JP6680259B2 - Image forming device - Google Patents

Description

  The present invention relates to an electrophotographic image forming apparatus.

  In an electrophotographic image forming apparatus, a two-component developer containing a magnetic carrier and a non-magnetic toner may be used as a developer for developing an electrostatic latent image. In this type of image forming apparatus, since only the toner in the developer is used for developing the electrostatic latent image, the concentration of the toner in the developer gradually decreases in the developing section that contains the developer. Therefore, in order to supply the toner to the developing unit and make the toner concentration in the developer constant, a toner detection device capable of detecting the toner concentration is provided. For example, there is known a toner detection device including an LC oscillation circuit that includes a coil arranged so as to face a developing unit and outputs an electric signal having a frequency corresponding to the magnetic permeability of the developer in the developing unit (for example, Patent Document 1). Reference 1).

JP, 10-62390, A

  By the way, in the image forming apparatus, when the substrate on which the LC oscillating circuit is mounted is attached to the developing portion, the attachment position may vary in the direction facing the developing portion. In this case, in the image forming apparatus, the accuracy of detecting the toner density by the toner detecting device varies.

  An object of the present invention is to provide an image forming apparatus capable of improving the detection accuracy of the toner detection device attached to the developing section.

  The image forming apparatus according to the present invention includes a developing unit, a substrate, a stray capacitance generating unit, and a supporting unit. The developing unit contains a developer containing toner, and develops the electrostatic latent image formed on the image bearing member using the toner contained in the developer. An LC oscillating circuit including a coil is mounted on the substrate, and the coil is arranged so as to face the developing unit in the extending direction of magnetic lines of force passing through the coil. The stray capacitance generating unit is conductive and is arranged to face at least a part of the conductor included in the LC oscillation circuit at a position opposite to the developing unit from the substrate in the extending direction. , Electrically grounded. The supporting unit supports the stray capacitance electrostatic unit separately from the substrate at a position spaced apart from the developing unit by a predetermined distance in the extending direction.

  According to the present invention, an image forming apparatus capable of improving the detection accuracy of the toner detection device attached to the developing unit is realized.

FIG. 1 is a view showing the arrangement of an image forming apparatus according to the first embodiment of the present invention. FIG. 2 is a diagram showing a configuration of an image forming unit in the image forming apparatus according to the first embodiment of the present invention. FIG. 3 is a diagram showing the configuration of the developing unit in the image forming apparatus according to the first embodiment of the present invention. FIG. 4 is a diagram showing the configuration of the LC oscillation circuit in the image forming apparatus according to the first embodiment of the present invention. FIG. 5 is a diagram showing the configurations of the internal frame and the stray capacitance generation unit in the image forming apparatus according to the first embodiment of the present invention. FIG. 6 is a diagram showing a configuration of an image forming unit in the image forming apparatus according to the second embodiment of the present invention. FIG. 7 is a diagram showing the configurations of the internal frame and the stray capacitance generation unit in the image forming apparatus according to the second embodiment of the present invention. FIG. 8 is a diagram showing a configuration of an image forming unit in the image forming apparatus according to the third embodiment of the present invention.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings to provide an understanding of the present invention. The following embodiments are examples of embodying the present invention and do not limit the technical scope of the present invention.

[First Embodiment]
First, the configuration of the image forming apparatus 10 according to the first embodiment of the present invention will be described with reference to FIGS. 1 and 2. Here, FIG. 1 is a schematic cross-sectional view showing the configuration of the image forming apparatus 10. Further, FIG. 2 is a schematic sectional view showing the configuration of the image forming unit 31.

  For convenience of explanation, the vertical direction is defined as the up-down direction D1 when the image forming apparatus 10 can be used (the state shown in FIG. 1). Further, the front-rear direction D2 is defined with the surface on the left side of the paper of the image forming apparatus 10 shown in FIG. 1 as the front surface. Further, the left-right direction D3 is defined with reference to the front of the image forming apparatus 10 in the installed state.

  The image forming apparatus 10 is a multi-function peripheral having a print function for forming an image based on image data and a plurality of functions such as a scan function, a facsimile function, and a copy function. The present invention is also applicable to image forming apparatuses such as printers, facsimile machines, and copy machines.

