JP2009175417A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus capable of preventing titanium spent on a carrier, preventing the degradation in a two-component developer and degradation in an image and carrying out stable image formation for a long period of time. <P>SOLUTION: The image forming apparatus includes: a means 111 that detects an image signal of a toner image to be formed and detects an image area ratio of the toner image; a means 85 that detects a driving time of a developing device 7 and calculates a development driving time in one job; and a means 100 that calculates a consumption amount of the toner per unit driving time from the image area ratio of the toner image in the job, the paper size, and the development driving time. If the consumption amount calculated by the means of calculating a consumption amount is larger than a predetermined given consumption amount, developing sleeves 71a, 71b are controlled to rotate for idling at the end of the job. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an image forming apparatus using an electrophotographic system such as a printer, a copier, or a fax machine. More specifically, an electrostatic latent image formed on a latent image carrier such as a photoconductor is developed with a two-component toner. The present invention relates to an electrophotographic image forming apparatus for imaging.

The toner in the two-component developer used in electrophotographic image forming apparatuses such as copying machines, printers, and facsimiles is a wax component for improving the separation at the fixing portion, ensuring fluidity and a charge control agent. And other external additives. Examples of the external additive include wax, silica, titanium oxide, aluminum oxide, zinc oxide, and magnesium oxide. In addition, some components in such external additives may be released from the toner depending on the use conditions, and may adhere to the carrier and become spent.
In particular, wax, titanium oxide, and the like can be cited as external additives that are easily spent on the carrier. As a result, the charging ability of the carrier is reduced, and it becomes difficult to control the toner density and the image density is lowered. In order to solve such a problem, the invention described in Patent Document 1 solves the above problems by forcibly consuming toner according to the development drive time.

However, if the toner is forcibly consumed according to the development drive time, the wax spent is effective, but the titanium spent by titanium oxide is adversely affected. In the case of wax, if the toner is consumed, it is discharged together with the toner. However, in the case of titanium oxide, the transition time to the carrier is short, and the carrier transitions to the carrier before the toner is consumed. Therefore, titanium spent tends to be generated depending on the toner consumption.
FIG. 4 is a graph showing the relationship between the cumulative development drive time and the amount of titanium transferred to the carrier.
For this reason, if the toner is consumed like forced consumption, the titanium spent will be accelerated. In order to prevent titanium spent, it is necessary to apply stress to the carrier as in the case of idling so that the carrier film is easy to be scraped and to prevent titanium spent. Titanium oxide is indispensable for stabilizing the environmental fluctuation of toner charging.

JP-A-8-314253

  Therefore, the present invention has been made in view of the above problems, and its problem is to prevent titanium spent on the carrier, prevent agent deterioration of the two-component developer, image deterioration, and stable image over a long period of time. An object of the present invention is to provide an image forming apparatus capable of forming images.

The features of the present invention, which is a means for solving the above problems, are listed below.
The image forming apparatus of the present invention comprises an image carrier, latent image forming means for exposing the image carrier to form an electrostatic latent image, and the electrostatic latent image on the image carrier using carrier and titanium. In an image forming apparatus comprising a developing device that develops a toner image by developing with a developer carrying means that carries a two-component developer comprising toner as an additive, an image signal of the toner image to be formed is detected, and the toner image Means for detecting the image area ratio, means for detecting the drive time of the developing device, calculating the development drive time in one job, and the image area ratio of the toner image in the job, the paper size, and the development drive time. Means for calculating a consumption amount per unit driving time in the job, and the image forming apparatus is configured to output a job end when the consumption amount calculated by the means for calculating the consumption amount is greater than a predetermined consumption amount. Sometimes the developing sleeve It is characterized by controlling to rotate and idle.
Further, the image forming apparatus of the present invention further rotates the developing sleeve at the end of the job when the consumption per unit driving time during the job exceeds a certain consumption by means for calculating the consumption, Control is performed to idle the developing sleeve.
The image forming apparatus of the present invention is further characterized in that the idling time of the developing sleeve is controlled in accordance with consumption.
The image forming apparatus of the present invention is further characterized by controlling the sleeve linear velocity when the developing sleeve idles.
The image forming apparatus of the present invention is further characterized in that the upper limit of the developing sleeve linear velocity is controlled in a range up to 2.5 in terms of the linear velocity ratio to the drum.
The image forming apparatus of the present invention is further characterized by using a two-component developer containing toner containing silica.
The image forming apparatus of the present invention is further characterized by using a two-component developer including a carrier coated with a resin.

