JP2011081152A - Developing device and image forming apparatus having the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a developing device preventing decrease in an image density or occurrence of filming on a photoreceptor, by controlling temperature not only through a detecting result of temperature of a developing tank, but by taking a state of a toner external additive into consideration, and also to provide an image forming apparatus using the developing device. <P>SOLUTION: The developing device includes: a temperature sensor sensing the temperature of the developing tank; and a temperature control means controlling the sensed temperature. The device prevents decrease in an image density, sticking of a developer and occurrence of filming on a photoreceptor in such a way that: when an image area rate of a document to be printed is not more than 1%, the developing tank is cooled by the temperature control means; with the image area rate of 15% or more, the tank is not cooled; and with the image area rate from 2% to 14%, the tank is cooled only when the temperature of the developing tank is equal to or higher than the glass transition temperature (60°C) of the toner resin. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a developing device used in an electrophotographic image forming apparatus such as a copying machine, a printer, and a facsimile, and an image forming apparatus using the same, and more particularly, a developing device using a two-component developer and an image forming using the same. Relates to the device.

  The image forming apparatus includes, for example, a photoreceptor, a charging unit, an exposure unit, a developing unit, a transfer unit, and a fixing unit. The photoreceptor is, for example, a drum-shaped member having a photosensitive layer on the surface thereof. The charging unit charges the surface of the photoconductor to a predetermined potential, and the exposure unit forms an electrostatic latent image on the charged photoconductor surface. The developing unit supplies toner to the electrostatic latent image on the surface of the photoconductor to form a toner image, and the transfer unit transfers the toner image on the surface of the photoconductor to a recording medium. The fixing unit heat-fixes the toner image on the recording medium, whereby an image is formed on the recording medium.

  In the image forming apparatus, as the developing unit, a developing device including a developing tank, a developing roller, a stirring member, a regulating member, a sink plate, and the like is generally used. The developing tank rotatably supports the developing roller and the stirring member, and stores the developer therein. The developing roller carries a developer layer on its surface and rotates, and supplies toner to the electrostatic latent image on the surface of the photoreceptor to form a toner image. The agitating member uniformly agitates the developer in the developing tank and conveys the developer toward the developing roller. The regulating member regulates the layer thickness of the developer layer on the surface of the developing roller. As the developer, a two-component developer containing toner and carrier is mainly used.

  Along with the rapid spread of image forming apparatuses to a wide range of fields, image forming apparatuses are required to have various performance enhancements, for example, higher printing speeds. The printing speed, which was 50 to 70 sheets / minute with A4 paper until several years ago, has recently reached 100 to 120 sheets / minute. Such speeding up is intended to advance into the field of light printing. In order to cope with an increase in printing speed, it is easiest in the developing device to increase the diameter of the developing roller and increase the capacity of the developing tank. However, the image forming apparatus is required to increase the printing speed and downsize the apparatus. Even in situations where downsizing is required, it is required to properly develop the latent image on the photoconductor to provide an image having a stable print quality. Are densely arranged, and the temperature of the developing device is likely to rise.

When the temperature of the developing device rises, the temperature of the developer accommodated therein also rises.
As the temperature of the developer rises, problems such as a decrease in the density of the developed image or toner adhesion due to difficulty in moving toward the photosensitive drum due to an increase in viscosity are likely to occur. In order to suppress the occurrence of such problems, it is necessary to cool the developing device.

  As for the cooling method of the developing device, generally, a method is provided in which a duct connected to the developing device is provided in the image forming apparatus to secure an air passage (air flow passage) and to reduce the ambient temperature around the developing device. Although it is adopted, as described above, the cooling becomes insufficient when the density of the electric member or the like is large.

  Therefore, as a more effective cooling method, for example, in Japanese Patent Application Laid-Open No. 2009-36852 (Patent Document 1), a Peltier element is attached to a casing that stores toner or developer. Since the casing is made of a material having a high thermal conductivity, the Peltier element mounting portion can absorb heat preferentially from the portion having the high thermal conductivity. There has been disclosed a developing device capable of efficiently conducting the heat on the casing side to the outside of the developing device via a Peltier device having a heat exchange effect because it is on the heat absorption side of the device.

  By controlling the temperature of the developing tank in this way, when a document having a small image area ratio is continuously printed, it is possible to prevent the toner external agent from being easily buried without being consumed, and it is possible to prevent external exposure due to temperature stress. It is possible to suppress charge-up due to the burying of the additive and suppress a decrease in image density.

JP 2009-36852 A

  However, simply controlling the temperature of the developing tank as in Patent Document 1 does not take into account the state of the toner external additive in the first place. Therefore, when a document having a large image area ratio is continuously printed, Since the temperature of the tank decreases and temperature stress (fatigue due to temperature rise, which occurs due to repeated friction between the developing means and the developer), the flow of the toner is improved in order to improve the fluidity and chargeability of the toner. In some cases, the toner additive added while the state is maintained increases and filming on the photosensitive drum occurs.

  In the present invention, the temperature control is not performed only based on the detection result of the temperature of the developing tank, but the state of the toner external additive is taken into consideration, so that a decrease in image density and filming on the photoreceptor may occur. An object of the present invention is to provide a developing device capable of preventing the occurrence of the occurrence and an image forming apparatus using the same.

