JP2010128031A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus having a cleaning function for an exposure part and an electrification part in order to prevent damage of an image and deterioration in image quality over a long term, and efficiently performing cleaning together with density control, to suppress failure leading to variation of color. <P>SOLUTION: An electrification cleaning part 65 and an exposure cleaning part 40 are independently or simultaneously driven and controlled with (A-B)/B>0.1 as a threshold when assuming that a result of detection at a pre-stage of a time series stored in an HDD 60 is A, and a result of detection at a post-stage of a time series stored in the HDD 60 is B. If (A-B)/B≤0.1, the electrification cleaning part 65 and the exposure cleaning part 40 are independently or simultaneously driven and controlled with (Bx-By)/By>0.1 as another threshold when assuming that a result of detection on one of right and left in a transfer paper conveying direction stored in the HDD 60 is Bx, and a result of detection on the other of right and left in the transfer paper conveying direction stored in the HDD 60 is By. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an image forming apparatus including an exposure unit that exposes an image carrier charged by a charging unit to form an electrostatic latent image.

  2. Description of the Related Art Conventionally, as an image forming processing unit installed in an image forming apparatus such as a printer, a copier, a facsimile machine, or a multifunction machine equipped with these functionally, an image carrier such as a photosensitive drum is charged by a charging unit, and an exposure unit The charged image carrier is exposed to form an electrostatic latent image by the developer, the exposed electrostatic latent image is visualized as a toner image by the developing unit, and the toner image is transferred to a transfer medium such as transfer paper by the transfer unit. In addition, it is well known to repeat the process of discharging the image carrier after the transfer for the next image forming process by the discharging unit.

  In addition, since it is preferable that the toner density of the toner image transferred onto the transfer paper is always stable, the toner density detection sensor detects the toner density of the toner image on the image carrier (including the intermediate transfer body). However, it is also well known to perform calibration for controlling the developing bias and the like according to the detection result.

  At this time, if the cause of detecting the toner density drop by the toner density detection sensor is related to the development, calibration such as improving the developability may be performed.

However, the cause of detecting that the toner concentration is lowered by the toner concentration detection sensor is not related to the development. For example, the amount of light in the exposure unit or charging unit due to contamination of scattered toner or the like in the apparatus main body, particularly in the vicinity of the image forming processing unit. For other causes such as lowering or lowering of charge, calibration for development is not particularly necessary, but changing the development bias value will reverse the development balance and excessively increase the toner density. There is a risk of further image density fluctuations and toner scattering due to proper calibration.
JP-A-2-179659 JP-A-11-212315 JP 11-327385 A

  However, in the image forming apparatus configured as described above, when the current detection value of the toner density detection sensor simply falls below a predetermined reference value, cleaning of the exposure part and the charging part is executed. Can be dealt with only when the toner density is low, and even if the current toner density is not low, there is a problem that it is not possible to cope with the problem of color variation when a toner density difference occurs before and after that. It was.

  In addition, when the detection sensors are arranged on the left and right in the transfer paper conveyance direction, the cleaning of the exposure unit and the charging unit is performed when one of the detection sensors simply falls below a predetermined reference value. There was a problem that it was not possible to deal with the problem of fluctuation.

  Therefore, in consideration of the above circumstances, the present invention has a cleaning function for the exposure unit and the charging unit in order to prevent image damage and image quality degradation for a long period of time, and can efficiently perform cleaning in combination with density control. It is an object of the present invention to provide an image forming apparatus capable of suppressing problems with fluctuations.

  An image forming apparatus according to the present invention includes an image forming processing unit having an exposure unit that exposes an image carrier charged by a charging unit to form an electrostatic latent image, and a toner density of the image carrier at a predetermined timing. Detection results of the plurality of toner concentration detection units, a charging cleaning unit that cleans the charging unit, an exposure cleaning unit that cleans the exposure unit, and a plurality of toner concentration detection units. In addition, when the toner density storage unit which is stored independently for each detection before and after the time series, and the detection result of the time series upstream stored in the toner density storage unit is A and the detection result of the time series downstream is B (A-B) / B> 0.1 An image forming apparatus comprising: a control unit that drives and controls the charge cleaning unit and the exposure cleaning unit independently or simultaneously when the relation is satisfied. Indicates that the toner density detection unit In the case of (A−B) /B≦0.1, one of the left and right detection results in the transfer sheet conveyance direction stored in the toner density storage unit is expressed as Ax. Or Bx, threshold (Ax−Ay) / Ay> 0.1 or (Bx−By) / By when the other detection result on the left and right of the transfer sheet conveyance direction stored in the toner density storage unit is Ay or By. The charge cleaning unit and the exposure cleaning unit are independently or simultaneously driven and controlled when> 0.1.

