Image forming apparatus and method for controlling option paper feed device in image forming apparatus

Abstract

To mount an option paper feed device in an image forming apparatus body and use the option paper feed device as a paper feed source to improve the CPM.SOLUTION: An image forming apparatus 10 according to the present disclosure comprises an image forming apparatus body 10a and an option paper feed device 100. When the option paper feed device 100 is used as a paper feed source, an acceleration and deceleration roller pair 108 are controlled so that a leading end of a sheet reaches a nip part Pb of a registration roller pair 72a at an ideal timing. Consequently, the option paper feed device 100 is mounted without a change in the specifications of the image forming apparatus body 10a and the option paper feed device 100 is used as the paper feed source to improve the CPM.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to an image forming apparatus and a control method for an optional paper feeder in an image forming apparatus, and more particularly to an image forming apparatus including an image forming apparatus main body and an optional paper feeder that can be optionally attached to the image forming apparatus main body, and a control method for the optional paper feeder in an image forming apparatus. [Background technology]

[0002] In image forming devices using electrophotography or inkjet printing, image formation processing, i.e., printing, may be performed continuously on multiple sheets of paper. In this case, multiple sheets of paper are transported one by one from a paper feed cassette, which is the paper feed source. However, when feeding from the paper feed cassette, the paper feed roller that feeds the paper may slip, causing a deviation in the paper feed timing, which may result in a paper feed delay. Patent Document 1 discloses an example of a technology that can maintain the number of sheets of paper transported per unit time, in other words the number of sheets of paper printed per unit time, CPM (or PPM).

[0003] According to the technology disclosed in this patent document, the acceleration time point for increasing the transport speed of the next sheet is calculated based on the inter-sheet time from the start of feeding a given sheet to the start of feeding the next sheet to be transported after the given sheet, and the paper feed linear speed curve of the latest next sheet when the start of feeding of the next sheet is the most delayed. Then, at the calculated acceleration time point, the transport speed of the next sheet being fed is switched from a first paper feed linear speed to a second paper feed linear speed that is higher than the first paper feed linear speed. This allows a constant CPM to be maintained even if a paper feed delay occurs. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2015-151203 A Summary of the Invention [Problem to be solved by the invention]

[0005] Incidentally, CPM is an index that indicates the performance of an image forming apparatus, and the larger the CPM value, the higher the productivity of the image forming apparatus. One measure to increase the CPM value is to increase the printing speed, or the so-called process speed, but this measure leads to high costs (high prices) of the image forming apparatus. Another measure is to reduce the interval between each sheet that is conveyed in sequence, specifically, the sheet interval between the trailing edge of the preceding sheet and the leading edge of the following sheet that follows the preceding sheet. However, this other measure reduces the allowable amount (length of time) of paper feed delay, or in other words the paper feed delay margin, so that conveyance errors are more likely to occur, and if one tries to reduce the likelihood of conveyance errors, the image forming apparatus will also become more expensive. Users who are conscious of the productivity of the image forming apparatus often print a large amount of paper, and therefore tend to purchase an optional paper feeder, which is one of the optional devices.

[0006] Therefore, an object of the present disclosure is to provide a new image forming device and a control method for an optional paper feeding device in an image forming device, which can improve CPM by attaching an optional paper feeding device to the image forming device main body and using the optional paper feeding device as the paper feeding source. [Means for solving the problem]

[0007] To achieve this object, the present disclosure includes a first disclosure related to an image forming apparatus, and a second disclosure related to a control method for an optional paper feeder in an image forming apparatus.

[0008] The first disclosure of the image forming apparatus includes an image forming apparatus main body and an optional paper feeder that can be attached to the image forming apparatus main body. The image forming apparatus main body includes an image forming means and a registration roller (sometimes called a "paper stop roller"). The image forming means performs an image forming process for forming an image on a sheet-shaped image recording medium. The registration roller conveys the image recording medium to an image forming process position by the image forming means, and more specifically, measures the timing for inserting the leading edge of the image recording medium into the image forming process position. Meanwhile, the optional paper feeder includes a first storage section, a first paper feed roller, and an acceleration / deceleration roller. The first storage section accommodates a plurality of image recording media. The first paper feed roller supplies the image recording media from the first storage section one by one to a first conveying path that leads to a conveying position of the image recording media by the registration roller. The acceleration / deceleration roller conveys the image recording media supplied to the first conveying path to a conveying position by the registration roller. Furthermore, the first disclosure includes a control means. The control means is provided in the image forming apparatus main body or the optional paper feeder, and controls the conveying speed of the image recording medium by the acceleration / deceleration rollers so that the leading edge of the image recording medium conveyed by the acceleration / deceleration rollers reaches the conveying position by the registration rollers at a predetermined time after the first paper feed rollers start to supply the image recording medium to the first conveying path.

[0009] In the first disclosure, a first detection means may be further provided. This first detection means is provided at a position between the position where the image recording medium is conveyed by the acceleration / deceleration rollers in the first conveying path and the position where the image recording medium is conveyed by the registration rollers, and is closer to the position where the image recording medium is conveyed by the acceleration / deceleration rollers, and detects the leading edge of the image recording medium. In this case, the control means may control the conveying speed by the acceleration / deceleration rollers based on the detection result by the first detection means. The first detection means is provided in the image forming apparatus main body or the optional paper feeder.

[0010] In addition, in the first disclosure, a second detection means may be further provided. This second detection means is provided at a position in the first transport path between a supply position of the image recording medium to the first transport path by the first feed roller and a transport position of the image recording medium by the acceleration / deceleration roller, and detects the leading edge of the image recording medium. In this case, the control means may control the transport speed by the acceleration / deceleration roller based on the detection result by the second detection means. The second detection means is provided in the optional paper feeder.

[0011] Furthermore, in the first disclosure, a first detection means and a second detection means may be provided. As described above, the first detection means is provided at a position between the conveying position of the image recording medium by the acceleration / deceleration rollers in the first conveying path and the conveying position by the registration rollers, closer to the conveying position by the acceleration / deceleration rollers, and detects the leading edge of the image recording medium. The second detection means is provided at a position between the supplying position of the image recording medium to the first conveying path by the first feed rollers in the first conveying path and the conveying position by the acceleration / deceleration rollers, and detects the leading edge of the image recording medium. In this case, the control means may control the conveying speed by the acceleration / deceleration rollers based on the detection results by the first detection means and the second detection means. Note that each of the first detection means and the second detection means is provided in the optional paper feeder.

[0012] The image forming apparatus main body may further include a second storage section and a second paper feed roller. The second storage section stores a plurality of image recording media. The second paper feed roller supplies the image recording media from the second storage section one by one to a second transport path that connects to a transport position by the registration roller. In this case, it is preferable that the image recording media supplied to the second transport path by the second paper feed roller is transported by the second paper feed roller to the transport position by the registration roller. In other words, it is preferable that no transport means other than the second paper feed roller and the registration roller is provided between the transport position of the image recording medium by the second paper feed roller on the second transport path and the transport position by the registration roller.

[0013] In addition, the image formation processing speed by the image forming means is the same whether the image formation processing is performed on an image recording medium transported from the first storage section via the first transport path to a transport position by the registration rollers or whether the image formation processing is performed on an image recording medium transported from the second storage section via the second transport path to a transport position by the registration rollers.

[0014] In addition, it is preferable that the first sheet interval, which is the interval between the image recording media at the conveying position by the registration roller when the multiple image recording media are continuously conveyed from the first storage unit to the conveying position by the registration roller via the first conveying path, is smaller than the second sheet interval, which is the interval between the image recording media at the conveying position by the registration roller when the multiple image recording media are continuously conveyed from the second storage unit to the conveying position by the registration roller via the second conveying path. Strictly speaking, the first sheet interval is the interval between the rear end of the preceding image recording medium at the conveying position by the registration roller when the multiple image recording media are continuously conveyed from the first storage unit to the conveying position by the registration roller via the first conveying path, and the front end of the following image recording medium following the preceding image recording medium. And the second sheet interval is the interval between the rear end of the preceding image recording medium at the conveying position by the registration roller when the multiple image recording media are continuously conveyed from the second storage unit to the conveying position by the registration roller via the second conveying path, and the front end of the following image recording medium following the preceding image recording medium.