  The developing device of the present invention includes a developing tank for storing a two-component developer containing toner and a carrier, a developing roller for supplying the two-component developer to the photosensitive drum, and a supply of the two-component developer to be supplied to the photosensitive drum. In a developing device including a regulating member that regulates the amount, a temperature sensor that detects the temperature of the developing tank, a calculation unit that obtains an image area ratio of an output image from image data, the temperature detected by the temperature sensor, and the calculation Temperature control means for controlling temperature according to the image area ratio obtained by the means.

  In the present invention, it is preferable that the material of the developing tank to which the temperature sensor is attached is made of metallic aluminum.

  In the present invention, it is preferable that the temperature control means includes a Peltier element.

  In addition, the present invention is characterized by using an image forming apparatus provided with the developing device.

  The present invention also relates to a method for controlling a developing device using a two-component developer including a toner and a carrier, a temperature detecting step for detecting the temperature of the developing tank, and a step for obtaining an image area ratio of an output image from image data. And a step of performing temperature control according to the detected temperature and the image area ratio of the output image.

  According to the image forming apparatus of the present invention, filming on the photoconductor occurs because the state of the external toner additive is not taken into account simply by controlling the temperature only by the detection result of the temperature of the developing tank. However, since the temperature control means for controlling the temperature according to the detected temperature and the image area ratio of the output image is provided, the state of the external toner additive can be taken into consideration, and the filming can be prevented.

  Furthermore, since the temperature of the developing tank can be quickly controlled by the temperature control means by making the developing tank made of metal aluminum, not only the filming on the photoconductor but also the image A decrease in concentration can also be prevented.

  Furthermore, by changing the direction of current flow by changing the temperature control means to a Peltier element, the surface in contact with the developing tank can be easily heated / cooled, so there is no need to provide a cooling fan for forced cooling. .

  Furthermore, according to the present invention, by using the image forming apparatus including the developing device, the image forming apparatus can improve the chargeability and developer transportability, and improve the quality of an image output after development. Can do.

  Still further, according to the present invention, as a control method of the developing device, a temperature detection step of detecting the temperature of the developing tank, and a control method of executing temperature control according to the detected temperature and the image area ratio of the output image By doing so, it is possible to prevent a decrease in image density and occurrence of filming on the photoreceptor.

1 is a schematic diagram showing an overall configuration of an image forming apparatus equipped with a developing device according to the present invention. It is sectional drawing which shows typically the structure of the developing device which concerns on this embodiment. It is explanatory drawing which shows the structure of a Peltier device. 1 is a block diagram illustrating an electrical configuration of an image forming apparatus according to an exemplary embodiment.

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is an explanatory view showing the configuration of an image forming apparatus equipped with a developing device according to the present invention, which is an example of an embodiment of the invention.

  In this embodiment, as shown in FIG. 1, a photosensitive drum (electrostatic latent image carrier) 15 on which an electrostatic latent image is formed, a charging device 16 for charging the surface of the photosensitive drum 15, and a photosensitive An exposure device 17 that forms an electrostatic latent image on the surface of the photosensitive drum 15; a developing device 1 that supplies toner to the electrostatic latent image on the surface of the photosensitive drum 15 to form a toner image; and a toner that is on the surface of the photosensitive drum 15 A developing device in an image forming apparatus 100 that includes a transfer device 18 that transfers an image to a recording medium and a fixing device 20 that fixes the transferred toner image to the recording medium, and forms an image using toner by an electrophotographic method. 1, the configuration of the developing device according to the present invention is adopted.

  First, the overall configuration of the image forming apparatus 100 will be described. The image forming apparatus 100 forms a monochrome image on a predetermined sheet based on, for example, image data transmitted from each terminal device on the network.

  As shown in FIG. 1, the image forming apparatus 100 includes a photosensitive drum (electrostatic latent image carrier) 15, a charging device 16, an exposure device 17, a developing device 1, a transfer device 18, and a fixing device 20. A cleaning device 19, a paper feed tray 23, a scanner unit 24, and a paper discharge tray 25.

  The photosensitive drum 15 is a drum-like member that is supported by a driving unit (not shown) so as to be rotatable about an axis, and has a photosensitive film on the surface of which an electrostatic latent image and thus a toner image is formed. For the photosensitive drum 15, for example, a drum-shaped member including a conductive substrate (not shown) and a photosensitive film (not shown) formed on the surface of the conductive substrate can be used. As the conductive substrate, a conductive substrate having a cylindrical shape, a columnar shape, a sheet shape or the like can be used, and among them, the cylindrical conductive substrate is preferable. Examples of the photosensitive film include an organic photosensitive film and an inorganic photosensitive film.

  As an organic photosensitive film, a laminate of a charge generation layer, which is a resin layer containing a charge generation material, and a charge transport layer, which is a resin layer containing a charge transport material, a charge generation material and a charge transport material in one resin layer And a resin layer (single layer body). Examples of the inorganic photosensitive film include films containing one or more selected from zinc oxide, selenium, amorphous silicon and the like. A base film may be interposed between the conductive substrate and the photosensitive film, and a surface film (protective film) for mainly protecting the photosensitive film may be provided on the surface of the photosensitive film.

