JP2000313550A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device eliminating a skew of a recording medium caused by the wear of a paper feeding roller. SOLUTION: Two bearings 220a, 222a are fixed to the inner sides of plates 220, 222 of an upper paper feeding unit. A rotating shaft 82 extending in the lengthwise direction of roll paper is rotatably provided between the two bearings 220a, 222a. Two bearings 224, 226 separated at a prescribed distance are engaged with the rotating shaft 82, and the bearings 224, 226 can move to an arbitrary position along the rotating shaft 82. The bearings 224, 226 are fixed with screws or the like to both ends in a crosswise direction of a guide plate 228 where paper feeding rollers 76 are rotatably fixed. A motor 230 is fixed on the guide plate 228.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an image forming apparatus for forming an image on a recording medium such as roll paper or cut paper.

[0002]

2. Description of the Related Art As an output device of a computer or a work station, an ink jet type image forming apparatus for forming an image on a recording medium by discharging ink, or an electrophotographic type forming apparatus for forming an image on a recording medium using a developer or the like. Image forming apparatuses are known. Among these image forming apparatuses, there is a type that can selectively use both a cut sheet cut (cut) into a predetermined size in advance and a roll-shaped recording medium in which the recording medium is wound in a roll shape. . Further, there is a type in which only a roll-shaped recording medium can be used as a recording medium.

A conventional plotter (an example of an ink jet type image forming apparatus) which can selectively use both a cut sheet and a roll-shaped recording medium will be described with reference to FIGS. 10 to 12.

FIG. 10 is a side view schematically showing a conventional plotter, and FIG. 11 is a side view schematically showing a plotter obtained by improving the plotter shown in FIG. FIG.
FIG. 4 is a side view schematically showing a plotter of a type capable of setting two roll-shaped recording media at the same time.

[0005] As shown in FIG.
Generally, an image forming area 12 where an image is formed on a recording medium
The roll paper 14 (an example of a roll-shaped recording medium) is arranged slightly below and behind. To form an image on the roll paper 14, the leading end 14 ′ of the roll paper 14 is pulled out, inserted into the insertion slot 16, and sent to the transport roller 18. Then, the carriage 2 on which the print head 20 is mounted
2 is reciprocated in the scanning direction (perpendicular to the plane of the paper of FIG. 10), ink is ejected to a portion of the roll paper 14 located in the image forming area to form an image.

When an image is to be formed on the cut sheet 24, the cut sheet 24 is inserted from the cut sheet insertion port 26 on the opposite side of the insertion port 16 and sent to the transport roller 18. in this case,
To feed the cut paper 24 to the transport roller 18, the leading end 14 ′ of the roll paper 14 is removed from the transport roller 18. When forming an image on the roll paper 14 after forming an image on the cut paper 24, the user (operator) may
4 is manually fed into the conveying roller 18 by hand. Thus, preparation for forming an image on the roll paper 14 instead of the cut paper 24 is completed.

However, in the plotter 10 having such a configuration, when the user wants to use the roll paper 14 after using the cut paper 24, the user needs to go near the plotter 10 and replace the recording paper. Therefore, in the plotter 10,
Remote operation that is compatible with the PC network cannot be performed.

Therefore, in order to enable the above remote operation, a plotter 30 of the type shown in FIG. 11 has been proposed. In this plotter 30, a pair of feed rollers 32a,
The roll paper 14 is conveyed while being pinched by 32b, and is sent to the conveyance roller 18. Then, the feed rollers 32a, 32
2b and the transport roller 18 are both rotated (forward rotation), and the roll paper 14 is transported to the image forming area 12 to form an image. When forming an image on the cut sheet 24, the plotter 3
0, a cut sheet mode signal is sent to a controller (not shown) to rotate both the feed rollers 32a and 32b and the transport roller 18 in the reverse direction, so that the leading end 14 'of the roll paper 14 obstructs the path of the cut paper 24. The roll paper 14 is rewound to a position where the roll paper 14 is not to be moved to a standby state in which the leading ends 14 'of the roll paper 14 are held between the feed rollers 32a and 32b.

When an image is to be formed on the roll paper 14, a signal of the roll paper mode is sent to the above-described controller, and both the feed rollers 32a and 32b and the transport roller 18 are rotated forward, and the roll paper is transferred to the image forming area 12. 14 is conveyed. By performing such control, the cut paper mode and the roll paper mode can be automatically switched. Therefore, it is not necessary to set the roll paper 14 every time the user switches the mode.

In the plotter 40 shown in FIG.
Roll papers 14 can be set at the same time. In such a type of plotter 40, the feed rollers 32a, 3
By arranging 2b for each roll paper 14,
Any one of the two roll papers 14 and 14 and the cut paper 24 can be selected and automatically conveyed.

The above three types of plotters 10, 3
In both cases, 0 and 40, the roll paper 14 is placed behind the plotter body, so the roll paper 14
In order to correct the skewing that occurs when the sheet is fed into the printer 8, it is necessary to work around the plotter body. Therefore, the work of correcting the skew is troublesome.

