JP2010002492A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus capable of using paper more effectively. <P>SOLUTION: The image forming apparatus 1 includes: a detecting section 80 that detects presence or absence of an existing image formed on the image forming side of paper A; and a control section 90 that recognizes, based on the result of the detection by the detecting section 80, an empty area where a part with no existing image continues, then calculates the ratio of the empty area to the paper A, and controls an image forming section 30 so that an image formed on the paper A is reduced based on the ratio and this image is formed in the empty area. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an image forming apparatus.

In recent years, as one method of activities for protecting the environment, effective use of transfer paper (hereinafter referred to as paper) used in an image forming apparatus has been demanded. As one method of effectively utilizing the paper, there is a utilization of a so-called back paper, in which an image is already formed on one side of the paper but an image is not formed on the other side. In the following description, a surface on which an existing image is formed on both sides of the backing paper is a printing surface, and a surface on which no image is printed is a non-printing surface. As an image forming apparatus for utilizing the non-printing side of the back paper, for example, a configuration in which both the front and back sides are read by a sensor after paper feeding and marking is performed on the back side (for example, Patent Document 1), and marking for back side judgment is performed. In such a case, a configuration is known in which the layout of the mark image is adjusted or reduced to secure a printing space on the back surface (for example, Patent Document 2).
JP 10-97112 A JP-A-8-237398

However, in the conventional image forming apparatus, there are cases in which effective use of paper cannot be sufficiently performed.
For example, when an existing image formed on the printing surface is within a small range with respect to the entire sheet, most of the surface is an area where no image is formed (hereinafter referred to as a blank area). Such a printing surface may be reused as a sheet for newly forming an image. However, in a conventional image forming apparatus using a backing paper, the printing surface is treated as a printing surface regardless of the number of blank areas and is not utilized. Therefore, the conventional image forming apparatus cannot effectively use a printing surface having many blank areas.

  SUMMARY An advantage of some aspects of the invention is that it provides an image forming apparatus capable of more effectively using paper.

  According to the first aspect of the present invention, a detection unit that detects whether or not an image is formed on an image forming surface of a fed paper, an image forming unit that forms an image on the paper, and detection by the detection unit Based on the result, a blank area on the image forming surface of the sheet is recognized, a ratio of the recognized blank area to the entire sheet is calculated, and image data with a reduction ratio corresponding to the calculated ratio is obtained. And a control unit that controls the image forming unit so as to form an image in the blank area based on the generated image data.

  According to a second aspect of the present invention, in the image forming apparatus according to the first aspect, when the ratio of the blank area to the entire sheet is smaller than a preset threshold value, the control unit applies the blank area to the blank area. Image formation is stopped.

  According to a third aspect of the present invention, in the image forming apparatus according to the first or second aspect, the detection unit is an optical sensor directed to an image forming surface of the paper, and the paper feed tray of the paper and the image forming It is provided in the paper conveyance path between the two parts.

  According to a fourth aspect of the present invention, in the image forming apparatus capable of forming images on both front and back sides of a sheet, the detection unit that detects whether images are formed on both the front and back sides of the fed paper, Based on the detection result of the image forming unit that forms images on both the front and back sides of the paper and the detection unit, the blank areas on both the front and back sides of the paper are recognized, and the recognized blank areas are all over the paper. Calculates the proportion of the image, generates image data with a reduction ratio corresponding to the calculated proportion, and controls the image forming unit to form an image in each of the blank areas based on the generated image data And a control unit.

  According to a fifth aspect of the present invention, in the image forming apparatus according to the fourth aspect, when the ratio of the blank area to the entire sheet is smaller than a preset threshold value, the control unit applies the blank area to the blank area. Image formation is stopped.

  According to a sixth aspect of the present invention, in the image forming apparatus according to the fourth or fifth aspect, the detection unit is an optical sensor directed to an image forming surface of the paper, and the paper feed tray of the paper and the image forming It is provided in the paper conveyance path between the two parts.

  According to a seventh aspect of the present invention, in the image forming apparatus according to the sixth aspect, the optical sensors are individually provided on both the front and back sides of the sheet.

