JP2004268485A - Printer and method of controlling printing - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent skewing of a paper sheet in a printing operation to a rear end of the paper sheet. <P>SOLUTION: This printer comprises a platen 8, a carriage 13 which has a print head 11 mounted thereon and is reciprocally held, and pairs of rollers consisting of feed rollers (1, 16) and pinch rollers (4, 17) which are respectively provided to an upstream side and a down stream side of the platen 8. A paper sensor 6 for detecting the rear end of the paper sheet is provided on a portion in the vicinity of the pair of rollers at the upstream side. When the rear end of the paper sheet is detected by the paper sensor 6, the carriage 13 is moved to a central portion of the paper sheet in the width direction thereof prior to the conveyance of the paper sheet by the feed roller 16 and the pinch roller 17, and then the unidirectional printing is performed. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a printing apparatus and a printing control method for preventing skew of a sheet.
[0002]
[Prior art]
Generally, a printing apparatus has a platen, a carriage mounted with, for example, an impact dot head and held in a reciprocating manner, and an ink ribbon covering the front surface of the impact dot head, between the ink ribbon and the platen. Characters and images are printed on the transported printing paper (hereinafter simply referred to as paper) based on the printing data. In this printing device, since the impact force is large, pressure-sensitive paper or back carbon paper or the like is sandwiched in the middle, and it is used in, for example, banks and the like, which is a type of business that prints on copy paper etc. which is spelled in multi-leaf sheets. I have. By the way, the gap between the tip of the impact dot head and the platen is uniquely defined by the product based on the head structure, impact force, repetition speed and the like. Therefore, a gap adjusting mechanism for adjusting the gap is provided on either the platen side or the carriage side. In this gap adjustment mechanism, for example, using a stepping motor, the carriage on which the impact dot head is mounted is brought closer to the platen side, and the paper is pressed back to the platen at the tip of the impact dot head, and is retracted by a predetermined number of steps to make the gap constant. Is secured. Also, when the type of cut sheet or copy sheet used is changed, it is necessary to adjust the gap between the impact dot head and the platen again.
[0003]
Therefore, when printing on copy paper with a conventional impact dot head, the paper is pinched between the feed roller and the pinch roller on the upstream side of the platen facing the print head and between the feed roller and the pinch roller on the downstream side. Then, the printing for each line by the impact dot head and the one-line feed of the sheet by the sheet transport mechanism are repeated a plurality of times. In this state, if the trailing edge of the sheet comes off from between the upstream feed roller and the pinch roller, air enters the trailing edge of a sheet having multiple sheets of copy paper, and an air layer is generated between the sheets. When this air layer is generated, the sheet rises from the platen, and a predetermined gap cannot be secured between the sheet and the platen, and a state in which the sheet comes into contact with the print head may occur. When the paper is conveyed in this state, a load is applied to the print head on the paper, which causes the paper to skew.
[0004]
FIG. 6 shows the state at this time. When the rear end of the sheet comes off from between the upstream side feed roller and the pinch roller, and the sheet is conveyed while the carriage is stopped on the right frame side as shown in FIG. Obliquely to the right frame side. Further, as shown in FIG. 6B, when the sheet is transported while the carriage is stopped on the left frame side, the sheet is skewed as a whole to the left frame side. Therefore, in order to prevent the skew of the sheet, it is conceivable to increase the urging force between the feed roller and the pinch roller on the downstream side of the platen to increase the holding force of the sheet. If the paper is used, it causes show-through, and the paper cannot be clamped beyond a certain urging force.
[0005]
Some inventions have been made which enable printing up to the last line of printing after detecting the trailing edge of the sheet. For example, moving means (carriage) for reciprocating the recording head with respect to the recording material, conveying means (feeding roller and pinch roller) for conveying the recording material to a recording position by the recording head, and conveying means for the rear end of the recording material And a control means for selecting a recording mode in accordance with the output of the detection means. The detection means detects the passage of the rear end of the recording material. The first recording mode (bidirectional recording) for performing recording in each of the forward movement and the backward movement is selected, and after the detecting means detects the passage of the trailing end of the recording material, either the forward movement or the backward movement of the moving means is performed. On the other hand, there is known an ink jet recording apparatus that changes print control so as to select a second recording mode (one-way recording) in which recording is performed. Then, on the carriage on which the recording head is mounted, further on the upstream side and the downstream side of the ink ejection surface of the recording head with respect to the moving direction of the recording head, the platen surface is brought into contact with the platen surface and the gap between the recording head and the recording material is formed. 2. Description of the Related Art There is known an ink jet recording apparatus having a carriage spur on a carriage for keeping a distance constant (for example, see Patent Document 1).
