JP6312501B2 - Sensor unit and image forming apparatus - Google Patents

Description

  The present invention relates to a sensor unit for detecting the state of a detection target on an image carrier such as a photosensitive member, an intermediate transfer member, and a transfer material carrier, and an image forming apparatus including the sensor unit.

  Conventionally, in an image forming apparatus using an electrophotographic process or the like, a reference image formed on an image carrier is read by a sensor as a detection unit, and a deviation amount from a reference of the read result is calculated to obtain a color deviation amount. The image density is corrected and kept at an appropriate level. In this case, an optical sensor is used as the sensor. Examples of the image carrier include a photosensitive member, an intermediate transfer member, and a transfer material carrier.

  For example, in the case of a tandem type image forming apparatus employing an intermediate transfer method, a reference image for correcting color misregistration of each color is formed on the intermediate transfer member by the image forming unit for each color, and the position of the reference image for each color is detected by a sensor. Detected and color misregistration correction is performed. Further, in such an image forming apparatus, a reference image for correcting the density of each color is formed on the intermediate transfer member by the image forming unit for each color, and the density of the reference image for each color is detected by the sensor to correct the density of each color. Is done.

  Here, one factor that deteriorates the detection accuracy of the sensor as described above is fluttering of the reference image that is the detection target. For example, if the endless belt-shaped intermediate transfer member varies in the depth direction of the sensor, the detection result of the reference image varies. In order to avoid this, it may be possible to suppress fluttering of the intermediate transfer member by disposing a roller at a position facing the sensor on the inner peripheral surface side of the intermediate transfer member. However, when the image (output image or reference image) transferred to the surface of the intermediate transfer member passes the position on the roller having a potential difference with respect to the image, toner is scattered from the surface of the intermediate transfer member. There are things to do. As a result, the toner may be scattered toward the detection surface of the sensor disposed in the vicinity of the intermediate transfer member, and the scattered toner may adhere to the detection surface of the sensor.

  For example, if the detection surface of the sensor becomes dirty due to scattered toner or the like for the reasons described above, the detection accuracy may deteriorate due to erroneous detection or a large variation in detection results.

  On the other hand, Patent Document 1 discloses that a detection surface of a sensor that reads a reference image on an intermediate transfer member is cleaned with a scraper that is interlocked with movement of a cover that protects the sensor.

  Japanese Patent Application Laid-Open No. H10-228561 discloses that an airflow generating unit that generates an airflow from the sensor toward the photoconductor is provided to prevent the density sensor from being soiled by the developer.

  In Patent Document 3, a first opening and a second opening are provided in a sensor housing, and the first opening is changed from the second opening by a pressure difference caused by an air flow accompanying the movement of the intermediate transfer member. It is disclosed that an air flow is generated to the part to prevent the developer from adhering to the sensor.

Japanese Patent No. 4724288 JP-A-5-158315 JP 2000-75564 A

  However, in the method described in Patent Document 1, since the scraper is brought into contact with the detection surface of the sensor, if the scraper becomes dirty, there is a possibility that the detection surface of the sensor is accelerated. In particular, in an image forming apparatus that frequently performs color misregistration correction and density correction between images, the cover is frequently opened and closed, and the detection surface of the sensor tends to become dirty.

  Further, in the method described in Patent Document 2, the airflow from the airflow generating means is directly blown onto the photoconductor through the flow path formed in the support member that supports the light source of the sensor and the photoelectric conversion unit. For this reason, the airflow may become too strong and the toner image may be disturbed.

  On the other hand, in the method described in Patent Document 3, although the disturbance of the toner image is suppressed, since the generation of the air flow depends on the movement of the intermediate transfer member, a sufficiently strong air flow is generated. It may not be obtained, and the effect of suppressing the adhesion of dirt to the sensor may not be sufficiently obtained.

  The conventional problem has been described above in the case where the image carrier is an intermediate transfer member and the detection target of the sensor is a toner image formed on the image carrier. However, for example, the same problem may occur when the image carrier is a photosensitive member or a transfer material carrier, or when the detection target is the surface potential of the image carrier.

  Accordingly, an object of the present invention is to provide a sensor unit and an image forming apparatus capable of suppressing the adhesion of dirt such as toner to the detection surface of the sensor.

The above object is achieved by a sensor unit and an image forming apparatus according to the present invention. In summary, the present invention includes a sensor having a detection surface arranged to face a movable image carrier, and detecting a state of a detection target on the image carrier through the detection surface, and the sensor. In the sensor unit used in the image forming apparatus, the housing and the image carrier are provided with a housing having a detection opening that exposes the detection surface to the image carrier. A shutter member that is movable between an open position that exposes the detection surface to the image carrier and a closed position that shields the detection surface from the image carrier. An exposed portion that exposes the detection surface to the image carrier when in the open position, and a shielding portion that is disposed between the detection surface and the image carrier when in the closed position. a shutter member having a and the housing An inlet that introduces air flowing inside the apparatus main body of the image forming apparatus from the outside of the housing, and the detection surface and the detection opening provided between the detection surface and the detection opening. the introduced air have a, a flow path for flowing out to the outside of the housing, the air flowing out of the housing through the flow path when the shutter member is in the open position the through the exposed portion The sensor unit is characterized in that air that flows toward the image carrier and flows out of the housing through the flow path when the shutter member is in the closed position is blown to the shielding portion .

According to another aspect of the present invention, a movable image carrier and a detection surface disposed to face the image carrier are provided, and a detection target state on the image carrier is detected via the detection surface. An image forming apparatus, and a sensor unit having a housing that houses the sensor and includes a detection opening that exposes the detection surface to the image carrier. A fan that sucks air from the outside of the apparatus main body of the apparatus or discharges air from the inside of the apparatus main body to the outside to generate an air flow inside the apparatus main body, and the sensor unit includes: Between an open position that is disposed between the housing and the image carrier and exposes the detection surface to the image carrier, and a closed position that shields the detection surface from the image carrier. It is a movable shutter member An exposed portion that exposes the detection surface to the image carrier when in the open position, and a shielding portion that is disposed between the detection surface and the image carrier when in the closed position. And the casing includes an inlet for introducing air generated by the fan and flowing through the inside of the apparatus main body into the casing from outside the casing, the detection surface, and the detection opening. have a, a flow path for flowing out to the outside of the air the housing which is introduced into the interior of the housing through the inlet port is provided between parts, said flow when said shutter member is in the open position Air that has flowed out of the housing through the path flows to the image carrier side through the exposed portion, and air that has flowed out of the housing through the flow path when the shutter member is in the closed position passes to the shielding portion. Blow Image forming apparatus is provided, characterized in that eclipsed.