  The charging device 16 receives a voltage applied from a power source (not shown) and charges the surface of the photosensitive drum 15 to a predetermined polarity and potential. In this embodiment, a charger-type charger is used, but the present invention is not limited to this, and a charger such as a charging brush-type charger, a roller-type charger, a saw-tooth type charger, an ion generator, or a magnetic brush can be used.

  The exposure device 17 receives image information of a document read by the scanner unit 24 (specifically, a reading unit 105 shown in FIG. 4) or image information from an external device, and charges signal light according to the image information. Irradiate the surface of the photosensitive drum 15 in a state. As a result, an electrostatic latent image corresponding to the image information is formed on the surface of the photosensitive drum 15.

  As the exposure device 17, a laser scanning device including a light source is used. The laser scanning device is a device that combines, for example, a light source, a polygon mirror, an fθ lens, a reflection mirror, and the like. As the light source, for example, a semiconductor laser, an LED array, an electroluminescence (EL) element, or the like can be used.

  The transfer device 18 is a roller-like member provided so as to be in pressure contact with the photosensitive drum 15, is rotatably supported by a support member (not shown), and is rotatably provided by a driving unit (not shown). For the transfer device 18, for example, a roller-shaped member including a metal cored bar having a diameter of 8 to 10 (mm) and a conductive elastic layer formed on the surface of the metal cored bar is used.

  As the metal forming the metal core, stainless steel, aluminum, or the like can be used. As the conductive elastic layer, a rubber material in which a conductive material such as carbon black is blended with a rubber material such as ethylene-propylene rubber (EPDM), foamed EPDM, or foamed urethane can be used.

  In synchronism with the toner image being conveyed by the rotation of the photosensitive drum 15 to a pressure contact portion (hereinafter referred to as “transfer nip portion”) 18 n between the transfer device 18 and the photosensitive drum 15, the paper feed tray 23 is synchronized. The recording medium is supplied one by one through a pickup roller and a registration roller (not shown). As the recording medium passes through the transfer nip portion 18n of the transfer device 18, the toner image on the surface of the photosensitive drum 15 is transferred to the recording medium.

  A power supply (not shown) is connected to the transfer device 18, and a voltage having a polarity opposite to the charging polarity of the toner constituting the toner image is applied to the transfer device 18 when the toner image is transferred to a recording medium. As a result, the toner image is smoothly transferred to the recording medium. In this manner, the toner image on the surface of the photosensitive drum 15 is transferred to the recording medium by the transfer device 18.

  The cleaning device 19 includes a cleaning blade (not shown) and a toner storage tank (not shown). The cleaning blade is a plate-like member that extends in parallel to the longitudinal direction of the photosensitive drum 15 and is provided so that one end in the short direction abuts the surface of the photosensitive drum 15. The cleaning blade removes toner, paper dust, and the like remaining on the surface of the photosensitive drum 15 from the surface of the photosensitive drum 15 after transferring the toner image to the recording medium. The toner storage tank is a container-like member having an internal space, and temporarily stores the toner removed by the cleaning blade. In this manner, the surface of the photosensitive drum 15 after the toner image is transferred is cleaned by the cleaning device 19.

  The fixing device 20 includes a fixing roller 21 and a pressure roller 22. The fixing roller 21 is a roller-like member, is rotatably supported by a support member (not shown), and is provided so as to be rotatable around an axis by a drive unit (not shown).

  The fixing roller 21 has a heating member (not shown) inside, and heats and melts the toner constituting the unfixed toner image carried on the recording medium conveyed through the transfer nip portion 18 n of the transfer device 18. To fix on the recording medium. As the fixing roller 21, for example, a roller-shaped member including a cored bar and an elastic layer is used. The core metal is formed of a metal such as iron, stainless steel, or aluminum. The elastic layer is formed of an elastic material such as silicone rubber or fluorine rubber, for example. The heating member receives heat from a power source (not shown) and generates heat. A halogen lamp, an infrared lamp, etc. can be used for a heating member.

  The pressure roller 22 is a roller-like member, is rotatably supported, and is provided so as to be in pressure contact with the fixing roller 21 by a pressure member (not shown). The pressure roller 22 rotates following the rotation of the fixing roller 21. A pressure contact portion between the fixing roller 21 and the pressure roller 22 is a fixing nip portion 20n. The pressure roller 22 promotes fixing of the toner image to the recording medium by pressing the toner in a molten state against the recording medium when the fixing roller 21 heat-fixes the toner image to the recording medium. For the pressure roller 22, a roller-like member having the same configuration as that of the fixing roller 21 can be used. A heating member may also be provided inside the pressure roller 22. A heating member similar to the heating member inside the fixing roller 21 can be used.

  The fixing device 20 passes the recording medium onto which the toner image has been transferred to the fixing nip portion 20n, melts the toner constituting the toner image, and presses the recording medium against the recording medium, thereby fixing the toner image on the recording medium. To print. The recording medium on which the image is printed is discharged and stacked on a discharge tray 25 provided on the side surface in the vertical direction of the image forming apparatus 100 in FIG. Note that the sheet feeding tray 23 accommodates a recording medium.

