JP2020134865A - Image formation device - Google Patents

Abstract

To execute a step of supplying toner and a step of recovering remaining toner on an intermediate transfer body by a structure which does not include means for applying a primary transfer voltage of the same polarity as that of normal toner in a predetermined station.SOLUTION: The present invention includes a negative voltage application unit 42d for applying a negative voltage to a primary transfer roller 26d of a fourth station. When a toner supply step is executed, a voltage is not applied to a primary transfer roller 26b of a second station, a voltage is not applied to a primary transfer roller 26c of a third station, and a negative-polarity voltage is applied to the primary transfer roller 26d of a fourth station by the negative voltage application unit 42d.SELECTED DRAWING: Figure 8

Description

The present invention relates to an image forming apparatus such as a printer or a copying machine using an electrophotographic method, and more particularly to a color image forming apparatus including a photosensitive drum capable of carrying a toner image on the surface.

[Intermediate transfer body cleaning means using a charged member]
In the intermediate transfer body type tandem color image forming apparatus, it is necessary to remove the toner remaining on the intermediate transfer body (hereinafter referred to as residual toner) from the intermediate transfer body after the printing step or the like. As a method for removing residual toner, a method using a charging member is disclosed (see, for example, Patent Document 1). In this method, a toner charging member is provided, the residual toner is charged by the toner charging member, and the residual toner is reverse-transferred to the image carrier by the primary transfer unit to recover the residual toner from the intermediate transfer body.

[Cleaning blade squeal]
As a means for cleaning unnecessary toner on the image carrier, there is a cleaning blade (hereinafter, referred to as C blade) that abuts on the image carrier and scrapes and collects the toner. In order to prevent problems such as squealing and turning of the C blade caused by toner depletion and the like, for example, the following method is disclosed. The squeal of the C blade refers to a phenomenon in which an abnormal noise is generated at the contact portion due to friction between the image carrier and the C blade. A means for forming a band-shaped toner image (hereinafter referred to as purge toner) in a non-image region of an image carrier and allowing the formed purge toner to reach the blade edge of the C blade to supply toner (hereinafter referred to as a toner supply step). Is disclosed (see, for example, Patent Document 2).

[Toner supply process]
When the toner supply process is performed with the image carrier and the intermediate transfer body in contact with each other, the purge toner is passed through the primary transfer portion without being transferred to the intermediate transfer body, so that the primary toner has the same polarity as the regular toner. There is a means to apply a transfer voltage.

[Simultaneous execution means of intermediate transfer cleaning and toner supply process]
The process of recovering residual toner at one station and the process of preventing transfer in the toner supply process at another station can be performed at the same time by applying a primary transfer voltage having a polarity required at each station.

Japanese Unexamined Patent Publication No. 2009-205012 Japanese Unexamined Patent Publication No. 11-21940

On the other hand, in order to reduce costs, a configuration may be adopted in which not all stations are provided with means for applying a primary transfer voltage having the same polarity as that of regular toner. For example, if the negative electrode voltage is shared from the first station (hereinafter referred to as st) to the 3st, the recovery of the toner having the opposite polarity to the regular toner and the toner supply process cannot be performed at the same time in the 1st to the 3st. On the other hand, in the configuration without the means for applying the primary transfer voltage having the same polarity as the 3st regular toner, sufficient transfer prevention cannot be performed in the toner supply process at the 3st. In particular, since toner recovery is performed at the same time, if a positive primary transfer voltage is applied at the 1st or 2st, the transfer cannot be sufficiently prevented at the 3st, and the toner is not sufficiently supplied to the C blade. There are challenges.

The present invention has been made under such circumstances, and has a configuration in which a means for applying a primary transfer voltage having the same polarity as that of regular toner is not provided at a predetermined station, and a toner supply process and residue on an intermediate transfer body are provided. The purpose is to carry out the toner recovery process together.

In order to solve the above-mentioned problems, the present invention includes the following configurations.

(1) A photoconductor, a developer for forming a toner image having a predetermined polarity on the photoconductor, a transfer means for transferring the toner image on the photoconductor, and the predetermined transfer means. A first application means for applying a voltage having a polarity opposite to that of the polarity and a voltage for the opposite polarity are applied to the transfer means to transfer a toner image of the predetermined polarity onto the photoconductor. A plurality of stations having a blade that abuts on the photoconductor for cleaning residual toner, and an intermediate that abuts on the plurality of photoconductors and superimposes and transfers a toner image on the plurality of photoconductors. A transfer body is provided, and the toner remaining on the intermediate transfer body after the toner image on the intermediate transfer body is transferred to a recording material is located upstream of a predetermined station in the moving direction of the intermediate transfer body. An image forming apparatus capable of performing a first operation of collecting at a station and a second operation of supplying a toner having a predetermined polarity to the blade of the predetermined station. When a second applying means for applying a voltage of the predetermined polarity is provided to the transfer means of a station adjacent to the station adjacent to the predetermined station in the moving direction and the second operation is executed, the said second operation is performed. No voltage is applied to the transfer means of the station adjacent to the upstream side in the moving direction of the predetermined station, and no voltage is applied to the transfer means of the predetermined station, and the station adjacent to the downstream side is not applied. The transfer means is an image forming apparatus, characterized in that a voltage having the predetermined polarity is applied by the second application means.

According to the present invention, it is possible to carry out both the toner supply step and the recovery step of the residual toner on the intermediate transfer body in a configuration in which a primary transfer voltage application means having the same polarity as that of the regular toner is not provided at a predetermined station. it can.

Configuration diagram of the color image forming apparatus of the tandem system (4 drum system) of Examples 1 and 2. Schematic diagram showing the residual toner recovery step of Example 1. Block diagram showing control units of Examples 1 and 2. Schematic diagram showing the toner supply process of Example 1. The conventional figure which shows the simultaneous execution of the residual toner recovery process and the toner supply process of Example 1. The conventional figure which shows the simultaneous execution of the residual toner recovery process and the toner supply process of Example 1. The figure which shows the simultaneous execution of the residual toner recovery process and the toner supply process of Example 1. The figure which shows the simultaneous execution of the residual toner recovery process and the toner supply process of Example 1. The conventional figure which shows the accumulation toner recovery process of the charge brush of Example 2. The conventional figure which shows the simultaneous execution of the accumulation toner recovery process and the toner supply process of the charge brush of Example 2. The conventional figure which shows the simultaneous execution of the accumulation toner recovery process and the toner supply process of the charge brush of Example 2. The figure which shows the simultaneous execution of the accumulation toner recovery process and the toner supply process of the charge brush of Example 2.

Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the drawings by way of examples.

In the first embodiment, the image forming apparatus does not have a means for applying a primary transfer voltage having the same polarity as the regular toner to a third station (hereinafter referred to as st) which is a predetermined station. In such a configuration, cleaning is performed when the recovery step of residual toner on the intermediate transfer belt having a predetermined polarity (first operation) and the toner supply step in 3st (second operation) are performed substantially simultaneously. A method for preventing blade squeal will be described.

[Explanation of the configuration of the image forming apparatus]
FIG. 1 is a configuration diagram of a color image forming apparatus 10 of a tandem system (4 drum system) and an intermediate transfer body system. In the image forming step, the recording material 12 unwound by the pickup roller 13 is located at a position where the tip slightly passes through the transport rollers 64, 65 after the tip position is detected by the registration (hereinafter referred to as resist) sensor 110. The transportation is temporarily stopped at. The scanner units 20a, 20b, 20c, and 20d include a reflection mirror and a laser diode (light emitting element). The color image forming apparatus 10 includes a plurality of stations. Specifically, the first station, the second station, the third station, and the fourth station (hereinafter, 1st to 4st) corresponding to each color of yellow (Y), magenta (M), cyan (C), and black (Bk). (Indicated as). Here, when the 3st is a predetermined station, the station located on the upstream side in the moving direction (described later) from the 3st is the 1st and the 2st, and the station located on the downstream side of the 3st is the 4st.

The 1st to 4st have photosensitive drums 22a, 22b, 22c, and 22d as photoconductors that are rotationally driven at a predetermined outer peripheral speed (hereinafter referred to as a process speed) in the moving direction D2 (clockwise direction). The scanner units 20a to 20d sequentially irradiate the photosensitive drums 22a to 22d with laser light 21a to 21d. The letters a attached to each code indicate yellow, b indicates magenta, c indicates cyan, and d indicates black components, and the same applies to the following description. Hereinafter, the alphabetic characters a to d will be omitted except when a specific color is described.

The photosensitive drum 22 is precharged by the charging roller 23. A voltage of, for example, -1200V is applied to each charging roller 23, and the surface of the photosensitive drum 22 is charged to, for example, -700V. When the surface of the photosensitive drum 22 charged in this way is irradiated with the laser beam 21 to form an electrostatic latent image, the potential of the portion irradiated with the laser beam 21 becomes, for example, −100 V. For example, a voltage of −350 V is applied to the developing sleeve 24 in the developing device 25, and toner having a negative electrode property (predetermined polarity) is supplied to the electrostatic latent image on the photosensitive drum 22 (on the photoconductor). A toner image is developed on the photosensitive drum 22. For example, a positive electrode (opposite polarity) primary transfer voltage (hereinafter referred to as T1 positive voltage) of + 1000 V is applied to the primary transfer roller 26 which is a transfer means. As a result, the toner image of the photosensitive drum 22 is sequentially superimposed and transferred on the intermediate transfer belt 30 (Intermediate Transfer Belt) as the intermediate transfer body. Hereinafter, the operation of transferring the toner image on the photosensitive drum 22 to the intermediate transfer belt 30 is referred to as primary transfer. The toner remaining on the photosensitive drum 22 without being transferred to the intermediate transfer belt 30 is cleaned by the cleaning blade 28. The cleaning blade 28 is an elastic blade made of, for example, urethane rubber.

The intermediate transfer belt 30 is composed of a film-like member endless thickness of about 50~150μm which gave a volume resistivity of from ^{10 7} 10 ¹⁴ Ωcm. The volume resistivity can be obtained by applying 50 to 100 V at a temperature of 25 ° C. and a relative humidity of 50% using a measurement probe conforming to JIS method K6911 and a high resistance meter R2340 manufactured by ADVANTEST. Value. Particularly, in the case of using an intermediate transfer belt 30 having a lower resistivity of about 10 ¹¹ [Omega] cm to 10 ^7, so through the intermediate transfer belt 30 is a current of the primary transfer interfere with each other.

The intermediate transfer belt 30 is provided with a charging brush 9 which is a charging member. The charging brush 9 is installed downstream of the secondary transfer nip portion and upstream of the most upstream primary transfer nip portion. Here, the secondary transfer nip portion is a nip portion formed by the tension roller 33 and the secondary transfer roller 27, and refers to a position where the toner image on the intermediate transfer belt 30 is transferred to the recording material 12. The primary transfer nip portion is a nip portion formed by the primary transfer roller 26 and the photosensitive drum 22, and refers to a position where the toner image on the photosensitive drum 22 is transferred onto the intermediate transfer belt 30. In Example 1, there are four primary transfer nip sections.

The intermediate transfer belt 30 is stretched by the drive roller 31, the tension rollers 32, and 33, and is driven by the drive roller 31 in the moving direction D1 (counterclockwise direction) at the same process speed as the photosensitive drum 22. The intermediate transfer belt 30 conveys the toner image to the position of the secondary transfer roller 27, which is the second transfer means. At this time, the recording material 12 is conveyed so that the transferred toner image and the transfer timing match at the secondary transfer position (or the secondary transfer nip portion) nipped by the secondary transfer roller 27 and the intermediate transfer belt 30. Is restarted. Then, the toner image is transferred from the intermediate transfer belt 30 onto the recording material 12 (on the recording material) by the action of the secondary transfer voltage applied to the secondary transfer roller 27. Hereinafter, the operation of transferring the toner image on the intermediate transfer belt 30 to the recording material 12 is referred to as secondary transfer. After that, the unfixed toner image of the recording material 12 is heat-fixed by the fixing rollers 76 and 77, and then the recording material 12 is output to the outside of the machine.

