JP2018120098A - Image formation apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect the toner concentration of a developer in the developing device with high accuracy without being affected by temperature and humidity even when the distance between the two-component developer in the developing device and the inductance sensor varies due to the attachment / detachment of the developing device. An image forming apparatus is provided. A developing device having magnetism to be detected provided inside a developing container, and a magnetic permeability detecting unit capable of detecting the magnetic permeability of the developer inside the developing container by applying a control voltage. And a control unit capable of controlling the developing device and the magnetic permeability detecting unit, and the control unit has no developer in the detection range of the magnetic permeability detecting unit after the developing device is mounted on the apparatus main body (step S2). In this state, a predetermined voltage is applied to the magnetic permeability detector (step S3), and the control voltage of the magnetic permeability detector is set based on the result of detecting the magnetic permeability of the detected part (step S4) (step S8). ) Execute the setting mode. [Selection] Figure 9

Description

  The present invention relates to an image forming apparatus that uses a developing device to form an image on a recording material by an electrophotographic method or an electrostatic recording method.

  2. Description of the Related Art Conventionally, when developing an electrostatic latent image formed on an image carrier, a two-component development method using a two-component developer of a nonmagnetic toner and a magnetic carrier has been widely used. The toner concentration of the two-component developer is an important factor in stabilizing the image quality. The toner concentration is a T / D ratio which is a ratio of the weight (T) of the toner to the total weight (D) of the carrier and the toner, or T / D (wt%) which is a weight percentage display. The toner in the two-component developer is consumed during development, and as a result, the T / D ratio changes. Therefore, the automatic toner replenishing device (ATR) detects the T / D ratio at the appropriate time, replenishes the toner according to the change, and keeps the image quality by controlling the T / D ratio constantly. Is done.

  In measuring the toner concentration of the two-component developer, an inductance detection method is widely used particularly in the developing device. In the inductance detection method, an inductance sensor serving as an inductance detection unit that detects an apparent magnetic permeability based on a mixing ratio of a magnetic carrier and a nonmagnetic toner and converts it into an electric signal is installed on a side wall of the developing device. The actual T / D ratio of the developer in the developing device is detected by the detection signal from the inductance sensor, and the toner is replenished by comparison with the reference value.

  In recent years, when the developing device can be detached from the image forming apparatus, an image forming apparatus main body is provided with an inductance sensor so as to reduce the price of the developing device. When the image forming apparatus main body is provided with an inductance sensor, for example, in order to ensure the distance between the detection surface of the detection unit and the two-component developer, the detection surface is brought into contact with the outside of the developing container of the developing device. It is conceivable to provide a reference plane that guarantees the distance. However, if the detection surface is not mounted correctly with respect to the reference surface or there may be deposits between the detection surface and the reference surface, the distance from the detection surface to the two-component developer should be constant. It is very difficult to guarantee. Further, due to the nature of the inductance sensor, a minute shift in the distance between the detection surface and the two-component developer greatly affects the detection accuracy.

  In order to solve this problem, after the developing device is mounted on the apparatus main body, the developer is stirred by the conveying screw, and then applied to the inductance sensor while increasing the control voltage to obtain the detection voltage. Based on the result, A technique for determining detection sensitivity is known (see Patent Document 1). According to this technique, even with the inductance sensor provided in the apparatus main body, the T / D ratio of the developer contained in the detachable developing device can be detected with high accuracy.

JP 2011-154124 A

  However, in the developing device of Patent Document 1 described above, the developer is stirred and then applied to the inductance sensor while increasing the control voltage, the detection voltage is obtained, and the detection sensitivity is determined based on the result. For this reason, for example, when an unused developing device is mounted on the apparatus main body and the developer is discharged from the developer enclosure in the developer container into the developer container, the difference in temperature and humidity inside and outside the developer enclosure The magnetic permeability of the developer may become unstable due to the influence of the above. If the magnetic permeability of the developer becomes unstable, the output of the inductance sensor becomes unstable, and the T / D ratio of the developer cannot be detected with high accuracy.

  In the present invention, even when the distance between the two-component developer in the developing device and the inductance sensor fluctuates due to the attachment / detachment of the developing device, the toner concentration of the developer in the developing device can be accurately adjusted without being affected by temperature and humidity. An object is to provide an image forming apparatus capable of detection.

  An image forming apparatus according to the present invention is provided in an apparatus main body, a developer container that can be attached to and detached from the apparatus main body and contains a nonmagnetic toner and a magnetic carrier, and the developer container. A developing device having magnetism to be detected; a magnetic permeability detecting unit capable of detecting the magnetic permeability of the developer inside the developing container by applying a control voltage; the developing device and the magnetic permeability detecting unit; A control unit that can control the magnetic permeability detection unit in a state in which there is no developer in the detection range of the magnetic permeability detection unit after the development device is mounted on the apparatus main body. A setting mode for setting the control voltage of the magnetic permeability detecting unit is executed based on a result of detecting a magnetic permeability of the detected portion by applying a predetermined voltage.