  According to an eighth aspect of the present invention, in the image forming apparatus according to the sixth aspect, after the image is formed on one surface of the paper, the image is formed on the other surface of the paper so that the image is formed on the other surface. A double-sided conveyance unit that conveys the sheet from the paper feed tray to the image forming unit, and the detection unit is provided in a path that overlaps the conveyance path of the sheet by the double-sided conveyance unit. It is characterized by being able to.

  According to the present invention, it is possible to provide an image forming apparatus capable of more effectively using paper.

(First embodiment)
Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a schematic cross-sectional configuration diagram of an image forming apparatus 1 according to the first embodiment.
The image forming apparatus 1 includes paper feeding trays 11 and 12 that can store paper A, paper feeding units 15 and 15 that pull out the paper A one by one from the paper feeding trays 11 and 12, and an image forming unit that will be described later. The image forming unit 30 that transfers an image to the paper A, the fixing unit 45 that fixes the image transferred to the paper A, and the paper A are discharged above the paper discharge receiving unit 2. Alternatively, a paper discharge unit 50 that transports the paper A to the reversing unit 60 described later, a reversing unit 60 that transports the paper A while changing the orientation when forming images on both sides of the paper A, and an existing one formed on the paper A. And a detection unit 80 for detecting the presence or absence of an image.

  The “image” includes characters, figures, symbols, photographs, and all other images. “Paper” includes not only paper but also all recording media capable of image formation by an OHP film or other image forming apparatus.

  The paper feed tray 11 is provided so that it can be pulled out from the side of the image forming apparatus 1. With the paper feed tray 11 pulled out, the paper A is placed from above and the paper feed tray 11 is set in the image forming apparatus 1, whereby the paper feeding operation of the paper A by the paper feed unit 15 becomes possible. The paper feed tray 11 has a raised bottom portion (not shown) on the bottom surface on which the paper A is placed, and when the paper feed tray 11 is set, the raised bottom portion on which the paper A is placed moves up. Accordingly, the upper surface of the uppermost sheet A among the plurality of sheets A stored in the sheet feed tray 11 comes into contact with the movable roller 16 of the sheet feeding unit 15. The paper feed tray 12 is the same as the paper feed tray 11.

The sheet feeding unit 15 includes a movable roller 16 having a rotation shaft that can move up and down, and a fixed roller 17 to which the rotation shaft is fixed. The movable roller 16 and the fixed roller 17 are driven to rotate by a driving unit (not shown) such as a motor.
The movable roller 16 contacts the upper surface of the uppermost sheet A among the plurality of sheets A stored in the sheet feed trays 11 and 12 as described above. When the movable roller 16 in contact with the paper A is rotationally driven, the paper A is pulled out one by one to the fixed roller 17 side. The fixed roller 17 sandwiches the paper A in cooperation with a roller 18 provided at a position facing the paper A drawn by the movable roller 16, and conveys the paper A by being driven to rotate.

  The paper A drawn out and conveyed by the paper supply unit 15 is conveyed to the image forming unit 30 by the conveyance rollers 21 and 21 of the conveyance unit 20. The transport rollers 21 and 21 are a pair of rollers provided at positions facing each other across the transport path of the paper A, and transport the paper A by being rotationally driven by a driving unit (not shown) such as a motor.

  The image forming unit 30 includes an intermediate transfer belt 31 as an intermediate transfer member, a secondary transfer driving roller 32 that stretches the intermediate transfer belt in cooperation with the tension roller 33 and drives the intermediate transfer belt 31, and each color (cyan). , Magenta, yellow, and black) toner drums 34C, 34M, 34Y, and 34K, and the intermediate transfer belt 31 between the photosensitive drums and the respective photosensitive drums are provided to the intermediate transfer. A platen roller 35 that transfers to the belt 31, a transfer roller 36 that transfers toner to the paper A, and a cleaning unit 41 that cleans the secondary transfer belt 31 are provided.

  In the vicinity of the photosensitive drums 34C, 34M, 34Y, and 34K, charging units 37C, 37M, 37Y, and 37K that perform charging processing on the photosensitive drums, and exposure units 38C, 38M, 38Y, and 38K that perform exposure processing on the photosensitive drums, respectively. Cleaning units 40, 40, 40, 40 for cleaning the toner cartridges 39C, 39M, 39Y, 39K for the respective colors and the respective photosensitive drums are provided. The secondary transfer drive roller 32 and each photosensitive drum are driven to rotate by a drive unit (not shown) such as a motor.

