JP5219478B2 - Concentration detector - Google Patents

Description

  The present invention relates to a density detection device that optically detects a toner image carried on an image carrier through a transparent member with a shutter, and more particularly to an arrangement of a cleaning member that cleans the transparent member.

  An image forming apparatus including a detecting unit that optically detects a control toner image carried on an image carrier (photosensitive member or intermediate transfer member) through a transparent member has been put into practical use.

  In the optical detection means, when toner scattered from the image carrier or the like adheres to the transparent member, the detection and detection performance of the toner image deteriorates because the detection light enters and exits through the transparent member. For this reason, various methods for avoiding toner contamination of the transparent member have been proposed.

  Patent Document 1 discloses an image forming apparatus of a tandem type direct transfer system in which a plurality of photosensitive drums having different development colors are arranged along a recording material conveyance belt. Here, a specular reflection type optical sensor for detecting a control toner image (color patch) carried on a photosensitive drum is shown. The toner adhering to the transparent window on which the detection light of the optical sensor is incident / exited is removed by a nonwoven fabric cleaning member that intermittently rubs the transparent window.

  Patent Document 2 discloses a direct transfer type image forming apparatus in which a photosensitive drum whose development color is black is arranged along a recording material conveyance belt. Here, a shielding member (shutter) is attached to the transparent window of the optical sensor disposed opposite the photosensitive drum, and the transparent window is shielded by the shielding member during a period when the optical sensor does not detect the control toner image (patch image). Yes. A neutralizing brush is provided on the surface of the shielding member that faces the transparent window, and the neutralizing brush rubs the transparent window as the shielding member reciprocates when detecting the control toner image. The adhered toner is scraped off.

  Patent Document 3 discloses an image forming apparatus that maintains the toner density of a two-component developer constant by detecting the density of a control toner image formed on a photosensitive drum and adjusting the toner replenishment amount. .

JP-A-5-158318 Japanese Patent Laid-Open No. 9-6203 JP-A-9-127757

  In the shielding member disclosed in Patent Document 2, toner particles floating in the air and entering the gap between the transparent window and the shielding member may adhere to the transparent window while the shielding member is waiting at the shielding position of the transparent window. is there.

  In addition, the neutralizing brush is disposed on the back side of the shielding member as viewed from the image carrier. However, toner particles that float in the air and wrap around the back side of the shielding member may adhere to the tip of the neutralizing brush. .

  The toner particles adhering to the transparent window and the neutralizing brush during standby decrease the cleaning effect of the transparent window by the neutralizing brush and shorten the replacement life of the neutralizing brush.

  Therefore, it has been studied to place a sealing member around the transparent window to close the gap between the transparent window and the shielding member. However, the friction between the sealing member and the shielding member hinders the smooth movement of the shielding member, and the response speed of opening and closing. Will be reduced.

  Further, it has been considered to provide a cover around the standby position of the static elimination brush or to provide a cleaning device for the static elimination brush. However, this increases the number of components and complicates the mechanism.

  The present invention provides a concentration detection device that can improve the replacement life of a cleaning member by suppressing the adhesion of toner particles to both the transparent window and the cleaning member that are waiting, without increasing the number of parts or complicating the mechanism. The purpose is to provide.

Concentration detecting apparatus of the present invention, a toner image borne on an image bearing member, a detection means for detecting optically through a transparent member, and an open position for opening said transparent member to the front Kizo carrier A shielding member capable of shielding the transparent member with respect to the image carrier by moving along a fixed movement path between a shielding position where the transparent member is shielded with respect to the image carrier; and the shielding member by driving a driving means for moving along said shielding member to said predetermined path of movement, and controls the pre-Symbol driving means, the open position of the shielding member when said detecting means detects the toner images to wait on, said sensing means is that a control means for waiting for the shielding member when not detect the toner image on the shielding position. And a cleaning member that is disposed on the shielding member and rubs the surface to be cleaned, which includes the transparent member and is located closer to the image carrier than the surroundings, as the shielding member moves. When the shielding member is waiting at the shielding position, the gap between the surface to be cleaned and the shielding member is blocked over the entire length of the surface to be cleaned in the moving direction of the shielding member .

