Image forming apparatus

Abstract

To make difficult falling of a discharged medium when the medium having an image formed therein is discharged.SOLUTION: Roll paper Rp having an image formed thereon by a head 5 is discharged from a paper discharge unit 7 so as to droop outside. A paper discharge roller pair 24 maintains the roll paper Rp to be discharged in a held state. The paper discharge roller pair 24 can change the size of a force for holding the roll paper Rp. A control unit 9 causes a conveyance roller pair 23 to adjust the size of the force for holding the roll paper Rp to be larger as the weight of the roll paper Rp is larger.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to an image forming apparatus that forms an image on a medium.

Background Art

[0002] In an image forming apparatus that forms an image on a medium, when discharging the medium on which an image has been formed to the outside, there is a configuration in which a pair of rollers for discharging holds the medium in a sandwiched state. In Patent Document 1 related to an example of such an image forming apparatus, the rear end of a print medium on which image recording has ended is held by a pair of paper discharge rollers while the recording medium is suspended in a state of being sandwiched by the pair of paper discharge rollers (see FIG. 3(b) of Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The weight of the medium on which an image has been formed varies depending on various factors such as the type and size of the medium, the content of the image, etc. When the weight of the medium is large, the pair of rollers for discharging may not be able to maintain the state of holding the medium, and there is a risk that the medium may fall.

[0005] An object of the present invention is to provide an image forming apparatus in which the discharged medium is difficult to fall.

Means for Solving the Problems

[0006] The image forming apparatus of the present invention comprises a media storage section for storing a medium, an image forming section for forming an image on the medium, a discharge section for discharging the medium so that it hangs outwards, a media transport section having a plurality of roller pairs for transporting the medium from the media storage section to the image forming section and discharging it from the discharge section along a predetermined transport direction, and a control unit, wherein the plurality of roller pairs are arranged downstream of the image forming section in the predetermined transport direction and are roller pairs that hold and maintain the discharge medium, which is the medium discharged from the discharge section, and include a discharge roller pair having two rollers whose gripping force on the discharge medium can be changed, and the control unit performs an image forming process in which it causes the medium to be transported to the media transport section and an image to be formed on the medium in the image forming section, and the medium on which the image has been formed is discharged from the discharge section to the media transport section, and a media maintenance process in which it causes the discharge roller pair to hold and maintain the discharge medium so that the gripping force when maintaining the medium in a gripping state increases as the weight of the discharge medium increases. [Effects of the Invention]

[0007] The discharged medium, which hangs outwards, is held in place by the pair of discharge rollers. At this time, the pair of discharge rollers grips the discharged medium with a force proportional to its weight. Therefore, even if the weight of the hanging discharged medium is large, the state in which the pair of discharge rollers grips the medium is easily maintained. Thus, the dropping of the discharged medium is suppressed. [Brief explanation of the drawing]

[0008] [Figure 1] This is a schematic side view showing the internal structure of a printer according to one embodiment of the present invention. [Figure 2] This block diagram shows the electrical configuration of the printer shown in Figure 1. [Figure 3] This flowchart shows how the magnitude of the force applied by the paper ejection roller pair shown in Figure 1 to grip the paper is selected. [Figure 4] This flowchart shows the method for determining the magnitude of the force selected using the selection method shown in Figure 3. [Figure 5] This is a schematic side view partially showing the internal structure of a printer according to another embodiment of the present invention. [Modes for carrying out the invention]

[0009] [First Embodiment] A printer 100 (corresponding to the "image forming apparatus" of the present invention) according to the first embodiment, which is a preferred embodiment of the present invention, will be described below with reference to Figures 1 to 5. The vertical, horizontal, and front-to-back directions shown in Figure 1 will be referred to as the vertical, horizontal, and front-to-back directions of the printer 100.

[0010] As shown in Figure 1, the printer 100 mainly comprises a housing 100a, a feed tray 1, a transport mechanism 2, a cutter 3, a carriage 4, a head 5, a moving mechanism 6, a paper output section 7, a cartridge mounting section 8, and a control section 9.

[0011] The feeding tray 1 (corresponding to the "media storage section" of the present invention) is located below the head 5 within the housing 100a. The feeding tray 1 can be inserted into and removed from the housing 100a in the front-rear direction through an opening 101 formed in the front wall of the housing 100a.

[0012] The feeding tray 1 is capable of accommodating a roll body R and cut paper Kp (corresponding to the "medium" in this invention). The feeding tray 1 may be capable of accommodating both the roll body R and cut paper Kp simultaneously, or it may be capable of selectively accommodating either the roll body R or cut paper Kp. The feeding tray 1 has a roll body support section 11 for supporting the roll body R and a mounting surface 12 on which the cut paper Kp is placed.

