JP2013235102A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately detect density of a toner image, and stably control the density and a color balance appropriately.SOLUTION: An image forming apparatus which forms a toner image corresponding to image data on an image carrier, and transfers the toner image on a recording sheet comprises: a sensor for detecting density of the toner image; a shutter member for shielding a detection surface of the sensor at the time of non-detection; a contact member provided on the shutter member in a contactable position with the detection surface of the sensor; a shutter driving part for operating the shutter member so as to allow the shutter member to shield the detection surface of the sensor at the time of non-detection, and to release the detection surface of the sensor at the time of detection; and a control part for controlling the detection surface to be frictionally charged by the contact member sliding with the detection surface when the shutter member is operated. The contact member is composed of a material based on characteristics of triboelectric series so as to charge the detection surface with the same polarity as a charging polarity of toner constituting the toner image.

Description

  The present invention relates to an image forming apparatus capable of stably and appropriately detecting the density and color balance of an image to be formed.

  In an electrophotographic image forming apparatus, an image is formed by transferring a toner image formed on a photoreceptor onto a recording sheet.

  At this time, a patch image of a predetermined density is formed, and this patch image is read by a sensor to adjust the charging potential, exposure intensity, development bias, toner density, etc., and form an image with an appropriate density and color balance. You are in control.

  In addition, as the patch image, a toner image on the photoconductor before being transferred onto the recording paper is also detected.

  When such control is performed, the toner may scatter from the toner image on the photosensitive member and adhere to the detection surface of the sensor. When toner contamination occurs on the sensor detection surface, an accurate detection result cannot be obtained, so that the above-described control is not performed properly, and the image density and color balance are affected.

  In order to eliminate such contamination of the sensor detection surface, various proposals have been made in the following patent documents.

Japanese Patent Application Laid-Open No. 09-6203 JP 2006-60428 A

  In Patent Document 1 described above, when using a sensor for measuring the density of a patch image in an image forming apparatus, a shutter that is opened only at the time of measurement is provided, and a cleaning member for removing dirt such as a brush and a blade is provided on the shutter. It has been proposed to clean the sensor detection surface as the shutter is opened and closed.

  Further, in Patent Document 2 described above, the sensor detection surface is scanned with a charged member (cleaning member using a charging member), thereby adhering substances on the sensor detection surface to the charging member side and cleaning the sensor detection surface. It has been proposed.

  The above proposal is to clean the sensor detection surface after it becomes dirty. By such cleaning, the dirt adhering to the sensor detection surface rises, and again adheres to another place, for example, another part slightly away from the part where the sensor detection surface is cleaned. It also happens.

  Moreover, it will be in the state which the dirt adhered to the cleaning member side by cleaning several times. At this time, the contaminated cleaning member may rub the sensor detection surface.

  The present invention has been made in view of such problems, and can accurately detect the density of a toner image and stably and appropriately control the density and color balance of an image formed. An object is to realize a forming apparatus.

  That is, the solution to the above-mentioned problem is solved by the following invention.

(1) An image forming apparatus according to the present invention is an image forming apparatus that forms a toner image corresponding to image data on an image carrier and transfers the toner image on the image carrier onto a recording paper, wherein the toner image A sensor for detecting the density of the sensor, a shutter member for shielding the detection surface when the sensor is not detected, a contact member disposed on the shutter member at a position that can contact the detection surface of the sensor, A shutter drive unit that operates the shutter member so that the shutter member shields the detection surface when not detected and the shutter member opens the detection surface when the sensor is detected, and the shutter member by the shutter drive unit A control unit that controls the detection surface to be frictionally charged by sliding the contact member with the detection surface during the operation of the contact member, Formed of a material in which the sensing surface in the same polarity as the charging polarity of the toner is selected based on the characteristics of the triboelectric series such that charge constituting the toner image.
(2) In the above (1), the sensor detects the untransferred toner density on the image carrier.

  (3) In the above (1)-(2), the control unit slides the contact member against the detection surface before the shutter member opens the detection surface by the shutter driving unit. The detection surface is controlled to be frictionally charged.

  (4) In the above (1) to (3), the control unit slides differently at the time of starting the operation of the image forming apparatus, when detecting the toner image, and when detecting the portion where the toner image does not exist. Control to do.

  (5) In the above (4), the control unit performs control so as to perform sliding at different times, different speeds, or different distances as the different sliding.

