JP2011197237A - Image forming apparatus and method for controlling the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus in which a paper conveyance path is shorter than that an image formation path, with the apparatus being configured so as to prevent wasteful consumption of toner and contamination with a toner image untransferred to paper, when a user does not set paper unintentionally and initiates printing on paper the size of which does not contribute to the detection of the presence or the absence of paper.SOLUTION: The image forming apparatus includes a paper conveyance path from a paper feed section for feeding paper to a transfer section for transferring an image to paper, and an image formation path from the image formation initiating position of an image formation section for forming an image to the transfer section, with the paper conveyance path being shorter than the image formation path. The image forming apparatus exerts paper pre-control for paper the size of which is unable to contribute to the detection of the presence or absence of paper by a paper presence/absence detecting means provided in the paper feed section, and the paper pre-control being configured such that image formation is initiated using the detection of paper, conveyed after fed by a paper feed operation, by the paper detecting means as a trigger. The apparatus exerts image pre-control for paper the size of which contributes to the detection of the presence or absence of paper by the paper presence/absence detecting means, the image pre-control being configured such that after image formation is initiated, paper feed conveyance is initiated in matching with the image.

Description

  The present invention relates to an image forming apparatus in which a paper conveyance path is shorter than an image forming path and a control method thereof.

The paper feed control in the image forming apparatus is roughly classified into two types: a control method (paper advance control) in which paper feed is first performed and image formation is triggered by detection of the leading edge of the paper, and an image after image formation is first started. In accordance with the control method, it can be classified into a control method (image advance control) for feeding and conveying paper.
The paper transport path from the paper feed position to the transfer unit is the image formation path (the length of the path from the exposure start position to the photoconductor to the transfer unit, and if there is an intermediate transfer belt, from the exposure start position to the primary transfer unit. In the case of a machine configuration longer than (the length from the primary transfer portion to the secondary transfer portion = image forming pass), the timing of the image and the recording paper is matched unless paper feeding is started before the start of image formation. Therefore, it makes sense to set the image formation timing to paper advance control that is performed after detection of the leading edge of the paper.

Here, as a conventional technique, in Patent Document 1 (Japanese Patent Laid-Open No. 4-34463), until a leading edge of a recording sheet to be fed is detected by a mechanical configuration paper feeding unit whose paper conveyance path is longer than an image forming path. In other words, the image forming timing is adjusted based on this time, and the above-described paper advance control is disclosed.
On the other hand, in a machine configuration in which the paper conveyance path is shorter than the image formation path, it is possible to shorten the paper waiting time at the registration roller or the like by using the image advance control in which the paper conveyance is performed after the image formation is started. Adopting image advance control which is advantageous in terms of performance.

  Japanese Patent Laid-Open No. 2001-296785 discloses an image forming apparatus in which a paper conveyance path is shorter than an image formation path, and adjusts the printing timing of the next page by measuring the paper conveyance time during continuous printing. The above-described image advance control is disclosed.

  By the way, in recent years, there is a demand for image formation by an image forming apparatus on narrow paper such as B6 half size. For example, there is a demand for printing on strip-shaped paper such as candy paper, or printing on an unused portion using paper that is separated from a regular standard size paper by a perforation. (The perforated paper that can divide the B5 size paper into 4 in the length direction, and the remaining part after printing in 3 places becomes the paper size (B6 half) whose length is B6 and the width is B6.

  When forming an image on such narrow paper, the paper is loaded on the manual feed tray of the paper feed unit and fed to the image forming apparatus. However, the manual feed tray is a part exposed to external light. Since there is a risk of false detection when the detection sensor is used as a paper presence / absence detection means, a filler type sensor (a sensor that detects the presence / absence of contact with paper) is used. The narrow paper cannot be detected due to the arrangement with the paper feeding roller, and it is determined that there is no paper, so that it is impossible to form an image on such a paper.

  Patent Document 3 (Japanese Patent Laid-Open No. 10-153893) discloses a first manual paper feed mode in which copying is possible only when the paper presence / absence detection provided in the manual paper feed tray detects a paper and the output result of the paper presence / absence detection. However, there is described an image forming apparatus capable of selecting a second manual paper feed mode that enables copying regardless of the above.

However, in the configuration of Patent Document 3, in the first and second manual paper feed modes, the relationship between the paper conveyance path and the image formation path, the image formation timing, and the paper feed timing are controlled. Not disclosed.
If the paper transport path has a shorter machine configuration than the image forming path, the image advance control is performed for the above-described reason. At this time, in order to form an image on a narrow sheet, the second manual feed mode described above is performed. Is selected, a toner image is formed on the photoreceptor even when the user accidentally presses the print start button without setting paper, and in an image forming apparatus using an intermediate transfer belt, the toner is formed on the intermediate transfer belt. Since an image is formed, the toner is wasted, and the toner that has not been transferred to the paper stains the secondary transfer roller with toner during recovery (when returning from a non-paper jam condition). As a result, there is a problem that the printed paper after the recovery is stained.

  The present invention has been made in view of the above-described problems of the prior art, and in an image forming apparatus in which the paper transport path is shorter than the image forming path, the user cannot detect the presence or absence of the paper without erroneously setting the paper. An object of the present invention is to provide an image forming apparatus capable of performing control so as not to cause wasteful consumption of toner or contamination due to a toner image that has not been transferred to paper when printing of a paper size is started, and a control method thereof. .

In order to achieve the above object, the present invention employs the following solutions.
(1): an image forming unit, a transfer unit that transfers an image formed by the image forming unit to a sheet, and a conveyance that conveys the sheet to the transfer unit in synchronization with the image formed by the image forming unit And a sheet feeding unit that feeds the sheet to the conveying unit, and a sheet detecting unit that detects the sheet fed from the sheet feeding unit in front of the conveying unit. In the image forming apparatus in which the paper transport path to the image forming section is shorter than the image forming path from the image forming start position of the image forming section to the transfer section, the paper feeding section has a paper presence / absence detecting means, For paper of a size for which it is determined that the presence or absence of the paper cannot be detected by the detection means, the paper advance that starts the image formation with the detection by the paper detection means of the paper fed and transported as a trigger Control, before For paper of a size that can detect the presence / absence of paper by the paper presence / absence detection means, it is provided with a control means for performing image advance control for starting paper feed conveyance in accordance with an image after starting image formation. (Claim 1).
(2): In the image forming apparatus according to (1), the image forming unit includes a plurality of image carriers, and the images formed on the plurality of image carriers are superimposed on an intermediate transfer member for primary transfer. After that, the image transferred to the intermediate transfer member is secondarily transferred to a sheet. The first transfer portion from the exposure position of the image carrier serving as an attachment reference at which image formation is first started to the first transfer portion. The length from the secondary transfer portion to the secondary transfer portion is the image forming pass (claim 2).
(3): In the image forming apparatus described in (1) or (2), the transfer unit or the secondary transfer unit from the position of the paper feed roller of the paper feed tray of the paper feed unit or the pickup roller of the manual feed tray The length up to is a paper conveyance path (claim 3).
(4): In the image forming apparatus according to any one of (1) to (3), in the case where the control unit forms an image on a sheet having a size determined to be undetectable by the sheet presence / absence detection unit. Then, after the paper feeding operation is performed and the paper detection unit detects the paper, the image formation is started (Claim 4).
(5): In the image forming apparatus according to any one of (1) to (4), the image forming apparatus further includes a paper size setting unit, and the control unit determines the paper size from the paper size set by the paper size setting unit. It is determined whether the presence / absence of the sheet can be detected by the sheet presence / absence detection unit, and when it is determined that the sheet presence / absence cannot be detected, the detection result of the sheet presence / absence detection unit is ignored.
(6): In the image forming apparatus according to any one of (1) to (5), the manual feed tray of the paper feeding unit includes a regulating unit that regulates a width direction of a set sheet, and A restriction position detecting means for detecting a position, and the control means determines whether the presence / absence of the sheet can be detected by the presence / absence detection means of the sheet based on the detection result of the position of the restriction means; The detection result of the paper presence / absence detection means is ignored (claim 6).
(7): In the image forming apparatus according to (6), when the control unit detects the movement of the restricting unit by the restricting position detecting unit, the detection result is used as a trigger to perform image advance control from paper advance control. (Claim 7).
(8): In the image forming apparatus according to any one of (1) to (7), the sheet presence / absence detecting unit includes a filler sensor in the sheet feeding tray and the manual feed tray of the sheet feeding unit. (Claim 8).
(9): In the image forming apparatus according to any one of (1) to (8), the conveyance unit is configured to convey the sheet on a center basis. .

