JP2010095366A - Conveying mechanism of printing device - Google Patents

Abstract

Image quality is improved by suppressing the floating of a recording sheet immediately before a recording operation is performed, and adverse effects such as ejection defects and contamination of printed matter caused by ink mist generated during ink ejection are avoided.
SOLUTION: A plurality of ink heads 110a for ejecting ink from ejection ports, an upstream guide roller 510a provided on the upstream side of the ink head 110a in the transport direction of the printing paper, and rotated by being pressed against the upper surface of the transport path, and transport And a downstream guide roller 510b that is provided on the downstream side of the ink head in the direction and is rotatably provided at a predetermined distance from the upper surface of the conveyance path. The diameter of the upstream guide roller 510a is the diameter of the downstream guide roller 510b. It is configured larger than.
[Selection] Figure 3

Description

  The present invention relates to a transport mechanism of a printing apparatus that forms an image on a print sheet that is transported on a transport path by ejecting ink.

  Conventionally, as an ink jet method, there is a full line type in which printing paper is recorded only by sub-scanning in the transport direction. With this full line type, recording for one line is continuously performed on the printing paper at a time. .

  By the way, the recording surface of the printing paper may float due to moisture absorption of the recording paper, and the recording paper and the ink head come into contact with each other, causing problems such as contamination of the ink head and failure. In order to prevent the sheet from being lifted up, conventionally, for example, a configuration in which paper pressing rollers are arranged on the upstream side and the downstream side of the ink as disclosed in Patent Document 1 is employed. Thus, the recording paper is pressed on the upstream side and the downstream side of the ink head to prevent the ink head from floating.

However, in the technique of Patent Document 1, since the support mechanism for the paper pressing roller located upstream and downstream of the ink head is provided, it is difficult for all the rollers to contact the platen belt with equal pressure. . Also, mist other than the main droplets is usually generated when ink is ejected from the ink head. This mist is soared by the wind generated by the paper transport platen belt, and is concentrated and accumulated on the paper pressing roller downstream of the ink head, thereby contaminating the recording paper.
JP 2006-137027 A

  In view of the above, the present invention has been made in view of the above points, and improves the image quality by suppressing the floating of the recording paper immediately before the recording operation is performed, and the ink mist generated at the time of ink ejection is concentrated in the vicinity of the ink head. It is an object of the present invention to provide a transport mechanism for a printing apparatus that can avoid problems such as ejection failure and contamination of printed matter caused by accumulation.

  In order to solve the above problems, the present invention provides a transport mechanism for a printing apparatus that forms an image on a print sheet by ejecting ink onto a print sheet that is transported on a transport path. A plurality of ink heads to be ejected, an upstream guide roller that is provided on the upstream side of the ink head in the transport direction of the printing paper and is pressed against the upper surface of the transport path, and is provided on the downstream side of the ink head in the transport direction. And a downstream guide roller rotatably provided at a predetermined distance from the upper surface, wherein the upstream guide roller has a diameter larger than that of the downstream guide roller.

  According to the present invention, since the upstream guide roller of each ink head is pressed against the upper surface of the transport path and rotates, when the print paper is transported to the upper surface of the transport path, the print paper is removed. By pinching between the guide roller and the upper surface of the transport path, the printing head can be prevented from floating immediately before the ink head ejects ink onto the printing paper, and contact between the image forming unit and the paper can be prevented. Thus, the recording head can be protected.

  In addition, since the diameter of the downstream guide roller is smaller than the diameter of the upstream guide roller and does not contact the upper surface of the paper transport path, the air flow path of the ink mist generated from the ink head is secured, and the guide roller The ink mist can be caused to flow by rotation, and mist adhesion to the printing paper and the platen belt can be prevented.

  In the said invention, it is preferable to have a stepped guide roller which connected and arrange | positioned the upstream guide roller and the downstream guide roller on the same rotating shaft as an upstream guide roller and a downstream guide roller. In this case, in the upstream guide roller on the same axis, the pressure against the printing paper becomes constant, and the image quality of the entire printing screen can be improved. In addition, since the downstream guide roller can be driven by the power that drives the upstream guide roller provided in the stepped guide roller that is connected and arranged on the same rotation shaft, it has its own drive mechanism. The number of production points can be reduced and the cost can be reduced.

