JP2011090037A - Developing system and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a developing system for preventing toner from scattering from an opening formed in a casing, and to provide an image forming apparatus. <P>SOLUTION: The developing system includes: a shutter means 38 opening and closing the opening 35a formed in the casing 35; and a drive control part which has a determination means for determining whether or not the electrification amount of the toner is in a reduced state when the formation of an image is started, and in which when the determination means determines that the electrification amount of the toner is in the reduced state, the opening 35a is closed by the shutter means 38, and a first conveying screw 11, a second conveying screw 12 and a developing sleeve 14 are driven for a predetermined time, to secure the electrification amount of the toner. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a developing system used in an electrophotographic image forming apparatus, and more particularly to a technique for preventing toner from scattering from an opening formed in a developing unit.

  A developing unit is one component of an electrophotographic image forming apparatus. The developing unit includes, for example, a casing provided with a rectangular opening, and a developer (toner and carrier) in the casing that is rotatably supported in the casing so that a part of the outer peripheral surface can be seen through the opening. ) Is conveyed toward the opening, and the developer is provided in the casing to stir the developer in the casing to charge the toner and move the developer to the vicinity of the developer carrier. Some of them are configured with an agent stirring mechanism. The developing unit is disposed in the image forming apparatus so that the developer carrying member, a part of the outer peripheral surface of which is exposed from the opening, faces the photosensitive member. Further, this developing unit is configured as a process unit that can be attached to and detached from the main body of the image forming apparatus together with the above-described photosensitive member and the photosensitive member unit configured to charge the surface of the photosensitive member. .

By the way, when the developing unit and the process unit described above perform an image forming operation immediately after being mounted on the main body of the image forming apparatus, the frictional charging of the toner caused by the agitation of the carrier and the toner remains in an insufficient state. Often transported. In such a case, the weakly charged toner or the uncharged toner is scattered from the opening without adhering to the photosensitive member disposed opposite to the developer carrying member, and the image forming apparatus is soiled.
Therefore, as a solution to such a problem, there has been proposed a shutter unit that shields the opening of the developing device when toner or developer is supplied when the developing unit or process unit is replaced to prevent toner scattering. (For example, refer to Patent Document 1).

  However, in the above, since the toner scattering by the shutter means is prevented only when the toner or developer is supplied when the process unit is replaced, the image forming operation is started when the image forming operation is not performed for a long time. For example, toner scattering when the toner charge amount during normal image formation is reduced is not taken into consideration.

  Accordingly, the present invention has been made in view of such a situation, and an object thereof is to provide a developing system and an image forming apparatus that can solve the above problems.

In order to solve the above problems, the developing system and the image forming apparatus according to the present invention employ the following technical means.
According to a first aspect of the present invention, there is provided a developing system used in an electrophotographic image forming apparatus, wherein the casing is formed with an opening, and a part of the outer peripheral surface is viewed from the opening. A roller-shaped developer carrier that conveys the developer stored in the casing toward the opening, and a roller-shaped developer carrier that is rotatably provided in the casing. A developer agitating section for agitating the developer stored in the container by rotation to charge the toner as one component of the developer and moving the developer to the vicinity of the developer carrying body; and the opening. A shutter unit that opens and closes the opening when necessary, and a determination unit that determines whether or not the charge amount of the toner is in a reduced state at the start of image formation. When the determination unit determines that the charge amount of the toner is in a lowered state, the shutter unit closes the opening, and drives the developer stirring unit and the developer carrier for a predetermined time. And a developing system including a drive control unit for ensuring the charge amount of the toner.
According to a second aspect of the present invention, in the first aspect, a counter is provided for measuring a time from the end of the previous image forming operation of the image forming apparatus. Is equal to or greater than a predetermined threshold value, it is determined that the charge amount of the toner is in a lowered state.
According to a third aspect of the present invention, in the first aspect, the determination unit applies heat and pressure to a sheet-like recording material carrying a toner image developed by the developer carrier, and records the toner image. When a thermostat for fixing temperature control, which is one component of a fixing unit for fixing to a material, is used, and the temperature detected by the thermostat is equal to or lower than a predetermined threshold, it is determined that the charge amount of the toner is in a lowered state. It is characterized by that.
According to a fourth aspect of the present invention, in the first aspect, a temperature / humidity sensor is provided in the vicinity of the casing or the opening, and the determination means has a predetermined temperature / humidity detected by the temperature / humidity sensor at the start of image formation. When the temperature is higher than the temperature and humidity, it is determined that the charge amount of the toner is in a lowered state.
According to a fifth aspect of the present invention, in the first aspect, the determination unit uses a magnetic permeability sensor that detects a toner concentration of the developer stored in the casing, and the image forming unit at the end of the previous image formation is used. When the difference between the output value of the magnetic permeability sensor and the output value of the magnetic permeability sensor at the start of the current image formation is equal to or greater than a predetermined threshold value, it is determined that the charge amount of the toner is in a lowered state. It is characterized by.
According to a sixth aspect of the present invention, in the first aspect of the present invention, there is provided a blower that allows dry air to flow inside the casing, a humidity sensor that detects the humidity inside the casing or the humidity of the developer, and the determination unit. Determines that the charge amount of the toner is in a lowered state when the detection result of the humidity sensor is equal to or greater than a predetermined threshold value at which the humidity is determined to be high, and the drive control unit The air blowing unit is also driven for a predetermined time together with the stirring unit and the developer carrying member.
According to a seventh aspect of the present invention, there is provided the optical sensor according to the first aspect, wherein the optical sensor for detecting the reflected light of the toner image and detecting the image density of the toner image is provided. When the density is equal to or higher than a predetermined threshold value determined to be appropriate or high, it is determined that the toner charge amount is in a lowered state.
The invention according to claim 8 is characterized in that the configurations according to claims 2 to 7 are arbitrarily combined.
According to a ninth aspect of the invention, there is provided an image forming apparatus including the developing system according to any one of the first to eighth aspects.