  The scanner unit 24 is provided with a document setting tray (not shown), an automatic document feeder (RADF), and the like, and a document reading device (not shown).

  The automatic document feeder conveys a document placed on a document set tray to a document placing table of a document reading device. The document reading device includes a document placing table, a document scanning device, a reflecting member, a photoelectric conversion device (hereinafter referred to as “CCD”) line sensor, and the like, and is placed on the document placing table. The image information of the original is read every plural lines, for example every ten lines.

The document placing table is a glass plate-like member for placing a document for reading image information.
The document scanning device includes a light source (not shown) and a first reflection mirror, and reciprocates at a constant speed V in parallel along the lower surface in the vertical direction of the document placement table, thereby forming an image of the document placed on the document placement table. Irradiate the surface with light. A reflected light image is obtained by this light irradiation.

  The light source is a light source for irradiating a document placed on the document table. The first reflecting mirror reflects the reflected light image toward a reflecting member (not shown).

  The reflecting member includes a second reflecting mirror, a third reflecting mirror, and an optical lens (not shown), and forms a reflected light image obtained by the document scanning device on the CCD line sensor. The reflecting member reciprocates at a speed of V / 2 following the reciprocating movement of the document scanning device.

  The second and third reflection mirrors reflect the reflected light image so that the reflected light image faces the optical lens. The optical lens forms a reflected light image on the CCD line sensor.

  The CCD line sensor includes a CCD circuit (not shown) that photoelectrically converts a reflected light image formed by the optical lens into an electric signal, and outputs an electric signal as image information to an image processing unit in the control means. The image processing unit converts image information input from an external device such as a document reading device or a personal computer into an electrical signal and outputs the electrical signal to the exposure device 17.

  Next, a characteristic configuration of the developing device 1 according to the present embodiment will be described in detail with reference to the drawings. FIG. 2 is an explanatory diagram showing the configuration of the developing device according to this embodiment, and FIG. 3 is an explanatory diagram showing the configuration of the Peltier device.

  As illustrated in FIG. 2, the developing device 1 of the present embodiment includes a developing tank 2, a developing roller 3, a first stirring member 4, a second stirring member 5, a conveying member 6, and a developer amount regulating member. 7, a regulating member support 8, a flow plate (developer peeling member) 9, a toner concentration detection sensor 12, a temperature sensor 13, and a temperature control means 14.

  Inside the developing tank 2, a developing roller 3, a first stirring member 4, a second stirring member 5, a conveying member 6, a developer amount regulating member 7, a sink plate 9, and the like are accommodated. The developer in the present embodiment is a two-component developer including toner and a carrier that is magnetic powder.

  As shown in FIGS. 1 and 2, the developing tank 2 is provided on the side facing the developing roller 3 provided in the image forming apparatus 100 when the developing apparatus 1 is mounted on the electrophotographic image forming apparatus 100. Opening 2a is formed. A toner replenishing port 2b is formed on the upper surface of the developing tank 2 in the vertical direction in the figure.

  Here, related members (not shown) around the developing device 1 will be described. A toner cartridge (not shown) and a toner hopper (not shown) are provided above the developing tank 2 in the vertical direction. Specifically, the toner cartridge, the toner hopper, and the developing tank 2 are provided in this order from the upper side to the lower side in the vertical direction. The toner cartridge accommodates toner in its internal space and is detachable from the main body of the image forming apparatus to which the developing device 1 is mounted.

  Further, the toner cartridge is formed of a cylindrical body, and is driven to rotate about the axis of the cylindrical body by a driving unit (not shown) provided in the image forming apparatus 100. An elongated opening extending in the longitudinal direction is formed on the side surface in the longitudinal direction along the axis of the toner cartridge. As the toner cartridge rotates, the toner falls from the elongated opening, whereby the toner is supplied to a toner hopper provided below the toner cartridge.

  The toner hopper has, for example, a toner supply port formed on the bottom surface in the vertical direction. The toner supply port is provided so as to communicate with the toner replenishing port 2b formed on the upper surface in the vertical direction of the developing tank 2 in the vertical direction.

  In the toner hopper, a toner supply roller (not shown) is provided above the toner supply port in the vertical direction. The toner replenishing roller is rotatably supported by a toner hopper and is rotationally driven by a driving unit (not shown). The rotation of the toner replenishing roller is controlled by a control unit (not shown) provided in the image forming apparatus 100 according to the detection result of the toner concentration in the developing tank 2 by the toner concentration detection sensor 12. The toner is supplied into the developing tank 2 through the toner supply port and the toner supply port 2b by the rotation of the toner supply roller.

  The developing roller 3 is a roller-like member that is at least partially supported by the developing tank 2 so as to be rotatable and is driven to rotate about an axis by a driving unit (not shown). Further, the developing roller 3 faces the photosensitive drum 15 through the opening 2 a of the developing tank 2.

  In this embodiment, the developing roller 3 is provided so as to be separated from the photosensitive drum 15 with a gap, and the closest portion where the developing roller 3 and the photosensitive drum 15 face each other is the developing nip portion 3n. It is.