  In the above invention, the ink heads are arranged in a plurality of rows in a direction orthogonal to the transport direction, and the ink heads included in each row in the plurality of rows are in the transport direction with ink heads included in other adjacent rows. It is preferable that the portions are arranged in a staggered manner so that non-overlapping portions are generated, and the upstream guide roller and the downstream guide roller are arranged in a staggered manner corresponding to the arrangement of the ink heads.

  In this case, since the ink heads in the other rows adjacent to the ink heads are arranged so as to generate a certain space or more in the transport direction, the downstream side of the ink head which is the air flow path of the ink mist generated during printing. A certain space can be secured on the side. In addition, the staggered arrangement makes it possible to maintain a uniform space on the downstream side of the ink head in the entire image forming unit with a uniform structure, thereby preventing contamination due to mist adhesion to the guide roller of the entire screen forming unit. it can. Furthermore, since the upstream guide roller is also arranged in a zigzag pattern with respect to the entire image forming unit, it is possible to prevent the entire printing paper from being lifted.

  In the above invention, each row of the ink heads is arranged at a predetermined interval in the transport direction, forms a main flow path between the rows, and the upstream guide roller and the downstream guide roller are within the main flow path. It is preferable to arrange | position. In this case, the upstream and downstream guide rollers can be attached using the space formed in the main direction flow path between the ink head rows, and the parts can be held together while ensuring the air flow path of the mist. Therefore, it is possible to optimize the size of the apparatus.

  As described above, according to the present invention, the image quality is improved by suppressing the lifting of the recording sheet immediately before the recording operation is performed, and the adverse effects such as ejection failure caused by ink mist generated at the time of ink ejection and contamination of printed matter are caused. To avoid.

(Overall configuration of printing device)
Embodiments of the present invention will be described with reference to the drawings. FIG. 1A is a diagram illustrating an outline of a printing paper conveyance path of the printing apparatus 100 according to the present embodiment. In the present embodiment, the printing apparatus 100 includes a plurality of ink heads having a large number of nozzles, prints black or color ink from each ink head, performs printing in units of lines, and prints on a recording sheet on a conveyance belt. An ink-jet line color printer that forms a plurality of images so as to overlap each other will be described as an example.

  As shown in FIG. 1, the printing apparatus 100 is an apparatus that forms an image on the surface of a sheet transported on an annular transport path. The transport path includes a paper feed system transport path FR that supplies the paper, and this paper feed. A general path CR from the system transport path FR through the head unit 110 to the paper discharge path DR and a reverse path SR branched and connected to the normal path CR are roughly configured.

  In the paper feed system conveyance path FR, as a paper feed mechanism for supplying printing paper, a side paper feed stand 120 disposed outside the side surface of the housing and a plurality of paper feed trays (inside the housing) 130a, 130b, 130c, 130d). A paper discharge port 140 is provided as a paper discharge mechanism for discharging printed printing paper.

  Printing paper fed from one of the side paper feeding tray 120 and the paper feeding tray 130 is conveyed along a paper feeding system conveyance path FR in the housing by a driving mechanism such as a roller, and the printing paper It is guided to the resist portion R which is the reference position of the head portion. A head unit 110 having a plurality of print heads is provided further on the registration direction R in the transport direction side. The printing paper is image-formed line by line with ink ejected from each printing head while being conveyed at a speed determined by printing conditions by a platen belt 160 which is a conveying belt provided on the opposite surface of the head unit 110.

  The printed printing paper is further conveyed on the normal route CR by a driving mechanism such as a roller. In the case of single-sided printing, in which printing is performed only on one side of the printing paper, the paper is directly discharged to the paper discharge port 140 through the paper discharge route DR, and is discharged as a tray for the paper discharge port 140. It is loaded on the table 150 with the printing surface facing down. The paper discharge table 150 has a tray shape protruding from the housing, and has a certain thickness. The paper discharge table 150 is inclined, and the printing paper discharged from the paper discharge port 140 is naturally arranged and overlapped by a wall formed at a position below the inclination.

  On the other hand, in the case of double-sided printing in which printing is performed on both sides of the printing paper, the front side (the first printed side is “front side” and the next printed side is “back side”). Without being guided to, the inside of the casing is further transported and sent out to the reverse path SR. For this reason, the printing apparatus 100 is provided with a switching mechanism 170 for switching the transport path for backside printing, and the printing paper that has not been sent to the discharge path by the switching mechanism 170 is drawn into the reversing path SR.