[0015] A second disclosure of the present disclosure, which relates to a method for controlling an optional paper feeder in an image forming apparatus, includes a control step. Here, the image forming apparatus includes an image forming apparatus main body and an optional paper feeder that can be arbitrarily attached to the image forming apparatus main body. The image forming apparatus main body has an image forming means and a registration roller. The image forming means performs an image forming process for forming an image on a sheet-shaped image recording medium. The registration roller transports the image recording medium to an image forming process position by the image forming means, and more specifically, measures the timing for inserting the leading end of the image recording medium into the image forming process position. Meanwhile, the optional paper feeder has a first storage section, a first feed roller, and an acceleration / deceleration roller. The first storage section stores a plurality of image recording media. The first feed roller supplies the image recording media from the first storage section to a first transport path that leads to a transport position of the image recording media by the registration roller, one by one. The acceleration / deceleration roller transports the image recording media supplied to the first transport path to a transport position by the registration roller. Then, in the control step, the transport speed of the image recording medium by the acceleration / deceleration rollers is controlled so that the leading edge of the image recording medium transported by the acceleration / deceleration rollers reaches the transport position by the registration rollers at a predetermined time point after a predetermined time has elapsed from the point at which the first paper feed rollers start supplying the image recording medium to the first transport path. Effect of the Invention

[0016] According to the present disclosure, by mounting an optional sheet feeding device on the image forming apparatus main body and using the optional sheet feeding device as a sheet feeding source, it is possible to improve the CPM. [Brief description of the drawings]

[0017] [Figure 1] FIG. 1 is a diagram illustrating an outline of the internal configuration of an image forming apparatus according to a first embodiment of the present disclosure. [Diagram 2] 2 is an enlarged schematic diagram showing a portion including a paper transport path from the paper feed rollers to the registration rollers of the image forming apparatus main body in FIG. 1 and a paper transport path from the paper feed rollers to the registration rollers of the optional paper feeder. [Diagram 3]FIG. 3 is a block diagram showing the electrical configuration of the image forming apparatus according to the first embodiment. [Figure 4] FIG. 4 is a diagram showing the relationship between the transport time and the transport distance of a sheet when the main body cassette in the first embodiment is used as the sheet feed source. [Diagram 5] FIG. 5 is a diagram showing specifications including the CPM when the main body cassette in the first embodiment is used as the paper feed source. [Figure 6] FIG. 6 is a diagram showing the relationship between the transport time and the transport distance of a sheet when the optional sheet feeder in the first embodiment is used as the sheet feed source. [Figure 7] FIG. 7 is a diagram showing specifications including the CPM when the optional paper feeder in the first embodiment is used as the paper feed source. [Figure 8] FIG. 8 is a flowchart showing the flow of the first control task in the first embodiment. [Figure 9] FIG. 9 is a flowchart showing the flow of the second control task in the first embodiment. [Figure 10] FIG. 10 is a diagram showing the relationship between the transport time and the transport distance of a sheet when the optional sheet feeder is set as the sheet feed source in the second embodiment of the present disclosure. [Figure 11] FIG. 11 is a diagram showing the relationship between the transport time and the transport distance of a sheet when the optional sheet feeder is set as the sheet feed source in the third embodiment of the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] [First Example] The first embodiment of the present disclosure will be described using an image forming apparatus 10 shown in FIG. 1 as an example.

[0019] The image forming apparatus 10 according to the first embodiment is a so-called multifunction peripheral (MFP) having multiple functions such as a copy function, a printer function, an image scanner function, and a fax function. FIG. 1 is a diagram showing the internal configuration of the image forming apparatus 10 installed in a usable state, as viewed from the front side of the image forming apparatus 10. That is, the up-down direction in FIG. 1 corresponds to the up-down direction of the image forming apparatus 10. And the left-right direction in FIG. 1 corresponds to the left-right direction of the image forming apparatus 10. Furthermore, the front side of the paper surface of FIG. 1 corresponds to the front of the image forming apparatus 10. And the back side of the paper surface of FIG. 1 corresponds to the rear of the image forming apparatus 10.

[0020] This image forming apparatus 10 includes an image forming apparatus main body 10a and an optional paper feeder 100 that is attached to the lower part of this image forming apparatus main body 10a. The optional paper feeder 100 is one of the optional devices, and can be attached to the image forming apparatus main body 10a. In other words, the image forming apparatus main body 10a can function as a multifunction device by itself, but this first embodiment is premised on the image forming apparatus 10 having the optional paper feeder 100 attached to the image forming apparatus main body 10a.

[0021] An image reading section 12 is provided at the top of the image forming apparatus 10 (image forming apparatus main body 10a) as an image reading means. The image reading section 12 performs image reading processing by reading an image of an original (not shown) and outputting two-dimensional read image data corresponding to the image of the original. For this purpose, the image reading section 12 has an original table 14 on which an original is placed. The original table 14 is formed of a transparent member such as glass having a roughly rectangular flat plate shape, and is provided so that both main surfaces are aligned in the horizontal direction. An image reading unit 16 is provided below the original table 14. Although detailed explanation is omitted, the image reading unit 16 has a light source, a mirror, a lens, a line sensor, etc., and has a linear image reading position Pr extending along the front-rear direction of the image forming apparatus 10 on the upper surface of the original table 14. Furthermore, a drive mechanism (not shown) for moving (scanning) the image reading position Pr of the image reading unit 16 along the left-right direction of the image forming apparatus 10 is provided below the original table 14. That is, with a document placed on document table 14, the image reading position Pr of image reading unit 16 is moved by a drive mechanism to read the image of the document, which is a so-called fixed reading method. The front-to-rear direction of image forming apparatus 10 is called the main scanning direction, and the left-to-right direction of image forming apparatus 10 is called the sub-scanning direction.

[0022] An automatic document feeder (ADF) 18 is provided above the document table 14, and also serves as a document pressing cover for pressing down a document placed on the document table 14. The automatic document feeder 18 is provided so as to be capable of transitioning between a state in which the top surface of the document table 14 is exposed to the outside and a state in which the top surface of the document table 14 is covered. For this reason, the automatic document feeder 18 is coupled to the image forming apparatus main body 10a (housing) via an appropriate movable support member such as a hinge (not shown). Note that FIG. 1 shows a state in which the automatic document feeder 18 covers the top surface of the document table 14. The automatic document feeder 18 exerts its original function when it is in a state in which it covers the top surface of the document table 14 as shown in FIG. 1.

[0023] The automatic document feeder 18 has a document placement tray 20. On this document placement tray 20, documents, strictly speaking, sheet-shaped documents, and particularly, a plurality of documents can be placed in a stacked state. Although a detailed description is omitted, the automatic document feeder 18 takes in the documents placed on the document placement tray 20 one by one (one by one), and transports them through a document transport path 22 in the automatic document feeder 18. On the way, the document passes through an image reading position Pr, and strictly speaking, passes through the image reading position Pr which is in a fixed state. As a result, the image of the document is read, and is read by a so-called skimming method. The document is then discharged to a document discharge tray 24.

[0024] An image forming unit 26 is provided below the image reading unit 12 as an image forming means. This image forming unit 26 is responsible for image formation processing, i.e., printing, for forming an image based on appropriate image data such as the above-mentioned read image data on a sheet-like image recording medium (not shown), such as paper. This printing is performed by a known electrophotographic method. The image forming unit 26 also employs a tandem method in order to perform color printing.

[0025] Specifically, the image forming section 26 has four process units (sometimes called "image forming stations") 28, 28, . . . as monochromatic toner image forming means for individually forming monochromatic toner images (not shown) of a plurality of different colors, for example, four colors of yellow, magenta, cyan, and black. In addition, the image forming section 26 has an exposure device 30 as an exposure means for performing exposure required for forming a monochromatic toner image by each of the process units 28, 28, . . . Furthermore, the image forming section 26 has a transfer unit 34 as a transfer means for sequentially transferring each monochromatic toner image formed by each of the process units 28, 28, . . . onto an intermediate transfer belt 32 described later, and transferring the toner image transferred onto the intermediate transfer belt 32 to a sheet of paper. In addition, the image forming section 26 has a fixing device 36 as a fixing means for fixing the toner image transferred onto the sheet of paper to the sheet of paper.

[0026] The transfer unit 34 has an intermediate transfer belt (sometimes called a "primary transfer belt") 32, a drive roller 39 that rotates the intermediate transfer belt 32, and a driven roller 40 that stretches the intermediate transfer belt 32 together with the drive roller 39. The transfer unit 34 further has four intermediate transfer rollers (sometimes called "primary transfer rollers") 42, 42, ... provided at positions corresponding to the process units 28, 28, ... on the inside of the intermediate transfer belt 32, a transfer roller (sometimes called a "secondary transfer roller") 44 as a transfer member, and the like.

[0027] The intermediate transfer belt 32 is stretched by a drive roller 39 and a driven roller 40. The drive roller 39 rotates by receiving a driving force from a motor as an intermediate transfer belt driving means (not shown), for example, counterclockwise in FIG. 1. Accordingly, the intermediate transfer belt 32 rotates (circulates) in the same direction, and the driven roller 40 also rotates in the same direction. The lower region 32a of the intermediate transfer belt 32 between the drive roller 39 and the driven roller 40 is stretched along the horizontal direction, and each process unit 28, 28, ... is arranged so as to face the region 32a stretched along the horizontal direction. The region 32a of the intermediate transfer belt 32 where each process unit 28, 28, ... is arranged is called an intermediate transfer region. In the intermediate transfer region 32a, the intermediate transfer belt 32 moves from the left side to the right side of the image forming apparatus 10, that is, moves along the sub-scanning direction.

[0028] The intermediate transfer belt 32 is a flexible endless belt-like body made of synthetic resin (e.g., polyimide or polycarbonate) appropriately mixed with conductive materials such as carbon black. Although not described in detail, the driven roller 40 also has the function of preventing the intermediate transfer belt 32 from slackening by applying an appropriate tension to the intermediate transfer belt 32.

