JP2007148013A - Developing apparatus and image forming apparatus equipped with the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a developing apparatus capable of preventing carrier from sticking on a photoreceptor, then, stably securing high image quality, and also, capable of preventing scratches on the photoreceptor, and also, preventing toner-scraping on the surface of the photoreceptor. <P>SOLUTION: Regarding the developing apparatus 1 for developing an electrostatic latent image carried on the surface of the photoreceptor by using two-component developer containing the toner and the carrier, the height (h) of a magnetic brush 11 coming in contact with the photoreceptor on the uppermost stream side in the photoreceptor rotating direction in a developing area, a developer quantity M per unit area on the photoreceptor to be supplied to the developing area, the bulk density ρ of the developer 2, the diameter DR of a developing roller 4, a distance D between the developing roller and the photoreceptor 12 at the closest position, and the contact length W of the magnetic brush of the developer carried by the developing roller with the photoreceptor in the developing area in the rotating direction of the developing roller are set so as to satisfy relation expressed by the following expressions; (DR/2+h)<SP>2</SP>>(DR/2+D)<SP>2</SP>+(W/2)<SP>2</SP>and D×ρ×100≥M≥10. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a developing device used for developing an electrostatic latent image formed by an electrophotographic method and an image forming apparatus including the developing device.

  2. Description of the Related Art Conventionally, in an image forming apparatus such as a copying apparatus or a printer using an electrophotographic method, various methods are used as developing methods for supplying toner in a developer to an electrostatic latent image formed on an electrostatic latent image carrier and developing it. Is used.

  As a typical developing method for image formation according to the electrophotographic method, there is a developing method using a two-component developer containing a toner and a carrier. In the developing method using a two-component developer, the surface of the charged electrostatic latent image carrier is exposed to form an electrostatic latent image on the surface of the electrostatic latent image carrier, and the two-component development is performed by the developer carrier. The developer is conveyed to a developing area where the developer carrying body and the electrostatic latent image carrying body face each other, and in the developing area, the toner in the developer is changed from the developer carrying body to the electrostatic latent image on the surface of the electrostatic latent image carrying body. Is supplied for development.

  The toner is transferred from the developer carrying member to the electrostatic latent image carrying member in the development area as follows. The developer magnetic brush formed on the developer carrier is brought into contact with the surface of the electrostatic latent image carrier, and the toner in the magnetic brush is transferred from the developer carrier to the electrostatic latent image carrier. In the developing method performed by forming such a magnetic brush, a developing roller having a plurality of magnets fixedly arranged in a cylindrical nonmagnetic sleeve, that is, a so-called magnet roller is used as a developer carrying member.

  However, when a developer magnetic brush is formed on the developer carrier and development is performed in contact with the electrostatic latent image carrier in the state of the magnetic brush, the toner supplied onto the electrostatic latent image carrier is In some cases, the toner image formed on the electrostatic latent image carrier may be disturbed by being scraped by a magnetic brush that rotates with the developer carrier.

  As one conventional technique for solving such problems, the carrier of the developer component having a low magnetic force is used to soften the ears of the magnetic brush contacting the electrostatic latent image carrier, It has been proposed to suppress toner image disturbance due to contact.

  However, if a carrier having a low magnetic force is used, the carrier's restraining force on the developer carrier is weakened, so that the carrier separates from the developer carrier and moves to the electrostatic latent image carrier, thereby A phenomenon of adhering to the image carrier occurs.

  When the carrier adheres to the electrostatic latent image carrier, the toner image formed by development is transferred to a recording medium such as a recording paper, and there is a problem that toner is lost due to the carrier in the formed image. Further, since the carrier is harder than toner, the surface of the electrostatic latent image carrier is damaged by the carrier attached to the electrostatic latent image carrier, and streaky noise is generated in the image formed due to the scratch. There is a problem that spotted noise occurs.

  As a conventional technique for preventing the toner on the surface of the electrostatic latent image carrier by the magnetic brush formed on the developer carrier, and preventing the carrier from adhering to the electrostatic latent image carrier, Defines the relationship between the amount of developer transported to the development area by the developer carrier, the bulk density of the developer, and the interval formed between the developer carrier and the electrostatic latent image carrier facing each other in the development area (For example, refer to Patent Document 1 and Patent Document 2).

  In Patent Document 1 and Patent Document 2, by defining the above relationship, the ratio of the developer conveyed to the development area by the developer carrier is set to an appropriate range, and the developer carrier is formed on the developer carrier. It is assumed that the toner on the surface of the electrostatic latent image carrier is not scraped off by the magnetic brush and the carrier is prevented from adhering to the electrostatic latent image carrier.

