JP2008275705A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus capable of stabilizing the circulation state (developer balance) of developer in a developing device. <P>SOLUTION: When the number of printing endurable sheets is under an optional value, control to make the rotational speed of motors M1 and M2 high (with high revolving speed) is performed. Meanwhile, when the number of printing endurable sheets is above the optional value, control to make the rotating speed of the motors M1 and M2 low (with low revolving speed) is performed. When temperature (or humidity) measured by a temperature and humidity sensor 76 is under an optional value (low temperature or low humidity state), control to make the rotating speed of the motors M1 and M2 high (with high revolving speed) is performed, and when temperature (or humidity) measured by the temperature and humidity sensor 76 is above the optional value (high temperature or high humidity state), control to make the rotating speed of the motors M1 and M2 low (make revolving speed low) is performed. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an image forming apparatus that forms an arbitrary image on a sheet, and more particularly, to an image forming apparatus including a developing unit that stores a developer.

Conventionally, a developing device is provided in an image forming apparatus. Inside the developing unit, a screw as a stirring means is rotatably provided. As the screw rotates, the developer contained in the developing device (in the case of a two-component developer: toner + carrier) is conveyed and circulated so that the developer is stably circulated in the developing device. The state (development balance) is maintained.
Japanese Patent Laid-Open No. 5-307304 JP 2005-10558 A

  By the way, the developer in the developing device is conveyed and circulated in the longitudinal direction of the developing device by a screw, but the characteristics (fluidity) of the developer changes depending on the number of printing sheets and the environmental conditions (temperature, humidity). When the characteristics (fluidity) of the developer change, the developer becomes easy to transport or difficult to transport, so the developer circulation state (development) in the developing device changes (becomes unstable). ). As a result, unevenness occurs in the density of the toner supplied from the developing device to the developing roller (developing sleeve), and further, this causes a problem that unevenness of the image on the paper occurs.

  Further, the developing device is provided with a toner concentration sensor (ADTC sensor) for detecting the toner concentration inside the developing device (meaning the ratio of toner to (toner + carrier)) and determining the timing of replenishing the toner. However, if the developer transported in the developing device is detected by the toner density sensor, the amount of developer transported varies due to changes in the developer characteristics (fluidity). The detection result and the actual toner density do not match, and the density control by the toner density sensor may vary. As a result, the toner density inside the developing device is not properly controlled, and the image formed on the paper becomes darker or thinner, and the printing accuracy (image forming accuracy) on the paper is greatly reduced. Become.

  The above problem also occurs depending on the installation state (tilt state) of the image forming apparatus. That is, when the image forming apparatus is not installed and the developer is inclined significantly, the developer in the developer is segregated, and the developer circulation state (debalance) changes (becomes unstable). As a result, the developer overflows from the inside of the developing unit, and, similarly to the above, image unevenness occurs on the paper. Printing accuracy (image formation accuracy) is greatly reduced.

  In view of the above circumstances, an object of the present invention is to provide an image forming apparatus capable of stabilizing the developer circulation state (development balance) in the developing device.

  The invention according to claim 1 is an image forming apparatus provided with a developing device in which a developer is accommodated, and is rotatably provided in the developing device, and conveys the developer in an arbitrary direction by rotating. A screw member; and a control unit that controls the rotation of the screw member, wherein the control unit controls the rotation of the screw member based on the number of printing sheets or the environmental state of the developing device. To do.

  The invention according to claim 2 is an image forming apparatus provided with a developing device in which a developer is accommodated, and is rotatably provided in the developing device, and conveys the developer in an arbitrary direction by rotating. A screw member; and a control unit configured to control rotation of the screw member, wherein the control unit controls rotation of the screw member based on an inclined state of the developing device.

  According to the first aspect of the present invention, the developer accommodated in the developing device is conveyed in an arbitrary direction as the screw member rotates. Here, since the rotation of the screw member is controlled by the control unit based on the number of printing durability or the environmental condition of the developing device, the developer characteristics change without being affected by the printing durability or the environmental condition of the developing device. It can be conveyed corresponding to (fluidity change). As a result, it is possible to always stabilize the developer transport without being affected by the number of printing durability or the environmental condition of the developing device, and thus maintain a stable circulation state (development) of the developer.