[0013] A roll of paper R is a long sheet of paper wound in a roll around the outer surface of a cylindrical core member Rc. Cut paper Kp is shorter than the long sheet of paper that makes up the roll of paper R, and is a standard size such as A4 or B5. In both cases where roll paper Rp or cut paper Kp is used, there are various types of paper. For example, there is plain paper and glossy paper, and the type of paper according to the application is stored in the feed tray 1.

[0014] The transport mechanism 2 transports the paper P from the feed tray 1 to the head 5 along a predetermined transport direction (the direction along the roll paper Rp shown in Figure 1). The transport mechanism 2 includes a feed roller 21, an intermediate roller pair 22, a transport roller pair 23, a paper discharge roller pair 24, and a guide member 25.

[0015] The feed roller 21 feeds the roll paper Rp unwound from the roll body R supported by the roll body support section 11, or the cut paper Kp placed on the mounting surface 12, from the feed tray 1. In the following description, when roll paper Rp and cut paper Kp are not distinguished, they will be referred to as "paper P".

[0016] The feed roller 21 rotates when driven by the feed motor 21a (see Figure 2). When the feed motor 21a is driven by the control unit 9, the feed roller 21 rotates, and a transport force is applied to the paper P that is in contact with the feed roller 21 in a direction from front to back. As a result, the paper P is fed out of the feed tray 1. The rear wall 15, which is provided at the rear end of the feed tray 1, is inclined so that its upper end is located behind its lower end. Therefore, the paper P fed out of the feed tray 1 is directed diagonally upward.

[0017] The intermediate roller pair 22 is composed of a driving roller that rotates by the drive of an intermediate motor 22a (see FIG. 2) and a driven roller that rotates along with the driving roller. When the intermediate motor 22a is driven under the control of the control unit 9, the intermediate roller pair 22 rotates while sandwiching the paper P to convey the paper P. The intermediate roller pair 22 is located above the rear end of the feeding tray 1. The intermediate roller pair 22 sandwiches the paper P sent out from the feeding tray 1 by the feeding roller 21 and moving obliquely upward, and conveys it upward. The guide member 25 is located above the intermediate roller pair 22. The guide member 25 guides the paper P conveyed upward by the intermediate roller pair 22 forward.

[0018] The conveyance roller pair 23 is downstream (forward) of the guide member 25 in the conveyance direction and is located slightly upstream (rearward) of the head 5. The conveyance roller pair 23 corresponds to the roller pair that is closest to the head 5 among the roller pairs provided in the conveyance mechanism 2 upstream of the head 5 in the conveyance direction. The conveyance roller pair 23 is composed of a driving roller 23p that rotates by the drive of a conveyance motor 23a (see FIG. 2) and a driven roller 23q that rotates along with the driving roller. The conveyance roller pair 23 sandwiches the paper P conveyed by the intermediate roller pair 22 and guided forward by the guide member 25 and conveys it further forward.

[0019] The paper discharge roller pair 24 (corresponding to the "discharge roller pair" of the present invention) is slightly downstream (forward) of the head 5 in the conveyance direction and is located upstream (rearward) of the paper discharge unit 7. The paper discharge roller pair 24 is composed of a driving roller 24p that rotates by the drive of a paper discharge motor 24a (see FIG. 2) and a driven roller 24q that rotates along with the driving roller. The driving roller 24p has a larger roller diameter than the driving roller 23p. The driving roller 24p is supported by the housing 100a so as to be movable in the vertical direction. The paper discharge roller pair 24 sandwiches the paper P conveyed forward by the conveyance roller pair 23 and conveys it further forward to the paper discharge unit 7.

[0020] Above the driving roller 24p, a pressing part 25 is installed. The pressing part 25 applies a force (hereinafter referred to as the pressing force) that presses the driving roller 24p downward as shown by the arrow A toward the driven roller 24q. A linear actuator or the like driven by a motor or a solenoid is used for the pressing part 25. The magnitude of the pressing force by the pressing part 25 is variable and is adjusted by the control of the control part 9. When the pressing force changes, the magnitude of the force by which the paper discharge roller pair 24 sandwiches the paper P changes according to the pressing force.

