Image forming apparatus

Abstract

To provide an image forming apparatus that can suitably clean a sensor detection surface and achieve appropriate density correction.SOLUTION: An image forming apparatus comprises a density detection unit 14, a cleaning unit 40, and a control unit. The density detection unit 14 has a substrate 151 and a sensor package 17, and outputs a detection value related to the density of toner in a toner image formed on an outer peripheral surface of an intermediate transfer belt 31. When the cleaning unit 40 cleans a sensor detection surface 17f, the control unit moves a brush 43 to a cleaning position where it is in contact with the sensor detection surface 17f, and when the cleaning unit 40 does not clean the sensor detection surface 17f, moves the brush 43 to a retreated position where it is not in contact with the sensor package 17 and the substrate 151.SELECTED DRAWING: Figure 5

Description

Technical Field

[0001] The present invention relates to an image forming apparatus.

Background Art

[0002] In electrophotographic image forming apparatuses such as copiers and printers, an apparatus that forms a toner image to be later transferred onto paper by supplying toner to an electrostatic latent image formed on the outer peripheral surface of a photoreceptor drum and developing it is widely used. The density of the toner image formed by the image forming apparatus changes over time for various reasons. For this reason, it is common to perform calibration in which a toner image (reference image) for density correction is formed on the outer peripheral surface of the photoreceptor drum or an intermediate transfer belt (image carrier), and the toner density of the toner image is detected by a sensor to perform density correction. In order to perform appropriate density correction, a cleaning process for removing foreign matter adhering to the detection surface of the sensor is important.

[0003] The conventional light detection apparatus disclosed in Patent Document 1 includes a light irradiation unit, a light detection unit, a removal unit (brush) for removing foreign matter adhering to a light transmission member on the optical path, and a drive unit for the removal unit. The drive unit of the removal unit drives the removal unit (brush) to remove foreign matter adhering to the light transmission member.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, when the tip of the brush is constantly in contact with a sensor or the like, there is a problem that the brush develops a bend. As a result, the cleaning of the sensor detection surface cannot be sufficiently performed, and there is a risk that foreign matter remains on the detection surface of the sensor. For this reason, there was a concern that appropriate density correction could not be achieved.

[0006] The present invention has been made in view of the above points, and an object thereof is to provide an image forming apparatus capable of suitably cleaning a sensor detection surface and realizing appropriate density correction.

Means for Solving the Problems

[0007] In order to solve the above problems, an image forming apparatus of the present invention includes a density detection unit, a cleaning unit, and a control unit. The density detection unit has a sensor that irradiates light toward the outer peripheral surface of an image carrier and receives reflected light from the image carrier, and outputs a detection value related to the toner density of a toner image formed on the outer peripheral surface of the image carrier. The cleaning unit has a brush that moves in a direction intersecting with the light irradiated by the sensor, and cleans the detection surface of the sensor with the brush. The control unit controls the operation of the cleaning unit. The density detection unit has a substrate and a sensor package fixed to a surface of the substrate facing the image carrier, protruding toward the image carrier, and holding the sensor. The cleaning unit has a slide member that holds the brush, a drive unit that moves the slide member in the intersecting direction, and the brush fixed to the slide member, protruding toward the sensor, contacting the detection surface, and having a length that does not contact the substrate. The control unit moves the brush to a cleaning position where it contacts the detection surface when the detection surface is cleaned by the cleaning unit, and moves the brush to a retracted position where it does not contact the sensor package and the substrate when the detection surface is not cleaned by the cleaning unit.

Effects of the Invention

[0008] According to the configuration of the present invention, when the sensor detection surface is not cleaned by the cleaning unit, the brush does not contact the sensor package and the substrate of the density detection unit. As a result, it becomes possible to maintain the brush in a straight state, and suitable cleanability of the sensor detection surface by the brush can be ensured. Therefore, it is possible to realize appropriate density correction.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Embodiments for Carrying Out the Invention

[0010] Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the present invention is not limited to the following content.

[0011] FIG. 1 is a schematic cross-sectional front view of an image forming apparatus 1 according to an embodiment. FIG. 2 is a block diagram showing the configuration of the image forming apparatus 1 of FIG. 1. FIG. 3 is a schematic cross-sectional front view of the periphery of an image forming unit 20 of the image forming apparatus 1 of FIG. 1. As an example of the image forming apparatus 1 of the present embodiment, it is a tandem type color printer that transfers a toner image to a sheet S using an intermediate transfer belt 31. The image forming apparatus 1 may be a so-called multifunction machine having functions such as printing, scanning (image reading), and facsimile transmission.

