JP7106871B2 - image forming device - Google Patents

Description

The present invention relates to an electrophotographic image forming apparatus such as a printer or a multifunction machine.

A conventional electrophotographic image forming apparatus includes a photosensitive drum, a charging device, an exposure device, a developing device, a transfer device, a fixing device, and a cleaning device. An exposure device exposes the surface of the photosensitive drum to form an electrostatic latent image. A developing roller of the developing device develops the electrostatic latent image to form a toner image on the photosensitive drum. The image is transferred to a recording medium, and the toner image is fixed by a fixing device for printing.
In such an image forming apparatus, when the developing roller and the photosensitive drum are left in contact with each other for a long time without printing, low-molecular-weight components (hereinafter referred to as "oligomers") precipitated from the rubber material of the developing roller. ) adheres to the photosensitive drum, causing defects in the printed image (horizontal white streaks) in the halftone image when printing on the first sheet of the print medium. As such, the photosensitive drum is idly rotated before printing is performed based on set values, environmental information, and the like (see, for example, Japanese Patent Laid-Open No. 2002-200013).

Japanese Patent Application Laid-Open No. 2005-173290

However, in the prior art, in order to improve poor printed images caused by oligomers, excessive idling of the photosensitive drum may occur, which shortens the life of the developing device as a developing unit that forms a toner image on the photosensitive drum. There is a problem that the length may be shortened more than necessary.
SUMMARY OF THE INVENTION It is an object of the present invention to solve such a problem, and to suppress the shortening of the life of the developing section.

Therefore, the present invention provides an image carrier, a driving section for rotating the image carrier, a developing section for supplying developer to the image carrier, and a voltage control section for controlling the developing voltage applied to the developing section. and a setting unit for setting an amount of idling of the image bearing member according to the developing voltage, and a control unit for controlling the voltage control unit and the driving unit, wherein the amount of idling is determined by the developing voltage. The control unit acquires the development voltage set by the setting unit before the idle rotation of the image carrier, and applies the acquired development voltage to the development voltage. idling operation of the image bearing member based on the idling amount.

According to the present invention thus configured, it is possible to obtain the effect of being able to suppress the shortening of the life of the developing section.

FIG. 2 is a block diagram showing the control configuration of the image forming apparatus according to the embodiment; Schematic side cross-sectional view showing the configuration of an image forming apparatus in an embodiment 4 is a flow chart showing the flow of photosensitive drum idling control processing in the embodiment; Graph showing the relationship between development voltage and horizontal white streaks in the example Graph showing the relationship between the development voltage and the amount of idling of the photosensitive drum in the example Graph showing the relationship between the developing voltage and the consumed drum count in the example

An embodiment of an image forming apparatus according to the present invention will be described below with reference to the drawings.

FIG. 2 is a schematic side sectional view showing the configuration of the image forming apparatus in the embodiment.
In FIG. 2, the image forming apparatus 100 is an electrophotographic color printer that forms an image on a recording medium P, for example. In this embodiment, the image forming apparatus 100 is described as a color printer, but it may be a monochrome printer.

The image forming apparatus 100 includes developing units 12K, 12Y, 12M, and 12C, a tray 28, a hopping roller 29, a registration roller 30, a transfer belt 32, a drive roller 33, an idle roller 34, and a belt cleaning device 35. , a fixing device 36 , a discharge roller 37 and a density sensor 38 .

The developing units 12K, 12Y, 12M, and 12C form toner images for each color of toner (K: black, Y: yellow, M: magenta, C: cyan) as developer. Although the developing units 12K, 12Y, 12M, and 12C handle different toners, they have the same configuration, so the configuration of the developing unit 12C will be described as a representative.
The developing unit 12</b>C includes a photosensitive drum 1 , a charging roller 2 arranged around the photosensitive drum 1 , an LED (Light Emitting Diode) head 3 , a developing device 4 , a transfer roller 5 , and a cleaning device 6 . have.

