JP2008310294A - Developing device and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a developing device capable of stably outputting a high-quality image from starting use of the device, until finishing the use by suppressing an increase in fogging, when supplying non-magnetic one-component developer, and to provide an image forming apparatus equipped with the developing device. <P>SOLUTION: A regulating blade 31b is conductive, and voltage applied to the regulating blade 31b, by a regulating bias power source 9, is larger than voltage applied to a developing roller 31a by a developing bias power source 8 by a predetermined voltage difference in a direction of the normal electrifying polarity of toner. The predetermined voltage difference is 50[V] or higher and 300[V] or lower, and the absolute value of the saturated triboelectric charge amount of the toner supplied to a developing chamber 31 is 40[mC/kg] or higher and 100[mC/kg] or lower. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an image forming apparatus such as a copying machine or a laser beam printer using an electrophotographic system or an electrostatic recording system, and more particularly to a developing device provided in these apparatuses.

  Conventionally, in an image forming apparatus using an electrophotographic system or an electrostatic recording system, an electrostatic latent image is formed on the surface of a photoconductor as a uniformly charged image carrier, and the electrostatic latent image is developed as a developer. A toner image is formed by developing using the toner. Then, the toner image is transferred and fixed on a recording material to obtain an image.

  As development methods, there are generally a two-component development method using a two-component developer composed of a toner and a carrier, and a one-component development method using a one-component developer composed only of a toner. Among these, the one-component development method is advantageous in terms of downsizing, cost reduction, ease of maintenance, and the like because the configuration of the developing device is simpler than the two-component development method. For this reason, in recent years, a large number of developing devices using the one-component developing method have been proposed. A number of developing devices using a non-magnetic one-component developing method that does not use magnetic toner have been proposed and put to practical use, particularly in color image forming apparatuses.

  The configuration of the developing device using the non-magnetic one-component developing method includes, for example, a photosensitive drum as an image carrier, a developing roller as a developer carrier, a regulating blade as a layer thickness regulating member, and a developer. One having a supply roller as a supply member is known. Here, the developing roller is disposed in contact with the photosensitive drum or in a non-contact state with a certain gap. The regulating blade is disposed in contact with the developing roller. The supply roller is disposed in contact with the developing roller.

  In such a configuration, the toner as the nonmagnetic one-component developer is supplied to the surface of the developing roller by the supply roller, and is carried and conveyed by the developing roller. Then, frictional charging is performed at the contact position with the regulating blade and the layer thickness is regulated. The toner whose layer thickness is regulated is conveyed by a developing roller and develops an electrostatic latent image formed on the surface of the photosensitive drum at a position facing the photosensitive drum.

  By the way, in any developing method, there is a problem that the image quality is deteriorated after the image forming apparatus is used for a long time.

  For example, transfer defects such as a decrease in transfer efficiency when transferring a toner image onto a recording material can be mentioned. This is because the developer deteriorates due to repeated image formation over a long period of time, and the triboelectric charging characteristics and adhesion of the developer change. In particular, in a developing device using a non-magnetic one-component developing method, the influence of rubbing by the respective members is large, and toner as a non-magnetic one-component developer is significantly deteriorated.

  Therefore, a developing device having a mechanism for supplying new toner (hereinafter referred to as a toner supply method) has been proposed. In such a developing device, a stable image quality can be obtained over a long period of time by replenishing toner that is not always deteriorated.

  FIG. 6 shows an example of a developing device using a conventional toner replenishment type non-magnetic one-component developing method.

In the figure, the developing device 40 includes a developing chamber 41 and a toner storage chamber 42 which is disposed above the developing chamber 41 and stores a toner Tp as a nonmagnetic one-component developer. .

  Here, the toner storage chamber 42 is detachable from the developing chamber 41. When the toner storage chamber 42 is detached, the openable / closable shutter in the opening 43 on the toner storage chamber 42 side is closed so that the toner Tp does not leak. On the other hand, at the time of mounting, the shutter is opened, and the developing chamber 41 and the toner storage chamber 42 are connected via the opening 43. The toner storage chamber 42 includes a toner storage chamber stirring member 44 as a rotatable developer storage chamber stirring member, and the toner Tp stirred by the toner storage chamber stirring member 44 is supplied to the development chamber 41 through the opening 43. The

  According to this configuration, a small amount of toner Tp is replenished at any time according to the amount of toner Tp consumed in the developing chamber 41 by dropping from the toner storage chamber 42 disposed above the developing chamber 41.

  The developing chamber 41 includes a developing roller 41a, a regulating blade 41b, a supply roller 41c, a developing chamber stirring member 45, and a supply body 46. Here, the developing roller 41a constitutes a rotatable developer carrier. Further, the regulating blade 41b constitutes a layer thickness regulating member having elasticity arranged in contact with the developing roller 41a. Further, the supply roller 41c constitutes a rotatable first developer supply member disposed in contact with the developing roller 41a. The developing chamber stirring member 45 constitutes a rotatable first developing chamber stirring member disposed between the supply roller 41 c and the opening 43. Further, the supply body 46 constitutes a rotatable second developing chamber stirring member and developer supply member disposed between the supply roller 41 c and the opening 43.

  In the developing chamber 41, the toner Tp is stirred by the developing chamber stirring member 45 and supplied to the supply roller 41c.

  Here, the supply body 46 has a role of suppressing the aggregation of the toner Tp in the vicinity of the supply roller 41c and enabling the supply of the toner Tp to the supply roller 41c efficiently. The supply roller 41c supplies the toner Tp to the developing roller 41a while rotating at a predetermined peripheral speed in the same direction as the developing roller 41a. The supplied toner Tp on the developing roller 41a is conveyed to a contact position with the regulating blade 41b as the developing roller 41a rotates, and is triboelectrically charged and the layer thickness is regulated at the contact position. The toner Tp whose charging / layer thickness is regulated is conveyed to a position facing the rotatable photosensitive drum 47 as the developing roller 41a rotates, and an electrostatic latent image formed on the surface of the photosensitive drum 47. Is developed to form a toner image. The toner Tp that has not contributed to the development is transported with the rotation of the developing roller 41a, and is peeled off from the developing roller 41a by the supply roller 41c.

  Among the toner replenishing methods, as shown in FIG. 6, a method of replenishing as many times as the amount of toner used for image formation does not depend on the toner replenishment timing detection means or the replenishment control means (hereinafter referred to as a small amount replenishing system). Has an advantage that toner can be replenished with a simple configuration.

  However, in a toner replenishment type developing device, an image defect called so-called fogging, in which uncharged toner or toner charged to a polarity opposite to the normal charge polarity (hereinafter referred to as reversal toner) adheres to a non-image portion, There is a problem that it increases at the time of replenishment. Hereinafter, the developing device shown in FIG. 6 will be described as an example.

When toner is replenished, in the developing chamber 41, toner replenished from the toner storage chamber 42 (hereinafter referred to as replenished toner) and toner that has been used for a long time are mixed. At this time, the toner that has been used for a long time is in a deteriorated state and often has a difference from the frictional charging characteristics of the replenishment toner. For this reason, toner in which replenished toner and toner that has deteriorated over a long period of time are mixed is not easily triboelectrically charged at the contact position between the developing roller 41a and the regulating blade 41b, and uncharged toner and reversal toner are likely to be generated. Therefore, it is considered that the fog increases.

  On the other hand, there has been proposed a method for suppressing fogging by discharging toner that has deteriorated after being used for a long time from the image forming apparatus after replenishing the toner (see Patent Document 1).

  However, this method requires sequence control for toner discharge, and forcibly discharges and consumes toner, which may lead to complicated control and increased running costs.

In view of this, there is a method of suppressing fog by applying a predetermined voltage to the conductive layer thickness regulating member to give a predetermined potential difference between the toner carrier and the layer thickness regulating member (see Patent Document 2). Proposed. In this method, even if the toner is a mixture of replenished toner and toner that has deteriorated over a long period of time due to the action of an electric field formed in and near the contact area between the toner carrier and the layer thickness regulating member, Charging becomes possible.
JP 2003-107857 A JP-A-11-327288

  However, it has been found that the conventional method of applying a voltage to the layer thickness regulating member may not be able to suppress the increase in fog during toner replenishment. For example, depending on the triboelectric charging characteristics of the replenished toner, the effect of the electric field formed in the contact area between the toner carrier and the layer thickness regulating member and in the vicinity thereof does not work effectively, and the fog increases during toner replenishment.

