Image forming system

Abstract

Accurately detects the transport direction of the recording medium. [Solution] The image forming system comprises a print belt unit 20 for transporting a sheet, and a recording head (10) for forming an image on the sheet transported by the print belt unit 20. The print belt unit 20 includes an endless print belt 25 that transports the sheet by rotating, a recording head positioning member 40 provided at the end of the print belt 25 in the width direction intersecting a reference direction (33), which is the ideal transport direction of the sheet, a belt position detection member 30 for detecting the position of the end of the print belt 25 in the width direction, and a control unit (70) that detects the transport direction of the sheet by the print belt 25 based on the detection result by the belt position detection member 30. The recording head (10) and the belt position detection member 30 are attached to the recording head positioning member 40.

Description

Technical Field

[0001] The present invention relates to an image forming system that forms an image on a recording medium conveyed by a belt member.

Background Art

[0002] An image forming system forms an image on a recording medium, which is an object to be printed and made of paper or resin. Such an image forming apparatus includes, for example, an inkjet recording apparatus that forms an image by ejecting ink droplets onto the recording medium. The inkjet recording apparatus includes a line head type recording apparatus that performs recording (printing) on the recording medium by ejecting ink droplets from a recording head fixed to the conveyed recording medium.

[0003] The conveyance of the recording medium is performed, for example, using an endless belt. The belt is stretched over a plurality of rollers and is driven by the rotation of the rollers to convey the recording medium. In order to print a high-quality image on the recording medium with high precision, the conveyance of the recording medium by the endless belt needs to be controlled with high precision. When using a plurality of recording heads, it is necessary to accurately align the position (alignment direction) of each recording head with the conveyance direction of the belt. This is because if the positions of the plurality of recording heads and the conveyance direction of the belt are misaligned, for example, misalignment of the images for each color occurs in the direction intersecting the conveyance direction (width direction).

[0004] Patent Document 1 discloses a belt conveyance device that controls the rotation direction (recording medium conveyance direction) of a belt by moving the belt in the width direction based on the detection result of the position of the belt end in the width direction. The position of the belt end is detected using a plurality of sensors provided at the belt end. The control of the conveyance direction is performed by moving the roller on which the belt is suspended in the roller axis direction (width direction). Patent Document 2 discloses a technique for adjusting the position of the belt by swinging one end of the roller.

Prior Art Documents

Patent Documents

[0005] [Patent Document 1] Japanese Patent Publication No. 2004-123349 [Patent Document 2] Japanese Patent Publication No. 2010-176125 [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] Multiple sensors that detect the belt end position are replaced due to aging or malfunction. Sensor replacement can introduce individual differences and mounting errors, potentially leading to errors in the detection of the belt end position. Furthermore, numerous actuators are used to transport the endless belt. Vibrations generated by these actuators can also cause errors in the sensor detection values. These errors make it difficult to accurately control the direction of transport of the recording medium by the belt. To suppress errors in detection values, a configuration in which the sensors are fixed to the belt is desired.

[0007] In view of the above-mentioned problems, the primary objective of the present invention is to provide an image forming system for accurately detecting the transport direction of a recording medium. [Means for solving the problem]

[0008] The image forming system of the present invention comprises a transport means for transporting a recording medium, and an image forming means for forming an image on the recording medium transported by the transport means, wherein the transport means includes an endless belt member that transports the recording medium by rotating, a positioning member provided at the end of the belt member in the width direction intersecting a reference direction which is the ideal transport direction of the recording medium, a detection means for detecting the position of the end of the belt member in the width direction, and a control means for detecting the transport direction of the recording medium by the belt member based on the detection result by the detection means, wherein the positioning member has a shape that extends linearly in the reference direction, and the image forming means and the detection means are attached to the positioning member. [Effects of the Invention]

[0009] According to the present invention, it becomes possible to accurately detect the transport direction of the recording medium. [Brief explanation of the drawing]