(10): an image forming unit, a transfer unit that transfers an image formed by the image forming unit to a sheet, and a conveyance that conveys the sheet to the transfer unit in synchronization with the image formed by the image forming unit And a sheet feeding unit that feeds the sheet to the conveying unit, and a sheet detecting unit that detects the sheet fed from the sheet feeding unit in front of the conveying unit. In the image forming apparatus control method, the paper conveyance path to the image forming unit is shorter than the image forming path from the image forming start position of the image forming unit to the transfer unit. For paper of a size for which it is determined that the presence or absence of paper cannot be detected, paper advance control is performed to start image formation using a paper feed operation and detection of the paper fed and transported by the paper detection means as a trigger. , The paper For paper sizes existence of sheet can be detected without detecting means, and performs image preceding control for starting the sheet feed conveyance in accordance with the image after the start of image formation (Claim 10).
(11): In the method for controlling an image forming apparatus according to (10), the image forming apparatus includes a plurality of image carriers in the image forming unit, and images formed on the plurality of image carriers are intermediate. In the case where the image transferred onto the intermediate transfer member is transferred onto the sheet after the primary transfer while being superimposed on the transfer member, the exposure position of the image carrier serving as an attachment reference at which image formation is started first. The length from the primary transfer portion to the primary transfer portion and the length from the primary transfer portion to the secondary transfer portion are used as the image forming path.
(12): In the control method of the image forming apparatus according to (10) or (11), the transfer unit or the 2 is controlled from the position of the paper feed roller of the paper feed tray of the paper feed unit or the pickup roller of the manual feed tray. The length to the next transfer portion is used as a paper conveyance path (claim 12).
(13): In the method for controlling an image forming apparatus according to any one of (10) to (12), when an image is formed on a sheet having a size determined to be undetectable by the sheet presence / absence detecting unit, A sheet operation is performed, and image formation is started after a sheet detection unit provided in front of the conveyance unit that conveys the sheet to the transfer unit detects the sheet (claim 13).
(14): In the image forming apparatus control method according to any one of (10) to (13), it is determined whether the sheet presence / absence detection unit can detect the presence / absence of the sheet from the sheet size set by the sheet size setting unit. When it is determined that the presence / absence of the sheet cannot be detected, the detection result of the sheet presence / absence detecting unit is ignored.
(15): In the control method of the image forming apparatus according to any one of (10) to (14), a restriction unit that restricts a width direction of the set sheet provided in the manual feed tray of the sheet feeding unit. From the detection result of the restriction position detection means for detecting the position, it is determined whether or not the paper presence / absence detection is possible by the paper presence / absence detection means, and when it is determined that the paper presence / absence cannot be detected, the detection result of the paper presence / absence detection means is ignored. (Claim 15).
(16): In the control method of the image forming apparatus described in (15), when movement of the restricting unit is detected by the restricting position detecting unit, the detection result is used as a trigger to switch from image advance control to paper advance control. (Claim 16).

  According to the present invention, even if the paper transport path is shorter than the image forming path, when the user starts printing on a paper size in which the presence of the paper cannot be detected without setting the paper by mistake, the toner is wasted. Therefore, it is possible to prevent the toner image from being consumed and from being contaminated by the toner image that has not been transferred to the paper. Further, since the normal image advance control is performed for a paper whose size can be detected by the paper presence / absence detection means, productivity is not impaired.

  In addition, in the present invention, when printing on a small size paper whose paper cannot be detected by the paper presence / absence detection unit, the information on the paper presence / absence detection unit is ignored and a paper feeding operation is performed before image formation. Small size that cannot detect the presence or absence of paper because the image forming is controlled after the paper waiting is confirmed by the transport means (registration unit) for image transfer (the paper detection means (registration sensor) detects the leading edge of the paper). Even when printing on paper, if there is no paper, image formation is not performed, so toner is not consumed wastefully and the secondary transfer roller of the secondary transfer unit is soiled. It is possible to prevent image defects such as back stains from occurring on the printing paper after resuming printing.

1 is a diagram showing an embodiment of an image forming apparatus according to the present invention, and is a schematic overall configuration diagram of a small full-color printer having an electrophotographic image forming apparatus. FIG. 2 is a diagram illustrating an image forming operation of an image forming unit of the image forming apparatus illustrated in FIG. 1. FIG. 2 is a perspective view of a manual sheet feeding unit of the image forming apparatus illustrated in FIG. 1. FIG. 4 is an enlarged view of a main part of the manual sheet feeding unit illustrated in FIG. 3. FIG. 4 is a side cross-sectional view of the manual sheet feeder shown in FIG. 3. It is a principal part front view of the image forming apparatus which shows the example of arrangement | positioning of a registration roller and a registration sensor filler. It is a principal part perspective view of the image forming apparatus which shows the example of arrangement | positioning of a registration roller and a registration sensor filler. It is a flowchart which shows the control action of 1st Example. It is a figure explaining the control timing of the image advance control at the time of normal printing operation. It is a figure explaining the state which set the strip-shaped small size paper (narrow paper) to the manual feed tray, (a) shows the small size paper set to the manual feed tray, the side fence, the pickup roller, and the paper presence detection filler. FIG. 5B is a view of a small-size sheet, a side fence, a pickup roller, and a sheet presence / absence detection filler set on the manual feed tray as viewed from the front. It is a figure explaining the control timing of paper advance control at the time of printing on a strip-like small size paper (narrow paper). It is a flowchart which shows the control operation of a 1st modification. It is a figure explaining the control timing at the time of printing on a strip-shaped small size paper (narrow paper). It is a flowchart which shows the control action of 2nd Example. It is a flowchart which shows the control operation of a 2nd modification.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a diagram showing an embodiment of an image forming apparatus according to the present invention, and is a schematic overall configuration diagram of a small full-color printer having an electrophotographic image forming apparatus.
In the small full-color printer shown in FIG. 1, as an image forming unit, for example, black (BK), cyan (C), magenta (M), and yellow (Y) toner images of each color are arranged in the order of image carriers (specifically, light carriers). Image forming devices 2a, 2b, 2c, and 2d formed on a conductive photoconductor), an exposure device 1 that writes a latent image on a photoconductor of each of the image forming devices 2a, 2b, 2c, and 2d, and toner of each color A belt-like intermediate transfer member (intermediate transfer belt) 3 for superimposing images is provided. The image forming devices 2a, 2b, 2c, and 2d for the respective colors Bk, C, M, and Y include a drum-shaped photoconductor, a charging device (not shown) disposed around the drum-shaped photoconductor, and a developing device (only the developing roller is illustrated). ) A primary transfer device (not shown) and a cleaning device (not shown) are provided, and a toner image of each color is formed on the photoreceptor through charging, exposure and development processes, and intermediate transfer is performed by the primary transfer device. Transfer to belt 3. The residual toner is removed from the photoreceptor after the transfer by a cleaning device.

  As the paper feed unit, a main body paper feed unit comprising a paper feed tray 10, a paper feed roller 11, and a separating unit 12, and a manual paper feed unit comprising a manual feed tray 13, a pickup roller 14, a paper feed roller 15, and a separating unit 16 are provided. I have. Each paper feed unit has paper presence / absence detection means (paper presence / absence detection fillers) 18 and 21 formed of a filler-type sensor.

  A sheet fed from a sheet feeding unit (main body sheet feeding unit or manual sheet feeding unit) is detected by a registration sensor 8 serving as a sheet detecting unit in front of a registration roller 4 serving as a conveying unit, and the leading end is detected. After correcting the skew of the sheet by striking against the registration roller 4 and correcting the skew of the sheet, the sheet feeding roller 11 or the sheet feeding roller 15 and the pickup roller 14 are stopped and waited. Then, the registration roller 4 is driven in synchronism with the image formed by the image forming unit, and the sheet is conveyed to the secondary transfer roller 5. The image is transferred from the intermediate transfer belt 3 to the sheet by the secondary transfer roller 5 and the image is fixed on the sheet by the fixing device 6, and then the printed sheet is discharged from the sheet discharge roller 7 onto the sheet discharge tray. The fixing paper discharge sensor 9 detects the leading edge of the paper conveyed from the fixing device 5 and the trailing edge of the paper discharged by the paper discharge roller 7 and monitors whether there is a conveyance abnormality. The operation unit 17 can set the paper size and type for a control unit (not shown), and can display the printer status on a liquid crystal screen.

  FIG. 1 shows an example of the configuration of a small full-color printer. If an image reading device (image scanner) that reads a document image and converts it into image data is installed above the discharge tray, the configuration of the small full-color copier is as follows. In addition, by providing a communication function with an external line, a compact full-color multifunction peripheral having a facsimile function can be obtained.