  Hereinafter, transfer of the toner image onto the paper A by the image forming unit 30 will be described using the photosensitive drum 34K as an example. First, a process in which the photosensitive drum 34K is charged by the charging unit 37K in the vicinity of the photosensitive drum 34K and the exposed portion of the photosensitive drum 34K is neutralized by exposure of the photosensitive drum by the exposure unit 38K, so-called development processing is performed. By the development processing, the toner of the toner cartridge 39K is carried on the photosensitive drum 34K. The development process is performed based on the image to be formed. The other photosensitive drums 34C, 34M, and 34Y are similarly developed.

  The intermediate transfer belt 31 is operated by driving the secondary transfer driving roller 32, and the toner carried on each photosensitive drum is transferred to the intermediate transfer belt 31 by the platen roller 35 (primary transfer). The intermediate transfer belt 31 carries toner by the primary transfer. At this time, the toners of the respective colors are transferred so as to overlap each other to form one image. The toner carried on the intermediate transfer belt 31 is transferred to the paper A at a position where the paper A is sandwiched between the intermediate transfer belt 31 and the transfer roller 36 (secondary transfer). In this manner, the toner image is transferred onto the paper A. Along with the transfer of the toner image onto the paper A, the paper A is conveyed to the fixing unit 45 by the operation of the secondary transfer belt 31 and the cooperation of the transfer roller 36. Each photosensitive drum after the primary transfer is cleaned by a cleaning unit 40 in the vicinity of each photosensitive drum, and the secondary transfer belt 31 after the secondary transfer is cleaned by the cleaning unit 41 for residual toner that has not been transferred.

The fixing unit 45 heats the sheet A to fix the toner transferred to the sheet A, and is provided at a position facing the fixing roller 46 across the conveyance path of the sheet A. And a pressure roller 47 that is brought into pressure contact with 46.
The sheet A on which the toner has been transferred by the image forming unit 30 is conveyed to the fixing unit 45 and guided between the fixing roller 46 and the pressure roller 47. The fixing roller 46 has a heat source (for example, a coil or a halogen lamp) inside, and the sheet A is heated by the heat source to perform a fixing process. At this time, the pressure roller 47 presses the paper A against the fixing roller 46. The fixing roller 46 and the pressure roller 47 convey the paper A upward by the rotational movement of the paper A together with the fixing process.

  The paper discharge unit 50 includes a paper discharge roller 51 that is rotationally driven by a drive unit (not shown) such as a motor, and a roller 52. The paper discharge roller 51 is driven to rotate, and discharges the paper A on which image formation has been completed above the paper discharge receiving portion 2. In the case where the image is formed on both sides of the sheet A and only the image formation on one side is completed, the sheet discharge roller 51 is rotationally driven to convey the sheet A to the reversing unit 60.

  The reversing unit 60 includes a plurality of paired transport rollers 61 and 61 provided at positions facing each other across the transport path of the paper A, and is arranged so that the paper A is transported between the respective transport rollers. Is done. Each conveyance roller 61, 61 is rotationally driven by a drive unit (not shown) such as a motor. As a result, the sheet A conveyed to the reversing unit 60 is returned to the conveying path provided with the conveying rollers 21 and 21, and the surface of the sheet A on which the image is not yet formed is directed to the image forming unit 30 side. It is guided to face (hereinafter referred to as paper reversal). The paper A returned to the conveyance path provided with the conveyance rollers 21 and 21 by the conveyance of the reversing unit 60 is again transferred and fixed through the image forming unit 30 and the fixing unit 45 and discharged by the discharge unit 50. The paper is discharged above the paper receiver 2. That is, the image forming apparatus 1 is an image forming apparatus that enables image formation on both sides of the paper A.

  The paper A can also be fed from the external paper feed unit 70. The paper A is placed on the external paper feed tray 71, pulled in by a paper feed roller 72 driven by a drive unit (not shown) such as a motor, and transported to the transport unit 20.

