JP2011062887A - Image forming device and double-side image forming device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming device and a double-side image forming device which permit flushing to be appropriately performed. <P>SOLUTION: The image forming device has a drum having openings on the outside periphery, a paper transfer belt wound around the outside periphery of the drum and having through-holes, nozzles for discharging ink toward the outside periphery of the drum, and a flushing control means to make the nozzles perform flushing. The flushing control means makes the nozzles perform flushing at the time when the drum rotates in the first direction and the part where the through-holes and the openings lie on top of one another reaches the position where the part faces the nozzles. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an image forming apparatus and a double-sided image forming apparatus.

  As this type of prior art, for example, there is one disclosed in Patent Document 1. That is, Patent Document 1 discloses a double-sided image forming apparatus provided with a line recording type front surface image forming apparatus such as a line printer and a line recording type back side image forming apparatus. For example, the front surface image forming apparatus is an ink jet printer that records (that is, prints) arbitrary information such as characters and images on the front side of the recording paper, and the back surface image forming apparatus has arbitrary information on the back side of the recording paper. It is an ink jet printer that prints.

  Each of the front surface image forming apparatus and the back surface recording apparatus is disposed opposite to the drum, a small-diameter roller, an annular endless belt, a driving source for conveying the belt by rotating the drum, and an outer peripheral surface of the drum. Line head. By ejecting ink from the nozzles of the line head toward the outer peripheral surface of the drum, it is possible to print arbitrary information on the recording paper held on the belt surface. The recording sheet is transferred from the front surface image forming apparatus to the back surface image forming apparatus while being held on the belt surface. At the time of this delivery, the delivery unit is configured so that the surface (that is, the surface to be printed) facing the line head of the recording paper is reversed and the delivery is performed smoothly.

JP 2009-137141 A

Incidentally, in an ink jet printer, there is a need to perform a maintenance operation called flushing in order to prevent and repair clogging caused by thickening of ink in the nozzles of the line head. Here, as the flushing method in the double-sided image forming apparatus disclosed in Patent Document 1, the following methods a and b are conceivable.
a) A method in which the printing process is temporarily stopped, the line head is retracted from a position facing the outer peripheral surface of the drum (that is, a steady position), and ink is forcibly ejected from the nozzles in an arbitrary direction at the retracted position.
b) A method of forcibly ejecting ink toward the margin of the recording paper while the line head is disposed at a steady position.

However, in the method a, it is necessary to reciprocate the head between the steady position and the retreat destination. For this reason, a certain time is required for the movement of the head, and the time required for the flushing is increased accordingly. On the other hand, in the above method b, a trace of flushing remains on the printing paper that is the result of printing.
Thus, in the conventional technology, it has been difficult to perform flushing appropriately.
Accordingly, some aspects of the present invention have been made in view of such circumstances, and an object thereof is to provide an image forming apparatus and a double-sided image forming apparatus that can appropriately perform flushing.

  In order to achieve the above object, an image forming apparatus according to an aspect of the present invention includes a drum having an opening on an outer peripheral surface, a belt for paper conveyance wound around the outer peripheral surface of the drum and having a through hole. A nozzle that discharges ink toward the outer peripheral surface of the drum, and a flushing control unit that causes the nozzle to perform flushing. The flushing control unit rotates the drum in a first direction, and The nozzle is flushed at a timing when a portion where the hole and the opening overlap with each other reaches a position facing the nozzle.

  With such a configuration, when flushing the nozzle, the ink can be ejected from the nozzle toward the portion where the through hole and the opening overlap (that is, the overlapping portion), and the ejected ink is overlapped. It can be received at the bottom of the part or discharged into the drum (if the overlapping part penetrates). Therefore, flushing can be performed without retracting the nozzle from the position facing the outer peripheral surface of the drum (that is, the steady position). Since flushing can be performed without moving the nozzle, the time required for flushing can be shortened. In addition, since the nozzle retreat destination is unnecessary, it is possible to contribute to downsizing of the image forming apparatus. Further, flushing can be performed without adhering ink to the paper (that is, without leaving a trace), so that the paper surface can be maintained at high quality.

  In the image forming apparatus, the outer peripheral surface of the drum includes a flushing corresponding area for causing the nozzle to perform flushing, and a suction area for sucking paper, and the opening includes the opening A first opening provided in the flushing-corresponding region and a second opening provided in the suction region, and the flushing control means includes a portion where the through hole and the first opening overlap. The nozzle may be flushed at a timing when it reaches a position facing the nozzle. With such a configuration, flushing can be performed between image forming (that is, printing) processing on a sheet. In order to perform flushing, for example, it is not necessary to stop the paper supply (that is, paper feeding), and the printing process and the flushing can be performed continuously. Accordingly, the throughput of the printing process can be improved.

  The image forming apparatus may further include a head in which a plurality of the nozzles are arranged in a second direction that intersects the first direction in plan view, and the drum rotates once in the first direction. In addition, the through hole and the first opening are respectively configured such that the portion where the through hole and the first opening overlap each other at least once with all the nozzles included in the head. It is good also as a feature. With such a configuration, all the nozzles included in the head can be flushed while the drum makes one rotation (that is, one round) in the first direction.