[0029] The process units 28, 28, ... are provided at regular intervals below the intermediate transfer region 32a of the intermediate transfer belt 32 along the moving direction of the intermediate transfer belt 32 in the intermediate transfer region 32a, that is, along the sub-scanning direction. As described above, each of the process units 28, 28, ... forms single-color toner images of four colors, yellow, magenta, cyan, and black, on the intermediate transfer belt 32 individually. Although it is not clear from each figure including FIG. 1, each of the process units 28, 28, ... is provided in the order of yellow, magenta, cyan, and black from the upstream side to the downstream side of the moving direction of the intermediate transfer belt 32 in the intermediate transfer region 32a (from the left side to the right side in FIG. 1). However, this order is an example and is not limited to this. Also, each of the process units 28, 28, ... has the same structure as each other except that they form single-color toner images of different colors on the intermediate transfer belt 32.

[0030] Each process unit 28 includes a photoconductor drum 46, a charging device 48, a developing device 50, a cleaning device 52, a charge removing device (not shown), and the like.

[0031] The photosensitive drum 46 is an image carrier that carries an electrostatic latent image and a single-color toner image, which will be described later, and has a cylindrical base made of a conductive material such as aluminum. A photosensitive layer is formed on the surface (outer circumferential surface) of this base. The photosensitive drum 46 is provided in the intermediate transfer region 32a so that the surface of the base is in contact with the outer surface of the intermediate transfer belt 32, and in this state, the photosensitive drum 46 receives a driving force from a motor as a drum driving means (not shown) and rotates, for example, clockwise in FIG. 1. The photosensitive drum 46 rotates at a speed that matches the moving speed of the intermediate transfer belt 32, and strictly speaking, the peripheral speed of the base rotates at a speed that is slightly slower than the moving speed of the intermediate transfer belt 32, for example, about 0.1% to 0.3%. This is to make it easier for the monochrome toner image formed on the surface of the photosensitive drum 46 as described below to be transferred to the outer surface of the intermediate transfer belt 32; in other words, to prevent the monochrome toner image from being properly transferred from the surface of the photosensitive drum 46 to the outer surface of the intermediate transfer belt 32, particularly the phenomenon of characters being hollowed out.

[0032] The charging device 48 is a charging means for charging the surface of the photosensitive drum 46 to a predetermined potential. The surface of the photosensitive drum 46 charged to a predetermined potential by the charging device 48 is exposed by the exposure device 30 described above. The exposure device 30 is provided below the row of each process unit 28, 28, ... and exposes the surface of the photosensitive drum 46 of each process unit 28 from below, that is, irradiates the surface of the photosensitive drum 46 with light in a manner corresponding to the image data to be printed. As a result, an electrostatic latent image in a manner corresponding to the image data to be printed is formed on the surface of the photosensitive drum 46. The exposure device 30 is, for example, a laser scanning unit (LSU) having a laser diode (not shown) as a light source and a polygon mirror as a deflection means, but instead of this, an LED unit having an LED array in which LEDs are arranged as light sources may be adopted as the exposure device 30.

[0033] The developing device 50 is a developing means that develops the electrostatic latent image formed on the surface of the photosensitive drum 46. That is, the developing device 50 stirs toner (not shown) to charge the toner, and causes the charged toner to adhere to the electrostatic latent image on the photosensitive drum 46, thereby visualizing, that is, developing, the electrostatic latent image as a monochromatic toner image.

[0034] The monochromatic toner image visualized by the development by the developing device 50 is transferred from the surface of the photosensitive drum 46 to the outer surface of the intermediate transfer belt 32 at the contact position between the surface of the photosensitive drum 46 and the outer surface of the intermediate transfer belt 32, so-called intermediate transfer (primary transfer). For this purpose, an intermediate transfer roller 42 is provided so as to face the photosensitive drum 46 across the intermediate transfer belt 32. The intermediate transfer roller 42 is provided so as to contact its own surface (outer circumferential surface) with the inner surface of the intermediate transfer belt 32, and rotates by receiving a driving force generated by the rotation of the intermediate transfer belt 32, that is, rotates counterclockwise in FIG. 1. A predetermined intermediate transfer voltage is applied to the intermediate transfer roller 42 from an intermediate transfer power source (not shown), so that a transfer electric field is formed between the surface of the photosensitive drum 46 and the outer surface of the intermediate transfer belt 32. The monochromatic toner image on the photosensitive drum 46 is transferred onto the intermediate transfer belt 32 by the action of this transfer electric field.

[0035] In this manner, four single-color toner images of yellow, magenta, cyan, and black are formed individually on the intermediate transfer belt 32. Then, these four single-color toner images are superimposed on each other to form a color toner image on the intermediate transfer belt 32.

[0036] The cleaning device 52 is a cleaning means that removes the residual toner on the photosensitive drum 46 after a single-color toner image is transferred from the photosensitive drum 46 onto the intermediate transfer belt 32. The static electricity removing device (not shown) is a static electricity removing means that removes static electricity on the photosensitive drum 46 after the residual toner has been removed by the cleaning device 52. After the static electricity has been removed by this static electricity removing device, the process following the charging by the charging device 48 described above is repeated.

[0037] The (color) toner image formed on the intermediate transfer belt 32 is transferred to a sheet at a transfer nip Nt, which is a contact portion between the intermediate transfer belt 32 and a transfer roller 44. Specifically, the transfer roller 44 is disposed so as to press the intermediate transfer belt 32 between itself and the drive roller 39, with the intermediate transfer belt 32 sandwiched therebetween. The transfer roller 44 rotates by receiving a driving force caused by the rotation of the intermediate transfer belt 32, that is, rotates clockwise in FIG. 1. Then, a transfer bias current having the same polarity as the charge polarity of the toner is applied to the drive roller 39 from a transfer bias power source (not shown). As a result, a transfer electric field is formed between the intermediate transfer belt 32 and the transfer roller 44, that is, at the transfer nip Nt. In this state, when a sheet passes through the transfer nip Nt, the toner image on the intermediate transfer belt 32 is transferred to the sheet. In short, the transfer nip Nt is a position where the image forming unit 26 forms an image on the sheet.

[0038] The fixing device 36 is provided downstream of the transfer nip Nt in the conveying direction of the paper conveyed along the paper conveying path 54 described later. As described above, the fixing device 36 fixes the toner image on the paper to the paper, specifically by heating and melting the toner image and pressing it, thereby fixing the toner image to the paper. For this purpose, the fixing device 36 has a heating roller 56 and a pressure roller 58. The heating roller 56 and the pressure roller 58 are provided in a state where their surfaces (outer circumferential surfaces) are in contact with each other. The heating roller 56 is heated to a predetermined temperature (fixing temperature) by an appropriate heat source such as a lamp heater (not shown) provided inside the heating roller 56. In addition, the heating roller 56 rotates by receiving a driving force from a motor as a fixing roller driving means (not shown), for example, counterclockwise in FIG. 1. Accordingly, the pressure roller 58 also rotates, that is, it is driven to rotate clockwise in FIG. 1. Then, the paper that has passed through the transfer nip Nt passes through the fixing nip Nf, which is the contact area between the surface of the heating roller 56 and the surface of the pressure roller 58, and the toner image on the paper is fixed onto the paper. This completes a series of processes for printing by the image forming unit 26.

[0039] Further, below the image forming section 26, in other words, at the bottom of the image forming apparatus main body 10a, a paper feed section 60 is provided as a paper feed means. The paper feed section 60 has a main body cassette 62. This main body cassette 62 can accommodate a plurality of sheets of paper in a stacked state. In addition, the paper feed section 60 has a paper feed roller (strictly speaking, a roller pair) 64 that also serves as a pickup roller. The paper feed roller 64 takes out the sheets accommodated in the main body cassette 62 one by one (one by one) and supplies them to the paper conveying path 54 via the main body side conveying path 66. The paper feed roller 64 rotates by receiving a driving force from a main body side paper feed motor 65 (see FIG. 3). In addition, by having the paper feed roller 64 also serve as a pickup roller in this way, the configuration of the image forming apparatus main body 10a is simplified and the cost (inexpensiveness) of the image forming apparatus main body 10a is reduced.

[0040] The paper transport path 54 is provided so that the paper supplied through the main body side transport path 66 passes through the transfer nip portion Nt and the fixing nip portion Nf and is discharged from the paper discharge port 68 to the paper discharge tray 70. A plurality of, for example, two, transport rollers (strictly speaking, roller pairs) 72 and 72 are provided at appropriate positions on the paper transport path 54 for transporting the paper along the paper transport path 54. Among the transport rollers 72 and 72, the transport roller 72a provided on the upstream side of the paper transport direction in the paper transport path 54, in other words, on the upstream side of the transfer nip portion Nt, is a registration roller that times the leading edge of the paper to enter the transfer nip portion Nt. For this reason, the registration roller 72a temporarily stops transporting the paper and then resumes transporting the paper, that is, causes the leading edge of the paper to enter the transfer nip portion Nt. On the other hand, transport roller 72b provided downstream in the paper transport direction in paper transport path 54, in other words provided near paper discharge port 68, is a paper discharge roller for discharging paper from paper discharge port 68 to paper discharge tray 70. Note that paper discharge tray 70 is provided between image reading unit 12 and image forming unit 26, and is provided in a so-called internal space, but is not limited to this.