  According to the present invention, the control unit, based on the result of detecting the permeability of the detected part by applying a predetermined voltage to the permeability detecting part in a state where there is no developer in the detection range of the permeability detecting part, A setting mode for setting the control voltage of the magnetic permeability detector is executed. For this reason, even when the unused developer is not affected by the temperature and humidity in the developing device, and the distance between the two-component developer and the inductance sensor in the developing device varies depending on the attachment / detachment of the developing device, the developing device The toner density of the developer inside can be detected with high accuracy.

1 is a cross-sectional view illustrating a schematic configuration of an image forming apparatus according to an embodiment. FIG. 3 is a control block diagram of the image forming apparatus according to the embodiment. 1 is a cross-sectional view illustrating a schematic configuration of a developing device according to an embodiment. It is sectional drawing of planar view which shows the developing device which concerns on embodiment. It is sectional drawing of the side view which shows the developing device which concerns on embodiment. It is a graph which shows the relationship between the control voltage and output voltage in the inductance sensor which concerns on embodiment. It is a graph which shows the relationship between the absolute moisture content of the developer and output voltage in the inductance sensor which concerns on embodiment. It is a graph which shows the relationship between the sensor gap and output voltage in the inductance sensor which concerns on embodiment. It is a flowchart which shows the procedure which sets the control voltage of the inductance sensor which concerns on embodiment.

  Hereinafter, a developing device according to an embodiment of the present invention will be described in detail with reference to FIGS. In the present embodiment, a case where the developing device is applied to a tandem type full-color printer as an example of an image forming apparatus is described. However, the present invention is not limited to a developing device of a tandem type image forming apparatus, and may be a developing device of an image forming apparatus of another type, and is not limited to a full color, and is monochrome or mono color. There may be. Alternatively, it can be implemented in various applications such as a printer, various printing machines, a copying machine, a FAX, and a multifunction machine by adding necessary equipment, equipment, and a housing structure. In the present exemplary embodiment, the image forming apparatus 1 includes the intermediate transfer belt 44b. After the primary transfer of the toner images of each color from the photosensitive drum 81 to the intermediate transfer belt 44b, the composite toner image of each color is applied to the sheet S. It is a system that performs secondary transfer in a batch. However, the present invention is not limited to this, and a method of directly transferring from the photosensitive drum to the sheet conveyed by the sheet conveying belt may be employed.

  In this embodiment, a two-component developer that is a mixture of a nonmagnetic toner and a magnetic carrier is used as the developer. The toner includes colored resin particles containing a binder resin, a colorant, and other additives as necessary, and colored particles to which an external additive such as colloidal silica fine powder is externally added. Yes. The toner is a negatively chargeable polyester resin, and in this embodiment, the volume average particle diameter is 7.0 μm. The carrier is produced by applying a resin coat to the surface layer of the core made of resin particles kneaded with ferrite particles and magnetic powder. As the carrier, for example, metal such as surface-oxidized or non-oxidized iron, nickel, cobalt, manganese, chromium, rare earth, alloys thereof, or oxide ferrite can be suitably used, and a method for producing these magnetic particles Is not particularly limited. In this embodiment, a carrier having a volume average particle diameter of 45 μm and having oxide ferrite as a core is used. The developer mixing ratio in this embodiment is 10% in terms of the total weight ratio of toner. However, it is needless to say that the present invention is not limited to these.

  As shown in FIG. 1, the image forming apparatus 1 includes an image forming apparatus main body (hereinafter referred to as an apparatus main body) 10 as a housing. The apparatus main body 10 includes a sheet feeding unit 30, an image forming unit 40, a sheet conveying unit 15, a sheet discharging unit 11, and a control unit 70. Note that the sheet S as a recording material is formed with a toner image, and specific examples include plain paper, a resin sheet as a substitute for plain paper, cardboard, and an overhead projector sheet. The apparatus main body 10 is provided with a temperature / humidity sensor (environment information detection unit) 12, an inductance sensor (magnetic permeability detection unit) 26, a drive source 29 of the developing device 20, and the like (see FIG. 2). The temperature / humidity sensor 12 can detect temperature / humidity as environmental information inside the apparatus main body 10.

  The sheet feeding unit 30 is disposed in the lower part of the apparatus main body 10, and includes a sheet cassette 31 that stacks and stores sheets S such as recording paper and a feeding roller 32, and the stored sheets S are imaged. Feed to the forming unit 40.