A photosensitive drum 1 as an image bearing member was formed by forming a 0.5 μm-thick charge generation layer and a 20 μm-thick charge transport layer on an aluminum tube having a thickness of 0.75 mm and an outer diameter of 30 mm. Further, the photosensitive drum 1 is configured to be rotatable in the direction indicated by the arrow in the figure by rotational driving of a drum motor (driving section).
The photosensitive drums 1 of the developing units 12K, 12Y, 12M, and 12C are simultaneously rotated by the same amount of rotation as the drum motors are driven to rotate.

The charging roller 2 as charging means is a device for uniformly charging the surface of the photosensitive drum 1. For example, a conductive elastic body such as epichlorohydrin is coated around a conductor made of SUS (stainless steel) as a shaft. It is arranged so as to contact the drum 1 .
The LED head 3 as exposure means is an exposure device for selectively exposing the surface of the photosensitive drum 1 uniformly charged by the charging roller 2 to form a latent image pattern as an electrostatic latent image. The LED head 3 includes an LED element, an LED driving element, and a lens array, and is arranged at a position where the light emitted from the LED element forms an image on the surface of the photosensitive drum 1 .

A developing device 4 as a developing unit is a developing device that supplies toner to the photosensitive drum 1 and forms a toner image as a developer image on the latent image pattern formed on the photosensitive drum 1 . The developing device 4 has a developing roller 8, a supply roller 9, and a regulating blade 10, and is configured to be replenished with toner from a toner cartridge containing toner.
The developing device 4 is provided for each of the developing units 12K, 12Y, 12M, and 12C, that is, for each toner color.

The developing roller 8 conveys toner to the latent image pattern formed on the photosensitive drum 1 to form a toner image as a developer image, and is arranged so as to be in contact with the surface of the photosensitive drum 1 .
The developing roller 8 has a structure in which an elastic layer is arranged in a roll shape on a conductive shaft (cored bar) made of SUS material, and a surface layer covering the elastic layer is provided. Urethane rubber or silicone rubber was used for the elastic layer, and the surface layer was treated with a urethane solution or coated with acrylic resin or acrylic-fluorocopolymer resin. Carbon black was added to the surface layer of acrylic resin or acrylic-fluorine copolymer resin to impart electrical conductivity.

A supply roller 9 as supply means supplies toner to the development roller 8 and is arranged so as to be in contact with the development roller 8 .
The supply roller 9 is formed of a conductive shaft (cored bar) made of SUS material and an elastic layer. The elastic layer is a conductive silicone rubber foam layer or a conductive urethane rubber foam layer. Acetylene black, carbon black, or the like is added when the elastic layer is to have semiconductivity.

A regulating blade 10 as a regulating means forms a toner layer on the developing roller 8 , and is arranged so that its tip portion is pressed against the developing roller 8 .
The regulating blade 10 is made of SUS with a plate thickness of 0.08 mm, and the contact portion with the developing roller 8 is bent. The curvature radius R of the bent portion was set to 0.2 mm, and the linear pressure to the developing roller 8 was set to 30 gf/cm. However, the curvature radius R and the linear pressure of the regulating blade 10 are not limited to these, and can be adjusted according to the amount of toner on the developing roller 8 and the amount of toner charge.

The transfer roller 5 as transfer means transfers the toner image formed on the photosensitive drum 1 to the recording medium P or the transfer belt 32, and is made of, for example, a conductive foamed elastic body.

A cleaning device 6 as a cleaning means is a device for scraping and discarding residual toner such as untransferred toner on the photosensitive drum 1 and waste toner moved from the developing device 4 onto the photosensitive drum 1 . The cleaning device 6 includes a cleaning blade 11 made of rubber, for example, and is arranged so that the tip of the cleaning blade 11 contacts the surface of the photosensitive drum 1 .

