JP2003307991A - Image forming apparatus and cartridge used for the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus capable of stably forming an image over a long term by preventing toner from being stuck and fused on a developer regulating member so as to prevent the thinning of image density and the vertical stripe of the image, and a process cartridge used for the image forming apparatus. <P>SOLUTION: The image forming apparatus is controlled so that potential relation between a developing roller and a developing blade while the developing roller is rotated is nearly the same potential (-300 V) in forming the image, and a specified potential difference (300 V) is provided at least at a part of image non-forming time such as preparatory pre-rotation, interpaper and preparatory post-rotation. At such a time, it is desirable to set the potential of the developing blade larger on the same polarity side as the electrifying polarity of developer than the potential of the developing roller. <P>COPYRIGHT: (C)2004,JPO

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 using an electrophotographic system or an electrostatic recording system, such as a copying machine or a printer, and a process cartridge detachable from the image forming apparatus.

[0002]

2. Description of the Related Art Conventionally, as this type of image forming apparatus,
For example, the configuration shown in FIG. 18 is known. FIG. 1 schematically shows an example of the basic configuration of a conventional image forming apparatus.

In this example, the photosensitive drum 1 is used as an image carrier.
00 is used. The photosensitive drum 100 is formed by forming a photosensitive material layer (for example, an organic photosensitive material layer) on the surface of a cylindrical base body made of aluminum, for example, and is driven to rotate. Around the photosensitive drum 100, a charging roller 101, a laser beam scanning optical system (not shown), a developing device 102 as a developing unit, a transfer roller 111, and a cleaner 109 are sequentially arranged from the upstream side in the rotation direction.

After uniformly charging the photosensitive drum 100 with the charging roller 101, an electrostatic latent image is formed on the photosensitive drum 100 by laser beam scanning light. Then, in accordance with the electrostatic latent image, it is visualized (developed) by the toner (developer) in the developing device.

The recording medium, that is, the transfer material P is fed from an unillustrated paper feed port in synchronism with the formation of the visible image (toner image), and a substantially contact portion between the photosensitive drum 100 and the transfer roller 111. Receives a visible image (toner image). Transfer material P
The upper image is fused and fixed by the fixing device 110.

The developing device 102 conveys the toner in the container to a developing roller 103 as a developer carrying member, a supplying roller 105 for supplying the non-magnetic one-component toner (negative polarity) to the developing roller 103, and the vicinity of the supplying roller 105. Stirring member 10
6, a developing blade 104 as a developer regulating member that regulates the amount of toner on the developing roller 103, and the like.

Since the developing roller 103 contacts the photosensitive drum 100, it is formed of an elastic body. Further, the developing blade 104 utilizes the elasticity of a thin metal plate to develop the developing roller 10.
Lightly contacted to 3.

To the developing roller 103, in order to transfer the toner from the developing roller 103 to the photosensitive drum 100 side,
A developing bias is applied by the developing bias power source 107 so as to have a predetermined potential. Further, a blade bias power source 108 is connected to the developing blade 104 in order to stabilize the charge amount of toner (Japanese Patent Laid-Open No. 05-011599).
A blade bias is applied so as to have a predetermined potential. There are various types of blade bias power supplies 108, such as one having the same potential as the developing bias power supply 107 and one supplying different potentials.

[0009]

As described above, in the conventional image forming apparatus, by applying a fixed DC bias or AC bias, it is possible to impart chargeability to toner or stabilize toner coat. Was there.

However, in the image forming apparatus of the conventional example, it is difficult to stabilize the toner coat while preventing the toner scattering, the fixing of the reverse toner to the developing blade, and the fusion of the toner to the developing blade.

For example, when the image forming operation shown in the above-mentioned conventional example is performed, the following problems are observed.

First, in the above conventional example, the developing bias power source 1
When 07 and the blade bias power source 108 are set to the same potential, vertical streak-shaped density unevenness occurs in a halftone image after about 1000 sheets of image formation. This also appeared on the developing roller 103 that has passed the developing blade 104.

As a result of observing the developing blade 104, a fused mass of toner is generated in the portion a of the developing blade 104 (in the vicinity of the contact portion between the developing blade 104 and the developing roller 103 and on the downstream side in the developing roller rotation direction). Was. Since the flow of toner is blocked at the portion where the fused mass of toner is present, the amount of toner on the developing roller 103 becomes thin, causing vertical stripe-shaped density unevenness on the image.

The reason for this will be described with reference to the toner fusion bonding schematic diagram of FIG. In FIG. 19, T is a non-magnetic one-component toner having a negative polarity, and the toner T is composed of toner particles and external additives as auxiliary particles.

The toner carried on the developing roller 103 has a negative polarity and, in a normal environment, the developing blade 104.
The toner layer carried on the developing roller 103 that has passed through has a potential of about −20 to −50 V (measured by a surface potential meter model 334 manufactured by Trek). At the contact portion between the developing roller 103 and the developing blade 104, the surface of the developing blade 104 is always rubbed by the toner, so that the adhesion of the external additive hardly occurs.

However, in the downstream side (a portion in the drawing) from the contact portion between the developing roller 103 and the developing blade 104,
Since the toner layer is gradually separated from the surface of the developing blade, a potential gradient will be generated.

That is, the developing roller 103 and the developing blade 1
Even if 04 has the same potential, the developing roller 10
Since the negatively charged toner layer carried on No. 3 has an electric potential, the outermost surface of the toner layer becomes more negative than the developing blade 104.

Therefore, the negative external additive G1 attached to the toner on the outermost surface of the toner layer is separated from the toner surface and attached to the surface a portion of the developing blade. The external additive adhering to the surface a portion of the developing blade gradually increases as image formation is advanced, and the surface of the developing blade 104 appears to be roughened by the adhering external additive.

Therefore, it is considered that the toner is captured on the rough surface and rubbed by the toner layer to be melted by frictional heat to generate a fused mass of the toner.

In the conventional image forming apparatus disclosed in Japanese Patent Laid-Open No. 05-011599, for example, the developing roller 10 is used.
3, the developing bias power supply 107 constantly supplies a voltage of −300 V, and the developing blade 104 is supplied with a blade bias power supply 108 of −400 V.
03 and the developing blade 104, a potential difference of about 100 V is generated. Therefore, the negative external additive G1 will not be separated from the toner surface from the toner layer surface even if the charge of the toner layer is added.

However, JP-A-05-011599
When the potential difference is provided as disclosed in the publication, the following problems occur.

For example, after the image formation of about 1500 sheets, the solid image has low density and vertical streaks. this is,
It also appeared on the developing roller 103 that has passed the developing blade 104.

To clarify the cause, the developing blade 104
As a result of observation, the portion b of the developing blade 104 (in the vicinity of the contact portion between the developing blade 104 and the developing roller 103,
In addition, the toner was attached to the entire surface on the upstream side in the rotation direction of the developing roller). The toner was not melted but adhered to the extent that it was not blown off even if air was blown with an air brush. The toner flow on the developing roller 103 was thinned because the toner flow was stopped by the toner adhering to the portion b, and vertical stripe-shaped density unevenness was generated on the image.

The developing roller 10 will be described below with reference to FIG.
3 (-300V) and developing blade 104 (-400V)
The case where the potential of is changed will be specifically described.

When the toner triboelectrically charged by the supply roller 105 reaches before the contact portion between the developing roller 103 and the developing blade 104 (near portion b), the reverse toner mixed in the toner layer (charged to the positive polarity). The toner) is attracted to the portion b on the surface of the developing blade 104 due to the influence of the potential difference. In particular, as the potential difference between the developing roller 103 and the developing blade 104 is increased, the reverse toner is attracted, so that the toner sticking at the portion b of the developing blade 104 becomes worse.

As the toner adhesion increases, before the contact portion between the developing roller 103 and the developing blade 104 (near the portion b).
Since the amount of toner that has entered the device is dammed, the toner layer is reduced. As a result, the solid image has a low density. Furthermore, since the amount of toner adhered to the developing blade 104b differs in the longitudinal direction, vertical streaks occur in addition to the low density.

This phenomenon becomes particularly remarkable when a positive external additive G2 is mixed with the negative external additive G1 as auxiliary particles of the toner. The positive polarity external additive G2 may be added in addition to the toner particles and the negative polarity external additive in order to stabilize the charging property and adjust the fluidity of the toner. Since the positive polarity external additive G2 behaves in the same manner as the reverse toner, it adheres to the portion b which is the free end tip of the developing blade 104. The fixed positive external additive G2 causes a thin concentration and vertical streaks as described above.

Further, the voltage applied to the developing blade 104 also requires fine control because the surface potential of the toner layer changes depending on the environment in which it is used. This is because the surface potential of the toner layer tends to be high in a low humidity environment and low in a high humidity environment.

Further, as described in JP-A-58-153972, when an AC bias is constantly applied to the developing blade 104, the developing roller 103 and the developing blade 1
A toner cloud is generated due to the AC bias on the downstream side (a portion in the figure) of the contact portion 04. The generation of the toner cloud causes the toner to be scattered unnecessarily, and the inside of the machine is polluted. Also, AC
When a bias is applied to the developing blade 104, since the developing roller 103 and the developing blade 104 are in contact with each other, an attack sound due to the AC bias is generated.

The present invention has been made in view of the above circumstances, and an object of the present invention is to prevent the fixing and fusion of the developer to the developer regulating member to prevent the image from having a low density and vertical stripes. An object of the present invention is to provide an image forming apparatus capable of preventing the above-mentioned problems and performing stable image formation for a long period of time, and a cartridge used in the image forming apparatus.

[0031]

In order to achieve the above object, an image forming apparatus of the present invention comprises an image carrier on which an electrostatic latent image is formed, and the electrostatic latent image is visualized by a developer. Developing means, which includes a rotatable developer carrier and a developer regulating member for regulating the amount of the developer carried on the developer carrier, and the developing device. A voltage applying unit that applies a voltage to each of the developer carrying member and the developer regulating member, and a control unit that controls the voltage applying unit are provided, and the control unit is configured to operate while the developer carrying member is rotating. It is preferable to control the voltage applying unit so that the potential relationship between the developer carrying member and the developer regulating member becomes substantially the same potential during image formation and has a predetermined potential difference at least in part during non-image formation. Characterize.

An image forming apparatus of another invention is an image carrier on which an electrostatic latent image is formed, and a means for visualizing the electrostatic latent image with a developer, which is rotatable. Developing means having a developer carrying member and a developer restricting member for restricting the amount of developer carried on the developer carrying member, and a voltage is applied to each of the developer carrying member and the developer restricting member. Voltage applying means and control means for controlling the voltage applying means, wherein the control means has a potential relationship between the developer carrying member and the developer regulating member during rotation of the developer carrying member, The potentials are substantially the same during image formation, and there is a predetermined potential difference at least in part during non-image formation, and
The voltage applying unit is controlled such that the potential of the developer regulating member is larger than the potential of the developer carrying member in the same polarity side as the charging polarity of the developer.

An image forming apparatus of another invention is an image carrier on which an electrostatic latent image is formed, and a means for visualizing the electrostatic latent image with a developer, which is rotatable. Developing means having a developer carrying member and a developer restricting member for restricting the amount of developer carried on the developer carrying member, and a voltage is applied to each of the developer carrying member and the developer restricting member. Voltage applying means and control means for controlling the voltage applying means, wherein the control means has a potential difference between the developer carrying member and the developer regulating member during rotation of the developer carrying member,
It is characterized in that the voltage applying means is controlled so as to become larger at least in part during non-image formation than during image formation.

In the above construction, it is preferable that at least the developing means is constructed as a cartridge which can be attached to and detached from the main body of the image forming apparatus.

An image forming apparatus of another invention is an image carrier on which an electrostatic latent image is formed, and a means for visualizing the electrostatic latent image with a developer, which is rotatable. A voltage is applied to both the developing means having a developer carrying member and a developer regulating member for regulating the amount of the developer carried on the developer carrying body, and both the developer carrying body and the developer regulating member. A single voltage application unit and a delay control unit that controls the delay of the voltage applied to the developer regulating member are provided, and when the image is formed by the developing unit, the voltage application unit develops the developer carrier and the developer. The voltage applied by the voltage applying unit is at least partly during non-image formation when the developer holding member is rotating and image formation is not performed by the developing unit while the developer regulating member is at substantially the same potential. And the developer regulating member by changing the applied voltage. And delay control voltage variation by the delay control means and causing a potential difference between said developer carrying member and the developer regulating member.

In addition to the above, the image forming apparatus of the present invention is an image carrier on which an electrostatic latent image is formed, and a means for visualizing the electrostatic latent image with a developer, which is rotatable. A voltage is applied to both the developing means having a developer carrying member and a developer regulating member for regulating the amount of the developer carried on the developer carrying body, and both the developer carrying body and the developer regulating member. A single voltage application unit and a delay control unit that controls the delay of the voltage applied to the developer regulating member are provided, and when the image is formed by the developing unit, the voltage application unit develops the developer carrier and the developer. The voltage applied by the voltage applying unit is at least partly during non-image formation when the developer holding member is rotating and image formation is not performed by the developing unit while the developer regulating member is at substantially the same potential. And the developer regulating member by changing the applied voltage. And delay control voltage variation by the delay control unit, the better the developer carrying member as compared to a developer regulating member, characterized in that to produce a charging polarity large potential difference of the same polarity side of the developer.

In addition, the image forming apparatus of the present invention is an image carrier on which an electrostatic latent image is formed, and a means for visualizing the electrostatic latent image with a developer, which is rotatable. A voltage is applied to both the developing means having a developer carrying member and a developer regulating member for regulating the amount of the developer carried on the developer carrying body, and both the developer carrying body and the developer regulating member. A single voltage application unit and a delay control unit for performing delay control of the voltage applied to the developer regulating member, wherein the developer is toner particles and a plurality of auxiliary additives externally added to the toner particles. One of the auxiliary particles is a particle having a polarity opposite to the charging polarity of the toner particles, and the developer carrying member and the developer are applied by the voltage applying means during image formation by the developing means. The regulating member is set to substantially the same potential, and when the developer carrier is rotating, The image forming means does not form an image, at least a part of the non-image forming time, the applied voltage by the voltage applying means is changed, and the delay control means controls the voltage fluctuation of the developer regulating member due to the change of the applied voltage. The developer control member causes a larger potential difference on the same polarity side as the charging polarity of the developer as compared with the developer carrying member.

In addition, the image forming apparatus of the present invention is an image bearing member on which an electrostatic latent image is formed, and a means for visualizing the electrostatic latent image with a developer, which is rotatable. A voltage is applied to both the developing means having a developer carrying member and a developer regulating member for regulating the amount of the developer carried on the developer carrying body, and both the developer carrying body and the developer regulating member. At least a part at the time of non-image formation, in which a single voltage application unit and a delay control unit for performing delay control of the voltage applied to the developer regulating member are provided, and image formation by the developing unit is not performed In the above, the voltage applied by the voltage applying means is changed.

In addition, the image forming apparatus of the present invention is an image bearing member on which an electrostatic latent image is formed, and a means for visualizing the electrostatic latent image with a developer, which is rotatable. A voltage is applied to both the developing means having a developer carrying member and a developer regulating member for regulating the amount of the developer carried on the developer carrying body, and both the developer carrying body and the developer regulating member. At least a part at the time of non-image formation, in which a single voltage application unit and a delay control unit for performing delay control of the voltage applied to the developer regulating member are provided, and image formation by the developing unit is not performed In the above, the voltage applied by the voltage applying means is changed so as to increase to the same polarity side as the charging polarity of the developer.

