JP4405872B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus including a paper feeding unit for placing recording paper and an image forming unit for forming an image on the recording paper fed from the paper feeding unit.

Conventionally, image forming with a plurality of paper feed units, such as a paper feed tray that contains a large number of sheets, and a manual feed tray that feeds non-size paper and special paper The device is known.
This image forming apparatus is provided with a paper size detecting means for detecting the paper size stored in each paper feeding unit in each paper feeding unit, and the paper size stored in the paper feeding unit when the paper feeding unit is replaced. Detected and stored in the storage unit of the image forming apparatus. Then, according to the image information read from the scanner or personal computer, the paper feed unit storing the required size paper is automatically selected from the stored paper size information and the paper feed unit is selected. Paper is sent out and an image is formed on the paper.

JP 2001-10151 A JP-A-5-131709

  However, in the conventional image forming apparatus as described above, it is necessary to provide the sheet size detecting means as many as the number of paper feeding units, and there is a problem that the number of parts increases and the cost of the image forming apparatus increases. . On the other hand, as disclosed in Patent Documents 1 and 2, there has been proposed one in which a size detection unit is provided on a carriage having an ink discharge head as an image forming unit. If the proposed technique is applied to an image forming apparatus having a plurality of paper feeding units, the above problem can be solved. However, Patent Documents 1 and 2 only detect the paper size conveyed to a position facing the carriage, and do not include a storage unit that stores paper size information stored in the paper feeding unit. For this reason, it is necessary to detect the paper size each time the paper is transported to check whether the transported paper is a paper corresponding to an image read from a scanner or a personal computer. As a result, there has been a problem that the image forming speed becomes slow.

  The present invention has been made in view of the above problems, and the object of the present invention is to eliminate the need to detect the paper size each time the paper is transported without providing size detection means as many as the number of paper feed units. Another object of the present invention is to provide an image forming apparatus that does not reduce the image forming speed.

In order to achieve the above object, the invention of claim 1 comprises two or more paper feed units for placing recording paper and an ink ejection head having an ejection port for ejecting ink, and reciprocates in the main scanning direction. In the image forming apparatus having an image forming unit that forms an image on a recording sheet fed from the paper feeding unit , the carriage moves when the ink for ink formation is ejected. A size detection unit that is provided downstream of the ejection head with respect to the direction and detects the size of the recording paper; and a storage unit that stores the size information of the recording paper detected by the size detection unit in association with the paper feeding unit. When the image is formed on the recording paper, the size information of the recording paper stored in the storage means is compared with the image size information. If the image size is larger than the size information of the recording paper, the And warning display on Heather performs control for confirming whether to execute printing, and operation detecting means for detecting the operation performed when the recording paper sheet feeding section is exchanged, said operating detecting means The recording paper of the paper feeding unit in which the exchange operation is detected is conveyed to a position facing the carriage, and when the recording paper is conveyed to a position facing the carriage, the carriage is moved and the size detection means A control means for detecting the size of the recording paper and controlling the recording paper size information detected by the size detection means to be stored in the storage means in association with the paper feed unit whose replacement operation is detected by the operation detection means; the is characterized in that it comprises.
Further, the invention of claim 2, the image forming apparatus according to claim 1, said operation detecting means comprises a paper detecting means for detecting the presence or absence of the recording paper sheet feeding section, the recording sheet in the recording sheet detecting means An image forming apparatus that detects a replacement operation by detecting a state with a recording sheet after detecting a state where there is no paper.
According to a third aspect of the present invention, in the image forming apparatus according to the first or second aspect , the operation detection unit includes an attachment / detachment detection unit that detects attachment / detachment of the sheet feeding unit. An image forming apparatus that detects an exchange operation by detecting that a sheet feeding unit is mounted in an image forming apparatus after detecting that the sheet is extracted from the forming apparatus.
According to a fourth aspect of the present invention, in the image forming apparatus according to the first, second, or third aspect , the recording paper size detection is performed when the image formation is performed using the recording paper of the paper feeding unit that has undergone the replacement operation. It is characterized by being performed.
According to a fifth aspect of the present invention, in the image forming apparatus of the first, second, third, or fourth aspect , the recording sheet guides the recording sheet so that the central portion of the recording sheet is positioned at a reference position in the width direction in the apparatus. A guide member is provided, and the paper size is detected by detecting one end of the recording paper by the size detecting means.
According to a sixth aspect of the present invention, in the image forming apparatus of the first, second, third, fourth, or fifth aspect , the image forming apparatus further comprises a position detecting unit that detects the position of the recording paper to be conveyed. It is also used as a means.
According to a seventh aspect of the present invention, in the image forming apparatus according to the first, second, third, fourth, or sixth aspect, an image reading device capable of reading image information is provided, and an image read by the image reading device. Based on the above, an image is formed on a recording sheet.

  According to the first to tenth aspects of the present invention, the size detection means is provided on the conveyance path through which the recording sheets conveyed from the respective sheet feeding sections pass in common, thereby detecting the size of the recording sheets of the plurality of supply sections. The size detection means can also be used. Thereby, the cost increase of the image forming apparatus can be suppressed. In addition, the detection result by the size detection means is stored in association with the paper feed unit. Thus, paper corresponding to the image size can be supplied from the paper feeding unit. As a result, it is not necessary to detect whether the sheet according to the image size is detected by the size detecting unit each time the sheet is transported as in the prior art. Therefore, the image forming speed can be increased as compared with the image forming apparatus that detects the image size every time the conventional sheet is conveyed.

Hereinafter, an image forming apparatus to which the present invention is applied will be described.
First, the basic configuration of the image forming apparatus will be described. FIG. 1 is a front view showing a schematic configuration of the image forming apparatus according to the present embodiment.