  The present invention has been made in view of the above-described circumstances, suppresses an increase in fog at the time of replenishment of non-magnetic one-component developer, and stably stabilizes a high-quality image from the start of use to the end of use. It is an object of the present invention to provide a developing device capable of outputting, and an image forming apparatus including the developing device.

In order to achieve the above object, the present invention provides:
A developer storage chamber for storing a non-magnetic one-component developer;
A developing chamber in which the developer is replenished through the opening from the developer containing chamber;
A developer carrier for carrying and conveying the developer;
A layer thickness regulating member for regulating the layer thickness of the developer carried on the developer carrying body;
First voltage applying means for applying a voltage to the developer carrying member;
A second voltage applying means for applying a voltage to the layer thickness regulating member;
In a developing device comprising:
The layer thickness regulating member is conductive;
The voltage applied to the layer thickness regulating member by the second voltage applying means is more in the direction of the normal charging polarity of the developer than the voltage applied to the developer carrier by the first voltage applying means. A voltage that is large by a predetermined voltage difference,
The predetermined voltage difference is 50 [V] or more and 300 [V] or less;
The absolute value of the saturated triboelectric charge amount of the developer supplied to the developing chamber is 40 [mC / kg] or more and 100 [mC / kg] or less.

According to the present invention, there is provided a developing device that suppresses an increase in fog at the time of replenishing a non-magnetic one-component developer and can stably output a high-quality image from the start of use to the end of use, and the developing device. An image forming apparatus can be provided.

  The best mode for carrying out the present invention will be exemplarily described in detail below with reference to the drawings. However, the dimensions, materials, shapes, and relative arrangements of the components described in this embodiment should be appropriately changed according to the configuration of the apparatus to which the invention is applied and various conditions. It is not intended to limit the scope to the following embodiments.

  First, the configuration and operation of the image forming apparatus according to Embodiment 1 of the present invention will be described.

  FIG. 1 is a schematic cross-sectional view illustrating a schematic configuration of an image forming apparatus 100 as an example of the image forming apparatus according to the present embodiment.

  In the figure, an image forming apparatus 100 includes a photosensitive drum 1 which is a rotatable drum type electrophotographic photosensitive member as an image carrier. The following components are arranged around the photosensitive drum 1. That is, the charging device 2 as a charging unit, the developing device 3 as a developing unit including a nonmagnetic toner T (hereinafter referred to as toner T) as a nonmagnetic one-component developer, and the transfer device 4 as a transfer unit. And a cleaning device 5 as a cleaning means.

  In this embodiment, the photosensitive drum 1, the charging device 2, the developing device 3, and the cleaning device 5 are integrally formed as a cartridge and can be attached to and detached from the image forming apparatus main body (not shown). A flexible process cartridge is configured. Here, the process cartridge is an image forming apparatus main body in which a photoconductor and at least one of a charging unit, a developing unit, and a cleaning unit as a process unit that acts on the photoconductor are integrally formed into a cartridge. Can be attached and detached.

  Further, an exposure device 6 as an exposure unit is arranged outside the process cartridge. Further, a fixing device 7 as a fixing unit is disposed downstream of the transfer position N formed between the photosensitive drum 1 and the transfer device 4 in the conveyance direction of the recording material P.

  The photosensitive drum 1 is driven to rotate at a predetermined peripheral speed in the arrow direction (clockwise direction) shown in FIG. The peripheral speed of the photosensitive drum 1 at this time is preferably 50 mm / s or more and 600 mm / s or less.

  In this embodiment, the photoconductor drum 1 is a negatively chargeable organic photoconductor having a diameter of 30 mm, and has a photoconductor layer on an aluminum drum base. At the time of image formation, the photosensitive drum 1 is rotationally driven at a peripheral speed of 200 mm / s in the direction of the arrow shown in FIG. 1 by a driving means (not shown).

  The surface of the photosensitive drum 1 is uniformly charged by the charging device 2. The uniformly charged surface of the photosensitive drum 1 is exposed by the exposure device 6 with a laser beam L corresponding to the image information. As a result, an electrostatic latent image corresponding to the image information is formed on the surface of the photosensitive drum 1.

  Next, the electrostatic latent image formed on the surface of the photosensitive drum 1 is visualized as a toner image by the developing action of the developing device 3. Here, in this embodiment, the toner T, which is normally charged to the same polarity as the charging polarity of the photosensitive drum 1 (negative polarity in this embodiment), was exposed on the surface of the photosensitive drum 1 from the developing roller 31a. A so-called reversal development system is used in which a toner image is formed by transferring and adhering to the portion.

  As the toner image formed on the surface of the photosensitive drum 1 reaches the transfer position N, the recording material P is conveyed to the transfer position N from a cassette or the like (not shown) as a recording material storage unit. Then, at the transfer position N, the toner image on the surface of the photosensitive drum 1 is transferred onto the recording material P.

  The recording material P to which the toner image has been transferred is conveyed to the fixing device 7. Then, the toner image is fixed on the recording material P by being heated and pressurized in the fixing device 7. Thereafter, the recording material P is discharged onto a discharge tray (not shown).

  On the other hand, in the toner image transfer step, the transfer residual toner that is not transferred onto the recording material P and remains on the surface of the photosensitive drum 1 is removed by the cleaning device 5. The surface of the photosensitive drum 1 from which the transfer residual toner has been removed is charged again by the charging device 2, and the above steps are repeated.

  Next, the configuration and operation of the developing device according to the present embodiment will be described.

  FIG. 2 is a schematic cross-sectional view illustrating a schematic configuration of the developing device 3 according to the present embodiment. The developing device 3 of the present embodiment employs a non-magnetic one-component developing method of a small amount replenishment method that can replenish toner with a simple configuration.

  In the figure, the developing device 3 includes a developing chamber 31 and a toner storage chamber 32 as a developer storage chamber connected to the developing chamber 31 via an opening 33.

  The developing chamber 31 includes a developing roller 31a as a rotatable developer carrier, a regulating blade 31b as an elastic layer thickness regulating member, and a supply roller 31c as a rotatable developer supply member. Here, the developing roller 31a carries and conveys toner, and is disposed opposite to the photosensitive drum 1 while being in contact therewith. The regulating blade 31b is disposed in contact with the developing roller 31a. In addition, the supply roller 31c is disposed to face the developing roller 31a.

  On the other hand, the toner storage chamber 32 is disposed above the developing chamber 31 in a use state, and includes a stirring member 32a as a rotatable developer stirring member and stores toner T.

  The toner storage chamber 32 is detachable from the developing chamber 31, and when the toner is replenished (replaced), the toner storage chamber 32 is detached from the developing chamber 31 and replaced with a toner storage chamber in which a new toner is stored. Here, when leaving, the openable / closable shutter in the opening 33 on the toner storage chamber 32 side is closed so that the toner T does not leak. At the time of mounting, the shutter is opened, and the developing chamber 31 and the toner storage chamber 32 are always connected via the opening 33.

  In the toner storage chamber 32, the toner T is agitated by the agitator 32a. This is to prevent the toner T from aggregating and causing poor conveyance to the developing chamber 31. Then, the stirred toner T is supplied to the developing chamber 31 through the opening 33. According to the configuration of the developing device 3, a small amount of toner T is replenished at any time by dropping from the toner storage chamber 32 disposed above the developing chamber 31 according to the consumption amount of the toner T in the developing chamber 31. .

In the developing chamber 31, the supply roller 31c rotates in contact with the developing roller 31a. With the rotation, the surrounding toner T is scraped off and supplied to the developing roller 31a. The toner T supplied to the surface of the developing roller 31a is conveyed to a contact position with the regulating blade 31b located on the downstream side in the rotation direction as the developing roller 31a rotates. Then, the toner is frictionally charged at the contact position and the layer thickness is regulated, and a toner thin layer is formed on the surface of the developing roller 31a.

