JP2023136038A - Image forming apparatus and image forming method - Google Patents

Abstract

To reduce the amount of toner unintendedly transferred to a transfer member.SOLUTION: An image forming apparatus applies a normal transfer bias to a transfer area between an image carrier 105 and a transfer member 108 to transfer a toner image on the image carrier to a recording material passing through the transfer area, thereby forming an image on the recording material. The image forming apparatus has reverse transfer bias application means that applies a reverse transfer bias having a polarity opposite to that of the normal transfer bias at a predetermined timing, and toner adhesion amount detection means 109 that detects the amount of toner adhered onto the image carrier. The image forming apparatus corrects the reverse transfer bias applied by the reverse transfer bias application means at a predetermined correction timing based on a detection result from the toner adhesion amount detection means obtained by detecting the amount of toner adhered to a predetermined toner pattern 205 for condition correction after passing through the transfer area to which the predetermined reverse transfer bias is applied.SELECTED DRAWING: Figure 7

Description

The present invention relates to an image forming apparatus and an image forming method.

Conventionally, a normal transfer bias is applied to a transfer area between an image carrier and a transfer member, and a toner image on the image carrier is transferred onto a recording material passing through the transfer area, thereby transferring the toner image to the recording material. Image forming apparatuses that form images on images are known.

For example, in Patent Document 1, a secondary transfer outer roller (transfer member) that forms a secondary transfer portion (transfer area) with an intermediate transfer belt (image carrier) has a charge polarity that is opposite to the normal charging polarity of toner. An image forming apparatus that applies a polar secondary transfer bias (regular transfer bias) is disclosed. In this image forming apparatus, the inter-image area ( A reverse transfer bias having a polarity opposite to that of the secondary transfer bias is applied in the inter-paper area).

However, in conventional image forming apparatuses, transfer of toner from an image carrier to a transfer member (unintentional transfer of toner) may not be sufficiently suppressed in some cases.

In order to solve the above-mentioned problems, the present invention applies a regular transfer bias to a transfer area between an image carrier and a transfer member, so that the image on the image carrier is transferred onto a recording material passing through the transfer area. an image forming apparatus that forms an image on the recording material by transferring a toner image; a reverse transfer bias applying means that applies a reverse transfer bias having a polarity opposite to the normal transfer bias at a predetermined timing; toner adhesion amount detection means for detecting the amount of toner adhesion on the image carrier; and toner for predetermined condition correction after passing through the transfer area with a predetermined reverse transfer bias applied at a predetermined correction timing. The present invention is characterized by comprising a correction means for correcting the reverse transfer bias applied by the reverse transfer bias application means based on the detection result of the toner adhesion amount detection means for the toner adhesion amount of the pattern.

According to the present invention, even if the transfer of toner from the image carrier to the transfer member cannot be sufficiently suppressed, the bias conditions of the reverse transfer bias can be corrected to reduce the amount of toner transferred to the transfer member. Can be suppressed.

FIG. 1 is a schematic configuration diagram showing an image forming process section (process engine section) that performs exposure, charging, development, transfer, and fixing in the printer of the embodiment. FIG. 2 is an explanatory diagram showing the configuration of an image forming unit that forms a black toner image in the same printer. FIG. 3 is a perspective view of an intermediate transfer belt in the same printer. A schematic diagram of the P/TM sensor in the same printer. FIG. 3 is a block diagram showing electrical connections of various parts included in the printer. 5 is a flowchart illustrating an example of toner discharge control (pattern image formation processing) in the embodiment. (a) and (b) are explanatory views showing an example of a test pattern formed on an intermediate transfer belt in an embodiment. 7 is a flowchart illustrating an example of reverse transfer bias correction control in the embodiment. (a) is a timing chart showing the state of writing operation of an electrostatic latent image, and (b) is a timing chart showing the state of applied bias of the secondary transfer section. 7 is a graph showing the relationship between the bias conditions of the reverse transfer bias applied to seven pattern portions constituting a test pattern and the amount of toner adhesion on each pattern portion detected by a P/TM sensor. 7 is a graph showing the relationship between the bias conditions of the reverse transfer bias applied to seven pattern parts constituting the test pattern and the amount of toner adhering to the secondary transfer roller.

An embodiment in which the present invention is applied to a printer as an image forming apparatus will be described below.
Note that the present invention performs recording by applying a regular transfer bias to a transfer region between an image carrier and a transfer member and transferring a toner image on the image carrier onto a recording material passing through the transfer region. The image forming apparatus is not limited to a printer as long as it forms an image on a material. For example, the present invention is also applicable to image forming apparatuses such as copying machines, facsimile machines, and multifunction devices.

FIG. 1 is a schematic configuration diagram showing an image forming process section (process engine section) that performs exposure, charging, development, transfer, and fixing in the printer 100 of this embodiment.
In addition to the structural members shown in FIG. 1, the printer 100 includes a print controller that processes image data sent from a PC (personal computer) or the like and converts it into exposure data, a high voltage generator that generates high voltage, and an image forming device. A main body control section for controlling operations is provided. The printer 100 also includes a paper feeder that supplies transfer paper 115 as a recording material, a manual feed tray that manually feeds the transfer paper 115, and an ejector for discharging the transfer paper 115 on which an image has been formed. There are paper trays etc.

In FIG. 1, the present printer 100 is provided with an endless belt-shaped intermediate transfer belt 105, which is an intermediate transfer body serving as an image carrier, and a primary transfer device 106. This intermediate transfer belt 105 has a three-layer structure including a base layer, an elastic layer, and a coat layer. The base layer is made of, for example, a combination of a fluororesin with low elongation, a rubber material with high elongation, and a material with low elongation such as canvas.

The elastic layer is made of, for example, fluorocarbon rubber or acrylonitrile-butadiene copolymer rubber, and is formed on the base layer. Further, the coat layer is formed by coating the surface of the elastic layer with, for example, a fluororesin. The intermediate transfer belt 105 is stretched around four support rollers 112, 113, 114, and 119 and is rotationally driven by a support roller 112 that functions as a drive roller.

Four image forming units for each color of yellow (Y), cyan (C), magenta (M), and black (K) are arranged in the stretched portion of the intermediate transfer belt 105. The four image forming units for each color have the same configuration and are composed of the same structural members. In FIG. magenta) and K (black). In each image forming unit, photoreceptor units 103Y, 103C, 103M, and 103K and developing devices 102Y, 102C, 102M, and 102K are arranged side by side. The developing devices 102Y, 102C, 102M, and 102K are supplied with toner from toner bottles 104K, 104Y, 104C, and 104M.