[0006]
A platen, a carriage on which a print head is mounted facing the platen, a paper feeding member for pressing the rear end of the paper against the platen, a sensor for detecting the end of the paper, and means for moving the paper feeding member in the paper feeding direction. In some cases, when a sensor detects the end of a sheet, the sheet feeding member is moved in the sheet feeding direction so that the sheet does not come off the sheet feeding member (for example, see Patent Document 2).
[0007]
[Patent Document 1]
JP-A-7-144455 (page 2-3, FIG. 4)
[Patent Document 2]
JP-A-7-1781 (pages 2-3, FIG. 4)
[0008]
[Problems to be solved by the invention]
In the conventional ink jet recording apparatus described in Patent Document 1, even if the trailing end of the paper is disengaged from the conveying member, the carriage spur provided on the carriage presses the recording paper held on the platen. Smoothness is maintained. Thereby, the distance between the recording head and the recording paper (the distance between the recording papers) becomes constant, so that one-way recording becomes possible. Further, by providing members (carriage spurs) on both the upstream side and the downstream side in the moving direction of the recording head, even if the recording paper comes off the conveying member, the recording paper does not rise, the smoothness is maintained, and Since the distance from the recording paper (inter-paper distance) is constant, bidirectional recording is possible, and there is an effect of expanding the printing area. However, the ink jet recording apparatus records by discharging ink on one sheet of recording paper. When applied to copy paper using pressure sensitive paper or back carbon paper, the copy paper is pressed against a platen by a carriage spur. Then, there is a problem that show-through occurs.
[0009]
In addition, the technique described in Japanese Patent Application Laid-Open No. H11-157572 discloses a method in which a paper feeding member that presses the rear end of a paper against a platen is provided, and when the paper rear end is detected, the paper feeding member is moved in a paper conveyance direction by a moving unit. Although it is possible to enlarge the area, if copy paper using pressure-sensitive paper or back carbon paper is applied as the paper, show-through will occur if the copy paper is pressed against the platen by the paper fly member in the same way There's a problem. Further, there are also problems such as an increase in size of the apparatus and a complicated structure, such as provision of a paper feeding member and moving means.
[0010]
Accordingly, the present invention has been made to solve the above problems, and provides a printing apparatus and a printing control method capable of preventing skew of a sheet and printing up to the last line without increasing the size of the printing apparatus. The purpose is to:
[0011]
[Means for Solving the Problems]
In order to achieve the above object, a printing apparatus according to the present invention includes a platen, a moving unit that reciprocates a carriage equipped with a print head that prints on a print medium based on print data with respect to the print medium, and the platen. Transport means for transporting the print medium to a print position, disposed upstream and downstream with respect to the print medium, detection means for detecting that the rear end of the print medium has passed a predetermined position on a transport path, and the detection means Control means for controlling different printing processes according to the output of the carriage, the control means moves the carriage back and forth until a signal for detecting the rear end passage of the print medium is received from the detection means. When bidirectional printing is performed and a signal for detecting the rear end passage of the print medium is received from the detection unit, printing is performed only when the carriage is moved in one direction, and the transport is performed. Is characterized by controlling so that the prior to carrying line by line printing medium, moving the carriage in a central portion of the print medium width by means. According to the present invention, when the trailing edge of the sheet is detected by the sheet sensor provided between the feed roller and the pinch roller on the upstream side of the platen, the carriage on which the print head is mounted is moved to the center of the sheet width in advance of the sheet conveyance. At the same time, since the printing control is changed from bidirectional printing to unidirectional printing, skewed paper can be prevented, and printing can be performed up to the last line of paper.
