JP2002059598A - Perfecting printer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To choose between a one-side printing mode and both sides printing mode with a reversal unit mounted and prevent wasteful copying or erroneous copying of a long strip of paper permitting printing to one side but not permitting printing to both sides in a perfecting printer. SOLUTION: A control section that executes, printing up to a minimum sheet length corresponding to a minimum transportable interval Ls in a mode of printing to one side, and does not execute printing to both sides in a mode of printing to both sides, when the length (actual length H1 of the sheet or sheet length H2 set by a user) is larger than a relay transport route L to a reversal unit 80 (H1>=L or H2>=L), is provided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a printing apparatus provided with a reversing conveyance path and capable of performing double-sided printing, and more particularly to a double-sided printing apparatus in consideration of the paper length.

[0002]

2. Description of the Related Art Conventionally, as a printing apparatus provided with a reversing conveyance path and capable of performing double-sided printing, for example, the one shown in FIG. 9 (Japanese Patent Laid-Open No. 9-327950) is known. The two-sided printing apparatus includes one side of a printing apparatus main body 101 (a paper feeding unit 10).
The sheet fed from 3) is conveyed in the forward direction by two sets of conveying rollers 107 and 108 provided inside the printing apparatus main body 101, and is printed on one side by an ink jet printing mechanism 105. The sheet is guided to the sheet reversing unit 102 provided on the other side of the printing apparatus main body 101 via the sorting mechanism 113, and after the sheet is turned over by the sheet reversing unit 102, the sheet is sent back from the other side of the printing apparatus main body 101 again. Printing mechanism 105 while transporting in the reverse feed direction
The printing is performed on the back side, and the printing is performed from one side of the printing apparatus main body 101.

Here, the sheet reversing unit 102 has a pair of large and small belt driving rollers 116 and a sheet transport belt 114.
And a fitted portion 111 that can be fitted to the fitting portion 104, and a pair of paper guide rollers 1
12 and a paper sorting mechanism 113. That is,
The paper reversing unit 102 is detachable from the printing apparatus main body 101. When performing one-sided printing, the sheet reversing unit 102 is removed from the printing apparatus main body 101, and sheets are fed from the sheet feeding unit 103. Then, printing is performed by the printing mechanism 105 in the same manner as described above. Is discharged from According to the above configuration example, the sheet reversing unit 10
2 can be removed from the printing apparatus main body 101, so that a large installation space is not required at the time of single-sided printing or non-printing.

[0004]

However, when performing one-sided printing, it is troublesome for the user to remove the paper reversing unit 102 from the printing apparatus main body 101.
It is desired to provide a printing apparatus that can perform one-sided printing and two-sided printing without such removal or attachment work.

Therefore, as a printing apparatus having such a configuration, for example, a description will be given with reference to FIG. 1 according to the embodiment of the present invention. Printing is performed on one side by merging before the print head 40 and passing the paper in the forward direction through the print head 40 portion of the common conveyance path 72 following the merging portion, and the paper S is reversely fed to reverse conveyance. After turning over at road 81,
It is conceivable that the print head 40 prints the back surface again.

However, in the case of such a configuration, the position of the sheet feeding conveyance path 71 and the position of the loop-shaped inversion conveyance path 81 are arranged so as to be sequentially separated in the direction away from the print head 40. That is, as viewed from the paper feed roller 20 provided on the entrance side of the print head 40, the paper feed conveyance path 71
The position of the small reversing roller 83 of the reversing unit 80 comes farther than the position of the paper feed roller 31 of FIG.

For this reason, as shown in FIG. 1, when the distance between the nip points between the paper feed roller 20 and the small reversing roller 83 is defined as the length L of the relay transport path, the length L of the relay transport path is
It is longer than the distance between the nip points of any of the rollers in the transport path from the paper feed transport path 71 to the paper discharge port via the common transport path 72. That is, the length L of the relay conveyance path is longer than the distance between the nip points between the paper feed roller 31 and the paper feed roller 20 and the distance between the nip points between the paper feed roller 20 and the paper discharge roller 50.

Accordingly, the longer one of the distance between the nip points between the paper feed roller 31 and the paper feed roller 20 and the distance between the nip points between the paper feed roller 20 and the paper discharge roller 50 is determined as the minimum transportable distance (minimum). Paper length) Ls, the hopper 33
Among the paper sizes fed from the paper feed conveyance path 71, there is a paper size that can be directly conveyed in the forward direction and enables one-sided printing (minimum conveyance interval Ls
Although the length is longer, the paper length is shorter than the relay conveyance path length (minimum required paper length at the time of back feed) L. There is a sheet of paper size that cannot reach the nip point of the small reversing roller 83 and cannot be pulled into the reversing unit 80.

Therefore, when a double-sided printing apparatus capable of selectively using single-sided printing and double-sided printing with the reversing unit mounted is constructed, as described above, a paper length that can perform single-sided printing but cannot perform double-sided printing. About paper of
It is desired to prevent useless copying operation and miscopying from occurring.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems, to enable a single-sided printing mode and a double-sided printing mode to be selectively used while the reversing unit is mounted, and to enable single-sided printing on paper. However, an object of the present invention is to provide a double-sided printing apparatus that prevents useless copying operation and erroneous copying on a sheet having a length that cannot perform double-sided printing.