[0021] The cutter 3 is located between the rear end of the feeding tray 1 and the intermediate roller pair 22. The cutter 3 is composed of, for example, a rotary blade in the shape of a disc and a driven blade. The cutter 3 rotates the rotary blade by the drive of a cutting motor 3a (see FIG. 2) and reciprocates along the left - right direction. The roll paper Rp unwound from the roll body R and conveyed is cut in the width direction of the roll paper Rp by the cutter 3 when the cutting motor 3a is driven under the control of the control part 9. Thereby, a rear end is formed on the roll paper Rp, and it becomes a sheet of paper and is discharged from the paper discharge part 7.

[0022] The head 5 (corresponding to the "image forming part" of the present invention) includes a plurality of nozzles formed on the lower surface and a driver IC 52 (see FIG. 2). Ink is supplied to the head 5 from an ink cartridge housed in the housing 100a through a tube or the like. When the driver IC 52 is driven by the control of the control part 9, ink is ejected from the nozzles 51. The ejected ink adheres to the ink ejection area of the paper P when the paper P conveyed by the conveyance mechanism 2 passes through the image recording position facing the lower surface of the head 5. Dots constituting an image are formed on the paper P by this adhered ink. The head 5 is mounted on the carriage 4.

[0023] The moving mechanism 6 includes two guide rails 61 and 62 and a carriage motor 63 (see Figure 2). The two guide rails 61 and 62 are spaced apart from each other in the front-rear direction and each extends in the left-right direction. The carriage 4 is positioned to straddle the two guide rails 61 and 62. The carriage 4 is connected to the carriage motor 63 via a belt (not shown) or the like. When the carriage motor 63 is driven by the control unit 9, the carriage 4 moves along the guide rails 61 and 62 in the left-right direction (scanning direction).

[0024] The paper discharge unit 7 is located in front of the head 5 within the housing 100a and above the feed tray 1. The paper discharge unit 7 has a tray 71 positioned in an opening 102 formed in the front wall of the housing 100a. The tray 71 can be manually inserted and removed from the housing 100a along the front-to-back direction, and can also be extended and retracted in the front-to-back direction. As a result, the tray 71 can selectively assume a state in which it is housed within the housing 100a, as shown by the solid line in Figure 1, and a state in which it protrudes forward from the opening 102 of the housing 100a, as shown by the dashed line in Figure 1.

[0025] When image formation is performed on cut paper Kp, the cut paper Kp with the image formed by the head 5 is discharged onto the protruding tray 71. When image formation is performed on roll paper Rp, the tray 71 is maintained in a retracted state, and the roll paper Rp with the image formed by the head 5 is discharged so as to hang down in front of the housing 100a from the opening 102, as shown in Figure 1. The discharged roll paper Rp (corresponding to the "discharge medium" of the present invention) is transported by the transport mechanism 2 until the rear end formed by the cutter 3 is positioned α between the paper discharge roller pair 24 and the head 5. After that, transport by the transport mechanism 2 is stopped, and the roll paper Rp is maintained in a state where its rear end is held by the paper discharge roller pair 24 and hangs down in front of the housing 100a from the opening 102.

[0026] The control unit 9 controls the entire printer 100. As shown in Figure 2, the control unit 9 is electrically connected to the feed motor 21a, intermediate motor 22a, transport motor 23a, paper ejection motor 24a, pressing unit 25, cutting motor 3a, driver IC 52, carriage motor 63, etc.

[0027] As shown in Figure 3, the control unit 9 includes a CPU (Central Processing Unit) 91, ROM (Read Only Memory) 92, RAM (Random Access Memory) 93, and ASIC (Application Specific Integrated Circuit) 94. The ROM 92 stores programs executed by the CPU 91 and ASIC 94, various fixed data, etc. In this embodiment, nip force 0 to nip force 8, which indicate the magnitude of the force with which the paper discharge roller pair 24 grips the roll paper Rp, are stored in the ROM 92. The RAM 93 temporarily stores data (such as image data) necessary when the program is executed. In this embodiment, a flag indicating which of nip force 1 to nip force 8 is selected and the cumulative value of the ink ejection amount are stored in the RAM 93.

[0028] Furthermore, the control unit 9 may perform various processing using only the CPU 91, or only the ASIC 94, or the CPU 91 and ASIC 94 may cooperate in performing various processing. Also, the control unit 9 may be performed by a single CPU 91 alone, or by multiple CPUs 91 sharing the processing. Furthermore, the control unit 9 may be performed by a single ASIC 94 alone, or by multiple ASICs 94 sharing the processing.

[0029] The control unit 9 performs image formation processing based on image data transmitted by the user from an external device (e.g., a PC or smartphone). The image data includes header data indicating various attributes of image formation and body data indicating the content of the image. The header data indicates the distinction between roll paper Rp and cut paper Kp, the type of paper, the print quality, and the paper length as attributes of image formation. The body data is data that instructs the density of ink to be applied to each dot on the paper P that constitutes the image.