[Explanation of Secondary Transfer Residual Toner Recovery Process by Secondary Transfer Residual Toner Charge Recovery Method]
Here, the toner that has not been transferred from the intermediate transfer belt 30 to the recording material 12 by the secondary transfer roller 27 is hereinafter referred to as the secondary transfer residual toner. If the secondary transfer residual toner remains without being cleaned and enters the secondary transfer section again, an image defect occurs when it overlaps with the next image on the intermediate transfer belt 30, or it adheres to the secondary transfer roller 27. It causes stains on the back of the paper. Therefore, a secondary transfer residual toner recovery step of removing the secondary transfer residual toner on the intermediate transfer belt 30 is performed. The secondary transfer residual toner recovery step will be described below with reference to FIG. In FIG. 2, RT1 indicates the secondary transfer residual toner charged positively and recovered on the photosensitive drum 22a, and TT1 is the negative electrode transferred from the photosensitive drum 22a to the intermediate transfer belt 30. Indicates toner. In FIG. 2, the 3rd and subsequent steps are omitted.

Each of the primary transfer rollers 26a to 26d has a positive voltage application unit 41a to 41d (first application means) for applying a positive primary transfer voltage and a negative voltage application unit for applying a negative primary transfer voltage. It is connected to an application means having 42a to 42d. Further, the charging brush 9 is connected to an application means having a positive voltage application unit 51 for applying a positive voltage and a negative voltage application unit 52 for applying a negative voltage. The other symbols indicate the same as in FIG.

The secondary transfer residual toner is removed from the intermediate transfer belt 30 by the cleaning step shown below using the charging brush 9. When the secondary transfer residual toner enters the nip portion of the intermediate transfer belt 30 and the charging brush 9, that is, the charging portion, a positive voltage is applied to the charging brush 9 by the positive voltage application unit 51 to release the secondary transfer residual toner. It is positively charged. When the toner positively charged by the charging brush 9 enters the primary transfer unit, a positive voltage is applied to any of the primary transfer rollers 26a to 26d by any of the positive voltage application units 41a to 41d. For example, in FIG. 2, when a positive voltage is applied to the primary transfer roller 26a by the positive voltage application unit 41a, the positively charged toner RT1 is transferred from the intermediate transfer belt 30 to the photosensitive drum 22a as shown in FIG. Toner. Transferring toner from the intermediate transfer belt 30 to the photosensitive drum 22a is hereinafter referred to as reverse transfer. By reverse-transferring the toner in this way, the secondary transfer residual toner is collected from the intermediate transfer belt 30. The charging brush 9 is made of, for example, conductive nylon and has a width of 4 mm and a bristle foot of 4 mm in the circumferential direction of the intermediate transfer belt 30. ..

The positive voltage used for the reverse transfer of the secondary transfer residual toner is also the voltage for the primary transfer of the printed image. Therefore, simultaneous transfer recovery is possible in which the recovery of the secondary transfer residual toner shown in RT1 of FIG. 2 and the primary transfer of the printed image shown in TT1 are performed substantially at the same time. The cleaning method in which the secondary transfer residual toner is charged by the charging brush 9 and is reverse-transferred to the photosensitive drum 22 to be recovered is called a charge recovery method for the secondary transfer residual toner.

[Control configuration of image forming apparatus]
FIG. 3 is a block diagram showing an example of the control unit. The CPU 101 uses the RAM 103 as a work area based on various control programs stored in the ROM 102 to control each part of the color image forming apparatus 10. Various control programs, various data, tables and the like are stored in the ROM 102. A program load area, a work area of the CPU 101, a storage area of various data, and the like are secured in the RAM 103. The drive control unit 108 controls the motor for driving the photosensitive drum 22, the charging roller 23, the scanner unit 20, the developing device 25, the intermediate transfer belt 30, the charging voltage, the developing voltage, and the like in accordance with the command from the CPU 101. The non-volatile memory 109 is a storage device that stores various types of data.

[Explanation of cleaning blade squeal and turning]
While the photosensitive drum 22 rotates in the above-mentioned image forming step or the like, it is necessary to stably maintain the contact of the cleaning blade 28 in a state where the toner can be reliably scraped and the blade does not squeak or turn over. .. Therefore, in addition to the material of the cleaning blade 28, these problems are prevented by optimizing the setting of the contact angle and the intrusion amount. However, even so, when the toner is not sufficiently supplied as described above, problems such as blade squeal and blade turning occur.

[Explanation of toner supply process]
Therefore, as a means for preventing blade squeal, the above-mentioned toner supply process is regularly performed. In the toner supply step, a latent image having a uniform amount in the longitudinal direction is formed in the non-image region of the photosensitive drum 22, and a band-shaped toner image (hereinafter referred to as purge toner) is developed. Then, the purge toner formed on the photosensitive drum 22 is brought to the edge of the cleaning blade 28 to reduce the friction coefficient between the blade and the photosensitive drum 22. Here, the longitudinal direction is a direction orthogonal to the driving direction of the photosensitive drum 22. The condition for executing the toner supply process is that, for example, when 50 pages (predetermined number of pages) are continuously printed, the print ratio, which is the ratio of the toner image portion to the area of the image area, is, for example, 1% or less on average (predetermined ratio or less). ). When this condition is reached, the print control is interrupted and the toner supply process is executed. If a print job remains, the toner supply process may be performed as a rear rotation, the printing process may be completed once, and then the job may be started again from the front rotation. Further, in order to reduce downtime, the toner supply process may be performed between papers and the process may be returned to the next image forming process. The post-rotation refers to a post-processing operation after the image forming operation, and the front rotation refers to a preparatory operation before the image forming operation.

A specific process of the toner supply process will be described with reference to FIG. Note that P1 indicates the purge toner supplied to the cleaning blade 28a. The other symbols indicate the same as those in FIGS. 1 and 2. When the purge toner is developed on the photosensitive drum 22a as described above and then enters the primary transfer section, the negative voltage application section 42a causes, for example, a negative electrode primary transfer voltage of −1000 V (hereinafter, T1 negative voltage). Is applied to the primary transfer roller 26a. By preventing the purge toner P1 from being primarily transferred by this T1 negative voltage, the purge toner P1 is held on the photosensitive drum 22a and reaches the cleaning blade 28a to be supplied.