In the image forming apparatus, the first opening is a slit extending in the second direction, and the length of the slit in the second direction is larger than the entire arrangement range of the nozzles. It may be a feature.
In the image forming apparatus, the slit group includes a plurality of slit groups in which the slits are arranged at a first interval in the first direction, and the slits included in one of the adjacent slit groups, and the other The interval between the slits included in the slit group is configured such that at least one of the slits included in one slit group and the slits included in the other slit group overlap with the through hole. This may be a feature.

The image forming apparatus may include a plurality of rows in which the plurality of through holes are arranged at a second interval in the second direction, and the plurality of rows are arranged in the first direction in the first direction. The through holes may be arranged so as to be shifted in the second direction between the one row adjacent to the other and the other row.
With such a configuration, for example, even when the belt is displaced with respect to the outer peripheral surface of the drum, all the nozzles included in the head face the overlapping portion while the drum rotates once in the first direction. And can be flushed.

  In the above image forming apparatus, the first opening is an opening that penetrates the outer peripheral surface of the drum, and ink that reaches the inside of the drum through the first opening. It is good also as providing the receiving part for receiving. With such a configuration, it is possible to prevent ink from adhering to a rotation mechanism inside the drum, a bearing used for the rotation mechanism, and the like.

The image forming apparatus may further include a detecting unit for detecting the degree of overlap between the through hole and the first opening at a position facing the outer peripheral surface of the drum. Flushing may be performed based on the detection result of the detection means. With such a configuration, it is possible to measure the timing at which the overlapping portion reaches the position facing the nozzle based on the detection result by the detection means.
In the image forming apparatus, the belt may be an annular endless belt, and the circumference of the belt may be set to an integral multiple of the circumference of the drum. If it is such a structure, the through-hole of the belt which overlaps with a 1st opening part can be limited to a specific hole, and the reproducibility of the overlap condition of a 1st opening part and a through-hole can be improved.

  In other words, if it is an integral multiple, the relative positional relationship between the drum and the belt is basically not shifted except when slippage occurs or when the circumferences of the drums extend differently due to temperature changes. For this reason, for example, the flushing timing can be predicted and determined based on the detection result before one revolution (that is, one round) of the drum before the flushing is performed. That is, the flushing timing can be determined based on the detection result at the previous passage, not the detection result immediately before the head, and the signal processing time can have a margin for one round of the drum.

  A double-sided image forming apparatus according to another aspect of the present invention includes a front surface image forming apparatus having the same configuration as the above image forming apparatus, a back surface image forming apparatus having the same configuration as the above image forming apparatus, and the front surface. A transfer unit that transfers the paper from the image forming apparatus to the back image forming apparatus in the reverse direction. With such a configuration, flushing can be executed in both the front surface image forming apparatus and the back surface image forming apparatus without retracting the nozzle and leaving no trace on the paper surface.

1 is a diagram illustrating a configuration example of a double-sided image forming apparatus 100. FIG. The figure which shows the outer peripheral surface of the drum 13. FIG. The figure which shows the surface of the belt 16. FIG. The figure which shows the structural example of control part 70 grade | etc.,. The figure which shows the procedure of flushing. The figure which shows an example of the overlap condition of the through-hole 16a and the slit 13c. The figure which shows the process of the flushing in the line head 19Y. The figure which shows an example of the timing of flushing. The figure which shows the structural example of the receiving part.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that, in each drawing described below, parts having the same configuration are denoted by the same reference numerals, and redundant description thereof is omitted.
(1) Configuration Example of Double-Sided Image Forming Apparatus FIG. 1 is a side sectional view showing a configuration example of a double-sided image forming apparatus 100 according to an embodiment of the present invention.
As shown in FIG. 1, the double-sided image forming apparatus 100 includes, for example, a front surface image forming apparatus 1 that is an ink jet type and line recording type printer, and a back side image forming apparatus that is an ink jet type and line recording type printer. 2 along the conveyance direction of the recording paper P.

  As shown in FIG. 1, the surface image forming apparatus 1 has, for example, a driving drum (hereinafter simply referred to as a drum) 13 and a driven roller (hereinafter simply referred to as a roller) as a transport unit for transporting the recording paper P. ) 14, 15, an annular endless belt (hereinafter simply referred to as a belt) 16 wound around the drum 13 and the rollers 14, 15, and a partition wall 63. The rotating shafts 13a, 14a, 15a of the drum 13 and the rollers 14, 15 pass through the cross-sectional centers of the drum 13 and the rollers 14, 15 and are rotatably supported by bearings (not shown).

  In the surface image forming apparatus 1, the three rotation shafts 13 a, 14 a, and 15 a rotate in the same direction (for example, clockwise), so that the belt 16 wound around the drum 13 and the rollers 14 and 15 is one. It is transported in the direction. For example, the output shaft of an electric motor or the like as a driving source is connected to the rotating shaft 13a directly or via a speed reduction mechanism, and the output of the electric motor or the like is transmitted to the rotating shaft 13a. ing. When an electric motor or the like that is a driving source is driven to rotate forward, the drum 13 is driven to rotate about the rotation shaft 13a. Further, a suction hole 13b and a slit 13c are provided on the outer peripheral surface of the drum 13.