An exposure device 200 is provided below these image forming units. The exposure apparatus 200 drives a semiconductor laser from a laser exposure unit provided inside the exposure apparatus 200 to emit writing light Lb based on the image information. Then, the exposure device 200 forms electrostatic latent images on the photoreceptor drums 101Y, 101C, 101M, and 101K, which serve as latent image carriers provided in each photoreceptor unit. Here, the emission of the writing light Lb is not limited to a laser, and may be, for example, an LED (light emitting diode).

Next, the configuration of the image forming unit will be explained.
FIG. 2 is an explanatory diagram showing the configuration of an image forming unit that forms a black toner image.
Although an image forming unit that forms a black toner image will be described below as an example, image forming units that form toner images of other colors also have a similar configuration.

In FIG. 2, the constituent members of the image forming unit for black toner are originally denoted by K at the end of the reference numerals, but are omitted here. This image forming unit is provided with a charging device 301 for charging the photoreceptor drum, a developing device 102, and a photoreceptor cleaning device 308 around the photoreceptor drum 101. Further, a primary transfer device 106 is provided at a position facing the photosensitive drum 101 with an intermediate transfer belt 105 interposed therebetween.

The charging device 301 is of a contact charging type that employs a charging roller, and uniformly charges the surface of the photoreceptor drum 101 by contacting the photoreceptor drum 101 and applying a voltage. The charging device 301 may also be of a non-contact charging type using a non-contact Scorotron charger or the like.

Further, the developing device 102 uses a two-component developer consisting of a magnetic carrier and a non-magnetic toner. Note that a one-component developer may be used as the developer. The developing device 102 can be roughly divided into an agitating section 303 and a developing section 304 provided within the developing case. In the stirring section 303, the two-component developer (hereinafter simply referred to as "developer") is conveyed while being stirred, and is supplied onto the developing sleeve 305 as a developer carrier.

This stirring section 303 is provided with two parallel screws 306. A partition plate is provided between these two screws 306 so that they can communicate with each other at both ends. Further, a toner concentration sensor 418 for detecting the toner concentration of the developer in the developing device 102 is attached to the developing case. On the other hand, in the developing section 304 , toner of the developer attached to the developing sleeve 305 is transferred to the photoreceptor drum 101 .

The developing section 304 is provided with a developing sleeve 305 that faces the photoreceptor drum 101 through the opening of the developing case, and a magnet is fixedly disposed within the developing sleeve 305. Further, a doctor blade 307 is provided so that its tip approaches the developing sleeve 305 .

In the developing device 102, the developer is conveyed and circulated while being stirred by two screws 306, and is supplied to the developing sleeve 305. The developer supplied to the developing sleeve 305 is drawn up and held by a magnet. The developer drawn up into the developing sleeve 305 is conveyed as the developing sleeve 305 rotates, and is regulated to an appropriate amount by a doctor blade 307. The regulated developer is returned to the stirring section 303. The developer thus conveyed to the development area facing the photoreceptor drum 101 becomes bristled by the magnet, forming a magnetic brush.

In the development area, a development bias applied to the development sleeve 305 forms a development electric field that moves the toner in the developer to the electrostatic latent image portion on the photoreceptor drum 101 . As a result, the toner in the developer is transferred to the electrostatic latent image portion on the photoreceptor drum 101, and the electrostatic latent image on the photoreceptor drum 101 is visualized to form a toner image. The developer that has passed through the development region is conveyed to a portion where the magnetic force of the magnet is weak, leaves the development sleeve 305 , and is returned to the stirring section 303 . When the toner concentration in the stirring section 303 becomes thin due to repetition of such operations, the toner concentration sensor 418 detects this and replenishes the toner to the stirring section 303 based on the detection result.

The primary transfer device 106 employs a primary transfer roller, and is installed so as to press against the photosensitive drum 101 with the intermediate transfer belt 105 interposed therebetween. Further, both ends of the primary transfer roller are in contact with each other in a range 203 corresponding to the maximum width of the transfer paper 115 (maximum paper passing width) within the belt width of the intermediate transfer belt 105 in FIG.

The primary transfer device 106 does not have to be in the form of a roller, but may be in the form of a conductive brush, a non-contact corona charger, or the like. Further, the maximum paper passing width 203 is determined by the transfer paper that has the longest length in the direction perpendicular to the rotational direction of the intermediate transfer belt (the transfer paper in which the largest paper used is fed horizontally) out of the transfer paper 115 to the primary transfer device 103. and the intermediate transfer belt 105.

The photoreceptor cleaning device 308 includes a cleaning blade 309 made of polyurethane rubber, for example, which is arranged so that its tip can be pressed against the photoreceptor drum 101 . Further, in this embodiment, a conductive fur brush 310 that contacts the photoreceptor drum 101 is also used in order to improve cleaning performance.

A bias is applied to this fur brush 310 from a metal electric field roller, and the tip of the scraper is pressed against the electric field roller. The toner removed from the photoreceptor drum 101 by the cleaning blade 309 and the fur brush 310 is stored inside the photoreceptor cleaning device 308 and collected by a waste toner collection device.

In the image forming unit having the above configuration, as the photoreceptor drum 101 rotates, the charging device 301 uniformly charges the surface of the photoreceptor drum 101. Next, the exposure device 200 irradiates laser writing light Lb based on image information from the print controller to form an electrostatic latent image on the photoreceptor drum 101 . Thereafter, the electrostatic latent image is visualized by the developing device 102 to form a toner image.

This toner image is primarily transferred onto intermediate transfer belt 105 by primary transfer device 106 . Transfer residual toner remaining on the surface of the photoreceptor drum 101 after the primary transfer is removed by a photoreceptor cleaning device 308 and used for the next image formation.

A secondary transfer roller 108 as a transfer member is provided at a position facing the support roller 112 with the intermediate transfer belt 105 in between. The secondary transfer roller 108 transfers the toner image formed on the intermediate transfer belt 105 onto a transfer paper using electrostatic force. When performing secondary transfer of the toner image on the intermediate transfer belt 105 onto the transfer paper 115, the secondary transfer roller 108 is pressed against the portion of the intermediate transfer belt 105 wound around the support roller 112 to perform the secondary transfer. conduct. The secondary transfer device does not have to use the secondary transfer roller 108, but may use another transfer member such as a transfer belt.

The belt width of the intermediate transfer belt 105 is larger than the axial length of the secondary transfer roller 108 , and the maximum sheet passing width 203 is less than or equal to the axial length of the secondary transfer roller 108 .