  As shown in FIG. 1, the image forming apparatus 10 includes an ADF 1, an image reading unit 2, an image forming unit 3, a paper feeding unit 4, and an operation display unit 5.

  The ADF 1 is an automatic document feeder that includes a document setting unit (not shown), a plurality of transport rollers, a document retainer, and a paper discharge unit, and transports a document read by the image reading unit 2.

  The image reading unit 2 includes a document table (not shown), a light source, a plurality of mirrors, an optical lens, and a CCD, and can read image data from a document.

  The operation display unit 5 includes a display unit such as a liquid crystal display which displays various information in accordance with a control instruction from a control unit (not shown), and an operation key which inputs various information into the control unit in response to a user operation. It has an operation unit such as a touch panel.

  The image forming unit 3 can form a color or monochrome image by an electrophotographic method based on the image data read by the image reading unit 2. The image forming unit 3 can also form an image based on image data input from an information processing device such as an external personal computer.

  As shown in FIG. 1, the image forming unit 3 includes a plurality of image forming units 31 to 34, an optical scanning device 35, an intermediate transfer belt 36, a secondary transfer roller 37, a fixing device 38, and a paper discharge tray 39. .

  The image forming unit 31 is an electrophotographic image forming unit corresponding to Y (yellow), the image forming unit 32 is C (cyan), the image forming unit 33 is M (magenta), and the image forming unit 34 is K (black). is there. As shown in FIG. 1, the image forming units 31 to 34 are provided side by side in the order of yellow, cyan, magenta, and black from the front of the image forming apparatus 10 along the front-rear direction D2 of the image forming apparatus 10.

  As shown in FIG. 2, the image forming unit 31 includes a photosensitive drum 311, a charging roller 312, a developing unit 313, a primary transfer roller 314, and a drum cleaning unit 315. Further, each of the image forming units 32 to 34 has the same configuration as the image forming unit 31.

  An electrostatic latent image is formed on the surface of the photoconductor drum 311. The charging roller 312 charges the photosensitive drum 311. The developing unit 313 contains a developer containing toner, and develops the electrostatic latent image formed on the photoconductor drum 311 using the toner contained in the developer. For example, the developer contains a magnetic carrier and the non-magnetic toner. The primary transfer roller 314 transfers the toner image formed on the surface of the photoconductor drum 311 by the developing unit 313 to the intermediate transfer belt 36. The drum cleaning unit 315 removes the toner remaining on the surface of the photoconductor drum 311. Here, the photosensitive drum 311 is an example of the image carrier in the present invention.

  The optical scanning device 35 forms an electrostatic latent image on the surface of the photoconductor drum included in each of the image forming units 31 to 34.

  The intermediate transfer belt 36 is an endless belt member to which the toner image formed on the surface of the photoconductor drum included in each of the image forming units 31 to 34 is transferred. The intermediate transfer belt 36 is stretched with a predetermined tension by a driving roller and a stretching roller. The intermediate transfer belt 36 moves along the front-rear direction D2 of the image forming apparatus 10 when the driving roller is rotationally driven by the driving force supplied from a power source (not shown).

  The secondary transfer roller 37 transfers the toner image attached to the surface of the intermediate transfer belt 36 onto the sheet supplied from the paper feeding unit 4.

  The fixing device 38 melt-fixes the toner image transferred onto the sheet by the secondary transfer roller 37 onto the sheet.

  The sheet on which the toner image is fixed by the fixing device 38 is discharged to the discharge tray 39.

  The paper feeding unit 4 includes a paper feeding cassette and a plurality of transport rollers, and supplies the sheets stored in the paper feeding cassette to the image forming unit 3. For example, the sheets accommodated in the paper feed cassette are sheet materials such as paper, coated paper, postcards, envelopes, and OHP sheets.

  In the image forming section 3, a color image is formed on the sheet supplied from the sheet feeding section 4 by the following procedure, and the sheet after the image formation is discharged to the sheet discharge tray 39.

  First, in the image forming unit 31, the charging roller 312 uniformly charges the photosensitive drum 311 to a predetermined potential. Next, the light scanning device 35 irradiates the surface of the photosensitive drum 311 with light based on the image data. As a result, an electrostatic latent image corresponding to the image data is formed on the surface of the photoconductor drum 311. Then, the electrostatic latent image on the photosensitive drum 311 is developed (visualized) as a yellow toner image by the developing unit 313.