  (6) In the above (1) to (5), the sensor is an active sensor having a light emitting unit that emits light to a target surface and a light receiving unit that receives reflected light on the target surface. The detection surface is a surface used for light emission of the light emitting unit and light reception of the light receiving unit.

  According to the image forming apparatus of the present invention, the following effects can be obtained.

  The present invention is an image forming apparatus that forms a toner image according to image data on an image carrier and transfers the toner image on the image carrier onto a recording paper, and detects the density of the toner image with a sensor. The shutter member is configured to shield the detection surface when the sensor is not detected and to open the detection surface when the sensor is detected, and the contact member detects the shutter member when the shutter drive unit operates. The detection surface is charged to the same polarity as the charging polarity of the toner by sliding with the surface.

  This makes it difficult for toner to adhere to the sensor detection surface, prevents contamination of the sensor detection surface with toner, accurately detects the density of the toner image, and stabilizes the density and color balance of the image formed. It becomes possible to control appropriately.

  The sensor also prevents the untransferred toner on the image carrier from adhering to the sensor detection surface even when detecting the density of the untransferred toner on the image carrier, and prevents the sensor detection surface from being soiled by the toner. Accordingly, it is possible to stably and appropriately control the density and color balance of an image formed.

  Further, since the contact member slides on the detection surface before the shutter member opens the detection surface, toner contamination on the sensor detection surface is effectively prevented, and the density and color balance of the image formed are stabilized. Can be controlled appropriately.

  In addition, at the start of the operation of the image forming apparatus, the detection of the toner image, and the detection of the portion where the toner image does not exist, the control unit slides at different times, at different speeds, or at different distances as different slides. By performing the above, toner contamination on the sensor detection surface is appropriately and effectively prevented according to the situation, and the density and color balance of an image formed can be stably and appropriately controlled.

  The sensor is an active sensor having a light emitting unit that emits light to the target surface and a light receiving unit that receives reflected light on the target surface, and the detection surface includes light emission of the light emitting unit and light reception of the light receiving unit. Since the toner contamination on the sensor detection surface is effectively prevented, the light emission intensity of the sensor and the light reception sensitivity of the sensor are properly maintained. It becomes possible to control the balance stably and appropriately.

  Further, since toner adhesion to the sensor is electrostatically prevented, it is possible to bring the sensor closer to the detection target than in the past. For this reason, the restriction | limiting by the distance of a sensor and a detection target object is lose | eliminated, and it becomes possible to use a short focus highly accurate sensor.

1 is a block diagram illustrating a configuration of an image forming apparatus according to an exemplary embodiment of the present invention. 1 is a configuration diagram illustrating a configuration of an image forming apparatus according to an exemplary embodiment of the present invention. FIG. 6 is an explanatory diagram illustrating an operation of a main part of the image forming apparatus according to the embodiment of the present invention. FIG. 6 is an explanatory diagram illustrating an operation of a main part of the image forming apparatus according to the embodiment of the present invention. FIG. 6 is an explanatory diagram illustrating an operation of a main part of the image forming apparatus according to the embodiment of the present invention. FIG. 6 is an explanatory diagram illustrating an operation of a main part of the image forming apparatus according to the embodiment of the present invention. FIG. 6 is an explanatory diagram illustrating charging characteristics in the image forming apparatus according to the embodiment of the present invention. 3 is a flowchart illustrating an operation of the image forming apparatus according to the embodiment of the present invention. FIG. 6 is an explanatory diagram illustrating an operation of a main part of the image forming apparatus according to the embodiment of the present invention. FIG. 6 is an explanatory diagram illustrating an operation of a main part of the image forming apparatus according to the embodiment of the present invention. FIG. 6 is an explanatory diagram illustrating an operation of a main part of the image forming apparatus according to the embodiment of the present invention. FIG. 6 is an explanatory diagram illustrating an operation of a main part of the image forming apparatus according to the embodiment of the present invention. FIG. 6 is an explanatory diagram illustrating an operation of a main part of the image forming apparatus according to the embodiment of the present invention.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments for carrying out the present invention (hereinafter referred to as embodiments) will be described in detail with reference to the drawings.

[1] Configuration:
Here, the configuration of the image forming apparatus 100 according to the first embodiment will be described in detail based on FIG. 1 (block diagram) and FIG. 2 (cross-sectional configuration diagram). Note that description of general parts that are known as image forming apparatuses and are not directly related to the characteristic operations and controls of the present embodiment is omitted.