  In the developing nip portion 3n, toner is supplied to the surface of the photosensitive drum 15 from a developer layer (not shown) on the surface of the developing roller 3. In the developing nip portion 3n, a developing bias voltage is applied to the developing roller 3 from a power source (not shown) connected to the developing roller 3, and toner is transferred from the developer layer on the surface of the developing roller 3 to the surface of the photosensitive drum 15. Proceed smoothly.

  The developing roller 3 includes a magnet roller 10 and a sleeve 11. The magnet roller 10 has both ends in the longitudinal direction supported by the developing tank wall of the developing tank 2, and magnetic poles, which are a plurality of bar magnets having a rectangular cross section, are spaced apart from each other at the circumferential position of the developing roller 3. 3 is a multi-pole magnetized magnet roller arranged radially in the radial direction.

  The sleeve 11 is a cylindrical member that externally fits the magnet roller 10, is rotatably supported by the developing tank 2 and a support member (not shown), and is rotatably provided by a drive unit (not shown).

  The sleeve 11 is formed using a nonmagnetic material. In this embodiment, the sleeve 11 rotates counterclockwise, and the photosensitive drum 15 may be clockwise or counterclockwise.

  Each of the first stirring member 4 and the second stirring member 5 is a roller-like member that is rotatably supported by the developing tank 2 and that can be driven to rotate about an axis by a driving unit (not shown). In the present embodiment, the first stirring member 4 rotates counterclockwise, and the second stirring member 5 rotates clockwise.

  The first stirring member 4 is provided at a position that faces the photosensitive drum 15 via the developing roller 3 and that is vertically lower than the developing roller 3.

  The second stirring member 5 is provided at a position facing the developing roller 3 through the first stirring member 4 and being vertically lower than the developing roller 3. The first agitating member 4 and the second agitating member 5 agitate the developer stored in the developing tank 2 to give a uniform charge to the toner, and pump up the charged developer to the developer roller 3. Supply to the surroundings.

  The conveyance member 6 is a roller-like member that is rotatably supported by the developing tank 2 and is rotatably driven by a driving unit (not shown). Further, the conveying member 6 faces the first stirring member 4 through the second stirring member 5 and is provided below the toner supply port 2b in the vertical direction. The conveying member 6 conveys the toner replenished into the developing tank 2 to the periphery of the second stirring member 5 through the toner replenishing port 2b.

  The developer amount regulating member 7 is a plate-like member extending in parallel with the axial direction of the developing roller 3, and one end in the short side direction of the developing roller 3 in the vertical direction is the developing tank 2 and the regulating member support 8. And the other end is provided so as to be separated from the surface of the developing roller 3 with a gap.

  Further, the developer amount regulating member 7 is formed of, for example, a nonmagnetic metal having elasticity such as stainless steel or aluminum, a synthetic resin, or the like. In the present embodiment, a thin plate-like stainless steel is used for the developer amount regulating member 7.

  The regulating member support 8 supports the developer amount regulating member 7 together with the developing tank 2. Specifically, one end of the developer amount regulating member 7 in the short direction and the vicinity thereof are supported so as to be sandwiched between the regulating member support 8 and the developing tank 2. The restricting member support 8 is formed of a material such as synthetic resin or metal. In this embodiment, it is formed from a synthetic resin.

  The developer amount regulating member 7 removes excess developer from the developer layer carried on the surface of the developing roller 3 and regulates the developer transport amount by regulating the layer thickness of the developer layer to be constant. Further, the developer amount regulating member 7 imparts electric charge to the developer that is insufficiently charged in the developer layer by rubbing between the other end in the lateral direction and the developer layer, and is contained in the developer layer. The developer to be charged is sufficiently charged.

  In the developing tank 2, the flow plate 9 is provided upstream of the developer amount regulating member 7 in the rotation direction of the developing roller 3 and above the first stirring member 4 and the second stirring member 5 in the vertical direction. The upper part is a member configured in a plate shape. The flow plate 9 has one end 9 b 1 in the short direction facing the surface of the developing roller 3 and spaced apart with a gap, and the other end 9 b 2 extending in a direction away from the developing roller 3.

In the present embodiment, the upper surface in the vertical direction of the sink plate 9 is parallel to the horizontal direction at one end 9b1 on the developing roller 3 side in the short direction of the sink plate 9 and the vicinity thereof, and the developing roller at other portions. It is provided to descend downward in the vertical direction as it is separated from 3.
In the present embodiment, the sink plate 9 is supported by a support member 9a that is formed so as to penetrate in the longitudinal direction of the sink plate 9 in the lower part in the vertical direction and is inserted into the through hole. By providing the flow plate 9, a smooth flow of the developer in the developing tank 2 is generated, and the occurrence of uneven charging of the toner, blocking of the toner and the like is prevented. Specifically, the developer removed from the surface of the developing roller 3 by the regulating member 7 temporarily stays in the space above the developing roller 3, but when the amount increases, the vertical upper surface of the sink plate 9 moves away from the developing roller 3. Begins to flow through. The developer flows along the upper surface of the sink plate 9, and falls toward the second stirring member 5 from the end 9 b 2 opposite to the developing roller 3 side in the short direction of the sink plate 9. The dropped developer is uniformly mixed with the other developer and newly supplied toner by the first stirring member 4 and the second stirring member 5, and is conveyed toward the developing roller 3.

