JP2010210765A - Transfer device and image forming device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To clean a lens surface of a density sensor with a simple structure. <P>SOLUTION: A cleaning device that becomes movable when a recording sheet P passes through an inversion pass 47 and slides and frictions on a lens surface 61 of a density sensor 60 for measuring density of toner on a face for which detection is to be performed, in the case where double-side printing is performed, is provided to the third housing part 56 of a transfer unit 50. A cleaning member 110 is provided to a link mechanism so as to face the lens surface 61 of the density sensor 60 when the cleaning device is moved, and is composed of felt or a cleaning brush. The dimension of the cleaning member 110 is, for example, 8 mm in horizontal width w1, 5 mm in vertical width w2, and 5 mm in thickness h1. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a transfer device and an image forming apparatus.

  2. Description of the Related Art Conventionally, an image forming apparatus that forms an image by transferring and fixing a toner image formed on a photoreceptor or an intermediate transfer belt onto a recording sheet is known. Some image forming apparatuses include a transfer device having a density sensor. In the image forming apparatus, a test patch image is transferred and formed on a transfer conveyance belt or the like, and the density of the patch image is measured by a density sensor.

  Japanese Patent Application Laid-Open No. 2004-228561 proposes a configuration in which a cleaning member provided on a cartridge rubs and cleans the lens surface of the density sensor when the cartridge is attached to and detached from the image forming apparatus.

  Patent Document 2 proposes a configuration in which the cleaning member slides and cleans the lens surface of the density sensor by moving a shutter member provided with a cleaning member using a solenoid.

JP 2006-91650 A JP 2007-231757 A

  An object of the present invention is to clean the lens surface of the density sensor with a simple structure.

  According to a first aspect of the present invention, there is provided a reversing surface on which a recording medium is transported during double-sided printing, and a reversing surface that is moved when the recording medium passes through the reversing surface to transfer toner on a surface to be detected. Cleaning means for rubbing the lens surface of the sensor for measuring the density.

  The transfer device according to a second aspect of the present invention is the transfer device according to the first aspect, wherein the cleaning means is moved by being in contact with the recording medium.

  The transfer device according to a third aspect of the present invention is the transfer device according to the second aspect, wherein the cleaning means is in contact with a cleaning member that rubs a lens surface of the sensor and the recording medium, and the cleaning member is A link mechanism that moves the lens surface of the sensor.

  The transfer device according to a fourth aspect of the present invention is the transfer device according to the third aspect, wherein the link mechanism is positioned on the reversal surface and rotates in contact with the recording medium by passing through the recording medium. A moving member that is connected to the rotating member and moves the cleaning member to the lens surface of the sensor as the rotating member rotates.

  According to a fifth aspect of the present invention, the transfer device according to the fourth aspect includes return means for positioning the rotating member on the reversing surface after passing through the recording medium.

  A transfer device according to a sixth aspect of the present invention is the transfer device according to the fourth or fifth aspect, wherein a conveying roller is provided on the reversing surface, and the rotating member is provided on an axis of the conveying roller.

  According to a seventh aspect of the present invention, there is provided an image forming apparatus comprising: a reverse path through which a recording medium is conveyed during double-sided printing; an image carrier that transfers a toner image to the recording medium; and a toner density of the toner image is measured. And a cleaning means that moves when the recording medium passes through the reversing path and rubs the lens surface of the sensor.

  The image forming apparatus according to an eighth aspect of the present invention prints the back surface of the recording medium when the single-sided printing is instructed when the double-sided printing is not executed during a predetermined time. Do not perform double-sided printing.

  According to the first aspect of the present invention, the lens surface of the sensor can be cleaned without a separate drive source, as compared with the case without this configuration.

  According to the second aspect of the present invention, the cleaning means can be driven by the recording medium transported during double-sided printing as compared with the case where this configuration is not provided.

  According to the third aspect of the present invention, the lens surface of the sensor away from the reversal surface can be cleaned by the link mechanism as compared with the case without this configuration.