FIG. 2 is a plan view showing the outer peripheral surface of the drum 13. In FIG. 2 and FIGS. 6 and 7 to be described later, the slit 13c is shown in gray for easy identification of the slit 13c and other openings.
As shown in FIG. 2, a suction area for sucking the recording paper P via the belt 16 and a flushing corresponding area for causing the nozzle to perform flushing are prepared on the outer peripheral surface of the drum 13. A suction hole 13b is provided in the suction area, and a slit 13c is provided in the flushing corresponding area. The suction hole 13 b is a through-opening portion (that is, a through hole) that penetrates the outer peripheral surface of the drum 13. The slit 13c is also a through hole, for example.

As shown in FIG. 2, the slit 13c is formed so as to extend in the width direction (CD direction) of the drum 13, and when the drum 13 makes one rotation (that is, one round), the slit 13c is formed on the outer peripheral surface of the drum 13. The shape, size, and arrangement of the slits 13c are adjusted so that the slits 13c provided pass through all the nozzles included in the later-described line head 19 at least once (that is, so as to face each other). This is because a flushing process described later is executed for all nozzles.
For example, the slit 13 c is provided from near one end of the drum 13 to the other end along the width direction, and the length in the width direction is set longer than the nozzle arrangement range of the line head 19. That is, when the length of the line head in the width direction is L1 and the length of the slit 13c in the width direction is L2, L1 <L2.

  Further, in this embodiment, two such slits 13c are made into one group (that is, a slit group), the slit 13c included in one group, and the slit 13c included in the other group adjacent thereto. Is set to a length different from the arrangement interval of the slits 13c in the group. For example, as shown in FIG. 2, a total of four slits 13c provided in the flushing corresponding region can be divided into a first group and a second group. Here, the arrangement interval of the slits 13c in the first group is set to 1 pitch, and the arrangement interval of the slits 13c in the second group is also set to 1 pitch. Further, the arrangement interval between the slit 13c on the right side in FIG. 2 of the first group and the slit 13c on the left side in FIG. 2 of the second group is set to 3/2 pitch. Further, the above-described 1 pitch is set to the same size (or an integer multiple thereof) as the pitch in the circumferential direction (MD direction) of through holes 16a described later.

In FIG. 2, a part of the scale is marked, but this scale is shown for convenience in order to make it easy to grasp the size of the slit 13c and the arrangement interval. Actually, the outer peripheral surface of the drum 13 need not be graduated.
Moreover, in FIG. 1, the ratio of each diameter of the drum 13 and the roller 14 is drawn typically. In practice, the drum 13 has a diameter in the range of 3 to 10 times the diameter of the roller 14. For example, when the roller diameter is 3 cm, the diameter of the drum 13 is preferably in the range of about 9 cm to 30 cm. The reason for setting the ratio of the diameters is to increase the diameter of the drum 13 to ensure a large inertia and obtain a stable rotation, and to secure an arrangement area for the line head 19 described later.

  The belt 16 is made of, for example, rubber, and a plurality of through holes 16a are provided on the surface thereof. The recording paper P is held on the surface of the belt 16 by, for example, sucking the through hole 16a of the belt 16 with a negative pressure through the suction hole 13b provided in the drum 13 (that is, the negative pressure suction method). Is called. Such a negative pressure is generated, for example, by sucking air into the drum 13 through the through hole 16a and the suction hole 13b.

  FIG. 3 is a plan view showing the surface of the belt 16. As shown in FIG. 2, all of the through holes 16a are formed in the same shape (for example, oval) in the plan view and the same size, for example, and at a certain interval in the width direction and the circumferential direction. Has been placed. In addition, each through hole 16a is adjusted in shape, size, and arrangement so that the plurality of through holes 16a pass under all nozzles when the drum 13 rotates once (that is, so as to face each other). Yes. This is because a flushing process described later is executed for all nozzles.

For example, a plurality of through holes 16a are arranged at a constant interval in the width direction to form one row, and the distance between adjacent through holes 16a in the row is set to be longer than the length of one through hole 16a in the width direction. Set it short. In FIG. 3, the length in the width direction of one through hole 16a is set to four scales, and the separation distance of the through holes 16a in each row is set to two scales.
Further, such rows are arranged at equal intervals (equal pitch) in the circumferential direction that is the conveyance direction of the recording paper P, and the first row and the second row that are adjacent in the circumferential direction have a predetermined distance in the width direction. Just staggered. In FIG. 3, the first row and the second row are arranged in a state shifted by a half pitch in the width direction. The distance in the width direction from one end of the first row to the other end of the second row is set to be longer than the entire arrangement range of the nozzles of the line head 19. That is, when the length in the width direction of the line head 19 is L1, and the distance in the width direction from one end of the first row to the other end of the second row is L3, L1 <L3 is set.