In addition, the image forming apparatus of the present invention is an image bearing member on which an electrostatic latent image is formed, and a means for visualizing the electrostatic latent image with a developer, which is rotatable. A voltage is applied to both the developing means having a developer carrying member and a developer regulating member for regulating the amount of the developer carried on the developer carrying body, and both the developer carrying body and the developer regulating member. A single voltage application unit and a delay control unit that controls the delay of the voltage applied to the developer regulating member are provided, and when the image is formed by the developing unit, the voltage application unit develops the developer carrier and the developer. The voltage applied by the voltage applying unit is at least partly during non-image formation when the developer holding member is rotating and image formation is not performed by the developing unit while the developer regulating member is at substantially the same potential. On the side of the same polarity as the developer's charging polarity compared to when image formation So as to be characterized by changing impulsive.

In addition, the image forming apparatus of the present invention is an image carrier on which an electrostatic latent image is formed, and a means for visualizing the electrostatic latent image with a developer, which is rotatable. A voltage is applied to both the developing means having a developer carrying member and a developer regulating member for regulating the amount of the developer carried on the developer carrying body, and both the developer carrying body and the developer regulating member. A single voltage application unit and a delay control unit for performing delay control of the voltage applied to the developer regulating member, wherein the developer is toner particles and a plurality of auxiliary additives externally added to the toner particles. One of the auxiliary particles is a particle having a polarity opposite to the charging polarity of the toner particles, and the developer carrying member and the developer are applied by the voltage applying means during image formation by the developing means. The regulating member is set to substantially the same potential, and when the developer carrier is rotating, In the non-image formation in which the image is not formed by the image forming means, the voltage applied by the voltage applying means is impulsive so that the voltage is increased to the same polarity side as the charging polarity of the developer as compared with the image forming time. It is characterized by changing to.

In these image forming apparatuses, the developing means develops the visible image to be transferred to the image forming area of the transfer material during the image forming, and the non-image forming occurs during the non-image forming. It is desirable that the developer carrying member is not in the image forming operation and is in the rotating state.

The surface resistance value of the developer carrier is 8 × 10.
⁵ Ω to 1 × 10 ¹² Ω, and bulk resistance value is 3 × 1
It is desirable that it is from 0 ⁵ Ω to ⁵ × 10 ⁸ Ω.

It is desirable that the surface resistance value of the developer carrying member is one digit or more larger than the bulk resistance value.

Further, in these image forming apparatuses,
In a part of the non-image formation, a potential difference of 60V to 500V is generated between the developer carrier and the developer regulating member, and the shape factor SF-1 of the toner particles is 100 to 100V.
160 and the value of the shape factor SF-2 is 100 to 140.
Is desirable.

Further, the cartridge of the present invention is characterized in that it has the developing means in these image forming apparatuses and is detachable from the main body of the image forming apparatus.

In addition, the cartridge of the present invention is characterized in that it has the developing means and the delay control means in these image forming apparatuses and is detachable from the main body of the image forming apparatus.

[0048]

BEST MODE FOR CARRYING OUT THE INVENTION Preferred embodiments of an image forming apparatus and a process cartridge according to the present invention will be described in more detail with reference to the drawings.

In the conventional image forming apparatus, by applying a fixed DC bias or AC bias,
It has been attempted to impart chargeability to the toner or stabilize the toner coat. However, in the image forming apparatus of the conventional example, it is difficult to stabilize the toner coat while preventing the toner scattering and the reversal toner from being fixed to the developing blade and being fused to the developing blade.

In this embodiment, the potential relationship between the developing roller and the developing blade (developer regulating member) during the rotation of the developing roller (developer carrying member) is substantially the same during image formation, and during non-image formation. It is characterized in that at least a part of them is controlled to have a predetermined potential difference. During non-image formation, the external additive attached to the developing blade is removed to refresh the developing blade.

Further, when a predetermined potential difference is provided between the developing roller and the developing blade at least in part during non-image formation, the potential of the developing blade is set to the same polarity side as the charging polarity of the developer than the potential of the developing roller. It is preferable to control so as to increase. This is because the external additive having the same polarity as the toner particles has the same polarity as that of the opposite polarity, so that the external additive that easily adheres to the developing blade has the same polarity as that of the toner particles. This is because it becomes an agent. However, when an external additive having a polarity opposite to the charge polarity of the toner particles is easily attached to the developing blade, a large voltage may be applied to the polarity opposite to the charge polarity of the toner particles.

Here, the image formation means the time during which the developing means develops the visible image to be transferred onto the image forming area (the area excluding the blank area) of the transfer material, and the non-image forming. Time means the time other than the time of image formation and the time when the developing roller is rotating, for example, the time during which the portion corresponding to the blank area of the transfer material is subjected to the developing process (during which the visible image is actually Not formed), during pre-rotation before image formation, during post-rotation after preparation after image formation, time between transfer materials (paper interval) when printing multiple sheets, before multi-rotation before power-on, etc. Say.

That is, in this embodiment, at the time of each printing, the negative external additive attached to the developing blade (a portion in FIG. 19) at approximately the same potential at the time of image formation is applied to the developing roller side at the time of non-image formation. The toner is fixed to and fused to the developing blade by transferring the toner to the developing blade and refreshing the developing blade.

This refresh operation is performed during non-image formation.
That is, the time during which the portion corresponding to the blank area of the transfer material is provided for development, during pre-preparation rotation before image formation, during pre-preparation rotation after completion of image formation, between sheets, etc., for example, −300 V to the developing roller. Is applied to the developing blade,
Voltages higher than 300V (for example, -400V to -90
By applying 0 V or the like for a short time, the negative external additive attached at the time of image formation works to return to the developing roller side.

As a result, since the external additive adhering to the developing blade is not deposited by setting the potentials to be substantially the same during image formation, the toner is not captured by the developing blade due to the apparent surface roughness. . As a result, it is possible to prevent fusion on the developing blade (a portion in FIG. 19).

In the present embodiment, substantially the same potential means a range of less than ± 60 V with respect to the applied developing bias.
For example, when the developing bias is -300V, -2
When the voltage is 40 V or less, the amount of toner passing through the developing blade decreases, and it becomes difficult to obtain a sufficient image density. Conversely, -36
When the voltage is 0 V or more, the positive external additive described below easily adheres to the developing blade, and the positive external additive adhering to the free end side of the developing blade causes the toner to enter the contact portion between the developing blade and the developing roller. The reason for this is that it becomes easy to be blocked, and vertical stripe-shaped density unevenness occurs.

Further, since this refresh operation is carried out in a short time during non-image formation, even if the reversal toner or the positive external additive is attached to the free end tip of the developing blade (part b in FIG. 19). Since it acts so as to return to the developing roller side during image formation, the external additive does not deposit on the developing blade as in the above, and image defects such as vertical stripes and low density do not occur.

Particularly in this embodiment, it is important that the developing roller is rotating when a potential difference is applied to the developing roller and the developing blade during the non-image formation. This is because even if a potential difference is applied in a stopped state, redeposition may occur. The positive external additive returned to the developing roller side due to the rotation of the developing roller is a downstream side portion in the rotation direction of the developing roller at the contact portion between the developing blade and the developing roller (see FIG. 19).
It becomes possible to keep away from the inside and the part a) and prevent reattachment.

Regarding the potential difference applied to the developing roller and the developing blade during the non-image formation, the range is 60V to 500V.
Is desirable. This is because if it is 60 V or less, the negative external additive adhering to the developing blade cannot be transferred to the developing roller side, and the effect of preventing fusion of the developing blade cannot be obtained. Further, the voltage of 500 V or less means that if the voltage is more than 500 V, discharge easily occurs between the developing roller and the developing blade, and the current flowing between the developing blade and the developing roller becomes large, so that a high capacity power source is required. It is because

Further, in this embodiment, it is possible to use a plurality of auxiliary particles as the auxiliary particles externally added to the toner. In particular, by using an external additive (positive polarity) having a polarity opposite to that of the toner as one of the auxiliary particles, it is possible to scrape off the negative external additive adhering to the developing blade together with the rotation operation of the developing roller. It will be possible.

The value of the shape factor SF-1 measured by the image analyzer of the toner particles is 100 to 160, and the shape factor S-1
When the value of F-2 is 100 to 140, the torque in rubbing between the developing roller and the developing blade is reduced,
By suppressing the generation of frictional heat, it becomes possible to further prevent toner fusion.

Further, it is preferable that at least the developing means is constructed as a cartridge detachably mountable to the main body of the image forming apparatus. In this case, only the developing means may be a developing cartridge, or a process cartridge in which an image carrier, a charging means, a cleaning means and the like are integrated in addition to the developing means. As a result, the labor of the user involved in various maintenance work such as toner replenishment and replacement of the developing device after the end of life can be reduced, and a stable output image can be obtained by a simple operation.

(First Embodiment) A first embodiment of the present invention will be described with reference to FIGS.

First, the image forming apparatus of this embodiment will be described with reference to FIG. The image forming apparatus of the present embodiment is a reversal development system in which toner is made visible by adhering toner to an exposed portion of an image carrier, and a developer carrier carrying negatively charged toner is brought into contact with the image carrier to develop. It is a one-component image forming apparatus for performing.

In FIG. 2, reference numeral 1 is a photosensitive drum as an image carrier, which is rotatable in the direction of arrow x. The surface of the photosensitive drum 1 is uniformly negatively charged by the charging roller 2 which is a primary charger. Then, as the photosensitive drum 1 rotates, the uniformly charged surface is exposed by the exposure device 3. Since the charge on the exposed portion disappears, the photosensitive drum 1
An electrostatic latent image is formed on it.

A developing device 4 is a developing means for transferring toner as a developer to the exposed portion of the electrostatic latent image to make the electrostatic latent image visible. The toner used is a non-magnetic one-component toner. Further, the present embodiment is a so-called reversal development system in which the toner is transferred to the exposed portion.

The toner transferred onto the photosensitive drum 1 is transferred onto the transfer material P by the transfer roller 5 as a transfer charger. The toner remaining on the photosensitive drum 1 without being transferred is removed from the photosensitive drum 1 by the cleaning unit 6.

The toner on the transfer material P is heat-melted by the fixing device 7 and fixed on the transfer material P to form a permanent image.

The developing device 4 is a developing roller 8 as a developer bearing member, and a supply roller 1 for supplying toner to the developing roller 8.
2, a developing blade 9 as a developer regulating member, and an agitating member 13 that conveys toner to the supply roller 12 side.

The developing roller 8 is a motor 1 as a driving device.
It is possible to rotate in the arrow y direction by 5. Since the developing roller 8 is so-called contact developing in which the developing roller 8 is brought into contact with the surface of the photosensitive drum 1 to perform development, it is desirable that the developing roller 8 has elasticity such as rubber. The developing bias power source 10 is applied to the developing roller 8.
Supplies a voltage of about -300V. The toner on the developing roller 8 is transferred to the exposed portion on the photosensitive drum 1 due to the potential difference between the exposed portion on the photosensitive drum 1 and the potential supplied from the developing bias power source 10.

The developing blade 9 is made of a thin metal plate and contacts the developing roller 8 by utilizing the elasticity of the thin plate.
The metal thin plate may be made of stainless steel, phosphor bronze, or the like, but in the present embodiment, a phosphor bronze thin plate having a thickness of 0.1 mm was used. Developing blade 9 and developing roller 8
The toner is triboelectrically charged due to the rubbing of the toner to give an electric charge, and at the same time, the layer thickness is regulated. A predetermined voltage is supplied to the developing blade 9 from the blade bias power supply 11.

In this embodiment, a thin metal plate is used as the developing blade 9. However, the developing blade 9 is not limited to this. For example, a conductive rubber or the like may be attached to the thin metal plate in a chip shape or coated with a conductive agent. Good.

The developing roller 8 and other members which are the features of this embodiment will be described below.

(Structure of Developing Roller) The developing roller 8 is a so-called elastic developing roller having an elastic layer on a core metal. In this embodiment, the first layer (base layer) made of solid rubber in which carbon is dispersed in budadiene rubber (BR) is formed on the core metal made of stainless steel having a diameter of 8 mm by about 4 mm.

Further, as the second layer (intermediate layer), a layer in which a spherical resin of about 20 μm to 60 μm is dispersed in nitrile rubber (NBR) is formed to have a thickness of about 10 μm. The spherical resin plays a role of adjusting the surface roughness of the developing roller.

A third layer (surface layer) is formed on the second layer. The surface layer is made of urethane rubber whose resistance is adjusted by carbon and has a layer thickness of about 10 μm. Since the resin of the surface layer has the purpose of charging the toner by being rubbed with the toner, a resin that can charge the toner to a predetermined polarity is preferably used.

(Material of developing roller) As materials for the base layer and the intermediate layer of the developing roller, in addition to the above, silicone rubber,
Commonly used rubbers such as butyl rubber, natural rubber, acrylic rubber, EPDM (ethylene / propylene copolymer) or a mixture thereof can be used.

A desired resistance value can be obtained by dispersing carbon resin particles, metal particles, an ion conductive agent and the like using these rubbers as a matrix. As the ionic conductive agent, it is possible to obtain conductivity by dispersing an ionic conductive agent such as lithium perchlorate or a quaternary ammonium salt in a binder.

As the resin binder for the surface layer, when a negatively chargeable toner is used, urethane resin, silicone resin, polyamide resin or the like is preferably used. Further, if a positively chargeable toner is used, a fluororesin or the like is preferably used. A desired resistance value can be obtained by dispersing the above-mentioned carbon resin particles, metal particles, an ionic conductive agent, etc. in these resins.

Although a three-layer structure is used in this embodiment,
It's not something you get stuck with. Although a spherical resin is used for the intermediate layer to form a desired surface roughness, it is also possible to use a two-layer structure by utilizing the surface roughness of the base layer.

(Developing Roller Resistance) As the resistance value of the developing roller, it is preferable to adapt the surface resistance and the bulk resistance described later to the following values.

The surface resistance is 2 × 10.^ThreeΩ ~ 8 x 1
0¹⁴Can be used up to Ω. Preferably 5 × 10^Four
Ω ~ 1 x 10¹²It is desirable to use in the range of Ω.
2 x 10^ThreeIf it is less than Ω, triboelectric charging to the toner becomes difficult.
Because it will be. 8 x 10 ¹⁴If it is more than Ω, friction
Due to residual charge due to electrification, uneven density (go
This is because a strike) is likely to occur.

The bulk resistance is 2 × 10 ⁴ Ω to 5
It is desirable that it be × 10 ⁸ Ω. This is because if it is 2 × 10 ⁴ Ω or less, a large amount of current flows through the elastic layer, and the required current capacity becomes large. Also 5 × 10 ⁸ Ω
This is because if the above is the case, the current flowing during development is likely to be disturbed.

(Method of Measuring Resistance of Developing Roller) (1) Method of Measuring Surface Resistance of Roller A method of measuring surface resistance of the roller will be described with reference to FIG. In the figure, 63 is a roller to be measured, and the roller 63 comprises a conductive cored bar 62 made of stainless steel or the like, an elastic layer 61 formed on the outer periphery thereof, and a roller surface 60. When the roller 63 is a single layer, the elastic layer 61 and the roller surface 60 are made of the same material.

The electrode 64 comprises application electrodes 64a and 64c for applying a voltage, which will be described later, and a measuring electrode 64b. Each of the electrodes has a thickness of 5 mm and has a circular hollowed central portion. The inner surface of the circularly hollowed electrode is in contact with the outer circumference of the roller 63 to be measured, and the respective electrodes are arranged at intervals of 5 mm.