  In the image forming apparatus 100, the control unit 101 includes a CPU or the like to control each unit of the image forming apparatus 100, and operates according to a control program.

  An operation unit 103 is used by an operator of the image forming apparatus to perform various operation inputs, and includes a display unit, a touch panel, various switches, keys, and the like.

  The storage unit 105 is a storage unit that stores various data. In this embodiment, the storage unit 105 includes the density and pattern of the patch image used when controlling the image conditions, the patch image formation position, various data at the time of control, and the like. Further, the storage unit 105 has data on a charging operation during a shutter operation, which will be described later.

  The exposure control unit 110 is a drive unit that generates an exposure drive signal in accordance with image processed image data, and adjusts the level of the exposure drive signal based on a density adjustment instruction from the control unit 101.

  The patch generation unit 120 generates patch image data based on a patch image generation instruction from the control unit 101, and supplies the patch image data to an image processing unit 130 described later. The patch generation unit 120 can generate various patches such as a density patch for density adjustment, a resist patch for resist adjustment, and a toner band patch.

  The image processing unit 130 executes image processing for making normal image data to be imaged and patch image data for density adjustment suitable for image formation, and the processed image data is exposed to the exposure control unit 110. To supply.

  The process unit 170 is a writing unit that executes various operations for forming an image (toner image) on transfer paper. The exposure unit 172 performs exposure using a light emitting element such as a laser diode and a scanning unit such as a polygon mirror. A photosensitive member 173 in which the electrostatic latent image to be formed is formed as a toner image by the developing unit, an intermediate transfer member 175 to which the toner image on the photosensitive member 173 is transferred, and an intermediate transfer member 175 before transfer onto the transfer paper Sensor 176 for detecting the density of the patch image and a transfer unit 177 for transferring the toner image on the intermediate transfer body 175 to the recording paper.

  In the case of the image forming apparatus 100 that performs color image formation, the exposure unit 172 includes a Y exposure unit 172Y, an M exposure unit 172M, a C exposure unit 172C, and a K exposure unit 172K. ing. Similarly, in the case of the image forming apparatus 100 that performs color image formation, the photoconductor 173 includes a Y photoconductor 173Y, an M photoconductor 173M, a C photoconductor 173C, and a K photoconductor 173K. Has been.

  The fixing unit 180 pinches and conveys the transfer paper onto which the toner image has been transferred, and performs fixing by heating and pressurization to make the toner image stable on the transfer paper.

  Next, the mechanical configuration of the image forming apparatus 100 and the arrangement of each unit will be described with reference to FIG.

  The paper feed unit 150 is a paper feed unit that feeds transfer paper placed on one or a plurality of paper feed trays 150T (150T1 to 150T3 in FIG. 2) to an image forming position by a paper feed roller.

  The transport unit 160 is a transport unit that transports the transfer paper fed from the paper feed unit 150 at a predetermined transport speed, and includes a registration roller, various other transport rollers, a transport belt, and the like.

  The process unit 170 is a writing unit that executes various operations for forming an image on a transfer sheet. The charging unit 171 charges the photoconductor 173 with a predetermined charge. The exposure unit 172 exposes the photoconductor 173 according to image data. A photosensitive member 173 as an image carrier on which an electrostatic latent image is formed by exposure, a developing unit 174 that develops the electrostatic latent image on the photosensitive member 173 into a toner image, and a toner image on the photosensitive member 173 are transferred. An intermediate transfer member 175 as an image carrier for supporting a toner image, a sensor 176 for detecting the density of a patch image on the intermediate transfer member 175 before transfer onto the transfer paper, and a toner image on the intermediate transfer member 175 as a transfer paper A transfer portion 177 for transferring to the recording medium.

  In the case where the image forming apparatus 100 is a color image forming apparatus that combines toner images of a plurality of colors, as shown in FIG. 2, in the process unit 170, a charging unit 171, an exposure unit 172, a photoconductor 173, and a development unit. The portions 174 are provided corresponding to the respective colors, and are configured such that the toner images of the respective colors are superimposed on the intermediate transfer member 175 and finally transferred onto the transfer paper.

  Further, a sensor 176 for detecting the density of the image transferred to the intermediate transfer body 175 is provided, and is used for detecting the density of the patch image before transfer.