FIG. 2 is an enlarged cross-sectional configuration diagram showing the vicinity of the paper feeding unit 15. As shown in FIG. 2, a detection unit 80 is provided in the vicinity of the conveyance path of the paper A from the paper supply unit 15 that pulls out the paper A from the paper supply tray 11 to the conveyance unit 20.
FIG. 3 is an enlarged configuration diagram showing the detection unit 80 viewed from the direction of arrow B in FIG. The detection unit 80 includes a plurality of light emitting elements 81 that emit light and a plurality of light receiving elements 82 that detect light and convert the intensity of the light into a signal. The plurality of light emitting elements 81 and the plurality of light receiving elements 82 are arranged substantially perpendicular to the conveyance direction C of the paper A and parallel to the paper width D direction along the surface of the paper A. As shown in FIG. 2, the rays of light emitted from the light emitting element 81 are reflected by the paper A and arranged so as to be detected by the light receiving element 82. The intensity of the light detected by the light receiving element 82 varies depending on the presence or absence of an image formed on the paper A irradiated with the light from the light emitting element 81. Therefore, based on a signal indicating the intensity of light detected by the light receiving element 82, it is possible to determine the presence or absence of an existing image on the surface on which the image of the paper A is formed (hereinafter referred to as an image forming surface).

  The length of the array in the width D direction of the plurality of light emitting elements 81 and the plurality of light receiving elements 82 is sufficient for the width D of the maximum sheet A that can be used in the image forming apparatus 1 by the light detection range of the light receiving elements 82. It is provided so that it can be covered. The entire sheet A is conveyed from the sheet feeding unit 15 to the conveyance unit 20, thereby receiving the light irradiation of the light emitting element 81 and the light detection process of the light receiving element 82 as a whole. Hereinafter, the process of the detection unit 80 for the image forming surface of the paper A is referred to as a scan process.

  FIG. 4 shows a functional block diagram of the image forming apparatus 1. The image forming apparatus 1 stores a control unit 90 that controls the operation of each unit of the image forming apparatus 1, a communication unit 110 that communicates with an external device, and image data that is formed on the paper A by the image forming apparatus 1. An image memory 120, a display unit 130 for displaying various information related to the image forming apparatus 1, and an operation unit 140 for performing various input operations on the image forming apparatus 1.

The control unit 90 includes a paper feeding unit 15, a conveyance unit 20, an image forming unit 30, a fixing unit 45, a discharge unit 50, a reversing unit 60, an external paper feeding unit 70, a detection unit 80, a communication unit 110, an image memory 120, a display. The unit 130 and the operation unit 140 are connected to each other via the bus 150, and each unit is controlled based on the input of each unit to control the operation of the image forming apparatus 1.
The control unit 90 includes a CPU 91, a RAM 92, a ROM 93, etc., which are connected to each other by a bus 94. The control unit 90 controls the operation of the image forming apparatus 1 by so-called software processing in which software corresponding to the processing content is called from the ROM 93 or the like, loaded into the RAM 92, and executed.

The communication unit 110 includes an interface (for example, a NIC (Network Interface Card) or the like) that can be connected to an external device (for example, a PC), and enables communication between the image forming apparatus 1 and the external device. For example, image data transmitted from a PC or the like is received by the image forming apparatus 1 via the communication unit 110 and stored in the image memory 120.
The image memory 120 is a storage area for storing image data to be formed on the paper A by the image forming apparatus 1, and includes a storage device (for example, a volatile memory).

  The operation unit 140 is configured to perform various input operations on the image forming apparatus 1, and is, for example, an input device using a plurality of keys and buttons, a touch panel device provided integrally with the display unit 130, or the like. Via the operation unit 140, the user of the image forming apparatus 1 can perform input operations such as various settings related to the image forming apparatus 1.

  Next, processing related to image formation on the paper A on which an existing image is formed will be described. The control unit 90 recognizes the blank area of the paper A based on the signal indicating the intensity of light detected by the light receiving element 82 of the detection unit 80, calculates the ratio of the blank area to the paper A, and based on the ratio. The image forming unit 30 is controlled so as to reduce the image formed on the paper A and form an image in the blank area. Hereinafter, the control will be described in detail.