[0011]

In order to achieve the above object, a double-sided printing apparatus according to the first aspect of the present invention joins a paper feed path and a loop-shaped reverse path in front of a print head. Then, printing is performed on one side by passing the paper in the forward direction through the print head portion of the common transport path following the junction, and the paper is reverse-fed and inverted by the reverse transport path, and then the print head is again rotated. A printing path for performing printing on the back side of the paper feed path from a feed roller of the feed path to a discharge port via a paper feed roller and a discharge roller provided before and after a print head of the common transfer path. The longest one of the distances between the roller nip points at the minimum transportable distance L
s, and the distance between the nip points between the paper feed roller and the reversing small roller of the reversing unit located farther from the paper feed conveyance path when viewed from here is the relay conveyance path length L (Ls
<L), and in the single-sided printing mode, printing is performed up to the minimum sheet length corresponding to the minimum transportable interval Ls,
In the double-sided printing mode, a control unit having a sequence in which double-sided printing is not executed unless the sheet length is longer than the relay conveyance path length L is provided.

Here, the paper length is grasped as the measured paper length H1 of the paper or the paper length H2 set by the user. In other words, the control unit determines whether the sheet length (the actual measured sheet length H1 or the sheet length H2 set by the user) is longer than the relay conveyance path length L (H1 ≧ L or H2 ≧ L) unless the sheet length is larger than the relay conveyance path length L. Do not execute. Therefore, a sheet having a size less than the minimum required sheet length at the time of back feeding, that is, a sheet having a length smaller than the relay conveyance path length L is discharged without being reversely fed for backside printing. Therefore, the single-sided printing mode and the double-sided printing mode can be executed without the necessity of attaching / detaching the reversing unit as in the related art.

According to a second aspect of the present invention, in the double-sided printing apparatus according to the first aspect, the control unit is always in a single-sided printing mode, and shifts to a double-sided printing mode by a selection command. According to this feature, it is possible to obtain the same ease of use as automatically selecting the one-sided printing mode that is frequently used with priority.

According to a third aspect of the present invention, in the double-sided printing apparatus according to the first or second aspect, the loop-shaped reversing conveyance path forms a part of the sheet feeding conveyance path. It is characterized by being constituted by a reversing unit detachably mounted on the frame side. According to this feature, since the reversing conveyance path is configured by the reversing unit detachably mounted on the back frame side of the sheet feeding device,
It can be removed when a paper jam occurs, and maintenance is easy.

According to a fourth aspect of the present invention, in the double-sided printing apparatus according to the third aspect, the reversing unit is tapered as a whole by a reversing large roller and a reversing small roller arranged apart from each other and a paper guide member. And an outer member that covers the outer periphery to form a reversing conveyance path, and switches the paper flow path between the receiving position and the discharging position on the leading end side where the small reversing roller is provided. And a reversible flap provided so as to be capable of being provided.

According to this feature, the inner member of the reversing unit has a configuration in which a large reversing roller and a small reversing roller arranged apart from each other and a paper guide member are formed as a whole to have a tapered shape. A reversing unit having a simple structure can be obtained.

According to a fifth aspect of the present invention, in the double-sided printing apparatus according to any one of the first to fourth aspects, the control unit determines the paper length H2 and the relay conveyance path length L set by a user. When the set paper length H2 of the user is smaller than the relay conveyance path length L (H2 <L), a means for issuing an alarm indicating that double-sided printing is not possible is provided. For example, a liquid crystal display device can be used as a means for issuing the alarm.

According to this feature, it is determined whether or not double-sided printing is possible based on the paper length H2 set by the user. Therefore, even if the user erroneously sets a sheet on which double-sided printing cannot be performed, the mismatch can be recognized before printing is started, and unnecessary processing and paper jam can be prevented.

According to a sixth aspect of the present invention, in the double-sided printing apparatus according to any one of the first to fifth aspects, in the double-sided printing mode, the controller sets the paper length H2 set by the user. , One-sided printing is performed up to the minimum paper length corresponding to the minimum transportable interval Ls, and the length of the paper is measured by a paper detector during this time. When the length is longer than the path length L (H1 ≧ L), double-sided printing is performed, and when the length is shorter than the relay conveyance path length L (H1 <L), the sheet is discharged as it is.

According to this feature, the user can set the actual paper length H.
Even if 1 is mistakenly input as a different paper length H2, the paper detector always measures the actual paper length H1 and double-sided printing is executed only when the paper length can be printed on both sides. In the case of a sheet that cannot be printed on both sides, the sheet is discharged as it is, so that erroneous copying can be reduced.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below based on the illustrated embodiment. FIG. 5 is a schematic side view illustrating an example of an inkjet printing apparatus having a reversing conveyance path and capable of performing double-sided printing.

