JP2008265098A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain an image forming apparatus which returns the recording sheet appropriately regardless of the type thereof. <P>SOLUTION: Recording papers P stacked in a paper feed cassette 4 are fed, sheet by sheet, to a carrying passage 14 by means of a paper feed roller 12 and the recording paper P on the carrying passage 14 is carried by means of a drive roller 24. The recording papers P are carried continuously from the paper feed cassette 4 by driving the paper feed roller 12 and the drive roller 24 in the same direction. At the time of reverse feed after printing, the recording paper P is returned to the paper feed cassette 4 by rotating the paper feed roller 12 at a speed dependent on the difference of the recording paper P (S260-S280). The difference of the recording paper P is either one of differences in the type of recording paper P and the size of recording paper P. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an image forming apparatus that prints an image on a recording medium.

  2. Description of the Related Art Conventionally, recording paper (recording medium) stacked on a paper feed cassette or the like is continuously conveyed at regular intervals so as to shorten the printing time. At that time, after the last page of the print data is printed on the recording paper, the recording paper conveyed following the conveyance path is left. If the recording paper is left in the middle of the transport path, the recording paper will be wrinkled according to the shape of the transport path.

Therefore, as disclosed in Patent Document 1, after a predetermined time has elapsed or when a return command signal is output from the control circuit, the recording sheet in the middle of the transport path is returned to the paper feed cassette or the like. .
JP 2000-159392 A

  In such a conventional apparatus, the structure becomes complicated if a sensor for detecting the return of the recording paper is provided. Therefore, when the recording paper is returned to the paper feeding cassette or the like, the paper feeding roller is rotated by a certain amount to return the recording paper. Yes.

  However, various types of recording paper are used, each having different characteristics such as surface roughness (friction coefficient), thickness, waist strength, size (size), and the like. If recording sheets having various characteristics having different characteristics are returned in the same manner by the paper feed roller, there is a possibility that a problem may occur. Specifically, when the recording roller is rotated by a certain amount and the recording paper is returned to the paper supply cassette, the amount of the recording paper returned may differ depending on the characteristics of each recording paper. For example, when slippery recording paper, that is, recording paper having a low surface friction coefficient is returned to the paper feed cassette, the paper feed roller slips on the surface of the recording paper and can be returned until it hits the stopper. There was a problem that I could not.

  An object of the present invention is to provide an image forming apparatus capable of appropriately returning a recording sheet regardless of the characteristics of the recording sheet.

  In order to achieve the above object, the invention described in claim 1 is directed to a printing unit that prints on a recording medium, and the recording medium stacked on the medium storage unit is fed to a conveyance path one by one by a paper feed roller. And a conveying unit that conveys the recording medium on the conveying path to the printing unit by a driving roller, and reversely rotating the paper feeding roller at a speed according to the characteristics of the recording medium during reverse feeding. Reverse feed control means for returning the medium to the medium storage means.

  According to a second aspect of the present invention, in the image forming apparatus according to the first aspect, the characteristic of the recording medium relates to at least a drag that the recording medium receives from the conveyance path, and the reverse feed control unit Is characterized in that when the recording medium having a large drag is conveyed, the paper feed roller is reversely rotated at a slower speed than when the recording medium having a small drag is conveyed.

  According to a third aspect of the present invention, in the image forming apparatus according to the first or second aspect, the characteristic of the recording medium relates to at least a frictional force generated between the recording medium and a paper feed roller. And the reverse feed control means reversely rotates the paper feed roller at a slower speed when transporting the recording medium having a large frictional force than when transporting the recording medium having a small frictional force. It is a feature.

  According to a fourth aspect of the present invention, in the image forming apparatus according to any one of the first to third aspects, the characteristic of the recording medium is that of the first element, the second element, and the third element. It is characterized by comprising at least one.

  According to a fifth aspect of the present invention, in the image forming apparatus according to any one of the first to fourth aspects, the conveyance path is formed in a substantially U-shape from the medium storage unit to the printing unit. It is characterized by including the route | root which was made.

  According to a sixth aspect of the present invention, in the image forming apparatus according to any one of the first to fifth aspects, the medium storage unit is disposed below the printing unit, and the conveyance path extends from the medium storage unit. The printing means is formed in a substantially U shape.

  According to a seventh aspect of the present invention, in the image forming apparatus according to the sixth aspect of the present invention, the sheet feeding roller and the driving roller are further rotationally driven in the same direction, and the recording medium is transferred from the medium storing unit. It is characterized by comprising continuous conveyance control means for conveying continuously.

  According to an eighth aspect of the present invention, in the image forming apparatus according to the sixth or seventh aspect, the recording medium is continuously conveyed by the continuous conveyance control unit. Thus, when there is no print data for the subsequent recording medium, the recording medium is returned to the medium storage means.