In FIG. 3, a part of the scale is marked, but this scale is shown for convenience in order to make it easy to grasp the size of the through holes 16a and the arrangement interval thereof. Actually, it is not necessary to place a scale on the surface of the belt 16.
Returning to FIG. 1, the partition wall 63 is provided in a space 47 that is inside the belt 16 and outside the drum 13. The partition wall 63 is provided to divide the space 47 where the negative pressure reaches. By this partition wall portion 63, a region surrounded by the partition wall portion 63, the back surface of the belt 16, and the outer peripheral surface of the drum 13 is sealed in a substantially sealed state, and negative pressure is maintained. As a result, on the surface of the belt 16, not only the portion wound around the drum 13 but also the portion not wound around the drum 13 (that is, the portion before and after being wound around the drum 13) is attracted by negative pressure. Has come to reach.

  Further, the surface image forming apparatus 1 includes, for example, a gate roller 17 as a paper feeding unit for supplying the recording paper P onto the belt 16. The gate roller 17 corrects the skew of the recording paper P by abutting the recording paper P against the roller surface, and also sets the timing so that the recording paper P is placed on the target position on the belt 16 by timing the drive start. At the same time, the recording paper P is sent out. In addition, when performing flushing, the gate roller 17 performs recording at a timing so that the recording paper P is placed on the suction area of the drum 13 via the belt 16 and the recording paper P is not placed on the flushing-corresponding area. The paper P is sent out. That is, when performing the flushing, the sheet feeding timing is controlled so that the recording sheet P is not placed at least in the flushing area.

  The surface image forming apparatus 1 includes a line recording type head (that is, a line head) 19 at a position facing the outer peripheral surface of the drum 13 as a recording unit for the recording paper P. For example, the line head 19 includes four line heads 19Y, 19M, 19C, and 19K. Here, the line heads 19Y, 19M, 19C, and 19K eject ink droplets of four colors of yellow (Y), magenta (M), cyan (C), and black (K), respectively. The ink to be supplied is supplied from an ink tank (not shown) of each color through an ink supply tube. The line heads 19Y, 19M, 19C, and 19K are arranged along the outer peripheral surface of the drum 13 at predetermined intervals in the circumferential direction.

  Further, each of the line heads 19Y, 19M, 19C, and 19K has a plurality of lengths over which the maximum sheet width can be recorded in a direction orthogonal to the conveyance direction of the recording sheet P (that is, the width direction). By having a nozzle and ejecting a necessary amount of ink droplets from these nozzles to a required location, minute ink dots are formed on the recording paper P. By forming such ink dots for each color, it is possible to perform printing on the front side of the recording paper P held by the belt 16.

  The line heads 19Y, 19M, 19C, and 19K having the required number of colors may be constituted by a single head, or a plurality of unit heads are formed in a line shape in the width direction so as to function as a line head. It is also possible to configure with a multi-head arranged and arranged. In addition, the number of colors required in the present invention is not limited to four, and may be six colors, for example, light magenta (LM) and light cyan (LC) added to the above four colors. In that case, the line heads 19Y, 19M, 19C, 19K, 19LM, and 19LC may be arranged at predetermined intervals in the circumferential direction (CD direction).

Further, the surface image forming apparatus 1 includes a drying device 61 such as a halogen lamp or a hot air blower as a drying unit that dries the ink ejected onto the recording paper P. As shown in FIG. 1, the drying device 61 is provided downstream of the line head 19 in the conveyance direction of the recording paper P and at a position facing the surface of the belt 16.
As shown in FIG. 1, the back surface image forming apparatus 2 has the same basic structure as that of the front surface image forming apparatus 1 described above. That is, the back surface image forming apparatus 2 is, for example, a drum 113, rollers 114, 115, a belt 116 wound around the drum 113 and rollers 114, 115 as a conveying unit for conveying the recording paper P, A partition wall portion 163. Further, the back surface image forming apparatus 2 has, for example, line heads 119Y, 119M, 119C, and 119K as a recording unit for the recording paper P at positions facing the outer peripheral surface of the drum 113, and dries the ink ejected onto the recording paper P. For example, a drying device 161 such as a halogen lamp or a hot air blower is provided as a drying means. The configurations and functions of these conveying means, recording means, drying means, and detecting means in the back surface image forming apparatus 2 are the same as those of each means in the front surface image forming apparatus 1, for example.

  Further, the double-sided image forming apparatus 100 includes a delivery unit 4 that delivers the recording paper P from the front side image forming apparatus 1 to the back side image forming apparatus 2 upside down. The delivery unit 4 is configured by arranging the surfaces of the belts 16 and 116 of the front surface image forming apparatus 1 and the back surface image forming apparatus 2 in surface contact with each other in a predetermined area along the conveyance direction. The delivery unit 4 is provided in an area between the roller 14 that forms the separation unit 6 of the recording paper P of the front surface image forming apparatus 1 and the roller 114 that forms the reception unit 8 of the recording paper P of the back surface image forming apparatus 2. . The angle θ1 formed by the belt 16 wound around the roller 14 forming the separation unit 6 is an acute angle, and the angle θ2 formed by the belt 116 wound around the roller 114 forming the receiving unit 8 is formed by an obtuse angle. Yes.