The charging roller 2, developing roller 8, supply roller 9, and transfer roller 5 are configured to be rotatable in directions indicated by arrows in the figure.

Also, in the case of a monochrome printer, only the developing unit 12K is provided, and the developing units 12Y, 12M, and 12C are not provided.

The tray 28 accommodates the recording media P in layers.
The hopping roller 29 separates and feeds the recording medium P contained in the tray 28 one by one.
The registration rollers 30 are a pair of rollers that correct the skew of the recording medium P fed by the hopping rollers 29 and convey it.

The transfer belt 32 conveys the recording medium P conveyed by the registration rollers 30 and transfers the developer image developed on the photosensitive drum 1 onto the recording medium P. As shown in FIG.
The drive roller 33 rotates the transfer belt 32 .
The idle roller 34 stabilizes the rotation of the transfer belt 32 .

The transfer belt 32 is an endless belt that is rotatably stretched around a drive roller 33 and an idle roller 34, and is rotated in the medium conveying direction indicated by an arrow A in the figure by the drive roller 33 being rotationally driven.
The belt cleaning device 35 cleans the toner on the transfer belt 32 .

The fixing device 36 is arranged on the conveying path of the recording medium P downstream of the transfer belt 32 in the medium conveying direction, and fixes the toner image transferred onto the recording medium P by heating and pressing. 36a and a pressure roller 36b.
The heat roller 36a has an elastic layer of silicone rubber arranged on an iron tube having an outer diameter of 28 mm, and a PFA tube as a toner peeling layer covering the elastic layer.
On the other hand, the pressure roller 36b does not have an elastic layer, and has a PFA tube on an iron base tube.

The heat roller 36a has a halogen lamp as a heat source inside the base tube.
The discharge roller 37 conveys the recording medium P on which the toner image has been fixed by the fixing device 36 and discharges it outside the apparatus.

The density sensor 38 is arranged to face the transfer belt 32 and detects the density of the test pattern image formed on the transfer belt 32 by the developing units 12K, 12Y, 12M and 12C. The density sensor 38 is used to correct and set the developing voltage applied to each developing roller 8 of the developing units 12K, 12Y, 12M and 12C based on the detected density of the test pattern image.

FIG. 1 is a block diagram showing the control configuration of the image forming apparatus in the embodiment.

1, the image forming apparatus 100 includes a control unit 21, a reception unit 22, an operation unit 23, an image output unit 24, a drive control unit 25, a fixing control unit 26, an exposure control unit 27, a voltage Control unit 28, belt motor 38, drum motor 39, fixing device 36, LED head 3, charging roller 2, developing roller 8, supply roller 9, regulation blade 10, and transfer roller 5 have.

The control unit 21 controls the overall operation of the image forming apparatus 100 based on a control program (software) stored in a storage unit such as a memory, and is control means such as a CPU (Central Processing Unit).

The control unit 21 is connected to the receiving unit 22, the operating unit 23, and the image output unit 24, and controls the overall operation of the image forming apparatus 100. The receiving unit 22 as a setting unit is communicably connected via a communication line. It transmits and receives information to and from a host computer as a host computer. When the reception unit 22 receives information such as a print instruction and setting information of various printing conditions (such as a set value of the idle rotation amount of the drum) from the host computer, the reception unit 22 notifies the control unit 21 of the information.

The operation unit 23 as a setting unit has a display unit such as a display for outputting various information, and an input unit such as an operation key, an operation button, a touch panel, or the like for receiving operation by an operator and receiving input operation of various information. be. The operation unit 23 displays various types of information on the display unit according to instructions from the control unit 21, and notifies the control unit 21 of the input information when an input operation is received by the input unit.

Further, the operation unit 23 can receive input of setting information of various printing conditions (such as a set value of the amount of idle rotation of the drum).

The receiving section 22 and the operating section 23 of this embodiment have a function as a setting section for setting the idling amount of the photosensitive drum 1 according to the developing voltage.