  According to the fourth aspect of the present invention, the conveyance force of the recording medium can be efficiently transmitted to the cleaning member as compared with the case where the present configuration is not provided.

  According to the fifth aspect of the present invention, the cleaning member can reciprocate as compared with the case where this configuration is not provided.

  According to the sixth aspect of the present invention, the rotating member can be easily rotated as compared with the case where this configuration is not provided.

  According to the seventh aspect of the present invention, the lens surface of the sensor can be cleaned without a separate drive source, as compared with the case without this configuration.

  According to the eighth aspect of the present invention, the sensor can be periodically cleaned as compared with the case where this configuration is not provided.

1 is a schematic side view illustrating a configuration of an image forming apparatus. FIG. 3 is a schematic perspective view showing a cover body and a main body frame to which a transport unit constituting the image forming apparatus is attached. It is a disassembled perspective view of the conveyance unit shown in FIG. It is explanatory drawing explaining the structure of a density sensor. FIG. 3 is an overview of the transfer unit according to the present embodiment as viewed from the guide plate side. It is AA arrow sectional drawing of the transcription | transfer unit shown in FIG. It is a general-view perspective view of the cleaning means shown in FIG. It is explanatory drawing which shows operation | movement of the transfer unit which concerns on this embodiment. (A) is a partial cross-sectional view of the transfer unit showing a state before the operation (initial state), (B) is a partial cross-sectional view of the transfer unit showing a state during the operation, (C) is an operation FIG. 6 is a partial cross-sectional view of the transfer unit showing a later state. FIG. 4 is a diagram illustrating an execution flow of a control unit of the image forming apparatus.

  DESCRIPTION OF THE PREFERRED EMBODIMENTS The best mode for carrying out the present invention will be described below in detail based on the embodiments shown in the drawings. In each figure, for each color of yellow (Y), magenta (M), cyan (C), and black (K), “Y”, “M”, “ Some of them are marked with the letters “C” and “K”.

  First, an outline of the image forming apparatus 10 according to the present invention will be described. As shown in FIGS. 1 and 2, the image forming apparatus 10 includes a main body frame 12 that detachably accommodates the photosensitive member 20 and the developing unit 16, and a cover member 14 that opens and closes the photosensitive member 20 and the developing unit 16. The transport unit 18 having a transport belt 34 that can transport the recording paper P is detachably attached to the cover body 14.

  The developing unit 16 irradiates the photoconductor 20 with image light based on the image data by charging the surface of the roll-shaped photoconductor 20 uniformly, and forms a latent image due to a difference in electrostatic potential. The optical box 24 to be developed, the developing roller 26 for selectively transferring the toner to the latent image to be visualized, and the photoconductor 20 after the toner image is transferred, slidably contacted, and the toner remaining on the photoconductor 20 is cleaned. And a cleaning member 28.

  The photoreceptor 20 has a photoreceptor layer on the surface (peripheral surface), and the surface (peripheral surface) is uniformly charged by the charging roller 22 and then is irradiated with laser light (image light) emitted from the optical box 24. ), The surface (peripheral surface) is exposed, and the potential of the exposed portion is attenuated to form an electrostatic latent image (image). The charging roller 22 is in contact with the photoconductor 20, a voltage is applied between them, and discharge is generated in a minute gap near the contact portion, so that the surface (circumferential surface) of the photoconductor 20 is substantially uniform. Is charged.

  The optical box 24 scans the surface (circumferential surface) of the photoconductor 20 with the blinking laser beam, and forms an electrostatic latent image based on the image data on the surface (circumferential surface) of the photoconductor 20. In addition, as the optical box 24, what arrange | positions light emitting elements, such as LED, and blinks these based on image data etc. can be considered.

  The developing roller 26 is disposed so as to face the photoconductor 20 in close proximity, and a developing bias voltage is applied between the developing roller 26 and the photoconductor 20. As a result, a developing bias electric field is formed between the developing roller 26 and the photoconductor 20, and the charged toner is transferred to the exposed portion on the photoconductor 20 to form a visible image.