  With such a configuration, the recording paper P that has been printed on the surface thereof by the line head 19 is transported on the belt 16 to the position of the roller 14 on the downstream side as viewed in the transport direction. Accordingly, the recording paper P is subjected to curvature separation on the curved surface of the belt 16 whose curvature has changed greatly according to the above, and is delivered to the back surface image forming apparatus 2. The recording paper P delivered to the back image forming apparatus 2 is carried on the belt 116. Then, the recording paper P that has been printed on the back surface thereof by the line head 119 is transported to the position of the roller 114 on the downstream side as viewed from the transport direction, and the belt 16 has a greatly changed curvature according to the diameter of the roller 114. On the curved surface, the recording paper P is separated in curvature and discharged to the outside.

  In the double-sided image forming apparatus 100, the belt 16 conveying speed V2 of the back surface image forming apparatus 2 is set to be slightly higher than the belt 16 conveying speed V1 of the front surface image forming apparatus 1. Further, a paper leading edge detector 65 is provided immediately after the delivery unit 4 as viewed from the transport direction. By this paper leading edge detector 65, the leading edge position of the recording paper P on which printing processing has been performed on the front surface can be detected and sent to the recording area of the back surface image forming apparatus 2. It is possible to execute printing.

The double-sided image forming apparatus 100 also includes sensors 21 and 121 provided at positions facing the outer peripheral surface of the drum 13 as flushing control means for causing each nozzle included in the line heads 19 and 119 to perform flushing. And a control unit (see FIG. 4) connected to the sensors 21 and 121, respectively.
The sensor 21 is a detecting means for detecting the degree of overlap between the through hole 16a provided in the belt 16 and the slit 13c provided in the drum 13. For example, a reflection or transmission type optical sensor is used. As described above, since the slit 13c is, for example, the through hole 16a, the portion where the slit 13c and the through hole 16a overlap (that is, the overlapping portion) is an opening that penetrates from the surface of the belt 16 to the inside of the drum 13. Become. Therefore, it is possible to detect the coincidence or mismatch between the through hole 16a and the slit 13c by an optical method using light irradiation.

  For example, when a reflective optical sensor is used as the sensor 21, light (eg, visible light, infrared light, etc.) is irradiated vertically from the light emitting portion of the sensor 21 toward the wound portion of the belt 16. The reflected light of the light is read by the light receiving portion of the sensor 21 to detect the coincidence or mismatch between the through hole 16a and the slit 13c. For example, when the through hole 16a and the slit 13c are coincident (that is, when an overlapping portion is generated), the light passes through the through hole 16a and the slit 13c and reaches the inside of the drum 13; Does not reflect. Further, when the through hole 16a and the slit 13c do not match, the light is reflected on either the belt 16 surface or the drum 13 surface. As described above, it is possible to detect coincidence or mismatch between the through hole 16a and the slit 13c depending on the presence or absence of reflected light.

  Further, for example, an optical line sensor having a configuration in which a plurality of optical sensors are arranged in the width direction can be used as the sensor 21, and in this case, not only one place on the belt 16 but also the width of the belt 16. Light can be simultaneously irradiated to a plurality of locations along the direction (for example, a region on a line along the width direction). Thereby, it is possible to detect the coincidence and disagreement between the through hole 16a and the slit 13c in a wider range along the width direction. The sensor 121 also has the same configuration as the sensor 21 and exhibits the same function in the back surface image forming apparatus 2.

The control unit has a function of determining the timing of flushing in the line heads 19 and 119 based on the detection result of the sensor, and has a configuration as shown in FIG. 4, for example.
FIG. 4 is a block diagram illustrating a configuration example of the control unit 70 and the like. As illustrated in FIG. 4, the control unit 70 includes, for example, a CPU (central processing unit) 71, a ROM (read only memory) 72, and a RAM (random access memory) 73. The CPU 71 is connected to the ROM 72, the RAM 73, the sensors 21 and 121, and the driver circuits 31 and 131, respectively. Here, the driver circuit 31 is a circuit for controlling, for example, the line heads 19Y, 19M, 19C, and 19K, an electric motor that is a driving source of the drum 13, and the like. The driver circuit 131 is a circuit for controlling, for example, the line heads 119Y, 119M, 119C, and 119K, an electric motor that is a driving source of the drum 113, and the like. Next, the flushing method in the double-sided image forming apparatus 100 will be specifically described.

(2) Flushing Method In the double-sided image forming apparatus 100 shown in FIG. 1, flushing can be performed by the same procedure in each of the front surface image forming apparatus 1 and the back surface image forming apparatus 2. For example, when performing flushing in the surface image forming apparatus 1, as shown in FIG. 5, in the first step (S1), the slit 13c provided in the drum 13 and the through hole 16a provided in the belt 16 Match or mismatch (that is, overlapped portion) is detected. Next, in the second step (S2), the flushing timing is determined based on the detection result of the overlapping portion. In the third step (S3), flushing is executed at the determined timing. Hereinafter, these steps S1 to S3 will be described.

