JP5857016B2 - Developing device, image forming apparatus, and toner concentration detection method - Google Patents

Description

  The present invention relates to a developing device, an image forming apparatus including the developing device, and a toner concentration detection method, and more particularly to a technique for detecting the toner concentration of a developer contained in the developing device.

  A toner concentration sensor having an LC oscillation circuit is known as a device for detecting the toner concentration of a developer contained in a developing device. This toner concentration sensor detects the toner concentration of the developer by detecting a change in magnetic permeability that changes depending on the toner concentration of the developer as a change in the oscillation frequency of the LC oscillation circuit. In recent years, for the purpose of downsizing and cost reduction, a toner density sensor using a planar coil as a coil constituting an LC oscillation circuit has also appeared.

  Here, in an image forming apparatus that performs color printing, it is necessary to install a toner density sensor for each developer of magenta, cyan, yellow, and black. When a planar coil is used as the coil constituting the LC oscillation circuit, the emission frequency increases because the oscillation frequency of each toner concentration sensor is as high as several MHz. For this reason, radiation noises emitted from a plurality of toner density sensors are added together, and there is a possibility that radiation noises emitted from the entire apparatus will be larger.

  Japanese Patent Application Laid-Open No. 2004-133830 discloses a technique for controlling radiation switching operation of an image forming apparatus including a plurality of toner density sensors and suppressing radiation noise generated by the entire apparatus by shifting the power supply timing to each toner density sensor. It is disclosed. Patent Document 2 discloses a technique in which a ground plate is provided on the back surface of the substrate of the toner concentration sensor, and radiation noise is magnetically shielded by the ground plate.

JP 2001-194960 A Japanese Patent Laid-Open No. 10-62390

  However, in the technique disclosed in Patent Document 1 described above, since the power supply timing to each toner density sensor is shifted, the toner density detection time for the magenta, cyan, yellow, and black color developer is reduced. For this reason, there is a problem that the accuracy of toner density detection is lowered. Further, the technique disclosed in Patent Document 2 has a problem in that the accuracy of toner density detection is reduced because the coil cannot be provided on the back surface of the substrate by providing the ground plate.

  The present invention has been made in view of the above circumstances, and an object thereof is to provide a developing device and an image forming apparatus that can suppress radiation noise emitted from the apparatus while maintaining the accuracy of toner density detection.

  A developing device according to an aspect of the present invention includes a plurality of developing units, and a plurality of toner concentration sensors each having an LC oscillation circuit and installed in each of the plurality of developing units. In the developing device, the electrostatic capacity of the capacitor constituting the LC oscillation circuit is different for each toner density sensor installed in the section.

  An image forming apparatus according to another aspect of the present invention is an image forming apparatus including the developing device.

  According to another aspect of the present invention, there is provided a toner concentration detection method that is installed in each of a plurality of developing units that store a developer that is a toner concentration detection target, and the capacitances of the capacitors are different from each other. In this toner density detection method, the toner density of the developer is detected by using a signal output from a toner density sensor having an LC oscillation circuit and the capacitance of the capacitor.

  According to the developing device, the image forming apparatus including the developing device, and the toner density detecting method according to one aspect of the present invention, the capacitor that configures the LC oscillation circuit for each toner density sensor installed in each of the plurality of developing units. Have different capacitances. As a result, since the oscillation frequency is shifted for each toner density sensor, radiation noise emitted from the entire developing device can be suppressed. Further, since the time for supplying power to the toner density sensor is not reduced, the accuracy of toner density detection is not lowered.

1 is a front sectional view showing a structure of an image forming apparatus including a developing device according to an embodiment of the present invention. 1 is a block diagram schematically showing a main internal configuration of an image forming apparatus according to an embodiment of the present invention. FIG. 3 is a perspective view showing a part of the developing unit cut out according to an embodiment of the present invention. It is the sectional view on the AA line in FIG. FIG. 3 is a plan view illustrating a configuration of a toner concentration sensor according to an embodiment of the present invention. FIG. 3 is a diagram illustrating a circuit configuration of a toner concentration sensor according to an embodiment of the present invention.

