JP7338253B2 - Developing device, image forming device, method for controlling developing device, and program for controlling developing device - Google Patents

Description

The present disclosure relates to a developing device, an image forming apparatus, a method for controlling the developing device, and a program for controlling the developing device.

Conventionally, there has been proposed a developing device that stores toner and carrier as developer in a storage unit, charges the toner by agitating the toner and carrier, and develops the toner as a toner image on a photosensitive member. ing. Japanese Unexamined Patent Application Publication No. 2004-100001 discloses a developing device that reduces unevenness in density of an image when a toner image is transferred onto a sheet as an image. The developing device of Patent Document 1 includes a toner density sensor that detects the toner density in the container, estimates the charge amount of the developer based on the toner density detected by the sensor, and determines that the charge amount falls within a predetermined range. or not. This developing device adjusts the toner density so as to reduce the charge amount of the developer when it is determined that the charge amount of the developer does not fall within a predetermined range. This developing device reduces the occurrence of image density unevenness by adjusting the toner density.

Japanese Unexamined Patent Application Publication No. 2012-128200

However, in the developing device disclosed in Patent Document 1, the charge amount of the developer is reduced based only on the detection result of the toner density sensor. However, for example, the developing device may be affected by other conditions, and in this case, there is a problem that the charge amount of the developer cannot be appropriately reduced.

The present disclosure has been made to solve the problems as described above, and an object in one aspect is to provide a technique for appropriately reducing the charge amount of developer.

According to one aspect of the present disclosure, the developing device includes a developing unit that develops an image on an object using a charged developer, a coverage acquiring unit that acquires coverage of the image, and a developing device. a humidity parameter acquisition unit that acquires the humidity parameter of the location, a reduction unit that reduces the charge amount of the developer based on the coverage acquired by the coverage acquisition unit and the humidity parameter acquired by the humidity parameter acquisition unit; A development device is provided, comprising:

In one aspect, an input unit to which a job is input is further provided, the developing unit develops the patch image and the specified image specified by the job on the object, and the reduction unit develops the specified image in the developing unit. By developing the patch image after applying the toner, the charge amount of the developer is reduced.

In one aspect, an input unit to which a job is input is further provided, the development unit can develop the patch image and the specified image specified by the job onto the object, and the reduction unit provides the development unit with two By developing patch images between designated images, the amount of developer charge is reduced.

In one aspect, the image developed on the object by the developing unit is formed on a recording medium, and the reducing unit reduces the number of recording media on which the image developed on the object by the developing unit is formed to a predetermined reference value. a calculation unit that calculates the total coverage of all recording media on which images developed by the development unit are formed on the object; and an amount of developer for developing the patch image. a determination unit that determines based on the difference between the multiplied value multiplied by the unit and the total coverage value calculated by the calculation unit; and developing the patch image on the development unit using the amount of developer determined by the determination unit and a control unit that causes the

In one aspect, the reduction unit causes the development unit to develop the patch image by executing control such that the density of the patch image is higher than the density of the designated image.

In one aspect, the development section includes a development roller, and the reduction section causes the development section to develop the patch image by applying a bias to the development roller that is greater than the bias for developing the designated image.

In one aspect, the reducing section causes the developing section to develop the patch image by applying to the developing roller a bias with a DC component that is greater than the DC component of the bias for developing the designated image.

In one aspect, the reduction section causes the development section to develop the patch image by applying to the development roller a bias having a peak-to-peak value that is greater than the peak-to-peak value of the AC component of the bias when developing the designated image.

In one aspect, the developer includes a toner and a carrier, the developer is charged by agitating the toner and the carrier, and the reducing unit reduces the weight of the toner to the weight of the toner and the weight of the carrier. By increasing the toner concentration obtained by dividing by the sum, the amount of developer charge is reduced.

In one aspect, the toner and the carrier are agitated, and the storage unit stores the toner and the carrier, and replenishes the toner to the storage unit when the toner concentration of the toner stored in the storage unit is less than a threshold value. and a supply unit, and the reduction unit increases the toner concentration by increasing the threshold value.

In one aspect, the reduction section reduces developer charge based on the drive speed of the development section in addition to coverage and humidity parameters.

In one aspect, the reduction section reduces the amount of developer charge based on the drive time of the development section in addition to the coverage and humidity parameters.

According to another aspect of the present disclosure, an image forming apparatus including the developing device described above is provided.
According to another aspect of the present disclosure, a method of controlling a developer system for developing an image on a substrate with a charged developer material, comprising the steps of obtaining coverage of the image; and reducing developer charge based on the coverage and the humidity parameter.

According to another aspect of the present disclosure, a program for controlling a developing device that develops an image on an object with a charged developer material, the program instructs a computer to obtain coverage of the image; A program is provided that causes the steps of obtaining a humidity parameter of the location where the developer is located and reducing the amount of developer charge based on the coverage and the humidity parameter.

According to the present disclosure, it is possible to appropriately reduce the charge amount of the developer.
The above and other objects, features, aspects and advantages of the present invention will become apparent from the following detailed description of the invention taken in conjunction with the accompanying drawings.

2 is a diagram illustrating an example of the internal configuration of an image forming apparatus; FIG. 3 is a diagram showing an example of the internal configuration of an image forming unit; FIG. 2 is a diagram illustrating an example hardware configuration of an image forming apparatus; FIG. FIG. 4 is a diagram showing the relationship between humidity and coverage; 1 is an example of a functional block diagram of an image forming apparatus; FIG. FIG. 4 is an example of a functional block diagram of a control unit; FIG. 10 is a diagram showing the relationship between total coverage and the number of printed sheets; FIG. 10 is a diagram showing correspondence between difference values and toner amounts for developing patch images; It is a figure which shows an example of a superimposed voltage. It is a figure which shows an example of the DC component of superimposition voltage. It is a figure which shows an example of the alternating current component of superimposed voltage. FIG. 10 is a diagram showing a specified image and patch images; 4 is a diagram showing a flowchart of processing of the image forming apparatus; FIG. FIG. 10 is a diagram showing designated images and patch images according to another embodiment;

An image forming apparatus in an embodiment based on the present invention will be described below with reference to the drawings. In the embodiments described below, when referring to the number, amount, etc., the scope of the present invention is not necessarily limited to the number, amount, etc., unless otherwise specified. The same reference numbers are given to the same parts and equivalent parts, and redundant description may not be repeated. In addition, it is planned from the beginning to use the configurations in each embodiment in combination as appropriate.

<First Embodiment>
[Configuration example of image forming apparatus]
FIG. 1 shows an image forming apparatus 100 as a color printer. Although the image forming apparatus 100 as a color printer will be described below, the image forming apparatus 100 is not limited to a color printer. For example, image forming apparatus 100 may be a monochrome printer, a copier, a facsimile machine, or a multi-functional peripheral (MFP: Multi-Functional Peripheral). Further, in this embodiment, the toner may be referred to as developer, and the toner and carrier may be referred to as developer (or two-component developer). Recording media include, for example, paper and sheets. Forming an image on a recording medium may also be referred to as "printing".

The image forming apparatus 100 includes image forming units 1Y, 1M, 1C, and 1K, an intermediate transfer belt 36, a primary transfer roller 31, a secondary transfer roller 33, a cassette 37, a driven roller 38, and a drive roller 39. , a pickup roller 41 , a timing roller 42 , and a fixing device 43 .

The image forming units 1Y, 1M, 1C, and 1K are arranged in order along the intermediate transfer belt . The image forming unit 1Y forms a yellow (Y) toner image. The image forming unit 1M forms a magenta (M) toner image. The image forming unit 1C forms a cyan (C) toner image. The image forming unit 1K forms a black (BK) toner image.

