIG. 5B, a partition wall 4 is provided between the stirring and conveying members R1 and R2. The partition wall 4 divides the inside of the developing container V vertically. Connection ports 4a and 4b for connecting the top and bottom of the partition wall 4 are formed at the front end and the rear end, and the developer in the developing container V is stirred while being circulated by the stirring and conveying members R1 and R2. . In FIG. 4, only the front connection port 4a is shown, and the illustration of the rear connection port 4b is omitted.

In FIG. 5B, a stagnant developer stirring member R3 is disposed between the stirring and conveying member R2 and the developing roll R0. The agitating member R3 is a member for agitating and conveying the developer staying between the agitating and conveying member R2 and the developing roll R0.
2 to 4, a developer replenishing port 6 is formed at the upper front end portion of the front upper connecting member 2a. 3, 4 and 5A, a developer discharge port 7 is formed on the side surface of the front upper connecting member 2a. The developer discharge port 7 is located upstream in the transport direction (rear side) from the position of the developer supply port 6 in order to reduce the rate at which new developer supplied from the developer supply port 6 is discharged immediately after supply. It is formed on the end side. The developer discharge port 7 discharges the developer in the developer container V when the developer amount in the developer container V exceeds a predetermined stable developer amount. When the height of the discharge port 7 is exceeded, the developer overflows and is discharged. In the developing device G of the first embodiment, the developer in the new developing device G is not deteriorated. When the developer is accommodated from the beginning until it overflows from the developer discharge port 7, the developing is not deteriorated. Since the waste of the developer is generated, the new developer G contains a smaller amount of developer than the amount of the stable developer. Further, in the first embodiment, even when the developer in the developing device G is once discarded due to repair of a failure or the like and a new developer is accommodated, an initial amount smaller than the stable developer amount as a new developer. It is set to accommodate the developer. Also, the operator may spill the developer, resulting in an amount less than the stable developer amount.

Further, a toner concentration sensor SN2 as an example of a toner concentration detection member for detecting the toner concentration of the developer in the developer container V is disposed upstream of the developer discharge port 7 in the developer transport direction. The toner concentration sensor SN2 according to the first exemplary embodiment includes a magnetic toner concentration sensor that detects a toner concentration based on a conventionally known magnetic permeability.
In FIG. 5B, a layer thickness regulating member 8 for regulating the layer thickness of the developer on the developing roll R0 is disposed in the developing container V.
Developing elements V (1 to 8) in this embodiment are constituted by the elements indicated by the reference numerals 1 to 8.

  3 and 5C, a gear G0 as an example of a rotation transmitting member is attached to the rear end portion (-X end portion) of the shaft of the developing roll R0, and the agitating and conveying members R1, R2 and the agitating member R3 are provided. Gears G1, G2, and G3 are attached to the rear end of the shaft. The gear G0 and the gear G1 are meshed with each other via an intermediate gear G4. The gears G1, G2, and G3 are in mesh with each other. During the developing operation, the rotational force of the developer motor M2 is sequentially transmitted to the gears G0, G4, G1, G2, and G3, and the developing roll R0, the stirring and conveying members R1 and R2, and the stirring member R3 are rotationally driven.

2 and 3, a developer supply cylinder support member 11 is disposed above the developer supply port 6 of the developer container V. A developer supply cylinder 12 is connected to the developer supply cylinder support member 11, and the inside of the developer supply cylinder 12 is connected to the developer supply port 6 of the developer container V via the developer supply cylinder support member 11. Communicate with.
Inside the developer supply cylinder 12, a supply developer transport member R4 is rotatably disposed. A gear G5 (see FIG. 2) is fixed to one end of the rotation shaft of the replenishment developer transport member R4, and the replenishment developer transport member R4 is a developer as an example of a replenishment drive source that meshes with the gear G5. It is rotationally driven by a replenishment motor M1.

A developer supply housing 14 is disposed above the developing container V. The developer supply housing 14 is provided below and below a developer storage container 16 in which a two-component developer having a toner concentration higher than that in the developer container V, that is, a so-called “high concentration developer” is stored. The developer agitation container 17 is provided. The high-concentration developer supplied from the developer storage container 16 to the developer stirring container 17 is stirred while circulating in the developer stirring container 17 and supplied to the developer supply cylinder 12 from the supply cylinder connection port 17a. . In the first embodiment, the high density developer contained in the developer storage container 16 is subjected to initial development when the developer G is replenished with the developer containing one carrier in the developer storage container 16. An amount of carrier from the amount of the agent to the amount of the stable developer is contained.
A developer replenisher (11-17 + G5) is constituted by the components indicated by the reference numerals 11-17 and G5.
The high-concentration developer supplied from the developer storage container 16 into the developer supply cylinder 12 is transported by the replenishment developer transport member R4 that is rotationally driven, and is replenished into the developer container V from the developer supply port 6. It has become so.

3 and 5A, a developer transport cylinder connecting portion 21 for discharge is disposed outside the developer discharge port 7 of the developer container V.
A front end portion (X end portion) of the discharge developer transport tube 22 is connected to the discharge developer transport tube connection portion 21, and a rear end portion (−X end portion) of the discharge developer transport tube 22. ) Is connected to a discharged developer recovery container 23 (see FIG. 3). A developer discharge path 22 a is formed inside the discharge developer transport cylinder 22.
In FIG. 3, a discharge developer transport member R5 is disposed inside the discharge developer transport cylinder 22.

  3 and 5C, a gear G6 is attached to the rear end portion of the rotating shaft of the discharging developer transport member R5. The gear G6 is used for discharging the developer as an example of a discharging drive source (not shown). The motor M3 is rotationally driven. When the gear G6 rotates, the discharging developer transport member R5 rotates. Excess developer discharged from the developer discharge port 7 into the discharge developer transport cylinder 22 through the discharge developer transport cylinder connection portion 21 by the rotation of the discharge developer transport member R5 is It is conveyed to the developer recovery container 23.

