JP2000147962A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus capable of always forming a uniform high quality image without nonuniform density. SOLUTION: When an image in a monochrome mode is formed, the revolving speed of a ventilating fan in the midst of forming the image in the monochrome mode is controlled, so that the ventilating fan rotates at 2,500 rpm which is 1/2 the revolving speed at the time of forming a full color image, whereby the speed of the current of air blowing off the surface of a photoreceptor drum 1 is 300 mm/s and the maximum ozone concentration in the vicinity of a developing device 4(4Y, 4C, 4M and 4Bk) which is not used is 2 ppm or less and NOX concentration is restrained to be 1 ppm or lower. Substance produced from discharge product hardly adheres to a developing sleeve 4a(4Ya, 4Ca, 4Ma and 4Bka) stopped of rotation, and the nonuniform density is not caused, even if image is formed by using the stopped sleeve 4a.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as a copying machine, a printer and a facsimile, and more particularly to an electrophotographic image forming apparatus.

[0002]

2. Description of the Related Art Conventionally, in this type of electrophotographic image forming apparatus, a corona charger is generally used as a charging means in a latent image forming step and a transferring step. If this charger is used continuously for a long time, ozone or N
O _X, etc. accumulate the discharge products, when these concentrations are too high, discharge may become difficult to discharge becomes unstable.

[0003] When the photosensitive drum as an image bearing member is stopped in a state in which discharge products such as ozone and NO _X remained much the charger vicinity photoreceptor charger vicinity degraded, image blurring, etc. Causes an abnormal image.

[0004] In order to prevent these problems, it is common to provide a blower system in which these discharge products are removed from the inside of the charger by a blower fan of blower means and blown toward the photosensitive drum side.

On the other hand, an electrophotographic image forming apparatus includes an image forming apparatus which includes a plurality of developing units as developing means and forms a color image using toners as developers of two or more colors. The image forming apparatus includes a first image forming mode for forming a color image using all developing units, and a second image forming mode for outputting a single-color image using only one developing unit when selected by a user. Mode (monochrome mode)
Many are equipped with

In such a single-color mode, there is a developing device which is not operated even once during the image forming operation.

Further, in an image forming apparatus for a single color having only one developing device and an image forming device having a plurality of developing devices, image forming process conditions such as charging exposure are adjusted in addition to the image forming operation. There are an idle rotation mode in which the photosensitive drum is idly rotated while the photosensitive drum is periodically charged by a charger, such as an adjustment mode and a cleaning mode in which the photosensitive drum and members around the photosensitive drum are cleaned.

In such an idling mode, the developing device is generally not operated in order to prevent the deterioration of the developer.

[0009]

Ozone and NO _X (nitrogen oxides) generated by corona discharge of the charger [0006] discharge products such as is discharged from the charger by the ventilation system. The discharge product discharged from the charger reacts with water (H ₂ O) in the air while diffusing into the image forming apparatus, and adheres to the member surface in the image forming apparatus.

However, as described above, in the image forming apparatus, the charging device discharges by the charging operation, but at least one of the plurality of developing devices is not used during image formation, that is, the developing device is not used. In the second image forming mode in which the developing sleeve, which is the developer carrying member, is stopped, or in the idle mode in which the photosensitive drum is idled while the developing sleeve of the developing device is stopped while the charger is discharged by the charging operation. There is a rotation mode.

In the second image forming mode and the idle rotation mode, only a part of the surface of the stopped developing sleeve (portion exposed from the frame of the developing device: portion A in FIG. 3) is discharged from the charging device. Substances made from the discharge products adhere.

When a large amount of a substance produced from such a discharge product adheres to only a part of the surface of the developing sleeve, the charge amount of the toner carried on the surface of the developing sleeve at the adhering part changes.

In the case of the two-component toner, a part of the toner is released from the carrier and adheres to the surface of the developing sleeve of the developing device. If the toner adheres to the surface, the adsorptivity of the surface changes, and the toner may easily adhere directly to only that portion.

As described above, when the charge amount of a part of the toner on the developing sleeve changes or the toner amount on the developing sleeve changes only partly, the image density at the time of development is partially different. That is, a so-called pitch-shaped density unevenness image may appear several times around the developing sleeve.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems of the prior art, and an object of the present invention is to provide an image forming apparatus capable of forming uniform and high-quality images without density unevenness. It is in.