  In this specification, the “number of printing durability” is not limited to the total number of sheets on which an image is formed, but is also the cumulative rotation drive time (or total rotation speed) of the photosensitive drum, the total rotation drive time (or the total rotation time) of the screw member. Number of revolutions). The “environmental state of the developing device” means the temperature or humidity level (in particular, the humidity level) where the developing device is placed.

  According to the second aspect of the present invention, the developer accommodated in the developing device is conveyed in an arbitrary direction as the screw member rotates. Here, since the rotation of the screw member is controlled by the control unit based on the inclination state of the developing device, it is possible to always stabilize the developer transport without being affected by the inclination state of the developing device. A stable circulation state (development) of the developer can be maintained.

  In the present specification, the “developing state of the developing device” means the degree of inclination of the developing device with respect to the horizontal plane, and includes the degree of inclination of the screw member with respect to the horizontal plane.

  Next, an image forming apparatus according to a first embodiment of the present invention will be described with reference to the drawings.

  First, the configuration of the image forming apparatus will be described with reference to FIG. FIG. 1 is a front sectional view showing an example of the configuration of an image forming apparatus according to an embodiment of the present invention. The image forming apparatus is a scanner, a printer, a copier, a facsimile, or a complex machine that combines these functions.

  As shown in FIG. 1, the image forming apparatus 10 mainly includes an image forming unit 12, an exposure unit 14, a developing unit 16, and a fixing unit 18, and each unit is located above the paper feed cassette 20. Yes.

Here, an outline of the image forming process performed by the image forming apparatus 10 will be described.
When the paper is fed from the paper feed cassette 20, the toner image formed on the photosensitive drum 22 of the image forming unit 12 is transferred onto the paper. Next, the transferred toner image is fixed on the paper by the fixing unit 18. Then, the sheet on which the fixing process has been completed is discharged to the discharge tray 62 via the main conveyance path 60.

  When the double-sided printing process is executed in the image forming apparatus 10, the paper for which the printing process on one side has been completed is re-supplied to the image forming unit 12 via the reverse path 64. In the image forming unit 12, an image forming process is executed on the other side of the sheet.

  The image forming unit 12 is an element that forms a toner image and transfers the toner image onto paper fed from the paper feed cassette 20. The image forming unit 12 mainly includes a photosensitive drum 22 that is used as a photosensitive member, a charging unit 24 that applies a negative charge to the outer peripheral surface of the photosensitive drum 22, and a cleaning unit 26.

  The photosensitive drum 22 has a photoconductive film on its outer peripheral surface, and is used as an electrophotographic photoreceptor. The photosensitive drum 22 is disposed near the lower portion of the image forming unit 12. Further, the photosensitive drum 22 is accommodated in the frame 28 so that the lower side thereof is exposed to the outside. Accordingly, when the portion of the photosensitive drum 22 exposed from the frame 28 comes into contact with the developing sleeve 46 and the transfer roller 66 of the developing unit 16, the toner supply and the transfer process can be performed.

  The cleaning unit 26 is accommodated in the frame 28 and collects toner remaining without being transferred from the photosensitive drum 22 by the cleaning blade 30. The collected used waste toner is stored in the waste toner tank 34 by the transport mechanism 32. Therefore, the image forming unit 12 can execute a good image forming process without being affected by the residual toner.

  The charging unit 24 is provided along the longitudinal direction (front-rear direction) of the photosensitive drum 22, and has a sawtooth electrode (not shown) that applies a negative charge to the photosensitive drum 22. Thus, when a high voltage is applied to the sawtooth electrode and corona discharge is generated, a negative charge is applied to the outer peripheral surface of the photosensitive drum 22.

  The exposure unit 14 includes a plurality of light emitting units (for example, LEDs (Light Emission Diode)) 36 arranged in a substantially linear shape. The exposure unit 14 is arranged obliquely below the photosensitive drum 22, and the light from the light emitting unit 36 is irradiated onto the photosensitive drum 22.

  Thus, when the lighting control (exposure processing) of each light emitting unit 36 is executed based on the image data printed on the paper, the portion of the outer peripheral surface of the photosensitive drum 22 irradiated with light from the light emitting unit 36 is displayed. Negative charge is removed. That is, an electrostatic latent image corresponding to the image data is formed on the outer peripheral surface of the photosensitive drum 22.