  This image forming apparatus can be inserted into and removed from the image forming unit 2 for forming an image and the front side (front side in FIG. 1) of the apparatus main body 1 inside the apparatus main body 1 and a large number of sheets P are stacked. The paper feed cassette 41 is provided. In addition, an image is recorded by the conveyance unit 3 that conveys the sheet P to a position facing the image forming unit 2, the supply unit 5 that supplies the sheet P of the paper feed cassette 41 to the conveyance unit 3, and the image forming unit 2. A paper discharge unit 7 that conveys the paper P to the switching unit 100 is provided. Further, in order to form images on both sides of the sheet, a duplex unit 10 is provided that performs switchback conveyance and conveys the image to the supply unit 5 again. The switching unit 100 includes a reverse conveyance path 70 that conveys the paper P conveyed from the paper discharge unit 7 to the paper discharge tray 8, a straight conveyance path 80 that conveys the straight paper discharge tray 67, and a double-side unit that conveys the double-side unit 10. Switching to one of the transport paths 90 is switched. An image reading unit 11 that reads a document is disposed above the apparatus body 1.

  In addition, the apparatus main body 1 includes a manual feed tray 46 and a paper discharge tray 67. The manual feed tray 46 is provided on the right side of the apparatus main body 1 in the figure and can be turned over with respect to the apparatus main body 1. The paper discharge tray 67 is provided on the left side of the apparatus main body 1 in the drawing, and can be turned over with respect to the apparatus main body 1. The paper P set on the manual feed tray 46 is discharged to the paper discharge tray 67, so that the paper P can be fed and discharged straight.

FIG. 2 is a schematic diagram when the manual feed tray 46 is viewed from the normal direction of the paper surface. As shown in FIG. 2, the manual feed tray 46 is provided with a first side guide member 461a and a second side guide member 461b for positioning the paper P at the center of the manual feed tray. A first rack 463 having teeth 463a formed at the top in FIG. 2 is attached to the first side guide member 461a located on the right side in FIG. 2 in parallel with the paper width direction. Further, a second rack 462 having teeth 462a formed in the lower part in FIG. 2 is attached to the second side guide member 461b in parallel to the paper width direction. And it has the pinion 465 arrange | positioned so that the tooth | gear 463a of the 1st rack 463 and the tooth | gear 462a of the 2nd rack 462 may mesh | engage together. The first rack 463, the second rack 462, and the pinion 465 are provided inside the manual feed tray.
When one of the side guides 461 protruding from the upper surface of the manual feed tray 46 is moved inward in the width direction of the paper P by manual operation, the other side guide 461 can also be moved inward in the width direction by an equal distance. When one side guide 461 is moved outward in the width direction of the paper P by a manual operation, the other side guide 461 can also be moved outward in the width direction by an equal distance. By bringing the side guides 461a and 461b into contact with the paper edges, the skew of the paper P can be prevented and the paper P can be arranged at the center of the tray. As a result, regardless of the size of paper placed on the manual feed tray, the paper can be transported so that the central portion of the paper comes to the central portion of the transport belt 31.

  FIG. 3 is a schematic view of the paper feed tray 41 as viewed from the normal direction of the paper surface. As shown in FIG. 3, a bottom plate 410 is rotatably attached to the bottom of the paper feed tray 41, and sheets are stacked on the bottom plate 410. A compression spring 411 is disposed between the bottom surface of the paper feed tray 41 and the bottom plate 410, and the bottom plate 410 is pushed upward by the spring 411 to press the paper on the top against the separation roller 42, thereby separating it from the uppermost paper. A sheet feeding pressure is generated between the rollers 42. A side guide 412 similar to the manual feed tray 46 is provided on the bottom plate 410. If one of the side guides 412a protruding from the upper surface of the bottom plate 410 is moved inward in the width direction of the paper P by manual operation, the other side guide 412b can also be moved inward in the width direction by an equal distance. Further, when one of the side guides 412a is moved outward in the width direction of the sheet by a manual operation, the other side guide 412b can also be moved outward in the width direction by an equal distance. As a result, no matter what size of paper is placed on the paper feed tray 41, the paper can be transported so that the central portion of the paper comes to the central portion of the transport belt 31.

  The guide mechanism of the paper feed tray is not limited to this, and a side fence may be provided and the position of the side fence may be changed according to the paper size to be exchanged. In this way, it is possible to transport the paper so that the central portion of the paper comes to the central portion of the transport belt 31 regardless of the size of the paper placed on the paper feed tray 41.

  In the above description, the reference position in the width direction in the apparatus is the central portion of the transport belt 31, but is not limited thereto.

  The duplex unit 10 includes a vertical transport unit 101 a having a vertical duplex transport path 90 c for transporting a sheet transported from the duplex unit transport path 90 to the lower side of the main body apparatus 1. Further, it also has a horizontal conveyance unit 101b including a horizontal double-sided conveyance path 90a for conveying the paper conveyed from the vertical double-sided conveyance path 90c in the horizontal direction and a switchback conveyance path 90b.

  The image forming unit 2 includes a carriage 23 and a carriage guide 21 that guides the carriage 23. The carriage 23 is provided with heads 24 each having discharge ports for discharging ink liquids of Y (yellow), M (magenta), C (cyan), and B (black) colors onto a sheet.

  The transport unit 3 includes a transport belt 31, and the transport belt 31 is stretched around the driving roller 32 and the driven roller 33 with appropriate tension. The drive roller 32 is rotationally driven at a predetermined rotational speed by a drive motor (not shown), and accordingly, the transport belt 31 is also rotated at a predetermined speed. In addition, a charging roller 34 for charging the surface of the conveyance belt 31 is provided, and a voltage is applied to the charging roller 34 from a high voltage power source (not shown). In addition, the transport unit 3 includes a guide member (platen) 35 that guides the transport belt 31 in a region facing the image forming unit 2, and a pressing roller 36 that presses the paper P against the transport belt 31 at a position facing the driving roller 32. And.