  In the density detection device of the present invention, the amount of toner adhering to the standby cleaning member and the transparent member is reduced by an amount corresponding to the contact area where the cleaning member and the transparent member are overlapped. As the amount of toner adhering to the cleaning member during standby decreases, the cleaning effect on the transparent member increases, and the replacement life of the cleaning member also increases.

  Therefore, the replacement life of the cleaning member can be improved by suppressing the adhesion of toner particles to both the waiting transparent window and the cleaning member without increasing the number of parts or complicating the mechanism.

  Hereinafter, some embodiments of the present invention will be described in detail with reference to the drawings. In the present invention, as long as the cleaning member is in contact with the transparent member in the standby state where the shielding member shields the transparent member, a part or all of the configuration of each embodiment is replaced with the alternative configuration. It can also be implemented in the embodiment.

  Accordingly, not only an optical sensor for detecting a toner image carried on a photosensitive drum, but also an optical sensor for detecting a toner image carried on an intermediate transfer member or a toner image carried on a recording material carried on a recording material conveyance body. But it can be done.

  Further, the operation of the shielding member is not limited to the reciprocating movement between the standby position and the open position, and may be a one-way movement that moves from one standby position to the other standby position via the open position.

  Further, not only a direct transfer type image forming apparatus that transfers a toner image formed on a photosensitive member to a recording material but also an intermediate transfer type image forming device in which one or more photosensitive drums are arranged along the intermediate transfer member. it can.

  In the present embodiment, only main parts related to toner image formation / transfer will be described. However, the present invention includes a printer, various printing machines, a copier, a fax machine, a composite machine, in addition to necessary equipment, equipment, and a housing structure. It can be implemented in various applications such as a machine.

  In addition, about the general matter of the control using the image forming apparatus and the control toner image disclosed in Patent Documents 1 to 3, the illustration is omitted and redundant description is omitted.

  In the description, the reference symbols in parentheses attached to the configuration names used in the claims are examples for assisting understanding of the invention, and the configuration is limited to the corresponding members in the embodiments. Is not.

<First Embodiment>
FIG. 1 is an explanatory diagram of a configuration of the image forming apparatus according to the first embodiment.

  As shown in FIG. 1, an image forming apparatus 100 according to the first embodiment is a direct transfer type image forming apparatus that directly transfers a toner image from a photosensitive drum 1 onto a recording material P carried on a recording material conveyance belt 6. is there.

  Surrounding the photosensitive drum 1, a charging device 2, an exposure device 3, a developing device 4, a transfer member 5, a cleaning device 9, and a density detection sensor unit 10 are arranged.

  The photosensitive drum 1 has an OPC (organic optical semiconductor) photosensitive layer formed on the outer peripheral surface of an aluminum cylinder, is rotatably supported, and rotates in the direction of arrow R1.

  The charging device 2 applies a negative DC voltage from the power source D3 to generate corona discharge, and irradiates the discharge particles to charge the surface of the photosensitive drum 1 to a uniform negative potential.

  The exposure device 3 scans the scanning line image data obtained by developing the image data with a rotating mirror, and writes an electrostatic image on the surface of the charged photosensitive drum 1.

  The developing device 4 stirs a two-component developer obtained by mixing a magnetic carrier with toner with screws 43 and 44 to charge the toner to a negative polarity. The charged developer is carried on the developing sleeve 41 rotating around the fixed magnetic pole 42 in the counter direction with the photosensitive drum 1, and rubs against the photosensitive drum 1.

  The power source D4 applies a voltage obtained by superimposing an AC voltage to a negative DC voltage to the developing sleeve 41, and causes the toner to adhere to the electrostatic image of the photosensitive drum 1 having a positive polarity relative to the developing sleeve 41. Then, the electrostatic image is reversely developed.

  The transfer member 5 sandwiches the recording material conveyance belt 6 between the photosensitive drum 1 and forms a transfer portion T 1 between the photosensitive drum 1 and the recording material P carried on the recording material conveyance belt 6.