  Subsequently, the yellow toner image formed on the photoconductor drum 311 is transferred to the intermediate transfer belt 36 by the primary transfer roller 314. On the other hand, the toner remaining on the surface of the photoconductor drum 311 is removed by the drum cleaning unit 315.

  In each of the image forming units 32 to 34, a toner image is formed on the photoconductor drum by the same processing procedure as that of the image forming unit 31. Then, the toner images of the respective colors formed on the photosensitive drums of the image forming units 32 to 34 are sequentially transferred onto the yellow toner images transferred to the intermediate transfer belt 36. As a result, the yellow, cyan, magenta, and black toner images are transferred and superposed on the surface of the intermediate transfer belt 36. Then, the color toner image transferred to the intermediate transfer belt 36 is transferred to the sheet supplied from the paper feeding unit 4 by the secondary transfer roller 37. After that, the sheet on which the toner image is transferred is fused and fixed by the fixing device 38 to form an image, and the sheet is ejected to the sheet ejection tray 39.

[Structure of developing unit 313]
Next, the configuration of the developing unit 313 of the image forming unit 31 will be described with reference to FIGS. Here, FIG. 3 is a sectional view taken along the line III-III in FIG. Note that, in FIG. 3, the position of the opening 313M in the developing unit 313 is indicated by a dashed line. The developing unit included in each of the image forming units 32 to 34 has the same configuration as the developing unit 313.

  As shown in FIGS. 2 and 3, the developing unit 313 includes a housing 313A, a first transport member 313B, a second transport member 313C, a magnet roller 313D, a developing roller 313E, and a toner detection unit 6.

  As shown in FIG. 2, the housing 313A houses a first transport member 313B, a second transport member 313C, a magnet roller 313D, and a developing roller 313E. Further, the housing 313A contains the developer. Specifically, the housing 313A contains the developer in an internal space formed by the side wall and the bottom surface 313F. As shown in FIG. 3, the housing 313A is elongated in the left-right direction D3.

  As shown in FIGS. 2 and 3, the housing 313A has a first transport path 313H and a second transport path 313J through which the developer is transported. Specifically, as shown in FIGS. 2 and 3, a partition wall 313G that separates the internal space of the housing 313A in the front-rear direction D2 is provided on the bottom surface 313F of the housing 313A. The side wall of the housing 313A, the bottom surface 313F, and the partition wall 313G form a first transfer path 313H and a second transfer path 313J through which the developer is transferred, inside the housing 313A.

  The 1st conveyance member 313B is provided in the 1st conveyance path 313H, as shown in FIG.2 and FIG.3. The first transport member 313B transports the developer along the transport direction D31 (see FIG. 3) in the first transport path 313H and agitates the developer to charge the toner contained in the developer. . For example, the first transport member 313B is a stirring screw.

  The second transport member 313C is provided in the second transport path 313J, as shown in FIGS. 2 and 3. The second transport member 313C transports the developer along a transport direction D32 (see FIG. 3) opposite to the transport direction D31 in the second transport path 313J, and stirs the developer to stir the developer. The toner contained in is charged. For example, the second transport member 313C is a stirring screw.

  A first connecting portion 313K that connects the first transport path 313H and the second transport path 313J is provided on the downstream side of the partition wall 313G in the transport direction D31. On the other hand, a second connecting portion 313L that connects the first transport path 313H and the second transport path 313J is provided on the downstream side of the partition 313G in the transport direction D32. As a result, the developer contained in the housing 313A is circulated and transported by the first transport member 313B and the second transport member 313C through the first transport path 313H and the second transport path 313J.

  The magnet roller 313D acquires the developer carried by the second carrying member 313C. Then, the magnet roller 313D supplies the toner contained in the developer acquired from the second transport member 313C to the developing roller 313E. The developing roller 313E develops the electrostatic latent image formed on the surface of the photoconductor drum 311 using the toner supplied from the magnet roller 313D.

  Here, in the image forming apparatus 10, since only the toner in the developer is used for developing the electrostatic latent image, the density of the toner in the developer in the developing unit 313 gradually decreases. Therefore, the image forming apparatus 10 is provided with a toner container 316 (see FIG. 1) capable of supplying the toner to the developing unit 313. The toner supplied from the toner container 316 is guided to the developing unit 313 by a toner transport path (not shown) connected to an opening 313M (see FIG. 2) formed on the outer surface of the housing 313A.

