Image forming system and its control method

Abstract

To enable an image reading device to more stably read out a lengthy sheet and a continuous form paper.SOLUTION: An image forming system comprises: image forming means 12 that forms an image on a recording medium formed of a continuous form paper P or of a lengthy sheet; first conveying means that conveys the recording medium through a first conveyance passage 13 having the image forming means arranged therein; image reading-out means 31 that reads out an image of the recording medium through a second conveyance passage 35 at a downstream side in a conveying direction of the recording medium with respect to the first conveyance passage; second conveying means 33 that conveys the recording medium through the second conveyance passage; and a control part 9 that performs speed control to a driving source 127 of the first conveying means and performs torque control to a driving source 333 of the second conveying means.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to an image forming system and a control method thereof.

Background Art

[0002] There is known an image forming system that reads a sheet of paper on which an image is formed with an image reading device, inspects for image and color defects, and processes it as defective paper (see, for example, Patent Document 1). In the case of an image reading device for such sheets of paper, by controlling the speed of the downstream conveyance roller to be slightly faster than that of the upstream conveyance roller with respect to the conveyance rollers provided before and after the image reading device, tension is applied to the sheet of paper to maintain the reading height (depth) of the image reading device constant and ensure reading performance.

[0003] On the other hand, in recent years, there has also been an increasing need for image formation on long sheets or continuous paper (roll paper) rather than sheets of paper (see, for example, Patent Document 2). And the application of an image reading device to such an image forming system for long sheets or continuous paper has also been considered.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] When applying an image reading device to an image forming system for long sheets or continuous paper, the following problems are a concern. Upstream of the paper transport direction in the image reading device, a process transport section in the image forming unit, such as a fuser roller, is provided. Typically, the fuser roller's speed is controlled to a target speed that matches the transport speed of the image forming process upstream, in order to prevent transfer misalignment caused by a speed difference between the transfer and fuser sections. In this context, the fixing roller is driven with a high driving force for stability, considering situations such as when a heavy roller made of a metal with high heat capacity is used due to the need to apply pressure and heat to the object such as paper, or when transport is performed under fixing nip pressure. On the other hand, the transport rollers other than the fuser roller have low nip pressure and weight, and do not possess as much driving force as the fuser roller. Therefore, when handling long sheets of paper or continuous paper, if the speed of the transport rollers of the image reader is controlled downstream of the fuser roller to be slightly faster than the fuser roller, as in the case of single-fed paper, the transport rollers of the image reader are affected by the fuser roller, which has high driving force. This makes it difficult to maintain the target speed on the image reader side, resulting in unstable transport speeds and potentially having a serious impact on reading performance.

[0006] The purpose of this invention is to improve the stability of reading by an image reading device, particularly for long sheets and continuous sheets. [Means for solving the problem]

[0007] To solve the above problems, the invention described in claim 1 is an image forming system, Image forming means for forming an image on a recording medium consisting of a continuous sheet or a long sheet, A first transport means that transports the recording medium along a first transport path on which the image forming means is arranged, An image reading means for reading an image formed on the recording medium in a second transport path downstream of the first transport path in the transport direction of the recording medium, A second transport means for transporting the recording medium along the second transport path, Speed ​​control is performed on the drive source of the first transport means to maintain the target speed, and speed control is performed on the drive source of the second transport means. The recording medium is capable of always applying tension to the downstream side. A control unit that performs torque control to maintain the target torque, It is characterized by being equipped with.

[0008] The invention described in claim 2 is an image forming system according to claim 1, The second transport means is characterized by being located downstream of the image reading means in the transport direction.

[0009] The invention described in claim 3 is an image forming system according to claim 1 or claim 2, The first conveying means is characterized by including a conveying means in the fixing section.

[0010] The invention described in claim 4 is an image forming system according to any one of claims 1 to 3, The drive source of the second transport means is characterized by driving the drive roller that transports the recording medium.

[0011] The invention described in claim 5 is an image forming system according to any one of claims 1 to 4, The drive source for the second transport means is characterized by being a DC motor or an AC motor.

[0012] The invention described in claim 6 is an image forming system according to any one of claims 1 to 5, The recording medium is equipped with a detection unit for detecting physical properties, The control unit is characterized by performing torque control of the drive source of the second transport means with a target torque corresponding to the physical property value detected by the detection unit.

[0013] The invention described in claim 7 is an image forming system according to claim 6, The aforementioned physical properties include the density of the recording medium.

[0014] The invention according to claim 8 is the image forming system according to claim 6 or claim 7, wherein the physical property value includes the moisture content of the recording medium.

[0015] The invention according to claim 9 is the image forming system according to any one of claims 6 to 8, wherein the physical property value includes the surface temperature of the recording medium.

[0016] The invention according to claim 10 is the image forming system according to any one of claims 1 to 9, wherein cooling means for cooling the recording medium is provided upstream in the conveyance direction of the recording medium with respect to the image reading means.

[0017] The invention according to claim 11 is the image forming system according to any one of claims 1 to 10, wherein winding means for winding up the recording medium is provided downstream in the conveyance direction with respect to the image reading means.

[0018] The invention according to claim 12 is the image forming system according to any one of claims 1 to 10, wherein post-processing means for post-processing the recording medium is provided downstream in the conveyance direction with respect to the image reading means.

[0019] The invention according to claim 13 is the image forming system according to any one of claims 1 to 12, wherein the control unit applies tension to the recording medium by driving the drive source of the reading unit conveyance means at a specified target conveyance speed while setting the drive source of the first conveyance means to a conveyance stop state, determines the value when the torque value of the drive source of the reading unit conveyance means saturates as the target torque value, and performs the torque control based on the target torque value.

[0020] The invention according to claim 14 is the image forming system according to any one of claims 1 to 13, wherein The invention is characterized by comprising a rotation speed detection means for detecting the rotation speed of the drive source of the second transport means.