This printing apparatus includes a paper feed roller 20 comprising a drive roller 21 and a driven roller 22 in contact therewith.
A sheet supply device 30 for supplying the paper S to the paper feed roller 20, a print head 40 for ejecting ink onto the surface of the paper S conveyed by the paper feed roller 20, and forming an image (including characters). And a discharge roller 50 for discharging the printed paper S. Further, a main frame 60 for mounting these devices and the like, a first sub-frame 61, a second sub-frame 62, and a pair of side frames (not shown) are provided.

The paper feed roller 20 has a drive roller 21
Are supported by a side frame (not shown), and are rotationally driven by appropriate driving means. The driven roller 22 is rotatably supported by the driving roller 21 by a support structure described later. The sheet supply device 30 includes a paper feed roller 31, a hopper 33 that urges the paper S toward the paper feed roller 31, and a separation pad that presses the paper S between the paper feed roller 31 and separates the sheet. 32.
At the time of sheet supply, the paper S is pressed by the hopper toward the paper feed roller 31 that rotates once, is separated by the separation pad 32, and only one sheet S is supplied toward the paper feed roller 20. ing. The supplied paper S includes a lower guide 63 attached to the first sub-frame 61,
The upper guide 64 attached to the main frame 60 guides the sheet to the transport device 1.

The print head 40 is mounted on a carriage 41. The carriage 41 is mounted on the main frame 6.
0 and a carriage guide shaft (not shown) so as to be movable in a direction perpendicular to the paper surface. An ink tank is mounted on the carriage 41.

In the printing operation, one line of printing is performed by ejecting ink from the head 40 while the carriage 41 moves in a direction perpendicular to the paper surface. The sheet S is conveyed by the roller 20 at a predetermined pitch (usually between lines), and these operations are repeated to perform one-sided printing. Reference numeral 44 denotes a regulating member that supports the lower surface of the paper S during printing and regulates the distance between the paper S and the head 40 to a predetermined value.

The paper discharge roller 50 includes a drive roller 51 and a driven star wheel 52 urged toward the drive roller 51, and discharges the printed paper S to the outside of the apparatus. The driven star wheel 52 is attached to the second sub frame 62.

In the above configuration, a pair of the lower guide 63 and the upper guide 64, a pair of the drive roller 21 and the transport roller 22 of the paper feed roller 20, a pair of the print head 40 and the defining member 44, and a discharge roller 50 Means print head 4
A common transport path (print transport path) 72 through which the paper passes in the forward direction (forward feed direction) or the reverse direction (reverse feed direction).
(See FIG. 5). Further, the hopper 33, the pair of the paper feed roller 31 and the separation pad 32, and the pair of the lower guide 63 and the upper guide 64 are used to transfer the paper on the hopper 33 between the paper feed roller 31 and the separation pad 32, Paper feed path 71 that joins common path 72 before 40
(See FIG. 6).

On the other hand, in the sheet feeding apparatus 30, the hopper 33 also serving as a paper feed tray is disposed obliquely upward, and a triangular space below the hopper 33 is provided with a closed loop reversing conveyance path 81. The unit 80 is detachably attached with its tip inserted.

The reversing unit 80 includes a reversing large roller 82 and a reversing small roller 83 which are arranged apart from each other.
The paper guide member 84 is supported by the left and right frames (not shown) of the reversing unit in a snap-fit state with respect to the large reversing roller 82, and is simply in contact with the small reversing roller 83. By being pivoted, the inner member has a tapered shape as a whole. In the case of this embodiment, the large reversing roller 82 and the small reversing roller 83 are
A plurality are provided side by side in the axial direction. Further, outer members 85a, 85b and 85c are provided to cover the outer periphery of the inner member and form the reversing conveyance path 81. The arc-shaped outer member 85b can be opened around the rotation shaft 88 by pressing the push button 86 to release the lock mechanism 87 in the event of a paper jam or the like. Note that the outer members 85a, 85
A guide roller 89 for nipping the sheet in the reversing conveyance path 81 toward the large roller 82 is pivotally mounted on the rollers b and 85c. A reversing flap 90 for switching the paper flow path is provided on the leading end side where the reversing small roller 83 is provided so as to be displaceable between a solid line receiving position and a dotted line discharging position. . In the present specification, a description will be given assuming that the relay path 91 that reverses and feeds the sheet printed on one side to the reversing flap 90 is also a part of the reversing conveyance path 81.

That is, in the printing apparatus of the present embodiment, the paper feed conveyance path 71 and the reversal conveyance paths 81 and 91 are joined at the junction 73 before the print head 40, and the common path following this junction is used. The sheet is printed on one side by passing the paper forward through the print head 40 in the transport path 72, and the sheet printed on one side is reversely fed to the reverse transport path 81 via the relay path 91 and the reverse flap 90. Then, the sheet reversed by the reversing conveyance path 81 is sent out again to the common conveyance path 72 by forward feeding, and the back surface is printed by the print head 40. Therefore, there is a first conveyance path from the paper supply conveyance path 71 to the common conveyance path 72 and a second conveyance path returning from the common conveyance path 72 to the common conveyance path 72 via the reversing conveyance path 81.

Further, a flap (first flap) 10 is provided at the junction 73. This flap 1
0 is an open position for forming an entrance passage to the reversing conveyance path 81, more precisely, an entrance passage to the relay passage 91 (FIGS. 7 and 8).
Self-return behavior is provided so that the sheet S is rotated following the sheet S from the sheet feeding conveyance path 71, and
Is guided by the shaft 11 so as to be guided to the auxiliary lever 4.