FIG. 2 is a diagram illustrating an image forming operation of the image forming unit of the image forming apparatus shown in FIG.
The laser beam is irradiated from the exposure device 1 to the point A of the photoreceptor of the most upstream image forming apparatus 2a on which the BK image serving as the reference color of the image is formed, and a latent image is written on the photoreceptor. Then, a Bk toner image is formed by the developing device, and the Bk toner image is transferred (primary transfer) onto the intermediate transfer belt 3 at point C. The intermediate transfer belt 3 is driven to rotate counterclockwise in FIG. 2, and toner images of C, M, and Y colors are formed on the photosensitive member even in the other color image forming devices 2b, 2c, and 2d. The toner images of the respective colors are primarily transferred sequentially from the photoreceptors of the image forming apparatuses 2b, 2c, and 2d of the respective colors onto the transfer belt 3. The image (color image of Bk, C, M, and Y) formed on the intermediate transfer belt 3 reaches the point E through the point D, and the sheet conveyed from the registration roller 4 by the secondary transfer roller 5 at the point E. (Secondary transfer).

  The start of the image formation described above is an exposure (writing) start position at point A of the image carrier (photosensitive member) of the Bk image forming apparatus 2a, which is an attachment reference, and secondary transfer onto the paper at point E. The image formation path length (image formation path) L1 (A → B → C → D → E) until reaching the secondary transfer roller 5 is fed from the paper feed tray 10 by the paper feed roller 11 and through the registration roller 4. Incoming paper feed path length (paper transport path) L2 and manual paper feed path length fed from the manual feed tray 13 by the pickup roller 14 and paper feed roller 15 to the secondary transfer roller 5 through the registration roller 4 (Paper transport path) It is longer than L3.

3 to 5 show a specific configuration example of the manual paper feed unit of the image forming apparatus shown in FIG. 1, FIG. 3 is a perspective view of the manual paper feed unit, and FIG. FIG. 5 is a side sectional view of the manual sheet feeder.
The manual paper feed unit includes a manual feed tray 13, a side fence 22 that is provided on the manual feed tray and restricts the width direction of set paper, a pickup roller 14, a paper feed roller 15, and a paper that is a separating unit. A separation member 16, a sheet presence / absence detection means (paper presence / absence detection filler) 21 including a filler-type sensor, and a restriction position detection means (not shown) for detecting the position and movement of the restriction means (side fence) 22 are provided. Yes.

Here, an example of the dimensions of each part of the manual sheet feeder is shown below.
The image forming apparatus according to the present embodiment is an A4 full-color printer for implementing small size mode control such as B6 half (width 64 mm, length 182 mm), 3 × 5 inch size (width 76.2 mm, length 127 mm). It is.
The paper width for manual paper feed is 64 mm to 216 mm, and among these, for paper with a width of 64 mm or more and less than 90 mm, dedicated paper feed control is performed in the small size mode. Note that the paper length corresponding to the manual paper feed is not limited as long as it can be stacked on the manual paper feed tray, and a paper having a length of 127 mm (3 × 5 inch size) or more can be used.
The manual feed tray 13 is provided with a paper presence / absence detection means (paper presence / absence detection filler) 21 comprising a filler-type sensor. A paper feed roller 15 having a width of 40 mm is disposed at a paper feed center position, and a paper feed roller drive gear, The detection part (filler protruding from the shaft) of the paper presence / absence detection filler 21 is disposed at a position about 40 mm away from the paper transport center while avoiding the paper feed roller shaft support part. Considering variations such as component dimensions and assembly, the minimum sheet width that can be detected by the sheet presence / absence detection filler 21 is about 88 mm.

In the present invention, a configuration is adopted in which the sheet is conveyed based on the center. The merit with respect to the side reference | standard by this structure is described below.
With the center reference for various sizes of paper, it becomes possible to arrange the conveyance rollers, conveyance guides and the like symmetrically.
By configuring symmetrically, it becomes easy to set the conveyance force, the conveyance speed, etc., including the passage of time from the beginning to be uniform (symmetric), and the conveyance quality such as skew can be maintained.
In addition, it is possible to make the gradient of the heater of the fixing device almost symmetrical, and there is no deflection even if the functional member that contacts the paper at the time of transfer, such as a photosensitive member or an intermediate transfer member, is not deflected. is there.

FIG. 6 and FIG. 7 show examples of arrangement of the registration roller 4 that is a conveyance unit and a filler type registration sensor (registration sensor filler) 8 that is a sheet detection unit when a configuration for conveying a sheet with a center reference is adopted. Yes.
As the paper transport means, a transport roller and the like are provided in addition to the registration roller 4, but the transport roller configuration has a roller at the center in the width direction even in the case of center standard paper transport. There is no need to be. A normal transport roller is composed of two rollers and does not have a roller at the center. In a grip roller or the like that requires gripping force, a roller is often arranged in the center portion with a three roller configuration. However, in order to cope with a narrow sheet, it is necessary to arrange rollers at positions where the sheet can be sufficiently nipped even with the minimum width sheet (at least about 5 and 6 mm on the left and right sides are necessary). Even in the case of a three-roller conveyance roller, it is unstable to convey a sheet with only one central roller, so it is necessary to arrange rollers so that the left and right rollers can also nip the sheet. In addition, it is desirable to provide a roller at the center of the paper discharge roller that discharges the paper to the paper discharge tray in consideration of the stiffness of the narrow paper and the trailing edge of the paper.

  The registration sensor (registration sensor filler) 8 is disposed near the center in the sheet conveyance width direction, but is not necessarily disposed at the center position. In order to handle punched paper (paper that has punch holes in advance), it is often arranged to avoid the center (in the case of odd holes, there is a high possibility that a punch hole is opened in the center, and false detection is performed). To prevent it, move the position a little to avoid the hole). In the embodiment of the present invention, as shown in FIGS. 6 and 7, the detection portion of the resist sensor filler 8 (filler protruding from the shaft) is disposed at a position displaced by about 10 mm from the paper center. Since the registration sensor filler 8 is designed to rotate with a light load so as not to damage the sheet, the skew of the sheet is not caused by the filler. Further, since the registration sensor filler 8 is disposed upstream of the registration roller 4, some skew can be corrected by the registration roller, so that there is no problem. In the embodiment of the present invention, the registration roller 4 is composed of a rubber drive roller 4a having a width substantially equal to the maximum sheet width and a metal driven roller 4b having a width wider than the maximum sheet width. It is the same structure as a roller.

The present invention is a small full-color printer configured as described above, such as a small-sized sheet (such as a strip-shaped narrow sheet having a small size in the width direction) in which the sheet presence / absence detection means (sheet presence / absence detection filler) 18 and 21 cannot detect the sheet. When printing on the sheet, the sheet having a size determined that the presence / absence of the sheet cannot be detected by the sheet presence / absence detection means (sheet presence / absence detection filler) 18 and 21 is fed and conveyed by feeding. Paper detection control (registration sensor) 8 is used as a trigger to perform paper advance control for starting image formation, and for paper of a size that can be detected by the paper presence / absence detection means (paper presence / absence detection filler) 18, 21 In this case, the image forming apparatus includes a control unit that performs image advance control for starting sheet feeding and conveyance in accordance with an image after starting image formation.
That is, according to the present invention, in order to ensure the printing speed in normal printing, after the image forming apparatuses 2a to 2d start image formation on the photosensitive member, the sheet feeding operation from the sheet feeding tray 10 or the manual feed tray 13 is performed. The roller 4 temporarily waits, and the sheet is conveyed from the registration roller 4 at the timing when the image on the intermediate transfer belt 3 comes to the secondary transfer portion (transfer portion to the sheet by the secondary transfer roller 5). If it is determined from the settings and detection results that the paper presence / absence detection means (paper presence / absence detection filler) 18 and 21 cannot detect the presence / absence of paper, the paper presence / absence detection means (paper presence / absence detection) is detected when a print request is made. (Fillers) 18 and 21 are detected in the absence of paper, and before the image is formed by the most upstream image forming device 2a (exposure to the photosensitive member to form a latent image), From Lee 10 or manual feed tray 13 by performing a sheet feeding operation of the registration rollers 4, thereby starting the image formation is set to feature after detecting the paper sheet detection means (registration sensor) 8.
The above features will be described below based on specific examples.