[0010] [Figure 1] Configuration diagram of an inkjet recording device. [Figure 2] A diagram illustrating the configuration of a printed circuit board. [Figure 3] Top view of the printed belt unit. [Figure 4] A diagram illustrating the positional relationship between the recording head and the sheet. [Figure 5] An explanatory diagram of the method for detecting the position of a printed belt in the width direction. [Figure 6] (a) and (b) are explanatory diagrams for conveying direction control. [Figure 7] An example diagram of the control unit configuration. [Figure 8] Installation diagram for the belt position detection component. [Figure 9] Installation diagram for the belt position detection component. [Modes for carrying out the invention]

[0011] Preferred embodiments of the present invention will be described below with reference to the attached drawings.

[0012] (Inkjet recording device) Figure 1 is a diagram showing the configuration of an inkjet recording device, which is an image forming system according to this embodiment. This inkjet recording device 100 is a printing press used, for example, in the commercial printing or industrial printing fields. The inkjet recording device 100 forms an image by ejecting ink droplets onto a sheet, which is a cut-sheet-shaped recording medium. The inkjet recording device 100 of this embodiment produces a finished product by forming an ink image on the sheet using two liquids, a reaction solution and ink. The sheet can be any ink-receiving recording medium, such as plain paper, cardboard, plastic film for overhead projectors, specially shaped sheets such as envelopes or index paper, or cloth.

[0013] The inkjet recording apparatus 100 includes a paper feeding module 1000, a printing module 2000, a drying module 3000, a fixing module 4000, a cooling module 5000, a reversing module 6000, and a paper discharging and stacking module 7000. The sheet is supplied from the paper feeding module 1000, predetermined processing related to image formation is performed in each module, and the sheet is discharged to the paper discharging and stacking module 7000. In the inkjet recording apparatus 100 of the present embodiment, each module has a separate housing, and the housings are connected to each other. Note that the inkjet recording apparatus 100 may incorporate the functions of each module in one housing.

[0014] The paper feeding module 1000 feeds the sheets one by one to the printing module 2000. The printing module 2000 functions as an image forming apparatus that forms an image by ejecting ink droplets onto the sheet fed from the paper feeding module 1000. The drying module 3000 dries the sheet by blowing warm air onto the sheet on which the ink image has been formed by the printing module 2000. The drying module 3000 reduces the liquid component contained in the ink by drying the sheet, thereby improving the fixing property between the sheet and the ink. As the drying method, for example, a method of applying hot air, a method of irradiating electromagnetic waves (such as ultraviolet rays and infrared rays) onto the sheet surface, any one of conduction heat transfer methods by contact with a heating element, or a combination of these methods can be adopted.

[0015] The fixing module 4000 fixes the image (ink image) onto the sheet by heating the sheet dried by the drying module 3000 to dry the ink. The cooling module 5000 cools the sheet on which the image has been fixed by the fixing module 4000, thereby solidifying the ink softened by heating and suppressing the temperature change of the sheet by the downstream apparatus.

[0016] The inversion module 6000 can invert the front and back surfaces of the conveyed sheet. Thereby, the orientation of the front and back surfaces of the discharged sheet can be changed. The paper discharge stacking module 7000 aligns and stacks the sheets conveyed from the inversion module 6000.

[0017] (Print Module) Figure 2 is a configuration diagram of the print module 2000. The print module 2000 includes a plurality of recording heads 10 and a print belt unit 20. The sheet S is sucked and adsorbed by the print belt unit 20 and conveyed, so that the conveying behavior is stabilized directly below the recording head 10. The sheet S is printed directly below the recording head 10 which is an image forming unit.

[0018] The print belt unit 20 includes a print belt 25 which is an endless belt member stretched around four stretching rollers 21, 22, 23, and 24. The belt surface of the print belt 25 stretched between the stretching roller 21 and the stretching roller 24 becomes an image forming surface 26 for performing image formation directly below the recording head 10. The print belt 25 rotates so that the image forming surface 26 moves in the conveying direction of the sheet S. The print belt 25 is provided with a large number of suction holes (not shown) for sucking the sheet S.