  Further, the developing unit 313 is provided with a toner detection unit 6 used by the control unit to control the supply amount of the toner from the toner container 316 to the developing unit 313.

[Configuration of Toner Detection Unit 6]
Next, the configuration of the toner detection unit 6 will be described with reference to FIGS. Here, FIG. 4 is a circuit diagram showing a configuration of the LC oscillation circuit 61. Further, FIG. 5 is a schematic cross-sectional view showing the configurations of the stray capacitance generating unit 63 and the internal frame 10A. Note that, in FIG. 5, among the magnetic force lines representing the magnetism generated in the coil 611, the magnetic force line M passing through the coil 611 is indicated by a dashed-dotted arrow. Further, in FIG. 5, for convenience of description, only the internal frame 10A, the developing unit 313, and the toner detection unit 6 are shown. Further, the toner detection unit of the developing unit included in each of the image forming units 32 to 34 has the same configuration as the toner detection unit 6.

  The toner detection unit 6 detects the concentration of the toner in the developer contained in the housing 313A of the developing unit 313.

  The toner detection unit 6 includes an LC oscillation circuit 61 (see FIG. 4). The toner detection unit 6 also includes a substrate 62 and a stray capacitance generation unit 63, as shown in FIGS.

  The LC oscillation circuit 61 outputs an electric signal S1 (see FIG. 4) having a frequency corresponding to the magnetic permeability of the developer contained in the developing unit 313. As shown in FIG. 4, the LC oscillation circuit 61 includes a coil 611, a conductive path 612, capacitors C1 and C2, resistors R1 and R2, and inverters Inv1 and Inv2. The LC oscillation circuit 61 is mounted on the substrate 62.

  As shown in FIG. 3, the substrate 62 has a rectangular shape and is arranged in a posture in which the longitudinal direction intersects the left-right direction D3 which is the longitudinal direction of the developing unit 313. Further, as shown in FIG. 5, the substrate 62 is arranged such that the coil 611 mounted on the substrate 62 faces the developing unit 313 in the vertical direction D1 which is the extending direction of the magnetic force lines M passing through the coil 611. It

  The substrate 62 is attached to the bottom surface of the developing unit 313. For example, the substrate 62 is attached to the bottom surface of the developing unit 313 by welding the substrate supporting unit 621 (see FIG. 5) supporting the substrate 62 to the bottom surface of the developing unit 313. A predetermined distance is provided in the vertical direction D1 between the substrate 62 and the developing unit 313.

  As shown in FIG. 2, the coil 611 is arranged to face the bottom surface of the first transport path 313H of the developing unit 313. The coil 611 is arranged on the first surface 62A (see FIG. 2), which is the outer surface of the substrate 62 facing the developing unit 313. For example, the coil 611 is a planar coil formed in a spiral shape along the first surface 62A.

  The conductive path 612 is a printed wiring formed on the substrate 62 and electrically connects each of the electric elements included in the LC oscillation circuit 61. For example, in the toner detection unit 6, each of the electric elements except the coil 611 included in the LC oscillation circuit 61 is provided on the second surface 62B (see FIG. 2) which is the outer surface on the back side of the first surface 62A of the substrate 62. There is. The conductive path 612 is formed on the second surface 62B of the substrate 62. Further, the coil 611 is electrically connected to the conductive path 612 through a through hole provided in the substrate 62.

  In the toner detection unit 6, each electric element including the coil 611 included in the LC oscillation circuit 61 and the conductive path 612 may be provided on the first surface 62A of the substrate 62.