[0021] The invention described in claim 15 is a method for controlling an image forming system, A control method for an image forming system comprising: an image forming means for forming an image on a recording medium consisting of a continuous sheet or a long sheet; a first transport means for transporting the recording medium along a first transport path on which the image forming means is arranged; an image reading means for reading the image on the recording medium along a second transport path downstream of the first transport path in the transport direction of the recording medium; and a second transport means for transporting the recording medium along the second transport path, wherein Speed ​​control is performed on the drive source of the first transport means to maintain the target speed, and speed control is performed on the drive source of the second transport means. The recording medium is capable of always applying tension to the downstream side. It is characterized by performing torque control to maintain the target torque. [Effects of the Invention]

[0022] According to the present invention, it is possible to stabilize the reading of long sheets and continuous sheets using an image reading device. [Brief explanation of the drawing]

[0023] [Figure 1] This is a schematic diagram of the image forming system according to this embodiment. [Figure 2] This is a block diagram showing the control system of an image forming system. [Figure 3] This is a process diagram showing the general steps performed sequentially on the continuous paper being transported during image formation. [Figure 4] This is an explanatory diagram showing the general configuration from the fixing unit to the second transport means. [Figure 5] This diagram shows the time evolution of each motor speed and torque when the transport motor is controlled at a speed somewhat faster than that of the fixing motor. [Figure 6] This is a flowchart of the target torque setting process. [Figure 7]Figure 7(A) is an explanatory diagram showing the continuous paper transport state when the transport motor is stopped, Figure 7(B) is an explanatory diagram showing the continuous paper transport state when the motor is running, and Figure 7(C) is a diagram showing the torque changes in these states. [Figure 8] This is a diagram showing an example of the relationship between density, moisture content, and elastic modulus for each type of continuous paper. [Figure 9] This diagram shows the time evolution of motor speed and torque when speed control is applied to the fixing motor and torque control is applied to the transport motor. [Figure 10] This is a schematic diagram of an image reading device with a calibration unit added. Figure 10(A) shows the state before the calibration unit is in operation, and Figure 10(B) shows the state after the calibration unit is in operation. [Figure 11] This is a schematic diagram of an image forming system equipped with post-processing means. [Figure 12] This is a flowchart of the target torque setting process in an image forming system having two control units. [Modes for carrying out the invention]

[0024] The image forming system in this embodiment will be described in detail with reference to the drawings. Note that the image forming system according to this embodiment is an example of the present invention and is not necessarily limited thereto.

[0025] [Example of an overall configuration of an image forming system] An example of the overall configuration of the image forming system 10 will be explained using drawings. Figure 1 is a schematic diagram of the image forming system 10, and Figure 2 is a block diagram of the control system of the image forming system 10. The image forming system 10 is for forming an image on a recording medium made of continuous paper P as a continuous sheet. As shown in Figures 1 and 2, the image forming system 10 comprises, in order from upstream of the transport path of the continuous paper P, a paper supply device 5, an image forming device 1, an image reading device 3, and a paper recovery device 6 as a winding means. Furthermore, the image forming system 10 includes a control unit 9 that comprehensively controls the entire configuration described above, and the control unit 9 is communicated via communication means provided by each of the paper supply device 5, image forming device 1, image reading device 3, and paper collection device 6.

[0026] Here, the continuous paper P used as the recording medium by the image forming system 10 refers to a long, continuous sheet of recording paper extending from the leading edge of the roll to the deepest end of the roll.

[0027] [Paper supply device] The paper supply device 5 supports a roll on which continuous paper P is wound before an image is formed, and includes a motor (not shown) as a drive source that rotates the roll in the feeding direction. The paper supply device 5 supplies the fed continuous paper P to the paper feed opening 131 of the image forming apparatus 1.

[0028] [Paper collection device] The paper collection device 6 is a winding means that collects the continuous paper P, on which an image has been formed and which has been read by the image reading device 3, while winding it up. The paper collection device 6 is equipped with a motor (not shown) as a drive source to rotate the roll in order to form a roll while winding up the continuous paper P. The paper collection device 6 is connected to the paper output slot 352 of the image reading device 3 and collects the continuous paper P that is fed out from the paper output slot 352.

[0029] [Image forming apparatus] Image forming apparatus 1 is, for example, an electrophotographic image forming apparatus such as a photocopier. As shown in Figure 1, image forming apparatus 1 is also called a tandem-type color image forming apparatus, and it is possible to form a full-color image on the intermediate transfer belt by arranging a single intermediate transfer belt to extend along a predetermined direction (up and down in this embodiment) and arranging a plurality of photosensitive drums facing the intermediate transfer belt in the direction in which the belt extends.

[0030] As shown in Figures 1 and 2, the image forming apparatus 1 includes, for example, a document reading unit 11, an image forming means 12, a first transport path 13, and an operation display unit 14. The various parts of the image forming apparatus 1 are interconnected via a bus (not shown).

[0031] [Image forming apparatus: Document reading unit] The document reading unit 11 is comprised of an automatic document feeder (ADF), a platen glass, an optical system, etc., and reads the document placed on the ADF or platen glass using the optical system to obtain image data. Furthermore, the image forming apparatus 1 can acquire image data not only from the document reading unit 11 but also from an external host device (for example, a PC: Personal Computer) via communication.

[0032] [Image forming apparatus: Image forming means] The image forming means 12 forms an image on continuous paper P using toner based on the acquired image data. The image forming means 12 includes, for example, an image forming unit 12C that forms a cyan (C) image, an image forming unit 12M that forms a magenta (M) image, an image forming unit 12Y that forms a yellow (Y) image, and an image forming unit 12K that forms a black (K) image, as well as an intermediate transfer belt 121, an intermediate transfer roller 122, and a fixing unit 124. Regarding the image forming units 12C to 12K, for example, the configuration may include only one of the image forming units 12C to 12K, or multiple configurations of only one type of image forming unit 12C to 12K.

[0033] Each image forming unit 12C to 12K includes a photoreceptor drum on which a toner image is formed, a charging unit that charges the photoreceptor drum to a predetermined potential, an exposure unit that exposes the charged image carrier to form an electrostatic latent image corresponding to the image data, a developing unit that develops the electrostatic latent image to form a toner image, and a drum cleaner that removes any remaining toner from the photoreceptor drum.

[0034] The images formed on each photoreceptor drum are sequentially transferred to predetermined positions on an intermediate transfer belt 121, which is a belt-shaped intermediate transfer body. The images, consisting of each color, transferred onto the intermediate transfer belt 121 are then transferred to the continuous paper P being transported along the first transport path 13, between the intermediate transfer belt 121 and the intermediate transfer roller 122. The intermediate transfer belt 121 is transported and the intermediate transfer roller 122 is rotated using a transfer motor 123 (see Figure 2) as the driving source. The transfer motor 123 is composed of, for example, a DC motor or an AC motor suitable for speed control or torque control. Here, we illustrate the case where the transfer motor 123 is a DC brushless motor. The transfer motor 123 is also equipped with an encoder 123a for detecting its rotation amount.

[0035] A fixing unit 124 is provided downstream of the intermediate transfer belt 121. The fixing unit 124 includes a fixing roller 125 and a pressure roller 126 that fix the secondary transferred toner image to the continuous paper P, and a fixing motor 127 (see Figure 2) that serves as the rotational drive source for these. The fixing motor 127 is composed of, for example, a DC motor or an AC motor. Here, the fixing motor 127 is exemplified as a DC brushless motor. An encoder 127a for detecting the amount of rotation is also attached to the fixing motor 127.