[0012] As shown in FIGS. 1, 2, and 3, the image forming apparatus 1 includes a paper supply unit 3, a paper conveyance unit 4, an exposure unit 5, an image forming unit 20, a transfer unit 30, a fixing unit 6, a paper discharge unit 7, a control unit 8, and a storage unit 9 provided in its main body 2.

[0013] The paper supply unit 3 is disposed at the bottom of the main body 2. The paper supply unit 3 stores a plurality of sheets of paper S before printing, and separates and feeds out the sheets of paper S one by one during printing. The paper conveyance unit 4 extends in the vertical direction along the side wall of the main body 2. The paper conveyance unit 4 conveys the sheet of paper S fed out from the paper supply unit 3 to the secondary transfer unit 33 and the fixing unit 6, and further discharges the sheet of paper S after fixing from the paper discharge port 4a to the paper discharge unit 7. The exposure unit 5 is disposed above the paper supply unit 3. The exposure unit 5 irradiates laser light controlled based on image data toward the image forming unit 20.

[0014] The image forming unit 20 is disposed above the exposure unit 5 and below the intermediate transfer belt 31. The image forming unit 20 includes an image forming unit 20Y for yellow, an image forming unit 20C for cyan, an image forming unit 20M for magenta, and an image forming unit 20B for black. These four image forming units 20 have the same basic configuration. Thus, in the following description, unless otherwise specifically limited, the identification symbols "Y", "C", "M", and "B" representing each color may be omitted.

[0015] The image forming unit 20 includes a photosensitive drum 21 rotatably supported in a predetermined direction (clockwise in FIGS. 1 and 3). The image forming unit 20 further includes a charging unit 22, a developing unit 23, and a drum cleaning unit 24 disposed around the photosensitive drum 21 along its rotation direction. Note that a primary transfer unit 32 is disposed between the developing unit 23 and the drum cleaning unit 24.

[0016] The photoreceptor drum 21 has a photosensitive layer formed on its outer peripheral surface. The charging unit 22 charges the outer peripheral surface of the photoreceptor drum 21 to a predetermined surface potential. The exposure unit 5 exposes the outer peripheral surface of the photoreceptor drum 21 charged by the charging unit 22 to form an electrostatic latent image of the document image with the charge attenuated on the outer peripheral surface of the photoreceptor drum 21. The developing unit 23 supplies toner to the electrostatic latent image on the outer peripheral surface of the photoreceptor drum 21 for development to form a toner image. Each of the four image forming units 20 forms a toner image of a different color. The drum cleaning unit 24 removes and cleans the toner and the like remaining on the outer peripheral surface of the photoreceptor drum 21 after the toner image is primarily transferred to the outer peripheral surface of the intermediate transfer belt 31. In this way, the image forming unit 20 forms an image (toner image) to be later transferred to the paper S.

[0017] The transfer unit 30 includes an intermediate transfer belt (image carrier) 31, primary transfer units 32Y, 32C, 32M, 32B, a secondary transfer unit 33, and a belt cleaning unit 34. The intermediate transfer belt 31 is disposed above the four image forming units 20. The intermediate transfer belt 31 is rotatably supported in a predetermined direction (counterclockwise in FIGS. 1 and 3), and is an endless intermediate transfer body on which the toner images formed by each of the four image forming units 20 are sequentially stacked and primarily transferred. The four image forming units 20 are arranged in a so-called tandem method in a row from the upstream side to the downstream side in the rotation direction of the intermediate transfer belt 31.

[0018] The primary transfer units 32Y, 32C, 32M, 32B are disposed above the image forming units 20Y, 20C, 20M, 20B of each color with the intermediate transfer belt 31 interposed therebetween. The secondary transfer unit 33 is located upstream of the fixing unit 6 with respect to the paper conveyance direction of the paper conveyance unit 4 and downstream of the four image forming units 20Y, 20C, 20M, 20B with respect to the rotation direction of the intermediate transfer belt 31. The belt cleaning unit 34 is disposed downstream of the secondary transfer unit 33 with respect to the rotation direction of the intermediate transfer belt 31.