  As shown in FIG. 4, in the LC oscillation circuit 61, one terminal of the coil 611 is electrically connected to the capacitor C1, the resistor R1, and the input terminal of the inverter Inv1. The other terminal of the coil 611 is electrically connected to the capacitor C2 and the resistor R2. Further, the capacitor C1 is electrically connected to the ground at a terminal different from the connection terminal with the coil 611. Further, the capacitor C2 is electrically connected to the ground at a terminal different from the connection terminal with the coil 611. Further, the resistor R1 has a terminal different from the connection terminal with the coil 611 electrically connected to the output terminal of the inverter Inv1. Further, the resistor R2 has a terminal different from the connection terminal with the coil 611 electrically connected to the output terminal of the inverter Inv1. The output terminal of the inverter Inv1 is electrically connected to the input terminal of the inverter Inv2. In the LC oscillation circuit 61, an electric signal S1 (see FIG. 4) having a frequency corresponding to the magnetic permeability of the developer accommodated in the developing unit 313 is output from the output terminal of the inverter Inv2. Here, the frequency f of the electric signal S1 is calculated based on the following equation (1).

f = 1 / 2π (LC) ^1/2 (1)

  In the above equation (1), L is the inductance of the coil 611, and C is the combined value of the electrostatic capacitances of the capacitors C1 and C2. The inductance L of the coil 611 is determined by the magnetic permeability of the developer accommodated in the developing unit 313 and the distance between the developing unit 313 and the coil 611 mounted on the substrate 62 arranged at the distance from the developing unit 313. It is defined by the distance X3 (see FIG. 5).

  The electric signal S1 output from the LC oscillation circuit 61 is input to the control unit. The control unit acquires the concentration of the toner in the developer housed in the developing unit 313 based on the electric signal S1, and from the toner container 316 to the developing unit 313 based on the acquired concentration of the toner. The amount of the toner supplied to the toner is controlled.

  The developer is not limited to the two-component developer containing the carrier and the non-magnetic toner, and may be a one-component developer containing the magnetic toner. In this case, the control unit acquires the amount of the toner at the detection position by the toner detection unit 6 (the position where the coil 611 faces the casing 313A) based on the electric signal S1, and the acquired toner amount The amount of toner supplied from the toner container 316 to the developing unit 313 may be controlled based on the amount.

  By the way, in the image forming apparatus 10, when the substrate 62 on which the LC oscillation circuit 61 is mounted is mounted on the developing unit 313, the mounting position is in the vertical direction D1 (see FIG. 5) which is the direction facing the developing unit 313. It may vary. Here, when the distance X3 between the developing unit 313 and the coil 611 changes, the inductance L of the coil 611 also changes. Therefore, if the mounting position of the substrate 62 varies in the vertical direction D1, the detection accuracy of the toner detection unit 6 also varies.

  On the other hand, in the image forming apparatus 10 according to the first exemplary embodiment of the present invention, as described below, it is possible to improve the detection accuracy of the toner detection unit 6 including the substrate 62 attached to the developing unit 313. is there.

  The stray capacitance generation unit 63 generates the stray capacitance C3 indicated by the broken line in FIG. Specifically, as shown in FIG. 2, the stray capacitance generating unit 63 is included in the LC oscillation circuit 61 at a position on the opposite side of the developing unit 313 from the substrate 62 in the vertical direction D1 which is the extending direction. It is arranged so as to face the conductor 612A (see FIG. 2). The stray capacitance generation unit 63 has conductivity and is electrically grounded.

  For example, as shown in FIG. 5, the stray capacitance generating unit 63 is a metal member that is long in the left-right direction D3 that is the longitudinal direction of the developing unit 313. The stray capacitance generation unit 63 is a magnetic body.

  Further, the image forming apparatus 10 includes an internal frame 10A as shown in FIG. The internal frame 10A supports the stray capacitance generating unit 63 separately from the substrate 62 at a position separated from the developing unit 313 by a predetermined distance X1 (see FIG. 5) in the vertical direction D1 which is the extending direction. . Here, the inner frame 10A is an example of the support portion in the present invention.

  For example, as shown in FIG. 5, the inner frame 10A includes a bottom plate portion 10A1 and a pair of side plate portions 10A2 and 10A3. The bottom plate portion 10A1 is provided on the bottom portion of the image forming apparatus 10. The pair of side plate portions 10A2 and 10A3 are provided upright on both ends of the bottom plate portion 10A1 in the left-right direction D3. For example, the inner frame 10A is integrally formed of metal and is electrically connected to the ground of the image forming apparatus 10. Note that each of the bottom plate portion 10A1, the side plate portion 10A2, and the side plate portion 10A3 may be formed by a separate member.