  Here, the opening 33 is provided in the shape of a long hole whose longitudinal direction is the rotational axis direction of the stirring member 32a, the developing roller 31a, the supply roller 31c, and the photosensitive drum 1.

  The toner T whose charging / layer thickness is regulated is conveyed to a contact position with the photosensitive drum 1 located on the downstream side in the rotation direction as the developing roller 31a rotates. Then, the electrostatic latent image formed on the surface of the photosensitive drum 1 is developed to form a toner image. The toner T that has not contributed to the development on the surface of the developing roller 31a is conveyed along with the rotation of the developing roller 31a, and is peeled off from the surface of the developing roller 31a by the supply roller 31c.

  Below, each said structural member is demonstrated in detail.

  As the developing roller 31a, for example, a single layer roller having an elastic layer formed of a rubber material such as silicone rubber, urethane rubber or hydrin rubber on a core metal can be used. In addition, a surface layer was formed by applying a silicone resin, a urethane resin, a polyamide resin, a fluororesin, or the like on the surface of the elastic layer formed of a rubber material such as silicone rubber, urethane rubber, or hydrin rubber on the core metal. A multi-layered roller can be used.

The surface roughness of the developing roller 31a depends on the particle diameter of the toner used, but the arithmetic average roughness Ra [JIS centerline average roughness (JIS B 0601: 2001)] is preferably 5.0 μm or less. . Thus, the toner T can be sufficiently frictionally charged at the contact position between the developing roller 31a and the regulating blade 31b. The volume resistance value of the developing roller 31a is preferably 1.0 × 10 ³ Ω or more and 4.0 × 10 ⁷ Ω or less. The volume resistance value of the developing roller 31a is measured as follows.

  The mirror metal cylindrical member is rotated at a peripheral speed of 1.0 rps with the mirror metal cylindrical member having a diameter of 30 mm and the developing roller in contact with each other over the entire length of the developing roller with a contact load of 500 gf (4.9 N). Let Then, a DC voltage of −50 V is applied between the core of the developing roller and the cylindrical metal cylindrical member, the voltage across the 10 kΩ resistor connected to the ground side is measured, and the current value and development are determined from the measured voltage value. Calculate the resistance value of the roller.

  The developing roller 31 a is in contact with the photosensitive drum 1 with a predetermined contact width, and is driven to rotate at a peripheral speed faster than the peripheral speed of the photosensitive drum 1.

  Further, a developing bias power source 8 as a first voltage applying unit is connected to the core of the developing roller 31a. By applying a predetermined voltage to the core of the developing roller 31a, the developing roller 31a and the photosensitive roller are photosensitive. An electric field is formed between the body drums 1. The toner T on the surface of the developing roller 31a whose charging and layer thickness are regulated is supplied to the surface of the photosensitive drum 1 by an electric field formed between the developing roller 31a and the photosensitive drum 1, and develops the electrostatic latent image.

In this embodiment, a developing roller 31a having a diameter of 16 mm is used which has an elastic layer made of silicone rubber having a layer thickness of 4 mm on a core metal having a diameter of 8 mm and is coated with an acrylic / urethane resin on the surface thereof. is doing. The surface roughness of the developing roller 31a is as described later, and the volume resistance value is 5.0 × 10 ⁴ Ω.

  Further, the developing roller 31a has a peripheral speed of 300 mm / s, and the direction of movement of the surface of the developing roller 31a and the direction of movement of the surface of the photosensitive drum 1 are the same at the contact position (the arrow direction shown in FIG. 2). Driven by rotation. The developing bias power source 8 applies a predetermined negative voltage to the core of the developing roller 31a.

  The regulation blade 31b has elasticity and conductivity, and is preferably composed of a thin metal plate such as stainless steel or phosphor bronze. It is also possible to use a rubber material such as silicone rubber or urethane rubber, or a metal thin plate such as stainless steel or phosphor bronze as a base, and a conductive rubber material or the like applied to the contact surface side with the developing roller 31a. Good.

  The vicinity of the free end side of the regulating blade 31b is disposed so as to be in surface contact with the outer peripheral surface of the developing roller 31a. The regulating blade 31b is connected to a regulating bias power source 9 as a second voltage applying means, and an electric field is applied between the regulating blade 31b and the developing roller 31a by applying a predetermined voltage to the regulating blade 31b. Form.

Here, the voltage applied to the regulating blade 31b is Vbl, the voltage applied to the core of the developing roller 31a is Vdev,
ΔVbl = Vbl−Vdev
It is defined as

  Then, a predetermined voltage is applied from the regulating bias power source 9 to the regulating blade 31b so that ΔVbl has the same polarity as the normal charging polarity of the toner T. At this time, an electric field that attracts the toner T charged to the normal charging polarity toward the developing roller 31a is formed in the contact area between the regulating blade 31b and the developing roller 31a and in the vicinity thereof.

  In this embodiment, a regulating blade 31b made of a phosphor bronze thin plate having a thickness of 0.1 mm is used. The contact direction of the regulating blade 31b with respect to the developing roller 31a is such that the free end of the regulating blade 31b is positioned upstream in the rotational direction of the developing roller 31a with respect to the contact position between the regulating blade 31b and the developing roller 31a. This is the so-called counter direction. Then, the regulation bias power source 9 applies a predetermined negative polarity voltage that is the normal charging polarity of the toner T to the regulation blade 31b.

The supply roller 31c preferably has the following structure in view of the supply performance of the toner T to the development roller 31a and the removal performance of the toner T from the development roller 31a. That is, it is preferable to have a foamed skeleton-like sponge structure made of a material such as foamed urethane rubber, foamed EPDM rubber, or foamed silicone rubber on the core metal. The volume resistance value of the supply roller 31c is preferably 1.0 × 10 ⁴ Ω or more and 1.0 × 10 ⁸ Ω or less.

  The supply roller 31c is rotationally driven in contact with the developing roller 31a with a predetermined contact width. Here, it is preferable to give a peripheral speed difference between the peripheral speed of the supply roller 31c and the peripheral speed of the developing roller 31a. Further, a supply bias power source 10 as a third voltage applying means is connected to the core of the supply roller 31c. By applying a predetermined voltage to the core of the supply roller 31c, the supply roller 31c and the development are developed. An electric field is formed between the rollers 31a.

Here, the voltage applied to the supply roller 31c is Vrs,
ΔVrs = Vrs−Vdev
It is defined as Then, a predetermined voltage is applied from the supply bias power supply 10 to the core of the supply roller 31c so that ΔVrs has the same polarity as the normal charging polarity of the toner T.

At this time, an electric field that attracts the toner T charged to the normal charging polarity toward the developing roller 31a is formed in the contact area between the supply roller 31c and the developing roller 31a and in the vicinity thereof. In stirring or the like, the toner T is slightly frictionally charged, and the amount of toner T supplied to the developing roller 31a is increased by the action of the electric field. As a result, a sufficient amount of toner T can be supplied from the supply roller 31c to the developing roller 31a, and an entire black image having a uniform image density from the leading edge of the image to the trailing edge of the image can be obtained.

  The absolute value of ΔVrs is preferably 0 V or more and 1000 V or less, and more preferably 50 V or more and 1000 V or less considering that the toner T is slightly frictionally charged.

  This is because if the absolute value of ΔVrs is less than 0V, the toner T cannot be sufficiently supplied to the developing roller 31a, and if it exceeds 1000V, a discharge occurs between the supply roller 31c and the developing roller 31a, and after charging / layer thickness regulation This is to cause unevenness in the toner T layer. Even if the absolute value of ΔVrs is the same, the electric field formed between the supply roller 31c and the development roller 31a varies depending on the volume resistance values of the supply roller 31c and the development roller 31a. Therefore, even when a full black image is output, it is necessary to adjust the absolute value of ΔVrs within a range of 0V to 1000V so that the image density is uniform from the leading edge of the image to the trailing edge of the image.