The image output section 24 is connected to the drive control section 25, the fixing control section 26, the exposure control section 27, and the voltage control section 28, and performs a printing operation of forming an image on a recording medium. The image output unit 24 controls the drive control unit 25, the fixing control unit 26, the exposure control unit 27, and the voltage control unit 28 according to instructions from the control unit 21, and forms an image on a recording medium.

Upon receiving the notification of the print instruction from the receiving unit 22, the control unit 21 controls the drive control unit 25, the fixing control unit 26, the exposure control unit 27, and the voltage control unit 28 via the image output unit 24, and controls the recording medium. to form an image.

Upon receiving an instruction from the control unit 21, the drive control unit 25 rotates a belt motor 38 that rotates the drive roller 33 and a drum motor 39 that rotates the photosensitive drum 1, as shown in FIG. be.
The drive control unit 25 rotates the belt motor 38 and the drum motor 39 to rotate the transfer belt 32 in the medium conveying direction and rotate the photosensitive drum 1 .

In this way, the control section 21 of this embodiment controls the rotation of the belt motor 38 and the drum motor 39 via the drive control section 25 .

Further, the drive control unit 25 rotates the hopping roller 29, the registration roller 30, the discharge roller 37, and the like shown in FIG. 2 to convey the recording medium.

Upon receiving instructions from the control unit 21, the voltage control unit 28 controls the voltage applied to the charging roller 2, the transfer roller 5, and the developing roller 8, supply roller 9, and regulation blade 10 of the developing device 4 shown in FIG. It is something to do.

The voltage control unit 28 applies a preset developing voltage stored in the storage unit to the developing rollers 8 of the developing units 12K, 12Y, 12M, and 12C, and applies toner to the latent image patterns formed on the respective photosensitive drums 1. to form a toner image.

Here, the developing voltage is determined based on the density of the test pattern image detected by the density sensor 38 so as to optimize the density, and is set for each of the developing rollers 8 of the developing units 12K, 12Y, 12M, and 12C. .

Upon receiving an instruction from the control unit 21, the exposure control unit 27 selectively causes the LED head 3 to emit light according to the print data of the print instruction to form an electrostatic latent image on the surface of the photosensitive drum 1 shown in FIG. be.

Upon receiving an instruction from the control unit 21, the fixing control unit 26 performs temperature control of the fixing device 36 and rotation control of the heat roller 36a and the pressure roller 36b shown in FIG. and pressure.

When the control unit 21 receives the notification of the print instruction from the reception unit 22, the control unit 21 controls the drive control unit 25, the fixing control unit 26, the exposure control unit 27, and the voltage control unit 28 via the image output unit 24, thereby controlling the drive. 2 from the tray 28 shown in FIG. An image forming operation is performed to transfer the toner image onto the recording medium P by the transfer roller 5 , the toner image transferred to the recording medium P is fixed by the fixing controller 26 , and the recording medium P is discharged from the apparatus by the discharge roller 37 . to end the printing operation.

2 before starting the printing operation based on the setting information of the printing conditions input by the operation unit 23 and the setting information of the printing conditions received from the host computer via the receiving unit 22. FIG. The idling amount of the photosensitive drum 1 (hereinafter referred to as "drum idling amount") is set in the storage section, and the drive control section 25 is caused to idle based on the set idling amount through the image output section 24. Notifies information instructing to perform an action.

The printing condition setting information is setting information as to whether or not the photosensitive drum 1 is idly rotated before starting the printing operation.

The amount of drum idling refers to the amount of rotation of the photosensitive drum 1 without feeding a recording medium with a predetermined voltage applied to the charging roller 2, the developing roller 8, the supply roller 9, and the transfer roller 5 before starting the printing operation. is the number of revolutions to rotate (idle) the

The operation of the configuration described above will be described.
First, the image forming operation performed by the image forming apparatus will be described with reference to FIGS. 1 and 2. FIG. The image forming operation performed by the developing unit 12C will be described below.