  However, in Patent Document 1 and Patent Document 2, only the ratio of the developer conveyed to the development region is defined, and the contact state of the magnetic brush formed on the developer carrier with respect to the electrostatic latent image carrier Is not defined at all. Therefore, even when the density of the developer in the development region is low, the density of the magnetic brush is high, and the scraping force of the surface of the electrostatic latent image carrier by the magnetic brush may be high, image distortion, In addition, problems such as carrier adhesion are assumed. Particularly recently, the carrier particles are reduced in magnetization and diameter for the purpose of improving the image quality and improving the developability, and the weight of the carrier tends to be reduced accordingly. There is.

  Further, as a conventional technique for smoothly transferring toner from a developer magnetic brush formed on a developer carrier to an electrostatic latent image carrier, the closest contact between the developer carrier and the electrostatic latent image carrier is provided. It is proposed that the difference between the length of the developer layer subtracted from the length and the porosity, which is the ratio and the ratio of the closest point of contact between the developer carrier and the electrostatic latent image carrier, are specified within an appropriate range. (See Patent Document 3).

  In Patent Document 3, by setting the porosity to an appropriate range, it is possible to secure a space in which the toner can move or move in the development region, so that the degree of freedom of movement of the developer near the surface of the electrostatic latent image carrier increases. It is assumed that the electrostatic latent image on the electrostatic latent image carrier can be adhered faithfully and a high-density and high-resolution image can be obtained.

  However, in the technique of Patent Document 3, although the porosity is defined within an appropriate range, in the development region, a magnetic brush having a length reaching the electrostatic latent image carrier is caused by the action of the developing magnetic pole of the developer carrier. The contact state of the magnetic brush with respect to the electrostatic latent image carrier is completely prescribed even though the magnetic brush rubs the surface of the electrostatic latent image carrier with the rotation of the developer carrier. Therefore, there is no concern that the magnetic brush may scrape off the toner on the surface of the electrostatic latent image carrier and that the carrier in the magnetic brush may adhere to the electrostatic latent image carrier.

JP-A-9-251239 JP 2001-5290 A Japanese Patent Laid-Open No. 11-73020

  It is an object of the present invention to prevent the carrier from adhering to the electrostatic latent image carrier to stably ensure high image quality and to stably develop the electrostatic latent image in a developing system in which a magnetic brush is formed on the developer carrier. It is an object of the present invention to provide a developing device capable of preventing the image carrier from being scratched and preventing the toner on the surface of the electrostatic latent image carrier from being scraped, and an image forming apparatus including the developing device.

The present invention carries a developer accommodating chamber that accommodates a two-component developer including toner and a carrier, and a developer that is rotatably provided in the developer accommodating chamber and accommodates the developer accommodated in the developer accommodating chamber. A developer magnetic brush formed on the outer peripheral surface of the developer carrier, and provided on the image forming apparatus to carry the electrostatic latent image. A developing device that supplies a developer to a latent electrostatic image through a development region formed by bringing the developer into a visible image,
The height of the magnetic brush in contact with the electrostatic latent image carrier on the most upstream side in the developing region rotation direction of the developer carrier in the development region is h [mm],
The amount of developer per unit area on the developer carrier supplied to the development area is M [mg / cm ² ],
The bulk density of the developer is ρ [g / cm ³ ],
The diameter of the developer carrier is DR [mm],
The distance at the closest position between the developer carrier and the electrostatic latent image carrier is D [mm],
When the magnetic brush of the developer carried on the developer carrying body is in contact with the electrostatic latent image carrying body in the developing region, and the length in the rotation direction of the developer carrying body is W [mm] ,
Development wherein the magnetic brush height h, developer amount M, developer bulk density ρ, developer carrier diameter DR, spacing D and length W satisfy the following equations: Device.
(DR / 2 + h) ² > (DR / 2 + D) ² + (W / 2) ²
100 × D × ρ ≧ M ≧ 10

  Further, the present invention includes a developer amount regulating member that is provided so as to have a predetermined interval with respect to the developer carrying member, and regulates the amount of developer conveyed by the developer carrying member. It is characterized by comprising a magnetic material.

  The present invention also includes a developing bias applying means for applying a developing bias to the developer carrying member, and the developing bias applying means applies a DC voltage applying means for applying a DC voltage and an AC voltage superimposed on the DC voltage. AC voltage application means.

The present invention also provides an electrostatic latent image carrier that is carried with an electrostatic latent image formed on the surface, a charging means that charges the electrostatic latent image carrier before the electrostatic latent image is formed, Exposure means for exposing the formed electrostatic latent image carrier with light according to image information to form an electrostatic latent image, and supplying a developer to the electrostatic latent image on the electrostatic latent image carrier to make it visible An image forming apparatus including a developing unit that forms an image,
The developing unit is an image forming apparatus according to any one of the above.

  According to the present invention, in the developing device, the height h of the magnetic brush that is in contact with the electrostatic latent image carrier on the most upstream side in the developer carrying member rotation direction in the developing region, and the developer carrying member supplied to the developing region. The developer amount M per unit area, the developer bulk density ρ, the diameter DR of the developer carrier, and the distance D at the closest position between the developer carrier and the electrostatic latent image carrier. The length of the magnetic brush of the developer carried on the developer carrying member is in contact with the electrostatic latent image carrying member in the developing region, and is specified between the length W in the rotation direction of the developer carrying member. The preferred relationship is defined.