In this embodiment, a supply roller 31c having a diameter of 16 mm in which a polyurethane foam (a sponge made of polyurethane) is provided on a core metal having a diameter of 5 mm is used. The volume resistance value of the supply roller 31c is about 1.0 × 10 ⁷ Ω. The supply roller 31c rotates at a circumferential speed of 200 mm / s in a direction (the arrow direction shown in FIG. 2) in which the movement direction of the supply roller 31c and the movement direction of the development roller 31a are opposite to each other at the contact position. Driven. The supply bias power supply 10 applies a predetermined negative polarity voltage that is the normal charging polarity of the toner T to the core of the supply roller 31c. The value of ΔVrs at that time is as shown in Table 3.

  The stirrer 32a is composed of a rod-shaped body made of a predetermined resin or metal, or a plurality of holes made in a thin plate made of a predetermined resin or metal, from the viewpoint of the stirring performance of the toner T and the torque applied during driving. The structure which used the stirring blade as the stirring blade is preferable.

  The stirrer 32 a is disposed substantially parallel to the longitudinal direction of the opening 33. And it is rotationally driven at a predetermined peripheral speed by a drive means (not shown). Here, the stirrer 32a only needs to be able to stir the toner T as it rotates, so the rotation direction of the stirrer 32a may be the same as or opposite to the rotation direction of the supply roller 31c.

  In the present embodiment, a stirrer 32a is used in which both ends of two metal rod-like bodies are connected to each other and a rotation shaft is provided at the central portion of the connecting portion. And in the stirring body 32a, the center part of the metal rod-shaped body is also connected. This is to prevent the stirrer 32a from being bent by the pressure received from the toner T during stirring. In addition, in the present Example, although it has a connection part in one place of the center part of metal rod-shaped bodies, you may have a connection part in multiple places. The stirrer 32a is rotationally driven in a direction (the arrow direction shown in FIG. 2) in which the moving direction of the metal bar of the stirrer 32a and the moving direction of the surface of the supply roller 31c are opposite to each other at the closest position. .

  Next, the toner T of this embodiment will be described.

  In this example, a suspension polymerization method under normal pressure or under pressure is used, and styrene and n-butyl acrylate as monomers, a salicylic acid metal compound as a charge control agent, a saturated polyester as a polar resin, and a wax and a colorant are added. The manufactured toner T is used. The volume average particle diameter of the toner T is 6.5 μm, and the average circularity is 0.980.

The volume average particle diameter of the toner T is, for example, a Coulter Counter TA-II type or Coulter Multisizer II (manufactured by Beckman Coulter, Inc.), etc. Bios) and a measuring device connected to a personal computer. In the measurement, an electrolytic solution is used. For the electrolytic solution, for example, a 1% NaCl aqueous solution prepared using primary sodium chloride or ISOTON R-II (manufactured by Coulter Scientific Japan Co., Ltd.) can be used. .

  As a measurement method, 0.1 to 5.0 ml of a surfactant (preferably alkylbenzene sulfonate) is added as a dispersant to 100 to 150 ml of the electrolytic aqueous solution, and 2 to 20 mg of a measurement sample is further added. The electrolyte in which the sample is suspended is subjected to a dispersion treatment with an ultrasonic disperser for about 1 minute, and the volume of the toner T of 2 μm or more is measured by the Coulter counter TA-II type using an aperture of 100 μm as the aperture. Calculate the distribution. Then, the volume average particle diameter obtained from the volume distribution of this example is obtained.

  The circularity of the toner T in this embodiment is used as a simple method for quantitatively expressing the shape of the toner particles.

In the present Example, it measured using the flow type particle image measuring device FPIA-1000 type | mold (Toa Medical Electronics (made by Sysmex) Corporation), and computed using the following Formula. The measurement conditions were such that the toner particle concentration during measurement was adjusted to 5000 to 15000 particles / μl, and 1000 or more toner particles were measured.
Circularity = (perimeter of a circle having the same area as the particle projection area) / (perimeter of the particle projection image)
Here, the “particle projected area” is the area of the binarized toner particle image, and the “peripheral length of the particle projected image” is the length of the contour line obtained by connecting the edge points of the toner particle image. Define.

  The following dispersion is used as the measurement dispersion. It is prepared by preparing 10 ml of ion-exchanged water from which impure solids and the like have been removed in advance in a container, adding a surfactant, preferably an alkylbenzene sulfonate as a dispersant, and further adding about 0.02 g of a measurement sample. In addition, the dispersion process was performed for 5 minutes and dispersed uniformly. As a means to disperse, an ultrasonic disperser UH-50 type (manufactured by SMT Co., Ltd.) having a φ5 mm titanium alloy chip as a vibrator is used.

  In this example, the toner T produced using the suspension polymerization method was used, but the present invention is not limited to this. For example, other polymerization methods such as a pulverization method and an emulsion polymerization method are used. The manufactured toner T may be used. In this embodiment, the toner T has a volume average particle diameter of 6.5 μm and an average circularity of 0.980. However, the present invention is not limited to this. However, the volume average particle diameter of the toner T is preferably 4 to 10 μm. This is because, when the volume average particle diameter of the toner T is less than 4 μm, the fluidity of the toner particles deteriorates, so that uniform frictional charging is performed at the contact position between the regulating blade 31b and the developing roller 31a. This is because there is a case where it will not be broken. In such a case, for example, there is a concern that fog may easily occur in a high humidity environment. On the other hand, if the volume average particle diameter of the toner T exceeds 10 μm, it is difficult to form a high-definition image, and there is a concern that the required image quality cannot be satisfied.

  Table 1 shows toners T of this example and the comparative example. In the present example, the external additive formulation shown in Table 1 was used, but the present invention is not limited to this.

  The external additive formulation in Table 1 indicates the number of parts by mass of the external additive with respect to 100 parts by mass of the toner base particles. In Table 1, the average primary particle size of silica A is 10 nm, the average primary particle size of silica B is 50 nm, the average primary particle size of titanium oxide is 10 nm, and the average primary particle size of hydrotalcite is 200 nm.

In this example, the average primary particle diameter of the external additive fine particles is measured using a scanning electron microscope. Specifically, in a photograph of toner T magnified by a scanning electron microscope, 100 or more primary particles of external additive fine particles that are attached to or separated from the toner surface are measured, and the number average particle diameter is determined. Ask. At this time, measurement is performed by contrasting a photograph of the toner T mapped with the elements contained in the external additive fine particles by an elemental analysis means such as XMA attached to the scanning electron microscope.

  As an external addition method, the external additives shown in Table 1 were added to 100 parts by mass of toner base particles, and dry-mixed with a Henschel mixer.

  As shown in Table 1, the regular charging polarity of the toner T of this example and the comparative example is negative.

  The measuring method of the saturated triboelectric charge amount in Table 1 is as follows.

  FIG. 3 is a schematic configuration diagram of a saturated triboelectric charge measuring device. In this embodiment, F813-3535 (manufactured by Powder Tech Co., Ltd.) is used as a carrier for measuring the saturated triboelectric charge amount. The measurement is performed in an environment of 23 ° C. and 50% RH.

  As a measuring method, first, a mixture obtained by adding 0.5 g of toner to 9.5 g of a carrier is placed in a 50 ml polyethylene bottle and shaken 200 times by hand. Next, 1.0 g of the mixture is placed in a metal measuring container 12 having a 500 mesh (opening 25 μm) screen 13 at the bottom, and a metal lid 14 is placed. And the mass of the whole measurement container 12 at this time is measured, and the measured value is set to W1 [g].

  Next, suction is performed from the suction port 17 in the suction machine 11 (at least the part in contact with the measurement container 12), and the air volume control valve 16 is adjusted so that the pressure of the vacuum gauge 15 is 250 mmAq. In this state, suction is performed for 1 minute to remove the toner by suction. The measured potential of the electrometer 19 at this time is V [V]. Here, 18 is a capacitor having a capacitance C [μF]. Next, the mass of the entire measurement container 12 after suction is measured, and the measured value is defined as W2 [g].

Using the above measurement results, the saturated triboelectric charge amount [mC / kg] of the toner is calculated by the following equation.
Saturated triboelectric charge [mC / kg] = CV / (W1-W2)

  Moreover, the measuring method of the aggregation degree of Table 1 is as follows.