In order to easily correct the skew, the roll paper 1
4 may be placed in front (front) of the plotter body. However, since there are many occasions in which the recording medium on which an image has been formed is often handled in front of the plotter main body, the roll paper 14 is placed behind the plotter main body, and the paper is often ejected in front of the plotter main body. .

When the roll paper 14 is also placed in front of the plotter main body and the paper is discharged in front of the plotter main body, the roll paper inserted from this front is made to make a U-turn and discharged to the front. The paper transport distance becomes longer.
For this reason, paper jams and the like are liable to occur, and it is necessary to increase the number of conveying rollers for conveying the roll paper, which complicates the structure of the plotter. Further, in the case of a configuration in which the roll paper is U-turned, the configuration is not suitable for thick roll paper. Furthermore, a stacker, a basket, a tray, and the like on which the discharged recording medium is loaded are usually placed in front of the plotter main body. However, the loading of the recording medium may be interrupted by roll paper.

[0014]

By the way, in order to feed a recording medium of A0 size or a size wider than the A0 size without skewing, a paper feed roller for feeding these recording media, It is necessary to arrange a plurality of driven rollers that rotate following the paper feed roller at predetermined intervals in the width direction of the recording medium having the above size. For this reason, the paper feed mechanism becomes large, and the cost of the image forming apparatus increases accordingly.

[0015] Further, even in an image forming apparatus for forming an image on a recording medium having a width larger than the A0 size or the A0 size, a recording medium having a width smaller than the A0 size, such as the A2 size or the A3 size, may be used. An image may be formed.
When setting recording media of various sizes like this,
Regardless of the size of the recording medium, the recording medium may be set with a position at one end in the width direction of the recording medium as a reference position.

In such a case, the frequency of use of the paper feed roller near the reference position is high, but the paper feed roller far from (distant from) the reference position may not be used depending on the size of the recording medium. Will be lower. Therefore, in general, the paper feed roller near the reference position is easily worn, while the paper feed roller far from the reference position is hardly worn. For this reason, there is a difference in the roller diameter between the paper feed roller near the reference position and the paper feed roller far from the reference position. When the recording medium is fed by simultaneously using the feed rollers having the difference in the roller diameter, skew is likely to occur.

In the above case, the case where one of the ends in the width direction of the recording medium is set as the reference position has been described. Even when the center in the width direction is set as the reference position, skew easily occurs. . As a technique for eliminating or reducing such skew, a paper feed roller corresponding to the width of a recording medium to be fed is installed, and when the width of the recording medium is changed, the feeding roller to be used is changed. A technique for changing the paper roller is also conceivable. However, in this technique, the number of paper feed rollers is extremely large, and a mechanism for changing the paper feed rollers is also complicated.

The present invention has been made in view of the above circumstances, and has as its object to provide an image forming apparatus in which skew caused by wear of a paper feed roller is eliminated.

[0019]

A first image forming apparatus according to the present invention for achieving the above object is provided with a paper feed roller for pulling out a roll-shaped recording medium wound from a roll from one end thereof. In an image forming apparatus which feeds a roll-shaped recording medium while pulling it out with a paper roller and forms an image on the drawn-out portion, (1) the paper feed roller is wound in a roll shape of the roll-shaped recording medium. The roll portion rotates while contacting the outer peripheral surface of the roll portion, and is configured to move in the length direction of the roll portion.

Further, the second image forming apparatus of the present invention includes a paper feed roller for pulling out a roll-shaped recording medium wound from a roll from one end thereof, and feeds the roll-shaped recording medium while drawing out the roll-shaped recording medium. In the image forming apparatus for forming an image on a drawn-out portion where the paper is drawn, (2) the paper feed roller contacts an outer peripheral surface of a roll portion of the roll-shaped recording medium that is still wound in a roll shape. And (3) a paper feed unit in which the paper feed roller and a driving means for driving the paper feed roller are integrated. (4) The paper feed unit has a length equal to the length of the roll portion. In such a manner as to move in the vertical direction.

Here, the image forming apparatus may include (5) a guide member for guiding the paper feed unit in the length direction of the roll portion.

(6) The guide member may have a hollow portion into which an electric signal line connected to the driving means is inserted.

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of an image forming apparatus according to the present invention will be described with reference to the drawings.

First, a schematic structure of a plotter which is an embodiment of the image forming apparatus of the present invention will be described with reference to FIGS.

FIG. 1 is a sectional view showing a plotter cut in a roll paper transport direction. FIG. 2 is a perspective view showing a mounting portion to which a roll-shaped recording medium is mounted, and FIG.
FIG. 4 is a plan view showing a roll-shaped recording medium before being mounted on a mounting section of FIG. In these figures, the same components as those shown in FIGS. 10 to 12 are denoted by the same reference numerals.

As shown in FIG. 1, the plotter 50 is of a type in which two roll papers 14a and 14b can be loaded simultaneously. As shown in FIG. 3, a roll receiver 64 for fixing the roll paper 14a is fixed near one end of a roll shaft 62 that passes through the center of the roll paper 14a. The roll receiver 64 is formed with a collar 64a having an outer diameter longer than the outer diameter of the roll paper 14a.
The collar 64a comes into contact with and contacts the end face of the roll paper 14a.