  As a result, the height and density of the magnetic brush formed on the developer carrier in the development region are optimized, so that the magnetic brush is low in density and soft, and has elasticity. Also, the resistance of the carrier brush is increased. Therefore, it is possible to reduce the adhesion of the carrier to the electrostatic latent image carrier and to prevent the toner on the surface of the electrostatic latent image carrier from being scraped by the magnetic brush. By preventing the carrier from adhering to the electrostatic latent image carrier, toner loss in the transferred image onto the recording medium is prevented, and in combination with the toner scraping prevention, high image quality can be ensured. become. Further, by preventing the carrier from adhering to the electrostatic latent image carrier, it is possible to prevent the electrostatic latent image carrier from being scratched by scratching the carrier, so that the life of the electrostatic latent image carrier can be extended. In addition, the carrier consumption can be reduced.

  According to the present invention, the developer amount regulating member that regulates the amount of developer conveyed by the developer carrying member is configured to include a magnetic material. Therefore, when regulating the developer conveyance amount, The gap with the agent carrier can be widened. As a result, the friction load on the conveyed developer is reduced, so that deterioration of the developer is suppressed.

  In addition, according to the present invention, the developing bias applying means that can apply the DC voltage and the AC voltage in a superimposed manner to the developer carrying member is included. The movement of the toner in the toner can be activated and the development efficiency can be increased.

  Further, according to the present invention, since the developing device of the present invention is provided as the developing means of the image forming apparatus, the carrier can be prevented from adhering to the electrostatic latent image carrier and a high-quality image can be stably secured. In addition, the life of the electrostatic latent image carrier can be extended.

  FIG. 1 is a diagram showing a simplified configuration of a developing device 1 according to a first embodiment of the present invention. The developing device 1 includes a developer storage chamber 3 that stores a two-component developer 2 including toner and a carrier, and a developer 2 that is rotatably provided in the developer storage chamber 3 and is stored in the developer storage chamber 3. The first and second agitating and conveying rollers 5 and 6 that stir the developer carrying body 4 carrying and carrying the developer and the developer 2 contained in the developer containing chamber 3 and supply the developer to the developer carrying body 4. A developer amount regulating member 7 for regulating the amount of developer conveyed by the developer carrier 4, a developing bias applying means 8 for applying a developing bias to the developer carrier 4, and the developer accommodating chamber 3. A toner sensor 9 for detecting the toner concentration in the developer 2 and toner replenishing means 10 for replenishing the developer storage chamber 3 with toner.

  In the developing device 1, a developer magnetic brush 11 formed on the outer periphery of the developer carrier 4 is brought into contact with an electrostatic latent image carrier 12 that is provided in the image forming device and carries an electrostatic latent image. The toner is used as a developer component to the electrostatic latent image through a development area formed thereby to form a visible image.

  An electrostatic latent image carrier 12 that is provided in an image forming apparatus and carries an electrostatic latent image is an electrophotography in which, for example, a photosensitive layer including an organic photoconductor is formed on the outer periphery of a cylindrical conductive support. Hereinafter, the electrostatic latent image carrier 12 is abbreviated as the photoconductor 12 here.

  The two-component developer 2 used in this embodiment includes a nonmagnetic toner and a magnetic carrier. Nonmagnetic toners include those produced by pulverization or polymerization methods in which additives such as color pigments or dyes are dispersed in a resin and having a volume average particle size of 4 to 10 μm. Examples of the magnetic carrier include iron powder, ferrite powder, nickel powder or those whose surfaces are coated with an organic polymer and having a volume average particle size of 30 to 100 μm. When the size of the toner and the carrier is less than the above lower limit, the fluidity is deteriorated and the stirring property is lowered. If the toner and carrier sizes exceed the above upper limits, a high-definition image cannot be obtained.

  The developer storage chamber 3 is a container-like member that is made of, for example, hard resin and extends in one direction, and is disposed to extend in parallel with the rotation axis direction of the photoreceptor 12. An opening 13 is formed in the developer storage chamber 3 so as to extend in the direction of the rotation axis of the photoconductor 12 at a position facing the photoconductor 12. The developer carrying member 4 faces the photoconductor 12 through the opening 13 formed in the developer containing chamber 3, and its rotation axis is parallel to the rotation axis of the photoconductor 12, so that the developer containing chamber 4. 3 is rotatably provided.