[0019] The print belt 25 sucks and adsorbs the sheet S through the suction holes located on the image forming surface 26, and conveys the adsorbed sheet S by rotating. That is, the image forming surface 26 is also a conveying surface for conveying the sheet S. The print belt 25 is created, for example, by forming suction holes in a strip-shaped single PET sheet wound in a roll shape, cutting it to a predetermined length, and then joining the ends by laser welding.

[0020] The sheet S, adsorbed onto the image forming surface 26, is transported with a predetermined clearance between it and the recording head 10. The multiple recording heads 10 constitute eight line-type recording heads, each corresponding to one of four colors (Y (yellow), M (magenta), C (cyan), and K (black)), as well as a reaction solution and three special colors, along the ideal transport direction (reference direction) of the sheet S. The inkjet method of the print module 2000 can employ methods using heating elements, piezoelectric elements, electrostatic elements, MEMS (Micro Electro Mechanical Systems) elements, etc. Ink for each color is supplied to the recording head from an ink tank (not shown) via an ink tube. The ink contains, for example, 0.1% to 20.0% by mass of resin components, water, water-soluble organic solvents, colorants, waxes, additives, etc., based on the total mass.

[0021] (Printed belt unit) As described above, the print belt unit 20 transports the sheet S by suction and adsorption onto the image forming surface 26 of the print belt 25. On the inner surface of the image forming surface 26 of the print belt 25, a platen (not shown) and a suction box supporting the platen are provided to make the image forming surface 26 flat. The suction box is kept under negative pressure relative to the atmosphere by a fan unit 50 provided on the inner surface side of the print belt 25. The suction box draws in air through the suction holes due to the negative pressure. As a result, the sheet S is adsorbed onto the image forming surface 26 of the print belt 25. The print belt 25 rotates with the tension roller 21 as the drive roller so that the image forming surface 26 moves in the direction of transport of the sheet S.

[0022] Figure 3 is a top view of the print belt unit 20 as seen from the recording head 10 side. The tension roller 21, which acts as a drive roller, is rotationally driven by the belt drive motor 28. When the tension roller 21 is rotationally driven, the print belt 25 starts to rotate and convey the sheet S. The belt drive motor 28 is provided at one end of the print belt 25 in a direction intersecting the reference direction (hereinafter referred to as the "width direction"). In Figure 3, the belt drive motor 28 is provided at the far end of the print belt 25 as shown in Figure 2.

[0023] The print belt unit 20 includes recording head positioning members 40 and 41 that extend linearly in the reference direction along both ends of the print belt 25 in the width direction. In Figure 3, the recording head positioning member 40 is provided on the belt drive motor 28 side, and the recording head positioning member 41 is provided on the front side in Figure 2. The recording head positioning members 40 and 41 include a plurality of spheres. The plurality of spheres are arranged linearly along the reference direction. The recording head 10 has three locations: a conical hole (not shown), a V-shaped section, and a flat surface. The mounting position of the recording head 10 is determined by the plurality of spheres provided on the recording head positioning members 40 and 41, and the three locations: the conical hole, the V-shaped section, and the flat surface. The recording head positioning members 40 and 41 and the tension rollers 21 and 24 are incorporated into the print belt unit 20 with high precision adjustment of their positions.

[0024] Figure 4 is an explanatory diagram of the positional relationship between the recording head 10 and the sheet S. In the example in Figure 4, the position of the recording head 10 in the width direction is determined by the recording head positioning member 40. In this case, the positioning center line 45, which connects the centers in the width direction of the sphere of the recording head positioning member 40, and the line 48, which connects the image write position that serves as the reference position for the ink ejection position of each recording head 10, are kept parallel. Line 48 is a line parallel to the reference direction.