In FIG. 1, a fixing device 111 for fixing the toner image transferred onto the transfer paper 115 is provided downstream of the secondary transfer roller 108 in the direction in which the transfer paper 115 is conveyed. This fixing device 111 has a configuration in which a pressure roller 118 is pressed against a heating roller 117.

At a position facing the support roller 112 with the intermediate transfer belt 105 in between, there is a photo sensor (hereinafter referred to as "P/TM sensor") 109 as a toner adhesion amount detection means for detecting the amount of toner adhesion in the toner pattern. is provided at the center of the support roller 112 in the axial direction. Further, a belt cleaning device 110 is provided at a position facing the support roller 113 with the intermediate transfer belt 105 in between. This belt cleaning device 110 removes residual toner remaining on the intermediate transfer belt 105 after transferring the toner image on the intermediate transfer belt 105 onto a transfer paper 115 using a cleaning blade 110a.

FIG. 4 is a schematic diagram of the P/TM sensor 109.
The P/TM sensor 109 of this embodiment has one light emitting element and two light receiving elements. This light emitting element is an infrared LED 602. The two light receiving elements are a specular reflection light receiving element 603 and a diffuse reflection light receiving element 604, which are provided at two locations, one in which the light specularly reflected on the intermediate transfer belt 105 can be received, and the other in a position that does not receive the specularly reflected light. It is. As the light emitting element, a laser light emitting element or the like may be used instead of the infrared LED.

Although phototransistors are used as the specular reflection light receiving element 603 and the diffuse reflection light receiving element 604, photodiodes may be amplified and used. Further, a condensing lens 605 is provided in the middle of the optical path. Note that in this configuration, a specular reflection light receiving element 603 and a diffuse reflection light receiving element 604 are provided as light receiving elements, but either one may be used depending on the object to be detected and necessary information.

FIG. 5 is a block diagram showing electrical connections of various parts included in the printer 100 of this embodiment.
The printer 100 of this embodiment includes a main body control section 406 configured as a computer, and this main body control section 406 controls each section. The main body control unit 406 is connected to a CPU (Central Processing Unit) 402 that executes various calculations and drive control of each part, and a ROM (Read Only Memory) 405 that stores fixed data such as computer programs in advance via a bus line 409. It is configured by being connected to a RAM (Random Access Memory) 403 which functions as a work area etc. for storing various data in a rewritable manner.

The ROM 405 stores toner pattern formation position and density information (toner adhesion amount information), bias conditions for forming toner pattern gradation, and output of the P/TM sensor 109 for estimating toner pattern adhesion amount. A conversion LUT (Look up table) for converting to the amount of toner adhesion is stored.

A print controller 410 is connected to the main body control unit 406, and the print controller 410 transmits image information from a PC (personal computer), FAX (facsimile), scanner, etc. to the main body control unit 406 as unified image data. . Also connected are an A/D conversion circuit 401 that converts various sensor information into digital data, a drive circuit that drives a motor and a clutch, a high voltage generator that generates the voltage necessary for image formation, and the like.

Next, the operation of the printer 100 of this embodiment will be explained.
When printing using information from a PC using the printer 100 having the above configuration, first, a print command and image information are transmitted using a printer driver on the PC. The print controller 410 starts a print job upon receiving a print command from the printer driver, performs necessary information processing on the image information, and then sends the image information to the main body control unit 406 . When a print job is started, the main body control unit 406 drives the drive motor, the support roller 112 is rotationally driven, and the intermediate transfer belt 105 is rotationally driven. At the same time, the main body control section 406 also rotationally drives the photosensitive drums 101Y, 101C, 101M, and 101K of each image forming unit.

Thereafter, the main body control unit 406 sends an exposure signal to the exposure apparatus 200 based on the image information from the print controller. The exposure device 200 irradiates the photoreceptor drums 101Y, 101C, 101M, and 101K of each image forming unit with writing light Lb based on an exposure signal. As a result, electrostatic latent images are formed on each of the photoreceptor drums 101Y, 101C, 101M, and 101K, and are visualized by the developing devices 102Y, 102C, 102M, and 102K. Yellow, cyan, magenta, and black toner images are formed on each photoreceptor drum 101Y, 101C, 101M, and 101K, respectively.

The toner images of each color thus formed are sequentially primarily transferred onto the intermediate transfer belt 105 by the respective primary transfer devices 106Y, 106C, 106M, and 106K so as to overlap each other. As a result, a composite toner image in which the toner images of each color are superimposed is formed on the intermediate transfer belt 105. Note that the transfer residual toner remaining on the intermediate transfer belt 105 after the secondary transfer is removed by the belt cleaning device 110.

Further, the main body control unit 406 rotates the paper feed roller of the paper feed device according to the transfer paper 115 selected by the user, and feeds the transfer paper 115 from one of the paper feed cassettes. The sent-out transfer paper 115 is separated into one sheet by a separation roller, enters a paper feed path, and is transported to a transport path within the printer main body by a transport roller. The transfer paper 115 transported in this manner is stopped when it hits the registration rollers 107.

Note that when using transfer paper 115 that is not set in the paper feed cassette, the transfer paper 115 set in the manual feed tray is sent out by a paper feed roller, separated into one sheet by a separation roller, and then passed through the manual feed path. transported. Similarly, it is stopped when it hits the registration roller 107.

The registration roller 107 starts rotating at the timing when the composite toner image formed on the intermediate transfer belt 105 as described above is conveyed to the secondary transfer section (transfer area) facing the secondary transfer roller 108. do. Here, the registration roller 107 is generally used while being grounded, but a bias may be applied to remove paper dust from the transfer paper 115.

The transfer paper 115 sent out by the registration roller 107 is sent between the intermediate transfer belt 105 and the secondary transfer roller 108, and the secondary transfer roller 108 transfers the composite toner image on the intermediate transfer belt 105 onto the transfer paper 115. Secondary transfer is made to . Thereafter, the transfer paper 115 is conveyed to the fixing device 111 while being attracted to the secondary transfer roller 108, and the fixing device 111 applies heat and pressure to fix the toner image. The transfer paper 115 that has passed through the fixing device 111 is discharged to a paper discharge tray by a discharge roller and stacked.

Note that when an image is to be formed on the reverse side of the surface on which the toner image is fixed, the conveying direction of the transfer paper 115 that has passed through the fixing device 111 is switched by a switching claw, and the transfer paper 115 is sent to a paper reversing device. The transfer paper 115 is then reversed and guided to the secondary transfer roller 108 again.

Next, toner discharge control performed by the CPU 402 of this embodiment based on a computer program will be described.
In this embodiment, by inputting toner into the belt cleaning device 110 of the intermediate transfer belt 105, toner is supplied to the belt cleaning device 110 of the intermediate transfer belt 105 to ensure adhesion due to the dam effect and reduce friction, thereby suppressing defects such as poor cleaning and blade curling. Execute discharge control.