The image forming units 1Y, 1M, 1C, and 1K each include a photoconductor 10, a charging section 11, an exposure section 12, a developing section 13, and a cleaning device 17. Photoreceptor 10 is typically an image carrier that carries a toner image. As an example, the photoreceptor 10 is a photoreceptor drum having a photosensitive layer formed on its surface. The photoreceptor 10 rotates in a direction corresponding to the driving direction of the intermediate transfer belt 36 (the direction of the arrow inside the photoreceptor 10 in FIG. 1).

In the color print mode, a yellow (Y) toner image, a magenta (M) toner image, a cyan (C) toner image, and a black (BK) toner image are superimposed in order and transferred to the intermediate transfer belt 36 . be. Thereby, a color toner image is formed on the intermediate transfer belt 36 . On the other hand, in the monochrome print mode, a black (BK) toner image is transferred from the photosensitive member 10 (latent image carrier) to the intermediate transfer belt 36 .

The intermediate transfer belt 36 is stretched around a driven roller 38 and a driving roller 39 . Drive roller 39 is rotationally driven by, for example, a motor (not shown). Intermediate transfer belt 36 and driven roller 38 rotate in conjunction with drive roller 39 . Thereby, the toner image on the intermediate transfer belt 36 is conveyed to the secondary transfer roller 33 .

Sheets S are accommodated in the cassette 37 . Sheets S are conveyed sheet by sheet from cassette 37 along conveying path 40 to secondary transfer roller 33 by pickup roller 41 and timing roller 42 . The secondary transfer roller 33 applies a transfer voltage having a polarity opposite to that of the toner image to the sheet S being conveyed. As a result, the toner image is attracted from the intermediate transfer belt 36 to the secondary transfer roller 33 and transferred onto the paper S at an appropriate position.

The fixing device 43 presses and heats the paper S passing through the fixing device 43 . As a result, the toner image formed on the sheet S is fixed on the sheet S. As shown in FIG. After that, the sheet S is discharged to the tray 48 .

Next, the toner supply section 200 will be described. Image forming apparatus 100 further includes toner supply section 200 . The toner supply unit 200 is a device for supplying toner to the developing unit 13 (see FIG. 2). The toner supply section 200 is provided between the intermediate transfer belt 36 and the tray 48 in the vertical direction.

The toner supply section 200 includes container receiving sections 21 (21Y, 21M, 21C, 21K) of respective colors and toner bottles 30 (30Y, 30M, 30C, 30K) of respective colors.

The toner bottle 30 contains toner for replenishing the developing section 13 . Toner bottle 30Y, toner bottle 30M, toner bottle 30C, and toner bottle 30K are provided corresponding to developing section 13 of image forming unit 1Y, image forming unit 1M, image forming unit 1C, and image forming unit 1K, respectively. . That is, toner bottle 30Y, toner bottle 30M, toner bottle 30C, and toner bottle 30K contain yellow (Y), magenta (M), cyan (C), and black (K) toners.

The container receiving section 21 is fixed to the image forming apparatus 100 . The toner bottle 30 is detachably attached to the container receiving portion 21 . The container receiving portion 21 is configured to receive the toner bottle 30 . Container receiving portion 21Y, container receiving portion 21M, container receiving portion 21C, and container receiving portion 21K are provided corresponding to toner bottle 30Y, toner bottle 30M, toner bottle 30C, and toner bottle 30K, respectively.

During operation of the image forming apparatus 100 , toner is supplied to the developing section 13 from the toner bottle 30 attached to the container receiving section 21 . When the toner in the toner bottle 30 has decreased, the user removes the toner bottle 30 from the container receiving portion 21 and attaches a new toner bottle 30 to the container receiving portion 21 .

The image forming apparatus 100 also has a humidity sensor 72 . Humidity sensor 72 detects the humidity in the location where image forming apparatus 100 is installed. In this embodiment, this humidity is referred to as "relative humidity".

[Internal Configuration of Image Forming Unit]
The internal structure of the image forming units 1Y, 1M, 1C, and 1K will be described with reference to FIG. FIG. 2 is a diagram showing an example of the internal structure of image forming units 1Y, 1M, 1C, and 1K.

As shown in FIG. 2, the image forming units 1Y, 1M, 1C, and 1K each include a drum unit 15, an exposure section 12, and a development section 13. As shown in FIG.

Drum unit 15 includes photoreceptor 10 , charging section 11 , cleaning device 17 , and support 19 .

The support 19 supports the photoreceptor 10, the charging section 11, and the cleaning device 17 to unitize these members.

The photoreceptor 10 includes a drum-shaped (cylindrical) base 10a made of aluminum or the like, and a photosensitive layer 10b formed on the outer peripheral surface of the base 10a. A toner image is formed on the outer peripheral surface of the photoreceptor 10 .

The charging unit 11 is a roller that uniformly charges the circumferential surface of the photoreceptor 10 to a negative polarity. The charging unit 11 is elongated along the rotation axis of the photoreceptor 10 . The rotation axis of charging unit 11 is parallel to the rotation axis of photoreceptor 10 .

Charging unit 11 includes a rigid cylindrical shaft made of metal (for example, stainless steel) and an elastic layer made of a conductive or semi-conductive elastic material formed on the peripheral surface of the shaft.

The cleaning device 17 is pressed against the photoreceptor 10 . The cleaning device 17 collects toner remaining on the surface of the photoreceptor 10 after the toner image is transferred.

The exposure unit 12 irradiates the photoreceptor 10 with laser light according to a control signal from the control unit 60, and exposes the surface of the photoreceptor 10 according to the inputted image pattern. As a result, charges are generated by the charge generation layer of the photosensitive layer 10b in the exposed portion, and the absolute value of the surface potential (negative polarity) of the exposed portion is the surface potential (negative polarity) of the unexposed portion. lower than the absolute value. In this manner, an electrostatic latent image is formed on the photoreceptor 10 according to the input image.

In this embodiment, the developing unit 13 develops the electrostatic latent image formed on the surface of the photoreceptor 10 with toner (using toner). The developing section 13 includes a developing tank 13a, a pair of stirring screws 13b and 13c, a toner concentration sensor 73, and a developing roller 13d. As the developing section 13 develops the electrostatic latent image, the amount of toner in the developing section 13 is reduced.

The developer tank 13a contains a two-component developer composed of non-magnetic toner and a carrier made of ferrite powder, iron powder, or the like. The developer tank 13a has two storage chambers 13e and 13f along the axial direction of the photoreceptor 10. As shown in FIG. The two housing chambers 13e and 13f communicate at both ends. Stirring screws 13b and 13c are arranged in the storage chambers 13e and 13f, respectively. The stirring screws 13b and 13c are members extending in the depth direction of the page of FIG. By rotating the stirring screws 13b and 13c, the two-component developer contained in the storage chambers 13e and 13f is stirred while circulating between the storage chambers 13e and 13f, and the toner and carrier are mixed. and triboelectrified.

The resin particles constituting the toner and the material of the resin coating the surface of the carrier are selected so that the toner used as the two-component developer of the present embodiment has a negative charging property and the carrier has a positive charging property. be done. Therefore, the toner is negatively charged and the carrier is positively charged by friction due to agitation. Then, the negatively charged toner adheres to the periphery of the positively charged carrier.

The developing roller 13d is a nonmagnetic cylindrical member made of, for example, stainless steel. The developing roller 13d incorporates a magnet (not shown) having a plurality of magnetic poles, and is rotationally driven while keeping a small distance from the photoreceptor 10. As shown in FIG.