  The image forming apparatus according to the present invention includes an image forming processing unit including an exposure unit that exposes the image carrier charged by the charging unit to form an electrostatic latent image, and sets the toner density of the image carrier to a predetermined value. A plurality of toner concentration detection units that detect at the timing, a charging cleaning unit that cleans the charging unit, an exposure cleaning unit that cleans the exposure unit, and the detection results of the plurality of toner concentration detection units A toner density storage unit that stores data independently for each detection in the left and right directions and before and after the time series, and a detection result in the previous time series stored in the toner density storage unit is A and a detection result in the subsequent time series is B. And (A-B) / B> 0.1, an image forming apparatus comprising: a control unit that controls driving of the charging cleaning unit and the exposure cleaning unit independently or simultaneously. The control unit is configured such that the toner density detection unit conveys the transfer paper. When a toner concentration detection cleaning unit that is disposed in at least two locations on the front, rear, left, and right and cleans each toner concentration detection unit is installed, when (A−B) /B≦0.1, Threshold value (Amax−Amin) / Amin> 0.1 or (where Amax or Bmax is the maximum value stored in the toner concentration storage unit, and the maximum value is Amax or Bmax, and the minimum value is Amin or Bmin. Bmax−Bmin) / Bmin> 0.1, each of the cleaning units is driven and controlled.

  At this time, when a plurality of image carriers are arranged, a plurality of the charge cleaning units and the exposure control units are arranged corresponding to the plurality of image carriers, and the plurality of image carriers are arranged. The toner density detected by the plurality of toner density detection units for each body is stored in the toner density storage unit corresponding to each of the plurality of image carriers, and the control unit is stored in the toner density storage unit. For each detection result for each of the plurality of toner density detection units, it is preferable that only the plurality of charging cleaning units and the plurality of exposure cleaning units that exceed the detection determination threshold are driven independently or simultaneously.

  Furthermore, the image forming apparatus of the present invention includes an image forming processing unit including an exposure unit that exposes the image carrier charged by the charging unit to form an electrostatic latent image, and sets the toner density of the image carrier to a predetermined value. A plurality of toner concentration detection units that detect at the timing, a charging cleaning unit that cleans the charging unit, an exposure cleaning unit that cleans the exposure unit, and the detection results of the plurality of toner concentration detection units A toner density storage unit that stores data independently for each detection in the left and right directions and before and after the time series, and a detection result in the previous time series stored in the toner density storage unit is A and a detection result in the subsequent time series is B. And (A-B) / B> 0.1, an image forming apparatus comprising: a control unit that controls driving of the charging cleaning unit and the exposure cleaning unit independently or simultaneously. The control unit is configured such that the toner density detection unit carries transfer paper. In the case where toner density detection cleaning units that are disposed at at least two locations on the left and right sides of the direction and that clean the respective toner concentration detection units are installed, detection of one of the left and right sides in the transfer sheet conveyance direction stored in the toner concentration storage unit When (Ax-Ay) / Ay> 0.1 or (Bx-By) / By> 0.1 when the result is Ax or Bx and the detection result on the other side of the transfer paper conveyance direction is Ay or By Further, only the toner density detection cleaning unit on the left and right sides in the transfer paper conveyance direction is driven and controlled.

  At this time, it is preferable that the control unit drives each of the cleaning units immediately before execution of calibration for the image forming processing unit.

  The image forming apparatus of the present invention has a cleaning function for the exposure unit and the charging unit in order to prevent image damage and image quality degradation for a long period of time, and can efficiently perform cleaning in combination with density control, thereby causing a problem with color variation. Can be suppressed.

  Next, an image forming apparatus according to an embodiment of the present invention will be described with reference to the drawings.

  FIG. 1 is an explanatory view of a color printer as an image forming apparatus according to an embodiment of the present invention, FIG. 2 is an explanatory view of an exposure device used in the image forming apparatus according to an embodiment of the present invention, and FIG. FIG. 4 is a plan view of an exposure device used in an image forming apparatus according to an embodiment of the present invention, and FIG. 5 is an embodiment of the present invention. FIG. 6 is a plan view of a drum unit used in an image forming apparatus according to an embodiment of the present invention, and FIG. 7 is an image forming apparatus according to an embodiment of the present invention. 8 is a side view of a drum unit used in the apparatus, FIG. 8 is a perspective view of a charger used in the image forming apparatus according to the embodiment of the present invention, and FIG. 9 is a perspective view of the image forming apparatus according to the embodiment of the present invention. The plane of the charger used FIG. 10 is a flow chart of the control routine of the image forming apparatus according to the embodiment of the present invention. FIG. 11 is a diagram showing the calibration control timing and cleaning timing of the image forming apparatus according to the embodiment of the present invention. It is explanatory drawing.

(Overall configuration of the color printer 11)
In FIG. 1, a color printer 11 according to an embodiment of the present invention includes a paper cassette 13 that stores transfer paper (not shown) inside a printer main body 12, and a paper supply that takes out the transfer paper from the paper cassette 13. An image forming processing unit 15 that performs image forming processing on transfer paper supplied from the paper unit 14, the paper feed cassette 13 or a manual feed tray (not shown), and transfer paper supplied from the paper feed cassette 13 or the manual feed tray Is provided with a transfer unit 17 that transfers the toner image subjected to the image formation processing by the image forming processing unit 15 while guiding the toner image on the transfer paper conveyance path 16, and a fixing unit 18 that fixes the toner image after transfer onto the transfer paper.