  Note that the dimensions of the first stirring member 4, the second stirring member 5, the conveying member 6, the regulating member 7, and the flow plate 9 are appropriately determined from an appropriate range according to the dimensions of the developing roller 3.

  As shown in FIG. 2, for example, the toner concentration detection sensor 12 is mounted on the bottom surface of the developing tank 2 below the second stirring member 5 in the vertical direction, and is provided so that the sensor surface is exposed inside the developing tank 2. The toner concentration detection sensor 12 is electrically connected to control means (not shown). The control means controls to rotate the toner cartridge according to the detection result by the toner concentration detection sensor 12 and replenish the toner into the developing tank 2 through the toner hopper.

  That is, when it is determined that the detection result by the toner density detection sensor 12 is lower than the toner density setting value, a control signal is sent to the driving means for driving the toner cartridge to rotate, and the toner cartridge is driven to rotate. As the toner concentration detection sensor 12, a general toner concentration detection sensor can be used, and examples thereof include a transmitted light detection sensor, a reflected light detection sensor, and a magnetic permeability detection sensor. Among these, a magnetic permeability detection sensor is preferable.

  A power supply (not shown) is connected to the magnetic permeability detection sensor. The power source applies a drive voltage for driving the magnetic permeability detection sensor and a control voltage for outputting a detection result of the toner density to the control means. Application of a voltage to the magnetic permeability detection sensor by the power source is controlled by the control means. The permeability detection sensor is a type of sensor that receives the control voltage and outputs the toner density detection result as an output voltage value. Basically, the sensitivity near the median value of the output voltage is good. It is used by applying a control voltage to obtain a voltage. Examples of this type of magnetic permeability detection sensor include TS-L, TS-A, and TS-K (all are trade names, manufactured by TDK Corporation).

  The control means may be provided exclusively for the developing device 1 or may also be used as the control unit 101 (see FIG. 4) provided in the image forming apparatus 100 to which the developing device 1 is attached.

  The temperature sensor 13 is composed of a thermistor and is attached to the bottom surface of the developing tank 2.

  Furthermore, since the temperature sensor 13 prevents contact with the two-component developer in the developing tank 2, the two-component developer is not fused and temperature detection with high reliability can be performed over a long period of time.

  Furthermore, since the material of the developing tank 2 is made of aluminum having good thermal conductivity, a rapid temperature rise in the developing tank 2 that occurs during continuous printing can be detected quickly, so that the reliability can be improved over a long period of time. High temperature detection is possible.

  Similar to the temperature sensor 13, the temperature control means 14 is attached to the bottom surface of the developing tank 2, and the two components in the developing tank 2 and the developing tank 2 are selected according to the temperature of the developing tank 2 detected by the temperature sensor 13. Heat or cool the developer. In the present embodiment, a Peltier element that can change the heating / cooling of the bottom surface of the developing tank 2 by changing the direction of current flow is used. As the Peltier element, a commercially available Peltier element can be used, and examples thereof include a thermo module 9500/018 / 018MP manufactured by Ferrotec Corporation. The Peltier element is connected to an electrical wiring (not shown) and a power supply power source, and the temperature control means 14 is composed of a Peltier element and a control means.

  In this embodiment, the control unit 101 and the calculation unit 109 that control the entire image forming apparatus shown in FIG. 4 are used as the control unit of the Peltier element that controls the temperature according to the image area ratio of the output image.

  As shown in FIG. 3, in the Peltier element, p-type semiconductors 50 and n-type semiconductors 51 are alternately arranged, and an insulating layer 52 is arranged between adjacent p-type semiconductors 50 and n-type semiconductors 51. One electrode 53 provided so as to sandwich the p-type semiconductor 50 and the n-type semiconductor 51 is insulated by the insulating layer 52, the other electrode 54 is insulated by the insulating layer 52, and both electrodes 53, Insulating films 55 and 56 are provided on the outer side of 54. A current is passed between the electrodes 53 and 54 so that the current flows from the n-type semiconductor 51 to the p-type semiconductor 50 with the electrode 53 on the developing tank 2 side. Then, the developing tank 2 side is cooled. In addition, 57 in FIG. 3 shows a lead wire.

  First, after the detection signal from the temperature sensor 13 and the image data of the document read by the scanner unit 24 are input to the control unit 101, the detection result of the temperature sensor and the image data of the document are stored in the storage unit 102 shown in FIG. In the calculation unit 109, the image area ratio is calculated from the image data, and the temperature control is determined based on the temperature sensor detection result and the image area ratio. Thereafter, in accordance with the determination result, a drive signal is output from the control unit 101 to a temperature control means supply power source (not shown) that supplies current to the Peltier element.

  Next, the electrical configuration of the image forming apparatus 100 according to the present embodiment will be described in detail with reference to a block diagram. FIG. 4 is a block diagram showing an electrical configuration of the image forming apparatus according to the present embodiment.