The two-component developer conveyed in the storage chamber 13e in the axial direction of the agitating screw 13b, that is, the toner-attached carrier adheres to the peripheral surface of the developing roller 13d due to the magnet built into the developing roller 13d.

The rotating developing roller 13d conveys the two-component developer adhering to the circumferential surface to a position facing the photoreceptor 10 (developing area).

A voltage supplied from a power supply unit 50 (see FIG. 3) is applied to the developing roller 13d. A voltage in which an AC voltage is superimposed on a DC voltage is applied to the developing roller 13d. In this embodiment, the DC voltage is −200 V to −900 V, and the AC voltage is a square wave and a sine wave with a frequency of 3 to 7 kHz and a Vpp (peak-to-peak value) of 1 to 3 kpp.

As the photosensitive member 10 rotates, when the electrostatic latent image forming portion reaches the position (development area) facing the developing roller 13d, the toner (negatively charged) separates from the carrier from the peripheral surface of the developing roller 13d. and move to the photoreceptor 10. At this time, the carrier is attracted to the developing roller 13d by the magnetic force of the magnet built into the developing roller 13d and does not move to the photoreceptor 10. FIG. In this manner, the toner is transferred from the developing roller 13 d to the photoreceptor 10 , and a toner image corresponding to the electrostatic latent image is developed on the surface of the photoreceptor 10 .

Further, the developing section 13 has a regulation member 13h. The regulation member 13h is a member that regulates (regulates) the amount of the two-component developer adhering to the developing roller 13d. Since the developing section 13 has the regulating member 13h, the amount of the two-component developer adhering to the developing roller 13d can be made appropriate. In this embodiment, a portion of the developer tank 13a serves as a regulating member 13h.

The toner density sensor 73 detects the toner density of the two-component developer in the developer tank 13a. The toner density is also called "Tc". Toner concentration sensor 73 typically includes a magnetic permeability sensor. The toner density sensor 73 measures the magnetic permeability of the processing area where toner is present in the development station 13 . Carriers are mainly composed of iron, and when the magnetic permeability is high, it is assumed that there are many carriers, so Tc is low. On the other hand, when the magnetic permeability is low, it is assumed that there are few carriers, so Tc is high. Also, the toner concentration sensor 73 converts the magnetic permeability detected by the magnetic permeability sensor into Tc. The conversion method may be, for example, a method using a predetermined formula. Also, the conversion method may be, for example, a method using a predetermined table. Note that the conversion from magnetic permeability to Tc may be executed by the control unit 60 .

Toner concentration is typically obtained by dividing the weight of toner by the weight of toner plus the weight of carrier. That is, the toner concentration is obtained by (toner weight)/(toner weight+carrier weight). An appropriate range is determined in advance as the toner density in the developing tank 13a. The appropriate range includes a lower limit value and an upper limit value.

When image forming apparatus 100 executes print processing with Tc lower than the proper range, the amount of toner in the image to be developed decreases, and the density of the printed image becomes lower than the proper density. The appropriate density is, for example, the density specified (input) by an administrator or the like.

On the other hand, when Tc is higher than the proper range, the toner may not be sufficiently agitated with respect to the carrier. In this case, the amount of charge on the toner is reduced, and the toner scatters from the developing section 13 . When the toner scatters from the developing unit 13, the toner is added to, for example, the inside of the image forming apparatus 100 or the background portion of the image (the portion where toner should not be added), resulting in a phenomenon such as an image defect. Therefore, Tc preferably belongs to the appropriate range.

[Hardware Configuration of Image Forming Apparatus]
An example of the hardware configuration of the image forming apparatus 100 will be described with reference to FIG. FIG. 3 is a block diagram showing the main hardware configuration of the image forming apparatus 100. As shown in FIG.

As shown in FIG. 3, the image forming apparatus 100 includes a power supply unit 50, a CPU 55 (Central Processing Unit), a sensor group 70, a ROM 102 (Read Only Memory), a RAM 103 (Random Access Memory), and an operation panel. 107 and a network interface 80 .

Power supply unit 50 supplies power to each unit of image forming apparatus 100 (for example, charging unit 11 and developing unit 13 in FIG. 2). The CPU 55 executes control programs. The ROM 102 nonvolatilely stores data including control programs executed by the CPU 55 . The RAM 103 volatilely stores data.

The sensor group 70 is composed of a plurality of sensors that measure various physical quantities in the image forming apparatus 100 . Sensor group 70 includes humidity sensor 72 and toner density sensor 73 shown in FIG.

The operation panel 107 is composed of a display and a touch panel. The display and touch panel are superimposed on each other. Operation panel 107 receives, for example, a command (for example, a print command, a scan command, etc.) to image forming apparatus 100 from a user. Image forming apparatus 100 receives a command from a user as a job.

A network interface 80 is connected to a network. Image forming apparatus 100 can communicate with an external device via network interface 80 . The external device includes, for example, a mobile communication terminal such as a smart phone, a server, and the like.

Processing in image forming apparatus 100 is implemented by each piece of hardware and software executed by CPU 55 . Such software may be pre-stored in flash memory. Software may also be stored in a memory card or other storage medium and distributed as a program product. Alternatively, the software may be provided as a downloadable program product by a so-called Internet-connected information provider. Such software is read from the storage medium by an IC card reader/writer or other reading device, or downloaded via the communication IF, and then temporarily stored in the flash memory. The software is read from the flash memory by the CPU 55 and stored in the flash memory in the form of an executable program. CPU 55 executes the program.

Each component constituting the image forming apparatus 100 shown in the figure is a general one. Therefore, it can be said that the essential part of the present invention is software stored in a flash memory, memory card or other storage medium, or software downloadable via a network. Since the operation of each hardware of image forming apparatus 100 is well known, detailed description thereof will not be repeated.

The recording medium is not limited to DVD-ROM, CD-ROM, FD (Flexible Disk), hard disk, magnetic tape, cassette tape, optical disk (MO (Magnetic Optical Disc) / MD (Mini Disc) / DVD (Digital Versatile Disc)), an optical card, a mask ROM, an EPROM (Electronically Programmable Read-Only Memory), an EEPROM (Electronically Erasable Programmable Read-Only Memory), a semiconductor memory such as a flash ROM, etc., which permanently carries a program. . Also, the recording medium is a non-transitory medium in which the program or the like can be read by the computer.

The program here includes not only a program that can be directly executed by the CPU, but also a program in source program format, a compressed program, an encrypted program, and the like.

An example of the hardware configuration of the developing device 120 is not shown, but includes, for example, a CPU, a ROM, a RAM, an imaging unit 13, and the like.

[Agitation performance of toner and carrier]
Next, the performance of agitating toner and carrier will be described. In recent years, miniaturization of the developing section 13 is demanded. When the developing section 13 is miniaturized, miniaturization of the storage chambers 13e, 13f and the like is also required. When the storage chambers 13e, 13f and the like are miniaturized, the amount of movement of the toner in the storage chambers 13e, 13f is reduced, and as a result, there is a tendency for a phenomenon in which the agitation performance between the toner and the carrier is lowered.

This phenomenon remarkably occurs particularly when the charge amount of the toner becomes high. As the charge amount of the toner increases, the toner and the carrier are strongly attracted to each other. Therefore, the toner (uncharged toner) replenished later is less likely to come into contact with the carrier. As a result, it becomes difficult to charge the replenished toner, and the stirring performance is lowered. When the stirring performance is lowered, there arises a problem that the density of an image formed on a sheet or the like is uneven due to the uneven charge amount.