  The transfer sheet on which the toner image has been transferred by the transfer unit 17 is fixed by the fixing unit 18 through the transfer sheet conveyance path 16 and then guided to the end of the transfer sheet conveyance path 16 as the upper surface of the printer main body 12. The paper is discharged toward the shared paper discharge tray 12a.

(Configuration of the image forming processing unit 15)
The image forming processing unit 15 performs, for example, a tandem system that performs image forming processing using toner (developer) of four colors of magenta (M), cyan (C), yellow (Y), and black (K) from the upstream side. A plurality of toner containers 19 containing replenishment toners corresponding to the respective colors (M, C, Y, K) and the toners of the respective colors (M, C, Y, K) are not shown. A drum-shaped photoconductor (image carrier) 20 that forms a toner image based on image data included in print data transmitted from a personal computer, and each color (M, C, Y, K) on the photoconductor 20. A developing device 21 that supplies toner, an endless intermediate transfer belt 22 to which a toner image formed on the photoreceptor 20 is transferred, a unit-shaped exposure device 23, and the intermediate transfer belt 22 in the vicinity of the transfer unit 17. Transcribed A toner density detection sensor 24 for detecting the toner density, and a belt cleaning device 25 disposed substantially on the opposite side of the toner density detection sensor 24 to remove residual toner and the like adhering to the surface of the intermediate transfer belt 22. Yes.

(Configuration of photoconductor 20)
Each photoreceptor 20 carries a toner image of each color (M, C, Y, K) on its surface based on the laser beam L emitted from the exposure device 23 and transfers the toner image to the intermediate transfer belt 22. It is disposed below the intermediate transfer belt 22 together with the developing device 21. Further, around each photoconductor 20, a charging device 26, an exposure device 23, a developing device 21, a temporary transfer roller 27, a cleaning device 28, and a charge eliminating device 29 are arranged in this order (developing process order).

(Configuration of developing device 21)
Each developing device 21 basically has the same configuration and is arranged adjacent to the lower side of the intermediate transfer belt 22 along the rotational movement direction.

(Configuration of the intermediate transfer belt 22)
The intermediate transfer belt 22 is an endless belt disposed in the printer main body 12 so as to extend in the horizontal direction, and is circulated and driven in accordance with an image forming operation. In addition, a primary transfer roller 27 is disposed inside the intermediate transfer belt 22 so as to face each other (photograph 20 for each color (M, C, Y, K)) and the intermediate transfer belt 22.

  The toner image transferred onto the intermediate transfer belt 22 by the cooperation of the photosensitive member 20 and the primary transfer roller 27 is transferred onto the transfer sheet conveyed from the sheet feeding cassette 13 or the manual feed tray through the transfer sheet transfer path 16. On the other hand, the image is transferred by the transfer unit 17. Further, the toner density of the intermediate transfer belt 22 is detected by a toner density detection sensor 24 disposed between the primary transfer unit 27 and the secondary transfer unit 17.

(Configuration of exposure device 23)
As shown in FIG. 2, the exposure device 23 irradiates each light beam emitted from a plurality of light sources 30 (M, C, Y, K) corresponding to each photoconductor 20 (M, C, Y, K) as shown in FIG. Polarizers 31 (MC) and 31 (31) such as polygon mirrors sharing a pair of units divided into light sources 30 (M) and 30 (C) and light sources 30 (Y) and 30 (K), respectively. The light beam L (only shown for the photoconductor 20 (K)) is imaged on the photoconductor 20 (M, C, Y, K) by reflecting the plurality of oblique mirrors 32 while performing polarization scanning with YK). Note that these two units are accommodated in a pair of adjacent housings 33 and 34. Further, the exposure device 23 covers a part of the surface of the housings 33 and 34 having a unit configuration incorporating these various optical systems with a cover glass 35, and the laser light L described above is emitted from the cover glass 35. . 3 and 4, the exposure device 23 is guided along the extending direction of the cover glass 35 by the guide screw 36 extending along the extending direction of the cover glass 35 and along the extending direction of the cover glass 35. An exposure cleaning unit 40 having a holder member 38 including a pair of pad-shaped cleaning members 37 that cleans the surface of the cover glass 35 by moving forward and backward, and a drive gear 39 that rotates the guide screw 36 is provided. . The drive gear 39 is in a cooperative state with the housings 33 and 34 and rotates the guide screw 36 in synchronization.

(Configuration of toner density detection sensor 24)
The toner density detection sensor 24 measures the reflection density of the toner image on the intermediate transfer belt 22 and, based on the detected value, development conditions such as toner replenishment of each development device 21 and bias voltage applied to the development device 21, charging device This is used to execute calibration of the charging conditions of 26, the exposure conditions such as the laser power of the exposure device 23, the erase light quantity of the static elimination device 29, and the like.

  A plurality of toner concentration detection sensors 24 can be provided in the rotational direction of the intermediate transfer belt 22 and the width direction perpendicular to the rotational direction (direction perpendicular to the paper surface of FIG. 1).

  At this time, the toner density detection sensor 24 is preferably arranged in the vicinity of both widths because the toner density on only one side in the width direction of the intermediate transfer belt 22 cannot be dealt with in the case of one side burn.