  In the reversing path SR, a sheet is transferred from the normal path CR, and a so-called switchback is performed in which the sheet is reversed by reciprocating the sheet. Then, it is returned to the normal route CR via the switching mechanism 172 by a driving mechanism such as a roller, is fed again through the registration portion R, and the back side is printed by the same procedure as the front side. After that, the printing paper on which the back side is printed and the image is formed on both sides is guided to the paper discharge port 140 through the paper discharge route DR and discharged, and the paper discharged as a receiving base of the paper discharge port 140 is discharged. It is loaded on the table 150.

  In the present embodiment, switchback at the time of duplex printing is performed using a space provided in the paper discharge tray 150. The space provided in the paper discharge tray 150 is configured to be covered so that the printing paper cannot be taken out from the outside at the time of switchback. As a result, it is possible to prevent the user from accidentally pulling out the printing paper being reversed. Further, the paper discharge tray 150 is originally provided in the printing apparatus 100, and by performing switchback using the space in the paper discharge tray 150, a separate switchback is provided in the printing apparatus 100. There is no need to provide space. Therefore, an increase in the size of the housing can be prevented. Furthermore, since the paper discharge path and the reverse path are not shared, the switchback process and the paper discharge of other sheets can be performed in parallel.

  In the printing apparatus 100, the printing paper that has already been printed on one side is also re-fed to the registration portion R that is the reference position of the leading portion of the fed printing paper. For this reason, a junction point where a transport path for newly fed printing paper and a refeed path for circulating and feeding back-side printing paper is formed immediately before the registration portion R. The Then, the registration unit R sends out the paper in the vicinity of the merging point between the paper feeding system conveyance path FR and the normal path CR.

  In the present embodiment, the path on the sheet feeding mechanism side is defined as the sheet feeding system conveyance path FR, and the other path is defined as the conveyance path with reference to the merging point. This transport path is annular, and includes the normal path CR and the reverse path SR as described above. FIG. 1B is a diagram schematically showing the sheet feeding system conveyance path FR, the normal path CR, and the reverse path SR. In the figure, the number of rollers constituting the drive unit is omitted as appropriate.

  In the paper feed system conveyance path FR, the side paper feed driving unit 220 for feeding paper from the side paper feed tray 120 and the paper feed from the paper feed trays 130 (130a, 130b, 130c, 130d) are provided. A tray 1 driving unit 230a, a tray 2 driving unit 230b,. These constitute a paper feeding means for feeding paper to the registration unit R.

  Further, any of the driving units (tray 1 driving unit 230a, tray 2 driving unit 230b...) In the above-described paper feeding system conveyance path FR includes a driving mechanism composed of a plurality of rollers or the like. Are taken one by one and conveyed in the direction of the registration portion R. Each drive unit can be driven independently, and necessary drive unit operations are performed in accordance with a paper feed mechanism that feeds paper.

  In addition, a plurality of conveyance sensors are arranged in the paper feeding system conveyance path FR so that a conveyance jam in the paper feeding system conveyance path FR can be detected. That is, each conveyance sensor is a sensor that detects the presence or absence of printing paper or the leading edge of printing paper. For example, a plurality of conveyance sensors are arranged at appropriate intervals on a conveyance path, and a conveyance sensor provided on the paper feeding side is provided. If the conveyance sensor on the conveyance direction side does not detect the printing paper within a predetermined time after detecting the printing paper, it can be determined that the conveyance jam has occurred.

  Among these conveyance sensors, the registration sensor in front of the registration unit R that sends out the paper measures the size of the paper that is being conveyed, and measures the size of the paper that is passing, for example, based on the passage speed and the passage time of the paper. If the conveyance sensor does not detect the printing paper within a predetermined time after driving the side paper feed driving unit 220, the tray 1 driving unit 230a, etc., it is determined that a conveyance jam (paper feeding error) has occurred. Can do.