  According to the present invention, the adhesion of dirt such as toner to the detection surface of the sensor can be suppressed.

1 is a schematic sectional view of an image forming apparatus. 2 is a schematic control block diagram of a main part of the image forming apparatus. FIG. It is a perspective view which shows the inside of a sensor unit. It is a perspective view of the vicinity of the attachment part of a sensor unit. It is a perspective view of a registration sensor. It is a perspective view of a density sensor. It is a perspective view of the shutter member provided in a sensor unit. 2 is a schematic cross-sectional view showing the flow of air inside the apparatus main body of the image forming apparatus. FIG. It is sectional drawing which shows the flow of the air inside a sensor unit. It is a perspective view which shows the flow of the air inside a sensor unit. It is sectional drawing which shows the flow of the air inside a sensor unit. It is a perspective view which shows the flow of the air inside a sensor unit. It is a top view which shows the flow of the air inside a sensor unit. It is a schematic diagram for demonstrating the flow of the air inside a sensor unit when a shutter member exists in an open position or a closed position. It is a conceptual diagram of the patch read waveform by the registration sensor. It is a conceptual diagram of the patch read waveform by the density sensor.

  Hereinafter, a sensor unit and an image forming apparatus according to the present invention will be described in more detail with reference to the drawings.

Example 1
1. FIG. 1 is a schematic sectional view of an image forming apparatus according to an embodiment of the present invention. The image forming apparatus 10 according to the present exemplary embodiment is a tandem type color copier that employs an intermediate transfer method that can form a full-color image using an electrophotographic method.

  The image forming apparatus 10 includes first, second, third, and fourth images that form yellow (Y), magenta (M), cyan (C), and black (K) images as a plurality of image forming units, respectively. It has an image forming unit (station) PY, PM, PC, PK. In this embodiment, the configurations and operations of the image forming units PY, PM, PC, and PK are substantially the same except that the color of the toner used is different. Therefore, hereinafter, unless there is a particular need for distinction, Y, M, C, and K at the end of a symbol indicating an element for any color will be omitted, and the element will be described generally. In the following description, the front side of the sheet of FIG. 1 is the front (front) side of the image forming apparatus 10 and the back side of the sheet of FIG. Further, the left side and the right side when the image forming apparatus 10 is viewed from the front side are the left side and the right side of the image forming apparatus 10, respectively. It is assumed that the depth direction connecting the front side and the back side of the image forming apparatus 10 is substantially parallel to the rotation axis direction of the photosensitive drum 1 described later.

  In the image forming portion P, a photosensitive drum 1 which is a drum type (cylindrical) electrophotographic photosensitive member (photosensitive member) as an image carrier is disposed. The photosensitive drum 1 is rotationally driven in the direction of arrow R1 in the figure by a drive motor (not shown) as a drive means. The following units are arranged around the photosensitive drum 1 along the rotation direction. First, a charger 2 as a charging unit is arranged. Next, an exposure device (laser scanner device) 3 as an exposure unit is arranged. Next, a developing device 4 as a developing unit is arranged. Next, a primary transfer roller 5 which is a roller-shaped primary transfer member as a primary transfer means is disposed. Next, a drum cleaner 6 as a photosensitive member cleaning means is disposed.

  The rotating photosensitive drum 1 is uniformly charged by a charger 2. The surface of the charged photosensitive drum 1 is scanned and exposed by the exposure device 3, whereby an electrostatic latent image (electrostatic image) is formed on the photosensitive drum 1. The electrostatic latent image formed on the photosensitive drum 1 is developed by the developing device 4 using toner as a developer.

  The exposure device 3 is provided with a laser whose emission is controlled in accordance with an image signal, and a plurality of mirror portions that guide the laser beam onto the photosensitive drum 1. By adjusting the laser emission timing and the mirror, the image writing timing can be adjusted, and the writing position of each color can be adjusted. Further, the image density can be adjusted by adjusting the potential of the photosensitive drum 1 and the laser light quantity.

  On the other hand, an intermediate transfer belt 7 that is an endless belt-like intermediate transfer member is provided below each photosensitive drum 1Y, 1M, 1C, and 1K in a manner that horizontally penetrates each image forming unit PY, PM, PC, and PK. Has been placed. The intermediate transfer belt 7 is an example of a movable image carrier. The intermediate transfer belt 7 is wound around a driving roller 71, a secondary transfer counter roller 72, a tension roller 73, and a backup roller 74 as a plurality of support rollers (stretching rollers). The intermediate transfer belt 7 rotates (circulates) in the direction of the arrow R2 in the figure when a driving force is input to a driving roller 71 from a driving motor (not shown) as a driving means. The intermediate transfer belt 7 is stretched around the plurality of support rollers in a state where a predetermined tension is applied by the tension roller 73 being urged from the inner peripheral surface side to the outer peripheral surface side. The primary transfer rollers 5 are arranged at positions facing the photosensitive drums 1 on the inner peripheral surface side of the intermediate transfer belt 7. The primary transfer roller 5 is biased (pressed) toward the photosensitive drum 1 via the intermediate transfer belt 7, and a primary transfer portion (primary transfer nip portion) N1 where the intermediate transfer belt 7 and the photosensitive drum 1 are in contact with each other. Is formed. Further, on the outer peripheral surface side of the intermediate transfer belt 7, a secondary transfer roller 8 that is a roller-like secondary transfer member as a secondary transfer unit is disposed at a position facing the secondary transfer counter roller 72. . The secondary transfer roller 8 is urged (pressed) toward the secondary transfer counter roller 72 via the intermediate transfer belt 7, and the secondary transfer portion where the intermediate transfer belt 7 and the secondary transfer roller 8 are in contact with each other. (Secondary transfer nip portion) N2 is formed. A belt cleaner 75 serving as an intermediate transfer member cleaning unit is disposed on the outer peripheral surface side of the intermediate transfer belt 7 at a position facing the driving roller 71. The intermediate transfer belt unit 70 is configured by the intermediate transfer belt 7, the support rollers 71, 72, 73, 74 of the intermediate transfer belt 7, the belt cleaner 75, and the like.