In the toner discharge control, for example, as shown in FIG. 3, a long toner pattern 201 is formed on the intermediate transfer belt 105 in the belt width direction (main scanning direction) of the intermediate transfer belt 105. This toner pattern 201 is then moved to the belt cleaning device 110 and input to the belt cleaning device 110. The toner pattern 201 of this embodiment preferably extends over the contact width 202 of the cleaning blade 110a of the belt cleaning device 110, as shown in FIG. Thereby, toner can be input to the entire contact width 202 of the cleaning blade 110a.

The execution timing of the toner discharge control is, for example, generally performed after the end of the print job, but it may be performed at a timing other than the time after the end of the print job. For example, the timing may be after inputting a print command (after starting a print job).

Note that if a print job is left ungenerated (no image forming operation is performed), the amount of toner present in the belt cleaning device 110 will be unevenly distributed in the belt width direction (main scanning direction) of the intermediate transfer belt 105. This increases the risk of the above-mentioned problems occurring. In order to avoid this, it is preferable to execute toner discharge control at a timing after inputting a print command (after starting a print job). However, on the other hand, if the toner discharge control is executed after the print command is input (after the print job starts), the image forming operation cannot be started until the toner discharge control is completed, and the first print time will be delayed. This problem occurs.

Therefore, in this embodiment, the toner discharge control is executed at a timing after a print command is input (after a print job is started), but a toner pattern is formed immediately before the first image to be formed. In this way, by forming the toner pattern immediately before the first image to be formed, it is possible to suppress the delay in the first print time due to execution of toner discharge control.

FIG. 6 is a flowchart showing an example of toner discharge control (pattern image formation processing) in this embodiment.
The main body control unit 406 determines whether or not it is necessary to execute toner discharge control at the timing when receiving a print command and starting a print job. Specifically, first, the CPU 402 executes an execution program for toner discharge control and obtains the current mileage stored in the ROM 405 (S101). This current travel distance is information indicating the amount of operation of the secondary transfer roller 108, and is information equivalent to the surface movement distance of the secondary transfer roller 108. This current traveling distance can be, for example, a value obtained by multiplying the cumulative time of the image forming operation (cumulative operating time of the secondary transfer roller 108) by the circumference of the secondary transfer roller 108.

Next, the CPU 402 uses the information about the mileage during the previous execution stored in the ROM 405 when executing the toner discharging control last time (when forming the toner pattern last time), and uses the information about the distance traveled at the time of the previous execution to the present time to perform the toner discharging control. A travel distance change amount ΔD1 is calculated (S102). After that, the CPU 402 determines whether the calculated travel distance change amount ΔD1 exceeds the execution determination threshold DC (S103).

In this determination, if the calculated travel distance change amount ΔD1 does not exceed the execution determination threshold DC (No in S103), the CPU 402 determines that execution of toner discharge control is unnecessary, and performs an image forming operation according to the print job. .

On the other hand, if the calculated travel distance change amount ΔD1 exceeds the execution determination threshold DC (Yes in S103), the CPU 402 determines that it is necessary to execute the toner discharge control, and functions as a pattern image forming processing means. do. Then, the CPU 402 executes an operation for forming a predetermined toner pattern 201 as shown in FIG. 3 (S104). This toner pattern 201 is formed, for example, with a single color toner by any one image forming unit, but may be formed with toner of two or more colors. The toner pattern 201 thus formed on the intermediate transfer belt 105 by the image forming unit passes through the secondary transfer section and is input to the belt cleaning device 110.

Further, if the calculated travel distance change amount ΔD1 exceeds the execution determination threshold DC (Yes in S103), the CPU 402 stores the current travel distance acquired in processing step S101 as the travel distance at the previous execution in the ROM 405. (S105). Thereafter, the CPU 402 performs an image forming operation according to the print job so that the first image of the print job is formed immediately after the toner pattern 201.

Here, in order to input the toner pattern formed on the intermediate transfer belt 105 to the belt cleaning device 110, the toner pattern needs to pass through a secondary transfer section. Since the transfer paper 115 is not present in the secondary transfer section during this passage, some toner forming the toner pattern (toner not intended to be transferred to the secondary transfer roller) may adhere to the secondary transfer roller 108 . When the toner adheres to the secondary transfer roller 108, the toner adheres to the back surface of the transfer paper 115 that is subsequently conveyed to the secondary transfer section, staining the back surface of the transfer paper 115.

Note that if there is a means for bringing the intermediate transfer belt 105 and the secondary transfer roller 108 into contact with and away from each other, the intermediate transfer belt 105 and the secondary transfer roller 108 are separated when the toner pattern passes through the secondary transfer section, and the It is possible to suppress toner adhesion to the next transfer roller 108. However, when forming a toner pattern immediately before the first image to be formed in a print job, the time from when the toner pattern passes through the secondary transfer section until the composite toner image of the first image enters the secondary transfer section is During this period, the separation state cannot be returned to the contact state by the contact/separation means. In order to be able to return the separated state to the contact state during this period, it is necessary to form the toner pattern at a timing considerably earlier than the first image to be formed, resulting in a delay in the first print time. cannot be suppressed.

Therefore, in this embodiment, during the period when the toner pattern formed on the intermediate transfer belt 105 passes through the secondary transfer section, the secondary transfer section receives a reverse transfer bias whose polarity is opposite to that of the secondary transfer bias during the image forming operation. Apply bias. As a result, when the toner pattern on the intermediate transfer belt 105 passes through the secondary transfer section, a force toward the intermediate transfer belt 105 (force in the reverse transfer direction) is applied to the normally charged toner constituting the toner pattern. do. As a result, toner constituting the toner pattern is prevented from adhering to the secondary transfer roller 108, and staining of the back surface of the transfer paper 115 can be suppressed.

However, in order to appropriately suppress the adhesion of the toner constituting the toner pattern to the secondary transfer roller 108, it is necessary to apply a reverse transfer bias under appropriate bias conditions. Optimal bias conditions may change over time. For example, when environmental changes such as temperature and humidity occur, the amount of charge on the toner changes, so a reverse transfer bias is applied to draw as much toner (toner) forming the toner pattern toward the intermediate transfer belt 105 as possible. The optimal bias conditions for will vary. In addition, when the characteristics (electrical resistance value, etc.) of the secondary transfer roller 108 change due to wear of the secondary transfer roller 108 due to operation of the secondary transfer roller 108 over time, the reverse transfer bias causes a change in the secondary transfer roller 108. The state of the electric field formed changes. As a result, the optimal bias conditions for the reverse transfer bias for drawing as much toner (toner) constituting the toner pattern toward the intermediate transfer belt 105 as possible changes.