[Explanation of simultaneous execution of the conventional secondary transfer residual toner recovery process and toner supply process]
In the secondary transfer residual toner charge recovery method, the secondary transfer residual toner continuously enters the primary transfer portion during continuous printing control. Therefore, when the execution conditions of the toner supply process are satisfied and the printing control is interrupted and executed, it is necessary to normally execute the toner supply process and the secondary transfer residual toner recovery process. It is also desirable to execute them at approximately the same time without affecting downtime. The conventional toner supply process and secondary transfer residual toner recovery process will be described below.

The secondary transfer residual toner recovery step and the toner supply step in the 3st in the configuration having the means for applying the T1 negative voltage to the 3st will be described with reference to FIG. RT2 indicates the secondary transfer residual toner charged positively and collected on the photosensitive drum 22, and P2 indicates the purge toner supplied to the cleaning blade 28c. The other symbols indicate the same as in FIG. The secondary transfer residual toner recovery step in the 1st can be normally executed by applying a positive voltage to the primary transfer roller 26a by the positive voltage application unit 41a in the 1st. Further, since the toner supply step in the 3st can also apply a negative voltage to the primary transfer roller 26c by the negative voltage applying unit 42c in the 3st, it can be normally executed in the same manner as the process shown in FIG. .. Next, the relationship between the time zone in which these processes are performed and the timing at which the primary transfer voltage is applied will be described.

FIG. 6 shows the relationship of the timing of applying the primary transfer voltage of each station when the secondary transfer residual toner recovery step is performed in the 1st and the toner supply step is performed in the 3st. FIG. 6A shows the primary transfer process at each station, and FIG. 6B shows the primary transfer voltage (positive voltage (+), negative voltage (−)). Note that T1a indicates the primary transfer process of the toner image on the photosensitive drum 22 at each station. R11 shows a process in which the residual toner after the secondary transfer of the toner image transferred onto the intermediate transfer belt 30 in the previous circuit enters the transfer nip portion of the 1st. PR13 shows the process in which the 3st purge toner enters the transfer nip portion. Further, Tb3 indicates the T1 negative voltage applied by the negative voltage application unit 42c in the 3st time zone of PR13.

First, in the secondary transfer residual toner recovery step, the positive voltage application unit 41a constantly applies the T1 positive voltage during the time zone of R11 in the 1st stage. Therefore, the secondary transfer residual toner does not remain on the intermediate transfer belt 30 and is normally recovered in the 1st stage. On the other hand, in the 3st toner supply process, a negative voltage T1 negative voltage Tb3 of −1000 V is applied by the negative voltage application unit 42c in the time zone of PR13. Therefore, the purge toner is normally supplied to the cleaning blade 28c without being first transferred to the intermediate transfer belt 30. As described above, in the conventional configuration having the negative voltage application unit 42c in the 3st, the secondary transfer residual toner recovery step and the toner supply step use the primary transfer voltage which does not affect each other independently. , In the configuration of FIG. 5, they can be executed substantially at the same time. As shown above, in the configuration having the negative voltage application unit 42c at the 3st, the secondary transfer residual toner recovery step and the toner supply step at the 3st can be executed normally and substantially simultaneously.

However, if the same control is performed in a configuration that does not have the negative voltage applying unit 42c in the 3st, the T1 negative voltage cannot be applied in the time zone of PR13, and it is affected by the primary transfer voltage of the adjacent station. .. Even if the application of the primary transfer voltage is stopped (off) at the 3rd stage, if a T1 positive voltage is applied at any of the adjacent stations as shown in FIG. 6, the purge toner will be applied to the intermediate transfer belt 30. It will be transferred. As described above, there is a problem that a sufficient amount of purge toner is not supplied to the cleaning blade 28c, and the effect of preventing blade squeal cannot be sufficiently obtained. Further, as a countermeasure in this case, it is conceivable to increase the width of the purge toner or perform the toner supply process after the completion of the secondary transfer residual toner recovery process, but in each case, wasteful consumption of toner and downtime are considered. It causes problems such as extension of.

[Explanation of Simultaneous Execution of Secondary Transfer Residual Toner Recovery Step and Toner Supply Step of Example 1]
Therefore, in the first embodiment, in the configuration in which the negative voltage application unit 42d (second application means) which is the negative voltage application means is provided only in the 4st, the secondary transfer residual toner recovery step and the toner supply step in the 3st are carried out substantially simultaneously. And explain how to prevent blade squeal. In the first embodiment, at least the 2st and 3st do not have the negative voltage applying portions (42b, 42c in FIG. 5) for applying the negative voltage to the primary transfer rollers 26b, 26c. FIG. 7 shows the relationship between the application timing of the primary transfer voltage and the voltage polarity of each station when the secondary transfer residual toner recovery step and the toner supply step in the 3st are performed in a configuration in which the negative voltage application unit 42d is provided only in the 4st. Is shown. FIG. 7A shows the primary transfer process and FIG. 7B shows the primary transfer voltage. Further, (c) shows the configuration of each station in the time zone of PR23. Note that R21 indicates a process in which the residual toner after the secondary transfer of the toner image transferred onto the intermediate transfer belt 30 in the previous circuit enters the transfer nip portion of the 1st. PR23 shows the process in which the 3st purge toner enters the transfer nip portion. Further, Tb1a to Tb4a indicate the primary transfer voltage applied at 1st to 4st in the time zone of PR23, respectively. Of the primary transfer voltages, the values (polarities) of the primary transfer voltages Tb2a and Tb4a represented by the broken lines are indefinite, and what kind of combination is appropriate will be described later. What T1a shows is the same as in FIG.

First, in the secondary transfer residual toner recovery step, the secondary transfer residual toner is normally recovered as in the conventional case. On the other hand, in the 3st toner supply process, the amount of purge toner supplied to the cleaning blade 28c differs depending on the setting of the values (polarity) of the primary transfer voltages Tb1a to Tb4a in the time zone of PR23, and the effect of preventing blade squeal. Is different.