  On the other hand, the transport unit 18 includes a transport belt 34 stretched around at least the driving roller 30 and the driven roller 32, and the transfer belt 34 has a transfer belt between the driving roller 30 and the driven roller 32 on the inner surface side thereof. A plurality of rollers 36 (four corresponding to each color to be described later) are arranged at predetermined intervals.

  When the cover body 14 is closed (when the cover body 14 is rotated toward the main body frame 12 to close the photoconductor 20 and the like), the transfer roller 36 faces the photoconductor 20 with the conveyance belt 34 interposed therebetween. By forming a transfer electric field with the photoconductor 20, the toner image (unfixed image) on the surface of the photoconductor 20 is transferred onto the recording paper P that is transported and passed by the transport belt 34. It is like that.

  Further, the transport unit 18 includes a double-sided transport unit 43 that reverses the recording paper P printed on the front side and transports it to the transport surface of the transport belt 34 when double-sided printing is instructed. The reverse path 47 of the double-sided conveyance unit 43 is formed by the first casing unit 52 attached to the cover body 14 and the transfer unit 50. In the first casing 52 and the transfer unit 50, a plurality of conveyance roller pairs 45 arranged in the vertical direction are arranged, and guide plates 47A and 47B for guiding the recording paper P conveyed by the conveyance roller pairs 45; Is provided.

  Here, for example, the developing unit 16 is arranged in the vertical direction in the order of yellow (Y), magenta (M), cyan (C), and black (K) from the bottom, and more than these developing units 16Y to 16K. A fixing device 38 is disposed on the downstream side in the conveyance direction of the recording paper P (upper part of the main body frame 12).

  The fixing device 38 includes a heating roller 40 and a pressure roller 42 that are pressed against each other with a predetermined pressure with their peripheral surfaces facing each other, and recording is performed by the heating roller 40 and the pressure roller 42. The toner image is fixed on the recording paper P by heating and pressurizing the unfixed toner image transferred onto the paper P.

  Note that the recording paper P on which the toner image is fixed by being heated and pressed by the fixing device 38 (the heating roller 40 and the pressure roller 42) is discharged onto the paper discharge tray 44. After the transfer of the toner image to the recording paper P, the surface (circumferential surface) of the photoconductor 20 is cleaned by the cleaning member 28 to prepare for the next image forming process.

  In addition, a detachable paper storage unit 46 for storing the recording paper P is provided at the lower part of the main body frame 12. The paper storage unit 46 can be pulled out in the direction opposite to the direction in which the recording paper P is sent out, and when the recording paper P is pulled out in the reverse direction, the recording paper P is fed.

  A paper feed roller pair 48 that feeds the recording paper P one by one from the paper storage portion 46 is provided at the top of the leading end of the paper storage portion 46, and the recording paper P delivered from the paper feed roller pair 48 is provided. Is sent to the conveyance surface of the conveyance belt 34 at a predetermined timing by the registration roller pair 49 and conveyed to the transfer position of the toner image of each color.

  Next, in the image forming apparatus 10 having the above configuration, the transport unit 18 that is detachably attached to the cover body 14 will be described.

  3 is an exploded perspective view of the transport unit 18 shown in FIG.

  As shown in FIG. 3, the transport unit 18 includes a first housing part 52 and a transfer unit 50.

  The first housing 52 has a guide plate 47B on which one of the pair of transport rollers 45 is arranged, and this guide plate 47B forms one road surface of the reversing path 47. That is, when the first casing 52 is assembled with the transfer unit 50, the reversing path 47 is formed by the guide plate 47A of the transfer unit 50 and the guide plate 47B of the first casing 52.

