JP2021189347A - Image forming apparatus - Google Patents

Abstract

To provide an image forming apparatus that can prevent erroneous detection made by an image detection unit caused by an attachment on an image carrier.SOLUTION: An image forming apparatus comprises: an image carrier that carries an image to be transferred to a recording medium and conveys the image toward a transfer nip; and two or more image detection units that are arranged opposite to the image carrier at different positions in a width direction of the image carrier and detect the image on a surface of the image carrier. The two or more image detection units are arranged at positions different in distance from a center line in the width direction of a transfer area of the image carrier corresponding to the transfer nip.SELECTED DRAWING: Figure 3

Description

The present invention relates to an image forming apparatus.

Conventionally, in an image forming apparatus, a configuration in which an image detection unit is provided at a position facing an image carrier such as an intermediate transfer belt is known. The image detection unit detects an image formed on the image carrier. For example, Patent Document 1 discloses a configuration having two image detection units facing each other at both ends in the width direction of the image carrier.

Japanese Unexamined Patent Publication No. 2013-41162

By the way, the image carrier comes into contact with the recording medium at the transfer nip that transfers the image to the recording medium, but foreign matter such as dust may adhere to the end of the recording medium, so that the transfer region in the image carrier The foreign matter is likely to adhere to the position corresponding to the end of the.

Therefore, if the image detection unit is arranged at a position corresponding to the end portion of the transfer region, there is a problem that erroneous detection of the image detection unit occurs due to the deposits (the above-mentioned foreign matter) on the image carrier. Occurs. In particular, when a continuous paper having a plurality of layers bonded to each other, such as tack paper, is used as a recording medium, the glue protruding from the edge of the recording medium adheres to the image carrier, so that the above problem occurs remarkably.

An object of the present invention is to provide an image forming apparatus capable of suppressing erroneous detection of an image detection unit caused by deposits on an image carrier.

The image forming apparatus according to the present invention is
An image carrier that carries an image to be transferred to a recording medium and conveys the image toward a transfer nip, and an image carrier.
Two or more image detection units that are arranged facing the image carrier at different positions in the width direction of the image carrier and detect an image on the surface of the image carrier.
Equipped with
The two or more image detection units are arranged at positions where the distances of the transfer regions corresponding to the transfer nips of the image carrier to the center line in the width direction are different.

According to the present invention, it is possible to suppress erroneous detection of the image detection unit due to the deposits on the image carrier.

It is a figure which shows schematically the whole structure of the image forming apparatus which concerns on embodiment of this invention. It is a figure which shows the main part of the control system of the image forming apparatus which concerns on this embodiment. It is a figure which shows the facing part of two image detection part and an intermediate transfer belt. It is a figure which shows an example of the patch image formed on the intermediate transfer belt. It is a figure which shows an example of the patch image formed on the intermediate transfer belt. It is a figure which shows an example of the tilt patch image formed on the intermediate transfer belt. It is a flowchart which shows the operation example of the selection control of the image detection part in an image forming apparatus. It is a figure which shows the facing part of three image detection part and an intermediate transfer belt.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a diagram schematically showing an overall configuration of an image forming apparatus 1 according to an embodiment of the present invention. FIG. 2 is a diagram showing a main part of the control system of the image forming apparatus 1 according to the present embodiment.

The image forming apparatus 1 is an apparatus for forming an image on the recording medium S by using the tack paper S1 or the paper S2 (non-tack paper) such as continuous paper or long paper shown by a thick line in FIG. 1 as the recording medium S. be. The tack paper S1 is composed of three layers, a surface layer, an adhesive layer, and a peeling layer, and is, for example, fed into the image forming apparatus 1 from a feeding device 2 configured separately from the image forming apparatus 1.

The image forming apparatus 1 shown in FIGS. 1 and 2 is an intermediate transfer type color image forming apparatus using an electrophotographic process technique. That is, the image forming apparatus 1 primary transfers the Y (yellow), M (magenta), C (cyan), and K (black) color toner images formed on the photoconductor drum 413 to the intermediate transfer belt 421. An image is formed by superimposing toner images of four colors on the intermediate transfer belt 421 and then secondary transfer to the recording medium S.

