JP2019135530A - Image forming apparatus - Google Patents

Abstract

To provide an image forming apparatus with which a good image can be obtained regardless of which of a recording medium placed on a recording medium placing means of a plurality of recording medium placing means is used.SOLUTION: An image forming apparatus comprises: a plurality of recording medium placing means, such as placing parts; image forming means; image reading means, such as an image reading unit; acquisition means that forms a test pattern on a recording medium, such as a recording sheet with the image forming means, and reads the test pattern on the recording medium with the image reading means to acquire image data of the test pattern; and correction value calculation means that calculates a predetermined correction value for optimizing an image on the basis of the image data of the test pattern. The acquisition means forms the test pattern on a recording medium having the longest length in a main scanning direction from among recording media placed respectively on the plurality of recording medium placing means.SELECTED DRAWING: Figure 21

Description

  The present invention relates to an image forming apparatus.

  Conventionally, a test pattern is formed on a recording medium by a plurality of recording medium mounting means, an image forming means, an image reading means, and an image forming means, and a test pattern on the recording medium is read by the image reading means, thereby forming an image of the test pattern. There is known an image forming apparatus having an acquisition unit that acquires data and a correction value calculation unit that calculates a predetermined correction value for optimizing an image based on image data of a test pattern.

  Japanese Patent Application Laid-Open No. 2004-151867 discloses an image forming apparatus that calculates an exposure correction value that is a correction value based on the image density of a test pattern read by an image reading unit. Based on the calculated exposure correction value, the driving of each LED element of the LED array as the latent image forming unit is controlled, and the LED element is arranged in the main scanning direction, which is the direction in which the LED elements are arranged and perpendicular to the recording medium conveyance direction. The image is optimized by suppressing density unevenness.

  However, when an operator selects a recording medium on which a test pattern is to be formed from a plurality of recording medium mounting means, there is a possibility that a good image cannot be obtained.

  In order to solve the above problems, the present invention provides a plurality of recording medium placing means, an image forming means, an image reading means, and a test pattern formed on the recording medium by the image forming means. An acquisition means for acquiring a test pattern image data by reading a test pattern on the recording medium, and a correction value calculation for calculating a predetermined correction value for optimizing the image based on the image data of the test pattern And the acquisition unit forms the test pattern on the recording medium having the longest length in the main scanning direction among the recording media respectively mounted on the plurality of recording medium mounting units. It is characterized by doing.

  According to the present invention, a good image can be obtained by using the recording medium placed on any recording medium placing means of the plurality of recording medium placing means.

1 is a schematic configuration diagram illustrating an image forming apparatus according to an embodiment. FIG. 3 is an enlarged configuration diagram illustrating an enlarged photoconductor and a surrounding configuration in the image forming apparatus. FIG. 3 is a perspective view showing a latent image writing device and a photoreceptor. The schematic block diagram of an evacuation mechanism. FIG. 3 is a block diagram showing a part of an electric circuit for density unevenness correction control in the main scanning direction. FIG. 6 is a control flow diagram of density unevenness acquisition control in the main scanning direction. (A) It is a graph which shows an example of a 1st light quantity correction value, (b) is a graph which shows the light quantity distribution of the main scanning direction when each LED element is controlled based on a 1st light quantity correction value. The figure which shows an example of the test pattern formed in a recording sheet. FIG. 5 is a control flow diagram of image forming processing of the present embodiment. (A) is the graph which showed an example of the density data memorize | stored in the memory | storage part, (b) is density data (solid line), density | concentration average value (broken line), and 2nd light quantity correction value (dashed-dot chain line). The graph which showed. (A) It is a graph which illustrates the relationship between a 1st light quantity correction value (dashed line), a 2nd light quantity correction value (one-dot chain line), and a 3rd light quantity correction value (solid line), (b) is a 3rd light quantity correction value. 5 is a graph showing the density of a test pattern when a latent image of the test pattern is formed based on FIG. FIG. 9 is a control flow diagram of main scanning direction density unevenness correction control according to a modified example. The figure which shows the state by which the initial screen (home screen) was displayed on the display part of the operation display part. The figure which shows the state by which the setting screen was displayed on the display part of the operation display part. The figure which shows the state by which the image adjustment inquiry screen was displayed on the display part of the operation display part. The figure which shows the state as which the pop-up screen which urges | hangs to set the recording sheet in which the test pattern was formed in the display part of the operation display part to the image reading part 60 was displayed. The figure explaining the case where a test pattern is formed in the recording sheet of the minimum size among the recording sheets mounted on the plurality of mounting portions. FIG. 4 is a diagram illustrating an example of detecting the length in the main scanning direction of a recording sheet provided in a paper feed cassette or a manual feed tray. The perspective view which shows the one side surface side of the paper feed cassette of the state which pulled out the paper feed cassette from the main body housing | casing. FIG. 3 is a schematic diagram illustrating one side surface of a paper feed cassette in a state where the paper feed cassette is set in a main body housing. FIG. 3 is a control flow diagram for selecting a recording sheet on which a test pattern is formed in the first embodiment. FIG. 9 is a control flow diagram for selecting a recording sheet on which a test pattern is formed in the second embodiment. The figure which shows the state which popped up the screen which prompts to set the recording sheet of the maximum size (3/4) or more to a mounting part on the display part of an operation display part. The figure explaining the case where a test pattern is formed in the recording sheet of the maximum size (3/4) or more. FIG. 9 is a control flow diagram for selecting a recording sheet on which a test pattern is formed in the third embodiment. Whether to form a test pattern on a recording sheet of the maximum size (3/4) or larger, or to form a test pattern on the recording sheet that is currently placed on the loading unit and that is the longest in the main scanning direction The figure which shows an example of the screen displayed when making a user select.

  Hereinafter, an electrophotographic image forming apparatus that forms an image by an electrophotographic method to which the present invention is applied will be described.

  First, a basic configuration of the image forming apparatus according to the embodiment will be described. FIG. 1 is a schematic configuration diagram illustrating an image forming apparatus according to an embodiment. In this figure, the image forming apparatus includes a photosensitive member 1 as a latent image carrier, and a plurality of paper feed cassettes 100 as recording medium mounting means configured to be detachable from a main body housing 50. Yes. Each sheet feeding cassette 100 contains recording sheets S as a plurality of recording media in a sheet bundle state.

  The recording sheet S in the paper feed cassette 100 is sent out from the cassette by a rotational drive of a feed roller 35 described later, and reaches the feed path 42 after passing through a separation nip described later. Thereafter, the sheet is sandwiched between the conveyance nips of the pair of feeding relay rollers 41 and conveyed in the feeding path 42 from the upstream side to the downstream side in the conveyance direction. A pair of registration rollers 49 are disposed near the end of the feeding path 42. The conveyance of the recording sheet S is temporarily stopped in a state where the leading end of the recording sheet S abuts against the registration nip of the registration roller 49. At the time of the abutting, the skew of the recording sheet S is corrected.

  The registration roller 49 starts rotating at a timing at which the recording sheet S can be superimposed on a toner image on the surface of the photoreceptor 1 at a transfer nip described later, and sends the recording sheet S toward the transfer nip. At this time, the feeding relay roller 41 starts to rotate at the same time, and the conveyance of the recording sheet S that has been temporarily stopped is resumed.

  In addition, the main body housing 50 holds a manual paper feed unit 26 including a manual feed tray 27, a manual feed roller 28, and a separation pad 29 that are recording medium placement means. The recording sheet S manually fed to the manual feed tray 27 of the manual feed unit 26 is sent out from the manual feed tray 27 by the rotational drive of the manual feed roller 28. Then, after passing through a separation nip due to the contact between the manual feed roller 28 and the separation pad 29, the paper feed path 20 enters an area upstream of the registration roller pair 11. Thereafter, similarly to the recording sheet S sent out from the paper feed cassette 100, after passing through the registration roller pair 11, it is sent to the transfer nip.

  An image reading unit 60 as image reading means is attached to the upper part of the main body housing 50. An automatic document feeder 61 is attached to the image reading unit 60. The automatic document feeder 61 separates documents one by one from a bundle of documents placed on the document tray 61a and automatically feeds them to a contact glass on the image reading unit 60. The image reading unit 60 reads a document conveyed on the contact glass by the automatic document conveyance device 61.

  FIG. 2 is an enlarged configuration diagram showing the photosensitive member 1 and its surrounding configuration in the image forming apparatus in an enlarged manner. Around the drum-shaped photoconductor 1 that is driven to rotate counterclockwise in the figure, there are a recovery screw 3, a cleaning blade 2, a charging roller 4, a latent image writing device 7 as a latent image forming means, and a developing means as a developing means. An apparatus 8, a transfer roller 10 serving as transfer means, and the like are provided. The charging roller 4 having a conductive rubber roller portion rotates while contacting the photoconductor 1 to form a charging nip. A charging bias output from a power source is applied to the charging roller 4. As a result, discharge occurs between the surface of the photoreceptor 1 and the surface of the charging roller 4 at the charging nip, so that the surface of the photoreceptor 1 is uniformly charged.

