Belt conveying device

Abstract

This allows for calibration of the belt-side control sensor even after the belt has been installed. [Solution] The belt has a plurality of first holes for detecting belt position and a second hole that is larger than the first holes and is used for calibration.

Description

Technical Field

[0001] The present invention relates to a belt conveyance device and an image forming apparatus including the same.

Background Art

[0002] In recent years, in the fields of commercial printing and industrial printing where analog printing such as offset printing is currently the mainstream, the need for an inkjet recording method as digital printing that can print small quantities of various designs without requiring a plate has been increasing. This inkjet recording method has many advantages such as the use of plain paper cut as a recording medium and the ability to print non-contact and high-quality products, so it has become extremely popular. And in order to print high-quality products, it is necessary to eject inkjets accurately onto the recording medium, so it is necessary to correct the meandering of the belt that conveys the recording medium with high precision. Hereinafter, the correction control of the meandering of the belt is referred to as belt-side control.

[0003] In a conventional belt-side control system, a home position sensor that detects a circumferential position detection mark provided on the belt is provided, and shape data of the belt end corresponding to the circumferential position based on the home position is acquired and stored in advance for one revolution. By doing so, the belt end shape component detected by the edge sensor is canceled, and belt-side control has been performed (Patent Document 1).

[0004] However, the shape data of the belt end is acquired in a state where the speed of the belt is set to a predetermined target speed. Therefore, if the speed of the belt during belt-side control deviates from the target speed, the position of the shape data of the belt end and the detection position of the edge sensor will deviate, and the shape component of the belt end cannot be completely canceled, resulting in a correction error.

[0005] Therefore, the following configuration has been proposed to perform belt alignment control without being affected by the shape of the belt end. Specifically, belt alignment control holes, which are provided at equal intervals in the circumferential direction of the belt, are detected by a belt alignment detection sensor consisting of a CIS (Contact Image Sensor) and an LED. This configuration has been proposed to perform belt alignment control with high precision. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2013-29630 [Overview of the Initiative] [Problems that the invention aims to solve]

[0007] Sensors composed of CIS and LEDs typically undergo calibration to compensate for variations in the sensitivity of each pixel in the CIS and the light intensity of the LEDs. However, calibration requires that the light emitted from the LEDs be received by all pixels in the CIS, which necessitates a state where there is nothing between the CIS and the LEDs, as shown in Figure 5(a). However, when a belt alignment detection sensor is placed on a sheet conveying device, as shown in Figure 6, the conveying belt is present between the CIS and the LEDs. The size of the holes for belt alignment control is set to a small size to improve detection accuracy. Therefore, even if light intensity correction is attempted through the holes for belt alignment control, it is not possible to receive light at all pixels in the CIS. Consequently, calibration can only be performed before assembly into the belt conveying device, i.e., before the product is shipped. Therefore, if the light intensity of the LEDs decreases over time, or if the sensitivity variations of each pixel in the CIS change due to dirt or other factors from the time of shipment, there is a risk that the position of the holes for belt alignment control may not be detected accurately.

[0008] Therefore, the object of the present invention is to provide a belt conveying device that can be easily calibrated even after the belt has been assembled to the belt conveying device, while suppressing a decrease in the accuracy of belt deviation detection. [Means for solving the problem]

[0009] To achieve the above objective, the belt conveying device according to the present invention comprises a belt for conveying a recording medium, a plurality of openings provided on the belt and arranged at predetermined intervals along the circumferential direction of the belt, a light-emitting unit that emits light toward the plurality of openings, and a light-receiving unit that receives light emitted from the light-emitting unit, with a plurality of light-receiving elements arranged along the belt width direction perpendicular to the circumferential direction of the belt at a position opposite the light-emitting unit across the belt, wherein the plurality of openings are a plurality of first openings arranged along the circumferential direction of the belt, wherein the opening width in the width direction of the belt is smaller than the width of the light-receiving area of ​​the light-receiving unit in the width direction of the belt, and the opening width in the width direction of the belt is larger than the width of the light-receiving area of ​​the second opening. [Effects of the Invention]

[0010] According to the present invention, it is possible to provide a belt conveying device that can be easily calibrated even after the belt has been assembled to the belt conveying device, while suppressing a decrease in the accuracy of belt deviation detection. [Brief explanation of the drawing]