  The developing unit 16 mainly includes a developing unit 38 that can store a two-component developer composed of toner and a carrier, two screw members 40 and 42, a paddle 44, and a developing sleeve 46. Non-magnetic toner is supplied to the outer peripheral surface of the photosensitive drum 22. That is, the toner and the carrier are properly mixed by the two screw members 40 and 42 to give a negative charge to the unused non-magnetic toner, and the negatively charged toner is scraped out by the paddle 44. To the developing sleeve 46 side. Further, the toner is supplied from the developing sleeve 46 to the surface of the photosensitive drum 22.

  As shown in FIG. 2, a first developer transport chamber 48 is formed inside the developing device 38. In the first developer transport chamber 48, a first screw member 40 for transporting the developer in an arbitrary direction (the arrow X direction in FIG. 2) while being stirred is rotatably disposed. As shown in FIG. 3, the first screw member 40 is driven to rotate by a motor M <b> 1 driven and controlled by a printer controller (control unit) 68, and conveys the developer in an arbitrary direction while stirring the developer. Therefore, the developer (toner and carrier) in the first developer transport chamber 48 is transported in the direction of arrow X in FIG. 2 while being stirred by the first screw member 40. Then, while being conveyed, the toner and the carrier are properly mixed, and the toner is negatively charged.

  In addition, a second developer transport chamber 52 is formed in the developing unit 38 with a first developer transport chamber 48 and a partition wall 50 therebetween. In the second developer transport chamber 52, a second screw member 42 for rotating the developer and transporting the developer in an arbitrary direction (the arrow Y direction in FIG. 2) is rotatably disposed. The second screw member 42 is disposed so as to be parallel to the first screw member 40. As shown in FIG. 3, the second screw member 42 is rotationally driven by a motor M2 that is driven and controlled by a printer controller 68, and conveys the developer in an arbitrary direction while stirring the developer. For this reason, the developer (toner and carrier) in the second developer conveyance chamber 52 is conveyed in the direction of arrow Y in FIG. 2 while being agitated by the second screw member 42. Then, while being conveyed, the toner and the carrier are appropriately mixed, and a negative charge is imparted to the toner.

  Thus, the developer is conveyed while being stirred from the one axial end side (T1 in FIG. 2) of the first screw member 40 toward the other axial end side (T2 in FIG. 2). At the same time, the developer that has reached the other end side in the axial direction of the first screw member 40 (T2 in FIG. 2) moves to the other end side in the axial direction of the second screw member 42 (T3 in FIG. 2). The developer is conveyed while being stirred from the other axial end side (T3 in FIG. 2) of the second screw member 42 toward the axial one end side (T4 in FIG. 2). Most of the toner constituting the developer conveyed by the second screw member 42 is supplied to the developing sleeve 46 by the paddle 44. Then, after the carrier constituting the developer conveyed by the second screw member 42 and the remaining toner reach the one axial end side (T4 in FIG. 2) of the second screw member 42, the first screw member 40 moves to one axial end side (T1 in FIG. 2). Thereafter, in the same manner, it is conveyed while being stirred by the first screw member 40.

  The developing sleeve 46 supplies the toner (negatively charged toner) supplied by the paddle 44 to the photosensitive drum 22 on which the electrostatic latent image is formed. As a result, the toner supplied from the developing sleeve 46 to the photosensitive drum 22 adheres to the portion of the outer peripheral surface of the photosensitive drum 22 from which negative charges have been removed.

  Here, as shown in FIG. 2, a toner supply port 54 is formed in the developing unit 38 on the one end side in the axial direction of the first screw member 40. A toner supply path 56 is connected to the toner supply port 54 as shown in FIG. One end of the toner supply path 56 is connected to a toner tank 58, and the other end is connected to a toner supply port 54. Further, the toner tank 58 incorporates a toner replenishing mechanism 70 that sends the toner in the toner tank 58 to the toner replenishment path 56. The toner supply mechanism 70 is controlled by the printer controller 68. Thus, when the toner replenishing mechanism 70 is driven and controlled by the printer controller 68, the toner in the toner tank 58 is sent to the toner replenishing path 56 and passes through the toner replenishing path 56 from the toner replenishing port 54 to the inside of the developing device 38. To be supplied.

  Further, as shown in FIGS. 2 and 3, the developing device 38 is provided with a toner concentration sensor (ADTC sensor, magnetic sensor) 72. The toner concentration sensor 72 is a conventionally known one (see, for example, Japanese Patent Application Laid-Open Nos. 2005-308913 and 2006-337757), and in the vicinity of the installation region of the toner concentration sensor 72 in the first developer conveyance chamber 48. Is for detecting the ratio of toner in the developer transported (toner concentration: toner amount / (toner amount + carrier amount)). As shown in FIG. 3, the toner density sensor 72 is electrically connected to the printer controller 68, and the toner density detection result by the toner density sensor 72 is output to the printer controller 68.