  FIG. 2 is a cross-sectional view showing a simplified configuration of the developer carrier 4. The developer used in this embodiment is a two-component developer containing toner and carrier as described above. Therefore, the developer carrier 4 of the present embodiment includes a cylindrical sleeve 21 made of a nonmagnetic material, and a magnet member 22 that is included in the sleeve 21 and in which N poles and S poles are disposed substantially alternately. Is a so-called magnet developing roller. Here, the developer carrier 4 is hereinafter referred to as a developing roller 4. The developing roller 4 is provided with two N1 magnetic poles 22a and N2 magnetic poles 22b and three S1 magnetic poles 22c, S2 magnetic poles 22d and S3 magnetic poles 22e, and the N1 magnetic pole 22a is a developing magnetic pole, that is, the photosensitive member 12. It is used as a magnetic pole arranged at a position closest to. The sleeve 21 of the developing roller 4 is rotationally driven by a rotational driving means (not shown), and the magnet member 22 is used for development in a fixed state without rotating.

  In the present embodiment, the case where the rotation direction 61 of the photoconductor 12 and the rotation direction 16 of the sleeve 21 of the developing roller 4 are forward directions is illustrated.

  The developing roller 4 faces the upper edge portion of the opening 13 formed in the developer containing chamber 3, and the amount of developer conveyed by the developing roller 4 is regulated so as to have a predetermined interval with respect to the developing roller 4. A developer amount regulating member 7 is provided. The developer amount regulating member 7 is a so-called doctor blade, and is a thin plate member including a magnetic material in the present embodiment. The magnetic body constituting the developer amount regulating member 7 may be, for example, a nickel plate, a magnetic stainless steel (such as SUS430 defined in JIS-G4305), or a magnetic member. Hard resin mixed with may be used.

  By configuring the developer amount regulating member 7 to include a magnetic material, the gap between the developer amount regulating member 7 and the developing roller 4, that is, a predetermined interval is widened when regulating the developer conveyance amount. Therefore, the frictional load on the developer 2 being conveyed is reduced, and the deterioration of the developer 2 is suppressed.

  The first and second agitating / conveying rollers 5 and 6 are arranged in order of the second agitating / conveying roller 6 and the first agitating / conveying roller 5 from the side closer to the developing roller 4. It is rotatably provided in the developer storage chamber 3 so as to be parallel. The first and second agitating and conveying rollers 5 and 6 of the present embodiment are both configured such that, for example, a screw member is attached to the outer periphery of the rotating shaft member, and the first agitating and conveying roller 5 is arranged on the paper surface of FIG. The developer 2 is agitated and conveyed from the near side to the far side, and the developer 2 is supplied to the second agitating and conveying roller 6. The second agitating and conveying roller 6 is directed from the far side to the near side of the paper surface of FIG. The developer 2 is stirred and conveyed to supply the developer 2 to the developing roller 4.

  A partition plate 23 is provided between the first stirring roller 5 and the second stirring roller 6 so as to extend parallel to the direction in which the first and second stirring rollers 6 extend. By providing the partition plate 23, the developer 2 in the developer storage chamber 3 must surely follow the route from the agitation conveyance by the first agitation conveyance roller 5 to the conveyance by the second agitation conveyance roller 6. Therefore, the toner and the carrier are sufficiently stirred and supplied to the developing roller 4 in a uniform state.

  A toner supply port 24 is formed in the portion of the developer storage chamber 3 located above the first agitation transport roller 5 so as to penetrate the wall member of the developer storage chamber 3. A toner supply means 10 is provided so as to be connected to the toner supply port 24. The toner replenishing means 10 includes a toner container 26 that contains toner 25 that is a component of the developer 2, and a toner replenishment that is rotatable on the toner container 26 and is slidable with respect to the toner replenishing port 24. And a roller 27. The toner supply roller 27 is formed of a porous material at least in the vicinity of the surface thereof, and the toner held in the hole portion is separated by rubbing when sliding with the toner supply port 24, and the developer supply chamber is removed from the toner supply port 24. Supply to 3.

  The toner sensor 9 is composed of a magnetic permeability sensor, for example, and detects the toner concentration in the developer 2 by utilizing the fact that the toner is non-magnetic and the carrier is magnetic. The toner density detection result of the toner sensor 9 is given to a control unit (not shown), and the control unit drives the toner supply roller 27 of the toner supply unit 10 to rotate in accordance with the toner density detection result, so that the toner 25 is transferred to the developer. Replenish the storage chamber 3. The toner 25 replenished to the developer storage chamber 3 falls on the first stirring and conveying roller 5 and is mixed and stirred with the developer 2 in the process of being stirred and conveyed by the first stirring and conveying roller 5. Then, it is supplied to the developing roller 4.

  In order to transfer the toner from the developer 2 supplied to the developing roller 4 to the photosensitive member 12, a developing bias applying unit 8 is provided in this embodiment, and the developing bias applying unit 8 is connected to the developing roller 4. The DC voltage applying means 14 for applying a DC voltage and the AC voltage applying means 15 for applying an AC voltage can be applied by superimposing the AC voltage on the DC voltage. By applying an alternating voltage to the developing roller 4 in a superimposed manner, toner movement in the magnetic brush 11 formed on the developing roller 4 is activated, and the toner is smoothly transferred to the photoconductor 12. Development efficiency can be increased.