[0030] The control unit 9 receives the header data before the main data and starts image formation processing according to the distinction between roll paper Rp and cut paper Kp, the type of paper, and the print quality indicated by the header data. Next, the control unit 9 starts receiving the main data. The main data is not transmitted all at once from the external device, but in parts. Each time the control unit 9 receives a predetermined amount of main data, it controls each part so that the image indicated by the received main data is formed on the paper P. Specifically, the control unit 9 repeatedly alternates between transport processing, which causes the transport mechanism 2 to transport the paper P by a predetermined distance in the transport direction, and scanning processing, which causes the moving mechanism 6 to move the carriage 4 in the scanning direction while ejecting ink from multiple nozzles 51 of the head 5 to the ink ejection area of ​​the paper P. The control unit 9 continues this process until all the main data has been received. Once the image corresponding to all the main data has been formed on the paper P, the control unit 9 causes the transport mechanism 2 to transport the paper P so that it is discharged from the paper discharge unit 7.

[0031] In the image formation process, if the header data instructs the use of roll paper Rp, the control unit 9 controls the cutter 3 to cut the paper to the length indicated by the image data. As a result, the portion of the roll paper Rp containing the area in which the image has been formed is separated from the roll body R. The separated roll paper Rp is discharged to the paper discharge unit 7 as individual recorded sheets. Hereinafter, the roll paper Rp discharged to the paper discharge unit 7 in this manner will be referred to as "discharged roll paper".

[0032] The discharged roll paper is held at its rear end by the discharge roller pair 24 and is maintained hanging down in front of the housing 100a from the opening 102. On the other hand, if the weight of the discharged roll paper is large, the discharge roller pair 24 may not be able to maintain its grip on the discharged roll paper, and the discharged roll paper may fall.

[0033] Therefore, the control unit 9 performs a paper holding process (corresponding to the "media holding process" of the present invention) in which the pair of paper discharge rollers 24 grips the discharged roll paper (hereinafter referred to as the "paper discharge gripping force") according to the weight of the discharged roll paper, and maintains the discharged roll paper in a state where it is gripped by the pair of paper discharge rollers 24.

[0034] In the paper holding process, the conditions that determine the magnitude of the paper clamping force during discharge include the type of paper used for the discharge roll, the print quality, the paper length, and the ink discharge rate. These conditions affect the weight of the discharge roll as follows: Paper type includes, for example, plain paper and glossy paper. Glossy paper has a greater weight per unit area than plain paper. Print quality includes, for example, normal quality and high quality. High quality tends to use more ink than normal quality. Therefore, high quality tends to result in a heavier discharge roll than normal quality. The longer the paper length, the heavier the discharge roll tends to be. The heavier the discharge roll tends to be, the greater the ink discharge rate.

[0035] The control unit 9 acquires the paper type, print quality, and paper length based on the header data included in the image data (corresponding to the function of the "length information acquisition unit" in the present invention). Then, as shown in the flowchart of Figure 3 relating to the method of selecting the paper ejection clamping force based on these conditions, the control unit 9 selects one of the nip forces 1 to 8 stored in the ROM 92. The control unit 9 determines whether the paper type is plain paper or not (S1), whether the print quality is normal or not (S2 and S5), and whether the paper length is below a certain threshold or not (S3, S4, S6 and S7), and based on each determination result, selects one of the nip forces 1 to 8 as shown in Figure 3. For example, if the paper type is plain paper, the print quality is normal, and the paper length is below a certain threshold, nip force 1 is selected through a branching of S1:Yes → S2:Yes → S3:YES. If the paper type is not plain paper (it is glossy paper), the print quality is not normal (it is high quality), and the paper length is not below a certain threshold (it exceeds it), then nip power 8 is selected through a branching sequence S1:No → S5:No → S7:No. If the paper type is not plain paper (it is glossy paper), the print quality is normal, and the paper length is below a certain threshold, then nip power 5 is selected through a branching sequence S1:No → S5:Yes → S6:Yes. The result of this selection is stored as a flag in RAM93.

[0036] The relationship between nip forces 0 and 8 used in this embodiment is as follows: Nipple strength 2 < Nipple strength 4 < Nipple strength 6 < Nipple strength 8 0 < Nip force 0 < Nip force 1 < Nip force 2 Nipple strength 3 < Nipple strength 4 Nipple strength 5 < Nipple strength 6 Nipple strength 7 < Nipple strength 8

[0037] Furthermore, the control unit 9 accumulates the amount of ink ejected each time it receives a predetermined amount of main unit data during the image forming process. This accumulation is performed as follows: As described above, the main unit data is data that instructs the density of ink to be applied to each dot formed on the paper P in order to form an image. Based on this, the control unit 9 calculates the total amount of ink used for all dots corresponding to the received main unit data. This calculation result is added to the accumulated value stored in the RAM 93. As a result, the RAM 93 stores the accumulated value of the amount of ink ejected corresponding to the received main unit data.