[0041] In addition, a reversing conveying path 74 for double-sided printing is provided in the image forming apparatus main body 10a. This reversing conveying path 74 is a conveying path for taking in a sheet that has once passed through the fixing nip portion Nf, that is, a sheet after printing, and providing the sheet for printing again. That is, the sheet taken in by the reversing conveying path 74 is supplied again to the sheet conveying path 54 via the reversing conveying path 74, and more specifically, is supplied to the upstream side of the registration rollers 72a. For this reason, a conveying roller 76 is also provided at an appropriate position on the reversing conveying path 74. Then, the sheet supplied to the upstream side of the registration rollers 72a via the reversing conveying path 74 is in a reversed state, and printing is performed on the reversed sheet, thereby realizing double-sided printing.

[0042] The registration rollers 72a, the paper discharge rollers 72b, and the respective transport rollers 76 provided on the reversing transport path 74 are rotated by a driving force from a transport motor 78 (see FIG. 3) which serves as a common transport drive source. The registration rollers 72a, the paper discharge rollers 72b, the transport rollers 76, and the transport motor 78 cooperate with the paper transport path 54 to form a paper transport section 80.

[0043] An optional paper feeder 100 is attached to the bottom of the image forming apparatus main body 10a. The optional paper feeder 100 has an optional cassette 102. The optional cassette 102 can accommodate a plurality of sheets of paper in a stacked manner. The optional paper feeder 100 also has a pickup roller 104, a paper feed roller (strictly speaking, a roller pair) 106, and an acceleration / deceleration roller (strictly speaking, a roller pair) 108. The pickup roller 104 picks up the sheets accommodated in the optional cassette 102 one by one (one by one). The paper feed roller 106 supplies the sheets picked up by the pickup roller 104 to the optional side conveying path 110. The optional side conveying path 110 is connected to the paper conveying path 54 via the optional connection conveying path 82 in the image forming apparatus main body 10a. In other words, the optional side conveying path 110 is connected to the nip portion of the registration roller 72a, which is the conveying position of the paper by the registration roller 72a, via the optional connection conveying path 82. The option side transport path 110 cooperates with the option connection transport path 82 to form an option transport path 112 .

[0044] The acceleration / deceleration rollers 108 are provided near a connection portion of the option side transport path 110 with the option connection transport path 82. The acceleration / deceleration rollers 108 transport the paper supplied to the option side transport path 110 by the paper feed rollers 106 via the option connection transport path 82, that is, via the option transport path 112 including the option side transport path 110 and the option connection transport path 82, to the nip portion of the registration rollers 72a.

[0045] The feed roller 106 rotates by receiving a driving force from an optional side feed motor 114 (see FIG. 3). The pickup roller 104 is connected to the feed roller 106 via a belt as a driving force transmission means (not shown), and rotates (follows rotation) with the rotation of the feed roller 106. The pickup roller is provided so as to be displaceable up and down by a vertical movement mechanism (not shown), and displaces downward and contacts the (top) paper in the optional cassette 102 only when paper is taken out from the optional cassette 102, otherwise it is in an upper position, that is, it is separated from the paper in the optional cassette 102. The acceleration / deceleration roller 108 rotates by receiving a driving force from an acceleration / deceleration motor 116 (see FIG. 3) as an acceleration / deceleration drive source. That is, the feed roller 106 (and the pickup roller 104) and the acceleration / deceleration roller 108 are driven by separate (i.e., two) drive sources.

[0046] 2, a paper detection sensor 120 is provided at a position upstream of the nip portion of registration roller 72a in the paper transport path 54 in the paper transport direction and near the nip portion of registration roller 72a. Note that Fig. 2 is a schematic diagram showing an enlarged view of a portion including the paper transport path from paper feed roller 64 of image forming apparatus main body 10a to registration roller 72a and the paper transport path from paper feed roller 106 of optional paper feeder 100 to registration roller 72a.

[0047] The paper detection sensor 120 is a paper detection means that detects the leading edge of the paper transported along the paper transport path 54, and the time when the leading edge of the paper reaches the nip portion of the registration rollers 72a (i.e., the position where the paper is temporarily stopped by the registration rollers 72a) is estimated based on the detection result by the paper detection sensor 120. The paper detection sensor 120 is, for example, a reflective photoelectric sensor, but is not limited to this, and may be, for example, a transmissive photoelectric sensor, or an appropriate sensor other than a photoelectric sensor.

[0048] A paper feed detection sensor 122 is provided at a position between a nip portion of the paper feed roller 106, which is the position in the optional transport path 112 where the paper feed roller 106 feeds the paper to the optional transport path 112, and a nip portion of the acceleration / deceleration roller 108, in the vicinity of the nip portion of the paper feed roller 106. This paper feed detection sensor 122 is a paper feed detection means that detects the leading edge of the paper fed to the optional transport path 112 by the paper feed roller 106, that is, that detects that the paper has been fed to the optional transport path 112 by the paper feed roller 106. This paper feed detection sensor 122 is also a reflective photoelectric sensor, similar to the paper detection sensor 120, but is not limited to this, and may be, for example, a transmissive photoelectric sensor, or an appropriate sensor other than a photoelectric sensor.

[0049] Furthermore, a delay detection sensor 124 is provided at a position between the nip portion of the acceleration / deceleration roller 108 and the nip portion of the registration roller 72a in the optional conveying path 112, in the vicinity of the nip portion of the acceleration / deceleration roller 108. This delay detection sensor 124 is a delay detection means that detects the leading edge of the paper conveyed by the acceleration / deceleration roller 108, and thus detects whether or not there is a feeding delay in the paper. This delay detection sensor 124 is also, for example, a reflective photoelectric sensor, but is not limited to this, and may be, for example, a transmissive photoelectric sensor, or an appropriate sensor other than a photoelectric sensor.

[0050] The paper feed roller 64 of the image forming apparatus main body 10a has two rollers 64a and 64b, one of which, the roller 64a, is a drive roller that rotates by receiving a driving force from the main body side paper feed motor 65 (see FIG. 3) described above, and the other roller 64b is a driven roller that rotates with the rotation of the one roller 64a. The paper feed roller 64 also functions as a pickup roller as described above, but the function of this pickup roller is performed by the one roller 64a. The other roller 64b is a separation roller (sometimes called a "separation roller") that separates multiple sheets of paper when the one roller 64a picks up multiple sheets of paper from the main body cassette 62 and supplies only one sheet of paper to the main body side transport path 66 when the one roller 64a picks up multiple sheets of paper.

[0051] The feed roller 106 of the optional paper feeder 100 also has two rollers 106a and 106b, one of which, roller 106a, is a drive roller that rotates by receiving a driving force from the optional paper feed motor 114 (see FIG. 3) described above, and the other roller 106b is a driven roller that rotates as the roller 106a rotates. The other roller 106b is a separation roller that separates multiple sheets of paper taken out of the optional cassette 102 by the pickup roller 104 and supplies only one sheet of paper to the optional transport path 112.

[0052] Hereinafter, the nip portion of the feed roller 64 of the image forming apparatus main body 10a may be indicated by the symbol "Pa". The nip portion of the registration roller 72a may be indicated by the symbol "Pb". The nip portion of the feed roller 106 of the optional feeder 100 may be indicated by the symbol "Pd", and the detection position by the feed detection sensor 122 may be indicated by the symbol "Pe". The nip portion of the acceleration / deceleration roller 108 may be indicated by the symbol "Pf", and the detection position by the delay detection sensor 124 may be indicated by the symbol "Pg".

[0053] 3 is a block diagram showing the electrical configuration of the image forming apparatus 10. As shown in FIG. 3, the image forming apparatus 10 has a control unit 200. The image reading unit 12, the automatic document feeder 18, the image forming unit 26, the paper feed unit 60, and the paper transport unit 80 are connected to the control unit 200 via a bus 202. In addition, the operation unit 204, the auxiliary storage unit 206, the communication unit 208, and the like are connected to the control unit 200 via the bus 202. The optional paper feeder 100 is also connected to the control unit 200 via the bus 202. The image reading unit 12, the automatic document feeder 18, the image forming unit 26, the paper feed unit 60, the paper transport unit 80, and the optional paper feeder 100 are as described above.

[0054] In particular, the paper feed section 60 has a paper feed roller 64 and a main body side paper feed motor 65 which is its drive source. The paper transport section 80 has a registration roller 72a and a transport motor 78 which is its drive source. The transport motor 78 is also the drive source for the paper discharge roller 72b and each transport roller 76 provided in the reverse transport path 74. The paper transport section 80 also has a paper detection sensor 120. The optional paper feeder 100 has a paper feed roller 106 and an optional side paper feed motor 114 which is its drive source, as well as an acceleration / deceleration roller 108 and an acceleration / deceleration motor 116 which is its drive source. In addition, the optional paper feeder 100 has a paper feed detection sensor 122 and a delay detection sensor 124.