  The image forming unit 40 includes an image forming unit 80, a toner bottle 41, a toner container 42, a laser scanner 43, an intermediate transfer unit 44, a secondary transfer unit 45, and a fixing device 46. The image forming unit 40 can form an image on the sheet S based on the image information. The image forming apparatus 1 according to the present embodiment is compatible with full color, and the image forming units 80y, 80m, 80c, and 80k are yellow (y), magenta (m), cyan (c), black ( Each of the four colors k) is provided separately with the same configuration. Similarly, the toner bottles 41y, 41m, 41c, and 41k and the toner containers 42y, 42m, 42c, and 42k have the same configuration for each of the four colors of yellow (y), magenta (m), cyan (c), and black (k). Are provided separately. For this reason, in FIG. 1, each component of four colors is shown with a color identifier after the same symbol, but in the specification, it may be described only with a symbol without adding a color identifier.

  The toner container 42 is, for example, a cylindrical bottle. The toner container 42 contains toner, and is connected and disposed above each image forming unit 80 via the toner bottle 41. The laser scanner 43 exposes the surface of the photosensitive drum 81 charged by the charging roller 82 to form an electrostatic latent image on the surface of the photosensitive drum 81.

  The image forming unit 80 includes four image forming units 80y, 80m, 80c, and 80k for forming toner images of four colors. Each image forming unit 80 includes a photosensitive drum 81 for forming a toner image, a charging roller 82, a developing device 20, and a cleaning blade (not shown). Further, the photosensitive drum 81, the charging roller 82, the developing device 20, and the developing sleeve 24 described later are also provided in four colors of yellow (y), magenta (m), cyan (c), and black (k), respectively. They are provided separately in the same configuration.

  The photosensitive drum 81 has a photosensitive layer formed on the outer peripheral surface of the aluminum cylinder so as to have a negative polarity, and rotates in a direction indicated by an arrow at a predetermined process speed (peripheral speed). The charging roller 82 contacts the surface of the photosensitive drum 81 and charges the surface of the photosensitive drum 81 to, for example, a uniform negative-polarity dark portion potential. On the surface of the photosensitive drum 81, after charging, an electrostatic image is formed by the laser scanner 43 based on the image information. The photosensitive drum 81 carries the formed electrostatic image, moves around, and is developed with toner by the developing device 20. The detailed configuration of the developing device 20 will be described later. The developed toner image is primarily transferred to an intermediate transfer belt 44b described later. The surface of the photosensitive drum 81 after the primary transfer is neutralized by a pre-exposure unit (not shown).

  The intermediate transfer unit 44 is disposed above the image forming units 80y, 80m, 80c, and 80k. The intermediate transfer unit 44 includes a plurality of rollers such as a driving roller 44a and primary transfer rollers 44y, 44m, 44c, and 44k, and an intermediate transfer belt 44b wound around these rollers. The primary transfer rollers 44y, 44m, 44c, and 44k are disposed to face the photosensitive drums 81y, 81m, 81c, and 81k, respectively, and contact the intermediate transfer belt 44b.

  By applying a positive transfer bias to the intermediate transfer belt 44b via the primary transfer rollers 44y, 44m, 44c, and 44k, toner images having respective negative polarities on the photosensitive drums 81y, 81m, 81c, and 81k. Are successively transferred onto the intermediate transfer belt 44b. Thus, the intermediate transfer belt 44b moves by transferring the toner image obtained by developing the electrostatic image on the surface of the photosensitive drums 81y, 81m, 81c, 81k.

  The secondary transfer unit 45 includes a secondary transfer inner roller 45a and a secondary transfer outer roller 45b. A full color image formed on the intermediate transfer belt 44b is transferred to the sheet S by applying a positive secondary transfer bias to the secondary transfer outer roller 45b. The fixing device 46 includes a fixing roller 46a and a pressure roller 46b. When the sheet S is nipped and conveyed between the fixing roller 46a and the pressure roller 46b, the toner image transferred to the sheet S is heated and pressurized and fixed to the sheet S.

  The sheet conveying unit 15 conveys the sheet S fed from the sheet feeding unit 30 from the image forming unit 40 to the sheet discharging unit 11. The sheet discharge unit 11 is a face-down tray, and stacks sheets S discharged in the arrow X direction from the discharge port 10a.

  As shown in FIG. 2, the control unit 70 is configured by a computer. For example, the CPU 71, a ROM 72 that stores a program for controlling each unit, a RAM 73 that temporarily stores data, and an input / output that inputs and outputs signals to and from the outside. Circuit (I / F) 74. The CPU 71 is a microprocessor that controls the entire control of the image forming apparatus 1 and is the main body of the system controller. The CPU 71 is connected to the sheet feeding unit 30, the image forming unit 40, the sheet conveying unit 15, and the operation unit via the input / output circuit 74, and exchanges signals with each unit and controls the operation. Connected to the control unit 70 are a temperature / humidity sensor 12, an inductance sensor 26 described later, a drive source 29 of the developing device 20, an unused detection sensor 75, and the like. The control unit 70 can control the developing device 20, the inductance sensor 26, and the like.

