JP2019117251A - Image forming apparatus - Google Patents

Abstract

To obtain an image forming apparatus including a toner concentration sensor that can be used in common for a model of a developing device with a different structure.SOLUTION: Developing devices 3a to 3d each stir a two-component developer with stirring screws 12 and includes a scraper 16. A toner concentration sensor 15 is installed on each of the developing devices 3a to 3d corresponding to a position of the scraper 16 and detects the concentration of toner in the two-component developer. The toner concentration sensor 15 includes (a) a coil 20 that has a planar shape and a spiral shape, and (b) a sensor signal output circuit 22 that outputs a sensor signal according to an inductance caused by a part or all of the coil 20 between two positions, out of at least three positions on the coil 20, for matching at least one of an electrical inner diameter and an electrical outer diameter of the coil with the scraper 16.SELECTED DRAWING: Figure 4

Description

  The present invention relates to an image forming apparatus.

  One image forming apparatus uses a toner concentration sensor to measure the toner concentration (that is, the ratio of magnetic carrier to nonmagnetic toner) of the two-component developer in the developing device. While the stirring screw which stirs an agent is provided, the scraper which scrapes off the developing agent on the developing device inner wall corresponding to the installation position of a toner concentration sensor is provided (for example, refer to patent documents 1).

JP, 2017-122842, A

  The toner concentration sensor includes a coil, and the inductance of the coil changes according to the toner concentration (here, the ratio of magnetic carrier to nonmagnetic toner, that is, the T / C ratio), and the frequency of the output signal of the toner concentration sensor Changes. Therefore, the toner concentration is specified based on the frequency of the output signal.

  In the above-mentioned developing device, although the developer at the measurement position of the toner concentration sensor is stirred by the scraper, a stagnant layer of the developer is formed in the clearance range between the stirring screw and the developing device inner wall at a location without the scraper. There is something to be done. The stagnant layer is unlikely to be stirred by the stirring screw, and may have a toner concentration different from the current toner concentration stirred by the stirring screw. Therefore, the measurement error of the toner concentration sensor may occur due to the developer in the portion without the scraper. Further, the sensitivity of the toner concentration sensor changes depending on the structure of the developing device (that is, the material and shape of the scraper, stirring screw, inner wall, etc.).

  Therefore, since the structure of the developing device differs depending on the model, it is necessary to use a toner density sensor designed for each model to reduce the measurement error due to the developer in the area without scraper, and to make the sensitivity appropriate. There is.

  The present invention has been made in view of the above problems, and it is an object of the present invention to obtain an image forming apparatus provided with a toner density sensor that can be commonly used even with models having different developing device structures.

  The image forming apparatus according to the present invention is installed in the developing device corresponding to the position of the scraper and the developing device provided with the scraper while stirring the two-component developer with a stirring screw, and the toner of the two-component developer And a toner concentration sensor for detecting the concentration. The toner concentration sensor may include (a) a flat and spiral coil, and (b) at least one of an electrical inner diameter and an outer diameter of the coil at least three positions on the coil. And a sensor signal output circuit that outputs a sensor signal according to an inductance of a part or all of the coil between two positions for making the scraper correspond.

  According to the present invention, it is possible to obtain an image forming apparatus provided with a toner density sensor that can be commonly used even with models having different developing device structures.

  The above or other objects, features and advantages of the present invention will become more apparent from the following detailed description in conjunction with the accompanying drawings.

FIG. 1 is a side view showing a mechanical internal configuration of an image forming apparatus according to an embodiment of the present invention. FIG. 2 is a cross-sectional view showing an example of the developing device 3a in FIG. FIG. 3 is a view for explaining the arrangement position of the toner concentration sensor 15 in FIG. FIG. 4 is a circuit diagram showing an electrical configuration of the toner concentration sensor 15 in FIG. 2 and FIG.

  Hereinafter, embodiments of the present invention will be described based on the drawings.

  FIG. 1 is a side view showing a mechanical internal configuration of an image forming apparatus according to an embodiment of the present invention. The image forming apparatus is an apparatus having an electrophotographic printing function, such as a printer, a facsimile machine, a copier, a multifunction machine, and the like.