[0011] [Figure 1] Schematic diagram of an image forming apparatus [Figure 2] Cross-sectional view of the belt unit [Figure 3] Belt unit perspective view [Figure 4] Block diagram of belt-side control [Figure 5] Cross-sectional view of the belt-side detection sensor [Figure 6] Belt proximity detection sensor layout diagram [Figure 7] Diagram explaining belt-side control [Figure 8] Diagram illustrating the sensor level of the belt-side detection sensor. [Figure 9] Calibration execution flowchart for belt-side detection sensor [Figure 10] Flowchart for belt stop control in calibration hole [Modes for carrying out the invention]

[0012] An embodiment of the image forming apparatus according to the present invention will be described in detail. Note that the dimensions, materials, and relative positions of the components of the image forming apparatus shown below do not limit the scope of the present invention to those components unless otherwise specifically stated. Furthermore, components denoted by the same reference numerals in the figures have the same configuration or function, and redundant explanations of these components will be omitted as appropriate.

[0013] <Image forming apparatus> Figure 1 is a schematic diagram showing an example of the general configuration of an inkjet recording device. This inkjet recording device uses two liquids, a reaction solution and ink, to form an ink image on a sheet S.

[0014] The inkjet recording device of this embodiment comprises the following modules: a paper feed module 1000, a print module 2000, a drying module 3000, a fixing module 4000, a cooling module 5000, a reversing module 6000, and a paper discharge and stacking module 7000. Cut sheets S supplied from the paper feed module 1000 are transported along the transport path, processed in each module, and discharged to the paper discharge and stacking module 7000.

[0015] The paper feeding module 1000 has three storage bins 1100a to 1100c for storing the sheets S, and the storage bins 1100a to 1100c are configured to be pulled out toward the front side of the apparatus. The sheets S are fed one by one in each of the storage bins 1100a to 1100c by a separation belt and a conveyance roller, and are conveyed to the printing module 2000. Note that the number of the storage bins 1100a to 1100c is not limited to three, and a configuration having one, two, or four or more may be employed.

[0016] The printing module 2000 includes a pre-image registration correction unit (not shown), a printing belt unit 2200, and a recording unit 2300. The sheet S conveyed from the paper feeding module 1000 is corrected for the inclination and position of the sheet by the pre-image registration correction unit and is conveyed to the printing belt unit 2200. The recording unit 2300 is disposed at a position facing the printing belt unit 2200 with respect to the conveyance path. The recording unit 2300 is a sheet processing unit that forms an image by performing a recording process (printing) on the conveyed sheet S from above by a recording head 24,00. The sheet S is adsorbed and conveyed by the printing belt unit 2200, thereby ensuring a clearance with the recording head 2400. Further, a plurality of recording heads 2400 are arranged along the conveyance direction. In this example, in addition to four colors of Y (yellow), M (magenta), C (cyan), and Bk (black), there are a total of eight line-type recording heads 2400 corresponding to the reaction liquid and three special features. Note that the number of colors and the number of the recording heads 2400 are not limited to eight. The inkjet method can employ a method using a heating element, a method using a piezo element, a method using an electrostatic element, a method using a MEMS element, or the like. The ink of each color is supplied from an ink tank (not shown) to the recording head 2400 through an ink tube. The sheet S printed by the recording unit 2300 is conveyed by the printing belt unit 2200. Then, the deviation and color density of the image formed on the sheet S can be detected by an in-line scanner (not shown) disposed on the downstream side in the conveyance direction of the recording unit 2300, and the printed image can be corrected.

[0017] The drying module 3000 includes a decoupling unit 3200, a drying belt unit 3300, and a warm air blowing unit 3400. It is a unit that reduces the liquid content in the ink applied on the sheet S by the recording unit 2300 and enhances the fixing property between the sheet S and the ink. The sheet S printed by the recording unit 2300 of the printing module 2000 is conveyed to the decoupling unit 3200 disposed within the drying module 3000. In the decoupling unit 3200, the sheet S can be conveyed by the air pressure from above and the friction of the belt. By weakly holding and conveying the sheet S on the belt, the deviation of the sheet S on the printing belt unit 2200 that forms the ink image is prevented. The sheet S conveyed from the decoupling unit 3200 is adsorbed and conveyed by the drying belt unit 3300, and at the same time, hot air is applied from the warm air blowing unit 3400 disposed above the belt to dry the ink-applied surface of the sheet S. In addition to the method of applying hot air, the drying method may be configured by combining a method of irradiating the surface of the sheet S with electromagnetic waves (such as ultraviolet rays and infrared rays) or a method of conduction heat transfer by contact with a heating element.