  Hereinafter, characteristic parts of the developing device 1 of the present invention will be described. FIG. 3 is a diagram showing a characteristic part in the developing device 1, and FIG. 4 is a diagram for explaining the developing region 31.

In the developing device 1, the height of the magnetic brush 11 in contact with the photoconductor 12 on the most upstream side in the rotation direction of the developing roller 4 in the developing region 31 formed between the developing roller 4 and the photoconductor 12 is h [mm]. The developer amount per unit area on the developing roller 4 supplied to the developing region 31 is M [mg / cm ² ], the bulk density of the developer 2 is ρ [g / cm ³ ], and the developing roller 4 DR [mm], the distance between the developing roller 4 and the photoreceptor 12 at the closest position is D [mm], and the magnetic brush 11 of the developer 2 carried on the developing roller 4 is in the developing region 31. When the length in contact with the photoconductor 12 and the length in the rotation direction of the developing roller 4 is W [mm], the developing device 1 has a height h of the magnetic brush 11, a developer amount M, a developer. 2 bulk density ρ, developing roller 4 diameter D , Distance D and length W is configured to satisfy a relation of the following equation (1) and (2).
(DR / 2 + h) ² > (DR / 2 + D) ² + (W / 2) ² (1)
100 × D × ρ ≧ M ≧ 10 (2)

  Here, the developing area 31 refers to an area where the magnetic brush 11 of the developer 2 formed on the outer peripheral surface of the developing roller 4 is in contact with the surface of the photoreceptor 12. The length W (this length W is hereinafter referred to as a development nip portion length) means the length of the development region 31 in the rotation direction of the development roller 4.

  The measurement of the development area 31 will be described with reference to FIG. The developer is supplied around the developing roller 4 in a state where the rotation is stopped to form the magnetic brush 11, and in this state, the developing device 1 is loaded into a predetermined position of the image forming apparatus. Next, the developing roller 4 of the developing device 1 is removed from the image forming apparatus without rotating. As a result, when the magnetic brush 11 formed on the outer periphery of the developing roller 4 is inserted into the image forming apparatus, the spike contacts with the photoconductor 12 and is pressed to form a deformed region. The area where the shape is broken can be visually observed, and the development nip width W can be measured by visual observation. Conversely, the development region 31 can be specified as the region where the developer is attached to the surface of the photoreceptor 12. Although the developing nip width W is the length of the curved section, it is actually a length of several millimeters, and is represented by linear approximation in FIG.

  FIG. 5 is a diagram showing an outline of a method for measuring the height h of the magnetic brush. An image of the magnetic brush 11 formed in a free state on the outer peripheral surface of the developing roller 4 without being brought into contact with the photoconductor 12 is viewed from the front direction shown in FIG. 5 using a digital microscope VHX-200 (manufactured by Keyence). Taken and measured.

  The developer amount M can be measured as follows. The magnetic brush 11 formed in a certain area on the surface of the developing roller 4 is forcibly peeled off by a magnet member having a magnetic force stronger than the developing magnetic pole, the weight is measured, and the measured weight is divided by the certain area. Sought by. The bulk density ρ of the developer 2 can be obtained by obtaining the weight and volume of an arbitrary amount of developer and dividing the weight by the volume.

  The diameter DR of the developing roller 4 and the distance D between the developing roller 4 and the photoconductor 12 (hereinafter simply referred to as the distance D) can be actually measured.

  Formula (1) is obtained by setting a side a obtained as the sum of the radius (DR / 2) of the developing roller 4 and the interval D and a side b obtained as ½ of the development nip width W as two sides sandwiching a right angle. This means that the height h of the magnetic brush is set to be larger (longer) than the length obtained by subtracting the radius of the developing roller 4 from the length of the hypotenuse obtained by the three-square theorem. Such setting can be realized by conducting a test in advance and selecting the strength of the magnetic force of the magnet member 22 and the material of the carrier that is a magnetic material. The upper limit of the height h of the magnetic brush 11 is not particularly limited, but is defined by a predetermined interval between the developer amount regulating member 7 and the developing roller 4 in terms of the apparatus configuration.

On the other hand, with respect to the expression (2), when the developer amount M is less than 10 mg / cm ² , the amount of the developer conveyed to the development region 31 is too small, so that an appropriate image density cannot be obtained. When the developer amount M exceeds (100 × D × ρ) mg / cm ² , the amount of the developer conveyed to the development region 31 becomes excessive, so that the rising of the carrier and the fog in the image to be developed increase. . Therefore, the developer amount M is set to 10 mg / cm ² or more and (100 × D × ρ) mg / cm ² or less.

  By increasing the height h of the magnetic brush 11 as described above, the magnetic brush 11 becomes soft and elastic with low density and the resistance of the carrier brush is increased. The toner is prevented from being scraped off, and the carrier is prevented from adhering to the photoreceptor 12. Although the height h of the magnetic brush 11 is long and low in density, the developer amount M supplied to the developing region 31 is set to an appropriate range, and thus supplied to the development of the electrostatic latent image through the magnetic brush 11. There is no excess or deficiency in the toner amount, and an appropriate image density can be obtained.