  According to the first aspect of the present invention, there is provided reverse feed control means for returning the recording medium to the medium storage means by reversely rotating the paper feed roller at a speed corresponding to the characteristics of the recording medium. . Therefore, regardless of the characteristics of the recording paper (recording medium), the recording paper can be appropriately returned to the medium storage unit. Specifically, when the recording paper is returned to the paper feed cassette, the paper feed roller slips on the surface of the recording paper, causing a problem such as the recording paper not returning until it hits the stopper. Is prevented.

  According to the second aspect of the invention, the characteristics of the recording medium relate to at least the drag that the recording medium receives from the transport path, and when the reverse feed control means transports the recording medium having a large drag, The paper feed roller is rotated in reverse at a slower speed than when a recording medium having a low drag force is conveyed. Therefore, the recording paper (recording medium) can be appropriately returned to the medium storage unit regardless of the drag that the recording paper (recording medium) receives from the conveyance path.

  According to the third aspect of the present invention, the characteristics of the recording medium relate to at least a frictional force generated between the recording medium and the paper feed roller, and the reverse feed control means is a recording target having a large frictional force. When the medium is transported, the paper feed roller is reversely rotated at a slower speed than when the recording medium having a small frictional force is transported. Therefore, the recording paper can be appropriately returned to the medium storage unit regardless of the friction force generated between the recording medium and the paper feed roller.

  According to the fourth aspect of the present invention, the characteristics of the recording medium are constituted by at least one of the first element, the second element, and the third element. Since the first element is the friction coefficient of the surface of the recording medium, the second element is the thickness of the recording medium, and the third element is the size of the recording medium, the friction coefficient, thickness of the surface of the recording medium, Depending on at least one of the sizes, the recording paper is returned to the medium storage means. That is, there is an effect that the recording medium can be appropriately returned to the medium storage unit according to the friction coefficient, thickness, and size of the surface of the recording medium.

  According to a fifth aspect of the present invention, in the image forming apparatus according to any one of the first to fourth aspects, the conveyance path is formed in a substantially U-shape from the medium storage unit to the printing unit. It includes the route. That is, when the recording medium is transported through the transport path, the transport path includes a path in which the posture of the recording medium is deformed into a substantially U shape. Therefore, even when the recording medium is transported along a transport path including a path that is deformed into a substantially U shape, the same effects as those of the first to fourth aspects of the invention can be achieved.

  According to the invention described in claim 6, in the invention described in any one of claims 1-5, the sheet feeding roller and the driving roller are further rotated in the same direction, and the recording medium is recorded from the medium storing means. Is provided with a continuous conveyance control means for conveying the color continuously. Therefore, even when the recording medium is continuously conveyed from the medium storage means, the same effects as those of the first to fifth aspects of the invention can be achieved.

  According to the seventh aspect of the present invention, when the recording medium is continuously conveyed by the continuous conveyance control means and there is no print data for the subsequent recording medium, the reverse feed control means is the recording medium. Is returned to the medium storage means. Therefore, since the subsequent recording medium is not left in the middle of the conveyance path, it is possible to prevent the recording medium from being wrinkled according to the shape of the conveyance path, and to appropriately return the medium to the medium storage unit. There is an effect.

  According to the eighth aspect of the present invention, the paper sensor for detecting the leading end portion of the recording medium is arranged upstream of the driving roller in the transport direction, and the reverse feed control means is continuously provided by the continuous transport control means. The recording medium is returned to the medium storage means when the leading end of the subsequent recording medium that has been transported is positioned upstream in the transport direction, which is not detected by the paper sensor. Therefore, as in the invention described in claim 7, since the subsequent recording medium is not left in the middle of the conveyance path, it is possible to prevent the recording medium from being wrinkled according to the shape of the conveyance path, and appropriately There exists an effect that it can return to a medium storage means.

  The best mode for carrying out the present invention will be described below in detail with reference to the drawings. FIG. 1 is a perspective view of an image forming apparatus provided with an ink jet recording head of the present invention, and FIG. 2 is an explanatory view showing a schematic configuration of the image forming apparatus of the present embodiment.

  The image forming apparatus 1 of the present embodiment is a multi-function device (MFD: MULTI FUNCTION DEVICE) having a printer function, a copy function, a scanner function, and a facsimile function. As shown in FIG. 1, a paper feeding unit 11 for feeding a recording paper P as a recording medium to the bottom of a housing 2 made of an injection molded product made of synthetic resin, which is a main body in the image forming apparatus 1. Is provided. In the paper feeding unit 11, a paper feeding cassette 4 as a medium storage unit that stores recording paper P in a stacked state is attached to and detached from the housing 2 through an opening 2 </ b> A formed on the front side of the housing 2. It is provided as possible. The paper feed cassette 4 is not limited to a removable one.

  In the present embodiment, the paper feed cassette 4 is a recording sheet P of A4 size, letter size, legal size, postcard size, etc., whose short side (width) is perpendicular to the transport direction (sub-scanning direction) (main scanning direction). ) And can be accommodated by stacking a plurality of sheets.