(Description of control unit)
FIG. 6 is a block diagram of the control unit of the image forming apparatus according to the first exemplary embodiment of the present invention.
In FIG. 6, the controller C includes an input / output interface that performs input / output of signals to / from the outside and adjustment of input / output signal levels, and a ROM (read-only memory) that stores programs and data for performing necessary processing. ), A RAM (random access memory) for temporarily storing necessary data, a central processing unit (CPU) for performing processing according to a program stored in the ROM, and a computer having a clock oscillator and the like Therefore, various functions can be realized by executing a program stored in the ROM.

(Signal input element connected to the controller C)
The controller C receives signals from the operation unit UI, the image density sensor SN1, the toner density sensor SN2, and other signal input elements.
The UI includes a display UIa, a copy start key UIb, a copy number setting input key UIc, a numeric keypad UId, a developing device replacement input key UIe, and the like.
The image density sensor SN1 detects the image density of the toner image formed on the surface of the photoreceptor PR.
The toner concentration sensor SN2 detects the toner concentration of the developer in the developing container V.

(Control element connected to the controller C)
The controller C is connected to a main motor drive circuit D0, a developer replenishment motor drive circuit D1, a developer motor drive circuit D2, a developer discharge motor drive circuit D3, and other control elements. A control signal is output.
The main motor drive circuit D0 rotationally drives the photoconductor PR and the like via a main motor M1 which is an example of a main drive source.
The developer replenishment motor drive circuit D1 rotates and drives the replenishment developer transport member R4 via a developer replenishment motor M1, a gear G5 (see FIG. 2), and the like.
The developing device motor drive circuit D2 rotationally drives the developing roll R0, the agitating / conveying members R1, R2, the agitating member R3, etc. of the developing device G through the developing device motor M2, gears G0 to G4, and the like.
The developer discharge motor drive circuit D3 rotationally drives the discharge developer transport member R5 via the developer discharge motor M3, the gear G6, and the like.

The power supply circuit E includes a development power supply circuit E1, a charging power supply circuit E2, a transfer power supply circuit E3, a fixing power supply circuit E4, and the like.
The developing power supply circuit E1 applies a developing bias to the developing roll R0 of the developing device G.
The charging power supply circuit E2 applies a charging bias to the charging roll CR.
The transfer power supply circuit E3 applies a transfer bias to the transfer roll Rt.
The fixing power supply circuit E4 supplies a heater heating current to the heater of the heating roll Fh of the fixing device F.

(Function of the controller C)
The controller C has a function of executing processing according to an input signal from the signal output element and outputting a control signal to each control element.
That is, the controller C has the following functions.
C1: Job control means (image recording control means)
The job control unit C1 controls the operations of the latent image forming device ROS, the photoconductor PR, the transfer roll T, the fixing device F, and the like according to the input of the copy start key UI2, and executes a job that is an image forming operation. To do.

C2: Main motor rotation control means The main motor rotation control means C2 controls the main motor M1 via the main motor drive circuit D0 to control the driving of the photoconductor PR and the like.
C3: Power supply circuit control means The power supply circuit control means C3 includes a development power supply control means C3A, a charging power supply control means C3B, a transfer power supply control means C3C, and a fixing power supply control means C3D, and controls the power supply circuit E. The power supply to each member of the image forming apparatus U is controlled.

C3A: Development power control means The development power control means C3A controls the development power supply circuit E1 to control the development voltage.
C3B: Charging power supply control means The charging power supply control means C3B controls the charging power supply circuit E2 to control the charging voltage.
C3C: Power supply control means for transfer (transfer voltage control means)
The transfer power supply control means C3C controls the transfer power supply circuit E3 to control the transfer voltage.
C3D: Fixing power supply control means The fixing power supply control means C3D controls the fixing power supply circuit E4 to control the fixing temperature of the fixing device F.

C4: In-Developer Developer Discriminating Unit The in-developer developer discriminating unit C4 discriminates whether or not the developer in the developing unit G is a new developer. In the developing device developer discriminating means C4 of the first embodiment, when the developer G is replaced or the developer in the developing device G is replaced, the developer replacement input key UIe is input by the operator. Then, it is determined that the developer in the developing device G is a new developer. The developer replacement input key UIe is a key for a service engineer as an example of an operator to input. For example, when the developer storage container 16 is replaced, the developer G Since the developer inside is not a new developer, the developer replacement input key UIe is not input, and the developer identifying means C4 in the developer determines that the developer in the developer G is a new developer. Not determined.

C5: Cumulative Drive Amount Measuring Unit The cumulative drive amount measuring unit C5 has a cumulative drive amount initializing unit C5A, and measures the cumulative drive amount of the developer replenisher (11-17 + G5). Note that the cumulative drive amount measuring unit C5 of the first embodiment measures the cumulative drive time tr as an example of the cumulative drive amount.
C5A: Cumulative drive amount initializing means The cumulative drive amount initializing means C5A initializes the cumulative drive amount when the developer in the developing device G is new. The accumulated drive amount initialization unit C5A according to the first exemplary embodiment performs accumulation as an example of the accumulated drive amount when the developer in the developer unit determination unit C4 determines that the developer in the developer unit G is new. The drive time tr is initialized to tr = 0.

C6: Target Toner Concentration Storage Unit The target toner concentration storage unit C6 stores a preset target toner concentration TC0 that is a target concentration of the toner concentration in the developing container V. In Example 1, the target toner density TC0 is not a specific numerical value but has a width, and a density range between the target toner density center T0, the density width lower limit Ta1, and the density width upper limit Tb1. Is set to That is, the target toner density lower limit value Ta (= T0−Ta1) or more and the target toner density upper limit value Tb (= T0 + Tb1) is set as the target toner density TC0. It is also possible to eliminate the density width Tb-Ta and set only the value of the target toner density center T0 as the target toner density.
C7: Density Correction Unit The density correction unit C7 includes a density correction function storage unit C7A and a corrected target value calculation unit C7B. Based on the cumulative drive time tr that is an example of the cumulative drive amount, the target toner density TC0. Correct. The density correction unit C7 according to the first exemplary embodiment corrects the target toner density TC0 by correcting the target toner density center T0.