  The latent image writing device 7 includes an LED array, and image data input from a personal computer or image data of a document read by the image reading unit 60 on the uniformly charged surface of the photoreceptor 1. Irradiation with LED light based on the above is performed. Of the uniformly charged background portion of the photoreceptor 1, the region irradiated with light attenuates the potential. As a result, an electrostatic latent image is formed on the surface of the photoreceptor 1.

  The electrostatic latent image passes through the developing area facing the developing device 8 as the photosensitive member 1 is rotated. The developing device 8 includes a circulation conveyance unit and a development unit, and the circulation conveyance unit contains a developer containing toner and a magnetic carrier. The circulation conveyance unit includes a first screw 8b that conveys the developer to be supplied to the developing roller 8a, which will be described later, and a second screw 8c that conveys the developer in an independent space located directly below the first screw 8b. doing. Furthermore, it also has an inclined screw 8d for delivering the developer from the second screw 8c to the first screw 8b. The developing roller 8a, the first screw 8b, and the second screw 8c are arranged in a parallel posture. On the other hand, the inclined screw 8d is disposed in a posture inclined from them.

  The first screw 8b conveys the developer from the back side to the near side in the direction orthogonal to the paper surface of the drawing in accordance with the rotation of the first screw 8b. At this time, a part of the developer is supplied to the developing roller 8a disposed to face the developing roller 8a. The developer transported by the first screw 8b to the vicinity of the end on the near side in the direction orthogonal to the paper surface of the drawing is dropped onto the second screw 8c.

  While receiving the used developer from the developing roller 8a, the second screw 8c conveys the received developer from the back side to the near side in the direction orthogonal to the paper surface of the drawing as it rotates. . The developer transported to the vicinity of the end on the near side in the direction orthogonal to the paper surface of the drawing by the second screw 8c is delivered to the inclined screw 8d. Then, along with the rotational drive of the inclined screw 8d, after being conveyed from the near side to the far side in the direction orthogonal to the paper surface of the figure, near the end on the far side in the same direction, the first screw 8b Delivered.

  The developing roller 8a includes a rotatable developing sleeve made of a cylindrical nonmagnetic member, and a magnet roller fixed in the sleeve so as not to rotate around the developing sleeve. A part of the developer conveyed by the first screw 8b is pumped up on the surface of the developing sleeve by the magnetic force generated by the magnet roller. When the developer carried on the surface of the developing sleeve passes along the position where the sleeve and the doctor grade are opposed to each other along the surface of the developing sleeve, the layer thickness thereof is regulated. After that, in the development area facing the photoconductor 1, it moves while rubbing against the surface of the photoconductor 1.

  A developing bias having the same polarity as the toner or the background potential of the photoreceptor 1 is applied to the developing sleeve. The absolute value of the developing bias is larger than the absolute value of the latent image potential and smaller than the absolute value of the background portion potential. For this reason, in the development area, a development potential for electrostatically moving the toner from the sleeve side to the latent image side acts between the electrostatic latent image on the photoreceptor 1 and the development sleeve. On the other hand, a background potential that electrostatically moves toner from the background portion side to the sleeve side acts between the background portion of the photoreceptor 1 and the developing sleeve. As a result, in the development area, the toner selectively adheres to the electrostatic latent image on the photoreceptor 1 and the electrostatic latent image is developed.

  The developer that has passed through the developing area enters the area where the sleeve and the second screw 8c face each other as the developing sleeve rotates. In the facing region, a repulsive magnetic field is formed by two magnetic poles having different polarities from among the plurality of magnetic poles provided in the magnet roller. The developer that has entered the facing region separates from the surface of the developing sleeve due to the action of the repulsive magnetic field and is collected on the second screw 8c.

  The developer conveyed by the inclined screw 8d contains the developer collected from the developing roller 8a, and the developer contributes to development in the development area, so that the toner density is lowered. The developing device 8 includes a toner concentration sensor that detects the toner concentration of the developer conveyed by the inclined screw 8d. Based on the detection result of the toner density sensor, a replenishment operation for replenishing toner to the developer conveyed by the inclined screw 8d is executed as necessary.

  A toner cartridge 9 is disposed above the developing device 8. The toner cartridge 9 agitates the toner contained therein by an agitator 9b fixed to the rotary shaft member 9a. Then, the toner replenishing member 9c is rotationally driven in accordance with a replenishment operation signal output from the main body control unit 52 (see FIG. 5), so that an amount of toner corresponding to the rotational driving amount is supplied to the first screw of the developing device 8. Replenish 8b.

  The toner image formed on the photoconductor 1 by development enters the transfer nip where the photoconductor 1 and the transfer roller 10 serving as a transfer unit come into contact with the rotation of the photoconductor 1. A charging bias having a polarity opposite to the latent image potential of the photoreceptor 1 is applied to the transfer roller 10, thereby forming a transfer electric field in the transfer nip.

  As described above, the registration roller 49 sends the recording sheet S toward the transfer nip at a timing at which the recording sheet S can be superimposed on the toner image on the photoreceptor 1 in the transfer nip. The toner image on the photosensitive member 1 is transferred to the recording sheet S that is brought into close contact with the toner image at the transfer nip by the action of a transfer electric field or nip pressure.

  Untransferred toner that has not been transferred to the recording sheet S adheres to the surface of the photoreceptor 1 after passing through the transfer nip. The transfer residual toner is scraped off from the surface of the photosensitive member 1 by the cleaning blade 2 that is in contact with the photosensitive member 1 and then sent out of the unit casing by the recovery screw 3. The transfer residual toner discharged from the unit casing is sent to the waste toner bottle by the waste toner conveying device.

  The surface of the photoreceptor 1 cleaned by the cleaning blade 2 is neutralized by the neutralizing means and then uniformly charged again by the charging roller 4. To the charging roller 4 that is in contact with the surface of the photoreceptor 1, foreign substances such as toner additives and toner that cannot be completely removed by the cleaning blade 2 adhere. The foreign matter is transferred to the cleaning roller 5 in contact with the charging roller 4 and then scraped off from the surface of the cleaning roller 5 by the scraper 6 in contact with the cleaning roller 5. The foreign matter scraped off falls onto the recovery screw 3 described above.

  In FIG. 1, the recording sheet S that has passed through the transfer nip where the photosensitive member 1 and the transfer roller 10 abut is sent to the fixing device 44. The fixing device 44 forms a fixing nip by contact between a fixing roller 44a including a heat source such as a halogen lamp and a pressure roller 44b pressed toward the fixing roller 44a. A toner image is fixed on the surface of the recording sheet S sandwiched between the fixing nips by the action of heat or pressure. Thereafter, the recording sheet S that has passed through the fixing device 44 passes through the paper discharge path 45, is sandwiched between the paper discharge nips of the paper discharge rollers 46, and is discharged to the outside by the paper discharge rollers 46. The discharged recording sheet S is stacked on a stack unit 51 provided on the upper surface of the main body housing 50.

FIG. 3 is a perspective view showing the latent image writing device 7 and the photoreceptor 1.
Since the LED array provided in the latent image writing device 7 has a short focal length, it is necessary to dispose the latent image writing device 7 close to the photosensitive member 1 as shown in FIG. In the present embodiment, a process cartridge in which the photosensitive member 1, the charging roller 4, the developing device 8, the cleaning blade 2 and the like are integrally configured is configured to be detachable from the main body housing 50. As shown in FIG. 3, since the latent image writing device 7 is arranged close to the photosensitive member 1, it becomes an obstacle when the process cartridge is attached to and detached from the apparatus main body. For this reason, in the present embodiment, a retraction mechanism for moving the latent image writing device 7 between a latent image forming position close to the photoconductor 1 and a retreat position separated from the photoconductor 1 is provided.

FIG. 4 is a schematic configuration diagram of the retracting mechanism 200. FIG. 4 shows a state in which the latent image writing device 7 is located at a latent image forming position where a latent image is formed on the photosensitive member 1.
As shown in FIG. 4, the retracting mechanism 200 holds the first link member 201 rotatably supported by the apparatus main body and the latent image writing device 7, and the first retracting mechanism 200 is rotatably supported by the apparatus main body. And two link members 202. Moreover, the connection mechanism 203 as a connection means which connects the 1st link member 201 and the 2nd link member 202 is provided.

  The connection mechanism 203 includes a first connection member 203a and a second connection member 203b. One end of the first connecting member 203a is rotatably supported by the first link member 201, and the other end is rotatably supported by the connecting shaft 203c. The second connecting member 203b has one end rotatably supported by the connecting shaft 203c and the other end rotatably supported by the second link member 202. The connecting shaft 203c passes through a connecting guide hole 205a provided in the cover member 205 and extending to the left and right in the drawing.

  In the second link member 202, support protrusions 72 provided at both ends in the longitudinal direction of the holder 75 that holds the LED array 74 of the latent image writing device 7 penetrate, and the second link member 202 serves as a pivot A1 for rotation. A long hole-like support hole 202a extending toward the surface is provided. The latent image writing device 7 is supported by the retracting mechanism 200 by the support protrusion 72 of the latent image writing device 7 passing through the support hole 202a. Further, the support protrusion 72 passes through the exposure guide hole 205 b which is a guide portion provided in the cover member 205. The holder 75 of the latent image writing device 7 is provided with a guide projection 73, which also penetrates the exposure guide hole 205b.