In mounting the roll paper 14a on the plotter 50, first, the roll paper 14a is inserted from the right side of the roll shaft 62 (the right side of the paper surface in FIG. 3), and the roll paper 14a is abutted against the collar 64a. Next, another roll receiver 66 is inserted into the roll shaft 62 from the right side and the roll paper 1 is inserted.
4a is fixed. The roll paper 14b has the same structure.

The roll paper 14a in this state is placed on the plotter 50.
As shown in FIG. 1, the upper paper feed unit 70 (which is an example of the paper feed unit according to the present invention) is turned upward and opened. As a result, the magnet 74 fixed to the cover 72 is attracted to the magnet receiving plate 52 fixed to the main body of the plotter 50, and the upper sheet feeding unit 70
Remains open, and the roll paper 14a can be mounted on the plotter 50.

When the roll paper 14a is mounted on the plotter 50, both ends of the roll shaft 62 are rotatably held by the roll holding members 54 and 56, as shown in FIG. The springs 54 for pressing the roll shaft 62 toward the center of rotation of the roll holding members 54 and 56, respectively.
a, 56a are fixed. These springs 54a, 56a
Is the resistance when the roll shaft 62 rotates, and the spring 5
The rotation of the roll shaft 64 is delayed as compared with the case where there is no 4a, 56a. A spring 56b is disposed adjacent to the spring 56a, and the spring 56b presses the roll shaft 62 in its longitudinal direction. Thereby, the roll paper 14a is moved to the left side of the paper surface of FIG. 2, and this position becomes the reference position of the roll paper 14a. Therefore, the roll paper 14a is pulled out from one end while rotating at this reference position.

After the roll paper 14a is mounted on the plotter 50, the upper paper feed unit 70 is lowered (closed) while pulling the leading end (one end) of the roll paper 14a in the direction of arrow A and pulling it out. A paper feed roller 76 that feeds the roll paper 14 a into the plotter 50 is disposed near the tip of the upper paper feed unit 70. A part of the paper feed roller 76 protrudes from the guide plate 228, and when the upper paper feed unit 70 is lowered, the protruded part comes into pressure contact with the outer peripheral surface of the roll paper 14a. A weight 80 is fixed near the paper feed roller 76, and presses the roll paper 14a more strongly. The weight 80 is not always necessary, and the weight of the weight 80 is determined according to the pressing force due to the weight of the upper paper feeding unit 70. The paper feed roller 76 also rotates (forward rotation) to pull out the leading end of the roll paper 14a in the direction of arrow A, but also rotates (reverse rotation) in the opposite direction to rewind the roll paper 14a.

The upper paper feed unit 70 rotates about a rotation shaft 82 by an angle within a predetermined range. In the vicinity of the rotation shaft 82, a detection sensor (not shown) for detecting the roll paper 14a is arranged. Roll paper 1
When 4a is detected, a paper feed signal is transmitted to a controller (not shown). For example, after 3 seconds, the paper feed roller 76 starts rotating,
Feeding of the roll paper 14a is started. The weight 80 is used to secure a pressure at which the paper feed roller 76 can pull out the roll paper 14a and feed the paper, and if this pressure is sufficient by the weight of the upper paper supply unit 70, the weight 80
Need not be arranged. Also, even if there is no weight 80, the upper paper feed unit 70 rotates downward by its own weight and
a.

Roll paper 1 pulled out by paper feed roller 76
The leading end of 4 a reaches the flapper 88 through a transport path formed by the guide plate 228 and the lower guide plate 86. The flapper 88 has an arm at its end, and is lifted up when the roll paper 14a passes below it. As a result, the detection sensor 90 is turned on, and the transport roller 18 starts rotating based on the ON signal. The pulled-out portion (pull-out portion) of the roll paper 14 a is further conveyed by the conveying roller 18, passes through the platen 92, and temporarily stops. The stop position where the drawer portion stops is measured based on the detection position of the detection sensor 94. The flapper 88
The rib of the flapper 88 may be partially extended without forming an arm at the end of the flapper.

When the drawing portion of the roll paper 14a stops,
The carriage 22 on which the print head 20 is mounted is reciprocated in a direction (scanning direction) orthogonal to the conveying direction of the draw-out portion, and the width direction of the draw-out portion is detected by a paper detection sensor (not shown) mounted on the carriage 22. Measure (read) edge and width. Thereafter, if the roll paper 14a has a width of, for example, A0 size, the drawn portion is further conveyed by 600 mm,
Measure the width direction end and width of the drawn portion again. Based on the first measurement value and the second measurement value, the skew amount of the drawn portion is calculated. If the skew amount is equal to or less than the predetermined value, the normal state is determined, the drawn portion is retracted by a predetermined amount, and the cutter 22a fixed to the carriage 22 is operated to cut the end of the drawn portion. Thereafter, the leading end of the drawn-out portion is returned to the detection sensor 94, and then advanced to convey the leading end of the drawn-out portion to a predetermined printing start position. If the skew amount exceeds a predetermined value, the conveyance of the roll paper 14a is stopped, and a warning to the user (such as "Please correct the skew") is displayed on the display panel (not shown) of the plotter 50. indicate.