Reference numeral 65 is a measuring circuit, which comprises a power source Ein1, a resistor Ro1, and a voltmeter Eout1. In this measurement, Ein1: 1
It was performed at 00V (DC). For the resistance Ro1, Ro1:
100Ω to 10MΩ can be used. Since the resistance Ro1 is for measuring a weak current, it is preferable to use a resistance value which is 2 to 4 digits lower than the roller surface resistance to be measured.
That is, if the roller surface resistance has a resistance of about 1 × 10 ⁸ Ω, Ro1 may be a resistance of 100 kΩ.

The surface resistance value Rs of the roller is calculated by the following equation.

[Equation 1]

The surface resistance is measured by measuring the electrodes 64a and 64b.
And the resistance between the electrodes 64c and 64b are in parallel, the effective resistance value at a 5 mm interval on the roller surface is doubled, and thus the coefficient “2” is applied.

In the present embodiment, the value of Eout1 10 seconds after the voltage was applied was measured and obtained.

(2) Method of Measuring Bulk Resistance of Roller The measurement of bulk resistance of the roller will be described with reference to FIG. In the figure, 63 is a roller to be measured, and the roller 63 is a conductive core metal 62 made of stainless steel or the like.
And the elastic layer 61 formed on the outer periphery thereof and the roller surface 6
It consists of zero. When the roller 63 is a single layer, the elastic layer 6
1 and the roller surface 60 are made of the same material.

Reference numeral 66 is a stainless steel cylindrical member having a diameter of 30 and rotates in the direction of the arrow at a speed of about 48 mm / sec. At this time, the roller 63 is driven to rotate with the rotation of the cylindrical member 66. An end roller 69 is fitted to the end of the roller to regulate the amount of penetration into the cylindrical member 66 to 50 μm (to keep the contact area between the roller and the cylindrical member constant). The end roller 69 is 100 μ larger than the outer diameter of the roller 63.
It has a cylindrical shape with a small outer diameter.

Reference numeral 67 denotes both ends of the roller 63 (conductive core metal 6
(2 parts), 500 g weight on each side,
The roller 63 is pressed against the cylindrical member 66 by a total load of 1 kg.

Reference numeral 68 is a measuring circuit, which comprises a power source Ein2, a resistor Ro2, and a voltmeter Eout2. In this measurement, Ein2: 3
It was performed at 00V (DC). For the resistor Ro2, see Ro2:
100Ω to 10MΩ can be used. Since the resistance Ro2 is for measuring a weak current, it is preferable to use a resistance value 2 to 4 digits lower than the bulk resistance of the roller to be measured. That is, if the bulk resistance of the roller has a resistance of about 1 × 10 ⁶ Ω, Ro2 may be 1 kΩ.

The bulk resistance value Rb of the roller is calculated by the following equation.

[Equation 2]

In the present embodiment, the value of Eout2 10 seconds after the voltage was applied was measured and obtained.

(Developing Roller Surface Roughness) The surface roughness of the developing roller 8 depends on the particle diameter of the toner used, but is preferably 10 μm to 10 μm in average roughness Rz of 3 μm to 15 μm. If the toner particle size to be used is 6 μm in average volume particle size, 10-point average roughness Rz is preferably 5 μm to 12 μm. When the toner particle size is smaller, it is preferable to make the ten-point average roughness Rz slightly smaller. 10-point average roughness Rz is 3
If it is less than μm, sufficient toner conveying force cannot be obtained and the density becomes insufficient, and if it is more than 15 μm, the toner cannot be sufficiently charged and toner adheres to the non-image area, so-called “fog”.
Will occur.

The ten-point average roughness Rz is JIS B0601.
The surface roughness tester “SE-30H” manufactured by Kosaka Laboratory was used for the measurement using the definition shown in FIG.

(Rubber Hardness) The rubber hardness of the developing roller is As.
A ker C rubber hardness meter (manufactured by Kobunshi Keiki Co., Ltd.) was used. The rubber hardness is 30 degrees to 65 degrees (Asker
C) The following are preferably used. 65 degrees (Ask
If it is more than r C), the toner is melted by the rubbing of the developing roller 8 to cause blade fusion or roller fusion, which is not preferable. Further, the developing roller 8 and the photosensitive drum 1
This is because the state of contact with and is likely to be unstable. If it is less than 30 degrees, it is difficult to use as a developing roller due to permanent deformation due to compression set. More preferably,
The hardness is 35 degrees to 55 degrees, and by setting the hardness within this range, triboelectric charging can be performed without applying excessive stress to the toner.

(Manufacturing Method of Developing Roller) An example of the manufacturing method of the developing roller in this embodiment will be described.

First, an adhesive for bonding rubber and ensuring conductivity is applied on the cored bar. Then, a solid rubber in which carbon resin particles and the like are dispersed is wrapped around the core metal, and the solid rubber is put in a mold. The mold is vulcanized by applying heat and pressure with a press machine, and after vulcanization, the surface is polished to obtain a solid elastic roller. The intermediate layer and the surface layer can be formed by a roll coater method, a spray method, a dipping method, or the like. The coating thickness of the ionic conductive layer is preferably about 3 μm to 50 μm. If it is 3 μm or less, abrasion due to rubbing against the photosensitive drum 1 may occur, and if it is 50 μm or more, coating must be repeated many times to obtain a desired coating thickness, which is not practical for production. Is.

(Developing Blade) The contact pressure of the developing blade is preferably a linear pressure of about 15 g / cm to 45 g / cm.
If it is 15 g / cm 3 or less, proper charging cannot be applied to the toner, resulting in “fog”, which deteriorates the image quality.
If it is 45 g / cm 2 or more, the external additive mixed in the toner due to pressure or the like easily peels off from the toner surface,
The toner is deteriorated, and the chargeability of the toner is reduced.

Although the developing blade is made of metal,
A resin or the like may be coated on a developing blade made of metal in order to improve the charging property of the toner. As the resin, a polyamide resin is preferably used when the charge polarity of the toner is negative, and a fluororesin or the like is used when the charge polarity of the toner is positive.

The linear pressure was measured by a thin stainless plate having a length of 100 mm × width of 15 mm × thickness of 30 μm, and a sandwich plate having a length of 180 mm × width of 30 mm.
B. A stainless thin plate having a thickness of 30 μm is folded so that its length is halved, a pull-out plate is inserted between the sandwiching plates, and the sandwiching plate is inserted between the developing roller 8 and the developing blade 9. In that state, pull out the extraction plate at a constant speed with a spring, etc., and the value of the spring at that time (unit:
Read g). The linear pressure when the unit is g / cm is obtained by dividing the value of the spring weight by 1.5.

(Contact pressure between developing roller and photosensitive drum) As the contact pressure of the developing roller 8 with respect to the photosensitive drum 1, a linear pressure of 20 g / cm.
120 g / cm is preferred. When the linear pressure is 20 g / cm or less, the contact state becomes unstable, and when the linear pressure is 120 g / cm or more, the external additive mixed with the toner is easily peeled off from the toner surface due to the pressure or the like, which deteriorates the toner.
This is because the charging property of the toner by the developing blade 9 will decrease.

Reference numeral 14 is a control circuit (control means). The control circuit 14 controls the rotation drive of the developing roller 8 and the voltage values of the developing bias power source 10 and the blade bias power source 11 as voltage applying means.

FIG. 1 is a diagram showing a sequence according to this embodiment. FIG. 1 shows a case where two sheets are continuously printed.

In FIG. 1, the graph of the photosensitive drum rotation and the graph of the developing roller rotation respectively show that the photosensitive drum 1 or the developing roller 8 is rotationally driven when it is convex upward.

In this embodiment, since the photosensitive drum 1 and the developing roller 8 are always in contact with each other, the rotation of the photosensitive drum 1 and the rotation of the developing roller 8 are synchronized. However, in the case of so-called non-contact development in which the photosensitive drum and the developing roller are always separated, or in the case of having a mechanism capable of separating even in the case of contact development, the rotation of the photosensitive drum 1 and the developing roller 8 is prevented. It is done asynchronously.

In FIG. 1, when a print output is requested from a personal computer (not shown) or the like, the developing bias power source 10 and the blade bias power source 11 send about -3 when the photosensitive drum 1 and the developing roller 8 start rotating.
The same potential of 00V is applied. At the beginning of rotation of the developing roller 8 and the like, it is the time of preparatory rotation before drawing an image, that is, at the time of non-image formation.

The image formation means the time of each step for forming the toner image on the portion of the transfer material P excluding the blank area. In addition, non-image formation means that the developing roller is rotating, except during image formation. For example, pre-preparation rotation, post-preparation rotation, or a so-called “paper interval” corresponding between prints corresponds to non-image formation.

The pre-preparation rotation is started, and a voltage of about -300 V is applied from the developing bias power source 10 and the blade bias power source 11, and then a voltage of about -600 V is momentarily applied to the blade bias power source 11. The time for applying −600 V is 100 msec in this embodiment.
And

At the time of non-image formation, which is the time when the image on the transfer material P is not affected, the developing blade 9 has a voltage of -600V.
Is applied to the developing roller 8. That is, a potential difference that can be transferred from the developing blade side to the developing roller side is supplied to the negatively chargeable particles (toner and external additive). Therefore, the negative external additive that adheres to the developing blade 9 immediately after the developing roller starts rotating (from the developing roller and the developing blade contact portion to the fixed end side: part a in FIG. 19) is transferred to the developing roller 8 side. It will be.

After applying -600V to the developing blade 9 and -300V to the developing roller 8 for a moment, the voltages of the developing bias power source 10 and the blade bias power source 11 become approximately the same potential of -300V, and the first image. It becomes a formation area and image formation is performed (at the time of image formation).

During this image formation, the developing roller 8 and the developing blade 9 have substantially the same potential, so that the rotating operation of the developing roller 8 causes the electric charge of the toner layer from the contact portion of the developing blade 9 to the fixed end side. The negative external additive is transferred.
However, the reversal toner, the positive external additive, and the like do not adhere to the developing blade 9.

When the image formation for the first sheet is completed, a so-called "sheet interval" between the next image formation is reached. Between these sheets, 100 msec as before rotation
During that time, a voltage of −600 V is applied to the developing blade 9.
Due to the bias applied to the developing blade 9, the negative external additive adhering to the fixed end side from the contact portion of the developing blade 9 during the image formation of the first sheet is transferred to the developing roller 8 side. Since this is performed while the developing roller 8 is rotating, the negative external additive does not return to the developing blade 9 side again.

Then, the second image is formed in the same manner as the first image is formed. At the time of image formation, the negative external additive is attached and deposited from the contact portion of the developing blade 9 to the free end tip in the same manner as described above.

The image formation for the second sheet is completed, and rotation is performed after preparation for the next printing.

At this time as well as the pre-preparation rotation and the sheet interval, 1
A voltage of -600 V is applied to the developing blade 9 for 00 msec. Due to the bias applied to the developing blade 9, the negative external additive adhering to the fixed end side from the contact portion of the developing blade 9 during the image formation of the first sheet is transferred to the developing roller 8 side. Since this is performed while the developing roller 8 is rotating, the negative external additive does not return to the developing blade 9 side again.

After the preparation, the rotation operation is completed, and the rotations of the developing roller 8 and the photosensitive drum 1 are stopped.

As described above, the developing blade 9 is used during image formation.
The negative external additive adhering to the fixed end side from the abutting part of the developing blade 9 is returned to the developing roller 8 side with a momentary potential difference between the developing blade 9 and the developing roller 8 during non-image formation to refresh the developing blade 9. It becomes possible. As a result, since the negative external additive adhering to the fixed end side from the developing blade contact portion is not deposited, it is possible to prevent the toner fusion to the developing blade 9.

Further, the timing for making a momentary electric potential difference between the developing blade 9 and the developing roller 8 when the image is not formed is restricted on the developing roller 8 when the electric potential difference is made from the same electric potential. This is because the amount of toner carried changes and a density difference occurs on the image.

Further, it is not necessary to perform the time for making a momentary potential difference between the developing blade 9 and the developing roller 8 each time, and it can be appropriately performed, for example, during pre-preparation rotation before image formation, only after pre-preparation rotation, etc. Is.

In the present embodiment, the time for which a potential difference is momentarily provided between the developing blade 9 and the developing roller 8 is 100 msec.
However, I am not particular about this. However, it takes about 5 msec to refresh the developing blade 9.
The above is necessary. There is no upper limit to the application time, but a long application time leads to a decrease in print speed, so an upper limit of several seconds is sufficient.

Further, in this embodiment, 100 mse
It is possible to make the potential difference a plurality of times during the pre-preparation rotation, but only once in c.

(Toner) In the one-component developing toner according to the present embodiment, when the cross-sectional surface observation of the toner particles using a transmission electron microscope (TEM), the wax component is substantially incompatible with the binder resin. It is preferable that they are dispersed in an island shape in a spherical shape and / or a spindle shape.

By dispersing the wax component and encapsulating it in the toner as described above, it is possible to prevent the toner from deteriorating and the image forming apparatus from being contaminated. Therefore, good chargeability is maintained and dot reproduction is achieved. It is possible to form an excellent toner image for a long period of time. In addition, since the wax component works efficiently during heating, the low temperature fixability and offset resistance are satisfied.

As a specific method for observing the tomographic plane of the toner particles, the toner particles are sufficiently dispersed in an epoxy resin which is curable at room temperature and then cured for 2 days in an atmosphere at a temperature of 40 ° C. After ruthenium tetraoxide and, if necessary, osmium tetraoxide were used together for dyeing, a flaky sample was cut out using a microtome equipped with diamond teeth, and a section of toner particles was cut using a transmission electron microscope (TEM). Observe the morphology.

In the present embodiment, it is preferable to use the ruthenium tetroxide dyeing method in order to make a contrast between the materials by utilizing a slight difference in crystallinity between the wax component used and the resin constituting the outer shell. . In the toner particles used in this embodiment, it was observed that the wax component was encapsulated by the outer shell resin.

As the wax component according to this embodiment, a wax component having a maximum endothermic peak in the region of 40 to 130 degrees at the time of temperature rise in the DSC curve measured by a differential scanning calorimeter is used. By having a maximum endothermic peak in the above temperature range, releasability is effectively exhibited while greatly contributing to low temperature fixing.

When the maximum endothermic peak is less than 40 degrees, the self-cohesive force of the wax component becomes weak, resulting in poor high temperature offset resistance and too high gloss. On the other hand, when the maximum endothermic peak exceeds 130 degrees, the fixing temperature becomes high, and it becomes difficult to appropriately smooth the surface of the fixed image. Therefore, when it is used for a color toner, the color mixing property is lowered, which is preferable. Absent. Further, when granulating and polymerizing in an aqueous medium to directly obtain a toner by a polymerization method, when the maximum endothermic peak temperature is high, problems such as precipitation of a wax component mainly during granulation occur, which is not preferable.

The maximum endothermic peak temperature of the wax component is measured according to "ASTM D 3418-8". For the measurement, for example, Perkin Elmer DSC-7 is used. The melting point of indium and zinc is used to correct the temperature of the device detection unit, and the heat of fusion of indium is used to correct the amount of heat. An aluminum pan is used as a measurement sample, an empty pan is set as a control, the temperature is raised and lowered once, and a previous history is taken, and then measurement is performed at a temperature rising rate of 10 degrees / min.

As the wax component, specifically, paraffin wax, polyolefin wax, Fischer-Tropish wax, amide wax, higher fatty acid, ester wax and derivatives thereof or graft / block compounds thereof can be used.