  FIG. 6 is a diagram showing a simplified configuration of the developing device 41 according to the second embodiment of the present invention. The developing device 41 of the present embodiment is similar to the developing device 1 of the first embodiment, and corresponding portions are denoted by the same reference numerals and description thereof is omitted.

  What should be noted in the developing device 41 of the present embodiment is that the developing bias applying means 42 is composed of only the DC voltage applying means 14. Other configurations of the developing device 41 are the same as those of the developing device 1 of the first embodiment.

  By using only the DC voltage applying means 14 as the developing bias applying means 42, the toner mobility in the developing region 31 is slightly lowered as compared with the case where the AC voltage is applied in a superimposed manner, but there is a problem in practical developing efficiency. Not what you want. Since the height h and the developer amount M of the magnetic brush 11 are set to be the same as those in the first embodiment, the developing device 41 can achieve the same effects as the developing device 1.

  FIG. 7 is a cross-sectional view seen from a side direction, showing a simplified configuration of an image forming apparatus 50 which is another embodiment of the present invention including the developing device of the present invention. An image forming apparatus 50 shown in FIG. 7 includes, for example, the developing device 1 of the present invention. For example, image information transmitted from an external device such as a personal computer or a digital camera, or image information read and transmitted by an image reading apparatus. In response to the above, it is recorded and output as a monochromatic image on a recording medium such as recording paper.

  The image forming apparatus 50 generally includes an image forming unit 51, a recording paper supply unit 52 that supplies recording paper as a recording medium, an image fixing unit 53, and a control unit 54.

  The image forming unit 51 includes the photosensitive member 12, a charging unit 56, an exposing unit 57, and the developing device 1 that are sequentially arranged from the upstream side to the downstream side in the rotation direction 61 of the photosensitive member 12 along the outer periphery of the photosensitive member 12. A transfer unit 58, a cleaning unit 59, and a charge eliminating unit 60 are included.

  The photoconductor 12 is a roller member including a cylindrical or columnar conductive substrate and a photoconductive layer formed on the surface of the conductive substrate, and is exposed to light according to image information. An electrostatic latent image is formed on the surface. The photoreceptor 12 is rotatably provided in the apparatus main body of the image forming apparatus 50, and is rotated in the direction of the arrow 61 by a driving unit (not shown).

  The charging unit 56 includes a contact type or non-contact type charger such as a charging roller or a charging charger, and charges the surface of the photoconductor 12 to a uniform potential. The exposure unit that is the exposure unit 57 is constituted by a laser unit such as a semiconductor laser, for example, and the surface of the photoreceptor 12 that is charged by the charging unit 56 in accordance with image information transmitted from the control unit 54 described later. Is irradiated with light to form an electrostatic latent image.

  The developing device 1 is the developing device 1 of the present invention, and supplies an appropriate amount of developer to the electrostatic latent image formed and carried on the surface of the photoreceptor 12 and is formed long at low density. The toner is supplied through the soft magnetic brush 11 to make the electrostatic latent image visible and form a toner image.

  The transfer unit 58 includes, for example, a transfer roller 62 that is in pressure contact with the outer peripheral surface of the photoconductor 12 and is rotatably provided, and a power source (not shown) that applies a transfer bias voltage to the transfer roller 62. The transfer unit 58 applies a transfer bias voltage from the transfer roller 62 side to charge the recording paper, and pressurizes the recording paper with the transfer roller 62 to thereby transfer the toner image formed on the surface of the photosensitive member 12 to the recording paper. Transcript to.

  The cleaning unit 59 is made of, for example, an elastic material and includes a cleaning blade that is a plate-like member provided so as to come into contact with the outer peripheral surface of the photoconductor 12. After the toner image is transferred to the recording paper, the photoconductor The toner, paper dust and the like remaining on the surface of 12 are removed. The neutralization means 60 is constituted by a neutralization lamp or the like, and removes the surface charge of the photoreceptor 12 after cleaning.

  The image fixing unit 53 includes a fixing (heating) roller 63, a pressure roller 64, a temperature sensor (not shown) that detects the temperature of the fixing roller 63, and the fixing roller 63 at a desired temperature according to the detection output of the temperature sensor. And a control power supply (not shown). In the image fixing unit 53, the recording paper on which the toner image has been transferred by the transfer unit 58 of the image forming unit 51 is fed to a pressure contact portion (fixing nip portion) between the fixing roller 63 and the pressure roller 64 and heated and pressed. In response, the toner image is fixed on the recording paper and an image is formed. The recording paper on which the toner image has been fixed by the image fixing unit 53 is discharged to a paper discharge unit 67 provided at the upper part of the apparatus main body by the transport operation of the transport roller 65 and the paper discharge roller 66.