  After the developing device 20 is mounted on the apparatus main body 10, the control unit 70 executes the setting mode in a state where there is no developer in the detection range of the inductance sensor 26. In the setting mode, the control unit 70 sets the control voltage of the inductance sensor 26 based on the result of detecting the magnetic permeability of the shaft portion 23a of the second conveying screw 23 by applying a predetermined voltage to the inductance sensor 26. The control unit 70 executes the setting mode while the second transport screw 23 is stopped. The control unit 70 controls the inductance sensor 26 based on the result of detecting the magnetic permeability of the shaft portion 23a of the second conveying screw 23 and the result of detecting the temperature and humidity of the temperature and humidity sensor 12 in the setting mode. Set the voltage. Further, after the developing device 20 is mounted on the apparatus main body 10, the control unit 70 applies a predetermined voltage higher than the control voltage to the inductance sensor 26 in a state where there is no developer in the detection range of the inductance sensor 26, and A value related to the magnetic permeability of the conveying screw 23 is detected.

  Next, an image forming operation in the image forming apparatus 1 configured as described above will be described. When the image forming operation is started, first, the photosensitive drum 81 is rotated and the surface is charged by the charging roller 82. Then, laser light is emitted from the laser scanner 43 to the photosensitive drum 81 based on the image information, and an electrostatic latent image is formed on the surface of the photosensitive drum 81. When toner adheres to the electrostatic latent image, it is developed and visualized as a toner image, and transferred to the intermediate transfer belt 44b.

  On the other hand, the feeding roller 32 rotates in parallel with the toner image forming operation and feeds the uppermost sheet S of the sheet cassette 31 while separating it. Then, the sheet S is conveyed to the secondary transfer unit 45 in synchronization with the toner image on the intermediate transfer belt 44b. Further, the image is transferred from the intermediate transfer belt 44b to the sheet S, and the sheet S is conveyed to the fixing device 46, where the unfixed toner image is heated and pressed to be fixed on the surface of the sheet S, and the discharge port 10a. Are stacked on the sheet discharge unit 11.

  Next, the developing device 20 will be described in detail based on FIG. 3, FIG. 4, and FIG. The developing device 20 is attachable to and detachable from the apparatus main body 10, and includes a developing container 21 that contains a developer, a first conveying screw 22, a second conveying screw (detected portion) 23, a developing sleeve 24, and a regulation sleeve. A blade 25 and an inductance sensor 26 are provided. The developing device 20 develops the electrostatic image formed on the photosensitive drum 81. The developing container 21 has an opening 21 a through which the developing sleeve 24 is exposed at a position facing the photosensitive drum 81.

  The developing container 21 has a partition wall 27 extending in the longitudinal direction at a substantially central portion. The developing container 21 is partitioned by the partition wall 27 into a developing chamber 21b and a stirring chamber 21c in the horizontal direction. The developer is accommodated in the developing chamber 21b and the stirring chamber 21c. The developing chamber 21 b supplies developer to the developing sleeve 24. The stirring chamber 21c communicates with the developing chamber 21b, collects the developer from the developing sleeve 24, and stirs it. In the partition wall 27 between the developing chamber 21b and the stirring chamber 21c, two connecting portions 27a and 27b are formed at both ends so that the developing chamber 21b and the stirring chamber 21c communicate with each other. In the developing device 20 of the present embodiment, the developing chamber 21b and the stirring chamber 21c are arranged in the horizontal direction, but the present invention is not limited to this, and the developing chamber and the stirring chamber are arranged vertically. Alternatively, another form of developing device may be used.

  The first conveying screw 22 is disposed in the developing chamber 21b along the axial direction of the developing sleeve 24 and substantially parallel to the developing sleeve 24, and conveys the developer in the developing chamber 21b while stirring. The first conveying screw 22 is rotatably provided in the developing container 21 and rotates integrally with the shaft part 22a having magnetism and the shaft part 22a, and conveys the developer inside the developing container 21 in the conveying direction D1 by rotation. And a spiral conveying blade 22b.

  The second transport screw 23 is disposed in the stirring chamber 21 c substantially parallel to the axis of the first transport screw 22, and transports the developer in the stirring chamber 21 c in the opposite direction to the first transport screw 22. The second conveying screw 23 is rotatably provided in the developing container 21 and rotates integrally with the shaft part (rotating shaft) 23a having magnetism and the shaft part 23a, and the developer in the developing container 21 is rotated in the conveying direction D1. And a spiral non-magnetic conveying blade (blade) 23b. The developing chamber 21b and the stirring chamber 21c constitute a developer circulation path for transporting the developer while stirring. Each of the screws 22 and 23 conveys the developer in a direction opposite to each other, and conveys the developer in a direction opposite to each other at a position opposite to the screws 22 and 23. When the toner is agitated by the screws 22 and 23, the toner is rubbed with the carrier and is triboelectrically charged to a negative polarity. That is, each of the screws 22 and 23 can stir and convey the developer stored in the developing container 21.