[0025] To form an image on the conveyed sheet S, any deviation in the conveying direction relative to the reference direction results in a positional shift of the image in the width direction of each recording head 10. Therefore, the recording head positioning members 40, 41, tension rollers 21, 24, etc., must be mounted with high precision. The recording head 10 may fluctuate in position due to vibrations generated by actuators, etc. For this reason, the recording head 10 is positioned and pressurized by the recording head positioning members 40, 41 to suppress positional fluctuations.

[0026] In this embodiment, one recording head 10 has a capacity of approximately 10 kgf / cm². 2 The recording head is pressed against the recording head positioning members 40 and 41 by the applied pressure of the actuator. This reduces the fluctuation in the position of the recording head 10 due to actuator vibration. The recording head positioning members 40 and 41 are made of blocks of a highly rigid material (for example, metal) so that they do not deform even when the recording head 10 is pressed against them.

[0027] (Conveyor direction control) In order to control the conveying direction of the sheet S by the printed belt 25, it is necessary to accurately detect the position of the end of the printed belt 25 in the width direction. In this embodiment, the printed belt unit 20 includes belt position detection members 30a, 30b, and 30c for detecting the position of the end of the printed belt 25 in the width direction, as shown in Figure 3. When distinction between the belt position detection members 30a, 30b, and 30c is not necessary, they are referred to as "belt position detection member 30".

[0028] Figure 5 is an explanatory diagram of the method for detecting the position of the printed belt 25 in the width direction. To detect the position of the end in the width direction, multiple belt position detection holes 32 are provided at the end of the printed belt 25 in the width direction. The belt position detection holes 32 have a diameter of, for example, about 1 [mm] and are provided around the entire circumference of the printed belt 25 at intervals of about 6 [mm] in the conveying direction of the sheet S.

[0029] The belt position detection member 30 reads the belt position detection hole 32 using an optical sensor, such as a CIS (Contact Image Sensor) type. Based on the reading result of the belt position detection hole 32 by the optical sensor, the belt position detection member 30 detects the center position of the belt position detection hole 32. The detected center position of the belt position detection hole 32 becomes the detection result of the end position in the width direction of the printed belt 25.

[0030] The belt position detection holes 32 are numbered. In the example in Figure 5, the belt position detection holes are 32a to 32z. The belt position detection hole where the spacing is larger than normal (e.g., 1.5 times or more) is numbered as the home position, starting with 1. In Figure 5, the spacing between belt position detection hole 32z and belt position detection hole 32a is larger than normal, and belt position detection hole 32a is numbered as the home position, starting with 1.

[0031] Figure 6 is an explanatory diagram of conveyance direction control. The conveyance direction of the sheet S is the same as the rotation direction (belt conveyance direction) of the print belt 25, and is adjusted by adjusting the belt conveyance direction. The print belt unit 20 is equipped with a roller oscillation drive source 60 and a roller oscillation cam 65 at one end in the width direction of each tension roller 21 and tension roller 24 in order to adjust the belt conveyance direction. The tension roller 21 and tension roller 24 are configured so that one end in the width direction on which the roller oscillation cam 65 is provided oscillates with respect to the other end in the width direction of each.

[0032] Based on the difference in the positions of the widthwise ends of the printed belt 25 detected by the belt position detection members 30a and 30c, the inclination of the belt transport direction with respect to the reference direction 33 is detected. The reference direction 33 is the same direction as the alignment of the multiple spheres of the recording head positioning member 40. ru.

[0033] As shown in Figure 6(a), when the printed belt 25 is conveyed at an angle with respect to the reference direction 33, the roller oscillation drive source 60 is driven so that the angle (difference) becomes a predetermined target value. When the roller oscillation drive source 60 is driven, the roller oscillation cam 65 rotates and the tension rollers 21 and 24 oscillate. Due to the oscillation of the tension rollers 21 and 24, the printed belt 25 is controlled to a state where there is no angle (difference) with respect to the reference direction 33, as shown in Figure 6(b). The target value of the angle (difference) is, for example, 0. In this way, the belt conveying direction is adjusted to match the reference direction 33 based on the detection results of the belt position detection members 30a and 30c.