Table 1 shows the electric field formed in the 3st primary transfer portion and the level of the blade squeal prevention effect when the polar combination of the primary transfer voltages Tb1a to Tb4a is changed.

In Table 1, the setting numbers (1 to 5) are shown in the first column, the polarity of the primary transfer voltage applied to each primary transfer roller 26 is shown in the second column, and the 3st column shows the polarity. The electric field formed in the primary transfer portion is shown, and the effect of preventing blade squeal is shown in the fourth row. The primary transfer voltage in the second row indicates the primary transfer voltage Tb1a applied to the primary transfer roller 26a and the primary transfer voltage Tb2a applied to the primary transfer roller 26b, respectively. Further, the primary transfer voltage Tb3a applied to the primary transfer roller 26c and the primary transfer voltage Tb4a applied to the primary transfer roller 26d are shown. Regarding the primary transfer voltage applied to each primary transfer roller 26 and the electric field formed, a strong positive voltage is indicated by ++, a weak positive voltage is indicated by +, a strong negative voltage is indicated by −−, and a weak negative voltage is indicated by −. .. The voltage near ± zero is indicated by 0. When the voltage is 0, the application of the voltage from each application unit to the primary transfer roller 26 is stopped. For the level of the blade squeal prevention effect, ○, Δ, and × are used, where ◯ indicates a sufficient effect, Δ indicates a slightly insufficient state, and × indicates an insufficient state. In the 1st, it is necessary to apply a T1 positive voltage for the secondary transfer residual toner recovery step, so the primary transfer voltage Tb1a is set to ++ at any setting number. Further, in the 3st, since it is necessary to avoid applying the T1 positive voltage in order to prevent the purge toner from being transferred to the intermediate transfer belt 30, the primary transfer voltage Tb3a is set to 0 (voltage application stop) at any setting number. ..

In setting number 1, the primary transfer voltages Tb1a, Tb2a, and Tb4a are all ++, and the electric field formed in the primary transfer section of the 3st is affected by the primary transfer voltage of the adjacent station (2st, 4st). In response, it has become ++. In setting number 2, the primary transfer voltage Tb2a is 0, but since the primary transfer voltage Tb4a is ++, the electric field formed in the 3st primary transfer section is affected by the 4st primary transfer voltage Tb4a. Is +. As described above, when the primary transfer voltage of ++ is applied to at least one of the two stations adjacent to the 3st, the 2st and the 4st, the electric field formed in the 3st becomes positive. Therefore, the purge toner is not supplied to the cleaning blade 28c, and the effect of preventing blade squeal is x.

In setting number 3, the primary transfer voltage Tb1a and tb2a are ++, and the primary transfer voltage Tb4a is −−, and the influence of the polarity of the primary transfer voltage of the adjacent station cancels out and the 3st primary transfer unit. The electric field formed in is 0. In setting number 4, the primary transfer voltage Tb1a is ++, the primary transfer voltages Tb2a and Tb4a are 0, and the electric field formed in the 3st primary transfer section is also 0. In this case, the purge toner is not supplied to the cleaning blade 28c as in the setting numbers 1 and 2, but the amount is insufficient and the effect of preventing the blade squeal is Δ.

In setting number 5, the primary transfer voltage Tb1a is ++, the primary transfer voltage Tb2a is 0, and the primary transfer voltage Tb4a is −−, and the electric field formed in the 3st primary transfer section is the 4st primary. It is negative due to the influence of the transfer voltage Tb4a. Since the electric field formed in the primary transfer portion of the 3st has a negative electrode property, the purge toner is supplied to the cleaning blade 28c, and the effect of preventing blade squeal is 〇.

From the results in Table 1, even in the 3st where the zero voltage was applied (in other words, the application of the voltage by the positive voltage application unit 41c was stopped), an electric field was formed although it was not strong due to the interference current from the adjacent station. There is. Then, when the 2st is set to zero and the 4st is set to a strong negative electrode property (++) as in the setting number 5, the electric field formed in the primary transfer portion of the 3st is the negative electrode property. This makes it possible to prevent the purge toner from being transferred to the intermediate transfer belt 30 even in the 3rd stage. As a result, a sufficient effect of preventing blade squeal could be obtained. 8A and 8B are views in the case where the primary transfer voltage at each station is set as shown in the setting number 5 in Table 1, where FIG. 8A shows the primary transfer process and FIG. 8B shows the primary transfer voltage. .. Further, (c) shows the configuration of each station in the time zone of PR23 of Example 1. R21 and the like are the same as in FIG.

Even in the setting number 5, the primary transfer voltage of the 1st is ++, but the electric field formed in the 3st is −, and it can be seen that the voltage applied in the 1st is not affected. This indicates that the resistance value of the intermediate transfer belt 30 used in Example 1 has almost no influence of the interference current at a distance straddling two stations. In this way, even if the primary transfer voltage of the 3st is set to zero, the interference current due to the primary transfer voltage of the adjacent station has an effect. Then, by setting 2st to zero and 4st to negative electrode, both the secondary transfer residual toner recovery step and the toner supply step can be executed normally and substantially simultaneously.

As shown above, even in the configuration in which the T1 negative voltage applying means is not provided in the 2st and 3st but is provided in the 4st, the recovery of the toner having the positive electrode property on the intermediate transfer belt 30 and the toner supply process in the 3st are performed. It can be performed almost at the same time and the blade squeal can be prevented. Further, for that purpose, in the toner supply process at 3st, a primary transfer voltage of zero voltage at 2st and 3st and a negative voltage at 4st may be applied.

[Modification example]
In Example 1, the case where the toner on the intermediate transfer belt 30 is a secondary transfer residual toner having a positive electrode property is shown. However, the configuration of Example 1 can be applied to cases other than the printing process, such as a jam treatment and a patch forming process for controlling image density, in which only the negative electrode toner remains on the intermediate transfer belt 30. .. That is, as described above, the processes after the 1st and 2st can be performed independently. Therefore, even if the residual toner on the intermediate transfer belt 30 has a negative electrode property, the secondary transfer residual toner can be recovered by applying the T1 negative voltage by the negative voltage application unit 42a at 1st. In this case as well, the toner supply steps in the 3rd stage can be performed substantially at the same time, and blade squeal can be prevented. However, in this case, the negative voltage application unit 42a, which is a means for applying the T1 negative voltage to the 1st, is required.