In this example, the degree of aggregation was measured using a conventionally known powder tester (PT-E type manufactured by Hosokawa Micron Corporation) by the following method. The measurement is performed in an environment of 23 ° C. and 50% RH.
(1) Weigh out 5.0 g of toner.
(2) A screen of 100 mesh (aperture 150 μm), 200 mesh (aperture 75 μm), and 400 mesh (aperture 38 μm) is stacked on the shaking table.
(3) Place precisely weighed 5.0 g of toner on the top sieve (100 mesh) and apply a voltage of 18V to the vibration system and vibrate for 15 seconds.
(4) The mass of the toner remaining on each sieve is precisely weighed.

Using the above measurement results, the toner aggregation degree [%] is calculated by the following equation.
Aggregation degree [%] = x + y + z
x = 100 × ((mass of toner remaining on 100 mesh [g]) / 5)
y = 100 × ((mass of toner remaining on 200 mesh [g]) / 5) × 3/5
z = 100 × ((mass of toner remaining on 400 mesh [g]) / 5) × 1/5

  Next, the feature of supplying a small amount of toner in the developing device according to the present embodiment will be described in detail.

  FIG. 4 is a schematic cross-sectional view of a main part of the developing device according to the present embodiment, and is a diagram for explaining the feature of supplying a small amount of toner. 4A is a diagram for explaining the relationship between the stirring member 32a in the toner storage chamber 32 and the opening 33, and the relationship between the supply roller 31c in the developing chamber 31 and the opening 33. FIG. FIG. 5B is a diagram for explaining the relationship between the stirring body 32a and the opening 33. FIG.

  As described above, in the developing device 3, a small amount of toner T is replenished at any time by dropping from the toner storage chamber 32 disposed above the developing chamber 31 according to the consumption amount of the toner T in the developing chamber 31. .

  In such a developing device, the fluidity of the toner T greatly affects the transport amount.

  For example, when the toner T aggregates due to the pressure due to the weight of the toner T, the toner T can be replenished from the toner storage chamber 32 to the developing chamber 31 and the toner T can be efficiently supplied to the developing roller 31a by the supply roller 31c. Disappear. Further, when the toner deteriorated after long-term use in the developing chamber 31 returns to the toner storage chamber 32 and is mixed with toner in a new state in the toner storage chamber 32, the difference between the triboelectric charging characteristics is large. Electrostatic aggregation causes the fluidity of the toner T to decrease. For this reason, the toner T cannot be efficiently supplied from the toner storage chamber 32 to the developing chamber 31. Therefore, a stable image density cannot be obtained.

  Therefore, as a result of intensive studies by the present inventors, a stable and small amount of replenishment can be performed even with a simple configuration in which the toner stirring member other than the supply roller 31c is not provided in the developing chamber 31 as in the developing device 3 of the present embodiment. I understood it.

  That is, assuming that the rotation radius of the stirring body 32a is r1 and the distance from the rotation center of the stirring body 32a to the opening 33 is r2, at the position where the stirring body 32a is close to the opening 33, (r2-r1) is It is preferable that it is 0 mm or more and 5 mm or less. (See FIGS. 4A and 4B)

  When (r2-r1) is less than 0 mm, the tip of the stirrer 32a enters the developing chamber 31 through the opening 33, so that the toner in the developing chamber 31 returns to the toner containing chamber 32. As a result, electrostatic aggregation may occur in the toner storage chamber 32 and the fluidity of the toner T may be reduced. On the other hand, when (r2-r1) exceeds 5 mm, the toner aggregated in the vicinity of the opening 33 cannot be stirred in the toner storage chamber 32. Therefore, in either case, the toner T cannot be efficiently supplied from the toner storage chamber 32 to the developing chamber 31.

  Further, the rotation radius of the supply roller 31c is r3, and the distance from the rotation center of the supply roller 31c to the opening 33 is r4. In such a case, it is preferable that (r4-r3) is 5 mm or more and 15 mm or less at a position where the supply roller 31c is close to the opening 33 (see FIG. 4A).

  When (r4-r3) is less than 5 mm, the toner in the developing chamber 31 returns to the toner storage chamber 32 through the opening 33 due to the rotation of the supply roller 31c. As a result, when electrostatic aggregation occurs in the toner storage chamber 32 and the fluidity of the toner T decreases, the toner T cannot be efficiently supplied from the toner storage chamber 32 to the developing chamber 31. On the other hand, when (r4-r3) exceeds 15 mm, the thickness of the non-moving layer of the toner T between the opening 33 and the surface of the supply roller 31c increases in the developing chamber 31. As a result, the aggregation of the toner T around the supply roller 31c becomes strong and is hardly scraped off by the supply roller 31c, so that the toner T cannot be sufficiently supplied to the developing roller 31a.

  Furthermore, in order to perform better small amount replenishment from the toner storage chamber 32 to the developing chamber 31, the width r5 of the opening 33 in the short direction (the direction orthogonal to the longitudinal direction in the opening 33) is 5 mm or more and 20 mm or less. It is preferable (see FIG. 4B).

  This is because when the width r5 in the short direction of the opening 33 is less than 5 mm, the opening 33 is too narrow and the toner T cannot be efficiently supplied from the toner storage chamber 32 to the developing chamber 31. It is. On the other hand, when the width r5 in the short direction of the opening 33 exceeds 20 mm, the opening 33 is conversely too wide, and the toner in the developing chamber 31 is transferred to the toner storage chamber 32 due to the influence of the rotation of the stirrer 32a. Return to. As a result, when electrostatic aggregation occurs in the toner storage chamber 32 and the fluidity of the toner T decreases, the toner T cannot be efficiently supplied from the toner storage chamber 32 to the developing chamber 31.

  As described above, according to this embodiment, it is possible to suppress the aggregation of the toner T in the toner storage chamber 32 and the developing chamber 31. Further, by providing a non-moving layer of toner T having an appropriate thickness in the vicinity of the opening 33 of the developing chamber 31, the toner in the developing chamber 31 returns to the toner containing chamber 32 through the opening 33, and the toner containing chamber. It is possible to prevent the occurrence of electrostatic aggregation within 32. Therefore, a stable small amount can be supplied, and the image density can be stabilized.

  In this example, (r2-r1) was set to about 1 mm at a position where the stirring body 32a was close to the opening 33. In the position where the supply roller 31c is close to the opening 33, (r4-r3) is about 6 mm. Furthermore, the width r5 in the short direction of the opening 33 was 13 mm.

  Next, suppression of fog at the time of toner replenishment in the developing device, which is a feature of this embodiment, will be described in detail.

  When the toner T is replenished from the toner storage chamber 32 of the developing device 3 to the developing chamber 31, toner in a new state and toner deteriorated after long-term use are mixed in the developing chamber 31. As described above, the toner in the new state is sufficiently frictionally charged because it has good frictional charging characteristics. However, the toner that has deteriorated after being used for a long period of time has a low triboelectric charge amount or a regular charge. It is charged to the opposite polarity. As a result, electrostatic agglomeration results in a large toner mass, and it becomes difficult to uniformly triboelectrically charge. Therefore, when toner in a new state and deteriorated toner are mixed, uncharged toner and reversal toner increase, and fog tends to increase.

In particular, a toner having high frictional charging characteristics in a new state tends to have a large difference in characteristics from a toner deteriorated after long-term use, and is likely to electrostatically aggregate. Table 2 shows an example.

  The toner 4 having a high initial saturated triboelectric charge amount has a large difference in the saturated triboelectric charge amount between the initial stage and after long-term use. Further, since the degree of aggregation of the mixed toner at the initial stage and after long-term use is larger than that of the toner after long-term use, it is considered that the toner is more aggregated. On the other hand, the toner 6 having an initial saturated triboelectric charge amount lower than that of the toner 4 has substantially the same saturated triboelectric charge amount after initial use and long-term use. Further, the increase in the cohesion degree of the mixed toner is smaller than that of the toner 4. In such a case, the toner 4 has a remarkable increase in fog when the toner is replenished.

  However, as a result of intensive studies by the present inventors, when an electric field is formed between the regulating blade 31b and the developing roller 31a by applying a predetermined voltage to the conductive regulating blade 31b, electrostatic aggregation is caused by the action of the electric field. It was found that it was crushed and uniformly triboelectrically charged. The reason for this is not clear enough, but is generally considered as follows.