Therefore, in this embodiment, reverse transfer bias correction control is executed to correct the optimum bias condition of the reverse transfer bias at a predetermined bias condition correction timing. Specifically, a test pattern is formed on the intermediate transfer belt 105 as a toner pattern for correcting predetermined conditions. Then, the P/TM sensor 109 detects the amount of toner adhering to the test pattern after the test pattern passes through a transfer area to which a reverse transfer bias of a predetermined bias condition is applied. Then, based on this detection result, the bias condition of the reverse transfer bias applied when the toner pattern 201 formed by the above-described toner discharge control passes through the secondary transfer section is corrected.

FIGS. 7A and 7B are explanatory diagrams showing an example of a test pattern formed on the intermediate transfer belt 105 in this embodiment.
FIG. 8 is a flowchart showing an example of reverse transfer bias correction control in this embodiment.
In this embodiment, the reverse transfer bias correction control is executed at the time when the printer is powered on and after the print job is completed, but it may be executed at other timings.

When the execution timing of the reverse transfer bias correction control arrives, the main body control unit 406 first determines whether or not to execute the reverse transfer bias correction control. If the execution frequency of reverse transfer bias correction control (the frequency of test pattern formation) is high, the risk of downtime occurrence increases. Therefore, in order to minimize the frequency of execution of reverse transfer bias correction control, reverse transfer bias correction control (test pattern formation) should be executed only at times when the optimum bias conditions for reverse transfer bias may change. is preferred.

Therefore, in this embodiment, the timing at which the optimum bias condition of the reverse transfer bias can be changed is determined as follows. Specifically, the main body control unit 406 determines the timing at which the temperature changes from the temperature at the time of the previous test pattern formation by the temperature change amount threshold T or more, and the humidity at the time of the previous test pattern formation (either relative humidity or absolute humidity). ) to the humidity change amount threshold H or more, and the timing when the travel distance exceeds the travel distance threshold D2 from the travel distance during the previous test pattern formation (the amount of operation of the secondary transfer roller 108). to judge. Then, when any one of these timings arrives, the main body control unit 406 determines that it is necessary to execute the transfer bias correction control. Note that the travel distance (operation amount) of the secondary transfer roller 108 may be determined by using other information such as the number of sheets passed or the operation time, as long as the information corresponds to this information.

In the main body control unit 406, when the execution timing for reverse transfer bias correction control arrives, the CPU 402 executes an execution program for reverse transfer bias correction control. Then, the CPU 402 first obtains information on the current temperature and current humidity from the temperature/humidity sensor 414, and also obtains the current mileage stored in the ROM 405 (S201). This current travel distance is information indicating the operating amount of the secondary transfer roller 108, and is information equivalent to the surface movement distance of the secondary transfer roller 108, and is used when determining whether or not to execute the toner discharge control described above. This is the same information used in

Next, the CPU 402 acquires the information of the temperature at the previous execution, the humidity at the previous execution, and the mileage at the previous execution, which were stored in the ROM 405 when the reverse transfer bias correction control was executed the previous time (when the test pattern was formed last time). . Then, the CPU 402 uses this information to calculate each amount of change from the time of the previous execution of reverse transfer bias correction control to the present, that is, the amount of temperature change ΔT, the amount of humidity change ΔH, and the amount of distance change ΔD2. (S202).

Thereafter, the CPU 402 determines whether the calculated temperature change amount ΔT, humidity change amount ΔH, and mileage change amount ΔD2 exceed the temperature change amount threshold T, the humidity change amount threshold H, and the mileage change amount threshold D2, respectively. is determined (S203). Note that these threshold values T, H, and D2 are each set experimentally based on, for example, changes in the characteristics of the secondary transfer roller 108.

In this determination, if none of the temperature change amount ΔT, humidity change amount ΔH, and travel distance change amount ΔD2 exceeds the corresponding threshold values T, H, and D2 (No in S203), the CPU 402 controls the reverse transfer bias It is determined that there is no need to perform correction control. As a result, the reverse transfer bias correction control ends without forming a test pattern, and the currently set bias conditions of the reverse transfer bias are not changed.

On the other hand, if any of the temperature change amount ΔT, humidity change amount ΔH, and travel distance change amount ΔD2 exceeds the corresponding threshold value T, H, D2 (Yes in S203), the CPU 402 performs reverse transfer bias correction. Determine that control execution is necessary. Then, the CPU 402 functions as a bias condition correction means and executes an operation for forming a predetermined test pattern 205 as shown in FIG. 7 (S204).

As shown in FIG. 7, the test pattern 205 in this embodiment is composed of seven pattern parts arranged in the surface movement direction (sub-scanning direction) of the intermediate transfer belt 105. In this embodiment, the bias conditions of the reverse transfer bias applied when each pattern section passes through the secondary transfer section are made different.

FIG. 9A is a timing chart showing the state of the electrostatic latent image writing operation.
FIG. 9(b) is a timing chart showing the state of the bias applied to the secondary transfer section.
If the CPU 402 determines that it is necessary to execute the reverse transfer bias correction control (Yes in S203), as shown in FIG. 9(a), the test pattern is A write operation 205 is performed. Then, when the test pattern 205, which has been developed from this electrostatic latent image and is primarily transferred onto the intermediate transfer belt 105, passes through the secondary transfer section, the CPU 402 applies a predetermined bias as shown in FIG. 9(b). Apply reverse transfer bias according to the conditions. That is, in this embodiment, as shown in FIG. 9B, reverse transfer biases having different bias values are applied to the seven pattern portions forming the test pattern 205.

After that, the amount of toner adhering to the seven pattern parts of the test pattern 205 is detected from the output of the P/TM sensor 109 when the test pattern 205 that has passed through the secondary transfer section passes the P/TM sensor 109. (S204).

Next, the CPU 402 determines the bias conditions of the reverse transfer bias used in the above-described toner discharge control based on the amount of toner adhering to the seven pattern portions of the test pattern 205 detected by the P/TM sensor 109. Specifically, the CPU 402 calculates the bias condition (bias value of the reverse transfer bias) that maximizes the toner adhesion amount based on the toner adhesion amount of the seven pattern parts of the test pattern 205 (S205).

FIG. 10 is a graph showing the relationship between the bias conditions of the reverse transfer bias applied to the seven pattern parts constituting the test pattern 205 and the toner adhesion amount of each pattern part detected by the P/TM sensor 109. It is.
FIG. 11 is a graph showing the relationship between the bias conditions of the reverse transfer bias applied to the seven pattern parts constituting the test pattern 205 and the amount of toner adhering to the secondary transfer roller 108.