  As shown in FIG. 2, an inclined separation plate 6 for separating recording sheets is disposed on the back side of the paper feed cassette 4. A base end of the paper feed arm 10 is mounted on a frame (not shown) so as to be rotatable in the vertical direction, and a paper feed roller 12 is provided at the lower end of the paper feed arm 10. The recording paper P stacked on the paper feed cassette 4 is separated and conveyed one by one by the paper feed roller 12 and the inclined separation plate 6.

  The separated recording paper P is fed into a paper feed cassette via a conveyance path 14 including a laterally U-shaped path formed in a gap between the curved first conveyance path wall 13A and the second conveyance path wall 13B. 4 is conveyed to a printing mechanism 16 as a printing means provided above 4.

  The printing mechanism 16 includes an ink jet recording head 18 that prints an image on the recording paper P by ejecting ink droplets from the lower surface, and a carriage 20 on which the recording head 18 is mounted and reciprocated in the main scanning direction. A platen 22 that is flat and supports the recording paper P from below so as to face the recording head 18 is provided on the lower surface of the recording head 18 in the carriage 20.

  Further, on the upstream side in the conveyance direction of the platen 22, as a registration roller pair for conveying the recording paper P to the upper surface of the platen 22, a driving roller 24 and a driven nip roller 26 facing the driving roller 24 from below are provided. Is arranged.

  In addition, on the downstream side of the platen 22 in the transport direction, a paper discharge roller 30 that is driven to transport the recording paper P that has passed through the printing mechanism 16 to the paper discharge unit 28 along the transport direction is opposed to the paper discharge roller 30. A spur roller 32 biased toward the paper roller 30 side is disposed.

  On the other hand, a paper discharge unit 28 on which the recording paper P on which an image is recorded by the printing mechanism 16 is discharged with its printing surface facing upward is disposed above the paper supply unit 11, and a paper discharge port 28 </ b> A is provided in the housing 2. It is opened in common with the front opening 2A. Then, the recording paper P discharged from the paper discharge unit 28 is stacked and accommodated on a paper discharge tray 28B disposed inside the opening 2A.

  FIG. 3 is an explanatory view showing an arrangement of gears of the gear transmission mechanism of the present embodiment. As shown in FIG. 3, the paper feed roller 12 and the drive roller 24 are rotationally driven via a gear transmission mechanism 36 by a transport motor 34 using a single DC motor. The paper discharge roller 30 is also rotationally driven by the transport motor 34 via a gear transmission mechanism (not shown), and the rotation of the transport motor 34 is detected by an encoder (not shown).

  A pinion gear 38 attached to the transport motor 34 and a large gear 40 attached to the drive roller 24 so as to be integrally rotatable are meshed with each other. A driving gear 42 is attached to the driving roller 24 so as to be integrally rotatable. An auxiliary gear 46 is engaged with the driving gear 42 and the first transmission gear 44, and the rotation of the driving gear 42 is transmitted to the first transmission gear 44. It is configured to be.

  On the other hand, the paper feed roller 12 is rotatably supported by the paper feed arm 10 and is provided with a driven gear 48 that can rotate integrally with the paper feed roller 12. The paper feeding arm 10 is rotatably provided on a frame (not shown) via a swing shaft 50, and a second transmission gear 52 is rotatably supported on the swing shaft 50.

  In the present embodiment, four intermediate gears 54 to 57 that are rotatably supported by the paper feed arm 10 are provided between the driven gear 48 and the second transmission gear 52. Is rotated so as to be transmitted to the driven gear 48 through the four intermediate gears 54 to 57 in order.

  A gear switching mechanism 58 is provided between the first transmission gear 44 and the second transmission gear 52. As shown in FIG. 3 (a), the gear switching mechanism 58 has a continuous paper feeding state in which rotation is transmitted to the first transmission gear 44 and the second transmission gear 52 via one switching gear 60, and FIG. As shown in (b), the first transmission gear 44 and the second transmission gear 52 can be switched to an intermittent paper feeding state in which rotation is transmitted via the two switching gears 62 and 64. The rotation directions of the first transmission gear 44 and the second transmission gear 52 are the same in the continuous feeding state, and are opposite in the intermittent feeding state.

  In this embodiment, the paper feed roller 12, the driving roller 24, the nip roller 26, the paper discharge roller 30, the spur roller 32, the transport motor 34, the gear transmission mechanism 36, and the like constitute a transport mechanism 66 as a transport means. Further, the diameters of the drive roller 24 and the paper feed roller 12, the gear ratio by the gear transmission mechanism 36, and the like are set so that the peripheral speed of the drive roller 24 is twice that of the paper feed roller 12. .

  An image reading unit 68 for reading a document in a copy function or a facsimile function is disposed on the housing 2. The rear end of the document cover body 69 that covers the upper surface of the image reading unit 68 is rotatably attached to the rear end of the image reading unit 68. On the upper side of the housing 2, as shown in FIG. 1, an operation panel unit 70 including various operation buttons 70 </ b> A, a liquid crystal display unit 70 </ b> B, and the like is provided in front of the image reading unit 68.