  A predetermined voltage is applied to the conductive regulating blade to form an electric field that attracts the normally charged toner to the developing roller 31a side in and near the contact area between the regulating blade 31b and the developing roller 31a.

  Then, due to the action of the electric field, the normally charged toner (mainly in a new state) is attracted to the developing roller 31a side, and the reverse toner (mainly deteriorated toner for a long time) is attracted to the regulating blade 31b side. Receive force in the direction. Then, the force received from the electric field and the frictional force are combined to separate electrostatic aggregation.

  Further, the reverse toner is retained in the contact area between the regulating blade 31b and the developing roller 31a until the toner is charged to the normal charging polarity by the action of the electric field. Therefore, only the normally charged toner leaves the contact area between the regulating blade 31b and the developing roller 31a and is transported to the area where the electrostatic latent image is developed.

  As described above, by forming a predetermined electric field between the regulating blade 31b and the developing roller 31a, frictional charging is promoted to enable uniform charging, and an increase in fog during toner supply is suppressed. Conceivable.

  Furthermore, it has been found that a toner having good frictional charging characteristics in a new state, that is, a toner that is more likely to be electrostatically aggregated, has a greater effect of suppressing fog during toner replenishment by an electric field. This is because when the difference in frictional charging characteristics between the new state toner and the toner deteriorated after long-term use is larger, each toner receives a stronger force from the electric field, and is attracted by the direction of the regulating blade 31b and the developing roller 31a. It is thought that this is because

  Next, the results of evaluating the effects of this example will be described.

Table 3 shows the image forming conditions of the present example and the comparative example. In this embodiment and the comparative example, the basic configuration of the developing device is the same as that of the developing device according to this embodiment, but images are formed under the conditions shown in Table 3, respectively.

  Further, in this example and the comparative example, the voltage Vdev applied to the core of the developing roller 31a was −300V. Moreover, there were six types of voltages Vbl applied to the regulating blade 31b: -300V, -350V, -400V, -500V, -600V, and -700V. Therefore, when expressed by ΔVbl, they are 0V, −50V, −100V, −200V, −300V, and −400V, respectively.

  The evaluation method is as follows. In the examples and comparative examples, the durability test and the fogging evaluation were performed in an environment of 23 ° C. and 50% RH.

  First, in order to create a deteriorated toner after long-term use, the developing chamber 31 of the developing device 3 is filled with 25 g of toner (equivalent to 1000 A4 size images with a printing ratio of 5.0%), and a character pattern image is formed. The output was output and a durability test was performed. As an endurance condition, assuming that there are many image outputs with a low printing ratio, which is a stricter condition, the output image was an A4 size character pattern image with a printing ratio of 1.0%. Then, 2000 images were output as an intermittent mode in which the image output mode is stopped for 5 seconds every time two images are output. Then, an entire white image was output and the fog was evaluated after the durability test.

  Next, toner in a new state was put into the toner storage chamber 32, 5 g of toner was supplied from the toner storage chamber 32 to the developing chamber 31, and the developing device 3 was driven to rotate for one minute. Then, a full white image was output to evaluate the fog at the time of toner replenishment.

  The method for measuring fog is as follows.

The whiteness (reflectance Ds (%)) of the white portion (non-image portion) of the output image and the whiteness (average reflection) of the output image, measured by “REFLECTMETER MODEL TC-6DS” (manufactured by Tokyo Denshoku Co., Ltd.) (Dr (%)), the fog density (%) was calculated. Here, the fog density is
Fog density (%) = Dr (%) − Ds (%)
It is represented by

In this example, as a filter used at the time of measurement, amber light was used for cyan, blue was used for yellow, and green was used for magenta and black. In addition, the evaluation of fogging was performed according to the following criteria.
○: Good Less than 1.5% △: Somewhat difficult 1.5% or more and less than 3.0% ×: Problem 3.0% or more

  In this example and the comparative example, as described above, ΔVbl was changed and the fog was evaluated after the durability test. As a result, in all cases, “good” or “somewhat difficult” was obtained. Table 4 shows the results of the evaluation of the fog at the time of toner replenishment by changing ΔVbl as described above in the present example and the comparative example.

  First, Examples 1-1 to 1-5 are compared with Comparative Examples 1-1 and 1-2.

  In the comparative example, the evaluation of the fog was “problematic” regardless of the value of ΔVbl. On the other hand, in this embodiment, in the region where ΔVbl is −50 V or more and −300 V or less, the evaluation of the fog is “good” or “somewhat difficult”, and the increase in fog during toner replenishment can be suppressed. . This is considered as follows.

  In Comparative Example 1-1, the saturated triboelectric charge amount of the toner to be replenished (that is, the toner in a new state) is as low as less than −29 mC / kg. In such a case, as shown in the toner 6 of Table 2, the difference in the triboelectric charge amount between the toner in the new state and the toner deteriorated after long-term use is small. Therefore, the action of destroying electrostatic aggregation due to the electric field formed between the regulating blade 31b and the developing roller 31a is weak, and the effect of promoting the frictional charging described above cannot be sufficiently obtained. As a result, uncharged toner and reversal toner are likely to occur during toner replenishment, and fog increases. Further, since the triboelectric charge amount of the toner in a new state is low, fogging is relatively likely to occur from the start of use of the image forming apparatus.

  On the other hand, in Comparative Example 1-2, the saturated triboelectric charge amount of the toner to be replenished is as high as −121 mC / kg. In such a case, since the amount of frictional charge of the toner is too high, a phenomenon occurs in which the toner adheres to the surface of the developing roller 31a and does not easily peel off. As a result, the toner T cannot be sufficiently frictionally charged with the surface of the developing roller 31a, and uncharged toner and reversal toner are likely to be generated. Therefore, fog increases when toner is replenished. Also in such a case, fogging is relatively likely to occur from the start of use of the image forming apparatus.

  On the other hand, in the toner T in this embodiment, when an electric field is formed between the regulating blade 31b and the developing roller 31a, electrostatic aggregation is broken by the force received from the electric field, and frictional charging is promoted. Therefore, uniform charging is possible, and it is considered that an increase in fog at the time of toner supply is suppressed.

  From the above, it is preferable that the absolute value of the saturated triboelectric charge amount of the toner T supplied from the toner storage chamber 32 to the developing chamber 31 is 40 mC / kg or more and 100 mC / kg or less. As a result, the effect of accelerating frictional charging by destroying electrostatic aggregation due to the electric field formed between the regulating blade 31b and the developing roller 31a can be obtained.

Next, according to Examples 1-1 to 1-5, in order to destroy electrostatic aggregation by the electric field formed between the regulating blade 31b and the developing roller 31a and promote frictional charging, the absolute value of ΔVbl is 50V or more and 300V or less is preferable. This is considered as follows.

  If the absolute value of ΔVbl is less than 50 V, the effect of the electric field formed between the regulating blade 31b and the developing roller 31a is weak, so that the effect of promoting frictional charging as described above cannot be obtained sufficiently. Therefore, uncharged toner and reversal toner are likely to be generated at the time of toner replenishment, and fog increases.

  On the other hand, when the absolute value of ΔVbl exceeds 300V, the action of the electric field formed between the regulating blade 31b and the developing roller 31a becomes too strong. Therefore, even the toner charged to the relatively reverse polarity side is attracted to the developing roller 31a side, and leaves the contact area between the regulating blade 31b and the developing roller 31a without being sufficiently frictionally charged. Therefore, uncharged toner and reversal toner are likely to be generated at the time of toner replenishment, and fog increases.

  Further, comparing Example 1-6 with Example 1-7, the lower the arithmetic average roughness Ra of the developing roller 31a, the greater the effect of suppressing fog during toner replenishment. This is because when the surface roughness of the developing roller 31a is lower, the electric field between the regulating blade 31b and the developing roller 31a becomes relatively parallel, and the action of the electric field described above works more effectively on the toner T. It is thought that. As a result of intensive studies by the present inventors, the arithmetic average roughness Ra of the developing roller 31a is more preferably 0.3 μm or less.