  The power supply D1 applies a positive DC voltage to the transfer member 5, charges the negative polarity and carries the toner image of the image carried on the photosensitive drum 1 on the recording material conveyance belt 6, and transfers the transfer portion T1. Transfer to the recording material P passing through.

  The recording material transport belt 6 is supported around a plurality of rotating bodies (not shown) and rotates in the direction of arrow R2.

  The cleaning device 9 slidably rubs the cleaning blade against the photosensitive drum 1 to remove the transfer residual toner remaining on the surface of the photosensitive drum 1 after passing through the transfer portion T1.

  The fixing device 8 heats and presses the recording material P to which the toner image is transferred and transferred from the recording material conveyance belt 6, and fixes the toner image on the surface of the recording material P.

  The density detection sensor unit 10 detects regular reflection light by irradiating the control toner image (patch image) carried on the photosensitive drum 1 with infrared light.

  The density detection sensor unit 10 is preferably disposed between the developing device 4 and the transfer unit T1. However, since there is a lot of scattered toner around the developing device 4, the concentration detection sensor unit 10 is disposed between the transfer unit T1 and the cleaning device 9. did. Another reason for arranging the transfer unit T1 between the transfer unit T1 and the cleaning device 9 is that the developing device 4 is large, so that the density detection sensor unit 10 is arranged opposite to the photosensitive drum 1 between the developing unit 4 and the transfer unit T1. Because it is not possible. This is because the cleaning device 9 is smaller than the developing device 4, so that the density detection sensor unit 10 can be disposed opposite the photosensitive drum 1 between the cleaning device 9 and the transfer portion T1.

  The control toner image formed on the photosensitive drum 1 on the surface facing the developing sleeve 41 passes through the transfer portion T1 without being transferred to the recording material conveying belt 6 by applying a negative voltage to the transfer member 5. Then, it reaches the opposite surface of the density detection sensor unit 10.

<Optical sensor>
FIG. 2 is an explanatory diagram of the density detection sensor unit when the photosensitive drum is viewed from above.

  As shown in FIG. 2, the control unit 110 controls the exposure device 3 to write an electrostatic image of a control toner image having a predetermined density gradation (reference density) on the photosensitive drum 1. The electrostatic image of the control toner image is developed into the control toner image by attaching the charged toner to the developing device 4.

  The control unit 110 opens the shutter 17 so that the transparent window 11a is directly opposed to the control toner image 1p carried on the photosensitive drum 1, and detects the density of the control toner image 1p.

  The control unit 110 emits infrared light from the light emitting element 12 to irradiate the control toner image 1p, causes the regular reflection light from the control toner image 1p to be taken into the light receiving element 18, and according to the output of the light receiving element 18 Thus, the density of the control toner image 1p is determined. The density detection sensor unit 10 inputs an analog voltage output corresponding to the regular reflection light from the control toner image 1p carried on the photosensitive drum 1 to the control unit 110.

  The controller 110 replenishes the developing device 4 with toner by controlling the supply screw 45 so as to cancel out the density difference between the measured actual density of the control toner image and the exposed gradation density.

  As shown in FIG. 1, toner supply from the toner cartridge 46 to the developing device 4 is performed by rotating the supply screw 45 of the developing device 4 in accordance with the density difference between the actual density of the control toner image and the exposed gradation density. The amount is adjusted. As a result, the ratio of the non-magnetic toner and the magnetic carrier in the two-component developer that is stirred and circulated in the developing device 4 is kept constant, and the toner concentration of the developer is kept constant.

  In the case of a black toner having strong light absorption, such as carbon black toner, the reflected light from the toner image itself cannot be obtained. For this reason, the actual density of the control toner image is evaluated by detecting the rate at which the specularly reflected light on the surface of the photosensitive drum 1 serving as the background is attenuated by the control toner image having the reference density. In order to improve the S / N of density measurement with respect to black toner, the density detection sensor unit 10 employs a regular reflection type.