  The image reading unit 11 includes a first traveling body 15 including a document illumination light source 13 and a mirror 14 for scanning a document (not shown) placed on the contact glass 12, and two mirrors 16. , 17 are disposed so as to be reciprocally movable. Image information scanned by the reading traveling bodies 15 and 18 is read as an image signal into an image reading element 20 such as a CCD installed behind the lens 19. The read image signal is digitized and subjected to image processing. Based on the image-processed signal, the image forming unit 2 forms an image on the paper P.

  The image forming apparatus can receive image data formed by the image forming unit 2 from an external device via a communication cable or a network, and can process the received image data to form an image. Examples of the external device that inputs image data formed by the image forming unit 2 include an information processing device such as a personal computer, an image reading device such as an image scanner, and an imaging device such as a digital camera.

Next, an image forming operation of the image forming apparatus 1 of the present embodiment will be described.
First, a document is set on the contact glass 12 of the image reading unit 11, and a start switch (not shown) is pressed. Then, the first traveling body 15 and the second traveling body 18 travel, and the first traveling body 15 emits light from the light source 13 and further reflects the reflected light from the document surface toward the second traveling body 18. . Reflected light from the document surface directed to the second traveling body 18 is reflected by the mirror of the second traveling body 18 and is input to the image reading element 20 through the lens 19 to read the document content and generate image data. The Alternatively, image data as image information is sent from an external device such as a personal computer (not shown) via a communication cable or the like.

  Next, the paper P is fed out from the paper feed cassette 41, separated one by one by the separation roller 42 and the friction pad 43, and conveyed to the supply unit 5. The paper transported to the supply unit 5 is transported to the transport unit 3 by the paper feed roller 49 of the supply unit 5. The paper P transported to the transport unit 3 is pressed against the transport belt 31 by the pressing roller 36. The surface of the conveyance belt 31 is charged by the charging roller 34 and electrostatically attracts the paper P. The electrostatically attracted paper P is transported to a position facing the image forming unit 2 by the transport belt 31. When the paper P reaches the position facing the image forming unit 2, the movement of the conveyor belt 31 is stopped, and the carriage 23 is reciprocated in the main scanning line direction according to the image data, and a predetermined position of the stopped paper is predetermined. The ink liquid is ejected to record an image for one line on the paper P. Here, one line refers to a range in the sub-scanning line direction in which the head 24 can record on the paper P while the paper P is stopped. When the recording for one line is completed in the main scanning line direction, the conveyance belt 31 is driven for a predetermined time, and the sheet is moved to the sheet discharge unit 7 side for one line and stopped. As described above, the carriage 23 reciprocates in the main scanning line direction according to the image data, but records an image for one line. Such a process is repeated a predetermined number of times to form a desired image on the paper. The paper P on which a desired image is formed is separated from the conveyance belt 31 by the separation claw 71 and conveyed to the paper discharge unit 7 by the paper discharge roller 72 and the spur 73. The paper P conveyed to the paper discharge unit 7 is conveyed to the switching unit 100 while being guided and conveyed by the first and second paper discharge conveyance roller pairs 74 and 75.

  In the case of single-sided printing, the reverse conveying path 70 for conveying to the paper discharge tray 8 is selected by the switching unit 100. The paper P conveyed from the paper discharge unit 7 is guided to the switching unit 100 and conveyed to the reverse conveyance path 70. The paper P conveyed to the reverse conveyance path 70 is guided to the reverse roller pair 77 and the reverse paper discharge roller pair 78 and discharged to the paper discharge tray 8.

  On the other hand, in the case of duplex printing, the duplex unit conveyance path 90 for conveying to the duplex unit 10 is selected by the switching unit 100. The paper P conveyed from the paper discharge unit 7 is guided to the switching unit 100 and conveyed to the duplex unit conveyance path 90. The sheet P transported to the duplex unit transport path 90 is guided to the duplex entrance roller pair 91 and is transported to the vertical duplex transport path 90c that transports the sheet P below the apparatus main body 1. The sheet P transported to the vertical duplex transport path 90c is guided and transported by the first and second duplex transport roller pairs 92a and 92b and transported to the horizontal duplex transport path 90a. The sheet P transported to the horizontal duplex transport path 90a is guided by the branch plate 96 and transported to the switchback transport path 90b. When the paper P is transported to the switchback transport path 90b, the reverse roller 94 is driven by rotating the paper P above the branch plate 96. Then, the paper P is guided to the three switchback transport roller pairs 95 and the branch plate 96 and is transported to the supply unit 5. The paper P transported to the supply unit 5 is transported to the transport unit 3 by a pair of double-sided paper feed transport rollers 48 and a paper feed roller 49. When the paper reaches a position facing the image forming unit 2, the same operation as described above is performed to form a desired image on the other surface of the paper P. Then, the paper P on which a desired image is formed on both sides passes through the paper discharge unit 7 and the reverse conveyance path 70 and is discharged to the paper discharge tray 8.

  Further, when the straight paper discharge tray 67 is turned down, it is conveyed to the straight paper discharge tray 67.

Next, the carriage 23 of this embodiment will be described.
FIG. 4 is a schematic configuration diagram when the carriage 23 is viewed from the normal direction of the paper surface. The carriage 23 includes an encoder sensor 231 and an infrared sensor 232 for density detection. An encoder sheet 231 a is provided at a position facing the encoder sensor 231. The encoder sheet 231a has the same length as the movement range of the carriage 23 in the main scanning line direction. The encoder sheet 231a is provided with a plurality of notches extending perpendicularly to the surface of the conveyor belt 31 with a constant interval in the main scanning line direction. In the present embodiment, the density detection sensor is the infrared sensor 232, but any sensor such as an optical sensor that can detect density can be used. The density detection signal of the infrared sensor 232 is noise-removed through a low-pass filter. The infrared sensor 232 and the encoder sensor 231 are connected to a control unit 230 provided in the apparatus main body. The control unit 230 includes an ASIC 233, a CPU 234, a RAM 235, and the like. The ASIC 233 is set so as to count the number of cutout portions of the encoder sheet read by the encoder sensor 231 and to determine whether or not it is a paper edge from the density detection signal of the infrared sensor 232. In the present embodiment, the ASIC 233 counts the number of notches and determines whether or not it is a paper edge. However, the present invention is not limited to this, and the CPU 234 may perform all these processes. .