[0036] The fixing unit 124 uses a pair of pressed fixing rollers 125 and a pressure roller 126 to transport the continuous paper P and perform a fixing process to fix the toner image. A heater is provided inside the fixing roller 125. This heater heats the continuous paper P as it passes through the fixing nip between the fixing roller 125 and the pressure roller 126, melting the toner image and fixing it to the continuous paper P.

[0037] [Image forming apparatus: First transport path] The first transport path 13 is the transport path for continuous paper P from the paper feed opening 131 located on one end of the continuous paper P in the transport direction of the image forming apparatus 1 (right side in Figure 1) to the paper discharge opening 132 located on the other end of the continuous paper P in the transport direction (left side in Figure 1), as shown in Figure 1. On the first transport path 13, the media sensor 15, which serves as a detection unit for detecting the physical properties of the continuous paper P, the intermediate transfer belt 121 and intermediate transfer roller 122 of the aforementioned image forming means 12, and the fixing unit 124 are arranged in order from the upstream side to the downstream side in the transport direction. Guide rollers may be provided along the path of the first transport route 13 to guide the transport of the continuous paper P.

[0038] The first transport path 13 is provided with a first transport means for transporting continuous paper P along the path. The first transport means consists of the intermediate transfer roller 122, transfer motor 123 of the image forming means 12, and the fixing roller 125, pressure roller 126, and fixing motor 127 of the fixing unit 124. In addition, a transport roller may be provided on the first transport path 13 as a separate first transport means.

[0039] [Image forming apparatus: Media sensor] The media sensor 15 detects the physical properties of the continuous paper P on the upstream side in the transport direction of the intermediate transfer belt 121. The media sensor 15 consists of one or more sensors that measure density and moisture content as characteristic values ​​of the continuous paper P to be fed, and outputs the measurement results to the control unit 9.

[0040] The media sensor 15 includes, for example, an optical sensor having a light-emitting unit that irradiates light onto the continuous paper P and a light-receiving unit that receives the reflected light reflected by the continuous paper P, and can obtain the basis weight (weight per unit area of ​​one sheet) of the continuous paper P from the voltage value output by the light-receiving unit. Furthermore, the media sensor 15 has a displacement sensor that detects the thickness of the continuous paper P, and can detect the density of the continuous paper P from the basis weight and thickness of the continuous paper P as described above. Furthermore, the media sensor 15 has a capacitive sensor that detects the moisture content of the continuous paper P.

[0041] [Image forming device: operation display section] The operation display unit 14 includes, for example, an operation unit 141 and a display unit 142. The operation unit 141 consists of a plurality of operation buttons and accepts user input. The display unit 142 is configured to include an LCD (Liquid Crystal Display) or an organic EL display, etc. The display also includes a pressure-sensitive touch panel with transparent electrodes arranged in a grid pattern. The display unit 142 presents the user with various screens such as guidance screens and messages related to job execution, displays images of operation buttons for touch operation, and accepts user touch input.

[0042] [Image reading device] The image reading device 3 includes a reading unit 31 as an image reading means, a second transport means 33, a cooling means 34, a temperature detection unit 36, and a second transport path 35.

[0043] As shown in Figure 1, the second transport path 35 guides the transport of the continuous paper P from the paper feed opening 351 located on one end of the continuous paper P transport direction of the image reading device 3 (right side in Figure 1) to the paper discharge opening 352 located on the other end of the continuous paper P transport direction (left side in Figure 1). The paper feed slot 351 is connected to the paper output slot 132 of the image forming apparatus 1, and the continuous paper P with the image formed is fed into it. The paper output slot 352 is connected to the paper recovery device 6, and the continuous paper P from which the image has been read is discharged and recovered by the paper recovery device 6. On the second transport path 35, the cooling means 34, temperature detection unit 36, and reading unit 31 are arranged in order from the upstream side to the downstream side in the transport direction.

[0044] Furthermore, the second transport path 35 is provided with a second transport means 33, which includes a guide roller 331, a transport roller 332 as a drive roller, and a transport motor 333 as a drive source (see Figure 2). The guide rollers 331 consist of multiple pairs of rollers provided on the second transport path 35, which grip the continuous paper P from both sides and guide its transport. The transport rollers 332 are located on the second transport path 35, downstream of the colorimeter 312 in the transport direction, and consist of a pair of rollers that transport the continuous paper P by sandwiching it from both sides. The transport motor 333 drives the rotation of the roller pair of the transport rollers 332, thereby transporting the continuous paper P downstream through the transport rollers 332. The transport motor 333 is composed of, for example, a DC motor or an AC motor suitable for speed control or torque control. Here, we illustrate the case where the transport motor 333 is a DC brushless motor. The transport motor 333 is also equipped with an encoder 333a that detects the amount of rotation.

[0045] The cooling means 34 cools the continuous paper P that has been heated by the heater of the fixing unit 124 of the image forming apparatus 1. The cooling means 34 cools the continuous paper P being transported along the second transport path 35 by blowing air. The cooling means 34 may also be configured to blow air cooled using a cooling element such as a Peltier element.

[0046] The temperature detection unit 36 ​​is one of the detection units that detects the physical properties of the continuous paper P. It is located upstream of the reading unit 31 and above the conveyed continuous paper P. It consists of, for example, a radiation thermometer that detects the surface temperature of the continuous paper P. It detects the surface temperature of the continuous paper P as it passes through the cooling means 34 and outputs it to the control unit 9.

[0047] The reading unit 31 comprises a reading scanner 311 and a colorimeter 312, with the reading scanner 311 positioned upstream of the colorimeter 312 in the transport direction. The reading scanner 311 is composed of a line sensor such as a CCD (Charge-Coupled Device) sensor. The colorimeter 312 is composed of a spectrophotometer. The reading scanner 311 and colorimeter 312 are capable of reading images printed on the upper surface of continuous paper P as it is transported along the second transport path 35. The reading data of the formed image on continuous paper P, read by the reading scanner 311 and colorimeter 312, is output to the control unit 9. Based on this reading data, the control unit 9 performs, for example, to determine the positional misalignment of the formed image and to compare the reading data with the image data that forms the basis of the formed image.

[0048] [Control Unit] As shown in Figure 2, the control unit 9 comprises a CPU (Central Processing Unit) 91, a ROM (Read Only Memory) 92, a RAM (Random Access Memory) 93, and an HDD (Hard Disk Drive) 94. The components of the control unit 9 are connected via a bus (not shown).

[0049] The CPU 91 reads and executes program code from the ROM 92 for software that performs various controls and processes for image formation on continuous paper P. ROM92 is used as an example of non-volatile memory and stores programs and data necessary for the CPU91 to operate. RAM93 is used as an example of volatile memory, and temporarily stores variables, parameters, etc. that arise during the calculation process required for each process performed by CPU91.