Further, in the image forming apparatus 1, the photoconductor drums 413 corresponding to the four colors of YMCK are arranged in series in the traveling direction of the intermediate transfer belt 421, and the toner images of each color are sequentially transferred to the intermediate transfer belt 421 in one procedure. The tandem method is adopted.

As shown in FIG. 2, the image forming apparatus 1 includes an image reading unit 10, an operation display unit 20, an image processing unit 30, an image forming unit 40, a paper transport unit 50, a fixing unit 60, an image detection unit 200, and a control unit 101. To prepare for.

The control unit 101 includes a CPU (Central Processing Unit) 102, a ROM (Read Only Memory) 103, a RAM (Random Access Memory) 104, and the like. The CPU 102 reads a program according to the processing content from the ROM 103, develops it in the RAM 104, and centrally controls the operation of each block of the image forming apparatus 1 in cooperation with the expanded program. At this time, various data stored in the storage unit 72 are referred to. The storage unit 72 is composed of, for example, a non-volatile semiconductor memory (so-called flash memory) or a hard disk drive.

The control unit 101 transmits and receives various data to and from an external device (for example, a personal computer) connected to a communication network such as a LAN (Local Area Network) and a WAN (WideArea Network) via the communication unit 71. .. The control unit 101 receives, for example, image data transmitted from an external device, and causes the recording medium S to form an image based on the image data (input image data). The communication unit 71 is composed of a communication control card such as a LAN card.

As shown in FIG. 1, the image reading unit 10 includes an automatic document feeding device 11 called an ADF (Auto Document Feeder), a document image scanning device 12 (scanner), and the like.

The automatic document feeding device 11 conveys the document D placed on the document tray by the conveying mechanism and sends it out to the document image scanning device 12. The automatic document feeding device 11 makes it possible to continuously read a large number of images (including both sides) of the original D placed on the original tray at once.

The document image scanning device 12 optically scans the document conveyed on the contact glass from the automatic document feeding device 11 or the document placed on the contact glass, and the reflected light from the document is a CCD (Charge Coupled Device). ) An image is formed on the light receiving surface of the sensor 12a, and the original image is read. The image reading unit 10 generates input image data based on the reading result of the original image scanning device 12. Predetermined image processing is performed on the input image data by the image processing unit 30.

As shown in FIG. 2, the operation display unit 20 is composed of, for example, a liquid crystal display (LCD: Liquid Crystal Display) with a touch panel, and functions as a display unit 21 and an operation unit 22. The display unit 21 displays various operation screens, image states, operation statuses of each function, and the like according to the display control signal input from the control unit 101. The operation unit 22 includes various operation keys such as a numeric keypad and a start key, receives various input operations by the user, and outputs an operation signal to the control unit 101.

The image processing unit 30 includes a circuit or the like that performs digital image processing according to initial settings or user settings for input image data. For example, the image processing unit 30 performs gradation correction based on the gradation correction data (gradation correction table) under the control of the control unit 101. Further, the image processing unit 30 performs various correction processes such as color correction and shading correction, compression processing, and the like, in addition to gradation correction, on the input image data. The image forming unit 40 is controlled based on the image data subjected to these processes.

As shown in FIG. 1, the image forming unit 40 has image forming units 41Y, 41M, 41C for forming an image with each colored toner of Y component, M component, C component, and K component based on the input image data. , 41K, intermediate transfer unit 42 and the like.

The image forming units 41Y, 41M, 41C, 41K for the Y component, the M component, the C component, and the K component have the same configuration. For convenience of illustration and description, common components are indicated by the same reference numerals, and when they are distinguished from each other, they are indicated by adding Y, M, C or K to the reference numerals. In FIG. 1, reference numerals are given only to the components of the image forming unit 41Y for the Y component, and the reference numerals are omitted for the other components of the image forming units 41M, 41C, and 41K.