  The normal path CR forms a part of the circulation transport path, and is a path from the paper feed system transport path FR for supplying paper to the paper discharge path DR through the head unit 110. An image is formed. In this normal path CR, a registration driving unit 240 that guides printing paper to the registration unit R, a belt driving unit 250 that drives the platen belt 160 provided on the opposite surface of the head unit 110 to move endlessly, and in the conveyance direction side. The first upper surface transport driving unit 260 and the second upper surface transport driving unit 265 arranged in order, the upper surface discharge driving unit 270 that guides the printed paper to the paper discharge port 140, and the drive for drawing the printing paper into the reverse path SR for back side printing. Means are provided. Each drive unit includes a drive mechanism composed of one or a plurality of rollers and the like, and conveys printing sheets one by one along the conveyance path. Each drive unit can be driven independently, and necessary drive unit operations are performed in accordance with the conveyance status of the printing paper.

  Further, a plurality of conveyance sensors are also arranged on the normal route CR so that a conveyance jam in the normal route CR can be detected. Further, it is possible to confirm that the printing paper is properly conveyed also in the registration portion R. In the normal route CR, a conveyance sensor is provided corresponding to the drive unit, and it is possible to specify in which drive unit of the normal route CR the conveyance jam has occurred.

  The reversing path SR is branched and connected to the normal path CR, the paper is delivered from the normal path CR, and the paper is reciprocated (switched back) to return to the normal path CR, thereby reversing the front and back of the paper and the transport mechanism. The reversing path SR is provided with a reversing drive unit 281 that reverses the sheet and guides it to the joining point. The reverse route SR can be transported at a speed different from that of the normal route CR. When the paper is taken over from the normal route CR, acceleration / deceleration is performed, and a stop time at the time of switchback is extended or shortened. can do.

  In this embodiment, after a certain printing paper is fed, the next printing paper is not fed after waiting for printing to be performed on the printing paper and discharged. Before the printing paper is discharged, subsequent printing paper can be fed and printed continuously at a predetermined interval. Therefore, in normal scheduling at the time of duplex printing, a space is secured in advance so as to secure a position where the sheet returned from the reversing path SR is inserted when feeding the front sheet. Thereby, in this apparatus, printing on the front surface and printing on the back surface can be performed in parallel, and half the productivity can be ensured with respect to single-sided printing.

  The platen belt 160 is wound around a driving roller 161 and a driven roller 162 disposed at the front end and the rear end of the surface facing the head unit 110, and rotates in a clockwise direction in FIG. In addition, on the upper surface of the platen belt 160, four ink heads of yellow (Y), magenta (M), cyan (C), and black (K) are arranged side by side along the belt moving direction, and a plurality of images are arranged. The head units 110 that form color images are arranged so as to face each other.

  Further, as illustrated in FIG. 1, the printing apparatus 100 includes an arithmetic processing unit 330. The arithmetic processing unit 330 is configured by a processor such as a CPU or DSP (Digital Signal Processor), memory, hardware such as other electronic circuits, software such as a program having the function, or a combination thereof. Various functional modules are virtually constructed by appropriately reading and executing a program, and various functional modules for processing related to image data, operation control of each unit, and user operations are constructed by each constructed functional module. Process. In addition, an operation panel 340 is connected to the arithmetic processing unit 330, and an instruction and a setting operation by a user can be received through the operation panel 340.

(Conveying mechanism in the image forming path)
FIG. 2 is an explanatory view showing an image forming path on which image formation is performed from the side, and FIG. 3A is an explanatory view showing a head holder 500 arranged above the image forming path from below. FIG. 3B is an explanatory diagram showing an enlarged side surface of the head holder 500. FIG. 4A is a perspective view showing the head holder 500 from above, and FIG. 4B is an explanatory view schematically showing the lower surface of the head holder 500.

  More specifically, the normal path CR of the sheet includes an image forming path CR1 including a platen belt 160, a driving roller 161, a driven roller 162, and the like, and a head holder is disposed above the image forming path CR1. 500 is provided. The head holder 500 is a box having a head holder surface 500a on the bottom surface, and holds and fixes the ink head 110a, and stores other functional parts for discharging ink from the ink head 110a as a unit. .

  Further, the head holder surface 500a that is the bottom surface of the head holder 500 is disposed so as to be parallel to the transport path. A plurality of mounting openings 500b having the same shape as the horizontal cross section of each of the plurality of ink heads 110a constituting the head unit 110 are arranged on the head holder surface 500a, and the plurality of ink heads 110a are respectively inserted into the mounting openings 500b. Thus, the discharge port is projected from the head holder surface 500a.