Further, in the first embodiment, the toner supply process in the 3rd st is shown, but when it is desired to supply the toner to the cleaning blade 28 at another station, for example, there are the following methods. When it is desired to supply toner to the 1st cleaning blade 28a, the toner recovered by the secondary transfer residual toner recovery step is supplied to the cleaning blade 28a. When it is desired to supply toner to the 4st cleaning blade 28d, since it has a negative voltage application unit 42d (second application means), the toner is prevented from being transferred to the intermediate transfer belt 30 in a time zone such as PR23. Perform the supply process. In each case, there is no unnecessary downtime. In order to perform the toner supply process on the 2st cleaning blade 28b, it is essential that the 1st has a negative voltage applying portion 42a. In order to perform the toner supply step in the 2st that does not have the negative voltage applying portion, the application state of the primary transfer voltage at the adjacent station is set to be the same as that in the 3st in the PR23 described with reference to FIG. That is, the toner supply process in the 2st is executed by setting the 2st and 3st to zero and the 1st to the negative electrode property according to the setting number 5 in Table 1. However, since it is necessary to set the 3st to zero voltage, in order to execute the toner supply process in the 2st, it is necessary to execute it after the timing when the primary transfer in the 3st is completed.

As described above, according to the first embodiment, the toner supply step and the residual toner recovery step on the intermediate transfer member are both carried out in a configuration in which the primary transfer voltage application means having the same polarity as that of the regular toner is not provided at the predetermined station. can do.

In the second embodiment, there is a configuration in which a means for applying a primary transfer voltage having the same polarity as that of the regular toner is applied only to the 1st and 4th sts. In the second embodiment, a method of preventing blade squealing will be described when the recovery step of the residual toner on the intermediate transfer belt 30 in which the toners of both polarities are mixed and the toner supply step in the 3st are performed substantially at the same time. As a case where toners of both polarities are mixed, a charging brush accumulated toner recovery step of cleaning the charging brush 9 is shown as an example.

[Explanation of charged brush accumulated toner recovery process]
In the charging brush 9, toner is accumulated in the gaps of the charging brush 9 when the secondary transfer residual toner is charged. The toner accumulated in the charging brush 9 (hereinafter referred to as the accumulated toner) causes a deterioration in charging performance, and then the secondary transfer residual toner entering the charging brush 9 is not normally charged. In this case, the residual toner for the secondary transfer remains on the intermediate transfer belt 30 during the primary transfer of the toner image, which causes an image defect. Therefore, the charging brush 9 needs to be cleaned regularly. For example, the CPU 101 executes the accumulated toner recovery step of the charging brush 9 when a condition such as the cumulative number of printed pages reaching a predetermined value is satisfied in the middle of the printing job.

The accumulated toner recovery step of the charging brush 9 will be described below with reference to FIG. Both RP1 and RN1 are toners ejected from the charging brush 9, and are positive and negative. RP1 is positive toner (hereinafter referred to as accumulated positive toner), and RN1 is negative toner (hereinafter referred to as negative toner). , Called accumulated negative toner). Ca1 shows an operation of alternately switching the polarity of the voltage applied to the charging brush 9. That is, switching between an operation of applying a positive voltage to the charging brush 9 by the positive voltage applying unit 51 and an operation of applying a negative voltage to the charging brush 9 by the negative voltage applying unit 52 is shown. The other symbols indicate the same as in FIG.

The accumulated positive toner RP1 and the accumulated negative toner RN1 accumulated in the charging brush 9 are electrostatically charged from the charging brush 9 by alternately applying + 2000V and -2500V to the charging brush 9 as shown by Ca1. It is repelled and discharged onto the intermediate transfer belt 30. Further, when the stored negative toner RN1 enters the 1st primary transfer unit, the negative voltage application unit 42a (first application means) applies a negative voltage of −1000 V to the primary transfer roller 26a to accumulate the toner. The negative toner RN1 is reverse-transferred to the photosensitive drum 22a. Further, when the stored positive toner RP1 invades the 2st primary transfer section, a positive voltage of + 1000 V is applied to the primary transfer roller 26b by the positive voltage applying section 41b, so that the stored positive toner RP1 is transferred to the photosensitive drum 22b. Reverse transcription. As a result, both the accumulated positive toner RP1 and the accumulated negative toner RN1 are recovered from the intermediate transfer belt 30.

[Explanation of simultaneous execution of the conventional charged brush accumulation toner recovery process and toner supply process]
As described above, in the secondary transfer residual toner charge recovery method, when a predetermined condition is reached in the middle of the printing job, the charge brush accumulated toner recovery step is executed, and the accumulated positive toner RP1 and the accumulated negative toner RN1 are generated. Enter the primary transfer section. Therefore, the execution conditions of the charging brush accumulation toner recovery process and the toner supply process are satisfied substantially at the same time, and when the printing control is interrupted and both are executed, it is necessary to execute them normally. It is also desirable to execute them at approximately the same time without affecting each other's downtime. The conventional toner supply process and charged brush accumulated toner recovery process will be described below.

The charging brush accumulation toner recovery step and the toner supply step in the 3st in the configuration having the negative voltage application unit 42c in the 3st will be described with reference to FIG. Both RP2 and RN2 are toners ejected from the charging brush 9, and are positive and negative. RP2 indicates accumulated positive toner, and RN2 indicates accumulated negative toner. P3 indicates the purge toner supplied to the 3st cleaning blade 28c. Ca2 shows an operation of alternately switching the voltage applied to the charging brush 9. The other symbols indicate the same as in FIG.

In the charging brush accumulation toner recovery step in the 1st and 2st, it is possible to apply a negative voltage by the negative voltage application unit 42a in the 1st and a positive voltage by the positive voltage application unit 41b in the 2st. Therefore, it can be normally executed in the same manner as the process shown in FIG. 9 described above. Further, since the toner supply process in the 3st stage can also apply a negative voltage by the negative voltage application unit 42c in the 3rd stage, it can be normally executed in the same manner as the 3st process in FIG. 5 of the first embodiment. Next, the relationship between the time zone in which these processes are performed and the application timing of the primary transfer voltage will be described.