  The recording paper supply unit 52 includes a recording paper tray 68, a pickup roller 69, and a registration roller 70. The recording paper tray 68 is a tray that can accommodate recording media such as plain paper, color copy paper, and overhead projector (OHP) film. The pickup roller 69 separates the recording paper in the recording paper tray 68 one by one and feeds it to the registration roller 70. The registration roller 70 transfers the recording paper to the transfer unit 58 in synchronization with the image forming area (particularly the formation start position on the most downstream side) of the electrostatic latent image formed on the surface of the photoreceptor 12 by the exposure of the exposure unit 57. To the transfer nip. The transport roller 65 is provided at various points along the path along which the recording paper fed from the recording paper tray 68 is transported, and transports the recording paper to a desired position by a rotating operation.

  The control unit 54 is a processing circuit that is provided above the exposure unit 57 in the internal space of the image forming apparatus 50 and is realized by a microcomputer having a central processing unit (CPU). The control unit 54 is in accordance with a program read from a memory described later. The overall operation related to image formation of the image forming apparatus 50 including the developing device 1 is controlled. The control unit 54 is provided with a memory serving as a storage unit. As the memory, for example, a read only memory (ROM), a random access memory (RAM), a hard disk drive (HDD), or the like that is commonly used in this field is used. it can. The control unit 54 includes a power source together with the processing circuit described above, and the power source supplies power not only to the control unit 54 but also to each device in the image forming unit 51, the recording paper supply unit 52, and the image fixing unit 53.

  An image forming operation in the image forming apparatus 50 will be briefly described. First, the memory of the control unit 54 stores image information transmitted from an external device and subjected to image processing such as gradation processing. In the image forming unit 51, the surface of the photoconductor 12 is charged to a substantially uniform potential by the charging unit 56, and light corresponding to the image information read from the memory is irradiated by the exposure unit 57, so that an electrostatic latent image is formed. It is formed.

  With respect to the electrostatic latent image formed on the surface of the photoreceptor 12, toner is supplied from the developer magnetic brush 11 in the developing region 31 to form a toner image. The toner image formed on the surface of the photoconductor 12 is transferred to a recording sheet by the transfer unit 58, further fixed by the image fixing unit 53, and discharged to the paper discharge unit 67. On the other hand, on the surface of the photoreceptor 12 after the toner image is transferred, residual toner and the like are removed by the cleaning unit 59, and the charge is removed by the charge removing means 60, which is used for the next image formation. By repeating this series of operations, an image is formed.

  Since the image forming apparatus 50 includes the developing device 1, a suitable developer amount M can be supplied to the electrostatic latent image through the soft magnetic brush 11 having a low density and a large height h. As a result, scraping of the toner image formed on the surface of the photoconductor 12 is prevented and carrier adhesion to the photoconductor 12 is also prevented, so that a high-quality image can be secured stably. In addition, the life extension of the photoconductor 12 is realized.

Examples of the present invention will be described below.
Using a printer (AR-450M modified type: manufactured by Sharp Corporation) corresponding to the image forming apparatus provided with the developing device 1 of the present invention, image formation is performed on A4 size recording paper under the following conditions, and on the photoreceptor. The development amount of the toner, the development amount and fog of the formed image, and the carrier rise, which is an index of carrier adhesion to the photoreceptor, were determined. Table 1 shows developer and apparatus setting conditions used in the image formation test, and Table 2 shows development bias application conditions. In the test, the developer amount M, the distance D between the developing roller and the photosensitive member, and the height h of the magnetic brush were used as variation factors.

  In the image formation test, Examples 1 to 6 in which the variation factors all satisfy the relationship of the formulas (1) and (2), the developer amount M and the height h of the magnetic brush are represented by the formula (1). And Comparative Example 1 that does not satisfy the relationship of Formula (2) and Comparative Example 2 in which the developer amount M does not satisfy the relationship of Formula (2).

The development amount of the toner was measured as follows. A solid image was formed on the photoreceptor, and the toner on the photoreceptor was aspirated. The weight of the sucked toner was measured with a balance, and the amount of toner per unit area was determined. When the toner development amount was 0.4 [mg / cm ² ] or more, it was evaluated that the image density was appropriate.

  The fog was measured as follows. The difference between the whiteness of the recording paper before image formation and the whiteness of the white portion after image formation is measured using a whiteness meter (hunter whiteness meter: manufactured by Nippon Denshoku Kogyo Co., Ltd.). The maximum value was defined as fog. The fog is evaluated as “good: ○” when the difference in whiteness is less than 0.4, “normal: Δ” when the difference is 0.4 or more and less than 1.0, and “bad” × when it is 1.0 or more. did.

  The carrier rise was measured as follows. A white solid image of A4 size is printed, the operation of the photoconductor is forcibly interrupted in the middle of printing, an adhesive tape with a width of 18 mm is applied to the photoconductor at that time, and then peeled off and attached to the adhesive tape. The number of completed carriers was counted. When the number of attached carriers was less than 15, it was evaluated as a good level that does not affect the image, and when it was 15 or more, it was evaluated as a defective level that affected the image.