  A control unit (not shown) which is a control unit of the image forming apparatus (small full-color printer) includes a central processing unit (CPU) composed of a microcomputer, and a memory (ROM, ROM) in which a control program and various control data are stored. RAM, non-volatile RAM), input / output devices, various control circuits, clocks, timers, etc., and various types of paper presence / absence detection means (paper presence / absence detection filler) 18, 21 and paper detection means (registration sensor) 8 described above. Based on the input information from the sensor and the setting information such as the paper size set by the operation unit 17, each part of the printer engine (image forming unit, paper feeding unit, paper transport unit, transfer unit, etc.) is controlled. The control operations of the first embodiment, the second embodiment, the first modification, and the second modification are shown.

[Example 1]
FIG. 8 is a flowchart showing the control operation of the first embodiment. The normal print operation is performed according to whether or not the paper size is detectable by the paper presence / absence detecting means, and the strip-like small size paper (width) It is a figure explaining the control operation in the case of performing the process printed on a (narrow paper).

Processing in each step (S-1 to S-22) of the flowchart of the first embodiment shown in FIG. 8 is shown below.
S-1: The printer engine receives a print request for each page.
S-2: It is determined whether the print size set by the operation unit (paper size setting means) 17 is a paper size that can be detected by the paper presence / absence detection means. When the print size is a size that can be detected by the paper presence / absence detection means (paper presence / absence detection filler 18 or 21), the process proceeds to S-3 (image advance control), and when the print size cannot be detected, S-18 (paper advance control). Go to).
S-3: It is determined whether or not there is a sheet in the tray (paper feed tray 10 or manual feed tray 13) from the information of the sheet presence / absence detection means (paper presence / absence detection filler 18 or 21). When there is no paper, the process proceeds to S-4, and when there is a paper, the process proceeds to S-5.
S-4: A message such as “Please set paper” is displayed on the operation unit 17 (message display 1).
S-5: When paper is present, exposure is started on the photoreceptors of the image forming devices 2a to 2d in order from the most upstream Bk image forming device 2a to form an image.
S-6: The paper feeding operation is started at a predetermined timing from the start of image writing (exposure) to the photoreceptor of the most upstream Bk image forming device 2a.
S-7: The registration sensor 8 checks the registration sensor information to detect the sheet by a predetermined time. If a sheet is not detected by the predetermined time, the process proceeds to S-8. If a sheet is detected, the process proceeds to S-9.
S-8: A message such as “paper misfeed” is displayed on the operation unit 17 (message display 2) to prompt the jam processing.
S-9: After the registration sensor 8 detects the paper, the paper feed drive is stopped at a predetermined timing to wait for the paper.
S-10: Registration roller at a predetermined timing from the start of image writing (exposure) with the timing synchronized so that the image and the paper are synchronized at the secondary transfer portion (position where the intermediate transfer belt 3 and the secondary transfer roller 5 abut). 4 is started.
S-11: The sheet reaches the secondary transfer portion, and image transfer to the sheet is started by the secondary transfer roller 5.
S-12: The sheet reaches the fixing device 6 and image fixing on the sheet is started.
S-13: The registration sensor 8 detects the trailing edge of the sheet (sensor information: sheet present → no sheet).
S-14: After the registration sensor 8 detects the trailing edge of the sheet, the driving of the registration roller 4 is stopped at a predetermined timing.
S-15: The fixing paper discharge sensor 9 detects the trailing edge of the paper (sensor information: paper present → no paper).
S-16: After the fixing sheet discharge sensor 9 detects the trailing edge of the sheet, it is determined that the sheet is completely discharged to the sheet discharge tray at a predetermined timing.
S-17: Printing for the print request is completed when the sheet is discharged to the discharge tray.
S-18: If the paper size cannot be detected by the paper presence / absence detection means (paper presence / absence detection filler 21 of the manual feed tray 13) in the determination of the paper size in S-2, the paper feeding operation is started immediately. .
S-19: The registration sensor 8 checks whether the registration sensor 8 detects a sheet by a predetermined time. If a sheet is not detected by the predetermined time, the process proceeds to S-20. If a sheet is detected, the process proceeds to S-21.
S-20: A message such as “paper is not set or paper misfeed” is displayed on the operation unit 17 (message display 3) to prompt confirmation of whether paper is set.
S-21: When the registration sensor 8 detects a sheet, exposure is started on the photoreceptors of the image forming devices 2a to 2d in order from the most upstream Bk image forming device 2a to form an image.
S-22: After the registration sensor 8 detects the paper, the paper feed drive is stopped at a predetermined timing to wait for the paper.
After S-22, the process proceeds to S-10, and the processes of S-10 to S-17 are executed.

In the above two control routes, the time from S-7 to S-10 is different from the time from S-19 to S-10.
Since the time from S-7 to S-9 and the time from S-19 to S-22 are the same, the time from S-9 to S-10 and the time from S-22 to S-10 are the two control routes. It can be paraphrased that the time is different.

Next, the description of the above control operation will be supplemented.
FIG. 9 is a diagram for explaining the control timing of image advance control during a normal printing operation (S-3 to S-10 in FIG. 8).
Since the image forming path length L1, which is an image forming path, is longer than the sheet feeding path length L2, which is a paper conveying path, and the manual sheet feeding path length L3, a print request is issued and the printer starts printing. In this case, the control unit determines whether there is a sheet in the sheet feeding unit (the sheet feeding tray 10 or the manual feed tray 13) designated by the operation unit (sheet size setting unit) 17 and the sheet presence / absence detection unit (sheet presence / absence detection filler 18). Alternatively, the information of 21) is confirmed, and if there is a sheet, the exposure apparatus 1 starts image writing on the photoreceptors of the image forming apparatuses 2a to 2d in order from the most upstream Bk image forming apparatus 2a. If there is no paper, a message indicating that there is no paper such as “Please set paper” is displayed on the operation unit 17 (message display 1).

  Next, using the start of image writing as a trigger, the control unit feeds paper (the feed roller 11 or the pickup roller 14 and the paper feed) of the paper feed unit (paper feed tray 10 or manual feed tray 13) selected after a predetermined time T2. The driving of the roller 15) is started. The time T2 is a time required for transporting the paper feed path length (paper transport path) L2 or L3 from the paper feed unit to the secondary transfer roller 5, and there is a margin in the paper skew correction and waiting time in the registration roller 4. This is the timing set for each sheet feeding unit as the time added.

  After the paper feed drive is started, it waits for the registration sensor 8 to detect the front end of the paper, and the paper feed roller drive is stopped at the timing when the front end of the paper reaches the registration roller 4 from the paper detection to form a deflection for skew correction. Then, the sheet is made to wait at the registration roller unit. If the registration sensor 8 does not detect a sheet from the start of sheet feeding drive to a predetermined timing, image formation of the image forming unit of the printer and sheet feeding driving of the sheet feeding unit are stopped as a sheet feeding conveyance abnormality, A message indicating that a paper jam such as “paper misfeed” has occurred is displayed on the operation unit 17 (message display 2).

  After a predetermined time T1 from the start of image writing, the registration roller 4 is driven and the standby paper is conveyed to the secondary transfer portion including the intermediate transfer belt 3 and the secondary transfer roller 5. The time T1 is determined from the image forming path length (image forming path) L1 and the sheet conveying path length from the registration roller 4 to the secondary transfer section in order to synchronize the image formed by the image forming section and the sheet in the secondary transfer section. It is a fixed timing. After the registration roller 4 is driven, the registration roller 8 is stopped when the registration sensor 8 detects the trailing edge of the sheet and the trailing edge of the sheet exits the registration roller 4.

  When printing on a plurality of sheets continuously, the first image writing is started, then the second image writing is started after a predetermined time T0, and thereafter image formation is performed at a constant interval T0. Do. The paper is transported by driving the paper feed roller after T2 from each image writing timing, and driving the registration roller after T1, and the image is transferred to the paper by the same process as the first sheet, and the image is fixed by the fixing device 6. Then, the paper is discharged from the paper discharge roller 7 onto the paper discharge tray.

FIG. 10 is a diagram illustrating a state in which strip-shaped small-size paper (narrow paper) is set on the manual feed tray. FIG. 10A is a diagram illustrating a small-size paper set on the manual feed tray, a side fence, a pickup roller, and paper. The figure which looked at the presence detection filler from the upper part, (b) is the figure which looked at the small size paper set to the manual feed tray, the side fence, the pickup roller, and the paper presence / absence detection filler from the front.
The manual feed tray 13 is required to support various types and sizes of paper. Among them, there is a demand for printing on paper having an extremely small size in the width direction. For example, there is a demand for printing on strip-shaped paper such as candy paper, or printing on an unused portion using paper that is cut off from regular regular size paper by perforation. For example, B5 size paper is perforated paper that can be divided into four in the length direction, and after printing at three locations, the remaining part becomes a paper size (B6 half) having a length of B6 and a width of B6.