Next, the humidity and coverage of this embodiment will be described. Coverage is the total amount of toner used per sheet of paper of a predetermined size (for example, A4 size). For example, when the entire A4 sheet is filled with solid black, the black toner coverage is 100%.

FIG. 4 shows the relationship between humidity and coverage in this embodiment. In FIG. 4, the horizontal axis indicates coverage and the vertical axis indicates temperature. In FIG. 4, circle marks indicate that there is no image unevenness or almost no image unevenness. Also, in FIG. 4, a triangle mark indicates that there is slight unevenness in the image. In addition, in FIG. 4, square marks indicate that there is a large amount of image unevenness. The curve in FIG. 4 indicates the boundary of whether there is much image unevenness. As shown in FIG. 4, it was confirmed that image unevenness occurs when coverage is low and humidity is low.

When the coverage is low, less toner is replaced in the developing section 13 . Therefore, the same toner is stirred with the carrier many times and the toner passes through the regulating member 13h, thereby increasing the charge amount of the toner.

In addition, when the humidity is low, the dielectric constant of air on the surface of the toner becomes low, and the charge leakage speed becomes slow.

Thus, image unevenness occurs in a state of low coverage and low humidity. Therefore, the developing device of the present embodiment estimates that the toner charge amount is high when it is determined that the coverage is low and the humidity is low. Therefore, when it is determined that the coverage is low and the humidity is low, the developing device of the present embodiment reduces the charge amount of the toner (developer), thereby reducing the occurrence of image unevenness.

[Developing device]
FIG. 5 is a block diagram showing the image forming apparatus 100, the developing section 13, and the like. As shown in FIG. 5 , image forming apparatus 100 includes developing section 13 . Developing section 13 includes control section 60 and developing section 13 . The control unit 60 is composed of, for example, a CPU, a ROM, a RAM, and the like. The control unit 60 of the developing device 120 may also be used as the control unit of the image forming apparatus 100 . Also, the control unit 60 of the developing device 120 may have a configuration different from that of the image forming apparatus 100 .

The developing unit 13 can develop the patch image and the designated image on the photosensitive member under the control of the control unit 60 . A "patch image" is an image formed on the photoreceptor 10 (intermediate transfer belt 36) to discharge old toner of the developer or to be used as a density reading pattern for density adjustment during image stabilization. , which is an image that is not transferred to a recording medium. In this embodiment, the patch image is an image that is mainly used to expel the old toner of the developer.

A designated image is an image designated by a job corresponding to a command input to image forming apparatus 100 by a user. This designated image is, for example, an image to be transferred to a recording medium (an image to be printed on paper).

[Control Unit of Developing Device]
FIG. 6 is a diagram showing a functional configuration example of the control unit 60 and the like. In the example of FIG. 6, the control unit 60 includes functions such as an input unit 602, a coverage acquisition unit 604, a reduction unit 608, a humidity acquisition unit 606, a humidity determination unit 610, a second storage unit 612, and the like.

The reduction unit 608 also has functions of a calculation unit 6082 , a multiplication unit 6084 , a first storage unit 6086 , a determination unit 6088 , a patch image control unit 6090 and an application unit 6092 .

When the user inputs a command to operation panel 107, the command is input to input unit 602 as a job. Instructions include, for example, copy instructions, scan instructions, and the like. Jobs include a copy job corresponding to a copy command, a scan job corresponding to a scan command, and the like. Information indicating a job is also referred to as "job information".

When job information is input to the input unit 602, the coverage acquisition unit 604 acquires coverage information included in the job information. Coverage information is information indicating coverage. In the present embodiment, coverage refers to "coverage of an image when a toner image developed on the photosensitive member 10 by the developing unit 13 is transferred (formed) onto a recording medium (sheet, paper, etc.)". The coverage information acquired by coverage acquisition section 604 is input to calculation section 6082 of reduction section 608 .

Also, the humidity acquisition unit 606 acquires the humidity of the place where the developing device 120 (image forming apparatus 100) is installed from the humidity sensor 72 . Information indicating humidity is referred to as "humidity information". Humidity acquisition unit 606 transmits humidity information to humidity determination unit 610 . Humidity determination unit 610 determines whether the humidity indicated by the humidity information is higher than second reference value B or not. Second reference value B is stored in second storage unit 612 . The 2nd memory|storage part 612 is comprised by ROM102, for example.

Humidity determination unit 610 determines whether the humidity acquired by humidity acquisition unit 606 is lower than second reference value B or not. Humidity determination unit 610 transmits the determination result to reduction unit 608 . If the determination result is that "the humidity acquired by the humidity acquisition unit 606 is equal to or higher than the second reference value B", the reduction unit 608 does not execute the process of reducing the low charge amount of the toner. On the other hand, if the determination result is that "the humidity acquired by the humidity acquisition unit 606 is less than the second reference value B," the reduction unit 608 executes processing to reduce the low charge amount of the toner. .

Next, processing of the reduction unit 608 (processing for reducing the low charge amount of toner) will be described. Here, a case where the instruction by the user is "an instruction to print a specified image on 50 sheets of paper" will be described. The calculation unit 6082 calculates the total value of the coverage for the number of sheets (here, 50 sheets) on which the image developed on the photoreceptor 10 by the developing unit 13 is formed. In this embodiment, the coverage information includes coverage for each of one or more sheets (here, 50 sheets). The coverage information of this embodiment includes, for example, the coverage of each of the first to fiftieth elements. The coverage information is, for example, that out of 50 sheets of paper, the coverage of the image formed on the first sheet is 3%, and the coverage of the image formed on the second sheet is 4%. Contains information. The calculating unit 6082 calculates the total value of coverage by adding the coverage of each of the one or more sheets.

FIG. 7 is a diagram showing an image of the calculation unit 6082 calculating the total coverage value. In the example of FIG. 7, the horizontal axis indicates the number of sheets on which an image is formed (hereinafter referred to as "printed number"), and the vertical axis indicates total coverage.

As shown in FIG. 7, as the number of prints increases, so does the total coverage. In the example of FIG. 7, the total coverage of images formed on 50 sheets of paper is assumed to be 50%. That is, the calculation unit 6082 calculates 50% as the calculation result. The calculation result (50%) by the calculation unit 6082 is output to the determination unit 6088 .

Multiplication section 6084 multiplies the number of sheets (here, 50 sheets) on which the image developed on photoreceptor 10 by development section 13 is formed, by a predetermined first reference value A. The number of sheets is an integer of 1 or more. Also, the first reference value A is a coverage reference value of an image formed on one sheet of paper. If the coverage of the image formed on one sheet of paper is less than the first reference value A, the toner in the developing section 13 will not be consumed much, and as a result, the toner will remain. When the toner remains, the same toner (remaining toner) is agitated with the carrier many times, thereby increasing the charge amount of the toner. Therefore, from the viewpoint of reducing the charge amount of the toner, it is preferable that the coverage of the image formed on one sheet of paper is equal to or greater than the first reference value A. Note that the first reference value A corresponds to the "reference value" of the present disclosure.

In this embodiment, it is assumed that the first reference value A is 3%. That is, in the present embodiment, the multiplication unit 6084 derives a multiplication value of 150% by performing a calculation of 50 sheets x 3%. Multiplying section 6084 outputs the multiplied value to determining section 6088 .

The determination unit 6088 determines the amount of toner for developing the patch image based on the difference value between the multiplication value multiplied by the multiplication unit 6084 and the total coverage value calculated by the calculation unit 6082 . Typically, the determining unit 6088 calculates the difference value by subtracting the total coverage value from the multiplied value. Further, when the difference value becomes 0 or a negative value, it means that the toner is appropriately consumed, so the developing device 120 does not develop the patch image. Further, when the difference value becomes a positive value, it means that the toner is not properly consumed, so the developing device 120 develops the patch image.