  According to the present invention, even when the charge amount of the toner is reduced at the time of normal image formation, such as at the start of image formation when the image formation operation has not been performed for a long period of time, the weakly charged toner or It is possible to prevent the charged toner from scattering from the opening.

1 is a schematic diagram showing an outline of an image forming apparatus according to an embodiment. It is a typical longitudinal section of the process unit concerning Embodiment 1 in the state where the shutter was opened. It is a typical longitudinal section of the process unit concerning Embodiment 1 of a state where the shutter was closed. FIG. 6 is a diagram showing measurement results of toner charge amounts in the image forming apparatus according to the first embodiment and a conventional image forming apparatus without a shutter. FIG. 6 is a diagram showing measurement results of toner scattering amounts in the image forming apparatus according to the first embodiment and a conventional image forming apparatus without a shutter. FIG. 3 is a flowchart illustrating an operation of the image forming apparatus according to the first embodiment. FIG. 6 is a diagram illustrating a relationship between a toner charge amount and a toner scattering amount. FIG. 6 is a diagram illustrating a relationship between a standing time after an image forming operation and a toner charge amount. FIG. 10 is a flowchart illustrating an operation of the image forming apparatus according to the second embodiment. FIG. 6 is a diagram showing a relationship between a standing time after an image forming operation is performed and a detected temperature of a thermostat for fixing temperature control. FIG. 5 is a diagram showing the relationship between the number of sheets passing through and the toner charge amount in a low temperature and low humidity environment and a high temperature and high humidity environment. FIG. 10 is a flowchart illustrating an operation of the image forming apparatus according to the fourth embodiment. FIG. 6 is a diagram illustrating a relationship between an output value of a magnetic permeability sensor that detects a toner concentration of a developer and a toner charge amount. FIG. 10 is a schematic longitudinal sectional view of a process unit according to a fifth embodiment. FIG. 10 is a flowchart illustrating the operation of the image forming apparatus according to the fifth embodiment. FIG. 6 is a diagram showing the relationship between the stirring time and the toner charge amount when the humidity condition is changed. FIG. 5 is a diagram showing the relationship between developer agitation time and toner charge amount with and without a dry air blowing operation. FIG. 10 is a flowchart illustrating an operation of an image forming apparatus according to a sixth embodiment.

  An embodiment of an image forming apparatus provided with a developing system according to the present invention will be described. The image forming apparatus according to the present embodiment exemplifies a full-color output compatible laser printer that receives image information transmitted from the outside and forms an image on a sheet based on the image information. First, a basic configuration of an image forming apparatus common to the respective embodiments will be described with reference to FIGS. 1 and 2.

  As shown in FIG. 1, the image forming apparatus according to the present embodiment includes four process units 1 for yellow, cyan, magenta, and black (hereinafter referred to as Y, C, M, and K). The four process units 1 have the same configuration except for the color of the toner to be used. Taking the process unit 1 for generating a Y toner image as an example, the process unit 1 has a photosensitive unit and a developing unit A as shown in FIG. These photosensitive unit and developing unit A can be integrally attached to and detached from the image forming apparatus main body.

FIG. 2 shows a schematic longitudinal sectional view of the process unit 1.
The photosensitive unit includes a photosensitive drum 2 as a photosensitive member, a drum cleaning device 3 that removes and collects transfer residual toner and the like adhering to the photosensitive drum 2, and a lubricant coating for setting the surface friction coefficient of the photosensitive drum 2 to a predetermined value. A brush 4 and a lubricant 5 (zinc stearate), a lubricant application blade 6 for uniformly applying the lubricant 5 onto the photosensitive drum 2, a charging roller 7 for uniformly charging the photosensitive drum 2, and the like are provided.

  The charging roller 7 uniformly applies a charging bias obtained by superimposing a DC voltage on an AC voltage from a charging bias applying unit (not shown) to the surface of the photosensitive drum 2 that is rotated in a clockwise direction in the drawing by a driving unit (not shown). It is charged. Subsequently, exposure scanning is performed with a laser beam emitted from the exposure unit 18 (FIG. 1) corresponding to the image signal to form an electrostatic latent image.

  The developing unit A includes a first conveying screw 11 that is rotatably supported by the first developer accommodating portion 8 and a second conveying screw 12 that is rotatably supported by the second developer accommodating portion 9. The formed developer agitating portion, the developing sleeve 14 as the developer carrying member, the first developer accommodating portion 8 and the second developer accommodating portion 9 are formed, and the first conveying screw 11 and the second conveying screw 12 are developed. A casing 35 for supporting the sleeve 14 and the like and having a rectangular opening 35a extending in the depth direction in FIG. 2 on the right upper side wall, and shutter means 38 for opening and closing the opening 35a of the casing 35 are provided. ing.

  Further, a magnetic permeability sensor 10 for detecting the toner concentration is installed on the lower surface of the first developer accommodating portion 8, and the mixing ratio between the carrier, which is a magnetic material, and the toner is calculated from the magnetic permeability, Toner density is replenished as necessary from a toner replenishing device (not shown).

  The first conveying screw 11 is rotationally driven by a driving unit (not shown), and conveys the developer in the first developer accommodating portion 8 from the back side to the near side in FIG. The developer is moved into the second developer accommodating portion 9 through a communication port (not shown) provided in the partition wall 13 erected between the two developer accommodating portions 9.

  The second conveying screw 12 is driven to rotate counterclockwise in FIG. 2 by a driving means (not shown), and conveys the developer in the second developer accommodating portion 9 from the near side to the far side in FIG. The developer is moved into the first developer accommodating portion 8 through a communication port (not shown) provided on the side opposite to the communication port, and a developer carrier described later provided above the second conveying screw 12. The developer is moved to the vicinity of the developing sleeve 14.