  In other words, the RAM 68 </ b> A of the printer controller 68 stores a table relating to toner density and driving of the toner replenishing mechanism 70. Specifically, a table for driving the toner supply mechanism 70 is stored when the toner density in the developing unit 38 becomes lower than an arbitrary value. As a result, when the toner density in the developing device 38 becomes lower than an arbitrary value, the toner replenishing mechanism 70 is driven and controlled by the printer controller 68, and toner is supplied into the developing device 38 from the toner replenishing path 56. Is done.

  Further, an inclination sensor 74 for measuring the inclination of the developing device 38 is attached to the developing device 38. The tilt sensor 74 is a conventionally known sensor (for example, see Japanese Patent Laid-Open Nos. 2006-044806 and 2005-208334) and measures the tilt angle of the developing unit 38 with respect to the horizontal direction (horizontal plane). It is. As shown in FIG. 3, the tilt sensor 74 is electrically connected to the printer controller 68, and the measurement result of the tilt angle by the tilt sensor 74 is output to the printer controller 68.

  A temperature / humidity sensor 76 is provided inside the image forming apparatus 10. This temperature / humidity sensor 76 is conventionally known and measures the temperature and humidity inside the image forming apparatus 10 (particularly, in the vicinity of the developing unit 38). The temperature / humidity sensor 76 is electrically connected to the printer controller 68, and the temperature and humidity measurement results from the temperature / humidity sensor 76 are output to the printer controller 68.

  As shown in FIG. 1, the transfer roller 66 is disposed on the opposite side of the photosensitive drum 22 with the main conveyance path 60 interposed therebetween. A bias voltage is applied to the transfer roller 66, and the transfer roller 66 is positively charged. As a result, when the sheet passes between the photosensitive drum 22 and the transfer roller 66, the negatively charged toner on the outer peripheral surface of the photosensitive drum 22 tends to move to the transfer roller 66 side. Therefore, the toner image on the photosensitive drum 22 is transferred to the paper. The sheet on which the toner image is transferred is conveyed to the fixing unit 18.

  As shown in FIG. 1, the fixing unit 18 includes a heat roller 78 and a press roller 80. The heat roller 78 is made of a metal having good heat conductivity (for example, aluminum), and a heater 82 composed of a halogen lamp is disposed therein. The press roller 80 is disposed on the opposite side of the heat roller 78 with the main conveyance path 60 interposed therebetween. Thus, when the sheet is conveyed to the nip portion between the heat roller 78 and the press roller 80, the sheet is heated and pressurized. Therefore, the transferred toner image is baked and fixed on the paper.

  Next, the main part of the control system of the image forming apparatus 10 of this embodiment will be described with reference to FIG.

  As shown in FIG. 3, the printer controller 68 is electrically connected to the drivers of the two motors M1 and M2, and by controlling the driving of the motors M1 and M2, the two screw members 40 and 42 are controlled. The rotation speed (number of rotations) can be controlled. As a result, the transport speed of the developer transported by the two screw members 40 and 42 is controlled by the printer controller 68.

  The printer controller 68 is electrically connected to the temperature / humidity sensor 76, and controls the driving of the motors M1 and M2 based on the measurement result from the temperature / humidity sensor 76. As a result, the rotational speed (number of rotations) of the two screw members 40 and 42 is controlled by the printer controller 68 based on the measurement result from the temperature / humidity sensor 76. As a result, the conveyance speed of the developer conveyed by the two screw members 40 and 42 is controlled by the printer controller 68 based on the measurement result from the temperature / humidity sensor 76.

  The printer controller 68 is electrically connected to the inclination sensor 74 and controls the driving of the motors M1 and M2 based on the measurement result from the inclination sensor 74. As a result, the rotational speeds (rotations) of the two screw members 40 and 42 are controlled by the printer controller 68 based on the measurement result from the inclination sensor 74. As a result, the conveyance speed of the developer conveyed by the two screw members 40 and 42 is controlled by the printer controller 68 based on the measurement result from the inclination sensor 74.

  Here, the printer controller 68 includes a RAM 68A. The RAM 68A stores a table indicating the relationship between the number of printing sheets of the image forming apparatus 10 and the rotation speeds (rotations) of the motors M1 and M2. Specifically, if the number of printing sheets is not more than an arbitrary value, the rotation speed of the motors M1 and M2 is high (the number of rotations is high), and if the number of printing sheets is not less than an arbitrary value, the motors M1 and M2 are. Is stored in such a table that the rotational speed of the motor is slow (the rotational speed is low). In other words, if the number of printing durability is less than an arbitrary value, the developer is in a smooth state close to the initial state, so that the developer is easy to slide with respect to the screw members 40 and 42. For this reason, the rotational driving force of the screw members 40 and 42 is difficult to be transmitted to the developer, and the developer transport speed is reduced. Therefore, the rotational speed of the motors M1 and M2 is increased (the number of revolutions is increased), and the developer Control is performed so that the conveyance speed does not decrease more than necessary. On the other hand, if the number of printing durability is greater than or equal to an arbitrary value, the developer is in a state where the developer itself has resistance unlike the initial state, so that the developer is less likely to slip with respect to the screw members 40 and 42. For this reason, the rotational driving force of the screw members 40 and 42 is easily transmitted to the developer as it is, and the developer conveyance speed is increased. Therefore, the rotation speed of the motors M1 and M2 is decreased (the number of rotations is decreased) to develop the developer. It is controlled so that the conveying speed of the agent does not increase more than necessary. In this way, the developer transport speed is kept constant regardless of the number of printing sheets of the image forming apparatus 10. Note that the printing durability of the image forming apparatus 10 is always recognized by the printer controller 68.

  As another control method, there is no need to always control each of the case where the number of printing sheets is less than an arbitrary value (developer is in a smooth state) and the case where the number is more than an arbitrary value (a state in which the developer is resistant). Based on the frictional state (sliding state) between the developer and the screw members 40 and 42, the rotational speed (rotational speed) of the motors M1 and M2 when the number of printing sheets is an arbitrary value or less (developer is in a smooth state) is a reference. As a fixed value, the rotational speed (number of rotations) of the motors M1 and M2 may be controlled so as to decrease when the number of printed sheets is an arbitrary value or more (the developer has resistance). . On the other hand, when the number of printing sheets is an arbitrary value or more (in a state where the developer is resistant), the rotation speed (number of rotations) of the motors M1 and M2 is fixed to a fixed value and the printing life is fixed. Control may be made to increase the rotational speed (number of rotations) of the motors M1 and M2 when the number of sheets is an arbitrary value or less (the developer is in a smooth state). As described above, depending on the frictional state (sliding state) between the developer and the screw members 40 and 42, the number of plate-proof sheets is an arbitrary value or less (the developer is in a smooth state) and an arbitrary value or more (development). Either one of the states in which the agent has resistance) may be fixed to a constant value, and the rotational speed (the number of rotations) of the motor M1 (M2) may be controlled on the other side.

  The RAM 68A of the printer controller 68 stores a table indicating the relationship between the environmental state (temperature, humidity) of the image forming apparatus 10 and the rotation speeds (rotations) of the motors M1 and M2. Specifically, if the temperature (or humidity) measured by the temperature / humidity sensor 76 is equal to or lower than an arbitrary value (low temperature and low humidity), the rotation speeds of the motors M1 and M2 are high (the rotation speed is high). If the temperature (or humidity) measured by the temperature / humidity sensor 76 is not less than an arbitrary value (high temperature and high humidity), the rotation speed of the motors M1 and M2 is slow (the rotational speed is low). Is stored. That is, if the temperature measured by the temperature / humidity sensor 76 is equal to or lower than an arbitrary value (low temperature state), the temperature of the developer is separated from the glass transition point, and the developer becomes smooth. If the humidity measured by the above is below an arbitrary value (low humidity state), the amount of water contained in the developer is reduced and the developer becomes smooth, so the developer fluidity is improved and the developer Becomes slippery with respect to the screw members 40, 42. For this reason, the rotational driving force of the screw members 40 and 42 is difficult to be transmitted to the developer, and the developer transport speed is reduced. Therefore, the rotational speed of the motors M1 and M2 is increased (the number of revolutions is increased), and the developer Control is performed so that the conveyance speed does not decrease more than necessary. On the other hand, if the temperature measured by the temperature / humidity sensor 76 is not less than an arbitrary value (high temperature state), the temperature of the developer approaches the glass transition point and the fluidity of the developer deteriorates, and the temperature / humidity sensor 76. If the humidity measured by the above is higher than an arbitrary value (high humidity state), the amount of water contained in the developer increases and the flowability of the developer deteriorates. It becomes difficult to slip. For this reason, the rotational driving force of the screw members 40 and 42 is easily transmitted to the developer as it is, and the developer conveyance speed is increased. Therefore, the rotation speed of the motors M1 and M2 is decreased (the number of rotations is decreased) to develop the developer. It is controlled so that the conveying speed of the agent does not increase more than necessary. In this way, the developer transport speed is kept constant regardless of the environmental conditions (temperature and humidity conditions) in which the developer is used.