The control unit 21 of the image forming apparatus 100 applies a charging voltage to the charging roller 2 by the voltage control unit 28 to uniformly charge the surface of the photosensitive drum 1, and then causes the LED head 3 to emit light by the exposure control unit 27. , to form an electrostatic latent image on the surface of the photosensitive drum 1 . At this time, the control unit 21 causes the drive control unit 25 to drive the belt motor 38 and the drum motor 39 to rotate the transfer belt 32 and the photosensitive drum 1, and rotate the hopping roller 29, the registration roller 30, and the discharge roller 37. etc. are rotated, and the conveyance of the recording medium P is started.

The control unit 21 applies a developing voltage from the voltage control unit 28 to the developing roller 8 having a thin toner layer formed on its surface to develop the electrostatic latent image on the photosensitive drum 1 to form a toner image.
At this time, in order to uniformly form a thin toner layer on the developing roller 8 on the supply roller 9 and the regulating blade 10 and to set the charge amount of the toner in the toner thin layer to a predetermined amount, the voltage control unit 28 supplies the voltage A regulation voltage is applied to each.

Next, the control section 21 applies a transfer voltage to the transfer roller 5 by the voltage control section 28 to transfer the toner image on the photosensitive drum 1 to the recording medium P. FIG.
After transferring the toner image onto the recording medium P, the control section 21 causes the fixing device 36 to fix the toner image transferred onto the recording medium P by the fixing control section 26 .

The control section 21 of the image forming apparatus 100 performs similar image forming operations in the developing units 12K, 12Y, and 12M.
The recording medium P on which the toner image is fixed is discharged outside the apparatus by the discharge roller 37, and the toner remaining on the photosensitive drum 1 without being transferred is removed by the cleaning device 6. FIG.

In this manner, the image forming apparatus 100 performs image forming operations with the developing units 12K, 12Y, 12M, and 12C.

Here, the control unit 21 of the image forming apparatus 100 of this embodiment sets the developing voltage to be applied to each developing roller 8 of the developing units 12K, 12Y, 12M, and 12C in advance before performing the image forming operation. It is assumed that there is The control unit 21 forms a test pattern image of each color on the transfer belt 32, detects the density of the test pattern image of each color by the density sensor 38, and controls the developing unit 12K based on the detected density of the test pattern image of each color. , 12Y, 12M, and 12C are corrected and stored in the storage unit.

Next, the idling operation of the photosensitive drum performed by the image forming apparatus will be described with reference to FIGS. 1 and 2. FIG.

Before performing the image forming (printing) operation described above, that is, before forming an electrostatic latent image on the photosensitive drum 1, the control unit 21 of the image forming apparatus 100 controls the charging roller 2, the developing roller 8, the supply roller 9, Then, while a predetermined voltage is applied to the transfer roller 5, the idling operation is performed to rotate the photosensitive drum 1 based on the drum idling amount without feeding the recording medium P. FIG.

In this embodiment, the amount of idle rotation of the photosensitive drum 1 is set based on the developing voltage applied to the developing roller 8 .
By performing the idling operation of the photosensitive drum 1 in this manner, the oligomer adhering to the photosensitive drum 1 is removed by the cleaning device 6 .

Further, the idling control of the photosensitive drum performed by the image forming apparatus will be described with reference to FIGS.

S101: The control unit 21 of the image forming apparatus 100 acquires setting information of printing conditions. This setting information is the setting information of the printing conditions input by the operation unit 23 or the setting information of the printing conditions received from the host computer via the receiving unit 22 .

S102: The control unit 21 determines whether or not to perform the idling operation of the photosensitive drum 1 based on the setting information acquired in S101. If it is determined not to perform the idling operation, the process proceeds to S106 in order to perform the printing operation without performing the idling operation.