FIG. 5 shows a plan view of an example of the paper A on which the existing images E and F are formed. In FIG. 5, FIG. 6 and the following description, the traveling direction side of the paper A is the up direction, the opposite side is the down side, and the direction orthogonal to the transport direction C is the left-right direction.
As shown in FIG. 5, when the existing image E is formed on the upper part of the paper A and the existing image F is formed on the lower part of the paper A, the light receiving element of the detection unit 80 for the portions where the existing images E and F are formed. The intensity of the light detected by 82 is different from the blank portion G of the paper A. The controller 90 determines existing images E and F on the paper A from the intensity of the light. Then, the control unit 90 recognizes a continuous rectangular area H between the existing images E and F as a blank area among the areas G of the paper A on which the images E and F of the paper A are not formed. At this time, as shown in FIG. 5, a predetermined interval I (for example, 10 mm) may be provided between the existing images E and F and the region H.

  When there is only the existing image E, the control unit 90 regards a continuous rectangular portion among the blank paper portions below the existing image E as a blank area. When there is only the existing image F, the control unit 90 regards a continuous rectangular portion of the blank paper portion above the existing image E as a blank area.

  When the area H is recognized as a blank area, the control unit 90 calculates the ratio of the vertical width H1 of the area H to the vertical width A1 of the paper A (hereinafter referred to as the vertical ratio) and also the horizontal direction of the paper A. The ratio of the width H2 in the left-right direction of the region H to the width A2 (hereinafter referred to as the left-right ratio) is calculated.

When the vertical ratio and the horizontal ratio are calculated, the control unit 90 calculates a reduction ratio of the image based on the smaller ratio, and performs reduced image data generation processing for reducing the image formed on the paper A.
In addition to the reduction control, the control unit 90 also controls an image forming position for forming a reduced image at a position in the area H of the paper A. As a result, the image transferred to the paper A by the image forming unit 30 is reduced and formed in the area H which is a blank area.

  Depending on the relationship between the size of the blank area and the size of the image to be formed, the control unit 90 forms an image with no reduction ratio, that is, no reduction at all. For example, there may be a case where an existing image is not formed on the paper P or a case where an unreduced image fits in a blank area.

  When the image reduction ratio is less than a predetermined threshold (for example, 10 [%]) when the image reduction ratio is formed on the entire sheet A, the control unit 90 stops image formation on the blank area of the sheet A, The image control unit 30 is controlled not to form an image in the blank area. In this case, an image is not formed on the image forming surface of the paper A and is discharged. In the comparison between the reduction ratio and the threshold, whether the determination criterion for stopping image formation is equal to or less than the threshold (threshold ≧ reduction ratio) or less than the threshold (threshold> reduction ratio) may be changed as appropriate. .

FIG. 6 shows a plan view of an example of paper A on which an existing image J different from FIG. 5 is formed.
As shown in FIG. 6, when the existing image J is formed on the paper A, the control unit 90 recognizes the areas K and L as blank areas individually. At this time, the control unit 90 controls the image forming unit 30 so as to form an image on a blank region having the largest area among the regions K and L that are individually recognized as blank regions. The same applies when three or more areas are recognized as blank areas.

  When a plurality of areas are recognized as blank areas, it can be changed as appropriate to which area the image is formed. For example, not only the size of the area but also the area where the largest image can be formed based on the vertical and horizontal ratios of the areas, that is, the blank area where the reduction ratio can be reduced may be used.

  Further, the intensity of light detected by the light receiving element 82 of the detection unit 80 may change depending on the color, gloss, etc. of the paper A, but the control unit 90 determines the determination criterion of the signal recognized as an existing image on the paper. It may be changed as appropriate according to the color, gloss, etc. of A. Settings based on the color, gloss, and the like of the paper A may be provided so as to be changed by the operation unit 140 or the like. The predetermined threshold may be set and changed by the operation unit 140 or the like.