  As described above, according to the present embodiment, frictional charging of the toner T is promoted by the electric field formed between the regulating blade 31b and the developing roller 31a, and uniform charging becomes possible. Therefore, an increase in fog at the time of toner supply is suppressed.

  Although not shown in the table, when Examples 1-1 to 1-5 and Example 1-6 are compared, in Examples 1-1 to 1-5 in which ΔVrs is set to −200 V, the leading edge of the image A black image with a relatively uniform image density from the image to the rear end of the image was obtained.

  Further, comparing Example 1-3 with Examples 1-4 and 1-5, in Examples 1-4 and 1-5 in which the degree of aggregation of the toner in the new state is less than 30%, a more uniform entire surface A black image was obtained. This is because the toner T having higher fluidity is more advantageous in supplying the toner from the toner storage chamber 32 to the developing chamber 31 and supplying the toner to the supply roller 31 c in the developing chamber 31. However, when the degree of aggregation is less than 5%, the toner T is not sufficiently charged at the contact position between the regulating blade 31b and the developing roller 31a, which is not preferable. Therefore, it is preferable that the aggregation degree of the toner in a new state supplied to the developing chamber 31 is 5% or more and less than 30%.

  Next, in order to evaluate under conditions closer to the actual usage of the image forming apparatus, the durability test was performed by changing the print ratio of the output image. At this time, the developing device 3 was filled with 200 g of toner (equivalent to 8000 A4 size images with a printing ratio of 5.0%). The output images were A4 size character pattern images with printing ratios of 0.5%, 1.0%, 3.0%, and 5.0%, respectively. Then, the durability test was performed until the toner remaining amount in the developing device 3 was about 50 g, that is, the toner remaining amount in the toner storage chamber 32 was approximately 0 g and the toner remaining amount in the developing chamber 31 was approximately 50 g. At this time, the image output mode was an intermittent mode that stopped for 5 seconds every time two images were output. After the durability test, a full white image was output to evaluate the fog.

  Evaluation was performed about Example 1-4 and Comparative Example 1-1. The voltage Vdev applied to the core of the developing roller 31a was −300V, and the voltage Vbl applied to the regulating blade 31b was −500V. Therefore, ΔVbl was −200V.

  Table 5 shows the fog evaluation results.

  As shown in Table 5, according to this example, the evaluation of the fog was “good” even after the developing device and the image forming apparatus were used for a long time.

  As described above, in the present embodiment, the regulation blade 31b is conductive, and the voltage applied to the regulation blade 31b is more predetermined in the direction of the normal charging polarity of the toner than the voltage applied to the developing roller 31a. The voltage difference is a large voltage. Here, the predetermined voltage difference is 50 [V] or more and 300 [V] or less. Further, the absolute value of the saturated triboelectric charge amount of toner supplied from the toner storage chamber 32 to the developing chamber 31 is set to 40 [mC / kg] or more and 100 [mC / kg] or less.

  As a result, even in the state where the newly supplied toner and the toner deteriorated after a long period of use are mixed in the developing chamber 31, the electric field formed at the facing portion between the developing roller 31a and the regulating blade 31b is effective. By acting, the frictional charging of the toner is promoted, and uniform charging becomes possible. Therefore, an increase in fog at the time of toner supply can be suppressed.

  Furthermore, when the arithmetic average roughness (Ra) of the surface of the developing roller 31a is 0.3 [μm] or less, the action of the electric field formed at the facing portion between the developing roller 31a and the regulating blade 31b is more effective. work. Therefore, an increase in fog at the time of toner supply can be suppressed.

  Further, the toner storage chamber 32 is disposed above the developing chamber 31 and includes a stirring member 32 a that is rotatable in the toner storage chamber 32 and a supply roller 31 c that is rotatable in the developing chamber 31. The relationship as described above (0 [mm] ≦ r2-r1 ≦ 5 [mm], 5 [mm] ≦ r4-r3 ≦ 15 [mm]) is satisfied.

  Thereby, in the toner storage chamber 32 and the developing chamber 31, it is possible to suppress the occurrence of conveyance failure due to toner aggregation, and to sufficiently supply the toner to the developing roller 31a. Further, it is possible to prevent the toner deteriorated after being used for a long period of time from being returned to the toner storage chamber 32 from the developing chamber 31 and being mixed with toner in a new state in the toner storage chamber 32. Therefore, a stable small amount of toner can be supplied, and the image density can be stabilized.

  Further, since the width of the opening 33 in the short direction is not less than 5 [mm] and not more than 20 [mm], toner can be supplied from the toner storage chamber 32 to the developing chamber 31 more smoothly. Further, it is possible to prevent the toner deteriorated after being used for a long period of time from being returned to the toner storage chamber 32 from the developing chamber 31 and being mixed with toner in a new state in the toner storage chamber 32. Therefore, a stable small amount of toner can be supplied, and the image density can be stabilized.

  Further, the voltage applied to the supply roller 31c is larger than the voltage applied to the developing roller 31a by a predetermined voltage difference in the normal charging polarity direction of the toner, and the predetermined voltage difference is 50 [V ] To 1000 [V] or less. As a result, the toner can be sufficiently supplied to the developing roller 31a by the action of an electric field formed at the opposing portion of the developing roller 31a and the supply roller 31c. Therefore, the image density can be stabilized.

  Further, when the aggregation degree of the toner supplied to the developing chamber 31 is 5% or more and less than 30%, the following effects can be obtained. That is, toner aggregation in the toner storage chamber 32 and the developing chamber 31 is reduced, and toner supply from the toner storage chamber 32 to the developing chamber 31 and toner supply to the developing roller 31a can be performed more smoothly. Therefore, the image density can be stabilized.

  Therefore, the image forming apparatus according to the present embodiment can stably output a high-quality image.

  In this embodiment, the toner storage chamber 32 is disposed substantially vertically above the developing chamber 31, but the present invention is not limited to this. If a small amount of toner can be supplied by dropping toner, for example, the developing device 3 may be slightly inclined with respect to the vertical direction.

  In this embodiment, toner having a normal charging polarity of negative polarity is used. However, the present invention is not limited to this, and a toner having a normal charging polarity of positive polarity may be used. In that case, the polarity of the voltage applied to each member including the charging device 2, the developing roller 31a, the regulating blade 31b, and the supply roller 31c is changed as necessary.

  Further, in the present embodiment, the photosensitive drum 1, the charging device 2, the developing device 3, and the cleaning device 5 are integrally formed into a cartridge, and the image forming apparatus main body (not shown) is used. A removable process cartridge is configured. However, the present invention is not limited to this. For example, image formation in which the photosensitive drum is fixedly disposed on the main body of the image forming apparatus and only the developing device is a cartridge (developing cartridge) that is detachable from the main body of the image forming apparatus. The present invention can be similarly applied to apparatuses and the like. Alternatively, the present invention can be similarly applied to an image forming apparatus having a configuration in which the developing device is fixedly disposed on the main body of the image forming apparatus.

  Further, regarding the toner replenishment (replacement) method, in this embodiment, it is possible to replenish toner in a new state by replacing the toner storage chamber 32 that is detachable from the developing chamber 31. However, the present invention is not limited to this. It is not done. For example, a method of replenishing toner using a toner replenishing bottle or the like in a toner storage chamber fixedly arranged in the developing device may be used.

  Further, in this embodiment, the replenished (replaced) toner is the same type of toner as that used before the replacement, but is not limited to this, and is not a non-magnetic one-component developer. The non-magnetic toner may be different.

  Next, the configuration and operation of an image forming apparatus according to Embodiment 2 of the present invention will be described.

  FIG. 5 is a schematic cross-sectional view illustrating a schematic configuration of a color image forming apparatus 200 as an example of the image forming apparatus according to the present embodiment.

  The color image forming apparatus 200 is a color image forming apparatus capable of forming a four-color full-color image.