  The first link member 201 has a fan shape with a central angle of approximately 90 °, and a first connecting member 203a is rotatably supported at one circumferential end of the first link member 201. A boss portion 201 a is provided at the other circumferential end of the first link member 201.

  The second link member 202 is provided with a hooking portion 202b for hooking one end of the torsion spring 204 as urging means. One end of the torsion spring 204 is hooked on the hooking portion 202b and the other end is hooked on the cover member 205, thereby urging the second link member 202 in the direction of arrow F in the figure.

  Due to the urging force of the torsion spring 204, the second link member 202 and the connecting shaft 203c (first and second connecting members a and b) receive a force that moves toward the first link member 201. At this time, the first link member support position A3 of the first connecting member 203a is on the lower side in the drawing with respect to the line segment A connecting the pivot A2 of the first link member 201 and the connecting shaft 203c. As a result, a force to move the connecting shaft 203c toward the first link member 201 causes a force to move the support position A3 in the direction of the arrow T1, and the first link member 201 rotates counterclockwise in the drawing. The force which tries to rotate is generated. As a result, the latent image writing device 7 is biased toward the photosensitive member 1 and is positioned at the latent image forming position.

  When the open / close cover of the main body housing 50 for attaching / detaching the process cartridge is opened, the hook lever provided on the open / close cover comes into contact with the boss portion 201a of the first link member 201, and the first link member 201 is torsioned. It rotates clockwise in the figure against the urging force of the spring 204. The first link member 201 is rotated against the urging force of the torsion spring 204, and the first link member 201 is placed on a line segment A connecting the rotation fulcrum A2 of the first link member 201 and the connecting shaft 203c. When the first link member 201 is moved upward from the first connecting member support position A3, the direction in which the first link member 201 is rotated by the urging force of the torsion spring 204 is switched from the counterclockwise direction in the figure to the clockwise direction in the figure. As a result, the first link member 201 automatically rotates in the rotation direction (counterclockwise in the figure) for moving the latent image writing device 7 to the retracted position by the urging force of the torsion spring 204, and the latent image writing is performed. The device 7 is moved to the retracted position.

  In the LED array 74, there are variations in the shape, characteristics, etc. of each LED element 74b, there is a slight deviation in the arrangement of the LED chips, and there are periodic or aperiodic changes in the optical characteristics of the lens array. By doing so, even if the same drive power is applied to each LED element 74b, the amount of emitted light is not the same. As a result, density unevenness occurs in an image formed on the recording sheet S in a direction orthogonal to the conveyance direction of the recording sheet S (hereinafter referred to as a main scanning direction). Thus, if there is density unevenness in the main scanning direction, vertical stripes, vertical bands, etc. extending in the conveyance direction of the recording sheet S (hereinafter referred to as the sub-scanning direction) occur, and the image quality deteriorates.

  Therefore, a first light amount correction is performed to measure the light amount of each LED element 74b using a predetermined device in advance and correct the driving power applied to each LED element 74b so that each LED element 74b has the same light emission amount. The value is obtained and stored. Then, by controlling the LED array 74 based on the first light quantity correction value, density unevenness in the main scanning direction caused by the LED array 74 can be suppressed.

  However, the density unevenness in the main scanning direction is caused not only by the LED array 74 but also by image forming engines such as the photoconductor 1, the charging roller 4, the developing device 8, the transfer roller 10, and the fixing device 44. There is a case. Therefore, in this embodiment, in order to eliminate density unevenness in the main scanning direction caused by the image forming engine, the test pattern is recorded on the recording sheet by controlling the LED array 74 based on the first light quantity correction value. The image reading unit 60 reads the test pattern formed on the recording sheet S and formed on the recording sheet S. Next, density unevenness in the main scanning direction caused by the image forming engine is obtained based on the read data read by the image reading unit 60. Next, a second light amount correction value for correcting the light emission amount (applied power) of each LED element is calculated based on the obtained density unevenness in the main scanning direction. Then, based on a first light amount correction value that suppresses density unevenness in the main scanning direction caused by the LED array 74 and a second light amount correction value that suppresses density unevenness in the main scanning direction caused by the image forming engine. The third light quantity correction value is calculated. At the time of image formation, the LED array 74 is controlled to write a latent image on the photosensitive member 1 based on the third light quantity correction value, thereby causing density unevenness in the main scanning direction caused by the LED array 74 and an image forming engine. Thus, it is possible to form a good image in which both the density unevenness in the main scanning direction due to the above are suppressed.

FIG. 5 is a block diagram showing a part of an electric circuit for density unevenness correction control in the main scanning direction.
As shown in FIG. 5, an LED array 74 provided in the latent image writing device 7 includes a plurality of LED elements 74b arranged in the main scanning direction, and an IC (Integrated Circuit) driver 74a for driving each LED element. A ROM (Read Only Memory) 74c that stores a first light amount correction value for correcting the variation in the light emission amount of the LED array 74 is provided.

  An image density for acquiring image density information in the main scanning direction based on the read data of the test pattern formed on the recording sheet S read by the image reading unit 60 is sent to the main body control unit 52 that controls the entire image forming apparatus. Based on the acquisition unit 86, the storage unit 87 that stores density data indicating the image density information acquired by the image density acquisition unit 86, and the image density information stored in the storage unit 87, the light emission amount of each LED element is corrected. It has the light quantity correction value calculation part 88 which calculates a 2nd light quantity correction value.

  The main body control unit 52 also includes a first light amount correction value acquisition unit 85 that acquires a first light amount correction value from the LED array 74, a first light amount correction value acquired by the first light amount correction value acquisition unit 85, and a light amount. Based on the second light amount correction value calculated by the correction value calculation unit 88, a calculation unit 82 for calculating a third light amount correction value used at the time of image formation is also provided. Further, the main body control unit 52 has a correction value transfer unit 83 that transfers the third light quantity correction value calculated by the calculation unit 82 to the LED array 74 at the time of image formation. The main body control unit 52 controls an image forming engine such as the photosensitive member 1, the charging roller 4, the developing device 8, the transfer roller 10, and the fixing device 44 to form an image on the recording sheet S. It has. The image forming processing unit 84 also performs control to form a test pattern on the recording sheet S. As will be described later, the length of the recording sheet in the sub-scanning direction acquired by the operation display unit 89 as length information acquisition means. Based on the information and the recording sheet conveyance distance between the conveyance members that convey the recording sheet, the position where the test pattern is formed and the length of the test pattern in the sub-scanning direction are set.

FIG. 6 is a control flowchart of density unevenness acquisition control in the main scanning direction.
First, the first light amount correction value acquisition unit 85 of the main body control unit 52 acquires the first light amount correction value stored in the ROM 74c of the LED array 74 (S1). As described above, the first light quantity correction value is obtained by measuring the light quantity of each LED element of the LED array 74 by using a predetermined device in advance, so that each LED element has the same light emission quantity. This is data for correcting the drive power applied to.

  Next, the main body control unit 52 transfers the acquired first light amount correction value to the IC driver 74a of the LED array 74 by the correction value transfer unit 83 (S2). In addition, the image forming processing unit 84 transmits a control signal to each device constituting the image forming engine, and executes an image forming process for forming a test pattern (S3). When the IC driver 74a of the LED array 74 receives the control signal and the test pattern data from the image formation processing unit 84, the IC driver 74a controls each LED element 74b based on the first light quantity correction value received from the correction value transfer unit 83. Then, a latent image of the test pattern is formed on the surface of the photoreceptor 1. Further, as will be described later, the irradiation timing and irradiation end timing of the LED array 74 are controlled based on the set test pattern formation position and the length in the sub-scanning direction.

FIG. 7A is a graph showing an example of the first light amount correction value, and FIG. 7B is a light amount in the main scanning direction when each LED element 74b is controlled based on the first light amount correction value. It is a graph which shows distribution.
As shown in FIG. 7A, a portion where the light amount correction value is large in the main scanning direction is a portion where the emitted light amount is small. Therefore, the light amount correction value (drive power) is increased at such a location, and the light amount is set as a reference light amount. On the other hand, a portion where the light amount correction value (correction driving power) is small is a portion where the amount of emitted light is large. Therefore, the light amount correction value (correction driving power) is reduced at such a location, and the light amount is set as a reference light amount. As a result, as shown in FIG. 7B, the amount of emitted light can be made substantially uniform in the main scanning direction.

  Thereafter, the latent image of the test pattern is developed by the developing device 8, transferred to a predetermined position of the recording sheet S by the transfer roller 10, and fixed to the recording sheet S by the fixing device 44. When the recording sheet S on which the test pattern is formed is discharged and printing is completed (Yes in S4), the process proceeds to a test pattern density data acquisition process (S5).