  Note that the photoconductor 173 may have a belt shape instead of a drum shape. Similarly, the intermediate transfer member 175 may have a drum shape instead of a belt shape.

  1 and 2 exemplify an image forming apparatus that performs color image formation, the present embodiment may be a monochrome image forming apparatus.

  In FIGS. 1 and 2, the sensor 176 is shown as detecting the density of the untransferred toner image on the intermediate transfer body 175, but it detects the density of the toner image on the photoreceptor 173. May be.

  Next, the configuration of the sensor 176 will be described with reference to FIGS. 2 is a cross-sectional view of the XZ plane, FIG. 3 shows a cross-sectional configuration of XY. In FIG. 2 and FIG. 3, XYZ is shown in a common state. In FIG. 3, the intermediate transfer member 175 is shown in a state of moving in the Z direction perpendicular to the paper surface.

  The sensor 176 has openings 176h1 and 176h2 on the surface facing the intermediate transfer member 175, and is configured by a shielding member other than the openings, and provided with a shutter member 176st that can move in the + Y to -Y directions. ing.

  The sensor 176 has a casing 176b other than the surface facing the intermediate transfer member 175. Therefore, the shutter member 176st and the casing 176b are configured to protect the inside from scattering of toner and the like.

  Further, sensor units 176s1 and 176s2 for measuring the density of the patch image on the intermediate transfer member 175 are arranged inside the sensor 176.

  The shutter member 176st is configured to be movable in the + Y to -Y direction by the drive unit 176, and is opened and closed as a shutter for the sensor units 176s1 and 176s2.

  When the shutter is closed, the driving unit 176d is driven so that the shielding portion of the shutter member 176st comes to the detection surface side of the sensor units 176s1 and 176s2. This state is shown in FIG. 3 as an overall view, and FIG. 4 as a partially enlarged view. 3 and 4 is the home position of the shutter member 176.

  Further, when the shutter is opened, the shutter member 176st is driven by the drive unit 176d so that the openings 176h1 and 176h2 come in front of the detection surfaces of the sensor units 176s1 and 176s2. This state is shown in FIG. 5 as an overall view, and FIG. 6 as a partially enlarged view.

  Although two sensor units 176s1 and 176s2 are shown here, the number and arrangement positions of the sensor units are not limited to those illustrated.

  The drive unit 176d can use various drive sources such as a stepping motor, a voice coil motor, and an ultrasonic motor, and is configured to be able to detect a shutter opening / closing state by the shutter member 176st by a sensor (not shown). ing.

  Further, the contact members 176e1 and 176e2 are arranged at positions on the shutter member 176st that can slide-contact with the sensor detection surfaces 176sf1 and 176sf2 when the shutter member 176st moves in the + Y to −Y direction.

  The sensor detection surfaces 176sf1 and 176sf2 are preferably flat surfaces so that good contact can be made with the contact members 176e1 and 176e2.

  Here, the contact members 176e1 and 176e2 are in sliding contact with the sensor detection surfaces 176sf1 and 176sf2, so that the sensor detection surface 176sf1 has the same polarity as the charging polarity of the toner constituting the toner image on the intermediate transfer body 175. And 176sf2 are made of a material selected based on the characteristics of the charging train (see FIG. 7) so as to be frictionally charged.

  Here, the triboelectric charge is a kind of electrostatic phenomenon, and is a phenomenon in which a charge is transferred from one to the other to cause a potential difference by rubbing two different substances together. In addition, the charged column is a table in which the materials that are easily charged on the + side are arranged on the upper side and those that are easily charged on the − side are arranged on the lower side when two kinds of materials are rubbed. If the material that rubs is more distant on the charge train, more charge will move.

  For example, it is assumed that the toner on the intermediate transfer body 175 is charged on the negative side and the sensor detection surfaces 176sf1 and 176sf2 are made of acrylic resin. In this case, a material is selected such that the contact members 176e1 and 176e2 are positively charged with respect to the acrylic resin, for example, rayon, nylon, wool or the like.

  Accordingly, the sensor detection surfaces 176sf1 and 176sf2 are charged to the negative side having the same charging polarity as that of the toner by friction. However, it is desirable that the sensor detection surfaces 176sf1 and 176sf2 be made of a soft material or a slippery material so as not to be damaged.