[0055] The control unit 200 is an example of a control means that controls the entire image forming apparatus 10. For this purpose, the control unit 200 has a computer, such as a CPU 200a, as a control execution means. In addition, the control unit 200 has a main memory unit 200b as a main memory means that can be directly accessed by the CPU 200a. The main memory unit 200b includes, for example, a ROM and a RAM (not shown). Of these, the ROM stores a control program (firmware) for controlling the operation of the CPU 200a. The RAM constitutes a working area and a buffer area when the CPU 200a executes processing according to the control program.

[0056] The operation unit 204 has a display with a touch panel (not shown). The display with a touch panel is a component in which a touch panel as an example of an operation receiving means capable of receiving an operation by a user (not shown) and a display as an example of a display means for displaying various information are integrally combined. In addition to the display with a touch panel, the operation unit 204 has an appropriate light emitting means such as an LED (not shown) and an appropriate hardware switch such as a push button (not shown).

[0057] The auxiliary storage unit 206 is an example of an auxiliary storage means. In other words, various data such as the above-mentioned scanned image data are appropriately stored in the auxiliary storage unit 206. The auxiliary storage unit 206 has, for example, a hard disk drive (not shown). In addition, the auxiliary storage unit 206 may have a rewritable non-volatile memory such as a flash memory.

[0058] The communication unit 208 is an example of a communication means. That is, the communication unit 208 is responsible for two-way communication processing via a LAN line (not shown). The communication unit 208 may be connected to the LAN line by wire or wirelessly. The communication unit 208 is also responsible for two-way communication processing via a public switched telephone network (not shown).

[0059] Now, when the supply source of the paper to be printed by the image forming unit 26, that is, the paper feed source, is the main cassette 62, the paper is taken out of the main cassette 62 by the paper feed roller 64 and then conveyed to the paper conveying path 54 via the main conveying path 66. The relationship between the paper conveying time and the conveying distance in this case is shown in a diagram in FIG.

[0060] In FIG. 4, the horizontal axis represents the transport time, and the vertical axis represents the transport distance. The time t0 when the feed roller 64 starts to rotate is set as the base point of the transport time. In contrast, the base point of the transport distance is set as the nip Pd of the feed roller 106 of the optional feeder 100, in consideration of a case where the optional feeder 100 (optional cassette 102) described later is set as the feed source. For this reason, in FIG. 4, the nip Pa of the feed roller 64 is set at a position corresponding to a transport distance of about 155 mm. Incidentally, the nip Pb of the registration roller 72a is located at a position about 255 mm from the nip Pd of the feed roller 106 of the optional feeder 100, which is the base point of the transport distance. In other words, the distance from the nip Pa of the feed roller 64 to the nip Pb of the registration roller 72a is about 100 mm (= about 255 mm - about 155 mm), which is relatively small. Therefore, no conveying means other than the paper feed roller 64 and the registration roller 72a is provided between the nip portion Pa of the paper feed roller 64 and the nip portion Pb of the registration roller 72a. This also contributes to simplifying the configuration of the image forming apparatus main body 10a and reducing costs.

[0061] Furthermore, the thick solid line in Fig. 4 shows the transition of the leading edge of the paper when the paper is transported as ideally (designed).The thick dashed line in Fig. 4 shows an example of the transition of the leading edge of the paper when a paper feed delay occurs.The thick dashed line in Fig. 4 shows the transition of the trailing edge of the preceding paper when multiple sheets of paper are printed continuously.

[0062] As shown in FIG. 4, particularly as indicated by the thick solid line, when the paper is transported as ideal, the leading edge of the paper reaches the nip Pb of the registration roller 72a at time tb when a predetermined time Tb has elapsed from the base point t0. In contrast, when a paper feed delay occurs, the leading edge of the paper reaches the nip Pb of the registration roller 72a at time tb', which is later than time tb, as indicated by the thick dashed line in FIG. 4. In order to absorb this time lag (variation), an appropriate paper feed delay margin Tm is provided, and the registration roller 72a does not rotate, that is, the paper is in a stopped state, until this paper feed delay margin Tm has elapsed. Then, at time tp when the paper feed delay margin Tm has elapsed, the registration roller 72a starts to rotate, and the paper is sent to the transfer nip Nt. At this time, the registration roller 72a transports the paper at a speed corresponding to (equivalent to) the process speed Vp, which is the printing speed (image formation processing speed) by the image forming unit 26. The time Tp from the base point t0 to the point in time tp is constant. If the leading edge of the paper does not reach the nip Pb of the registration rollers 72a before the time Tp has elapsed, that is, by the point in time tp, a conveyance error occurs.

[0063] Here, the larger (longer) the paper feed delay margin Tm is, the less likely a transport error will occur, and so to speak, the greater the safety (adaptability) against paper feed delays. On the other hand, when multiple sheets of paper are printed continuously, the transport interval between each sheet, specifically the process sheet interval Lp, which is the interval between the trailing edge of the preceding sheet at the nip Pb of the registration roller 72a and the leading edge of the succeeding sheet following this preceding sheet, must be increased accordingly. This will result in a decrease in CPM.

[0064] Specifically, as shown in FIG. 5A, when the main cassette 62 is the paper feed source, the paper feed delay margin Tm is set to, for example, 250 ms. And the process paper interval Lp is set to, for example, 93 mm. These are values ​​derived through experiments. And, if the process speed Vp is 260 mm / s, the CPM is 40.0. Note that each value shown in FIG. 5A is an example when A4 size (297 mm×210 mm) paper is transported with its length direction aligned with the transport direction. This also applies to each value described hereinafter.

[0065] Consider the following measures for increasing the CPM value by 20% to 48.0 in an image forming apparatus 10 (image forming apparatus main body 10a) with such specifications. As a first measure, as shown in FIG. 5B, a measure of increasing the process speed Vp while maintaining the feed delay margin Tm at 250 ms and the process sheet interval Lp at 93 mm is considered. According to this first measure, the CPM can be set to 48.0 by increasing the process speed Vp to 312 mm / s. However, increasing the process speed Vp incurs a corresponding cost, which means that the image forming apparatus 10 becomes more expensive.

[0066] Separately from this, as a second measure, as shown in Fig. 5C, a measure can be considered in which the feed delay margin Tm is reduced and the process sheet interval Lp is reduced while maintaining the process speed Vp at 260 mm / s. According to this second measure, the feed delay margin Tm is set to 35 ms and the process sheet interval Lp is set to 28 mm, so that the CPM can be set to 48.0. However, reducing the feed delay margin Tm makes it easier for transport errors to occur, and attempting to reduce these transport errors also results in higher costs for the image forming apparatus 10.

[0067] In the first embodiment, when the optional paper feeder 100 (optional cassette 102) is set as the paper feed source, the paper feed distance (transport path) from the paper feed source (strictly speaking, from the nip Pd of the paper feed roller 106) to the nip Pb of the registration roller 72a is considerably larger (longer) than the paper feed distance from the paper feed source (strictly speaking, from the nip Pa of the paper feed roller 64) to the nip Pb of the registration roller 72a when the main cassette 62 is set as the paper feed source, and the CPM is improved. That is, the transport speed of the paper is controlled so that the paper feed delay is made up during the process of the paper being transported from the optional paper feeder 100, which is the paper feed source, to the nip Pb of the registration roller 72a. This will be described with reference to FIG. 6.

[0068] FIG. 6 is a diagram showing the relationship between the transport time and the transport distance of a sheet when the optional sheet feeder 100 is the feed source. In FIG. 6, the time t0 when the feed roller 106 of the optional sheet feeder 100 starts to rotate is set as the base point of the transport time. The nip Pd of the feed roller 106 of the optional sheet feeder 100 is set as the base point of the transport distance. The thick solid line in FIG. 6 shows the transition of the leading edge of the sheet when the sheet is transported as ideal. The thick dashed line in FIG. 6 shows an example of the transition of the leading edge of the sheet when a feeding delay occurs. Furthermore, the thick dashed line in FIG. 6 shows the transition of the trailing edge of the preceding sheet when multiple sheets of paper are printed continuously.

[0069] As shown in FIG. 6, particularly as shown by the thick solid line, when the paper is transported as ideally, the leading edge of the paper reaches the detection position Pg by the delay detection sensor 124 at time tg when a predetermined time Tg has passed from the base point t0, that is, the leading edge is detected by the delay detection sensor 124. During this time, the paper is transported at a speed Vg (>Vp) higher than the process speed Vp (turbo paper feeding), that is, the optional paper feed motor 114 and the acceleration / deceleration motor 116 are controlled so that this happens. Also, this speed Vg is set to a value such that the leading edge of the paper does not catch up with the trailing edge of the preceding paper. Then, after time tg has passed, the paper transport speed is set to the same speed as the process speed Vp, and the paper continues to be transported. Then, at time tb when a predetermined time Tb has passed from the base point t0, the leading edge of the paper reaches the nip portion Pb of the registration roller 72a.