  Further, the infrared sensor 232 is provided on the downstream side of the head 24 with respect to the moving direction when the ink ejection operation of the carriage 23 is performed. For this reason, the position of the end of the paper can be detected by the infrared sensor 232 before the head 23 reaches the end of the paper. As a result, the sheet position can be detected simultaneously with the image forming operation. In the present embodiment, since the ink ejection operation is performed when the carriage 23 moves from the right to the left in FIG. 4, the infrared sensor 232 is provided on the left side of the carriage 23. In the case where the ink ejection operation is performed not only when the carriage 23 moves from right to left in FIG. 4 but also from left to right in FIG. 4, infrared sensors 232 are provided at both ends of the carriage 23.

Next, processing for detecting the paper size in this embodiment will be described.
In this embodiment, the paper size is detected by detecting the position of the edge of the paper. The paper edge position detection process is performed by detecting the density with the infrared sensor 232 and detecting the density change from the detection result. In this embodiment, the conveyance belt 31 is formed of a member having a high density such as black so that the density becomes high with respect to the paper. When density detection is performed by the infrared sensor 232, a detection result is obtained that the density detection signal level is high at the surface portion of the conveyance belt 31 and the density signal level is low at the paper P portion. By detecting a change in density at the boundary between the belt surface portion and the paper portion, the end position of the paper is detected. Then, from the detected paper edge position information, the paper width is calculated to detect the paper size.

FIG. 5 is a control block diagram of the detection processing of the paper edge position in the present embodiment.
As shown in FIG. 5, the density detection signal output from the infrared sensor 232 is stored in the registration unit 200 of the ASIC 233. The density detection signal for a predetermined period stored in the registration unit 200 is calculated by the calculation unit 201 of the CPU 234 to calculate the average density value. This density average value is an average value of density signals detected in a period that is a predetermined period after the new density detection signal is input to the resist unit 200. Each time a new density detection signal is input to the registration unit 200, the density average value is calculated. This density average value is used as a density detection result.

For example, when detecting the paper edge position in the main scanning line direction, the density detection signal at this time is input to the registration unit 200 when the count number of the notch counted by the encoder sensor 231 is updated. The registration unit 200 stores five density detection signals. When a new density detection signal is input to the registration unit 200, the oldest density signal among the density detection signals stored in the registration unit 200 is stored. Updated to a new density detection signal. Then, an average value of the five density detection signals stored in the registration unit 200 is calculated by the calculation unit 201, and this value is used as the density detection result.
The detection of the sheet edge position in the sub-scanning line direction is performed by, for example, causing the density detection signal to be input to the registration unit 200 when the driving roller rotates by a predetermined angle, or the density detection signal to the registration unit 200 every predetermined time. So that it can be entered. The subsequent processing is the same as the detection of the sheet edge position in the main scanning line direction.

  The density detection result calculated by the calculation unit 201 is classified into high density or low density by the comparison unit 202 according to the threshold value held in the threshold value holding unit 203. This threshold value is, for example, a value that is half the sum of the density of the conveyance belt 31 measured in advance at the time of shipment and the density of the paper P measured in advance, and the density detection result is a density lower than this value. If the concentration is higher than this value, it is classified as a high concentration. Further, when a certain range is determined from the density of the conveyance belt 31 measured in advance, and the density detection result is a value within this area, the density is classified as high density and is based on the density of the paper P measured in advance. A certain range is determined, and if the density detection result is a value within this region, it is classified as low density. The classified concentration detection results are stored in the resist unit 200. Then, the comparison unit 202 compares the density detection result classified by the threshold with the classification of the previous density detection result stored in the registration unit 200. As a result of comparison by the comparison unit 202, if the classification of the density detection results is different, it is determined that there is a density change. If it is determined that there is a density change, the count number stored in the registration unit 200 is referred to at this time, and the count number is stored in the registration unit 200 as a density change position. The paper size is calculated by the calculation unit 201 from the count number stored in the registration unit 200 and the paper size information is stored in the storage unit 205. Further, the recording start position is calculated by the calculation unit 101 from the count number stored in the registration unit 200 and is sent to the image control unit 204 as a control unit to control the ink droplet discharge position.

The detection of the paper size in the present embodiment is performed when the paper feed tray 41 is detached from the image forming apparatus or when the paper in the manual feed tray 46 is replaced. Specifically, a detection unit that detects the presence or absence of the paper feed tray 41 is provided in the paper feed tray attaching / detaching unit of the image forming apparatus, and when the detection unit detects that the paper feed tray 41 is not present, the paper replacement flag is set. To do. When image formation is performed using the paper placed in the paper feed cassette, it is detected whether there is a paper exchange flag corresponding to the paper feed tray 41, and if there is a paper exchange flag, Perform paper size detection. When the paper size is detected, the paper size information is stored in the storage unit 205 in association with the paper feed tray 41.
In the case of the manual feed tray 46, paper detection means for detecting the presence of paper in the manual feed tray 46 is provided. When the presence or absence of paper is detected by the paper detection means and the paper detection means determines that there is no paper, a paper replacement flag corresponding to the manual feed tray is set. Then, paper is set in the manual feed tray 46, and it is detected whether or not there is a paper exchange flag when an image is formed with the paper in the manual feed tray 46. If there is a paper exchange flag, paper size detection is executed. When the paper size is detected, the paper size information is stored in the storage unit 205 in association with the manual feed tray 46.