  As shown in FIG. 2, the control unit 110 controls the density detection sensor unit 10 to detect the density of a control toner image (patch image) having a plurality of levels of density gradation formed on the photosensitive drum 1. Then, based on the density detection result, the power source D3 is controlled to adjust the charging potential of the photosensitive drum 1, the exposure device 3 is controlled to adjust the exposure intensity, and the power source D4 is controlled to control the DC voltage used for development. adjust. This ensures the reproducibility of the image density by offsetting the influence of changes over time on the machine side and changes in temperature and humidity.

<Shutter>
FIG. 3 is an explanatory diagram of the operation of the shutter, FIG. 4 is an explanatory diagram of the open state of the transparent window by the shutter, FIG. 5 is an explanatory diagram of the shielding state of the transparent window by the shutter, and FIG. It is explanatory drawing of a state.

  As shown in FIG. 2, in the density detection sensor unit 10, a light emitting element 12 and a light receiving element 18 are disposed inside a light shielding casing 11 provided with a transparent window 11 a, and the transparent window 11 a is a surface of the photosensitive drum 1. It is located at a distance of about 5 mm. The light emitting element 12 and the light receiving element 18 are arranged so that the infrared light emitted from the light emitting element 12 is regularly reflected on the surface of the photosensitive drum 1 and enters the light receiving element 18.

  The transparent window 11a is made of an insulating transparent member such as acrylic, and the light emitted from the light emitting element 12 irradiates the control toner image on the photosensitive drum 1 through the transparent window 11a. The regular reflection light of the image is received through the transparent window 11a.

  Therefore, if the toner scattered from the developing device 4 or the cleaning device 9 adheres to the transparent window 11a, the control toner image cannot be normally detected.

  Therefore, in the first embodiment, the shutter 17 is provided between the transparent window 11a and the surface of the photosensitive drum 1, and the transparent window 11a is shielded from the photosensitive drum 1 during a period other than when the control toner image is detected. Stain due to toner adhesion on the transparent window 11a is prevented.

  The casing 11 and the shutter cover 16 are fixed to a support unit (not shown) attached to the main body frame of the image forming apparatus 100. The shutter 17 moves in the axial direction of the photosensitive drum 1 along the shutter cover 16 to shield / open the transparent window 11a from the photosensitive drum 1.

  The shutter cover 16 is disposed at a distance between the transparent window 11 a and the photosensitive drum 1 so as to have a fixed positional relationship with respect to the casing 11, and the shutter 17 is bent upward and downward to form a movement path of the shutter 17. The shutter cover 16 is formed with a fixed opening 16a corresponding to the transparent window 11a, and the opening 16a is always fixed at a position facing the transparent window 11a.

  The shutter 17 is movable in the axial direction of the photosensitive drum 1 along a movement path set along the shutter cover 16 at a distance between the transparent window 11 a and the shutter cover 16. The shutter 17 is formed with a moving-side opening 17 a corresponding to the transparent window 11 a, and the opening 17 a moves as the shutter 17 moves. The shutter 17 is urged toward the front side in the axial direction of the photosensitive drum 1 by a spring 26.

  When opening the shutter 17, the shutter motor 20 drives a rack gear 17 g that fixes the shutter 17, and moves the shutter 17 to the back side in the axial direction of the photosensitive drum 1 against the urging force of the spring 26.

  The scattered toner scattered from the rotating photosensitive drum 1, the rotating developing sleeve (41: FIG. 1), the cleaning device (9: FIG. 1), etc. is also floating around the density detection sensor unit 10. Part of the scattered toner enters the gap between the shutter 17 and the transparent window 11a and accumulates in the transparent window 11a, thereby reducing the density detection accuracy of the control toner image.

Therefore, in the first embodiment, the cleaning member 25 is provided on the shutter 17, and the surface to be cleaned of the transparent window 11 a is cleaned with the opening / closing operation of the shutter 17. A cleaning member 25 is fixed to the surface of the shutter 17 facing the transparent window 11 a, and the cleaning member 25 rubs the surface to be cleaned of the transparent window 11 a as the shutter 17 moves.

  As the cleaning member 25, the following conductive brush member was used.