[0019] The primary transfer unit 32 transfers the toner image formed on the outer peripheral surface of the photosensitive drum 21 to the intermediate transfer belt 31. In other words, the toner image is primarily transferred to the outer peripheral surface of the intermediate transfer belt 31 by the primary transfer units 32Y, 32C, 32M, and 32B for each color. Then, as the intermediate transfer belt 31 rotates, the toner images of the four image forming units 20 are successively and continuously superimposed and transferred to the intermediate transfer belt 31 at a predetermined timing, whereby a color toner image in which toner images of yellow, cyan, magenta, and black are superimposed is formed on the outer peripheral surface of the intermediate transfer belt 31.

[0020] The color toner image on the outer peripheral surface of the intermediate transfer belt 31 is transferred to the sheet S that has been fed in synchronization by the sheet conveyance unit 4 at the secondary transfer nip formed in the secondary transfer unit 33. The belt cleaning unit 34 removes and cleans deposits such as toner remaining on the outer peripheral surface of the intermediate transfer belt 31 after secondary transfer. In this way, the transfer unit 30 transfers (records) the toner image formed on the outer peripheral surface of the photosensitive drum 21 to the sheet S.

[0021] The fixing unit 6 is disposed above the secondary transfer unit 33. The fixing unit 6 heats and presses the sheet S onto which the toner image has been transferred to fix the toner image to the sheet S.

[0022] The sheet discharge unit 7 is disposed above the transfer unit 30. The sheet S on which the toner image has been fixed and the printing is completed is conveyed to the sheet discharge unit 7. The printed sheet (printed matter) is taken out from above by the sheet discharge unit 7.

[0023] The control unit 8 includes a CPU, an image processing unit, and other electronic circuits and electronic components (all not shown). The CPU controls the operations of the respective components provided in the image forming apparatus 1 based on the control programs and data stored in the storage unit 9, and performs processes related to the functions of the image forming apparatus 1. Each of the sheet supply unit 3, the sheet conveyance unit 4, the exposure unit 5, the image forming unit 20, the transfer unit 30, and the fixing unit 6 receives individual commands from the control unit 8 and cooperates to perform printing on the sheet S.

[0024] The memory unit 9 is composed of a combination of a non-volatile memory device (not shown), such as a program ROM (Read Only Memory), a data ROM, etc., and a volatile memory device (not shown), such as a RAM (Random Access Memory).

[0025] Subsequently, the image forming unit 20 and its peripheral configuration will be described with reference to FIG. 3. Since each of the image forming units 20 for each color has the same basic configuration, the description of the components with the identification symbols representing each color and the explanation will be omitted unless particularly limited.

[0026] The image forming unit 20 includes a photosensitive drum 21, a charging unit 22, a developing unit 23, and a drum cleaning unit 24.

[0027] The photosensitive drum 21 has a cylindrical shape that is rotatably supported with its central axis horizontal and is rotated at a constant speed around the central axis by a driving unit (not shown). The photosensitive drum 21 has a photosensitive layer made of an inorganic photosensitive material such as amorphous silicon on the outer peripheral surface of a drum base tube made of a metal such as aluminum. An electrostatic latent image is formed on the outer peripheral surface of the photosensitive drum 21.

[0028] The charging unit 22 has, for example, a charging roller 221. The charging roller 221 extends parallel to the axial direction of the photosensitive drum 21 and is rotatably supported with its central axis horizontal. The charging roller 221 rotates following the rotation of the photosensitive drum 21 by contacting the outer peripheral surface of the photosensitive drum 21. The charging roller 221 has a conductive layer made of, for example, a crosslinked rubber containing an ion conductive material on the outer peripheral surface of a core metal. When a predetermined charging voltage is applied to the charging roller 221, the outer peripheral surface of the photosensitive drum 21 is uniformly charged.

[0029] The developing unit 23 is disposed on the downstream side in the rotation direction of the photosensitive drum 21 with respect to the charging unit 22. The developing unit 23 includes a developing container 231, a first conveying member 232, a second conveying member 233, a developing roller (developer carrier) 234, and a regulating member 235.

[0030] The developing container 231 has an elongated shape extending along the axial direction of the photosensitive drum 21 (the depth direction of the paper in FIG. 3), and is arranged with its longitudinal direction horizontal. The developing container 231 accommodates, as a developer containing toner supplied to the photosensitive drum 21, for example, a two-component developer containing toner and a magnetic carrier.