  The image forming apparatus of this embodiment has a tandem type color developing device. This color developing device has photosensitive drums 1a to 1d, an exposure device 2, and developing devices 3a to 3d. The photoreceptor drums 1a to 1d are photoreceptors of four colors of cyan, magenta, yellow and black, and electrostatic latent images are formed on the photoreceptor drums 1a to 1d. The exposure device 2 is a device that applies laser light to the photosensitive drums 1 a to 1 d to form an electrostatic latent image. The exposure device 2 has a laser diode which is a light source of laser light, and an optical element (a lens, a mirror, a polygon mirror, etc.) for guiding the laser light to the photosensitive drums 1a to 1d.

  The developing devices 3a to 3d cause the toner in the toner cartridge to adhere to the electrostatic latent images on the photosensitive drums 1a to 1d to form a toner image. The photosensitive drum 1a and the developing device 3a develop magenta, the photosensitive drum 1b and the developing device 3b develop cyan, and the photosensitive drum 1c and the developing device 3c develop yellow. The black development is performed by the photosensitive drum 1d and the developing device 3d.

  The intermediate transfer belt 5 is an annular intermediate transfer member in contact with the photosensitive drums 1 a to 1 d and onto which the toner images on the photosensitive drums 1 a to 1 d are transferred. The intermediate transfer belt 5 is stretched around a drive roller 6a and a tension roller 6b, and revolves in the direction from the contact position with the photosensitive drum 1a to the contact position with the photosensitive drum 1d by the driving force from the drive roller 6a. To go.

  The secondary transfer roller 7 brings the conveyed sheet into contact with the intermediate transfer belt 5 and secondarily transfers the toner image on the intermediate transfer belt 5 onto the sheet. The sheet on which the toner image has been secondarily transferred is conveyed to a fixing device (not shown), and the toner image is fixed to the sheet.

  At the time of adjustment, the sensor 8 irradiates the intermediate transfer belt 5 with light, detects the reflected light (for example, regular reflection light and diffuse reflection light), and based on the detected light amount of the reflected light, on the intermediate transfer belt 5. Is a reflective optical sensor that detects the density of the toner mark. In particular, at the time of adjusting the toner density and the gradation, the sensor 8 detects the density of the toner mark carried on the intermediate transfer belt 5.

  The primary transfer rollers 9a to 9d are disposed opposite to the photosensitive drums 1a to 1d, respectively, with the intermediate transfer belt 5 interposed therebetween, and the toner images on the photosensitive drums 1a to 1d are primary transferred onto the intermediate transfer belt 5 Do.

  FIG. 2 is a cross-sectional view showing an example of the developing device 3a in FIG. Although FIG. 2 shows the developing device 3a, the developing devices 3b to 3d have the same configuration.

  As shown in FIG. 2, the developing device 3 a has a housing 11, a stirring screw 12, a magnetic roller 13, and a developing roller 14.

  A toner container (not shown) is connected to the developing device 3a, and toner is supplied from the toner container into the housing 11 via a supply port (not shown). In the housing 11, the two-component developer including the nonmagnetic toner and the magnetic carrier is stirred by the stirring screw 12.

  The magnetic roller 13 holds the two-component developer in the form of a brush on its surface. The toner of the two-component developer is transferred to the developing roller 14 according to the transport bias which is a voltage between the magnetic roller 13 and the developing roller 14.

  The developing roller 14 holds the toner transferred from the magnetic roller 13 on its surface as a toner thin layer. That is, the developing roller 14 holds the toner to be attached to the electrostatic latent image on the photosensitive drum 1 a The toner layer formed on the surface of the developing roller 14 has a voltage between the developing roller 14 and the photosensitive drum 1 a The photosensitive drum 1a is moved by the developing bias. The photosensitive drum 1 a is an image carrier on the surface of which an electrostatic latent image is formed by the exposure device 2. The toner transferred from the developing roller 14 adheres to the electrostatic latent image on the photosensitive drum 1a.