[0018] The fixing module 4000 includes a fixing belt unit 4100 and can fix the ink to the sheet S by passing the sheet S conveyed from the drying module 3000 between the heated upper belt unit and the lower belt unit.

[0019] The cooling module 5000 has multiple cooling units 5100 and cools the high-temperature sheet S transported from the fuser module 4000. The cooling unit 5100 is configured to draw outside air into the cooling box with a fan, increase the pressure inside the cooling box, and cool the sheet S by blowing air from nozzles formed in the transport guide onto the sheet S. The cooling units 5100 are arranged on both sides of the transport path, so that the sheet S can be cooled from both sides. The cooling module 5000 also has a transport path switching unit, which can switch the transport path of the sheet S depending on whether the sheet S is being transported to the inversion module 6000 or to the double-sided transport path used during double-sided printing. During double-sided printing, the sheet S is transported to the transport path below the cooling module 5000. The sheet S then passes through the fuser module 4000, and the front and back sides of the sheet S are inverted at the inversion unit 1 (4200) of the fuser module 4000. Subsequently, the sheet S is further transported along the double-sided transport path of the drying module 3000, print module 2000, and paper feed module 1000. Then, the sheet S is transported again to the pre-image registration correction unit, print belt unit 2200, and recording unit 2300 of the print module 2000, where it is printed by the recording head 2400.

[0020] The reversal module 6000 has a reversal unit 2 (6400) that can reverse the front and back sides of the conveyed sheet S, and the orientation of the ejected sheet S can be freely changed.

[0021] The paper output and stacking module 7000 has a top tray 7200 and a stacking section 7500, and aligns and stacks the sheets S transported from the reversing module 6000.

[0022] <Print Module> Figure 2 is a cross-sectional view of the image forming section of the print module 2000. The print module 2000 is an image forming section that forms an image on a conveyed sheet S by recording processing from above by the recording section 2300. To ensure stable conveyance of the sheet S in the image forming section, a print belt unit 2200 is arranged as a belt conveying device that suctions and picks up the sheet S for conveyance. In this embodiment, the print belt unit 2200 has a print belt 25 stretched by four tension rollers 21 to 24. Image formation is performed on the belt surface stretched by tension rollers 21 and 24 directly below the recording section 2300 of the print belt unit 2200, so this surface is designated as the image forming surface 26. The print belt 25 has suction holes for sucking up the sheet S, and the sheet S is suctioned and picked up on the image forming surface 26 in the inward direction of the print belt 25 (direction of arrow A in the figure) for conveyance.

[0023] The sheet S being transported on the image-forming surface 26 is transported with clearance ensured between it and the recording unit 2300. The recording unit 2300 has multiple recording heads 2400 arranged along the paper transport direction. In this embodiment, in addition to the four colors of black, yellow, magenta, and cyan, there are eight line-type recording heads 2400 corresponding to the reaction solution and three special colors. The inkjet method can employ a method using a heating element, a method using a piezoelectric element, a method using an electrostatic element, a method using a MEMS element, etc. Ink for each color is supplied to the recording head 2400 from an ink tank (not shown) via an ink tube.

[0024] <Printed Belt Unit> Next, the control of the print belt unit 2200 in the belt width direction in this embodiment will be described. The belt width is the direction perpendicular to the conveying direction of the sheet S. Figure 3 shows a schematic perspective view of the print belt unit 2200. In the print belt unit 2200 in this embodiment, there are tension rollers 21 to 24 that tension the print belt 25. The tension roller 21 is a drive roller that rotates the print belt 25 and is operated by a belt drive motor 51. The tension roller 22 is a tension roller that applies force to the print belt 25 from the inner surface outward to tension the belt. The tension roller 23 is a steering roller that can move one shaft end of the roller and tilt the roller in order to suppress meandering of the print belt 25. The tension roller 23 is operated by a steering motor 50. The tension roller 24 is a driven roller that follows the rotation of the print belt 25. A belt position detection sensor 30 is placed to read the belt position detection hole 35 located at the end of the print belt 25 near the tension roller 24. Since the sheet S is adsorbed to the image forming surface 26, the image accuracy can be improved by precisely positioning the image forming surface 26. To achieve this, the steering motor 50 is operated based on the belt position detection result of the belt position detection sensor 30, and the position of the print belt 25 is adjusted, thereby precisely positioning the entire image forming surface 26.