The image forming unit 41 includes an exposure device 411, a developing device 412, a photoconductor drum 413, a charging device 414, a drum cleaning device 415, and the like.

The photoconductor drum 413 is made of an organic photoconductor in which, for example, a photosensitive layer made of a resin containing an organic photoconductor is formed on an outer peripheral surface of a drum-shaped metal substrate.

The control unit 101 rotates the photoconductor drum 413 at a constant peripheral speed by controlling the drive current supplied to the drive motor (not shown) that rotates the photoconductor drum 413.

The charging device 414 is, for example, a charging charger, and by generating a corona discharge, the surface of the photoconductive drum 413 is uniformly charged to a negative electrode.

The exposure apparatus 411 is composed of, for example, a semiconductor laser, and irradiates the photoconductor drum 413 with a laser beam corresponding to an image of each color component. As a result, an electrostatic latent image of each color component is formed in the image region irradiated with the laser beam on the surface of the photoconductor drum 413 due to the potential difference from the background region.

The developing device 412 is a two-component reversing type developing device, and a toner image is formed by visualizing an electrostatic latent image by adhering a developer of each color component to the surface of the photoconductor drum 413.

For example, a DC development bias having the same polarity as the charging polarity of the charging device 414 or a development bias in which a DC voltage having the same polarity as the charging polarity of the charging device 414 is superimposed on the AC voltage is applied to the developing device 412. As a result, reverse development is performed in which toner is adhered to the electrostatic latent image formed by the exposure apparatus 411.

The drum cleaning device 415 has a flat plate-shaped drum cleaning blade 415A or the like which is abutted against the surface of the photoconductor drum 413 and is made of an elastic body, and remains on the surface of the photoconductor drum 413 without being transferred to the intermediate transfer belt 421. Remove the toner.

The intermediate transfer unit 42 includes an intermediate transfer belt 421, a primary transfer roller 422, a plurality of support rollers 423, a secondary transfer roller 424, a belt cleaning device 426, and the like. The intermediate transfer belt 421 corresponds to the "image carrier" of the present invention.

The intermediate transfer unit 42 is composed of an endless belt and is stretched in a loop on a plurality of support rollers 423. At least one of the plurality of support rollers 423 is composed of a driving roller, and the other is composed of a driven roller. For example, it is preferable that the roller 423A arranged on the downstream side in the belt traveling direction with respect to the primary transfer roller 422 for the K component is the drive roller. This makes it easier to keep the running speed of the belt at the primary transfer nip constant. As the drive roller 423A rotates, the intermediate transfer belt 421 travels at a constant speed in the direction of arrow A.

The primary transfer roller 422 is arranged on the inner peripheral surface side of the intermediate transfer belt 421 so as to face the photoconductor drum 413 of each color component. The primary transfer roller 422 is pressed against the photoconductor drum 413 with the intermediate transfer belt 421 interposed therebetween, thereby forming a primary transfer nip for transferring the toner image from the photoconductor drum 413 to the intermediate transfer belt 421.

The secondary transfer roller 424 is arranged on the outer peripheral surface side of the intermediate transfer belt 421 so as to face the backup roller 423B arranged on the downstream side of the drive roller 423A in the belt traveling direction. The secondary transfer roller 424 is pressed against the backup roller 423B with the intermediate transfer belt 421 interposed therebetween, thereby forming a secondary transfer nip for transferring the toner image from the intermediate transfer belt 421 to the recording medium S.

When the intermediate transfer belt 421 passes through the primary transfer nip, the toner image on the photoconductor drum 413 is sequentially superimposed on the intermediate transfer belt 421 and the primary transfer is performed. Specifically, a toner image is applied by applying a primary transfer bias to the primary transfer roller 422 and applying a charge having the opposite polarity to the toner on the back surface side of the intermediate transfer belt 421, that is, the side in contact with the primary transfer roller 422. Is electrostatically transferred to the intermediate transfer belt 421.