[0038] The control unit 9 selects the final paper-removing clamping force to be used based on the cumulative value of the ink ejection amount stored in RAM 93 and a flag stored in RAM 93. Specifically, as shown in Figure 4, the control unit 9 determines whether the cumulative value of the ink ejection amount is greater than or equal to a threshold (S11). If the cumulative value of the ink ejection amount is greater than or equal to the threshold (S11, Yes), the control unit 9 makes the final decision on the magnitude of the paper-removing clamping force to be the one indicated by the flag among nip force 1 to nip force 8 (S12). For example, if the flag indicates nip force 1, the magnitude of the paper-removing clamping force is finally determined to be nip force 1. On the other hand, if the cumulative value of the ink ejection amount is less than the threshold (S11, No), the control unit 9 makes the final decision on the magnitude of the paper-removing clamping force to be smaller than the one indicated by the flag (S13).

[0039] As part of the S13 process, for example, if the flag indicates a nip force of 1, the final nip force is determined to be 0. Also, for example, if the flag indicates a nip force of 2, 4, 6, or 8, the final nip force is determined to be one of nip forces 0, 1, 2, 4, and 6 that is smaller than the original nip force. Alternatively, for example, if the flag indicates a nip force of 2, the final nip force may be 1; if the flag indicates a nip force of 4, it may be 2; if the flag indicates a nip force of 6, it may be 4; and if the flag indicates a nip force of 8, it may be 6. In other words, a nip force one step smaller than what the flag indicates may be selected. Or, the final force may be determined to be slightly larger than a nip force one step smaller than what the flag indicates. For example, if the flag indicates a nip force of 2, the final determination may be made as (nip force 2 - α1); if the flag indicates a nip force of 4, as (nip force 4 - α2); if the flag indicates a nip force of 6, as (nip force 6 - α3); and if the flag indicates a nip force of 8, as (nip force 8 - α4). Here, α1, α2, α3, and α4 are all positive real numbers, satisfying α1 < (nip force 2 - nip force 1), α2 < (nip force 4 - nip force 2), α3 < (nip force 6 - nip force 4), and α4 < (nip force 8 - nip force 6).

[0040] Furthermore, if the flag indicates a nip force of 3, 5, or 7, the final force magnitude is determined to be smaller than these, for example, (nip force 3 - β1), (nip force 5 - β2), or (nip force 7 - β3), respectively. Here, β1, β2, and β3 are each positive real numbers, and each of them may have a relatively small value. For example, each of β1, β2, and β3 may be set to a value smaller than the absolute value of the difference between the two closest values ​​of nip forces 3, 5, and 7.

[0041] Based on the above, the paper ejection clamping force selected by the selection method shown in Figures 3 and 4 will have the following relationship (a) to (d) with respect to each condition such as the type of paper. I: Glossy paper has a greater paper-thinning force than regular paper. B: Higher print quality results in greater paper ejection clamping force than average print quality. H: The paper ejection clamping force is greater when the paper length exceeds the threshold (i.e., the longer the ejected roll of paper) than when it is below the threshold. II: When the ink ejection amount is above the threshold (i.e., the more ink used for image formation), the greater the paper ejection clamping force.

[0042] According to the above (a) through (d), the paper ejection clamping force is adjusted to a size that is appropriate for the weight of the ejected roll paper according to each condition. In other words, the paper ejection clamping force is adjusted so that the greater the weight of the ejected roll paper according to each condition, the greater the paper ejection clamping force.

[0043] Furthermore, as an external factor, the paper ejection clamping force may be adjusted based on the humidity level in the environment in which the printer 100 is used. In a high-humidity environment, the ejected roll paper may absorb moisture and become heavier. Therefore, if the control unit 9 obtains information indicating use in a high-humidity region or location, it adjusts the paper ejection clamping force to be greater than in other cases. Such information may be directly input to the printer 100 by the user through an input unit such as a touch panel installed on the front of the housing 100a, or the information may be input by the user via an external device and transmitted to the printer 100.