The toner adhesion amount of the test pattern 205 after passing through the secondary transfer section with a reverse transfer bias applied under a predetermined bias condition is calculated from the toner adhesion amount of the test pattern 205 before passing through the secondary transfer section. The amount of toner attached to the transfer roller 108 is subtracted. Therefore, among the bias conditions of the reverse transfer bias applied to the seven pattern portions of the test pattern 205, the bias condition corresponding to the pattern portion with the largest amount of toner adhesion after passing through the secondary transfer portion is the optimum bias condition. It can be estimated that the condition is the closest to the condition.

In this embodiment, the CPU 402 sets the bias condition corresponding to the pattern portion with the largest amount of toner adhesion after passing through the secondary transfer section as the bias condition of the reverse transfer bias used during toner discharge control (S206), and stores it in the ROM 405. save. Therefore, when executing the toner discharge control from next time onward, the bias condition of the reverse transfer bias applied when the toner pattern 201 to be formed passes through the secondary transfer section is stored in the ROM 405 by the current reverse transfer bias correction control. bias conditions are used. As a result, even if the bias conditions of the reverse transfer bias deviate from the optimal conditions, the reverse transfer bias correction control corrects the optimal bias conditions, and prevents toner from adhering to the secondary transfer roller 108 from the toner pattern 201. can be suppressed.

In this embodiment, since toner adhesion to the secondary transfer roller 108 occurs when the test pattern 205 passes through the secondary transfer section, a cleaning operation for the secondary transfer roller 108 is also performed (S208). . Specifically, while applying the reverse transfer bias under the bias condition set in processing step 206, the secondary transfer roller 108 is rotated idly for two revolutions, for example. As a result, the toner adhering to the secondary transfer roller 108 is reversely transferred to the intermediate transfer belt 105 side by the reverse transfer bias, and is collected by the belt cleaning device 110.

In addition, if the CPU 402 determines that it is necessary to execute the reverse transfer bias correction control, the CPU 402 converts the current temperature, current humidity, and current mileage acquired in processing step S201 into the temperature at the previous execution, the humidity at the previous execution, and the It is stored in the ROM 405 as the hourly mileage (S208).

Note that if the environment such as temperature and humidity changes excessively, or if the characteristics of the secondary transfer roller 108 change excessively, even if the bias conditions of the reverse transfer bias are optimized, toner may not be transferred to the secondary transfer roller 108. This results in a situation where adhesion cannot be sufficiently suppressed. In such a case, even if the bias condition of the reverse transfer bias is set to the optimal condition, every time the toner pattern 201 is formed during toner discharge control, the back side of the transfer paper 115 will be damaged due to toner adhering to the secondary transfer roller 108. Dirt will occur. Therefore, in such a situation, it is preferable not to execute toner discharge control.

Whether or not this situation has occurred can be determined as follows, for example, if a contacting and separating means for bringing the intermediate transfer belt 105 and the secondary transfer roller 108 into contact with and away from each other is provided. That is, a comparison toner pattern is imaged on the intermediate transfer belt 105 at a predetermined timing. Then, the P/TM sensor 109 detects the toner adhesion amount of the comparative toner pattern after passing through the secondary transfer section in which the intermediate transfer belt 105 and the secondary transfer roller 108 are separated by the contact/separation means. Save it. Next, after executing the reverse transfer bias control described above and determining the bias conditions (bias value of reverse transfer bias) for the pattern portion with the largest amount of toner adhesion, this largest amount of toner adhesion and the stored The difference between the toner adhesion amount and the comparison toner pattern is calculated. If this difference is greater than or equal to a predetermined amount of toner adhesion, it is determined that the situation is such that toner adhesion to the secondary transfer roller 108 cannot be sufficiently suppressed even if the bias conditions of the reverse transfer bias are optimized. . As a result, after that, even if the execution timing (predetermined pattern creation timing) of the toner discharge control arrives, the toner discharge control is not executed.

What has been explained above is an example, and each of the following aspects has a unique effect [first aspect]
In the first aspect, a normal transfer bias (for example, a secondary transfer bias) is applied to a transfer area (for example, a secondary transfer portion) between an image carrier (for example, an intermediate transfer belt 105) and a transfer member (for example, a secondary transfer roller 108). An image forming device (for example, a printer) that forms an image on the recording material by applying the toner image on the image carrier onto the recording material (for example, the transfer paper 115) passing through the transfer area. 100), a reverse transfer bias applying means (for example, a high voltage generator) that applies a reverse transfer bias having a polarity opposite to the normal transfer bias at a predetermined timing (for example, the timing at which the toner pattern 201 passes through the transfer area). 416), a toner adhesion amount detection means (for example, P/TM sensor 109) that detects the amount of toner adhesion on the image bearing member, and a toner adhesion amount detection means (for example, P/TM sensor 109) that detects the amount of toner adhesion on the image carrier, and Based on the detection result of the toner adhesion amount of a predetermined condition correction toner pattern (for example, test pattern 205) after passing through the transfer area by the toner adhesion amount detection means, the reverse transfer bias application means applies the toner adhesion amount. The present invention is characterized in that it includes bias condition correction means (for example, main body control section 406) that corrects the bias conditions of the reverse transfer bias.
When applying a reverse transfer bias to a transfer area to suppress the transfer of toner from an image carrier to a transfer member, the optimal bias conditions for the reverse transfer bias may change over time. For example, when environmental changes such as temperature and humidity occur, the amount of charge on the toner changes, and the optimum bias conditions for the reverse transfer bias change. In addition, when the characteristics of the transfer member change due to wear due to operation of the transfer member over time, the state of the electric field formed in the transfer area due to the reverse transfer bias changes, so the optimum reverse transfer bias bias Conditions will change. If the bias conditions of the reverse transfer bias deviate from the optimal conditions, the transfer of toner from the image bearing member to the transfer member cannot be sufficiently suppressed, and the amount of toner transferred to the transfer member increases. This causes problems such as toner stains on the back side of the recording material.
In this aspect, a predetermined condition correction toner pattern is imaged on the image carrier at a predetermined bias condition correction timing. Then, the toner adhesion amount detection means detects the toner adhesion amount of the condition correction toner pattern after the condition correction toner pattern passes through the transfer area to which a predetermined reverse transfer bias is applied. Then, based on this detection result, the bias condition of the reverse transfer bias applied by the reverse transfer bias applying means is corrected.
The toner adhesion amount of the condition correction toner pattern after passing through the transfer area with a predetermined reverse transfer bias applied is calculated from the toner adhesion amount of the condition correction toner pattern before passing through the transfer area, which is transferred to the transfer member. minus the amount of toner used. Therefore, the amount of toner to be transferred to the transfer member can be estimated from the detection result obtained by detecting the amount of toner adhesion after the condition correction toner pattern passes through the transfer area by the toner adhesion amount detection means. Therefore, according to this aspect, it is possible to correct the bias condition of the reverse transfer bias (that is, the optimal bias condition) that can sufficiently suppress the amount of toner transferred to the transfer member. As a result, even if the bias condition of the reverse transfer bias in the reverse transfer bias applying means deviates from the optimum condition, the bias condition of the reverse transfer bias can be corrected by the bias condition correction means. can be returned to optimal conditions. Therefore, even if the bias conditions of the reverse transfer bias in the reverse transfer bias applying means deviate from the optimal conditions, the amount of toner transferred to the transfer member can be suppressed.