  Further, as shown in FIG. 5, the toner concentration detection sensor 24 is disposed inside the casing 41, a protective cover 42 that closes the detection light entrance / exit window of the casing 41, and an intermediate transfer. A light emitting element 43 such as a light emitting diode that emits detection light toward the belt 22, an output side polarization separation element 44 disposed on the front surface of the light emitting element 43, a correction light receiving element 45 such as a phototransistor, and an intermediate transfer A light receiving side polarization separation element 46 that separates the detection light reflected by the belt 22 into a regular reflection component (P wave) and a diffuse reflection component (S wave), and first and second light receiving elements 47 such as photodiodes. , 48, and a brush-like cleaning member 49 as a toner concentration detection cleaning unit that removes scattered toner or the like that is normally retracted from the protective cover 42 and adhered to the front surface of the protective cover 42.

  An LED laser beam light source or the like is used as the light emitting element 43, and when a predetermined control voltage is output from the differential amplifier circuit (amplifier circuit) 50, the light emission threshold current of the control voltage is output from the drive circuit 51 to the light emitting element 43. To be supplied.

  A polarization beam splitter, a polarizing prism, a half mirror, or the like is used for the output side polarization separation element 44. The detection light is emitted from the light emitting element 43 toward the intermediate transfer belt 22 and is emitted from the light emitting element 43. A part of the detected light is detected by the correction light receiving element 45. When a polarization beam splitter is used as the output side polarization separation element 44, a part of the detection light emitted from the light emitting element 43 is transmitted in a state where the polarization is aligned with the P wave.

  The correction light receiving element 45 receives a part of the detection light reflected (refracted) by the output side polarization separation element 44, detects the amount of light by the monitor light detection circuit (monitor circuit) 52, and then the impedance conversion circuit. The photoelectric current impedance-converted by the (conversion circuit) 53 is fed back to the differential amplifier circuit (amplifier circuit) 50 as a light amount detection voltage.

  The light receiving side polarization separation element 46 separates the detection light reflected by the intermediate transfer belt 22 into a regular reflection component (P wave) and a diffuse reflection component (S wave).

  The detection results of the light receiving elements 47 and 48 are converted into voltages by the IV conversion circuits (conversion circuits) 54 and 55, and then the gain is adjusted by the gain adjustment circuits (adjustment circuits) 56 and 57. The received S wave detection voltage value and the P wave detection voltage value received by the light receiving element 47 are output to the control circuit 58.

(Function of control circuit 58)
Based on the control program stored in the ROM 59, the control circuit 58 supplies the developing conditions such as the toner replenishment of each developing device 21 and the bias voltage applied to the developing device 21, the charging conditions of the charging device 26, and the exposure device 23. Calibration of exposure conditions such as laser power and the erase light quantity of the charge removal device 29 is controlled. The ROM 59 also stores a control program related to cleaning unit drive timing control of the present invention. Note that image data and the like when executing the image forming process are temporarily stored in a storage medium such as a RAM (not shown) different from the ROM 59 or the HDD 60.

(Configuration of charging device 26)
The charging device 26 is, for example, a charge wire (not shown in detail) obtained by applying gold plating to a tungsten wire having a wire diameter of 0.08 mm to 0.1 mm, and a voltage applied to the charge wire by being disposed opposite to the surface of the photoreceptor 20. A non-contact scorotron type equipped with a grit 61 (see FIG. 8) for controlling the amount of electrons of corona discharge generated along with this is employed. Further, for example, as shown in FIGS. 6 and 7, the charging device 26 has a unit configuration on the photosensitive member 20 together with the charge eliminating device 29 and the cleaning device 28, and as shown in FIGS. 8 and 9, A charging cleaning unit 65 including a guide screw 62 extending along, a cleaning member 63 that cleans the charge wire and the grid by moving forward and backward by the guide screw 62, and a drive gear 64 that rotates the guide screw 62. I have.

(Example of drive control of the control circuit 58)
In the above configuration, the control circuit 58 of the present invention determines the degree of deterioration of the intermediate transfer belt 22 from the S wave and P wave received by the light receiving elements 47 and 48 so that the amount of emitted light corresponds to the degree of deterioration. In addition, the light emitting element 43 is controlled.

  The control circuit 58 also has a solenoid 66 (which may be a drive motor or the like) 66 for moving a brush-like cleaning member 49 as a toner concentration detection sensor cleaning unit forward and backward based on the detection result of the toner concentration detection sensor 24, and exposure. The motor 67 that drives the drive gear 39 of the cleaning unit 40 in a cooperative state and the motor 68 that drives the drive gear 64 of the charging cleaning unit 65 are driven and controlled.

(Light amount control of the light emitting element 43)
Specifically, the detection light emitted from the light emitting element 43 passes through the emission side polarization separation element 44 and the protective cover 42 and is reflected by the intermediate transfer belt 22.

  The reflected light passes through the protective cover 42, then partly passes through the light receiving side polarization separating element 46 and is received by the first light receiving element 47, and the other part is reflected by the light receiving side polarization separating element 46. The second light receiving element 48 receives the light.