[0044] According to the embodiment described above, the discharged roll paper Rp (discharged roll paper) that is discharged hanging outwards is held in place by the discharge roller pair 24. At this time, the discharge roller pair 24 holds the discharged roll paper with a force proportional to its weight. Therefore, even if the weight of the hanging discharged roll paper is large, the discharge roller pair 24 is more likely to maintain its grip on the discharged roll paper. Thus, the dropping of the discharged roll paper is suppressed.

[0045] Furthermore, in this embodiment, the diameter of the drive roller 24p of the paper discharge roller pair 24 is larger than that of the drive roller 23p of the transport roller pair 23. As a result, the contact area between the drive roller 24p of the paper discharge roller pair 24 and the discharged roll paper is relatively large, making it easier to stably maintain the discharged roll paper in a state where it is held between the paper discharge roller pair 24.

[0046] [Second Embodiment] The following describes a second embodiment according to another embodiment of the present invention. The main difference between this embodiment and the first embodiment is that, instead of the paper discharge roller pair 24, the paper discharge roller pair 124A and 124B shown in Figure 5 (corresponding to the "discharge roller pair" of the present invention) is used. Other configurations are common to both the first and second embodiments. Therefore, the following will mainly describe the differences from the first embodiment, and the same reference numerals will be used for components common to both embodiments, with their descriptions omitted as appropriate.

[0047] The paper discharge roller pairs 124A and 124B are located slightly downstream (forward) of the head 5 in the transport direction, and upstream (rear) of the paper discharge section 7. Paper discharge roller pair 124A consists of a drive roller 124p that rotates by the drive of a motor, and a driven roller 124q that moves along with the drive roller 124p. The drive roller 124p is supported by the housing 100a so that it can move in the vertical direction. On the other hand, paper discharge roller pair 124B consists of two driven rollers. These two driven rollers grip the roll paper Rp and rotate in conjunction with the movement of the roll paper Rp. Both paper discharge roller pairs 124A and 124B use a material with a higher coefficient of friction on the roller surface compared to the roller surface of the transport roller pair 23. Paper discharge roller pairs 124A and 124B grip the paper P that has been transported forward by the transport roller pair 23 and transport it further forward to the paper discharge section 7. The roll paper Rp (discharged roll paper) discharged to the paper discharge section 7 is held at its rear end by the paper discharge roller pairs 124A and 124B and is maintained in a state where it hangs down in front of the housing 100a from the opening 102.

[0048] Above the drive roller 124p, a pressing unit 25 is installed that applies a pressing force to the drive roller 124p, pushing it downward toward the driven roller 124q. The magnitude of the pressing force applied by the pressing unit 25 is adjusted by the control unit 9. When the pressing force is changed, the magnitude of the force with which the paper discharge roller pair 124A grips the paper discharge roll (paper discharge gripping force) is changed. Similar to the first embodiment, the control unit 9 adjusts the magnitude of the paper discharge gripping force to be appropriate for the weight of the paper discharge roll, which varies depending on the type of paper, print quality, paper length, and ink discharge amount.

[0049] According to this embodiment, similar to the first embodiment, the paper discharge roller pair 124A grips the discharged roll paper with a force proportional to its weight. Therefore, even if the weight of the sagging discharged roll paper is large, the state in which the paper discharge roller pair 24 grips the discharged roll paper is easily maintained. Thus, the dropping of the discharged roll paper is suppressed.

[0050] Furthermore, in this embodiment, the two pairs of paper discharge rollers, 124A and 124B, maintain a state in which the discharged paper roll is held. Therefore, compared to the case where only one pair of rollers is used, the discharged paper roll is more easily and stably maintained in a held state. In addition, the surfaces of the rollers of the paper discharge roller pair 124A and 124B are made of a material with a relatively high coefficient of friction. As a result, the frictional force acting between the discharged paper roll and the roller surface is increased, making it even easier to stably maintain the discharged paper roll in a held state.

[0051] In this embodiment, a pressing portion 25 may also be installed above the paper discharge roller pair 124B, and this pressing portion 25 may apply a pressing force to the upper roller of the paper discharge roller pair 124B, pressing it downwards toward the lower roller. Alternatively, the upper roller of the paper discharge roller pair 124B may be a drive roller.

[0052] <Variation> Although embodiments of the present invention have been described above with reference to the drawings, it should be understood that the specific configurations are not limited to these embodiments. The scope of the present invention is indicated by the claims rather than the above description of embodiments, and all modifications within the meaning and scope equivalent to the claims are included.