Determination unit 6088 stores a table in which difference values are associated with toner amounts for developing patch images. FIG. 8 is an example of this table. This table is stored in a predetermined storage area (eg, ROM 102). In the example of FIG. 8, B1 is associated with the difference value A1% as the toner amount for developing the patch image. B2 is associated with the difference value A2% as the toner amount for developing the patch image. The table in FIG. 8 is defined such that the larger the difference value, the larger the toner amount for developing the patch image.

The determination unit 6088 refers to the table in FIG. 8 and determines the toner amount corresponding to the difference value. In this embodiment, the multiplication value is 150% and the total coverage value is 50%. That is, the difference value is 150%-50%=100%. In other words, in this embodiment, 100% of the toner amount is insufficiently consumed.

A determination unit 6088 determines the amount of toner for developing the patch image based on the difference. In the present embodiment, since the difference is 100%, the image forming apparatus 100 develops the patch image on one sheet of A4 paper as the toner amount for developing the patch image. As a result, the image forming apparatus 100 of this embodiment can eliminate consumption of 100% of the toner amount.

The determination unit 6088 transmits the determined toner amount (the toner amount of the patch image) to the patch image control unit 6090 . The patch image control unit 6090 causes the developing unit 13 to develop the patch image with the amount of toner determined by the determination unit 6088 . Typically, the patch image control section 6090 causes the exposure section 12 to expose the surface of the photoreceptor 10 according to the image pattern of the patch image with the determined amount of toner.

Further, when the difference value calculated by the determining unit 6088 is positive, the determining unit 6088 transmits a positive signal indicating the positive to the applying unit 6092 . This positive signal is a signal indicating that the image forming apparatus 100 develops the patch image. Also, when the difference value calculated by the determining unit 6088 is 0 or negative, the determining unit 6088 does not transmit the signal. Hereinafter, the voltage applied to the developing roller 13d to develop the toner image of the designated image on the photoreceptor 10 is referred to as "normal voltage".

The case where the image forming apparatus 100 develops the patch image is the case where the charge amount of the toner is high. A toner with a high charge amount adheres to the developing roller 13d more strongly than a toner with a low charge amount. Therefore, when a normal voltage is applied to the developing roller 13d, the highly charged toner is less likely to fly to the photoreceptor 10. FIG. Therefore, in the present embodiment, in order to cause the highly charged toner (toner for developing a patch image) adhering to the developing roller 13d to fly to the photoreceptor 10, the voltage of the applying section 6092 is higher than the normal voltage. A voltage is applied to the developing roller 13d.

In addition, applying a voltage higher than the normal voltage to the developing roller 13 d means that “the reducing unit 608 performs control such that the density of the patch image is higher than the density of the designated image, so that the developing unit 13 Developing the patch image on the photoreceptor 10".

Next, the voltage applied by the applying section 6092 will be described. As described above, the voltage applied by the applying unit 6092 to the developing roller 13d is a superimposed voltage obtained by superimposing a DC voltage and an AC voltage.

FIG. 9 is a diagram showing superimposed voltages. In FIG. 9 and FIGS. 10 and 11 to be described later, the voltage value increases in the upward direction. FIG. 9A shows a superimposed voltage applied to the developing roller 13d by the applying unit 6092 to develop the patch image on the photoreceptor 10. FIG. FIG. 9B shows the superimposed voltage applied to the developing roller 13d by the applying unit 6092 to develop the patch image on the photoreceptor 10. FIG.

10 and 11 are diagrams showing the DC voltage and the AC voltage that form the superimposed voltage. FIG. 10 is a diagram showing a DC component of voltage. FIG. 10A shows the DC component of the voltage when developing the patch image, and FIG. 10B shows the DC component of the voltage when forming the specified image.

10A and 10B, V1a and V2a indicate the voltage of the photoreceptor 10 when the photoreceptor 10 is charged by the charging section 11. In FIG. 10(A) and 10(B), V1b and V2b indicate the DC component of the voltage applied by the applying section 6092 to the developing roller 13d. 10A and 10B, V1c and V2c indicate the voltage of the photoreceptor 10 when the photoreceptor 10 is charged by the exposure unit 12. FIG. 10A and 10B, ΔV1 indicates the potential difference between V1b and V1c, and ΔV2 indicates the potential difference between V2b and V2c. Further, as indicated by V1a and V2a in FIG. 10, the voltage value of the photoreceptor 10 when the photoreceptor 10 is charged by the charging unit 11 is higher than that of the designated image when the patch image is developed. is higher than when developing a toner image of Further, as indicated by V1b and V2b in FIG. 10, the DC component of the voltage applied to the developing roller 13d by the applying unit 6092 is more effective in developing the toner image of the designated image when developing the patch image. Higher than when developing. Also, as indicated by V1c and V2c in FIG. 10, the voltage values of the photoreceptor 10 when the photoreceptor 10 is charged by the exposure unit 12 are different when developing the patch image and when developing the designated image. are the same in all cases.

As shown in FIGS. 10A and 10B, ΔV1 is greater than ΔV2. In this way, under the control of the reducing unit 608, the applying unit 6092 applies to the developing roller 13d a DC component voltage that has a larger potential difference when developing a patch image than when forming a designated image. do. The patch image is developed on the photosensitive member 10 by the developing unit 13 by applying the voltage of the DC component. In other words, the applying unit 6092 applies a voltage having a larger DC component to the developing roller 13d when developing a patch image than when forming a designated image.

FIG. 11 is a diagram showing DC voltage. FIG. 11A shows the AC component of the voltage when developing the patch image, and FIG. 11B shows the AC component of the voltage when forming the designated image.

In FIGS. 11A and 11B, ΔVpp1 indicates the peak-to-peak value of the AC component of the voltage when developing the patch image, and ΔVpp2 indicates the peak value of the AC component of the voltage when forming the specified image. Peak values are indicated. The peak-to-peak value is also called "peak-to-peak".

As shown in FIGS. 11A and 11B, ΔVpp1 is greater than ΔVpp2. In this way, under the control of the reducing unit 608, the applying unit 6092 applies the DC voltage so that the potential difference is greater when developing the patch image than when forming the designated image. The reducing unit 608 causes the developing unit 13 to develop the patch image on the photosensitive member 10 by applying the AC component voltage.

Next, positions where patch images are formed on the photoreceptor 10 will be described. FIG. 12 is a diagram for explaining positions where patch images are formed. FIG. 12 shows an example in which a toner image 410 of a designated image and a patch image 420 are developed on the photoreceptor 10 . The patch image 420 is developed with a predetermined density and a predetermined shape along the rotation direction of the photoreceptor 10 (along the longitudinal direction of the peripheral portion of the photoreceptor).

In the example of FIG. 12, when developing the toner images 410 of a plurality of designated images, the developing device 120 develops the patch image 420 after developing the last toner image 410 of the plurality of designated images. . A plurality of specified images are a plurality of images specified in one job.

Further, the control unit 60 transfers the patch image 420 to the intermediate transfer belt 36, but controls so as not to transfer the patch image 420 to the paper. As a modification, the control section 60 may prevent the patch image 420 from being transferred to the intermediate transfer belt 36 . For example, when the patch image 420 developed on the photoreceptor 10 reaches the primary transfer roller 31 , the control section 60 may perform control to separate the intermediate transfer belt 36 from the photoreceptor 10 .