The toner according to this embodiment preferably has a shape factor SF-1 of 100 to 160 and a shape factor SF-2 of 100 to 140 measured by an image analyzer. It is more preferable that the value of SF-1 is 100 to 140 and the value of shape factor SF-2 is 100 to 120. Further, the above condition is satisfied, and (S
By setting the value of F-2) / (SF-1) to 1.0 or less, not only the characteristics of the toner but also the matching with the image analysis device becomes extremely good.

The shape factors SF-1 and SF-2 are FE-SEM (S-800) manufactured by Hitachi Ltd., and the magnification is 500.
Randomly sample 100 toner images that have been magnified twice, and introduce the image information into the image analysis device (Luzex3) manufactured by Nicolet Co.
It is a parameter defined by the value calculated by the following formula.

[Equation 3]

The toner shape factor SF-1 indicates the degree of roundness of toner particles, and gradually changes from a spherical shape to an irregular shape. SF
-2 indicates the degree of unevenness of the toner particles, and the unevenness of the toner surface becomes remarkable.

When the shape factor SF-1 exceeds 160, the rolling resistance becomes low and the torque increases. Further, since friction increases, frictional heat also increases and thermal deterioration easily occurs.

In order to improve the transfer efficiency of the toner image, the shape factor SF-2 of the toner particles is 100 to 140, and the value of (SF-2) / (SF-1) is 1.0 or less. Is good. When the shape factor SF-2 of the toner particles is larger than 140 and the value of (SF-2) / (SF-1) exceeds 1.0, the surface of the toner particles is not smooth and the toner particles have many irregularities. Therefore, the transfer efficiency from the photosensitive drum 1 to the transfer material P or the like tends to decrease.

Particularly, by setting the shape factor SF-1 to 160 or less and the shape factor SF-2 to 140, the developing blade 9
When a potential difference is provided between the developing roller 8 and the developing roller 8, the toner easily separates from the developing blade 9, which is effective in preventing blade fusion.

Further, as the toner particles used in the present embodiment, it is preferable to use toner particles whose surface is coated with an external additive so that the toner is given a desired charge amount.

In that sense, the coverage of the external additive on the toner surface is preferably 5% to 99%, more preferably 10% to 99%.

The external additive coverage on the toner surface was 100% for the toner image using FE-SEM (S-800) manufactured by Hitachi Ltd.
An image analysis device (Luzex) manufactured by Nicolet Co., Ltd.
Introduce into 3) and measure. Since the obtained image information has different lightness between the surface portion of the toner particles and the external additive portion, the image information is binarized to have the area SG of the external additive portion and the area of the toner particle portion (including the area of the external additive portion). Calculated by the following formula, even if divided into ST.

[Equation 4]

As the external additive used in this embodiment,
From the viewpoint of durability when added to the toner, the particle size is preferably 1/10 or less of the weight average particle size of the toner particles.
The particle size of the additive means the average particle size thereof obtained by observing the surface of the toner particles with an electron microscope. As the external additive, for example, the following ones are used.

Metal oxide (aluminum oxide, titanium oxide, strontium titanate, cerium oxide, magnesium oxide, chromium oxide, tin oxide, zinc oxide, etc.), nitride (silicon nitride, etc.), carbide (silicon carbide, etc.), metal Salts (calcium sulfate, barium sulfate, calcium carbonate, etc.), fatty acid metal salts (zinc stearate, calcium stearate, etc.), carbon black, silica, etc.

In the present embodiment, the toner particles (1
Auxiliary particles were externally added to (00 parts by weight). To the auxiliary particles added externally, 1 part by weight of silica as a negative external additive and 0.1 part by weight of titanium oxide as a positive external additive were added. In particular, when a positive external additive is added, the fluidity of the toner can be adjusted and the toner can be stably charged. In the conventional example, the positive external additive cannot be used because the positive external additive adheres to the tip of the free end of the developing blade 9, but in the present embodiment, the positive external additive is used for image formation. Since it is peeled off from the tip of the free end of the developing blade 9 by rubbing against the developing roller 8 and toner during operation, it does not affect the image.

These external additives are used in an amount of 0.01 to 10 parts by weight, preferably 0.05 to 5 parts by weight, based on 100 parts by weight of the toner particles. These external additives may be used alone or in combination. Those subjected to a hydrophobic treatment are more preferable.

When the amount of the external additive added is less than 0.01 parts by weight, the fluidity of the one-component type developer is deteriorated, and the transfer and development efficiencies are lowered, resulting in uneven image density and image. Toner is scattered around the area, so-called scattering occurs.

On the other hand, when the amount of the external additive exceeds 10 parts by weight, the excessive external additive adheres to the photosensitive drum 1 and the developing roller 8 to deteriorate the chargeability of the toner and disturb the image. To do

As described above, the potential relationship between the developing roller 8 and the developing blade 9 during rotation of the developing roller is substantially the same during image formation, and there is at least a partial potential difference during non-image formation. At the same time, the potentials acting on the potential difference are set to be larger in the developing blade 9 than the developing roller 8 in the same polarity side as the charging polarity of the developer, thereby preventing toner adhesion, deposition, and fusion on the developing blade 9. It is possible to prevent defective image density and vertical stripes.

(Second Embodiment) The second embodiment of the present invention will be described below with reference to FIGS. The same parts as those in the first embodiment are designated by the same reference numerals and the description thereof will be omitted.

FIG. 5 is a schematic view of the image forming apparatus according to this embodiment. This image forming apparatus is a color image forming apparatus, and roughly includes a photosensitive drum 1 which is an image carrier, a charging roller 2 as a charging unit, an exposure device 3 which gives image information, and an electrostatic latent image on the photosensitive drum 1. The developing device 22 for visualizing the image and the intermediate transfer member 24 are used.

The developing device 22 includes a rotary 22x as a rotary support, a yellow developing cartridge 22a, a magenta developing cartridge 22b, and a cyan developing cartridge 22.
c, a black developing cartridge 22d.

In the present embodiment, the image forming apparatus is an electrophotographic color printer, and based on image data from a personal computer, a workstation, or the like (not shown), yellow Y, magenta M, cyan C, and black Bk are used. The toner images of the respective colors are sequentially formed by separating the images into four colors, and the separated image data are superposed on the intermediate transfer member 24 and collectively transferred to a transfer material (recording medium) such as paper to obtain a full-color image. . The image forming apparatus according to the present embodiment is a so-called rotary type color printer that employs a developing device configured by mounting a plurality of developing means, that is, developing cartridges 22a, 22b, 22c, 22d in a rotary 22x. To be done.

In FIG. 5, the image forming apparatus comprises a photoconductive organic photosensitive drum 1 as an image carrier. When the image forming operation is started, the photosensitive drum 1 is rotationally driven in the direction of arrow q. The surface of the photosensitive drum 1 is uniformly charged to a predetermined dark portion potential by applying a bias to the core metal of the charging roller 2 as the contact charging means. Then the first
In accordance with the image data of yellow (Y) of the color, the exposure device 3
Scanning exposure is performed by a laser beam whose ON / OFF is controlled by, and a first electrostatic latent image is formed as a bright portion potential.

The electrostatic latent image thus formed is visualized by being developed by the developing means (developing cartridge) mounted in the rotary 22x of the developing device 22. The rotary 22x includes a first developing cartridge 22a containing a yellow (Y) toner as a first color toner, and a second developing cartridge 22a.
The second developing cartridge 22b containing magenta (M) toner as the color toner, the third developing cartridge 22c containing the cyan (C) toner as the third color toner, and the black ( Bk)
The fourth developing cartridge 22d containing the toner is mounted and integrated, and is rotationally moved to the position facing the photosensitive drum (in the direction of arrow r) during image formation of each color.

The developing cartridge (22a, 22b, 22c or 22d) located at the developing position facing the photosensitive drum 1 is a developing roller as a developer carrying member carrying toner regulated to a predetermined layer thickness. Is driven to rotate by a motor 23, and a predetermined bias is applied to a core metal of the developing roller to perform development. Also, Y, M,
C, Bk developing cartridges 22a, 22b, 22
The c and 22d are each one cartridge (developing cartridge), and can be individually replaced depending on the degree of wear.

First, the first electrostatic latent image is developed and visualized by the first developing cartridge 22a containing Y toner as the first color toner. The developing method may be contact / non-contact, but in the present embodiment, a contact developing method using a non-magnetic one-component toner in which image exposure and reversal development are combined is used.

The visualized toner image of the first color is
An intermediate transfer member 2 formed of a conductive elastic layer and a releasable surface layer on a cylinder at a first transfer portion which is a nip portion with an intermediate transfer member 24 as a second image carrier.
Electrostatic transfer (primary transfer) is performed on the surface of No. 4.

The intermediate transfer member 24 has a peripheral length longer than the length of the maximum transfer material that can pass the paper, and while being pressed against the photosensitive drum 1 with a predetermined pressing force, it is substantially equal to the peripheral speed of the photosensitive drum 1. The photosensitive drum 1 is rotationally driven in a direction opposite to the rotational direction of the photosensitive drum 1 (direction of arrow s in FIG. 5) at a constant peripheral speed (the surface of the photosensitive drum 1 and the surface of the intermediate transfer member 24 move in the same direction at the contact portion). To).

The toner image formed on the surface of the photosensitive drum 1 as described above is applied to the cylinder portion of the intermediate transfer member 24 with a voltage (primary transfer bias) having a polarity opposite to the charging polarity of the toner. By doing so, electrostatic transfer (primary transfer) is performed on the surface of the intermediate transfer member 24.

The toner remaining on the surface of the photosensitive drum 1 after the primary transfer is removed by the cleaning means 6 to prepare for the next latent image formation.

Subsequently, the same steps are repeated, and each time, the toner image of the second color developed by the M toner, C
A third color toner image developed with toner and a fourth color toner image developed with Bk toner are sequentially transferred and laminated on the surface of the intermediate transfer member 24 to form a color toner image.

After that, the transfer belt 18, which was in a state of being separated from the surface of the intermediate transfer body 24, is pressed against the surface of the intermediate transfer body 24 with a predetermined pressing force and driven to rotate. The transfer belt 17 includes a transfer roller 17. By applying a voltage (secondary transfer bias) having a polarity opposite to the charging polarity of the toner to the transfer roller 17, the intermediate transfer member 24 is transferred onto the surface of the transfer material P conveyed at a predetermined timing. The color toner images laminated on the surface are collectively transferred (secondary transfer), and the transfer material P is conveyed to the fixing device 7. After the toner image is fixed on the transfer material P by the fixing device 7 as a permanent image, the transfer material P is discharged to the outside of the apparatus, and a desired color print image is obtained.

The intermediate transfer member 24 after the secondary transfer is completed
The toner remaining on the surface is removed by the intermediate transfer body cleaning device 16 which comes into contact with the surface of the intermediate transfer body 24 at a predetermined timing.

FIG. 7 shows the developing means Y,
FIG. 6 is a configuration diagram showing developing cartridges 22a, 22b, 22c, and 22d that respectively store M, C, and Bk toners. The developing cartridges 22a to 22d are rotary type color printers that are the image forming apparatuses shown in FIG. On the other hand, the developing cartridge replacement cover (not shown) is opened and closed to be detachable, and in FIG. 5, the cyan developing cartridge 22c at the take-out position can be taken out in the upward arrow D direction.

In the rotary type color printer shown in FIG. 5, it is necessary to attach / detach the developing cartridge at the take-out position.
When replacing the other yellow, magenta, and black developing cartridges 22a, 22b, 22d, it is necessary to rotate the rotary 22x to rotate the cartridge to be taken out to the attachment / detachment position (position 22c in the figure).

Hereinafter, the case of the Y toner developing cartridge 22a will be described for simplification of description, but the same applies to the developing cartridges 22b, 22c, 22d of other colors.

The developing cartridge 22a of this embodiment shown in FIG. 7 is a reversal developing means in which a non-magnetic one-component Y toner is contained as a developer.

This developing cartridge 22a supplies the toner to the developing roller 8a which contacts the photosensitive drum 1 for development while being rotated in the direction of arrow e in the drawing, and rotates in the direction of f in the drawing to rotate. A supply roller 12a serving as a toner supply unit, a developing blade 9a serving as a developer regulating member that regulates a toner application amount and a charge amount on the developing roller 8a, a stirring member 13a that supplies toner to the supply roller 12a and stirs the toner. ing.

In FIG. 6, when a print output is requested from a personal computer (not shown) or the like, the photosensitive drum 1 rotates and the developing cartridge 2 for the first color
The rotary 22x starts revolving so that 2a is brought to a position facing the photosensitive drum 1.

Developing cartridge 2 for the first color (yellow)
When 2a comes to a position facing the photosensitive drum 1, the developing roller 8
a starts rotation before preparation. At the same time, under the control of the control unit (control means) 21, voltages are supplied from the developing bias power source 19 and the blade bias power source 20 as voltage applying means. At this time, the developing bias power source 19 applies a voltage of about −300 V to the developing roller 8 a, and the blade bias power source 20 applies −6 V to the developing blade 9 a.
A sawtooth voltage having a peak of 00V is applied. The sawtooth voltage applied from the blade bias power source 20 is 2
Waves are applied, and the cycle is applied for 90 msec per wave.

At the time of non-image formation, which is the time when the image on the transfer material P is not affected, -600 V is applied to the developing blade 9a.
A sawtooth voltage having a peak at − is applied to the developing roller 8a.
A voltage of 300V is applied. That is, a potential difference that can be transferred from the developing blade 9a side to the developing roller 8a side is supplied to the negatively chargeable particles (toner and external additive). Therefore, the negative external additive attached to the developing blade 9a immediately after the developing roller 8a starts to rotate is the developing roller 8a.
Will be transferred to the side.

-600V (sawtooth wave) on the developing blade 9a
After a momentary application of −300 V to the developing roller 8a, the developing bias power source 19 and the blade bias power source 20
Becomes approximately 300V, which is almost the same potential, and image formation is performed on the image formation region of the first color (during image formation).

At the time of image formation, the developing roller 8
Since a and the developing blade 9a have substantially the same potential, the negative external additive is transferred from the contact portion of the developing blade 9a to the fixed end side by the charge of the toner layer due to the rotating operation of the developing roller 8a. However, the reversal toner, the positive external additive, and the like do not adhere to the developing blade 9a.

When the image formation for the first color is completed, the developing cartridge 22a is rotated after the preparation, and at this time, one sawtooth voltage having a peak of -600V is applied from the blade bias power source 20. By this operation, the negative external additive attached to the developing blade 9a of the yellow developing cartridge 22a during image formation is transferred to the developing roller 8a side, and the developing blade 9a can be refreshed.

The rotation of the developing roller 8a is turned off, and the rotary 22x revolves during the next color (magenta) image formation. When the rotary 22x revolves, the voltage supply from the developing bias power source 19 and the blade bias power source 20 is turned off.

After the revolution of the rotary 22x is completed, the developing cartridge 22b for the second color (magenta) becomes the photosensitive drum 1.
Stop at the opposite position.

Then, similarly to the first color (yellow), the developing roller 8b starts pre-preparation rotation. At the same time, a voltage is supplied from the developing bias power source 19 and the blade bias power source 20. At this time, a voltage of about −300 V is applied from the developing bias power source 19, and a sawtooth voltage having a peak of −600 V is applied from the blade bias power source 20. Two sawtooth-shaped voltages applied from the blade bias power source 20 are applied, and the cycle is 90 m per wave.
applied for sec. Then, the image formation of the second color is performed similarly to the image formation of the first color. During image formation,
Similarly to the above, the negative external additive is deposited and deposited from the contact portion of the developing blade 9b to the free end tip. The above operation is performed up to the fourth color.