  As shown in FIG. 4, the image forming apparatus 100 is, for example, a multifunction device including a scanner unit 24, a printer main body 100 </ b> A, and a peripheral device 100 </ b> B, a reading unit 105 that reads a document image, An image processing unit 106 that generates image data by converting it into an electrical signal, an image forming unit 107 that visualizes the generated image data using toner and forms an image on a recording medium (transfer paper), an image forming unit A fixing unit (not shown) for fixing by heating and fixing to the recording medium visualized in 107, and a peripheral device control unit 108 for controlling a peripheral device 100B such as a finisher or a sorter as a post-processing device are provided.

The printer main body 100A includes a control unit 101, a storage unit 102, an input unit 103, a display unit 104, an image processing unit 106, an image forming unit 107, a calculation unit 109, and the like.
In the storage unit 102, a print command via an input unit (for example, an operation panel) 103 disposed on the upper surface of the image forming apparatus 100, detection results from various sensors (not illustrated) disposed at various locations inside the image forming apparatus 100, and the like. , Image information input from an external device via USB (registered trademark) / LAN, various setting values and data tables for controlling the operation of each device in the image forming apparatus 100, and various controls Programs can be entered.

  Further, a memory or the like commonly used in this field can be used as the storage unit 102. For example, a read only memory (ROM), a random access memory (RAM), a hard disk drive (HDD), a Blu-ray disk (registered trademark). ) And the like. As the external device, an electrical / electronic device that can form or acquire image information and can be electrically connected to the image forming apparatus 100 can be used, and examples thereof include a computer and a digital camera.

  The arithmetic unit 109 retrieves various data (print command, detection result, image information, etc.) stored in the storage unit 102 and a program for performing various controls, and performs various detections and / or determinations.

  The control unit 101 sends a control signal to the corresponding device according to various determination results, calculation results, and the like in the calculation unit 109 to perform operation control. The control unit 101 and the calculation unit 109 are, for example, processing circuits realized by a microcomputer, a microprocessor, or the like that includes a central processing unit (CPU).

  The control unit configured as described above includes a main power supply together with the storage unit 102, the calculation unit 109, and the control unit 101. The main power supply supplies power not only to the control means but also to each device in the image forming apparatus 100.

  Next, image formation by the developing device 1 in the image forming apparatus 100 of the present embodiment will be described in detail with reference to examples.

  Table 1 is a table showing the test results of the examples showing the influence on the image when the temperature of the developing tank 2 by the developing device is set to each set temperature and the original of each image area ratio is continuously printed.

  In the present embodiment, a copying machine MX-M1100 manufactured by Sharp Corporation is used as the image forming apparatus, and the temperature of the developing tank 2 of the image forming apparatus 100 having the configuration of the developing apparatus 1 according to the present invention is set to each set temperature. Using an A4 document with an image area ratio of 1%, 2%, 5%, 10%, 14%, 15%, plain paper (cata paper) was passed continuously, and a live-action test was conducted. After the sheet and 100K sheets, the image, the developer, and the influence on the photoconductor drum 15 were visually evaluated, and the image density was measured, the developer was fixed, and the photoconductor filming was determined.

As for the evaluation method, first, regarding the image density, “x” is less than 1.20,
“△” is 1.20 or more and less than 1.29,
“◯” was 1.30 or more.
For the measurement, a spectrocolorimetric densitometer (X-Rite 938, manufactured by X-Rite) was used.
Next, regarding photoconductor filming,
"X" means that there is no photoconductor filming visually.
“◯” indicates that the photoconductor filming is visually observed.
Finally, regarding developer fixing,
“X” means that the developer sticking is visually observed and is not easily unraveled at the tip of the spatula,
“△” means that the developer sticking can be visually observed, but is easily unraveled at the tip of the spatula,
“◯” means that the developer sticking is not visually observed.

  On the other hand, Table 2 visually evaluates the influence on the image, the developer, and the photosensitive drum 15 when the developing tank 2 is cooled by the temperature control means 14 from the beginning of the printing durability, and measures the image density. 6 is a table showing test results of examples in which determination of developer adhesion and determination of presence or absence of photoconductor filming were performed. The evaluation method is the same as in Table 1.

  When the image area ratio of the document to be printed is 1% or less, as is apparent from the evaluation results in Table 1, as the temperature of the developing tank 2 increases, the temperature due to the friction accumulated with the stirring member received so far In combination with the stress, the decrease in image density and the fixing of the developer became noticeable due to the printing durability.

  As is apparent from the evaluation results in Table 2, when the image area ratio is 1% or less, the toner is not consumed, and the toner external additive is buried in the toner particles due to the influence of temperature stress due to the accumulation of friction with the stirring member. Therefore, it is possible to prevent the image density from being lowered due to charge up.

  Further, when the temperature of the developing tank 2 is 60 ° C., not only the image density is lowered, but also corresponds to the glass transition point of the toner resin employed in this embodiment, so that the developer sticking occurs from the beginning. In view of this, it is necessary to cool the developing tank 2, and as is clear from the evaluation results in Table 2, it is possible to prevent a decrease in image density and fixing of the developer. As described above, when the temperature control operation is performed, whether the temperature of the bottom surface of the developing tank 2 exceeds 60 ° C. is determined by the toner glass contained in the two-component developer used in the present embodiment. This is because the transition point is 60 ° C., and is set according to the characteristics of the two-component developer used.