  The material of the contact members 176e1 and 176e2 can be selected according to the charging polarity of the toner and the material of the sensor detection surfaces 176sf1 and 176sf2.

[2] Operation:
The operation of the image forming apparatus 100 according to the embodiment will be described below with reference to the flowchart of FIG.

  The image forming apparatus 100 operates according to the control program of the control unit 101, and the control program includes a subroutine for the shutter operation shown in the flowchart of FIG. 8, and the control unit 101 uses the flowchart of FIG. Run regularly.

  When the operation of the image forming apparatus 100 is started, the control unit 101 confirms whether the shutter member 176st is in the shutter closed state, that is, the home position via the drive unit 176d (step S101 in FIG. 8). . Note that the driving unit 176d may move the shutter member 176st and check the position with a home position sensor (not shown).

  Further, when the contact members 176e1 and 176e2 and the sensor detection surfaces 176sf1 and 176sf2 are in sliding contact, the control unit 101 performs appropriate charging necessary for preventing toner contamination in each situation. Next, the driving state is calculated (step S102 in FIG. 8).

  Here, each situation corresponds to, for example, the start of the operation of the image forming apparatus, the detection of a portion where no toner image exists, the detection of a toner image, and the like.

  The detection of the part where the toner image does not exist is executed when the light emission intensity of the light emitting unit of the sensor units 176s1 and 176s2 is adjusted. In addition, the time when the operation of the image forming apparatus starts is charging before the measurement, but as a precaution to prevent toner contamination in the subsequent operation.

  In this case, when a toner image is detected, there is a high possibility that untransferred toner on the intermediate transfer body 175 will fly to the sensor detection surfaces 176sf1 and 176sf2 via the openings 176h1 and 176h2 of the shutter member 176st. For this reason, as the driving state, the control unit 101, when the number of sliding times is variable, the number of sliding times is large, and when the sliding speed is variable, the sliding speed is large and the sliding distance is variable. In this case, the sliding distance is set to be large.

  Further, the number, size, and density of patch images to be detected, that is, the amount of toner, may be finely determined as a criterion.

  Further, when a portion where no toner image exists is detected, no toner image exists on the intermediate transfer member 175, but image formation is performed on the sensor detection surfaces 176sf1 and 176sf2 via the openings 176h1 and 176h2 of the shutter member 176st. There is a possibility that toner may fly from anywhere in the apparatus 100. For this reason, as the driving state, the control unit 101 has a variable number of sliding times when the number of sliding times is variable, and when the sliding speed is variable, the sliding speed is medium and the sliding distance is variable. Is set, the sliding distance = medium.

  At the start of the operation of the image forming apparatus, the shutter member 176st is in a closed state, and there is little possibility that toner will fly to the sensor detection surfaces 176sf1 and 176sf2. For this reason, as the driving state, the control unit 101, when the number of sliding times is variable, the number of sliding times is small, when the sliding speed is variable, the sliding speed is small, and the sliding distance is variable. In this case, the sliding distance is set to be small.

  Even in other situations, the control unit 101 is required to prevent toner contamination when the contact members 176e1 and 176e2 and the sensor detection surfaces 176sf1 and 176sf2 are in sliding contact. What is necessary is just to calculate a drive state so that it may be charged easily.

  Note that the above driving state may not be calculated every time, but may be stored in the storage unit 105 in a table format and read according to each situation.

  When the calculation of the driving state is completed, the control unit 101 drives the shutter member 176st by the shutter driving unit 176d, and the contact member 176e1, the sensor detection surface 176sf1, and the contact member 176e2 according to the calculated driving state. And the sensor detection surface 176sf2 are brought into sliding contact (steps S103 and S104 in FIG. 8).

  This state is shown in FIGS. That is, the contact member 176e1 and the sensor detection surface 176sf1 and the contact member 176e2 and the sensor detection surface 176sf2 that are in the state of FIG. 9 as the home position are set to the state of FIG. 10, the state of FIG. 11, the state of FIG. As shown in FIG. Thereby, the sensor detection surfaces 176sf1 and 176sf2 are appropriately charged as necessary to prevent toner contamination in each situation.

  Here, the charging is realized by sliding by reciprocating motion, but it may be a single movement of FIGS. 9 to 11.