[0050] HDD94 is used as an example of non-volatile storage, and it stores programs for the CPU91 to control various parts, the OS (Operating System), controller programs, and data. Furthermore, the recording medium storing the program executed by the control unit 9 is not limited to ROM 92 and HDD 94, but may also be a recording medium such as an SSD (Solid State Drive), CD-ROM, or DVD-ROM.

[0051] The control unit 9 is connected to the paper supply device 5 of the image forming system 10, the document reading unit 11, media sensor 15, image forming means 12 and operation display unit 14 of the image forming apparatus 1, the cooling means 34, second transport means 33 and reading unit 31 of the image reading device 3, and the paper collection device 6. The control unit 9 performs various processes involving operation control and information communication with these components, and executes image formation on continuous paper P.

[0052] Here, we will explain the general steps that are sequentially performed on the continuous paper P being transported during image formation, based on the process diagram in Figure 3. The continuous paper P is transported through the first transport path 13 of the image forming apparatus 1 and the second transport path 35 of the image reading apparatus 3 by the driving of the paper supply device 5, the first transport means, the second transport means 33, and the paper collection device 6.

[0053] In the continuous paper P, a toner image based on image data previously acquired by reading by the document reading unit 11 or by external communication is transferred by the cooperation of the intermediate transfer belt 121 and the intermediate transfer roller 122 (step S1). Then, the toner image transferred to the continuous paper P is fixed by pressurized heating in the fixing unit 124 downstream (step S3).

[0054] The continuous paper P on which the toner image has been fixed and an image has been formed is cooled by the cooling means 34 of the image reading device 3 (step S5), and the formed image is read by the reading scanner 311 and the colorimeter 312 (step S7). At this time, the CPU 91 compares the read image data of the formed image with the original image data to determine whether the image and color reproduction are appropriate and whether any defects (such as misaligned images, scratches or creases in the continuous paper P) have occurred, and records the results. Furthermore, correction values ​​for the formed image for image formation may be determined from the obtained suitability judgment results, and correction processing may be performed during subsequent image formation. Then, the continuous paper P on which the image has been formed is wound up by the paper recovery device 6, and the image formation process is completed.

[0055] Furthermore, the processing of each step S1 to S7 for the continuous paper P described above is executed in parallel at each part of the transported continuous paper P under the control of the CPU 91.

[0056] [Motor control of the first and second transport means] In each of the image formation processes described above, the CPU 91 of the control unit 9 performs speed control to maintain the target speed for the transfer motor 123 and fixing motor 127 (first transport means) located on the upstream side of the transport path within the system, and performs torque control to maintain the target torque for the transport motor 333 (second transport means 33) located on the downstream side of the transport path. The significance of controlling these motors 123, 127, and 333 will be explained below.

[0057] When conveying continuous paper P using rollers driven by separate motors on the upstream and downstream sides of the conveying direction, setting the target speed of the downstream motor to be slightly faster than that of the upstream motor, and controlling the speed of each motor, can prevent sagging of the continuous paper P.

[0058] Therefore, the control unit 9 controls the speed of the transfer motor 123 of the first transport means and the fixing motor 127 downstream of it by setting the target speed of the fixing motor 127 to a target speed that is slightly faster than the target speed of the transfer motor 123, thereby suppressing the occurrence of sagging in the continuous paper P.

[0059] On the other hand, as shown in Figure 4, a reading scanner 311 for reading the formed image is positioned between the fixing unit 124 and the second transport means 33. Since the reading accuracy of the reading scanner 311 is greatly affected by the distance g to the image forming surface of the continuous paper P, it is important to suppress the occurrence of slack in the continuous paper P even in this area. However, when controlling the speed of the fixing motor 127 and the downstream transport motor 333 by setting the target speed of the transport motor 333 to be slightly faster than the target speed of the fixing motor 127, the following problems arose.

[0060] The fixing motor 127 affects the overall behavior of the continuous paper P being transported within the first transport path 13 and significantly impacts the quality of the formed image. Therefore, in order to eliminate influences from other transport systems and achieve stable transport of the continuous paper P, a motor with a large torque output is employed. Furthermore, due to the nature of the fixing unit 124, which heats and pressurizes the continuous paper P, fixing rollers 125 and pressure rollers 126 made of metal materials with a large heat capacity tend to be used to suppress temperature changes, and rollers with high inertia are employed.

[0061] Figure 5 shows the time variation of each motor speed (upper figure) and the time variation of the torque of the transport motor 333 (lower figure) when the fixing motor 127 is speed-controlled and the transport motor 333 is speed-controlled to be slightly faster than the fixing motor 127. In the upper figure of Figure 5, the solid line shows the speed change of the transport motor 333, and the dotted line shows the speed change of the fixing motor 127.

[0062] If the upstream fixing motor 127 is a motor with a larger torque output, the downstream transport motor 333 will not be able to maintain its target speed in order for the fixing motor 127 to stably maintain its target speed, and overshoot and undershoot will occur alternately starting from the occurrence of a speed decrease (state u1 in the upper part of Figure 5). In this case, the transport motor 333 will experience repeated increases and decreases in torque output, and may even develop into an oscillation state with a larger amplitude (state u2 in the upper part of Figure 5). As a result, the continuous paper P was transported between the fixing roller 125 and the pressure roller 126 and the pair of transport rollers 332 while the tension was repeatedly increased and decreased, which could impair the image reading accuracy of the reading scanner 311.

[0063] Therefore, the CPU 91 of the control unit 9 performs torque control on the transport motor 333 of the image reading device 3 to maintain a target torque, rather than speed control to maintain a target speed. If the transport motor 333 is a DC brushless motor, the generated torque T can be calculated from equation (1), and furthermore, the relationship shown in equation (2) can be obtained from equation (1).

[0064] T = Kt·Im …(1)

number

[0065] Vm: Motor power supply voltage [V] Rm: Motor armature resistance [Ω] Kt: Motor torque constant [N·m / A] Ke: Motor back EMF [V / rpm] N: Motor rotation speed [rpm] Im: Motor drive current [A]

[0066] The CPU 91 of the control unit 9 controls the torque T generated by the transport motor 333 to maintain the target torque. Specifically, the CPU 91 detects the motor rotation speed N and motor power supply voltage V, which are variables in equation (2) above, for the transport motor 333, and calculates the generated torque T from these detected values. Then, it controls the motor power supply voltage V so that the generated torque T maintains the target torque. The adjustment of the motor power supply voltage V is performed based on increasing or decreasing the duty cycle in PWM (Pulse Width Modulation) control.

[0067] [Target Torque Setting Process] The target torque value for the torque control of the transport motor 333 described above should be such that the transport speed Vs (see Figure 4) by the transport motor 333 always maintains Vs > Vf relative to the transport speed Vf (see Figure 4) by the fixing motor 127, that is, it should be a value that allows tension to always be applied downstream to the continuous paper P between the fixing unit 124 and the second transport means 33.