FIG. 7 is an explanatory diagram of the density correction function according to the first embodiment of the present invention.
The density correction function storage unit C7A stores a density correction function for correcting the target toner density TC0. As shown in FIG. 7, the density correction function of the first embodiment is a function derived in advance through experiments or the like. In the first embodiment, the target toner density correction value is Th1, and the target toner density correction value is an example. When the target toner density initial correction value, which is the initial value, is Th, the cumulative driving time tr, and the correction end amount tr1, the following expressions (1) and (2) are used.
Th1 = Th−α1 × tr (when tr ≦ tr1) (1)
= 0 (when tr> tr1) (2)
In the first embodiment, α1 = Th / tr1 is set.

C7B: Corrected target density calculation means The corrected target value calculation means C7B is a correction in which the target toner density TC0 is corrected based on the target toner density TC0 and the target toner density correction value Th1 derived by the density correction function. The completed target density TC0 ′ is calculated. The corrected target value calculation means C7B of Embodiment 1 calculates the corrected target density TC0 ′ by adding the target toner density correction value Th1 from the target toner density TC0. That is, in the first embodiment, the corrected target lower limit value Ta ′ = Ta + Th1 or more and the corrected density upper limit value Tb ′ = Tb + Th1 or less become the corrected target concentration TC0 ′. Therefore, when the center of the corrected target density TC0 ′ is T0 ′, the corrected target density center T0 ′ is calculated by the following equations (3) and (4).
T0 ′ = T0 + Th−α1 × tr (in the case of tr ≦ tr1) (3)
= T0 (when tr> tr1) (4)
Accordingly, the density correction unit C7 of Example 1 is corrected so that the target toner density TC0 of the target toner density TC0 is higher by the preset target toner density initial correction value Th in the state where the cumulative drive time tr is initialized. The target density TC0 ′ is corrected, and the corrected target density TC0 ′ is decreased so as to approach the target toner density TC0 as the cumulative driving time tr increases, that is, the target toner density correction value Th1 is decreased. Then, when the cumulative drive amount tr reaches the correction end amount tr1, the corrected target density TC0 ′ is made to coincide with the target toner density TC0. The correction end amount tr1 of the first embodiment is set so that the developer amount stored in the developer container V becomes the stable developer amount when the developer replenisher (11 to 17 + G5) is driven by the correction end amount tr1. Is set to reach.

C8: Toner Consumption Measuring Unit The toner consumption measuring unit C8 includes a cumulative print pixel number measuring unit C8A and a print pixel number initializing unit C8B, and measures the amount of toner consumed by the image forming operation. The toner consumption measuring unit C8 according to the first exemplary embodiment measures the amount of toner consumed indirectly by measuring the cumulative value of the number of printed pixels.
C8A: Printed Pixel Number Cumulative Value Measuring Unit The printed pixel number cumulative value measuring unit C8A calculates the number of pixels of the image written by the laser beam L emitted from the latent image forming device ROS, that is, the so-called cumulative number N1 of dots. measure.
C8B: Printed Pixel Number Cumulative Value Initializing Unit The printed pixel number cumulative value initializing unit C8B is a pixel number cumulative value N1 when the developer replenisher (11-17 + G5) is driven to replenish the developer. Is initialized to 0.

C9: Developer replenishment control means The developer replenishment control means C9 has a replenishment time calculation means C9A and a replenisher drive means C9B. The developer replenishment motor drive circuit D1 is connected to the developer replenishment motor M1. Control the driving to control the replenishment of developer.
C9A: Replenishment time calculation means The replenishment time calculation means C9A has density dependent replenishment time calculation means C9A1 and pixel number dependent replenishment time calculation means C9A2, and replenishes the developer by driving the replenishment developer transport member R4. The replenishment time td to be calculated is calculated. That is, the developer replenishment amount is indirectly calculated. The replenishment time calculation means C9A according to the first embodiment calculates the sum of a density-dependent replenishment time tc and a pixel number-dependent replenishment time tp, which will be described later, as a replenishment time td (= tc + tp).

FIG. 8 is an explanatory diagram for calculating the replenishment time according to the first embodiment of the present invention, and FIG. 8A is an explanatory diagram for calculating the concentration-dependent replenishment time. FIG. 8B is an explanatory diagram for calculating the pixel number dependent supply time.
C9A1: Density-dependent replenishment time calculation means The density-dependent replenishment time calculation means C9A1 is made to depend on the toner density based on the detected toner density T1 that is a detection value of the toner density sensor SN2 and the corrected target density TC0 ′. A concentration-dependent replenishment time tc that is a replenishment time is calculated. The density-dependent replenishment time calculation means C9A1 of the first embodiment is based on the concentration-dependent replenishment time calculation formula shown in FIG. 8A, which is the same as that obtained through experiments and the like, the detected toner density T1, and the corrected target density TC0 ′. A concentration-dependent replenishment time tc is calculated. In FIG. 8A, the concentration-dependent replenishment time calculation formula of Example 1 is the following formula (6) when the upper limit replenishment time ta, the lower limit replenishment time tb, the replenishment time lower limit concentration T0-Ta2, and the replenishment time upper limit concentration T0 + Tb2. It is expressed by (10).
tc = ta (when T1 <T0′−Ta2) (6)
= −α2 × (T1−T0 ′ + Ta1)
(T0′−Ta2 ≦ T1 <T0′−Ta1) (7)
= 0 (when T0′−Ta1 ≦ T1 ≦ T0 ′ + Tb1) (8)
= −α2 ′ × (T1−T0′−Tb1)
(T0 ′ + Tb1 <T1 ≦ T0 ′ + Tb2) (9)
= Tb (when T0 '+ Tb2 <T1) (10)
In the first embodiment, α2 = ta / (Ta1-Ta2) and α2 ′ = tb / (Tb1-Tb2) are set. Therefore, in the first embodiment, the upper limit value ta and the lower limit value tb are set for the concentration-dependent supply time tc, and a negative supply time tb is also set.
That is, in other words, the density-dependent replenishment time tc based on the corrected density-dependent replenishment time arithmetic expression translated from the target toner density center T0 to the corrected target density center T0 ′. calculate.