  The overall evaluation was made based on the results of toner development, fogging and carrier rising. A case where all of the above items are good is determined as “excellent: ◎”, a case where the evaluation result is normal is determined as “good: ◯”, and a case where any one of the evaluation results is defective is determined as “defective: X ”was determined.

  The test results are shown together in Table 3. In Examples 1 to 6 satisfying the relationship of the present invention, the overall evaluation was good or excellent. On the other hand, in Comparative Example 1 in which the developer amount M and the magnetic brush height h do not satisfy the relationship of the present invention, the toner development amount is insufficient, the image density is low, the carrier rise is remarkably high, and the overall evaluation is poor. there were. In Comparative Example 2 in which the developer amount M does not satisfy the relationship of the present invention, the toner development amount is large and the image density is high, but the fog is poor, the carrier rise is also poor, and the overall evaluation is poor. It was.

  As described above, in this embodiment, the image forming apparatus is configured as a printer that forms a single color image. However, the present invention is not limited thereto, and the printer, copying machine, and facsimile apparatus that form a multicolor image are not limited thereto. And so on. Further, although the developing device 1 of the present invention is mounted on the image forming apparatus, the present invention is not limited to this, and the developing device 41 of the present invention may be mounted.

1 is a diagram showing a simplified configuration of a developing device 1 according to a first embodiment of the present invention. 2 is a cross-sectional view showing a simplified configuration of a developer carrier 4. FIG. FIG. 3 is a diagram illustrating a characteristic part in the developing device 1. FIG. 3 is a diagram illustrating a development area 31. It is a figure which shows the outline | summary of the method of measuring the height h of a magnetic brush. It is a figure which simplifies and shows the structure of the developing device 41 which is 2nd Embodiment of this invention. FIG. 6 is a cross-sectional view seen from the side direction, showing a simplified configuration of an image forming apparatus 50 that is another embodiment of the present invention including the developing device 1 of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,41 Developing device 2 Developer 3 Developer accommodating chamber 4 Developing roller 5, 6 Agitating and conveying roller 7 Developer amount regulating member 8, 42 Developing bias applying means 9 Toner sensor 10 Toner replenishing means 11 Magnetic brush 12 Electrophotographic photosensitive member DESCRIPTION OF SYMBOLS 14 DC voltage application means 15 AC voltage application means 50 Image forming apparatus 51 Image formation part 52 Recording paper supply part 53 Image fixing part 54 Control part

Claims (4)

A developer storage chamber that stores a two-component developer including toner and a carrier, and a developer carrier that is rotatably provided in the developer storage chamber and supports and transports the developer stored in the developer storage chamber A developer magnetic brush formed on the outer peripheral surface of the developer carrying member is brought into contact with an electrostatic latent image carrying member that is provided in the image forming apparatus and carries the electrostatic latent image. A developing device that supplies a developer to an electrostatic latent image through a development area to be formed to make a visible image,
The height of the magnetic brush in contact with the electrostatic latent image carrier on the most upstream side in the developing region rotation direction of the developer carrier in the development region is h [mm],
The amount of developer per unit area on the developer carrier supplied to the development area is M [mg / cm ² ],
The bulk density of the developer is ρ [g / cm ³ ],
The diameter of the developer carrier is DR [mm],
The distance at the closest position between the developer carrier and the electrostatic latent image carrier is D [mm],
When the magnetic brush of the developer carried on the developer carrying body is in contact with the electrostatic latent image carrying body in the developing region, and the length in the rotation direction of the developer carrying body is W [mm] ,
Development wherein the magnetic brush height h, developer amount M, developer bulk density ρ, developer carrier diameter DR, spacing D and length W satisfy the following equations: apparatus.
(DR / 2 + h) ² > (DR / 2 + D) ² + (W / 2) ²
100 × D × ρ ≧ M ≧ 10 A developer amount regulating member that is provided to have a predetermined interval with respect to the developer carrying member and regulates the amount of developer conveyed by the developer carrying member;
The developing device according to claim 1, wherein the developer amount regulating member includes a magnetic material. A developing bias applying means for applying a developing bias to the developer carrying member;
3. The developing device according to claim 1, wherein the developing bias applying means includes a DC voltage applying means for applying a DC voltage and an AC voltage applying means for applying an AC voltage superimposed on the DC voltage. An electrostatic latent image carrier on which an electrostatic latent image is formed and carried; a charging means for charging the electrostatic latent image carrier before the electrostatic latent image is formed; An exposure unit that exposes the image carrier with light according to image information to form an electrostatic latent image, and a developing unit that supplies a developer to the electrostatic latent image on the electrostatic latent image carrier to visualize the image. An image forming apparatus including:
Development means
An image forming apparatus comprising the developing device according to claim 1.

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