The color image forming apparatus 200 includes an electrostatic conveyance belt 20 as a recording material carrier that circulates and process cartridges Ua, Ub, Uc, Ud as first, second, third, and fourth image forming units. Is provided. Here, the process cartridges Ua, Ub, Uc, Ud are horizontally arranged in parallel on the electrostatic conveyance belt 20, and form images of each color of cyan, yellow, magenta, and black. Further, outside the process cartridge, exposure apparatuses 6a, 6b, 6c, and 6d as exposure means corresponding to the process cartridges Ua, Ub, Uc, and Ud, and transfer apparatuses 4a, 4b, 4c as transfer means, respectively. 4d is arranged. Further, a fixing device 7 as a fixing unit is disposed on the downstream side in the conveyance direction of the recording material P. Here, the configuration and operation of each process cartridge, exposure apparatus, and transfer apparatus are substantially the same except that the color of the toner used is different. Accordingly, in the following description, if no distinction is required, the subscripts a, b, c, and d given to the reference numerals in FIG. 5 are omitted to indicate that the elements are provided for any color. The overall explanation is as follows.

  The process cartridge U is detachable from the main body of the color image forming apparatus 200, and the configuration and operation thereof are the same as those of the process cartridge in the image forming apparatus 100 described in the first embodiment. The configuration and operation of the developing device 3 are the same as those of the developing device 3 in the image forming apparatus 100 described in the first embodiment. However, the non-magnetic toners as non-magnetic one-component developers accommodated in the developing devices 3a, 3b, 3c, and 3d are cyan toner, yellow toner, magenta toner, and black toner, respectively.

  The electrostatic conveyance belt 20 is disposed so as to face the photosensitive drums 1 of all the process cartridges U. Each transfer device 4 is in contact with the photosensitive drum 1 of each process cartridge U via the electrostatic conveyance belt 20, and forms a transfer region in the contact region and the vicinity thereof.

  The toner image formed on the surface of the photosensitive drum 1 in the process cartridge U is transferred onto the recording material P sequentially from the toner image of the process cartridge Ua as the recording material P is conveyed by the electrostatic conveyance belt 20. Then, the toner image transferred and superimposed on the recording material P is heated and pressurized in the fixing device 7 to be fixed, whereby a four-color full-color image is formed on the recording material P. Thereafter, the recording material P is discharged onto a discharge tray (not shown).

  Also in the color image forming apparatus 200, when toner is supplied from the toner storage chamber of the developing device 3 to the developing chamber, toner in a new state and toner deteriorated after long-term use are mixed in the developing chamber. Therefore, as described above, when there is a difference in the frictional charging characteristics, electrostatic aggregation is likely to occur.

  Furthermore, in a color image forming apparatus, a single color image, for example, a black character pattern image, is often output. In such a case, the process cartridges of other colors are simultaneously operated. For this reason, the toner in each developing chamber is repeatedly rubbed by each member without being used for image formation. That is, in the color image forming apparatus 200, the toner in the developing chamber is more likely to deteriorate. Therefore, the difference in frictional charging characteristics with the toner in a new state is likely to increase, and electrostatic aggregation is more likely to occur.

  However, according to the present exemplary embodiment, in the color image forming apparatus 200, the electric field formed between the regulating blade and the developing roller is more effectively applied, so that the triboelectric charging of the toner is promoted and uniform. Charging becomes possible. Furthermore, toner aggregation can be suppressed in the toner storage chamber and the developing chamber, and electrostatic aggregation can be prevented from occurring in the toner storage chamber. Therefore, an increase in fog at the time of toner replenishment can be suppressed while stably supplying a small amount, so that a high-quality image can be stably output.

  In this embodiment, the process cartridges Ua, Ub, Uc, Ud are horizontally arranged in parallel on the electrostatic conveyance belt 20, but the present invention is not limited to this. For example, the process cartridges Ua, Ub, Uc, Ud are inclined. It may be arranged in parallel on the electrostatic conveyance belt provided.

  In this embodiment, the process cartridges containing the respective color toners are arranged so that the transfer order of the respective color toner images onto the recording material P is cyan, yellow, magenta, and black. However, the present invention is not limited to this. Absent.

  Furthermore, in this embodiment, the color image forming apparatus 200 is used as an image forming apparatus capable of forming a multicolor image such as a full color image using an electrophotographic method, but the present invention is not limited to this. For example, a color image forming apparatus in which a plurality of developing devices each having a different color developer are provided for a single photoconductor may be used. In such a color image forming apparatus, the electrostatic latent images sequentially formed on the photoreceptor are sequentially developed by a plurality of developing devices. The toner image formed on the photosensitive member is directly transferred to the recording material, or transferred to the recording material after being transferred to the intermediate transfer member. Further, in a color image forming apparatus having a plurality of image forming units including a photoconductor and a developing device, such as the color image forming apparatus 200, toner images formed on the plurality of photoconductors are transferred to an intermediate transfer body. Then, it may be transferred to a recording material.

1 is a diagram illustrating a schematic configuration of an image forming apparatus according to Embodiment 1 of the present invention. 1 is a diagram illustrating a schematic configuration of a developing device according to Embodiment 1 of the present invention. It is a figure which shows schematic structure of the saturated friction charge amount measuring apparatus of a developer. It is a figure explaining the characteristic of the small amount replenishment of the developer in the developing device concerning Example 1 of the present invention. It is a figure which shows schematic structure of the image forming apparatus which concerns on Example 2 of this invention. It is a figure which shows schematic structure of the developing device which employ | adopted the conventional small amount replenishment system.

Explanation of symbols

3 Developing Device 8 Developing Bias Power Supply 9 Regulating Bias Power Supply 31 Developing Chamber 31a Developing Roller 31b Regulating Blade 32 Toner Storage Chamber 33 Opening

Claims (7)

A developer storage chamber for storing a non-magnetic one-component developer;
A developing chamber in which the developer is replenished through the opening from the developer containing chamber;
A developer carrier for carrying and conveying the developer;
A layer thickness regulating member for regulating the layer thickness of the developer carried on the developer carrying body;
First voltage applying means for applying a voltage to the developer carrying member;
A second voltage applying means for applying a voltage to the layer thickness regulating member;
In a developing device comprising:
The layer thickness regulating member is conductive;
The voltage applied to the layer thickness regulating member by the second voltage applying means is more in the direction of the normal charging polarity of the developer than the voltage applied to the developer carrier by the first voltage applying means. A voltage that is large by a predetermined voltage difference,
The predetermined voltage difference is 50 [V] or more and 300 [V] or less;
A developing device, wherein an absolute value of a saturated triboelectric charge amount of a developer supplied to the developing chamber is 40 [mC / kg] or more and 100 [mC / kg] or less.   The developing device according to claim 1, wherein an arithmetic average roughness (Ra) of the surface of the developer carrying member is 0.3 [μm] or less. A developer agitating member that is rotatably provided in the developer accommodating chamber and agitates the developer;
A developer supply member which is rotatably provided in the developing chamber and supplies the developer to the developer carrying member;
With
The developer storage chamber is disposed above the development chamber in a use posture.
When the rotation radius of the developer stirring member is r1 and the distance from the rotation center of the developer stirring member to the opening is r2, the developer stirring member is at a position close to the opening. ,
0 [mm] ≦ r2-r1 ≦ 5 [mm]
Satisfied with the relationship
When the rotation radius of the developer supply member is r3 and the distance from the rotation center of the developer supply member to the opening is r4, the developer supply member is at a position close to the opening. ,
5 [mm] ≦ r4-r3 ≦ 15 [mm]
The developing device according to claim 1, wherein the following relationship is satisfied. The opening is provided in the shape of a long hole whose longitudinal direction is the rotation axis direction of the developer supply member,
The developing device according to claim 3, wherein a width of the opening in a direction orthogonal to the longitudinal direction is 5 mm or more and 20 mm or less. A third voltage applying means for applying a voltage to the developer supply member;
The voltage applied to the developer supply member by the third voltage application means is more predetermined in the direction of the normal charging polarity of the developer than the voltage applied to the developer carrier by the first voltage application means. The voltage difference of
5. The developing device according to claim 1, wherein the predetermined voltage difference is 50 [V] or more and 1000 [V] or less. The developing device according to claim 1, wherein a degree of aggregation of the developer supplied to the developing chamber is 5% or more and less than 30%. An image carrier on which an electrostatic latent image is formed;
The developing device according to any one of claims 1 to 6, which performs a developing action on the image carrier;
An image forming apparatus comprising:

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