C9A2: Pixel Number Dependent Supply Time Calculation Unit The pixel number dependent supply time calculation unit C9A2 is a supply time dependent on the number of pixels based on the pixel number accumulated value N1 measured by the print pixel number accumulated value measuring unit C8A. The pixel number dependent supply time tp is calculated. The pixel number dependent replenishment time calculation means C9A2 according to the first embodiment calculates the pixel number dependent replenishment time tp based on the pixel number accumulated value N1 and a pixel number dependent replenishment time arithmetic expression derived in advance through experiments or the like. In FIG. 8B, the pixel number-dependent replenishment time calculation formula of the first embodiment is set to tp when a monotonically increasing linear function is set and the replenishment time lower limit pixel number corresponding to the lower limit replenishment time tb is Nb. = Α3 × N1. In the first embodiment, α3 = tb / Nb is set.

C9B: Replenisher drive means The replenisher drive means C9B makes the true toner density in the developing container V become the target toner density TC0 based on the corrected target density TC0 ′ corrected by the density correction means C7. The developer replenisher (11-17 + G5) is driven as described above. The replenisher driving unit C9B according to the first embodiment drives the developer replenisher (11 to 17 + G5) for the replenishment time td calculated by the replenishment time calculating unit C9A to replenish the developer. Note that, when the replenishment time td is negative, the replenisher driving unit C9B of Example 1 does not drive the developer replenisher (11 to 17 + G5), and the developer is not replenished.
C10: Developing device drive control means The developing device drive control means C10 controls the driving of the developing device motor M2 via the developing device motor driving circuit D2, and controls the driving of the developing roller R0 and the like of the developing device G.
C11: Developer Discharge Control Unit The developer discharge control unit C11 controls the drive of the developer discharge member R5 by controlling the drive of the developer discharge motor M3 via the developer discharge motor drive circuit D3.

(Description of Flowchart of Example 1)
FIG. 9 is a flowchart of developer supply processing in the image forming apparatus according to the first exemplary embodiment of the present invention.
The processing of each ST (step) in the flowchart of FIG. 9 is performed according to a program stored in the ROM of the controller C. This process is executed in a multitasking manner in parallel with other various processes of the image forming apparatus. When the image forming operation is executed in the image forming apparatus U according to the first exemplary embodiment, the pixel number measurement process for measuring the pixel number cumulative value N1 of the number of pixels of the formed image, or the developer replacement input key UIe. Since the accumulated drive amount initialization process for detecting the input and initializing the accumulated drive amount tr is simple, illustration and detailed description thereof are omitted.
The developer supply process shown in FIG. 9 is started when the image forming apparatus U is turned on.

In ST (step) 1 of FIG. 9, it is determined whether or not an image forming operation is started. If yes (Y), the process proceeds to ST2. If no (N), ST1 is repeated.
In ST2, the toner density is acquired. That is, the detected toner concentration T1 is acquired from the toner concentration sensor SN2. Then, the process proceeds to ST3.
In ST3, the cumulative drive time tr measured by the cumulative drive amount measuring means C5 is acquired. Then, the process proceeds to ST4.
In ST4, the following processes (1) and (2) are executed, and the process proceeds to ST5.
(1) A toner density correction value Th1 is calculated based on the cumulative driving time tr.
(2) The corrected target density TC0 ′ is calculated from the target toner density TC0 and the toner density correction value Th1.

In ST5, the pixel count cumulative value N1 measured by the print pixel count cumulative value measuring means C8A is acquired. Then, the process proceeds to ST6.
In ST6, the density-dependent replenishment time tc is calculated from the detected toner density T1, the corrected target density TC0 ′, and the density-dependent replenishment time calculation formula shown in FIG. 8A. Then, the process proceeds to ST7.
In ST7, the pixel number dependent supply time tp is calculated from the pixel number accumulated value N1 and the pixel number dependent supply time calculation formula shown in FIG. 8B. Then, the process proceeds to ST8.
In ST8, the replenishment time td = tc + tp is calculated based on the density dependent replenishment time tc and the pixel number dependent replenishment time tp. Then, the process proceeds to ST9.

In ST9, the following processes (1) to (3) are executed, and the process proceeds to ST10.
(1) During the replenishment time td, the developer replenisher (11-17 + G5) is driven to replenish the developer.
(2) Cumulative driving time tr = tr + td. That is, the replenishment time td is added to the cumulative drive time tr.
(3) The pixel number accumulated value N1 is initialized to 0.
In ST10, it is determined whether or not the image forming operation is finished. If yes (Y), the process returns to ST1, and if no (N), the process returns to ST2.

FIG. 10 is an explanatory diagram of the output of the magnetic toner density sensor of Example 1. FIG. 10A is a graph in which the toner concentration is plotted on the horizontal axis and the output of the magnetic toner density sensor is plotted on the vertical axis for a predetermined developer amount. 10B is a graph in which the developer amount is plotted on the horizontal axis and the output of the toner density sensor is plotted on the vertical axis at a predetermined toner concentration. FIG. 10C is the vertical axis where the toner concentration is plotted on the horizontal axis when the developer amount varies. 6 is a graph showing the toner density.
(Operation of Example 1)
In the image forming apparatus U of Example 1 having the above-described configuration, the two-component developer containing toner and carrier is accommodated in the developing container V of the developing device G, and the toner is consumed as the image is formed. The changing toner density is detected by the toner density sensor SN2.