[0016]

In order to achieve the above object, according to the present invention, there is provided an image carrier, a charging device for charging the image carrier, and air outside the apparatus is sent to the charging device. An image forming apparatus comprising: a blowing unit configured to remove discharge products generated by discharge from the charging unit; and a developing unit having a developer carrier that supplies a developer by rotating the image carrier. It is characterized in that wind speed control for changing the wind speed of the air sent by the blowing means is performed.

In the wind speed control, it is preferable to make the wind speed slower than when the developer carrier rotates while the charging means charges the image carrier.

Preferably, when the charging means stops the rotation of the developer carrier while charging the image carrier, the wind speed control is performed.

When a plurality of the developing units are provided, and the charging unit stops the rotation of at least one of the plurality of developing units while charging the image carrier, the wind speed is reduced. Preferably, control is performed.

A plurality of developing means are provided, and a first image forming mode in which a developer is supplied by all of the plurality of developing means during image formation, and at least one of the plurality of developing means during image formation. A second image forming mode in which the rotation of the two developer carrying members is stopped, wherein the wind speed control is performed by changing the wind speed of the blowing unit in the second image forming mode to the first image forming mode. It is preferable to make the wind speed lower than the wind speed of the blowing means.

A non-image forming operation, wherein the rotation of the developer carrier is stopped, and the charging means rotates the image carrier while charging the image carrier; Wind speed control, the wind speed of the blower in idle rotation mode, than the wind speed of the blower during image forming operation,
Preferably, it is slow.

When the absolute water content is larger than a predetermined amount,
It is preferable to perform the wind speed control.

It is preferable that the wind speed control is performed stepwise according to the absolute water content.

It is preferable that an environment detecting means for detecting temperature and humidity is provided, and the absolute moisture content is calculated from a detection result detected by the environment detecting means.

It is preferable that the blowing means includes a blowing fan, and the wind speed control changes a wind speed by changing a rotation speed of the blowing fan.

[0026]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS (First Embodiment) FIG. 1 is a sectional view showing a schematic configuration of a digital four-color full-color image forming apparatus as an image forming apparatus according to a first embodiment.

The image forming apparatus shown in FIG. 1 includes a lower digital color image printer unit (hereinafter referred to as "printer unit") I and an upper digital color image reader unit (hereinafter referred to as "reader unit") II. For example, the printer unit I forms an image on a recording material P, which is a sheet, based on the image of the document D read by the reader unit II.

The configuration of the reader unit II is a conventionally used image reading means such as an optical system moving type for reading an image of an original D on an original platen glass, and a description thereof will be omitted.

Hereinafter, the configuration of the printer unit I will be briefly described. The printer section I has a photosensitive drum 1 as an image carrier that is driven to rotate in the direction of arrow R1.

Around the photosensitive drum 1, a primary charger 2 as a charging unit, an exposing unit 3, a developing unit 4 as a developing unit, a transfer unit 5, a cleaning unit 6, a pre-exposure A lamp 7 and the like are arranged.

Below the transfer device 5 in FIG. 1, that is, in the lower half of the printer unit I, a paper feeder 11 for the recording material P is disposed. Further, above the transfer device 5, a separating means 8 is provided. On the downstream side of the separating means 8 (downstream side in the conveying direction of the recording material P), a fixing device 9 and subsequently a paper discharge unit 10 are arranged.

The photosensitive drum 1 has an aluminum drum-shaped substrate and an OPC (organic optical semiconductor) photosensitive member covering the surface thereof, and is driven by an arrow R by driving means (not shown).
It is configured to be driven to rotate in one direction at a predetermined process speed (peripheral speed).

FIG. 2 is an enlarged view showing the periphery of the photosensitive drum 1. As shown in FIG. 2, the primary charger 2 includes a photosensitive drum 1
A shield 2a having an opening at a portion facing the
This is a corona charger having a discharge wire 2b arranged inside the photosensitive drum 1 in parallel with the generatrix of the photosensitive drum 1, and a grid 2c arranged at an opening of the shield 2a to regulate a charging potential.