FIG. 11 shows the relationship between the application timings of the primary transfer voltage of each station when the charged brush accumulated toner recovery step is performed in the 1st and 2st steps and the toner supply step is performed in the 3rd st. FIG. 11A shows the primary transfer process at each station, and FIG. 11B shows the primary transfer voltage (+, −). Note that R4P and R4N indicate a process in which the accumulated positive toner RP2 and the accumulated negative toner RN2 on the intermediate transfer belt 30 enter the transfer nip portions of the 2st and 1st, respectively. PR33 shows the process in which the 3st purge toner enters the transfer nip portion. Further, Tb1b to Tb3b indicate the primary transfer voltage applied at 1st to 3st in the time zone of PR33, respectively. What T1a shows is the same as in FIG.

First, in the charging brush accumulated toner recovery step, a T1 negative voltage of −1000 V is constantly applied by the negative voltage application unit 42a in the time zone of R4N in the 1st. Further, in the time zone of R4P in the 2st, the positive voltage application unit 41b constantly applies a T1 positive voltage of + 1000V. That is, since the charging brush accumulated toner recovery step is in the state described with reference to FIG. 10, both the accumulated positive toner RP2 and the accumulated negative toner RN2 are normally recovered. On the other hand, in the 3st toner supply process, the primary transfer voltage Tb3b, which is a T1 negative voltage of −1000 V, is applied by the negative voltage application unit 42c in the time zone of PR33. Therefore, the purge toner is normally supplied to the cleaning blade 28c without being first transferred to the intermediate transfer belt 30. Since the primary transfer voltage that does not affect each other independently is used in the charging brush accumulation toner recovery step and the toner supply step, they can be executed at the same time. As described above, in the conventional configuration having the means for applying the T1 negative voltage to the 3st, the charging brush accumulation toner recovery step and the toner supply step in the 3st can be executed normally and substantially simultaneously.

However, if the same control is performed in a configuration that does not have a means for applying the T1 negative voltage to the 3st, the T1 negative voltage cannot be applied in the 3st during the time zone of PR33, and the influence of the primary transfer voltage of the adjacent station is affected. I will receive it. For example, as shown in FIG. 11, when a T1 positive voltage is applied at any of the adjacent stations, the purge toner is transferred to the intermediate transfer belt 30 at the 3st primary transfer nip portion under the influence of the T1 positive voltage. Then, a sufficient amount of purge toner is not supplied to the cleaning blade 28c, and there is a problem that the effect of preventing blade squeal cannot be sufficiently obtained. Further, as a countermeasure in this case, it is conceivable to increase the width of the purge toner or perform the toner supply process after the completion of the secondary transfer residual toner recovery process, but in each case, wasteful consumption of toner and downtime are considered. Causes issues such as extension.

[Explanation of Simultaneous Execution of Charged Brush Accumulated Toner Recovery Step and Toner Supply Step of Example 2]
Therefore, in the second embodiment, the negative voltage application units 42a and 42d for applying the T1 negative voltage only to the 1st and 4st are configured. The 2st and 3st do not have a negative voltage application part. In such a configuration, a method for preventing blade squealing will be described when the charging brush accumulation toner recovery step and the toner supply step in 3st are performed substantially at the same time.

FIG. 12 shows a configuration in which negative voltage application portions 42a and 42d are provided only on the 1st and 4st, and the application timing and voltage of the primary transfer voltage of each station when performing the charging brush accumulation toner recovery step and the toner supply step in the 3st It shows the relationship of polarity. FIG. 12A shows the primary transfer process and FIG. 12B shows the primary transfer voltage. Further, (c) shows the configuration of each station in the time zone of PR43 of Example 2. Note that R5N indicates a process in which the accumulated negative toner on the intermediate transfer belt 30 enters the 1st T1 nip portion. R5P shows the process in which the accumulated positive toner on the intermediate transfer belt 30 enters the 2st T1 nip portion. PR43 shows the process in which the 3st purge toner enters the T1 nip portion. Tb2c, Tb3c1, and Tb4c indicate the primary transfer voltage applied at 2st to 4st in the time zone of PR43, respectively. PT43 shows the process in which the toner that has passed through the 2st during the time period when the primary transfer voltage Tb2c is applied in the 2st enters the T1 nip portion of the 3st. Tb3c2 indicates the primary transfer voltage applied at 3st in the time zone of PT43. What T1a shows is the same as in FIG.

First, in the time zone of PR43, because of the 3st toner supply process, the 2st and 3st primary transfer voltages Tb2c and Tb3c1 are zero voltages (application stop) as in the configuration in Example 1 (setting number 5 in Table 1). ), A negative voltage is applied to the 4st primary transfer voltage Tb4c. As a result, it is possible to prevent the purge toner from being transferred to the intermediate transfer belt 30 in the 3rd stage as in the first embodiment, and a sufficient effect of preventing blade squeal can be obtained.

Further, regarding the charge brush accumulated toner recovery step, the accumulated negative toner is normally recovered by applying a T1 negative voltage of −1000 V by the 1st negative voltage applying unit 42a at R5N as in the conventional case. On the other hand, the accumulated positive toner is normally recovered by applying a T1 positive voltage of + 1000 V by the 2st positive voltage application unit 41b at R5P as in the conventional case, except for the time zone of PR43. However, in the time zone of PR43, 0V is set for the primary transfer voltage Tb2c in the 2st as described above. Therefore, the accumulated positive toner is not normally recovered in the time zone of PR43, and passes through the 2st primary transfer unit. Therefore, in the time zone of PT43 when the accumulated positive toner that was not recovered in the 2st enters the 3st, the primary transfer voltage Tb3c2, which is a positive voltage of + 1000V suitable for recovering the secondary transfer residual toner, is applied to the positive voltage application unit 41c of the 3st. Apply by. As a result, the accumulated positive toner that has passed through the T1 nip portion of the 2st is reverse-transferred to the photosensitive drum 22c at the 3st and recovered. In this way, all accumulated positive toner can be recovered. If the primary transfer voltage of the 3st is set to 0V for the toner supply process of the 3st in this way, the voltage polarities of other stations will affect it. However, with the settings as described above, both the charging brush accumulation toner recovery step and the toner supply step can be executed normally and substantially simultaneously.