[0034] Figure 7 is an example diagram of the configuration of a control unit that controls the transport direction of such a printed belt 25. The control unit 70 is built into, for example, the printed belt unit 20.

[0035] The control unit 70 has a memory 71. The memory 71 stores the position detection results of the belt position detection holes 32a to 32z. The position detection results are stored in association with the numbering of each belt position detection hole 32a to 32z. The control unit 70 is configured by, for example, a CPU (Central Processing Unit), an MPU (Micro-Processing Unit), etc., executing a computer program. Alternatively, the control unit 70 may be implemented by an ASIC (Application Specific Integrated Circuit) or a SOC (System-On-a-Chip). The memory 71 is, for example, RAM (Random Access Memory).

[0036] The control unit 70 is connected to the belt drive motor 28 described in Figure 3, the two roller oscillation drive sources 60 described in Figure 6, and the belt position detection members 30a, 30b, and 30c. Each belt position detection member 30a, 30b, and 30c is provided with optical sensors 31a, 31b, and 31c for reading the belt position detection hole 32.

[0037] The control unit 70 rotates the printed belt 25 using the belt drive motor 28. The control unit 70 detects the amount of inclination of the belt conveying direction relative to the reference direction according to the position of the belt position detection hole 32 detected by the belt position detection members 30a, 30b, and 30c. The control unit 70 controls the inclination of the belt conveying direction by driving the roller swing drive source 60 to swing the tension rollers 21 and 24 according to the detected amount of inclination.

[0038] (Installation of belt position detection member) Controlling the belt transport direction is important to suppress color shifts caused by positional misalignments of images of each color formed by multiple recording heads 10. As described above, the belt transport direction is detected based on the detection results of multiple belt position detection holes 32 by multiple belt position detection members 30a to 30c.

[0039] The belt position detection members 30a to 30c are installed with high precision, adjusted to the position of the recording head positioning members 40 and 41. The print belt unit 20 is equipped with many actuators, such as the belt drive motor 28 and the fan unit 50. For this reason, the belt position detection members 30a to 30c need to be installed in a highly rigid location that is not affected by the vibrations of the actuators.

[0040] Figures 8 and 9 are explanatory diagrams for the installation of the belt position detection members 30a to 30c. As described above, the belt position detection members 30a to 30c are attached to the recording head positioning member 40 provided inside the print belt unit 20.

[0041] As shown in Figure 9, the belt position detection members 30a to 30c are attached to the base plate 34. The base plate 34 is a member that extends in the same reference direction as the recording head positioning member 40. The belt position detection members 30a to 30c and the base plate 34 are unitized and integrated, making maintenance such as parts replacement easy. The recording head positioning member 40 has a height adjustment plate 35. A retaining plate 36 is provided on the height adjustment plate 35. The height adjustment plate 35 is a member for adjusting the distance between the print belt 25 and the belt position detection members 30a to 30c. The retaining plate 36 is a member for sandwiching and fixing the base plate 34 between itself and the height adjustment plate 35. The base plate 34 is provided with an opening 34a into which the retaining plate 36 is inserted. In Figure 9, the retaining plate 36 is inserted into the opening 34a, and the base plate 34 is moved from top to bottom, so that the base plate 34 is fitted between the height adjustment plate 35 and the retaining plate 36.

[0042] The base plate 34 is fitted between the height adjustment plate 35 and the retaining plate 36, thereby fixing the belt position detection members 30a to 30c to the recording head positioning member 40. In this way, the belt position detection members 30a to 30c are fixed to the recording head positioning member 40 with the height adjustment plate 35 acting as the positioning member.

[0043] In this configuration, the base plate 34 is attached to the height adjustment plate 35 without any gaps by the retaining plate 36. As a result, the belt position detection members 30a to 30c can be attached to the recording head positioning member 40 with high precision. This ensures that the belt position detection members 30a to 30c are positioned precisely in the predetermined location within the print belt unit 20. Furthermore, because the recording head positioning member 40 has high rigidity, the effects of vibrations from actuators such as the belt drive motor 28 and the fan unit 50 are minimized.