A charging bias is applied to the primary charger 2 by a power supply (not shown), whereby the primary charger 2 is uniformly charged to a predetermined polarity and a predetermined potential on the surface of the photosensitive drum 1.

The primary charger 2 is located above the primary charger 2.
A suction duct 12 for guiding air outside the apparatus to the vicinity is provided, and a blower fan 13 as a blower is provided at a suction port of the duct 12 on the side of the image forming apparatus shown in FIG.

The air blown from the outside of the apparatus by the blower fan 13 is guided to the duct 12 and blows onto the surface of the photosensitive drum 1 from above the primary charger 2 and is generated in the primary charger 2 by discharge. ozone, and a discharge product such as NO _X constitutes a ventilation system to exclude from the primary charger 2.

The rotation speed of the blower fan 13 is controlled by the main body CPU.

Exposure means 3 shown in FIG. 1 includes a laser output section (not shown) for emitting a laser beam E based on an image signal of a document D read by a reader section II, and a laser beam E (not shown). A polygon mirror that reflects light, a lens, and a mirror.

The exposure means 3 is configured to irradiate the surface of the photosensitive drum 1 with the laser beam E to expose the photosensitive drum 1 and remove an electric charge of an exposed portion to form an electrostatic latent image. I have.

In the present embodiment, the electrostatic latent image formed on the surface of the photosensitive drum 1 is separated into four colors of yellow, cyan, magenta, and black based on the image of the document D, and each color is separated. Are sequentially formed.

The developing devices 4 are arranged in order from the upstream side along the rotation direction of the photosensitive drum 1 (the direction of arrow R1), that is, yellow, cyan, magenta,
Developing devices 4Y, 4C, 4M, and 4Bk that store toner as a developer for each color of black are provided.

Each of the developing units 4Y, 4C, 4M, and 4 is mixed with a magnetic carrier at a predetermined ratio.
Bk.

Each of the developing units 4Y, 4C, 4M, 4B
k is a developing sleeve 4Ya, 4Ca, as a developer carrier made of a rotatable SUS or the like having a magnet inside.
It has 4Ma and 4Bka. Hereinafter, it is simply referred to as a developing sleeve 4a.

The toner is carried on the developing sleeve 4a, and is conveyed by the rotation of the developing sleeve 4a.

During the developing operation, the developing device 4 of a predetermined color is selectively disposed at a developing position close to the surface of the photosensitive drum 1 by the eccentric cams 4Yb, 4Cb, 4Mb, and 4Bkb (hereinafter simply referred to as the eccentric cam 4b). And the developing sleeve 4a
Are rotated, the toner conveyed near the electrostatic latent image formed on the surface of the photosensitive drum 1 is developed, and a toner image (visible image) as a visible image is formed.

The developing devices 4 of three colors other than the predetermined developing device 4 to be used for development are in a state where the developing sleeve 4a is retracted from the photosensitive drum 1 with a gap of about 5 mm and the rotation is stopped. Waiting at.

The transfer device 5 includes a transfer drum (recording material carrier) 5a having a recording material P on its surface, a transfer charger 5b for transferring the toner image on the photosensitive drum 1 to the recording material P, and a recording material P.
And a suction roller 5g opposed thereto, an inner charger 5d, and an outer charger 5e.

A recording material carrying sheet 5f made of a dielectric material is integrally stretched in a cylindrical shape in a peripheral opening area of the transfer drum 5a which is rotatably supported in the direction of arrow R5. . The recording material supporting sheet 5f uses a dielectric sheet such as a polycarbonate film.

The transfer device 5 is configured to adsorb and carry the recording material P on the surface of the transfer drum 5a.

The cleaning device 6 includes a cleaning blade 6a for scraping off residual toner remaining on the surface of the photosensitive drum 1 without being transferred to the recording material P, and a cleaning container 6b for collecting the scraped toner.

The pre-exposure lamp 7 is disposed adjacent to the upstream side of the primary charger 2 and removes unnecessary charges on the surface of the photosensitive drum 1 cleaned by the cleaner 6.