  FIG. 6 is a flowchart showing the flow of detection processing for detecting the paper size. For detection of the paper size, first, when a detection start command is output from the CPU 234 and input to the ASIC 233, the ASIC 233 starts accepting an input of a density detection signal from the infrared sensor 232 (S1). When the reception of the input of the density detection signal is started in this way, the comparison unit 202 determines whether the density has changed from the high density to the low density based on the above-described density average value (S2). If it is determined that there is no change in this determination, it is then determined whether or not the low density has changed to the high density (S4). If it is determined that there is no change in this determination, the input of the next density detection signal is accepted (S1), and the steps after S2 are repeated.

  When it is determined in S2 that the density has changed from high density to low density, the count number of the notch by the encoder sensor 231 at this time is stored in the registration unit 200 as the edge position information of the sheet (S3). The count number of this notch becomes the first density change position, and the count number of this notch becomes the first density change position, which is the position of one end of the sheet in the main scanning line direction.

  If it is determined in S4 that the density has changed from low density to high density, the count number of the notch by the encoder sensor 234 at this time is stored in the registration unit 200 as the edge position information of the paper (S5). The count number of the notch is the second density change position, and is the position of the other end of the sheet in the main scanning line direction. Then, the paper width is obtained by subtracting the second density change position and the first density change position, and the paper size is detected from the paper width. When the paper size is detected, the density detection is finished (S6), and the acceptance of the density detection signal is finished (S7).

  In the above flow, the paper size is detected by detecting the edge in the paper main scanning line direction, but after detecting the edge in the paper main scanning line direction, the edge in the paper sub-scanning line direction is also detected. The paper size may be detected. In this case, first, the carriage 23 is moved to the central portion of the conveyance belt where the central portion of the sheet is located. When the carriage 23 moves to the central portion of the conveyance belt, conveyance of the sheet is started to a position facing the carriage 23. At the same time, the infrared sensor 232 checks whether the density has changed from high to low. When the density changes from high density to low density, the driving of the belt is stopped and the end of the paper in the main scanning line direction is detected. When the end of the sheet in the main scanning line direction is detected, the carriage 23 is moved again to the center of the sheet, and the driving of the transport belt 31 is resumed. When driving is resumed, input acceptance of the density detection signal is started, and it is checked whether the density has changed from low density to high density. At the same time, the amount of angular displacement after restarting driving, the detection time after restarting driving, and the like are measured. And if it changes from low density to high density, the amount of angular displacement at this time and detection time are memorized. The length of the paper in the sub-scanning line direction is calculated from the stored angular displacement amount and detection time. The sheet size is detected from the calculation result of the length in the sheet sub-scanning line direction and the sheet width information in the main scanning line direction.

Next, image formation according to this embodiment will be described. FIG. 7 is a flowchart showing the flow of image formation. Although the case of forming an image on the paper in the manual feed tray 46 will be described, the same flow is applied to the case of forming an image on the paper in the paper feed tray 41. First, when the start of manual copying is instructed from a personal computer via a communication cable or by operating the operation panel of the image forming apparatus, the carriage 23 is moved to the center in the belt main scanning line direction (S10). Specifically, the encoder sensor 231 counts the number of notches, and stops the movement of the carriage 23 when the count number reaches the count number located at the center in the belt main scanning line direction. When the carriage 23 is positioned at the center in the belt main scanning line direction, a detection start command is output from the CPU 234 and input acceptance of the density detection signal from the infrared sensor 232 is started (S11). Next, the paper on the manual feed tray 46 is conveyed to a position facing the carriage 23 (S12). When the conveyance of the paper is started, the comparison unit 202 determines whether the density has changed from high density to low density based on the above-described density average value (S13). When a change from high density to low density is detected, the end of the sheet in the sub-scanning line direction is conveyed to a position facing the carriage 23, and the driving of the belt is stopped (S14). When the driving of the belt is stopped, it is checked whether there is a paper replacement flag (S15). If there is a paper replacement flag (YES in S15), the paper size detection process described above is executed because the paper in the manual feed tray 46 has been replaced (S16). When the paper size is detected, the paper size information is associated with the manual feed tray 46 and written in the storage unit 205 of the image forming unit (S17), and the paper replacement flag is cleared (S18). When the paper size is written, the written paper size information is compared with the image size input from the image reading unit 11 of the image forming apparatus or the personal computer via the communication cable (S19). If the image size is larger than the paper size (YES in S19), a warning is displayed on the display panel of the image forming apparatus or a personal computer that the image protrudes from the paper (S20), and it is confirmed whether to execute printing (S20). S21). When the user gives an instruction to execute printing (YES in S21), an image with a cut edge is formed on the sheet (S22). At this time, an image is formed while detecting the edge of the sheet by the infrared sensor 232 of the carriage 23. When the edge of the sheet is detected by the infrared sensor 232, an image is not formed beyond the edge of the sheet by prohibiting the image forming operation. Therefore, the belt is not contaminated. When the image is formed, the sheet is discharged (S23) and the process is terminated. If the user cancels printing (NO in S21), the paper is discharged as it is without forming an image on the paper (S23), and the process is terminated.
On the other hand, if the paper size is larger than the image size (NO in S19), an image is formed on the paper (S22). Then, the sheet is discharged (S23), and the process ends.
If there is no paper replacement flag (NO in S15), the paper in the manual feed tray 46 has not been exchanged, and the steps after S19 are executed without executing the paper edge detection.

  In the present embodiment, when the image size is larger than the paper size, the image with the image edge portion cut is formed on the paper. However, the present invention is not limited to this. For example, image formation may be executed by reducing the image size to fit within the paper. Further, the user may be allowed to select whether to reduce the image size to fit within the paper or to form an image with the image edge cut off on the paper. Further, without confirming whether or not to execute printing, the user may be warned that the image protrudes from the sheet, and discharged without forming the image on the sheet.