  Durability tests were performed on various cleaning members 25 by opening and closing the shutter 17 10,000 times under image forming conditions with a large amount of scattered toner, and evaluating the change in dirt on the transparent window 11a during that time by the change in the output of the density detection sensor unit 10. . Then, the toner fusing level on the surface of the transparent window 11a after the durability test and the toner clogging state on the cleaning member 25 were observed visually and with a microscope, and the following best brush material was selected.

Bristle brush resistance: 1 × 10 ⁶ to 1 × 10 ⁸ Ω
The length of the bristle brush: 2 mm ingress with respect to the surface of the transparent window 11a
Bristle brush hardness: 6 denier Bristle brush density: 150 / mm ²

  The conductive brush selected in this way was attached to the back surface of the edge of the opening 17a of the shutter 17 with double-sided tape.

  As shown in FIG. 3A, when the control toner image is detected, the control unit 110 controls the shutter motor 20 to superimpose the opening 17a on the opening 16a, thereby temporarily opening the transparent window 11a. To set.

  As shown in FIG. 4, the state in which the transparent window 11a directly faces the photosensitive drum 1 is referred to as a shutter open state below, and the density of the control toner image carried on the photosensitive drum 1 can be detected.

  As shown in FIG. 3B, during normal image formation, the control unit 110 controls the shutter motor 20 to wait for the opening 17a at a position away from the opening 16a, thereby changing the shielding state of the transparent window 11a. Set.

  As shown in FIG. 5, the state in which the transparent window 11a is shielded from the photosensitive drum 1 by the shutter 17 is hereinafter referred to as a shutter closed state. After detecting the density of the control toner image in the shutter open state, the shutter 17 returns to the shutter closed state by the drive of the shutter motor 20 and the restoring force of the spring 26.

  The most important feature of the first embodiment is that, in the shutter closed state, not only the transmission region of the detection light in the transparent window 11a but also the entire surface of the transparent window 11a is covered with the cleaning member 25 without a gap and scattered. This is to completely block the intrusion of the toner.

  When the shielding member (17) stands by at the shielding position, not only at least a part of it is overlapped, but also the cleaning member (25) extends over the entire circumference of the transparent member (11a) with the transparent member (11a) and the shielding member. The gap with (17) is closed.

  As a result, the tip of the cleaning member 25 itself is also in contact with the transparent window 11a, so that it is not affected by the scattered toner.

  In the first embodiment, since the transparent window 11a is covered with the cleaning member 25 in the shutter closed state, both the dirt due to the scattered toner on the transparent window 11a and the dirt due to the scattered toner at the tip of the cleaning member 25 are removed. It can be prevented at the same time.

  On the other hand, as shown in FIG. 6, in the shutter mechanism disclosed in Patent Document 2, the transparent window 11a and the brush tip of the cleaning member 11a are exposed to the space where the scattered toner floats when the shutter is closed. Yes. For this reason, it is impossible to prevent contamination of the transparent window 11a and contamination of the cleaning member due to the scattered toner.

  As shown in FIG. 4, when the shielding member (17) is moved to a position where the transparent member (11a) is opened, the cleaning member (25) is not in contact with anything. Thereby, a part of the scattered toner adhering to the cleaning member 25 is shaken off from the cleaning member 25, and the cleaning effect on the transparent window 11a is slightly recovered.

<Experiment 1>
FIG. 7 is an explanatory diagram of the transparent window shielding rate in the shutter closed state, and FIG. 8 is an explanatory diagram of the toner contamination progressing state of the transparent window due to the difference in the transparent window shielding rate.

As shown in FIG. 7, when the ratio of the transparent window 11a that is in contact with the cleaning member 25 in the shutter closed state is referred to as the transparent window shielding ratio, the transparent window shielding ratio is expressed by the following equation. Is done.
Transparent window shielding rate = (area where transparent window 11a and cleaning member 25 overlap) / (area of transparent window)

  In Experiment 1, the state of progress of toner contamination of the transparent window was compared by changing the shielding ratio of the transparent window in the shutter closed state.