  In the present embodiment, the first conveying screw 22 has a screw structure in which a conveying blade 22b made of a nonmagnetic material is provided in a spiral shape around a shaft portion 22a, and the screw diameter is 20 mm in diameter and the screw pitch. Is 20 mm, and the rotational speed is set to 400 rpm. The 2nd conveyance screw 23 is also a screw structure which provided the conveyance blade 23b comprised with the nonmagnetic material around the axial part 23a in spiral shape. The screw diameter of the second conveying screw 23 is 20 mm, the screw pitch is 30 mm on the side where the replenishing port 28 is disposed, and the pitch on the side where the replenishing port 28 is not disposed is 20 mm. The transportability of the installed one is increased. The rotation speed is set to 400 rpm.

  In the stirring chamber 21c, a replenishing port 28 opened upward is formed at the upstream end of the developer conveying direction D1, and a toner bottle 41 (see FIG. 1) is connected to the replenishing port 28. The toner bottle 41 contains a two-component developer for replenishment in which toner and a carrier are mixed (usually toner / replenishment developer = 100% to 80%). The toner supplied from the toner bottle 41 is supplied from the supply port 28 to the stirring chamber 21c.

  The developing sleeve 24 carries a developer having non-magnetic toner and a magnetic carrier, and rotates and conveys the developer to a developing region facing the photosensitive drum 81. The developing sleeve 24 is made of a nonmagnetic material such as aluminum or nonmagnetic stainless steel, and is made of aluminum having a diameter of 20 mm in the present embodiment. Inside the developing sleeve 24, a roller-shaped magnet roller 24m is fixedly installed in a non-rotating state with respect to the developing container 21. The magnet roller 24m has a developing magnetic pole S2 and magnetic poles N1, S1, N2, and N3 that convey the developer. Among these, the N3 pole and the N1 pole, which are the same poles, are installed adjacent to each other on the inner side of the developing container 21, and a repulsive magnetic field is formed between the poles, so that the developer is separated from the surface of the developing sleeve 24. The developer thus peeled off is collected in the developing chamber 21b.

  The developer in the developing device 20 is carried on the developing sleeve 24 by the magnet roller 24m. Thereafter, the layer thickness of the developer on the developing sleeve 24 is regulated by the regulating blade 25, and the developer sleeve 24 is transported to the developing area facing the photosensitive drum 81 as the developing sleeve 24 rotates. In the development area, the developer on the developing sleeve 24 spikes to form a magnetic spike. By bringing the magnetic spike into contact with the photosensitive drum 81, the toner is supplied to the photosensitive drum 81, whereby the electrostatic latent image on the photosensitive drum 81 is developed as a toner image.

The regulating blade 25 is composed of a nonmagnetic member made of plate-like aluminum or the like extending along the longitudinal axis of the developing sleeve 24, and is disposed upstream of the developing region in the rotational direction of the developing sleeve 24. ing. Then, both the toner of the developer and the carrier pass between the tip of the regulating blade 25 and the developing sleeve 24 and are sent to the developing area. By adjusting the gap (gap) between the regulating blade 25 and the surface of the developing sleeve 24, the amount of spike of the developer magnetic brush carried on the developing sleeve 24 is regulated, and the development conveyed to the developing region. The dosage is adjusted. In the present embodiment, the amount of developer coat per unit area on the developing sleeve 24 is regulated to 30 mg / cm ² by the regulating blade 25.

  As shown in FIGS. 3 and 5, a developer enclosure 50 is provided inside the developing container 21 and above the stirring chamber 21 c. The developer enclosure 50 contains a two-component developer D in which a magnetic carrier and nonmagnetic toner are mixed at a predetermined ratio as a start agent (initial developer). An opening 51 is formed in the bottom of the developer enclosure 50 over almost the entire length thereof, and a seal member (sealing means) 52 is provided below the developer enclosure 50 so as to close the opening 51. Is pasted. That is, the developer enclosure 50 has an opening 51 opened in the developer container 21 and can enclose the developer D before use. Further, the seal member 52 encapsulates the developer D in the developer enclosure 50 by sealing the opening 51. One edge portion along the longitudinal direction of the seal member 52 is attached to a winding member (removal portion) 53. The winding member 53 can remove the seal member 52 from the opening 51. When the winding member 53 winds up the seal member 52 by rotational driving, the opening 51 is opened, and the developer D inside the developer enclosure 50 is filled into the stirring chamber 21 c through the opening 51.