  As shown in FIG. 5, the side plate portion 10A2 has a fixing portion 10A4 fixed to the left end portion of the developing portion 313 in the left-right direction D3 which is the longitudinal direction of the developing portion 313. Further, the side plate portion 10A2 has a fixed portion 10A6 to which the left end portion of the floating capacitance generation portion 63 in the left-right direction D3 is fixed. The fixed portion 10A4 and the fixed portion 10A6 are integrally formed with the side plate portion 10A2. Here, the fixing portion 10A4 is an example of the first fixing portion in the present invention. The fixing portion 10A6 is an example of the second fixing portion in the present invention. The area from the fixed portion 10A4 to the fixed portion 10A6 in the side plate portion 10A2 is an example of the connection portion in the present invention.

  Further, as shown in FIG. 5, the side plate portion 10A3 has a fixing portion 10A5 fixed to the right end portion of the developing portion 313 in the left-right direction D3. Further, the side plate portion 10A3 has a fixed portion 10A7 to which the right end portion of the floating capacitance generation portion 63 in the left-right direction D3 is fixed. The fixed portion 10A5 and the fixed portion 10A7 are integrally formed with the side plate portion 10A3. Here, the fixing portion 10A5 is an example of the first fixing portion in the present invention. The fixing portion 10A7 is an example of the second fixing portion in the present invention. The area from the fixed portion 10A5 to the fixed portion 10A7 in the side plate portion 10A3 is an example of the connection portion in the present invention.

  As described above, in the image forming apparatus 10, the floating capacitance generating unit 63 and the developing unit 313 are both supported by the pair of side plate units 10A2 and 10A3. As a result, the stray capacitance generating unit 63 is positioned at a position separated from the developing unit 313 in the vertical direction D1 by the separation distance X1.

  Here, the stray capacitance C3 (see FIG. 4) generated by the conductor 612A included in the stray capacitance generator 63 and the LC oscillation circuit 61 is equal to the distance X2 between the stray capacitance generator 63 and the conductor 612A (see FIG. 5). Refer to)). Specifically, the stray capacitance C3 decreases as the separation distance X2 increases, and increases as the separation distance X2 decreases. On the other hand, the inductance L of the coil 611 decreases as the distance X3 increases, and increases as the distance X3 decreases.

  Therefore, in the image forming apparatus 10, when the mounting position of the substrate 62 is shifted to the developing unit 313 side, the separation distance X3 decreases and the inductance L increases, and the separation distance X2 increases and the capacitors C1 to C2. And the combined value of the stray capacitance C3 decreases (see FIG. 5). On the other hand, in the image forming apparatus 10, when the mounting position of the substrate 62 is displaced toward the stray capacitance generating unit 63 side, the separation distance X3 increases and the inductance L decreases, and the separation distance X2 decreases and the capacitor C1 increases. The combined value of C2 and stray capacitance C3 increases. That is, in the above formula (1), the change in the inductance L due to the variation in the mounting position of the substrate 62 is canceled by the combined value of the capacitors C1 to C2 and the stray capacitance C3. Therefore, it is possible to suppress variations in the detection accuracy of the toner detection unit 6 due to variations in the mounting position of the substrate 62.

  For example, when the mounting position of the substrate 62 deviates in the vertical direction D1 from the target position, the separation distance X1 is the rate of increase / decrease in the inductance L due to the amount of deviation from the target position and the amount of deviation from the target position in the capacitor C1 It is desirable that the distances such that C2 and the increase / decrease rate of the combined value of the stray capacitances C3 have reciprocal relations with each other.

  For example, the conductor 612A is a part of the conductive path 612 in the LC oscillation circuit 61. Specifically, as shown in FIG. 3, the conductor 612A is a metal pattern portion formed in a planar shape along the second surface 62B of the substrate 62.

  On the other hand, the stray capacitance generating unit 63 has a facing surface 63A facing the conductor 612A, as shown in FIG. In the image forming apparatus 10, the stray capacitance C3 can be arbitrarily adjusted by appropriately adjusting the area of the conductor 612A.

  Further, as shown in FIG. 3, the conductor 612A is arranged on the substrate 62 so as to be separated from the coil 611 in the front-rear direction D2 which is a direction intersecting the left-right direction D3 which is the longitudinal direction of the developing unit 313. The stray capacitance generation unit 63 is arranged so as to face the conductor 612A. That is, the stray capacitance generation unit 63 is arranged at a position separated in the front-rear direction D2 from the position P1 (see FIG. 2) facing the coil 611. This prevents the inductance L from being changed by the stray capacitance generation unit 63.