[0025] The belt position detection holes 35 are multiple openings for detecting the belt position, provided at the end of the printed belt 25 and arranged at predetermined intervals along the circumferential direction of the belt. In this embodiment, for detecting the belt position, holes of approximately Φ1 mm are provided as belt position detection holes 35 at intervals of approximately 6 mm around the circumference of the printed belt 25. As shown in Figure 5(b), the belt position detection sensor 30 consists of a CIS (Contact Image Sensor) as a light-receiving unit and an LED as a light-emitting unit. The CIS has multiple light-receiving elements arranged along the width direction of the belt, and the area where multiple light-receiving elements are arranged is the light-receiving area of ​​the CIS. Using this sensor, the holes of the belt position detection holes 35 are read, the center position of the holes is calculated, and this is used as the belt position detection result.

[0026] By controlling the belt position so that the position in the belt width direction detected by the belt position detection sensor 30 is the same, belt meandering (deviation in the belt width direction) can be corrected by the steering control described later.

[0027] <Belt-side control block diagram> Next, we will explain the belt position control using the belt position detection sensor 30. Figure 4 is a block diagram of the belt alignment control. The control unit 70 includes a CPU 100, a ROM 101, and a RAM 102. The CPU 100 is a control circuit that controls the printed belt unit 2200. The ROM 101 stores control programs for controlling various processes performed by the printed belt unit 2200. The RAM 102 is a system work memory for the operation of the CPU 100 and also functions as a memory for temporarily storing calculation results of the belt alignment control.

[0028] The belt drive motor 51 is a motor for driving the tension roller 21 that rotates the printed belt 25. The CPU 100 controls the rotation speed of the printed belt 25 by controlling the belt drive motor 51.

[0029] The detection signal from the belt position detection sensor 30 is transmitted to the CPU 100, where it performs calculations and calculates the steering amount for controlling the steering motor 50 based on the detection signal.

[0030] The CPU 100 controls the tilt of the tension roller 23 by rotating a cam (not shown) based on the steering amount, thereby controlling the steering motor 50.

[0031] The encoder sensor 60 transmits the detected signal to the CPU 100. The detected signal from the encoder sensor 60 is a digital pulse signal whose period changes in accordance with the rotational speed of the tension roller 24. The CPU 100 indirectly detects the speed of the printed belt 25 by counting the period of the digital pulse signal from the encoder sensor 60 over time to detect the rotational speed of the tension roller 24.

[0032] <Calibration of the belt-edge detection sensor> Next, we will explain how to perform calibration.

[0033] As mentioned earlier, Figure 5(a) shows that calibration is performed with nothing between the CIS32 and LED31 before assembly into the sheet transport device, i.e., before shipping the product. This is because each pixel of the CIS has sensitivity variations, and even if the same light is received, variations will occur in the output analog value. Therefore, it is necessary to correct for sensitivity variations by having the light emitted from LED31 be received by all pixels of the CIS32. In addition, the light intensity of the LEDs must be adjusted so that the sensor level at all pixels of the CIS32 is the target level T. Figures 8(a) and 8(b) show the sensor levels of each pixel of the CIS32 before calibration. In Figure 8(a), the sensor level varies at all pixels due to sensitivity variations in the CIS32. In Figure 8(b), in addition to the sensitivity variations of the CIS32, the light intensity of the LED31 has not been adjusted, and the sensor level is lower than the target level T.

[0034] Then, by performing calibration, as shown in Figure 8(c), the variation in each pixel of the CIS32 is corrected, and the light intensity of the LED31 is adjusted so that the sensor level becomes the target level T. Here, the correction of the variation in each pixel of the CIS32 is performed as follows: The level received by each photodetector of the CIS32 is stored, and the microcontroller is configured to correct the light reception sensitivity so that it becomes flat. With the calibration of the belt position detection sensor 30 performed in this way, as shown in Figure 8(d), the sensor level of each pixel of the CIS32 becomes a waveform as shown in the graph. That is, when the belt position detection hole 35 is detected, the light that has passed through the belt position detection hole 35 is detected with the same output value when received by each pixel of the CIS32. As a result, the center position of the light that has passed through the belt position detection hole 35 can be detected with high accuracy.