[0031] The first conveying member 232 and the second conveying member 233 are rotatably supported by the developing container 231 about an axis extending parallel to the photosensitive drum 21. By rotating about their axes, the first conveying member 232 and the second conveying member 233 convey the developer while stirring it in opposite directions along the axial direction of the rotation.

[0032] The developing roller 234 is located above the second conveying member 233 in the developing container 231 and is arranged to face the photosensitive drum 21. The developing roller 234 is rotatably supported by the developing container 231 about an axis extending parallel to the axis of the photosensitive drum 21. A part of the outer peripheral surface of the developing roller 234 is exposed from the developing container 231, faces, and is close to the photosensitive drum 21. The developing roller 234 carries the developer containing toner in the developing container 231 and supplies it to the photosensitive drum 21. In other words, the developing roller 234 adheres the toner in the developing container 231 to the electrostatic latent image on the outer peripheral surface of the photosensitive drum 21 to form a toner image.

[0033] The regulating member 235 is arranged on the upstream side in the rotation direction of the developing roller 234 in the facing area between the developing roller 234 and the photosensitive drum 21. The regulating member 235 faces close to the developing roller 234 and is arranged with a predetermined interval between its tip and the outer peripheral surface of the developing roller 234. The regulating member 235 extends over the entire axial direction of the developing roller 234.

[0034] The developer in the developing container 231 is circulated, agitated, and charged by the rotation of the first conveying member 232 and the second conveying member 233, and is carried on the outer peripheral surface of the developing roller 234. The layer thickness of the developer carried on the outer peripheral surface of the developing roller 234 is regulated by the regulating member 235. When a predetermined developing voltage is applied to the developing roller 234, toner in the developer carried on the outer peripheral surface of the developing roller 234 moves to the outer peripheral surface of the photosensitive drum 21 in the facing area with the photosensitive drum 21 due to the potential difference from the surface potential of the outer peripheral surface of the photosensitive drum 21. Thereby, the electrostatic latent image on the outer peripheral surface of the photosensitive drum 21 is developed with toner.

[0035] The drum cleaning unit 24 is disposed on the downstream side of the primary transfer unit 32 with respect to the rotation direction of the photosensitive drum 21. The drum cleaning unit 24 includes a recovery container 241, a cleaning blade 242, and a recovery spiral 243.

[0036] The recovery container 241 has an elongated shape extending along the axial direction of the photosensitive drum 21 (the depth direction of the paper surface in FIG. 3), and is disposed with its longitudinal direction horizontal. The recovery container 241 accommodates residues such as toner removed from the outer peripheral surface of the photosensitive drum 21 by the cleaning blade 242.

[0037] The cleaning blade 242 has a plate shape extending along the axial direction of the photosensitive drum 21, and is formed of an elastic member such as polyurethane rubber. The cleaning blade 242 is disposed on the downstream side in the drum rotation direction with respect to the contact point so as to form a predetermined angle with respect to the tangential direction of the photosensitive drum 21 at the contact point with the photosensitive drum 21. The cleaning blade 242 contacts the outer peripheral surface of the photosensitive drum 21 with a predetermined pressure. The cleaning blade 242 removes residues including toner remaining on the outer peripheral surface of the photosensitive drum 21 after primary transfer.

[0038] The recovery spiral 243 is disposed in the lower part within the recovery container 241, in a region separated from the photoreceptor drum 21 with the cleaning blade 242 in between. The recovery spiral 243 is rotatably supported by the recovery container 241 so as to be rotatable about an axis extending parallel to the rotation axis of the photoreceptor drum 21. The recovery spiral 243 has, for example, spiral conveyance blades extending in the axial direction. The recovery spiral 243 conveys residues such as toner removed from the outer peripheral surface of the photoreceptor drum 21 to a recovery waste container (not shown) provided outside the drum cleaning unit 24.

[0039] The image forming apparatus 1 further includes a density detection unit 14 and a cleaning unit 40. The density detection unit 14 and the cleaning unit 40 are disposed on the downstream side of the secondary transfer unit 33 with respect to the rotation direction of the intermediate transfer belt 31 and are spaced apart from the intermediate transfer belt 31 above the intermediate transfer belt 31. The density detection unit 14 faces the outer peripheral surface of the intermediate transfer belt 31 in the vertical direction. The cleaning unit 40 is disposed below the density detection unit 14 and between the density detection unit 14 and the intermediate transfer belt 31.