  The transfer unit 50 includes a frame-shaped second housing part 54. The driving roller 30 is rotatably supported on the upper end portion of the second casing portion 54, and the driven roller 32 is rotatably supported on the lower end portion. A transport belt 34 capable of electrostatically attracting the recording paper P is wound and stretched around the driving roller 30 and the driven roller 32.

  On the inner surface side of the conveying belt 34, between the driving roller 30 and the driven roller 32, transfer rollers 36Y to 36K are arranged at predetermined intervals for each color, and the transfer rollers 36Y to 36K are arranged. Is also rotatably supported by the second housing portion 54.

  Further, the transfer unit 50 includes a box-shaped third housing portion 56. A plurality (four in the figure) of coil springs 58 are provided on the outer surface side (the cover body 14 side) of the third housing portion 56, and the transfer unit 50 is moved to the main body when the cover body 14 is closed. The frame 12 is pressed with a predetermined pressure. As a result, the transfer rollers 36Y to 36K and the transport belt 34 are pressed against the photoconductors 20Y to 20K with a predetermined pressure.

  Further, a flange portion 56 </ b> A projects from the upper end portion of the third housing portion 56 and faces the driving roller 30. A density sensor 60 that measures the density of a test toner image transferred and formed on the conveyor belt 34 is disposed at the center of the upper surface of the flange 50A.

  FIG. 4 is an explanatory diagram illustrating the configuration of the density sensor 60.

  As shown in FIG. 4, the density sensor 60 is provided with an LED irradiation unit 60 </ b> A so that light enters from the conveyance direction of the conveyance belt 34, and the toner image on the conveyance belt 34 from the LED irradiation unit 60 </ b> A. Then, light is irradiated at a predetermined angle, and reflected light from the toner image is incident on the lens 60B at an angle of 90 ° with respect to the toner image. Then, the reflected light is imaged on the light receiving surface of the photodiode 60C through the lens 60B. Here, a mask 60D is provided immediately before the photodiode 60C to restrict the detection area of the toner image. Then, the electric signal converted by the reflected light imaged on the photodiode 60C is transmitted to a detection device (not shown), and the toner density is detected.

  Here, a transparent plastic 61 (hereinafter referred to as “lens surface 61”) is provided on the surface of the density sensor 60 so as to face the conveyance belt 34, and protects the components in the density sensor 60 such as the lens 60B. .

  However, the floating toner around the photoconductor 20 (so-called cloud toner) may adhere to the lens surface 61 and the lens surface 61 may be contaminated.

  Therefore, in this embodiment, a cleaning unit that cleans the lens surface 61 is provided in the transfer unit 50 in order to remove contamination of the lens surface 61.

  FIG. 5 is a schematic view of the transfer unit 50 according to this embodiment as viewed from the guide plate 47A side, and FIG. 6 is a cross-sectional view of the transfer unit 50 shown in FIG.

  A hollow portion 102 is formed in the third housing portion 56 of the transfer unit 50 according to the present embodiment, and a cleaning device 100 is provided in the hollow portion 102 as an example of a cleaning unit (see FIG. 6). . Further, the guide plate 47A is provided with one of the plurality of transport roller pairs 45, the transport rollers 45A, 45B, 45C, and 45D. Furthermore, an opening 104 connected to the hollow portion 102 is provided in the guide plate 47A between the transport roller 45A and the transport roller 45B (see FIG. 5).

  FIG. 7 is a schematic perspective view of the cleaning device 100 shown in FIG.

  As shown in FIG. 7, the cleaning device 100 includes a cleaning member 110, a support shaft 112, and a link mechanism 114.

  The cleaning member 110 is provided in the link mechanism 114 so as to face the lens surface 61 of the density sensor 60 when the cleaning device 100 is moved, and is configured by a felt or a cleaning brush. The size of the cleaning member 110 is, for example, a horizontal width w1 of 8 mm, a vertical width w2 of 5 mm, and a thickness h1 of 5 mm.

  The support shaft 112 extends in the horizontal direction so as to face the opening 104, and both ends of the support shaft 112 are supported by the third housing portion 56 of the transfer unit 50 to support the link mechanism 114.