Further, in the above description, the size of the replaced paper in the manual feed tray 46 and the paper feed tray 41 is detected and stored in the storage unit 205 at the time of image formation. However, the present invention is not limited to this, and the manual feed tray 46 and the paper feed tray are not limited thereto. When 41 sheets are replaced, preloading may be performed to detect the sheet sizes of the manual feed tray 46 and the sheet feed tray 41 and store them in the storage unit 205.
FIG. 8 is a flowchart showing a preload flow when the paper in the manual feed tray 46 is replaced. First, it is checked whether there is paper in the manual feed tray 46 (S30). If there is no sheet (NO in S30), a sheet replacement flag is set (S31), and the sheet size information in the manual feed tray 46 stored in the image forming apparatus is erased (S32). On the other hand, if there is a sheet in the manual feed tray 46 (YES in S30), it is checked whether or not the sheet replacement flag is set (S33). If the paper replacement flag is not set (NO in S33), there is no possibility that the paper has been removed from the manual feed tray 46 and the paper size has been changed, and the process is terminated.
On the other hand, if the paper replacement flag is set (YES in S33), the paper size of the manual feed tray 46 may have been changed, so preloading is executed (S34). First, the carriage 23 is moved to the center position in the belt main scanning line direction (S35), and input reception of the density detection signal from the infrared sensor 232 is started (S36). Next, the belt or the like is driven to start conveying the paper on the manual feed tray 46 (S37). When the conveyance of the paper is started, the comparison unit 202 determines whether the density has changed from high density to low density based on the above-described density average value (S38). If a change from high density to low density is detected, the end of the sheet in the sub-scanning line direction is conveyed to a position facing the carriage 23, and the driving of the belt is stopped (S39). When the driving of the belt is stopped, the above-described sheet size detection is executed (S40).
When the paper size of the manual feed tray 46 is grasped, the paper size of the manual feed tray 46 is stored in the storage unit 205 of the image forming apparatus (S41). When the paper size is stored, the paper replacement flag is cleared (S42), and the paper is discharged (S43).
In the above description, the manual feed tray 46 has been described. However, the paper feed tray 41 can be preloaded by the same flow to detect the paper size of the paper feed tray 41. In the case of the manual feed tray 46, the presence or absence of paper in the manual feed tray 46 is determined in S30, and the paper replacement flag is set. However, in the case of the paper feed tray 41, it is detected that the paper feed tray 41 is not present in S30. If this is the case, the paper replacement flag is set.

  In the above description, the paper size is detected by detecting the positions of both ends in the paper main scanning line direction, but is not limited thereto. For example, the position of one end in the paper main scanning line direction can be detected, and the paper size can be detected therefrom. In this case, the position of one end portion in the paper main scanning line direction in the process of moving the carriage located in the central portion in the belt main scanning line direction to the right in FIG. 4 in order to detect the end portion in the sub scanning line direction of the paper. Can be detected.

  FIG. 9 is a flowchart showing the flow of detection processing for detecting the position of one end in the paper main scanning line direction and detecting the paper size. First, input acceptance of the density detection signal from the infrared sensor 232 is started (S50). Next, in order to detect the end portion of the paper in the sub-scanning line direction, the carriage located at the center in the belt main scanning line direction is moved in the main scanning line direction (S51). At the same time, the encoder sensor starts counting the number of notches, and based on the above-described concentration average value, the comparison unit 202 determines whether or not the resistance concentration has changed to a high concentration (S52). . When it is determined that the density has changed from the low density to the high density, the count number of the notch by the encoder sensor 231 at this time is stored in the registration unit 200 as the edge position information of the sheet (S53). The paper size can be calculated by doubling the count number. When the paper size is calculated (S54), the acceptance of the density detection signal is terminated (S55).

  In the above description, the paper size is detected when the paper feed tray 41 is detached from the image forming apparatus or when the paper in the manual feed tray 46 is replaced. However, the paper size is detected even when the image forming apparatus is turned on. May be performed. This is because the paper feed tray 41 may be attached to and detached from the image forming apparatus while the power of the image forming apparatus is turned off and the paper is changed, or the paper in the manual feed tray 46 may be changed. is there. Therefore, the recording unit 205 for storing the paper size information is a volatile memory so that the paper size information is erased when the image forming apparatus is turned off. Then, referring to the volatile memory at the time of printing, if there is no storage in the volatile memory, the sheet replacement flag is set and the flow shown in FIG. 7 is performed. Further, the sheet exchange flag may be set when the power is turned on, and the flow shown in FIG. 8 may be performed.

In the above description, the paper replacement flag is set when it is detected that there is no paper. However, the paper replacement flag may be set when it is detected that there is a change from a state where there is no paper to a certain state. . Further, an open / close detection means for detecting opening / closing of the manual feed tray 41 may be provided, and the paper replacement flag may be set when the manual feed tray changes from the closed state to the open state.
Also, in the paper feed tray 46, the sheet replacement flag is set when it is detected that the paper feed tray 41 is pulled out from the image forming apparatus, but the paper feed tray is pulled out from the image forming apparatus. Thus, the paper replacement flag may be set when it is detected that the paper has been mounted again.

  Further, in the present embodiment, the infrared sensor 232 as the paper edge detection means is attached to the carriage 23, but the present invention is not limited to this. For example, as shown in FIG. 10, a plurality of sensors 400 may be provided in the main scanning line direction of the transport belt 31 to detect the paper size. When the paper is transported to the area where the plurality of sensors are attached by the transport belt 31, several sensors detect the paper. When some of the plurality of sensors arranged side by side in the main scanning line direction of the conveyor belt 31 detect the sheet, the conveyor belt is stopped. Then, by detecting the area of the sensor that detects the paper, the edge position of the paper can be detected. Further, the paper size can be detected from the paper edge position information. As a result, it is possible to detect the sheet end and the sheet size without moving the carriage 23 in the belt main scanning line direction.