  The cleaning member 25 is the above-described brush material having a cleaning surface with a width of 7 mm and a length of 10 mm, and the size of the transparent window 11a of the density detection sensor unit 10 is a width of 5 mm and a length of 10 mm.

  As shown in FIG. 4, the light quantity of the light emitting element 12 of the density detection sensor unit 10 is fixed (1.4 V), and the reflected light quantity on the surface of the photosensitive drum 1 that does not carry the toner image when the shutter is opened is the light receiving element (18). : Measured by FIG. At this time, if the transparent window 11a is contaminated with scattered toner, the amount of reflected light detected by the light receiving element (18: FIG. 2) becomes small.

  As shown in FIG. 1, the toner scattering amount from the developing sleeve 41 is made constant by keeping the toner concentration in the developing device 4 constant. In the opening / closing control of the shutter 17, the change in the amount of reflected light on the surface of the photosensitive drum 1 carrying no toner image was examined with the open state being 1 second and the closed state being 4 seconds.

  As shown in FIG. 8, the shutter mechanism that shields the transparent window 11a with the cleaning member 25 when the shutter is closed is significantly different from the shutter mechanism in which the transparent window shielding ratio = 0 (Patent Document 1). Dirt is reduced.

<Experiment 2>
FIG. 9 is an explanatory diagram of the size relationship between the transparent window and the cleaning member in the shutter closed state, and FIG. 10 is an explanatory diagram of the toner contamination progressing state of the transparent window due to the difference in size between the transparent window and the cleaning member.

  As shown in FIG. 9, in the concentration detection sensor unit (10: FIG. 2) of the first embodiment, the area of the cleaning member 25 was changed, and the optimum area of the cleaning member 25 was examined.

  The cleaning member 25 was the above-described brush material fixed to a width of 7 mm, and the length was changed in three stages from 5 mm to 15 mm. However, the stop position of the cleaning member 25 in the shutter closed state is a position where the center of the transparent window 11a coincides with the center of the plane of the cleaning member 25.

  As shown in FIG. 1, similarly to the examination in Experiment 1, the toner scattering amount from the developing sleeve 41 was made constant by keeping the toner concentration in the developing device 4 constant. In the opening / closing control of the shutter 17, the change in the amount of reflected light on the surface of the photosensitive drum 1 carrying no toner image was examined with the open state being 1 second and the closed state being 4 seconds.

  As shown in FIG. 10, it was found that even when the transparent window shielding rate = 1.0, if the size of the cleaning member 25 is too large than the transparent window 11a, the transparent window 11a is more dirty.

  This is because the cleaning member 25 that protrudes to the outside of the transparent window 11a in the shutter closed state is contaminated by scattered toner, and the cleaning ability of the transparent window 11a by the cleaning member 25 is reduced.

  In Experiment 2, when the length of the cleaning member 25 in the moving direction is 10 mm to 12 mm which is substantially equal to the length of the transparent window 11a, the contamination of the transparent window 11a is minimized and the light receiving element (18: FIG. 2) detects it. The amount of reflected light has increased.

  Note that the optimum length in the moving direction of the cleaning member 25 differs depending on the amount of scattered toner, the material of the brush, and the type of the density detection sensor unit 10.

  In the first embodiment, the density detection control for controlling the toner replenishment to the developing device 4 has been described. However, the present invention is not limited to this, and can be used to control other image forming conditions. It is.

  According to the first embodiment, in the density detection device in which the cleaning member is attached to the shutter, the correct density can be stably detected over a long period of time by effectively preventing contamination of the transparent window due to toner scattering.

Second Embodiment
FIG. 11 is an explanatory diagram of a density detection sensor unit in the second embodiment.

  In the second embodiment, a flat portion is provided around the transparent window 11a, and the area of the cleaning member 25 is optimized to the area of the flat portion. Since the other parts are configured in the same manner as in the first embodiment, in FIG. 11, the same reference numerals as those in FIG. .

  As shown in FIG. 11, in the second embodiment, a flat portion 11h having the same height as the transparent window 11a is formed around the transparent window 11a. The length of the cleaning member 25 in the moving direction is aligned with the length from end to end of the flat portion 11h.