The fixing device 9 includes a fixing roller 9a having a heater inside, and a pressure roller 9b disposed below the fixing roller 9a and pressing the recording material P against the fixing roller 9a. The toner image is fixed on the recording material P.

Next, the operation for forming a full-color image with the image forming apparatus having such a configuration will be briefly described while adding some components.

In the following description, yellow,
Assume that four full-color images are formed in the order of cyan, magenta, and black.

The image of the original D placed on the original platen glass of the reader unit II is irradiated by an exposure line, color-separated, and the yellow image is first read by a full-color sensor, subjected to predetermined processing, and subjected to image signal processing. To the printer unit I.

In the printer section I, the photosensitive drum 1 has an arrow R
It is driven to rotate in one direction, and the surface is uniformly charged by the primary charger 2.

Based on the image signal sent from the reader unit II, a laser beam E is emitted from the laser output unit of the exposure unit 3, and the surface of the charged photosensitive drum 1 is irradiated with the laser beam via a polygon mirror or the like. Exposure by E. The exposed portion of the surface of the photosensitive drum 1 has its charge removed, whereby an electrostatic latent image corresponding to yellow is formed.

In the developing device 4, the yellow developing device 4Y is arranged so as to be close to the photosensitive drum 1 by rotation of the cam 4Yc, and the other developing devices 4C, 4M and 4Bk are located at a position 5 mm away from the photosensitive drum 1. Stopped in a evacuated state.

The electrostatic latent image on the photosensitive drum 1 is transferred to the developing device 4Y
As a result, yellow toner is adhered to the toner, and the toner is visualized to form a toner image. The yellow toner image on the photosensitive drum 1 is transferred to the recording material P carried on the transfer drum 5a.

By the way, as for the recording material P, a recording material P having a size suitable for the image of the original D is fed from a predetermined paper feeding cassette 14 to a paper feeding roller (not shown), a conveying roller, and a registration roller. This is supplied to the transfer drum 5a at a predetermined timing via the unit 11.

The recording material P supplied in this manner is attracted so as to wind around the surface of the transfer drum 5a, is rotated in the direction of arrow R5 of the transfer drum 5a, and is transferred to the yellow surface of the photosensitive drum 1 by the transfer charger 5b. Is transferred.

On the other hand, the photosensitive drum 1 after the transfer of the toner image
The residual toner on the surface is removed by the cleaning device 6 and unnecessary charges are removed by the pre-exposure lamp 7 to be used for the next image forming process starting from primary charging.

The processes from the reading of the image of the original D by the reader unit II, the transfer of the toner image to the recording material P on the transfer drum 5a, the cleaning of the photosensitive drum 1, and the elimination of the electricity are performed in a process other than yellow. Another color, namely cyan,
Magenta and black are sequentially performed in the same manner, and four color toner images are transferred onto the recording material P on the transfer drum 5a so as to overlap.

Recording material P to which four color toner images have been transferred
Is separated from the transfer drum 5a by the separating means 8 and is conveyed to the fixing device 9 while the unfixed toner image is carried on the surface.

The recording material P is heated and pressurized by the fixing device 9 so that the toner image on the surface is melted and fixed and fixed. The recording material P after fixing is discharged onto a discharge tray 10 by a discharge roller (not shown).

When a full-color image is formed by the above-described image forming apparatus, the blower fan 13 is controlled so as to rotate at 5000 rpm during full-color image formation. It is blown from above the primary charger 2 onto the surface of the photosensitive drum 1 at a wind speed of 500 m / s.

[0067] Accordingly, discharge products such as ozone and NO _X generated by the discharge of the primary charger 2 is excluded from the primary charger 2. Even if image formation is continued for a long time at this wind speed, the ozone concentration in the primary charger 2 is 10 ppm or less,
O _X concentration is suppressed to 5ppm or less.

[0068] Incidentally, in this image forming apparatus, the primary charger ozone concentration in 2 20ppm or less, as long as NO _X concentration is 10ppm or less, or become unstable discharge of the primary charger 2, the photosensitive member There is no deterioration.