[0068] To obtain the target torque value for such a transport motor 333, the CPU 91 of the control unit 9 performs a target torque setting process when not forming an image. Figure 6 is a flowchart of the target torque setting process, Figures 7(A) and 7(B) show the transport state of the continuous paper P, and Figure 7(C) shows the torque change. In Figures 7(A) and 7(B), arrow H indicates the transport direction of the continuous paper P. The target torque setting process is executed, for example, when the paper feeder 5 is replaced, when a new roll of continuous paper P is set in the paper feeder 5, or when an execution command is input from the operation display unit 14. It may also be executed periodically.

[0069] The CPU 91 of the control unit 9 first reads the target speed setting value for the speed control of the fixing motor 127 (step S31). The target speed setting value for the fixing motor 127 is set by the user via the operation display unit 14 and stored in the HDD 94, so it is read from there. Then, the CPU 91 calculates the target speed of the transport motor 333 from the target speed of the fixing motor 127 (step S33). The target speed of the transport motor 333 in the target torque setting process is, for example, a value obtained by adding 1 to several percent to the target speed of the fixing motor 127.

[0070] Next, the CPU 91 controls the fixing motor 127 to a stopped state (a state in which stopping torque is generated) so that the fixing roller 125 and the pressure roller 126 do not rotate, while driving the transport motor 333 in the transport direction (step S35). At this time, the transport motor 333 is controlled to reach the calculated target speed.

[0071] The CPU 91 then repeatedly determines whether the rotational speed detected from the encoder 333a of the transport motor 333 has reached the target speed (step S37), and when the target speed is reached, it determines whether the torque of the transport motor 333 has reached a saturated state (step S39).

[0072] Here, the torque change of the transport motor 333 will be explained with reference to Figures 7(A) to 7(C). First, in section (1) of Figure 7(C), the transport motor 333 is not yet driven, and the continuous paper P is slack. Then, when the transport motor 333 is driven, the torque increases toward the target speed, as shown in section (2). When the target speed is reached and the slack in the continuous paper P is eliminated, tension is generated in the continuous paper P, the rate of increase in the torque of the transport motor 333 decreases, and the torque reaches a saturation state. In other words, the saturation state is the state in which the slope in the torque change is sufficiently reduced (the flat portion in section (2)). Furthermore, as shown in section (3), once the saturation state is exceeded, the transport roller 332 slips relative to the continuous paper P, and the torque of the transport motor 333 decreases sharply.

[0073] In step S39, the CPU 91 calculates the torque of the transport motor 333 at a specified sampling interval using equation (2) described above, and monitors its change. Furthermore, the torque saturation state can be detected by determining whether or not the slope of the torque change has become smaller than a predetermined threshold. When the torque saturation state is detected, the CPU 91 records the duty cycle value of the PWM control corresponding to the torque value during the saturation period and determines a representative value from multiple duty cycle values ​​during the saturation period. Statistical methods such as averaging, selecting the mode, minimum, and maximum can be used to determine the representative value, but here averaging is used as an example (step S41). Then, the torque value corresponding to the average value of the duty cycle during the saturation period is set as the target torque (step S43).

[0074] When the torque of the transport motor 333 is saturated, the continuous paper P is in a state where there is no slack and tension is applied. By setting the torque value of the transport motor 333 at this time as the target torque for torque control, it is possible to transport the continuous paper P between the fixing unit 124 and the second transport means 33 while applying tension to the downstream side so that no slack occurs in the continuous paper P, regardless of the transport speed of the fixing motor 127.

[0075] [Torque correction based on the physical properties of the paper] The tension of continuous paper P during expansion and contraction varies depending on its physical properties. The force F required for the conveying motor 333 can be expressed by the following equation (3). The force F is correlated (for example, proportional) with the torque of the conveying motor 333.

[0076] F = Fr - Fp …(3) Fr: The force required to transport continuous paper using the transport rollers. Fp: Tension during expansion and contraction of continuous paper

[0077] Furthermore, the force Fr can be expressed by equation (4), and the tension Fp by equation (5). Furthermore, equation (6) is an equation that approximates the strain ε of the continuous paper P included in equation (5) from the transport speed Vs of the transport motor 333 and the transport speed Vf of the fixing motor 127.

number

[0078] J: Motor Inertia r: Roller radius μ: Coefficient of friction between continuous paper and roller m: Mass of continuous paper T L : Mechanical load on the motor and rollers A: Cross-sectional area of ​​continuous paper E: Elastic modulus of continuous paper ε: Distortion of continuous paper

[0079] As shown in equations (3) to (5), the tension Fp of the continuous paper P included in the force F required by the transport motor 333 is proportional to the elastic modulus E of the continuous paper. Figure 8 is a diagram showing an example of the relationship between the density, moisture content, and elastic modulus of continuous paper P for each paper type. As shown in Figure 8, the density and moisture content of continuous paper P are correlated (for example, proportional) with the elastic modulus.

[0080] Therefore, if the target torque value has already been obtained for a continuous paper P whose density and moisture content are already known through the target torque setting process described above, it is possible to correct the existing target torque value when transporting other continuous paper P with different physical properties to determine the target torque for the other continuous paper P with different physical properties.

[0081] Specifically, when a new or unknown type of continuous paper P is set, the CPU 91 of the control unit 9 detects the density and moisture content of the continuous paper P using the media sensor 15 of the image forming apparatus 1 before image formation. Next, the CPU 91 calculates the change or rate of change in the elastic modulus based on the numerical difference between the density and moisture content of the continuous paper P for which the target torque value has already been obtained and the density and moisture content of the new continuous paper P. Based on this, it can calculate the corrected tension Fp of the new continuous paper P. Once the corrected tension Fp is determined, the force F required for the transport motor 333 can be determined, and from this, the target torque can be calculated.

[0082] Furthermore, as shown in the example in Figure 8, if the density and moisture content are generally fixed values ​​for each type of paper, the corrected tension Fp calculated in advance for each type of paper can be prepared as table data. Then, by detecting the density and moisture content of the continuous paper P before image formation, the paper type can be identified from the table data, and a corrected tension Fp defined for each paper type can be obtained. Then, the target torque can be calculated from the corrected tension Fp in the same manner as described above.

[0083] Furthermore, the surface temperature of the continuous paper P is also correlated with the elastic modulus. Since the image reading device 3 is equipped with a temperature detection unit 36, for example, if the target torque value has already been obtained through the target torque setting process described above, the change in the elastic modulus or the rate of change can be calculated from the temperature difference between the surface temperature of the continuous paper P when the target torque was obtained and the surface temperature of the continuous paper P newly detected during image formation, and the corrected tension Fp can be calculated based on this. Then, in the same manner as described above, the target torque corresponding to the temperature change can be calculated.