  In addition, the developer agitation unit configured with the first conveyance screw 11 and the second conveyance screw 12 is a component of the developer that agitates the developer stored in the casing 35 by rotation. A certain toner is charged.

  The developing sleeve 14 is formed in a cylindrical shaft shape by a nonmagnetic material (aluminum) whose surface is roughened by sandblasting in order to enhance the developer conveying capability, and the second developing screw 14 is located at the upper right of the second conveying screw 12. It is arranged so as to be parallel to the conveying screw 12 and a part of the outer peripheral surface is viewed from the opening 35a, and is driven to rotate counterclockwise in the figure by a driving means (not shown). going on. In addition to the rough surface by sandblasting, the developing sleeve 14 is provided with grooves with equal intervals (axial groove, iris shape, lattice shape, etc.) in addition to the rough surface by sandblasting. It is.

  A magnet roller 16 having magnetic poles 15 alternately formed in the circumferential direction is inserted into the developing sleeve 14, and a part of the developer conveyed by the second conveying screw 12 is emitted from the magnet roller 16. It is pumped up to the surface of the developing sleeve 14 by the magnetic force, and rises.

  Also, a doctor blade 17 capable of scraping off excess developer out of the developer pumped and adhered to the surface of the developing sleeve 14 is provided so as to maintain a predetermined gap with the developing sleeve 14. After the developer layer thickness is regulated by the doctor blade 17, the developer drum 2 is transported to a developing area facing the photosensitive drum 2, and is applied to the developing sleeve 14 from a developing bias applying unit (not shown) by the developing bias. Toner is attached to the electrostatic latent image formed thereon, and developed into a toner image. The developer that has consumed toner by this development is returned to the second conveying screw 12 as the developing sleeve 14 rotates. And if it conveys to the back end in a figure, it will return in a 1st accommodating part through the communication port which is not shown in figure.

  As shown in FIGS. 2 and 3, the shutter unit 38 is provided below the opening 35 a and the shutter 36 formed in a plate shape having a required size capable of closing the opening 35 a. The driving unit 37 is configured to support and to open and close the opening 35a by moving the shutter 36 forward and backward. The drive unit 37 is electrically connected to a drive control unit described later. FIG. 2 shows a state where the shutter 36 is moved backward and the opening 35a is opened, and FIG. 3 shows a state where the shutter 36 is moved forward and the opening 35a is closed. A series of operations by the drive control unit will be described in detail in Embodiments 1 to 6 described later.

  Below the process unit 1, as shown in FIG. 1, an exposure unit 18 as electrostatic latent image writing means is disposed. The exposure unit 18 irradiates the surface of the photosensitive drum 2 of each process unit 1 with laser light based on the image information. Thereby, an electrostatic latent image is formed on the photosensitive drum 2.

  The exposure unit 18 scans laser light emitted from a laser diode as a light source by a polygon mirror that is rotationally driven by a motor, and irradiates the photosensitive drum 2 through a plurality of optical lenses and mirrors. Instead of such a configuration, an exposure unit 18 using an LED array may be employed.

  Below the exposure unit 18, a first paper feed cassette 19 and a second paper feed cassette 20 are disposed. Each of these paper feed cassettes stores recording paper as a recording medium, and the recording paper is discharged to the paper feed path 22 by a paper feed means 21 composed of a plurality of rollers or the like. there.

  A registration roller pair 23 is disposed in the paper feed path 22. The registration roller pair 23 waits while sandwiching the recording paper, and is driven in accordance with the timing at which a toner image formed on an intermediate transfer belt 24 described later reaches the secondary transfer nip, thereby transferring the recording paper to the secondary transfer. It is designed to feed toward the nip. The secondary transfer nip is an area where a driving roller 28 and a secondary transfer roller 30 described later are in pressure contact with each other via the intermediate transfer belt 24.

  Above each process unit 1, an endless intermediate transfer belt 24 spanned by a plurality of rollers is provided, and a transfer unit that rotates the intermediate transfer belt 24 counterclockwise in the drawing is disposed. . Above the transfer unit, four toner bottles 25 for storing toners of respective colors Y, C, M, and K are disposed. The toner of each color stored in the toner bottle 25 is appropriately supplied to the developing unit A of the process unit 1 of each color. These toner bottles 25 are detachable from the main body of the image forming apparatus so that they can be replaced when the remaining amount of toner in the bottles is exhausted.

  In addition to the above-described intermediate transfer belt 24, the transfer unit described above receives a belt cleaning unit 26, a primary transfer roller 27 disposed at a position where the photosensitive drums 2 of the respective colors face each other, and external driving, and receives the intermediate transfer belt 24. And a driven roller 29 provided at a predetermined interval from the driving roller 28. The drive roller 28 also serves as a counter roller for the secondary transfer roller 30.

  The primary transfer roller 27 is pressed against the photosensitive drum 2 with the lower belt of the intermediate transfer belt 24 interposed therebetween, and forms a primary transfer nip. The toner image on the photosensitive drum 2 is transferred onto the intermediate transfer belt 24 by applying a transfer bias having a polarity opposite to that of the toner image formed on the photosensitive drum 2 to the primary transfer roller 27. The toner images of the respective colors formed by the image forming units of the respective colors are sequentially primary transferred onto the intermediate transfer belt 24 so as to overlap each other, and a color toner image is formed on the intermediate transfer belt 24.

  The color toner image formed on the intermediate transfer belt 24 is moved to the secondary transfer nip by the rotational drive of the intermediate transfer belt 24, and at the same time, is recorded in synchronization with the toner image entering the secondary transfer nip from the registration roller pair 23. The paper enters the secondary transfer nip.

  The color toner image is secondarily transferred onto the recording paper by a secondary transfer electric field and a nip pressure formed between the secondary transfer roller 30 and the secondary transfer counter roller. The electric field for secondary transfer is formed by applying a transfer bias having the same polarity as the toner to the secondary transfer counter roller and grounding the secondary transfer roller 30.