  A developing device and an image forming apparatus including the developing device according to an embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a front sectional view showing the structure of an image forming apparatus including a developing device according to an embodiment of the present invention.

  An image forming apparatus 1 according to an embodiment of the present disclosure is a multifunction machine having a plurality of functions such as a copy function, a printer function, a scanner function, and a facsimile function. The image forming apparatus 1 includes an apparatus main body 11 that includes an operation unit 47, an image forming unit 12, a fixing unit 13, a paper feeding unit 14, a document feeding unit 6, a document reading unit 5, and the like.

  When the image forming apparatus 1 performs a document reading operation, the document reading unit 5 optically reads a document fed by the document feeding unit 6 or a document placed on the document placing glass 161, Generate image data. Image data generated by the document reading unit 5 is stored in a built-in HDD or a network-connected computer.

  When the image forming apparatus 1 performs an image forming operation, the image forming unit 12 is supplied from the paper supply unit 14 based on the image data generated by the document reading operation or the image data stored in the built-in HDD. A toner image is formed on a recording paper P as a recording medium to be paper.

  The image forming unit 12 forms an image forming unit 12-M that forms a magenta (M) color image, an image forming unit 12-C that forms a cyan (C) color image, and a yellow (Y) color image. The image forming unit 12-Y and the image forming unit 12-Bk that forms a black (Bk) color image are included. The image forming units 12-M, 12-C, 12-Y, and 12-Bk include a photosensitive drum 121, a charging device 123, an exposure device 124, a developing unit 122, and a primary transfer roller 126, respectively. I have.

  Among the above-described configurations, the photosensitive drum 121, the charging device 123, the exposure device 124, and the primary transfer roller 126 are common to the image forming units 12-M, 12-C, 12-Y, and 12-Bk. It is. Regarding the developing unit 122, the image forming units 12-M, 12-C, 12-Y, and 12-Bk are partially different in configuration. In the following, when the image forming unit is described separately for the developing unit 122 and the components constituting the developing unit 122, “−M”, “−C”, and the like are added to the end of the reference numerals.

  The image forming apparatus 1 according to the present embodiment uses a two-component developer including a toner and a carrier, and each developing unit of the image forming units 12-M, 12-C, 12-Y, and 12-Bk. 122 stores a two-component developer (hereinafter, simply referred to as a developer). The developing unit 122 supplies the toner contained in the developer to the surface of the photosensitive drum 121 that has been charged by the charging device 123 and exposed by the exposure device 124.

  When performing color printing, each of the image forming units 12-M, 12-C, 12-Y, and 12-Bk of the image forming unit 12 is based on an image composed of each color component constituting image data. Then, a toner image is formed on the photosensitive drum 121 by charging, exposing and developing processes, and the toner image is transferred onto the intermediate transfer belt 125 stretched between the driving roller 125a and the driven roller 125b by the primary transfer roller 126. Let

  The intermediate transfer belt 125 is driven by a driving roller 125 a in a state where an image carrying surface on which a toner image is transferred is set on the outer peripheral surface thereof and in contact with the peripheral surface of the photosensitive drum 121. The intermediate transfer belt 125 travels endlessly between the driving roller 125a and the driven roller 125b while being synchronized with each photosensitive drum 121.

  The toner images of the respective colors transferred onto the intermediate transfer belt 125 are superimposed on the intermediate transfer belt 125 with the transfer timing adjusted to become a color toner image. The secondary transfer roller 210 conveys the color toner image formed on the surface of the intermediate transfer belt 125 from the sheet feeding unit 14 through the conveyance path 190 at the nip N between the intermediate transfer belt 125 and the driving roller 125a. The recording sheet P is transferred. Thereafter, the fixing unit 13 fixes the toner image on the recording paper P to the recording paper P by thermocompression bonding. The recording paper P on which the color image has been formed after completion of the fixing process is discharged to a discharge tray 151.

  Next, the internal configuration of the image forming apparatus 1 will be described. FIG. 2 is a block diagram schematically showing the main internal configuration of the image forming apparatus 1.