  At this time, the light receiving side polarization separation element 46 separates the detection light reflected by the intermediate transfer belt 22 into a regular reflection component (P wave) and a diffuse reflection component (S wave). In the present embodiment, A part of the incident light to the light receiving side polarization separating element 46 is received by the first light receiving element 47 in a state where the polarized light is aligned as detection light of the regular reflection component (P wave) transmitted through the light receiving side polarization separating element 46. However, the other part is received by the second light receiving element 48 as detection light of the diffuse reflection component (S wave) reflected by the light receiving side polarization separation element 46.

  Each of the light receiving elements 47 and 48 outputs an S wave detection voltage value and a P wave detection voltage value based on the received reflected light to the control circuit 58.

  The control circuit 58 executes toner density correction control (light quantity correction of the light emitting element 43) according to the toner density correction control program stored in the ROM 59 from each output voltage value.

(Cleaning control of protective cover 42)
For example, the control circuit 58 detects the toner density when a predetermined number of continuous image forming processes are executed or when an image forming process is executed continuously for a predetermined time (or when a user operation or the like is performed). The contamination state of the sensor 24, that is, the contamination state of the protective cover 42 is confirmed. When the protective cover 42 is contaminated to a predetermined value or more, the protective cover cleaning is executed.

  The contamination state of the toner concentration detection sensor 24 is, for example, a calibration that is always retracted from the front surface of the protective cover 42 that is the surface of the toner concentration detection sensor 24 and the reflectance is set in consideration of the reflectance of the intermediate transfer belt 22 and the like. A member (not shown) is disposed in front of the protective cover 42, the detection light emitted from the light emitting element 43 is reflected by the calibration member, and the light receiving elements 47 and 48 receive the reflected light to detect the detection value. The detected value and the threshold value stored in the ROM 59 are compared by the control circuit 58 and confirmed.

  Then, the control circuit 58 determines that the protective cover 42 is dirty when the detected value is equal to or greater than the threshold value, and normally drives the cleaning member 49 such as a brush retracted from the surface of the protective cover 42 to drive the solenoid 66. The scattered toner or the like that is displaced by the above and adheres to the surface of the protective cover 42 is wiped off.

Example 1
Next, Example 1 of the cleaning control example in the control circuit 58 of the present invention will be described with reference to the flowchart of FIG.

(Step S1)
In step S1, the control circuit 58 receives detection signals from the toner density sensors 24 arranged at two positions on the left and right of the transfer sheet conveyance direction of the intermediate transfer belt 22 at a predetermined timing, and transfers the detection signals to the transfer sheet conveyance. The data is stored in a storage medium such as the HDD 60 in a state of being divided into tables so that the directions can be identified by right and left and by time series, and the process proceeds to step S2.

(Step S2)
In step S2, the control circuit 58 determines whether there is a detection signal already stored in the storage medium such as the HDD 60 in the preceding stage in time series, apart from the latest detection result stored in the storage medium such as the HDD 60 in step S1. If the detection signal is stored before and after the time series, the process proceeds to step S3. If the detection signal is not stored before and after the time series, the process loops to step S1.

(Step S3)
In step S3, the control circuit 58 uses the voltage value A as the detection signal stored in the storage medium such as the HDD 60 in the previous time series and the voltage value B as the detection signal stored in the storage medium such as the HDD 60 in the subsequent time series. As a result of comparing the voltage values A and B before and after the time series, if (AB) / B> 0.1 as a threshold value, the process proceeds to step S5, and (AB) / When B ≦ 0.1, the process proceeds to step S4.

  Note that the comparison between the voltage value A and the voltage value B in step S3 is made when any one of the toner concentration detection sensors 24 is arranged at the left and right positions in the transfer paper conveyance direction. This is done using the detection signal from.

(Step S4)
In step S4, when (A−B) /B≦0.1 in step S3, the control circuit 58 arranges, for example, the toner concentration detection sensors 24 on the left and right in the transfer sheet conveyance direction of the intermediate transfer belt 22. In this case, among the detection signals stored in the storage medium such as the HDD 60, for example, when the left and right detection results of the latest time-series latter stage B are Bx and the other detection result is By, If (Bx−By) / By> 0.1, the process proceeds to step S5. If (Bx−By) / By> 0.1 is not satisfied, the process loops to step S1.

  By the way, in this step S4, it is preferable to use the voltage value B in the latter part of the time series that is the detection signal from the latest (most recent) toner density detection sensor 24, but even if the voltage value A in the former part of the time series is used. These voltage values A and B may be used in combination.

(Step S5)
In step S5, the control circuit 58 drives the motors 67 and 68 to clean the exposure device 23 and the charging device 26, and also drives the solenoid 66 to remove deposits such as toner attached to the toner concentration sensor 24. To do.

  At this time, the control circuit 58 adheres to the cover glass 35 and the charge wires and the grid by continuing the driving until the cleaning members 37 and 63 move the guide screws 36 and 62 forward or backward or reciprocate once. Remove adhered toner and other deposits.