After that, when the recording medium S passes through the secondary transfer nip, the toner image on the intermediate transfer belt 421 is secondarily transferred to the recording medium S. Specifically, a secondary transfer bias is applied to the backup roller 423B to apply a charge having the same polarity as the toner to the surface side of the recording medium S, that is, the side in contact with the intermediate transfer belt 421. It is electrostatically transferred to the recording medium S, and the recording medium S is conveyed toward the fixing unit 60.

The belt cleaning device 426 removes the transfer residual toner remaining on the surface of the intermediate transfer belt 421 after the secondary transfer. Instead of the secondary transfer roller 424, a so-called belt-type secondary transfer unit in which the secondary transfer belt is stretched in a loop shape may be adopted for a plurality of support rollers including the secondary transfer roller. ..

Further, an image detection unit 200 is provided at a position of the intermediate transfer unit 42 facing the intermediate transfer belt 421. By feeding back the detection result of the image detecting unit 200 to the image forming condition (control unit 101), it is possible to improve and stabilize the image quality in the image forming unit 40. The details of the image detection unit 200 will be described later.

The fixing portion 60 is an upper fixing portion 60A having a fixing surface side member arranged on the fixing surface of the recording medium S, that is, the surface side on which the toner image is formed, and the back surface side of the recording medium S, that is, the opposite surface side of the fixing surface. It is provided with a lower fixing portion 60B having a back surface side support member arranged in, a heating source 60C, and the like. By pressing the back surface side support member against the fixing surface side member, a fixing nip that sandwiches and conveys the recording medium S is formed.

The fixing unit 60 secondarily transfers the toner image and heats and pressurizes the conveyed recording medium S with the fixing nip to fix the toner image on the recording medium S. The fixing portion 60 is arranged as a unit in the fixing device F. Further, the fuser F may be provided with an air separation unit that separates the recording medium S from the fixing surface side member or the back surface side support member by blowing air.

The paper transport unit 50 includes a paper feed unit 51, a paper discharge unit 52, a transport path unit 53, and the like. Paper S (standard paper, special paper) identified based on the basis weight, size, etc. is stored in the three paper feed tray units 51a to 51c constituting the paper feed unit 51 for each preset type. .. The transport path portion 53 has a plurality of transport rollers such as a resist roller pair 53a.

The paper S2 housed in the paper feed tray units 51a to 51c is sent out one by one from the uppermost portion, and is conveyed to the image forming unit 40 by the transfer path unit 53. At this time, the resist roller portion in which the resist roller pair 53a is arranged corrects the inclination of the fed paper S2 and adjusts the transfer timing. Then, in the image forming unit 40, the toner image of the intermediate transfer belt 421 is collectively secondarily transferred to one surface of the paper S2, and the fixing step is performed in the fixing unit 60.

Further, the tack paper S1 fed from the paper feeding device 2 to the image forming apparatus 1 is conveyed to the image forming unit 40 by the conveying path unit 53. Then, in the image forming unit 40, the toner image of the intermediate transfer belt 421 is collectively secondarily transferred to one surface of the tack paper S1, and the fixing step is performed in the fixing unit 60. The image-formed recording medium S is ejected to the outside of the machine by the paper ejection unit 52 provided with the paper ejection roller 52a.

Next, the details of the image detection unit 200 will be described. FIG. 3 is a diagram showing facing portions of the two image detection units 200 and the intermediate transfer belt 421.

As shown in FIG. 3, the image detection unit 200 is a known sensor that detects an image on the surface of the intermediate transfer belt 421, and two image detection units 200 are provided side by side in the width direction of the intermediate transfer belt 421. The width direction of the intermediate transfer belt 421 is a direction orthogonal to the transport direction of the intermediate transfer belt 421 and a direction parallel to the surface of the intermediate transfer belt 421. In the example shown in FIG. 3, the width direction of the intermediate transfer belt 421 is the left-right direction in FIG.

The two image detection units 200 are arranged at different positions in the width direction of the intermediate transfer belt 421 so as to face the intermediate transfer belt 421. Specifically, the two image detection units 200 are arranged at positions where the distances of the transfer region R in the intermediate transfer belt 421 with respect to the center line C in the width direction are different.