FIGS. 6A to 6F are a plan view and a cross-sectional view showing an example of how the through hole 16a and the slit 13c overlap each other. 6B is a cross-sectional view of FIG. 6A taken along line X1-X′1, and FIG. 6D is a cross-sectional view of FIG. 6C taken along line X2-X′2. FIG. 6F is a cross-sectional view of FIG. 6E taken along line X3-X′3.
6A and 6B show a case where the phase shift between the slit 13c and the through hole 16a is zero (that is, the reference position), and FIGS. 6C and 6D show the above phase shift of 1. / 4 pitch (that is, when there is a displacement of one scale from the reference position), FIGS. 6E and 6E show the case where the above phase shift is ½ pitch (that is, the reference). (When there is a position shift of two scales from the position).

  Such a phase shift occurs due to a cause such as the belt 16 slipping with respect to the outer peripheral surface of the drum 13, but in this embodiment, the shape, size and arrangement of the slit 13c are adjusted as shown in FIG. In addition, as shown in FIG. 3, the shape, size and arrangement of the through holes 16a are adjusted. For this reason, even when a deviation occurs in the overlapping state, the maximum deviation amount is suppressed to ½ pitch, and the portion where the slit 13c and the through hole 16a overlap in at least one of the first group or the second group ( That is, an overlapping portion) 18 is always generated.

Therefore, in the first step (S1), the overlapping portion 18 is detected while the drum 13 is rotating. This detection is performed by the sensor 21 shown in FIG. For example, the CPU 71 transmits a detection start signal to the sensor 21 in accordance with a control program stored in the ROM 72 shown in FIG. Upon receiving this signal, the sensor 21 detects the overlapping portion 18 by the optical method described above, and transmits the detection result to the CPU 71.
In the second step (S2), the CPU 71 sets the flushing timing based on the detection result transmitted from the sensor 21 (for example, the position where the overlapping portion 18 is detected and the time during which the overlapping portion 18 is detected). decide. This determination is performed by the CPU 71 in accordance with the control program stored in the ROM 72 shown in FIG.

  That is, the overlapping portion 18 always passes under the line head 19 from the time when it is detected by the sensor 21 until the next time it is detected (that is, while the drum 13 rotates once). Therefore, the CPU 71 calculates the execution timing so that flushing is performed when the overlapping portion 18 reaches below the line head 19, and stores the calculation result in the RAM 73. For example, as shown in FIGS. 6A and 6B, when the phase shift is zero and the overlapping portion 18 is generated only in the slit 13c of the first group, “no phase shift” is detected as the detection result. It is transmitted from the sensor 21 to the CPU 71. In that case, the CPU 71 calculates the timing at which the overlapping portion 18 generated on the first group side sequentially reaches the line heads 19Y, 19M, 19C, and 19K, and stores the calculation result in the RAM 73.

In the third step (S 3), flushing is performed on each nozzle included in the line head 19 based on the calculation result stored in the RAM 73. This flushing is performed by the driver circuit 31 receiving a signal from the controller 70 forcibly ejecting ink to each nozzle included in the line head 19.
For example, when the phase shift is zero as shown in FIGS. 6A and 6B and the line head 19Y is flushed, the process proceeds from FIG. 7A to FIG. 7B. In the meantime, ink is ejected a plurality of times (for example, 100 times) from the nozzle located directly above the overlapping portion 18 to the overlapping portion 18 among the plurality of nozzles included in the line head 19Y. As a result, a part of the plurality of nozzles included in the line head 19Y (that is, a portion indicated by hatching) is in a flushed state.

  Next, during the transition from FIG. 7B to FIG. 7C, the ink is ejected a plurality of times (for example, 100 times) again from the nozzle located directly above the overlapping portion 18 toward the overlapping portion 18. Let As a result, flushing is also performed on the remaining portion that was not flushed during the transition from FIG. 7A to FIG. 7B. As a result, as shown in FIG. 7C, all the nozzles included in the line head 19Y are flushed.

FIG. 8 is a diagram illustrating an example of the timing of flushing. In FIG. 8, the horizontal axis represents time, T _{0 to} T ₁ indicate a period during which the first slit 13c of the first group passes under the line head 19Y, and T _{2 to} T ₃ indicate the _second of the first group. Indicates a period in which the slit 13c of the second group passes under the line head 19Y, T _{4 to} T ₅ indicate a period in which the first slit 13c of the second group passes under the line head 19Y, and T _{6 to} T ₇ indicate the second period. A period during which the second slit 13c of the group passes under the line head 19Y is shown.
As shown in FIGS. 6A and 6B, when the phase shift is zero (that is, the reference position), the true value of the overlapping portion 18 is obtained in each period of T _{0 to} T ₁ and T _{2 to} T _3. For example, ink is ejected from the nozzle located above toward the overlapping portion 18 100 times, for example. Thereby, all the nozzles included in the line head 19Y can be in a flushed state.