On the intermediate transfer belt 24 after passing through the secondary transfer nip, a small amount of toner that has not been transferred onto the recording paper remains and adheres. This is cleaned by the belt cleaning unit 26. In the belt cleaning unit 26, the cleaning blade is brought into contact with the surface of the intermediate transfer belt 24, whereby the transfer residual toner on the belt is scraped and removed.
The transfer residual toner removed from the intermediate transfer belt 24 is accommodated in the waste toner bottle 31 and discarded.

  A fixing unit is disposed above the secondary transfer nip. The fixing unit includes a fixing roller 32 including an electromagnetic induction heat generating layer, a pressure roller 33 which is pressed against the fixing roller 32 with a predetermined pressure to form a predetermined nip width, a thermostat 39 for fixing temperature control, and a fixing unit. On the left side of the roller 32 in the figure, an IH coil unit 34 that generates heat from the electromagnetic induction heat generating layer in the fixing roller 32 is provided. The fixing roller 32 is heated by electromagnetic induction by an IH coil. Each roller is configured such that a pressure roller 33 is rotated in a clockwise direction and a fixing roller 32 is rotated in a counterclockwise direction by a driving source (not shown).

The recording paper that has passed through the secondary transfer nip is separated from the intermediate transfer belt 24 and then fed into the fixing unit. In the process of being conveyed from the lower side to the upper side in the figure while being sandwiched between the fixing nips of the fixing unit, the toner image is fixed on the recording paper by being heated by the fixing roller 32 and simultaneously being pressurized by the fixing nip. .
The recording paper subjected to the fixing process in this manner is discharged out of the apparatus via a pair of paper discharge rollers and is stacked on the upper surface of the main body of the image forming apparatus.

Hereinafter, each embodiment of the development system will be described in detail. The developing system includes the above-described developing unit A and a drive control unit described later.
(Embodiment 1)
In the first embodiment, in addition to the basic configuration of the image forming apparatus described above, a counter (not shown) that records the time from the end of the previous image forming operation of the image forming apparatus is provided. Drive control that closes the opening 35a by the shutter means 38 and drives the first conveying screw 11, the second conveying screw 12, and the developing sleeve 14 for a predetermined time when the counter value becomes equal to or greater than a predetermined threshold at the start. This is an example in which a section (not shown) is provided.

  In FIG. 4, after the developer is left for 72 hours in an environment of 27 ° C. and 80% RH, the opening 35a is closed by the shutter means 38, and the first conveying screw 11 and the second conveying screw 12 and the developing sleeve 14 are left for a predetermined time. The measurement results of the toner charge amount (Q / M) in the case of driving (hereinafter referred to as “preprocessing operation”) (preprocessing operation ant) and in the case of not performing the operation (preprocessing operation pear) are shown.

From FIG. 4, it can be seen that the pre-processing operation ant has a significantly higher toner charge amount than the pre-processing operation pear.
FIG. 5 shows the result of monitoring the toner scattering amount from the start of image formation with a dust track (light scattering digital dust meter). It can be seen that the pre-processing operation ant significantly reduces the toner scattering amount compared to the pre-processing operation pear.
By performing the pre-processing operation as described above, it is possible to prevent toner scattering from the opening 35a and problems associated therewith.

  In the case of an image forming device that is used to form a large amount of printed images at once (for production printing applications), the pre-processing operation is executed at the start of each image formation because the movable time for one image formation is long. However, side effects such as waiting time of the user (user of the image forming apparatus), increase in power consumption, and deterioration of the developer with respect to the amount of the printed matter are almost negligible. In an image forming apparatus (for office use) that is used to form an image, the side effect on the printing amount becomes a big problem.

For example, when comparing A and B image forming apparatuses as described below, the weight of the side effect per printed matter is B is 1000 times that of A.
A: Image forming apparatus with an average of 5000 printed pages at one time (for production printing)
B: Image forming apparatus with an average of 5 printed pages at once: B (for office use)

  Therefore, in the first embodiment, the drive control unit performs control as shown in FIG. 6 in order to be applicable to an image forming apparatus for office use. That is, when the image forming operation is completed (S11), integration of the OFF time by the counter is started (S12), and the count value a is set on condition that the image forming request by the user is input or the image forming request is made from the PC. A comparison between [sec] and the threshold value X1 [sec] is performed (S13 (determination means)).

Only when the count value a [sec] reaches or exceeds the threshold value X1 [sec] (S13Y), the above pre-processing operation is executed (S14), the count value a is set to “0”, and the shutter unit 38, the opening 35a is opened, and the image forming operation is started (S15).
On the other hand, when the count value a has not reached the threshold value X1 (S13N), the count value a is set to “0” without executing the above-described preprocessing operation, and the image forming operation is started (S15).

  In order to enable the preprocessing operation only immediately before the image formation, as described above, S13 is determined on the condition that an image formation request by the user is input or an image formation request is made from the PC. However, when the pre-processing operation is appropriately performed even when the image formation is not performed, the determination at S13 may be performed at any time regardless of the image formation request time.

The threshold value X1 is determined as follows, for example.
First, using the image forming apparatus illustrated in FIG. 1, the relationship between the toner scattering amount and the toner charge amount shown in FIG. 7 was obtained. As shown in FIG. 7, when the toner charge amount (Q / M) becomes smaller than 20 [−μC / g], it can be seen that the toner scattering amount rapidly increases. Therefore, the toner charge amount (Q / M) at the start of image formation needs to be 20 [−μC / g] or more.