Here, as the toner concentration sensor SN2 of Example 1, a magnetic toner concentration sensor using magnetic permeability is used, so that the developer amount in the developing container V is a predetermined developer as shown in FIG. 10A. In the case of an amount, for example, a stable developer amount, the output of the toner concentration sensor SN2 fluctuates in a one-to-one correspondence with the change in toner concentration, and the toner concentration is detected. When the developer is consumed, the developer replenisher (11-17 + G5) is driven based on the toner density detected by the toner density sensor SN2 and the toner consumption calculated based on the number of print pixels, and development is performed. The developer is supplied to the developing device G.
As shown in FIG. 10B, since the magnetic toner density sensor SN2 changes the ease of passing of magnetic force when the developer amount fluctuates, the output of the toner concentration sensor SN2 also fluctuates according to the fluctuation of the developer amount. To do. In the developing device G of Example 1, a new developing device G contains an initial developer that is less than the stable developer amount so that undegraded developer is not discharged, and a developer replenisher (11 The amount of the developer gradually increases by replenishing the carrier that is not consumed together with the toner by ˜17 + G5). When the developer amount reaches the stable developer amount, the developer including the developer that is gradually deteriorated is discarded from the developer discharge port 7.

  That is, from the graphs of FIGS. 10A and 10B, as shown in FIG. 10C, the toner density sensor is used in the case where the developer whose true toner density is the target toner density center T0 is contained but the developer quantity is stable. The output of SN2 is the output corresponding to T10, but when the initial developer amount is smaller than the stable developer amount, the corresponding output is T10 ′. That is, in the conventional technique in which the correction by the density correction unit C7 is not performed and the determination is made based on the stable developer amount, the toner density sensor SN2 outputs the true toner density when T0 is the initial developer amount. Based on the value T10 ′, the developing device G detects that the detected toner density (T0 ′) is high, erroneously discriminates, sets a negative replenishment time to the density-dependent replenishment time tc, and sets the toner by image formation. The developer was not replenished smoothly even if was consumed.

Even when the true toner density reaches the target toner density lower limit Ta, the output of the toner density sensor SN2 is T1a with the stable developer amount, but the output is T1a 'with the initial developer amount. The detected toner density (Ta ′) corresponding to the output T1a ′ is erroneously determined as the toner density in the developing container V. That is, since the detected toner density (Ta ′) is equal to or higher than the target toner density upper limit value Tb, a negative supply time is set as the density-dependent supply time tc, and the true toner density falls below the target toner density lower limit value Ta. However, a negative replenishment time is set.
Therefore, in the conventional control method, for example, when the output of the toner density sensor SN2 is T10, the true toner density coincides with the target toner density center T0 and satisfies the target toner density TC0 if the amount is a stable developer amount. As a result, in the case of the initial developer amount, the true toner density is lower than the target toner density lower limit Ta, and the toner density needs to be replenished with the developer.

FIG. 11 is a graph showing the transition of the developer amount and the true toner density with respect to the cumulative drive time in Example 1. FIG. 11A is a graph in which the cumulative drive time is taken on the horizontal axis and the developer amount is taken on the vertical axis. 11B is a graph in which the cumulative driving time is plotted on the horizontal axis and the true toner density is plotted on the vertical axis.
Therefore, in the conventional control method, as shown by the broken lines in FIGS. 11A and 11B, in a state where a new developer is accommodated immediately after the replacement of the developer G or the like, the developer concentration is detected by the toner concentration sensor SN2 and mis-determination. Since the replenishment is not performed, the toner density is decreased to be larger than the target toner density immediately after the replacement. Then, when the pixel number dependent replenishment time tp based on the print pixel number cumulative value N1 exceeds the density dependent replenishment time tc, the developer is replenished. With the developer replenishment, there is a carrier that is not consumed in image formation. As the developer amount increased and increased from the initial developer amount, the influence of misclassification gradually decreased.

  In the image forming apparatus U of Embodiment 1, when the developer in the developing device G is replaced with a new one, the cumulative drive time tr of the developer replenisher (11-17 + G5) is initialized, and the cumulative drive time tr is If it is small and has not reached the stable developer amount, the target toner density TC0 having a width between the target toner density lower limit value Ta and the target toner density upper limit value Tb is set by the density correction means C7 to the corrected lower limit value Ta. ′ (= T0′−Ta1) to the corrected target density TC0 ′ having a width between the corrected upper limit value Tb ′ (= T0 ′ + Tb1). Then, as the developer amount increases, the corrected target density TC0 ′ approaches the target toner density TC0. Therefore, the true toner density is held at the target toner density TC0 as shown by the solid lines in FIGS. 11A and 11B.

  Next, the image forming apparatus having the developer damming member according to the second embodiment of the present invention will be described. In the description of the second embodiment, the same components as those of the first embodiment are the same. Reference numerals are assigned and detailed description thereof is omitted. The second embodiment is different from the first embodiment in the following points, but is configured in the same manner as the first embodiment in other points.

(Description of control unit)
FIG. 12 is a block diagram of the control unit of the image forming apparatus according to the second exemplary embodiment of the present invention, and corresponds to FIG. 6 according to the first exemplary embodiment.
In FIG. 12, in the image forming apparatus U according to the second embodiment, the controller C replaces the density correction unit C7 and the density dependent supply time calculation unit C9A1 according to the first embodiment with the following density correction unit C7 ′ and density dependent supply time. Calculation means C9A1 'is included.
C7 ′: Density Correction Unit The density correction unit C7 includes a density width correction function storage unit C7A ′ and a corrected target value calculation unit C7B ′, and is based on an accumulated drive time tr that is an example of an accumulated drive amount. The target toner density TC0 is corrected. The density correction unit C7 ′ according to the second embodiment corrects the target toner density TC0 by correcting the density width Tb−Ta of the target toner density TC0.