[Second aspect]
In a second aspect, in the first aspect, a toner pattern 201 that is not transferred onto the recording material is imaged on the image carrier at a predetermined pattern creation timing, and when the toner pattern passes through the transfer area, the toner pattern 201 is The bias condition correction means includes a pattern imaging processing means (for example, main body control section 406) that executes pattern imaging processing (toner discharge control) in which the reverse transfer bias is applied by the reverse transfer bias application means, and the bias condition correction means The present invention is characterized in that bias conditions of the reverse transfer bias applied during image forming processing are corrected.
According to this, even if the bias conditions of the reverse transfer bias during the pattern image forming process deviate from the optimal conditions, the toner pattern 201 formed by the pattern image forming process will not be transferred to the transfer member. The amount of stored toner can be suppressed.

[Third aspect]
In a third aspect, in the second aspect, the image bearing member and the transfer member are brought into contact with each other and separated from each other, and the pattern image forming processing unit is configured to form a comparative toner pattern that is not transferred onto the recording material. The toner adhesion amount of the comparative toner pattern after an image is formed on the image carrier and the transfer area is passed through the transfer area where the image support and the transfer member are separated by the contact/separation means is defined as the toner adhesion amount. An image is formed when the detection result detected by the detection means and the bias condition correction means corrects the bias condition of the reverse transfer bias, and the image is formed when the image passes through the transfer area with the reverse transfer bias of the bias condition applied. If the difference between the toner adhesion amount of the subsequent condition correction toner pattern and the detection result detected by the toner adhesion amount detection means is equal to or more than a predetermined toner adhesion amount, even if the predetermined pattern creation timing arrives, This method is characterized in that the pattern image forming process is not executed.
According to this, when it becomes impossible to sufficiently suppress toner adhesion to the transfer member even if the bias conditions of the reverse transfer bias are optimized, it is possible to prevent the pattern image forming process from being executed. . As a result, when this situation occurs, it is possible to prevent problems such as toner stains on the back side of the recording material from occurring by executing the pattern image forming process.

[Fourth aspect]
In a fourth aspect, in any one of the first to third aspects, the bias condition correction means applies the predetermined reverse transfer biases that are different from each other when the condition correction toner pattern passes through the transfer area, The bias condition of the reverse transfer bias is corrected based on the detection result by the toner adhesion amount detection means of each toner adhesion amount of the condition correction toner pattern corresponding to each predetermined reverse transfer bias. It is.
According to this, it becomes easy to correct the bias conditions of the reverse transfer bias that can sufficiently suppress the amount of toner transferred to the transfer member.

[Fifth aspect]
In a fifth aspect, in any one of the first to fourth aspects, the bias condition correction means adjusts the bias condition under which the amount of toner adhesion detected by the toner adhesion amount detection means is the largest to the bias of the reverse transfer bias. This is characterized by correction as a condition.
According to this, it is possible to easily correct the bias condition of the reverse transfer bias that can sufficiently suppress the amount of toner transferred to the transfer member.

[Sixth aspect]
A sixth aspect, in any one of the first to fifth aspects, includes temperature detection means (for example, temperature/humidity sensor 414), and the predetermined bias condition correction timing is determined by the detection result of the temperature detection means (for example, the current temperature ), the condition correction toner pattern is corrected based on the timing at which the temperature changes by a predetermined temperature difference (e.g., temperature change threshold T) or more from the temperature at the time of image formation of the condition correction toner pattern (e.g., the temperature at the previous execution). It is characterized by:
According to this, the bias condition correction means can correct the bias condition of the reverse transfer bias at the timing when the optimum bias condition of the reverse transfer bias changes due to a temperature change and a change in the amount of charge of the toner. can. As a result, it is possible to reduce the frequency with which the bias condition correction means corrects the bias conditions of the reverse transfer bias at unnecessary timing, and it is possible to suppress the occurrence of downtime.

[Seventh aspect]
A seventh aspect, in any one of the first to sixth aspects, includes a humidity detection means (for example, a temperature/humidity sensor 414), and the predetermined bias condition correction timing is determined by a detection result of the humidity detection means (for example, a current humidity sensor 414). ), the condition correction toner pattern is corrected based on the timing at which the humidity changes by a predetermined humidity difference (for example, humidity change amount threshold H) or more from the humidity at the time of image formation of the condition correction toner pattern (for example, the humidity at the time of the previous execution). It is characterized by:
According to this, the bias condition correction means can correct the bias condition of the reverse transfer bias at the timing when the optimum bias condition of the reverse transfer bias changes due to a change in humidity and a change in the amount of charge of the toner. can. As a result, it is possible to reduce the frequency with which the bias condition correction means corrects the bias conditions of the reverse transfer bias at unnecessary timing, and it is possible to suppress the occurrence of downtime.

[Eighth aspect]
An eighth aspect is an eighth aspect according to any one of the first to seventh aspects, further comprising operation amount detection means (for example, CPU 402, ROM 405) for detecting the operation amount of the transfer member (for example, the traveling distance of the secondary transfer roller); The predetermined bias condition correction timing is based on the detection result of the operation amount detection means (for example, the current mileage), and the predetermined operation is adjusted from the operation amount at the time of image formation of the condition correction toner pattern (the mileage during the previous execution). The present invention is characterized in that the amount (for example, the amount of change in travel distance ΔD2) or more is corrected based on the timing at which the transfer member operates.
According to this, when the characteristics of the transfer member change due to wear of the transfer member due to operation of the transfer member over time, and the optimum bias condition of the reverse transfer bias changes, the bias condition correction means adjusts the reverse transfer. The bias condition of the bias can be corrected. As a result, it is possible to reduce the frequency with which the bias condition correction means corrects the bias conditions of the reverse transfer bias at unnecessary timing, and it is possible to suppress the occurrence of downtime.