FIG. 8 shows the relationship between the standing time after the image forming operation is executed and the toner charge amount in the normal environment (23 ° C., 50% RH). The toner charge amount (Q / M) also decreases as the standing time increases, but the toner charge amount (Q / M) is 20 [−μC / g] during the standing time of 40000 to 50000 [sec]. You can see that
As a result of considering the experimental results shown in FIGS. 7 and 8, the margin X1 in the image forming apparatus of the first embodiment is set to 40000 [sec] in consideration of the margin. Note that the threshold value X1 can be changed by a service person or a user because an appropriate value varies depending on the machine specification and the use environment.

  As described above, according to the image forming apparatus according to the first embodiment, the execution condition of the preprocessing operation is set to the time when the developer is left, so that even in an image forming apparatus for office use, the drive control unit The pre-processing operation is executed, and the charge amount of the lowered toner becomes a sufficient charge amount, and it is possible to reliably prevent the toner from scattering from the opening 35a.

(Embodiment 2)
In the image forming apparatus according to the second embodiment, when the temperature detected by the fixing temperature control thermostat 39 (see FIG. 1) provided in the fixing unit is equal to or lower than the predetermined threshold value X2, the shutter unit 38 opens the opening. This is an example in which a drive control unit (not shown) that closes 35a and drives the first conveying screw 11, the second conveying screw 12, and the developing sleeve 14 for a predetermined time is provided.

FIG. 9 shows a series of operations to which control by the drive control unit of the second embodiment is added.
First, the image forming operation is finished (S21), and the fixing unit is shifted to the OFF state due to the power of the image forming apparatus being turned off or the energy saving mode (S22). As a result, the fixing temperature is lowered, but the drive control unit of the second embodiment uses the thermostat 39 for fixing temperature control to start detecting the fixing temperature gradually lowering (S23). On the condition that the image formation request is input or the image formation is requested from the PC, a comparison determination is made between the detected temperature T of the thermostat 39 and the threshold value X2 (S24 (determination means)).

Only when the detected temperature T is equal to or lower than the threshold value X2 (S24Y), the above-described preprocessing operation is executed (S25). When the preprocessing operation is completed, the opening 35a is opened by the shutter unit 38, and the detected temperature is detected. The image forming operation is started by controlling the temperature so as to be a predetermined temperature (S26).
On the other hand, when the detected temperature T is equal to or higher than the threshold value X2 (S24N), the image forming operation is started without executing the above-described preprocessing operation (S26).

The threshold value X2 is determined as follows, for example.
FIG. 10 shows the time transition of the detected temperature of the thermostat 39 of the fixing unit after the image forming apparatus according to the second embodiment has performed image formation in a normal environment (23 ° C. and 50% RH). As can be seen from FIG. 10, in the normal environment (23 ° C. and 50% RH), the detected temperature at the standing time of 40000 [sec] is about 40 ° C. or less, so the threshold value X2 in the image forming apparatus of the second embodiment is 40 ° C. The threshold value X2 varies depending on the machine specifications and usage environment, and can be changed by a service person or a user.

  As described above, according to the image forming apparatus according to the second embodiment, the preconditioning operation is performed using the temperature using the thermostat 39 of the fixing unit, so that functions such as an increase in parts such as a timer and a counter are added. Even in an image forming apparatus such as an office use, the pre-processing operation by the drive control unit is executed, and the toner charge amount that has been reduced becomes a sufficient charge amount, and the toner scatters from the opening 35a. the can be reliably prevented.

(Embodiment 3)
In the image forming apparatus according to the third embodiment, a temperature / humidity sensor 40 is provided in the vicinity of the casing 35 or the opening 35a, the temperature / humidity is detected by the temperature / humidity sensor 40 at the start of image formation, and the detection result is a predetermined temperature. An example in which a drive control unit (not shown) is provided that closes the opening 35a by the shutter means 38 and drives the first conveying screw 11, the second conveying screw 12, and the developing sleeve 14 for a predetermined time when the humidity is higher. It is.

  First, the image forming apparatus according to this embodiment is left in a low-temperature and low-humidity environment (10 ° C. and 15% RH) and a high-temperature and high-humidity environment (27 ° C. and 80% RH) for a predetermined time, and then an image forming operation is performed. In this case, the relationship between the number of sheets passed and the toner charge amount was examined. The result is shown in FIG.

  In a low temperature and low humidity environment, the toner charge increases with the number of sheets passed. However, in a high temperature and high humidity environment, it is understood that a considerable number of sheets need to be passed in order to increase the toner charge amount. Specifically, it can be seen that 300 sheets are required for the toner charge amount to be Q / M ≧ 20 [−μC / g].

  Therefore, in the low-temperature and low-humidity environment, the absolute necessity of the above-described pre-processing operation is low in view of the increase in toner charge with the number of passing sheets and the amount of toner scattered from the opening 35a. Therefore, in the third embodiment, the temperature / humidity (temperature T2, humidity H) is detected by the temperature / humidity sensor 40 around the developing unit A at the start of image formation, and the pre-processing operation presence / absence conditions (threshold values) shown in Table 1 below are detected. In accordance with the above, it is determined whether or not the preprocessing operation is executed. Here, the presence / absence conditions shown in Table 1 are appropriately changed according to the developer and machine specifications.

  As described above, in the image forming apparatus according to the third embodiment, even in an image forming apparatus for office use, the pre-processing operation by the drive control unit is executed, and the charge amount of the toner that has been reduced is sufficient. In addition to reliably preventing the toner from scattering from the opening 35a, the pre-processing operation is performed when the toner charge easily rises immediately after the start of image formation due to the temperature and humidity conditions and the toner hardly occurs. Therefore, it is possible to eliminate the waiting time of the user for the pre-processing operation, and to reduce side effects such as an increase in power consumption and developer deterioration.

(Embodiment 4)
The toner charge amount of the developer decreases as the standing time increases, but the speed of charge reduction greatly varies depending on environmental conditions and agent deterioration conditions. In terms of environmental conditions, the toner charge decreases slowly in a low-temperature and low-humidity environment, and the toner charge decreases rapidly in a high-temperature and high-humidity environment. In terms of developer deterioration conditions, the initial charge of the developer is slow to lower the toner charge, and if the developer is deteriorated, the charge of the toner is rapidly lowered.