[0069] Incidentally, the primary charger 2 as ozone and NO _X or the like which is excluded from that stream diffuse into the developing device 4 direction together with rotation of the photosensitive drum 1. At this time, the maximum ozone concentration in the vicinity of the position where the developing sleeve 4a faces the photosensitive drum 1 is 5 ppm,
NO _X concentration is 3ppm.

[0070] discharge products such as these ozone and NO _X reacts with moisture in the air, material made from discharge products to the developing sleeve 4a surface adheres.

However, when a full-color image is formed, the yellow, cyan, magenta, and black developing devices 4
Y, 4C, 4M, 4Bk developing sleeves 4a
Are all rotated during image formation, so that the developing sleeve 4a
A large amount of the substance produced from the discharge product does not adhere to only a part of the surface.

When the developing sleeve 4a rotates even if it adheres, the toner (mainly the carrier) is removed from the developing sleeve 4a.
As a result, even if image formation is performed using the developing device 4 having the developing sleeve 4a, density unevenness does not occur.

Next, the monochrome mode will be described. In the present image forming apparatus, it is possible for a user to output a black monochrome image using only the black developing device 4Bk by making a selection on an operation panel (not shown).

In the single-color mode, the charging operation by the primary charger 2 and the rotation of the photosensitive drum 1 are performed, but the developing devices 4 of three colors other than the black developing device 4Bk used for development are used.
Y, 4C, and 4M stand by while the rotation of the developing sleeve 4a is stopped. FIG. 2 shows a state in which a black monochrome image is being formed.

When such a single-color mode is continuously performed for a long time, the developing sleeves 4Y, 4C, and 4M are stopped.
a will be only partially exposed to the discharge products. As mentioned above, these discharge products react with moisture,
Developing sleeve 4 in which the substance formed from the discharge product is stopped
If a large amount adheres to a, density unevenness occurs during image formation using the developing units 4Y, 4C, and 4M.

In order to prevent this problem, in the present embodiment, when forming an image in the single color mode, the number of rotations of the blower fan 13 during image formation in the single color mode is reduced to 回 転 of that in full color image formation. It is controlled to rotate at 2500 rpm which is a number.

By controlling in this manner, the photosensitive drum 1
The wind speed blown to the surface of is 300 mm / s,
Unused developing units 4 (developing units 4Y, 4C, 4 in FIG. 2)
M) Maximum ozone concentration near 2ppm or less, NO _X concentration is suppressed to 1ppm or less.

According to an experiment, in the present image forming apparatus, the maximum ozone concentration in the vicinity of the unused developing unit 4 is 4 p.
pm or less and the NO _x concentration is 2.5 ppm or less, the developing sleeve 4a (the developing sleeves 4Ya, 4Ca, and 4Ma in FIG. 2) in which the substance formed from the discharge product stops rotating.
The toner did not adhere to the surface, and no density unevenness or the like occurred in image formation using the developing sleeve 4a.

[0079] On the other hand, in this way slow down the wind, when it discharge product such as ozone and NO _X accumulated in the primary charger 2 is increased, which was continued for image formation for a long time continuously wind speed 300 mm / s However, the ozone concentration in the primary charger 2 is 1
5ppm or less, NO _X concentration is less 8 ppm, discharge becomes unstable, the surface of the photosensitive drum 1 has not occurred the problem of deteriorated.

However, the ozone concentration in the primary charger 2 and N
O _X concentration, in terms of extended life improvement of the photosensitive drum 1,
The lower the lower, the better. As described above, in the full-color image forming mode of the present image forming apparatus, the air velocity blown to the primary charger 2 is set at 500 mm / s.

When the amount of water in the air is small,
Since the discharge product hardly reacts with water and the substance formed from the discharge product hardly adheres to the stopped developing sleeve 4a, the density unevenness during image formation using the developing device 4 of the stopped developing sleeve 4a. Is unlikely to occur.

Focusing on this point, the absolute water content is determined from the detection value of an environment detection sensor (not shown) as the environment detection means for detecting the temperature and humidity in the image forming apparatus. For example, when it is higher than 9 g / kg, the rotation speed of the blower fan 13 in the monochrome mode is set to 25 as described above.
00 rpm and the wind speed was slowed down, and the absolute water content was 9 g /
When the weight is not more than kg, the rotation speed of the blower fan 13 in the single-color mode may be set to 5000 rpm, which is the same as in full-color image formation.