[0070] On the other hand, when a paper feed delay occurs, as shown by the thick dashed line in FIG. 6, the leading edge of the paper reaches the detection position Pg by the delay detection sensor 124 at time tg', which is later than time tg. Here, a conveying speed Vx is calculated so that the leading edge of the paper reaches the nip part Pb of the registration roller 72a at time tb, that is, so that the leading edge of the paper reaches the nip part Pb of the registration roller 72a at the ideal timing. The conveying speed Vx is calculated by the following formula 1. Note that ΔT in formula 1 is the time from time tg' to time tb, that is, the difference (ΔT=Tb-Tg') between the time Tg' from the base point t0 of the conveying time to time tg' and the time Tb from the base point t0 to time tb. ΔL is the distance from the detection position Pg by the delay detection sensor 124 to the nip part Pb of the registration roller 72a, and is constant.

[0071] 《Formula 1》 Vx=ΔL / ΔT

[0072] Then, after time tg' has passed, the paper is transported (accelerated) at the transport speed Vx calculated by this formula 1, that is, the option side paper feed motor 114 and the acceleration / deceleration motor 116 are controlled so that this happens. As a result, basically (approximately) at time tb, the leading edge of the paper reaches the nip part Pb of the registration rollers 72a, and the paper feed delay is made up for.

[0073] Incidentally, an appropriate tolerance is provided for the time when the leading edge of the paper reaches the detection position Pg by the delay detection sensor 124, i.e., a paper feed delay margin Tm' is provided. This paper feed delay margin Tm' is set to a value that allows the paper feed delay to be fully compensated for by conveying (accelerating) the paper at the conveying speed Vx, and therefore may be set to, for example, 250 ms, although it depends on the maximum value of the conveying speed Vx. If the leading edge of the paper does not reach the detection position Pg by the delay detection sensor 124 before this paper feed delay margin Tm' has elapsed, that is, by time tg', a conveying error occurs.

[0074] When such a conveying error does not occur, the leading edge of the paper basically reaches the nip portion Pb of the registration roller 72a at time tb as described above, but the timing at which the leading edge of the paper reaches the nip portion Pb of the registration roller 72a varies slightly. The variation in timing is caused by the response delay when switching (accelerating) to the conveying speed Vx based on the above-mentioned formula 1 and the variation in the diameter of the acceleration / deceleration roller 108, but is extremely small. Therefore, an appropriate margin is provided for the time at which the leading edge of the paper reaches the nip portion Pb of the registration roller 72a, so to speak, an adjustment margin Tj is provided, but this adjustment margin Tj is much smaller than the above-mentioned paper feed delay margin Tm', for example, about 20 ms. That is, until this adjustment margin Tj has passed, the registration roller 72a does not rotate and the paper is in a stopped state. Then, at time tp when the adjustment margin Tj has passed, the registration roller 72a starts to rotate and the paper is sent to the transfer nip portion Nt. In this case, the registration roller 72a also transports the paper at a speed corresponding to the process speed Vp. Note that the time Tp from the base point t0 of the transport time to the point in time tp is constant. If the leading edge of the paper does not reach the nip part Pb of the registration roller 72a before the time Tp has elapsed, that is, by the point in time tp, a transport error occurs.

[0075] In this way, when the optional sheet feeder 100 is used as the sheet feed source, the sheet feed delay margin Tm' is set to 250 ms, and the adjustment margin Tj, which is the margin at the nip of the registration roller 72a, is set to 20 ms. This allows the process sheet interval Lp to be 28 mm, as shown in FIG. 7. Therefore, if the process speed Vp is 260 mm / s, the CPM is 48.0, which is 20% higher than when the main cassette 62 is used as the sheet feed source. In short, the specifications of the image forming apparatus main body 10a remain unchanged, and the CPM is improved by using the optional sheet feeder 100 as the sheet feed source.

[0076] To improve the CPM in this manner, the control unit 200, or more precisely the CPU 200a, executes a first control task according to a first control program included in the control programs stored in the main storage unit 200b, and executes a second control task according to a second control program included in the first control program. These tasks are executed in parallel (multitasking).

[0077] First, the first control task will be described. The flow of this first control task is shown in Fig. 8. The first control task is executed in response to the acceptance of a print job that uses optional paper feeder 100 as the paper feed source. The print job referred to here includes not only print jobs in the printer function, but also print jobs in the copy function and fax function (fax reception function).

[0078] According to this first control task, in the first step S1, the CPU 200a resets and starts a first timer (not shown) for measuring time. This first timer is, for example, a software timer configured by the CPU 200a, but may also be a hardware timer configured by hardware elements such as an RTC (Real-Time Clock). After executing this step S1, the CPU 200a advances the process to step S3.

[0079] In step S3, the CPU 200a executes the second control task, or more precisely, starts the execution of the second control task. This second control task will be described in detail later. Then, the CPU 200a advances the process to step S5.

[0080] In step S5, the CPU 200a judges whether all printing based on the print job described above has been completed. If all printing has been completed (S5: YES), the CPU 200a ends the first control task. On the other hand, if all printing has not been completed (S5: NO), the CPU 200a advances the process to step S7.

[0081] In step S7, the CPU 200a waits for the current time measured by the first timer to reach a predetermined paper feed cycle Ta, in other words, waits for the paper feed cycle Ta to elapse (S7: NO). The paper feed cycle Ta here is a value obtained by dividing a unit time of 1 minute (60 s) by CPM, that is, when the CPM is 48.0, the paper feed cycle Ta is 1.25 s (= 60 s / 48.0). When the paper feed cycle Ta has elapsed (S7: YES), the CPU 200a returns the process to step S1.

[0082] Next, the second control task will be described. As described above, the execution of the second control task begins in step S3 of the first control task.

[0083] According to this second control task, in the first step S101, the CPU 200a resets and starts a second timer (not shown) for measuring time. This second timer is, for example, a software timer like the above-mentioned first timer, but may also be a hardware timer. Then, the CPU 200a advances the process to step S103.

[0084] In step S103, the CPU 200a starts the rotation of the feed roller 106 and the acceleration / deceleration roller 108, that is, controls the option-side feed motor 114 and the acceleration / deceleration motor 116 to rotate the feed roller 106 and the acceleration / deceleration motor 116. At this time, the CPU 200a controls the option-side feed motor 114 and the acceleration / deceleration motor 116 to transport the paper at the above-mentioned speed Vg (>Vp). Then, the CPU 200a advances the process to step S105.

[0085] In step S105, the CPU 200a controls the pickup roller 104, more precisely the up-down movement mechanism, to pick up one sheet of paper from the optional cassette 102. As a result, one sheet of paper is picked up from the optional cassette 102, and the picked up sheet is supplied to the optional conveying path 112 and conveyed at a speed of Vg. Then, the CPU 200a advances the process to step S107.

[0086] In step S107, the CPU 200a waits for the leading edge of the paper to reach the detection position Pg by the delay detection sensor 124, that is, waits for the leading edge of the paper to be detected by the delay detection sensor 124 (S107: NO). Then, when the leading edge of the paper reaches the detection position Pg by the delay detection sensor 124 (S107: YES), the CPU 200a advances the process to step S109.

[0087] In step S109, the CPU 200a checks the current time measured by the second timer described above, that is, checks the time Tg' from the base point t0 of the transport time to the time tg' when the leading edge of the paper reaches the detection position Pg by the delay detection sensor 124. Then, the CPU 200a advances the process to step S111.

[0088] In step S111, the CPU 200a calculates the conveying speed Vx for making the leading edge of the paper reach the nip Pb of the registration rollers 72a at the ideal timing, that is, the time tb, based on the above-mentioned formula 1. Then, the CPU 200a advances the process to step S113.

[0089] In step S113, the CPU 200a adjusts (accelerates) the conveying speed of the paper feed roller 106 and the acceleration / deceleration roller 108 so as to convey the paper at the conveying speed Vx based on the formula 1, that is, controls the option side paper feed motor 114 and the acceleration / deceleration motor 116. Then, the CPU 200a advances the process to step S115.

[0090] In step S115, the CPU 200a waits for the leading edge of the paper to reach the nip Pb of the registration rollers 72a (S115: NO). When the leading edge of the paper reaches the nip Pb of the registration rollers 72a (S115: YES), the CPU 200a advances the process to step S117.

[0091] In step S117, the CPU 200a stops the rotation of the paper feed roller 106 and the acceleration / deceleration roller 108, that is, controls the option side paper feed motor 114 and the acceleration / deceleration motor 116. Then, the CPU 200a advances the process to step S119.

[0092] In step S119, the CPU 200a waits for the time tp when the registration roller 72a is rotated to arrive, in other words, for the time measured by the first timer to reach the time Tp (S119: NO). When the time tp arrives (S119: YES), the CPU 200a advances the process to step S121.

[0093] In step S121, the CPU 100a executes a print task for printing by the image forming unit 26, including rotating the registration roller 72a, and strictly speaking starts execution of the print task. This print task is a task separate from the first control task and the second control task, and is executed in parallel with the first control task and the second control task. As a result, printing is performed by the image forming unit 26. With this, the CPU 200a ends the second control task. Note that a detailed description of the print task will be omitted.