  The toner image formed on the photosensitive drum 1 is transferred (primary transfer) to the intermediate transfer belt 7 by the action of the primary transfer roller 5 to which a primary transfer voltage (primary transfer bias) is applied in the primary transfer portion N1. . For example, when forming a full-color image, the toner images of the respective colors are transferred so as to be sequentially superimposed on the intermediate transfer belt 7 in the first, second, third, and fourth image forming portions PY, PM, PC, and PK. The The toner image transferred to the intermediate transfer belt 7 is transferred to a transfer material (sheet) such as recording paper by the action of the secondary transfer roller 8 to which a secondary transfer voltage (secondary transfer bias) is applied in the secondary transfer portion N2. The material is transferred (secondary transfer) to S. For example, when a full-color image is formed, the four color toner images superimposed on the intermediate transfer belt 7 are transferred onto the transfer material S all at once. The transfer material S is fed from the storage 11 of the transfer material supply unit, adjusted in posture by the registration adjusting unit 12, and then conveyed to the secondary transfer unit N2.

  The transfer material S onto which the toner image has been transferred is carried and transported on a transport belt 13 which is an endless belt-shaped transport member. The conveyor belt 13 is driven by a drive motor (not shown) as drive means. A suction fan (not shown) is disposed on the inner peripheral surface side of the conveyance belt 13 to adsorb the transfer material S, whereby the transfer material S is adsorbed onto the conveyance belt 13. Thereafter, the transfer material S is transported to a fixing device 14 as a fixing unit disposed downstream of the transport belt 13 in the transport direction. The transfer material S is heated and pressurized by the fixing device 14, and the toner image is fixed thereon. Thereby, an image is obtained on the transfer material S. Thereafter, the transfer material S is conveyed to a transfer material discharge unit and discharged onto a transfer material discharge tray 15 outside (outside the apparatus) the apparatus main body 9 of the image forming apparatus 10.

  Further, deposits such as toner (primary transfer residual toner) remaining on the photosensitive drum 1 after the primary transfer are removed from the photosensitive drum 1 by the drum cleaner 6 and collected. Further, deposits such as toner (secondary transfer residual toner) remaining on the intermediate transfer belt 7 after the secondary transfer are removed from the intermediate transfer belt 7 by the belt cleaner 75 and collected.

  The image forming apparatus 10 is arranged so as to face the outer peripheral surface of the intermediate transfer belt 7 downstream of the most downstream primary transfer portion N1K in the transfer direction of the transfer material S and upstream of the secondary transfer portion N2. A sensor unit 100 is included. The sensor unit 100 includes a registration sensor 102 (FIG. 5) and a density sensor 103 (FIG. 6) which are optical sensors. A backup roller 74 is disposed at a position facing the sensor unit 100 on the inner peripheral surface side of the intermediate transfer belt 7. The sensor unit 100 will be described in more detail later.

  The image forming apparatus 10 also includes first and second intake fans 16 and 17 as fans that generate air flow inside the apparatus main body 9 by sucking air into the apparatus main body 9 from the outside. Have The first intake fan 16 is provided on the left side surface of a housing (main body housing) 19 of the apparatus main body 9. Air for mainly cooling each exposure apparatus 3 flows from the left side surface of the apparatus main body 9 toward the right side surface around each exposure apparatus 3 of each image forming unit P by the first intake fan 16 ( FIG. 8). The second intake fan 17 is provided on the right side surface of the main body casing 19. The second intake fan 17 generates an air flow for cooling the inside (inside the apparatus) of the apparatus main body 9 of the image forming apparatus 10. This air flow mainly suppresses the temperature rise of elements other than each exposure apparatus 3 in each image forming unit P.

  In addition, the image forming apparatus 10 includes an exhaust fan 18 as a fan that generates air flow inside the apparatus main body 9 by discharging air from the inside of the apparatus main body 9 to the outside. Since it is the fixing device 10 that has a high temperature inside the apparatus main body 9, the exhaust fan 18 is provided above the fixing apparatus 14 so that the heat of the fixing apparatus 10 does not raise the temperature inside the apparatus main body 9. . The exhaust fan 18 is provided on the left side of the main body housing 19 and exhausts toward the rear of the apparatus main body 9. As will be described in detail later, the air sucked into the apparatus main body 9 from the outside by the second intake fan 17 flows toward the exhaust fan 18 (FIG. 8).

  FIG. 2 shows a schematic control mode of the main part of the image forming apparatus 10 of the present embodiment. A control unit 200 as a control unit provided in the image forming apparatus 10 includes a CPU 201 that is a central element that performs arithmetic processing, a memory 202 such as a ROM and RAM that are storage elements, and the like. The RAM stores sensor detection results, calculation results, and the like, and the ROM stores control programs, data tables obtained in advance, and the like. In this embodiment, the control unit 200 comprehensively controls each unit of the image forming apparatus 10. In relation to this embodiment, the control unit 200 corrects the operation of the image forming unit P based on the detection results of the registration sensor 102 and the density sensor 103, and adjusts the writing position of each color and the image density. Execute control. The control unit 200 controls the driving of the shutter opening / closing cam drive motor 171 and the second intake fan (also simply referred to as “fan” here) 17 of the sensor unit 100 as will be described in detail later.

2. Next, with reference to FIG. 15 and FIG. 16, the influence of contamination on the detection surfaces of the registration sensor 102 and the density sensor 103 will be described.