[0012]
BEST MODE FOR CARRYING OUT THE INVENTION
An embodiment of the present invention will be described below with reference to FIGS. FIG. 1 is a perspective view of a printing apparatus according to an embodiment of the present invention. FIG. 2 is a cross-sectional view of the trailing end of the paper when the paper according to the embodiment of the present invention comes off from between the upstream feed roller and the pinch roller. FIG. 3 is a plan view showing a print head position and a sheet conveyance state according to the embodiment of the present invention. FIG. 4 shows a block diagram of the printing device. FIG. 5 is an operation flowchart of the print control unit of the present invention.
[0013]
The printing apparatus of the present invention forms an upstream roller pair in a state where the feed roller 1 and the pinch roller 4 are in contact with each other. The feed roller 1 has a plurality of elastic bodies (rubber or the like) inserted through a feed roller shaft 2 and is fixed to the feed roller shaft 2 by a split pin or the like (not shown). At one end of the feed roller shaft 2, a gear 3 configured to obtain a driving force from a conveying means (not shown) is attached, and is fixed by an E-ring or the like (not shown). The other end of the feed roller shaft 2 is rotatably fixed and held on a frame of the printing apparatus main body. The pinch roller 4 has a plurality of elastic members (rubber or the like) inserted through the pinch roller shaft 5 and is fixed to the pinch roller shaft 5 by a split pin (not shown) or the like. Both ends of the pinch roller shaft 5 are rotatably fixed to the left and right frames by E-rings or the like.
[0014]
A paper sensor 6 is provided near the upstream feed roller 1 on the paper transport path, and detects the presence or absence of the paper 7 passing on the paper transport path. The paper sensor 6 detects “no paper” immediately after the start of paper feeding, and detects “paper present” when the leading edge of the paper reaches a position sandwiched between the upstream feed roller 1 and the pinch roller 4. Further, the paper sensor 6 operates so as to detect “no paper” when the trailing edge of the paper comes off from between the upstream feed roller 1 and the pinch roller 4. The paper sensor 6 is of an optical reflection type, and the above detection result is supplied to the operation panel control circuit 48 in FIG.
[0015]
The platen 8 is fixedly held between the left frame 9 and the right frame 10 by a known method (not shown). A carriage 13 on which a print head 11 and a ribbon cassette 12 are mounted facing the platen 8 is mounted on a carriage shaft 14 and a carriage guide 15. The carriage 13 is connected to a carriage motor drive circuit 47 and is configured to be movable on the carriage shaft 14 and the carriage guide 15 in the left-right direction along the platen 8 under the control of the control unit 40 shown in FIG. I have. An ink ribbon 16 pulled out of the ribbon cassette 12 is stretched on the front surface of the leading end of the print head 11 via a ribbon guide (not shown) and a ribbon mask (not shown). The downstream feed roller 17 and the pinch roller 18 have the same configuration as the upstream feed roller 1 and the pinch roller 4.
[0016]
A liquid crystal display 20, an operation switch 21, an LED 22, and the like are provided on the operation panel 19, and display the operation contents of the operator or the state of the printing apparatus through the input / output circuit unit of the control unit 40. Then, the sheet 7 which has been subjected to a predetermined printing process on the sheet 7 pulled out from the sheet cassette 23 is conveyed to the sheet discharge tray 24 and discharged outside the printing apparatus.
[0017]
FIG. 4 is a block diagram showing a connection relationship between a control unit for controlling the printing apparatus of the present invention and various drive circuits.
[0018]
An MPU (Micro Processing Unit) 41 is a processor that plays a central role in the printing apparatus. A RAM (Random Access Memory) 42 is a memory used for primary storage of received data, for storage in data processing, and as a buffer for print data. A ROM (Read Only Memory) 43 is used for storing programs for software processing and for storing constants and the like for software processing. The MPU 41, the RAM 42, and the ROM 43 constitute the control unit 40. The external interface 44 is connected to an external PC or the like, and receives print data and a control code under the control of the control unit 40, or transmits the status of the printing apparatus to the external PC via the external interface 44. The print head drive circuit 45 drives the print head pins included in the print head 11 at a predetermined timing based on the print data. The transport motor drive circuit 46 drives each transport roller that transports the paper 7. The carriage motor drive circuit 47 drives a carriage motor that moves the carriage 13 to move the carriage 13 right and left. The operation panel control circuit 48 is connected to each of the liquid crystal display unit 20 provided on the operation panel 19, a display unit such as a display of the LED 22, the operation switch 21, and input means such as the paper sensor 6 to set printing conditions. The control unit 40 reads the status of the printing device via the operation panel control circuit 48 and controls the printing device.