  FIG. 4 is a block diagram showing an electrical system of the image forming apparatus 1. The image forming apparatus 1 includes a CPU 71 that executes a processing program, a ROM 72 that stores processing programs, a RAM 74 that temporarily stores processing results, an operation panel unit 70, an image reading unit 68, a transport mechanism 66, a printing mechanism 16, A paper sensor 75 (see FIG. 3) that is provided upstream of the drive roller 24 and detects the leading edge of the recording paper P is connected to an external device PC such as a personal computer via a network 76 such as a LAN. A network interface 78 and a facsimile interface 79 are provided, and these are connected via a bus 80 so that data can be exchanged with each other.

  The image forming apparatus 1 develops print data supplied from the external device PC via the network interface 78 in a frame memory in the RAM 74 to form image data. Based on the image data developed in the frame memory in the RAM 74, the transport mechanism 66, the printing mechanism 16, and the like are controlled to print an image on the recording paper P. The printing may be color printing or monochrome printing. In addition, the printing mechanism 16 is not limited to the ink jet recording head 18, and may include an ink ribbon recording head. Furthermore, a laser type printing mechanism provided with a photosensitive drum may be used.

Next, the printing process performed in the above-described image forming apparatus 1 will be described with reference to the flowchart of FIG. FIG. 5 is a flowchart showing the printing process of this embodiment.
When print data from the external device PC is input via the network interface 78, this print processing is executed. Further, the type and size of the recording paper P on which the print data is printed are set by the driver software installed in the external device PC in advance when printing the print data edited by the application software of the external device PC. The print data includes information on the type and size of the recording paper P. Here, the type of recording paper P refers to the type of paper such as plain paper, glossy paper, postcard, and inkjet paper. The size of the recording paper P includes A4 size, B5 size, legal size, letter size, postcard size, L size, and the like.

  First, when print data to be printed on a recording paper P as a recording medium is input, it is determined whether or not continuous paper feed printing is set (step 100; hereinafter referred to as S100, and so on). Information indicating whether or not continuous paper feed printing is set is stored in a predetermined area of the RAM 74. More specifically, when the user operates the operation button 70A of the operation panel unit 70, an instruction as to whether the print data is to be printed by continuous paper feed printing or intermittent paper feed printing is preset, and the RAM 74 Is stored in a predetermined area. Note that the external device PC may instruct the continuous paper feed printing or the intermittent paper feed printing.

  If intermittent paper feed printing is set and it is determined that it is not continuous paper feed printing (S100: NO), intermittent paper feed is performed (S110). In the intermittent paper feeding, as shown in FIG. 3B, the gear switching mechanism 58 intermittently transmits rotation between the first transmission gear 44 and the second transmission gear 52 via the two switching gears 62 and 64. Switch to paper feed state.

  FIG. 6 is an explanatory diagram of intermittent sheet feeding according to the present embodiment. As shown in FIG. 6A, the transport motor 34 rotates the driving roller 24 in the direction opposite to the transport direction (clockwise rotation in FIG. 6A), and rotates the paper feed roller 12 in the transport direction. (Clockwise rotation in FIG. 6 (a)).

  Accordingly, the recording paper P stacked on the paper feeding cassette 4 is separated and conveyed by the paper feeding roller 12 in the conveying direction. At this time, since the driving roller 24 rotates in the direction opposite to the conveyance direction, the leading edge of the recording paper P hits the nip portion between the driving roller 24 and the nip roller 26 and is temporarily stopped. The line is corrected.

  Next, as shown in FIG. 6B, the drive roller 24 is rotated in the transport direction (counterclockwise in FIG. 6B) to transport the recording paper P by a predetermined amount, and the recording paper P is moved to a predetermined position. The cueing operation to carry is performed. At this time, the paper feed roller 12 rotates in the direction opposite to the conveyance direction (counterclockwise in FIG. 6B), but the nip force by the drive roller 24 and the nip roller 26 is supplied at the location of the paper feed cassette 4. The recording paper P nipped by the driving roller 24 and the nip roller 26 is set to be larger than the conveying force (the biting force of the paper feeding roller 12 on the recording paper P) by the paper roller 12. In contrast, the sheet feeding arm 10 has a releasing action of swinging upward about the swing shaft 50.

  After completion of the cueing operation, printing is performed by the printing mechanism 16 (S120). When printing, the drive roller 24 is rotated in the transport direction (counterclockwise rotation in FIG. 6), and the paper feed roller 12 is rotated in the direction opposite to the transport direction (counterclockwise rotation in FIG. 6) to record. The paper P is fed in the transport direction. Further, at the time of cueing operation and printing, the swing shaft 50 rotates in the reverse direction, whereby the paper feed arm 10 rotates upward and the paper feed roller 12 rotates in the reverse direction (counterclockwise in FIG. 6B). is doing. The recording head 18 is reciprocated in the main scanning direction to eject ink droplets, and the recording paper P is intermittently conveyed according to printing for one pass of the recording head 18 to perform printing for one page.