FIG. 8 is a diagram illustrating an example of the test pattern 171 formed on the recording sheet S.
As shown in FIG. 8, the test pattern 171 is a halftone image that is uniform in all of the sub-scanning direction (conveyance direction) and the main scanning direction (direction orthogonal to the conveyance direction) of the recording sheet S. By making the test pattern a halftone image, it is possible to detect well both a location that is brighter than the specified brightness (image density is light) and a location that is darker than the specified brightness (the image density is high). . Further, it is preferable that the length of the recording sheet forming the test pattern in the main scanning direction is the maximum size (3/4 or more) in the main scanning direction that can be formed by the image forming apparatus. Further, it is preferable that the test pattern 171 formed on the recording sheet is formed so as to be full in the main scanning direction so that there is no margin. Thereby, correction can be applied to the end in the main scanning direction.

  If the test pattern 171 formed on the recording sheet has density unevenness in the main scanning direction, vertical stripes, vertical bands, etc. extending in the sub-scanning direction are generated. The test pattern 171 is a latent image formed by controlling each LED element 74b based on the first light quantity correction value shown in FIG. 7A, as shown in FIG. 7B. As described above, the amount of light emitted from the LED elements 74b to the surface of the photoreceptor is substantially uniform in the main scanning direction. Therefore, in the main scanning direction, the surface of the photosensitive member is attenuated almost uniformly to a certain potential, and thus the density unevenness in the main scanning direction of the test pattern is mainly caused by a factor other than the LED array 74. .

  After printing the test pattern 171 on the recording sheet S, the main body control unit 52 sets the recording sheet S on which the test pattern 171 is formed on the operation display unit 89 of the image forming apparatus in the image reading unit 60, and the test pattern 171. Instructs reading of. When the operator sets the recording sheet S on which the test pattern 171 is formed on the image reading unit 60 and starts reading an image based on an instruction from the operation display unit, the image density acquisition unit 86 of the main body control unit 52 starts the image reading. Then, image density data in the main scanning direction as image density information is acquired (S5). The acquired image density data is stored in the storage unit 87 (S6).

  As an example of an image density data acquisition method in the image density acquisition unit 86, as shown in FIG. 8, the test pattern 171 is divided into a plurality of areas 1 to n having a predetermined area (Xdot × Ydot). The method of acquiring an average density | concentration for every -n is mentioned.

  For example, when Xdot = 1 dot and density data in the main scanning direction of an A4 size recording sheet S is acquired at a resolution of 600 dpi, image density data of 210 mm × (600 dpi / 25.4 mm) ≈4960 areas is obtained. It is done. When the image density data is expressed by 8 bits (0-255), a storage capacity of 4960 × 8 bits = 4.96 kBytes is required. If Xdot = 2 dots or 4 dots, the required storage capacity becomes 1/2 or 1/4, and the storage unit 87 (see FIG. 5) can be configured at low cost. However, if Xdot is made too large, the density of a wide area is averaged, so that the accuracy of density information decreases. The value of Xdot and the resolution of the image density data may be appropriately determined according to the image forming apparatus. For example, the value of Xdot may be determined after grasping whether the density unevenness in the main scanning direction is dominated by the high-cycle density unevenness or the low-cycle density unevenness.

  On the other hand, since the Ydot value of each area 1 to n does not affect the storage capacity, the Ydot value is uneven density in the sub-scanning direction (conveyance direction) in the target image forming apparatus (one rotation cycle of the photosensitive member 1, transfer). In consideration of periodic density unevenness or non-periodic density unevenness due to one rotation period of the roller 10, one rotation period of the developing roller 8 a, etc., it is set so that a large difference does not occur in the density detection result. Good. However, if the Ydot value is too large, it takes time to acquire density data. Therefore, it is preferable to determine the Ydot value in consideration of the balance between the required accuracy and the data acquisition time (processing capability).

  The density unevenness acquisition control in the main scanning direction shown in FIG. 6 is performed at an arbitrary timing by a user or a service person, a timing at which members constituting an image forming engine such as the photosensitive member 1 or the latent image writing device 7 are replaced, and image formation. This is done when the power is turned on. By carrying out each time the power is turned on, there is an advantage that an image without density unevenness can always be output in the main scanning direction. On the other hand, the density unevenness acquisition control according to the present embodiment requires the user to set the recording sheet S on which the test pattern 171 is formed on the image reading unit 60 and read the test pattern 171. For this reason, some users feel troublesome to carry out each time the power is turned on. Therefore, it is preferable that the user can set so as not to perform density unevenness acquisition control when the power is turned on.

FIG. 9 is a control flow diagram of the image forming process of the present embodiment.
As shown in FIG. 9, when the main body control unit 52 receives the image formation start signal, first, the density data stored in the storage unit 87 is read, and based on the density data read by the light amount correction value calculation unit 88. Then, the second light quantity correction value is calculated (S11).

FIG. 10A is a graph showing an example of density data stored in the storage unit 87, and FIG. 10B shows density data (solid line), density average value (broken line), and second light amount correction. It is the graph which showed the value (one-dot chain line). The density average value shown in FIG. 10B indicates the average value of the image density indicated by the image density data.
Due to factors other than the LED array, density unevenness occurs in the main scanning direction as shown in FIG. Such density unevenness in the main scanning direction is density unevenness in the main scanning direction mainly caused by the image forming engine (the photoreceptor 1, the charging roller 4, the developing device 8, the transfer roller 10, and the fixing device 44).

  As shown in FIG. 10B, the second light quantity correction value is calculated based on the image density average value (average image density of the test pattern) and the image density at each position in the main scanning direction indicated by the image density data. The As shown in FIG. 10B, the position where the image density indicated by the broken line in the figure is light (bright) is corrected so that the amount of light emitted from the LED element 74b corresponding to that position is increased, and is darker than the average density. The (dark) position is corrected so that the amount of light emitted from the LED element corresponding to the position is reduced. Specifically, for a position where the density is lighter (brighter) than the average density, a correction value for increasing the drive power applied to the LED element 74b corresponding to that position is obtained, and the density is darker (darker) than the average density. As for the position, a correction value for reducing the driving power applied to the LED element 74b corresponding to the position is obtained.

  When the second light quantity correction value is thus calculated by the light quantity correction value calculation unit 88, the calculation unit 82 calculates the third light quantity correction value used for image formation (S12 in FIG. 9). Specifically, the third light amount correction value is calculated based on the second light amount correction value calculated by the light amount correction value calculation unit 88 and the first light amount correction value acquired from the LED array 74 by the first light amount correction value acquisition unit 85. Calculate the value. Then, the calculated third light quantity correction value is transferred to the IC driver 74a of the LED array 74 by the correction value transfer unit 83 (S13). When the correction value transfer unit 83 transfers the data to the IC driver 74a of the LED array 74, image forming processing is performed based on the image data (S14). In this image forming process, the IC driver 74a forms a latent image on the surface of the photoconductor based on the third light quantity correction value transferred from the correction value transfer unit 83 and the image data.

FIG. 11A is a graph illustrating the relationship among the first light amount correction value (broken line), the second light amount correction value (one-dot chain line), and the third light amount correction value (solid line), and FIG. 10 is a graph showing the density of a test pattern when a latent image of the test pattern is formed based on a third light quantity correction value.
As shown in FIG. 11A, the third light quantity correction value is calculated by adding the first light quantity correction value and the second light quantity correction value. Note that the calculation method of the third light quantity correction value is not limited to this, and may be appropriately determined according to the calculation method of the first light quantity correction value and the second light quantity correction value.

  The third light quantity correction value is a first light quantity correction value that corrects density unevenness in the main scanning direction caused by the LED array 74, and a second light intensity correction value that corrects density unevenness in the main scanning direction caused mainly by the image forming engine. It is calculated based on the light amount correction value. Therefore, the image formed based on the third light quantity correction value is an image in which density unevenness in the main scanning direction due to the LED array 74 and the image forming engine is suppressed. Therefore, an image in which a latent image is formed with a corrected light amount based on the third light amount correction value becomes an image having a uniform density distribution in the main scanning direction as shown in FIG. A high-quality image without a vertical band can be obtained.

  In the present embodiment, the density unevenness acquisition control in the main scanning direction shown in FIG. 6 ends with acquiring the density unevenness in the main scanning direction of the test pattern 171. You may perform even calculation. When performing the calculation up to the second light amount correction value, the storage unit 87 stores the second light amount correction value. Further, in the density unevenness acquisition control in the main scanning direction, calculation up to the third light quantity correction value may be performed. When the third light quantity correction value is calculated, the third light quantity correction value is stored in the storage unit 87. In this case, it is not necessary to acquire the first light quantity correction value from the LED array during image formation, and the third light quantity correction value stored in the storage unit 87 is transmitted to the IC driver 74a of the LED array 74. .

  Further, based on the detection result of the test pattern 171, it is determined whether or not correction of density unevenness in the main scanning direction is necessary. If it is determined that correction of density unevenness in the main scanning direction is not required, image formation is performed. At this time, the LED array 74 may be controlled based on the first light quantity correction value without calculating the third light quantity correction value.