  As the sealing member 52, a polyester film, a nylon film, a polyethylene film, a polypropylene film, a laminate product thereof, a laminate product of a polyester film and an aluminum foil, or the like is preferably used. In the present embodiment, a laminate of a polyester film, a nylon film, and a polyethylene film is used as the seal member 52. As a method for attaching the seal member 52, there are thermal welding, adhesion, and the like. In this embodiment, thermal welding is employed. In the present embodiment, the developing sleeve 24, the first conveying screw 22, the second conveying screw 23, the winding member 53, and the like of the developing device 20 are driven by a drive source 29 (FIG. 2) controlled by the control unit 70. Drive). The developing device 20 includes a memory (not shown). The apparatus main body 10 is provided with an unused detection sensor (unused detection unit) 75 that can be connected to the memory of the developing device 20 and read information (see FIG. 2). The unused detection sensor 75 can detect whether the developing device 20 is unused or has been used by reading information from the developing device 20 attached to the apparatus main body 10.

  The inductance sensor 26 is provided in the apparatus main body 10, abuts on the side surface of the developing container 21 attached to the apparatus main body 10, and is attached to the shaft portion 23 a of the second transport screw 23 via the side wall of the developing container 21. Opposed to each other. The inductance sensor 26 is connected to the control unit 70, detects the toner concentration of the developer conveyed in the stirring chamber 21 c, and transmits an electric signal to the control unit 70. The development of the electrostatic latent image on the photosensitive drum 81 reduces the toner density of the developer in the developing device 20, so that the inductance sensor 26 provided facing the developer in the stirring chamber 21c causes the stirring chamber 21c to The toner density of developer D is detected. The inductance sensor 26 can detect the magnetic permeability of the developer inside the developing container 21 by applying a control voltage. The control unit 70 can perform automatic toner supply control (ATR) using the inductance sensor 26. Thus, the control unit 70 agitates and conveys the toner supplied from the replenishing port 28 and the developer in the agitating chamber 21c by the second conveying screw 23, and the toner concentration of the developer D is made constant. I have control.

  Here, detection of the T / D ratio by the inductance sensor 26 will be described. Since the two-component developer contains a magnetic carrier and a non-magnetic toner as main components, when the T / D ratio of the developer D changes, the apparent permeability due to the mixing ratio of the carrier and the toner changes. Therefore, if the apparent permeability is detected by the inductance sensor 26, an output signal corresponding to the T / D ratio can be obtained from the inductance sensor 26.

  FIG. 6 shows the relationship between the input voltage (control voltage) and the output voltage for a developer having a T / D ratio of 8% in a standard environment of 23 ° C. and 60% RH in the inductance sensor 26 applied in this embodiment. . As shown in FIG. 6, the rate of change of the output voltage is greatest around the control voltage of 12.5V. Therefore, in the present embodiment, the control voltage of the inductance sensor 26 under the standard environment is 12.5V, and the output voltage 2.5V at that time is the standard output voltage. The output voltage (V) of the inductance sensor 26 changes substantially linearly according to the T / D ratio.

  By the way, since the output voltage of the inductance sensor 26 changes when the apparent permeability of the developer changes, the output voltage changes when the temperature and humidity of the environment change and the state of the developer changes. In a low-temperature and low-humidity environment, the amount of water contained in the developer is reduced, and the toner charge due to friction between the toner and the carrier is increased, resulting in greater repulsion between the developers, which reduces the bulk density of the developer. The output value becomes smaller. On the other hand, in a high temperature and high humidity environment, the amount of water contained in the developer increases, and the toner charge due to friction between the toner and the carrier decreases. The bulk density increases and the output value increases.

  FIG. 7 shows the relationship between the absolute water content of the environment and the output voltage when a constant control voltage of 12.5 V is input to the inductance sensor 26 for the developer having a T / D ratio of 8%. It can be seen that as the absolute moisture content of the environment increases, the output voltage increases as described above. It is also possible to change the control voltage so that the constant output voltage is 2.5V. That is, when the absolute moisture content of the environment is small, the control voltage is set higher than the standard control voltage of 12.5 V under the standard environment. Conversely, when the absolute moisture content is large, the output voltage is reduced by reducing the control voltage. It can be kept constant at 2.5V.

  FIG. 8 shows the relationship between the sensor gap and the output voltage when the T / D ratio of the two-component developer is constant and the control voltage applied to the inductance sensor 26 is constant. As shown in FIG. 8, it can be seen that the output voltage of the inductance sensor 26 changes greatly even if the sensor gap changes by several tens of micrometers. Further, the detection sensitivity of the inductance sensor 26 also depends on the sensor gap, and when the sensor gap widens, the detection sensitivity of the inductance sensor 26 decreases.