As described above, during the pre-preparation rotation of each color, the negative external additive adhering to the developing blade during the previous image formation is transferred to the developing roller side to prevent the external additive from accumulating on the developing blade. In addition, a stable image forming apparatus can be provided.

When the image formation for the fourth color is completed, the rotation is performed after the preparation for the fourth color.
From 0, one sawtooth voltage having a peak of -600 V is applied. After that, the rotation of the developing roller 8d is turned off, and the rotary 22x revolves. This rotary 22x
The voltage supply from the developing bias power source 19 and the blade bias power source 20 is turned off before the revolution.

When the image formation is completed and the revolution of the rotary 22x is completed, the intermediate transfer body 24, the photosensitive drum 1 and the like are rotated after the main body for the next printing, and when the rear rotation of the main body is completed, the photosensitive drum 1 is stopped. To do.

As described above, even in the full-color image forming apparatus, the developing roller 8 (8a) is rotating while the developing roller is rotating.
.About.8d) and the developing blade 9 (9a to 9d) have substantially the same potential at the time of image formation, and have a potential difference at least in a part at the time of non-image formation, and at the same time, the potential difference acts. By making the potential of the developing blade 9 larger than that of the developing roller 8 on the same polarity side as the charging polarity of the developer, toner adhesion / accumulation / fusion on the developing blade 9 is prevented, and image density defects and vertical stripes are prevented. It becomes possible.

At the same time, among the image forming elements, the developing means containing toner, which is relatively exhaustive, is a process cartridge which can be attached to and detached from the main body of the image forming apparatus. It became possible to reduce it.

(Third Embodiment) Next, the third embodiment of the present invention will be described.
The embodiment will be described with reference to FIGS. 8 and 9. The same components as those in the first embodiment are designated by the same reference numerals and the description thereof will be omitted.

In the above-described embodiment, as the timing for providing the potential difference between the developing roller and the developing blade, the pre-preparation rotation, the post-preparation rotation, the paper interval, and the like, which are during non-image formation, are described.

In the present embodiment, the developing blade is refreshed by counting the number of prints instead of the "sheet interval" and using the recovery sequence at the predetermined number of prints.

In FIG. 8, reference numeral 25 is an integrating counter, which is controlled by the control circuit 14. Integration counter 25
Counts the number of prints, and when the number of prints reaches a predetermined number, the fact is transmitted to the control circuit 14.

FIG. 9 shows a recovery sequence according to this embodiment.

In FIG. 9, a print request is awaited in step S1. When a print request is made, the photosensitive drum 1 and the developing roller 8 start rotating. At the same time, pre-preparation rotation starts, -600V is applied to the developing blade 9, and -300V is applied to the developing roller 8, and the developing blade 9 is refreshed (step S2). That is, a potential difference that can be transferred from the developing blade 9 side to the developing roller 8 side is supplied to the negatively chargeable particles (toner and external additive). Therefore, the negative external additive that adheres to the developing blade 9 immediately after the developing roller 8 starts rotating (from the developing roller and the developing blade contact portion to the fixed end side: part a in FIG. 19) is transferred to the developing roller 8 side. Will be.

After applying -600V to the developing blade 9 and -300V to the developing roller 8 for a moment, the voltages of the developing bias power source 10 and the blade bias power source 11 become approximately the same potential of -300V. An image is formed in the forming area (step S3).

Since the developing roller 8 and the developing blade 9 have substantially the same potential during this image formation, the rotation of the developing roller 8 causes a charge from the toner layer from the contact portion of the developing blade 9 to the fixed end side. The negative external additive is transferred.
However, the reversal toner, the positive external additive, and the like do not adhere to the developing blade 9.

During the formation of the first image, the integration counter is set to "+
1 ”is added (step S4). Then, it is confirmed whether the integration counter has reached 10 (step S
5).

If the total counter reaches 10,
-600V for the developing blade 9 and -3 for the developing roller 8.
The developing blade 9 is refreshed by applying 00V (step S6). In the present embodiment, step S6
The refresh time was set to 3 seconds.

When the refresh operation (step S6) is completed, or the integration counter is set to 10 in step S5.
If the number of sheets is less than or equal to the number of sheets, the next print request is made (step S7). In this case, the image formation is continued without refreshing the developing blade 9 between the sheets.

If there is no additional print request, a rotation operation is performed after preparation, and -600V is applied to the developing blade 9 and -300V is applied to the developing roller 8 to refresh the developing blade 9 (step S8). .

After the negative external additive of the developing blade 9 is transferred to the developing roller 8 side, the rotational driving of the developing roller 8, the application of the developing bias power source 10, the blade bias power source 11 and the driving of the photosensitive drum 1 are stopped. (Step S
9).

The timing at which a potential difference is momentarily provided between the developing blade 9 and the developing roller 8 is not limited to every 10 sheets of printing. If it is continuous printing, it can be appropriately performed, such as every predetermined number of sheets. However, since the negative external additive is deposited during continuous printing, the developing blade 9 needs to be refreshed at least once every 100 sheets from the viewpoint of preventing toner fusion.

As described above, during continuous printing, the negative external additive is returned to the developing roller 8 with a momentary potential difference between the developing blade 9 and the developing roller 8 at the time of non-image formation after counting a predetermined number of sheets, thereby developing The blade 9 can be refreshed. As a result, since the negative external additive adhering to the fixed end side from the developing blade contact portion is not deposited, it is possible to prevent the toner fusion to the developing blade 9.

(Fourth Embodiment) Hereinafter, another preferred embodiment of the image forming apparatus and the process cartridge according to the present invention will be described in detail.

In the image forming apparatus of this embodiment, the potential relationship between the developing roller (developer carrying member) and the developing blade (developer regulating member) is set to substantially the same potential at the time of image formation, at least as in the above-described embodiment. It is characterized in that it is controlled so as to have a predetermined potential difference in a part during non-image formation. As described above, in the image forming apparatus, at the time of non-image formation, a potential difference is generated between the developing roller and the developing blade, the external additive adhering to the developing blade is removed, and the developing blade is refreshed (refresh operation). )
This prevents the occurrence of thin images and vertical stripes.

Further, in the image forming apparatus of this embodiment, a bias is applied to the developing roller and the developing blade by a single voltage applying means, and the developing roller and the developing blade are set to substantially the same potential at the time of image formation, When the applied voltage is changed during image formation to change the potentials of the developing roller and the developing blade, the delay control means delays the potential fluctuation of the developing blade with respect to the potential fluctuation of the developing roller (delay control). Thus, a potential difference is generated between the developing roller and the developing blade.

That is, in the power supply circuit, the relatively expensive transformer and the circuit system associated with the transformer can be replaced with an inexpensive delay circuit, so that the cost of the power supply circuit can be kept low.

As described above, in the image forming apparatus, since the potential difference can be generated between the developing roller and the developing blade by the single voltage applying means, it is possible to prevent the image thinning and the vertical streaking from occurring with a simple structure.

Therefore, as compared with the above-mentioned embodiment, a separate power source is not required, so that the present invention can be implemented at a low cost.

Further, when the potential difference is generated between the developing roller and the developing blade to perform the refresh operation, the potential of the developing blade is made larger than the potential of the developing roller to the same polarity side as the charging polarity of the developer. It is similar to the form.

Further, by changing the voltage applied by the voltage applying means for a predetermined time so as to be larger on the charge polarity side of the toner than during image formation, the potential difference can be increased and the effect of refreshing the developing blade can be increased. it can.

That is, in this embodiment, the negative external additive adhering to the developing blade (part a in FIG. 19) is made to have substantially the same potential relationship between the developing roller and the developing blade during image formation for each print. By transferring the toner to the developing roller side and refreshing the developing blade at the time of non-image formation, adhesion and fusion of the toner to the developing blade are prevented.

This refresh operation is performed during non-image formation.
That is, the time during which the portion corresponding to the blank area on the transfer material is provided for development, during pre-rotation before image formation, during post-rotation after preparation after image formation, between sheets, etc.
When 300V is applied, the developing blade is -3
Voltage greater than 00V (for example, -400V to -900V)
V) is applied for a short time (changing in impulse)
As a result, the negative external additive attached at the time of image formation acts to return to the developing roller side.

Here, the impulse-like change means
Larger in the same direction as the charge polarity of the developer than during image formation 1
It means that the voltage is applied only for a short time of about 5 msec to 20 msec. The voltage may be applied for 20 msec or more, but if the application time is too long, the paper interval, pre-rotation, etc. must be taken long, leading to a decrease in throughput, so 20 msec or less is desirable. . The application time may be set to 15 msec or less, but it is difficult to obtain the target voltage if it is set shorter than 15 msec because of the delay in the response of the power source.
It is desirable to set it to 15 msec or more.

As a result, the external additive adhering to the developing blade will not be deposited, and the toner will not be captured by the developing blade due to the apparent surface roughness. As a result, it is possible to prevent fusion on the developing blade (a portion in FIG. 19).

Further, since this refreshing operation is performed in a short time during non-image formation, even if the reverse toner or the positive external additive is attached to the free end tip of the developing blade (part b in FIG. 19). Since it acts so as to return to the developing roller side during image formation, the external additive does not deposit on the developing blade as in the above, and image defects such as vertical stripes and low density do not occur.

Particularly in this embodiment, it is important that the developing roller is rotating when a potential difference is applied to the developing roller and the developing blade during the non-image formation. This is because even if a potential difference is applied in a stopped state, redeposition may occur. The positive external additive returned to the developing roller side due to the rotation of the developing roller is a downstream side portion in the rotation direction of the developing roller at the contact portion between the developing blade and the developing roller (see FIG. 19).
It becomes possible to keep away from the inside and the part a) and prevent reattachment.

The potential difference applied to the developing roller and the developing blade during the non-image formation may be 60 V or more, preferably 60 V or more and 700 V or less, and more preferably 60 V or more and 500 V or less. this is,
If it is 60 V or less, the negative external additive adhering to the developing blade cannot be transferred to the developing roller side, and the effect of preventing fusion of the developing blade cannot be obtained.

Further, since the larger the potential difference is, the larger the effect is, the upper limit is not set, but the permissible limit of leakage (dielectric breakdown) between the developing roller and the developing blade is substantially the upper limit. However, since it is a single voltage applying means and the accumulated charges are not large, even if a potential difference of 700 V is generated, no leakage occurs. The potential difference is 7
If the voltage is 00V, the object of the present invention can be achieved.
More preferably, it is set to 500 V or less because discharge is likely to start between the developing roller and the developing blade at 500 V or more.

In the present embodiment, it is possible to use a plurality of auxiliary particles as the auxiliary particles externally added to the toner. In particular, by using an external additive having a polarity opposite to that of the toner (positive polarity if the toner has a negative polarity) as one of the auxiliary particles, the negative external force attached to the developing blade is coupled with the rotation operation of the developing roller. It is also possible to scrape off the additive.

Further, it is preferable that at least the developing means is constructed as a cartridge (process cartridge) which can be attached to and detached from the main body of the image forming apparatus. In this case, only the developing means may be a developing cartridge, or a process cartridge in which an image carrier, a charging means, a cleaning means and the like are integrated in addition to the developing means. As a result, the labor of the user involved in various maintenance work such as toner replenishment and replacement of the developing device after the end of life is reduced, and a stable output image can be obtained by a simple operation.

A fourth embodiment of the present invention will be described with reference to FIGS.

First, the image forming apparatus of this embodiment will be described with reference to FIG. The image forming apparatus of this embodiment is
This is a reversal development system that visualizes toner by attaching toner to the exposed portion of the image carrier, and is a one-component image forming apparatus that develops by bringing a developer carrier carrying negatively charged toner into contact with the image carrier. .

In FIG. 11, reference numeral 31 is a photosensitive drum as an image bearing member, which is rotatable in the direction of arrow x. The photosensitive drum 31 is charged by a charging roller 32, which is a primary charger,
The surface is uniformly negatively charged. And the photosensitive drum 3
With the rotation of 1, the uniformly charged surface is exposed by an exposing device 33 such as a laser. An electrostatic latent image is formed on the exposed portion due to the disappearance of the charged electric charge.

Reference numeral 34 is a developing device. The developing device 34 is a so-called reversal developing system developing unit that transfers toner as a developer to the exposed portion of the electrostatic latent image to make the electrostatic latent image a visible image. A non-magnetic one-component toner is used as the toner. Further, the developing device 34 is detachable from the image forming apparatus main body H and can be replaced depending on the degree of wear.

The toner transferred onto the photosensitive drum 31 is transferred onto the transfer material P by the transfer roller 35 as a transfer charger. Then, the toner remaining on the photosensitive drum 31 without being transferred is cleaned by the cleaning means 36.
1 is removed from above.

The toner on the transfer material P is heat-melted by the fixing device 37 and fixed on the transfer material P to form a permanent image.

The developing device 34 includes a developing roller 38 as a developer carrying member, a supply roller 42 for supplying toner to the developing roller 38, a developing blade 39 as a developer regulating member, and an agitating member for conveying toner to the supply roller 42 side. It consists of 43.

The developing roller 38 can be rotated in the arrow y direction by a motor 45 as a driving device. Developing roller 3
Since the reference numeral 8 is so-called contact development for contacting the surface of the photosensitive drum 31 for development, it is desirable that the developing roller 38 is made of an elastic member such as rubber and has elasticity on the roller surface.

The developing bias contact 4 is attached to the developing roller 38.
A voltage of 0 to about -300 V is supplied, which causes a potential difference between the exposed portion potential on the photosensitive drum 31 and the developing roller 38, and this potential difference causes the toner on the developing roller 38 to be exposed on the photosensitive drum 31. Transfer to the exposed area.

The developing blade 39 is made of a thin metal plate and is brought into contact with and abutted on the developing roller 38 by utilizing the spring elasticity of the thin plate. The material of the thin metal plate may be stainless steel, phosphor bronze, or the like, but in the present embodiment, the thickness is 0.1 m.
m phosphor bronze sheet was used. By the rubbing of the developing blade 39 and the developing roller 38, the toner is frictionally charged to be given an electric charge, and at the same time, the layer thickness is regulated. A predetermined voltage is supplied to the developing blade 39 from the blade bias contact 41.

Reference numeral 44 is a control circuit (control means). The control circuit 44 controls the rotation drive of the developing roller 38 and the voltage value supplied to the developing bias contact 40 and the blade bias contact 41.

Reference numeral 46 is a high voltage power source as a voltage applying means. The high-voltage power supply 46 supplies a voltage to the developing roller 38 and the developing blade 39 via the developing bias contact 40 and the blade bias contact 41.

Reference numeral 47 is a delay control means arranged in the high voltage power supply 46. The delay control means 47 controls the delay of the voltage branched from the developing bias contact 40 and supplied to the blade bias contact 41.

This delay control means 47 includes a diode D1,
It is composed of a resistor R1 and a capacitor C1, and in this embodiment, R1: 100 MΩ and C1: 2200 pF.

In this embodiment, the developing roller 38 has a surface resistance of 6.8 × 10 ¹⁰ Ω and a bulk resistance of 2.8 × 10 ⁶ Ω.

FIG. 10 is a diagram showing a sequence according to this embodiment. FIG. 10 shows a case where two sheets are continuously printed.