  In the image forming apparatus of the present invention, by performing idling after the job is completed, titanium transfer to the carrier can be prevented, so that agent deterioration and image deterioration due to titanium spent can be prevented, and stable image formation can be performed over a long period of time. .

  The best mode for carrying out the present invention will be described below with reference to the drawings. Note that it is easy for a person skilled in the art to make other embodiments by changing or correcting the present invention within the scope of the claims, and these changes and modifications are included in the scope of the claims. The following description is an example of the best mode of the present invention, and does not limit the scope of the claims.

FIG. 1 is a schematic diagram showing the configuration of an image forming apparatus according to an embodiment of the present invention. The image forming apparatus 1 forms a latent image by exposing a photosensitive member (image carrier) 10, a charging device 2 for uniformly charging the photosensitive member 10, and laser light to the surface of the charged photosensitive member 10. An exposure device 3; a developing device 7 for supplying a toner as a developer to the latent image on the surface of the photoreceptor 10 to make it visible; a toner replenishing unit 8 for supplying toner to the developing device 7; The image forming apparatus mainly includes a transfer device 6 that transfers the imaged toner image onto transfer paper, and a registration roller 5 that temporarily stops the transfer paper supplied between the photoconductor 10 and the transfer unit 6.
In the image forming apparatus 1 having such a configuration, after the surface of the photoconductor 10 is uniformly negatively charged to about −900 V by the charging device 2, the image memory of the image memory control unit 111 that stores image information such as a document is stored. The controller 100 replaces the signal read out by the laser beam with an electrostatic latent image of about −50V. Next, a toner image is formed by the negatively charged nonmagnetic toner. The developing device 7 is a two-component developing device. In the developing device 7, nonmagnetic toner is included in a carrier made of a magnetic material so as to have a predetermined ratio (toner concentration).

  The developing device 7 includes developing rollers 71a and 71b that apply toner in the developer to the photoreceptor 10, a developing doctor 72 that regulates the amount of developer on the developing roll 71a, and stirring members 73, 74, and 75 that stir the developer. It has. The developing device 7 is driven by a developing motor 87. A toner replenishing portion 8 is provided adjacent to the developing device 7, and toner supplied from a toner cartridge (not shown) is gradually replenished into the developing device 7 by a replenishing roller 81. The toner replenishment is controlled by the toner replenishing clutch so that only the shortage is replenished according to the developer concentration in the developing device 7. The replenished toner is agitated with the carrier by the agitating members 73, 74, 75, and adheres to the carrier and is negatively charged.

The toner is attracted to and adhered to the magnets of the developing rollers 71a and 71b. The toner conveyed to the developing doctor 72 by the rotation of the developing rollers 71a and 71b is regulated to a predetermined amount and then supplied to the developing area on the photoconductor 10. About −550 V is supplied to the developing rolls 71a and 71b from a developing bias power source (not shown), and only the negatively charged toner in the developer moves to the electrostatic latent image to form a toner image.
At this time, the transfer paper is conveyed from the paper feed cassette (not shown) that accommodates the transfer paper in the direction of arrow B, and is temporarily stopped by the registration roller 5. In accordance with the timing of the toner image on the photoconductor 10, the transfer paper is sent from the registration roller 5, and the toner image on the photoconductor 10 is transferred to the transfer paper by the transfer belt 61 of the transfer device 6. The transfer belt 61 is made of, for example, a material in which rubber has an intermediate resistance. A driving roller 62, a driven roller 63, and a bias roller 64 are disposed inside the transfer belt 61. The bias roller 64 is connected to a high-voltage transfer power supply 65, and is controlled so that a transfer bias is applied and the current flowing to the photoconductor 10 side becomes constant. The transfer paper onto which the toner image has been transferred reaches the fixing device 90, where the toner image is fixed on the transfer paper and then discharged from the image forming apparatus 1. The toner remaining on the surface of the photosensitive member without being transferred to the transfer paper is collected by the brush roller 92 and the cleaning blade 93 of the photosensitive member cleaning device 91. Thereafter, the surface of the photoreceptor 10 is neutralized by a neutralizing lamp 94 which is a neutralizing unit.