  When the sliding of the contact member 176e1 and the sensor detection surface 176sf1 and the contact member 176e2 and the sensor detection surface 176sf2 by the driving of the shutter member 176st is completed (YES in step S104 in FIG. 8), the control unit 101 It is determined whether or not measurement is performed by the units 176s1 and 176s2 (step S105 in FIG. 8).

  When the operation of the image forming apparatus is started, measurement by the sensor units 176s1 and 176s2 is not performed (NO in step S105 in FIG. 8). Therefore, the control unit 101 determines whether the shutter member 176st is in the shutter closed state. That is, the home position is confirmed via the drive unit 176d (step S109 in FIG. 8), and the operation is terminated (END in FIG. 8).

  When measurement is performed by the sensor units 176s1 and 176s2 (YES in step S105 in FIG. 8), the control unit 101 drives the shutter member 176st by the shutter drive unit 176d, and before the detection surface of the sensor units 176s1 and 176s2. Then, the shutter is opened so that the openings 176h1 and 176h2 come (step S106 in FIG. 8).

  At this time, the detection surfaces of the sensor detection surfaces 176sf1 and 176sf2 are charged to the same polarity as the toner charging polarity by the previous sliding. As a result, the sensor detection surfaces 176sf1 and 176sf2 are less likely to adhere to the toner, so that the contamination by the toner is prevented. As a result, it is possible to accurately detect the density of the patch image and stably and appropriately control the density and color balance of the image formed. The sensor also prevents the untransferred toner on the image carrier from adhering to the sensor detection surface even when detecting the density of the untransferred toner on the image carrier, and prevents the sensor detection surface from being soiled by the toner. Is done. In addition, even when the contact members 176e1 and 176e2 slide on the detection surface before the shutter member opens the sensor detection surfaces 176sf1 and 176sf2, the sensor detection surfaces 176sf1 and 176sf2 are less likely to adhere to the toner. Pollution is prevented.

  Then, the control unit 101 processes the detection signals from the sensor units 176s1 and 176s2 and measures the density of the patch image (step S107 in FIG. 8). The control unit 101 refers to the measurement result and performs calculations for adjusting the density and color balance of the image formed.

  Then, when a predetermined measurement time determined in advance has passed (YES in step S108 in FIG. 8), the control unit 101 drives the shutter member 176st by the shutter drive unit 176d, and the sensor units 176s1 and 176s2 The shutter is closed so that the shielding portion of the shutter member 176st comes to the detection surface side (step S109 in FIG. 8).

  Further, the control unit 101 confirms through the drive unit 176d whether the shutter member 176st is in the shutter closed state, that is, the home position, and ends the operation (END in FIG. 8).

  The control unit 101 periodically and repeatedly executes the subroutine for the shutter operation shown in the flowchart of FIG.

[3] Effects obtained by the embodiment:
The above embodiment is an image forming apparatus 100 that forms a toner image corresponding to image data on an image carrier and transfers the toner image on the image carrier onto a recording paper. The density is detected by the sensor 176, the sensor detection surfaces 176sf1 and 176sf2 are shielded by the shutter member 176st when not detected, and the shutter member 176st is configured to open the sensor detection surfaces 176sf1 and 176sf2 when detected. During the operation of the shutter member 176st by the driving unit 176d, the contact members 176e1 and 176e2 slide with the sensor detection surfaces 176sf1 and 176sf2, and the sensor detection surfaces 176sf1 and 176sf2 are charged to the same polarity as the charging polarity of the toner.

  As a result, the sensor detection surfaces 176sf1 and 176sf2 are less likely to adhere to the toner, so that the contamination by the toner is prevented. Accordingly, it is possible to accurately detect the density of the patch image and stably and appropriately control the density and color balance of the image formed.

  Further, even when the sensor detects the untransferred toner density on the intermediate transfer member 175 that is an image carrier, the untransferred toner on the intermediate transfer member 175 is less likely to adhere to the sensor detection surfaces 176sf1 and 176sf2. Further, the sensor detection surface is prevented from being soiled by toner, and the density and color balance of an image formed can be controlled stably and appropriately.

  Further, before the shutter member 176st opens the sensor detection surfaces 176sf1 and 176sf2, the contact members 176e1 and 176e2 slide with the sensor detection surfaces 176sf1 and 176sf2, so that the toner contamination of the sensor detection surfaces 176sf1 and 176sf2 is effectively performed. Thus, it is possible to stably and appropriately control the density and color balance of an image formed and prevented.