  Also, if the user or service person sees the image output after correcting the density unevenness in the main scanning direction and determines that the density unevenness in the main scanning direction is not improved or has deteriorated, A user or a service person may be set so that the light amount correction value is not calculated. When the user or service person sets not to calculate the third light amount correction value, for example, the density data stored in the storage unit 87 is deleted, and the LED array 74 is controlled based on the first light amount correction value. To do.

  Further, the test pattern 171 was formed without using the first light quantity correction value, and the main scanning direction density unevenness caused by the LED array 74 and the main scanning direction density unevenness caused by other than the LED array were superimposed. The density unevenness in the main scanning direction is acquired from the read data. Then, a third light amount correction value is calculated based on the main scanning direction density unevenness in which the main scanning direction density unevenness caused by the LED array 74 and the main scanning direction density unevenness caused by other than the LED array are superimposed. Also good.

  However, after the density unevenness in the main scanning direction due to the LED array 74 is suppressed with the first light quantity correction value, the test pattern 171 is formed, and the density in the main scanning direction mainly using the test pattern 171 other than the LED array. It is preferable to acquire unevenness. This is because when the test pattern 171 is formed without using the first light quantity correction value, the density unevenness in the main scanning direction of the test pattern 171 is the density unevenness in the main scanning direction caused by the LED array 74 and other than the LED array. Is superimposed with density unevenness in the main scanning direction. As a result, for example, when a location where the density is increased due to the LED array 74 overlaps with a location where the density is increased due to factors other than the LED array, the upper limit value of the density may be reached. More specifically, for example, a test pattern is formed with an image density that becomes a halftone (127 gradations) of 255 gradations, and is darkened by 70 gradations (density is high) due to the LED array 74. When a location that is darker by 70 gradations (density is higher) due to factors other than the LED array 74 overlaps, the location that is darker (density is higher) by 140 gradations is originally the upper limit value (gradation value 0). Therefore, only 127 gradations can be detected. Therefore, even if the light amount of each LED element is corrected with the correction data calculated based on the image density data of the test pattern, the density unevenness remains.

  On the other hand, as in the present embodiment, the first light amount correction value suppresses density unevenness in the main scanning direction caused by the LED array 74 and then forms the test pattern 171 so that the test pattern 171 has the main scanning direction. Density unevenness can be suppressed, and problems such as the density reaching the upper limit can be suppressed. Thereby, there is an advantage that density unevenness in the main scanning direction can be satisfactorily suppressed.

FIG. 12 is a control flow chart of main scanning direction density unevenness correction control according to a modification. FIG. 12A is a flow chart of main scanning direction density unevenness acquisition control, and FIG. FIG.
In this modification, first, as shown in FIG. 12A, the density data (first density data) of the test pattern 171 formed based on the first light quantity correction value is stored as in the embodiment. It memorize | stores in the part 87 (S21-S25). Next, similarly to the embodiment, the third light quantity correction value is calculated based on the second light quantity correction value calculated based on the first density data and the first light quantity correction value (S26 to S27). Next, based on the calculated third light quantity correction value, the test pattern 171 is formed again on the recording sheet, the test pattern 171 formed on the recording sheet S is read by the image reading unit 60, and the second Is stored in the storage unit 87 (S28 to S31).

  At the time of image formation, first, a second light amount correction value is calculated based on the first density data stored in the storage unit 87 (S41). Next, a fourth light quantity correction value is calculated based on the second density data stored in the storage unit 87 (S42). Next, the calculation unit 82 adds the first light amount correction value, the second light amount correction value, and the fourth light amount correction value to calculate a fifth light amount correction value (S43). Then, an image is formed based on the fifth light quantity correction value (S44 to S45).

  In this modified example, the third light quantity correction value can also suppress density unevenness in the main scanning direction that could not be removed, and can further improve density unevenness in the main scanning direction.

The density unevenness acquisition control in the main scanning direction shown in FIG. 6 can be performed at an arbitrary timing by the user operating the operation display unit.
FIG. 13 is a diagram illustrating a state where an initial screen (home screen) is displayed on the display unit 89 a of the operation display unit 89.
As shown in FIG. 13, the operation display unit 89 includes a display unit 89a including a liquid crystal display (LCD) or the like, and an operation unit 89b having a numeric keypad and a start button. The display unit 89a has a touch panel function and can detect the contact position of the user along with various displays. The operation unit 89b may be a GUI component that is displayed on the touch panel.

  When performing density unevenness acquisition control in the main scanning direction, the user first presses the “setting” GUI component C1 displayed on the display unit 89a. Then, as shown in FIG. 14, the screen displayed on the display unit 89a is switched from the initial screen to the setting screen. Next, when the user presses the “image adjustment” GUI component C2 displayed on the display unit 89a, the screen of the display unit 89a is switched to the image adjustment inquiry screen as shown in FIG. Then, when the user presses the “Density unevenness correction” GUI component C3 on the image adjustment inquiry screen displayed on the display unit 89a, density unevenness acquisition control in the main scanning direction shown in FIG. 6 is started.

  Further, when the recording sheet on which the test pattern is formed is discharged from the apparatus, a pop-up screen that prompts the user to set the recording sheet on which the test pattern is formed on the image reading unit 60 is displayed as shown in FIG. . Note that the recording sheet on which the test pattern is formed is guided to be set in the image reading unit 60 by voice, or the warning lamp is turned on to set the recording sheet on which the test pattern is formed in the image reading unit 60. You may be encouraged.

  If the user looks at the test pattern and determines that it is necessary to correct the density unevenness, the user sets the recording sheet on which the test pattern is formed on the image reading unit 60 in the image reading unit 60 and displays “reading start” on the pop-up screen. Press the GUI part to start reading the test pattern. On the other hand, if it is determined that it is not necessary to correct the density unevenness by looking at the test pattern, the “Cancel” GUI component on the pop-up screen is pressed to stop the density unevenness acquisition.

Next, features of the present embodiment will be described.
In the case where the user selects the size of the recording sheet S on which the test pattern is to be formed, the recording that is placed on a placement unit that is a recording medium placement unit such as a plurality of paper feed cassettes 100 and manual feed trays 27. There is a risk of selecting a recording sheet of the minimum size among the sheets.

FIG. 17 is a diagram for explaining a case where a test pattern is formed on a recording sheet having a minimum size among the recording sheets placed on a plurality of placement units such as the paper feed cassette 100 and the manual feed tray 27.
As shown in FIG. 17, when a test pattern is formed on a minimum size recording sheet among a plurality of recording sheets placed on each placement unit, the length A of the test pattern 171 in the main scanning direction is the LED array. It becomes shorter than the light emitting area B of 74. When such a test pattern is read by the image reading unit 60 and density unevenness in the main scanning direction is corrected, density unevenness can be corrected only at the center in the main scanning direction. Therefore, when an image is formed on a recording sheet having a longer length in the main scanning direction than the smallest recording sheet among the plurality of recording sheets S, density unevenness occurs on both sides in the main scanning direction.

  Therefore, in the present embodiment, the maximum size recording sheet is automatically selected from the plurality of recording sheets placed on the plurality of paper feed cassettes 100 and the manual feed tray 27, and the maximum size recording sheet is tested. A pattern was formed.

FIG. 18 is a diagram illustrating an example of detecting the length in the main scanning direction of a recording sheet provided in the paper feed cassette 100 or the manual feed tray 27.
A width sensor 69 for detecting the position of the side fence in the main scanning direction is provided on each of the pair of side fences 63 a and 63 b of the paper feed cassette 100 and the manual feed tray 27. As the width sensor 69, for example, a known encoder sensor can be used. Based on the output value of the encoder sensor, the positions of the side fences 63a and 63b in the main scanning direction are detected, and the main scanning direction of the recording sheet S is detected. Detect the length of. The main scanning direction length of the recording sheet S detected in this way is stored in the storage unit 87 (see FIG. 5).

  Another example of the detection of the size of the recording sheet placed in the paper feed cassette 100 will be described with reference to FIGS. FIG. 19 is a perspective view showing one side surface of the paper feed cassette in a state in which the paper feed cassette 100 is pulled out from the main body housing 50.

  A size dial 55 is provided on the right side of the paper feed cassette 100. The size dial 55 is rotatably supported by a boss 57 projecting outside the side surface of the paper feed cassette 100. Further, on the size dial 55, characters and figures representing standardized size names (A4, A3, etc.) and sheet conveying directions (vertical direction, horizontal direction) are drawn as sheet size information at a plurality of locations on the outer peripheral surface. A cylindrical size display portion 554 is provided. The outer peripheral surface of the size display portion 554 is located at a position facing the size display window 514 provided on the front panel 511 of the sheet feeding cassette 100, and the sheet size information drawn on the size display portion 554 is the size display window 514. It is visible from the outside via.

  The user rotates the size dial so that the same sheet size information as the recording sheet set in the paper feed cassette 100 is displayed in the size display window 514. Further, a mechanism for stopping the rotation of the size dial 55 when the sheet size information drawn on the outer peripheral surface of the size display unit 554 faces the size display window 514 is provided. Specifically, a cylindrical portion having a plurality of concave portions in the rotation direction is provided on the inner side of the size display window 514 of the size dial, and the outer peripheral surface of the cylindrical portion is brought into contact with the sheet feeding or set to be elastically deformed. A fastening member is provided. When the sheet size information drawn on the outer peripheral surface of the size display portion 554 faces the size display window 514, the fastening portion fits into the concave portion of the cylindrical portion, and the rotation of the size dial is restricted. When the user rotates the size dial from this restricted state, the stop portion is elastically deformed and gets over the concave portion of the cylindrical portion, so that the size dial rotates.