  Therefore, it is only necessary to always monitor the toner charge amount in the developing unit A. However, if a mechanism for monitoring the toner charge amount is added in the developing unit A, the number of parts, the configuration becomes complicated, and the cost increases significantly. Become.

  Thus, the image forming apparatus according to the fourth embodiment uses the existing magnetic permeability sensor 10 for toner replenishment control in the image forming apparatus, and the output value of the magnetic permeability sensor 10 at the end of the previous image formation and the current value. When the difference from the output value of the magnetic permeability sensor 10 at the start of image formation (estimation of how much the toner charge amount has decreased when the image forming operation is stopped) becomes a predetermined threshold value X4 or more, the shutter unit 38, the opening 35a is closed, and a drive control unit (not shown) for driving the first conveying screw 11, the second conveying screw 12, and the developing sleeve 14 for a predetermined time is provided.

  As in the image forming apparatus according to the present embodiment, an image forming apparatus using a developer composed of toner and a carrier includes a magnetic permeability sensor 10 in the developing unit A or around the developing unit A for toner replenishment control. ing. The magnetic permeability sensor 10 detects the volume ratio of the magnetic body (carrier) around the sensor (inside the developing device), estimates the volume ratio (toner concentration) of the insulator (toner) at that time, and performs toner replenishment control. It has the function of feedback.

  Since the magnetic permeability sensor 10 detects the volume ratio of the magnetic body (carrier) around the sensor (inside the developing device), the detection result varies depending on the toner charge amount even if the toner concentration is the same. That is, when the toner charge amount is high, the electrostatic repulsion force between the toners increases, so the volume of the voids in the developer increases. Therefore, since the bulk density of the developer is reduced, the volume specific gravity of the magnetic body (carrier) around the sensor is reduced, and the output value (Vt value) of the magnetic permeability sensor 10 is reduced.

Conversely, when the toner charge amount is low, the electrostatic repulsion force between the toners becomes small, so the volume of the void during development becomes small. Therefore, since the bulk density of the developer increases, the volume specific gravity of the magnetic body (carrier) around the sensor increases, and the output value (Vt value) of the magnetic permeability sensor 10 increases.
Furthermore, considering that the toner density cannot change when the image forming operation is stopped, the output value (Vt (β)) of the magnetic permeability sensor 10 at the end of the previous image forming operation and the time at which the image forming operation is started. If the difference (Vt (α)) − (Vt (β)) from the output value (Vt (α)) of the magnetic permeability sensor 10 is calculated, how much the toner charge amount is reduced when the image forming operation is stopped. Can be estimated.

A series of operations to which control by the drive control unit of the fourth embodiment is added are shown in FIG.
First, when the image forming operation is completed (S41), the output value (Vt (β)) of the magnetic permeability sensor 10 at the end of the image forming operation is stored in the memory (S42). The output value (Vt (α)) of the magnetic permeability sensor 10 is detected (S44) on the condition that an image formation request by the user is input or an image formation request is made from the PC (S43), and the toner charge amount is reduced. The amount (Vt (α)) − (Vt (β)) is compared with the threshold value X4 (S45 (determination means)).

  When the toner charge amount decrease amount (Vt (α)) − (Vt (β)) is equal to or greater than the threshold value X4 (S45Y), the above preprocessing operation is executed (S46). The opening 35a is opened by the means 38, and the image forming operation is started (S47). On the other hand, when the toner charge amount decrease amount (Vt (α)) − (Vt (β)) is less than the threshold value X4 (S45N), the image forming operation is started without executing the above pre-processing operation (S47). ).

The threshold value X4 is determined as follows, for example.
The threshold value X4 is determined by the relationship between the toner charge amount (Q / M) and the output value (Vt) of the magnetic permeability sensor 10 (see FIG. 13) when the toner concentration is 7 [wt%] obtained experimentally. The toner charge amount at the time of image formation in the environment (23 ° C., 50% RH) is about 40 [−μC / g], and is thus set to 0.2 [V]. The optimum value of the threshold value X4 varies depending on the machine specifications, developer characteristics, and sensors, and can be changed by a serviceman or a user.

  As described above, according to the image forming apparatus according to the fourth embodiment, the execution condition of the pre-processing operation is the amount of change in the output value of the existing magnetic permeability sensor 10, thereby increasing the number of components such as a timer and the counter. Even in an image forming apparatus such as an office application without adding a function, the pre-processing operation by the drive control unit is executed, and the reduced charge amount of the toner becomes a sufficient charge amount. Can be reliably prevented from splashing. In addition, since the parameter directly related to the decrease in the toner charge amount corresponding to the change in the output value of the magnetic permeability sensor 10 is set as the execution condition of the preprocessing operation, the preprocessing operation for preventing the toner from scattering from the opening 35a. Can be performed more efficiently.

(Embodiment 5)
In general, in a high-temperature and high-humidity environment, the developer resistance becomes low and it becomes difficult to hold the charge. Therefore, even when the developer agitating operation is executed, the toner charge hardly rises. If the temperature and humidity are too high, in some cases, the toner charge may not rise at all by only the stirring operation of the developer.
In view of this, the image forming apparatus according to the fifth embodiment is provided with a blower 41 that allows dry air to flow inside the casing 35, and a humidity sensor 42 that detects the humidity inside the casing 35 or the humidity of the developer (FIG. 14). ) When the detection result of the humidity sensor 42 is equal to or higher than a predetermined threshold value X5 at which the humidity is judged to be high, the opening 35a is closed by the shutter means 38, and the first conveying screw 11 and the second conveying screw 12 In this example, a drive control unit (not shown) that drives the developing sleeve 14 for a predetermined time is provided.