This flap 10 is, as shown in FIG.
A rotating member having a guide surface 10 a formed in a “F” shape with the shaft 11 as a rotation fulcrum, and a counter arm 12 having a “reverse L” shape with respect to the flap 10 at both ends of the shaft 11.
Is provided, and a metal rod 13 as a weight is stretched over the tip. The lower surface of the flap 10 is provided with a plurality of ribs 10b in the axial direction, the rib 10b having the lower surface of the curved flap as a flat guide surface, and the upper surface of the flap 10 is prevented from being caught when a passing sheet is delivered from a paper feeding unit. A plurality of ribs 10c (FIG. 6) are provided. Then, on one side in the width direction of the flap 10 in the common conveyance path 72,
A notch (not shown) is provided in a slit shape from the front end side in a direction orthogonal to the shaft 11, and the main lever 3 and the auxiliary lever 4 of the paper detector 2 pass through and cross the notch. . The counter arm 12 regulates the rotation angle at which the main lever 3 and the auxiliary lever 4 obliquely intersecting with the flap 10 are balanced and stationary, so that when there is no sheet, the reversing conveyance is performed. The self-return behavior is given to the flap 10 so as to be in an open position (see FIGS. 7 and 8) for forming an entrance passage to the relay passage 91 of the road 81.

The operational relationship between the paper detector 2 and the flap 10 as viewed from the paper is such that the flap 10 is moved in accordance with the paper from the paper feed path 71 in a retracted position (FIG. ), The force required to rotate the main lever and the auxiliary lever of the paper detector integrally in the forward direction is Fp, where Ff <Fp.
It is set so that it may become. This is because the flap 10 detects the leading edge of the sheet and performs the retreat operation, and then the auxiliary lever 4 detects the leading edge of the sheet and rotates and displaces. The position at which the movement is started is prevented from shifting with respect to the traveling direction of the sheet, the time when the photo sensor 8 changes from the light-shielded state to the non-light-shielded state is fixed, and the detection accuracy is improved.

Next, the operation of the double-sided printing apparatus provided with the paper detecting device having the above configuration will be described. FIG. 6 shows a state in which the front side of the sheet S is printed on one side and the front side is fed. The sheet is fed from the sheet feeding roller 31 of the sheet feeding device 30 to the junction 73 along the sheet feeding path 71. At this time, the flap 10 is in an open position (upper position) forming an entrance path to the reversing conveyance path 81. In the paper detector 2, the main lever 3, the auxiliary lever 4, and the light shielding plate 7 are in the upright posture (FIG. 5), and the main lever 3 intersects the flap 10 in the notch as shown in FIG. Only the lever 4 protrudes from the lower guide surface of the flap 10, that is, the lower surface of the rib 10b, and hangs down in the common conveyance path 72 as shown by a chain line in FIG. The photo sensor 8 is in a paper-out detection state because the light shielding plate 7 is in the upright posture.

First, the sheet S is placed on the guide surface 10 of the flap 10.
a, and comes into contact with the main lever 3 and the flap 10, and a force acts on both the main lever 3 and the flap 10. At this time, the easiness of movement between the two is that the force Ff required to retract the flap 10 is smaller than the force Fp required to rotate the main lever 3 and the relationship of Ff <Fp is satisfied. It is pushed down gradually.
Therefore, the main lever 3 and the auxiliary lever 4 gradually appear on the upper side of the flap 10 through the notch. When the auxiliary lever 4 appears on the upper side of the flap 10, the auxiliary lever 4 rotates around the shaft 6 in the forward direction of the paper, and after rotating within a certain range, the main lever 3 is entrained and rotated. To be integrated. Then, from the time when the flap 10 is pushed down to the predetermined retracted position shown in FIG. 6, the main lever 3 and the auxiliary lever 4 that have appeared gradually start to rotate integrally and change to the inclined state in FIG. The photo sensor 8 is in a non-light-shielded state (a paper presence detection state).

Thereafter, the paper is printed on one side by the print head 40, and the trailing edge of the paper exits the paper detector 2 so that
The paper detector 2 returns to the state of FIG. 5, and the light-shielding plate 7 blocks the optical path of the photosensor 8 to enter the paper-free detection state, and the trailing edge of the paper is detected.

FIG. 7 shows a state in which the sheet S on which single-side printing has been performed is conveyed in the reverse feed direction toward the reversing conveyance path 81 during front-side back feeding. At this time, the flap 10 has returned to the open position (upper position) where the entrance path to the reversing conveyance path 81 is formed. In the paper detector 2, the main lever 3, the auxiliary lever 4, and the light-shielding plate 7 are in the upright posture, the main lever 3 intersects the flap 10 in the notch, and the auxiliary lever 4
Only the common conveyance path 72 protrudes from the lower guide surface of the flap 10, that is, the lower surface of the rib 10b, as shown by a chain line in FIG.
In a state of hanging inside. The photo sensor 8
Is in the detection state of no paper because the light shielding plate 7 is in the upright posture.