[0083] That is, no pitch-like uneven density, the absolute water content is low condition, by lowering the ozone concentration and concentration of NO _X in the primary charger 2 even slightly, it is possible to improve the life of the photosensitive drum 1.

Further, according to the absolute water content, the rotation speed of the blower fan 13 in the monochromatic mode may be changed stepwise so that the higher the absolute water content, the smaller the rotation speed and the lower the wind speed.

(Second Embodiment) In the second embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and description thereof will be omitted.

In the image forming apparatus shown in FIG.
When the recording material P is repeatedly attracted to the recording material carrying sheet 5f on the surface of the transfer drum 5a, the recording material P is not sufficiently attracted to the recording material carrying sheet 5f, peels off, and causes a paper jam. .

The reason for this is that as the image forming apparatus is used for a long time, the paper dust that has fallen from the recording material P on the recording material carrying sheet 5f adheres and accumulates on the recording material carrying sheet 5f, and the recording material P
This is because the force for electrostatically adsorbing the recording material onto the recording material carrying sheet 5f decreases.

In order to prevent such a problem, the present image forming apparatus is provided with a polishing roller 5K, which is a polishing means for polishing and cleaning the surface of the soiled recording material supporting sheet 5f. Each time the operation is performed, the polishing mode of the recording material supporting sheet 5f is performed.

The operation in the polishing mode will be described. When the number of copies reaches 3,000 from the previous polishing mode operation, the image forming apparatus enters a standby state in which the image forming operation is stopped.

During the non-image forming operation, the photosensitive drum 1 rotates while the four developing devices 4 are stopped, and the transfer drum 5a rotates by receiving the drive from the rotation of the photosensitive drum 1. Recording material carrying sheet 5 of rotating transfer drum 5a
and the polishing roller 5k is pressed against the recording material-carrying sheet 5f by rotating in a counter direction with respect to the rotation of the transfer drum 5a.
Is polished and cleaned.

At this time, the discharge of the primary charger 2 charges the photosensitive drum 1 to the same polarity (negative electrode) as that during image formation. This is to prevent a potential memory from being generated on the photosensitive drum 1 even if a peeling discharge occurs at a contact portion between the transfer drum 5a and the photosensitive drum 1.

In the present embodiment, even in such a polishing mode, the rotation speed of the blower fan 13 is controlled so as to rotate at 2500 rpm which is １ ／ that at the time of full-color image formation.

[0093] When doing so, performing the maximum ozone concentration of the developing unit 4 near that stop or wait, and NO _X concentrations can be lowered, the image formed after polishing mode end,
This prevents pitch unevenness in the developing sleeve 4a.

The above polishing mode is an example of the present embodiment. In the image forming apparatus, there are other idle rotation modes in which the developing device 4 is stopped, for example, in a potential adjustment mode for adjusting a charging condition, and the photosensitive drum 1 is rotated while charging is performed by the primary charger 2. In these idle rotation modes, the rotation speed of the blower fan 13 is controlled so as to rotate at a lower rotation speed than during full-color image formation.

In this embodiment, it goes without saying that the number of rotations of the blower fan 13 during the idling mode may be changed according to the absolute water content in the image forming apparatus.

[0096]

According to the present invention, by performing wind speed control for changing the wind speed of the air blown by the blowing means, the discharge products of the charging means are eliminated from the charging means and the discharge products eliminated from the charging means are used. In addition, it is possible to prevent a substance formed from a discharge product from adhering to the developer carrier on which the rotation of the developing unit is stopped, thereby enabling high-quality image formation without density unevenness.

[0097] The wind speed control is performed by lowering the wind speed as compared with the case where the charging device charges the image carrier and the developer carrier rotates, so that the discharge product is supplied to the developer carrier where the rotation of the developing device is stopped. Can be prevented from adhering to the substance made from the product.

A first image forming mode in which a plurality of developing means are provided, and a developer is supplied by all of the plurality of developing means during image formation; and at least one of the plurality of developing means during image formation. A second image forming mode in which the rotation of the carrier is stopped, wherein the wind speed control is such that the wind speed of the blower in the second image forming mode is set to be smaller than the wind speed of the blower in the first image forming mode. In addition, the delay can prevent the substance formed from the discharge product from adhering to the developer carrier on which the rotation of the developing unit is stopped.