  The color misregistration correction patch read by the registration sensor 102 is a reference image having a pattern as shown in FIGS. 15 (a) -1 and 15 (b) -1. When the detection surface of the registration sensor 102 is not dirty, the analog waveform read by the registration sensor 102 is as shown in FIG. The figure shows the result of reading using an optical sensor that detects irregularly reflected light. Since the optical sensor for detecting the irregularly reflected light has a small output for the black color, the patches of other colors are sandwiched between the patches of the black color and the outputs are aligned. The registration sensor 102 measures the shift amount of each color patch based on the difference between the light amount reflected from the intermediate transfer belt 7 and the light amount reflected from the patch, and calculates the correction amount of the writing position of each color. At this time, if the detection surface of the registration sensor 102 is dirty, the analog waveform read by the registration sensor 102 is as shown in FIG. When the detection surface of the registration sensor 102 becomes dirty, the difference between the amount of reflected light from the surface of the intermediate transfer belt and the amount of reflected light from the patch becomes small, and at the same time, the edge of the patch is not sharp. As a result, when the digital processing is performed, the position of the center of gravity of the patch varies, or reading failure occurs (see FIGS. 15A-3 and 15B-3). Due to the variation in the center of gravity and poor reading, a difference between the actual positional deviation amount of each patch and the measured value of each patch occurs, and color deviation occurs.

  The density correction patch read by the density sensor 103 is a reference image having a pattern as shown in FIGS. 16 (a) -1 and 16 (b) -1. When the detection surface of the density sensor 103 is not dirty, the analog waveform read by the density sensor 103 is as shown in FIG. Here, in controlling the image density, a density reference is set. The density reference is set by, for example, reading the density of a density reference member (described later) provided on the shutter member of the density sensor 103 with the density sensor 103 so that a predetermined light output of the density sensor 103 can be obtained. . The light output of the density sensor 103 can be adjusted by adjusting the LED current value as a light source. Then, the image density is adjusted from the density reference and the read patch density. That is, the density sensor 103 measures the difference between the light amount reflected from the density reference member and the light amount reflected from the patch. Based on this difference, the image density of each color patch is measured, and the correction amount of the image density of each color is calculated. In this case, for example, if the detection surface of the density sensor 103 becomes dirty after the density reference is set, the patch density reading level with respect to the density reference fluctuates. Therefore, the reading level of the density sensor 103 changes despite reading the same density patch (see FIGS. 16A-1 and 16B-2). Therefore, incorrect density control is performed, and as a result, image density level fluctuation occurs (see FIGS. 16A-3 and 16B-3). The same thing occurs when the density reference member is dirty before the density reference is set, or when both the detection surface of the density sensor 103 and the density reference member are stained.

  If the detection surfaces of the registration sensor 102 and the density sensor 103 become dirty in this way, erroneous detection may occur or variations in detection results may increase, resulting in poor color misalignment and image density correction accuracy. . On the other hand, there are prior arts disclosed in Patent Documents 1 to 3, but each has a problem as described above.

  In addition, when the density reference member becomes dirty as described above, the image density correction system may deteriorate. On the other hand, Japanese Patent Laid-Open No. 5-322760 provides a cleaning member for cleaning the density reference member between the density sensor and the movable density reference member, and cleaning is performed when the density reference member moves. It discloses that the density reference member is cleaned with the member. However, in this method, since the cleaning member is directly brought into contact with the concentration reference member for cleaning, there is a possibility that the contamination of the concentration reference member may be accelerated when the cleaning member becomes dirty. Therefore, the amount of reflected light varies when the density reference member is detected by the density sensor, and the correction result of the image density may vary.

3. Next, the overall configuration and operation of the sensor unit 100 of this embodiment will be described. FIG. 3 is a perspective view showing the inside of the sensor unit 100. FIG. 4 is a perspective view of the vicinity of the attachment portion of the sensor unit 100. FIG. 5 is a perspective view of the registration sensor 102. FIG. 6 is a perspective view of the density sensor 103. FIG. 7 is a perspective view of the shutter member 106 provided in the sensor unit 100. As will be described in detail later, FIGS. 8 to 14 show the flow of air inside and outside the sensor unit 100 in the image forming apparatus 10.

  In the present embodiment, as will be described in detail below, the sensor unit is introduced through the flow path provided in the vicinity of the detection surfaces of the registration sensor 102 and the concentration sensor 103 by introducing the air flowing inside the apparatus main body 9 into the sensor unit 100. 100 is discharged to the outside. Thereby, adhesion of dirt such as toner to the detection surface is suppressed. In this embodiment, the flow of air discharged through the flow path merges with the flow of air that flows outside the sensor unit 100 and flows between the detection surface and the intermediate transfer belt 7, and efficiently moves to the detection surface. It is possible to suppress the adhesion of dirt such as toner. In the present embodiment, when the shutter member provided in the sensor unit 100 is in the closed position, the air discharged through the flow path is blown to the concentration reference member provided in the shutter member. This makes it possible to remove dirt such as toner adhering to the density reference member without providing a special means for cleaning the density reference member.

  The sensor unit 100 includes a detection surface 112 (FIGS. 5 and 6) disposed opposite to a movable image carrier 7 serving as an intermediate transfer belt, and detects on the image carrier via the detection surface 112. A registration sensor 102 and a density sensor 103 are provided as sensors for detecting the state of the target. The sensor unit 100 is a housing 110 that accommodates the registration sensor 102 and the density 103, and a detection opening 113 (FIG. 11, FIG. 11) that exposes the detection surface 112 of the registration sensor 102 and the density sensor 103 to the image carrier 7. 12). The housing 110 has an introduction port 120 (FIGS. 4 and 9) through which air flowing inside the apparatus main body 9 of the image forming apparatus 10 is introduced from the outside to the inside of the housing 110. Further, the housing 110 is provided between the detection surface 112 and the detection opening 113, and has a flow path 123 (FIG. 11) through which air introduced into the housing 110 through the introduction port 120 flows out of the housing 110. 12 and 13).