Here, a technique for preventing the drawn-out portion of the roll paper 14a from becoming loose will be described.

When the roll paper 14a is pulled out or rewound, the feed roller 76 and the transport roller 18 rotate. Therefore, if the transport amount of the paper feed roller 76 and the transport roller 18 is not matched, the drawn-out portion of the roll paper 14a is pulled (tensile work) or slackened. If the extent of pulling or loosening increases, the transport amount of the transport roller 18 becomes inaccurate, or the drawn portion may be bent. To prevent such troubles,
On the guide plate 228 of the upper paper feed unit 70, a looseness detection sensor 96 for detecting looseness of the drawer portion is fixed.

When the pull-out portion is detected by the slack detection sensor 96 (when the pull-out portion is not slack), the transport amount by the paper feed roller 76 is increased. When the pull-out portion is not detected (when the pull-out portion is loose), the feeding is performed. The rotation of the paper roller 76 is stopped to interrupt the paper feeding.

The case where the above-mentioned skew exceeds a predetermined value will be described.

In this case, as described above, the roll paper 1
The conveyance of 4a is stopped, and a warning to the user is displayed on the display panel of the plotter 50. In accordance with this display, the operator (user) tilts the pressure lever 98 in the direction of arrow B to raise the pressure roller 100. Next, hold the left and right ends of the drawn portion and pull lightly toward the front to apply tension, and then return the pressure lever 98 to its original position. A sensor 9 for detecting the pressurized state by the pressurizing roller 100 is provided near the center of rotation of the pressurizing lever 98.
8a is installed. After the pressure is detected by the sensor 98a, the carriage 22 is moved to detect the end of the drawn portion, and the drawn portion is retracted. The skew amount of the drawn portion is measured in a state where the drawn portion is retracted, and if the skew amount is equal to or smaller than a predetermined value, the leading end (paper leading end) of the drawn portion is returned once until the detection sensor 94 detects it. The sheet is advanced by a predetermined amount to cut the leading edge of the sheet. The subsequent movement of the sheet is the same as the case where the skew amount is equal to or less than the predetermined value. The leading edge of the paper is automatically cut only when the roll paper 14a is mounted on the plotter 50.

Next, the roll paper 14 is placed below the plotter 50.
The case in which b is mounted and transported will be described.

In this case, first, a lower roll mode in which the roll paper 14b is mounted on the lower tier of the plotter 50 is set by an operation unit (not shown). If the upper roll mode has been set before this setting, the transport roller 18 and the paper feed roller 76 are rotated in the reverse direction, the roll paper 14a is rewound, and the drawn portion (paper) is retracted. As a result, the leading end of the drawn-out portion of the roll paper 14a passes through the flapper 88, and after the detection sensor 20 detects the leading end of the drawn-out portion, the drawn-out portion is stopped and waits at that position.

The lower roll paper 14b is the lower paper feed unit 1
10 (which is an example of a sheet feeding unit according to the present invention). When the roll paper 14b is pulled out by the lower paper feed unit 110, it is detected by the detection sensor 94 that there is no paper in the transport path through which the pulled-out portion is transported, and the pressing lever 98 is moved to the normal position ( (The position where the sheet can be transported). When the above detection and confirmation are performed, the paper feed roller 11
2 operates, and if these detections and confirmations are not performed, the paper feed roller 112 does not operate.

The procedure for mounting the lower roll paper 14b on the main body of the plotter 50 is the same as the procedure for mounting the upper roll paper 14a on the main body of the plotter 50. Roll paper 14
When the leading end of the roll paper 14b is inserted into the main body of the plotter 50, a tension is applied between the rolled portion of the roll paper 14b and the leading end of the drawn-out portion. If the roll is pressed against the roll, the drawer can be moved straight without skewing. When the lower roll paper 14b is attached to the main body of the plotter 50, as shown in FIG.
The end of the roll paper 4b abuts, and the roll paper 14b is reliably located at the reference position. For this reason, when the roll paper 14b is pulled out from one end, the straightness of the drawn-out portion is increased and skew is less likely to occur.

As described above, the roll papers 14a, 14b
The upper paper feed unit 70 and the lower paper feed unit 110 rotate while responding to the decrease in the diameter of the roll paper 14.
When the diameters of a and b decrease, the upper paper feed unit 70 and the lower paper feed unit 110 also approach the roll papers 14a and 14b corresponding to their diameters, and the distance between the roll papers 14a and 14b and the insertion opening 16 becomes the shortest distance. Get closer. The cut sheet is inserted from the insertion slot 16 and transported to the image forming area 12. Therefore, both the roll paper 14a, 14b and the cut paper are transported to the image forming area 12 with a short transport distance. As a result, the size of the plotter 50 can be reduced as much as the transport distance can be shortened.