  Outside the size display portion 554, a size information output portion 552 is formed which includes a concave portion 552b and a convex portion 552a protruding in the radial direction with respect to the concave portion 552b. The size information output unit 552 is opposed to the detection unit 54 provided in the main body casing 50.

FIG. 20 is a schematic view showing one side surface of the paper feed cassette in a state where the paper feed cassette is set in the main body casing 50.
The detection unit 54 includes a plurality of spacers 56 that are slidably held in the attachment / detachment direction (A and B directions in the drawing) of the paper feed cassette, and a movable element 541 whose one end abuts against the spacer 56. The movable element 541 is slidably held in the paper cassette insertion / removal direction (A and B directions in the figure), and is attached to the paper cassette 100 in the drawing direction (arrow B direction in the figure) by a biasing means such as a spring. It is energized.

  As shown in FIG. 20, the spacer 56 that contacts the convex portion 552a of the size information output unit 552 is attached in the pressing direction of the paper feed cassette 100 (the direction of arrow A in the figure) by the convex portion 552a of the size information output unit 552. It is pushed together with the movable element 541 against the biasing force of the biasing means. When the mover 541 is pushed in the paper cassette 100 in the pushing direction (arrow A direction in the figure), the switch corresponding to the mover is turned ON. On the other hand, the spacer 56 facing the concave portion 552b of the size information output unit 552 is pushed together with the movable element 541 in the direction of arrow B by the urging force of the urging means. Thus, the switch corresponding to the mover pushed out by the urging force of the urging means is turned off. The size of the recording sheet set in the paper feed cassette 100 is detected by detecting ON / OFF of each movable element. In this manner, the detected size information of the recording sheet is stored in the storage unit 87 (see FIG. 5).

  In addition, the recording information set in the paper feed cassette 100 or the manual feed tray 27 is not limited thereto, and the recording sheet size information set in the paper feed cassette 100 or the manual feed tray 27 is input to the operation display unit 89 by the user. Sheet size information may be acquired.

  Next, control for selecting a recording sheet on which a test pattern is formed will be described using Examples 1 to 3.

[Example 1]
FIG. 21 is a control flowchart for selecting a recording sheet on which a test pattern is formed in the first embodiment.
When the user presses the “density unevenness correction” GUI component C3 (see FIG. 15) displayed on the display unit 89a of the operation display unit 89, the control flow shown in FIG. 21 is performed.
First, the main body control unit 52 (see FIG. 5) receives size information (main information) of the recording sheets placed on each placement unit such as the manual feed tray 27 and the paper feed cassette 100 from the storage unit 87 (see FIG. 5). (Length information in the scanning direction) is acquired (S51). Next, the main body control unit 52 specifies the placement unit on which the recording sheet having the longest length in the main scanning direction is placed based on the acquired recording sheet size information of each placement unit (S52). ).

When there is only one placement section on which the recording sheet having the longest length in the main scanning direction is placed (S53 Yes), the recording sheet placed on the placement section is selected. The recording sheet for forming the test pattern is set. On the other hand, if there are multiple placement parts on which the recording sheet with the longest length in the main scanning direction is placed, test the recording sheet placed on the placement part with a short transport distance to the transfer nip. Set the recording sheet to form the pattern. For example, when recording sheets of the same size are placed on the upper and lower feed cassettes, the recording sheets placed on the upper feed cassette with a short transport distance are tested. Set the recording sheet to form the pattern.
When the recording sheet for forming the test pattern is set in this way, the density unevenness acquisition control in the main scanning direction shown in FIG. 6 is started.

  As described above, in Example 1, the length in the main scanning direction is the longest among the recording sheets placed on a plurality of placement units (in this embodiment, the two paper feed cassettes 100 and the manual feed tray 27). A test pattern is formed on a long recording sheet, and density unevenness is acquired in the range of the recording sheet having the longest length in the main scanning direction. Therefore, the second light amount correction value and the third light amount correction value are calculated within this range, and an image in which density unevenness is suppressed within this range can be obtained. The length in the main scanning direction of the recording sheet placed on the plurality of placement portions is equal to or shorter than the length in the main scanning direction of the recording sheet on which the test pattern is formed. Therefore, by obtaining an image in which the density unevenness is suppressed in the above range, the density unevenness is suppressed over the entire region in the main scanning direction even if the image is formed on the recording sheet placed on any placement unit. An image can be obtained.

  In the first embodiment, since the recording sheet on which the test pattern is to be formed is automatically selected, the user's labor can be reduced compared to the case in which the user selects the recording sheet on which the test pattern is to be formed.

  In the first embodiment, when there are a plurality of placement portions on which the recording sheet having the longest length in the main scanning direction is placed, the transport distance to the transfer nip is as follows. The recording sheet placed on the short placement portion is set as the recording sheet for forming the test pattern. This is for the following reason. In other words, the longer the conveyance distance to the transfer nip, the larger the skew may be. In this embodiment, the skew correction is performed by abutting the leading edge of the recording sheet against the registration roller. However, if the skew is large, the skew may not be completely corrected. When a test pattern is formed on a skewed recording sheet, the relationship between the image data read from the test pattern and the LED elements of the LED array is shifted, and there is a possibility that the correction value cannot be calculated correctly.

  As in the first embodiment, among the plurality of placement units, when there are a plurality of placement units on which the recording sheet having the longest length in the main scanning direction is placed, the conveyance distance to the transfer nip is short. Skew can be suppressed by setting the recording sheet placed on the placement unit to be a recording sheet on which a test pattern is formed. As a result, it is possible to suppress a situation in which the correction value cannot be calculated correctly. In addition, when there are a plurality of placement portions on which the recording sheet having the longest length in the main scanning direction is placed, the placement portion is placed on the placement portion having a short conveyance distance to the transfer nip. By setting the recorded recording sheet as the recording sheet for forming the test pattern, the process for forming the test pattern on the recording sheet can be shortened.

  In the first embodiment, a recording sheet that is longer in the main scanning direction than the recording sheet on which the test pattern is formed is set on any of the plurality of placement units, and an image is formed on the set recording sheet. Density unevenness occurs at both ends of the image in the main scanning direction. Therefore, when a recording sheet that is longer in the main scanning direction than the recording sheet on which the test pattern is formed is set on any of the plurality of placement units, an image prompting the user to perform density unevenness acquisition control is displayed on the operation display unit. It is preferable to display.

[Example 2]
Next, Example 2 will be described.
FIG. 22 is a control flowchart for selecting a recording sheet on which a test pattern is formed in the second embodiment.
In the second embodiment, the length in the main scanning direction is based on the size information of the recording sheet placed on the manual feed tray 27 and each paper feed cassette 100, and the main scanning direction in which the image forming apparatus can form an image. It is checked whether or not there is a placement portion on which a recording sheet having a maximum size of (3/4) or more is placed (S61, S62).

  When a recording sheet of (3/4) or more of the maximum size is placed on at least one of the plurality of placement portions (Yes in S62), the maximum size (3 / 4) It is checked whether or not there are a plurality of placement sections on which the above recording sheets are placed (S63). If there is only one placement section on which a recording sheet of the maximum size (3/4) or more is placed (No in S63), the recording sheet placed on the placement section is tested. Set the recording sheet to form the pattern. On the other hand, if there are a plurality of recording sheets, the recording sheet placed on the placement portion having a short conveyance distance to the transfer nip is set as the recording sheet for forming the test pattern (Yes in S63, S64).

  On the other hand, when the maximum size (3/4) or larger recording sheet is not set on any placement section (No in S62), the maximum size (3/4) or larger recording sheet is used. Then, the user is informed so as to be set on any one of the placement portions (S65).

FIG. 23 is a diagram illustrating an example of notification to the user.
When a recording sheet having the maximum size of (3/4) or more is not set on any placement unit, the maximum size (3) is displayed on the display unit 89a of the operation display unit 89 as shown in FIG. / 4) A screen pops up to prompt the user to set the above recording sheet on the loading unit. On this screen, a recording sheet (“paper A horizontal” size, “paper B horizontal” size in FIG. 23) having the maximum size of (3/4) or more is displayed. When the user places the recording sheet of the size displayed on this screen on any of the plurality of placement units, the above-mentioned maximum size (3/4) or more recording sheet is set on the placement unit. Will be. For example, when the maximum size is the letter size side, the recording sheets displayed as (3/4) or more of the maximum size are “letter size side” and “A4 side”.

  When the main body control unit 52 detects that a recording sheet of the size displayed on the screen is placed on any of the plurality of placement units, the GUI component of “print start” that is lightly displayed and cannot be selected is clearly displayed. Displayed and selectable. When the user presses the GUI component on the pop-up screen “print start”, the density unevenness acquisition control shown in FIG. 6 is started.