  Further, in the present embodiment, an ink jet printer has been described as an example of the image forming apparatus, but the present invention is not limited to this. For example, the present invention can also be applied to an image forming apparatus in which a toner image is carried on a photosensitive member and an image is formed on a sheet conveyed by the conveyance belt 31. In this case, an infrared sensor is provided on the upstream side of the photosensitive member with respect to the moving direction of the transport belt 31 to detect the paper size. The infrared sensor may be movable in the conveying belt width direction, or a plurality of sensors may be provided in the conveying belt width direction as shown in FIG. Also in this image forming apparatus, when the paper feed tray 46 is attached or detached, or when the paper placed on the manual feed tray is exchanged, the paper exchange flag is set. Then, the sheet replacement flag is detected at a predetermined timing, and when there is a sheet replacement flag, sheet size detection is executed. When an infrared sensor is provided so as to be movable in the conveyance belt width direction, the density is detected by moving the infrared sensor in the conveyance belt width direction, and the position in the conveyance belt width direction, which has changed from one density to another density, is detected. Stored in the storage unit as the end position. Based on the paper position information stored in the storage unit, the paper size is calculated and stored in the storage unit. As shown in FIG. 10, when a plurality of sensors are provided, the size of the paper is detected and stored in the storage unit by detecting the area of the sensor that has detected the paper.

  For only the paper placed on the manual feed tray 41, the paper size is detected by the infrared sensor 232 as the paper position detecting means attached to the carriage 23, and the paper size of the paper feed cassette 46 is detected by the paper feed tray 46. It may be detected by a paper size detecting means provided in 46. As described above, the infrared sensor 232 as the paper position detecting means attached to the carriage 23 is also used as the paper size detecting means of the manual tray 41, thereby eliminating the paper size detecting means conventionally provided in the manual tray 41. be able to.

(1)
As described above, according to the image forming apparatus of the present embodiment, the size of the paper such as the paper feed tray 41 or the manual feed tray 46 as the paper feed unit is detected by the infrared sensor 232 as the size detection unit provided in the carriage 23. . As described above, since the paper size detection of the plurality of supply units is performed by one detection unit, the image forming apparatus can be made inexpensive. Further, the sheet size detection result is stored in the storage unit 205 as a recording unit in association with a sheet feeding unit such as the sheet feeding tray 41 or the manual feed tray 46. Therefore, paper corresponding to the image size can be supplied from the paper feed unit, and the image forming speed can be increased as compared with the image forming apparatus that detects the image size every time the conventional paper is conveyed.
(2)
Further, according to the image forming apparatus of the present embodiment, the detection unit that detects the replacement work is provided, and when the replacement work is performed, the sheet of the paper feeding unit that has been replaced is replaced with the paper size detection unit. Control is performed so that the paper size is detected by being conveyed to the opposite position. Therefore, it is possible to grasp whether or not the paper size of the paper feeding unit has been changed and the paper size has been changed. Therefore, it is possible to suppress the difference between the paper size information stored in the storage unit in association with the paper feeding unit and the paper size loaded in the actual supply unit, and the paper corresponding to the image size can be reliably received from the manual feed tray 46. Can be supplied.
(3)
In addition, according to the image forming apparatus of the present embodiment, when the presence or absence of the paper in the manual feed tray 46 is detected and the state of the manual feed tray 46 is changed from the absence of paper to the state with paper, the paper in the manual feed tray is replaced. Judgment is made and paper size detection is executed (preload). Specifically, when the detection unit detects that there is no paper in the manual feed tray 46, a paper replacement flag is set. If there is a sheet in the manual feed tray 46, it is checked whether a sheet replacement flag is set. If there is a paper replacement flag, it is determined that a paper replacement operation has been performed, and the detection of the paper size of the manual feed tray 46 is executed. In this manner, it is possible to detect the presence or absence of a paper replacement operation based on the presence or absence of paper in the manual feed tray. Therefore, it is possible to reliably detect whether the paper in the manual feed tray has been replaced. As a result, it is possible to prevent the paper size of the manual feed tray 46 from being different from the paper size information of the manual feed tray 46 stored in the storage unit. Therefore, paper corresponding to the image size can be reliably supplied from the manual feed tray 46.
(4)
Further, according to the image forming apparatus of the present embodiment, it is detected that the paper feed tray 41 has been attached / detached from the image forming apparatus. Paper size detection is being performed (preload). Specifically, when the detection unit detects that the paper feed tray 41 is pulled out of the image forming apparatus and is not inside the image forming apparatus, a paper replacement flag is set. When the paper feed tray 41 is mounted in the image forming apparatus and the detecting means detects that there is a paper feed tray in the image forming apparatus, it is checked whether there is a paper replacement flag. If there is a paper replacement flag, it is determined that a paper replacement operation has been performed, and the detection of the paper size of the paper feed tray 41 is executed. In this way, by detecting the presence or absence of the replacement work by attaching and detaching the paper feed tray 41, it is possible to reliably grasp the change in the paper size of the paper feed tray 41. Therefore, it is possible to prevent the paper size of the paper feed tray 41 from being different from the paper size information of the paper feed tray 41 stored in the storage unit. Therefore, the paper corresponding to the image size can be reliably supplied from the paper feed tray 41.
(5)
Further, according to the image forming apparatus of the present embodiment, paper size detection is performed when the paper of the paper supply unit that has undergone the replacement operation is used for image formation. Specifically, when image formation is executed, it is checked whether a paper replacement flag is set. If the paper replacement flag is set, paper size detection is executed. In the case of the preload, a blank sheet on which nothing is printed is discharged after the sheet size detection is executed, and one sheet is surely wasted. However, as described above, when the sheet size detection of the sheet feeding unit that has undergone the replacement operation at the time of image formation is executed, and the sheet size and the image size match, Since it is sufficient to form an image on a sheet, it is possible to prevent the sheet from being wasted.
(6)
Further, according to the image forming apparatus of the present embodiment, in order to position the paper central portion of the manual feed tray 46 at the central portion of the conveying belt 31 as the reference position in the width direction in the image forming apparatus, A guide member 461 is provided. A similar guide member is also provided in the paper feed tray 41 so that the central portion of the paper in the paper feed tray 41 is located at the central portion of the transport belt 31 as a reference position in the width direction in the image forming apparatus. ing. Then, one end of the paper is detected by the infrared sensor 232. The paper size can be detected by doubling the distance from the belt center (reference position) to one end of the paper detected by the infrared sensor 232. In this way, the paper size can be detected simply by detecting one end of the paper, so the paper size detection time can be shortened compared to the method of detecting the paper size by detecting both ends of the paper. it can. As a result, it is possible to shorten the preload time and the time of image formation that is performed first after the paper is replaced.
(7)
Further, according to the image forming apparatus of the present embodiment, the infrared sensor 232 as the sheet position detecting unit also serves as a size detecting unit that detects the sheet size, so that one sensor is not necessary, and the cost of the image forming apparatus is reduced. Can be achieved.
(8)
Further, according to the image forming apparatus of the present embodiment, by providing the carriage 23 with the infrared sensor 232 as a paper position detecting unit, it is possible to detect that the paper has been conveyed to a position facing the carriage 23.
(9)
Further, according to the image forming apparatus of the present embodiment, the infrared sensor 232 is provided on the downstream side of the head 24 with respect to the moving direction when the ink ejection operation of the carriage 23 is performed. For this reason, the position of the end of the paper can be detected by the infrared sensor 232 before the head 23 reaches the end of the paper. As a result, the sheet position can be detected simultaneously with the image forming operation. That is, while the infrared sensor is not detecting one end of the paper, ink ejection from the head is prohibited. When one end of the sheet is detected by the infrared sensor 232 and moved by a predetermined distance, ink ejection from the head is started. When the other end of the sheet is detected by the infrared sensor 232 by moving the carriage while ejecting ink from the head to form an image, the ink ejection of the head is prohibited. Thereby, ink does not adhere to the conveyor belt 31. Further, since the sheet edge position can be detected while forming an image in this way, it is not necessary to perform a detection operation for detecting the sheet edge position before image formation, and the printing time can be shortened.