On the other hand, when the phase shift is ¼ pitch as shown in FIGS. 6C and 6D, it is directly above the overlapping portion 18 in each period of T _{0 to} T ₁ and T _{2 to} T _3. For example, the ink is ejected from the nozzle located toward the overlapping portion 18 by 50 times, for example. In addition, in each period of T _{4 to} T ₅ and T _{6 to} T ₇ , ink is ejected, for example, 50 times from the nozzle positioned directly above the overlapping portion 18 toward the overlapping portion 18. Thereby, all the nozzles included in the line head 19Y can be in a flushed state. Further, as shown in FIGS. 6C and 6D, when the phase shift is ½ pitch, in each period of T _{4 to} T ₅ and T _{6 to} T ₇ , it is directly above the overlapping portion 18. For example, ink is ejected from the nozzle located toward the overlapping portion 18 100 times, for example. Thereby, all the nozzles included in the line head 19Y can be in a flushed state.
As described above, by dividing the ink discharge at different timings according to the phase shift state, it is possible to flush all the nozzles included in the line head 19Y regardless of the presence or absence of the phase shift.

  The line heads 19M, 19C, and 19K are arranged on the upstream side or the downstream side of the line head 19Y when viewed from the conveyance direction of the recording paper P. The line heads 19M, 19C, and 19K are also line heads. As in the case of 19Y, ink is ejected from the nozzle toward the overlapping portion 18 at the timing when the overlapping portion 18 reaches under the nozzle. As a result, all the nozzles included in the line heads 19M, 19C, and 19K can be flushed, and this increase can be achieved even when the ink is thickened and clogged in each nozzle. The viscous ink can be forcibly ejected to supply fresh ink that is not thickened into each nozzle. Further, the ejected ink can be discharged into the drum 13 through the overlapping portion 18.

  Thus, according to the embodiment of the present invention, when the nozzle is flushed, the ink can be ejected from the nozzle toward the portion 18 where the through hole 16a and the slit 13c overlap (that is, the overlapping portion) 18. The discharged ink can be discharged into the drum 13 through the overlapping portion 18. Accordingly, flushing can be performed without retracting the nozzle from the position facing the outer peripheral surface of the drum 13 (that is, the steady position). Since flushing can be performed without moving the nozzle, the time required for flushing can be shortened. In addition, since the nozzle retreat destination is unnecessary, it is possible to contribute to downsizing of the double-sided image forming apparatus 100. Furthermore, since the flushing can be performed without attaching ink to the front and back surfaces of the recording paper P (that is, without leaving a trace), the paper surface can be kept in high quality.

  In the above embodiment, the circumferential direction (that is, the MD direction) corresponds to the “first direction” of the present invention, and the width direction (that is, the CD direction) corresponds to the “second direction” of the present invention. Yes. The slit 13c corresponds to the “first opening” of the present invention, and the suction hole 13b corresponds to the “second opening” of the present invention. Further, the line heads 19 and 119 correspond to the “head” of the present invention. Further, the arrangement interval in the circumferential direction of the slits 13c in the first group (or the second group) corresponds to the “first interval” of the present invention, and the arrangement interval in the width direction of the plurality of through holes 16a is the main interval. This corresponds to the “second interval” of the invention. Further, the double-sided image forming apparatus 100 corresponds to the “image forming apparatus” of the present invention.

(3) Others In the present invention, for example, as shown in FIGS. 9A and 9B, the receiving portion 40 for receiving ink that reaches the inside of the drum 13 through the slit 13 c is provided as the drum 13. It may be provided inside. The receiving portion 40 includes, for example, a counter plate 41 provided to face the line head 19, and a discharge path 42 that extends from the counter plate 41 to the outside of the drum 13 through the inside of the rotary shaft 13 a and the like. Moreover, it is preferable that this receiving part 40 is fixed so that it may always be in the same position with respect to the line head 19 without rotating.
With such a configuration, the ink that has reached the inside of the drum 13 can be discharged from the counter plate 41 to the outside of the drum 13 via the discharge path 42.

  In the present invention, the circumference of the belt 16 is preferably an integral multiple of the circumference of the drum 13. This is because, if it is an integral multiple, the relative positional relationship between the drum 13 and the belt 16 basically does not deviate except when slippage occurs or when the circumferences of the belts 16 extend differently due to temperature changes. This is because the timing of flushing can be predicted and determined based on the detection result before one revolution (that is, one round) of the drum 13 before the flushing is performed. That is, the flushing timing can be determined based on the detection result at the previous passage, not the detection result immediately before the head, and there is a margin for one round of the drum in the signal processing time.

In the present invention, the end portion along the circumferential direction of the belt 16 is preferably linear. That is, it is preferable that the through hole 16 a does not face the end portion of the belt 16. Thereby, it becomes easy to maintain the strength of the belt 16 at a certain level or more.
Moreover, although said embodiment demonstrated the case where the slit 13c was a through-hole, this invention is not limited to this. That is, the slit 13c may be an opening that does not penetrate (that is, has a bottom surface). Even with such a configuration, the ink ejected from the nozzles can be received by the bottom surface of the slit 13 c through the through hole 16 a provided in the belt 16. Therefore, as in the above embodiment, flushing can be performed without retracting the nozzle and leaving no trace on the paper surface.