The single-sided printed sheet S is conveyed in the reverse feed direction through the common conveyance path 72, and enters the lower space of the flap 10 which maintains the open position (upper position) at the merging section 73, where it is moved downward. It comes into contact with the auxiliary lever 4 protruding from the side guide surface. Since the auxiliary lever 4 can rotate in the reverse feed direction about the shaft 6, the auxiliary lever 4 is conveyed in the reverse feed direction from the relay passage 91 toward the reversal conveyance path 81 while pushing back the auxiliary lever 4. The movement of the auxiliary lever 4 is performed independently, and the main lever 3 does not move, so that the photo sensor 8 is in the detection state of no paper.

The sheet conveyed in the reverse feed direction is a reversing flap 90 whose free end is always at the lower position by its own weight.
Is received above the reversing conveyance path 81, and after making a round of the reversing conveyance path 81, when passing under the reversing flap 90, the sheet feeding force pushes up the reversing flap 90 to the upper position. . By pushing up the reversing flap 90 to the upper position in this way, the paper is
The sheet is discharged from the lower side of the reversing conveyance path 81 and is again returned to the relay path 9.
1 is returned to the common transport path 72. The reversing flap 90 may have a structure in which the upper position and the lower position are switched according to the position of the sheet by a normal switching mechanism, instead of the self-weight structure.

FIG. 8 shows a state in which the sheet returned from the reversing conveyance path 81 to the common conveyance path 72 is fed back. Also at this time, the flap 10 is in the open posture (upper position) forming an entrance passage to the reversing conveyance path 81. Paper detector 2
The main lever 3, the auxiliary lever 4, and the light-shielding plate 7 are in the upright position, the main lever 3 intersects the flap 10 in the notch, and only the auxiliary lever 4 has the flap 10 as shown by a chain line in FIG. It is in a state of protruding from the lower guide surface, that is, the lower surface of the rib 10b and hanging down in the common transport path 72. In addition,
The photo sensor 8 is in the detection state of no paper since the light shielding plate 7 is in the upright posture.

From the reversing conveyance path 81 to the common conveyance path 72
The paper returned to the flap 10 enters the lower space of the flap 10 which maintains the open posture (upper position) at the merging portion 73, and abuts on the auxiliary lever 4 protruding from the lower guide surface. The auxiliary lever 4 can rotate in the reverse feed direction about the shaft 6 but cannot rotate in the forward feed direction, so that the auxiliary lever 4 is entrained by the auxiliary lever 4 and the main lever 3 is moved as shown in FIG. It rotates in the forward direction about the shaft 5. Accordingly, the light detector 2 of the paper detector 2 is changed to the inclined position as shown in FIG. 8 and the light path of the photo sensor 8 is in the non-light-shielded state, so that the paper detector 2 is in the detection state of the presence of paper. .

The paper is conveyed in the forward direction to the print head 40 in the common conveyance path 72 while pushing the auxiliary lever 4 and the main lever 3 integrated therewith, and after the print head 40 prints on the back surface, Is discharged.

As described above, according to the paper detecting apparatus of the present embodiment, the paper detection (detection of the paper in the forward feed) in the first transport path from the paper transport path 71 to the common transport path 72 and the common transport Not only paper passing through the second transport path from the path 72 to the reversing transport path 81 (passing of paper in reverse feeding), but also paper passing through the second transport path returning from the reversing transport path 81 to the common transport path 72 Detection (forward paper detection) can also be performed by a common mechanism. Therefore, it is suitable for downsizing of the printing device,
A small and low-cost paper detection device can be configured.

Next, although not shown, the control unit of the printing apparatus having the above-described configuration includes an input interface for receiving print data and control commands from a host computer, analysis of print data, creation of intermediate data, and creation of bitmap memory. A CP that controls the printing device, including the unfolding and refeeding processes
U, a ROM for storing a control program of the CPU and various data, a RAM for temporarily storing various data, and the like.

Next, the processing contents of the control unit will be described. First, FIG. 1 shows the configuration of the printing apparatus in an easily understood form. As described above, this printing apparatus joins the paper feed conveyance path 71 and the loop-shaped inversion conveyance path 81 in front of the print head 40, and prints the print head in the common conveyance path 72 following the junction 73. The printing is performed on one side by passing the paper in the forward direction through the portion 40, the paper S is reversely fed and reversed by the reversing conveyance path 81, and then the back side is printed by the print head 40 again. ing.

The loop-shaped reversing conveyance path 81 is constituted by a reversing unit 80 detachably mounted on the back frame side of the sheet feeding device 30 forming a part of the sheet feeding conveyance path. From the position of the paper feed path 71 and the position of the loop-shaped reversal path 81
In a direction away from the camera. That is, the small reversing roller 83 of the reversing unit 80 is located farther than the sheet feeding roller 31 of the sheet feeding conveyance path 71 when viewed from the sheet feeding roller 20 provided on the entrance side of the print head 40. ing.