[0040] FIG. 4 is a schematic cross-sectional side view around the density detection unit 14 in FIG. 3. FIG. 5 is a partially enlarged cross-sectional side view of the sensor unit 15 of the density detection unit 14 in FIG. 4. FIG. 6 is a partially enlarged cross-sectional side view of the sensor unit 15 of the density detection unit 14 in FIG. 4, showing a state where the brush 43 of the cleaning unit 40 is moved to the cleaning position. FIG. 7 is a perspective view of the sensor unit 15 of the density detection unit 14 in FIG. 4. In these figures, an arrow line indicating the paper width direction Dw orthogonal to the paper conveyance direction is appropriately drawn.

[0041] The density detection unit 14 has a sensor unit 15 and a holder 16.

[0042] The sensor unit 15 is juxtaposed at three positions with respect to the paper width direction Dw (the horizontal direction from left to right in FIG. 4) orthogonal to the paper conveyance direction. Specifically, the sensor unit 15 is arranged at three positions, namely, the central part and both end parts in the paper width direction Dw. That is, the density detection unit 14 detects the toner density of the toner image formed on the outer peripheral surface of the intermediate transfer belt 31 at three positions, namely, the central part and both end parts in the paper width direction Dw. The holder 16 extends in the paper width direction Dw and holds the three sensor units 15.

[0043] The sensor unit 15 includes a substrate 151, screws (fixing members) 152, a connector 153, and a sensor package 17.

[0044] The substrate 151 is a plate-like member extending in the paper width direction Dw and is fixed to the holder 16 by two screws 152. The substrate 151 has a hole portion 151a and a groove portion 151b into which the screws 152 are inserted. The screws 152 are juxtaposed at two positions spaced apart in the paper width direction Dw and are inserted into the holder 16 from below upward to fix the substrate 151. The substrate 151 holds the connector 153 and the sensor package 17.

[0045] The connector 153 is fixed to the lower surface (the surface facing the intermediate transfer belt 31) of the substrate 151 at one end in the paper width direction Dw of the substrate 151. The connector 153 is arranged at a distance from the sensor package 17. The connector 153 is electrically connected to a sensor 17S (to be described later) in the sensor package 17. The sensor unit 15 supplies power to the sensor 17S from the outside via the connector 153 and outputs the detection value of the sensor 17S to the outside.

[0046] The sensor package 17 is disposed at substantially the center in the paper width direction Dw of the substrate 151 and between the two screws 152. The sensor package 17 is fixed to the lower surface of the substrate 151 (the surface facing the intermediate transfer belt 31) and protrudes downward toward the intermediate transfer belt 31. The sensor package 17 is disposed at a position facing the lower intermediate transfer belt 31 and has a recess 17a that is recessed upward. The sensor package 17 holds the sensor 17S in the recess 17a. The sensor detection surface 17f of the sensor 17S is located within the recess 17a.

[0047] The sensor package 17 includes a reflective optical sensor 17S having a light emitting unit 171 including a light emitting element such as an LED (Light Emitting Diode) and a light receiving unit 172 including a light receiving element such as a photodiode. The light emitting unit 171 irradiates detection light at a predetermined angle toward the toner image primarily transferred onto the outer peripheral surface of the intermediate transfer belt 31. The light receiving unit 172 receives the detection light (reflected light) irradiated by the light emitting unit 171 toward the toner image and reflected by the toner image.

[0048] Note that, as a method for detecting the toner density of the toner image, two types are used: a method of receiving detection light of regular reflection and a method of receiving detection light of diffuse reflection. In the present embodiment, the explanation will be given by the method of detecting regular reflection.

[0049] The sensor package 17 outputs the level of the detection light received by the light receiving unit 172 as a detection value (voltage value) related to the toner density, thereby deriving the toner amount of the toner image primarily transferred onto the outer peripheral surface of the intermediate transfer belt 31 and detecting the toner density of the toner image. When there is no toner on the outer peripheral surface of the intermediate transfer belt 31, the detection light irradiated from the light emitting unit 171 is regularly reflected without being diffusely reflected by the toner and is incident on the light receiving unit 172 in a large amount. As a result, the detection value (voltage value) related to the toner density becomes high. And as the toner amount on the outer peripheral surface of the intermediate transfer belt 31 increases, more light is diffusely reflected by the toner, and gradually the amount of light incident on the light receiving unit 172 decreases. That is, the detection value (voltage value) related to the toner density gradually becomes low.