[0019]
Next, the operation according to the embodiment of the present invention in the above configuration will be described with reference to FIG. The print data transmitted from the external PC or the like is received via the external interface 44 of the printing device (step S10). The print data also includes information such as the size of the paper, the top, bottom, left and right margins, header and footer, line pitch, and character pitch. Then, under the control of the control unit 40, the transport motor drive circuit 46 is activated, and starts feeding the paper 7 from the paper feed cassette 23 (step S11). The paper 7 sent from the paper feed cassette 23 is transported on a paper transport path, and reaches between the upstream feed roller 1 and the pinch roller 4. At this time, the paper sensor 6 detects "paper presence" by the reflected light from the paper 7 being incident (step S12). The sheet 7 is subsequently conveyed onto the platen 8 while being sandwiched between the upstream feed roller 1 and the pinch roller 4, and further conveyed toward the downstream feed roller 17 and the pinch roller 18. The paper 7 transported between the downstream feed roller 17 and the pinch roller 18 is nipped between the downstream feed roller 17 and the pinch roller 18 until the first print column of the paper 7 reaches the print position of the print head 11. Conveyed.
[0020]
Next, the control unit 40 that receives the detection signal from the paper sensor 6 determines whether or not there is print data based on the detection signal. If there is no data, the process proceeds to a step of determining whether or not there is a next page (step S22) (step S13).
[0021]
Next, when “print data exists”, the carriage motor drive circuit 47 is activated under the control of the control unit 40. Thus, the print head drive circuit 45 is driven under the control of the control unit 40 when the carriage 13 is accelerated and reaches a constant speed. The print head drive circuit 45 drives a predetermined print head pin at a print timing based on print data, and prints characters, graphics, etc. on the paper 7 on the platen 8 via the ink ribbon 16 pulled out to the print head tip. Print one line. Next, under the control of the control unit 40, the transport motor drive circuit 46 is driven to perform a predetermined one-line sheet feed. Thereafter, under the control of the control unit 40, bi-directional printing is repeatedly performed until the paper sensor 6 detects "no paper", and print data is printed until one-line printing and paper feeding based on the print data are detected (step S14). .
[0022]
FIG. 3 is a plan view showing the print head position and the paper conveyance state when the paper sensor 6 detects "no paper".
[0023]
That is, under the control of the control unit 40, the printing process is continued, and when the detection signal of “no paper” is received from the paper sensor 6 (Yes in step S15), air enters from the rear end of the paper, and Then, an air layer is generated, the paper is lifted from the platen, and the uppermost paper is lightly in contact with the print head. The control unit 40 sets the data of the number of steps corresponding to the center of the sheet width (a value obtained by halving the width of the sheet) in a counter 47A provided in the carriage motor drive circuit 47, and activates the carriage motor drive circuit 47. Thus, the carriage motor drive circuit 47 drives the carriage 13, moves to the center of the sheet width, and stops (step S16).
[0024]
Next, the control unit 40 drives the transport motor drive circuit 46 to drive the paper (steps S17) by the number of steps corresponding to one row (step S17). At this time, since the carriage 13 on which the print head 11 is mounted is moved to the center of the sheet width, the load is evenly distributed even when the leading end of the print head comes into contact with the sheet. The paper pinched between the pinch rollers 18 is transported straight without skewing. Next, the control unit 40 resets the step number data corresponding to the central portion of the sheet width to the counter 47A of the carriage motor drive circuit 47, and starts the carriage motor drive circuit 47 in the reverse direction. Accordingly, the carriage motor drive circuit 47 drives the carriage 13 in the reverse direction, moves from the center of the sheet width to the original position, and stops (step S18).
[0025]
Next, the control unit 40 activates the carriage motor drive circuit 47 based on the print data. When the carriage 13 is accelerated by the carriage motor drive circuit 47 and reaches a constant speed, the print head drive circuit 45 is driven under the control of the control unit 40, and a predetermined print head pin is driven at a print timing based on print data. Is driven to print one line of characters, figures, and the like in one direction on the paper 7 on the platen 8 via the ink ribbon 16 pulled out at the print head end (step S19). Next, under the control of the control unit 40, based on the print data immediately after printing, the step number data for driving the carriage 13 is set in the counter 47A of the carriage motor drive circuit 47, and the carriage motor drive circuit 47 is operated in the reverse direction. Start to The carriage motor drive circuit 47 drives the carriage 13 in the reverse direction, moves to the original position, and stops (step S20).