  Since the tray portion of the manual feed tray 13 is exposed outside the printer main body, the paper presence / absence detection means (paper presence / absence detection filler) 21 is often disposed in the vicinity of the paper feed means such as the pickup roller 14. In the embodiment, as shown in FIG. 1, the sheet presence / absence detection means (paper presence / absence detection filler) 21 is disposed in the vicinity of or substantially overlapping the pickup roller 14 in the projection plane orthogonal to the sheet conveyance direction.

  As shown in FIG. 10, the paper presence / absence detection means (paper presence / absence detection filler) 21 has a filler portion 21a that contacts the upper surface of the paper stacked on the manual feed tray 13 and a light shielding portion 21b that is linked to the angular position of the filler portion 21a. The presence / absence of a sheet is detected based on whether or not the light shielding unit 21b shields a transmissive photo interrupter (not shown). Since it is necessary to arrange the filler portion 21a outside the pickup roller 14 in the width direction, in the case of the strip-like paper 23 having a small paper width, the filler portion 21a is outside the paper width, and the presence or absence of the paper can be detected. Can not. Even when the sheets are stacked, the sheets cannot be detected, and the output of the sheet presence / absence detection means (sheet presence / absence detection filler) 21 is out of sheets.

  For this reason, the paper size of the manual feed tray 13 cannot be detected by the paper presence / absence detection means (paper presence / absence detection filler) 21 by the input from the operation unit 17 (the size in which the end surface in the width direction of the paper is inside the filler portion 21a position). ) Is set, the control unit ignores the output of the paper presence / absence detection means (paper presence / absence detection filler) 21. In other words, when printing on a small size paper (such as a strip-shaped narrow paper having a small size in the width direction), a paper of a size that is determined to be undetectable by the paper presence / absence detection means (paper presence / absence detection filler) 21. On the other hand, paper advance control for starting image formation is triggered by the detection by the paper detection means (registration sensor filler) 8 of the paper fed and conveyed by performing the paper feeding operation.

FIG. 11 is a diagram for explaining the control timing of the paper advance control when printing on a strip-shaped small size paper (narrow paper) (S-18 to S-10 in FIG. 8).
When the print size set by the operation unit (paper size setting unit) 17 determines that the paper size cannot be detected by the paper presence / absence detection unit (paper presence / absence detection filler) 21, the control unit detects the paper presence / absence detection unit. The output of (paper presence / absence detection filler) 21 is ignored. When a print request is issued for this paper size and the printer starts printing, the driving of the pickup roller 14 and paper feed roller 15 of the manual feed tray 13 is started first. When paper is set on the manual feed tray 13, the registration sensor 8 detects the leading edge of the fed paper. After the registration sensor 8 detects the paper, image writing is started and image formation is started. After the registration sensor 8 detects the leading edge of the paper, the pickup roller 14 and the paper feeding roller 15 stop driving at the timing when the leading edge of the paper reaches the registration roller 4 and forms a deflection for skew correction. Wait at the registration roller section.

  If the registration sensor 8 does not detect a sheet from the start of feeding from the manual feed tray 13 to a predetermined timing, it is determined that no paper is set on the manual feed tray 13 or that a paper feed conveyance abnormality has occurred. Then, the drive of the paper feeding unit is stopped, and a message for confirming whether paper is set in the manual feed tray 13 such as “paper is not set or paper misfeed” is displayed on the operation unit 17 (message display 3). To do. For this reason, even when no paper is set on the manual feed tray 13, image formation is not performed until the registration sensor 8 detects the paper, so that toner is wasted and the intermediate transfer belt 3 on the intermediate transfer belt 3 is recovered. It is possible to prevent the secondary transfer roller 5 from being soiled with untransferred toner.

  After the start of image formation, after a predetermined time T1 from the start of image writing, the registration roller 4 is driven and the waiting paper is conveyed to the secondary transfer unit including the intermediate transfer belt 3 and the secondary transfer roller 5. The time T1 is determined from the image forming path length (image forming path) L1 and the sheet conveying path length from the registration roller 4 to the secondary transfer section in order to synchronize the image formed by the image forming section and the sheet in the secondary transfer section. It is a fixed timing. After the registration roller 4 is driven, the registration roller 8 is stopped when the registration sensor 8 detects the trailing edge of the sheet and the trailing edge of the sheet exits the registration roller 4.

When printing on a plurality of sheets continuously, after the first registration roller drive is started, the second sheet feed drive is started after a predetermined time T3, and the registration sensor 8 detects the leading edge of the sheet. After that, image writing is started to form a second image. At time T3, the timing at which the trailing edge of the first sheet turns off the registration sensor 8 and the timing at which the leading edge of the second sheet fed from the manual feed tray 13 turns on the registration sensor 8 do not change. The timing is set so that the OFF state time can be secured. Similarly to the first sheet, the second sheet is made to wait for the sheet by the registration roller unit, and after a time T1 from the start of image writing, the registration roller 4 is driven to transfer the image to the sheet, and is discharged from the sheet discharge roller 7 through the fixing device 6. Eject paper onto the paper tray.
The third and subsequent sheets are also printed with the same processing and control timing.

  As described above, in this embodiment, when printing on a small-size sheet in which the sheet presence / absence detection unit (sheet presence / absence detection filler) 21 cannot detect the sheet, the control unit detects the sheet presence / absence detection unit (sheet presence / absence detection filler). ) Ignoring the information of 21 and performing a paper feeding operation before image formation, and confirming that the paper is waiting at the registration unit for image transfer to the paper (the registration sensor 8 detects the leading edge of the paper) and then forming the image. Therefore, even when printing is performed on a small size paper that cannot detect the presence or absence of paper, image formation is not performed if there is no paper, so toner is not wasted. It is possible to prevent the next transfer roller and the like from being soiled, and to prevent image defects such as back stains from occurring on the printing paper after printing is resumed.

[Modification 1]
Next, as a modification of the present invention, when an image is formed on a sheet of a size that is determined to be undetectable by the sheet presence / absence detection unit (sheet presence / absence detection filler 21), a sheet feeding operation is performed to perform sheet detection unit (registration sensor). 8) starts image formation after detecting the paper and sets a paper presence flag. When the paper presence flag is set, it is determined that the paper presence detection means (paper presence detection filler 21) cannot detect the paper. It is also possible to perform control such that image formation is started prior to the paper feeding operation even for a paper of a size to be processed.
In this control,
(1) When a sheet is not detected by a sheet detection means (registration sensor 8) after a sheet feeding operation is started, a sheet presence flag is canceled.
(2) When a jam occurs, cancel the paper presence flag.
(3) When it is determined that the paper size has been changed, the paper presence flag is canceled.
(4) The paper presence flag is canceled when the power is turned off or the power saving mode is entered.
Etc. are controlled.

  FIG. 12 is a flowchart showing the control operation of the first modified example. In the case of a paper size that cannot be detected by the paper presence / absence detection means, a paper presence flag is set and a strip-like small size paper (narrow paper) FIG. 6 is a diagram for explaining a control operation when printing processing is performed.