[0050] In this way, the density detection unit 14 irradiates the detection light from the light emitting unit 171 toward the toner image, reflects it with the toner image, and detects the toner density of the toner image transferred to the outer peripheral surface of the intermediate transfer belt 31 based on the detection light received by the light receiving unit 172. In other words, the density detection unit 14 detects the toner density by outputting a detection value related to the toner density of the toner image formed on the outer peripheral surface of the photosensitive drum 21 in the image forming unit 20.

[0051] The cleaning unit 40 includes a slide member 41, a cleaning drive unit 42, and a brush 43.

[0052] The slide member 41 is a plate-like member extending in the paper width direction Dw, and is supported by a guide portion (not shown) so as to be movable in the paper width direction Dw. The slide member 41 is reciprocally moved in the paper width direction Dw by the cleaning drive unit 42. The slide member 41 holds the brush 43.

[0053] The cleaning drive unit 42 moves the slide member 41 in the paper width direction Dw. In other words, the cleaning drive unit 42 moves the slide member 41 in the direction intersecting the light irradiated by the sensor 17S. The operation of the cleaning drive unit 42 is controlled by the control unit 8. The cleaning drive unit 42 includes, for example, a guide portion, a power transmission portion, and a drive motor (all not shown).

[0054] The guide portion extends in the paper width direction Dw and supports the slide member 41. The slide member 41 is reciprocally movable in the extending direction of the guide portion, that is, in the paper width direction Dw. The power transmission portion is constituted by, for example, a rack and pinion mechanism. That is, by rotating a pinion meshing with a rack formed on the slide member 41 by a drive motor, the slide member 41 moves in the paper width direction Dw along the guide portion. In this way, the cleaning drive unit 42 can reciprocally move the slide member 41 along the paper width direction Dw. Note that the power transmission portion may be another mechanism such as a belt mechanism constituted by a pair of pulleys and a belt wound around the pulleys.

[0055] Three brushes 43 are provided, which is the same number as the sensor units 15. That is, the brushes 43 are arranged at three positions, namely, the central part and both end parts in the paper width direction Dw, corresponding to the arrangement of the sensor units 15. The three brushes 43 are fixed to the slide member 41. The brush 43 moves along with the reciprocating movement of the slide member 41 in the paper width direction Dw. That is, the brush 43 moves in the direction intersecting with the light irradiated by the sensor 17S.

[0056] The brush material 43a of the brush 43 protrudes upward toward the sensor 17S of the sensor package 17. As shown in FIG. 6, when the brush 43 is arranged at the facing position with the sensor 17S, the brush material 43a of the brush 43 has a length that contacts the sensor detection surface 17f. As shown in FIG. 5, when the brush 43 is arranged at a position separated from the sensor package 17, the brush material 43a of the brush 43 has a length that does not contact the substrate 151. The cleaning unit 40 cleans the sensor detection surface 17f with the brush 43.

[0057] And when the control unit 8 cleans the sensor detection surface 17f by the cleaning unit 40, as shown in FIG. 6, the brush 43 is moved to the cleaning position where it contacts the sensor detection surface 17f. Also, when the sensor detection surface 17f is not cleaned by the cleaning unit 40, as shown in FIG. 5, the brush 43 is moved to the retracted position where it does not contact the sensor package 17 and the substrate 151.

[0058] According to the above configuration, when the sensor detection surface 17f is not cleaned by the cleaning unit 40, the brush 43 does not contact the sensor package 17 and the substrate 151 of the density detection unit 14. Thereby, it becomes possible to maintain the brush material 43a of the brush 43 in a straight state, and it is possible to ensure suitable cleanability of the sensor detection surface 17f by the brush 43. Therefore, in the image forming apparatus 1, it is possible to realize appropriate density correction.

[0059] Also, the retracted position of the brush 43 is arranged adjacent to the side of the sensor package 17. Specifically, the retracted position of the brush 43 is immediately lateral in the paper width direction Dw where it does not contact the sensor package 17, and is a position facing the substrate 151 in the vertical direction.

[0060] In addition, in the example shown in FIG. 5, the retracted position of the brush 43 is on the connector 153 side with respect to the sensor package 17, but it may be on the side opposite to the connector 153 side. FIG. 4 shows a state where the brush 43 is arranged at the retracted position. Regarding the sensor unit 15 at the left end shown in FIG. 4, the retracted position of the brush 43 is arranged on the side opposite to the connector 153 side.