[0084] Furthermore, since temperature changes in the continuous paper P can occur steadily regardless of the type of paper, temperature detection may be performed more frequently or continuously during image formation, not just when the continuous paper P is replaced, and the target torque may be corrected each time in response to the temperature change. Furthermore, regarding the correction of the target torque according to the various physical properties of the continuous paper P, the example given was that the correction is made based on the target torque obtained by the target torque setting process described above. However, the target torque value used as the reference can be obtained by any method, such as the target torque value obtained by calculation or simulation, or the target torque value obtained by experimental measurement.

[0085] [Regarding the effect of torque control of the second transport means] As described above, in the image forming system 10, the control unit 9 performs speed control on the fixing motor 127, which is the drive source for the first transport means, and torque control on the transport motor 333, which is the drive source for the second transport means 33 of the image reading device 3. Figure 9 shows the time variation of the motor speeds (upper figure) and the time variation of the torque of the transport motor 333 (lower figure) when the fixing motor 127 is speed-controlled and the transport motor 333 is torque-controlled. In the upper figure of Figure 9, the solid line shows the speed change of the transport motor 333, and the dotted line shows the speed change of the fixing motor 127.

[0086] As mentioned above, since the fixing motor 127 employs a motor with a large torque output, the target speed can be stably maintained through speed control during transport. In contrast, the transport motor 333 is subjected to torque control to maintain the target torque. Therefore, even if the transport motor 333 has a lower torque output than the fixing motor 127, overshoot and undershoot are avoided, reducing speed fluctuations and allowing the continuous paper P to be transported while maintaining constant tension. As a result, the reading unit 31 can read the formed image of the continuous paper P while maintaining a constant elongation rate of the continuous paper P, and the reading unit 31 can maintain a constant reading height (depth), making it possible to stably maintain high reading accuracy.

[0087] In particular, in the image reading device 3, the second transport means 33 is positioned downstream of the reading unit 31 in the transport direction, so that the image of the continuous paper P, which is under constant tension, can be read by the reading unit 31, enabling stable reading with high reading accuracy.

[0088] Furthermore, although the first transport means includes a fixing motor 127 which serves as the transport means for the fixing unit 124, even if a motor with a large torque output is selected as the fixing motor 127 in order to ensure stable transport of the continuous paper P in the first transport path 13 where image formation takes place, the second transport means 33 can transport the continuous paper P while stably applying a constant tension to it. Therefore, the image forming means 12 can achieve high-quality image formation while the reading unit 31 can stably maintain high reading accuracy.

[0089] Furthermore, since the transport motor 333 of the second transport means 33 is configured to drive the transport roller 332 that transports the continuous paper P, it is possible to easily achieve transport that maintains a constant tension on the continuous paper P by torque control of the transport motor 333.

[0090] Furthermore, the image forming system 10 utilizes a DC brushless motor as the transport motor 333. In configurations such as continuous paper P, where the paper supply device 5 and paper collection device 6 are involved in paper transport, using a stepping motor, which is commonly used for paper transport, as the transport motor 333 may result in step loss due to load fluctuations. However, since the transport motor 333 of the image forming system 10 is a DC brushless motor and is also torque-controlled, step loss does not occur even when affected by load fluctuations. This suppresses the occurrence of misalignment of the read image relative to the reading unit 31, making it possible to stably maintain high reading accuracy.

[0091] Furthermore, since the transport motor 333 is equipped with an encoder 333a that detects its rotational speed, it is possible to stably control the torque so that it does not fluctuate with the rotational speed.

[0092] Furthermore, the image forming system 10 includes a media sensor 15 and a temperature detection unit 36 ​​for detecting the physical properties of the continuous paper P, and the control unit 9 controls the torque of the transport motor 333 with a target torque adjusted based on the density, moisture content, and surface temperature of the continuous paper P detected by these sensors. Therefore, even when the type of paper is changed or the temperature changes, fluctuations in tension on the continuous paper P are suppressed, and high reading accuracy can be stably maintained in the reading unit 31.

[0093] Furthermore, the image forming system 10 has a cooling means 34 for cooling the continuous paper P on the upstream side of the transport direction of the continuous paper P relative to the reading unit 31. The image formed on the continuous paper P, which is in a high-temperature state immediately after being fixed by heating and pressurizing in the fixing unit 124, may still be unstable. However, since the image forming system 10 has a cooling means 34, the image formed on the continuous paper P can be stabilized during the transport process from the fixing unit 124 to the reading unit 31, and it is possible to stably maintain high reading accuracy in the reading unit 31. Furthermore, while high temperatures of the continuous paper P may affect the detection accuracy of the reading scanner 311 and colorimeter 312 of the reading unit 31, the presence of a cooling means 34 reduces the effects of high temperatures, making it possible to maintain high reading accuracy in the reading unit 31.

[0094] Furthermore, the image forming system 10 has a paper recovery device 6 that winds up the continuous paper P on the downstream side of the continuous paper P transport direction relative to the reading unit 31. If a paper collection device 6 is located downstream of the reading unit 31 in the transport direction, it is conceivable that torque control could be applied to the drive source of the paper collection device 6, rather than to the second transport means 33, thereby contributing to improving the reading accuracy of the reading unit 31. However, in the paper collection device 6, the diameter of the roll increases as the continuous paper P is wound into a roll, making it difficult to maintain a constant tension on the continuous paper P in the reading unit 31. Therefore, providing a second transport means 33 separately from the paper collection device 6 and performing torque control on the transport motor 333, which is its drive source, makes it possible to maintain the tension of the continuous paper P more stably and at a constant level, and is also advantageous for maintaining high reading accuracy of the reading unit 31.

[0095] Furthermore, the image forming system 10 has a control unit 9 that performs a target torque setting process in which it stops the fixing motor 127, drives the transport motor 333 at a specified target transport speed, and obtains the duty cycle of the PWM control corresponding to the value when the torque value of the transport motor 333 saturates as a value equivalent to the target torque value. This makes it possible to set the target torque to a value that can maintain the tension generated in the continuous paper P when the transport motor 333 is driven at a speed somewhat faster than the target speed of the fixing motor 127, thereby enabling torque control that applies a constant tension to the continuous paper P.

[0096] [Equipped with a calibration unit for shading correction] The image reading device 3 of the image forming system 10 may be further equipped with a calibration unit 37 for determining the correction value of the shading correction performed when the reading unit 31 reads the image. Figures 10(A) and 10(B) are schematic diagrams of the image reading device 3 with the calibration unit 37 added, showing the state before and after the operation of the calibration unit 37.