S103: The control unit 21 that has determined to perform the idling operation acquires the value of the developing voltage preset in the storage unit.

S104: The control unit 21 sets the amount of idle rotation of the drum based on the acquired value of the developing voltage.

The set value of the amount of idle rotation of the drum is set according to the developing voltage by the setting section (the receiving section 22 and the operating section 23), and the details thereof will be described later.

S105: The controller 21 sets the amount of idling rotation of the photosensitive drum 1 without feeding the recording medium P in a state in which a predetermined voltage is applied to the charging roller 2, the developing roller 8, the supply roller 9, and the transfer roller 5. Performs an idle action that rotates based on a value.

S106: The control section 21 starts the above-described image forming operation and starts the printing operation.

When the photosensitive drum 1 performs the idling operation in S<b>105 , the control unit 21 continues the idling operation of the photosensitive drum 1 and starts the printing operation without stopping the operation of the photosensitive drum 1 .

As described above, the control unit 21 of the image forming apparatus 100 controls the drum idle rotation set according to the development voltage by the setting unit (the receiving unit 22 and the operation unit 23) before the developing device 4 supplies the toner to the photosensitive drum 1. Based on the amount, the photosensitive drum idling control for idling the photosensitive drum 1 is performed.

FIG. 4 is a graph showing the relationship between the development voltage and horizontal white stripes in the example. In FIG. 4, the horizontal axis represents the development voltage (-V), and the vertical axis represents the horizontal white stripe level.

Here, the horizontal white streaks are white streaks in which toner is not transferred in the direction perpendicular to the conveying direction of the recording medium in the printing result of the recording medium. The smaller the numerical value, the more clearly horizontal white streaks appear and the lower the image quality.

As shown in FIG. 4, the smaller the absolute value of the development voltage, the lower the horizontal white stripe level and the worse the image quality. Further, when the absolute value of the development voltage is large (greater than 170), horizontal white stripes do not appear and the horizontal white stripe level is "10".

Since the image forming apparatus 100 of this embodiment uses the developing voltage in the range of -100V to -230V, the worst horizontal white stripe level is "5".

Here, the reason why oligomer-induced horizontal white streaks occur is that when a portion of the photosensitive drum 1 to which the oligomer is attached and a portion to which the oligomer is not attached are exposed by the LED head 3, the oligomer is attached. The post-exposure potential (absolute value) of the area becomes higher than the post-exposure potential (absolute value) of the area where the oligomer is not adhered, and the difference from the development voltage (absolute value) becomes smaller, and the oligomer adheres. This is probably because the amount of toner transferred from the developing roller 8 to the portion where the toner is present is reduced.

In addition, the smaller the absolute value of the development voltage, the lower (worse) the level of horizontal white stripes. On the other hand, this is because the ratio of the post-exposure potential difference due to the influence of the oligomer increases. As a result, the density difference between the normal portion and the oligomer-attached portion on the image becomes large, which tends to appear as horizontal white streaks.

FIG. 5 is a graph showing the relationship between the developing voltage and the idling amount of the photosensitive drum in the example. In FIG. 5, the horizontal axis represents the developing voltage (-V), and the vertical axis represents the drum idling amount (rotational speed).

As shown in FIG. 5, it can be seen that the smaller the absolute value of the developing voltage, that is, the worse the horizontal white stripe level, the larger the drum idling amount is required. In the image forming apparatus 100 of this embodiment, the amount of drum idle rotation required to improve horizontal white streaks of level 5, which is the worst, was 10 revolutions. Further, the amount of idle rotation of the drum required to improve horizontal white streaks of level 9 was 3 revolutions.

Table 1 shows the set values of the amount of idle rotation of the drum in this embodiment. It is assumed that the setting value of the amount of idle rotation of the drum is set by the receiving section 22 or the operating section 23 .