It is explanatory drawing of a structure of the image forming apparatus of 1st Embodiment. It is explanatory drawing of the density | concentration detection sensor unit which looked at the photosensitive drum from upper direction. It is explanatory drawing of operation | movement of a shutter. It is explanatory drawing of the open state of the transparent window by a shutter. It is explanatory drawing of the shielding state of the transparent window by a shutter. It is explanatory drawing of the shielding state of the transparent window by the shutter in a comparative example. It is explanatory drawing of the transparent window shielding rate in a shutter closed state. It is explanatory drawing of the toner contamination progress state of a transparent window by the difference in transparent window shielding rate. It is explanatory drawing of the magnitude relationship of the transparent window and cleaning member in a shutter closed state. It is explanatory drawing of the toner contamination progress state of a transparent window by the difference in the magnitude relationship of a transparent window and a cleaning member. It is explanatory drawing of the density | concentration detection sensor unit in 2nd Embodiment.

Explanation of symbols

1 Image carrier (photosensitive drum)
2 Charging device 3 Exposure device 4 Developing device 5 Transfer member 10 Density detection device (density detection sensor unit)
11 Casing 11a Transparent member (transparent window)
11h Flat part 12 Light emitting element 16 Movement path (shutter cover)
17 Shielding member (shutter)
17g Rack gear 18 Light receiving element 20 Driving means (shutter motor)
25 Cleaning member 100 Image forming apparatus 110 Control means (control unit)

Claims (5)

Detection means for optically detecting the toner image carried on the image carrier through a transparent member;
The image bearing member to move along a predetermined path of movement between the shielding position for shielding the transparent member relative to said image bearing member and an open position for opening said transparent member to the front Kizo carrier A shielding member capable of shielding the transparent member ,
Driving means for driving the shielding member to move the shielding member along the fixed movement path;
And controls the pre-Symbol driving means, said detecting means to wait the shielding member when detecting the toner image to the open position, said shielding member when said detecting means does not detect the toner image on the shielding position A concentration detection device comprising a control means for waiting;
A cleaning member that is disposed on the shielding member and rubs with the movement of the shielding member a cleaning surface that includes the transparent member and is positioned closer to the image carrier than the surroundings;
The cleaning member closes a gap between the surface to be cleaned and the shielding member over the entire length of the surface to be cleaned in the moving direction of the shielding member when the shielding member is waiting at the shielding position. A density detector characterized by the above. The concentration detection apparatus according to claim 1, wherein a length of the cleaning member in the moving direction of the shielding member is equal to a length of the surface to be cleaned in the moving direction of the shielding member . The density detection apparatus according to claim 2 , wherein the surface to be cleaned includes a flat portion that surrounds the outer periphery of the transparent member and is formed at the same height as the transparent member. The cleaning member is a conductive brush member,
4. The concentration detection device according to claim 1, wherein the open position is set so that the shielding member waits in a state where the cleaning member does not contact the surface to be cleaned. . Detection means for optically detecting the toner image carried on the image carrier via an upward transparent member;
The image carrier is moved along a fixed movement path between an open position where the transparent member is opened with respect to the image carrier and a shielding position where the transparent member is shielded with respect to the image carrier. A shielding member capable of shielding the transparent member;
Driving means for driving the shielding member to move the shielding member along the fixed movement path;
The driving unit is controlled so that the shielding member stands by at the open position when the detection unit detects a toner image, and the shielding member stands by at the shielding position when the detection unit does not detect a toner image. A concentration detecting device comprising:
A cleaning member which is disposed downward on the shielding member and rubs the surface to be cleaned, which includes the transparent member and is positioned closer to the image carrier than the surroundings, as the shielding member moves. With
The cleaning member is in contact with the surface to be cleaned by overlapping at least a part of the upward surface with the surface to be cleaned when the shielding member is waiting at the shielding position,
The concentration detection apparatus according to claim 1, wherein the cleaning member is located at a position away from the surface to be cleaned in the moving direction of the shielding member when the shielding member is waiting at the open position.

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