  As described above, the cause of the change in the relationship between the control voltage and the output voltage of the inductance sensor 26 is the change in the temperature and humidity inside the apparatus main body 10 and the positional relationship between the developing container 21 and the inductance sensor 26 due to the replacement of the developing container 21. There is. Further, when there is a difference between the temperature and humidity inside the developer enclosure 50 and the temperature and humidity of the developer container 21, it takes time for the developer D to reach the temperature and humidity inside the developer container 21. It takes a long time to realize. Therefore, in the present embodiment, as the correction control of the inductance sensor 26 when the developing container 21 is replaced, not the magnetic permeability of the developer D but the magnetic permeability of the shaft portion 23a of the transport screw 23 is detected. Thereby, the unused developer D is not affected by the temperature and humidity inside the developing device 20. Even when the distance between the two-component developer inside the developing device 20 and the inductance sensor 26 varies due to the attachment / detachment of the developing device 20, the toner concentration of the developer inside the developing device 20 can be detected with high accuracy.

  Next, a sequence when the developing device 20 or a process cartridge equipped with the developing device 20 is mounted on the apparatus main body 10 and used (sequence during initial installation) will be described with reference to the flowchart of FIG. When the image forming apparatus 1 is turned on (step S1), the control unit 70 determines whether or not the developing device 20 attached to the apparatus main body 10 is an unused product (step S2). This is determined based on the controller 70 reading product information relating to the developing device 20 stored in advance in a memory (not shown) provided in the developing device 20. When the control unit 70 determines that the developing device 20 is not an unused product, the control unit 70 shifts to a normal operation without executing the setting mode. At this time, the drive source 29 is not operating and the screws 22 and 23 are stopped.

  When the control unit 70 determines that the developing device 20 is an unused product, the memory of the developing device 20 is rewritten after use of the developing device 20, recorded as a used product, and the setting mode is executed. Further, the controller 70 executes the setting mode before the winding member 53 starts removing the seal member 52 from the opening 51 (see step S9). At this time, in the stirring chamber 21c, the developer is not stirred, and there is no developer in the detection range of the inductance sensor 26, and the inductance sensor 26 detects the magnetic permeability of the shaft portion 23a that is a magnetic body. . For this reason, the control unit 70 applies a predetermined voltage, for example, 24 V as the position correction voltage to the inductance sensor 26, and detects the output voltage (step S3). That is, in order to detect the magnetic permeability of the shaft portion 23a located farther than the magnetic permeability of the developer near the inductance sensor 26 at normal times, the predetermined voltage applied here is a voltage higher than the normal control voltage. Value. Further, after the developing device 20 is mounted on the apparatus main body 10, the control unit 70 applies a predetermined voltage higher than the control voltage to the inductance sensor 26 in a state where there is no developer in the detection range of the inductance sensor 26, and A value related to the magnetic permeability of the conveying screw 23 is detected.

  The controller 70 detects the output voltage of the inductance sensor 26 (step S4). The control unit 70 calculates a first control voltage V1 of the control voltage based on the detected output voltage (step S5). That is, the first control voltage V1 is a control voltage corrected based on the distance between the developing container 21 and the inductance sensor 26.

  Next, the control unit 70 detects the temperature and humidity inside the apparatus main body 10 using the temperature and humidity sensor 12 (step S6). The control unit 70 calculates a second control voltage V2 of the control voltage based on the detected temperature and humidity (step S7). That is, the second control voltage V2 is a control voltage corrected based on the absolute moisture amount according to the detected temperature and humidity. The calculation of the second control voltage V2 is performed based on a table of temperature and humidity stored in advance in the control unit 70 and the second control voltage V2. Then, the control voltage to the inductance sensor 26 is set in consideration of these control voltages V1 and V2 (step S8).

  After setting the control voltage, the control unit 70 drives the developing device 20, winds up the seal member 52 by the winding member 53, and puts the developer D into the stirring chamber 21c from the developer sealing unit 50 (step S9). ). The controller 70 agitates the developer with the screws 22 and 23, and detects the toner density with the inductance sensor 26 after 30 seconds have elapsed (step S10). In the present embodiment, the control unit 70 inputs the output value Vs of the inductance sensor 26 to the comparator, compares it with the standard output voltage value Vr ahead of the reference concentration value by the comparator, and detects the difference between the detected signal values. It is determined whether (Vs−Vr) / Vr is 5% or less (step S11). When the controller 70 determines that the detection signal difference is 5% or less, the controller 70 stops driving the developing device 20 and ends the setting mode. In this case, even if the environment in which the apparatus main body 10 is installed differs from the environment in which the developer D is familiar, the developer D is installed in the apparatus main body 10 by focusing on the values calculated from the table. Judged to be familiar with the environment. On the other hand, when the control unit 70 determines that the detection signal difference is not 5% or less, the control unit 70 further continues stirring (step S10).