  More specifically, as shown in FIG. 3, the sensor unit 100 of the present embodiment has the following elements as main components. First, the sensor unit 100 includes a frame 101 that serves as a base of the sensor unit 100. The sensor unit 100 also includes a registration sensor 102 that is an optical sensor that reads a color misregistration correction reference image (color misregistration correction patch) that is a toner image formed on the intermediate transfer belt 7. The sensor unit 100 includes a density sensor 103 that is an optical sensor that reads a density correction reference image (density correction patch) that is a toner image formed on the intermediate transfer belt 7. The sensor unit 100 also includes a sensor support plate 104 to which the registration sensor 102 and the density sensor 103 are attached. The frame 101 and the sensor support plate 104 constitute a housing 110 that houses the registration sensor 102 and the density sensor 103. A detection opening 113 (FIGS. 11, 12, and 13) that exposes the detection surfaces 112 (FIGS. 5 and 6) of the registration sensor 102 and the density sensor 103 to the intermediate transfer belt 7 is formed in the sensor support plate 104. The The sensor unit 110 also has a duct (sensor duct) 105 that seals the registration sensor 102 and the concentration sensor 103 inside the housing 110 and guides air to the detection opening 113. The sensor unit 100 also includes an openable / closable shutter member (protective member, open / close member) 106 that protects the detection surface 112 of the registration sensor 102 and the density sensor 103 when the registration sensor 102 and the density sensor 103 do not operate. The sensor unit 100 also includes a shutter driving unit 107 that opens and closes the shutter member 106. Furthermore, the sensor unit 100 includes an electrical substrate 108 that processes electrical signals from the registration sensor 102, the density sensor 103, and the shutter driving unit 107.

  As shown in FIGS. 3 and 4, the casing 110 including the frame 101 and the sensor support plate 104 has a box shape that is long in the width direction of the intermediate transfer belt 7 (direction substantially orthogonal to the transport direction). . The frame 101 forms the front, rear, left, right, and upper side surfaces of the housing 110, and the sensor support plate 104 forms the lower side surface. In the sensor unit 100, a positioning portion 109 provided on the frame 101 is fitted to a unit positioning portion (not shown) provided on the apparatus main body 9 and is fixed to the apparatus main body 9. The sensor support plate 104 is attached to the frame 101 so as to be slidable in a substantially vertical direction with respect to the intermediate transfer belt 7. The sensor support plate 104 is urged toward the intermediate transfer belt 7 by a pressing spring (not shown) as urging means provided inside the casing 110. A sensor positioning unit 119 is provided on the sensor support plate 104 in order to keep the distance between the intermediate transfer belt 7 and the registration sensor 102 and the density sensor 103 constant. The sensor positioning portion 119 is abutted against an abutting portion 76 provided in the intermediate transfer belt unit 70. The abutting portion 76 is provided on the rotation shaft of the backup roller 74 disposed on the inner peripheral surface side of the intermediate transfer belt 7. Further, the back-up roller 74 suppresses flapping of the intermediate transfer belt 7. Thereby, the detection performance of the registration sensor 102 and the density sensor 103 is stabilized.

  In this embodiment, the backup roller 74 is provided for the purpose of suppressing the flapping of the intermediate transfer belt 7, but the present invention is not limited to this. For example, another arbitrary form of support member (backup member) such as a support sheet metal that suppresses flapping of the intermediate transfer belt 7 may be provided.

  As shown in FIGS. 11 and 12, the detection surface 112 of the registration sensor 102 and the density sensor 103 attached to the sensor support plate 104 is formed on the surface of the intermediate transfer belt 7 through the detection opening 113 provided in the sensor support plate 104. Come on. As a result, the registration sensor 102 and the density sensor 103 can detect a color misregistration correction patch and a density correction patch, which are detection targets on the surface of the intermediate transfer belt 7, respectively. Three registration sensors 102 are arranged in the width direction of the intermediate transfer belt 7. Then, based on the detection result of the positional deviation correction patch for each color of yellow, magenta, cyan, and black by the registration sensor 102, the deviation amount of each color is calculated. The amount of misregistration calculated here is the misalignment of each color in the transport direction of the intermediate transfer belt 7, the misalignment of each color in the width direction of the intermediate transfer belt 7, the misalignment of each color with respect to the reference direction, and the magnification misalignment of each color. Is included. The calculated shift amount is processed by the image controller of the control unit 200 and fed back to the output image. Three density sensors 103 are arranged in the width direction of the intermediate transfer belt 7. The registration sensor 103 detects the density correction patches for each color of yellow, magenta, cyan, and black, and the density change amount of each color is calculated based on the detection result. The calculated density change amount is processed by the density controller of the control unit 200 and fed back to the control of the image forming unit P. The numbers of the registration sensors 102 and the density sensors 103 are not limited to those in the present embodiment.

  As shown in FIG. 5, the registration detection sensor 102 has the following elements as main components. First, the registration sensor 102 has a sensor housing 114. In addition, the registration sensor 102 includes a light source (LED light source in this embodiment) 115, a lens 116 that collects reflected light from a detection target, and a light receiving unit that receives the collected light. (A photodiode in this embodiment) 117. In addition, the registration sensor 102 includes a substrate 118 on which the light source 115 and the light receiving unit 117 are mounted. In addition, the registration sensor 102 has a detection surface (cover glass) 112 formed of a glass plate as a dust-proof member and provided to face the intermediate transfer belt 7 so as to face the direction of the detection target. The distance between the detection surface 112 and the surface of the intermediate transfer belt 7 is set to about 5 mm. The configuration of the registration sensor 102 is not limited to that of the present embodiment.

  As shown in FIG. 6, the density sensor 103 has the following elements as main components. Elements having the same or corresponding functions as those of the registration sensor 102 are denoted by the same reference numerals. First, the density sensor 103 has a sensor housing 114. In addition, the density sensor 103 includes a light source (LED light source in this embodiment) 115 and a light receiving unit (photodiode in this embodiment) 117 that receives reflected light from a detection target inside the sensor housing 114. Have. Further, the density sensor 103 includes a substrate 118 on which the light source 115 and the light receiving unit 117 are mounted. Further, the density sensor 103 has a detection surface (cover glass) 112 formed of a glass plate as a dust-proof member and provided to face the intermediate transfer belt 7 so as to face the direction of the detection target. The distance between the detection surface 112 and the surface of the intermediate transfer belt 7 is set to about 5 mm. The configuration of the density sensor 103 is not limited to that of the present embodiment.