FIG. 24 is a diagram for explaining a case where the test pattern 171 is formed on the recording sheet having the maximum size of (3/4) or more.
As shown in FIG. 24, when the test pattern 171 is formed on the recording sheet having the maximum size of (3/4) or more, the length A of the test pattern 171 in the main scanning direction is the light emitting area B of the LED array 74. It becomes almost the same length. Therefore, it is possible to correct the density unevenness in almost the entire area in the main scanning direction, and obtain a good image in which the density unevenness is suppressed regardless of the size of the recording sheet placed on the paper feed cassette 100 or the manual feed tray 27. Can do.

  In Example 1, when a recording sheet that is longer in the sheet main scanning direction than the recording sheet placed on each placement unit at the time of density unevenness acquisition control is placed on any of the plurality of placement units. The density unevenness acquisition control needs to be performed again, but the second embodiment has an advantage that the density unevenness acquisition control need not be performed when the recording sheet is changed.

  On the other hand, in Example 2, the density unevenness cannot be obtained unless there is a recording sheet having the maximum size of (3/4) or more. There is a demerit that a user who does not use a recording sheet of (3/4) or more of the maximum size needs to prepare a recording sheet of (3/4) or more of the maximum size for obtaining density unevenness. On the other hand, in Example 1, since the recording sheet currently mounted on the mounting portion is used, it is not necessary to prepare a recording sheet of (3/4) or more of the maximum size, and density unevenness is not required. There is an advantage that acquisition control can be easily performed.

  When the maximum size in the main scanning direction that can be read by the image reading unit 60 is less than (3/4) of the maximum size in the main scanning direction in which an image can be formed, the length in the main scanning direction is the image reading unit. The operator may be urged to set a recording sheet of (3/4) or more of the maximum size in the main scanning direction in which 60 can be read.

  In the above description, the operation display unit displays a screen for instructing to set the recording sheet having the maximum size of (3/4) or more on the loading unit. Then, guidance may be given so as to instruct the user to set a recording sheet of (3/4) or more of the maximum size on the loading unit. In addition, a warning lamp may be turned on to instruct to set a recording sheet of (3/4) or more of the maximum size on the loading unit.

[Example 3]
Next, Example 3 will be described.
FIG. 25 is a control flowchart for selecting a recording sheet on which a test pattern is formed in the third embodiment.
As shown in FIG. 25, also in the third embodiment, first, based on the size information of the recording sheets placed on a plurality of placement units such as the manual feed tray 27 and the paper feed cassettes 100, the main scanning direction It is checked whether there is a placement portion on which a recording sheet having a length of (3/4) or more of the maximum length in the main scanning direction in which the image forming apparatus can form an image is placed (S71, S72). ).

  When a recording sheet having the maximum size of (3/4) or more is placed on at least one of the plurality of placement sections (Yes in S72), the maximum size (3 / 4) It is checked whether or not there are a plurality of placement portions on which the above recording sheets are placed (S73). If there is only one placement section on which the recording sheet of the maximum size (3/4) or more is placed (No in S73), the recording sheet placed on the placement section is tested. Set the recording sheet to form the pattern. On the other hand, if there are a plurality of recording sheets, the recording sheet placed on the placement portion having a short conveyance distance to the transfer nip is set as the recording sheet for forming the test pattern (Yes in S73, S74).

  On the other hand, when the recording sheet having the maximum size of (3/4) or more is not set in any placement unit (No in S72), as shown in FIG. 26, the display unit of the operation display unit 89 In 89a, a screen pops up to select whether to set a recording sheet of the maximum size (3/4) or more on the loading unit or to use the currently set recording sheet (S76).

  When the user can easily prepare a recording sheet of the above-mentioned maximum size (3/4) or more, press the “paper A horizontal” GUI part or the “paper B horizontal” GUI part on the pop-up screen shown in FIG. The recording sheet having the maximum size of (3/4) or more may be selected to be set on the loading unit. On the other hand, when a user cannot easily prepare a recording sheet of (3/4) or more of the maximum size, or a user who is not planning to use a recording sheet of (3/4) or more of the maximum size for the time being, What is necessary is just to select using the set recording sheet.

  The user presses the “paper A side” GUI part or the “paper B side” GUI part on the pop-up screen shown in FIG. 26, and sets the recording sheet of the above-mentioned maximum size (3/4) or more on the placement unit. When the selection is made (Yes in S76), if it is detected that a recording sheet having the size displayed on the screen is placed on any of the plurality of placement units, the selection is displayed lightly. Impossible “print start” GUI parts are clearly displayed and can be selected. Then, when the user presses the GUI part on the pop-up screen “print start”, the density unevenness acquisition control shown in FIG. 6 is started (S77).

  In this way, when a recording sheet longer than the currently set recording sheet is set in the main scanning direction by selecting to set the recording sheet of (3/4) or more of the maximum size on the loading unit, Also, it is possible to suppress the occurrence of density unevenness at the end portion in the main scanning direction.

  On the other hand, when the user presses the “Use currently loaded paper” GUI part on the pop-up screen shown in FIG. 26, the “print start” GUI part that is lightly displayed and cannot be selected is clearly displayed and can be selected. It becomes. Also, if the user presses the “Use currently set paper” GUI part, density unevenness may occur when an image is formed on a recording sheet that is longer in the main scanning direction than the currently set recording sheet. There may be a pop-up confirmation screen to confirm that it is OK.

  Then, when the user presses the “print start” GUI component on the pop-up screen, the placement unit on which the recording sheet having the longest length in the main scanning direction is placed is specified (S78). ), It is checked whether or not there are a plurality of placement portions on which the recording sheet having the longest length in the main scanning direction is placed (S79).

  When there is only one placement portion on which the recording sheet having the longest length in the main scanning direction is placed (No in S79), the recording placed on this placement portion. The sheet is set as a recording sheet for forming a test pattern. On the other hand, when there are a plurality of placement portions on which the recording sheet having the longest length in the main scanning direction is placed (Yes in S79), the placement is made on the placement portion with a short transport distance to the transfer nip. The recording sheet is set as a recording sheet for forming a test pattern.

  As described above, in the third embodiment, the operator can select whether to set the recording sheet having the maximum size of (3/4) or more on the loading unit or to use the currently set recording sheet. The advantages of both Example 1 and Example 2 can be obtained.

  Also in the third embodiment, when the maximum size in the main scanning direction that can be read by the image reading unit 60 is less than (3/4) of the maximum size in the main scanning direction in which image formation is possible, The operator may be prompted to set a recording sheet having a length of (3/4) or more of the maximum size in the main scanning direction that can be read by the image reading unit 60.

What was demonstrated above is an example, and there exists an effect peculiar for every following aspect.
(Aspect 1)
Recording medium placement means such as a plurality of placement portions (in this embodiment, two paper feed cassettes and a manual feed tray correspond), and image forming means (in this embodiment, the photosensitive member 1, the charging roller 4, and the latent image). A writing device 7, a developing device 8, a transfer roller 10, a fixing device 44, etc.), an image reading unit such as an image reading unit 60, and a test pattern is formed on a recording medium such as a recording sheet by the image forming unit, An acquisition unit (in the present embodiment, configured by the image formation processing unit 84, the image density acquisition unit 86, and the like) that acquires the test pattern image data by reading the test pattern of the recording medium by the image reading unit, and an image of the test pattern Correction value calculation means for calculating a predetermined correction value for optimizing the image based on data (in the present embodiment, it is constituted by a light amount correction value calculation unit 88 and a calculation unit 82); In the image forming apparatus having acquisition means, among placed on the recording medium in a plurality of recording medium stacking means each, the length of most primary scanning direction to form the test pattern in the long record medium.
When the recording medium on which the test pattern is to be formed is selected by the operator from the plurality of recording medium placing means, the length in the main scanning direction is the longest among the recording media placed on each of the plurality of recording medium placing means. The operator may select a recording medium mounting unit on which a short recording medium (hereinafter referred to as a small size recording medium) is mounted. In this case, the correction value can be calculated only in the main scanning direction length range of the small size recording medium, and the image can be optimized only in the main scanning direction range of the small size recording medium. Therefore, when an image is formed on a recording medium having the longest length in the main scanning direction among the recording media mounted on the plurality of recording medium mounting units, the main scanning direction is larger than the range of the small size recording medium. The image on the outside is not optimized and results in a poor quality image.
On the other hand, in the aspect 1, the test pattern is automatically formed on the recording medium having the longest length in the main scanning direction among the recording media placed on each of the plurality of recording medium placing means. As a result, an optimized image can be obtained in the entire range in the main scanning direction, regardless of the recording medium placed on any of the plurality of recording medium placement means.
In addition, when the operator forms the test pattern, it is not necessary to select any of the plurality of recording medium placing means, and the burden on the operator can be reduced.