  As shown in FIG. 4B, the ink head 110a is arranged in a plurality of rows in a direction (main scanning direction) orthogonal to the transport direction (sub-scanning direction), and is included in each row within these multiple rows. The ink heads 110a are arranged in a staggered manner so that the other ink heads 110a included in other adjacent rows overlap with each other in the transport direction, and the central portion of each ink head is arranged in the transport direction. The part which does not overlap is produced. In other words, the ink head 110a is formed with a plurality of rows L1, L2, L3... In the main scanning direction, and each row L1, L2, L3. Further, the plurality of rows L1, L2, L3,... Are arranged in a staggered manner so that a portion b2 overlapping with another adjacent plurality of rows is generated in the sub-scanning direction.

  Each of these ink head rows L1, L2, L3... Is arranged at a predetermined interval in the transport direction, and a main scanning channel 111 is formed between the rows, and each adjacent ink head in the same row is The sub-scanning flow path 112 is formed between the ink heads arranged at a predetermined interval. The main scanning channel 111 and the sub-scanning channel 112 communicate with each other to form a mesh-like mist discharge channel. As shown in FIG. 3B, in the present embodiment, the protruding length H of the ink head 110a from the head holder surface 500a is larger than the width L of the main flow path.

  Each main direction channel 111 is provided with a stepped guide roller 510. The stepped guide roller 510 is formed by connecting guide rollers having different diameters as a single roller, and is formed by cutting a metal rod, for example. Specifically, the stepped guide roller 510 includes an upstream guide roller 510a having a large diameter and a downstream guide roller 510b having a diameter smaller than that of the upstream guide roller 510a alternately connected on the same rotation axis. The arrangement is arranged. The upstream guide roller 510a is provided on the upstream side of each ink head 110a in the transport direction, is biased downward, is pressed against the upper surface of the transport path, and rotates. On the other hand, the downstream guide roller 510b is provided on the downstream side of each ink head 110a in the transport direction, and is rotatably supported at a predetermined distance from the upper surface of the transport path.

  In correspondence with the staggered arrangement of the ink heads, the upstream guide roller 510a and the downstream guide roller 510b are also staggered. In addition, since the stepped guide roller 510 is disposed in the main direction flow path 111, the upstream guide roller 510a and the downstream guide roller 510b are also alternately disposed in the main direction flow path 111. Become. In the present embodiment, the stepped guide roller 510 is rotatably supported by bearings 520 disposed on both sides of the head holder surface 500 a and has an integrated structure with the head holder 500.

  Next, the paper transport mechanism in the image forming path CR1 will be described. FIG. 5 is a top view showing the paper transport mechanism of the image forming path CR1 according to the present embodiment with a part cut away. As shown in FIG. 5, the image forming path CR <b> 1 includes a platen belt 160, a driving roller 161, a driven roller 162, and a plastic template 620.

  The platen belt 160 is an endless belt member that has a large number of belt holes 165 for adsorbing the printing paper and slides in a range facing the ink head 110a in the conveyance path to convey the printing paper. Specifically, the platen belt 160 is wound around a pair of driving rollers 161 and driven rollers 162 arranged orthogonal to the transport direction, and circulates in the transport direction.

  The platen template 620 supports the platen belt 160 slidably on the upper surface of the platen belt 160 at a position facing the ink head 110a, and has a large number of suction holes 622 that penetrate the belt hole 165. It is a plate-shaped member. Below the plastic template 620, a suction fan is provided as a suction means for generating negative pressure for sucking the printing paper on the top surface of the plastic template 620 through the suction holes 622 and the belt holes 165.

  Further, the suction holes 622 on the upper surface of the plastic template 620 are expanded on the upper surface side of the plastic template 620, so that a large number of recesses 621 that communicate with the suction holes 622 are defined on the upper surface of the plastic template 620. In the present embodiment, the recess 621 is defined independently of other adjacent recesses to form a minute space divided on the upper surface of the plate. These minute spaces have a so-called staggered arrangement, and their ranges do not coincide with each other in the direction perpendicular to the transport direction. In order to prevent this range from matching, a staggered arrangement is employed in this embodiment, but for example, the area and position of the recesses may be changed alternately.