Processing in each step (S-1 to S-24) of the flowchart of the first modification shown in FIG. 12 is shown below.
S-1: The printer engine receives a print request for each page.
S-2: It is determined whether the print size set by the operation unit (paper size setting means) 17 is a paper size that can be detected by the paper presence / absence detection means. If the print size is a size that can detect the presence / absence of paper by the paper presence / absence detection means (paper presence / absence detection filler 18 or 21), the process proceeds to S-3.
S-3: The flow when the size of the paper presence / absence detection sensor (paper presence / absence detection filler 18 or 21) can be detected is the same as that of the first embodiment (S-3 to S-17 in FIG. 8). The description is omitted here.
S-4: When the paper size cannot be detected, the “paper present flag” is checked. When the “paper present flag” is not set, the process proceeds to S-5 (paper advance control), and when it is set, the process proceeds to S-19 (image advance control).
S-5: When the “paper present flag” is not set, the paper feeding operation is immediately started.
S-6: The registration sensor 8 checks whether the registration sensor 8 detects a sheet by a predetermined time. If a sheet is not detected by the predetermined time, the process proceeds to S-7. If a sheet is detected, the process proceeds to S-8.
S-7: A message such as “paper is not set or paper misfeed” is displayed on the operation unit 17 (message display 3) to prompt confirmation of whether paper is set.
S-8: When the registration sensor 8 detects a sheet, exposure is started on the photoreceptors of the image forming apparatuses 2a to 2d in order from the most upstream Bk image forming apparatus 2a to form an image.
S-9: “Paper presence flag” is set. (The “paper present flag” is retained until it is released.)
S-10: After the registration sensor detects the paper, the paper feed drive is stopped at a predetermined timing to wait for the paper.
S-11: A registration roller at a predetermined timing from the start of image writing (exposure) with the timing adjusted so that the image and the paper are synchronized at the secondary transfer portion (position where the intermediate transfer belt 3 and the secondary transfer roller 5 abut). 4 is started.
S-12: The sheet reaches the secondary transfer portion and image transfer to the sheet is started.
S-13: The sheet reaches the fixing device 6 and image fixing is started on the sheet.
S-14: The registration sensor 8 detects the trailing edge of the sheet (sensor information: sheet present → no sheet).
S-15: After the registration sensor 8 detects the trailing edge of the sheet, the driving of the registration roller 4 is stopped at a predetermined timing.
S-16: The fixing paper discharge sensor detects the trailing edge of the paper (sensor information: paper present → no paper).
S-17: After the fixing sheet discharge sensor detects the trailing edge of the sheet, it is determined that the sheet has been discharged to the sheet discharge tray at a predetermined timing.
S-18: Printing for the print request is completed when the sheet is discharged to the discharge tray.
S-19: When the “paper present flag” is set in S-4, exposure is started on the photoreceptors of the image forming devices 2a to 2d in order from the most upstream Bk image forming device 2a to form an image. I do.
S-20: The paper feeding operation is started at a predetermined timing from the start of image writing (exposure) to the photoconductor of the most upstream Bk image forming device 2a.
S-21: The registration sensor information is checked by the registration sensor 8 to detect the sheet by a predetermined time. If a sheet is not detected by the predetermined time, the process proceeds to S-22. If a sheet is detected, the process proceeds to S-24.
S-22: When the registration sensor 8 does not detect a sheet by a predetermined time, the “sheet present flag” is canceled.
S-23: A message such as “paper is not set or paper misfeed” is displayed on the operation unit 17 (message display 3) to prompt confirmation of whether paper is set.
S-24: After the registration sensor 8 detects the paper, the paper feed drive is stopped at a predetermined timing to wait for the paper.
After S-24, the process proceeds to S-11, and the processes of S-11 to S-18 are executed.

Next, the description of the above control operation will be supplemented.
FIG. 13 is a diagram for explaining the control timing when printing on a strip-like small size paper (narrow paper).
At the control timing of the first embodiment shown in FIG. 11 described above, image formation is started after the registration sensor 8 detects a sheet for each sheet. Therefore, while the image is conveyed through the image formation path length L1, the sheet is Since waiting is performed at the registration roller section, the waiting time becomes longer, and productivity may be reduced when printing a plurality of sheets. Therefore, as a modified example when the paper presence / absence detection means (paper presence / absence detection filler) 21 of the manual feed tray 13 determines that the paper size cannot be detected, the control timing shown in FIG. 13 can be used.
When the control unit determines that the sheet size cannot be detected by the paper presence / absence detection unit (paper presence / absence detection filler) 21, the output of the paper presence / absence detection unit (paper presence / absence detection filler) 21 is ignored and the first printing is performed. In response to the request, similarly to the first embodiment, driving of the pickup roller 14 and the paper feed roller 15 of the manual feed tray 13 is started according to the paper advance control processing (S-5 to S-10 in FIG. 12).

  When paper is set on the manual feed tray 13, the registration sensor 8 detects the leading edge of the fed paper. After the registration sensor 8 detects a sheet, the control unit starts image writing to start image formation and sets a sheet presence flag. After the registration sensor 8 detects the leading edge of the paper, the pickup roller 14 and the paper feeding roller 15 stop driving at the timing when the leading edge of the paper reaches the registration roller 4 and forms a deflection for skew correction. Wait at the registration roller section.

If the registration sensor 8 does not detect paper between the start of paper feed from the manual feed tray 13 and a predetermined timing, the control unit does not set paper on the manual feed tray 13 or a paper feed conveyance error occurs. And the operation unit 17 stops the driving of the paper feeding unit and displays a message for confirming whether paper is set in the manual feed tray 13 such as “paper is not set or paper misfeed” (message) Display 3).
After the start of image formation, after a predetermined time T1 from the start of image writing, the registration roller 4 is driven and the waiting paper is conveyed to the secondary transfer unit including the intermediate transfer belt 3 and the secondary transfer roller 5. After the registration roller 4 is driven, the registration roller 8 is stopped when the registration sensor 8 detects the trailing edge of the sheet and the trailing edge of the sheet exits the registration roller 4.

  Since the paper presence flag is set for the second and subsequent print requests, the process proceeds to image advance control, image writing is performed, and image formation is started. After time T2 from the start of image writing, the pickup roller 14 and paper feed roller 15 are driven to feed the paper. Thereafter, the printing operation is performed at the same control timing as the normal paper size (paper presence detecting means (paper presence detecting filler 21) can detect the paper).

  Accordingly, when continuous printing is performed on a plurality of sheets, the second and subsequent sheets start to be written on the second sheet after a predetermined time T0 from the start of writing the first sheet, and thereafter the images are printed at a constant interval T0. Form. The paper is fed and transported after T2 from each image writing timing by driving the paper feed roller, and after T1, the registration roller is driven to transfer the image onto the paper, and after fixing the image in the fixing device 6, the paper is discharged from the paper discharge roller 7. Eject onto the tray. For this reason, the second and subsequent sheets can be printed at the same interval as usual, and productivity does not decrease.

  When the paper set in the manual feed tray 13 runs out, the registration sensor 8 does not detect the leading edge of the paper, so that the control unit determines that there is no paper in the manual feed tray 13 or that a paper feed conveyance abnormality has occurred. And the image writing flag is canceled, and a message prompting the operator to confirm whether there is paper in the manual feed tray 13 such as “paper is not set or paper misfeed” is displayed on the operation unit 17. (Message display 3). In this case, since image formation has already been started, a toner image is formed on the intermediate transfer belt, but recovery processing is performed in the same manner as in a normal jam.

When printing on strip-shaped small-size paper (narrow paper) that is a special paper size, it is considered that the number of paper sets is the same as the number of prints or the number of sheets with a margin is set. It is considered that the frequency of the absence of paper on the way is low.
When paper is set again in the manual feed tray 13 and printing is resumed, the paper presence flag is cleared, so the control unit performs a paper feeding operation in response to the print request, and the registration sensor 8 detects the leading edge of the paper. After that, image formation is started.

In addition to the case where the registration sensor 8 does not detect the leading edge of the sheet as described above, the registration sensor 8 does not detect the trailing edge of the sheet after driving the registration roller, or the fixing discharge sensor 9 detects the leading edge and trailing edge of the sheet. The paper presence flag is also released when it is determined that a paper conveyance error (paper jam) has occurred, such as when no detection is made.
Further, in order to prevent image formation in the absence of a sheet as much as possible, if the sheet size setting of the manual feed tray 13 is changed, the sheet may be removed from the manual feed tray 13 and therefore the sheet presence flag is canceled. . The paper presence flag is also released when the paper presence / absence detection means (paper presence / absence detection filler) 21 outputs a paper detection signal.
Furthermore, even when the printer is turned off or enters the power saving mode, the paper presence flag is canceled because the paper set on the manual feed tray may be removed.

It is also possible to have the control methods of the first embodiment and the first modification as modes and switch the control modes according to how the user uses the printer.
For example, it is possible to configure such that the printer driver is provided with an item “small size mode setting” and switched, or “operation mode setting” is switched from the operation unit (operation panel) of the printer main body.

[Example 2]
In the image forming apparatus according to the present invention, as shown in FIGS. 3 to 5 and FIG. 10, the manual feed tray 13 is provided with side fences 22 (22 a and 22 b) that are regulating means for regulating the paper width direction. A method for detecting the position of the side fence 22 (22a, 22b) by a regulation position detecting means (side fence position detecting means) (not shown) and automatically detecting the paper width size is well known.
Therefore, since it is possible to determine that the size of the paper loaded on the manual feed tray 13 from the side fence position is a size that cannot be detected by the paper presence / absence detection means (paper presence / absence detection filler) 21, in the second embodiment, When the control unit detects the movement of the side fence 22 (22a, 22b) by the restriction position detection means (side fence position detection means), the detection result is used as a trigger to switch from the image advance control to the paper advance control. It is a thing. Hereinafter, the control operation will be described.

  FIG. 14 is a flowchart showing the control operation of the second embodiment, and detects the side fence position of the manual feed tray and performs a normal print operation depending on whether the paper size can be detected by the paper presence / absence detection means. FIG. 6 is a diagram illustrating a control operation when performing a process of performing printing and a process of printing on a strip-shaped small-size sheet (narrow sheet).