In FIG. 10, the rotation of the photosensitive drum and the rotation of the developing roller are rotationally driven when the thick line indicating the driving state is ON (when convex). In the present embodiment, since the photosensitive drum 31 and the developing roller 38 are always in contact with each other, the rotation of the photosensitive drum 31 and the rotation of the developing roller 38 are synchronized. However, in the case where the photosensitive drum 31 and the developing roller 38 have a mechanism capable of separating so-called non-contact development in which the developing roller 38 is always separated or contact development,
The rotation of the photosensitive drum 31 and the developing roller 38 is performed asynchronously.

In FIG. 10, when a print output request is made from a personal computer (not shown) or the like, the development bias contact 40 and the blade bias contact 41 cause the development roller 38 to move as the photosensitive drum 31 and the development roller 38 start rotating. Each developing blade 39 has about -30
At the same time as the voltage of 0V is applied, the voltage of about -300V is applied to the blade bias contact 41. That is, the voltages supplied to the developing bias contact 40 and the blade bias contact 41 rise at almost the same timing. At the beginning of the rotation of the developing roller 38 and the like, it is the preparatory rotation time before drawing an image and at the time of non-image formation, but since the refresh operation is not necessary, it is not necessary to generate a potential difference.

With the voltages of the developing bias contact 40 and the blade bias contact 41 at approximately the same potential of -300 V,
An image is formed in the first image forming area (at the time of image formation).

During this image formation, since the developing roller 38 and the developing blade 39 have substantially the same potential, the developing roller 38
Due to the rotation of the developing blade 39, the negative external additive is transferred from the contact portion of the developing blade 39 to the fixed end side by the charge of the toner layer. However, the reversal toner, the positive external additive, and the like do not adhere to the developing blade.

When the image formation for the first sheet is completed, a so-called "sheet interval" between the next image formation is reached. During this sheet interval, the application of the developing bias is turned off.
When the voltage supplied to the developing bias contact 40 and the blade bias contact 41 falls, the voltage supplied to the developing bias contact 40 immediately falls, but for the blade bias contact 41, the resistance R1 of the delay control means 47 and The capacitor C1 causes a fall with a time constant.

As described above, the voltage applied to the developing roller 38 immediately falls and the voltage applied to the developing blade 39 gradually decreases, so that a potential difference is generated between the developing roller 38 and the developing blade 39. Becomes Therefore,
A maximum of 300 is provided between the developing roller 38 and the developing blade 39.
A potential difference of V will occur. And up to 300V
The potential difference of becomes smaller as time passes.

This potential difference acts so as to transfer the negative external additive adhering from the abutting portion of the developing blade 39 to the fixed end side to the developing roller 38 side. as a result,
The negative external additive attached to the surface of the developing blade 39 is refreshed. Since this is performed while the developing roller 38 is rotating, the negative external additive does not return to the developing blade 39 side again.

In this embodiment, the speed of the voltage drop of the delay control means 47 is mainly determined by the electric charge accumulated in the capacitor C1. However, when the developing roller rotates and rubs against the developing blade and toner, a negative charge is supplied from the developing blade. Therefore, the actual voltage drop due to the delay control means 47 is shorter than the time constant of the resistor R1 and the capacitor C1.

In this embodiment, the potential difference between the developing roller 38 and the developing blade 39 is almost zero in about 900 msec.
It was. In addition, in this embodiment, the sheet interval is 1 s.
Since it is set to ec, it is possible to apply a potential difference due to the delay control between the developing roller 38 and the developing blade 39 during this sheet interval, and sufficiently perform the refresh operation.

Then, the second image is formed in the same manner as the first image is formed. At the time of image formation, the negative external additive is adhered and deposited from the contact portion of the developing blade to the tip of the free end, as described above.

When the image formation for the second sheet is completed and the rotation after the preparation for the next printing is started, the application of the voltage from the high voltage power source 46 is turned off as described above.

At this time as well, it is about 900 msec in the same manner as the paper interval.
During this period, delay control of the voltage applied to the developing blade 39 is performed, and a voltage difference occurs between the developing roller 38 and the developing blade 39.

Due to the voltage difference between the developing roller 38 and the developing blade 39, the developing blade 39 is formed during the second image formation.
The negative external additive adhering to the fixed end side from the abutting part of (3) is transferred to the developing roller 38 side. Since this is performed while the developing roller 38 is rotating, the negative external additive does not return to the developing blade 39 side again.

After the preparation, the rotation operation is completed, and the rotations of the developing roller 38 and the photosensitive drum 31 are stopped.

As described above, in the present embodiment, the negative external additive adhering to the fixed end side from the abutting portion of the developing blade 39 at the time of image formation is treated with a predetermined potential difference between the developing blade and the developing roller at the time of non-image formation. (Potential difference gradually decreasing by delay control)
By causing the negative external additive to be returned to the developing roller,
The developing blade can be refreshed. As a result, the negative external additive adhering to the fixed end side from the contact portion of the developing blade is not deposited, so that the toner fusion to the developing blade can be prevented.

The timing at which a predetermined potential difference is generated between the developing blade and the developing roller is during non-image formation. When a potential difference is generated between the two members during image formation, the developing roller 38 is regulated. This is because the amount of toner carried varies, and a density difference occurs on the image.

In the present embodiment, the time required to establish a predetermined potential difference between the developing blade 39 and the developing roller 38 is 900 m.
Although it is set to sec, it is not particular about this. There is no upper limit to the application time, but a long application time leads to a decrease in print speed, so an upper limit of several seconds is sufficient. Further, if the application time is shortened, it is desirable to provide a larger potential difference.

In the present embodiment, among the image forming elements, the developing means containing toner, which is relatively exhaustive, is a cartridge that can be attached to and detached from the image forming apparatus main body H, and is involved in various maintenance work. The effort of the user was reduced.

Further, the cartridge is not limited to the developing means, but may be a so-called process cartridge PC having a charging roller 32 which is a primary charging device and a cleaning means 36 as shown by a dotted line in FIG. .

Further, in the present embodiment, the voltage delay control means is provided in the high voltage power supply 46 of the image forming apparatus, but the present invention is not limited to this. If the potential of the developing blade can be controlled (specifically, the voltage If it is in the circuit to apply),
It may be configured separately from the high-voltage power supply, and may be contained in a cartridge, for example.

As described above, this embodiment has a single voltage applying means for applying a voltage to both the developing roller and the developing blade, and the voltage imprinting means allows the developing roller and the developing blade to be used during image formation. When both members are made to have the same electric potential by applying a voltage to the developing roller, when the image formation is finished (part of the non-image forming), the delay control means causes the electric potential of the developing blade to charge the developer more than the developing roller. By increasing the polarity to the same polarity as the polarity, the developing blade can be refreshed and the purpose is achieved.

That is, OF of the voltage applying means at the time of non-image formation
By providing a difference between the voltage drop of the developing roller and the voltage drop of the developing blade at the time of F and generating a potential difference between them, the negative external additive attached to the developing blade is returned to the developing roller. As a result, it is possible to prevent fusion of the toner due to the external additive adhering to the developing blade, and prevent defective image density and vertical streaks.

(Fifth Embodiment) The fifth embodiment of the present invention will be described below. The same parts as those in the above-mentioned embodiment are designated by the same reference numerals and the description thereof will be omitted.

In the above-described embodiment, since there is a sufficient margin of about 1 sec between the paper and the rotation time after the preparation, the developing blade can be refreshed even when the potential difference between the developing blade and the developing roller is low. .

In the present embodiment, the developing blade can be refreshed sufficiently even when the interval between paper sheets or the rotation time after preparation is short.

That is, when the image forming area is finished and the non-image forming is started, the voltage of the high-voltage power supply 46 is raised for a moment and then the delay control of the voltage is effected to act between the developing blade and the developing roller. The potential difference is increased. As a result, the developing blade is sufficiently refreshed even if the time period of the potential difference acting is short.

FIG. 13 is a diagram showing a sequence according to this embodiment.

In FIG. 13, when a print output is requested from a personal computer (not shown) or the like, about -300 V is applied from the developing bias contact 40 and the blade bias contact 41 as the photosensitive drum 31 and the developing roller 38 start rotating. The same electric potential is applied. That is, regarding the voltages supplied to the developing bias contact 40 and the blade bias contact 41, the rising edges are almost at the same timing.

The voltage of the developing bias contact 40 and the voltage of the blade bias contact 41 are substantially the same potential of -300 V, and the image forming area for the first sheet is formed (at the time of image forming).

During this image formation, the developing roller 38 and the developing blade 39 have substantially the same potential, so the developing roller 38
Due to the rotation of the developing blade 39, the negative external additive is transferred from the contact portion of the developing blade 39 to the fixed end side by the charge of the toner layer. However, the reversal toner, the positive external additive, and the like do not adhere to the developing blade.

When the image formation for the first sheet is completed, a so-called "sheet interval" between the next image formation is reached.

When entering the space between sheets, the high voltage power supply 46 is set to -600.
Raise to V. As a result, the developing bias contact 40 and the blade bias contact 41 rise to -600V. At this time, the surface potential of the photosensitive drum 31 is -700V.
The above is preferable. This is to prevent "fogging" in which the toner is developed in the margins and the like when the developing bias is increased.

The measurement result of the rising speed of the high-voltage power supply 46 was about 15 msec.

After the voltage of the high voltage power supply 46 rises after 15 msec has passed, the output of the high voltage power supply 46 is turned off.
When the high-voltage power supply 46 is turned off, the output voltage of the developing bias contact 40 drops in a short time.

However, the output of the blade bias contact 41 is lowered with a gentle slope because the accumulated charge of the capacitor C1 of the delay control means 47 is discharged.

Therefore, the developing roller 38 and the developing blade 3
A maximum potential difference of 600 V will be generated between 9 and 9.
Then, the maximum potential difference of 600 V becomes smaller as time passes.

This potential difference acts so as to transfer the negative external additive adhering to the fixed end side from the contact portion of the developing blade 39 to the developing roller 38 side. as a result,
The negative external additive attached to the surface of the developing blade 39 is refreshed. Further, since this refreshing operation is performed while the developing roller 38 is rotating, the negative external additive does not return to the developing blade 39 side again.

In this embodiment, the time between sheets is set to 50.
Although it was set to 0 msec, the output of the blade bias contact 41 was −300 V or less in the time of about 400 msec. If the output of the blade bias contact 41 is -300 V or less, it does not affect the next image formation (second sheet).

Then, the second image is formed in the same manner as the first image is formed. At the time of image formation, the negative external additive is deposited and deposited from the abutting portion of the developing blade 39 to the free end tip in the same manner as described above.

When the image formation for the second sheet is completed and the rotation is performed after the preparation for the next printing, the blade bias contact 41 is applied for about 400 msec at this time as well as the sheet interval.
Output becomes -300 V or less, but since there is no next image formation, the charge of the capacitor C1 is discharged with a time constant. Even in the post-preparation rotation, due to the voltage difference between the developing roller 38 and the developing blade 39, the negative external additive adhered from the contact portion of the developing blade 39 to the fixed end side during the image formation of the second sheet, as in the case of the sheet interval. Will be transferred to the developing roller 38 side. In addition, the transition of this negative external additive,
Since this is performed while the developing roller 38 is rotating, the negative external additive does not return to the developing blade 39 side again.

After the preparation, the rotation operation is completed, and the rotations of the developing roller 38 and the photosensitive drum 31 are stopped.

As described above, the developing blade 3 is used during image formation.
The negative external additive adhering to the fixed end side from the abutting part of 9 is returned to the developing roller 38 with a momentary potential difference between the developing blade 39 and the developing roller 38 during non-image formation. The developing blade 39 can be refreshed. Particularly, according to the present embodiment, the output of the high voltage power supply 46 is momentarily increased during non-image formation, and the developing blade 3
After the electric potentials of the developing roller 38 and the developing roller 38 are raised, the delay control means 47 gives a difference in voltage drop to obtain a large electric potential difference, so that the developing blade 39 can be refreshed even when the non-image forming time is short. . As a result, the negative external additive adhering to the fixed end side from the developing blade abutting portion is not deposited, so that it is possible to prevent toner fusion to the developing blade 39.

(Sixth Embodiment) FIG. 14 shows a sixth embodiment of the present invention.
FIG. 3 is a schematic view of the image forming apparatus according to the exemplary embodiment. The image forming apparatus according to the present embodiment is a color image forming apparatus, and mainly includes a photosensitive drum 31, which is an image carrier, a charging roller 32 as a charging unit, and an exposing device for providing image information in the image forming apparatus main body H. 33, a developing device 52 that visualizes the electrostatic latent image on the photosensitive drum 31, and an intermediate transfer member 54.

The developing device 52 includes a rotary 52x as a rotary support, a yellow developing device 52a, and a magenta developing device 52.
b, a cyan developing device 52c, and a black developing device 52d.

In the present embodiment, the image forming apparatus is an electrophotographic color printer, and based on image data from a personal computer, a workstation or the like (not shown), yellow Y, magenta M, cyan C and black Bk are recorded. The toner image of each color is sequentially formed by separating the image data into four colors, and the separated image data are superposed on the intermediate transfer member and collectively transferred to a transfer material (recording medium) such as paper to obtain a full-color image. In this embodiment, the color printer is a so-called rotary type color printer that employs a developing device having a plurality of developing means, that is, developing devices mounted in a rotary.

In FIG. 14, the color printer comprises a photoconductive organic photosensitive drum 31 as an image bearing member, and the photosensitive drum 31 is rotationally driven in the direction of arrow q. The surface of the photosensitive drum 31 is uniformly charged to a predetermined dark portion potential by applying a bias to the core metal of the charging roller 32 as the contact charging means. Next, according to the image data of the first color yellow (Y),
Scan exposure is performed by the N / OFF-controlled laser beam, and a first electrostatic latent image is formed as a bright portion potential.

The electrostatic latent image thus formed is developed and visualized by the developing means (developing device) mounted in the rotary 52x of the developing device 52. This rotary 52x
Is a first developing device 52a containing a yellow (Y) toner as a first color toner and a second developing device 52 containing a magenta (M) toner as a second color toner.
b, a third developing device 52c containing cyan (C) toner as the third color toner, and a fourth developing device 52d containing black (Bk) toner as the fourth color toner.
Is mounted and integrated, and is rotationally moved to a position facing the photosensitive drum (in the direction of arrow r) during image formation of each color. In the developing unit located at the developing position facing the photosensitive drum 31, a developing roller as a developer carrying member carrying toner regulated to a predetermined layer thickness is rotationally driven by a motor 53, and the developing roller of this developing roller is driven. Development is performed by applying a predetermined bias to the cored bar. Further, the Y, M, C, and Bk developing devices 52a, 52b, 52
Each of c and 52d is a cartridge (developing cartridge), is detachably attached to the image forming apparatus main body H, and can be individually replaced depending on the degree of wear. Hereinafter, the first to fourth developing devices 52a to 52d are
The fourth developing cartridges 52a to 52d are referred to.

First, the first electrostatic latent image is developed and visualized by the first developing cartridge 52a containing Y toner as the first color toner. The developing method may be contact / non-contact, but in the present embodiment, a contact developing method using a non-magnetic one-component toner in which image exposure and reversal development are combined is used.

The visualized toner image of the first color is
At the first transfer portion, which is the nip portion with the intermediate transfer member 54 as the second image carrier, the intermediate transfer member 5 is formed on the cylinder from the conductive elastic layer and the releasable surface layer.
Electrostatic transfer (primary transfer) is performed on the surface of No. 4.