FIG. 13 is an explanatory diagram for correcting the target toner density according to the second embodiment of the present invention, FIG. 13A is an explanatory diagram of a density correction function corresponding to FIG. 7 of the first embodiment, and FIG. It is explanatory drawing which calculates the corresponding density-dependent replenishment time.
C7A ′: Density width correction function storage means The density width correction function storage means C7A ′ corrects the density width of the target toner density TC0, that is, the density width correction for correcting the density width between the upper limit value Tb1 and the lower limit value Ta1. Memorize functions. As shown in FIG. 13A, the density width correction function of the second embodiment uses a function derived in advance through experiments or the like. In the second embodiment, the density as an example of the density width correction value of the target toner density lower limit Ta1 is used. When the width lower limit correction amount is Th1a ′, which is an example of the density width correction value and the density width lower limit initial value as an initial value is Ta3, the cumulative drive time tr, and the correction end amount tr1, the following equation (11) , (12).
Th1a ′ = Ta3-Ta1-α1 ′ × tr (when tr ≦ tr1) (11)
= 0 (when tr> tr1) (12)
In the first embodiment, α1 ′ = (Ta3−Ta1) / tr1 is set. Similarly, the target toner density upper limit value Tb1 is calculated from the density width upper limit correction amount Th1b ′ and the density width upper limit initial value Tb3 as an example of the density width correction value.

C7B ′: Corrected target density calculation means The corrected target value calculation means C7B ′ is based on the target toner density TC0 and the density width correction amounts Th1a ′ and Th1b ′ derived by the density width correction function. A corrected target density TC0 ′ corrected with TC0 is calculated. The corrected target value calculation unit C7B ′ according to the second exemplary embodiment corrects the lower limit value Ta and the upper limit value Tb, which are density ranges of the target toner density TC0, and calculates a corrected target density TC0 ′. That is, in Example 2, the corrected lower limit value Ta ′ = Ta−Th1a ′ and the corrected upper limit value Tb ′ = Tb + Th1b ′ are equal to or lower than the corrected target density TC0 ′.
Accordingly, the density correction means C7 ′ of the second embodiment corrects the corrected target in which the target density width Tb−Ta is expanded to preset density width initial correction values Ta3 and Tb3 in a state where the cumulative drive time tr is initialized. The target toner density TC0 is corrected to the density TC0 ′, and the density width Tb′-Ta ′ of the corrected target density TC0 ′ is decreased so as to approach the target density width Tb-Ta as the cumulative driving time tr increases. To correct. When the cumulative drive amount tr reaches a preset correction end amount tr1, the density range Tb'-Ta 'of the corrected target density TC0' is set to coincide with the target density range Tb-Ta. .

C9A1 ′: Density-dependent replenishment time calculation means The density-dependent replenishment time calculation means C9A1 ′ depends on the toner density based on the detected toner density T1 that is a detection value of the toner density sensor SN2 and the corrected target density TC0 ′. The concentration-dependent replenishment time tc, which is the replenishment time that has been set, is calculated. The density-dependent replenishment time calculation means C9A1 ′ according to the second embodiment is based on the concentration-dependent replenishment time arithmetic expression shown in FIG. 13B, which is the same as that obtained in advance through experiments or the like, the detected toner density T1, and the corrected target density TC0 ′. The concentration dependent replenishment time tc is calculated. In FIG. 8A, the concentration-dependent replenishment time calculation formula of Example 1 is the upper limit replenishment time ta, the lower limit replenishment time tb, the replenishment time upper limit concentration T0-Ta2, the replenishment time lower limit concentration T0 + Tb2, the corrected lower limit value Ta ′, When the value is Tb ′, it is expressed by the following formulas (13) to (17).
tc = ta (when T1 <Ta′−Ta2 + Ta1) (13)
= −α2 × (T1-Ta ′)
(Ta′−Ta2 + Ta1 ≦ T1 <Ta ′) (14)
= 0 (when Ta ′ ≦ T1 ≦ Tb ′) (15)
= −α2 ′ × (T1−Tb ′)
(Tb ′ <T1 ≦ Tb ′ + Tb2−Tb1) (16)
= Tb (when Tb '+ Tb2-Tb1 <T1) (17)
In the second embodiment, α2 = ta / (Ta1−Ta2) and α2 ′ = tb / (Tb1−Tb2) are set.

(Explanation of flowchart of embodiment 2)
FIG. 14 is a flowchart of developer replenishment processing in the image forming apparatus according to the second embodiment of the present invention, and is a flowchart corresponding to FIG. 9 according to the first embodiment.
In FIG. 14, the developer supply process of the second embodiment is the same as the first embodiment except that the following ST4 ′ is executed instead of ST4 of the developer supply process of the first embodiment. .
In ST4 ′ of FIG. 14, the following processes (1) and (2) are executed, and the process proceeds to ST5.
(1) Based on the cumulative driving time tr, density width correction amounts Th1a ′ and Th1b ′ are calculated.
(2) The corrected target density TC0 ′ is calculated from the target toner density TC0 and the density width correction amounts Th1a ′ and Th1b ′.

FIG. 15 is a graph showing the transition of the developer amount and the true toner density with respect to the cumulative driving time of Example 2 corresponding to FIG. 11 of Example 1. FIG. 15A shows the cumulative driving time on the horizontal axis and the vertical axis. FIG. 15B is a graph in which the horizontal axis represents the cumulative driving time and the vertical axis represents the true toner density.
(Operation of Example 2)
In the image forming apparatus U according to the second embodiment having the above-described configuration, the target toner density TC0 and the corrected target density TC0 ′ in which the density width is extended are corrected according to the cumulative driving time tr. Therefore, in the image forming apparatus according to the second exemplary embodiment, the toner density is extended to the darker side corresponding to the case where the initial developer amount is smaller than the stable developer amount and the negative concentration-dependent replenishment time tc is easily set. If the toner density is reduced in a state where the amount of the developer is less than the stable developer amount, the developer is appropriately replenished.