At the time of non-image forming operation, an idle rotation mode is provided in which the rotation of the developer carrier is stopped and the charging means rotates the image carrier while charging the image carrier.
By making the wind speed of the blower in the idle rotation mode slower than the wind speed of the blower in the image forming operation, the substance formed from the discharge product adheres to the developer carrier on which the rotation of the developing unit is stopped. Can be prevented.

When the absolute water content is higher than a predetermined amount, the wind speed control is performed to prevent the substance formed from the discharge product from adhering to the developer carrier on which the rotation of the developing means is stopped. It is possible to always form an image without density unevenness, and at the same time, it is possible to remove the discharge product from the charging means, thereby improving the life of the image carrier.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram illustrating an image forming apparatus.

FIG. 2 is an enlarged view showing a part of the image forming apparatus.

FIG. 3 is an enlarged view showing a part of a conventional image forming apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Photosensitive drum 2 Primary charging device 3 Exposure means 4 Developing device 5 Transfer device 6 Cleaning device 7 Pre-exposure lamp 8 Separation means 9 Fixing device 10 Paper ejection tray 11 Paper feeder section 12 Duct 13 Blow fan 14 Paper feed cassette

Continuing on the front page (72) Inventor Kazuhiro Hasegawa 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Tsuneji Masuda 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. F-term (reference) 2H003 AA01 AA18 CC01 2H027 DA13 DA14 DA32 DA35 DA50 EB06 EC06 EC14 ED30 EE04 EF09 EG06 FA28 JA02 JB24 JC02 ZA07 2H030 AD02 AD08 AD16 BB23 2H077 AD02 BA10 DA18 DA47 GA02 GA03 GA15

Claims (10)

[Claims] An image carrier; a charging unit configured to charge the image carrier; a blowing unit configured to send air outside the apparatus to the charging unit and remove a discharge product generated by discharge from the charging unit; And a developing unit having a developer carrier that supplies the developer by rotating the image carrier.In the image forming apparatus, a wind speed control that changes a wind speed of air blown by the blowing unit is performed. Image forming apparatus. 2. The image according to claim 1, wherein the wind speed control reduces a wind speed as compared with a case where the charging unit charges the image carrier and the developer carrier rotates. Forming equipment. 3. The image forming apparatus according to claim 2, wherein when the charging unit stops rotating the developer carrier while charging the image carrier, the wind speed control is performed. . 4. When a plurality of the developing units are provided, and the charging unit stops rotating at least one of the plurality of the developing units while charging the image carrier, The image forming apparatus according to claim 2, wherein the wind speed control is performed. 5. A first image forming mode in which a plurality of said developing means are provided, wherein a developer is supplied by all of said plurality of developing means during image formation, and one of said plurality of said developing means during image formation. A second image forming mode in which the rotation of at least one of the developer carriers is stopped; and wherein the wind speed control controls the wind speed of the blower in the second image forming mode to a first image forming mode. 2. The image forming apparatus according to claim 1, wherein the air velocity is lower than the air velocity of the air blower in a mode. 6. An idle rotation mode in which the rotation of the developer carrier is stopped and the charging unit rotates the image carrier while charging the image carrier during a non-image forming operation. 2. The image forming apparatus according to claim 1, wherein the wind speed control is performed such that a wind speed of the blower in an idle rotation mode is lower than a wind speed of the blower in an image forming operation. 7. The image forming apparatus according to claim 2, wherein the wind speed control is performed when an absolute water content is larger than a predetermined amount. 8. The image forming apparatus according to claim 2, wherein the wind speed control is performed stepwise according to an absolute water content. 9. The image forming apparatus according to claim 7, further comprising environment detecting means for detecting temperature and humidity, and calculating an absolute water content from a detection result detected by said environment detecting means. 10. The air blower according to claim 1, wherein the blower includes a blower fan, and the wind speed control changes a wind speed by changing a rotation speed of the blower fan. The image forming apparatus according to claim 1.