  The link mechanism 114 includes a first link 120, a second link 122, and a third link 124.

  The first link 120 is an L-shaped plate member, and the central portion 120 </ b> A is supported by the support shaft 112.

  The first link 120 is urged counterclockwise (arrow A direction) by the urging means (return means) such as the weight of the link mechanism 114 or a coil spring (not shown) around the support shaft 112. Due to this urging, one end 120B of the first link 120 protrudes from the opening 104 of the guide plate 47A to the reversing path 47, and the one end 120B is located between the transport roller 45A and the transport roller 45B arranged on the guide plate 47A. And are located on these axes.

  As a result, the first link 120 comes into contact with the recording paper P passing through the reverse path 47.

  The width w3 of the one end 120B of the first link 120 is, for example, 5 mm to 10 mm. When the one end 120 </ b> B comes into contact with the recording paper P passing through the reverse path 47, the first link 120 starts to rotate clockwise around the support shaft 112 toward the lower side of the reverse path 47. Here, the recording paper P passing through the reversing path 47 has an increased conveying force when it comes into contact with the rotating conveying roller pair 45. Therefore, if the first link 120 is provided on the axes of the conveying roller 45A and the conveying roller 45B. The first link 120 rotates easily.

  The other end 120 </ b> C of the first link 120 extending downward is connected to the one end 122 </ b> A of the second link 122 using the pin 126 as a connecting portion.

  The second link 122 is a rod member and extends into the hollow portion 102 toward the concentration sensor 60.

  The other end 122B of the second link 122 is connected to one end 124A of the third link 124 with the pin 128 as a connecting portion.

  The third link 124 is a plate member, and the central portion 124B is sandwiched between a pair of sandwiching members 106 fixed to the third housing portion 56 of the transfer unit 50 so as to be slidable in the axial direction.

  Further, the other end portion 100B of the third link 124 is provided with a cleaning member 110 at an upper portion thereof.

  Next, the operation of the transfer unit 50 according to this embodiment will be described.

  In the image forming apparatus 10 in which the transfer unit 50 according to the present embodiment is mounted, when double-sided printing is executed by the user, first, the surface of the recording paper P is formed by the image forming unit including the transfer roller 36 and the photoreceptor 20. An image is formed. Thereafter, the recording sheet P is reversed and conveyed to the reversing path 47.

  Here, the cleaning device 100 of the transfer unit 50 according to the present embodiment operates as follows when the recording paper P passes through the reversing path 47.

  FIG. 8 is an explanatory diagram showing the operation of the cleaning device 100 shown in FIG. FIG. 8A is a partial cross-sectional view of the transfer unit 50 showing a state (initial state) before the cleaning device 100 operates, and FIG. 8B shows a state in which the cleaning device 100 starts operating. FIG. 8C is a partial cross-sectional view of the transfer unit 50, and FIG. 8C is a partial cross-sectional view of the transfer unit 50 showing a state after the cleaning device 100 is operated.

  As shown in FIGS. 8A to 8C, the cleaning device 100 provided in the transfer unit 50 according to the present embodiment moves in contact with the leading edge of the recording paper P passing through the reverse path 47, and has a density. The lens surface 61 of the sensor 60 is rubbed. Thereafter, the cleaning device 100 continues to contact the recording paper P until the trailing edge of the recording paper P passes, and when the trailing edge of the recording paper P passes and the contact with the recording paper P is released, FIG. The state returns to the same initial state as in FIG.

  Specifically, each member of the cleaning member 110 and the link mechanism 114 of the cleaning device 100 operates as follows.

  First, as shown in FIG. 8A, in the initial state, the first link 120 of the link mechanism 114 is urged counterclockwise by an urging means such as its own weight or a coil spring (not shown). The one end 120B of the first link 120 protrudes from the opening 10 of the guide plate 47A to the reversing path 47. This state is maintained until immediately before the leading edge of the recording paper P passes through the position where the one end 120B of the first link 120 is located in the reverse path 47.