  As shown in FIG. 2, the toner concentration sensor 15 is a sensor which is installed on the bottom of the developing device 3a and detects the toner concentration of the two-component developer in the housing 11 of the developing device 3a.

  Further, the scraper 16 is a flat member extending substantially perpendicular to the rotation shaft of the agitating screw 12 and substantially parallel to the rotation shaft, and rotates along with the rotation of the rotation shaft to correspond to the installation position of the toner concentration sensor 15 Scrape off the developer on the inner wall of the housing 11. The toner concentration sensor 15 is installed corresponding to the position of the scraper 16.

  FIG. 3 is a view for explaining the arrangement position of the toner concentration sensor 15 in FIG. FIG. 4 is a circuit diagram showing an electrical configuration of the toner concentration sensor 15 in FIG. 2 and FIG.

  Specifically, as shown in FIG. 3, the coil 20 in the toner concentration sensor 15 is disposed below the passing range of the scraper.

  Further, as shown in FIG. 4, the toner concentration sensor 15 includes a substrate 21 and a sensor signal output circuit 22 in addition to the coil 20.

  The coil 20 is a flat and spiral coil. The spiral shape of the coil 20 may be a circular spiral shape or a polygonal spiral shape.

  The sensor signal output circuit 22 is configured to set the coil 20 between two positions for making at least one of the electrical inner diameter and the outer diameter of the coil 20 correspond to the scraper 16 out of at least three positions on the coil 20. Output sensor signal according to the inductance by part or all. The circuit of the existing toner concentration sensor can be used for portions other than the coil 20 (that is, the inductor) of the sensor signal output circuit 22.

  In this embodiment, the sensor signal output circuit 22 is between two of the at least three positions on the coil 20 for making the electrical inner diameter and the outer diameter of the coil 20 correspond to the scraper 16. The sensor signal according to the inductance by the coil conductor (ie, part or all of the coil 20) is output.

  For example, the sensor signal output circuit 22 is a resonant circuit including the coil 20 (that is, a resonant circuit whose resonant frequency changes due to a change in the inductance of the coil 20) and an oscillator circuit including the coil 20 (that is, the change in the inductance of the coil 20). And a sensor signal having a frequency corresponding to the inductance (that is, the T / C ratio) of the coil 20.

  The substrate 21 is disposed such that the vertical direction of the planar substrate 21 is directed to the rotation axis (that is, the upper side) of the stirring screw 12, and the coil 20 is formed as a wiring (here, pattern wiring) on the substrate 21. ing.

  The substrate 21 is a double-sided substrate or a multilayer substrate, and at least two (six in FIG. 4) through holes 31 to 36 are provided on the lead of the coil 20. The through holes 31 to 36 electrically connect the coil 20 to a layer or a back surface of the substrate 21 different from the coil 20.

  The through holes 31 to 36 may be arranged at equal intervals from the end of the coil 20, or may be arranged at equal intervals in a specific intermediate section of the conductive wire of the coil 20.

  In the layer other than coil 20 or on the back surface, through holes 31 to 36 are connected to pattern interconnections 41 to 46, respectively, and land pairs 61 to 61 electrically connected to pattern interconnections 41 to 46, respectively. 67 are formed on the surface of the substrate 21.

  In the case shown in FIG. 4, land pairs 61 to 67 are formed on the same substrate surface as coil 20, through holes 51 to 56 are connected to pattern wirings 41 to 46, respectively, and through holes 51 to 56 are formed. And the lands 61 to 66 are electrically connected to pattern lands 71 to 76, respectively. The outer peripheral end of the coil 20 is electrically connected to one land of the land pair 67 by a pattern wiring 77.

  The coil 20 is disposed on another layer or the back of the substrate 21, and in addition to the through holes 31 to 36, another through hole is provided at the outer peripheral end of the coil 20. The lands 61 to 67 may be electrically connected to each other by the pattern wiring of FIG.