In the image forming apparatus 1 of the present invention, during the image forming process, the image signal of the toner image to be formed is detected, and the image memory control unit 111 as means for detecting the image area ratio of the toner image and the developing device 7 As a means for detecting the driving time and calculating the developing driving time in one job, the developing driving time measuring circuit 85, the image area ratio of the toner image in the job, the paper size, the developing driving time per unit driving time in the job The image forming apparatus 1 includes a consumption measuring circuit 83 as a means for calculating the consumption amount. When the consumption amount calculated by the means for calculating the consumption amount is greater than a predetermined consumption amount, The developing sleeves 71a and 71b are rotated and controlled to idle.
The image signal read by the document reading unit 110 is accumulated in the image memory control unit 111. This image signal includes monochrome and color signals. Therefore, the image memory control unit 111 can calculate the image area ratio of the document including not only the monochrome monochrome pattern but also the color image by comparing these ratios from the image signal.
Next, the developing drive measuring circuit 85 measures the driving time of the developing device 7 during the job. Using the driving time measured by the development driving time measuring circuit 85, and further from the above-described image area ratio and the paper size detected by the paper size detection unit 84 from the paper feed cassette mounted on the image forming apparatus. The consumption per unit driving time in the job is calculated by means for calculating the consumption.

The saturated adhesion amount in the calculation formula is the adhesion amount of the toner image on the photoconductor 10 necessary for outputting the top image density (image density 1.4). When the consumption amount is larger than a predetermined consumption amount, the development drive motor 87 is driven at the end of the job and the development sleeves 71a and 71b are rotated by a signal from the controller 100. By idling in this way, stress is applied to the developer and titanium migration to the carrier can be prevented, so that deterioration of the agent due to titanium spent can be suppressed. The predetermined constant consumption is the consumption for the total number of image formations. For example, when the consumption for 10,000 prints is larger than the predetermined consumption, the idle consumption is performed. Or, in a continuous image forming job, for example, when it is larger than a predetermined consumption amount in a job of about 10 to 100 sheets, it is idled. Further, the image forming apparatus 1 rotates the developing sleeves 71a and 71b at the end of the job when the consumption per unit driving time during the job exceeds a certain consumption by the means 83 for calculating the consumption. The developing sleeves 71a and 71b may be controlled to idle.
Further, although the developing sleeves 71a and 71b are idled, the stirring members 73, 74, and 75 may be idled. However, in the developing sleeves 71a and 71b, since the carrier is vigorously moved by the magnetism of the carrier and the magnet in the developing sleeve, the film on the surface of the carrier is peeled off, resulting in a low situation. Similarly, the agitating members 73, 74, and 75 are vigorously agitated. However, since the agitation is not as high as the developing sleeves 71a and 71b, the developing sleeves 71a and 71b are preferably idled to suppress the deterioration of the carrier. In the present embodiment, two developing sleeves 71a and 71b are shown, but one may be used. Idle rotation refers to rotation without replenishing toner. Accordingly, since the spent titanium oxide is easily peeled off together with the coating resin of the carrier, new titanium oxide is not replenished, so that the fresh surface is exposed, so that deterioration of the carrier can be suppressed.

FIG. 2 is a diagram showing a relationship of occurrence of a defect based on the cumulative development driving time and the amount of titanium transferred to the carrier. The drive time T on the horizontal axis in the figure is the drive time determined as the developer life. A on the vertical axis is the amount of titanium transfer (titanium spent amount) at which problems such as toner charge reduction and toner scattering occur. The consumption M per unit driving time is a consumption that causes a trouble due to titanium spent when the driving time T is reached.
The consumption M is measured in advance by the consumption measuring circuit 83 per unit driving time and stored in the controller 100. First, the consumption amount per unit driving time of a toner image formed during a job is calculated. When the calculated consumption amount is larger than M, the developing drive motor 87 is driven at the end of the job and the developing sleeves 71a and 71b are rotated by a signal from the controller 100. By controlling in this way, when the consumption per unit driving time when the spent begins to deteriorate, by performing idling, it is possible to reduce unnecessary idling and to suppress agent deterioration due to titanium spent. .