  When the leading edge of the recording paper P passes through the position where the one end 120B of the first link 120 is located, the leading edge of the recording paper P contacts the one end 120B of the first link 120. As shown in FIG. 8 (B), the one end 120B in contact with the recording paper P is pushed down by the conveying force toward the lower side of the reverse path 47 of the recording paper P, and the first link 120 is centered on the support shaft 112. The reversing path 47 is rotated downward in the clockwise direction.

  Along with this, the second link 122 coupled to the first link 120 by the pin 126 moves in the upper oblique direction toward the density sensor 60 side. Further, the third link 124 coupled to the second link 122 by the pin 128 moves parallel to the lens surface 61 of the density sensor 60 while being slidably sandwiched by the sandwiching member 106.

  As the third link 124 moves, the cleaning member 110 provided on the third link 124 moves to the lens surface 61 of the density sensor 60 and rubs it. As shown in FIG. 8C, the cleaning member 110 is in contact with the recording paper P until the trailing edge of the recording paper P passes through the position where the one end 120B of the first link 120 is located in the reverse path 47. Until it is released).

  In the state shown in FIG. 8C, when the rear end of the recording paper P passes through the position where the one end portion 120 </ b> B of the first link 120 is located in the reversing path 47, the first link 120 has its own weight of the link mechanism 114 or By an urging means such as a coil spring (not shown), the support shaft 112 is rotated about the support shaft 112 in the counterclockwise direction. Accordingly, the second link 122 coupled to the first link 120 with the pin 126 moves toward the inversion path 47 in the lower diagonal direction. Further, the third link 124 coupled to the second link 122 by the pin 128 moves in the lower diagonal direction toward the inversion path 47 while being slidably sandwiched by the sandwiching member 106.

  Along with the movement of the third link 124, the cleaning member 110 provided on the third link 124 moves in a lower oblique direction from the position in contact with the lens surface 61 of the density sensor 60 toward the inversion path 47. The contact with the lens surface 61 is released away from the sensor 60. As a result, the cleaning apparatus 100 returns from the state shown in FIG. 8C to the initial state shown in FIG.

  As described above, according to the present embodiment, the conveyance force of the recording paper P at the time of double-sided printing is used as the drive source of the cleaning device 100, which is simpler than the structure using the solenoid as the drive source described in the cited document 2. The lens surface 61 of the density sensor is cleaned with a simple structure.

  In addition, when the cartridge is attached to and detached from the image forming apparatus described in Cited Document 1, the cleaning member provided on the cartridge slides and cleans the lens surface of the density sensor to clean and remove the cartridge. It is presumed that the frequency of duplex printing is higher than the frequency of duplex printing, and according to the present embodiment, the lens surface 61 of the density sensor 60 is appropriately cleaned.

  Further, the conveyance force of the recording paper P conveyed during single-sided printing may be used as the drive source of the cleaning device 100. In this case, the lens surface 61 of the density sensor 60 is frequently cleaned. In the present embodiment, the conveyance force of the recording paper P that is reversed and conveyed during double-sided printing is used as the drive source of the cleaning device 100, so the cleaning frequency of the lens surface 61 of the density sensor 60 is adjusted appropriately.

  The present invention is not limited to the above-described embodiment, and various modifications, changes, and improvements can be made without departing from the gist of the present invention.

  For example, the link mechanism 114 has been described as having the first link 120, the second link 122, and the third link 124, but the number of links is not limited.

  Further, although the cleaning device 100 has been described to be movable by being in contact with the recording paper P, the cleaning device 100 may be moved by using a conveying roller pair 45 that is movable during double-sided printing as a drive source.

  Furthermore, although the transfer unit 50 has been described as a unitized configuration that is detachable from the image forming apparatus 10, each component of the transfer unit 50 may be integrated with the image forming apparatus 10.