  The image forming apparatus 1 includes a control unit 10, a document reading unit 5, a document feeding unit 6, an image forming unit 12, a fixing unit 13, a paper feeding unit 14, and the like.

  The control unit 10 includes a CPU (Central Processing Unit), a RAM, a ROM, a dedicated hardware circuit, and the like, and controls overall operation of the image forming apparatus 1. The control unit 10 includes a control unit 100. The control unit 100 is connected to the document reading unit 5, the document feeding unit 6, the image forming unit 12, the fixing unit 13, the paper feeding unit 14, and the like, and performs drive control of these units.

  The developing device 127 includes a magenta developing unit 122-M, a cyan developing unit 122-C, a yellow developing unit 122-Y, and a black developing unit 122-Bk.

  The toner density sensor 128-M is installed in the developing unit 122-M of the magenta image forming unit 12-M and detects the toner density of the magenta developer. The toner density sensor 128-C is installed in the developing unit 122-C of the cyan image forming unit 12-C and detects the toner density of the cyan developer. The toner density sensor 128-Y is installed in the developing unit 122-Y of the yellow image forming unit 12-Y and detects the toner density of the yellow developer. The toner density sensor 128-Bk is installed in the developing unit 122-Bk of the black image forming unit 12-Bk, and detects the toner density of the black developer.

  The control unit 100 includes a toner density control unit 101. The toner density control unit 101 is connected to each toner density sensor 128 of the image forming apparatus 1, and from each oscillation frequency output from the toner density sensors 128 -M, 128 -C, 128 -Y, and 128 -Bk, The toner density of the developer is detected. Then, the toner density control unit 101 controls the image forming apparatus 1 based on the detected toner density of each color developer. For example, when the toner density of the developer is equal to or lower than a predetermined density, the toner density control unit 101 displays that the toner should be replenished on the display unit 41 such as an LCD (Liquid Crystal Display).

  Next, the configuration of the developing device 127 will be described with reference to FIGS. 3 and 4. 3 and 4 show the configuration of the developing unit 122-M for magenta in the developing unit 122 of the developing device 127. FIG.

  FIG. 3 is a perspective view of the developing unit 122-M with a part thereof cut away. 4 is a cross-sectional view taken along line AA in FIG. 3 and 4, the XX direction is referred to as the left-right direction, and the Y-Y direction is referred to as the front-rear direction. In particular, the -X direction is referred to as the left, the + X direction is referred to as the right, the -Y direction is referred to as the front, and the + Y direction is referred to as the rear. . Here, the configuration of the developing unit 122-M for magenta will be described. However, for the components not having “−M” at the end of the reference numerals, the developing unit 122-C for cyan and the unit for yellow are used. The developing unit 122-Y and the black developing unit 122-Bk have the same configuration.

  As illustrated in FIGS. 3 and 4, the developing unit 122 -M includes a first spiral feeder 51, a second spiral feeder 52, and a developing roller 53 in the housing 58.

  The casing 58 plays a role as a storage unit that stores the developer. A partition wall 581 is formed inside the housing 58 inside. Thereby, the inside of the housing 58 is divided into a first chamber 582 in which the first spiral feeder 51 is arranged and a second chamber 583 in which the second spiral feeder 52 is arranged. The toner supplied from the toner container 59 to the first chamber 582 is agitated by the first spiral feeder 51 and conveyed toward the second chamber 583. The toner conveyed to the second chamber 583 is conveyed forward by the second spiral feeder 52.

  A toner concentration sensor 128 -M is attached to the outer surface of the housing 58 in the lower part of the first chamber 582. The toner concentration sensor 128 -M is a so-called magnetic permeability detection type sensor having an LC oscillation circuit, and outputs a signal having an oscillation frequency corresponding to the toner concentration of the developer stored in the first chamber 582. By providing the toner concentration sensor 128 -M at the above position, it is possible to detect the toner concentration of the developer before it is recirculated from the developing roller 53 and new toner is supplied from the toner container 59.