Processing in each step (S-1 to S-23) of the flowchart of the second embodiment shown in FIG. 14 is shown below.
S-1: The printer engine receives a print request for each page.
S-2: The position of the side fence 22 (22a, 22b) of the manual feed tray 13 is detected by the side fence position detecting means.
S-3: From the side fence position information of the manual feed tray 13, it is determined whether the set paper has a paper width that can be detected by the paper presence / absence detection means (paper presence / absence detection filler) 21. When the paper width can be detected, the process proceeds to S-4 (image advance control), and when the paper width cannot be detected, the process proceeds to S-19 (paper advance control).
S-4: It is determined from the information of the paper presence / absence detection means (paper presence / absence detection filler) 21 whether or not there is paper in the tray. When there is no paper, the process proceeds to S-5, and when there is a paper, the process proceeds to S-6.
S-5: A message such as “Set paper” is displayed on the operation unit 17 (message display 1).
S-6: When paper is present, exposure is started on the photoreceptors of the image forming devices 2a to 2d in order from the most upstream Bk image forming device 2a to form an image.
S-7: The paper feeding operation is started at a predetermined timing from the start of image writing (exposure) to the photoconductor of the Bk image forming device 2a.
S-8: The registration sensor information is checked by the registration sensor 8 to detect the sheet by a predetermined time. If a sheet is not detected by the predetermined time, the process proceeds to S-9. If a sheet is detected, the process proceeds to S-10.
S-9: A message such as “paper misfeed” is displayed on the operation unit 17 (message display 2) to prompt jam processing.
S-10: After the registration sensor 8 detects the paper, the paper feed drive is stopped at a predetermined timing to wait for the paper.
S-11: A registration roller at a predetermined timing from the start of image writing (exposure) with the timing adjusted so that the image and the paper are synchronized at the secondary transfer portion (position where the intermediate transfer belt 3 and the secondary transfer roller 5 abut). 4 is started.
S-12: The sheet reaches the secondary transfer portion and image transfer to the sheet is started.
S-13: The sheet reaches the fixing device 6 and image fixing is started on the sheet.
S-14: The registration sensor 8 detects the trailing edge of the sheet (sensor information: sheet present → no sheet).
S-15: After the registration sensor 8 detects the trailing edge of the sheet, the driving of the registration roller 4 is stopped at a predetermined timing.
S-16: The fixing paper discharge sensor 9 detects the trailing edge of the paper (sensor information: paper present → no paper).
S-17: After the fixing sheet discharge sensor 9 detects the trailing edge of the sheet, it is determined that the sheet has been discharged to the sheet discharge tray at a predetermined timing.
S-18: Printing for the print request is completed when the sheet is discharged to the discharge tray.
S-19: When it is determined in S-3 from the side fence position information of the manual feed tray 13 that the set paper cannot be detected by the paper presence / absence detection means (paper presence / absence detection filler) 21, the paper feeding operation is immediately performed. To start.
S-20: The registration sensor information is checked by the registration sensor 8 to detect the sheet by a predetermined time. If a sheet is not detected by the predetermined time, the process proceeds to S-21. If a sheet is detected, the process proceeds to S-22.
S-21: A message such as “paper is not set or paper misfeed” is displayed on the operation unit 17 (message display 3) to prompt confirmation of whether paper is set.
S-22: When the registration sensor 8 detects a sheet, exposure is started on the photoreceptors of the image forming devices 2a to 2d in order from the most upstream Bk image forming device 2a to form an image.
S-23: After the registration sensor 8 detects the paper, the paper feed drive is stopped at a predetermined timing to wait for the paper.
After S-23, the process proceeds to S-11, and the processes of S-11 to S-18 are executed.

The control operation of the second embodiment described above is such that the position of the side fence (jogger fence) 22 (22a, 22b) of the manual feed tray is in the width direction and inside the filler 21a of the paper presence / absence detection means (paper presence / absence detection filler) 21. It is a configuration that triggers that it has moved. Specifically, when receiving a print request, the control unit of the printer engine detects the side fence position of the manual feed tray 13 by the side fence position detection means, and the paper set on the manual feed tray 13 is detected from the side fence position information. The detection means (paper presence / absence detection filler) 21 determines whether the paper width can be detected. Therefore, in the present embodiment, the control unit can automatically detect the paper width from the side fence position information, so that the trouble of setting the paper size by the operation unit 17 can be saved.
For detecting the side fence position, a rotary encoder installed on the pinion gear linked to the side fence rack or a sliding position that detects the contact position that slides linked to the movement of the side fence is used. Detection means such as a detection substrate can be used.

  In the present embodiment, when the control unit determines from the side fence position information that the set sheet has a sheet width capable of detecting the presence / absence of the sheet, the control unit detects the presence of the sheet based on the information of the sheet presence / absence detection unit (sheet presence / absence detection filler) 21. Starts image formation and executes printing (the same operation as the image advance control described in the first embodiment). If the paper width is not detected by the paper presence / absence detection means (paper presence / absence detection filler) 21, the paper feeding operation is started, the paper is detected by the registration sensor 8, the image formation is started, and printing is started. Execute (the same operation as the paper advance control described in the first embodiment). Therefore, even when printing is performed on a small size paper that cannot detect the presence or absence of paper, image formation is not performed if there is no paper, so that toner is not wasted and a secondary transfer roller or the like is used. It is possible to prevent contamination and to prevent image defects such as back stains from occurring on the print paper after resuming printing.

[Modification 2]
Since the control method of the second embodiment can be implemented in combination with the control method using the paper presence flag as in the first modified example, the combined control method is referred to as a second modified example below. Shown in
FIG. 15 is a flowchart showing the control operation of the second modified example. The side fence position of the manual feed tray is detected, and when the paper width cannot be detected by the paper presence / absence detection means, the paper presence flag is set. FIG. 6 is a diagram for explaining a control operation in the case of performing processing for printing on a strip-shaped small-size paper (narrow paper).

Processing in each step (S-1 to S-25) of the flowchart of the modification shown in FIG. 15 is shown below.
S-1: The printer engine receives a print request for each page.
S-2: The position of the side fence 22 (22a, 22b) of the manual feed tray 13 is detected.
S-3: From the side fence position information of the manual feed tray 13, it is determined whether the set paper has a paper width that can be detected by the paper presence / absence detection means (paper presence / absence detection filler) 21. If the paper width can be detected, the process proceeds to S-4. If the paper width cannot be detected, the process proceeds to S-5.
S-4: Since the flow (normal image advance control) when the paper width can be detected by the paper presence / absence detection means (paper presence / absence detection filler) 21 is the same as that in the first embodiment, the description thereof is omitted here. To do.
S-5: When the paper width cannot be detected by the paper presence / absence detection means (paper presence / absence detection filler) 21, the “paper presence flag” is checked. When the “paper present flag” is not set, the process proceeds to S-6 (paper advance control), and when it is set, the process proceeds to S-20 (image advance control).
S-6: When the “paper present flag” is not set, the paper feeding operation is immediately started.
S-7: The registration sensor 8 checks the registration sensor information to detect the sheet by a predetermined time. If a sheet is not detected by the predetermined time, the process proceeds to S-8. If a sheet is detected, the process proceeds to S-9.
S-8: A message such as “paper is not set or paper misfeed” is displayed on the operation unit 17 (message display 3) to prompt confirmation of whether paper is set.
S-9: When the registration sensor 8 detects the paper, exposure is started on the photoreceptors of the image forming devices 2a to 2d in order from the most upstream Bk image forming device 2a to form an image.
S-10: “Paper presence flag” is set. (The “paper present flag” is retained until it is released).
S-11: After the registration sensor 8 detects the paper, the paper feed drive is stopped at a predetermined timing to wait for the paper.
S-12: Registration roller at a predetermined timing from the start of image writing (exposure) with the timing synchronized so that the image and the paper are synchronized at the secondary transfer portion (position where the intermediate transfer belt 3 and the secondary transfer roller 5 abut). 4 is started.
S-13: The sheet reaches the secondary transfer portion and image transfer to the sheet is started.
S-14: The sheet reaches the fixing device 6 and image fixing on the sheet is started.
S-15: The registration sensor 8 detects the trailing edge of the sheet (sensor information: sheet present → no sheet).
S-16: After the registration sensor 8 detects the trailing edge of the sheet, the driving of the registration roller 4 is stopped at a predetermined timing.
S-17: The fixing paper discharge sensor 9 detects the trailing edge of the paper (sensor information: paper present → no paper).
S-18: After the fixing sheet discharge sensor 9 detects the trailing edge of the sheet, it is determined that the sheet is completely discharged to the sheet discharge tray at a predetermined timing.
S-19: Printing for the print request is completed when the sheet is discharged to the discharge tray.
S-20: When the “paper present flag” is set in S-5, exposure is started on the photoreceptors of the image forming apparatuses 2a to 2d in order from the most upstream Bk image forming apparatus 2a to form an image. I do.
S-21: The paper feeding operation is started at a predetermined timing from the start of image writing (exposure) to the photoconductor of the Bk image forming device 2a.
S-22: The registration sensor 8 checks the registration sensor information to detect the sheet by a predetermined time. If a sheet is not detected by the predetermined time, the process proceeds to S-23. If a sheet is detected, the process proceeds to S-25.
S-23: When the registration sensor 8 does not detect a sheet by a predetermined time, the “sheet presence flag” is canceled.
S-24: A message such as “paper is not set or paper misfeed” is displayed on the operation unit 17 (message display 3) to prompt confirmation of whether paper is set.
S-25: After the registration sensor 8 detects the paper, the paper feed drive is stopped at a predetermined timing to wait for the paper.
After S-25, the process proceeds to S-12, and the processes of S-12 to S-19 are executed.