  As shown in FIG. 11, the cleaning of the charging device 26 and the exposure device 23 may be performed immediately before the calibration.

  Thus, the cleaning can be completed by the end of calibration by cleaning the density patch area for calibration immediately before the execution of calibration.

  In the color printer 11 in which the photoconductors 20 (M, C, Y, K) as a plurality of image carriers are arranged as in the present embodiment, the detection control step of step 1 described above is performed for each color ( For each photoconductor 20), by driving only the exposure device 23 and the charging device 26 corresponding to the color that needs to be cleaned exceeding the threshold, productivity can be improved by shortening the cleaning time. In addition, color variation can be suppressed.

(Example 2)
Next, Example 2 of the cleaning control example in the control circuit 58 of the present invention will be described with reference to the flowchart of FIG.

(Step S1)
In step S1, the control circuit 58 receives detection signals from the toner density sensors 24 arranged at least at any two positions in the front and rear, left and right of the intermediate transfer belt 22 in the transfer sheet conveyance direction at predetermined timings. The signals are stored in a storage medium such as the HDD 60 in a state of being divided into tables so that the signals can be identified by front and rear, right and left in the transfer paper conveyance direction and by time series, and the process proceeds to step S2.

(Step S2)
In step S2, the control circuit 58 determines whether there is a detection signal already stored in the storage medium such as the HDD 60 in the preceding stage in time series, apart from the latest detection result stored in the storage medium such as the HDD 60 in step S1. If the detection signal is stored before and after the time series, the process proceeds to step S3. If the detection signal is not stored before and after the time series, the process loops to step S1.

(Step S3)
In step S3, the control circuit 58 uses the voltage value A as the detection signal stored in the storage medium such as the HDD 60 in the previous time series and the voltage value B as the detection signal stored in the storage medium such as the HDD 60 in the subsequent time series. As a result of comparing the voltage values A and B before and after the time series, if (AB) / B> 0.1 as a threshold value, the process proceeds to step S5, and (AB) / When B ≦ 0.1, the process proceeds to step S4-2.

  Note that the comparison between the voltage value A and the voltage value B in this step S3 is made when any one of the toner density detection sensors 24 is arranged in at least any one of the front, rear, left and right in the transfer sheet conveyance direction. This is performed using a detection signal from the toner concentration detection sensor 24.

(Step S4-2)
In step S4-2, when (A−B) /B≦0.1 in step S3, for example, the control circuit 58 moves the toner density detection sensor 24 forward, backward, left, right, and left in the transfer sheet conveyance direction of the intermediate transfer belt 22. When the maximum voltage value is Bmax and the minimum voltage value Bmin among the detection signals stored in the storage medium such as the HDD 60, the maximum voltage value Bmax and the minimum of the detection signal The voltage value Bmin is compared, and if the comparison result shows that Bmax−Bmin / Bmin> 0.1 as another threshold value, the process proceeds to step S5 and Bmax−Bmin / Bmin ≦ 0.1. If so, loop to step S1.

  By the way, in this step S4-2, it is preferable to use the voltage value B in the latter stage of the time series that is the detection signal from the latest toner density detection sensor 24, but the voltage value A in the former stage of the time series may be used. These voltage values A and B may be used in combination.

(Step S5)
In step S5, when the control circuit 58 has shifted from step S3, the motors 67 and 68 are driven to clean the exposure device 23 and the charging device 26, and the solenoid 66 is driven to drive the toner density sensor 24. Remove deposits such as toner adhering to.

  At this time, the control circuit 58 adheres to the cover glass 35 and the charge wires and the grid by continuing the driving until the cleaning members 37 and 63 move the guide screws 36 and 62 forward or backward or reciprocate once. Remove adhered toner and other deposits.

  In the second embodiment, when the toner density detection sensors 24 are arranged only at the left and right positions of the intermediate transfer belt 22 in the conveyance direction of the transfer paper, the routine is substantially the same as that of the first embodiment.

  In the color printer 11 in which the photoconductors 20 (M, C, Y, K) as a plurality of image carriers are arranged as in the present embodiment, the detection step of step S1 is performed for each color (each photoconductor). 20), and driving only the exposure device 23 and the charging device 26 corresponding to the color that needs to be cleaned exceeding the threshold value, it is possible to improve the productivity by shortening the cleaning time and the color. Taste fluctuation can be suppressed.

(Example 3)
Next, Embodiment 3 of the cleaning control example in the control circuit 58 of the present invention will be described with reference to the flowchart of FIG.

(Step S1)
In step S1, the control circuit 58 receives detection signals from the toner density sensors 24 arranged at two positions on the left and right of the transfer sheet conveyance direction of the intermediate transfer belt 22 at a predetermined timing, and transfers the detection signals to the transfer sheet conveyance. The data is stored in a storage medium such as the HDD 60 in a state of being divided into tables so that the directions can be identified by right and left and by time series, and the process proceeds to step S2.

(Step S2)
In step S2, the control circuit 58 determines whether there is a detection signal already stored in the storage medium such as the HDD 60 in the preceding stage in time series, apart from the latest detection result stored in the storage medium such as the HDD 60 in step S1. If the detection signal is stored before and after the time series, the process proceeds to step S3. If the detection signal is not stored before and after the time series, the process loops to step S1.