  The developing roller 53 includes a magnet roller 531 and a developing sleeve 532. The developing sleeve 532 is externally mounted on the magnet roller 531. The developing sleeve 532 is rotatably supported by the housing 58 at a position adjacent to the surface of the photosensitive drum 121 and the second spiral feeder 52.

  The developer moved from the first spiral feeder 51 and the second spiral feeder 52 by the magnetic force of the magnet roller 531 is carried on the peripheral surface of the developing sleeve 532.

  The toner in the developer adhering to the developing roller 53 flies to the photosensitive drum 121 due to the potential difference between the surface potential of the photosensitive drum 121 and the developing bias applied to the developing roller 53, and the surface of the photosensitive drum 121. A toner image is formed.

  The regulating blade 81 regulates the developer carried on the peripheral surface of the developing sleeve 532 to a predetermined layer thickness, and a predetermined interval between the developing sleeve 532 and the surface of the developing sleeve 532. And is supported by the housing 58.

  Next, the configuration of the toner density sensor will be described with reference to FIGS. 5 and 6 show the configuration of the magenta toner density sensor 128-M. The components having “−M” at the end of the reference numerals have the same configurations as the other cyan toner density sensor 128-C, yellow toner density sensor 128-Y, and toner density sensor 128-Bk. is there.

  FIG. 5 is a plan view showing the configuration of the toner density sensor 128-M. As shown in FIG. 5, the toner density sensor 128 -M has a planar coil 1281 formed on one surface of a rectangular substrate 1287. The substrate 1287 is a so-called flexible substrate, and has a shape along the outer surface of the housing 58 when the toner concentration sensor 128-M is attached to the housing 58 (see FIG. 4).

  The planar coil 1281 has a rectangular outer shape. The toner density sensor 128 -M is arranged so that the surface on which the planar coil 1281 is formed is on the side in contact with the outer surface of the housing 58.

  On the back surface of the surface on which the planar coil 1281 is formed, other circuit components 1282-M such as a capacitor constituting the LC oscillation circuit are mounted. Connection members 1288 and 1289 that penetrate the substrate 1287 are formed at the end of the planar coil 1281, and the planar coil 1281 and other circuit components 1282 -M are connected by the connection members 1288 and 1289.

  FIG. 6 is a diagram illustrating a circuit configuration of the toner density sensor 128-M. As shown in FIG. 6, in the toner density sensor 128 -M, a planar coil 1281 is connected to both ends of the inverter 1286. Capacitors 1283-M and 1284-M are connected between the planar coil 1281 and the ground. A resistor 1285 is connected between the output side of the inverter 1286 and one end of the planar coil 1281. The oscillation frequency f output from the toner density sensor 128-M having this circuit configuration is expressed by the following mathematical formula.

In the above formula, L represents the inductance of the planar coil 1281, C ₁ represents the capacitance of the capacitor 1283-M, and C ₂ represents the capacitance of the capacitor 1284-M. As shown in the above equation, the oscillation frequency f of the toner density sensor 128-M is output and the inductance L of the planar coil 1281, and the capacitance _{C 1} of the capacitor 1283-M, the capacitance C of the capacitor 1284-M ₂ is determined.

  In the image forming apparatus 1 according to the present embodiment, the electrostatic capacity of the capacitor 1283 constituting the LC oscillation circuit is different for each toner density sensor 128 that detects the toner density of the developer of different colors. In the present embodiment, a capacitor 1283-M constituting the LC oscillation circuit of the toner density sensor 128-M, a capacitor 1283-C constituting the LC oscillation circuit of the toner density sensor 128-C, and the toner density sensor 128-Y. Capacitors 1283-Y constituting the LC oscillation circuit and capacitors 1283-Bk constituting the LC oscillation circuit of the toner density sensor 128-Bk have different electrostatic capacities.

  Note that the electrostatic capacity of the capacitor 1284 may be different for each toner density sensor 128 instead of the electrostatic capacity of the capacitor 1283. Further, the capacitances of both the capacitors 1283 and 1284 may be different for each toner density sensor 128.