Here, as shown in FIG. 1, when the distance between the nip points between the paper feed roller 20 and the small reversing roller 83 is defined as the length L of the relay conveyance path, the length L of the relay conveyance path is It is longer than the distance between the nip points of any of the rollers in the transport path from the transport path 71 for use to the discharge port via the common transport path 72. That is, the sheet feeding roller 31 of the sheet feeding conveyance path 71
Between the paper feed roller 20 and the paper discharge roller 50 provided in front of the print head 40 in the common transport path 72 and the nip point of the rollers in the transport path to the discharge port (between the paper feed roller 31 and the paper feed roller 20). (Distance between nip points and distance between nip points between paper feed roller 20 and paper discharge roller 50)
When the longest one is set as the minimum transportable interval Ls, the relay transport path length L is longer than the minimum transportable interval Ls. In this embodiment, as shown in FIG. 1, the distance between the nip points between the paper feed roller 20 and the paper feed roller 31 is the minimum transportable distance Ls.

Therefore, among the paper sizes fed from the paper feed path 71 of the hopper 33, a paper size (longer than the minimum transportable interval Ls) that can be directly transported (single-sided printing) in the forward direction. Size), but is smaller than the relay conveyance path length (minimum required paper length during back feed) L, so that even if the paper is conveyed from the paper feed roller 20 in the reverse direction, the tip of the reversing small roller The nip point of 83 cannot be reached, so that there is a sheet of paper size that cannot be pulled into the reversing unit 80.

Therefore, the control unit considers the minimum required sheet length (L) when feeding back the sheet longer than the minimum sheet length (Ls) that can be printed on one side to the relay path 91 of the reversing conveyance path. Then, when the actual paper length is shorter than the set value L, control is performed to stop double-sided printing.

In the flowchart of FIG. 2, the CPU first checks whether the user has selected the one-sided printing mode or the two-sided printing mode (step S10). This print mode can be selected by the user using a personal computer. If the user does not specify otherwise, the default setting value "single-sided print mode" is selected and the user instructs the selection. Only in this case, the mode shifts to the duplex printing mode.

If the determination in step S10 is NO and the single-sided printing mode is selected (double-sided printing is not selected), normal paper feeding, normal printing, and normal paper discharging are performed, and single-sided printing is executed (step S11). To S13).

If the user has instructed the selection of the double-sided printing mode, the flow advances to step S14 to check whether the reversing unit 80 is attached. If there is no reversing unit 80, a warning (caution display) to that effect is issued by a liquid crystal display device (not shown), and the first step S
Return to 10. The program will wait for either the reversing unit 80 to be installed or a change to simplex printing.

If it is confirmed that the reversing unit 80 is attached, that is, if there is a reversing unit, the process proceeds from step S14 to S16, where the use is determined based on the paper size selected by the user on the personal computer. Then, the paper length H2 set by the user and the above-mentioned relay conveyance path length L are compared. As a result of the comparison, if the set paper length H2 of the user is smaller than the relay conveyance path length L (H2 <L), a warning (caution display) indicating that double-sided printing is not possible is performed on the liquid crystal display device (step S17). The process returns to the first step S10. The program will wait for the user to change the paper.

The paper size set by the user is the length of the relay conveyance path (the minimum required paper length during back feed) L
If the paper length is H2, that is, if the paper size (postcard to A4 / LTR) can be confirmed to be a length that can be fed backward to the reversing unit 80, double-sided printing is performed. to go into. That is, first, in order to perform single-sided printing, normal paper feeding and normal printing are performed (step S1).
8, S19). Specifically, the paper S is transferred from the paper feed roller 31 of the sheet feeding device 30 of FIG.
Further, the paper S is sequentially sent to the paper discharge roller 50 via the print head 40, and the print head 40 performs predetermined printing on one surface of the sheet S.

In the single-sided printing process, the paper actually passes through the paper detector 2, and the paper length is actually measured from the length of the paper. This is performed by counting the number of pulses of the driving pulse motor with a counter in a section from when the paper detector 2 is turned on (start of printing) to when it is turned off during the paper feeding.

Here, in order to cope with the case where the user inputs the paper length H2 by mistake, the paper length (actually measured paper length) H1 of the paper actually measured by the paper detector 2 is checked (step S20). . That is, it is checked whether or not the measured paper length H1 of the paper is longer than the above-mentioned relay conveyance path length L,
If the actual paper length H1 is smaller than the relay conveyance path length (L) (H1 <L), it is determined that the user has input the paper length H2 incorrectly, and an alarm (caution display) indicating that the back side printing is impossible is issued. The operation is performed by the liquid crystal display device (step S21), and the sheet on which one side is printed is normally discharged as it is (step S22). On the other hand, if it is confirmed that the measured paper length H1 of the paper is equal to or longer than the relay conveyance path length L (H1 ≧ L), the flow of FIG.

In the flow of FIG. 3, first, in order to confirm safety, the reversing unit 80 is used in the same manner as in step S14.
Is checked (step S30). If there is no reversing unit, a warning (caution display) indicating that the back side printing is not possible is performed on the liquid crystal display device (step S31),
It is checked whether the double-sided printing is stopped (step S32). If double-sided printing is stopped, discharge normally (step 3
3) If double-sided printing is continued, the process returns to step S30.