(Step S3)
In step S3, the control circuit 58 uses the voltage value A as the detection signal stored in the storage medium such as the HDD 60 in the previous time series and the voltage value B as the detection signal stored in the storage medium such as the HDD 60 in the subsequent time series. As a result of comparing the voltage values A and B before and after the time series, if (AB) / B> 0.1 as a threshold value, the process loops to step S1, and (AB) / When B ≦ 0.1, the process proceeds to step S4-3.

  Note that the comparison between the voltage value A and the voltage value B in step S3 is made when any one of the toner concentration detection sensors 24 is arranged at the left and right positions in the transfer paper conveyance direction. This is done using the detection signal from.

(Step S4-3)
In step S4-3, the control circuit 58 arranges the toner density detection sensor 24 on the left and right in the transfer sheet conveyance direction of the intermediate transfer belt 22 when (A−B) / B> 0.1 in step S3. Of the detection signals stored in the storage medium such as the HDD 60, for example, when the left and right detection results of the most recent time-series latter stage B are Bx and the other detection results are By, (Bx-By) If /By>0.1 is not satisfied, the process proceeds to step S5. If (Bx−By) / By> 0.1, the process proceeds to step S6.

  By the way, in this step S4-3, it is preferable to use the voltage value B at the latter stage of the time series, which is the detection signal from the latest (most recent) toner density detection sensor 24, but the voltage value A at the former stage of the time series is used. These voltage values A and B may be used in combination.

(Step S5)
In step S5, the control circuit 58 drives the motors 67 and 68, cleans the exposure device 23 and the charging device 26, and removes deposits such as toner.

  At this time, the control circuit 58 adheres to the cover glass 35 and the charge wires and the grid by continuing the driving until the cleaning members 37 and 63 move the guide screws 36 and 62 forward or backward or reciprocate once. Remove adhered toner and other deposits.

(Step S6)
In step S6, the control circuit 58 drives and protects only the solenoid 66 on one side exceeding the threshold among the detection signals from the toner density detection sensors 24 at the left and right positions in the transfer sheet conveyance direction of the intermediate transfer belt 22. Wipe off scattered toner and the like adhering to the surface of the cover 42.

  At this time, the control circuit 58 may drive the motors 67 and 68 to clean the exposure device 23 and the charging device 26, or the adhering matter such as toner once adhering to the toner concentration sensor 24 in step S 6. Is deleted, and the voltage value B as the detection signal stored in the storage medium such as the HDD 60 in the latest (after the time series) is deleted, and then the process loops to step S1 to return to the latest (after the time series) again. By acquiring the detection value, the toner scattering state before and after the time series in the state after cleaning the protective cover 42 is confirmed, and if (Bx−By) / By> 0.1 still remains, step S5 is performed. Then, the exposure device 23 and the charging device 26 may be cleaned.

  In the above embodiment, the image forming apparatus of the present invention is applied to the color printer 11. However, the image forming apparatus can be applied to all image forming apparatuses such as a copying machine, a facsimile machine, or a multifunction machine. Of course you can.

  As described above, in the color printer 11 as the image forming apparatus of the present invention, the detection result from the toner density detection sensor 24 is compared with the front, back, left and right, and the presence or absence of cleaning is determined by the control circuit 58. It is possible to suppress a decrease in exposure amount and an increase in surface potential due to dirt, and to prevent deterioration in image quality such as image unevenness.

1 is an explanatory diagram of a color printer as an image forming apparatus according to an embodiment of the present invention. FIG. It is explanatory drawing of the exposure device used for the image forming apparatus which concerns on one Embodiment of this invention. 1 is a plan view of an exposure unit used in an image forming apparatus according to an embodiment of the present invention. It is a front view of the exposure device used for the image forming apparatus which concerns on one Embodiment of this invention. FIG. 5 is an explanatory diagram of a toner density sensor used in the image forming apparatus according to an embodiment of the present invention. 1 is a plan view of a drum unit used in an image forming apparatus according to an embodiment of the present invention. 1 is a side view of a drum unit used in an image forming apparatus according to an embodiment of the present invention. 1 is a perspective view of a charger used in an image forming apparatus according to an embodiment of the present invention in a bottom direction. 1 is a perspective view of a charger used in an image forming apparatus according to an embodiment of the present invention in a planar direction. FIG. 6 is a flowchart of a control routine of the image forming apparatus of Example 1 according to the embodiment of the present invention. FIG. 6 is an explanatory diagram of calibration control timing and cleaning timing of the image forming apparatus according to the embodiment of the present disclosure. FIG. 10 is a flowchart of a control routine of the image forming apparatus of Example 2 according to an embodiment of the present invention. FIG. 10 is a flowchart of a control routine of the image forming apparatus of Example 3 according to an embodiment of the present invention.