[0094] Thus, according to the first embodiment, the CPM is improved by using the optional paper feeder 100 as the paper feed source. That is, although the specifications of the image forming apparatus main body 10a remain unchanged, the CPM of the image forming apparatus 10 as a whole is improved, that is, the productivity is improved. In particular, users who are conscious of productivity tend to print a large amount of paper and therefore tend to purchase the optional paper feeder 100, and the first embodiment is extremely beneficial for such users. On the other hand, for users who do not need to emphasize productivity and who emphasize cost, it is sufficient to purchase only the image forming apparatus main body 10a. In particular, the image forming apparatus main body 10a is a so-called low-cost machine with a small number of conveying rollers 72, and such an image forming apparatus main body 10a is extremely convenient for users who emphasize cost. That is, it is possible to provide various variations to the market.

[0095] The optional cassette 102 in the first embodiment is an example of the first storage unit according to the present disclosure. The optional transport path 112 and the feed roller 106 in the first embodiment are an example of the first transport path and the first feed roller according to the present disclosure. The optional feed motor 114, which is the drive source of the feed roller 106, is a first feed drive source, so to speak. Furthermore, the delay detection sensor 124 in the first embodiment is an example of the first detection means according to the present disclosure. This delay detection sensor 124 is provided in the optional feed device 100, but may be provided in the image forming apparatus main body 10a. In addition, the feed detection sensor 122 in the first embodiment is an example of the second detection means according to the present disclosure.

[0096] Furthermore, the main cassette 62 in the first embodiment is an example of the second storage section according to the present disclosure. The main conveying path 66 and the paper feed roller 64 in the first embodiment are examples of the second conveying path and the second paper feed roller according to the present disclosure. The main feed motor 65, which is the drive source of the paper feed roller 64, is a second paper feed drive source, so to speak. Furthermore, the process paper interval Lp when the optional paper feed device 100 is the paper feed source is an example of the first paper interval according to the present disclosure. The process paper interval Lp when the main cassette 62 is the paper feed source is an example of the second paper interval according to the present disclosure.

[0097] [Second Example] Next, a second embodiment of the present disclosure will be described.

[0098] In this second embodiment, the detection results from the paper feed detection sensor 122 are also used to control the paper transport when the optional paper feeder 100 is the paper feed source. Fig. 10 is a diagram showing the relationship between the paper transport time and the transport distance in this second embodiment. The thick solid line in Fig. 10 shows the transition of the leading edge of the paper when the paper is transported as ideal. The thick dashed line in Fig. 10 shows an example of the transition of the leading edge of the paper when a paper feed delay occurs. Furthermore, the thick dashed line in Fig. 10 shows the transition of the trailing edge of the preceding paper when multiple sheets of paper are printed continuously.

[0099] As shown in FIG. 10, particularly as indicated by the thick solid line, when the paper is transported as ideally, the leading edge of the paper progresses in the same manner as in the first embodiment (FIG. 6) described above, but at time te when a predetermined time Te has elapsed from the base point t0, the leading edge of the paper reaches the detection position Pe by the paper feed detection sensor 122, that is, is detected by the paper feed detection sensor 122. Then, at time tg when an even longer predetermined time Tg has elapsed from the base point t0, the leading edge of the paper reaches the detection position Pg by the delay detection sensor 124, that is, is detected by the delay detection sensor 124. During this time, the paper is transported at the aforementioned speed Vg, which is higher than the process speed Vp. Then, after time tg, the paper transport speed is set to the same speed as the process speed Vp, and the paper continues to be transported, and at time tb when a predetermined time Tb has elapsed from the base point t0, the leading edge of the paper reaches the nip portion Pb of the registration roller 72a.

[0100] In contrast, when a paper feed delay occurs, the leading edge of the paper reaches the detection position Pe by the paper feed detection sensor 122 at time te', which is later than time te, as shown by the thick dashed line in Fig. 10. At this point, the paper transport speed is increased, for example to its maximum value, and so to speak, a rough control is performed. This makes up for some of the paper feed delay.

[0101] Furthermore, an appropriate tolerance is set for the time when the leading edge of the paper reaches detection position Pe' by paper feed detection sensor 122; in other words, a first paper feed delay margin Tm" is set. This first paper feed delay margin Tm" is set to be smaller than the paper feed delay margin Tm when main cassette 62 is the paper feed source, for example, to be specific, 200 ms. If the leading edge of the paper does not reach detection position Pg by paper feed detection sensor 122 before this paper feed delay margin Tm" has elapsed, that is, by time te', a transport error occurs.

[0102] If such a transport error does not occur, the leading edge of the paper reaches the detection position Pg by the delay detection sensor 124 at time tg', which is later than time te'. Here, a transport speed Vx is calculated so that the leading edge of the paper reaches the nip Pb of the registration rollers 72a at time tb, that is, so that the leading edge of the paper reaches the nip Pb of the registration rollers 72a at the ideal timing. The calculation of this transport speed Vx is also based on the above-mentioned formula 1. Then, the paper is transported at the calculated transport speed Vx, so to speak, detailed control is performed. As a result, basically (approximately) at time tb, the leading edge of the paper reaches the nip Pb of the registration rollers 72a, that is, the paper feed delay is made up. From this point on, it is the same as in the first embodiment.

[0103] Incidentally, an appropriate tolerance is provided for the time when the leading edge of the paper reaches the detection position Pg by the delay detection sensor 124, which is a so-called second paper feed delay margin Tm'. This second paper feed delay margin Tm' is set to 250 ms, which is equivalent to the paper feed delay margin Tm when the main body cassette 62 is the paper feed source, for example. If the leading edge of the paper does not reach the detection position Pg by the delay detection sensor 124 before the second paper feed delay margin Tm' has elapsed, that is, by time tg', a transport error also occurs.

[0104] Thus, according to the second embodiment, the paper transport control is performed in two stages, that is, coarse control and fine control. That is, when the leading edge of the paper reaches the detection position Pe by the paper feed detection sensor 122, that is, before the leading edge of the paper reaches the detection position Pg by the delay detection sensor 124, if a paper feed delay occurs, a so-called first stage transport control is performed to make up for this paper feed delay to some extent. Then, when the leading edge of the paper reaches the detection position Pg by the delay detection sensor 124, if a paper feed delay still occurs, a second stage transport control is performed to make up for this paper feed delay precisely. This substantially expands the tolerance range for the paper feed delay, that is, it is possible to deal with a larger paper feed delay. And, as in the first embodiment, the optional paper feeder 100 is used as the paper feed source, thereby improving the CPM.

[0105] [Third Example] Next, a third embodiment of the present disclosure will be described.

[0106] In the third embodiment, the delay detection sensor 124 is removed from the configuration of the image forming apparatus 10. That is, in the first and second embodiments described above, the detection result by the delay detection sensor 124 is used for paper transport control when the optional paper feeder 100 is set as the paper feed source, but in the third embodiment, the detection result by the delay detection sensor 124 is not used for paper transport control when the optional paper feeder 100 is set as the paper feed source. FIG. 11 is a diagram showing the relationship between the paper transport time and the transport distance in the third embodiment. Note that the thick solid line in FIG. 11 shows the transition of the leading edge of the paper when the paper is transported as ideal. And the thick dashed line in FIG. 11 shows an example of the transition of the leading edge of the paper when a paper feed delay occurs. Furthermore, the thick dashed line in FIG. 11 shows the transition of the trailing edge of the preceding paper when multiple sheets of paper are continuously printed.

[0107] 11, particularly as indicated by the thick solid line, when the paper is transported as ideally, the leading edge of the paper reaches the detection position Pe by the paper feed detection sensor 122 at time te when a predetermined time Te has elapsed from the base point t0, that is, is detected by the paper feed detection sensor 122. Then, at time tf when an even longer predetermined time Tf has elapsed from the base point t0, the leading edge of the paper reaches the nip portion of the acceleration / deceleration roller 108. During this time, the paper is transported at the aforementioned speed Vg, which is higher than the process speed Vp. Also, at time te, the time tf when the leading edge of the paper reaches the nip portion of the acceleration / deceleration roller 108 is predicted, and the paper feed roller 106 and the acceleration / deceleration roller 108 are rotated so that the paper transport speed becomes the same as the process speed Vp at this predicted time tf, that is, the option side paper feed motor 114 and the acceleration / deceleration motor 116 are controlled. As a result, at a time tb when a predetermined time Tb has elapsed from the base point t0, the leading edge of the sheet reaches the nip portion Pb of the registration rollers 72a.

[0108] On the other hand, when a paper feed delay occurs, the leading edge of the paper reaches the detection position Pe by the paper feed detection sensor 122 at a time te' later than the time te, as shown by the thick dashed line in FIG. 11. At this time te', the time tf' at which the leading edge of the paper reaches the nip portion of the acceleration / deceleration roller 108 is predicted. In addition, a conveying speed Vx' is calculated at the time te' to make the leading edge of the paper reach the nip portion Pb of the registration roller 72a in the time ΔT' from the time tf' to the time tb, that is, to make the leading edge of the paper reach the nip portion Pb of the registration roller 72a at the ideal timing. The conveying speed Vx' is calculated by the following formula 2. Note that ΔT' in formula 2 is the time from the time tf' to the time tb as described above, that is, the difference (ΔT'=Tb-Tf') between the time Tf' from the base point t0 of the conveying time to the time tf' and the time Tb from the base point t0 to the time tb. Also, ΔL′ is the distance from the nip portion Pf of the acceleration / deceleration roller 108 to the nip portion Pb of the registration roller 72a, and is constant.