If there is a reversing unit, first confirm that the cover is not open. If the cover is open, a warning (caution display) to that effect is issued on the liquid crystal display device (step S35), and the process returns to step S34 to wait for the cover to be closed.

Next, it waits until the ink printed on one side (front print) will dry (step S36). This drying wait time is determined by the print duty. For example, where the table is printed and the amount of ink (the number of ink shots)
Is determined and stored in consideration of the paper type at the time of printing, and the degree of drying of the ink amount (the maximum amount of ink applied per unit area) at the location where the ink is applied the most is obtained from the storage table of the ink distribution. Determine the required drying wait time for the location you are currently printing.

After waiting for the drying, the reverse side sheet feeding (step S37) is performed, the sheet is turned over by the reversing unit 80, and then the sheet is again sent to the print head 40 to perform normal printing and discharge (steps S38 and S39). However, in this backside printing, the top and bottom of the paper are reversed, so the print data is reversed by 180 ° so that the top and bottom images are aligned.

FIG. 4 shows a subroutine of the reverse side sheet feeding process (step S37) in the double-sided printing. In the reverse side reverse feeding, the sheet is reversely fed from the paper feed roller 20, nipped by the small inversion roller 83 of the reversing unit 80, and the reversing unit 80 reverses the sheet.
The paper must be sent from the reversing unit 80 to the paper feed roller 20, nipped by the paper feed roller 20, and printed on the back side by the print head 40 while feeding forward.

Therefore, first, the content of a counter for counting the number n of paper feed steps for the paper feed roller 20 is represented by n =
Reset to 0 (step S40). The number of paper feeding steps is obtained by counting the number of pulses applied to the driving pulse motor (PF motor).

Subsequently, the driving pulse motor is started in the counterclockwise direction CCW (the direction in which the sheet is conveyed in the reverse feed direction) (step S41), and the sheet feed roller 20 is rotated in the reverse direction, thereby feeding the sheet in the reverse direction. Then, the content of the counter is incremented by 1 (step S42), and the state of the paper detector 2 is checked (step S43). The paper detector 2 is turned on when the paper fed from the paper feed roller 20 is reversed by the reversing unit 80 and then passes through the paper detector 2 again. Therefore, the determination in step S43 is initially "no paper". Becomes Therefore, the process returns from step S43 to step S44 via step S44, and the counter is incremented by one each time the sheet is fed one step in the reverse feed direction (step S4).
2) The driving pulse motor keeps rotating counterclockwise. During this time, the paper is detected by the paper detector 2,
At that point, the process exits the motor reverse rotation routine and proceeds to step S46. In step S44 inserted on the way from step S43 to step S41, the number of steps a2, which is set to a value slightly longer than the path length, is compared with the counter content n. If there is no paper even at the position where it should come (count value n), it is determined that a paper jam has occurred, a jam error is displayed, and the process ends (step S45).

If the paper is successfully detected by the paper detector 2, the process proceeds to step S46, where the extra paper is fed by a step a3 to remove the skew, and then the driving pulse motor is rotated forward. The direction is switched, and normal feed is performed by the c4 step of cueing.

Thus, the sheet is turned over and delivered to the sheet feed roller 20, and the above-described normal printing and normal sheet discharging are performed (steps S38 and S39).

In the above embodiment, when the paper length H2 set in advance by the user is longer than the length L of the relay conveyance path (H2 ≧ H2).
L) is confirmed in step S16, and unless this confirmation is obtained, double-sided printing is not executed. However, this confirmation processing (step S16) is omitted, and single-sided printing is executed for the time being (step S18, S19), the measured paper length H1 of the paper detected during that is the relay conveyance path length L
It may be configured such that it is confirmed that the case is larger (H1 ≧ L) (step S20), and the double-sided printing is not executed unless the confirmation is obtained.

[0067]

According to the first aspect of the present invention, a sheet smaller than the minimum required sheet length during back feed, that is, a sheet shorter than the relay conveyance path length L, is reversely fed for backside printing. The sheet is discharged without being printed or printed on the reverse side even if the sheet is fed backward. Therefore, the single-sided printing mode and the double-sided printing mode can be executed without the necessity of attaching / detaching the reversing unit as in the related art.

The one-sided printing mode, which is normally set, and the mode is shifted to the two-sided printing mode by a selection command has the same ease of use as the one-sided printing mode, which is frequently used, is automatically selected. Obtainable. In addition, when the reversing conveyance path is configured by a reversing unit that is detachably mounted on the back frame side of the sheet feeding apparatus, the reversing unit can be detached when a paper jam occurs, thereby facilitating maintenance.

Further, the inside member of the reversing unit includes a large reversing roller and a small reversing roller arranged apart from each other;
Since the sheet guide member is formed as a whole to be tapered, the reversing unit has a simple structure.

Further, in the case where a double-sided printing impossible warning is issued when double-sided printing is impossible, it is possible to determine a mismatch of sheets before starting printing. Also, even if the user enters the paper length incorrectly,
In the case where the actual paper length H1 is actually measured, double-sided printing is executed only when the paper length is a double-sided printable paper.
Miscopy can be reduced.

[Brief description of the drawings]

FIG. 1 is a diagram showing an outline of a two-sided printing apparatus of the present invention.