Explanation of symbols

11. Color printer (image forming apparatus)
DESCRIPTION OF SYMBOLS 15 ... Image formation process part 20 ... Photoconductor (image carrier)
22 ... Intermediate transfer belt 23 ... Exposure device (exposure part)
24. Toner concentration detection sensor (toner concentration detection unit)
26: Charging device (charging unit)
65: Charge cleaning unit 40 ... Exposure cleaning unit 49 ... Cleaning member (toner density detection cleaning unit)
58 ... Control circuit (comparison / control unit)
60. HDD (toner density storage unit)

Claims (5)

An image forming processing unit including an exposure unit that exposes the image carrier charged by the charging unit to form an electrostatic latent image, and a plurality of toner density detections that detect toner density of the image carrier at a predetermined timing. Each of the detection results of the transfer sheet conveyance direction left and right, and before and after the time series, for each of the detection results of the toner cleaning unit, the charging cleaning unit for cleaning the charging unit, the exposure cleaning unit for cleaning the exposure unit, and the plurality of toner concentration detection units. (A−B) / B> where the toner density storage unit that is stored independently, and the detection result of the time series upstream stored in the toner density storage unit is A and the detection result of the time series downstream is B An image forming apparatus comprising: a control unit that independently or simultaneously drives and controls the charge cleaning unit and the exposure cleaning unit when reaching 0.1.
When the toner density detectors are arranged in at least two locations on the left and right of the transfer paper conveyance direction, the control unit is configured to store the toner density storage unit when (A−B) /B≦0.1. Ax or Bx is the detection result of one of the left and right of the transfer paper conveyance direction stored in, and Ay or By is the detection result of the other left and right of the transfer paper conveyance direction stored in the toner density storage unit. An image forming apparatus, wherein the charge cleaning unit and the exposure cleaning unit are independently or simultaneously driven and controlled when Ay) / Ay> 0.1 or (Bx-By) / By> 0.1. . An image forming processing unit including an exposure unit that exposes the image carrier charged by the charging unit to form an electrostatic latent image, and a plurality of toner density detections that detect toner density of the image carrier at a predetermined timing. Each of the detection results of the transfer sheet conveyance direction left and right, and before and after the time series, for each of the detection results of the toner cleaning unit, the charging cleaning unit for cleaning the charging unit, the exposure cleaning unit for cleaning the exposure unit, and the plurality of toner concentration detection units. (A−B) / B> where the toner density storage unit that is stored independently, and the detection result of the time series upstream stored in the toner density storage unit is A and the detection result of the time series downstream is B An image forming apparatus comprising: a control unit that independently or simultaneously drives and controls the charge cleaning unit and the exposure cleaning unit when reaching 0.1.
When the toner concentration detection unit is disposed at least at two positions on the front and rear, right and left in the transfer sheet conveyance direction, and a toner concentration detection cleaning unit for cleaning each toner concentration detection unit is installed, (A -B) When /B≦0.1, when the maximum value of front, rear, left and right stored in the toner density storage unit is Amax or Bmax and the minimum value is Amin or Bmin An image forming apparatus, wherein the cleaning unit is driven and controlled when a threshold value (Amax−Amin) / Amin> 0.1 or (Bmax−Bmin) / Bmin> 0.1. When a plurality of image carriers are arranged, a plurality of charging cleaning units and exposure control units are arranged corresponding to each of the plurality of image carriers, and for each of the plurality of image carriers. Toner concentrations detected by the plurality of toner concentration detection units are stored in the toner concentration storage unit corresponding to the plurality of image carriers,
The control unit includes the plurality of charge cleaning units and the plurality of exposure cleaning units that exceed a detection determination threshold for each detection result for each of the plurality of toner concentration detection units stored in the toner concentration storage unit. The image forming apparatus according to claim 1, wherein the image forming apparatus is driven independently or simultaneously. An image forming processing unit including an exposure unit that exposes the image carrier charged by the charging unit to form an electrostatic latent image, and a plurality of toner density detections that detect toner density of the image carrier at a predetermined timing. Each of the detection results of the transfer sheet conveyance direction left and right, and before and after the time series, for each of the detection results of the toner cleaning unit, the charging cleaning unit for cleaning the charging unit, the exposure cleaning unit for cleaning the exposure unit, and the plurality of toner concentration detection units. (A−B) / B> where the toner density storage unit that is stored independently, and the detection result of the time series upstream stored in the toner density storage unit is A and the detection result of the time series downstream is B An image forming apparatus comprising: a control unit that independently or simultaneously drives and controls the charge cleaning unit and the exposure cleaning unit when reaching 0.1.
When the toner density detection unit is disposed at least at two positions on the left and right of the transfer paper conveyance direction, and the toner density detection cleaning unit for cleaning each toner density detection unit is installed, the control unit (Ax−Ay) / Ay> 0.1 or when the detection result on the left and right of the transfer paper conveyance direction stored in the storage unit is Ax or Bx and the detection result on the left and right of the transfer paper conveyance direction is Ay or By An image forming apparatus, wherein when (Bx−By) / By> 0.1, only the toner density detection cleaning section on the left and right sides in the transfer sheet conveyance direction is driven and controlled.   The image forming apparatus according to claim 1, wherein the control unit drives each of the cleaning units immediately before execution of calibration for the image forming processing unit.

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