The transfer region R is a region corresponding to a transfer nip in the intermediate transfer belt 421, that is, a contact position with the recording medium S. The center line C has a substantially constant position because the center in the width direction of the recording medium S passing through the transfer nip is substantially constant on the transport path regardless of the size of the recording medium S. Further, the center line C may be located within a minute range including a position corresponding to the center position in the width direction of the recording medium S.

The two image detection units 200 are arranged so as to sandwich the center line C. In the example shown in FIG. 3, the first image detection unit 200A on the left side of the center line C is arranged at a position farther from the center line C than the second image detection unit 200B on the right side of the center line C. That is, the distance L1 between the first image detection unit 200A and the center line C is longer than the distance L2 between the second image detection unit 200B and the center line C.

The control unit 101 detects an image on the surface of the intermediate transfer belt 421 from the two image detection units 200 based on the width direction distance between the widthwise end of the transfer region R and the image detection unit 200. Select the image detection unit 200 to be used. The control unit 101 corresponds to the "selection unit" of the present invention.

Specifically, the control unit 101 does not select the image detection unit 200 in which the distance between the widthwise end portion of the transfer region R and the image detection unit 200 in the width direction is within a predetermined distance, and the distance is predetermined. Select the image detection unit 200 that is larger than the distance.

The width-wise distance between the widthwise end of the transfer region R and the image detection unit 200 is the widthwise end R1 and R2 of the transfer region R that are closer to the image detection unit 200 and the image. This is the distance from the detection unit 200. R1 is the left end portion in the width direction of the transfer region R, and corresponds to the end portion close to the first image detection unit 200A. R2 is the right end portion in the width direction of the transfer region R, and corresponds to the end portion close to the second image detection unit 200B.

Specifically, the distance in the width direction between the widthwise end portion of the transfer region R and the first image detection unit 200A is the distance L3 between R1 and the first image detection unit 200A. Further, the distance in the width direction between the widthwise end portion of the transfer region R and the second image detection unit 200B is the distance L4 between R2 and the second image detection unit 200B.

The predetermined distance is a distance within a range in which there is a possibility that deposits adhering to the intermediate transfer belt 421 may exist from the end of the recording medium S when the recording medium S passes through the transfer nip, and is based on experiments and the like. It is a distance that can be set arbitrarily. In the example shown in FIG. 3, the predetermined distance is set to, for example, L5. Further, predetermined distances are set on both the left and right sides of the ends R1 and R2 of the transfer region R, respectively.

When the recording medium S is tack paper, the deposits are foreign substances such as glue and the like that protrude from the end when the tack paper is crushed by the transfer nip, and dust and the like that adhere to the end. Further, when the recording medium S is paper, the deposit is a foreign substance such as dust or paper dust that adheres to the end portion of the paper due to loosening of fibers.

For example, the first image detection unit 200A is arranged at a position within a predetermined distance from the end portion of the transfer region R, and the second image detection unit 200B is arranged at a position larger than a predetermined distance from the end portion of the transfer region R. Suppose.

In this case, the detection result of the image detected by the first image detection unit 200A may be affected by the deposits, and the image may not be detected accurately.

In this case, the control unit 101 does not select the first image detection unit 200A as the image detection unit 200 for detecting the image, but selects the second image detection unit 200B as the image detection unit 200 for detecting the image.

As a result, since the first image detection unit 200A is not used for image detection, it is possible to suppress the influence of the deposits on the intermediate transfer belt 421 in the image detection by the image detection unit 200. Then, since the second image detection unit 200B arranged at a position that is not affected by the deposit is used for image detection, the image can be detected without being affected by the deposit. ..

That is, in the present embodiment, it is possible to suppress erroneous detection of the image detection unit 200 due to the deposits on the intermediate transfer belt 421.