このように、現像電圧に応じてドラム空転量を変更するようにしている。本実施例では、現像電圧の絶対値が小さくなるほどドラム空転量が多くなるようにしている。

In this way, the amount of idle rotation of the drum is changed according to the developing voltage. In this embodiment, the smaller the absolute value of the developing voltage, the greater the amount of idle rotation of the drum.

In FIG. 4, even in the range where the absolute value of the development voltage is −180 V or higher when the horizontal white streak level is “10”, the amount of drum idling is set to 3 revolutions. This is because the amount of idling rotation of the photosensitive drum 1, in which no idling operation is not performed, is not set to 0 rotations, and the horizontal white streak level can be improved from "9" to "10" at 3 rotations. This is because the setting of "perform drum idling operation" is performed when the quality of the toner image, which is the result of printing, is degraded. It is rotated.

In this embodiment, the set value of the drum idle rotation amount is set so that the horizontal white stripe level is "10" as shown in Table 1. ” or “8” may be set. In this case, both the set value of the drum idle rotation amount at which the horizontal white streak level is "10" and the set value of the drum idle rotation amount at which the horizontal white streak level is "9" are stored in advance in the storage unit. You may make it select by operation of .

Here, if the image forming apparatus 100 is a color printer and the developing voltage differs for each toner color (developing units 12K, 12Y, 12M, and 12C), the developing voltage with the smallest absolute value among the developing voltages for each color is selected. The amount of idle rotation of the drum is set as a reference. Thus, by setting the drum idling amount based on the development voltage having the smallest absolute value among the development voltages of the respective colors, the horizontal white stripe level can be reliably improved.

The drum idling amount may be set based on the development voltage of the development unit 12K arranged most upstream in the medium conveying direction. This is because the deterioration of the horizontal white streak level of the developing unit 12K, which handles black toner, is most conspicuous.

Also, if the image forming apparatus 100 is a monochrome printer, the drum idling amount is set based on the developing voltage of the developing unit 12K.

Furthermore, in this embodiment, the amount of drum idling is set based on the development voltage having the smallest absolute value among the development voltages of the respective colors. A set value of the amount of idle rotation of the drum is stored in advance in a storage unit, the amount of idle rotation of the drum of each developing unit is extracted based on the developing voltage of each developing unit, and the photosensitive drum 1 is rotated based on the largest amount of idle rotation of the drum. You can let them do it.

FIG. 6 is a graph showing the relationship between the developing voltage and the consumed drum count in the example, showing the consumed drum count of the comparative example and the consumed drum count of the present example per 100 drum idling operations.

In FIG. 6, the horizontal axis represents the developing voltage (-V), and the vertical axis represents the consumed drum count. The solid line indicates the consumed drum count when the drum idling amount of the present embodiment is set, and the broken line indicates the consumed drum count when the drum idling amount (10 rotations regardless of the developing voltage) is set in the comparative example.

Here, the drum count is an index representing the usage amount of the developing units 12 (C, M, Y, K) shown in FIG. The larger the value of the drum count, the shorter the life of the developing unit.

As shown in FIG. 6, in this embodiment, when the absolute value of the developing voltage is less than -140 V, the consumed drum count is 200; In this case, the consumed drum count is 60.

On the other hand, in the comparative example, the consumed drum count is 200 regardless of the developing voltage.

Therefore, in this embodiment, the consumed drum count in the drum idling operation can be halved compared to the comparative example when the absolute value of the developing voltage is -140 V or more and less than -180 V, and when it is -180 V or more, The consumption drum count can be reduced by 70%.

In the comparative example, variations in the characteristics of the developing units 4 of the developing units 12K, 12Y, 12M, and 12C used in the image forming apparatus 100 are not considered. In some cases, the photosensitive drum 1 may idle, and the life of the developing devices 4 of the developing units 12K, 12Y, 12M, and 12C may be shortened more than necessary.