  The other land of each of the land pairs 61 to 67 is electrically connected to the sensor signal output circuit 22. The sensor signal output circuit 22 and the coil 20 are not electrically connected in the state where the surface mounted element is not mounted on the land pair 61 to 67.

  In this embodiment, two surface mounting elements 81 and 82 such as a jumper element and a surface mounting resistor are mounted on two selected from the land pairs 61 to 67 corresponding to the scraper 16 of the developing device 3a. ing. That is, the effective inner diameter and the effective outer diameter of the coil 20 which contribute to the inductance of the coil 20 are determined by the land pair on which the two surface mounting elements 81 and 82 are mounted.

  In this embodiment, the other lands of the plurality of land pairs 61 to 63 are electrically connected to each other, and one of the land pairs 61 to 63 is selectively connected by the surface mounting element 81, Thereby, the effective inside diameter of the coil 20 is set. Similarly, the other lands of the plurality of land pairs 64-67 are electrically connected to each other, and one of the land pairs 64-67 is selectively connected by the surface mounting element 82, whereby The effective outer diameter of the coil 20 is set. Then, the sensor signal output circuit 22 generates and outputs a sensor signal (of frequency) corresponding to an inductance between the other land of the land pair 61 to 63 and the other land of the land pair 64-67.

  Here, the electrical outer diameter (effective outer diameter) of the coil 20 is equal to or less than the width W of the scraper 16.

  Thus, toner concentration sensor 15 further includes at least three wires (through holes 31 to 36 and wires 41 to 46 and wire 77) extending from at least three positions on coil 20, respectively. Among the wires, two wires corresponding to the above-described two positions are selectively electrically connected to the sensor signal output circuit 22 by the surface mount elements 81 and 82 as conductive elements.

  Next, the operation of the image forming apparatus will be described.

  For example, at the time of manufacture, the effective inner diameter and the effective outer diameter of the coil 20 are selectively set as described above according to the types of the developing devices 3a to 3d of the image forming apparatus.

  Each time the stirring screw 12 of each of the developing devices 3a to 3d rotates, the scraper 16 scrapes off the developer in the passing range of the scraper 16 and is stirred without stagnation (that is, the current average toner concentration) Developer) enters its passage range.

  In the toner concentration sensor 15, the effective inner diameter and the effective outer diameter of the coil 20 are set corresponding to the developing devices 3 a to 3 d, and the inductance of the coil 20 does not pass through the scraper 16. The influence of the developer staying in the clearance range CL between the inner wall of the toner and the inner wall of the toner is suppressed, and at each time point, the developer scraped state and the developer having the current average toner concentration It becomes a value according to the transferred status. Therefore, the sensor signal output circuit 22 outputs a sensor signal of a frequency corresponding to the inductance at each time point. The controller (not shown) detects the frequency of this sensor signal, identifies the current toner concentration (ratio of carrier to toner) from the detected frequency, and performs various processing (toner supply etc.) according to the toner concentration. Control or detect out of toner.

  As described above, according to the above embodiment, the developing devices 3 a to 3 d include the scraper 16 while stirring the two-component developer with the stirring screw 12. The toner concentration sensor 15 is installed in the developing devices 3 a to 3 d corresponding to the position of the scraper 16, and detects the toner concentration of the two-component developer. Then, the toner concentration sensor 15 has at least one of an electric inner diameter and an outer diameter of (a) a flat and spiral coil 20 and (b) at least three positions on the coil 20. And a sensor signal output circuit 22 that outputs a sensor signal according to the inductance of part or all of the coil 20 between two positions for making the scraper 16 correspond.

  As a result, even when the structure of the developing device (in particular, the structure of the scraper) differs depending on the model, the common toner density sensor 15 can be used only by changing the connection setting between the coil 20 and the sensor signal output circuit 22. It is possible. That is, the influence of the above-mentioned stagnant developer is appropriately suppressed according to the structure of the developing device based on the effective outer diameter, and the sensor sensitivity is appropriately adjusted according to the structure of the developing device based on the effective inner diameter.