[0109] 《Formula 2》 Vx'=ΔL' / ΔT'

[0110] Then, at time tf', the paper is transported at the transport speed Vx' calculated by this formula 2, that is, the paper is accelerated. As a result, basically (approximately) at time tb, the leading edge of the paper reaches the nip part Pb of the registration roller 72a, and the paper feed delay is made up for. After this, the process is the same as in the first embodiment.

[0111] Incidentally, an appropriate tolerance is set for the time when the leading edge of the paper reaches the detection position Pe by the paper feed detection sensor 122, i.e., a paper feed delay margin Tm" is set. This paper feed delay margin Tm" is made smaller than the paper feed delay margin Tm when the main body cassette 62 is the paper feed source, for example, and more specifically, is set to 200 ms, the same as the first paper feed delay margin Tm" in the second embodiment described above. If the leading edge of the paper does not reach the detection position Pe by the paper feed detection sensor 122 before this paper feed margin Tm" has elapsed, that is, by time te', a transport error occurs.

[0112] Thus, according to the third embodiment, even if the delay detection sensor 124 is eliminated, the CPM is improved by using the optional sheet feeding device 100 as the sheet feeding source, as in the first and second embodiments. Furthermore, by eliminating the delay detection sensor 124, the entire structure of the image forming apparatus 10 can be further simplified and the cost can be reduced.

[0113] Furthermore, for example, in the above-mentioned first embodiment, when the leading edge of the paper reaches the detection position Pg by the delay detection sensor 124 (if a paper feed delay occurs), paper transport control (acceleration) to make up for the paper feed delay is started, whereas according to this third embodiment, when the paper reaches the nip portion Pf of the acceleration / deceleration rollers 108, which is located upstream in the paper transport direction from the detection position Pg by the delay detection sensor 124 (if a paper feed delay occurs), paper transport control to make up for the paper feed delay is started. Therefore, compared to the first embodiment, the tolerance range for paper feed delay is expanded, which means that it is possible to deal with a larger paper feed delay.

[0114] [Other application examples] The above-described embodiments are specific examples of the present disclosure and do not limit the technical scope of the present disclosure. The present disclosure can be applied to aspects other than the embodiments.

[0115] For example, the values ​​of the feed delay margin Tm, the process sheet interval Lp, and the like in each embodiment are merely examples, and the present invention is not limited to these values.

[0116] Also, although the paper feed roller 106 and the acceleration / deceleration roller 108 of the optional paper feeder 100 are driven by separate drive sources (optional paper feed motor 114 and acceleration / deceleration motor 116), they may be driven by a common (single) drive source. In this case, it is preferable that a clutch is provided on one or both of the paper feed roller 106 and the acceleration / deceleration roller 108, and that this clutch is appropriately turned on / off.

[0117] Furthermore, although optional sheet feeding device 100 is configured to be controlled by control unit 200 of image forming apparatus main body 10a, this is not limiting. For example, a separate control unit may be provided for optional sheet feeding device 100, and optional sheet feeding device 100 may be controlled by this separate control unit.

[0118] In addition, although the image forming apparatus 10 in each embodiment is a color multifunction machine, the present disclosure can also be applied to a monochrome multifunction machine. Also, although the image forming apparatus 10 in each embodiment is an electrophotographic type, the present disclosure can also be applied to an inkjet type. Furthermore, the present disclosure can also be applied to image forming apparatuses other than multifunction machines, such as dedicated printers, dedicated copiers, and dedicated fax machines.

[0119] The present disclosure is not limited to the form of an image forming apparatus, but can also be provided in the form of a method for controlling an optional paper feeder in an image forming apparatus. [Explanation of symbols]

[0120] 10. Image forming device 26 … Image forming section 60 … Paper feed section 62 … Main cassette 64 ... Paper feed roller 72a ... Registration roller 100 … Optional paper feeder 106 ... Paper feed roller 108 ... Acceleration / deceleration roller 120 ... Paper detection sensor 122 ... Paper feed detection sensor 124 ... Delay detection sensor

Claims

1. An image forming apparatus including an image forming apparatus main body and an optional paper feeder that can be attached to the image forming apparatus main body, The image forming apparatus main body includes: an image forming unit for performing an image forming process to form an image on a sheet-shaped image recording medium; a registration roller for conveying the image recording medium to an image forming processing position by the image forming means; The optional paper feed device is a first storage section for storing a plurality of the image recording media; a first feed roller that feeds the image recording medium from the first storage unit one by one to a first transport path that leads to a transport position of the image recording medium by the registration roller; and an acceleration / deceleration roller that conveys the image recording medium supplied to the first conveying path to the conveying position by the registration roller; An image forming apparatus comprising: a control means provided in the image forming apparatus main body or the optional paper feeding device, which controls the transport speed of the image recording medium by the acceleration / deceleration rollers so that the leading edge of the image recording medium transported by the acceleration / deceleration rollers reaches a transport position by the registration rollers at a predetermined time point a predetermined time after the first paper feed roller starts to supply the image recording medium to the first transport path.

2. a first detection means for detecting a leading edge of the image recording medium, the first detection means being provided at a position between a conveying position of the image recording medium by the acceleration / deceleration rollers in the first conveying path and a conveying position of the image recording medium by the registration rollers and closer to the conveying position by the acceleration / deceleration rollers; The image forming apparatus according to claim 1 , wherein the control unit controls the conveying speed of the acceleration / deceleration rollers based on a result of detection by the first detection unit.

3. a second detection means provided at a position between a supply position of the image recording medium to the first transport path by the first paper feed roller and a transport position of the image recording medium by the acceleration / deceleration roller, the second detection means detecting a leading edge of the image recording medium; The image forming apparatus according to claim 1 , wherein the control unit controls the conveying speed of the acceleration / deceleration rollers based on a result of detection by the second detection unit.

4. a first detection unit that is provided at a position between a conveying position of the image recording medium by the acceleration / deceleration rollers in the first conveying path and a conveying position by the registration rollers, the first detection unit being closer to the conveying position by the acceleration / deceleration rollers and configured to detect a leading edge of the image recording medium; and a second detection means provided at a position in the first transport path between a supply position of the image recording medium to the first transport path by the first paper feed roller and a transport position by the acceleration / deceleration roller, the second detection means detecting a leading edge of the image recording medium; 2. The image forming apparatus according to claim 1, wherein the control unit controls the conveying speed of the acceleration / deceleration rollers based on the detection results of the first detection unit and the second detection unit.

5. The image forming apparatus main body includes: a second storage section for storing a plurality of the image recording media; and a second feed roller that feeds the image recording medium from the second storage unit to a second transport path that connects the image recording medium to a transport position by the registration rollers, 2. The image forming apparatus according to claim 1, wherein the image recording medium supplied to the second transport path by the second feed roller is transported by the second feed roller to a transport position by the registration roller.

6. An image forming apparatus as described in claim 5, wherein the image forming processing speed by the image forming means is the same both when the image forming processing is performed on the image recording medium transported from the first storage section via the first transport path to a transport position by the registration rollers and when the image forming processing is performed on the image recording medium transported from the second storage section via the second transport path to a transport position by the registration rollers.

7. 7. An image forming apparatus as described in claim 6, wherein a first sheet spacing, which is the distance between the rear end of a preceding image recording medium at the transport position by the registration roller and the front end of a following image recording medium following the preceding image recording medium at the transport position by the registration roller when a plurality of the image recording media are continuously transported from the first storage section via the first transport path to the transport position by the registration roller, is smaller than a second sheet spacing, which is the distance between the rear end of a preceding image recording medium at the transport position by the registration roller and the front end of a following image recording medium following the preceding image recording medium at the transport position by the registration roller when a plurality of the image recording media are continuously transported from the second storage section via the second transport path to the transport position by the registration roller.

8. 1. A method for controlling an optional paper feeder in an image forming apparatus including an image forming apparatus main body and an optional paper feeder that can be attached to the image forming apparatus main body, the method comprising: The image forming apparatus main body includes: an image forming unit for performing an image forming process to form an image on a sheet-shaped image recording medium; a registration roller for conveying the image recording medium to an image forming processing position by the image forming means; The optional paper feed device is a first storage section for storing a plurality of the image recording media; a first feed roller that feeds the image recording medium from the first storage unit one by one to a first transport path that leads to a transport position of the image recording medium by the registration roller; and an acceleration / deceleration roller for conveying the image recording medium supplied to the first conveying path to the conveying position by the registration roller; A control method including a control step of controlling a transport speed of the image recording medium by the acceleration / deceleration rollers so that a leading edge of the image recording medium transported by the acceleration / deceleration rollers reaches a transport position by the registration rollers at a predetermined time point a predetermined time after the first feed rollers start supplying the image recording medium to the first transport path.

Images