[0026]
Thereafter, the carriage 13 shown in steps S16 to S20 is moved to the center of the sheet width, one-line sheet conveyance, the carriage 13 is moved to the original position, and one-line printing by one-way printing is repeatedly executed until there is no print data. Printing is performed up to the end of the sheet (step S21).
[0027]
Next, under the control of the control unit 40, the presence / absence of print data of the next page is determined. If “data exists”, the printed paper is conveyed and discharged onto the paper discharge tray 24, and the next Then, the process proceeds to the step of feeding new paper from the paper feed cassette 23 in preparation for the printing of. In the case of "no data", the printing process ends (step S22).
[0028]
According to the embodiment of the present invention, the paper 7 such as a multi-leaf copy paper is nipped and conveyed between the feed rollers 1 and 17 and the pinch rollers 4 and 18 respectively on the upstream side and the downstream side of the print head 11. In the printing apparatus, even if the trailing edge of the paper comes off from between the upstream feed roller 1 and the pinch roller 4 during printing, the carriage 13 on which the print head 11 is mounted is moved to the center of the paper width before the paper is transported. Thus, even if the leading end of the print head comes into contact with the sheet 7, the load is evenly distributed. Therefore, when the sheet is transported, the load is not applied to only one side, and the sheet can be prevented from skewing.
[0029]
【The invention's effect】
ADVANTAGE OF THE INVENTION According to this invention, the printing apparatus which can prevent skew of a sheet | seat with a simple structure and prints to the last line of a sheet | seat can be provided.
[Brief description of the drawings]
FIG. 1 is a perspective view of a printing apparatus according to an embodiment of the present invention.
FIG. 2 is a cross-sectional view of a rear end of the sheet when the sheet according to the embodiment of the present invention has separated from an upstream feed roller and a pinch roller.
FIG. 3 is a plan view showing a print head position and a sheet conveyance state according to the embodiment of the present invention.
FIG. 4 is a circuit block diagram according to an embodiment of the present invention.
FIG. 5 is a flowchart according to an embodiment of the invention.
FIG. 6 is a cross-sectional view of a rear end of a conventional sheet when the sheet comes off an upstream feed roller and a pinch roller.
[Explanation of symbols]
1 feed roller (upstream side)
2 Feed roller shaft (upstream side)
4 Pinch roller (upstream side)
5 Pinch roller shaft (upstream side)
6 Paper sensor 7 Paper 8 Platen 11 Print head 13 Carriage 17 Feed roller (downstream side)
18 Pinch roller (downstream side)
40 control unit 45 print head drive circuit 46 transport motor drive circuit 47 carriage motor drive circuit

Claims (2)

A platen, a moving unit for reciprocating a carriage mounted with a print head for printing on a print medium based on print data with respect to the print medium, and the print medium disposed upstream and downstream with the platen interposed therebetween. Conveying means for conveying to a printing position, detecting means for detecting that the rear end of the print medium has passed a predetermined position on a conveying path, and control means for controlling different printing processes according to the output of the detecting means. Have
The control means,
Until receiving a signal for detecting the rear end passage of the print medium from the detection means, perform bidirectional printing by reciprocating the carriage,
When a signal for detecting the rear end passage of the print medium is received from the detection means, printing is performed only when the carriage is moved in one direction, and before the print medium is conveyed line by line by the conveyance means, A printing apparatus wherein a carriage is controlled to move to a central portion of the print medium width. A carriage equipped with a print head that prints on a print medium facing the platen reciprocates with respect to the print medium, and is disposed upstream and downstream with the platen interposed between the print medium and the print position. Conveying, a printing control method for controlling a different printing process according to a detection signal of a detecting means for detecting that the rear end of the print medium has passed a predetermined position on a conveyance path,
Until the detection signal is output from the detection means, perform bidirectional printing by reciprocating the carriage,
When the detection signal is detected, printing is performed only when the carriage is moved in one direction, and before the print medium is conveyed line by line, the carriage is moved to a central portion of the print medium width. And a print control method.

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