[Processing Flow of Developing Device]
Next, the processing flow of the developing device 120 will be described. FIG. 13 is a flow chart showing main processing of the developing device 120 . FIG. 13 shows processing executed when job information is input to the input unit 602, for example. Note that steps S10 and S12 indicated by dashed lines in FIG. 13 will be described later.

First, in step S2, the coverage acquisition unit 604 acquires coverage information. Next, in step S4, the humidity acquisition unit 606 acquires humidity.

Next, the humidity determination unit 610 compares the humidity with the second reference value B in step S6. In step S6, when humidity determination unit 610 determines that the humidity is equal to or less than second reference value B (NO in step S6), the process of FIG. 13 ends. When humidity determination unit 610 determines that the humidity is higher than second reference value B (YES in step S6), the process proceeds to step S8.

Next, in step S8, the determination unit 6088 compares the total coverage (the value calculated by the calculation unit 6082) with the number of prints×first reference value A (the value calculated by the multiplication unit 6084). If the determining unit 6088 determines that the total coverage is smaller than the number of printed sheets×the first reference value A (YES in step S8), the process proceeds to step S14.

In step S14, the reduction unit 608 reduces the charge amount of the toner by developing the patch image 420 on the photoreceptor 10 (image forming apparatus 100 develops the patch image).

[Brief Summary]
(1) In the present embodiment, as described with reference to FIG. 6 and the like, the developing unit 13 develops an image (toner image) on the photoreceptor 10 using charged toner. Further, the coverage acquisition unit 604 acquires “coverage of an image when a toner image developed on the photoreceptor 10 by the development unit 13 is transferred (formed) on a recording medium (sheet, paper, etc.)”. Humidity acquisition unit 606 acquires the humidity of the location where developing device 120 (image forming apparatus 100) is installed. A reduction unit 608 reduces the charge amount of toner based on the coverage acquired by the coverage acquisition unit and the humidity acquired by the humidity acquisition unit 606 . Therefore, the developing device 120 of the present embodiment can reduce the amount of toner charge in consideration of the influence of humidity and the influence of coverage.

(2) As described with reference to FIG. 10, the developing unit 13 develops the patch image 420 on the photoreceptor 10 after developing the toner image 410 of the designated image on the photoreceptor 10 . Therefore, the patch image 420 can be developed without affecting the specified image specified by the job based on the user's instruction.

(3) Further, the multiplication unit 6084 of the reduction unit 608 adds the first reference value A (3% in this embodiment) is multiplied. In the example above, the multiplier value is 150%. Further, the calculation unit 6082 calculates the total coverage value of all the sheets (50 sheets) on which the image developed on the photoreceptor 10 by the developing unit 13 is formed. In the example above, the total value is 50%. The determination unit 6088 determines the amount of toner for developing the patch image by multiplying the multiplied value (=150%) by the multiplication unit 6084 and the total coverage value (=50%) calculated by the calculation unit 6082. Determined based on the difference (=100%). The determination unit 6088 determines the amount of toner for developing the patch image based on a table (see FIG. 8) that associates the difference with the amount of toner for developing the patch image. The patch image control unit 6090 causes the developing unit 13 to develop the patch image with the amount of toner determined by the determination unit 6088 . Therefore, the developing device 120 can develop an appropriate amount of patch images even if the number of sheets to be printed is plural.

(4) Further, for example, as described with reference to FIGS. 10 and 11, the reduction unit 608 performs control to make the density of the patch image 420 higher than the density of the toner image 410 of the designated image. With this control, the reducing unit 608 causes the developing unit 13 to develop the patch image. Therefore, the developing device 120 appropriately discharges the toner from the developing roller 13d to the photoreceptor 10, even if the toner is highly charged and it is difficult for the toner to fly from the developing roller 13d to the photoreceptor 10. can be made to fly to

(5) As described with reference to FIGS. 10 and 11, the applying unit 6092 of the reducing unit 608 applies a bias larger than the bias for developing the designated image to the developing roller 13d, thereby The developing unit 13 is caused to develop the patch image. Therefore, the developing device 120 appropriately discharges the toner from the developing roller 13d to the photoreceptor 10, even if the toner is highly charged and it is difficult for the toner to fly from the developing roller 13d to the photoreceptor 10. can be made to fly to

(6) A case where the voltage applied to the developing roller 13d is divided into a DC component and an AC component will be described. As shown in FIGS. 10A and 10B, by applying a bias with a DC component (ΔV1) larger than the DC component (ΔV2) of the bias when developing the designated image to the developing roller 13d, The developing unit 13 is caused to develop the patch image. Therefore, the developing device 120 appropriately discharges the toner from the developing roller 13d to the photoreceptor 10, even if the toner is highly charged and it is difficult for the toner to fly from the developing roller 13d to the photoreceptor 10. can be made to fly to

(7) As shown in FIGS. 11A and 11B, a bias having a peak-to-peak value (ΔVpp1) larger than the peak-to-peak value (ΔVpp2) of the AC component of the bias when developing a designated image is applied to the developing roller 13d to cause the developing unit 13 to develop the patch image. Therefore, the developing device 120 appropriately discharges the toner from the developing roller 13d to the photoreceptor 10, even if the toner is highly charged and it is difficult for the toner to fly from the developing roller 13d to the photoreceptor 10. can be made to fly to

[Second embodiment]
As described in FIG. 12, the developing device 120 of the first embodiment develops the patch image 420 after developing the toner image 410 of the last specified image among the plurality of specified images. FIG. 14 is a diagram showing a patch image 420 according to the second embodiment. As shown in FIG. 14, the developing device 120 develops a patch image 420 between one designated image 410A and the next designated image 410B. In other words, developing device 120 develops patch image 420 between two designated images 410A and 410B.

Further, as shown in FIG. 14, one patch image 420 developed between one specified image 410A and the next specified image 410B may not be able to consume all of the toner that should be consumed. In this case, the developing device 120 may develop a patch image between the next specified image 410B and the next specified image. According to such a configuration, the developing device 120 can not consume all the toner amount to be consumed with one patch image 420 developed between one designated image 410A and the next designated image 410B. However, the entire amount of toner that should be consumed can be consumed.

As shown in FIG. 14, the developing device 120 can develop the patch image 420 so that the designated image designated by the job based on the user's instruction is not affected even if the patch image 420 is developed. can.

[Third Embodiment]
In the above-described embodiment, the reduction unit 608 performs control (hereinafter referred to as “first control”) in which the density of the patch image is higher than the density of the specified image as the reduction processing for reducing the charge amount of the toner. described as executing (see FIGS. 10 and 11)
However, the reduction unit 608 may perform other reduction processing. As described above, an appropriate range is defined for the toner density. When the toner concentration falls outside the proper range, the control unit 60 controls the toner supply unit 200 to supply toner to the developing unit 13 . In other words, when the toner concentration falls below the lower limit of the appropriate range, the toner replenishing section 200 replenishes toner to the developing section 13 under the control of the control section 60 .

Here, the toner replenished by the toner replenishing unit 200 is toner that has not been agitated with the carrier. Therefore, the toner replenished by the toner replenishing section 200 is uncharged toner. When the toner supply unit 200 supplies uncharged toner to the developing unit 13 (developer tank 13a), a phenomenon occurs in which the overall charge amount of the toner in the developer tank 13a is reduced.

Therefore, in this modified example, in view of this phenomenon, the reduction unit 608 executes control to increase the lower limit (hereinafter referred to as “second control”). When the lower limit is increased, the controller 60 replenishes toner (toner before agitation with carrier) so that the toner concentration in the developing section 13 is equal to or higher than the increased lower limit. By performing this replenishment, the controller 60 can reduce the overall charge amount of the toner in the developer tank 13a. Therefore, as a result, it is possible to appropriately reduce the charge amount of the toner.