Next, the operation of the image forming apparatus 1, particularly the processing at the time of image formation for the blank area of the paper A will be described with reference to the flowchart of FIG. 7.
The control unit 90 drives the drive motor of each unit to operate each unit. As a result, the paper feed unit 15 operates, and the paper A is pulled out from the paper feed tray 11. The control unit 90 operates the detection unit 80, and scans the entire image forming surface of the paper A by the detection unit 80 while the paper A is conveyed from the paper supply unit 15 to the conveyance unit 20 (step S1). Next, the controller 90 recognizes a blank area based on the signal from the light receiving element 82 of the detector 80 (step S2). At this time, when there are a plurality of blank areas (step S3: YES), the control unit 90 individually calculates the areas of the plurality of blank areas (step S4), and selects the blank area having the largest area among the plurality of blank areas. The image is to be formed (step S5). After step S5 or when there is one blank area (step S3: NO), the control unit 90 calculates the vertical ratio and horizontal ratio of the blank area, and calculates the reduction ratio of the image formed in the blank area (step S3). S6). At this time, it is determined whether or not the reduction ratio is equal to or greater than a predetermined threshold (for example, 10 [%]) (step S7). If it is equal to or greater than the predetermined threshold (step S7: YES), the control unit 90 generates reduced image data based on the reduction ratio calculated in step S6 (step S8), and forms an image based on the reduced image data in a blank area. The image forming unit 30 is controlled (step S9). If it is less than the predetermined threshold (step S8: NO), the controller 90 stops image formation (step S10). After step S9 or step S10, the paper A passes through the fixing unit 45 and the paper discharge unit 50 and is discharged above the paper discharge receiving unit 2 (step S11).

  In the present embodiment, the detection unit 80 is provided in the vicinity of the paper feed unit 15 that pulls out the paper A from the paper feed tray 11, but may be in another position. For example, a similar arrangement may be provided in the vicinity of the paper feed unit 15 that pulls out the paper A from the paper feed tray 12. You may provide in the vicinity of each of the two paper supply parts 15 and 15. It may be provided toward the image forming surface of the paper A in the vicinity of the transport path from the paper feed roller 72 to the transport unit 20.

  As shown in FIGS. 1 and 2, when the image forming apparatus 1 is provided with the detection unit 80 only in the vicinity of the paper supply unit 15 that pulls out the paper A from the paper supply tray 11, for example, an existing image is stored in the paper supply tray 11. There is an operation method in which the formed paper A is stored as the paper A on which no existing image is formed in the paper feed tray 12. As a result, the paper A on which the existing image is formed is scanned by the detecting unit 80 to control the image forming process for the blank area, and the paper A on which the existing image is not formed is controlled. It is possible to perform a normal image forming process by omitting the scan process.

  Settings related to control of scan processing by the detection unit 80 and image formation processing based on the presence or absence of an existing image may be input via the operation unit 140. Examples of the setting include setting a predetermined threshold value for a reduction rate at which image formation is not performed, whether or not to perform control of image formation processing based on the presence or absence of scan processing and existing images, and the like.

  As described above, according to the first embodiment, the control unit 90 recognizes the blank area of the paper A based on the detection result of the detection unit 80 and calculates the ratio of the blank area to the paper. Then, the control unit 90 controls the image forming unit 30 to reduce the image based on the ratio and form an image in the blank area. Thereby, for example, an image can be formed in a blank area on the printing surface of the paper. Therefore, it is possible to provide an image forming apparatus that can make more effective use of paper.

  Further, the control unit 90 controls the image forming unit 30 not to form an image in the blank area when the reduction ratio of the image to be formed is below a predetermined threshold. When an image with a high reduction ratio is formed in a small blank area, it may be difficult to interpret characters included in the image, or part or all of the image may be crushed or the details may be impaired. By controlling not to form an image in a blank area where 90 is below a predetermined threshold, it is possible to prevent such an image with a high reduction ratio from being formed. Therefore, it is possible to provide an image forming apparatus capable of achieving both effective use of paper and good image formation.

  Further, the detection unit 80 is provided toward the image forming surface of the paper A in the vicinity of the transport path for transporting the paper A from the paper feed tray 11 to the image forming unit 30. As a result, the paper A is pulled out from the paper feed tray 11 and conveyed, and scanning processing by the detection unit 80 can be performed.

(Second Embodiment)
Next, a second embodiment different from the first embodiment will be described. In addition, about the structure similar to 1st Embodiment, the same code | symbol is attached | subjected and description is abbreviate | omitted.
FIG. 8 is an enlarged cross-sectional configuration diagram in the vicinity of the paper feeding unit 15 of the image forming apparatus according to the second embodiment. As shown in FIG. 8, the image forming apparatus according to the second embodiment includes two detection units 80. The two detection units 80 are provided at positions facing each other across the conveyance path through which the paper A is conveyed from the paper supply unit 15 to the conveyance unit 20, and the paper A passes between the two detection units 80 when the paper A is conveyed. Pass through. The two detection units 80 are provided toward different sides of the paper A, and perform scanning processing on the different sides. As a result, the scanning process for both sides of the paper A can be performed.