[0035] Figure 6 shows the product after it has been shipped and the belt position detection sensor 30 is placed on the sheet conveying device. In this state, the printed belt 25 is located between the CIS 32 and the LED 31, so calibration cannot be performed.

[0036] <Belt position detection hole> Next, we will explain how to perform calibration after the product has been shipped.

[0037] As shown in Figure 7, the printed belt 25 is provided with a plurality of belt position detection holes 35 (first openings) arranged at equal intervals in the circumferential direction at the belt end.

[0038] The multiple belt position detection holes 35 are approximately circular in shape, and their opening width in the belt width direction is set to be smaller than the light-receiving area of ​​the CIS (the area where multiple light-receiving elements are arranged) in order to detect the belt position. In addition, the printed belt 25 is provided with a calibration hole (second opening) for the belt position detection sensor 30.

[0039] In this embodiment, the calibration hole 36 can be stopped directly below the belt position detection sensor 30 when the device is powered on or before the print job starts, thereby performing calibration of the belt position detection sensor 30. Here, the shape of the calibration hole 36 is larger than the shape of the CIS 32 so that all pixels of the CIS 32 can receive light from the LED 31, and the shape takes into account the amount of deviation in the belt width direction due to the meandering of the print belt 25. In other words, the opening width of the calibration hole 36 is set to be larger in the belt width direction than the light-receiving area of ​​the CIS (the area in which multiple light-receiving elements are arranged) so that all pixels of the CIS 32 can receive light from the LED 31. Specifically, if the shape of the CIS 32 is 10 mm x 3 mm, the deviation in the belt width direction is 1 mm, and the stopping variation of the print belt 25 is 1 mm, then a calibration hole of 11 mm x 4 mm or larger is sufficient.

[0040] In this embodiment, the calibration hole is described as rectangular, but it is not limited to a rectangular shape. Furthermore, the calibration hole 36 is formed such that the opening width in the belt width direction is larger than the opening width in the belt circumferential direction. This allows for improved calibration accuracy while reducing the belt's opening area.

[0041] <Calibration control flowchart> In this embodiment, the CPU 100 is capable of performing calibration control of the belt position detection sensor 30 (adjustment control of the light emission amount of the LED and adjustment control of the light receiving sensitivity of the CIS).

[0042] Figure 9 is a flowchart of the calibration control in this embodiment.

[0043] First, the CPU 100, acting as the control unit, controls the belt drive motor 51, acting as the drive unit, to start the rotation of the printed belt 25 (S101). Next, the CPU 100 determines whether the printed belt 25 has rotated stably at the target speed (S102). If the printed belt 25 has not reached the target speed, the process returns to S102. If the printed belt 25 has reached the target speed, the CPU 100 determines whether the calibration hole 36 has been detected (S103). Here, the belt position detection sensor 30 detects both the belt position detection hole 35 and the calibration hole 36, but which hole was detected is determined from the time the hole was detected. For example, in this embodiment, in the transport direction of the printed belt 25, the belt position detection hole 35 is 1 mm and the calibration hole 36 is 4 mm. Therefore, the time the hole is detected at the target speed of the printed belt 25 makes it possible to determine whether the belt position detection hole 35 or the calibration hole 36 was detected.

[0044] If calibration hole 35 is not detected, the process returns to S103. If calibration hole 36 is detected, the belt hole count value CNT is initialized to 0 (S104). Next, it is determined whether belt position detection hole 35 has been detected (S105). If belt position detection hole 35 is not detected, the process returns to S105. If belt position detection hole 35 is detected, the belt hole count value CNT is incremented. CNT = CNT+1 (S106)

[0045] Then, it is determined whether the count value CNT of the belt holes is a predetermined count value A (for example, 195) (S107).

[0046] If the count value CNT is A, the calibration hole belt stop control sequence is executed (S108). On the other hand, if the count value of the belt hole is not A, the process returns to S105.