  Note that various changes and modifications to the above-described embodiment will be apparent to those skilled in the art. Such changes and modifications may be made without departing from the spirit and scope of the subject matter and without diminishing the intended advantages. That is, such changes and modifications are intended to be included in the scope of the claims.

  For example, although both the effective outer diameter and the effective inner diameter of the coil 20 are variable in the above embodiment, one of the effective outer diameter and the effective inner diameter of the coil 20 may be fixed and the other may be variable. In that case, for example, one of the two wires corresponding to the above-mentioned two positions among the above-mentioned at least three wires is fixedly electrically connected to the sensor signal output circuit 22, and the two wires The other of the wires is selectively electrically connected to the sensor signal output circuit 22 by a conductive element (for example, the surface mount element described above). Specifically, for example, in FIG. 4, when the effective outer diameter is fixed, the other lands of the plurality of land pairs 61 to 66 are electrically connected to each other in order to set the effective inner diameter of the coil 20, One of the land pairs 61 to 66 is selectively connected by the surface mount element 81, the land pair 67 is omitted, the pattern wiring 77 is electrically connected to the sensor signal output circuit 22, and the sensor signal output circuit 22 generates and outputs a sensor signal (of frequency) corresponding to an inductance between the other land of the land pair 61 to 66 and the pattern wiring 77. Also, for example, in FIG. 4, when the effective inner diameter is fixed, the other lands of the plurality of land pairs 62 to 67 are electrically connected to each other in order to set the effective outer diameter of the coil 20. One of the pairs 62 to 67 is selectively connected by the surface mounting element 82, the land pair 61 is omitted, the pattern wiring 71 is electrically connected to the sensor signal output circuit 22, and the sensor signal output circuit 22 is A sensor signal (of frequency) corresponding to an inductance between the pattern wiring 71 and the other land of the land pair 62 to 67 is generated and output.

  The present invention is applicable to, for example, an image forming apparatus using a two-component developer.

3a to 3d developing device 12 stirring screw 15 toner concentration sensor 16 scraper 20 coil 21 substrate 22 sensor signal output circuit 31 to 36 through hole (part of an example of wiring)
41 to 46 Pattern wiring (part of an example of wiring)
51 to 56 through holes (part of an example of wiring)
61 to 67 land pairs (part of an example of wiring)
71 to 77 Pattern wiring (part of an example of wiring)
81, 82 Surface mount device (an example of a conductive device)

Claims (6)

A developing device provided with a scraper while stirring the two-component developer with a stirring screw;
And a toner concentration sensor installed in the developing device corresponding to the position of the scraper, for detecting the toner concentration of the two-component developer.
The toner concentration sensor includes (a) a flat and spiral coil, and (b) at least one of an electric inner diameter and an outer diameter of the coil of at least three positions on the coil. Providing a sensor signal output circuit for outputting a sensor signal according to an inductance by a part or all of the coil between two positions corresponding to a scraper;
An image forming apparatus characterized by And at least three wires each extending from at least three locations on the coil,
Of the at least three wires, one of the two wires corresponding to the two positions is fixedly electrically connected to the sensor signal output circuit,
The other of the two wires is selectively electrically connected to the sensor signal output circuit by a conductive element;
The image forming apparatus according to claim 1, wherein   The sensor signal output circuit is a portion of the coil between two positions for making both the electrical inner diameter and the outer diameter of the coil correspond to the scraper among at least three positions on the coil. The image forming apparatus according to claim 1, wherein a sensor signal corresponding to an inductance due to all or all the signals is output. And at least three wires each extending from at least three locations on the coil,
Of the at least three wires, two wires corresponding to the two positions are selectively electrically connected to the sensor signal output circuit by a conductive element,
The image forming apparatus according to claim 3, wherein   The image forming apparatus according to any one of claims 1 to 4, wherein the electrical outer diameter of the coil is equal to or less than the width of the scraper. The toner concentration sensor further comprises a substrate,
The coil is disposed on the substrate and comprises at least two through holes,
At least two of the at least three wires are respectively electrically connected to the through holes;
The conductive element is a surface mount element,
The image forming apparatus according to claim 2 or 4, wherein

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