[0097] The calibration unit 37 is provided between the cooling means 34 of the second transport path 35 and the colorimeter 312, and includes two arm members 373 whose upper ends are rotatable, an upper roller 371 provided at the upper end of each arm member 373, a lower roller 372 provided at the lower end of each arm member 373, and a white reference plate 374 that is read by the reading scanner 311 for calibration.

[0098] In the image reading device 3 equipped with the calibration unit 37 described above, the reading scanner 311 is positioned above the cooling means 34 and the colorimeter 312. The two arm members 373 and the rollers 371 and 372 form a path through which the continuous paper P deviates, passing near the lower side of the reading unit of the reading scanner 311.

[0099] One arm member 373 has its lower end positioned near the downstream side of a guide roller 331 provided on the downstream side of the cooling means 34 in the transport direction, while the other arm member 373 has its lower end positioned near the upstream side of a guide roller 331 provided on the upstream side of the colorimeter 312 in the transport direction. Within the image reading device 3, each arm member 373 is supported so that its lower end can rotate around a pivot axis parallel to the rotation axis of each guide roller 331. Similarly, each upper roller 371 and each lower roller 372 are also supported by the arm members 373 so that they can rotate around a pivot axis parallel to the rotation axis of each guide roller 331. These rollers 371 and 372 are not driven by a power source, but are driven to rotate by the continuous paper P being transported.

[0100] The continuous paper P is then transported in order, passing over the lower roller 372 and upper roller 371 of the arm member 373 on the upstream side in the transport direction, and then over the upper roller 371 and lower roller 372 of the arm member 373 on the downstream side in the transport direction. As a result, as shown in Figure 10(A), the continuous paper P can pass near the lower side of the reading section of the scanner 311 when it moves between the upper roller 371 of the arm member 373 on the upstream side in the transport direction and the upper roller 371 of the arm member 373 on the downstream side in the transport direction, allowing the image formed on the continuous paper P to be read. Hereafter, the transport path of the continuous paper P in Figure 10(A) will be referred to as the reading path.

[0101] Furthermore, as shown in Figure 10(B), each arm member 373 can be simultaneously rotated by an actuator (not shown) whose operation can be controlled by the control unit 9, from a state where the upper end of each arm member 373 is facing upward, toward one side (for example, the upstream side) in the conveying direction of the continuous paper P. This allows the transported continuous paper P to be separated downwards from the reading unit of the scanner 311. Hereafter, the transport path of the continuous paper P shown in Figure 10(B) will be referred to as the retraction path.

[0102] The white reference plate 374 is supported within the image reading device 3 so as to be slidable along the transport direction of the continuous paper P. The white reference plate 374 can be switched by the above-mentioned sliding movement between a position located upstream of the reading section of the scanner 311 in the transport direction and a position located close to and opposite the lower side of the reading section of the scanner 311.

[0103] Furthermore, the white reference plate 374 is configured to be able to move in conjunction with each arm member 373. Specifically, as shown in Figure 10(A), when each arm member 373 is forming a reading path, the white reference plate 374 retracts to the upstream side in the transport direction of the reading scanner 311. Also, as shown in Figure 10(B), when the actuator causes each arm member 373 to form a retraction path, the white reference plate 374 moves to a position close to and facing the reading portion of the reading scanner 311.

[0104] With the above configuration, the calibration unit 37 primarily forms a reading path during image formation, enabling the reading scanner 311 to read the formed image of the continuous paper P being transported. Then, periodically or when specified conditions are met, each arm member 373 is rotated to form a retraction path and move the white reference plate 374 to a position opposite the reading scanner 311. As a result, the reading scanner 311 reads the white surface of the white reference plate 374 and calibrates the correction value for shading correction.

[0105] As described above, the calibration unit 37 periodically or when predetermined conditions are met, moves each roller 371, 372 between the arrangement of the reading path (Figure 10(A)) and the arrangement of the retraction path (Figure 10(B)). As a result of this path change, the path length of the transport path for the continuous paper P may fluctuate. Furthermore, the continuous paper P continues to be transported even while the calibration unit 37 is forming a retraction path. At this time, the second transport means 33 drives the transport roller 332 with the transport motor 333 downstream of the calibration unit 37 in the transport direction to transport the continuous paper P. Furthermore, since torque control is performed on the transport motor 333, even if the operation of the calibration unit 37 causes a change in the path length of the transport path of the continuous paper P, a constant tension can be applied to the continuous paper P, and even when the calibration unit 37 returns to the reading path, the reading unit 31 can maintain high reading accuracy.

[0106] [Installation of post-processing means] The image forming system 10 may also be configured to include a post-processing means 6A instead of the paper collection device 6. Figure 11 shows a schematic diagram of the image forming system 10 equipped with the post-processing means 6A. As shown in Figure 11, the post-processing means 6A is equipped with a transport path connected to the paper output port 352 of the image reading device 3, and performs post-processing on the continuous paper P that is fed into the transport path from the paper output port 352 as needed. Examples of post-processing include slitting, dob slittering, CD cutting, creasing (upper or lower convex), and FD / CD perforation. Post-processing other than CD cutting is not mandatory and is performed only when an execution instruction is input from the operation display unit 14, for example. Furthermore, the CD cutting process is performed when the continuous paper P reaches a set length in the transport direction, and the cut paper is discharged into the purge tray 65A.

[0107] As shown in Figure 11, the post-processing means 6A has post-processing modules 61A to 64A arranged along the transport path. The number of post-processing modules can be increased or decreased. For example, a slitter is installed as the uppermost post-processing module 61A, a downward creaser is installed as post-processing module 62A to perform creasing, which creates a downward crease on the paper, a gutter slitter is installed as post-processing module 63A to cut the paper in the center in the CD direction (paper width direction), and a CD cutter is installed as post-processing module 64A to cut the paper in the CD direction (paper width direction). In addition to those mentioned above, post-processing modules include an upward-facing creaser for creating raised lines on the paper, an FD perforator for creating perforations in the FD direction (paper transport direction), and a CD perforator for creating perforations in the CD direction (paper width direction Y).

[0108] The various post-processing operations of the post-processing means 6A must be performed at the appropriate positions relative to the image formed on the continuous paper P. In contrast, the continuous paper P is transported while post-processing is being performed by the post-processing means 6A. At this time, the second transport means 33 drives the transport roller 332 with the transport motor 333 on the upstream side of the transport direction of the post-processing means 6A to transport the continuous paper P. Furthermore, since torque control is performed on the transport motor 333, a constant tension can be applied to the continuous paper P, and the amount of elongation can be kept constant while the continuous paper P is transported to the post-processing means 6A. Therefore, the post-processing means 6A can perform post-processing with high precision in the transport direction on the image formed on the continuous paper P.