  As shown in FIG. 3, the shutter member 106 is connected to the shutter driving unit 107 via a follower 165 that is formed integrally with the shutter member 106 or connected to the shutter member 106. The shutter member 106 is a substantially rectangular plate-like member that is long in the width direction of the intermediate transfer belt 7, and is attached to the frame 101 so as to be slidable in the width direction of the intermediate transfer belt 7. The shutter member 106 is urged rearward along the width direction of the intermediate transfer belt 7 by a tension spring (not shown) as urging means. The shutter member 106 is opened and closed by a driving motor (shutter opening / closing cam driving motor) 171 and a driving cam (shutter opening / closing cam) 172 provided in the shutter driving unit 107.

  The shutter member 106 is disposed between the housing 110 and the intermediate transfer belt 7. The shutter member 106 is between an open position where the detection surface 112 of the registration sensor 102 and the density sensor 103 is exposed to the intermediate transfer belt 7 and a closed position where the detection surface 112 is shielded from the intermediate transfer belt 7. It is possible to move with. In this embodiment, the shutter member 106 is moved forward by the driving cam 172 against the urging force of the tension spring, so that the shutter member 106 is moved to the closed position by releasing the pressure applied by the driving cam 172. Open position. As shown in FIG. 7, the shutter member 106 has an exposed portion 161 that exposes the detection surface 112 of the registration sensor 102 and the density sensor 103 to the intermediate transfer belt 7 when in the open position. Further, the shutter member 106 includes a shielding portion 162 disposed between the detection surface 112 of the registration sensor 102 and the density sensor 103 and the intermediate transfer belt 7 when in the closed position. An exposed portion 161 that is an opening is arranged below the detection surface 112 so that the registration sensor 102 and the density sensor 103 can detect the detection target of the surface of the intermediate transfer belt 7 when the shutter member 106 is in the open position. When the shutter member 106 is in the closed position, the detection surface 112 is covered with the shielding portion 162 so that dirt such as toner does not adhere to the registration sensor 102 and the density sensor 103. Further, the shutter member 106 has a density reference member (density reference) for correcting the detection result of the density sensor 103 so that the shutter member 106 is disposed below the detection surface 112 of the density sensor 103 when the shutter member 106 is in the closed position. Plate) 163 is arranged.

  In this embodiment, all the sensors 102 and 103 of the sensor unit 100 can be detected when the shutter member 106 is in the open position, and all the sensors 102 and 103 of the sensor unit 100 are detected when the shutter member 106 is in the closed position. It becomes impossible. For example, the shutter member 106 is set to the open position immediately before a series of patches that are continuously detected in one period are conveyed to a portion facing the sensor, and immediately after the series of patches pass the portion facing the sensor. The shutter member 106 can be controlled to be in the closed position.

4). Next, the flow of air in the apparatus main body 9 and the sensor unit 100 in the image forming apparatus 10 will be described.

  As described above, an air flow as shown in FIG. 8 is generated inside the apparatus main body 9 of the image forming apparatus 10.

  As shown in FIGS. 4 and 9, the right side surface of the frame 101 of the sensor unit 100 is provided with an introduction port 120 that is an opening for taking air into the housing 110. The inlet 120 is provided downstream of the air flow generated by the fan 17 which is an intake sirocco fan in this embodiment. As shown in FIGS. 9 and 10, the apparatus main body 9 is provided with a rectifying member 121 that directs air to flow toward the introduction port 120, and is thereby introduced from the outside to the inside of the housing 110. Air flow rate is secured.

  As shown in FIGS. 9 and 10, the air taken into the housing 110 from the inlet 120 flows through a duct (frame duct) 122 provided in the frame 101. The exhaust port of the frame duct 122 is directed toward the registration sensor 102 and the concentration sensor 103.

  Here, it is conceivable to install an intake fan directly on the sensor unit 100. However, in that case, the vibration of the fan propagates to the registration sensor 102 and the density sensor 103, and the detection accuracy may deteriorate due to the vibration, which is not desirable.

  As shown in FIGS. 11 and 12, the air directed toward the registration sensor 102 and the concentration sensor 103 by the frame duct 122 is attached to the sensor support plate 104 so as to seal the registration sensor 102 and the concentration sensor 103. To be introduced. The air taken into the sensor duct 105 flows toward the detection opening 113 formed in the sensor support plate 104.

  When the shutter member 106 is in the open position, from the flow path 123 that is a gap provided between the detection opening 113 formed in the sensor support plate 104 and the detection surface 112 of the registration sensor 102 and the density sensor 103. Air is exhausted. Thus, the air discharged from the housing 110 is discharged outside the sensor unit 100 through the exposed portion 161 of the shutter member 106. As shown in FIGS. 8, 9, and 11, the air discharged from the sensor unit 100 flows between the sensor unit 100 and the intermediate transfer belt 7, and a floating substance such as toner is placed on the flow to exhaust fan. It flows toward 18. Thereby, it is possible to suppress adhesion of dirt such as toner to the detection surface 112 of the registration sensor 102 and the density sensor 103.

  Here, as described above, the exhaust fan 18 is provided on the left side of the main body housing 19. Accordingly, the air flow around the image forming unit P flows from the right side surface of the apparatus main body 9 toward the left side surface, and the air discharged from the sensor unit 100 also merges with the flow to the right side of the apparatus main body 9. It flows from the surface toward the left side. Therefore, in the present embodiment, as shown in FIGS. 11, 12, and 13, the flow path 123 is disposed on the right side with respect to the detection surface 112 of the registration sensor 102 and the density sensor 103. More specifically, the flow path 123 is formed between the right side surface of the sensor casing 114 and the edge of the detection opening 112. That is, the flow path 123 is provided on the upstream side of the detection surface 112 in the direction of air flow that flows outside the housing 110 and passes between the detection surface 112 and the intermediate transfer belt 7. Thereby, the air discharged from the flow path 123 merges with the air flowing from the right side surface of the device main body 9 flowing outside the sensor unit 100 toward the left side surface, and the air efficiently flows on the detection surface 112. To go. In the present embodiment, the flow of air introduced into the sensor unit 100 and discharged through the flow path 123 and the air outside the sensor unit 100 that merges with the air discharged from the flow path 123 The flow is generated by a common fan 17. Therefore, it is possible to efficiently suppress adhesion of toner or the like to the detection surface 112 with a simple configuration.