When the operator sets the cut paper mode, the lower roll paper 14b also retreats to the standby position as in the case of the upper roll paper 14a. In addition, a weight 114 is fixed near the paper feed roller 112,
The roll paper 14b is pressed more strongly. This weight 11
4 is not necessarily required, and the weight of the weight 114 is determined according to the pressing force based on the weight of the lower paper feeding unit 110. Further, the magnet 118 fixed to the cover 116 is attracted to the magnet receiving plate 119 fixed to the main body of the plotter 50, the lower paper feed unit 110 is kept open, and the roll paper 14b can be mounted on the plotter 50. Become.

A guide plate 186 for guiding the cut sheet to the insertion slot 16 is formed on the plotter 50. The cut paper is guided by the guide plate 186 and the roll paper 14
a from the insertion port 16 without entering the transport path
Go to the back of the body. The upper paper feed unit 70 and the lower paper feed unit 110 are arranged on both sides of the guide plate 186. In such a configuration, the upper paper feeding unit 70 and the lower paper feeding unit 110 do not interfere with each other, and the distance between the roll papers 14a, 14b and the insertion slot 16 is close to the shortest distance.

Referring to FIG. 4, a structure in which the upper paper feed unit 70 can move in the length direction of the roll paper 14a will be described.
The structure of the lower sheet feeding unit 110 is the same.

FIG. 4 is a perspective view showing the schematic structure of the upper paper feed unit 70.

The upper paper supply unit 70 has the roll paper 14a
Side plates 220 and 222 are arranged at both ends in the length direction of the rim. The two side plates 220 and 222 face each other and are substantially orthogonal to the length direction of the roll paper 14a. Bearings 220a and 222a are fixed inside the two side plates 220 and 222, respectively. A rotating shaft 82 extending in the length direction of the roll paper 14a is rotatably disposed between the two bearings 220a and 222a.
The upper surface 82a of the rotating shaft 82 is flat. Also, two bearings 22 spaced apart from each other by a predetermined distance
4,226 are fitted. The bearings 224 and 226 can move to any position along the rotation shaft 82. This movement can be stopped by tightening a screw 226a provided on the bearing 226.

The two bearings 224 and 226 are fixed to both ends in the width direction of a guide plate 228 (an example of a guide member according to the present invention) to which the paper feed roller 76 is rotatably fixed by screws or the like. I have. The guide plate 228 has a motor 23
0 (an example of a driving unit according to the present invention) is fixed. A pulley 232 is fitted and fixed to the rotation shaft of the motor 230. The pulley 232 is
It is in mesh with a transmission pulley 234 for transmitting zero driving force. The transmission pulley 234 includes two feed rollers 76.
Pulley 236 fitted and fixed to the rotary shaft 76a of the
Are engaged. Therefore, when the motor 230 rotates, the two paper feed rollers 76 also rotate.

Referring to FIG. 5, the structure of the rotating shaft 82 will be described.

FIG. 5 is a sectional view showing the internal structure of the rotating shaft. In this figure, the same components as those shown in FIG. 4 are denoted by the same reference numerals.

A hollow portion 82b is formed inside the rotating shaft 82. An opening 82c extending in the longitudinal direction of the rotating shaft 82 is formed below the rotating shaft 82.
In the hollow portion 82b, a fixed plate 240 to which the electric signal lines 240a and 240b are fixed is arranged movably in the longitudinal direction of the rotating shaft 82. The fixed plate 240 is formed of a non-conductive material.
The tips of 40a and 240b are inserted. The remaining portions of the electrical signal lines 240a and 240b other than the distal end are accommodated in portions of the hollow portion 82b above the fixed plate 240.

Below the fixed plate 240, the electric signal line 24
Electrical connectors 242 connected to Oa and 240b are fixed. The electrical connector 242 is formed of a non-conductive material.
Electric signal lines 238a and 238b passing through c are connected. Electric signal line 238a corresponds to electric signal line 240a, and electric signal line 238b corresponds to electric signal line 240b. Electric connector 242 and electric signal lines 238a, 238
When the guide plate 228 (refer to FIG. 4) moves along the rotation axis 82, b moves along the rotation axis 82 with this movement. Therefore, the electric signal lines 238a and 238b
30 (see FIG. 4) and the electrical connector 242 are not loosened and protrude into the sheet feeding path. Therefore, the electric signal line 2
The transport of the roll paper 14a is not hindered by the rolls 38a and 238b. Although two electric signal lines 238a and 238b are illustrated here as the electric signal lines, any number of such electric signal lines may be used.

As described above, when the user arbitrarily moves the guide plate 228 according to the width of the recording medium, the paper feed roller 76 can be constantly brought into contact with the roll paper 14a. As a result, the wear amount of the plurality of paper feed rollers 76 can be made uniform, so that the skew caused by the wear of the paper feed rollers 76 can be eliminated.

Referring to FIGS. 4, 6, and 7, an example of the remaining amount detecting means for detecting the remaining amount of roll paper will be described.

FIG. 6 is a side view showing the vicinity of the rotation shaft of the upper paper feed unit. FIG. 7 is an explanatory diagram showing the relationship between the remaining amount of roll paper and the detection signal.