(Prevention of mist from the head holder surface)
In the present embodiment, the head holder surface 500a described above prevents mist generated during ink ejection from adhering to other functional parts. 6 to 8 are explanatory views for preventing mist adhesion by the head holder surface.

  As described above, in the present embodiment, the ink head 110a is held by the head holder surface 500a of the head holder 500, and the space between the ink heads 110a is covered by the head holder surface 500a. Prevents mist from adhering to other functional parts.

  In particular, in this embodiment, the protruding length H of the ink head 110a from the head holder surface 500a is set to be larger than the width L of the main-direction flow path. FIG. 6 is an explanatory diagram for comparing the state of airflow generated around the ink head when the height of the head holder surface 500a is changed.

  As shown in FIG. 6A, when the protrusion length h1 of the ink head is set to be smaller than the width L of the main flow path, the head holder surface 500a, the front and rear ink head side surfaces, and the platen belt The space surrounded by 160 becomes narrower. The mist wound up in such a narrow space is wound up by the stepped guide roller 510. However, since the swirl radius of the swirled vortex is small, the air flow is remarkably attenuated due to the viscous resistance of the vortex, and the mist is It becomes easy to adhere to the nearby head holder surface 500a. On the other hand, in this embodiment, as shown in FIG. 6B, the protrusion length h1 of the ink head is set to be larger than the width L of the main-direction flow path, so that the space becomes wider. The rotation radius of the vortex of the mist wound around the stepped guide roller 510 is increased, and it is possible to reduce the mist from being diffused on the airflow and concentrated and collected in the vicinity of the ink head.

  Further, in the present embodiment, a mesh-like mist discharge path is formed on the head holder surface 500a by the ink head 110a where the staggered pattern is positioned. FIG. 7 is an explanatory view showing the mist air flow generated around the head holder surface 500a, (a) is a plan view showing the lower surface of the head holder 500, and (b) is a mist around the ink head 110a. It is a side view which shows an airflow.

  As shown in FIG. 7A, each column of the ink heads 110a is arranged at a predetermined interval in the transport direction, and a main direction flow path 111 is formed between the columns, and is arranged at a predetermined interval in the same column. Thus, a sub-direction flow path 112 is formed between the ink heads, and the main direction flow path 111 and the sub-direction flow path 112 communicate with each other to form a mesh-like mist discharge path 116. In the columns adjacent to each other in the transport direction, the ink heads 110a are arranged so that both end portions d thereof overlap each other, and 112 included in each column do not overlap each other.

  According to such a mist discharge path, as shown in FIG. 8, a certain space extending in the sub scanning direction and the main scanning direction is formed around the ink head 110a, and the main direction flow path 111 and the sub direction flow are formed. Since the paths 112 communicate with each other in a mesh shape, an air flow path for dissipating ink mist generated during printing can be secured.

  In particular, in the present embodiment, the protrusion length H of the ink head 110a from the head holder surface 500a is set to be larger than the width L of the main direction flow path 111, so that the ink discharge surface and the head of the ink head 110a are set. A space can be secured in the holder surface 500a, and as shown in FIG. 7B, the ink mist ejected from the ink head 110a can be diffused by wind pressure, and the head holder 500 and the ink head 110a can be dispersed. Mist adhesion can be prevented. At this time, in the present embodiment, the stepped guide roller 510 that is pressed against the upper surface of the transport path and rotates is provided in the main-direction flow path 111 on the upstream side of each ink head 110a. The ink mist is rolled up by the roller 510 and can be dissipated by placing the mist on the airflow in the mist discharge path 116.

  Here, the stepped guide roller 510 is configured by connecting an upstream guide roller 510a having a large diameter and a downstream guide roller 510b having a small diameter on the same rotation shaft. The upstream guide roller 510a is provided on the upstream side of the ink head 110a in the conveyance direction of the printing paper, is pressed against the upper surface of the conveyance path and rotated, and the downstream guide roller 510b is disposed on the downstream side of the ink head 110a. Provided, spaced from the upper surface of the transport path by a predetermined distance and not in contact with the upper surface of the paper transport path. For these reasons, the ink mist generated from the upstream ink head 110a flows downstream from the gap around the small-diameter downstream guide roller 510b (arrows f1 and f2 in FIG. 7B) and further downstream. A certain upstream side guide roller 510a rotates while being pressed against the upper surface of the conveyance path, so that a constant rotational speed is maintained by sliding of the platen belt 160. By this rotation, ink mist from the upstream downstream side guide roller 510b is maintained. Can be wound up (arrow f2 in FIG. 7 (b)) and dissipated on the airflow in the mist discharge passage 116.