FIG. 2 is a flowchart illustrating a part of a process of a control unit of the duplex printing apparatus according to the present invention.

FIG. 3 is a flowchart showing processing subsequent to FIG. 2 in the control unit of the duplex printing apparatus of the present invention.

FIG. 4 is a flowchart illustrating details of a reverse side sheet feeding process of FIG. 3 in a control unit of the duplex printing apparatus of the present invention.

FIG. 5 is a diagram showing a side surface of the duplex printing apparatus of the present invention in a partial cross section.

6 is a diagram showing a detection state at the time of front-side paper feeding for single-sided printing by the printing apparatus of FIG. 5;

FIG. 7 is a diagram illustrating a state in which the printing apparatus of FIG. 5 performs a front-side back feed in which a sheet is reversely fed toward a reversing conveyance path.

FIG. 8 is a diagram illustrating a detection state at the time of back sheet feeding in which the sheet is forward-fed from the reversing conveyance path in the printing apparatus of FIG. 5;

FIG. 9 is a diagram showing a configuration of a conventional duplex printing apparatus.

[Explanation of symbols]

2 Paper Detector 3 Main Lever 4 Auxiliary Lever 5 Axis 6 Axis 7 Light Shield 8 Photo Sensor 10 Flap 20 Paper Feed Roller (Sheet Conveying Device) 40 Print Head 44 Determining Member 50 Discharge Roller 71 Feeding Transport Path 72 Road 73 Junction 80 Reversing unit 81 Reversing conveyance path 82 Large reversing roller 83 Small reversing roller 84 Paper guide members 85a, 85b, 85c Outer member 86 Push button 87 Lock mechanism 88 Rotating shaft 89 Guide roller 90 Reversing flap 91 Relay path S Paper Ls Minimum transportable interval (Minimum paper length) L Relay transport path length (Minimum required paper length during back feed) H1 Actual measured paper length H2 Paper length set by user

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) B65H 85/00 B41J 3/04 101Z 3F102 F-term (Reference) 2C056 EA20 EB13 EB29 EB46 EC12 EC26 EC28 FA10 HA27 2C058 AB02 AC07 AE02 AF15 AF55 CA01 DA10 2C059 AA18 AA22 AA54 BB21 DD10 DD13 DD32 3F053 BA03 BA12 EA05 EB01 EB04 EC02 ED15 LA07 LB03 3F100 AA02 CA12 CA13 CA15 CA16 EA02 EA03 3F102 AA11 AB01 EA03 BA03 DA15 EA15

Claims (6)

[Claims] 1. A paper feed conveyance path and a loop-shaped reversal conveyance path are merged in front of a print head, and the paper is forward-forwarded to a print head portion of a common conveyance path following the junction. A printing apparatus that performs printing on one side, reverses the paper in a reverse transport path and reverses the paper in a reverse transport path, and then prints the back surface with a print head again. The longest distance between the nip points of the rollers in the transport path through the paper feed roller and the paper discharge roller provided before and after the print head in the common transport path to the discharge port is defined as the minimum transportable distance Ls; And the longest one between the nip points of the rollers in the reversing conveyance path of the reversing unit positioned farther than the paper feeding conveyance path as seen from now on is defined as the relay conveyance path length L (Ls <L). Printing mode In the duplex mode, printing is performed up to the minimum sheet length corresponding to the minimum transportable interval Ls. In the double-sided printing mode, double-sided printing is not executed unless the sheet length is longer than the relay transport path length L. A double-sided printing apparatus, comprising: a control unit including: 2. The double-sided printing apparatus according to claim 1, wherein the control unit is always in a single-sided printing mode, and shifts to a double-sided printing mode by a selection command. 3. The reversing unit according to claim 1, wherein the loop-shaped reversing conveyance path is detachably mounted on a back frame side of a sheet feeding device forming a part of the sheet feeding conveyance path. A double-sided printing apparatus characterized by comprising: 4. The reversing unit according to claim 3, wherein the reversing unit comprises a reversing large roller and a reversing small roller arranged apart from each other, an inner member formed as a whole by a paper guide member to be tapered, and an outer periphery thereof. An outer member for forming a reversing conveyance path, and a reversing flap provided on the leading end side where the reversing small roller is provided so as to be able to switch the paper flow path between a receiving position and a discharging position. A double-sided printing apparatus characterized by being configured as follows. 5. The control unit according to claim 1, wherein the control unit compares a paper length H2 set by a user with the relay conveyance path length L, and determines a user-set paper length H2. A double-sided printing apparatus, further comprising means for issuing a warning that double-sided printing is impossible when the length is smaller than the relay conveyance path length L (H2 <L). 6. The control unit according to claim 1, wherein in the double-sided printing mode, the length of the sheet set by the user is the minimum sheet length corresponding to the minimum transportable interval Ls. One-sided printing is performed up to the length, and the length of the paper is actually measured by the paper detector during this time. Then, the measured paper length H1 of the paper is longer than the relay conveyance path length L (H1 ≧
L), a duplex printing is performed, and if the length is smaller than the relay conveyance path length L (H1 <L), the sheet is discharged as it is.