  The image forming apparatus according to the second embodiment has the same configuration as that of the first embodiment except for the configuration other than the two detection units 80 shown in FIG. The control unit 90 recognizes a blank area for each side of the paper A, calculates a reduction ratio, and controls the image forming unit 30 based on the scanning processing on both sides of the paper A by the two detection units 80.

  Next, of the operations of the image forming apparatus according to the second embodiment, processing when images are formed on both sides of the paper A will be described with reference to the flowchart of FIG. In FIG. 9 and the following description, a surface on which an image is formed after the paper A is returned to the transport unit 20 through the reversing unit 60 is a back surface, and a surface opposite to the back surface is a front surface.

  The control unit 90 drives the drive motor of each unit to operate each unit. As a result, the paper feed unit 15 operates, and the paper A is pulled out from the paper feed tray 11. The control unit 90 operates the detection unit 80, and scans the entire image forming surface of the paper A by the detection unit 80 while the paper A is conveyed from the paper supply unit 15 to the conveyance unit 20 (step S21). Next, the control unit 90 recognizes a blank area based on the signal from the light receiving element 82 of the detection unit 80 (step S22). At this time, when there are a plurality of blank areas (step S23: YES), the control unit 90 individually calculates the areas of the plurality of blank areas (step S24), and selects the blank area having the largest area among the plurality of blank areas. The image is to be formed (step S25). After step S25 or when there is one blank area (step S23: NO), the controller 90 calculates the vertical ratio and the horizontal ratio of the blank area, and calculates the reduction ratio of the image formed in the blank area (step S23). S26). The processes in steps S21 to S26 are individually performed on both the front and back surfaces of the paper A.

  After step S26, it is determined whether the reduction ratio of the surface is equal to or greater than a predetermined threshold (for example, 10 [%]) (step S27). If it is equal to or greater than the predetermined threshold (step S27: YES), the control unit 90 generates reduced image data based on the reduction ratio of the surface calculated in step S26 (step S28), and converts the image based on the reduced image data into a blank on the surface. The image forming unit 30 is controlled to form in the region (step S29). If it is less than the predetermined threshold (step S28: NO), the controller 90 stops the image formation on the surface (step S30). After step S29 or step S30, it is determined whether or not the reduction ratio of the back surface is equal to or greater than a predetermined threshold (for example, 10 [%]) (step S31). If it is equal to or greater than the predetermined threshold (step S31: YES), the control unit 90 controls the drive of the paper discharge roller 51 of the paper discharge unit 50 to convey the paper A to the reversing unit 60 and reverse the paper (step) (S32), reduced image data based on the reduction ratio of the back surface calculated in step S26 is generated (step S33), and the image forming unit 30 is controlled to form an image based on the reduced image data in the blank area on the back surface (step S34). ). If it is less than the predetermined threshold value in step S31 (step S31: NO), the controller 90 stops the image formation on the back surface (step S35). After step S34 or step S35, the paper A is discharged above the paper discharge receiving portion 2 (step S36).

  As described above, according to the second embodiment, in addition to the operational effects of the first embodiment, the presence or absence of an existing image by the two detection units 80 is separately detected on both sides of the paper A. Thereby, for example, even when an existing image is formed on both sides of the paper A, it is possible to form an image with a reduction ratio corresponding to the blank area on each side of the paper A.

  Further, the detection unit 80 is individually provided toward each of both surfaces of the paper A in the vicinity of the conveyance path for conveying the paper A from the paper feed tray 11 to the image forming unit 30. As a result, the paper A is pulled out from the paper feed tray 11 and conveyed, and the scanning processing by the two detection units 80 can be performed in parallel on both sides.