  On the other hand, when the shutter member 106 is in the closed position, the air discharged from the flow path 123 flows toward the surface of the shielding portion 162 of the shutter member 106. At this time, the air discharged from the flow path 123 between the detection surface 112 of the concentration sensor 103 and the detection opening 113 flows toward the surface of the concentration reference member 163 below the detection surface 112. The air can blow off and remove toner and dust adhering to the density reference member 163. The air flowing toward the surface of the shielding portion 162 of the shutter member 106 flows along the wall 164 (FIG. 7) extending in the longitudinal direction of the shutter member 106 and is provided at the front end portion and the rear end portion of the sensor unit 100. It is discharged from the opened opening. The discharged air flows toward the exhaust fan 18 in the same manner as when the shutter member 106 is in the open position.

  As described above, in this embodiment, when the shutter member 106 is in the open position, the air that flows out of the housing 110 through the flow path 123 passes through the exposed portion 161 of the shutter member 106 and is on the intermediate transfer belt 7 side (image carrier side). Flowing into. In addition, when the shutter member 106 is in the closed position, the air that has flowed out of the housing 110 through the flow path 123 is blown to the shielding portion 162 of the shutter member 106. In the present embodiment, the shielding member 162 of the shutter member 106 is provided with a reference member 163 whose state (density) is detected by the density sensor 103 in order to correct the detection result of the density sensor 103. Therefore, the air blown to the shielding portion 162 when the shutter member 106 is in the closed position is blown to the reference member 163.

  Here, as shown in FIG. 14A, when the shutter member 106 is in the open position, the positional deviation correction patch or the density correction patch formed on the intermediate transfer belt 7 faces the sensor unit 100. Pass through the department. For this reason, if the flow rate (wind velocity) of the air discharged from the center unit 100 is too large, the positional deviation correction patch or the density correction patch may be disturbed. On the other hand, as shown in FIG. 14B, when the shutter member 106 is in the closed position, the air blown to the concentration reference member 163 has a certain flow rate (in order to blow off toner and dust on the concentration reference member 163). Wind speed) is required. If this is too small, there is a possibility that toner and dust cannot be blown away. Further, when the shutter member 106 is in the closed position, the air discharged from the sensor unit 100 is not directly blown onto the surface of the intermediate transfer belt 7, and a positional deviation correction patch or density correction patch is applied to the intermediate transfer belt 7. The patch is not formed. Therefore, there is no possibility that the air discharged from the sensor unit 100 disturbs the positional deviation correction patch or the density correction patch. Therefore, when the shutter member 106 is in the closed position, the output of the fan 17 can be increased more than when the shutter member 106 is in the open position. That is, the control unit 200 drives the fan 17 so that the amount of air introduced into the housing 110 through the introduction port 120 changes between when the shutter member 106 is in the open position and when it is in the closed position. Can be controlled. In particular, the control unit 200 determines that the amount of air introduced into the housing 110 through the inlet 120 is less when the shutter member 106 is in the open position than when the shutter member 106 is in the closed position. Can be controlled. Thereby, the density reference member 163 can be effectively cleaned without disturbing the positional deviation correction patch or the density correction patch.

  As described above, according to this embodiment, it is possible to suppress the adhesion of dirt such as toner to the detection surfaces 112 of the registration sensor 102 and the density sensor 103. In addition, according to the present embodiment, dirt such as toner adhered to the density reference member 163 can be removed. According to the present embodiment, since the cleaning member is not brought into contact with the detection surfaces 112 of the registration sensor 102 and the density sensor 103, the contamination of the detection surface 112 is not accelerated when the cleaning member becomes dirty. Similarly, according to the present embodiment, since the cleaning member is not brought into contact with the concentration reference member 163, the contamination of the concentration reference member 163 is not accelerated by the contamination of the cleaning member. Further, according to the present embodiment, the air flow generated by the fan 17 provided in the apparatus main body 9 is taken into the sensor unit 100, and the air flow is generated in the vicinity of the detection surface 112 of the registration sensor 102 and the concentration sensor 103. Generate. As a result, the flow of air blown onto the intermediate transfer belt 7 is suppressed from becoming too strong. Further, according to the present embodiment, by controlling the driving of the fan 17 that generates a flow of air taken into the sensor unit 100, an air flow having an appropriate flow rate can be obtained without depending on the movement of the intermediate transfer belt 7. Can be generated.

Other Embodiments Although the present invention has been described with reference to specific embodiments, the present invention is not limited to the above-described embodiments.

  In the above-described embodiment, an aspect is described in which both the suppression of the adhesion of dirt such as toner to the detection surface of the sensor and the removal of dirt such as toner attached to the reference member of the sensor provided on the shutter member are described. did. However, for example, when the sensor unit has only a positional deviation sensor out of the positional deviation sensor and the density sensor and the reference member is not provided on the shutter member, there is no configuration for blowing air to the reference member. Also good. Also in this case, when the shutter member is provided, an effect of removing dirt such as toner that may adhere to and accumulate on the inside of the shutter member can be obtained.

  In the above-described embodiment, the sensor unit is described as being provided with the shutter member. However, the shutter member may not be provided as desired.

  In the above-described embodiment, the case where the image carrier is an intermediate transfer member has been described. However, the present invention is not limited to this. For example, as is well known to those skilled in the art, the image carrier generally has a transfer material carrier instead of the intermediate transfer member in the above-described embodiment, and the toner is formed on the transfer material carried on the transfer material carrier. There is a direct transfer type image forming apparatus that transfers an image to form an image. As the transfer material carrier, for example, a transfer material carrier belt similar to the intermediate transfer belt in the above-described embodiment is used. Also in such an image forming apparatus, a reference image (adjustment toner image such as a color misregistration correction patch or a density correction patch) is formed on the transfer material carrier or on the transfer material carried on the transfer material carrier. Then, this is detected by a sensor, and control is performed to correct color misregistration and image density. Therefore, by applying the present invention to the sensor unit of such an image forming apparatus, it is possible to obtain the same effect as in the above-described embodiment. In addition, the image carrier may be a drum-type or endless belt-like photoconductor, and the present invention relates to a sensor unit that detects a reference image (toner image for adjustment such as a density correction patch) formed thereon. By applying the invention, it is possible to obtain the same effects as in the above-described embodiments.