Further, the distance difference between the two image detection units 200 is larger than twice the above-mentioned predetermined distance. For example, the distance between the image detection unit 200 and the center line C in the image detection unit 200 not selected by the control unit 101 is (W / 2-L5) when the width of the recording medium S is W and the predetermined distance is L5. It is within the range of (W / 2 + L5). Since the minimum value of the distance of the image detection unit 200 that is not selected by the control unit 101 is (W / 2-L5), in order for at least one image detection unit 200 to be selected by the control unit 101, the said The condition is that the distance of the image detection unit 200 is shorter than (W / 2-L5) or longer than (W / 2 + L5).

Therefore, by making the distance difference between the two image detection units 200 larger than twice the above-mentioned predetermined distance (L5), it is possible to prevent the control unit 101 from selecting all the image detection units 200. Image detection by the image detection unit 200 can be performed reliably and accurately.

Further, the two image detection units 200 are arranged so that the distance difference between the two image detection units 200 is larger than twice the predetermined distance related to all types of recording media S that can be used in the image forming apparatus 1. It is preferable to do so.

By doing so, it is possible to suppress that the condition that the distance difference between the two image detection units 200 is larger than twice the predetermined distance is not satisfied depending on the type of the recording medium S.

Further, as shown in FIG. 4, the control unit 101 controls the image forming unit 40 so as to form a patch image to be read by the image detecting unit 200 on the intermediate transfer belt 421. The image forming unit 40 corresponds to the "patch image forming unit" of the present invention.

Specifically, the control unit 101 controls the image forming unit 40 so as to form a patch image at a position corresponding to the two image detecting units 200, for example.

The two image detection units 200 are arranged at the same position in the transport direction of the intermediate transfer belt 421.

As a result, the image detection by the two image detection units 200 can be performed at the same timing, so that, for example, the two patch images can be detected by each of the two image detection units 200 at the same timing. As a result, two patch images of different colors can be detected at the same timing, and the image detection efficiency can be improved.

The colors of the four patch images in FIG. 4 and the like are different colors (for example, any of Y, M, C, and K).

Further, as shown in FIG. 5, the control unit 101 controls the image forming unit 40 so as to change the position of forming the patch image on the intermediate transfer belt 421 based on the selection result.

For example, when the control unit 101 selects only the second image detection unit 200B as the image detection unit 200 for detecting an image, the first image detection unit 200A does not detect the image, so the position corresponding to the first image detection unit 200A. There is no need to form an image.

Therefore, the control unit 101 controls the image forming unit 40 so as to form the patch image for forming at the position corresponding to the first image detecting unit 200A at the position corresponding to the second image detecting unit 200B.

That is, the control unit 101 sets the image forming unit 40 so as to form the patch image on the intermediate transfer belt 421 so that the number of times the patch image is detected by one image detecting unit 200 is changed based on the selection result. Control. In the example shown in FIG. 5, the number of detections of the second image detection unit 200B is changed from 2 to 4, and the number of detections of the first image detection unit 200A is changed from 2 to 0.

By doing so, all of the patch images to be detected can be reliably detected by the image detection unit 200.

Further, the control unit 101 controls to detect the inclination of the image on the intermediate transfer belt 421 by using the two image detection units 200. The control unit 101 corresponds to the "tilt detection unit" of the present invention.

Specifically, as shown in FIG. 6, the control unit 101 controls the image forming unit 40 so as to form a tilt patch image for tilt detection at a position corresponding to each of the two image detecting units 200. .. Then, the control unit 101 detects the deviation amount of each inclination patch image based on the deviation of the detection timing of the inclination patch image in each of the two image detection units 200, and determines the inclination of the image on the intermediate transfer belt 421. To detect.

Further, when at least one of the two image detection units 200 is not selected as the image detection unit 200 used for image detection, the control unit 101 does not control to detect the tilt of the image.

As a result, when the image detection unit 200 may erroneously detect due to the influence of the deposits on the intermediate transfer belt 421, the image tilt is not detected, so that it is possible to suppress inaccurate image tilt detection control. ..

An operation example of the selection control of the image detection unit 200 in the image forming apparatus 1 configured as described above will be described. FIG. 7 is a flowchart showing an operation example of selection control of the image detection unit 200 in the image forming apparatus 1. The process in FIG. 7 is appropriately executed, for example, when the control unit 101 receives a command to form a patch image on the intermediate transfer belt 421.