As shown in FIG. 4, a receiving plate 172 is fixed to the rotating shaft 82 by spot welding. Receiving plate 172
Is formed with a hole 172b. This receiving plate 172
Are two detection sensors 17 according to the amount of rotation of the rotation shaft 82.
The optical paths of 4a and 174b (photo interrupters) (see FIG. 6) are blocked. In addition, the above hole 17
Depending on the position of 2b, the optical paths of the detection sensors 174a and 174b are not interrupted.

The amount of rotation of the rotation shaft 82 corresponds to the inclination angle of the guide plate 228, and the inclination angle corresponds to the remaining amount of the roll paper 14a. When the remaining amount of the roll paper 14a is large (when it is almost unused), the inclination angle of the guide plate 228 is large, and the extended portion 172a of the receiving plate 172 blocks the optical paths of both the two detection sensors 174a and 174b. In this case, as shown in FIG. 7, a signal of (0, 0) is transmitted to a controller or the like from both of the two detection sensors 174a and 174b, and it is determined that the upper paper supply unit 70 is open.

When the roll paper 14a has been used but still has a sufficient amount, the inclination angle of the guide plate 228 becomes slightly small, and the optical path of the detection sensor 174a is cut off. 172b is located and is not blocked. For this reason, as shown in FIG. 7, the signal of (0, 1) is transmitted to a controller or the like, and it is determined that there is still a sufficient remaining amount.

When the remaining amount of the roll paper 14a is reduced to about one fourth, the inclination angle of the guide plate 228 becomes considerably small, and the hole 172b is located in the optical path of both the two detection sensors 174a and 174b. Therefore, these optical paths are not blocked.
Therefore, as shown in FIG. 7, the signal (1, 1) is transmitted to the controller or the like, and it is determined that the remaining amount of the roll paper 14a is reduced to about a quarter.

When the roll paper 14a is not set (when the roll paper 14a is completely used),
The inclination angle of the guide plate 228 becomes very small, and the optical path of the detection sensor 174b is blocked. However, the hole 172b is located in the optical path of the detection sensor 174a and is not blocked. Therefore, as shown in FIG. 7, the signal (1, 0) is transmitted to the controller or the like, and it is determined that the roll paper 14a is not set.

When an image is formed on the surface of a large-format (large-size) recording medium by intermittent feeding by the ink-jet method as in the plotter 50 of the present embodiment, the landing accuracy of the ink dots to be ejected depends on the formation accuracy. Greatly affects the image quality. One of the factors for improving and stabilizing the intermittent feeding accuracy is a force (grip force) by which a transport roller that transports a recording medium while nipping the recording medium grips the recording medium. In order to reduce the fluctuation of the grip force during the conveyance, it is preferable that the resistance of the component that comes into contact with the recording medium during the conveyance is as small as possible. In particular, in the case of an image forming apparatus such as the plotter 50, which can selectively use a plurality of recording media, the recording medium is conveyed while being curved, so that the conveyance path is curved. Therefore,
A tension acts on the recording medium being conveyed, and in this case, the recording medium being conveyed always contacts a guide member or the like that forms the conveyance path.

Therefore, as shown in FIG. 1, the plotter 50 moves the roll paper 14a in the transport path of the roll paper 14a.
The protruding roller 136 is disposed at a portion where the sheet a is conveyed while being curved. The protruding roller 136 protrudes into the transport path and rotates even with a very small force. Therefore, the protruding roller 136 rotates when the protruding roller 136 comes into contact with the roll paper 14a being conveyed along the conveyance path where the protruding roller 136 protrudes. As a result, the resistance that the roll paper 14a receives from the transport path is reduced, and the load on the transport roller 18 is also reduced. Therefore, the feeding accuracy when the roll paper 14a is transported can be kept very good. Moreover, since the protruding roller 136 is attached to the rotation shaft 82 when the guide plate 228 rotates, there is an advantage that the configuration is simplified without requiring an extra member.

Here, what is considered as one of the causes of the skew will be discussed.

When the roll paper 14a is transported, the transport roller 18 (see FIG. 1) that transports the roll paper 14a to the image forming area 12 (see FIG. 1), and the roll paper that is transported by the transport roller 18 When the roll paper 14a is kept parallel, the drawn portion of the roll paper 14a drawn by the paper feed roller 76 hardly skews. However, when another transport roller that transports the sheet while nipping the drawn portion is disposed between the sheet feeding roller 76 and the transport roller 18, the parallelism between the other transport roller and the drawn portion is oblique. It is important in preventing lines. In order to prevent the drawer from skewing, it is necessary to keep the other transport roller and the drawer parallel as described above, and extremely strict control is required for assembling the plotter 50 and the like. So, plotter 5
0, the distance between the paper feed roller 76 and the transport roller 18 is
The transport roller that transports while holding the drawer is not provided. Thereby, the skew of the drawer portion is further reduced.

Referring to FIG. 8, a member for switching from the roll paper 14a to the cut sheet when forming an image on the cut sheet will be described.