  When the printing of one sheet is completed, the recording paper P is discharged onto the discharge tray 28B by the discharge roller 30 and the spur roller 32 (S130). Then, when there is a next page in the print data, it is determined that printing has not ended (S140: NO), and the processing from S110 onward is repeated for each sheet of recording paper P, so that a plurality of recording papers P are obtained. Print intermittently. If it is determined that all the print data has been printed and printing has been completed (S140: YES), this printing process is terminated.

  On the other hand, if it is determined by the process of S100 described above that continuous paper feed printing is set (S100: YES), continuous paper feed is started (S150). In the continuous sheet feeding, as shown in FIG. 3A, the gear switching mechanism 58 transmits the rotation between the first transmission gear 44 and the second transmission gear 52 via one switching gear 60. Switch to state.

  FIG. 7 is an explanatory diagram of continuous sheet feeding according to the present embodiment. As shown in FIG. 7, in continuous paper feed printing, the drive motor 24 is rotated in the transport direction by the transport motor 34 (counterclockwise rotation in FIG. 7), and the paper feed roller 12 is rotated in the transport direction (FIG. 7). Then turn clockwise). The peripheral speed of the drive roller 24 is twice as large as the peripheral speed of the paper feed roller 12.

  The recording paper P stacked on the paper feeding cassette 4 is separated and conveyed by the paper feeding roller 12 in the conveying direction, and the recording paper P is sandwiched between the driving roller 24 and the nip portion of the nip roller 26. Be transported.

  After the continuous paper feeding is started, printing on the recording paper P is started by controlling the printing mechanism 16 (S160). In the printing, similarly to the process of S120 described above, the recording head 18 is reciprocated in the main scanning direction to eject ink droplets, and the recording paper P is intermittently printed according to printing for one pass of the recording head 18. Transport and print.

  Subsequently, it is determined whether there is a subsequent page (S170). Whether there is a subsequent page is determined based on the print data input from the external device PC. If it is determined that there is a subsequent page (S170: YES), whether printing for one page has been completed. It is determined whether or not (S180).

  When printing for one page is not completed (S180: NO), printing is continued until printing is completed. When printing for one page is completed (S180: YES), recording is performed by the drive roller 24 and the nip roller 26. Without stopping the paper P, the drive roller 24, the paper feed roller 12, and the paper discharge roller 30 are continuously rotated in the transport direction to discharge the recording paper P that has been printed, A recording sheet P is conveyed (S190).

Then, the processes from S160 onward are repeated, and a plurality of recording papers P are continuously conveyed and printed.
If it is determined that there is no subsequent page by executing the process of S170 (S170: NO), it is determined whether printing of the final page is completed (S195). If it is determined that the last page has been printed (S195: YES), a recording paper return process (S200) is executed.

  FIG. 8 is a flowchart showing the recording sheet returning process of the present embodiment. As shown in FIG. 8, in the recording paper return process, first, it is determined whether or not the paper sensor 75 has detected the leading edge of the recording paper P (S210). In continuous paper feed printing, the recording paper P is continuously transported, so that the subsequent recording paper P is transported to the transport path 14 by the paper feed roller 12 when the last page is printed.

  When the leading edge of the recording paper P is detected by the paper sensor 75 (S210: YES), it is determined that the leading edge of the recording paper P is transported deep inside the transport path 14 and it is difficult to return the recording paper P to the paper feed cassette 4. Then, the paper feed roller 12 starts to rotate forward so as to transport the recording paper P in the transport direction (S220).

  Then, it is determined whether or not the paper feed roller 12 has been rotated by a predetermined amount (S230). The recording paper P is rotated by a predetermined amount and conveyed to a position where the recording paper P can be conveyed by the driving roller 24 and the nip roller 26. If it is determined that the sheet has been rotated by a predetermined amount (S230: YES), the rotation of the paper feed roller 12 is stopped (S240), and the recording paper P is discharged (S250).

  At the time of paper discharge, the gear switching mechanism 58 is switched to an intermittent paper feeding state in which the first transmission gear 44 and the second transmission gear 52 transmit rotation via the two switching gears 62 and 64, and FIG. As shown in FIG. 6B, the drive roller 24 is rotated in the transport direction (counterclockwise rotation in FIG. 6B), and the paper feed roller 12 is rotated in the direction opposite to the transport direction (FIG. 6B). Then, the recording paper P is discharged. After the paper is discharged, the process returns to the original process and the print process is terminated.

  On the other hand, when the leading edge of the recording paper P is not detected by the paper sensor 75 in the process of S210 (S210: NO), the return speed by the paper feed roller 12 is determined (S260). The return speed is the speed of the roller surface when the paper feed roller 12 is rotated in the reverse direction so as to return the recording paper P to the paper feed cassette 4 in the direction opposite to the transport direction. The return speed is determined by the characteristics of the recording paper P. In this embodiment, as shown in Table 1, a table in which the return speed and the type of the recording paper P are associated is stored in the ROM 72 in advance, and print data The return speed is determined by comparing the table with the information on the type and size of the recording paper P included in the table.