The intermediate transfer member 54 has a peripheral length longer than the length of the maximum transfer material that can pass the paper, and is pressed against the photosensitive drum 31 with a predetermined pressing force, and at the same time as the peripheral speed of the photosensitive drum 31. The photosensitive drum 31 is rotationally driven in a direction opposite to the rotational direction of the photosensitive drum 31 (each in the direction of arrow s in FIG. 14 and in the same direction at the contact portion) with a constant peripheral speed. The toner image formed on the surface of the photosensitive drum 31 as described above is applied to the cylinder portion of the intermediate transfer member 54 by applying a voltage (primary transfer bias) having a polarity opposite to the charging polarity of the toner. , Electrostatic transfer (primary transfer) to the surface of the intermediate transfer member 54
To be done.

The toner remaining on the surface of the photosensitive drum 31 after the primary transfer is removed by the cleaning means 36 to prepare for the next latent image formation.

Subsequently, the same steps are repeated, and each time, the toner image of the second color developed with the M toner, C
A third color toner image developed with toner and a fourth color toner image developed with Bk toner are sequentially transferred and laminated on the surface of the intermediate transfer member 54 to form a color toner image.

After that, the transfer belt 48, which was in a state of being separated from the surface of the intermediate transfer body 54, is brought into pressure contact with the surface of the intermediate transfer body 54 with a predetermined pressing force and is driven and rotated. The transfer belt 48 includes a transfer roller 57. By applying a voltage (secondary transfer bias) having a polarity opposite to the charging polarity of the toner to the transfer roller 57, the intermediate transfer member 54 is transferred onto the surface of the transfer material P conveyed at a predetermined timing. The color toner images laminated on the surface are collectively transferred (secondary transfer), and the transfer material P is conveyed to the fixing device 37. After the toner image is fixed on the transfer material P by the fixing device 37 as a permanent image, the transfer material P is ejected to the outside of the apparatus to obtain a desired color print image.

The intermediate transfer member 54 after the secondary transfer is completed.
The toner remaining on the surface is removed by the intermediate transfer body cleaning device 56 that comes into contact with the surface of the intermediate transfer body 54 at a predetermined timing.

FIG. 15 is a block diagram showing developing cartridges 52a, 52b, 52c and 52d, which store the toners of Y, M, C and Bk, which are the developing means of the present embodiment. These developing cartridges 52a to 52d. Figure 1
The rotary type color printer which is the image forming apparatus shown in FIG. 4 is configured to be attachable / detachable by opening and closing a developing cartridge replacement cover (not shown). In FIG. 14, the cyan developing cartridge 52c at the take-out position is shown.
Can be taken out in the direction of the upper arrow D.

In the rotary type color printer shown in FIG. 14, it is necessary to attach and detach the developing cartridge at the take-out position.
When replacing the yellow, magenta, and black developing cartridges 52a, 52b, and 52d other than c, it is necessary to rotate the rotary 52x to rotate the cartridge to be taken out to the attachment / detachment position (position 52c in the drawing).

Hereinafter, the case of the Y toner developing cartridge 52a will be described for simplification of description, but the same applies to the developing cartridges 52b, 52c, 52d of other colors.

The developing cartridge 52a of this embodiment shown in FIG. 15 is a reversal developing means in which a non-magnetic one-component Y toner is contained as a developer.

The developing cartridge 52a supplies the toner to the developing roller 38a by rotating the developing roller 38a in the direction of an arrow e in the drawing to come into contact with the photosensitive drum 31 to develop the developing roller 38a. Supply roller 42a and developing roller 38a as toner supply means
A developing blade 39a as a developer regulating member that regulates the toner application amount and the charge amount on the upper side, and a toner supply roller 42
It is provided with a stirring member 43a and the like for supplying and stirring to a.

FIG. 16 shows a sequence diagram of this embodiment. In this embodiment, the high voltage power supply 58
Of the developing roller 38a and the developing blade 39a are instantaneously increased, and immediately after that, the voltage is controlled to a predetermined developing bias (-300V). At this time, delay control is performed on the voltage of the developing blade 39a to generate a potential difference between the developing roller 38a and the developing blade 39a.

In the present embodiment, the delay control means 59.
Resistance R2: 100MΩ, capacitor C2: 4700p
It was set to F.

Further, the time for causing the potential difference in the pre-preparation rotation can be adjusted by the time for maintaining the overshoot. In this embodiment, the potential difference time was 220 msec.

The time required to generate the potential difference in the pre-preparation rotation is shorter than the post-preparation rotation time described later. this is,
This is because the capacitor C2 is in a state of not being charged when the developing bias is started.

In FIG. 16, when a print output is requested from a personal computer (not shown) or the like, the photosensitive drum 31 rotates, and the revolution of the first color developing device 52a starts so as to come to face the photosensitive drum 31. To do. When the developing device 52a for the first color (yellow) comes to a position facing the photosensitive drum 31, the developing roller 38a starts pre-preparation rotation.
At the same time, a voltage (-750V) is supplied to the developing bias contact 49 and the blade bias contact 50.

Immediately thereafter, the output of the high voltage power source 58 is lowered to a predetermined developing bias voltage (-300V). The voltage of the developing bias contact 49 immediately drops to -300V, but the voltage of the blade bias contact 50 gradually drops because of delay control by the delay control means 59, that is, because of the accumulated charge of the capacitor C2. As a result, a potential difference that can be transferred from the developing blade side to the developing roller side is generated for the negatively chargeable particles (toner and external additive).

Therefore, the negative external additive attached to the developing blade 39a immediately after the developing roller starts rotating is the developing roller 3
It is transferred to the 8a side (the refresh operation is performed).

When the discharge from the capacitor C2 is completed, the output values of the developing bias contact 49 and the blade bias contact 50 become the same value (-300V), and the image forming area for the first color is formed (at the time of image forming).

Since the developing roller 38a and the developing blade 39a have substantially the same potential during this image formation, the rotation of the developing roller 38a causes the electric charge of the toner layer from the contact portion of the developing blade 39a to the fixed end side. The negative external additive is transferred. However, the reversal toner, the positive external additive, and the like do not adhere to the developing blade 39a.

When the image formation for the first color is completed, the developing device 52a is rotated after preparation. At this time, the output value of the high-voltage power supply 58 is increased to -600 V as in the fifth embodiment, and the output is immediately output. Turn off. As a result, the output value of the developing bias contact 49 immediately drops, but the output value of the blade bias contact 50 drops over time because the capacitor C2 is sufficiently charged. As a result, a potential difference is generated between the developing roller 38a and the developing blade 39a. By this operation, the negative external additive adhering to the developing blade 39a of the yellow developing device during image formation is transferred to the developing roller side, and the developing blade can be refreshed.

Then, the rotation of the developing roller 38a is turned off,
The rotary 52x revolves until the next color (magenta) image is formed. When the rotary 52x revolves, the voltage supply from the developing bias contact 49 and the blade bias contact 50 is turned off.

The revolution of the rotary 52x is completed, and the developing device 52b for the second color (magenta) is stopped at the position facing the photosensitive drum 31.

Then, similarly to the first color (yellow), the developing roller 38b starts pre-preparation rotation. At the same time,
Overshooted voltage is supplied from the developing bias contact 49 and the blade bias contact 50. And 1
The image formation of the second color is performed similarly to the image formation of the color.
At the time of image formation, the negative external additive is deposited and deposited from the contact portion of the developing blade 39b to the free end tip in the same manner as described above. After that, the developing blade 39b is refreshed, and these operations are performed up to the fourth color.

As described above, during the pre-preparation rotation of each color, the negative external additive adhering to the developing blade during the previous image formation is transferred to the developing roller side to prevent the external additive from accumulating on the developing blade. In addition, a stable image forming apparatus can be provided.

When image formation for the fourth color is completed, rotation is performed after preparation for the fourth color, and a bias having a potential difference is applied as described above. After that, the rotation of the developing roller is turned off,
The rotary 52x orbits. By this revolution of the rotary, the developing bias contact 49 and the blade bias contact 5
Since it is separated from 0, the voltage supply is turned off. The electric charge in the capacitor C2 is removed by the resistor R2.

When the image formation is completed and the revolution of the rotary is completed, the intermediate transfer member 54, the photosensitive drum 31 and the like are rotated after the main body for the next printing, and when the rear rotation of the main body is completed, the photosensitive drum 31 is stopped. .

In the present embodiment, the bias applied during pre-preparation rotation is created by overshooting. However, this is not the only concern, and a similar voltage can be set in advance by setting a voltage higher than a predetermined voltage output. It is possible to get an effect.

Further, in the present embodiment, among the image forming elements, the developing means containing toner, which is relatively exhaustive, is a cartridge that can be attached to and detached from the image forming apparatus main body H, and is involved in various maintenance work. The effort of the user was reduced.

Further, in the present embodiment, the voltage delay control means is provided in the high voltage power source 58 of the image forming apparatus, but it is not limited to this, and if the potential of the developing blade can be controlled (specifically, the voltage is If it is in the circuit to apply),
It may be configured separately from the high-voltage power supply, and may be contained in a cartridge, for example.

As described above, the full-color image forming apparatus also has a single voltage applying means for applying a voltage to both the developing roller and the developing blade, and has a potential relationship between the developing roller and the developing blade during rotation. , The potential is almost the same during image formation, and there is a potential difference in a part during non-image formation, and at the same time, the potentials acting on the potential difference are closer to the same polarity side as the charging polarity of the developer in the developing blade than in the developing roller. By increasing the size, the developing blade can be refreshed as in the above-described embodiment, and the object can be achieved.

That is, the voltage applying means is turned on during non-image formation.
When the applied voltage is sometimes overshooted and then lowered, a difference is provided between the voltage drop of the developing roller and the voltage drop of the developing blade, and a potential difference is generated between the two. This potential difference causes the negative external additive adhering to the developing blade to return to the developing roller. As a result, it is possible to prevent fusion of the toner due to the external additive adhering to the developing blade, and prevent defective image density and vertical streaks.

(Image Evaluation Experiment) Next, the results of image evaluation experiments of the image forming apparatuses of the first to sixth embodiments and the image forming apparatus prepared as a comparative example are shown.

The following image forming apparatuses were prepared as comparative examples.

Comparative Example 1: In the image forming apparatus of the first embodiment, a bias of the same potential (-300 V) is applied to the developing roller 8 and the developing blade 9 during image formation and non-image formation. That is, this is an example in which there is no potential difference between the developing roller 8 and the developing blade 9.

Comparative Example 2: In the image forming apparatus of the first embodiment, the developing roller 8 is biased with a potential of -300 V, and the developing blade 9 is biased with a potential of -400 V during image formation and non-image formation. Bias is applied. That is, this is an example in which there is a potential difference between the developing roller 8 and the developing blade 9 even during image formation.

Regarding the image forming apparatus of each of the above-described embodiments and the image forming apparatus of the comparative example, about 2000 sheets in a normal environment,
When a pattern with a predetermined printing rate was output, the occurrence of thin image density and vertical streaks were evaluated. The evaluation was performed by outputting a solid image and a halftone image for every 500 sheets.

The evaluation was evaluated as ◯ when there was no image defect, and as × when light density and vertical streaks occurred.

The results are shown in Table 1. As a result, it was found that in the image forming apparatus according to each of the embodiments of the present invention, stable image formation can be performed for a long period of time without toner fusion to the developing blade.

[Table 1]

In this embodiment, a monochrome copying machine and a full-color copying machine are given as examples of the structure of the image forming apparatus, but the invention is not limited to this, and a printer, a facsimile, a monochrome copying machine, or the like can be used. It can be widely applied to those provided with a developing means for forming a developer image by a photographic system or an electrostatic recording system.

(Seventh Embodiment) The seventh embodiment of the present invention will be described below with reference to FIG. The first
The same parts as those in the above embodiment are designated by the same reference numerals and description thereof will be omitted. FIG. 17 is a diagram for explaining the uncoated state of the developing roller. FIG. 17A shows the developing roller and the developing blade, and FIG. 17B is a sectional view taken along the line JJ ′ of FIG.

In the above-described embodiments, the toner layer is interposed between the developing roller and the developing blade. Since the toner has an insulating property, it has a very large resistance between the developing roller and the developing blade.

However, as shown in FIG. 17B, for example, at the end of the endurance, the toner is consumed and the toner is not normally carried on the developing roller, or there is a foreign substance (paper dust) between the developing roller and the developing blade. And the like) and the toner layer disappears, the following problems occur. That is, when the toner layer between the developing roller and the developing blade disappears, the developing blade 9 directly contacts the developing roller 8 (K in FIG. 17B).
Department)

In particular, when the current capacity is small and the surface layer resistance of the developing roller 8 is low, the surface of the developing roller follows the voltage applied to the developing blade 9. As a result, a desired potential difference could not be applied between the developing roller and the developing blade, and vertical streaks were generated on the image.

In view of the above problems, in the present embodiment, even when the developing roller and the developing blade are in direct contact with each other, a potential difference is generated between the developing roller and the developing blade to prevent image defects such as vertical stripes. did.

As a result of earnest study, in the first embodiment, a sufficient current capacity could be secured by the two power supplies.
However, in the fourth embodiment and the like, the delay control means 4
The electric charge accumulated in the capacitor C1 in
In the process of being discharged through 8, the potential difference was generated between the developing roller 38 and the developing blade 39.

However, since the discharge charge from the capacitor C1 is used, if the surface resistance of the developing roller or the resistance of the bulk is lowered, the charge escapes to the surface in the longitudinal direction and a desired potential difference is obtained. It gets harder. Further, the time constant is not dependent on the resistance R1 of the delay control means 47, and the time constant is suddenly shortened.

Therefore, in this embodiment, by selecting the resistance of the developing roller, a desired potential difference can be obtained even if the developing roller and the developing blade are directly touched.

As described above, since it depends on the amount of electric charge that can flow, the range of resistance values of the developing roller that can be used depends on whether two power sources are used or one power source.
Will be different. A single power supply has a narrower range. This means that when two power supplies are used, as long as there is enough power capacity, the current flowing to the developing roller via the developing blade can be increased, but in the case of one power supply, the discharge charge from the capacitor C1 can be increased. This is because it depends on the amount of charge that can be stored in the capacitor.

Therefore, as the resistance value of the developing roller, it is preferable to adapt the surface resistance and the bulk resistance described later to the following values.

As the surface resistance, 8 × 10 ⁵ Ω or more can be used. Preferably, it is desirable to use in the range of 7 × 10 ⁶ Ω or more. This is because if the developing blade comes into direct contact with the developing roller in the case of 8 × 10 ⁵ Ω or less, it becomes difficult to form a desired potential difference between the developing roller and the developing blade.

The bulk resistance is preferably 3 × 10 ⁵ Ω or more. This is because if it is 3 × 10 ⁵ Ω or less, it becomes difficult to obtain a desired time constant. More preferably, it is 1 × 10 ⁶ Ω or more.

More preferably, the resistance value of the surface resistance is larger than that of the bulk by one digit (one order) or more. It is better to increase the surface resistance
This is because it becomes easier to obtain a potential difference between the developing roller and the developing blade.

As described above, the resistance value of the developing roller is narrower than that of the above-mentioned embodiment, but the manufacturing condition of the developing roller is not difficult, and a sufficient resistance value range can be secured.

(Evaluation of Image) In this embodiment, as the resistance of the developing roller, surface resistance: 3 × 10 ⁶ Ω and bulk resistance: 8 × 10 ⁵ Ω were used.

In the comparative example, as the resistance of the developing roller, surface resistance: 1.2 × 10 ⁵ Ω, bulk resistance: 9 ×
The one with 10 ⁴ Ω was used.