FIG. 8 is a perspective view showing a guide plate provided with a flapper for switching from the roll paper transport path to the cut paper transport path.

On the downstream side in the transport direction of the roll paper 14a from the upper paper feed unit 70 (see FIG. 1) and on the upstream side from the transport roller 18, a flapper 88 for switching from the roll paper 14a to cut paper is provided. Guide plate 1 on which is arranged
80 are installed. The guide plate 180 transports the roll paper 14 a passing through the upper paper feed unit 70
To guide. The guide plate 180 extends in a direction orthogonal to the transport direction of the roll paper 14a, and both ends thereof are fixed to the left side plate 120 and the right side plate 130. Information board 180
, A pair of flapper receiving members 182 having an L-shaped cross section are fixed in a line in three sets in the above orthogonal direction (three sets in FIG. 8).

A flapper shaft 184 extending in the above-described orthogonal direction is fixed to each set. 4 on each flapper shaft 184
Up to five flapper 88 are held swingably, and each flapper 88 is swung by a light force and pushed up. Of the plurality of flappers 88, a detection sensor 90 that detects the flapper 88 that has been swung up and pushed up is disposed slightly above the leftmost (reference side of the recording medium) flapper 88 in FIG.

The flapper 88 is formed in a rib shape from a resin. The lower end 88a of each flapper 88 is
Path (medium path) through opening 180a opened in
It protrudes under its own weight. For this reason, when the roll paper 14a passes below the guide plate 180, the flapper 88 is pushed up by the passing roll paper 14a, and the detection sensor 90
Operates. By this operation, a signal is transmitted from the detection sensor 90 to the controller, and the transport roller 18 is rotated at a predetermined timing.

As described above, when the roll paper 14a is in the standby state, the roll paper 14a disappears below the guide plate 180, and the flapper 88 falls down by its own weight. In addition, the flapper 88 is positioned in front of the main body of the plotter 50 (arrow C).
Direction) is not pushed up depending on the recording medium conveyed from the direction (1). Therefore, when a cut sheet is inserted from the front of the main body of the plotter 50, the flapper 88 guides the cut sheet, and the cut sheet is guided by a guide plate 186 (see FIG. 1) extending substantially parallel to the arrow C direction. Then, the sheet advances to the rear of the main body of the plotter 50 without entering the transport path of the roll paper 14a.

Referring to FIG. 9, the members for switching from roll paper 14b to cut paper when forming an image on the cut paper will be described.

FIG. 9 is a perspective view showing a guide plate provided with a flapper for switching from the roll paper transport path to the cut paper transport path.

A flapper for switching from the roll paper 14b to the cut paper is located downstream of the lower paper feed unit 110 (see FIG. 1) in the transport direction of the roll paper 14b and upstream of the transport rollers 18. Guide plate 19 arranged
0 is formed. The guide plate 190 transports the roll paper 14 b passing through the lower paper feed unit 110 to the transport roller 18.
To guide. The guide plate 190 extends in a direction perpendicular to the direction of transport of the roll paper 14b, and both ends thereof are fixed to the left side plate 120 and the right side plate 130. Information board 19
A plurality of L-shaped holding plates 192 are fixed to 0 (three in FIG. 9) in the orthogonal direction. A shaft 194 is fixed between the plurality of holding plates 192. Axis 19
4 holds a plurality of swing plates 196 that swing about the shaft 194 as a central axis.

A flapper 198 is rotatably held by the two swinging plates 196 facing each other. Flapper 1
Reference numeral 98 denotes resin molded such that a plurality of thin disks are arranged at intervals. The plurality of thin disks enter into a skewer-shaped slit formed in the platen 92 (see FIG. 1) in a non-contact state. End 196 of rocking plate 196
a, a tension spring 200 is hung on the end 196a.
The end 196b on the opposite side is urged to rotate about the shaft 194 in the direction of arrow D (substantially upward).

Therefore, although the flapper 198 is urged upward, the flapper 198 is disposed at a predetermined position because the swinging plate 196 abuts against the platen 92. A detection sensor 202 for detecting the position of the flapper 198 is disposed on the reference side in the width direction of the roll paper 14b (the left side in FIG. 9). For this reason, the roll paper 14
When b passes through the guide plate 204 (see FIG. 1), the flapper 198 is pushed down by the passing roll paper 14b, and the detection sensor 202 operates. By this operation, a signal is transmitted from the detection sensor 202 to the controller, and the conveyance roller 1
8 is rotated at a predetermined timing.

As described above, when the roll paper 14b enters the standby state, the roll paper 14b retreats, and the flapper 198 rises. The flapper 198 is connected to the plotter 5.
It cannot be pushed down by the recording medium conveyed from the front of the main body of the No. 0 (in the direction of arrow C). Therefore, when a cut sheet is inserted from the front of the main body of the plotter 50, the flapper 198 guides the cut sheet toward the guide plate 186, and the cut sheet is guided by the guide plate 186 to convey the roll paper 14b. The user proceeds to the rear of the main body of the plotter 50 without entering the road.