表１から戻し速度が決定されると、給紙ローラ１２をこの決定した戻し速度で搬送方向とは逆方向に記録紙Ｐを給紙カセット４側に戻すように逆回転させる（Ｓ２７０）。ここで例えば、印刷データに含まれている記録紙Ｐの情報がＡ４サイズの普通紙であった場合、給紙ローラ１２は８インチ／秒（以下、ＩＰＳ：ＩＮＣＨＥＳ ＰＥＲ ＳＥＣＯＮＤという）の戻し速度で逆回転される。

When the return speed is determined from Table 1, the paper feed roller 12 is rotated in the reverse direction so as to return the recording paper P to the paper feed cassette 4 in the direction opposite to the transport direction at the determined return speed (S270). Here, for example, when the information of the recording paper P included in the print data is A4 size plain paper, the paper feed roller 12 is at a return speed of 8 inches / second (hereinafter referred to as IPS: INCES PER PERCOND). Reversely rotated.

  Next, it is determined whether or not the sheet feed roller 12 has been rotated by a predetermined amount (S280), and it is determined that the sheet feed roller 12 has been rotated at a return speed determined until the sheet is rotated by a predetermined amount, and has been rotated by a predetermined amount (S280). : YES), the process returns to the original process and the print process is terminated. That is, the recording paper P is returned to the paper feed cassette 4.

Hereinafter, the relationship between the characteristics of the recording paper P and the return speed will be described in detail.
Regardless of the type of recording paper P, in order to return the recording paper P appropriately, the conveyance force when the recording paper P is moved (conveyed) by the paper feed roller 12 is appropriately set according to the characteristics of the recording paper P. Just do it. In the present embodiment, the conveying force is changed by setting the rotation speed of the paper feed roller 12 according to the characteristics of the recording paper P.

  When the recording paper P is returned to the paper feeding cassette 4 by the paper feeding roller 12, a force (conveying force) for moving the recording paper P toward the paper feeding cassette 4 by the paper feeding roller P is applied to the recording paper P. A force that hinders the movement of the recording paper P against the force acts. That is, when the conveyance force is larger than the force that hinders the movement of the recording paper P, the recording paper P is moved to the paper feed cassette 4 side. In the present embodiment, the magnitude of the force that hinders the movement of the recording paper P is determined by the thickness (second element) and size (third element) of the recording paper P.

  Specifically, before the recording paper P is returned to the paper feed cassette 4, a part of the recording paper P is in the transport path 14, and a part of the recording paper P is deformed into the shape of the transport path 14. . That is, it is in contact with the transport path 14 and deformed by receiving a drag from the transport path 14. The drag that the recording paper P receives from the transport path 14 varies depending on the characteristics of the recording paper P. Generally, in the recording paper P having a small thickness (second element) and the recording paper P having a large thickness, the recording paper P having a large thickness has a force (waistness) to return from the deformed state to the original state. Large, that is, the drag received from the conveyance path 14 is large. Further, in the recording paper P having a large size (third element) and the recording paper P having a small size, the recording paper P having a large size (third element) has a larger area in contact with the paper transport path 14, and Since the weight of the paper P itself is heavy, the drag force received from the transport path 14 is large. For this reason, as the recording paper P has a larger thickness (second element) and size (third element), the force that prevents the recording paper P from being moved by the paper supply roller 12 is larger.

As described above, when the conveyance force of the paper feed roller 12 is larger than the force that prevents the recording paper P from moving, the recording paper P is moved to the paper feed cassette 4 side.
In general, the conveying force is determined by the pressing force of the paper supply roller 12 against the recording paper P and the state of the interface where the surface of the paper supply roller 12 contacts the recording paper P. Specifically, the conveyance force increases as the pressing force of the paper supply roller 12 against the recording paper P and the frictional force generated at the interface between the surface of the paper supply roller 12 and the recording paper P increase. In the present embodiment, the conveying force is changed by changing the frictional force generated at the interface between the surface of the paper feed roller 12 and the surface of the recording paper P.

  As described above, when the recording paper P is (moved) and conveyed by the paper feed roller 12, frictional force acts at the interface where the paper feeding roller 12 and the recording paper P are in contact with each other. At this time, a slip occurs depending on the frictional force at the interface. The slip refers to a state in which the amount of movement of the surface of the paper feed roller 12 is not equal to the amount of movement of the recording paper P that is in contact with the paper feed roller 12 and is moved by the paper feed roller 12. The smaller the frictional force generated at the interface between the surface and the surface of the recording paper P, the easier it is to slip.

  The frictional force generated at the interface between the surface of the paper feed roller 12 and the surface of the recording paper P is the amount of movement of the surface of the paper feed roller 12, that is, the rotational speed (return speed) of the paper feed roller 12 and the surface of the recording paper P. And the friction coefficient (first element). Specifically, as the friction coefficient (first element) on the surface of the recording paper P is larger and the rotation speed (returning speed) of the paper feeding roller 12 is slower, the surface of the paper feeding roller 12 and the surface of the recording paper P are larger. The frictional force generated at the interface with the That is, the conveying force increases as the friction coefficient (first element) on the surface of the recording paper P increases and the rotation speed (return speed) of the paper supply roller 12 decreases.