As shown in FIG. 2, when the consumption per unit driving time is larger than the consumption M and the driving time until reaching the titanium spent amount A at which the titanium coverage per unit surface area of the carrier is a certain value is short, Developer deterioration occurs. Therefore, when the consumption amount per unit driving time calculated during the job is large, it is necessary to always make it smaller than the consumption amount M by performing idling after the end of the job. First, the consumption amount per unit driving time of a toner image formed during a job is calculated.
FIG. 3 is a diagram illustrating a situation in which the idling time is controlled based on the cumulative development driving time and the amount of titanium transferred to the carrier. As shown in FIG. 3, the driving time measured at this time is T ₀ , the toner consumption amount V ₀ , and the consumption amount per unit driving time is M ₀ = V ₀ / T _0. To record. If the measured consumption per unit driving time is M ₀ > M, the target consumption is M ₁ and a coefficient B such that M ₀ × B = M ₁ <M is obtained. Next, a driving time T ₁ that results in a consumption M ₁ is calculated from M ₁ = V ₀ / T ₁ , and T ₁ = V ₀ / (M ₀ × B) is obtained. As a result, the difference between the driving times T ₁ and T ₀ so that the target consumption M ₁ per unit driving time is obtained is calculated by the consumption measuring circuit 83 per unit driving time, and the development from the signal from the controller 100 is performed. The drive motor 87 is driven at the end of the job, and the developing sleeves 71a and 71b are controlled to rotate. By controlling in this way, even if the consumption per unit driving time is extremely high, the consumption per driving time is controlled to be reduced for each job. Can be suppressed.
Thus, by controlling the idling time according to the consumption per unit driving time measured during the job, it is possible to stably prevent agent deterioration and image deterioration due to titanium spent over time.
The driving time T and the toner consumption amount V depend on the outer diameters of the developing sleeves 71a and 71b in the developing device 7, the developer amount in the developing device, and the like. A, toner consumption amount M per unit driving time is determined. However, since the image forming apparatus 1 of the present invention, including the basic concept, can prevent titanium migration to the carrier, agent deterioration and image deterioration due to titanium spent can be prevented, and stable image formation can be performed over a long period of time. Can do.

  The size of titanium is preferably in the range of 20 to 50 nm in terms of a sphere from the surface area measured by the BET measurement method. This is because it is difficult to spend when the particle size is larger, and if it is less than 20 nm, the spent becomes intense and it is difficult to extend the life. If it exceeds 50 nm, the abrasiveness increases, the carrier coating is worn, and the life of the carrier is shortened. The addition amount is 0.1 to 5.0% by weight, preferably 0.5 to 3.0% by weight of titanium with respect to the toner. When the amount is less than 0.1% by weight, the effect of the addition is hardly exhibited, and when the amount added exceeds 5.0% by weight, the toner is not sufficiently held on the surface and desorption occurs. There is a possibility that. Moreover, it is preferable to hydrophobize with so-called coupling agents such as various titanium coupling agents and silane coupling agents, and silicone oil. Since the chargeability of titanium is positively chargeable unlike toner, the effect of deterioration due to spent etc. is more pronounced than other external additives such as silica, so titanium is mainly controlled as an external additive. As a result, it is possible to prevent agent deterioration and image deterioration due to titanium spent stably over time.

In the image forming apparatus 1 of the present invention, various inorganic fine particles, organic fine particles, and the like can be used as an external additive in addition to titanium. Examples of the inorganic fine particles include various oxides, nitrides, borides and the like. For example, silica, alumina, zirconia, barium titanate, aluminum titanate, strontium titanate, magnesium titanate, zinc oxide, chromium oxide, cerium oxide, antimony oxide, tungsten oxide, tin oxide, tellurium oxide, manganese oxide, boron oxide , Silicon carbide, boron carbide, titanium carbide, silicon nitride, titanium nitride, boron nitride and the like. Further, it may be subjected to a hydrophobic treatment. In the case of performing the hydrophobizing treatment, the hydrophobizing treatment is preferably performed using a so-called coupling agent such as various titanium coupling agents and silane coupling agents, silicone oil, or the like.
On the other hand, silica is preferable as an external additive other than titanium oxide, and the size is preferably in the range of 7 to 30 nm in terms of a sphere from the surface area measured by the BET measurement method. Within this range, the fluidity of the toner can be improved and the charging property can be controlled. The addition amount is 0.2 to 5.0% by weight, preferably 0.5 to 3.0% by weight, based on the toner. When the amount is less than 0.2% by weight, the effect of the fluidity and chargeability due to the addition is hardly exhibited, and when the amount exceeds 5.0% by weight, the toner surface is sufficiently retained. In other words, desorption occurs. As the external additive, the external additive such as titanium: silica is preferably in a ratio of 10 to 40:60 to 90. As a result, the chargeability and fluidity can be controlled, and the lifetime can be controlled simultaneously.

  Used as a two-component developer, but mixed with a magnetic carrier. When used as a two-component developer, the mixing ratio (content ratio) of the carrier and toner of the developer is preferably 1 to 10 parts by weight of toner with respect to 100 parts by weight of carrier. As the magnetic carrier, known ones from iron powder, ferrite powder, magnetite powder, magnetic resin carrier and the like having a particle diameter of about 20 to 200 μm are used. In addition, as a coating material for the magnetic carrier, acrylic resins, polymethyl methacrylate resins, polyacrylonitrile resins, polyvinyl acetate resins, polyvinyl alcohol resins, polyvinyl butyral resins, polystyrene resins such as polystyrene resins and styrene acrylic copolymer resins, and Silicone resin or the like can be used. Furthermore, you may make conductive powder etc. contain in coating resin as needed. As the conductive powder, metal powder, carbon black, titanium oxide, tin oxide, zinc oxide or the like can be used. These conductive powders preferably have an average particle diameter of 1 μm or less. When the average particle diameter is larger than 1 μm, it becomes difficult to control electric resistance.