  The stray capacitance generation unit 63 may be formed integrally with the internal frame 10A.

  Further, the stray capacitance generating unit 63 may be formed of a non-magnetic member. In this case, the stray capacitance generation unit 63 may be arranged at the position P1 facing the coil 611.

  The stray capacitance generating unit 63 may be a flat plate member made of metal provided on the upper surface of a support member that is long in the left-right direction D3 and is supported by the pair of side plate units 10A2 and 10A3. In this case, the stray capacitance generation unit 63 may be arranged at the position P1 facing the coil 611.

  Further, the conductor 612A may be a linear pattern portion made of metal. The conductor 612A may be any of the electric elements included in the LC oscillation circuit 61. In addition, the conductor 612A may be arranged to face all the conductors included in the LC oscillation circuit 61.

  As described above, the image forming apparatus 10 is provided with the stray capacitance generation unit 63 arranged to face the conductor 612A included in the LC oscillation circuit 61. The stray capacitance generating unit 63 is supported at a position separated from the developing unit 313 in the vertical direction D1 which is the direction in which the developing unit 313 and the coil 611 face each other, with a separation distance X1. This makes it possible to improve the detection accuracy of the toner detection unit 6 including the substrate 62 attached to the developing unit 313.

[Second Embodiment]
Hereinafter, the image forming apparatus 10 according to the second exemplary embodiment of the present invention will be described with reference to FIGS. 6 and 7. Here, FIG. 6 is a schematic cross-sectional view showing the configuration of the image forming unit 31 of the image forming apparatus 10 according to the second embodiment. Further, FIG. 7 is a schematic cross-sectional view showing the configurations of the stray capacitance generating unit 63 and the internal frame 10A of the image forming apparatus 10 according to the second embodiment.

  In the image forming apparatus 10 according to the second exemplary embodiment, the configuration of the toner detection unit 6 is different from that of the first exemplary embodiment. The other configurations are common to the first embodiment and the second embodiment.

  Specifically, in the image forming apparatus 10 according to the second exemplary embodiment, as shown in FIGS. 6 and 7, the substrate 62 is arranged in a posture in which the longitudinal direction is along the left-right direction D3 which is the longitudinal direction of the developing unit 313. To be done. The conductor 612A is arranged on the substrate 62 so as to be separated from the coil 611 in the left-right direction D3 which is the longitudinal direction of the developing unit 313. The stray capacitance generation unit 63 is arranged so as to face the conductor 612A. That is, the stray capacitance generation unit 63 is arranged at the position P1 (see FIG. 7) facing the coil 611.

  In addition, in the image forming apparatus 10 according to the second embodiment, the stray capacitance generation unit 63 includes a magnetic blocking unit 631 as shown in FIGS. 6 and 7.

  The magnetic blocking unit 631 is provided at a position P1 (see FIG. 7) facing the coil 611 in the stray capacitance generating unit 63, and blocks the magnetism generated in the coil 611. For example, the magnetic blocking unit 631 is a sheet-shaped member placed on the facing surface 63A of the stray capacitance generating unit 63. This prevents the inductance L from being changed by the stray capacitance generation unit 63.

  As described above, in the image forming apparatus 10 according to the second embodiment, the stray capacitance generating unit 63 is provided with the magnetic blocking unit 631. Therefore, as shown in FIG. 6, the conductor 612A and the stray capacitance generating unit 63 can be arranged below the developing unit 313. Therefore, as compared with the image forming apparatus 10 according to the first exemplary embodiment, it is possible to prevent the size of the image forming unit 31 from increasing in the front-rear direction D2 (see FIGS. 2 and 6).

[Third Embodiment]
Hereinafter, the image forming apparatus 10 according to the third exemplary embodiment of the present invention will be described with reference to FIG. Here, FIG. 8 is a schematic cross-sectional view showing the configuration of the image forming unit 31 of the image forming apparatus 10 according to the third embodiment.