[0053] For example, in the embodiments described above, the paper ejection clamping force is selected according to each condition according to the flowcharts in Figures 3 and 4. However, the magnitude of the paper ejection clamping force may be adjusted by a different method. For example, an evaluation value for the weight of the ejection roller paper may be calculated based on a function with paper type, print quality, paper length, and ink ejection amount as variables, and the magnitude of the paper ejection clamping force may be selected according to that evaluation value. Alternatively, some of the paper type, print quality, paper length, and ink ejection amount may be used to select the magnitude of the paper ejection clamping force, or other conditions may be used in place of or in addition to these conditions.

[0054] Furthermore, in the flowchart of Figure 3, in each of S3, S4, S6, and S7, the paper ejection clamping force is selected from two nip forces depending on whether the paper length exceeds a threshold (for example, depending on the determination in S3, the paper ejection clamping force is selected from two nip forces, nip force 1 and nip force 2). Alternatively, the paper ejection clamping force may be selected from three or more nip forces depending on the size of the paper. Also, in the flowchart of Figure 4, the paper ejection clamping force is selected from two nip forces depending on whether the ink ejection amount is above a threshold. Alternatively, the paper ejection clamping force may be selected from three or more nip forces depending on the ink ejection amount.

[0055] Furthermore, in the above-described embodiment, the paper retention process is executed when image formation is performed on the roll paper Rp during the image formation process. In other words, the paper retention process is executed as a trigger when the image data indicates that the roll paper Rp should be used. Alternatively, the paper retention process may be executed based on the detection result when the output tray 71 is in a stowed state, using a sensor or the like. Also, the paper retention process may be executed when cut paper Kp is used.

[0056] Furthermore, in the first embodiment described above, the roller diameter of the drive roller 24p of the paper discharge roller pair 24 is larger than the roller diameter of the drive roller 23p of the transport roller pair 23. Alternatively, the roller diameter of the drive roller 24p may be the same as the roller diameter of the drive roller 23p.

[0057] In addition, although the embodiments described above have described the application of the present invention to a printer 10, the invention is not limited thereto. The present invention may also be applied to other inkjet-type image forming apparatuses that eject ink from a head, such as multifunction printers and copiers. Furthermore, the present invention may be applied to laser-type image forming apparatuses or other image forming apparatuses that perform image recording processing by attaching toner to the paper P instead of ink using an inkjet method. [Explanation of symbols]

[0058] 1 Feeding tray 2. Conveying mechanism 3 cutters 5 heads 7. Paper output section 9. Control Unit 23 Conveyor roller pair 24 Paper output roller pair 25 Pressing part 124A Paper output roller pair 124B Paper output roller pair 100 Printers

Claims

1. A media storage section capable of accommodating a roll body in which a sheet-like medium is wound into a roll shape, An image forming unit that forms an image on the aforementioned sheet-like medium, The discharge section from which the sheet-like medium is discharged so as to hang down to the outside, A media transport unit having a plurality of roller pairs that transport the sheet-like medium from the media storage unit to the image forming unit and discharge it from the discharge unit along a predetermined transport direction, A cutting section for cutting the aforementioned sheet-like medium, A length information acquisition unit that acquires information regarding the length of the discharge medium, which is the sheet-like medium discharged from the discharge unit, It is equipped with a control unit, The aforementioned plurality of roller pairs, A pair of rollers positioned downstream of the image forming unit in the predetermined transport direction, which holds the discharge medium in a clamping position, and which includes a pair of discharge rollers having two rollers capable of changing the magnitude of the clamping force on the discharge medium. The control unit, The image forming process involves transporting the sheet-like medium to the medium transport unit while forming an image on the sheet-like medium in the image forming unit, cutting the sheet-like medium in the cutting unit so that the portion containing the formed image is separated from the portion wound around the roll body and becomes the discharge medium, and discharging the discharge medium from the discharge unit. An image forming apparatus characterized by performing a media maintenance process, at least based on the information acquired by the length information acquisition unit, to maintain the discharge medium in a state of being held between the discharge roller pair such that the longer the discharge medium, the greater the gripping force.

2. A media storage section for housing media, An image forming unit that forms an image on a medium by applying a coloring agent to the medium, An outlet section from which the medium is discharged so that it hangs outwards, A media transport unit having a plurality of roller pairs that transport media from the media storage unit to the image forming unit and discharge it from the discharge unit along a predetermined transport direction, It is equipped with a control unit, The aforementioned plurality of roller pairs, A pair of rollers positioned downstream of the image forming unit in the predetermined transport direction, which holds and maintains the discharge medium, which is the medium discharged from the discharge unit, and which includes a pair of discharge rollers having two rollers capable of changing the magnitude of the force that holds the discharge medium, The control unit, An image forming process in which a medium is transported to the medium transport unit while an image is formed on the medium in the image forming unit, and the medium on which the image is formed is discharged from the discharge unit to the medium transport unit, An image forming apparatus characterized by performing a media holding process such that the more coloring agent used to form an image on the medium the greater the clamping force, the greater the clamping force, and maintaining the discharge medium in a clamped state between the discharge roller pair.