  In the above-described embodiments, the sensor is an optical sensor. However, the present invention is not limited to this, and a detection surface disposed opposite to a movable image carrier is provided, and an image is detected via the detection surface. Any sensor may be used as long as it detects the state of the detection target on the carrier. For example, when the image carrier is a photoconductor, the sensor may be a potential sensor that detects the surface potential of the photoconductor as a state on the photoconductor.

7 Intermediate transfer belt 17 Fan 74 Back-up roller 100 Sensor unit 102 Registration sensor 103 Concentration sensor 105 Sensor duct 106 Shutter member 163 Concentration reference member 112 Detection surface 113 Detection opening 120 Introduction port 122 Frame duct 123 Flow path

Claims (17)

A sensor having a detection surface arranged to face the movable image carrier, and detecting a state of a detection target on the image carrier through the detection surface;
A housing that houses the sensor and includes a detection opening that exposes the detection surface to the image carrier; and
In the sensor unit used in the image forming apparatus,
Between an open position that is disposed between the housing and the image carrier and exposes the detection surface to the image carrier, and a closed position that shields the detection surface from the image carrier. A movable shutter member, an exposed portion that exposes the detection surface to the image carrier when in the open position, and a detection surface and the image carrier when in the closed position. A shutter member provided with a shielding portion disposed between,
The housing is provided between an introduction port for introducing air flowing inside the apparatus main body of the image forming apparatus from the outside to the inside of the housing, and the housing is provided between the detection surface and the detection opening, and passes through the introduction port. the air introduced into have a, a flow path for flowing out to the outside of the housing of,
Air that has flowed out of the housing through the flow path when the shutter member is in the open position flows to the image carrier side through the exposed portion, and passes through the flow path when the shutter member is in the closed position. The sensor unit according to claim 1, wherein air that has flowed out of the housing is blown onto the shielding portion .   The flow path is provided on the upstream side of the detection surface in a direction of air flow that flows outside the housing and passes between the detection surface and the image carrier. The sensor unit according to 1. The flow path is provided between the detection surface and an edge of the detection opening, and air introduced into the housing through the introduction port crosses the detection surface to the outside of the housing. sensor unit according to claim 1 or 2, characterized in that to flow out to. The shielding portion is provided with a reference member whose state is detected by the sensor for correcting the detection result of the sensor, and air blown to the shielding portion when the shutter member is in the closed position. a sensor unit according to any one of claims 1 to 3, characterized in that blown to the reference member.   The sensor unit according to any one of claims 1 to 4, wherein the casing includes a duct that directs air introduced into the casing through the introduction port toward the flow path.   The image carrier is an endless belt wound around a plurality of support rollers, and the detection surface is disposed at a position facing one of the plurality of support rollers via the image carrier. The sensor unit according to claim 1, wherein:   The detection target of the sensor is a toner image formed on the image carrier or a transfer material carried on the image carrier. Sensor unit. A movable image carrier;
A sensor that includes a detection surface disposed to face the image carrier and detects a state of a detection target on the image carrier through the detection surface, and a housing that houses the sensor, the detection surface A sensor unit having a housing with a detection opening that exposes the image carrier to the image carrier;
In an image forming apparatus having
A fan that sucks air from the outside of the apparatus main body of the image forming apparatus or discharges air from the inside of the apparatus main body to generate an air flow inside the apparatus main body;
The sensor unit is disposed between the housing and the image carrier, and has an open position where the detection surface is exposed to the image carrier, and a closed position where the detection surface is shielded from the image carrier. A shutter member movable between a position and an exposed portion that exposes the detection surface to the image carrier when in the open position, and the detection surface and the position when in the closed position. A shutter member provided with a shielding portion disposed between the image carrier and
The housing is provided between an introduction port for introducing the air generated by the fan and flowing inside the apparatus main body into the interior from the outside of the housing, and is provided between the detection surface and the detection opening and passes through the introduction port. the air introduced into the interior of the housing have a, a flow path for flowing out to the outside of the housing,
Air that has flowed out of the housing through the flow path when the shutter member is in the open position flows to the image carrier side through the exposed portion, and passes through the flow path when the shutter member is in the closed position. The image forming apparatus according to claim 1, wherein air that has flowed out of the housing is blown onto the shielding portion .   The flow path is provided on the upstream side of the detection surface in a direction of air flow that flows outside the housing and passes between the detection surface and the image carrier. The image forming apparatus according to 8.   The image forming apparatus according to claim 9, wherein an air flow that flows outside the housing and passes between the detection surface and the image carrier is generated by the fan. The flow path is provided between the detection surface and an edge of the detection opening, and air introduced into the housing through the introduction port crosses the detection surface to the outside of the housing. The image forming apparatus according to claim 8, wherein the image forming apparatus is caused to flow out of the image forming apparatus. The shielding portion is provided with a reference member whose state is detected by the sensor for correcting the detection result of the sensor, and air blown to the shielding portion when the shutter member is in the closed position. The image forming apparatus according to claim 8 , wherein the image forming apparatus is sprayed on the reference member. Control means for controlling the drive of the fan so that the amount of air introduced into the housing through the inlet changes between when the shutter member is in the open position and when it is in the closed position. The image forming apparatus according to claim 8, further comprising:   The control means is configured so that the amount of air introduced into the housing through the introduction port is smaller when the shutter member is in the open position than when the shutter member is in the closed position. The image forming apparatus according to claim 13, wherein the driving of the image forming apparatus is controlled.   The image forming apparatus according to claim 8, wherein the housing includes a duct that directs air introduced into the housing through the introduction port toward the flow path.   The image carrier is an endless belt wound around a plurality of support rollers, and the detection surface is disposed at a position facing one of the plurality of support rollers via the image carrier. The image forming apparatus according to claim 8, wherein the image forming apparatus is an image forming apparatus.   The detection target of the sensor is a toner image formed on the image carrier or a transfer material carried on the image carrier. Image forming apparatus.

Images