(A) is a block diagram showing an outline of a printing paper transport path of the printing apparatus according to the present embodiment, and (b) schematically shows a paper feed system transport path FR, a normal path CR, and a reverse path SR. It is explanatory drawing shown. It is explanatory drawing which shows the image formation path | route in which the image formation which concerns on embodiment is performed from a side. (A) is explanatory drawing which shows the head holder arrange | positioned above an image form path | route from the downward direction, (b) is explanatory drawing which expands and shows the side surface of a head holder. (A) is a perspective view which shows the head holder which concerns on embodiment from upper direction, (b) is explanatory drawing which shows a head holder lower surface typically. FIG. 6 is a top view showing the paper transport mechanism of the image forming path according to the embodiment with a part cut away. FIG. 10 is an explanatory diagram comparing the state of airflow generated around the ink head when the height of the head holder surface according to the embodiment is changed. It is explanatory drawing which shows the mist airflow which generate | occur | produced around the head holder surface which concerns on embodiment, (a) is a top view which shows the lower surface of a head holder, (b) shows the mist airflow around an ink head. It is a side view. It is a perspective view which shows a mode that ink mist is dissipated by the mist discharge path which concerns on embodiment.

Explanation of symbols

CR: Normal path DR: Paper discharge path FR: Paper feed system transport path R: Registration section SR ... Reverse path 100 ... Printing device 110 ... Head unit 110a ... Ink head 111 ... Main direction flow path 112 ... Sub-direction flow path 116 ... Mist discharge path 120 ... Side paper feed tray 130 ... Paper feed tray 140 ... Discharge port 150 ... Discharge tray 160 ... Platen belt 161 ... Drive roller 162 ... Driving roller 165 ... Belt hole 170 ... Switching mechanism 172 ... Switching mechanism 220 ... Side paper feed driving unit 230a ... driving unit 230b ... driving unit 240 ... registration driving unit 250 ... belt driving unit 260 ... first upper surface transport driving unit 265 ... second upper surface transport driving unit 270 ... upper surface discharge driving unit 281 ... reverse driving unit 330 ... arithmetic processing unit 340 ... operation panel 500 ... head holder 500a ... head holder surface 50 DESCRIPTION OF SYMBOLS 0b ... Installation opening part 510 ... Step guide roller 510a ... Upstream side guide roller 510b ... Downstream side guide roller 520 ... Bearing part 620 ... Plastic template 621 ... Recessed part 622 ... Suction hole

Claims (4)

A transport mechanism of a printing apparatus that forms an image on the print paper by ejecting ink onto the print paper transported on a transport path,
A plurality of ink heads for ejecting the ink from ejection ports;
An upstream guide roller that is provided on the upstream side of the ink head in the transport direction of the printing paper and that is pressed against the upper surface of the transport path and rotates;
A downstream guide roller provided on the downstream side of the ink head in the transport direction and provided rotatably at a predetermined distance from the upper surface of the transport path;
The conveyance mechanism of a printing apparatus, wherein a diameter of the upstream guide roller is larger than a diameter of the downstream guide roller.   2. The stepped guide roller having the upstream guide roller and the downstream guide roller connected to each other on the same rotation shaft as the upstream guide roller and the downstream guide roller. The conveyance mechanism of the printing apparatus as described in 2. The ink heads are arranged in a plurality of rows in a direction perpendicular to the transport direction, and the ink heads included in each row in the plurality of rows overlap with the ink heads included in other adjacent rows in the transport direction. It is arranged in a staggered pattern so that there is no part,
The transport mechanism of the printing apparatus according to claim 1, wherein the upstream guide roller and the downstream guide roller have a staggered arrangement corresponding to the arrangement of each ink head. Each row of the ink heads is arranged at a predetermined interval in the transport direction, forming a main direction flow path between the rows,
The transport mechanism of the printing apparatus according to claim 1, wherein the upstream guide roller and the downstream guide roller are disposed in the main direction flow path.