  Furthermore, even when the user does not execute double-sided printing, the image forming apparatus 10 cleans the lens surface 61 of the density sensor 60. When the user gives an instruction to execute printing processing, the image forming apparatus 10 performs the following flow. Control means for executing the above may be provided. The control means includes at least a memory, a CPU, and a program.

  FIG. 9 is a diagram illustrating an execution flow of the control unit of the image forming apparatus 10.

  In step 100, it is determined whether the print type of the print process instructed to execute is single-sided printing or double-sided printing. If it is determined that single-sided printing is selected, the process proceeds to step 102. If it is determined that double-sided printing is selected, the process proceeds to step S104.

  In step 102, single-sided printing of the recording paper P is executed.

  In step 104, double-sided printing of the recording paper P is executed.

  In step 106, for example, a predetermined period such as one day or one week or a predetermined number of printed sheets such as 100 sheets or 500 sheets is measured by a timer, and it is determined whether double-sided printing has not been performed during this period. If the determination is affirmative, the process proceeds to step 108, and if the determination is negative, the process proceeds to step 110.

  In step 108, the recording paper P on which the front surface is printed is conveyed to the reverse path 47, the cleaning device 100 is moved, and then the recording paper P is discharged onto the discharge unit 44 without printing the back surface.

  In step 110, it is determined whether the printing process has been completed. If the determination is affirmative, the process ends. If the determination is negative, the process returns to step 100.

  As a result of the above control, the recording sheet P is transported to the reversing path 47 and the cleaning device 100 is moved even when there is an instruction to execute single-sided printing. Therefore, the lens surface 61 of the density sensor 60 is periodically cleaned. Note that the timing for transporting the recording paper P to the reversing path 47 is not limited to the case where the user has issued an instruction to execute the printing process as shown in FIG. 9, and duplex printing is performed by an interrupt process by a software timer or a hardware timer. You may make it do.

DESCRIPTION OF SYMBOLS 10 Image forming apparatus 20 Photosensitive body (Image holding body)
34 Conveyor belt (Detected surface)
45A, 45B Conveying roller
47 Reverse path 47A Guide plate (reverse surface)
50 Transfer unit (transfer device)
60 Concentration sensor (sensor)
61 Lens surface 100 Cleaning device (cleaning means)
110 Cleaning member 114 Link mechanism (link mechanism, return means)
120 First link (rotating member)
122, 124 Second link, third link (moving member)
P Recording paper (recording medium)

Claims (8)

A reversing surface on which the recording medium is conveyed during duplex printing;
Cleaning means that moves when the recording medium passes through the reversing surface and rubs the lens surface of a sensor that measures the concentration of toner on the detection surface;
A transfer device having   The transfer device according to claim 1, wherein the cleaning unit is movable by being in contact with the recording medium. The cleaning means includes
A cleaning member for rubbing the lens surface of the sensor;
A link mechanism that contacts the recording medium and moves the cleaning member to the lens surface of the sensor;
The transfer device according to claim 2, comprising: The link mechanism is
A rotating member positioned on the reversing surface and rotating in contact with the recording medium by passing the recording medium;
A moving member connected to the rotating member and moving the cleaning member to the lens surface of the sensor as the rotating member rotates;
The transfer device according to claim 3, comprising:   The transfer device according to claim 4, further comprising return means for positioning the rotating member on the reversal surface after passing through the recording medium.   The transfer device according to claim 4, wherein a conveying roller is provided on the reverse surface, and the rotating member is provided on an axis of the conveying roller. A reversing path through which the recording medium is conveyed during duplex printing;
An image carrier for transferring a toner image to the recording medium;
A sensor for measuring the toner density of the toner image;
A cleaning unit that moves when the recording medium passes through the reversing path and rubs the lens surface of the sensor;
An image forming apparatus.   The image forming apparatus according to claim 7, wherein when the double-sided printing is not executed during a predetermined time, double-sided printing that does not print the back surface of the recording medium is executed when single-sided printing is instructed.

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