  Further, when the developer in the developing device G is replaced with a new one by repairing a failure or the like, the internal cleaning is insufficient and the amount of developer is larger than the intended initial developer amount. Contrary to the case where the toner density is low, in the conventional technique, as shown in FIGS. 15A and 15B, the developer may be supplied even when the toner density is higher than the upper limit. Then, when the initial developer exceeding the amount of the stable developer is accommodated by the portion expanded to the side where the toner density is thin, the setting of the positive concentration-dependent replenishment time tc is reduced, and the stable developer Unnecessary developer replenishment operation in a state exceeding the amount is suppressed.

(Example of change)
As mentioned above, although the Example of this invention was explained in full detail, this invention is not limited to the said Example, A various change is performed within the range of the summary of this invention described in the claim. It is possible. Modification examples (H01) to (H010) of the present invention are exemplified below.
(H01) In the above-described embodiment, the copying machine as the image forming apparatus has been illustrated. However, the present invention is not limited to this, and a FAX, a printer, or a multifunction machine having all or a plurality of functions may be used. Further, the image forming apparatus is not limited to single-color development, so-called monochrome image forming apparatus, and can be constituted by multi-color development, so-called full-color image forming apparatus.

(H02) In the above-described embodiment, the cumulative drive time is exemplified as an example of the cumulative drive amount. However, the present invention is not limited to this, and any argument such as the cumulative rotation speed and the cumulative rotation angle, so-called parameter cumulative drive amount can be adopted. It is.
(H03) In the above embodiment, the target toner density is corrected by the density correction means C7, C7 ', but the present invention is not limited to this. The output value of the toner density sensor SN2, that is, the detected toner density is determined according to the cumulative drive amount. By correcting to an output value corresponding to the stable developer amount (for example, decreasing the detected toner density or increasing the output value T1), it is possible to have the same effect as in the first and second embodiments. . It is also possible to correct both. In the second embodiment, both the target toner density lower limit value and the target toner density upper limit value are corrected. However, only one of them can be corrected.

(H04) In the above embodiment, the upper limit replenishment time ta, the lower limit replenishment time tb, the replenishment time lower limit density T0-Ta2, the replenishment time upper limit density T0 + Tb2, the density width lower limit value Ta1, the density width upper limit value Tb1, and the target toner density lower limit value Ta. The numerical relationship such as the target toner density upper limit value Tb can be arbitrarily set according to the design. For example, the upper limit replenishment time ta and the lower limit replenishment time tb are not provided, and the upper limit and the lower limit can be eliminated, the density width lower limit value Ta1 = the density width upper limit value Tb1, or the density width can be set to 0. .
(H05) In the above embodiment, the density correction function and the density width correction function are linear functions. However, the present invention is not limited to this, and any function such as a quadratic function or a cubic function can be adopted. In addition to this, it is also possible to adopt a function in which the cumulative drive time changes stepwise every 100 seconds without using a continuously changing function. Furthermore, it is also possible to use a table that stores values for the cumulative driving time, such as a so-called look-up table, without using a function.

(H06) In the above-described embodiment, the toner concentration sensor SN2 using the magnetic permeability has been illustrated. However, the present invention is not limited to this, and can be applied to any toner concentration sensor in which the output of the toner concentration varies according to the developer amount. is there. Further, as shown in FIG. 10, the toner density sensor in which the toner density and the output value are in a right-down relationship is illustrated, but the invention is not limited to this, and the toner density sensor in which the toner density and the output value are in a right-up relationship is also illustrated. It can be used.
(H07) In the above-described embodiment, the developing device G is a so-called vertical developing device in which the developer transport paths are arranged up and down. However, the developing device G is not limited to this, and can also be applied to a horizontal developing device. It is. Further, the position of the developer discharge port 7 and the position where the toner density sensor SN2 is arranged can be arbitrarily changed according to the design.

(H08) In the above embodiment, the amount of the initial developer is set to be smaller than the amount of the stable developer. However, the amount is not limited to this and can be set to an arbitrary amount.
(H09) In the above-described embodiment, the cumulative drive amount is initialized by determining whether or not a new developer is stored based on the developer replacement input key UIe. However, the present invention is not limited to this. However, any method can be adopted such as manually initializing the cumulative drive amount or replacing the storage medium storing the cumulative drive amount.
(H010) In the above embodiment, the case where developer replenishment control is performed based on not only the detection result of the toner density sensor SN2 but also the cumulative value N1 of the number of print pixels is exemplified, but the present invention is not limited to this. It is also possible to calculate (estimate) the toner consumption based on the driving time of the developing device G and the accumulated value of the number of printed sheets. Although it is desirable to execute the replenishment operation based on the detection result of the toner concentration sensor SN2 and the amount of toner consumed by another measurement method, it is impossible to use only the detection result of the toner concentration sensor SN2. Absent.