  The embodiment of the present invention should be considered that the embodiment disclosed this time is illustrative and not restrictive in all respects. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  For example, in the first embodiment, the position where the detection unit 80 is provided may be the position of the sheet A as indicated by the arrow M in FIG. In this case, the front surface of the paper A pulled out from the paper supply unit 15 and transported to the transport unit 20 and the back surface of the paper A reversed by the reversing unit 60 may be subjected to a scanning process by one detection unit 80. It becomes possible. In this case, the interval of the conveyance path from the position where the detection unit 80 is provided to the position where the sheet A is transferred by the image forming unit 30 is equal to or greater than the maximum width in the direction along the conveyance direction C of the sheet A. It is desirable. In addition, the image forming apparatus 1 takes time for the control unit 90 to recognize the blank area, calculate the reduction ratio, and control the image forming unit 30 based on the time until the toner image is transferred after the scanning process. It is conceivable to have a configuration for obtaining. For example, a configuration in which the time is taken into consideration for an interval from a position where the detection unit 80 is provided to a position where the paper A is transferred by the image forming unit 30, or a conveyance speed of the paper A by the conveyance unit 20. A configuration for performing control or suspension, a configuration for improving the processing speed performance of the control unit 90, and the like can be given.

  In addition, the image formation by the image forming unit is not limited to the transfer of toner, but may be performed by, for example, an inkjet method or other methods capable of forming an image on paper.

1 is a schematic cross-sectional configuration diagram of an image forming apparatus according to a first embodiment. FIG. 3 is an enlarged cross-sectional configuration diagram showing the vicinity of a paper feed unit. It is an enlarged block diagram which shows the detection part seen from the arrow B direction of FIG. 2 is a functional block diagram of the image forming apparatus. FIG. It is a top view of an example of the paper with which the existing image was given. FIG. 6 is a plan view of an example of a sheet on which an existing image different from FIG. 5 is applied. 6 is a flowchart illustrating processing during image formation for a blank area of a sheet. FIG. 6 is an enlarged cross-sectional configuration diagram in the vicinity of a sheet feeding unit of an image forming apparatus according to a second embodiment. FIG. 10 is a flowchart illustrating processing in a case where an image is formed on both sides of a sheet of the operation of the image forming apparatus according to the second embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 Paper feed tray 15 Paper feed part 20 Conveyance part 30 Image formation part 40 Fixing part 50 Paper discharge part 60 Inversion part 80 Detection part 81 Light emitting element 82 Light receiving element 90 Control part 110 Communication part 120 Image memory 130 Display part 140 Operation part

Claims (8)

A detection unit for detecting whether an image is formed on the image forming surface of the fed paper;
An image forming unit for forming an image on the paper;
Based on the detection result of the detection unit, the blank area on the image forming surface of the sheet is recognized, the ratio of the recognized blank area to the entire sheet is calculated, and the reduction according to the calculated ratio is performed. A control unit that generates image data of a rate and controls the image forming unit to form an image in the blank area based on the generated image data;
An image forming apparatus comprising:   The image forming apparatus according to claim 1, wherein the control unit stops image formation in the blank area when a ratio of the blank area to the entire sheet is smaller than a preset threshold value. .   2. The detection unit is an optical sensor directed to an image forming surface of the sheet, and is provided in a sheet conveyance path between the sheet feeding tray and the image forming unit. Or the image forming apparatus according to 2; In an image forming apparatus capable of forming images on both front and back sides of paper,
A detection unit for detecting whether or not images are formed on both the front and back sides of the fed paper;
An image forming unit that forms images on both front and back sides of the paper;
Based on the detection result of the detection unit, the blank areas on both the front and back sides of the sheet are recognized, the ratio of the recognized blank areas to the entire sheet is calculated, and the ratio corresponding to the calculated ratio is calculated. A control unit that generates image data of a reduction ratio and controls the image forming unit to form an image in each of the blank areas based on the generated image data;
An image forming apparatus comprising:   The image forming apparatus according to claim 4, wherein the control unit stops image formation in the blank area when a ratio of the blank area to the entire sheet is smaller than a preset threshold value. .   5. The detection unit is an optical sensor directed to an image forming surface of the sheet, and is provided in a sheet conveyance path between the sheet feeding tray and the image forming unit. Or the image forming apparatus according to 5.   The image forming apparatus according to claim 6, wherein the optical sensors are individually provided on both front and back sides of the paper. A double-sided transport unit that transports the paper to the image forming unit so as to form an image on the other side of the paper after image formation on one side of the paper;
7. The detection unit according to claim 6, wherein the detection unit is provided in a route in which a conveyance route for conveying the paper from a paper feed tray to the image forming unit overlaps a conveyance route for the paper by the double-side conveyance unit. Image forming apparatus.

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