Processing of this modified example will be described with reference to FIG. 13 . As shown in parentheses in step S14 in FIG. 13, the reduction unit 608 reduces the charge amount of the toner by increasing the lower limit of the appropriate range.

Also, the reduction unit 608 may execute both the first control and the second control as the reduction processing.

[Fourth Embodiment]
In the above-described embodiment, the execution condition for the reduction unit 608 to execute the reduction processing is, as described in FIG. “the first condition”)” and “the condition that the humidity is lower than the second reference value B (hereinafter referred to as the “second condition”)”.

The fourth embodiment describes an embodiment in which this execution condition includes other conditions. Another condition is that the number of sheets printed per unit time by the image forming apparatus 100 is greater than a third reference value C (hereinafter referred to as "third condition"). Per unit time may be any time, for example, "one second".

If it is determined that the number of printed sheets per unit time is greater than the reference value (third reference value C), it is determined that the number of printed sheets per unit time is equal to or less than the reference value (third reference value C). This means that the period during which the developing device 120 is driven is longer than the case. Since the pair of stirring screws 13b and 13c are driven while the developing device 120 is being driven, the toner and carrier are continuously stirred. As the toner and carrier continue to be stirred, the charge amount of the toner increases. In other words, when it is determined that the number of printed sheets per unit time is greater than the reference value (third standard value C), it is determined that the number of printed sheets per unit time is equal to or less than the standard value (third standard value C). The charge amount of the toner tends to be higher than when the

Accordingly, when it is determined that the number of sheets printed per unit time by the image forming apparatus 100 is greater than the third reference value C, the reduction unit 608 executes reduction processing.

The developing device 120 of the present embodiment will be described using the information acquisition section 620 indicated by the dashed line in FIG. 6 and step S10 indicated by the dashed line in FIG. After YES is determined in step S8 in FIG. 13, in step S10, the information acquisition unit 620 indicated by the dashed line in FIG. 6 acquires the number of printed sheets per unit time. In step S10, after acquiring the number of printed sheets per unit time, the information acquiring section 620 compares the number of printed sheets per unit time with the third reference value C. FIG. If information acquisition unit 620 determines that the number of printed sheets per unit time is greater than third reference value C (YES in step S10), the process proceeds to step S14. When it is determined that the number of printed sheets per unit time is greater than the third reference value C, the charge amount of the toner tends to increase. Execute.

In this embodiment, the execution conditions include a third condition in addition to the first and second conditions. In other words, the developing device 120 of the present embodiment executes reduction processing in consideration of the number of printed sheets per unit time as well as the total coverage and humidity. Therefore, the developing device 120 of this embodiment can perform the reduction process more precisely than in the above-described embodiments.

As a modification of the fourth embodiment, the execution condition may be that the stop time of the developing unit 13 is shorter than the fifth reference value. When the stop time of the developing section 13 is shorter than the fifth reference value, the stop time of stirring the toner and carrier by the pair of stirring screws 13b and 13c is short. In other words, when the stop time of the developing section 13 is shorter than the fifth reference value, the stirring time of the toner and carrier by the pair of stirring screws 13b and 13c is long. When the toner and carrier are stirred for a long time, the charge amount of the toner tends to increase.

In the modified example of the fourth embodiment, the processing of step S10 is "processing in which the information acquisition section 620 determines whether or not the stop time of the developing section 13 is shorter than the fifth reference value".

When the control unit 60 satisfies both the first condition and the second condition (in FIG. 13, when both step S6 and step S8 are determined to be YES), in step S10, the information acquisition unit 620 connects the developing unit 13 is determined whether or not the stop time is shorter than the fifth reference value. When the information acquiring unit 620 determines that the stop time of the developing unit 13 is shorter than the fifth reference value (YES in step S10), the reducing unit 608 executes reduction processing in step S14. On the other hand, when the information acquiring unit 620 determines that the stop time of the developing unit 13 is equal to or longer than the fifth reference value (NO in step S10), the reducing unit 608 does not execute the process of step S14, and end the processing of

[Fifth embodiment]
In the fifth embodiment, execution conditions for executing reduction processing by the reduction unit 608 include the fourth condition. The fourth condition is that the driving speed of the developing section (developing roller 13d) is higher than the fourth reference value D.

If the driving speed (rotational speed) of the developing roller 13d is high for a certain period of time, the toner adhering to the developing roller 13d is regulated by the regulating member 13h, and the amount of toner returning to the developer tank 13a increases. When the amount of toner returning to the developer tank 13a increases, the returned toner and the carrier originally present in the developer tank 13a are agitated, and as a result, the charge amount of the toner tends to increase. Note that when the user instructs normal printing, the driving speed of the developing roller 13d becomes the normal speed. When the user instructs high-speed printing, the driving speed of the developing roller 13d becomes faster than the normal speed. When forming an image on a sheet of normal thickness, the driving speed of the developing roller 13d is the normal speed. tends to be slow.

Accordingly, when it is determined that the number of sheets printed per unit time by the image forming apparatus 100 is greater than the third reference value C, the reduction unit 608 executes reduction processing.

The developing device 120 of the present embodiment will be described using the information acquisition section 620 indicated by the dashed line in FIG. 6 and step S12 indicated by the dashed line in FIG. After YES is determined in step S8 in FIG. 13, in step S12, the information acquisition unit 620 indicated by the dashed line in FIG. 6 acquires the driving speed of the developing roller 13d. In step S12, when the information acquisition unit 620 acquires the driving speed of the developing roller 13d, the driving speed of the developing roller 13d and the fourth reference value D are compared. When the information acquisition unit 620 determines that the driving speed of the developing roller 13d is higher than the fourth reference value D (YES in step S12), the process proceeds to step S14. When it is determined that the driving speed of the developing roller 13d is higher than the fourth reference value D, the charge amount of the toner tends to increase. Execute.

In this embodiment, the execution conditions include a fourth condition in addition to the first and second conditions. In other words, the developing device 120 of the present embodiment executes reduction processing in consideration of the speed of the developing roller 13d (driving speed of the developing section 13) in addition to the total coverage and humidity. Therefore, the developing device 120 of this embodiment can perform the reduction process more precisely than in the above-described embodiments.

Note that in the present embodiment, the developing device 120 may execute both the processing of step S10 and the processing of step S12, and the developing device 120 may execute the processing of step S12 without executing the processing of step S10. You may make it perform a process.

<Modification>
(1) In the above embodiments, relative humidity was explained as a humidity parameter. However, the humidity parameter may be absolute humidity instead of relative humidity. That is, the humidity sensor 72 detects absolute humidity. Also, the humidity acquisition unit 606 acquires absolute humidity as a humidity parameter. In this way, the developing device 120 adopting a configuration in which the humidity parameter is the absolute humidity has the same effect as the above-described embodiment.

(2) In the image forming apparatus 100 of the above-described embodiment, the object on which an image is formed by the developing unit 13 is the "photoreceptor 10". However, the object may be another object. The object may be, for example, paper.