  As described above, as the two elements of the thickness (second element) and size (third element) of the recording paper P are larger, the necessary conveyance for returning the recording paper P to the paper feed cassette 4 is performed. Strength increases. Further, as the friction coefficient (first element) on the surface of the recording paper P is larger and the rotation speed (return speed) of the paper feeding roller 12 is slower, the conveying force becomes larger. That is, as the friction coefficient (first element) on the surface of the recording paper P is smaller and the two elements of the thickness (second element) and size (third element) of the recording paper P are larger, the rotational speed (return) The recording paper P can be appropriately returned to the paper feed cassette 4 by reducing the speed) and obtaining a large conveying force. Further, when the friction coefficient (first element) on the surface of the recording paper P is large and the two elements of the thickness (second element) and the size (third element) of the recording paper P are small, the rotational speed Even if the (return speed) is increased, the recording paper P can be appropriately returned to the paper feed cassette 4.

  In the present embodiment, a table made in consideration of the characteristics (surface friction coefficient, thickness, size) of the recording paper P is stored in the ROM 72 in advance, and the recording paper P included in this table and print data. The rotational speed (return speed) is determined by comparing the data of the type and size (see Table 1).

  Examples of the recording paper P include plain paper, glossy paper, postcard, and inkjet paper. The size of the recording paper P includes A4 size, B5 size, legal size, letter size, postcard size, L size, and the like.

  The friction coefficient (first element) of the surface of the recording paper P and the thickness (second element) of the recording paper P differ depending on the type of the recording paper P. Therefore, in the table of the present embodiment, as shown in Table 1, the recording paper P has three groups (first paper type group, second paper type group, and third paper type group) depending on the type. It is divided into.

  Comparison of friction coefficient and thickness of recording paper P (common paper, glossy paper, postcard, ink-jet paper) that is commonly used, and the recording paper P of a type having a small friction coefficient and thickness is classified into the first paper type group. The type of recording paper P having a large friction coefficient or thickness is assigned to the second paper type group, and the type of recording paper P having a large friction coefficient and thickness is assigned to the third paper type group.

  The rotation speed (return speed) is slower for the recording paper P of the type belonging to the second paper type group and the third paper type group than the second paper type group than the first paper type group. Is set.

  In the table of this embodiment, as shown in Table 1, the recording paper P is divided into two groups (first paper size group and second paper size group) according to size.

  The size of recording paper P that is generally used (A4 size, B5 size, legal size, letter size, postcard size, L size) is compared, and the smaller type of recording paper P is the first paper size group. In addition, the large-sized type of recording paper P is assigned to the second paper size group.

The rotation speed (return speed) is set slower for the recording paper P having a size belonging to the second size group than for the first paper size group.
In this embodiment, plain paper is assigned to the first paper type group, postcards are assigned to the second paper type group, and glossy paper and inkjet paper are assigned to the third paper type group. The method of allocating the recording paper P of this type may not be as described above. In the present embodiment, the recording paper P is allocated to three groups of a first paper type group, a second paper type group, and a third paper type group depending on the type, but there are fewer than three. You may make it allocate to a group or more than three groups.

  Further, in the present embodiment, the recording paper P is allocated to the first paper size group and the second paper size group according to the size. However, the recording paper P is assigned to less than two groups or more than two groups. It may be allocated.

  Furthermore, in the present embodiment, the table is configured as a two-dimensional table including a paper type group and a paper size group, but the paper type group is divided into the frictional force on the surface of the recording paper P and the thickness of the recording paper P. And may be configured as a three-dimensional table.

  As described above, in this embodiment, the return speed of the paper feed roller 12 is determined according to the type and size of the recording paper P. Therefore, the recording paper P is loaded regardless of characteristics such as the type and size of the recording paper P. The paper can be properly returned to the paper feed cassette 4. That is, the recording paper P can be moved to the paper feeding cassette 4 while preventing slippage between the paper feeding roller 12 and the recording paper P. Specifically, when the recording paper P is returned to the paper feeding cassette 4, the recording paper P is moved to the paper feeding cassette 4 side by rotating the paper feeding roller 12 by a certain amount. At this time, since the return speed of the paper feed roller 12 is changed according to the type and size of the recording paper P, the occurrence of slippage between the paper feeding roller 12 and the recording paper P is prevented. That is, the recording paper P that is in contact with the paper feed roller 12 and is moved by the paper feed roller 12 is moved by the amount of movement of the surface of the paper feed roller 12 by a certain amount. Therefore, regardless of the type and size of the recording paper P, the recording paper P can be moved by the amount of rotation of the paper feed roller 12 by a certain amount. Therefore, the recording can be performed without providing a sensor for detecting the return of the recording paper. There is an effect that it can be appropriately returned to the paper P paper feed tray 12.