[Ninth aspect]
In the ninth aspect, by applying a regular transfer bias to a transfer region between an image carrier and a transfer member, and transferring a toner image on the image carrier onto a recording material passing through the transfer region, The image forming method for forming an image on the recording material includes a reverse transfer bias application step of applying a reverse transfer bias having a polarity opposite to the normal transfer bias at a predetermined timing, and toner adhesion on the image carrier. A toner adhesion amount detection step of detecting the amount, and a toner adhesion amount of a toner pattern for predetermined condition correction after passing through the transfer area with a predetermined reverse transfer bias applied at a predetermined bias condition correction timing. The present invention is characterized by comprising a bias condition correction step of correcting the bias condition of the reverse transfer bias applied in the reverse transfer bias application step based on the detection result detected in the toner adhesion amount detection step.
According to this aspect, it is possible to correct the bias condition (that is, the optimal bias condition) of the reverse transfer bias that can sufficiently suppress the amount of toner transferred to the transfer member. As a result, even if the bias condition of the reverse transfer bias in the reverse transfer bias applying means deviates from the optimum condition, the bias condition of the reverse transfer bias can be corrected by the bias condition correction means. can be returned to optimal conditions. Therefore, even if the bias conditions of the reverse transfer bias in the reverse transfer bias applying means deviate from the optimal conditions, the amount of toner transferred to the transfer member can be suppressed.

100: Printer 101: Photoconductor drum 102: Developing device 103: Photoconductor unit 104: Toner bottle 105: Intermediate transfer belt 106: Primary transfer device 107: Registration roller 108: Secondary transfer roller 109: P/TM sensor 110: Belt Cleaning device 110a: Cleaning blade 111: Fixing device 115: Transfer paper 200: Exposure device 201: Toner pattern 202: Cleaning blade contact width 203: Maximum paper passing width 205: Test pattern 301: Charging device 308: Photoconductor cleaning device 402 :CPU
403: RAM
405: ROM
406: Main body control unit 410: Print controller 414: Temperature/humidity sensor 418: Toner density sensor

Patent No. 4464092

Claims (9)

By applying a regular transfer bias to the transfer area between the image carrier and the transfer member and transferring the toner image on the image carrier onto the recording material passing through the transfer area, the toner image on the image carrier is transferred onto the recording material. An image forming apparatus that forms an image,
a reverse transfer bias applying means for applying a reverse transfer bias having a polarity opposite to the normal transfer bias at a predetermined timing;
and a toner adhesion amount detection means for detecting the amount of toner adhesion on the image carrier,
At a predetermined correction timing, the toner adhesion amount detecting means measures the toner adhesion amount of the toner pattern for predetermined condition correction after passing through the transfer area to which a reverse bias having a polarity opposite to the normal transfer bias is applied. An image forming apparatus characterized in that the reverse transfer bias applied by the reverse transfer bias applying means is corrected based on the detected detection result. The image forming apparatus according to claim 1,
At a predetermined pattern creation timing, a toner pattern that is not transferred onto the recording material is imaged on the image carrier, and when the toner pattern passes through the transfer area, the reverse transfer bias is applied by the reverse transfer bias applying means. comprising a pattern imaging processing means for performing pattern imaging processing to apply the voltage;
The image forming apparatus is characterized in that the correction corrects the reverse transfer bias applied during the pattern image forming process. The image forming apparatus according to claim 2,
comprising a means for bringing the image carrier and the transfer member into contact with and away from each other;
The pattern image forming processing means forms an image on the image bearing member of a comparison toner pattern that is not transferred onto the recording material, and performs the transfer in a state where the image bearing member and the transfer member are separated by the contacting and separating means. A detection result obtained by detecting the toner adhesion amount of the comparison toner pattern after passing through the region by the toner adhesion amount detection means, and a state in which an image is created when correcting the reverse transfer bias and the reverse transfer bias is applied. If the difference between the toner adhesion amount of the condition correction toner pattern after passing through the transfer area and the detection result detected by the toner adhesion amount detection means is equal to or more than a predetermined toner adhesion amount, the predetermined pattern is created. An image forming apparatus characterized in that the pattern image forming process is not executed even if the timing comes. The image forming apparatus according to any one of claims 1 to 3,
Applying the different reverse biases when the condition correction toner pattern passes through the transfer area, and detecting each toner adhesion amount of the condition correction toner pattern corresponding to each reverse bias by the toner adhesion amount detection means. An image forming apparatus characterized in that the reverse transfer bias is corrected based on the result. The image forming apparatus according to any one of claims 1 to 4,
The image forming apparatus is characterized in that the correction is performed by setting, as the reverse transfer bias, a reverse bias that causes the largest amount of toner adhesion detected by the toner adhesion amount detection means. The image forming apparatus according to any one of claims 1 to 5,
It has a temperature detection means,
The predetermined correction timing is corrected based on the detection result of the temperature detection means, based on the timing at which a temperature change of more than a predetermined temperature difference occurs from the temperature at the time of image formation of the condition correction toner pattern last time. An image forming apparatus characterized by: The image forming apparatus according to any one of claims 1 to 6,
Has humidity detection means,
The predetermined correction timing is corrected based on the detection result of the humidity detection means, based on the timing at which a change in humidity by a predetermined humidity difference or more occurs from the humidity at the time of image formation of the previous condition correction toner pattern. An image forming apparatus characterized by: The image forming apparatus according to any one of claims 1 to 7,
comprising a working amount detection means for detecting the working amount of the transfer member,
The predetermined correction timing is based on the detection result of the operation amount detection means, and is corrected based on the timing at which the transfer member operates by a predetermined operation amount or more from the operation amount at the time of image formation of the condition correction toner pattern last time. An image forming apparatus characterized in that: By applying a regular transfer bias to the transfer area between the image carrier and the transfer member and transferring the toner image on the image carrier onto the recording material passing through the transfer area, the toner image on the image carrier is transferred onto the recording material. An image forming method for forming an image, the method comprising:
a reverse transfer bias application step of applying a reverse transfer bias having a polarity opposite to the normal transfer bias at a predetermined timing;
a toner adhesion amount detection step of detecting the amount of toner adhesion on the image carrier;
At a predetermined correction timing, the toner adhesion amount of the toner pattern for predetermined condition correction after passing through the transfer area with a predetermined reverse transfer bias applied is detected based on the detection result obtained in the toner adhesion amount detection step. and a correction step of correcting the reverse transfer bias applied in the reverse transfer bias application step.

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