[0047] Then, when the calibration hole 36 stops directly below the belt position detection sensor 30 due to the calibration hole belt stop control sequence described later, the CPU 100 performs calibration of the belt position detection sensor 30 (S109).

[0048] The above calibration control is performed when the device is powered on or before the print job starts.

[0049] Next, Figure 10 is a flowchart illustrating the belt stop control of the printed belt 25 to stop the calibration hole 36 directly below the belt position detection sensor 30.

[0050] The CPU 100 controls the belt drive motor 51, which acts as the drive unit, to reduce the rotation speed of the printed belt 25 (S201).

[0051] Next, the encoder value ENC of the encoder sensor 60 is obtained (S202).

[0052] Then, it is determined whether the encoder value ENC of the encoder sensor 60 is B (for example, 50) (S203).

[0053] Here, the encoder value ENC becomes B when the distance from the center position of the belt position detection hole 35 (where the count value CNT of the belt hole in Figure 7 is A, for example, 195) to the center position of the calibration hole 36 is equal to this value. If the encoder value ENC is not B, the process returns to S202; if the encoder value ENC matches B, the printed belt 25 is stopped (S204).

[0054] As described above, the calibration of the belt position detection sensor 30 is performed by stopping the calibration hole 36 directly below the belt position detection sensor 30.

[0055] As described above, even if the printed belt 25 is present between the CIS 32 and LED 31 of the belt position detection sensor 30, calibration of the belt position detection sensor 30 can be performed. That is, calibration can be performed by stopping the calibration hole 36 directly below the belt position detection sensor 30 when the device is powered on or before the print job starts. Therefore, even if the light intensity of the LED decreases over time or the sensitivity of each pixel of the CIS changes from the time of shipment due to dirt, a decrease in the detection accuracy of the hole for belt position control can be suppressed. [Explanation of Symbols]

[0056] 1000 paper feed modules 1000a Storage Unit 1 1000b Storage Room 2 1000c Storage Unit 3 2000 Print Module 2200 Print Belt Unit 2300 Records Section 2400 recording heads 3000 drying module 3200 Decoupling section 3300 Drying Belt Unit 3400 Hot air blowing section 4000 Fuser Module 4100 Fixing Belt Unit 4200 Reversal section 1 5000 Cooling Modules 5100 Cooling section 6000 Inverting Module 6400 Reversal section 2 7000 Paper Output Module 7200 Top Tray 7500 Loading section S Seat 21-24 Tensioning rollers 25 Printed Belts 26 Image forming surface 35 Belt position inspection hole 36 calibration holes 30 Belt position detection sensor 31 CIS 32 LED 50 Steering motor 51 Belt-driven motor 60 Encoder Sensors 70 Control Unit 100 CPU 101 ROM 102 RAM 100 CPU

Claims

1. A belt for transporting recording media, The belt is provided with a plurality of openings arranged at predetermined intervals along the circumferential direction of the belt, A light-emitting unit that emits light toward the plurality of openings, A belt conveying device comprising: a light receiving unit that receives light emitted from the light-emitting unit, and which includes a plurality of light-receiving elements arranged along the belt width direction perpendicular to the circumferential direction of the belt at a position opposite the light-emitting unit across the belt, The belt conveying device is characterized in that the plurality of openings are a plurality of first openings arranged along the circumferential direction of the belt, wherein the opening width in the width direction of the belt is smaller than the width of the light-receiving area of ​​the light-receiving unit in the width direction of the belt, and the opening width in the width direction of the belt is larger than the width of the light-receiving area.

2. The belt conveying device according to claim 1, characterized in that the first opening is a substantially circular hole, and the second opening is a hole whose width in the belt width direction is longer than the width in the circumferential direction of the belt.

3. The belt conveying device according to claim 1 or 2, characterized in that the width of the first opening in the belt circumferential direction is narrower than the width of the second opening in the belt circumferential direction.

4. The belt conveying device according to any one of claims 1 to 3, further comprising a drive unit for driving the belt and a control unit for controlling the drive unit, wherein the control unit is capable of performing calibration to correct the amount of light emitted by the light-emitting unit by emitting light from the light-emitting unit while the second opening is stopped in a position facing the light-emitting unit, and detecting the light emitted from the light-emitting unit with the light-receiving unit.

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