[0061] According to the above configuration, the moving distance between the cleaning position and the retracted position of the brush 43 can be shortened. In other words, the moving distance of the slide member 41 related to the cleaning of the brush 43 can be shortened, and the required time for the movement can be shortened. Thereby, it becomes possible to reduce the size and noise of the image forming apparatus 1.

[0062] Also, the screw 152, which is a fixing member of the substrate 151, is arranged at the retracted position of the brush 43 and at a position where it does not contact the brush 43. Specifically, the screw 152 is immediately lateral in the paper width direction Dw where it does not contact the sensor package 17, and is arranged at two positions on one end side and the other end side of the sensor package 17.

[0063] According to the above configuration, by arranging the screw 152 at the retracted position of the brush 43, the size of the substrate 151 can be reduced. Thereby, the occupied area related to the installation of the sensor unit 15 can be narrowed, and it becomes possible to reduce the size of the density detection unit 14. That is, the size reduction of the image forming apparatus 1 can be realized.

[0064] Further, the connector 153 is fixed to the lower surface of the substrate 151 (the surface facing the intermediate transfer belt 31) and protrudes downward toward the intermediate transfer belt 31. And the retracted position of the brush 43 is arranged between the sensor package 17 and the connector 153 in the paper width direction Dw.

[0065] According to the above configuration, when the brush 43 is arranged at the retracted position, it is possible to prevent the brush 43 from contacting the connector 153. Thereby, it is possible to suppress the bristles 43a of the brush 43 from contacting the connector 153 and bending, and it becomes possible to maintain the bristles 43a of the brush 43 in a straight state.

[0066] As described above, the embodiments of the present invention have been described. However, the scope of the present invention is not limited to this, and various modifications can be made without departing from the gist of the invention.

[0067] For example, in the above embodiment, the image forming apparatus 1 is a so-called tandem type color printing image forming apparatus that sequentially forms images of a plurality of colors. However, the present invention is not limited to such a model. The image forming apparatus may be a color printing image forming apparatus that is not of the tandem type or a monochrome printing image forming apparatus.

Industrial Applicability

[0068] The present invention can be used in an image forming apparatus.

Explanation of Reference Numerals

[0069] 1 Image forming apparatus 8 Control unit 14 Density detection unit 15 Sensor unit 16 Holder 17 Sensor package 17S Sensor 17f Sensor detection surface 20 Image forming unit 21 Photoconductor drum 30 Transfer unit 31 Intermediate transfer belt (image carrier) 40 Cleaning unit 41 Slide member 42 Cleaning drive unit 43 Brush 151 Substrate 152 Screw (fixing member) 153 Connector 171 Light emitting unit 172 Light receiving unit Dw Paper width direction S Paper

Claims

1. A density detection unit that irradiates light toward the outer peripheral surface of an image carrier, receives reflected light from the image carrier, and outputs a detection value related to the toner density of a toner image formed on the outer peripheral surface of the image carrier; A cleaning unit having a brush that moves in a direction intersecting the direction of the light irradiated by the sensor, and cleaning the detection surface of the sensor with the brush; A control unit that controls the operation of the cleaning unit; Comprising: The density detection unit includes: A substrate; A sensor package fixed to the surface of the substrate facing the image carrier, protruding toward the image carrier, and holding the sensor; Having; The cleaning unit includes: A slide member that holds the brush; A cleaning drive unit that moves the slide member in the intersecting direction; The brush fixed to the slide member, protruding toward the sensor, contacting the detection surface, and having a length that does not contact the substrate; Having; The control unit moves the brush to a cleaning position in contact with the detection surface during cleaning of the detection surface by the cleaning unit, and moves the brush to a retracted position where it does not contact the sensor package and the substrate during non-cleaning of the detection surface by the cleaning unit. An image forming apparatus characterized by this.

2. The image forming apparatus according to claim 1, wherein the retracted position of the brush is arranged adjacent to the side of the sensor package.

3. The density detection unit has a fixing member for fixing the substrate, The image forming apparatus according to claim 1, wherein the fixing member is arranged at the retracted position of the brush and does not contact the brush.

4. The density detection unit has a connector that is fixed to the surface of the substrate facing the image carrier with a space from the sensor package and is electrically connected to the sensor, The image forming apparatus according to claim 1, wherein the retracted position of the brush is arranged between the sensor package and the connector.

Images