When the upper roll paper 14a is pulled out and fed, the light weight of the flapper 88 acts on the portion where the paper is fed. On the other hand, the lower roll paper 14
When tension acts between b and the pair of transport rollers 18,
The weight of the roll paper 14b acts on the flapper 198, and the flapper 198 is pressed downward.
4b only makes light contact with the guide plate 204. However, when the downward force is large, the roll paper 14b comes into strong contact with the guide plate 204, and the transport roller 18
This has a bad effect on the gripping force (clamping force) for pinching. Therefore, when a downward force acts on the flapper 198 from the roll paper 14b, the swinging plate 196 is stopped by the stopper 206 so as not to drop below the predetermined position. For this reason, the flapper 198 is made to protrude into the transport path so that the flapper 198 rotates even with a small force. As a result, even if tension is applied to the roll paper 14b being transported, the transport rollers 1b
8 has less influence on the gripping force and can be stably transported.

[0079]

As described above, according to the first image forming apparatus of the present invention, since the paper feed roller moves in the length direction of the roll portion, by appropriately moving this paper feed roller, The paper feed roller can always contact the roll portion. As a result, the wear amounts of the plurality of paper feed rollers can be made uniform, so that the skew caused by the wear of the paper feed rollers can be eliminated.
According to the second image forming apparatus of the present invention, since the paper feed unit moves in the length direction of the roll portion, the paper feed roller is always in contact with the roll portion by appropriately moving the paper feed roller. Let me do. As a result, the amount of wear of the plurality of paper feed rollers can be made uniform by moving the paper feed unit, so that skew caused by wear of the paper feed rollers can be eliminated.

Here, when the image forming apparatus has a guide member for guiding the paper feed unit in the length direction of the roll portion, the paper feed unit is guided by the guide member. Move more reliably along the length of the roll. For this reason, the wear amount of the plurality of paper feed rollers can be more reliably made uniform, so that the skew caused by the wear of the paper feed rollers can be more reliably eliminated.

Further, when the guide member has a hollow portion into which the electric signal line connected to the driving means is inserted, the electric signal line is inserted into the hollow portion of the guide member. The transport of the roll paper is not hindered by the electric signal line.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a plotter cut in a transport direction of roll paper.

FIG. 2 is a perspective view showing a mounting portion on which a roll-shaped recording medium is mounted.

FIG. 3 is a plan view showing a roll-shaped recording medium before being mounted on a mounting section in FIG. 2;

FIG. 4 is a perspective view showing an upper sheet feeding unit.

FIG. 5 is a side view showing the inside of the rotation shaft of the upper paper feed unit.

FIG. 6 is a side view showing the vicinity of a rotation shaft of the upper paper feeding unit.

FIG. 7 is an explanatory diagram illustrating a relationship between a remaining amount of roll paper and a detection signal.

FIG. 8 is a perspective view showing a guide plate on which a flapper for switching from a roll paper transport path to a cut paper transport path is arranged.

FIG. 9 is a perspective view showing a guide plate provided with a flapper for switching from a roll paper transport path to a cut paper transport path.

FIG. 10 is a side view schematically showing a conventional plotter.

11 is a side view schematically showing a plotter obtained by improving the plotter shown in FIG.

FIG. 12 is a side view schematically showing a type of plotter in which two roll-shaped recording media can be set at the same time.

[Explanation of symbols]

 14a, 14b Roll paper 50 Plotter 70 Upper feed unit 76 Feed roller 82 Rotating shaft 110 Lower feed unit 112 Feed roller 228 Guide plate 230 Motor

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Ryoma Suzuki, Inventor F-term (reference) 2C060 BA01 3F052 AA01 AB05 BA07 CA02 3F105 AA01 AB04 BA20 CA03 DA61 6-3-3 Shimorenjaku, Mitaka-shi, Tokyo

Claims (4)

[Claims] 1. A paper feed roller for pulling out a roll-shaped recording medium wound from a roll from one end thereof, feeding the roll-shaped recording medium while pulling out the roll-shaped recording medium with the paper feed roller, and forming an image on the drawn-out portion. In the image forming apparatus, the paper feed roller rotates while being in contact with the outer peripheral surface of the roll portion of the roll-shaped recording medium that is still wound in a roll shape,
An image forming apparatus configured to move in a length direction of the roll portion. 2. A paper feed roller for pulling out a roll-shaped recording medium wound from a roll from one end thereof, feeding the roll-shaped recording medium while pulling out the roll-shaped recording medium by the paper feed roller, and forming an image on the drawn-out portion. In the image forming apparatus, the paper feed roller rotates while being in contact with the outer peripheral surface of a roll portion of the roll-shaped recording medium that is still wound in a roll shape. An image forming apparatus comprising: a paper feed unit in which driving means for driving a paper roller is integrated; wherein the paper feed unit is configured to move in a length direction of the roll portion. apparatus. 3. The image forming apparatus according to claim 2, further comprising a guide member that guides the paper feed unit in a length direction of the roll portion. 4. The image forming apparatus according to claim 3, wherein the guide member has a hollow portion into which an electric signal line connected to the driving unit is inserted.