In the present embodiment, the control unit 21 of the image forming apparatus 100 causes the operation unit 23, the receiving unit 22, etc., to detect defects in the printed image due to oligomer before the printing operation in which the developing roller 8 supplies toner to the photosensitive drum 1. By idling the photosensitive drum 1 based on the drum idling amount set in accordance with the development voltage, which is correlated with the degree of development, the idling amount of the photosensitive drum 1 can be adjusted in accordance with the horizontal white streak generation level due to the oligomer. It is possible to control the excessive idling of the photosensitive drum 1 and prevent the life of the developing devices 4 of the developing units 12K, 12Y, 12M, and 12C from being shortened.

Further, by setting the amount of idling of the drum according to the developing voltage, it is possible to set the amount of idling of the photosensitive drum 1 suitable for removing oligomers that cause defective printed images. The amount of unnecessary idling of the drum 1 can be suppressed.

When setting the amount of idle drum rotation based on empirical rules such as setting the amount of idle drum rotation according to the type of print image and the drum count value, the photosensitive drum 1 may idle more than necessary. Although the life of the developing units 4 of 12Y, 12M, and 12C may be shortened, when the drum idling amount is set according to the developing voltage as in the present embodiment, an appropriate idling amount of the photosensitive drum 1 is set. can be set, unnecessary idling of the photosensitive drum 1 can be suppressed, and shortening of the life of the developing devices 4 of the developing units 12K, 12Y, 12M, and 12C can be suppressed.

It should be noted that the drum idling amount and the development voltage value used as a reference for setting the drum idling amount in the present embodiment are not limited to those described above, and may be appropriately changed according to the characteristics of the developing device 4. can be done.

As described above, in this embodiment, before the printing operation, the photosensitive drum is idly rotated on the basis of the drum idling amount set according to the developing voltage, thereby preventing excessive idling of the photosensitive drum. can be suppressed, and shortening of the life of the developing device of the developing unit can be suppressed.

In this embodiment, the image forming apparatus is described as a printer, but the image forming apparatus is not limited to this, and may be a copier, a facsimile machine, a multifunction peripheral (MFP), or the like.

1 Photosensitive Drum 2 Charging Roller 3 LED Head 4 Developing Device 5 Transfer Roller 6 Cleaning Device 8 Developing Roller 9 Supply Roller 10 Regulating Blade 12K, 12Y, 12M, 12C Developing Unit 28 Tray 29 Hopping Roller 30 Registration Roller 32 Transfer Belt 33 Drive Roller 34 idle roller 35 belt cleaning device 36 fixing device 37 discharge roller 38 density sensor 100 image forming apparatus

Claims (5)

an image carrier;
a driving unit that rotates the image carrier;
a developing unit that supplies a developer to the image carrier;
a voltage control unit that controls a developing voltage applied to the developing unit;
a setting unit for setting an amount of idling of the image carrier according to the development voltage;
a control unit that controls the voltage control unit and the driving unit;
has
The idling amount is set to increase as the absolute value of the developing voltage decreases,
The control unit acquires the development voltage set by the setting unit before the image carrier is idling, and applies the acquired development voltage to the development unit , based on the idling amount. An image forming apparatus, characterized in that the idling operation of the image bearing member is executed by the image carrier. The image forming apparatus according to claim 1,
A plurality of the developing units are provided for each color of the developer,
The development voltage is set for each development section,
The image forming apparatus, wherein the idling amount is set based on the developing voltage having the smallest absolute value. In the image forming apparatus according to claim 1 or claim 2,
The image forming apparatus, wherein the idling amount is the number of revolutions of the image carrier. In the image forming apparatus according to any one of claims 1 to 3,
The image forming apparatus, wherein the setting unit is an operation unit that receives an operator's operation for setting the amount of idling. In the image forming apparatus according to any one of claims 1 to 4,
The image forming apparatus, wherein the setting unit is a receiving unit that receives setting information including information on the amount of idling from a host device.

Images