3. A media storage section capable of accommodating multiple types of media, An image forming unit that forms an image on a medium, An outlet section from which the medium is discharged so that it hangs outwards, A media transport unit having a plurality of roller pairs that transport media from the media storage unit to the image forming unit and discharge it from the discharge unit along a predetermined transport direction, It is equipped with a control unit, The aforementioned plurality of roller pairs, A pair of rollers positioned downstream of the image forming unit in the predetermined transport direction, which holds and maintains the discharge medium, which is the medium discharged from the discharge unit, and which includes a pair of discharge rollers having two rollers capable of changing the magnitude of the force that holds the discharge medium, The control unit, An image forming process in which a medium is transported to the medium transport unit while an image is formed on the medium in the image forming unit, and the medium on which the image is formed is discharged from the discharge unit to the medium transport unit, A media maintenance process is performed such that the clamping force used to maintain the discharged medium in the clamped state increases as the weight of the discharged medium increases, and the discharged medium is maintained in a clamped state by the pair of discharged rollers. The control unit, Selectively perform the image forming process on any of the aforementioned multiple types of media. An image forming apparatus characterized in that the media maintenance process is performed such that the clamping force differs depending on which of the aforementioned multiple types of media is selected.

4. A media storage section for housing media, An image forming unit that forms an image on a medium, An outlet section from which the medium is discharged so that it hangs outwards, A media transport unit having a plurality of roller pairs that transport media from the media storage unit to the image forming unit and discharge it from the discharge unit along a predetermined transport direction, It is equipped with a control unit, The aforementioned plurality of roller pairs, A pair of rollers positioned downstream of the image forming unit in the predetermined transport direction, which holds and maintains the discharge medium, which is the medium discharged from the discharge unit, and which includes a pair of discharge rollers having two rollers capable of changing the magnitude of the force that holds the discharge medium, The control unit, An image forming process in which a medium is transported to the medium transport unit while an image is formed on the medium in the image forming unit, and the medium on which the image is formed is discharged from the discharge unit to the medium transport unit, A media maintenance process is performed such that the clamping force used to maintain the discharged medium in the clamped state increases as the weight of the discharged medium increases, and the discharged medium is maintained in a clamped state by the pair of discharged rollers. The control unit, The quality of image formation when performing the aforementioned image formation process can be changed. An image forming apparatus characterized in that the media maintenance process is performed such that the clamping force differs according to the quality of the image formation.

5. A media storage section for housing media, An image forming unit that forms an image on a medium, An outlet section from which the medium is discharged so that it hangs outwards, A media transport unit having a plurality of roller pairs that transport media from the media storage unit to the image forming unit and discharge it from the discharge unit along a predetermined transport direction, A humidity information acquisition unit that acquires information indicating the level of humidity in the operating environment, It is equipped with a control unit, The aforementioned plurality of roller pairs, A pair of rollers positioned downstream of the image forming unit in the predetermined transport direction, which holds and maintains the discharge medium, which is the medium discharged from the discharge unit, and which includes a pair of discharge rollers having two rollers capable of changing the magnitude of the force that holds the discharge medium, The control unit, An image forming process in which a medium is transported to the medium transport unit while an image is formed on the medium in the image forming unit, and the medium on which the image is formed is discharged from the discharge unit to the medium transport unit, A media maintenance process is performed such that the clamping force used to maintain the discharged medium in the clamped state increases as the weight of the discharged medium increases, and the discharged medium is maintained in a clamped state by the pair of discharged rollers. The control unit, An image forming apparatus characterized in that the media maintenance process is performed such that the clamping force differs according to the humidity level indicated by the humidity information acquisition unit.

6. The image forming apparatus according to any one of claims 1 to 5, characterized in that the roller diameter of the discharge roller pair is greater than the roller diameter of the roller pair closest to the image forming section in the upstream direction of the transport among the plurality of roller pairs.

7. The image forming apparatus according to any one of claims 1 to 6, characterized in that the coefficient of friction of the material constituting the surface of the discharge roller pair is greater than the coefficient of friction of the material constituting the surface of the roller pair closest to the image forming section in the upstream direction of the transport among the plurality of roller pairs.

8. The image forming apparatus according to any one of claims 1 to 7, characterized in that the media transport section includes a plurality of pairs of discharge rollers.

Images