1 is a schematic front configuration diagram of an image forming apparatus according to an embodiment. FIG. 4 is a schematic diagram in a normal direction of a paper surface of a manual feed tray. FIG. 3 is a schematic diagram in a normal direction of a sheet surface of a sheet feeding tray. FIG. 2 is a schematic configuration diagram when the carriage of the inkjet printer is viewed from the normal direction of the paper surface. FIG. 7 is a control block diagram of detection processing for a sheet edge position. 6 is a flowchart showing a flow of detecting a paper size. 6 is a flowchart illustrating a flow of an image forming operation when paper replacement is performed. The flowchart which shows the flow of a preload. 12 is a flowchart showing a flow of detection of other paper sizes. FIG. 6 is a schematic configuration diagram illustrating a sheet size detection unit of another image forming apparatus.

Explanation of symbols

Reference Signs List 3 Conveying section 7 Discharging section 23 Carriage 31 Conveying belt 41 Paper feed tray 46 Manual feed tray 230 Control section 231 Encoder sensor 232 Infrared sensor

Claims (7)

Two or more paper feeders on which recording paper is placed;
An image forming apparatus including an ink discharge head having an ejection port for ejecting ink, a carriage that reciprocates in the main scanning direction, and an image forming unit that forms an image on a recording sheet fed from the paper feeding unit In the device
A size detection unit that is provided downstream of the ejection head with respect to a moving direction in which the carriage moves during ink ejection for image formation, and detects the size of the recording paper;
Storage means for storing the size information of the recording paper detected by the size detection means in association with the paper feed unit ;
When forming an image on recording paper, the size information of the recording paper stored in the storage means is compared with the image size information, and if the image size is larger than the size information of the recording paper, a warning is displayed to the user. Control to confirm whether or not to execute printing,
An operation detecting means for detecting an operation performed when the recording paper of the paper supply unit is replaced ;
The recording sheet of the paper feeding unit whose exchange operation is detected by the operation detection unit is conveyed to a position facing the carriage. When the recording sheet is conveyed to a position facing the carriage, the carriage is moved to move the recording sheet Control to detect the size of the recording paper by the size detection means and store the size information of the recording paper detected by the size detection means in the storage means in association with the paper feed unit in which the replacement operation is detected by the operation detection means. an image forming apparatus characterized by comprising a control means for. The image forming apparatus according to claim 1 .
The operation detecting unit includes a recording sheet detecting unit that detects the presence or absence of the recording sheet in the paper feeding unit, and detects the absence of the recording sheet by the recording sheet detecting unit, and then detects the presence of the recording sheet. An image forming apparatus that detects an exchange operation. The image forming apparatus according to claim 1 or 2 ,
The operation detection unit includes an attachment / detachment detection unit that detects attachment / detachment of the sheet feeding unit. After the attachment detection unit detects that the sheet feeding unit has been extracted from the image forming apparatus, the sheet feeding unit is moved to the image forming apparatus. An image forming apparatus that detects an exchange operation by detecting that it is mounted inside. The image forming apparatus according to claim 1, 2 or 3 .
The image forming apparatus is characterized in that the recording sheet size detection is performed when image formation is performed using the recording sheet of the sheet feeding unit on which the replacement operation has been performed. The image forming apparatus according to claim 1, 2, 3, or 4 .
A recording paper guide member is provided for guiding the recording paper so that the central portion of the recording paper is positioned at a reference position in the width direction in the apparatus. By detecting one end of the recording paper with the size detection means, the paper An image forming apparatus characterized by detecting a size. The image forming apparatus according to claim 1, 2, 3, 4, or 5 .
An image forming apparatus comprising: a position detection unit that detects a position of a recording sheet to be conveyed; and the position detection unit is also used as the size detection unit. The image forming apparatus according to claim 1, 2, 3, 4, 5 or 6 .
An image forming apparatus comprising an image reading apparatus capable of reading image information, and forming an image on a recording sheet based on an image read by the image reading apparatus.

Images