  As described above, the capacitance of the capacitor 1283 and / or the capacitor 1284 is made different for each toner density sensor 128, so that the oscillation frequency output from the toner density sensor 128 is made different for each toner density sensor 128. Can do. For example, in the present embodiment, the output oscillation frequency is varied by 1 kHz or more and 10 kHz or less for each toner density sensor 128 that detects toner densities of different colors. In this way, even when the toner density sensors 128 are operated simultaneously, radiation noise emitted from the developing device 127 and the image forming apparatus 1 can be suppressed.

  Each toner density sensor 128 can use the same configuration except for the capacitor 1283 and / or the capacitor 1284 that constitute the LC oscillation circuit. For this reason, the manufacturing cost of the developing device 127 and the image forming apparatus 1 can be suppressed.

  Further, since radiation noise emitted from the developing device 127 and the image forming apparatus 1 can be suppressed, EMI (electromagnetic interference) countermeasure parts such as shield parts provided in the image forming apparatus 1 can be reduced. . For this reason, the manufacturing cost of the developing device 127 and the image forming apparatus 1 can be suppressed.

  The present invention is not limited to the configuration of the above embodiment, and various modifications can be made. The configuration shown in each of the above embodiments using FIGS. 1 to 6 is only one embodiment of the present invention, and the configuration of the present invention is not limited to this.

  For example, the shape of the coil constituting the LC oscillation circuit is not limited to a circle. That is, the shape may be any shape as long as it is spirally wound, and the outer shape may be, for example, a rectangle.

  Further, a variable capacitor whose capacitance can be varied may be used as the capacitor constituting the LC oscillation circuit. As a result, the same configuration can be used for all the circuit components and the substrates of each toner concentration sensor 128, so that the manufacturing cost of the developing device 127 can be further reduced.

  In the above embodiment, the case where the coil is formed on one surface of the substrate of the toner concentration sensor has been described. However, the present invention is not necessarily limited to this case. You may form a coil in the surface of the both sides of a board | substrate. By doing so, the toner density detection performance of the toner density sensor can be improved.

  In the above-described embodiment, the image forming apparatus that performs image formation using the two-component developer including the toner and the carrier has been described. However, the present invention is not necessarily limited to this case. Even in an image forming apparatus that forms an image using a so-called one-component developer, the toner density can be detected by using the magnetic permeability detection type toner density sensor described in the above embodiment.

  In the above-described embodiment, a case has been described in which a plurality of developing units contain different color developers, but the present invention is not necessarily limited to this case. The present invention only needs to detect the toner concentration of the developer contained in the plurality of developing units. For example, the same color developer may be stored in a plurality of developing units.

  The circuit configuration of the toner density sensor shown in FIG. 6 is merely an example, and the present invention is not necessarily limited to this case.

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 12 Image forming part 12-M, 12-C, 12-Y, 12-Bk Image forming unit 51 1st spiral feeder 52 2nd spiral feeder 53 Developing roller 58 Case 59 Toner container 121 Photosensitive drum 122 −M, 122-C, 122-Y, 122-Bk Developing unit 123 Charging device 124 Exposure device 125 Intermediate transfer belt 127 Developing device 128-M, 128-C, 128-Y, 128-Bk Toner density sensor 581 Partition wall 101 Toner density controller 1281 Planar coils 1283, 1284 Capacitor 1285 Resistor 1286 Inverter 1287 Substrate

Claims (5)

A plurality of developing units;
A plurality of toner concentration sensors each having an LC oscillation circuit and installed in each of the plurality of developing units;
A developing device in which electrostatic capacity of a capacitor constituting the LC oscillation circuit is different for each of the toner density sensors installed in the plurality of developing units.   The developing device according to claim 1, wherein the coil constituting the LC oscillation circuit is a planar coil.   The developing device according to claim 1, wherein the capacitor is a variable capacitor having a variable capacitance.   An image forming apparatus comprising the developing device according to claim 1.   A signal output from a toner concentration sensor installed in each of a plurality of developing units containing a developer for detecting toner concentration and having an LC oscillation circuit having different capacitances of the capacitors, and the capacitor A toner concentration detection method for detecting a toner concentration of the developer using a capacitance of the developer.

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