  As described above, in the second modified example, the control method according to the second example is combined with the control method using the paper presence flag as in the first modified example, and the first modified example. Is different in that the position of the side fence 22 is detected in step S-2. Therefore, in the second modification, the same effects as in the first modification can be obtained, and the paper width can be automatically detected from the side fence position information, so that the trouble of setting the paper size by the operation unit 17 can be saved. it can.

1: Exposure device 2a, 2b, 2c, 2d: Image forming device 3: Intermediate transfer belt 4: Registration roller 5: Secondary transfer roller 6: Fixing device 7: Paper discharge roller 8: Registration sensor (paper detection means)
9: fixing paper discharge sensor 10: paper feed tray 11: paper feed roller 12: separation means 13: manual feed tray 14: pickup roller 15: paper feed roller 16: paper separation member (separation means)
17: Operation unit (paper size setting means)
18: Paper presence / absence detection means (paper presence / absence detection filler)
21: Paper presence / absence detection means (paper presence / absence detection filler)
21a: Filler part 21b: Light shielding part 22 (22a, 22b): Side fence (regulating means)
23: Strip paper (narrow paper)

JP-A-4-34463 JP 2001-296785 A JP-A-10-153893

Claims (16)

An image forming unit, a transfer unit that transfers an image formed by the image forming unit to a sheet, a conveying unit that conveys the sheet to the transfer unit in synchronization with the image formed by the image forming unit, A sheet feeding unit configured to supply a sheet to the conveying unit; and a sheet detecting unit configured to detect a sheet fed from the sheet feeding unit before the conveying unit, and the sheet from the sheet feeding unit to the transfer unit. In the image forming apparatus, the transport path is shorter than the image forming path from the image forming start position of the image forming unit to the transfer unit.
The paper feed unit has a paper presence / absence detection unit, and for paper of a size that is determined to be undetectable by the paper presence / absence detection unit, a paper feed operation is performed and Paper advance control for starting image formation is triggered by the detection by the paper detection means, and for paper of a size that can detect the presence or absence of paper by the paper presence / absence detection means, in accordance with the image after the start of image formation An image forming apparatus comprising control means for performing image advance control for starting paper feed conveyance. The image forming apparatus according to claim 1.
The image forming unit includes a plurality of image carriers, and the images formed on the plurality of image carriers are superimposed on an intermediate transfer member for primary transfer, and then the image transferred to the intermediate transfer member is transferred to a sheet of paper 2 It is configured to perform the next transfer, and the length from the exposure position of the image carrier, which is an attachment reference at which image formation is first started, to the primary transfer portion, and the length from the primary transfer portion to the secondary transfer portion is the image. An image forming apparatus comprising a formation pass. The image forming apparatus according to claim 1 or 2,
An image forming apparatus, wherein a length from a position of a paper feed roller of a paper feed tray of the paper feed unit or a pickup roller of a manual feed tray to the transfer unit or the secondary transfer unit is a paper transport path. The image forming apparatus according to any one of claims 1 to 3,
When forming an image on a sheet having a size determined to be undetectable by the sheet presence / absence detecting unit, the control unit performs a paper feeding operation and starts image formation after the sheet detecting unit detects the sheet. An image forming apparatus. The image forming apparatus according to claim 1,
Paper size setting means, and the control means determines from the paper size set by the paper size setting means whether the paper presence / absence detection means can detect the presence / absence of the paper; An image forming apparatus characterized by ignoring the detection result of the presence / absence detection means. The image forming apparatus according to any one of claims 1 to 5,
The manual feed tray of the paper feed unit includes a restricting unit that restricts the width direction of the set sheet and a restricting position detecting unit that detects a position of the restricting unit, and the control unit detects the position of the restricting unit. An image forming apparatus characterized in that, based on the result, it is determined whether the sheet presence / absence detection unit can detect the presence / absence of a sheet, and if it is determined that the sheet presence / absence cannot be detected, the detection result of the sheet presence / absence detection unit is ignored. The image forming apparatus according to claim 6.
An image forming apparatus according to claim 1, wherein when the restriction position detection means detects the movement of the restriction means, the control means switches from the image advance control to the paper advance control using the detection result as a trigger. The image forming apparatus according to any one of claims 1 to 7,
An image forming apparatus according to claim 1, wherein the sheet presence / absence detecting means includes a filler type sensor in a paper feed tray and a manual feed tray of the paper feed unit. The image forming apparatus according to claim 1,
The image forming apparatus according to claim 1, wherein the transport unit is configured to transport the paper with a center reference. An image forming unit, a transfer unit that transfers an image formed by the image forming unit to a sheet, a conveying unit that conveys the sheet to the transfer unit in synchronization with the image formed by the image forming unit, A sheet feeding unit configured to supply a sheet to the conveying unit; and a sheet detecting unit configured to detect a sheet fed from the sheet feeding unit before the conveying unit, and the sheet from the sheet feeding unit to the transfer unit. In the control method of the image forming apparatus, the transport path is shorter than the image forming path from the image forming start position of the image forming unit to the transfer unit.
For paper of a size that is determined that the presence / absence of paper cannot be detected by the paper presence / absence detection unit provided in the paper feeding unit, the paper detection unit detects the paper that has been fed and conveyed by performing a paper feeding operation. Is used as a trigger to perform paper advance control to start image formation, and for paper of a size that can detect the presence or absence of paper by the paper presence / absence detection means, paper feed conveyance is started in accordance with the image after image formation is started A method for controlling an image forming apparatus, wherein image advance control is performed. The method of controlling an image forming apparatus according to claim 10.
The image forming apparatus includes a plurality of image carriers in the image forming unit, and images formed on the plurality of image carriers are primarily transferred to the intermediate transfer member and then transferred to the intermediate transfer member. In the case of a configuration in which the transferred image is secondarily transferred to a sheet, the image transfer member from the exposure position to the primary transfer portion, which is an attachment reference at which image formation is first started, and from the primary transfer portion to the secondary transfer portion A method for controlling an image forming apparatus, characterized in that the length up to is the image forming path. 12. The method of controlling an image forming apparatus according to claim 10 or 11,
The length from the position of the paper feed roller of the paper feed tray of the paper feed unit or the pickup roller of the manual feed tray to the transfer unit or the secondary transfer unit is a paper transport path. Control method. The method of controlling an image forming apparatus according to any one of claims 10 to 12,
When an image is formed on a paper whose size is determined to be undetectable by the paper presence / absence detecting means, a paper feeding operation is performed, and the paper detecting means provided in front of the conveying means for conveying the paper to the transfer unit detects the paper. A method of controlling an image forming apparatus, wherein image formation is started after The method for controlling an image forming apparatus according to claim 10, wherein:
It is determined from the paper size set by the paper size setting means whether the paper presence / absence detection means can detect the presence / absence of the paper, and when it is determined that the paper presence / absence cannot be detected, the detection result of the paper presence / absence detection means is ignored. A method for controlling an image forming apparatus. 15. The method for controlling an image forming apparatus according to claim 10, wherein:
From the detection result of the restriction position detection means for detecting the position of the restriction means for restricting the width direction of the set paper provided in the manual feed tray of the paper feed unit, it is determined whether the paper presence / absence detection means can be detected. A control method for an image forming apparatus, characterized in that when it is determined that the presence / absence of a sheet cannot be detected, the detection result of the sheet presence / absence detecting means is ignored. The method of controlling an image forming apparatus according to claim 15.
A control method for an image forming apparatus, wherein when the movement of the restriction means is detected by the restriction position detection means, the detection result is switched from image advance control to paper advance control.

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