(Aspect 2)
Recording medium placing means such as a placing portion (in this embodiment, two paper feed cassettes and a manual feed tray are applicable), and image forming means (in this embodiment, the photosensitive member 1, the charging roller 4, the latent image writing) Device 7, developing device 8, transfer roller 10, fixing device 44, etc.), image reading means such as image reading unit 60, and image forming means to form a test pattern on a recording medium such as a recording sheet, and image reading Means for acquiring the test pattern image data by reading the test pattern of the recording medium by the means (in the present embodiment, the image forming processing unit 84, the image density acquisition unit 86, etc.), and the image data of the test pattern Correction value calculating means for calculating a predetermined correction value for optimizing the image based on this (in the present embodiment, comprising a light amount correction value calculating unit 88 and a calculating unit 82). In the image forming apparatus, the length in the main scanning direction of the recording medium placing unit is (3/4) the maximum size in the main scanning direction that the image forming unit can form an image or the image reading unit can read. When the above recording medium is placed, a test pattern is formed on the recording medium placed on the recording medium placing means, and the recording medium placing means has a maximum size of (3/4) or more. When the recording medium is not placed, the operator is notified that the recording medium having the maximum size (3/4) or more is placed on the recording medium placing means.
According to this, as described in the second embodiment, it is possible to correct the density unevenness almost in the entire area in the main scanning direction, and no matter what size recording sheet is placed on the paper feed cassette 100 or the manual feed tray 27. A good image with suppressed density unevenness can be obtained.

(Aspect 3)
Recording medium placement means such as a plurality of placement portions (in this embodiment, two paper feed cassettes and a manual feed tray correspond), and image forming means (in this embodiment, the photosensitive member 1, the charging roller 4, and the latent image). A writing device 7, a developing device 8, a transfer roller 10, a fixing device 44, etc.), an image reading unit such as an image reading unit 60, and a test pattern is formed on a recording medium such as a recording sheet by the image forming unit, An acquisition unit (in the present embodiment, configured by the image formation processing unit 84, the image density acquisition unit 86, and the like) that acquires the test pattern image data by reading the test pattern of the recording medium by the image reading unit, and an image of the test pattern Correction value calculation means for calculating a predetermined correction value for optimizing the image based on data (in the present embodiment, it is constituted by a light amount correction value calculation unit 88 and a calculation unit 82); In the image forming apparatus, the acquisition unit may have a length in the main scanning direction on any one of the plurality of recording medium mounting units, the image forming unit can form an image, or the image reading unit can read When a recording medium of (3/4) or more of the maximum size in the main scanning direction is placed, a test pattern is formed on the recording medium of (3/4) or more of the maximum size,
When the recording medium having the maximum size of (3/4) or more is not placed on all the recording medium placing means, the most main recording medium is placed among the plurality of recording medium placing means. Whether to form a test pattern on a recording medium having a long length in the scanning direction, or to place a recording medium of the maximum size (3/4) or more on any one of a plurality of recording medium mounting means Let the person choose.
According to this, as described in the third embodiment, the length in the main scanning direction is (3 / the maximum size in the main scanning direction that the image forming unit can form an image or the reading unit can read. 4) Users who can easily prepare the above recording medium, the length in the main scanning direction is the maximum size in the main scanning direction that the image forming unit can form an image or the reading unit can read (3/4) It is possible to provide a user-friendly image forming apparatus that does not use the above recording medium.

(Aspect 4)
In any one of the first to third aspects, the recording medium is provided with a plurality of the recording medium mounting means, and the acquisition means is a recording medium that is suitable for test pattern formation among the recording media mounted on each of the plurality of recording medium mounting means ( In aspect 1, the recording medium having the longest length in the main scanning direction among the recording media placed on each of the plurality of recording medium placing means, in aspects 2 and 3, the image forming means can form an image, or When there are a plurality of (3/4) or larger recording media having a maximum size in the main scanning direction that can be read by the image reading unit, image formation is performed among the plurality of recording medium mounting units on which the appropriate recording medium is mounted. A test pattern is formed on the recording medium placed on the recording medium placing means having the shortest recording medium conveyance distance to the means.
According to this, as described in the first to third embodiments, it is possible to suppress the occurrence of skew in a recording medium such as a recording sheet on which a test pattern is formed.

(Aspect 5)
In any one of the first to fourth aspects, the test pattern is formed on the recording medium with no margin in the main scanning direction.
According to this, as described in the embodiment, correction can be applied to the end in the main scanning direction.

(Aspect 6)
In any one of aspects 1 to 5, the image forming means exposes the surface of a latent image carrier such as the photosensitive member 1 to form a latent image on the latent image carrier and forms a latent image such as a latent image writing device 7. Developing means such as a developing device 8 that develops the latent image, and transfer means such as a transfer roller 10 that transfers the image developed by the developing means onto a recording medium conveyed by the conveying means. The correction value calculation means calculates an exposure correction value for correcting the amount of exposure light based on the read image data of the test pattern.
According to this, as described in the embodiment, it is possible to calculate a highly accurate exposure amount correction value, and to satisfactorily suppress image density unevenness in the main scanning direction.

1: Photoconductor 2: Cleaning blade 4: Charging roller 5: Cleaning roller 7: Latent image writing device 8: Developing device 10: Transfer roller 11: Registration roller pair 20: Paper feed path 26: Manual paper feed unit 27: Manual feed Tray 42: Feeding path 44: Fixing device 50: Main body casing 52: Main body control unit 54: Detection unit 55: Size dial 56: Spacer 60: Image reading unit 63a: Side fence 63b: Side fence 69: Width sensor 74: LED array 74a: IC driver 74b: LED element 74c: ROM
75: Holder 82: Calculation unit 83: Correction value transfer unit 84: Image formation processing unit 85: First light amount correction value acquisition unit 86: Image density acquisition unit 87: Storage unit 88: Light amount correction value calculation unit 89: Operation display unit 89a: Display unit 89b: Operation unit 100: Paper feed cassette 171: Test pattern 514: Size display window

JP2015-085525A

Claims (6)

A plurality of recording medium placing means;
Image forming means;
Image reading means;
An acquisition means for forming a test pattern on a recording medium by the image forming means, and reading the test pattern of the recording medium by the image reading means to acquire image data of the test pattern;
In an image forming apparatus, comprising: a correction value calculating unit that calculates a predetermined correction value for optimizing an image based on image data of the test pattern.
The image forming apparatus, wherein the acquisition unit forms the test pattern on a recording medium having the longest length in the main scanning direction among the recording media mounted on the plurality of recording medium mounting units. Recording medium placing means;
Image forming means;
Image reading means;
An acquisition means for forming a test pattern on a recording medium by the image forming means, and reading the test pattern of the recording medium by the image reading means to acquire image data of the test pattern;
In an image forming apparatus, comprising: a correction value calculating unit that calculates a predetermined correction value for optimizing an image based on image data of the test pattern.
The acquisition means includes
On the recording medium placing means, the length in the main scanning direction is not less than (3/4) of the maximum size in the main scanning direction that the image forming means can form an image or the image reading means can read. When a medium is placed, the test pattern is formed on the recording medium placed on the recording medium placing means,
When the recording medium having the maximum size of (3/4) or more is not placed on the recording medium placing means, the recording medium placing means has the recording of the maximum size of (3/4) or more. An image forming apparatus that notifies an operator to place a medium. A plurality of recording medium placing means;
Image forming means;
Image reading means;
An acquisition means for forming a test pattern on a recording medium by the image forming means, and reading the test pattern of the recording medium by the image reading means to acquire image data of the test pattern;
In an image forming apparatus, comprising: a correction value calculating unit that calculates a predetermined correction value for optimizing an image based on image data of the test pattern.
The acquisition means includes
The length in the main scanning direction of any one of the plurality of recording medium placing units is not less than (3/4) of the maximum size in the main scanning direction in which the image forming unit can form an image or the image reading unit can read. When the recording medium is mounted, the test pattern is formed on a recording medium of (3/4) or more of the maximum size,
When the recording medium having the maximum size of (3/4) or more is not placed on all the recording medium placing means, the most main recording medium is placed among the plurality of recording medium placing means. Whether the test pattern is formed on a recording medium having a long length in the scanning direction, or whether the recording medium of the maximum size (3/4) or more is placed on any of a plurality of recording medium placing means, An image forming apparatus that allows an operator to select an image. The image forming apparatus according to any one of claims 1 to 3,
A plurality of the recording medium mounting means;
The acquisition means includes
When there are a plurality of recording media suitable for test pattern formation among the recording media respectively mounted on the plurality of recording medium mounting means,
Of the plurality of recording medium mounting units on which the adapted recording medium is mounted, the test pattern is applied to the recording medium mounted on the recording medium mounting unit having the shortest recording medium transport distance to the image forming unit. An image forming apparatus that forms the image. The image forming apparatus according to any one of claims 1 to 4,
The image forming apparatus, wherein the test pattern is formed on the recording medium with no margin in a main scanning direction. The image forming apparatus according to any one of claims 1 to 5,
The image forming means is developed by a latent image forming means for exposing the surface of the latent image carrier to form a latent image on the latent image carrier, a developing means for developing the latent image, and the developing means. A transfer means for transferring the image to the recording medium conveyed by the conveyance means,
The image forming apparatus, wherein the correction value calculating means calculates an exposure correction value for correcting the amount of exposure light based on the read image data of the test pattern.