(3) In the above-described embodiment, when the humidity determination unit 610 determines that the humidity is less than the second reference value B (if YES in step S6), the humidity and the second reference value B It has been described that the reduction unit 608 executes the process of step S14 regardless of the difference between the . However, based on the difference between the humidity and the second reference value B, the determination unit 6088 may determine the amount of toner for developing the patch image. For example, "a combination of 'difference value between humidity and second reference value B' and 'difference value between multiplied value by multiplication unit 6084 and total value of coverage calculated by calculation unit 6082'" and the "toner amount for developing the patch image" may be stored in advance in a predetermined storage area. Humidity determination unit 610 calculates a difference value between the humidity and the second reference value B. FIG. The determining unit 6088 refers to the combination table, and obtains the “difference value between the humidity and the second reference value B” and the sum of the multiplied value multiplied by the multiplying unit 6084 and the coverage calculated by the calculating unit 6082. The "toner amount for developing the patch image" corresponding to the "combination with the difference value with the value" is determined.

Developing device 120 of this modified example calculates not only “the difference value between the multiplied value multiplied by multiplication unit 6084 and the total coverage value calculated by calculation unit 6082”, but also “humidity and second reference value B The "toner amount for developing the patch image" is also determined based on the "difference value with respect to". Therefore, compared to the developing device that determines the "toner amount for developing the patch image" without based on the "difference value between the humidity and the second reference value B", the "development of the patch image" can be performed more accurately. can determine the amount of toner for

Further, in the above-described embodiment, the determination unit 6088 determines the number of patches for developing the patch image based on the difference value between the multiplication value multiplied by the multiplication unit 6084 and the total coverage value calculated by the calculation unit 6082. described as determining the amount of toner. However, the determination unit 6088 may determine a predetermined amount of toner regardless of the difference value. In such a configuration, the patch image control unit 6090 creates a patch image with a predetermined amount of toner when it is determined that the total coverage value (total coverage) is smaller than the multiplication value. develop.

(4) The developing device may have any configuration as long as it reduces the charge amount of the developer based on the humidity in which the developing device is installed and the coverage of the image. For example, the developing device estimates the charge amount of the developer based on the humidity in which the developing device is installed and the coverage of the image. The unit may reduce the charge amount of the developer so that the estimated charge amount becomes lower than the reference value.

(5) Further, the developing device may be configured to estimate the charge amount of the developer based on the humidity in which the developing device is installed and the coverage of the image. Further, an appropriate range may be determined in advance for the charge amount of the developer. If the developing device determines that the estimated charge amount of the developer does not belong to this appropriate range (for example, if it determines that it exceeds the upper limit of the appropriate range), the developing device The charge amount may be reduced.

Moreover, each embodiment disclosed this time should be considered as an illustration and not restrictive in all respects. The scope of the present invention is indicated by the scope of the claims rather than the above description, and is intended to include all modifications within the scope and meaning equivalent to the scope of the claims. In addition, the inventions described in the embodiments and modifications are intended to be implemented either singly or in combination as much as possible.

602 input unit, 604 coverage acquisition unit, 606 humidity acquisition unit, 608 reduction unit, 610 humidity determination unit, 612 second storage unit, 620 information acquisition unit, 6082 calculation unit, 6084 multiplication unit, 6086 first storage unit, 6088 determination section, 6090 patch image control section, 6092 application section.

Claims (12)

A developing device,
a development station that develops an image on an object using a charged developer;
a coverage acquisition unit that acquires coverage, which is a value relating to the usage amount of the developer per sheet of paper for the image;
a humidity parameter acquisition unit that acquires a humidity parameter of a location where the developing device is installed;
a reduction unit that reduces the charge amount of the developer based on the coverage acquired by the coverage acquisition unit and the humidity parameter acquired by the humidity parameter acquisition unit ;
an input unit for inputting a job,
The developing unit develops the patch image and the designated image designated by the job onto the object,
an image developed on the object by the developing unit is formed on a recording medium;
The reduction unit is
a multiplication unit that calculates a first value by multiplying the number of recording media on which an image developed on the object by the development unit is formed by a predetermined reference value;
a calculating unit that calculates the total value of the coverage of all the recording media on which the image developed on the object by the developing unit is formed;
an amount of said developer for developing said patch image when said sum is less than said first value and said humidity parameter is less than said second value; a determination unit that determines based on the difference;
a control unit that causes the development unit to develop the patch image with the amount of the developer determined by the determination unit;
The control section reduces the charge amount of the developer by causing the developing section to develop the patch image after developing the designated image or between two designated images. 2. The developing device according to claim 1, wherein the reducing section causes the developing section to develop the patch image by executing control such that the density of the patch image is higher than the density of the designated image. The developing unit includes a developing roller,
3. The developing device according to claim 2, wherein the reducing section causes the developing section to develop the patch image by applying a bias larger than a bias for developing the designated image to the developing roller. 4. The reducing unit according to claim 3, wherein the developing unit develops the patch image by applying to the developing roller a bias with a DC component that is larger than a DC component of a bias for developing the designated image. development equipment. The reducing unit applies to the developing roller a bias having a peak-to-peak value that is greater than the peak-to-peak value of the alternating current component of the bias when developing the designated image, thereby causing the developing unit to develop the patch image. 5. The developing device according to claim 3 or 4 . The developer is
including a toner and a carrier;
The developer is charged by agitating the toner and the carrier,
2. The reducing unit reduces the charge amount of the developer by increasing the toner concentration obtained by dividing the weight of the toner by the sum of the weight of the toner and the weight of the carrier. 6. The developing device according to claim 5 . an accommodation unit that agitates the toner and the carrier and accommodates the toner and the carrier;
a replenishing unit that replenishes the toner to the storage unit when the toner concentration of the toner stored in the storage unit is less than a threshold;
7. The developing device according to claim 6 , wherein said reducing unit increases said toner concentration by increasing said threshold value. 8. The reducing unit reduces the charge amount of the developer based on the driving speed of the developing unit in addition to the coverage and the humidity parameter. Developing apparatus as described. 9. The reducing unit reduces the charge amount of the developer based on the driving time of the developing unit in addition to the coverage and the humidity parameter . Developing apparatus as described. An image forming apparatus comprising the developing device according to any one of claims 1 to 9 . A method of controlling a developing device for developing an image on a substrate with a charged developer material, comprising:
obtaining a coverage, which is a value for the amount of developer used per sheet of paper of the image;
obtaining a humidity parameter of the location where the developer is located;
reducing the developer charge based on the coverage and the humidity parameter;
developing the patch image and the designated image designated by the input job onto the object;
forming an image developed on the object on a recording medium;
The step of reducing the charge amount of the developer includes:
calculating a first value by multiplying a predetermined reference value by the number of recording media on which a developed image is formed on the object;
calculating the sum of the coverages of all the recording media on which the developed image is formed on the object;
an amount of said developer for developing said patch image when said sum is less than said first value and said humidity parameter is less than said second value; determining based on the difference;
reducing the charge amount of the developer by developing the patch image with the determined amount of the developer after developing the designated image or between two of the designated images; A method of controlling a developing device. A program for controlling a developing device that develops an image on an object using a charged developer, comprising:
The program, in a computer,
obtaining a coverage, which is a value for the amount of developer used per sheet of paper of the image;
obtaining a humidity parameter of the location where the developer is located;
reducing the developer charge based on the coverage and the humidity parameter;
developing the patch image and the designated image designated by the input job onto the object;
and forming an image developed on the object on a recording medium;
The step of reducing the charge amount of the developer includes:
calculating a first value by multiplying a predetermined reference value by the number of recording media on which a developed image is formed on the object;
calculating the sum of the coverages of all the recording media on which the developed image is formed on the object;
an amount of said developer for developing said patch image when said sum is less than said first value and said humidity parameter is less than said second value; determining based on the difference;
reducing the charge amount of the developer by developing the patch image with the determined amount of the developer after developing the designated image or between two of the designated images; A program that controls the developing device.

Images