  In addition, by sliding the image forming apparatus at different times, at different speeds, or at different distances at the time of starting the operation of the image forming apparatus, at the time of detecting the toner image, and at the time of detecting the part where the toner image does not exist In addition, toner contamination on the sensor detection surfaces 176sf1 and 176sf2 is appropriately and effectively prevented according to the situation, and the density and color balance of an image formed can be controlled stably and appropriately.

  The sensor 176 is an active sensor having a light emitting unit that emits light to the measurement target surface and a light receiving unit that receives reflected light from the measurement target surface. The sensor detection surfaces 176sf1 and 176sf2 are light emitting units. This is a surface used for light emission and light reception by the light receiving unit, and by effectively preventing toner contamination on the sensor detection surfaces 176sf1 and 176sf2, the light emission intensity of the sensor and the light reception sensitivity of the sensor are appropriately maintained. Therefore, it is possible to stably and appropriately control the density and color balance of an image formed.

  In this embodiment, toner adhesion to the sensor 176 is electrostatically prevented, so that the sensor 176 can be brought closer to a detection target such as the intermediate transfer member 175 and the photosensitive member 173 than in the past. . Conventionally, in order to avoid toner adhesion to the sensor, the sensor is separated from the detection target as much as possible. For this reason, in this embodiment, the restriction | limiting by the distance of the sensor 176 and a detection target object is lose | eliminated, and it becomes possible to use a highly accurate sensor with a short focus.

  The present embodiment prevents the contamination from occurring, and does not perform cleaning after the sensor detection surface becomes dirty as in the known art. For this reason, by cleaning, the dirt adhering to the sensor detection surface rises, and again adheres to another place, for example, another part slightly away from the part where the sensor detection surface is cleaned. This does not occur in this embodiment.

  Further, in this embodiment, the electrostatic sensor 176 is prevented from being damaged, and unlike the conventional method in which the dirt is scraped off with a brush or a blade after being dirty, the durability of each part is superior to that of the conventional technique. Results are obtained.

[4] Other embodiments:
In the above embodiment, the untransferred toner image on the intermediate transfer member 175 is measured by the sensor 176, but the present invention is not limited to this. For example, an untransferred toner image on the photoconductor 173 may be measured by the sensor 176. It is also possible to measure the transferred toner image on the recording paper with the sensor 176.

DESCRIPTION OF SYMBOLS 100 Image forming apparatus 101 Control part 103 Operation part 105 Storage part 110 Exposure control part 120 Patch generation part 130 Image processing part 170 Process unit 176 Sensor 177 Transfer part 180 Fixing part

Claims (6)

An image forming apparatus for forming a toner image corresponding to image data on an image carrier and transferring the toner image on the image carrier onto a recording paper,
A sensor for detecting the density of the toner image;
A shutter member that shields the detection surface when the sensor is not detected;
A contact member disposed on the shutter member at a position that can contact the detection surface of the sensor;
A shutter drive unit that operates the shutter member so that the shutter member shields the detection surface when the sensor is not detected and the shutter member opens the detection surface when the sensor is detected;
A control unit configured to control the detection surface to be frictionally charged by sliding the contact member with the detection surface during the operation of the shutter member by the shutter driving unit;
The contact member is made of a material selected on the basis of the characteristics of the charge train so that the detection surface is charged to the same polarity as the charge polarity of the toner constituting the toner image.
An image forming apparatus. The sensor detects an untransferred toner density on the image carrier;
The image forming apparatus according to claim 1. The controller is
Before the shutter member opens the detection surface by the shutter drive unit, the contact member slides on the detection surface to control the detection surface to be frictionally charged.
The image forming apparatus according to claim 1 or 2. The controller is
Control to perform different sliding at the start of operation of the image forming apparatus, at the time of detection of the toner image, and at the time of detection of a portion where the toner image does not exist,
The image forming apparatus according to claim 1, wherein the image forming apparatus is an image forming apparatus. The controller is
The different slides are controlled to perform different times, different speeds, or different distances.
The image forming apparatus according to claim 4. The sensor is an active type sensor having a light emitting unit that emits light to a target surface and a light receiving unit that receives reflected light from the target surface.
The detection surface is a surface used for light emission of the light emitting unit and light reception of the light receiving unit,
The image forming apparatus according to claim 1, wherein the image forming apparatus is an image forming apparatus.

Images