  Moreover, although said embodiment demonstrated the case where the sensors 21 and 121 were optical sensors, this invention is not limited to this. For example, the sensors 21 and 121 may be magnetic sensors. In that case, for example, magnetic indexes are respectively attached to the drum 13 and the belt 16, and these indexes are read by a magnetic sensor at the time of flushing. Even with such a configuration, it is possible to detect coincidence or inconsistency between the through hole 16a provided in the belt 16 and the slit 13c provided in the drum.

  In the above embodiment, the double-sided image forming apparatus 100 that performs the printing process on both sides of the recording paper P has been described as an example of the “image forming apparatus” of the present invention. However, the present invention is not limited to this. . For example, an image forming apparatus that performs a printing process only on the front surface or the back surface of the recording paper P may be used. That is, the “image forming apparatus” of the present invention may be the front surface image forming apparatus 1 or the back surface image forming apparatus 2. Also in this case, flushing can be performed without retracting the nozzle in each apparatus and without leaving a trace on the paper surface.

  DESCRIPTION OF SYMBOLS 1 Front image forming apparatus, 2 Back surface image forming apparatus, 6 Separation part, 8 Receiving part, 13, 113 Drum, 13a Rotating shaft, 13b Suction hole, 13c Slit, 14, 15 Roller, 14a, 15a Rotating shaft, 16, 116 Belt, 16a Through hole, 17 Gate roller, 18 Overlap part, 19, 19Y, 19M, 19C, 19K, 119, 119Y, 119M, 119C, 119K Line head, 21, 121 Sensor, 31, 131 Driver circuit, 40 Receiving 41, counter plate, 42 discharge path, 47, 147 space, 61, 161, drying device, 63, 163 partition, 65 paper tip detector, 70 control unit, 71 ROM, 72 RAM, 100 double-sided image forming apparatus

Claims (10)

A drum having an opening on the outer peripheral surface;
A belt for paper conveyance wound around the outer peripheral surface of the drum and having a through hole;
A nozzle for discharging ink toward the outer peripheral surface of the drum;
Flushing control means for causing the nozzle to flush,
The flushing control means includes
An image forming apparatus that causes the nozzle to perform flushing at a timing when the drum rotates in a first direction and a portion where the through hole and the opening overlap each other reaches a position facing the nozzle. . The outer peripheral surface of the drum has a flushing corresponding area for causing the nozzle to perform flushing, and an adsorption area for adsorbing paper,
The opening includes a first opening provided in the flushing corresponding area, and a second opening provided in the suction area,
The flushing control unit causes the nozzle to perform flushing at a timing when a portion where the through hole and the first opening overlap each other reaches a position facing the nozzle. Image forming apparatus. A head in which a plurality of the nozzles are arranged in a second direction intersecting the first direction in plan view;
When the drum rotates once in the first direction, the portion where the through hole and the first opening overlap each other at least once with all the nozzles included in the head. The image forming apparatus according to claim 2, wherein a through hole and the first opening are configured. The first opening is a slit extending in the second direction;
The image forming apparatus according to claim 3, wherein a length of the slit in the second direction is larger than a total length of the arrangement range of the nozzles. A plurality of slit groups in which a plurality of the slits are arranged at a first interval in the first direction;
The interval between the slit included in one of the adjacent slit groups and the slit included in the other slit group is the slit included in one slit group and the slit included in the other slit group. The image forming apparatus according to claim 4, wherein at least one of the first and second holes overlaps the through hole. A plurality of rows in which the plurality of through holes are arranged at a second interval in the second direction;
The plurality of rows are arranged at the first interval in the first direction,
6. The image forming apparatus according to claim 5, wherein the through hole is arranged so as to be shifted in the second direction between one of the adjacent rows and the other of the rows. The first opening is an opening penetrating the outer peripheral surface of the drum,
The receiving part for receiving the ink which reaches the inside of the said drum through the said 1st opening part in the inside of the said drum is provided, The any one of Claims 2-6 characterized by the above-mentioned. The image forming apparatus described.   Detection means for detecting the degree of overlap between the through hole and the first opening at a position facing the outer peripheral surface of the drum, and the flushing control means is configured to perform flushing based on a detection result of the detection means. The image forming apparatus according to claim 2, wherein the image forming apparatus performs the following operations. The belt is an annular endless belt;
The image forming apparatus according to claim 2, wherein a circumferential length of the belt is set to an integral multiple of a circumferential length of the drum. A surface image forming apparatus having the same configuration as the image forming apparatus according to any one of claims 1 to 9,
A back surface image forming apparatus having the same configuration as the image forming apparatus according to any one of claims 1 to 9,
A double-sided image forming apparatus, comprising: a transfer unit that transfers paper from the front side image forming apparatus to the back side image forming apparatus in an upside down manner.

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