The developing roller is applied to the sixth embodiment, and an uncoated portion of toner is intentionally formed on the developing roller so that the developing blade directly contacts the developing roller. Then, in that state, when a pattern with a predetermined printing rate of about 2000 sheets was output in a normal environment, the occurrence of vertical stripes was evaluated. The evaluation was performed by outputting a solid image and a halftone image for every 500 sheets.

(Results of Examination) As a result, in the comparative example, vertical streaks were generated on 1000 sheets, but no vertical streaks were observed on the developing roller of this embodiment.

In this embodiment, the case of one power source has been described, but the present invention is not limited to this, and the capacity of the power source can be reduced by setting the resistance value of the developing roller to the range of two power sources. Is possible.

As described above, by adjusting the resistance value of the developing roller, it is possible to prevent the generation of vertical stripes even when the developing blade and the developing roller come into direct contact with each other by causing an uncoated portion on the developing roller. became.

[0340]

As described above, according to the present invention, it is possible to prevent the developer from sticking and sticking to the developer regulating member. As a result, it is possible to prevent the occurrence of image defects such as low image density and vertical stripes, and to perform stable image formation for a long period of time.

[Brief description of drawings]

FIG. 1 is a diagram illustrating a sequence according to a first embodiment of the present invention.

FIG. 2 is a schematic configuration diagram showing an image forming apparatus according to a first embodiment of the present invention.

FIG. 3 is an explanatory diagram of a roller surface resistance measuring method.

FIG. 4 is an explanatory diagram of a method for measuring the resistance of the roller bulk.

FIG. 5 is a schematic configuration diagram showing an image forming apparatus according to a second embodiment of the present invention.

FIG. 6 is a diagram illustrating a sequence according to a second embodiment of the present invention.

FIG. 7 is a schematic configuration diagram of a developing cartridge according to a second embodiment of the present invention.

FIG. 8 is a schematic configuration diagram showing an image forming apparatus according to a third embodiment of the present invention.

FIG. 9 is a flowchart showing an operation according to the third embodiment of the present invention.

FIG. 10 is a diagram illustrating a sequence according to a fourth embodiment of the present invention.

FIG. 11 is a schematic configuration diagram showing an image forming apparatus according to a fourth embodiment of the present invention.

FIG. 12 is a schematic configuration diagram showing a modified example of the image forming apparatus according to the fourth embodiment of the present invention.

FIG. 13 is a diagram for explaining a sequence according to the fifth embodiment of the present invention.

FIG. 14 is a schematic configuration diagram showing an image forming apparatus according to a sixth embodiment of the present invention.

FIG. 15 is a schematic configuration diagram of a developing cartridge according to a sixth embodiment of the present invention.

FIG. 16 is a diagram for explaining a sequence according to the sixth embodiment of the present invention.

FIG. 17 is a diagram illustrating an uncoated state of a developing roller.

FIG. 18 is a schematic configuration diagram showing a conventional image forming apparatus.

FIG. 19 is a diagram for explaining toner fusion to a developing blade in a conventional developing device.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Photosensitive drum (image carrier) 2 Charging roller 3 Exposure device (exposure device) 4 Developing device (developing device) 5 Transfer roller 6 Cleaning device 7 Fixing device 8, 8a, 8b, 8c, 8d Development roller (developer carrier) ) 9, 9a, 9b, 9c, 9d developing blade (developer regulating member) 10 developing bias power source (voltage applying means) 11 blade bias power source (voltage applying means) 12, 12a, 12b, 12c, 12d supply rollers 13, 13a , 13b, 13c, 13d Stirring member 14 Control circuit (control means) 15 Motor 16 Intermediate transfer member cleaning device 17 Transfer roller 18 Transfer belt 19 Development bias power supply (voltage application means) 20 Blade bias power supply (voltage application means) 21 Control unit (Control means) 22 Developing devices 22a, 22b, 22c, 22d Developing cartridge (developing means ) 22x rotary 23 motor 24 intermediate transfer body 25 integrating counter 31 photosensitive drum (image carrier) 32 charging roller 33 exposing device (exposure means) 34 developing device (developing means) 35 transfer roller 36 cleaning means 37 fixing devices 38, 38a, 38b, 38c, 38d developing roller (developer carrying member) 39, 39a, 39b, 39c, 39d developing blade (developer regulating member) 40 developing bias contact 41 blade bias contact 42, 42a, 42b, 42c, 42d supply roller 43 , 43a, 43b, 43c, 43d Stirring member 44 Control circuit 45 Motor 46 High-voltage power supply (voltage applying means) 47 Delay control means 48 Transfer belt 49 Development bias contact 50 Blade bias contact 51 Control section 52 Developers 52a, 52b, 52c, 52d Development cartridge (developer 52x rotary 53 motor 54 intermediate transfer member 56 intermediate transfer member cleaning device 57 transfer roller 58 high-voltage power supply (voltage applying means) 59 delay control means 60 roller surface 61 elastic layer 62 conductive core 63 roller 64 electrodes 64a, 64c application Electrode 64b Measurement electrode 65 Measurement circuit 66 Cylindrical member 67 Load 68 Measurement circuit 69 End roller C1 Capacitor C2 Capacitor D1 Diode R1 Resistor R2 Resistor PC Process cartridge P Transfer material T Toner (developer)

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) G03G 15/06 101 G03G 15/08 501D 15/08 501 504A 504 21/00 372 (72) Inventor Satoshi Tsuruya 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. F term (reference) 2H005 AA08 CB07 CB13 EA10 2H027 DA03 DA04 DA32 DA34 DE05 DE07 DE09 EA05 EA15 EA18 EA20 EC20 ED02 ED08 ED09 EE01 EE04 EE07 BA02 EF09 EF09 2 BA07 BA09 BA12 BA13 BA21 BA41 BA45 CA02 2H077 AD02 AD06 AD13 AD17 AD35 AD37 BA09 DB08 DB14 EA11 FA21 FA25

Claims (22)

[Claims] 1. An image carrier on which an electrostatic latent image is formed, a means for visualizing the electrostatic latent image with a developer, and a rotatable developer carrier and the developer carrier. Developing means having a developer regulating member for regulating the amount of developer carried on the body, voltage applying means for applying a voltage to each of the developer carrying body and the developer regulating member, and the voltage applying means. A control means for controlling the means, wherein the potential relationship between the developer carrier and the developer regulating member during rotation of the developer carrier is substantially the same during image formation, An image forming apparatus, characterized in that the voltage applying means is controlled so that a predetermined potential difference is present in at least a part of image formation. 2. An image bearing member on which an electrostatic latent image is formed, a means for visualizing the electrostatic latent image with a developer, and a rotatable developer bearing member and the developer bearing member. Developing means having a developer regulating member for regulating the amount of developer carried on the body, voltage applying means for applying a voltage to each of the developer carrying body and the developer regulating member, and the voltage applying means. A control means for controlling the means, wherein the potential relationship between the developer carrying member and the developer regulating member during rotation of the developer carrying member is substantially the same during image formation, There is a predetermined potential difference at least in part during image formation, and the potential of the developer regulating member is larger than the potential of the developer carrying member on the same polarity side as the charging polarity of the developer. In addition, the voltage applying means is controlled. Image forming apparatus. 3. An image carrier on which an electrostatic latent image is formed, a means for visualizing the electrostatic latent image with a developer, and a rotatable developer carrier and the developer carrier. Developing means having a developer regulating member for regulating the amount of developer carried on the body, voltage applying means for applying a voltage to each of the developer carrying body and the developer regulating member, and the voltage applying means. A control means for controlling the means, wherein the control means controls the potential difference between the developer carrying member and the developer regulating member during rotation of the developer carrying member to be greater than that at the time of image formation and at the time of non-image formation. An image forming apparatus, characterized in that the voltage applying means is controlled so as to be increased at least in a part. 4. The image forming apparatus according to claim 1, wherein the predetermined potential difference is 60V to 500V. 5. The image forming is when the developing means is developing a visible image to be transferred to an image forming area of a transfer material, and the non-image forming is other than the image forming. The image forming apparatus according to claim 1, 2, 3 or 4, wherein the image forming apparatus is present and the developer carrier is rotating. 6. The developer according to claim 1, wherein the developer has toner particles and auxiliary particles having a polarity opposite to a charging polarity of the toner particles and externally added to the toner particles. 5
The image forming apparatus according to claim 1. 7. The toner particles have a shape factor SF-1 of 100 to 160 and a shape factor SF-2 of 100.
7. The image forming apparatus according to claim 6, wherein the image forming apparatus is from 140 to 140. 8. The image forming apparatus according to claim 1, wherein the developing unit is configured as a cartridge that is detachable from the main body of the image forming apparatus. 9. An image carrier on which an electrostatic latent image is formed, a means for visualizing the electrostatic latent image with a developer, and a rotatable developer carrier and the developer carrier. A developing means having a developer regulating member for regulating the amount of the developer carried on the body; a single voltage applying means for applying a voltage to both the developer carrying body and the developer regulating member; A delay control unit that controls the delay of the voltage applied to the developer regulating member, and when the image is formed by the developing unit, the voltage applying unit causes the developer carrier and the developer regulating member to have substantially the same potential. Changing the voltage applied by the voltage applying means during at least a part of non-image formation in which the image forming by the developing means is not performed while the developer carrying body is rotating,
An image forming apparatus characterized in that a voltage variation of the developer regulating member due to a change of the applied voltage is delayed and controlled by the delay control means to generate a potential difference between the developer carrying member and the developer regulating member. 10. An image carrier on which an electrostatic latent image is formed, a means for visualizing the electrostatic latent image with a developer, and a rotatable developer carrier and the developer carrier. A developing means having a developer regulating member for regulating the amount of the developer carried on the body; a single voltage applying means for applying a voltage to both the developer carrying body and the developer regulating member; A delay control unit that controls the delay of the voltage applied to the developer regulating member, and when the image is formed by the developing unit, the voltage applying unit causes the developer carrier and the developer regulating member to have substantially the same potential. Changing the voltage applied by the voltage applying means during at least a part of non-image formation in which the image forming by the developing means is not performed while the developer carrying body is rotating,
The delay control means delay-controls the voltage fluctuation of the developer regulating member due to the change of the applied voltage, and the developer regulating member has a larger potential difference on the same polarity side as the charging polarity of the developer as compared with the developer carrying member. An image forming apparatus, characterized in that: 11. An image carrier on which an electrostatic latent image is formed, a means for visualizing the electrostatic latent image with a developer, and a rotatable developer carrier and the developer carrier. A developing means having a developer regulating member for regulating the amount of the developer carried on the body; a single voltage applying means for applying a voltage to both the developer carrying body and the developer regulating member; A delay control unit that controls the delay of the voltage applied to the developer regulating member, wherein the developer has toner particles and a plurality of auxiliary particles externally added to the toner particles, One of the auxiliary particles is a particle having a polarity opposite to the charging polarity of the toner particles, and at the time of image formation by the developing unit, the developer carrying member and the developer regulating member are set to substantially the same potential by the voltage applying unit, Image formation is performed by the developing unit while the developer carrier is rotating. In at least a part of the non-image formation, the voltage applied by the voltage applying unit is changed, and the voltage fluctuation of the developer regulating member due to the change of the applied voltage is delayed by the delay control unit to delay the development. An image forming apparatus characterized in that the developer regulating member causes a larger potential difference on the same polarity side as the charging polarity of the developer as compared with the developer carrying member. 12. An image bearing member on which an electrostatic latent image is formed, a means for visualizing the electrostatic latent image with a developer, and a rotatable developer bearing member and the developer bearing member. A developing means having a developer regulating member for regulating the amount of the developer carried on the body; a single voltage applying means for applying a voltage to both the developer carrying body and the developer regulating member; A delay control unit that controls the delay of the voltage applied to the developer regulating member, and is applied by the voltage applying unit at least in part during non-image formation when the image formation is not performed by the developing unit. An image forming apparatus characterized by changing a voltage. 13. An image carrier on which an electrostatic latent image is formed, a means for visualizing the electrostatic latent image with a developer, and a rotatable developer carrier and the developer carrier. A developing means having a developer regulating member for regulating the amount of the developer carried on the body; a single voltage applying means for applying a voltage to both the developer carrying body and the developer regulating member; A delay control unit that controls the delay of the voltage applied to the developer regulating member, and is applied by the voltage applying unit at least in part during non-image formation when the image formation is not performed by the developing unit. An image forming apparatus characterized in that the voltage is changed so as to increase to the same polarity side as the charging polarity of the developer. 14. An image carrier on which an electrostatic latent image is formed, a means for visualizing the electrostatic latent image with a developer, and a rotatable developer carrier and the developer carrier. A developing means having a developer regulating member for regulating the amount of the developer carried on the body; a single voltage applying means for applying a voltage to both the developer carrying body and the developer regulating member; A delay control unit that controls the delay of the voltage applied to the developer regulating member, and when the image is formed by the developing unit, the voltage applying unit causes the developer carrier and the developer regulating member to have substantially the same potential. During the non-image forming time when the image forming by the developing means is not being performed while the developer carrying body is rotating, the voltage applied by the voltage applying means is compared with that at the time of image forming by the developer. Impulsively to increase to the same polarity side as the charging polarity of Image forming apparatus, characterized in that to reduction. 15. An image carrier on which an electrostatic latent image is formed, a means for visualizing the electrostatic latent image with a developer, and a rotatable developer carrier and the developer carrier. A developing means having a developer regulating member for regulating the amount of the developer carried on the body; a single voltage applying means for applying a voltage to both the developer carrying body and the developer regulating member; A delay control unit that controls the delay of the voltage applied to the developer regulating member, wherein the developer has toner particles and a plurality of auxiliary particles externally added to the toner particles, One of the auxiliary particles is a particle having a polarity opposite to the charging polarity of the toner particles, and at the time of image formation by the developing unit, the developer carrying member and the developer regulating member are set to substantially the same potential by the voltage applying unit, Image formation is performed by the developing unit while the developer carrier is rotating. In at least a part of the non-image formation, the voltage applied by the voltage application unit is changed in an impulse manner so as to be larger to the same polarity side as the charging polarity of the developer as compared with the image formation. Image forming apparatus. 16. The image forming operation is when the developing means is developing a visible image to be transferred to an image forming area of a transfer material, and the non-image forming operation is other than the image forming operation. The image forming apparatus according to any one of claims 9 to 15, wherein the image forming apparatus is present and the developer carrier is rotating. 17. The surface resistance value of the developer carrying member is 8 × 1.
It is 0 ⁵ Ω to 1 × 10 ¹² Ω, and the bulk resistance value is 3 ×.
The image forming apparatus according to claim 9, wherein the image forming apparatus has a resistance of 10 ⁵ Ω to ⁵ × 10 ⁸ Ω. 18. The image forming apparatus according to claim 17, wherein the surface resistance value of the developer carrying member is larger than the bulk resistance value by one digit or more. 19. The potential difference of 60 V to 500 V is generated between the developer carrying member and the developer regulating member in a part of the non-image formation, according to any one of claims 9 to 18. Image forming device. 20. The toner particles have a shape factor SF-1 of 100 to 160 and a shape factor SF-2 of 10.
It is 0-140, The claim 11 or 1 characterized by the above-mentioned.
9. The image forming apparatus according to item 9. 21. A cartridge characterized in that it has the developing means in the image forming apparatus according to any one of claims 9 to 20 and is attachable to and detachable from a main body of the image forming apparatus. . 22. The image forming apparatus according to any one of claims 9 to 20, comprising the developing means and the delay control means, and being detachable from a main body of the image forming apparatus. Cartridge characterized by.