As shown in FIG. 7, the control unit 101 determines whether or not the first image detection unit 200A is located within a predetermined distance from the end of the transfer region R (step S101). As a result of the determination, when the first image detection unit 200A is not located within a predetermined distance (step S101, NO), the control unit 101 selects the second image detection unit 200B (step S102).

On the other hand, when the first image detection unit 200A is located within a predetermined distance (step S101, YES), the control unit 101 determines whether or not the second image detection unit 200B is located within a predetermined distance from the end of the transfer region R. (Step S103).

As a result of the determination, when the second image detection unit 200B is not located within a predetermined distance (step S103, NO), the control unit 101 selects the first image detection unit 200A (step S104).

On the other hand, when the second image detection unit 200B is located within a predetermined distance (step S103, YES), the control unit 101 sets the first image detection unit 200A and the second image detection unit 200B (two image detection units 200). Select (step S105). After step S104 or step S105, this control ends.

According to the present embodiment configured as described above, it is possible to suppress erroneous detection of the image detection unit 200 due to the deposits on the intermediate transfer belt 421.

Further, since the distance difference between the two image detection units 200 is larger than twice the predetermined distance, it is possible to prevent the image detection unit 200 from being selected by the control unit 101, and the image detection is reliable and accurate. Can be done.

Further, continuous paper such as tack paper is arranged in the paper feed device 2 in a state of being configured in a roll shape, and such continuous paper is stored in a state where the end surface in the width direction is grounded. Since it is often used, foreign matter easily adheres to the end.

In the present embodiment, even if such continuous paper is used, even if the image detection unit 200 is provided at a position close to the transfer region R corresponding to the end portion, another image detection unit 200 displays an image. It is detectable. As a result, erroneous detection of the image can be further suppressed, and by extension, the image can be detected accurately.

In the above embodiment, two image detection units 200 are provided, but the present invention is not limited to this, and two or more image detection units 200 may be provided. For example, as shown in FIG. 8, the image detection unit 200 may have a third image detection unit 200C in addition to the first image detection unit 200A and the second image detection unit 200B.

The third image detection unit 200C is provided on the left side of the center line C (on the side of the first image detection unit 200A), and the distance L6 from the center line C is the distance between the second image detection unit 200B and the center line C. It is arranged at a position smaller than the distance L2.

Here, when the patch image is formed on the intermediate transfer belt 421 and the patch image is detected by the image detection unit 200, the patch image is detected by using the first image detection unit 200A and the second image detection unit 200B. Suppose.

For example, it is assumed that only the first image detection unit 200A out of the three image detection units 200 is not selected as the image detection unit 200 used for image detection. In this case, the control unit 101 changes the position of the intermediate transfer belt 421 to form the patch image according to the selection result. Specifically, the control unit 101 controls the image forming unit 40 so as to form a patch image at a position corresponding to the second image detecting unit 200B and the third image detecting unit 200C.

As a result, the usable image detection unit 200 can be effectively utilized, and the number of times the patch image is detected can be reduced as a whole.

Further, when the tilt patch image is formed on the intermediate transfer belt 421 and the tilt of the image on the intermediate transfer belt 421 is detected by using the image detection unit 200, the control unit 101 determines the tilt of the image based on the selection result. The image detection unit 200 to be detected is selected.

For example, when only the first image detection unit 200A of the three image detection units 200 is not selected as the image detection unit 200 used for image detection, the control unit 101 serves as the image detection unit 200 for detecting the tilt of the image. , The second image detection unit 200B and the third image detection unit 200C are selected.

By doing so, the tilt of the image can be reliably detected.

Further, the control unit 101 selects an image detection unit 200 that detects the inclination of the image based on the distance of each image detection unit 200. Specifically, the control unit 101 selects the two image detection units 200 having the longest distance from the three image detection units 200. In the example shown in FIG. 8, the first image detection unit 200A and the second image detection unit 200B are selected.