  The blower 41 (FIG. 14) described above is configured using a blower fan (not shown) that takes in outside air and sends it out, and dehumidifies the air sent out by the blower fan, which is configured using a hollow fiber membrane, a Peltier element, a hygroscopic agent, or the like. A dehumidifier (not shown) and a blower pipe 41 a (FIG. 14) that sends dry air, which is provided inside the casing 35 and dehumidified by the dehumidifier, to the inside of the casing 35.

  The humidity sensor 42 has a well-known structure and is provided inside the casing 35. The humidity sensor 42 is electrically connected to a drive control unit described later, and the drive control unit is electrically connected to the air blowing unit 41 described above. The humidity sensor 42 described above may be disposed in a location that does not directly contact the developer inside the casing 35 or may be disposed so that it directly contacts the developer, and is not particularly limited.

  The preprocessing operation by the drive control unit is a first preprocessing operation in which the opening 35a is closed by the shutter unit 38, and the first conveying screw 11 and the second conveying screw 12 and the developing sleeve 14 are driven for a predetermined time. The two preprocessing operations are executed in time series. Details will be described in a series of operations described below.

FIG. 15 shows a series of operations to which control by the drive control unit of the fifth embodiment is added.
First, when the image forming operation is completed (S51) and the image forming request by the user is input or the image forming request is received from the PC, the drive control unit closes the opening 35a by the shutter unit 38. One pre-processing operation is executed (S52), and then humidity detection inside the casing 35 by the humidity sensor 42 is executed (S53).
A comparison is made between the detected humidity d in the casing 35 detected by the humidity sensor 42 and the threshold value X5 (S54 (determination means)).

  When the detected humidity d is equal to or higher than the threshold value X5 (S54Y), the blower 41 is driven to start blowing dry air from the blower pipe 41a into the casing 35 (S55). A second pretreatment operation for driving the two conveying screw 12 and the developing sleeve 14 for a predetermined time is executed (S56).

Then, when the second pre-processing operation is finished, the blowing of the dry air by the blower 41 is finished, the opening 35a is opened by the shutter means 38, and the image forming operation is started (S57).
On the other hand, in S54, when the detected humidity d is less than the threshold value X5 (S54Y), the first conveying screw 11 and the second conveying screw 12 and the developing sleeve 14 are driven for a predetermined time without blowing dry air. The second pre-processing operation is executed (S56), the opening 35a is opened by the shutter means 38, and the image forming operation is started (S57).

The threshold value X5 is determined as follows, for example.
As described above, the developer is more easily charged with toner in a low humidity environment. This is because it is difficult for the developer to contain moisture in a low humidity environment. Conversely, in a high humidity environment, the developer contains a large amount of moisture, so the resistance of the developer decreases, it becomes difficult to hold the charge (charge leakage is likely to occur), and the toner charge is reduced. difficult.

FIG. 16 shows the relationship between the stirring time and the toner charge amount when the humidity condition is changed at the normal temperature (23 ° C.).
When stirring is performed for 600 [sec], charging starts up to a toner charge amount (20 [-μC / g]) where toner scattering does not pose a problem when the humidity is 70% RH or less, but is charged when the humidity is 80% RH or more. It does not rise up to the amount (20 [-μC / g]).
Only when the humidity was 95% RH, the toner charge did not rise at all even with stirring. Therefore, in the fifth embodiment, the threshold value X5 is set to 70% RH including the margin. The threshold value X5 varies depending on machine specifications, use environment, and developer, and can be changed by a service person or a user.

  Here, at a normal temperature (23 ° C.), the relationship between the developer agitation time and the toner charge amount (Q / M) in the presence / absence of dry air by the air blowing unit 41 in an 80% humidity RH environment. It is shown in Figure 17. From FIG. 17, it can be seen that when dry air is blown, the toner charge amount surely rises with a stirring time of 600 [sec].

  As described above, according to the image forming apparatus according to the fifth embodiment, even in a developer having a high water content in a high humidity environment, moisture contained in the developer is removed by blowing a dry air current into the developing device. The pre-processing operation ensures that toner charging is started up to a level at which toner scattering does not become a problem. Therefore, it is ensured that the reduced toner charging amount is sufficient and toner is scattered from the opening 35a. It can be prevented.

(Embodiment 6)
In this embodiment, in order to prevent toner scattering associated with a decrease in the toner charge amount, image formation is started after a pre-processing operation is performed to secure the toner charge amount. At the beginning of image formation, the toner charge amount is reduced by leaving the developer in most cases, so the toner adhesion amount is excessive, so that the image density becomes low even if the preprocessing operation is executed. There is no.
However, for example, when the previous image formation is in a high-temperature and high-humidity environment and the image formation is completed when the toner density is low, and the next image formation is executed in a low-temperature and low-humidity environment, the toner concentration is reduced by the preprocessing operation. The charge amount may be increased in a lower state, and a problem of low image density may occur. Also, if the toner charge amount increases too much due to some abnormality (apparatus abnormality, environmental abnormality), the electrostatic adhesion force between the carrier and the toner increases, so the developing ability of the developer decreases, and the image density May become thinner.

  Therefore, the image forming apparatus according to the sixth embodiment is provided with the optical sensor 43 that detects the reflected light of the toner image and detects the image density of the toner image (FIG. 1), and the detection result of the optical sensor 43 is Only when the image density is equal to or higher than a predetermined threshold value X6 that is determined to be appropriate or dark, the opening 35a is closed by the shutter means 38, and the blower 41, the first conveying screw 11, the second conveying screw 12, and the developing sleeve 14 are closed. Are provided with a drive control unit (not shown) for driving for a predetermined time.

  The above-described optical sensor 43 is a well-known reflection-type optical sensor that irradiates a toner image (test image) formed on an intermediate transfer belt, a recording sheet, or the like, and detects the image density based on the amount of reflected light. It has become.