FIG. 1 is an overall explanatory view of an image forming apparatus according to Embodiment 1 of the present invention. FIG. 2 is an enlarged explanatory view of the developing device which is a main part of FIG. FIG. 3 is a perspective view of a developing device as a main part of the developing device. 4 is an enlarged explanatory view of the developer replenishing port portion of the developing device shown in FIG. 3, and is a partial cross-sectional view seen from the direction of arrow IV in FIG. 5 is an explanatory view of the developing device, FIG. 5A is a sectional view taken along the line VA-VA of FIG. 4, FIG. 5B is a sectional view taken along the line VB-VB of FIG. 4, and FIG. It is. FIG. 6 is a block diagram of the control unit of the image forming apparatus according to the first exemplary embodiment of the present invention. FIG. 7 is an explanatory diagram of the density correction function according to the first embodiment of the present invention. FIG. 8 is an explanatory diagram for calculating the replenishment time according to the first embodiment of the present invention, and FIG. 8A is an explanatory diagram for calculating the concentration-dependent replenishment time. FIG. 8B is an explanatory diagram for calculating the pixel number dependent supply time. FIG. 9 is a flowchart of developer supply processing in the image forming apparatus according to the first exemplary embodiment of the present invention. FIG. 10 is an explanatory diagram of the output of the magnetic toner density sensor of Example 1. FIG. 10A is a graph in which the toner concentration is plotted on the horizontal axis and the output of the magnetic toner density sensor is plotted on the vertical axis for a predetermined developer amount. 10B is a graph in which the developer amount is plotted on the horizontal axis and the output of the toner density sensor is plotted on the vertical axis at a predetermined toner concentration. FIG. 10C is the vertical axis where the toner concentration is plotted on the horizontal axis when the developer amount varies. 6 is a graph showing the toner density. FIG. 11 is a graph showing the transition of the developer amount and the true toner density with respect to the cumulative drive time in Example 1. FIG. 11A is a graph in which the cumulative drive time is taken on the horizontal axis and the developer amount is taken on the vertical axis. 11B is a graph in which the cumulative driving time is plotted on the horizontal axis and the true toner density is plotted on the vertical axis. FIG. 12 is a block diagram of the control unit of the image forming apparatus according to the second exemplary embodiment of the present invention, and corresponds to FIG. 6 according to the first exemplary embodiment. FIG. 13 is an explanatory diagram for correcting the target toner density according to the second embodiment of the present invention, FIG. 13A is an explanatory diagram of a density correction function corresponding to FIG. 7 of the first embodiment, and FIG. It is explanatory drawing which calculates the corresponding density-dependent replenishment time. FIG. 14 is a flowchart of developer replenishment processing in the image forming apparatus according to the second embodiment of the present invention, and is a flowchart corresponding to FIG. 9 according to the first embodiment. FIG. 15 is a graph showing the transition of the developer amount and the true toner density with respect to the cumulative driving time of Example 2 corresponding to FIG. 11 of Example 1. FIG. 15A shows the cumulative driving time on the horizontal axis and the vertical axis. FIG. 15B is a graph in which the horizontal axis represents the cumulative driving time and the vertical axis represents the true toner density.

Explanation of symbols

7 ... Developer outlet,
11-17 + G5 ... developer replenisher,
C4: Developer identifying means in developer unit,
C5: Cumulative drive amount measuring means,
C6: Target toner density storage means;
C7, C7 '... density correction means,
C9B: Replenisher driving means,
G ... Developer,
SN2 ... toner density detecting member,
T1 ... detected toner density,
Ta3, Tb3 ... density range correction value Tb-Ta ... target density range TC0 ... target toner density,
TC0 '... corrected target density Th1 ... target toner density correction value,
tr ... Cumulative drive amount,
tr1 ... correction end amount,
U: Image forming apparatus,
V: Developer container.

Claims (8)

A developer container containing a developer containing toner and a carrier; and a developer discharge port for discharging the developer in the developer container when the developer amount in the developer container exceeds a predetermined stable developer amount; A developing device for developing an electrostatic latent image into a toner image by the developer;
A developer replenisher for replenishing the developer with a new developer containing toner and a carrier;
Cumulative driving amount measuring means for measuring the cumulative driving amount of the developer replenisher;
A toner concentration detecting member for detecting a toner concentration which is a ratio of toner and carrier contained in the developing container;
A target toner density storage means for storing a preset target toner density which is a target density of the toner density in the developing container;
Density correction means for correcting at least one of the detected toner density detected by the toner density detection member and the target toner density based on the cumulative drive amount;
Based on at least one of the detected toner density and the target toner density corrected by the density correction means, a replenisher driving means for driving the developer replenisher so that the toner density becomes the target toner density. When,
An image forming apparatus comprising: The target toner density has an upper limit value and a lower limit value, and the density correction unit corrects at least one of the upper limit value and the lower limit value based on the cumulative driving amount;
The replenisher drive means for driving the developer replenisher so that the toner density is within a target density range between the upper limit value and the lower limit value after being corrected by the density correction means;
The image forming apparatus according to claim 1. A developer discriminating means in the developing device for discriminating whether or not the developer in the developing device is a new developer;
The cumulative drive amount measuring means for initializing the cumulative drive amount when the developer in the developing device is new;
The image forming apparatus according to claim 1, further comprising: The developing device in which the amount of the new developer accommodated in the developing container is set to be smaller than the amount of the stable developer;
The image forming apparatus according to claim 1, further comprising: The toner concentration detecting member for detecting the toner concentration by detecting a magnetic permeability of a developer including a non-magnetic toner and a magnetic carrier;
In a state in which the cumulative drive amount is initialized, the target toner density is corrected to a corrected target density that is higher by a preset target toner density correction value, and the target drive density increases as the cumulative drive amount increases. The density for reducing the corrected target density so as to approach the toner density, and for making the corrected target density coincide with the target toner density when the cumulative drive amount reaches a preset correction end amount Correction means;
The image forming apparatus according to claim 4, further comprising: The density correction means for correcting the target toner density by correcting the target density width of the target toner density;
The image forming apparatus according to claim 2, further comprising: The toner concentration detecting member for detecting the toner concentration by detecting a magnetic permeability of a developer including a non-magnetic toner and a magnetic carrier;
In the state where the cumulative drive amount is initialized, the target toner density is corrected to the corrected target density obtained by expanding the target density range by a preset density width correction value, and the cumulative drive amount increases. Accordingly, correction is performed to reduce the density range of the corrected target density so as to approach the target density range, and the density of the corrected target density is reached when the cumulative drive amount reaches a preset correction end amount. The density correction means for matching a width with the target density width;
The image forming apparatus according to claim 6, further comprising: The correction end amount set so that the amount of developer accommodated in the developer container reaches the stable developer amount when the developer supply device is driven by the correction end amount;
The image forming apparatus according to claim 5 or 7, further comprising: