JP2015055823A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus configured to properly keep the amount of toner to be supplied to a developing apparatus, in consideration of heat stress at the end and start of image formation.SOLUTION: A control unit 5 supplies toner from a toner container 39 to a developing apparatus 34, on the basis of a value of a toner concentration sensor 67 for detecting permeability of developer in the developing apparatus 34, so that the concentration of the toner in the developing apparatus 34 is equal to a reference concentration value M1. The control unit 5 acquires temperatures from an external temperature sensor 56 and an internal temperature sensor 58 at the end of image formation, to calculate a first differential value H1 thereof. The control unit 5 acquires temperatures from the external temperature sensor 56 and the internal temperature sensor 58 at the start of image formation, to calculate a second differential value H2. The control unit 5 corrects the reference concentration value M1 on the basis of a third differential value H3 obtained from the first and second differential values H1 and H2.

Description

  The present invention relates to an image forming apparatus including a detecting unit that detects a magnetic permeability of a developer.

  2. Description of the Related Art Image forming apparatuses such as copying machines and printers that form images on paper by electrophotography are equipped with a developing device that performs development using toner. As an example of the developing device, a developing device that performs development by a two-component developing method using toner and a magnetic carrier is known. An electrostatic latent image formed on an image carrier such as a photosensitive drum is developed as a toner image by being supplied with toner by a developing device. The toner image is transferred from the photosensitive drum onto the paper by a transfer device. The sheet on which the toner image is transferred is heated and pressed by a fixing device. As a result, the toner image is fixed on the paper and an image is formed on the paper. This completes a series of image forming operations.

  A developer containing toner used in the above-described image forming operation is accommodated in the developing device. When the image forming operation is repeated, the toner contained in the developing device is consumed and the amount of toner is reduced. Therefore, the developing device is provided with a magnetic permeability sensor for detecting the remaining amount of toner from the magnetic permeability of the developer, and the amount of toner in the developing device is determined based on the detected remaining amount of toner. Toner is automatically replenished from the toner container so as to always have a specified amount. In addition, the developing device is provided with a stirring unit that transports the toner in one direction while stirring the toner. The supplied toner is appropriately stirred by the stirring means. As a result, the toner necessary for development is charged in the toner.

  When the image forming operation by the image forming apparatus is completed and the driving of the developing device is stopped, the developer is left without being stirred. Further, since the image forming operation is not performed for a long time, the use environment such as the external temperature and the external humidity of the image forming apparatus changes. The bulk density of the developer changes due to a decrease in the toner charge amount due to such neglect and a change in the viscosity of the toner due to a change in use environment. The magnetic permeability sensor mainly detects the magnetic permeability in the vicinity of the detection surface, and the detection accuracy decreases as the distance from the detection surface increases. Therefore, even if there is no change in the remaining amount of toner, the output value of the magnetic permeability sensor changes as the bulk density changes. As a result, although the toner is not consumed, a signal indicating that the toner has decreased is output from the magnetic permeability sensor. In this case, although the specified amount of toner is actually stored, toner is supplied from the toner container to the developing device in accordance with a signal indicating a decrease in toner, so that an excessive toner state occurs. For this reason, a phenomenon in which the density of an image developed by the developing device becomes excessively high or a toner scatters during development by the developing device occurs. On the other hand, in Patent Document 1, the toner supply method is changed according to the difference between the output value of the magnetic permeability sensor at the end of image formation and the output value of the magnetic permeability sensor at the time of resuming image formation. A technique for appropriately maintaining the replenishment amount of toner is disclosed.

Japanese Patent No. 3720720

  By the way, it is known that when the temperature of the developer rises by driving the developing device, the magnetism of the developer changes due to thermal stress caused by the temperature rise. When the magnetic property of the developer changes due to thermal stress, the output value of the magnetic permeability sensor deviates from a numerical value indicating the actual remaining amount of toner, and the remaining amount of toner cannot be accurately detected. In particular, if the degree of thermal stress at the end of image formation differs from the degree of thermal stress at the time of restarting image formation, the output value of the permeability sensor at the end of image formation and the output value of the permeability sensor at the time of restarting image formation Is different. In this case, the toner is replenished by mistake, and an excessive toner state may occur. As described above, the toner replenishment due to thermal stress fluctuation cannot be limited by the toner replenishment amount changing method disclosed in Patent Document 1, and the toner replenishment quantity in consideration of thermal stress fluctuation. Cannot be maintained properly.

  An object of the present invention is to provide an image forming apparatus capable of appropriately maintaining the amount of toner to be replenished to the developing device in consideration of the thermal stress at the end of image formation and the thermal stress at the start of image formation. There is to do.

  An image forming apparatus according to an aspect of the present invention includes a developing container, a detection unit, a toner supply unit, a first acquisition unit, a second acquisition unit, a first calculation unit, a second calculation unit, and a correction unit. The developer container is provided inside the apparatus main body and contains a magnetic developer. The detection means detects the magnetic permeability of the developer stored in the developer container. The toner replenishing unit controls toner replenishment to the developing container so that the detection value of the detecting unit becomes a reference value indicating a predetermined amount of developer. The first acquisition unit acquires first information in an external environment of the apparatus main body that changes the magnetic permeability of the developer in the developer container. The second acquisition unit acquires second information in an internal environment of the apparatus main body that changes the magnetic permeability of the developer in the developer container. The first calculation means calculates a first difference value from the first information acquired by the first acquisition means and the second information acquired by the second acquisition means at a predetermined first timing. . The second calculation means includes the first information acquired by the first acquisition means at a predetermined second timing after the first timing and the second information acquired by the second acquisition means. To calculate a second difference value. The correction means corrects the reference value based on the third difference value obtained from the first difference value and the second difference value.

  According to the present invention, the amount of toner to be replenished to the developing device can be appropriately maintained in consideration of the thermal stress at the end of image formation and the thermal stress at the start of image formation.

1 is a diagram illustrating a configuration of an image forming apparatus according to an embodiment of the present invention. FIG. 2 is a perspective view of a developing device provided in the image forming apparatus of FIG. 1. The figure which shows the cross section of the cutting line III-III in FIG. FIG. 2 is a block diagram illustrating a configuration of the image forming apparatus in FIG. 1. The reference value table figure of the toner density sensor corresponding to external temperature and external humidity. FIG. 6 is a diagram illustrating output values of a toner density sensor at the end of development and at the start of development. FIG. 5 is a correction table diagram of a reference value of a toner density sensor corresponding to a temperature difference. The figure which shows the temperature difference at the time of the image formation start and image formation end. The figure which shows the difference of the correction value table with respect to a temperature difference, and an actual correction value. The flowchart which shows an example of the correction process which the control part of FIG. 4 performs.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings for understanding of the present invention.

[Schematic Configuration of Image Forming Apparatus 100]
First, a schematic configuration of the image forming apparatus 100 according to the embodiment of the present invention will be described. As shown in FIG. 1, the image forming apparatus 100 includes an image reading unit 1, an ADF (Automatic Document Feeder) 2, an image forming unit 3, a paper feeding unit 4, a control unit 5, an operation display unit 6, and an external temperature sensor 56. (See FIG. 4 for an example of the first acquisition means of the present invention), an external humidity sensor 57 (see FIG. 4 for an example of the first acquisition means of the present invention), and an internal temperature sensor 58 (for the second acquisition means of the present invention). One example, see FIG. 4). The operation display unit 6 is a touch panel that displays various types of information in accordance with control instructions from the control unit 5 and inputs various types of information to the control unit 5 in response to user operations. Here, FIG. 1A is a front view of the image forming apparatus 100, and FIG. 1B is a plan view of the image reading unit 1. For convenience of explanation, the vertical direction in a state where the image forming apparatus 100 is installed is defined as the vertical direction 7, and the side where the operation display unit 6 is provided is the front side (front side), and the front-rear direction 8 is defined. The horizontal direction 9 is defined with the operation display unit 6 as the front. The image forming apparatus 100 is only an example of the image forming apparatus of the present invention, and may be, for example, a printer, a FAX apparatus, a copying machine, or the like.

  The image reading unit 1 acquires image data from the paper P. The image reading unit 1 is an image reading unit including a document cover 2A, a contact glass 11, a reading unit 12, a mirror 13, a mirror 14, an optical lens 15, a CCD (Charge Coupled Device) 16, and the like. The contact glass 11 is provided on the upper surface of the image reading unit 1, and is a transparent paper base on which a paper P that is an image reading target of the image forming apparatus 100 is placed.

  The document cover 2A covers the contact glass 11 as necessary. The image reading unit 1 reads an image from the paper P placed on the contact glass 11 under the control of the control unit 5.

  The reading unit 12 includes an LED light source 121 and a mirror 122, and is configured to be movable in the sub-scanning direction (the horizontal direction 9 in FIG. 1) by a moving mechanism (not shown) such as a stepping motor. When the reading unit 12 is moved in the sub-scanning direction by the moving mechanism, the light emitted from the LED light source 121 toward the contact glass 11 is scanned in the sub-scanning direction.

  The LED light source 121 includes a large number of white LEDs arranged along the main scanning direction of the image forming apparatus 100 (front-rear direction 8 in FIG. 1). The LED light source 121 emits white light for one line toward the paper P at the reading position 12 </ b> A on the contact glass 11. Note that the reading position 12A moves in the sub-scanning direction as the reading unit 12 moves in the sub-scanning direction.

  The mirror 122 reflects the reflected light when the light is irradiated from the LED light source 121 to the paper P at the reading position 12 </ b> A toward the mirror 13. The light reflected by the mirror 122 is guided to the optical lens 15 by the mirror 13 and the mirror 14. The optical lens 15 collects incident light and makes it incident on the CCD 16.

  The CCD 16 is a photoelectric conversion element that converts received light into an electrical signal (voltage) corresponding to the amount of light and outputs it to the control unit 5. Specifically, the CCD 16 generates image data based on an electrical signal corresponding to an image on the paper P based on light reflected from the paper P when light is emitted from the LED light source 121.

  The ADF 2 is provided on the document cover 2A. The ADF 2 is an automatic document feeder including a paper tray 21, a feeding mechanism 22, a plurality of transport rollers 23, a paper press 24, a paper discharge unit 25, and the like. The ADF 2 drives each of the feeding mechanism 22 and the transport roller 23 with a stepping motor (not shown), thereby causing the paper P set on the paper tray 21 to pass through the reading position 12A on the contact glass 11 and the paper discharge unit 25. Transport to. At this time, the image reading unit 1 reads the image of the paper P passing through the reading position 12A.

  The sheet presser 24 is provided at a position above the reading position 12 </ b> A on the contact glass 11 with an interval through which the sheet P can pass. The sheet presser 24 is formed in an elongated shape in the main scanning direction, and a white sheet is attached to the lower surface (the surface on the contact glass 11 side). In the image forming apparatus 100, the image data of the white sheet is read as white reference data. The white reference data is used for known shading correction and the like.

  The image forming unit 3 is an electrophotographic system that executes image forming processing (printing processing) based on image data read by the image reading unit 1 or image data input from an information processing apparatus such as an external personal computer. Image forming means. The image forming unit 3 includes a photosensitive drum 31, a charging device 32, an LSU (Laser Scanner Unit) 33, a developing device 34, a transfer device 35, a charge eliminating device 36, a fixing roller 37, a pressure roller 38, a toner container 39, and the like. I have.

  In the image forming unit 3, an image is formed on the paper S fed from the paper feeding unit 4 according to the following procedure, and the paper S after the image formation is discharged to the paper discharge tray 40. Specifically, first, the photosensitive drum 31 is uniformly charged to a predetermined potential by the charging device 32. Next, the light based on the image data is irradiated on the surface of the photosensitive drum 31 by the LSU 33. As a result, an electrostatic latent image is formed on the surface of the photosensitive drum 31. The electrostatic latent image on the photosensitive drum 31 is developed (visualized) as a toner image by the developing device 34. Subsequently, the toner image formed on the photosensitive drum 31 is transferred onto the paper S by the transfer device 35. Thereafter, the toner image transferred to the paper S is heated by the fixing roller 37 and melted and fixed to the paper S when the paper S passes between the fixing roller 37 and the pressure roller 38 and is discharged. The electric potential of the photosensitive drum 31 is neutralized by the neutralization device 36. Details of the developing device 34 will be described later.

  The paper feeding unit 4 feeds the paper S on which an image is formed in the image forming unit 3. The paper feed unit 4 feeds a plurality of sheets S placed in a paper feed cassette (not shown) mounted in a cassette mounting unit (not shown) one by one to the image forming unit 3.

  As shown in FIG. 4, the external temperature sensor 56 acquires external temperature information in the external environment of the image forming apparatus 100 and outputs a temperature signal based on the acquired temperature information to the control unit 5. The external temperature sensor 56 uses an NTC thermistor whose resistance is proportionally reduced as the temperature rises. The detection unit of the external temperature sensor 56 is disposed near the operation display unit 6 that easily measures the external temperature of the image forming apparatus 100. The external temperature information acquired by the external temperature sensor 56 is one piece of information for changing the magnetic permeability of the developer in the developing device 34.

  The external humidity sensor 57 acquires external humidity information in the external environment of the image forming apparatus 100 and outputs a humidity signal based on the acquired humidity information to the control unit 5. The external humidity sensor 57 is of an electric resistance type, and the moisture sensitive element absorbs / desorbs water vapor according to the change in humidity, and the electrical characteristics between the two electrodes connected to the moisture sensitive element change. A humidity sensor is provided. The detection part of the external humidity sensor 57 is arranged near the operation display unit 6 that can easily measure the external temperature of the image forming apparatus 100, similarly to the detection part of the external temperature sensor 56. The external humidity information acquired by the external humidity sensor 57 is one piece of information for changing the magnetic permeability of the developer in the developing device 34.

  The internal temperature sensor 58 acquires internal temperature information in the internal environment of the image forming apparatus 100 and outputs a temperature signal based on the acquired temperature information to the control unit 5. As with the external temperature sensor 56, the internal temperature sensor 58 uses an NTC thermistor whose resistance decreases proportionally as the temperature rises. A detection portion of the internal temperature sensor 58 is disposed near the developing device 34. The internal temperature information acquired by the internal temperature sensor 58 is one piece of information for changing the magnetic permeability of the developer in the developing device 34.

[Configuration of Developing Device 34]
Next, the developing device 34 will be described in detail with reference to FIGS. The developing device 34 is a developing device that stores a magnetic developer composed of two components of a toner and a magnetic carrier and develops the developer using the developer.

  As shown in FIG. 2, the developing device 34 is formed in a shape that is long in the front-rear direction 8. The developing device 34 has a casing 60 (an example of a developing container of the present invention) that is long in the front-rear direction 8. The housing 60 plays a role of a frame that supports the developing roller 61 and a role of a container that accommodates the developer inside. A replenishing port 70 is formed outside the developing device 34, and a shutter 69 that opens and closes the replenishing port 70 is provided. The shutter 69 is slid by a solenoid to open the supply port 70 when non-magnetic toner is supplied from the toner container 39 (see FIG. 1A) to the developing device 34. When the toner is not replenished, the shutter 69 is slid by a solenoid to close the replenishment port 70. As described above, the internal temperature sensor 58 is installed in contact with the developing device 34.

  Inside the housing 60 of the developing device 34, a developer reservoir 63, a screw feeder 64A, a screw feeder 64B, a scraper 66, a toner concentration sensor 67, a developing roller 61, a magnetic roller 62, a developer regulating blade 71, and the like are provided. It has been. As shown in FIG. 3, the developer reservoir 63 is formed at the bottom of the housing 60, and stores developer including nonmagnetic toner and magnetic carrier replenished from the toner container 39. (Contained) container. A magnetic roller 62 that is a developer carrying member is disposed above the developer reservoir 63. The developing roller 61 that is a toner carrier is disposed opposite to the magnetic roller 62 at a position obliquely above the magnetic roller 62. The developer regulating blade 71 is disposed to face the magnetic roller 62.

  As shown in FIG. 4, the developing roller 61, the magnetic roller 62, the screw feeder 64 </ b> A, and the screw feeder 64 </ b> B are connected to a stepping motor 77 via a gear 78. The stepping motor 77 supplies a rotational force via the gear 78 to rotate the screw feeder 64A, the screw feeder 64B, the developing roller 61, and the magnetic roller 62 in conjunction with each other. The developing roller 61 and the magnetic roller 62 are rotated in a forward rotation direction (directions of arrows 91 and 92 in FIG. 2) for supplying toner to the photosensitive drum 31 during development, and in conjunction with this, the screw feeder 64A and the screw feeder are rotated. 64B also rotates in the forward rotation direction defined by the gear 78 (in the directions of arrows 93 and 94 in FIGS. 2 and 3). The rotation amounts of the developing roller 61, the magnetic roller 62, the screw feeder 64A, and the screw feeder 64B are determined by the gear ratio of the gear 78.

  The developer storage unit 63 includes two adjacent developer storage chambers 63A and 63B extending in the longitudinal direction (front-rear direction 8) of the developing device 34. Each of the developer storage chambers 63A and 63B is formed in a cylindrical shape that is long in the front-rear direction 8. The developer storage chambers 63 </ b> A and 63 </ b> B are separated from each other by a partition plate 111 that is formed integrally with the housing 60 and extends in the front-rear direction 8. However, the developer storage chambers 63A and 63B are not completely partitioned, and the partition plates 111 are not provided at both ends in the front-rear direction 8. Specifically, both end portions in the front-rear direction 8 of the developer storage chambers 63A and 63B are communicated with each other through a communication path.

  Each of the developer storage chambers 63A and 63B accommodates screw feeders 64A and 64B that agitate and convey the developer by rotating around the axis. The screw feeders 64A and 64B are provided with spiral wings around the axis. The screw feeders 64 </ b> A and 64 </ b> B are rotated by a stepping motor 77. The rotation directions of the screw feeders 64A and 64B are set in opposite directions. Accordingly, the developer is circulated and conveyed between the developer storage chamber 63A and the developer storage chamber 63B while being stirred. By this stirring, the toner of the developer in which the toner and the carrier are mixed has a charge.

  A detection surface 68 is formed in the vicinity of one end (front end) of the developer storage chamber 63A. As will be described later, an opening is formed in the bottom surface of the developer storage chamber 63A, and the sensor housing portion 80 of the toner concentration sensor 67 is fitted into this opening, whereby the outer surface (specifically, the upper surface of the sensor housing portion 80). ) Is exposed to the developer storage chamber 63A. The exposed portion appears as a detection surface 68 on the bottom surface of the developer storage chamber 63A.

  A support part 79 for attaching the scraper 66 is formed on the screw feeder 64A in the vicinity of the detection surface 68. The support portion 79 is integrally formed of the same resin as that of the screw feeder 64A, and has a shape protruding in the vertical direction with respect to the rotation shaft 65 of the screw feeder 64A.

  Further, the scraper 66 is formed such that the joint surface on the end portion side on the screw feeder 64A side is joined to the support portion 79, and the other end portion extends in the vertical direction. The joint surface is a surface opposite to the contact surface on which the scraper 66 contacts the detection surface 68 when the screw feeder 64A is rotated in the forward rotation direction. The scraper 66 is a flexible plate-like member made of a polyethylene terephthalate film or the like. The scraper 66 is attached to the support portion 79 of the screw feeder 64A with a double-sided tape or the like. At the time of development, when the screw feeder 64A is rotated in the forward rotation direction, the scraper 66 moves in the forward rotation direction, the contact surface side hits the detection surface 68, and abuts against the detection surface 68 while being buckled.

  The magnetic roller 62 is disposed along the longitudinal direction (front-rear direction 8) of the developing device 34. The magnetic roller 62 is rotated in the clockwise direction in FIG. 3 (the direction of the arrow 92 in FIG. 3) during development. A fixed so-called magnet roll (not shown) is arranged inside the magnetic roller 62. The magnet roll has a plurality of magnetic poles, and in this embodiment, has a drawing pole 73, a regulation pole 74, and a main pole 75. The scooping pole 73 faces the developer storage portion 63, the regulation pole 74 faces the developer regulation blade 71, and the main pole 75 faces the developing roller 61.

  The magnetic roller 62 magnetically pumps the developer from the developer reservoir 63 onto the magnetic roller peripheral surface 62A by the magnetic force of the pumping pole 73. The developer thus pumped up is magnetically held as a developer layer (magnetic brush layer) on the magnetic roller peripheral surface 62 </ b> A, and is conveyed toward the developer regulating blade 71 as the magnetic roller 62 rotates.

  The developer regulating blade 71 is disposed upstream of the developing roller 61 as viewed from the rotation direction of the magnetic roller 62, and regulates the layer thickness of the developer layer that is magnetically attached to the magnetic roller peripheral surface 62A. The developer regulating blade 71 is a plate member made of a magnetic material that extends along the front-rear direction 8 of the magnetic roller 62, and is supported by a predetermined support member fixed at an appropriate position of the housing 60. Further, the developer regulating blade 71 has a regulating surface 71A (that is, the leading end surface of the developer regulating blade 71) that forms a regulating gap 72 having a predetermined size with the magnetic roller peripheral surface 62A.

  The developer regulating blade 71 formed from a magnetic material is magnetized by the regulating pole 74 of the magnetic roller 62. As a result, a magnetic path is formed between the regulating surface 71A of the developer regulating blade 71 and the regulating pole 74, that is, in the regulating gap 72. When the developer layer adhering to the magnetic roller circumferential surface 62 </ b> A by the scooping pole 73 is conveyed into the regulation gap 72 as the magnetic roller 62 rotates, the layer thickness of the developer layer is regulated in the regulation gap 72. . Thus, a uniform developer layer having a predetermined thickness is formed on the magnetic roller peripheral surface 62A.

  The developing roller 61 is disposed so as to extend along the longitudinal direction (front-rear direction 8) of the developing device 34 and in parallel with the magnetic roller 62. The developing roller 61 is rotated in the clockwise direction in FIG. 3 (the direction of the arrow 91 in FIG. 3) during development. The developing roller 61 has a developing roller peripheral surface 61A that receives toner from the developer layer and carries the toner layer while rotating in contact with the developer layer held on the magnetic roller peripheral surface 62A. During the development in which the developing operation is performed, the toner in the toner layer is supplied to the peripheral surface of the photosensitive drum 31.

  The developing roller 61 and the magnetic roller 62 are rotated by a stepping motor 77. A gap 76 (see FIG. 3) having a predetermined size is formed between the developing roller peripheral surface 61A and the magnetic roller peripheral surface 62A. For example, the gap 76 is set to about 130 μm. The developing roller 61 is disposed so as to face the photosensitive drum 31 through an opening formed in the housing 60, and a gap (for example, a predetermined dimension) is also formed between the developing roller peripheral surface 61A and the peripheral surface of the photosensitive drum 31. About 110 μm).

[Toner density sensor 67]
The toner concentration sensor 67 is a magnetic permeability sensor that detects the magnetic permeability of the developer accommodated in the housing 60 via the detection surface 68. The toner concentration sensor 67 detects a voltage value based on the detected magnetic permeability, and outputs the detected voltage value to the control unit 5. The controller 5 calculates the toner density of the developer from the voltage value input from the toner density sensor 67. The control unit 5 transfers the toner from the toner container 39 to the developing device 34 so that the calculated toner density becomes a reference density value M1 (an example of the reference value of the present invention, see FIG. 6) indicating a predetermined toner density. In order to supply, the shutter 69 that opens and closes the supply port 70 is opened and closed. Specifically, the magnetic permeability measured by the toner concentration sensor 67 changes according to the toner concentration. When the toner concentration is low with respect to the magnetic carrier, the magnetic permeability increases. Further, the voltage value changes according to the magnetic permeability. As the permeability increases, the voltage value also increases. That is, there is a relationship in which the magnetic permeability and the voltage value increase as the remaining amount of toner decreases and the toner density relative to the carry decreases. The toner concentration sensor 67 detects the magnetic permeability of the developer by measuring the voltage value of the detection surface 68. The toner concentration sensor 67 outputs information on the detected magnetic permeability to the control unit 5. The controller 5 determines the toner concentration of the developer based on the input magnetic permeability. As described above, the control unit 5 detects the toner density by detecting the magnetic permeability of the developer containing toner by the toner density sensor 67. That is, the toner density sensor 67 and the control unit 5 are examples of the detection unit of the present invention. Since the toner concentration varies depending on the remaining amount of toner, the remaining amount of toner in the housing 60 can be detected by detecting the toner concentration. Note that the toner density sensor 67 may include a control board for determining the toner density. Further, the toner density sensor 67 has temperature dependence, and the output voltage value changes due to temperature fluctuation.

  As shown in FIG. 3, the toner density sensor 67 has a sensor housing portion 80 having a flat upper surface. A sensor main body capable of detecting the magnetic permeability of the developer is provided in the sensor housing portion 80. In the present embodiment, an opening that penetrates the bottom wall is formed in the bottom surface of the developer storage chamber 63A, and the sensor housing portion 80 is fitted into this opening. Thereby, the flat surface of the upper surface of the sensor accommodating part 80 is provided in the bottom face of the developer storage chamber 63A.

[Relationship between temperature and humidity characteristics of developer and reference density value M1]
Next, the temperature characteristics and humidity characteristics of the developer and a plurality of reference density values M1 corresponding thereto will be described. The developer has a characteristic that the chargeability is low when the temperature is high and the humidity is high, and the chargeability is high when the temperature is low and the humidity is low. Specifically, when the developer is in a high temperature and high humidity environment, the chargeability of the toner is reduced. Since the amount of charge to be charged is small, the repulsive force between the toner particles and the carrier particles is weakened, and the interval between the particles is narrowed. As the particle spacing decreases, the bulk density of the developer increases. Therefore, even if the concentration of toner contained in the developer is the same, the toner concentration sensor 67 detects the magnetic permeability indicating that the concentration of toner is high in the developer under high temperature and high humidity. On the other hand, when the developer is in a low temperature and low humidity environment, the chargeability of the toner increases. Since the amount of charge to be charged is large, the repulsive force between the toner particles and the carrier particles is increased, and the interval between the particles is widened. As the particle spacing increases, the bulk density of the developer decreases. Therefore, even if the concentration of toner contained in the developer is the same, the toner concentration sensor 67 detects the magnetic permeability indicating that the developer under low temperature and low humidity has a low toner concentration. As described above, even if the toner concentration of the developer is the same, the magnetic permeability detected by the toner concentration sensor 67 varies depending on the external temperature and external humidity at which the developer is used. Therefore, the control unit 5 changes the reference density value M1 according to the external temperature and external humidity at which the developer is used, and performs toner replenishment processing so that the amount of toner in the developing device 34 becomes constant. In the present embodiment, the ROM 5B stores a reference value table (see FIG. 5) indicating a plurality of reference density values M1 determined according to the external temperature and external humidity at which the developer is used. In the reference value table shown in FIG. 5, for example, when the external temperature is 25 degrees and the external humidity is 50 percent, the toner density that is the reference density value M1 is 9.0 percent. Similarly, when the external temperature is 20 degrees and the external humidity is 25%, the density of the toner having the reference density value M1 is 10.0%.

[Toner replenishment processing according to change in detected density of toner density sensor 67]
The control unit 5 selects a reference density value M1 corresponding to the external temperature and external humidity at which the developer is used from the reference value table and uses it as a reference for toner replenishment processing. However, if the reference density value M1 is used as it is, the following disadvantage may occur. In order to eliminate this inconvenience, the control unit 5 performs the following toner supply process. Hereinafter, the toner supply process will be described with reference to FIG. Here, in FIG. 6, the horizontal axis indicates time, and the vertical axis indicates the toner density value of the toner density determined based on the magnetic permeability detected by the toner density sensor 67. The polygonal line 81 and the polygonal line 82 appearing in the figure are as follows. 4 is a graph showing a change in toner density value over time. In the following description, a description will be given in order of a normal toner replenishment process using the reference density value M1, a problem of the toner replenishment process using the reference density value M1, and a toner replenishment process that has solved the problem. First, normal toner replenishment processing executed by the control unit 5 based on the detection value of the toner density sensor 67 and the reference density value M1 will be described. Here, it is assumed that the external temperature and external humidity of the image forming apparatus 100 are constant. As shown in FIG. 6, when the image forming apparatus 100 is performing an image forming operation, the control unit 5 causes the toner density value based on the magnetic permeability acquired from the toner density sensor 67 to become the reference density value M1. The toner supply and supply stop are repeated by opening and closing the shutter 69. Therefore, while the image forming apparatus 100 performs the image forming operation, the toner density value detected by the toner density sensor 67 and the control unit 5 is centered on the reference density value M1, as indicated by the broken line 81 in FIG. The reference density value M1 is generally maintained while vibrating up and down.

  By the way, when the image formation of the set number of images is completed in the image forming apparatus 100 (timing T1 in FIG. 6), the operation of the developing device 34 is stopped. In this case, the control unit 5 of the image forming apparatus 100 also stops the toner supply process, and stops the detection of the magnetic permeability by the toner concentration sensor 67. Furthermore, when a time during which the image forming apparatus 100 does not form an image has elapsed, the control unit 5 shifts the image forming apparatus 100 to the sleep mode and stops heating the fixing roller 37. When the sleep mode is continued, the internal temperature of the image forming apparatus 100 decreases to a temperature substantially equal to the room temperature. If the stop time in which the operation of the image forming apparatus 100 is stopped becomes long, the toner density sensor 67 and the control unit 5 detect the toner density even though the toner in the developing device 34 is not consumed. The toner density gradually decreases from the toner density value D1 detected immediately before shifting to the sleep mode. This is because the magnetic permeability changes due to a decrease in the toner charge amount due to the stirring stop or a change in the viscosity of the toner due to a change in external temperature, external humidity, or the like.

  Next, problems in the toner supply process using the reference density value M1 will be described. When the image forming apparatus 100 starts the image forming operation again after the sleep mode has elapsed for a long time (timing T2 in FIG. 6), the developing device 34 operates in a low temperature state. At this time, the first detected toner density value is set as a toner density value D2 (see FIG. 6). While the image forming apparatus 100 is not operating, the amount of toner in the developing device 34 does not change. However, if the toner amount has not changed, but the toner density value D2 is lower than the reference density value M1 because the developing device 34 is in a low temperature state, the control unit 5 determines that the toner density sensor 67 The toner supply and the supply stop are repeated by opening and closing the shutter 69 so that the toner density value based on the acquired magnetic permeability becomes the reference density value M1. That is, toner is further supplied in the developing device 34 even though there is a reference amount of toner supplied based on the reference density value M1.

  When the control unit 5 executes the toner supply process using the reference density value M1 as it is, a problem of toner oversupply occurs. Therefore, the controller 5 needs to correct the reference density value M1 to a numerical value corresponding to the external temperature, and use the corrected reference density value M1 to replenish toner. Therefore, the control unit 5 uses the corrected reference density value M2 corrected according to the external temperature and the external humidity until the developing device 34 is warmed from the low temperature to the operating temperature. Toner replenishment processing is performed so that the amount of toner becomes constant.

  Next, a toner replenishing process that solves the problem will be described. In the present embodiment, the ROM 5B of the control unit 5 stores a correction value table (see FIG. 7) indicating a plurality of density correction values determined according to the external temperature and the external humidity. In the correction value table shown in FIG. 7, for example, when the external temperature is 25 degrees and the external humidity is 50%, the density correction value is 1. Since the reference density value M1 at this time is 9.0 percent in terms of toner, the control unit 5 assumes that the corrected reference density value M2 after correction is 10.0 percent in terms of toner density. Similarly, when the external temperature is 20 degrees and the external humidity is 25%, the density correction value is −2. Since the density of the toner that becomes the reference density value M1 at this time is 10.0%, the control unit 5 assumes that the corrected reference density value M2 after correction is 8.0% in terms of toner density. As the correction reference density value M2, a time until the developing device 34 is sufficiently warmed is determined in advance, and the reference density value M1 whose correction amount gradually decreases with the passage of time is used. Therefore, the control unit 5 opens and closes the shutter 69 so that the toner density value based on the magnetic permeability acquired from the toner density sensor 67 becomes the corrected reference density value M2, as indicated by the broken line 82 in FIG. Repeated toner supply and supply stop. Therefore, the toner density value detected by the toner density sensor 67 and the control unit 5 oscillates up and down around the correction reference density value M2 in the period immediately after the image forming apparatus 100 starts image formation. When a sufficient time has elapsed and the temperature of the developing device 34 is sufficiently warmed and the developer is sufficiently stirred, the control unit 5 controls the replenishment of toner using the uncorrected reference density value M1. To do.

[Correction of reference density value taking into account the influence of heat at the end of image formation processing and at the start of image formation]
Even if the control unit 5 selects the reference density value M1 corresponding to the external temperature and humidity where the developer is used, and executes the toner replenishment process using the correction reference density value M2 described above, it is necessary for correction. There are cases where sufficient factors cannot be fully considered. Specifically, when the temperature of the developing device 34 rises due to driving of the screw feeders 64A and 64B of the developing device 34, the developer is subjected to thermal stress, and the magnetic permeability detected by the toner concentration sensor 67 changes. Therefore, the thermal stress received by the developer at the end of the image forming process is different from the thermal stress received by the developer at the start of image formation. It is necessary to consider this difference in heat stress. Further, since the toner density sensor 67 has temperature dependency, it is affected by the internal temperature of the image forming apparatus 100. Therefore, the thermal stress received by the toner density sensor 67 at the end of the image forming process is different from the thermal stress received by the toner density sensor 67 at the start of image formation. It is necessary to consider this difference in heat stress.

  Hereinafter, the toner replenishing process will be described with reference to FIGS. Here, in FIG. 8, the horizontal axis indicates time, and the vertical axis indicates the temperature detected by the external temperature sensor 56 and the internal temperature sensor 58. Lines 95 and 96 appearing in the figure indicate the temperature over time. It is a graph which shows a change. A line 95 indicates a change in the internal temperature around the developing device 34 of the image forming apparatus 100, and a line 96 indicates a change in the external temperature around the image forming apparatus 100. In the following description, since the external temperature is assumed to be constant, the line 96 is represented by a straight line. In FIG. 9, the horizontal axis shows the amount of fluctuation of the thermal stress, and the vertical axis shows the amount of correction of the correction reference concentration value M2. It is a graph which shows the change of correction amount. A broken line 46 indicates a change in the correction amount of the correction reference density value M2 due to a change in the amount of change in thermal stress, and a solid line 85 indicates a change in the correction amount considering all factors along with the change in the amount of change in thermal stress. Show.

  With reference to FIG. 8, the toner replenishing process executed by the control unit 5 using the revised corrected reference density value M3 obtained by correcting the reference density value M1 in consideration of thermal stress will be described. As shown in FIG. 8, when the image forming apparatus 100 is performing an image forming operation, heat generated from the fixing roller 37, heat generated by driving the screw feeders 64 </ b> A and 64 </ b> B of the developing device 34, etc. The internal temperature of the image forming apparatus 100 including the developing device 34 is higher than the external temperature. When the number of images set in the image forming apparatus 100 has been formed (timing T3 in FIG. 8), the operation of the developing device 34 is stopped. At the timing when this image forming operation ends, the control unit 5 acquires the internal temperature from the internal temperature sensor 58, acquires the external temperature from the external temperature sensor 56, and calculates a first difference value H1 that is the difference between them. And stored in the EEPROM 5D. The first difference value H1 is information indicating the state of thermal stress received by the developer and toner density sensor 67 at the end of the image forming process. Further, when a time during which the image forming apparatus 100 does not perform image formation elapses, the control unit 5 shifts the image forming apparatus 100 to the sleep mode (timing T4 in FIG. 8) and stops heating the fixing roller 37. When the sleep mode is continued, the internal temperature of the image forming apparatus 100 decreases to a temperature substantially equal to the room temperature.

  Next, a case where the image forming apparatus 100 starts an image forming operation after a sufficient time has passed so that the internal temperature around the developing device 34 is the same as the external temperature (timing T5 in FIG. 8) will be described. To do. At the timing of starting image formation, the control unit 5 acquires the internal temperature from the internal temperature sensor 58, acquires the external temperature from the external temperature sensor 56, and calculates a second difference value H2 that is the difference between them. The second difference value H2 is information indicating the state of thermal stress received by the developer and toner density sensor 67 at the start of the image forming process. Further, the control unit 5 acquires the first difference value H1 stored in the EEPROM 5D, calculates the difference between the acquired first difference value H1 and the second difference value H2, and sets it as the third difference value H3. . The third difference value H3 indicates the amount of change between the influence of thermal stress at the end of the image forming process and the influence of thermal stress at the start of image formation.

  Next, with reference to FIG. 9, the revision of the corrected reference concentration value M2 depending on the presence or absence of thermal stress fluctuation will be described. As shown by the broken line 46, if the influence of the thermal stress is not changed, the image forming apparatus 100 is under the same thermal stress condition when the image forming process is finished and when the image forming process is started. is there. Therefore, the influence of the temperature change between when the image forming process ends and when the image forming process starts can be eliminated with the correction amount B1. When the reference density value M1 is corrected with the corrected reference density value M2, the correction amount B1 is obtained. Thus, the control unit 5 can eliminate the influence of thermal stress. On the other hand, as shown by the solid line 85, if the influence of the thermal stress is changed, the image forming apparatus 100 has different thermal stress conditions when the image forming process ends and when the image forming process starts. Below. Therefore, the influence of the temperature change between when the image forming process ends and when the image forming process starts can be eliminated with the correction amount B2. When the reference density value M1 is corrected with the corrected reference density value M2, the correction amount B1 is obtained. Therefore, the control unit 5 cannot eliminate the influence of thermal stress by this correction. Therefore, the control unit 5 calculates the difference between the correction amount B2 and the correction amount B1 based on the third difference value H3 as the revised correction reference density value M3. The controller 5 corrects the corrected reference density value M2 with the revised corrected reference density value M3, and corrects the reference density value M1 with the corrected corrected reference density value M2. By performing such correction, the control unit 5 can execute the toner replenishment process based on a value that takes into account the change in the influence of thermal stress.

[Configuration of Control Unit 5]
The control unit 5 performs overall control of the image forming apparatus 100. As shown in FIG. 1, the control unit 5 is configured as a microcomputer including a CPU 5A, ROM 5B, RAM 5C, EEPROM 5D, DRIVER 5E, and the like as main components. The control unit 5 may be configured by an electronic circuit such as an integrated circuit (ASIC, DSP).

  The control unit 5 is connected to the image reading unit 1, the ADF 2, the image forming unit 3, the paper feeding unit 4, the operation display unit 6, and the like inside the image forming apparatus 100, and controls these components. Further, the control unit 5 includes each element constituting the image forming unit 3, specifically, the charging device 32, the LSU 33, the developing device 34, the transfer device 35, the charge eliminating device 36, the fixing roller 37, and the pressure roller 38. It is connected to the. The ROM 5B stores a program for executing image forming processing. The CPU 5A controls each element connected to the control unit 5 by executing a control program in the ROM 5B, and prints an image on printing paper.

  In the present embodiment, the ROM 5B of the control unit 5 stores a program for executing correction processing described later. The CPU 5A executes the correction process by executing this program. In addition, when the CPU 5A executes the program, in the correction process, the control unit 5 includes a first calculation unit 51 (an example of a first calculation unit of the present invention) and a second calculation unit 52 (a second calculation unit of the present invention). An example of a calculation unit), a correction unit 53 (an example of a correction unit of the present invention), a first storage unit 54 (an example of a first storage unit of the present invention), and a second storage unit 55 (a second storage unit of the present invention). As an example) (see FIG. 3). The control unit 5 functions as a toner replenishing unit 50 (an example of the toner replenishing unit of the present invention) and a detection unit 59 (an example of the detecting unit of the present invention).

  In addition to the program, the ROM 5B stores a voltage value, a calculation formula, a threshold value, a toner density value, and the like used for the correction process. For example, a conversion formula between a voltage value based on the magnetic permeability of the toner concentration sensor 67 and the toner concentration is stored in the ROM 5B so that the detection unit 59 acquires the toner concentration. A calculation formula for the first calculation unit 51 to calculate the first difference value H1 is stored. A calculation formula for the second calculation unit 52 to calculate the second difference value H2 is stored. A calculation formula for the correction unit 53 to calculate the third difference value H3, a correction amount calculation formula for calculating a correction amount based on the third difference value H3, a threshold value R1 for determining whether or not to correct, and the like are the ROM 5B. Is remembered. A plurality of reference density values M1 corresponding to the external temperature and the external humidity for executing the toner supply process in the first storage unit 54 are stored in the ROM 5B. A plurality of density correction values for correcting a plurality of reference density values M1 in the second storage unit 55 are stored in the ROM 5B. The EEPROM 5D stores the first difference value H1 calculated by the first calculator 51. The RAM 5C temporarily stores the third difference value H3 calculated by the correction unit 53, the correction amount based on the third difference value, and the like. The DRIVER 5E operates a stepping motor 77 that drives each roller of the developing device 34 and the like.

  The first calculation unit 51 calculates the first difference value H1 from the external temperature acquired by the external temperature sensor 56 and the internal temperature acquired by the internal temperature sensor 58 at the end of image formation, and stores it in the EEPROM 5D. The second calculator 52 calculates the second difference value H2 from the external temperature acquired by the external temperature sensor 56 and the internal temperature acquired by the internal temperature sensor 58 at the start of image formation. A specific calculation method will be described later.

  The first storage unit 54 stores a reference value table including a plurality of reference concentration values M1 determined in advance according to the external temperature and the external humidity. The second storage unit 55 stores a correction value table including a plurality of correction values for correcting the plurality of reference density values M1 corresponding to the external temperature and the external humidity.

  The correcting unit 53 corrects the reference density value M1 based on the third difference value H3 obtained from the first difference value H1 and the second difference value H2. The correction unit 53 corrects the reference density value M1 with a correction amount corresponding to the third difference value H3 when the third difference value H3 is equal to or greater than the threshold value R1. Further, the correction unit 53 selects and corrects a target value from each table stored in the first storage unit 54 and the second storage unit 55. A specific calculation method will be described later.

  The detection unit 59 detects the magnetic permeability of the developer in the developing device 34 by the toner density sensor 67, and acquires the toner density based on the magnetic permeability. The toner replenishing unit 50 controls toner replenishment from the toner container 39 to the developing device 34 so that the toner density value acquired by the detecting unit 59 becomes a reference density value M1 indicating a predetermined developer amount.

[Correction process]
Hereinafter, the procedure of the correction process executed by the control unit 5 will be described with reference to FIG. In the flowchart of FIG. 10, steps S1, S2,... Represent processing procedure (step) numbers. The correction process by the control unit 5 is performed when the image forming process of the image forming apparatus 100 ends and when the image forming process starts. Here, the control unit 5 when executing the correction processing corresponds to a first calculation unit, a second calculation unit, a correction unit, a first storage unit, and a second storage unit according to the present invention.

  In step S <b> 1, the control unit 5 determines whether the image forming operation of the image forming apparatus 100 is finished. Specifically, it is determined whether all the image forming processes instructed by the user have been completed or whether the time for shifting to the sleep mode has elapsed. The control unit 5 waits until the image forming operation is finished (NO side of S1). When the image forming operation ends, the control unit 5 shifts the process to step S2 (YES side of S1).

  In step S <b> 2, the control unit 5 acquires information on the external temperature detected by the external temperature sensor 56. In step S <b> 3, the control unit 5 acquires information on the internal temperature detected by the internal temperature sensor 58. In step S4, the control unit 5 calculates the first difference value H1 from the external temperature acquired by the external temperature sensor 56 and the internal temperature acquired by the internal temperature sensor 58, and stores it in the EEPROM 5D. The control unit 5 when executing step S4 is an example of the first calculation unit 51 of the present invention. As a result, the control unit 5 acquires information on thermal stress at the end of image formation.

  Next, in step S <b> 5, the control unit 5 determines whether an instruction to start image formation of the next image forming apparatus 100 has been received. Specifically, this is the case when a new image formation instruction is received from the user, or when an image formation instruction is received from another information processing apparatus. The control unit 5 waits for an instruction to start image formation (NO side of S5). If there is an instruction to start image formation, the control unit 5 proceeds to step S6 (YES side of S5).

  Next, in step S <b> 6, the control unit 5 acquires information on the external humidity detected by the external humidity sensor 57. In step S <b> 7, the control unit 5 acquires information on the external temperature detected by the external temperature sensor 56. In step S <b> 8, the control unit 5 acquires information on the internal temperature detected by the internal temperature sensor 58. Subsequently, in step S9, the control unit 5 calculates the second difference value H2 from the external temperature acquired by the external temperature sensor 56 and the internal temperature acquired by the internal temperature sensor 58, and stores it in the RAM 5C. The control unit 5 when executing step S9 is an example of the second calculation unit 52 of the present invention. Thereby, the control part 5 acquires the information of the heat stress at the time of image formation start.

  In step S10, the control unit 5 takes out the first difference value H1 stored in the EEPROM 5D. The control unit 5 calculates the third difference value H3 by subtracting the second difference value H2 from the first difference value H1. Further, the control unit 5 calculates a revised correction reference density value M3 that is a correction amount based on the third difference value H3 (see FIG. 9) and stores it in the RAM 5C. Thereby, the control unit 5 revises the corrected reference density value M3 for revising the corrected reference density value M2 for correcting the reference density value M1, based on the difference between the thermal stress at the end of image formation and the thermal stress at the start of image formation. Can be obtained.

  Next, in step S11, the control unit 5 acquires a reference concentration value M1 corresponding to the acquired external temperature and external humidity from the reference value table stored in the ROM 5B. Further, in step S12, the control unit 5 acquires a correction reference density value M2 corresponding to the acquired external temperature and external humidity from the correction value table stored in the ROM 5B.

  In step S13, the control unit 5 determines whether or not the third difference value H3 is equal to or greater than a predetermined threshold value R1. If the 3rd difference value H3 is less than threshold value R1, control part 5 will shift processing to Step S15 (NO side of S13). When the value is equal to or greater than the threshold value R1, the control unit 5 moves the process to step S14 (YES side of S13). In step S14, the control unit 5 corrects the correction reference density value M2 based on the revised correction reference density value M3 calculated according to the third difference value H3.

  In step S15, the control unit 5 corrects the reference density value M1 with the acquired corrected reference density value M2 or the revised corrected reference density value M2. In order to use the corrected reference density value M1 as the reference value for the toner supply process, the control unit 5 stores the value in the RAM 5C and ends the process. The control unit 5 when executing Step S10 and Step S15 is an example of the correction unit 53 of the present invention.

[Effect of the embodiment]
As described above, according to the image forming apparatus 100 of the present invention, the density of toner to be supplied to the developing device 34 is adjusted in consideration of the thermal stress at the end of image formation and the thermal stress at the start of image formation. The reference density value M1 can be corrected. For this reason, the control unit 5 causes the developing device 34 to transfer the toner to the developing device 34 based on the reference density value M1 in consideration of the change in the influence of the developer heat at the end of the image formation and the start of the image formation and the change in the temperature characteristic of the toner density sensor 67. Can be replenished. Therefore, the control unit 5 can appropriately maintain the replenishment amount of toner to be replenished to the developing device 34.

[Modification of Embodiment]
In the correction process, the control unit 5 corrects the reference density value M1 by revising the corrected reference density value M2. However, the present invention is not limited to this. The control unit 5 may directly correct the reference density value M1 based on the third difference value H3. Moreover, although the control part 5 demonstrated the case where the reference | standard density | concentration value M1 was correct | amended based on the difference of external temperature and internal temperature, it is not restricted to this case. For example, the image forming apparatus 100 may include an internal humidity sensor that measures internal humidity, and the control unit 5 may correct the reference density value M1 based on the external humidity and the internal humidity. In the description of the correction process, the external temperature and the external humidity at which the image forming apparatus 100 is installed are constant for convenience. However, the present invention is not limited to this. The external temperature and external humidity of the place where the image forming apparatus 100 is installed may vary. In the above description, the control unit 5 performs the correction process based on the toner density in the developing device 34. However, the control unit 5 may perform the correction process based on the magnetic permeability.

  In the correction process, the control unit 5 corrects the reference density value M1 with the revised corrected reference density value M2 when the third difference value H3 is equal to or greater than the threshold value R1, but the present invention is not limited to this. Other conditions are conceivable as conditions for correcting the reference density value M1. For example, when the magnetic permeability indicated by the reference density value M1 corresponding to the external temperature acquired by the external temperature sensor 56 does not match the magnetic permeability acquired by the toner density sensor 67 at the start of image formation. It is conceivable to correct the density value M1 and maintain the reference density value M1 when they coincide. If they match, the change in the temperature environment of the developing device 34 is small from the end of image formation to the start of image formation, and the necessity of correcting the reference density value M1 is low.

  In the description of the embodiment, the case where the developer of the developing device 34 is a two-component developer composed of toner and carrier has been described, but the present invention is not limited to this. It is conceivable that the developer is a one-component developing device. This is because in the case of a one-component developer, the remaining amount of toner and the magnetic permeability have a direct proportional relationship.

  Since the scope of the present disclosure is defined not by the detailed description preceding the description of the claims but by the description of the appended claims, the embodiments described herein are merely exemplary and non-limiting I want to be understood. Therefore, all the changes which do not deviate from a claim, or an equivalent are included in a claim.

100: image forming apparatus 5: control unit 34: developing device 39: toner container 50: toner replenishing unit 51: first calculation unit 52: second calculation unit 53: correction unit 54: first storage unit 55: second storage unit 56: External temperature sensor 57: External humidity sensor 58: Internal temperature sensor 67: Toner density sensor H1: First difference value H2: Second difference value H3: Third difference value R1: Threshold value M1: Reference density value M2: Correction reference Concentration value M3: Revised standard concentration value

Claims (8)

A developer container provided inside the apparatus main body and containing a magnetic developer;
Detection means for detecting the magnetic permeability of the developer contained in the developer container;
Toner replenishing means for controlling toner replenishment to the developing container so that the detection value of the detecting means becomes a reference value indicating a predetermined amount of developer;
First acquisition means for acquiring first information in an external environment of the apparatus main body for changing the magnetic permeability of the developer in the developer container;
Second acquisition means for acquiring second information in the internal environment of the apparatus main body for changing the magnetic permeability of the developer in the developer container;
First calculation means for calculating a first difference value from the first information acquired by the first acquisition means and the second information acquired by the second acquisition means at a predetermined first timing;
The second difference value is calculated from the first information acquired by the first acquisition unit at the second predetermined timing after the first timing and the second information acquired by the second acquisition unit. Second calculating means for
Correction means for correcting the reference value based on the third difference value obtained from the first difference value and the second difference value;
An image forming apparatus comprising:   The image forming apparatus according to claim 1, wherein the correction unit corrects the reference value with a correction amount corresponding to the third difference when the third difference is equal to or greater than a predetermined threshold. A first storage means for storing a plurality of reference values determined in advance according to a plurality of the first information;
The correction unit selects and selects the reference value corresponding to the first information acquired by the first acquisition unit at the second timing from the plurality of reference values stored in the first storage unit. The image forming apparatus according to claim 1, wherein the reference value is corrected based on the third difference value. A second storage means for storing a plurality of correction values for correcting the plurality of reference values corresponding to the plurality of first information;
The correction means selects and selects the correction value corresponding to the first information acquired by the first acquisition means at the second timing from the plurality of correction values stored in the second storage means The image forming apparatus according to claim 1, wherein the reference value is corrected by correcting the correction value based on the third difference value.   The correction unit is configured to detect the reference value when the reference value corresponding to the first information acquired by the first acquisition unit at the second timing does not match the magnetic permeability of the detection unit at the second timing. The image forming apparatus according to claim 1, wherein the reference value is maintained when the values coincide with each other. The first timing is when the image forming operation ends.
The image forming apparatus according to claim 1, wherein the second timing is a time when a next image forming operation is started. The developer includes a toner and a magnetic carrier,
The image forming apparatus according to claim 1, wherein the detection unit acquires a toner concentration of the developer by detecting a magnetic permeability of the developer. The first information is either or both of external temperature and external humidity in the external environment,
The image forming apparatus according to claim 1, wherein the second information is both or either of an internal temperature and an internal humidity in an internal environment.

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