  Next, when the image area ratio of the document to be printed is 15% or more, as is apparent from the evaluation results in Table 1, the image density is reduced and filming on the photosensitive drum is performed regardless of the temperature of the developing tank 2. In addition, no fixing of the developer was observed. This is because when the document having a high image area ratio is continuously printed, the replenished toner is constantly consumed, so that the temperature of the developing tank 2 becomes high and the developer sticking easily occurs. This is because it does not lead to fixing.

  On the other hand, as is clear from the evaluation results in Table 2, when the image area ratio is 15% or more, when the cooling by the temperature control means 14 is performed from the beginning of the printing durability, the temperature of the developer decreases, Since the temperature stress due to friction is reduced, the toner external additive is liberated from the toner particles, and filming on the photosensitive drum occurs.

  Finally, when the image area ratio of the document to be printed is 2% to 14% or more, as is apparent from the evaluation results in Table 1, the image density is decreased except when the temperature of the developing tank 2 is 60 ° C. In addition, filming on the photosensitive drum and fixing of the developer were not observed. This is because the image area ratio of the document to be printed is neither too low nor too high, so there is almost no concern that the toner external additive is liberated or buried. However, when the temperature of the developing tank 2 is 60 ° C., a high image area ratio that does not lead to the fixing of the developer is not printed, so that the fixing of the developer or the fixing of the developer A decrease in image density occurs.

  On the other hand, as is apparent from the evaluation results in Table 2, when the image area ratio is in the range of 2% to 14%, the temperature of the developing tank 2 is 60 ° C. of the glass transition point of the toner resin employed in this embodiment. As long as the developing tank 2 was cooled so as not to exceed the range, developer sticking did not occur.

  From the above, when the image area ratio of the document to be printed is 1% or less, the temperature control means cools the developing tank, but when the image area ratio is 15% or more, the cooling is not performed. When the image area ratio is 2% to 14%, cooling is performed when the temperature of the developing tank is equal to or higher than the glass transition point (60 ° C.) of the toner resin, thereby reducing the image density, fixing the developer, and photoreceptor film. Can be prevented.

  In the above-described embodiment, the example in which the developing device 1 according to the present invention is applied to the image forming apparatus 100 as illustrated in FIG. 1 has been described. However, the image forming apparatus uses a developing device that uses a two-component developer. If so, the present invention is not limited to the image forming apparatus and the copying machine having the above-described configuration, and can be developed to other image forming apparatuses.

  For example, the development device can be applied to full-color image forming devices by arranging four colors (yellow, cyan, magenta, black) or six colors (yellow, cyan, magenta, black, light cyan, light magenta). Is possible.

  As described above, any embodiment obtained by combining technical means appropriately changed without departing from the gist of the present invention is included in the technical scope of the present invention.

DESCRIPTION OF SYMBOLS 1 Developing apparatus 2 Developing tank 2a Opening 2b Toner replenishing port 3 Developing roller 3n Developing nip part 4 1st stirring member 5 2nd stirring member 6 Conveying member 7 Developer amount control member 8 Control member support body 9 Sink plate 9a Support member 10 Magnet roller 11 Sleeve 12 Toner density detection sensor 13 Temperature sensor 14 Temperature control means 15 Photosensitive drum 16 Charging device 17 Exposure device 18 Transfer device 18n Transfer nip portion 19 Cleaning device 20 Fixing device 20n Fixing nip portion 21 Fixing roller 22 Pressure roller 23 Paper feeding tray 24 Scanner unit 25 Paper discharge tray 50 P-type semiconductor 51 N-type semiconductor 52 Insulating layer 53 Electrode 54 Other electrode 55 Insulating film 56 Insulating film 57 Lead wire 100 Image forming apparatus 100A Printer main body 100B Peripheral device 101 Control unit 102 storage unit 103 input unit 104 display unit 10 5 Reading unit 106 Image processing unit 107 Image forming unit 108 Peripheral device control unit 109 Calculation unit

Claims (4)

  A developing tank for storing a two-component developer containing toner and a carrier, a developing roller for supplying the two-component developer to the photosensitive drum, and a regulating member for regulating the supply amount of the two-component developer to be supplied to the photosensitive drum; In the image forming apparatus including the developing device, the temperature sensor for detecting the temperature of the developing tank, the calculation means for obtaining the image area ratio of the output image from the image data, the temperature detected by the temperature sensor, and the calculation means An image forming apparatus comprising: temperature control means for controlling the temperature according to the image area ratio obtained by the above.   The image forming apparatus according to claim 1, wherein the developing tank is made of metal aluminum.   The image forming apparatus according to claim 1, wherein the temperature control unit includes a Peltier element. In a method for controlling an image forming apparatus using a two-component developer including toner and carrier, a temperature detecting step for detecting the temperature of the developing tank, a step for obtaining an image area ratio of an output image from image data, and a detected temperature And a method for controlling the temperature according to the image area ratio.