By doing so, it is possible to easily detect the deviation amount of the tilt patch image, and it is possible to improve the detection accuracy of the tilt of the image.

Further, in the above embodiment, the control unit 101 constitutes the selection unit and the tilt detection unit, but the present invention is not limited to this, and the selection unit and the tilt detection unit are provided separately from the control unit. May be. If it is not necessary to detect the tilt, it is not necessary to provide the tilt detection unit.

Further, in the above embodiment, the two image detection units 200 sandwich the center line C, but the present invention is not limited to this, and all the image detection units are arranged on only one side with respect to the center line C. It may have been done.

Further, in the above embodiment, the image detection unit 200 is provided inside the transfer region R, but the present invention is not limited to this, and the image detection unit may be provided outside the transfer region R. ..

Further, in the above embodiment, the two image detection units 200 are arranged at the same position in the transport direction of the intermediate transfer belt 421, but the present invention is not limited to this, and the two image detection units 200 are not arranged at the same position. Is also good.

Further, in the above embodiment, the intermediate transfer belt 421 is exemplified as an image carrier, but the present invention is not limited to this, and as long as the image carrier conveys an image toward the transfer nip, other than the intermediate transfer belt. The image carrier may be used. Further, not only the image carrier that comes into contact with the recording medium at the transfer nip such as the intermediate transfer belt, but also indirectly with the recording medium via the intermediate transfer belt at the transfer nip such as the photoconductor drum shown in FIG. It may be an image carrier that comes into contact with the image carrier.

In addition, the above embodiments are merely examples of embodiment of the present invention, and the technical scope of the present invention should not be construed in a limited manner by these. That is, the present invention can be implemented in various forms without departing from its gist or its main features.

1 Image forming device 40 Image forming unit 101 Control unit 200 Image detection unit 200A First image detection unit 200B Second image detection unit 421 Intermediate transfer belt C Center line R Transfer area

Claims (10)

An image carrier that carries an image to be transferred to a recording medium and conveys the image toward a transfer nip, and an image carrier.
Two or more image detection units that are arranged facing the image carrier at different positions in the width direction of the image carrier and detect an image on the surface of the image carrier.
Equipped with
The two or more image detection units are arranged at positions where the distances of the transfer regions corresponding to the transfer nips of the image carrier to the center line in the width direction are different.
Image forming device. Based on the widthwise distance between the widthwise end of the transfer region and the image detection section, the image on the surface of the image carrier is detected from among the two or more image detection sections. A selection unit for selecting an image detection unit is provided.
The image forming apparatus according to claim 1. The selection unit does not select an image detection unit in which the widthwise distance between the widthwise end of the transfer region and the image detection unit is within a predetermined distance, and the image whose distance is larger than the predetermined distance. Select the detector,
The image forming apparatus according to claim 2. The distance difference between the two image detection units included in the two or more image detection units is larger than twice the predetermined distance.
The image forming apparatus according to claim 3. A tilt detection unit for detecting the tilt of an image on the image carrier using two image detection units is provided.
The tilt detection unit does not detect the tilt of the image when at least one of the two image detection units is an image detection unit that is not selected by the selection unit.
The image forming apparatus according to any one of claims 2 to 4. The tilt detection unit selects an image detection unit that detects the tilt of the image from the two or more image detection units based on the selection result of the selection unit.
The image forming apparatus according to claim 5. A patch image forming unit for forming a patch image to be read by the image detecting unit on the image carrier is provided.
The patch image forming unit changes the position of forming the patch image on the image carrier according to the selection result of the selection unit.
The image forming apparatus according to any one of claims 2 to 6. The patch image forming unit forms the patch image on the image carrier so that the number of times the patch image is detected in one image detecting unit is changed based on the selection result of the selection unit.
The image forming apparatus according to claim 7. The two or more image detection units are arranged at the same position in the transport direction of the image carrier.
The image forming apparatus according to any one of claims 1 to 8. The recording medium is continuous paper.
The image forming apparatus according to any one of claims 1 to 9.

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