FIG. 18 shows a series of operations to which control by the drive control unit of the sixth embodiment is added.
First, the image forming operation is completed (S61), and the power of the image forming apparatus is turned off or the power saving mode is entered (S62). On the condition that an image formation request by the user is input or an image formation request is made from the PC (S63), the drive control unit starts to create a toner image (test image) (S64). Subsequently, the density of the toner image (test image) is detected by the optical sensor 43. The optical sensor 43 outputs a voltage (corresponding to the image density) corresponding to the reflected light of the toner image (test image), and the drive control unit outputs the output value (Vsp [V]) of the optical sensor 43 and the threshold value X6. (S65 (determination means)).

When the image density is appropriate or dark and the amount of reflected light is small and the output value (Vsp [V]) of the optical sensor 43 is less than the threshold value X6 (S65Y), the above pre-processing operation is executed (S66). When the processing operation is completed, the opening 35a is opened by the shutter means 38, and the image forming operation is started (S67).
In S65, when the image density is low and the amount of reflected light is large and the output value (Vsp [V]) of the optical sensor 43 is equal to or greater than the threshold value X6 (S65N), the image forming operation is performed without executing the above preprocessing operation. Start (S67).

  The threshold value X6 is set to 0.3 as a case where it is highly possible that the image density is low from the experimental results, and toner scattering hardly occurs even if the preprocessing operation is not executed. When the output value (Vsp [V]) of the optical sensor 43 is larger than 0.3 [V], the image forming operation is executed without executing the preprocessing operation. Note that the threshold value X6 can be changed by a service person or a user in consideration of machine specifications, developer characteristics, user's demands, etc. (weight of toner scattering and low density defect).

  As described above, according to the image forming apparatus according to the sixth embodiment, the pre-processing operation is not executed when the toner scattering from the opening 35a does not occur at the start of image formation (the image density is low). Side effects such as unnecessary user waiting time, increased power consumption, and developer deterioration can be reduced.

The image forming apparatus according to the present embodiment has been described above. However, the above-described embodiment shows an example of a preferred embodiment of the present invention, and the present invention is not limited thereto. Various modifications can be made without departing from the scope of the invention.
For example, in the present embodiment, the conditions divided into the first to sixth embodiments are exemplified as the conditions for executing the preprocessing operation. However, the conditions and configuration for executing the preprocessing operations illustrated in the first to sixth embodiments are exemplified. May be appropriately combined.

A. Developing unit 11. First conveying screw (developer stirring part) 12. Second conveying screw (developer stirring part) 35. Casing 35 a. Opening 10. Magnetic permeability sensor 36. Shutter 37. Means 39 ... Thermostat 40 ... Temperature / humidity sensor 41 ... Blower part 41a ... Blower pipe 42 ... Humidity sensor 43 ... Optical sensor

JP 2006-84892 JP

Claims (9)

A development system used in an electrophotographic image forming apparatus,
A casing having an opening formed therein;
A roller-shaped developer carrying member that is rotatably provided inside the casing so that a part of the outer peripheral surface can be seen from the opening, and conveys the developer stored in the casing toward the opening. When,
The developer is rotatably provided in the casing, and the developer stored in the casing is agitated by rotation to charge the toner as one component of the developer and in the vicinity of the developer carrier. A developer stirring section for moving the developer;
Shutter means provided to be capable of opening and closing the opening, and opening and closing the opening when required;
And determining means for determining whether or not the charge amount of the toner is in a reduced state at the start of image formation, and when the determination means determines that the charge amount of the toner is in a reduced state, the shutter means And a drive control section for closing the opening and driving the developer agitating section and the developer carrying member for a predetermined time to ensure the charge amount of the toner. A counter for measuring a time from the end of the previous image forming operation of the image forming apparatus;
2. The development according to claim 1, wherein the determination unit determines that the charge amount of the toner is in a reduced state when the value of the counter becomes equal to or greater than a predetermined threshold at the start of image formation. system.   The determination means is a fixing member that is a component of a fixing unit that applies heat and pressure to a sheet-like recording material carrying a toner image developed by the developer carrier and fixes the toner image to the recording material. 2. The developing system according to claim 1, wherein a temperature control thermostat is used, and when the temperature detected by the thermostat is not more than a predetermined threshold value, it is determined that the charge amount of the toner is in a lowered state. . A temperature and humidity sensor is provided in the vicinity of the casing or the opening,
2. The determination unit according to claim 1, wherein when the temperature and humidity detected by the temperature and humidity sensor at the start of image formation is equal to or higher than a predetermined temperature and humidity, the charge amount of the toner is in a lowered state. The developing system described in 1.   The determination unit uses a magnetic permeability sensor that detects the toner concentration of the developer stored in the casing, and outputs the output value of the magnetic permeability sensor at the end of the previous image formation and the start of the current image formation. 2. The developing system according to claim 1, wherein when the difference from the output value of the magnetic permeability sensor at the time exceeds a predetermined threshold value, it is determined that the charge amount of the toner is in a lowered state. Providing a blower for flowing dry air inside the casing, providing a humidity sensor for detecting the humidity inside the casing or the humidity of the developer;
The determination unit determines that the charge amount of the toner is in a lowered state when the detection result of the humidity sensor is equal to or higher than a predetermined threshold value at which the humidity is determined to be high;
The developing system according to claim 1, wherein the drive control unit drives the blowing unit together with the developer stirring unit and the developer carrying member for a predetermined time. An optical sensor for detecting the reflected light of the toner image and detecting the image density of the toner image is provided.
The determination unit determines that the charge amount of the toner is in a lowered state when the detection result of the optical sensor is equal to or higher than a predetermined threshold value at which the image density is determined to be appropriate or high. Item 2. The developing system according to Item 1.   A development system comprising any combination of the configurations according to claim 2.   An image forming apparatus comprising the developing system according to claim 1.

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