  Further, in the present embodiment, as the characteristics of the recording paper P, there are three elements that are considered to have a large influence when the recording paper P is conveyed (the friction coefficient (first element) of the surface of the recording paper P, the recording paper). In consideration of the thickness (second element) and size (third element) of P, the return speed by the paper feed roller 12 is determined based on a table in which these characteristics are replaced with the type and size of the recording paper P. Is done. More specifically, the characteristics of the recording paper P take into account factors that are considered to have a large effect when the recording paper P is transported, that is, the transport path 14 and the paper feed roller that vary depending on the characteristics of the recording paper P. By considering the relationship between the recording paper 12 and the recording paper P, the return speed by the paper feed roller 12 can be set appropriately. In the present embodiment, the return speed by the paper feed roller 12 is obtained by experiments. Furthermore, in the present embodiment, the return speed by the paper feed roller 12 is determined based on a table in which the characteristics of the recording paper P are replaced with the type and size of the recording paper P. 12 can be set to a speed according to the characteristics of the paper.

In this embodiment, the execution of the processes of S210, S260 to S280 serves as a reverse feed control means, and the execution of the processes of S150 to S190 serves as a continuous transport means.
The present invention is not limited to such embodiments as described above, and can be implemented in various modes without departing from the gist of the present invention.

1 is a perspective view of an image forming apparatus provided with an ink jet recording head of the present invention. 1 is an explanatory diagram illustrating a schematic configuration of an image forming apparatus according to an exemplary embodiment. It is explanatory drawing which shows the arrangement | sequence of the gear of the gear transmission mechanism of this embodiment. 1 is a block diagram illustrating an electrical system of an image forming apparatus according to an exemplary embodiment. 6 is a flowchart illustrating print processing according to the present exemplary embodiment. It is explanatory drawing of the intermittent paper feed of this embodiment. It is explanatory drawing of the continuous paper feed of this embodiment. It is a flowchart which shows the recording paper return process of this embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Image forming apparatus 2 ... Housing 4 ... Paper feed cassette 6 ... Inclined separation plate 10 ... Paper feed arm 11 ... Paper feed part 12 ... Paper feed roller 14 ... Conveyance path 16 ... Printing mechanism 18 ... Recording head 20 ... Carriage 24 ... Drive roller 28 ... paper discharge unit 30 ... paper discharge roller 34 ... transport motor 36 ... gear transmission mechanism 58 ... gear switching mechanism 66 ... transport mechanism 68 ... image reading unit 70 ... operation panel unit 75 ... paper sensor P ... recording paper PC ... External device

Claims (8)

Printing means for printing on a recording medium;
A transport unit that feeds the recording medium stacked on the medium storage unit to a transport path one by one by a paper feed roller, and transports the recording medium on the transport path to the printing unit by a drive roller;
Reverse feed control means for returning the recording medium to the medium storage means by reversely rotating the paper feed roller at a speed according to the characteristics of the recording medium during reverse feeding;
An image forming apparatus comprising:   The characteristics of the recording medium relate to at least the drag that the recording medium receives from the transport path, and the reverse feed control means records the recording medium having a small drag when transporting the recording medium having a large drag. The image forming apparatus according to claim 1, wherein the sheet feeding roller is reversely rotated at a slower speed than when the medium is conveyed.   The characteristic of the recording medium relates to at least a frictional force generated between the recording medium and a paper feed roller, and the reverse feed control means is configured to transfer the recording medium having a large frictional force when the recording medium is conveyed. 3. The image forming apparatus according to claim 1, wherein the sheet feeding roller is reversely rotated at a slower speed than when a recording medium having a small frictional force is conveyed. The characteristics of the recording medium are constituted by at least one of a first element, a second element, and a third element,
The first element is a coefficient of friction of a surface of the recording medium, the second element is a thickness of the recording medium, and the third element is a size of the recording medium. The image forming apparatus according to any one of 1 to 3.   The image forming apparatus according to claim 1, wherein the conveyance path includes a path formed in a substantially U shape from the medium storage unit to the printing unit.   2. The apparatus according to claim 1, further comprising continuous conveyance control means for continuously conveying the recording medium from the medium storing means by rotating and driving the paper feed roller and the driving roller in the same direction. The image forming apparatus according to any one of?   When the recording medium is continuously transported by the continuous transport control means and there is no print data for the succeeding recording medium, the reverse feed control means stores the recording medium in the medium storage means. The image forming apparatus according to claim 6, wherein the image forming apparatus is returned. A paper sensor for detecting the leading end of the recording medium is disposed upstream of the driving roller in the transport direction,
The reverse feed control means is configured to move the recording medium when the leading end of the succeeding recording medium continuously conveyed by the continuous conveyance control means is positioned upstream in the conveyance direction not detected by the paper sensor. The image forming apparatus according to claim 6, wherein the image forming apparatus is returned to the medium storage unit.

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