  As another control method, when the temperature (or humidity) measured by the temperature / humidity sensor 76 is not more than an arbitrary value (developer has good fluidity) and not less than an arbitrary value (developer has a fluidity). It is not always necessary to control each of the bad states), and the temperature (or humidity) measured by the temperature / humidity sensor 76 is an arbitrary value according to the friction state (sliding state) between the developer and the screw members 40 and 42. Measured by the temperature / humidity sensor 76 with the rotation speed (number of rotations) of the motors M1 and M2 fixed at a fixed value as a reference in the following (low temperature / low humidity state: good developer fluidity). Control may be performed so that the rotational speeds (number of rotations) of the motors M1 and M2 when the temperature (or humidity) is equal to or higher than an arbitrary value (high temperature / high humidity state: poor developer fluidity). Conversely, when the temperature (or humidity) measured by the temperature / humidity sensor 76 is an arbitrary value or higher (high temperature / high humidity state: poor developer fluidity), the rotational speeds of the motors M1, M2 ( When the temperature (or humidity) measured by the temperature / humidity sensor 76 is not more than an arbitrary value (low temperature / humidity state: good developer fluidity) The motors M1 and M2 may be controlled to increase the rotational speed (number of rotations). Thus, when the temperature (or humidity) measured by the temperature / humidity sensor 76 is not more than an arbitrary value according to the frictional state (sliding state) between the developer and the screw members 40 and 42 (low temperature / low humidity state: Either one of the developer fluidity is good) or more than an arbitrary value (high temperature / high humidity state: developer fluidity is poor) is fixed at a fixed value, and the motor M1 is used in the other. , M2 rotational speed (rotational speed) may be controlled.

  Next, the operation of the image forming apparatus 10 according to the first embodiment will be described.

  As shown in FIGS. 2 and 3, the two motors M1 and M2 are driven and controlled by the printer controller 68 based on a table stored in the RAM 68A. Thereby, the two screw members 40 and 42 are rotationally driven based on the table stored in the RAM 68A.

  Specifically, in relation to the number of printing sheets of the image forming apparatus 10, if the number of printing sheets is equal to or less than an arbitrary value, the motors M1 and M2 are controlled so that the rotation speed is high (the rotation speed is high). The This is because if the number of printing durability is not more than an arbitrary value, the developer is in a smooth state close to the initial state, so that the developer is easily slipped with respect to the screw members 40 and 42. For this reason, the rotational driving force of the screw members 40 and 42 is difficult to be transmitted to the developer, and the developer transport speed is reduced. Therefore, the rotational speed of the motors M1 and M2 is increased (the number of revolutions is increased), and the developer This is to prevent the conveyance speed from decreasing more than necessary. On the other hand, if the printing durability is greater than or equal to an arbitrary value, the motors M1 and M2 are controlled so that the rotational speed is slow (the rotational speed is low). This is because, if the number of printing durability is not less than an arbitrary value, the developer is in a state of resistance to the developer itself unlike the initial state, so that the developer is less likely to slip with respect to the screw members 40 and 42. . For this reason, the rotational driving force of the screw members 40 and 42 is easily transmitted to the developer as it is, and the developer conveyance speed is increased. Therefore, the rotation speed of the motors M1 and M2 is decreased (the number of rotations is decreased) to develop the developer. This is to prevent the conveying speed of the agent from increasing more than necessary.

  Further, the relationship with the environmental state (temperature, humidity) of the image forming apparatus 10 is controlled based on the measurement result of the temperature and humidity from the temperature / humidity sensor 76 and the table stored in the RAM 68A. Specifically, if the temperature (or humidity) measured by the temperature / humidity sensor 76 is equal to or lower than an arbitrary value (low temperature or low humidity state), the rotation speeds of the motors M1 and M2 are high (the rotation speed is high), If the temperature (or humidity) measured by the temperature / humidity sensor 76 is equal to or higher than an arbitrary value (high temperature or high humidity state), the motors M1 and M2 are controlled so that the rotational speed is slow (the rotational speed is low). . If the temperature measured by the temperature / humidity sensor 76 is not more than an arbitrary value (low temperature state), the temperature of the developer is separated from the glass transition point, and the developer becomes smooth, and the temperature / humidity sensor If the humidity measured by 76 is less than or equal to an arbitrary value (low humidity state), the amount of water contained in the developer is reduced and the developer is in a smooth state. The agent becomes slippery with respect to the screw members 40 and 42. For this reason, the rotational driving force of the screw members 40 and 42 is difficult to be transmitted to the developer, and the developer transport speed is reduced. Therefore, the rotational speed of the motors M1 and M2 is increased (the number of revolutions is increased), and the developer This is to prevent the conveyance speed from decreasing more than necessary. On the other hand, if the temperature measured by the temperature / humidity sensor 76 is not less than an arbitrary value (high temperature state), the temperature of the developer approaches the glass transition point and the fluidity of the developer deteriorates, and the temperature / humidity sensor 76. If the humidity measured by the above is higher than an arbitrary value (high humidity state), the amount of water contained in the developer increases and the flowability of the developer deteriorates. It becomes difficult to slip. For this reason, the rotational driving force of the screw members 40 and 42 is easily transmitted to the developer as it is, and the developer conveyance speed is increased. Therefore, the rotation speed of the motors M1 and M2 is decreased (the number of rotations is decreased) to develop the developer. This is to prevent the conveying speed of the agent from increasing more than necessary.

  As described above, according to the image forming apparatus 10 of the first embodiment, when the printing durability or the environmental state (temperature / humidity) of the developing device 38 changes, the developer characteristic change (fluidity change) also changes. However, since the rotation of the two screw members 40 and 42 is controlled based on the table stored in the RAM 68A of the printer controller 68, the influence due to the change in the number of printing sheets or the environmental condition (temperature / humidity) of the developing unit 38 is caused. The developer can be always conveyed at a constant speed without receiving the toner. As a result, it is possible to always stabilize the developer transport without being affected by the number of printing durability or the environmental condition (temperature / humidity) of the developing device 38, and thus a stable circulation state (development) of the developer. Can be maintained.

Next, an image forming apparatus according to a second embodiment of the present invention will be described.
Note that the same components as those in the image forming apparatus 10 according to the first embodiment of the present invention are denoted by the same reference numerals, and description thereof will be omitted as appropriate.

  The RAM 68A of the printer controller 68 of the image forming apparatus according to the second embodiment stores a table indicating the relationship between the inclination angle of the developing device 38 with respect to the horizontal plane and the rotational speeds (rotations) of the motors M1 and M2. . Here, the inclination angle of the developing unit 38 with respect to the horizontal plane means the inclination angle α (see FIG. 4) of the two screw members 40 and 42 accommodated in the developing unit 38 with respect to the horizontal plane. The measurement result is the inclination angle α (see FIG. 4) of the screw members 40 and 42 with respect to the horizontal plane.

  Specifically, as shown in FIG. 4, when the developing unit 38 is inclined so that one end portion in the axial direction of the screw members 40 and 42 is lowered and the other end portion in the axial direction is raised, A measurement result for the tilt angle is output from the tilt sensor 74 to the printer controller 68, and a table indicating the relationship between the tilt angle at this time and the rotation speeds (rotations) of the motors M1 and M2 is stored in the RAM 68A. . That is, in the inclined state shown in FIG. 4, since the developer conveyed by the first screw member 40 that conveys the developer in the direction of the arrow X is inclined upward, the conveying speed tends to decrease. On the other hand, since the developer conveyed by the second screw member 42 that conveys the developer in the arrow Y direction is inclined downward, the conveyance speed tends to increase. Therefore, unless the rotational speed of the screw members 40 and 42 is controlled, the developer conveyed by the first screw member 40 does not advance so much and the developer conveyed by the second screw member 42 advances well. become. As a result, the developer accumulates and increases in a portion S1 on one side in the axial direction of the first screw member 40 and the second screw member 42, and a portion S2 on the other side in the axial direction of the first screw member 40 and the second screw member 42. With less developer. As a result, the developer is segregated in the developing unit 38, so that the detection result of the toner amount by the toner concentration sensor 72 and the actual toner amount do not coincide with each other, and the toner concentration in the developing unit 38 is controlled appropriately. Can not be. Therefore, in order to prevent this problem, the RAM 68A controls the driving of the motor M1 so that the rotation speed of the first screw member 40 is increased in the inclined state shown in FIG. A table for controlling the driving of the motor M2 is stored so as to reduce the speed. That is, in the RAM 68A, when the developer conveyed is inclined upward, the rotational speed of the screw member conveying the developer is increased, and when the developer conveyed is inclined downward, the development is performed. A table showing a relationship in which the rotational speed of the screw member that transports the agent decreases is stored.