  In the image forming apparatus 10 according to the third exemplary embodiment, the configuration of the toner detection unit 6 is different from that of the first exemplary embodiment. Note that the other configurations are common to the first and third embodiments.

  Specifically, in the image forming apparatus 10 according to the third embodiment, the substrate 62 has a longitudinal direction along the left-right direction D3 that is the longitudinal direction of the developing unit 313, as in the image forming apparatus 10 according to the second embodiment. Arranged in a posture. The conductor 612A is arranged on the substrate 62 so as to be separated from the coil 611 in the left-right direction D3 which is the longitudinal direction of the developing unit 313. The stray capacitance generation unit 63 is arranged so as to face the conductor 612A. That is, the stray capacitance generation unit 63 is arranged at the position P1 (see FIG. 7) facing the coil 611.

  Further, in the image forming apparatus 10 according to the third exemplary embodiment, the stray capacitance generation unit 63 includes an opening 632 as shown in FIG.

  The opening 632 is formed at a position P1 (see FIG. 7) facing the coil 611 in the stray capacitance generator 63. Specifically, the opening 632 is a through hole formed at the facing position P1. This prevents the inductance L from being changed by the stray capacitance generation unit 63.

  As described above, in the image forming apparatus 10 according to the third embodiment, the floating capacitance generation unit 63 is provided with the opening 632. Therefore, as shown in FIG. 8, the conductor 612A and the stray capacitance generating unit 63 can be arranged below the developing unit 313. Therefore, similarly to the image forming apparatus 10 according to the second embodiment, it is possible to prevent the size of the image forming unit 31 from increasing in the front-rear direction D2 (see FIGS. 2 and 8).

1 ADF
2 image reading unit 3 image forming unit 4 paper feeding unit 5 operation display unit 6 toner detection unit 10 image forming apparatus 10A internal frames 31 to 34 image forming unit 35 optical scanning device 36 intermediate transfer belt 37 secondary transfer roller 38 fixing device 39 Paper discharge tray 61 LC oscillation circuit 62 Substrate 63 Stray capacitance generation unit 311 Photosensitive drum 312 Charging roller 313 Development unit 314 Primary transfer roller 315 Drum cleaning unit 316 Toner container 611 Coil 612 Conductive path 612A Conductor 621 Substrate support 631 Magnetic interruption Part 632 opening

Claims (10)

A developing unit that contains a developer containing toner and develops an electrostatic latent image formed on an image carrier using the toner contained in the developer;
A substrate on which an LC oscillation circuit including a coil is mounted, and the coil is arranged so as to face the developing unit in a direction in which magnetic lines of force passing through the coil extend.
Generation of a conductive stray capacitance, which is arranged to face at least a part of conductors included in the LC oscillation circuit at a position opposite to the developing unit from the substrate in the extending direction and is electrically grounded. Department,
A support unit that supports the floating capacitance generation unit separately from the substrate at a position spaced apart from the development unit by a predetermined distance in the extending direction;
An image forming apparatus including. The developer includes a magnetic carrier and the non-magnetic toner.
The image forming apparatus according to claim 1. The conductor is a conductive path that electrically connects each of the electric elements included in the LC oscillation circuit.
The image forming apparatus according to claim 1. The conductor is a flat pattern portion formed on the substrate,
The stray capacitance generation unit has a facing surface facing the pattern unit,
The image forming apparatus according to claim 3. The supporting unit includes a first fixing unit fixed to the developing unit, a second fixing unit fixing the floating capacitance generating unit, and a connecting unit connecting the first fixing unit and the second fixing unit. Is an integrally formed member,
The image forming apparatus according to claim 1. The floating capacitance generating unit is elongated along the longitudinal direction of the developing unit, and one or both ends in the longitudinal direction are supported by the supporting unit.
The image forming apparatus according to claim 5. The stray capacitance generation unit is arranged at a position separated from a position facing the coil in a direction intersecting the longitudinal direction,
The image forming apparatus according to claim 6. The stray capacitance generation unit is arranged to face the coil,
The image forming apparatus includes an opening formed at a position facing the coil in the stray capacitance generating unit,
The image forming apparatus according to claim 6. A substrate supporting unit that supports the substrate and is welded to the developing unit,
The image forming apparatus according to claim 1. The coil is a planar coil,
The image forming apparatus according to any one of claims 1 to 9.

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