  As described above, according to the developing device 20 of the present embodiment, the control unit 70 executes the setting mode with no developer in the detection range of the inductance sensor 26. In this setting mode, the control voltage of the inductance sensor 26 is set based on the result of detecting the magnetic permeability of the shaft portion 23a by applying a predetermined voltage to the inductance sensor 26. Therefore, the unused developer is not affected by the temperature and humidity inside the developing device 20, and the distance between the two-component developer of the developing device 20 and the inductance sensor 26 varies depending on the attachment / detachment of the developing device 20. However, the toner density of the developer of the developing device 20 can be detected with high accuracy.

  Further, according to the developing device 20 of the present embodiment, the first control voltage V1 corrected based on the distance between the developing container 21 and the inductance sensor 26, and the second control corrected based on the detected temperature and humidity. The control voltage is set based on the two control voltages of the voltage V2. For this reason, since not only the sensor gap but also the temperature and humidity are taken into account, the control voltage can be set with higher accuracy.

  In the developing device 20 of the above-described embodiment, the case where the control voltage is set based on the two control voltages of the first control voltage V1 and the second control voltage V2 has been described, but the present invention is not limited to this. . For example, the second control voltage V2 corrected based on the detected temperature and humidity does not necessarily have to be referred to. In this case, for example, steps S6 to S8 can be omitted in the flowchart shown in FIG.

DESCRIPTION OF SYMBOLS 1 ... Image forming apparatus, 10 ... Apparatus main body, 12 ... Temperature / humidity sensor (environment information detection part), 20 ... Developing apparatus, 21 ... Developing container, 23 ... 2nd conveyance screw (stirring means, to-be-detected part) 23a ... Shaft portion (rotating shaft), 23b ... Conveying blade (blade), 26 ... Inductance sensor (permeability detecting portion), 50 ... Developer enclosing portion, 51 ... Opening, 52 ... Seal member (sealing means), 53 ... Winding Take-off member (removal part), 70 ... control part, 75 ... unused detection sensor (unused detection part).

Claims (9)

The device body;
A developing device that can be attached to and detached from the apparatus main body and that contains a developer container containing a non-magnetic toner and a magnetic carrier, and a magnetic detection target provided inside the developer container. When,
A magnetic permeability detector capable of detecting the magnetic permeability of the developer inside the developer container by applying a control voltage;
A control unit capable of controlling the developing device and the magnetic permeability detection unit,
The controller is configured to apply a predetermined voltage to the magnetic permeability detector in a state where there is no developer in the detection range of the magnetic permeability detector after the developing device is mounted on the apparatus main body. Based on the result of detecting the magnetic permeability, a setting mode for setting the control voltage of the magnetic permeability detector is executed.
An image forming apparatus. The detected portion is a stirring means having a rotating shaft having magnetism and a nonmagnetic blade provided on the rotating shaft and capable of stirring and transporting the developer stored in the developing container.
The image forming apparatus according to claim 1. The control unit executes the setting mode while the stirring unit is stopped.
The image forming apparatus according to claim 2. The predetermined voltage is greater than the control voltage;
The image forming apparatus according to claim 1, wherein the image forming apparatus is an image forming apparatus. An unused detector that can detect that the developing device mounted on the apparatus body is unused,
The control unit executes the setting mode when the developing device is unused.
The image forming apparatus according to claim 1, wherein the image forming apparatus is an image forming apparatus. The magnetic permeability detector is provided in the apparatus main body.
The image forming apparatus according to claim 1, wherein the image forming apparatus is an image forming apparatus. An environmental information detection unit capable of detecting environmental information inside the apparatus body,
The control unit is configured to control the control voltage of the magnetic permeability detection unit based on a result of detecting the magnetic permeability of the detected unit and a result of detecting environmental information of the environmental information detection unit in the setting mode. Set
The image forming apparatus according to claim 1, wherein the image forming apparatus is an image forming apparatus. The developing device has an opening opened inside the developer container and can enclose a developer before use, and enclose the developer in the developer enclosure by sealing the opening. Sealing means to be removed, and a removing portion capable of removing the sealing means from the opening,
The control unit executes the setting mode before the removal unit starts removing the sealing means from the opening.
The image forming apparatus according to claim 1, wherein the image forming apparatus is an image forming apparatus. The device body;
A developer container that is detachable from the apparatus main body and contains a developer containing a non-magnetic toner and a magnetic carrier, and is provided inside the developer container and is provided on the magnetic rotating shaft and the rotating shaft. A developing device having a nonmagnetic blade and stirring means capable of stirring and transporting the developer contained in the developer container;
A magnetic permeability detector capable of detecting the magnetic permeability of the developer inside the developer container by applying a control voltage;
A control unit capable of controlling the developing device and the magnetic permeability detection unit,
The control unit applies a predetermined voltage higher than the control voltage to the magnetic permeability detection unit in a state where there is no developer in the detection range of the magnetic permeability detection unit after the developing device is attached to the apparatus main body. Detecting a value related to the magnetic permeability of the rotating shaft;
An image forming apparatus.

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