As shown above, the second embodiment has a configuration having negative voltage application units 42a and 42d for applying a T1 negative voltage to the 1st and 4th. Even in such a configuration, the recovery of the residual toner on the intermediate transfer belt 30 in which the toners of both polarities are mixed and the toner supply step in the 3st can be performed substantially at the same time, and blade squeal can be prevented. Further, for that purpose, in the recovery of the bipolar toner, a negative electrode voltage may be applied at 1st and a positive voltage may be applied at 2st. In the toner supply step at 3st, a primary transfer voltage of zero voltage at 2st and 3st and a negative voltage at 4st is applied as in Example 1. In addition, a positive primary transfer voltage may be applied at the 3st in the time zone when the region on the intermediate transfer belt 30 that has passed the 2st for the 3st toner supply process enters the 3st.

[Modification example]
Further, in the second embodiment, the toner supply process in the 3st is shown, but when it is desired to supply the toner to the cleaning blade at another station, for example, the following method is available. In the 1st, the toner recovered by the secondary transfer residual toner recovery step is supplied to the cleaning blade 28a. Further, the 4st has a negative voltage application unit 42d, and performs a toner supply step for preventing transfer in a time zone such as PR43. There is no unnecessary downtime in either case. In the 2st, the application state of the primary transfer voltage at the adjacent station is set to be the same as that in the 3st in the PR43. That is, the 2st and 3st are set to the primary transfer voltage of zero voltage, and the 1st is set to the negative primary transfer voltage. As a result, the toner supply process in the 2st is executed. However, since it is necessary to set the primary transfer voltage of the 3st to zero voltage, in order to execute the toner supply process in the 2st, it is necessary to execute it after the timing when the primary transfer in the 3st is completed.
Further, as shown in FIG. 7C, when the 2st and 3st have only one positive voltage application unit 41b and 41c, respectively, the positive voltage application units 41b and 41c are shared to have one positive voltage application unit. It may be configured.

As described above, according to the second embodiment, both the toner supply step and the recovery step of the residual toner on the intermediate transfer member are carried out in a configuration in which the primary transfer voltage application means having the same polarity as that of the regular toner is not provided at the predetermined station. can do.

22a to 22d Photosensitive drums 26a to 26d Primary transfer rollers 28a to 28d Cleaning blade 30 Intermediate transfer belt 41a to 41d Positive voltage application part 42d Negative voltage application part

Claims (7)

The photoconductor, a developing device for forming a toner image having a predetermined polarity on the photoconductor, a transfer means for transferring the toner image on the photoconductor, and the transfer means having the predetermined polarity. The toner remaining on the photoconductor after the transfer of the toner image of the predetermined polarity by applying the voltage of the opposite polarity to the first application means for applying the voltage of the opposite polarity and the transfer means. With a plurality of stations having a blade abutting the photoconductor for cleaning the
An intermediate transfer body that comes into contact with the plurality of photoconductors and is transferred by superimposing toner images on the plurality of photoconductors.
With
After transferring the toner image on the intermediate transfer body to the recording material, the toner remaining on the intermediate transfer body is collected at a station located upstream of a predetermined station in the moving direction of the intermediate transfer body. An image forming apparatus capable of performing the operation of the above and a second operation for supplying the toner of the predetermined polarity to the blade of the predetermined station.
A second applying means for applying a voltage of the predetermined polarity to the transfer means of a station adjacent to the station downstream of the predetermined station in the moving direction is provided.
When performing the second operation,
No voltage is applied to the transfer means of the station adjacent to the upstream side in the moving direction of the predetermined station.
No voltage was applied to the transfer means at the predetermined station.
An image forming apparatus, characterized in that a voltage of the predetermined polarity is applied to the transfer means of a station adjacent to the downstream side by the second application means. The plurality of stations are provided in the order of a first station, a second station, a third station, and a fourth station from the upstream side in the moving direction.
The station located at the most upstream in the moving direction is the first station.
The station adjacent to the upstream side is the second station.
The predetermined station is the third station,
The image forming apparatus according to claim 1, wherein the station located on the downstream side is the fourth station. With respect to the moving direction, the toner provided on the downstream side of the position where the toner image on the intermediate transfer body is transferred to the recording material and on the upstream side of the first station, and remains on the intermediate transfer body. A charging member for charging to the opposite polarity is provided.
In the first station, by applying a voltage of the opposite polarity to the transfer means by the first applying means, the first is applied to the toner charged to the opposite polarity by the charging member. The image forming apparatus according to claim 2, wherein the operation is performed. With respect to the moving direction, the toner provided on the downstream side of the position where the toner image on the intermediate transfer body is transferred to the recording material and on the upstream side of the first station, and remains on the intermediate transfer body. A charging member for charging to the predetermined polarity and the opposite polarity is provided.
The first application means of the first station can apply a voltage of the predetermined polarity.
In the first station, by applying a voltage of the predetermined polarity to the transfer means by the first application means, the first is charged with respect to the toner charged to the predetermined polarity by the charging member. Do the action,
In the second station, by applying a voltage of the opposite polarity to the transfer means by the first applying means, the first is applied to the toner charged to the opposite polarity by the charging member. The image forming apparatus according to claim 2, wherein the operation is performed. After the second operation is completed, the first applying means of each of the second station, the third station and the fourth station has a voltage of the opposite polarity to each of the transfer means. The image forming apparatus according to claim 3 or 4, wherein the image forming apparatus is applied. The image forming apparatus according to any one of claims 2 to 5, wherein the fourth station is a black station. The second operation is executed when the number of pages printed continuously reaches a predetermined number of pages and the condition that the print ratio is equal to or less than the predetermined ratio is satisfied. The image forming apparatus according to any one of claims 1 to 6.

Images