[0044] Although a base plate 34 and height adjustment plate 35 are provided to maintain maintainability, these are not essential components. Therefore, even if the belt position detection member 30 is directly attached to the recording head positioning member 40, it can be fixed with high precision.

[0045] With the above configuration, the recording head positioning member 40 is used as a common position reference member, and the belt position detection member 30 and the recording head 10 are positioned accordingly. Therefore, the relative positional relationship between the recording head 10 and the belt position detection member 30 does not change, for example, even if the belt position detection member 30 is replaced. Furthermore, since the recording head positioning member 40 is provided at the end of the print belt 25 in the width direction, the relative positional relationship between the belt position detection member 30 and the print belt 25 also does not change even if the belt position detection member 30 is replaced.

[0046] Due to this configuration, the degree of inclination in the belt conveying direction is detected with high precision. As a result, the belt conveying direction can be controlled with high precision. This high-precision control of the belt conveying direction allows for high-precision control of the image formation position, suppressing image quality degradation such as color shift.

[0047] In this embodiment, an example in which the print belt unit 20 is provided in an inkjet type print module 2000 has been described. The print belt unit 20 of this embodiment is also effective when provided in other devices such as electrophotographic image forming systems. The above configuration is effective as long as the print belt unit 20 is configured to form an image on a recording medium conveyed by a belt member such as a print belt 25.

Claims

1. A transport means for transporting a recording medium, The system comprises an image forming means for forming an image on the recording medium transported by the transport means, The aforementioned conveying means is An endless belt member that transports the recording medium by rotating, A positioning member is provided at the end of the belt member in the width direction intersecting the reference direction, which is the ideal transport direction of the recording medium, A detection means for detecting the position of the end of the belt member in the width direction, The system includes a control means for detecting the direction of transport of the recording medium by the belt member based on the detection result by the detection means, The positioning member has a shape that extends linearly in the reference direction, The image forming means and the detection means are characterized by being attached to the positioning member. Image forming system.

2. It includes a base plate to which the aforementioned detection means is attached, The base plate is characterized by being attached to the positioning member. The image forming system according to claim 1.

3. The positioning member has an adjustment plate for adjusting the distance between the belt member and the detection means. The adjustment plate is characterized by having a retaining plate for sandwiching and fixing the base plate between itself and the adjustment plate. The image forming system according to claim 2.

4. The base plate is characterized in that a plurality of the detection means are attached to it. The image forming system according to claim 3.

5. The positioning member includes a plurality of spheres arranged in a straight line in the reference direction, The image forming means has a conical hole, a V-shaped portion, and a plane, The image forming means is characterized in that the mounting position to the positioning member is determined by the plurality of spheres, the conical hole, the V-shaped portion, and the plane. The image forming system according to claim 1.

6. The device is characterized by having an adjustment means for adjusting the rotation direction of the belt member to match the reference direction based on the detection result of the transport direction. The image forming system according to claim 5.

7. The belt member is equipped with a plurality of tension rollers for rotating the belt member, The adjustment means is characterized by adjusting the rotational direction of the belt member by swinging each end of the plurality of tension rollers. The image forming system according to claim 6.

8. The belt member has a plurality of position detection holes at its end in the width direction, The detection means is characterized by detecting the positions of the plurality of position detection holes and detecting the position of the end of the belt member in the width direction based on the detected positions. The image forming system according to claim 1.

9. The belt member is characterized by suctioning and adsorbing the recording medium and transporting it. The image forming system according to claim 1.

10. The image forming means is characterized in that a plurality of recording heads are arranged in the transport direction at a predetermined distance from the surface of the belt member to which the recording medium is attracted and adsorbed, and an image is formed on the recording medium by an inkjet method. The image forming system according to claim 9.

Images