  As another control method, the rotational speeds of the screw member that conveys the developer that is inclined upward for the developer to be conveyed and the screw member that conveys the developer that is inclined downward for the developer to be conveyed. Need not be controlled, and only the rotational speed of one of the screw members may be controlled. That is, according to the friction state (sliding state) between the developer and the screw member, the rotation speed of the screw member that conveys the developer that is inclined upward for the conveyed developer is fixed to a constant value, Control may be performed so that the rotational speed of the screw member that conveys the developer that is inclined downward is reduced. Conversely, depending on the frictional state (sliding state) between the developer and the screw member, the rotational speed of the screw member that conveys the developer that is inclined downward for the developer being conveyed is fixed to a constant value, You may control so that the rotational speed of the screw member which conveys the developer which becomes an upward inclination with respect to the developer conveyed will increase.

  Next, the operation of the image forming apparatus according to the second embodiment of the present invention will be described.

  In the case of the inclined state of the developing device 38 (respective screw members 40 and 42) shown in FIG. 4, the printer is configured so that the rotational speed of the first screw member 40 that conveys the developer that advances upward is increased in the arrow X direction. The motor 68 is driven and controlled by the controller 68. As a result, the developer conveyed in the direction of the arrow X by the first screw member 40 advances against the gravity, but the rotation speed of the first screw member 40 increases, so the developer conveyance speed decreases. Can be prevented. Conversely, the motor M2 is driven and controlled by the printer controller 68 so that the rotational speed of the second screw member 42 that conveys the developer that advances downward in the direction of the arrow Y decreases. Accordingly, the developer conveyed in the direction of the arrow Y by the second screw member 42 tends to be high speed due to the action of gravity, but the rotation speed of the second screw member 42 decreases, so the developer is conveyed. It is possible to prevent the speed from increasing.

  As described above, according to the image forming apparatus of the second embodiment, the developer conveyance speed may change depending on the inclination state of the developing device 38, but based on the table stored in the RAM 68 </ b> A of the printer controller 68. Since the rotation of the two screw members 40 and 42 is controlled, the developer can always be conveyed at a constant speed without being affected by the inclined state of the developing device 38. As a result, it is possible to always stabilize the developer transport without being affected by the inclined state of the developing device 38, and to maintain a stable circulation state (development) of the developer.

1 is a front sectional view of an image forming apparatus according to an embodiment of the present invention. 1 is a configuration diagram illustrating an internal configuration of a developing unit used in an image forming apparatus according to an embodiment of the present invention. 1 is a block diagram illustrating a main part of a control system of an image forming apparatus according to an embodiment of the present invention. FIG. 4 is a schematic diagram illustrating an inclined state of each screw member housed in a developing device of the image forming apparatus according to the embodiment of the present invention.

Explanation of symbols

10 Image forming apparatus 38 Developer 40 First screw member (screw member)
42 Second screw member (screw member)
68 Printer controller (control unit)

Claims (2)

An image forming apparatus including a developing device in which a developer is accommodated,
A screw member that is rotatably provided in the developing device and conveys the developer in an arbitrary direction by rotating;
A control unit for controlling the rotation of the screw member;
Have
The image forming apparatus according to claim 1, wherein the control unit controls rotation of the screw member based on a printing durability or an environmental state of the developing device. An image forming apparatus including a developing device in which a developer is accommodated,
A screw member that is rotatably provided in the developing device and conveys the developer in an arbitrary direction by rotating;
A control unit for controlling the rotation of the screw member;
Have
The image forming apparatus according to claim 1, wherein the control unit controls rotation of the screw member based on an inclined state of the developing device.

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