  Further, in the image forming apparatus 1 according to the present invention, the sleeve linear velocity during idling of the developing sleeves 71a and 71b is controlled. When idling at the end of the job, control is performed to increase the rotation speed of the developing motor 87 by a signal from the controller 100. By performing control in this way, the time required for idling can be reduced, the time until the next job can be input can be shortened, and the productivity of image formation can be increased. On the other hand, if the rotation speed of the developing motor 87 is increased too much during idling at the end of the job, excessive stress is applied to the developer, the wax component oozes out from the toner, and the wax is spent on the carrier surface. End up. If the wax is spent, there is a problem that the charging ability of the agent is lowered. Therefore, when the idling at the end of the job is performed, the rotation speed of the developing motor 87 is photosensitized by a signal from the controller 100. Control is performed to increase the linear speed ratio with respect to the body drum in a range up to 2.5. By performing control in this way, it is possible to reduce the time required for idling without causing side effects such as wax spent, and to shorten the time until the next job can be input. The linear speed ratio is controlled to exceed 1.0. When the ratio is 1.0 or less, it is difficult to obtain a high-density image regardless of the transport amount of the developing sleeves 71a and 71b. Further, it is difficult to reduce the time required for idling, the time until the next job can be input cannot be shortened, and the productivity of image formation cannot be increased.

  Although the above description has been made on a monochrome image forming apparatus, the present invention can also be applied to a color image forming apparatus that is used in a relatively high image area ratio.

1 is a schematic diagram illustrating a configuration of an image forming apparatus according to an embodiment of the present invention. It is the figure which showed the relationship of generation | occurrence | production of malfunction from cumulative development drive time and the amount of titanium transfer to a carrier. It is the figure which showed the condition which controls idling time from cumulative development drive time and the amount of titanium transfer to a carrier. It is the figure which showed the relationship between accumulation development drive time and the amount of titanium transfer to a carrier.

Explanation of symbols

1: Image forming device 2: Charging device 3: Exposure device 5: Registration roller 6: Transfer device 7: Developing device 8: Toner replenishing unit 10: Photoconductor 61: Transfer belt 62: Drive roller 63: Drive roller 64: Bias roller 65: transfer power supply 66: electrode member 67: resin case 67a: fulcrum 69: motor 71a, 71b: developing roller 72: developing doctor 73, 74, 75: stirring member 81: supply roller 83: consumption measurement circuit per unit time 84: paper size detection unit 85: development drive time measurement circuit 86: write signal memory 87: motor 90: fixing device 91: cleaning device 92: brush roller 93: cleaning blade 94: static elimination lamp 100: controller 110: document reading unit 111 : Image memory control unit 112: CCD

Claims (7)

An image carrier;
Latent image forming means for exposing the image carrier to form an electrostatic latent image; and
An image forming apparatus comprising: a developing device that develops an electrostatic latent image on the image carrier with a developer carrying means that carries a two-component developer comprising a carrier and a toner containing titanium oxide as an additive to form a toner image. In
Means for detecting an image signal of a toner image to be formed and detecting an image area ratio of the toner image;
Means for detecting a driving time of the developing device and calculating a developing driving time in one job;
Means for calculating the consumption per unit driving time during the job from the image area ratio of the toner image during the job, the paper size, and the development driving time;
The image forming apparatus controls the idling of the developing sleeve at the end of the job when the consumption calculated by the means for calculating the consumption is larger than a predetermined consumption. The image forming apparatus according to claim 1.
The image forming apparatus is characterized in that when the consumption per unit driving time during a job exceeds a certain consumption by means for calculating the consumption, the developing sleeve is controlled to idle at the end of the job. Image forming apparatus. The image forming apparatus according to claim 1 or 2,
The image forming apparatus is characterized in that the idling time of the developing sleeve is controlled according to consumption. The image forming apparatus according to any one of claims 1 to 3,
The image forming apparatus controls the sleeve linear velocity when the developing sleeve idles. The image forming apparatus according to claim 4.
The image forming apparatus controls the upper limit of the developing sleeve linear velocity within a range of up to 2.5 in terms of the linear velocity ratio to the drum. The image forming apparatus according to claim 1,
The image forming apparatus uses a two-component developer containing a toner containing silica. The image forming apparatus according to claim 1,
The image forming apparatus uses a two-component developer including a carrier coated with a resin.

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