[0109] [About the control unit] The image forming system 10 described above is exemplified as having a control unit 9 that comprehensively controls the entire system, but it is not limited to this configuration. For example, two or more of the paper supply device 5, image forming device 1, image reading device 3, and paper collection device 6 may each have a control unit, and each control unit may be connected to communicate via a communication unit. For example, let's describe an example where the image forming apparatus 1 and the image reading apparatus 3 each have their own control units.

[0110] When the image forming apparatus 1 and the image reading apparatus 3 each have a control unit, the speed control of the transfer motor 123 and the fixing motor 127, which are the first transport means of the image forming apparatus 1, is performed by the CPU of the control unit of the image forming apparatus 1. Furthermore, the torque control of the transport motor 333 of the second transport means 33 of the image reading device 3 is performed by the CPU in the control unit of the image reading device 3.

[0111] In the above case, in the torque control of the transport motor 333 of the image reading device 3, the target torque setting process for obtaining the target torque, as explained in Figure 6, is primarily performed by the control unit of the image reading device 3 and secondary by the control unit of the image forming device 1, with each control unit working in cooperation. This process will be explained based on the flowchart in Figure 12.

[0112] The control unit (CPU) of the image reading device 3 first requests the control unit (CPU) of the image forming device 1 to transmit the target speed setting value for the speed control of the fixing motor 127 (step S61). Then, the control unit of the image reading device 3 obtains the target speed of the fixing motor 127 transmitted from the control unit of the image forming device 1 (step S63), and calculates the target speed of the transport motor 333 (step S65). The calculation of the target speed is the same as in the case of Figure 6.

[0113] Next, the control unit of the image reading device 3 requests the control unit of the image forming device 1 to control the fixing motor 127 to a stopped state (state where stopping torque is generated) (step S67). Then, the transport motor 333 is driven in the transport direction (step S69). The transport motor 333 is controlled to maintain the calculated target speed.

[0114] Then, the control unit of the image reading device 3 repeatedly determines whether the rotational speed detected from the encoder 333a of the transport motor 333 has reached the target speed (step S71), and when the target speed is reached, it determines whether the torque of the transport motor 333 has reached a saturated state (step S73). As a result, when torque saturation is detected, the control unit of the image reading device 3 records the duty cycle values ​​of the PWM control corresponding to the torque value during the saturation period and averages them (step S75). Furthermore, the torque value corresponding to the average value of the duty cycle during the saturation period is set as the target torque (step S77).

[0115] Thus, even when there are multiple control units, they can perform the same processing and control as a control unit that comprehensively controls the entire configuration.

[0116] [others] The details shown in the embodiments of the invention described above can be modified as appropriate without departing from the spirit of the invention. For example, continuous paper P was given as an example of a recording medium for the image forming system 10, but it is not limited to this, and long sheets of paper (long sheets) may also be used as a recording medium. Furthermore, the recording medium is not limited to paper, but may also be a sheet material made of other materials such as resin. For example, even when using a long sheet of paper as a recording medium, extending to the length of the path from the fixing unit 124 to the transport roller 332, the same technical effects as in the case of continuous paper P can be obtained by applying the characteristic motor control shown in this embodiment.

[0117] Furthermore, the transfer motor 123, fixing motor 127, and transport motor 333 may be DC motors or AC motors other than DC brushless motors. In that case, stepping motors can also be used for the transfer motor 123 and the fixing motor 127. On the other hand, the use of a stepping motor is not suitable for the transport motor 333. [Explanation of symbols]

[0118] 1. Image forming apparatus 11. Manuscript Reading Section 12 Image forming means 12C~12K Image forming section 121 Intermediate transfer belt 122 Intermediate Transfer Roller 123 Transfer motor 123a Encoder (rotation speed detection means) 124 Fixing section 125 Fixing Roller 126 Pressure Roller 127 Fixing motor (drive source) 127a Encoder (rotation speed detection means) 13. First transport route 15. Media sensor (detection unit) 3. Image reading device 31 Reading unit (image reading means) 311 Scanner 312 Colorimeter 33 Second conveying means 331 Guide Roller 332 Conveyor roller (drive roller) 333 Transport motor (drive source) 333a Encoder (rotation speed detection means) 34 Cooling means 35. Second transport route 36 Temperature detection unit 37. Calibration Department 5 Paper feeding device 6. Paper collection device (winding mechanism) 6A Post-processing means 9. Control Unit 91 CPU 10 Image Forming Systems P Continuous paper (recording medium)

Claims

1. Image forming means for forming an image on a recording medium consisting of a continuous sheet or a long sheet, A first transport means that transports the recording medium along a first transport path on which the image forming means is arranged, An image reading means for reading an image formed on the recording medium in a second transport path downstream of the first transport path in the transport direction of the recording medium, A second transport means for transporting the recording medium along the second transport path, A control unit that performs speed control on the drive source of the first transport means to maintain a target speed, and torque control on the drive source of the second transport means to maintain a target torque that can always apply tension to the recording medium downstream, An image forming system characterized by being equipped with [a specific feature].

2. The image forming system according to claim 1, characterized in that the second transport means is located downstream of the image reading means in the transport direction.

3. The image forming system according to claim 1 or 2, characterized in that the first transport means includes a transport means in the fixing section.

4. The image forming system according to any one of claims 1 to 3, characterized in that the drive source of the second transport means drives a drive roller for transporting the recording medium.

5. The image forming system according to any one of claims 1 to 4, characterized in that the drive source of the second transport means is a DC motor or an AC motor.

6. The recording medium is equipped with a detection unit for detecting physical properties, The image forming system according to any one of claims 1 to 5, characterized in that the control unit controls the torque of the drive source of the second transport means with a target torque corresponding to the physical property value detected by the detection unit.

7. The image forming system according to claim 6, characterized in that the aforementioned physical property value includes the density of the recording medium.

8. The image forming system according to claim 6 or 7, characterized in that the aforementioned physical property value includes the water content of the recording medium.

9. The image forming system according to any one of claims 6 to 8, characterized in that the aforementioned physical property value includes the surface temperature of the recording medium.

10. The image forming system according to any one of claims 1 to 9, characterized in that it has a cooling means for cooling the recording medium on the upstream side of the transport direction of the recording medium relative to the image reading means.

11. The image forming system according to any one of claims 1 to 10, characterized in that it has a winding means for winding the recording medium on the downstream side in the transport direction relative to the image reading means.

12. The image forming system according to any one of claims 1 to 10, further comprising a post-processing means for performing post-processing of the recording medium on the downstream side in the transport direction relative to the image reading means.

13. The control unit drives the drive source of the second transport means at a predetermined target transport speed while stopping the transport of the drive source of the first transport means to apply tension to the recording medium, sets the value at which the torque value of the drive source of the second transport means saturates as the target torque value, and performs the torque control based on the target torque value, as described in any one of claims 1 to 12.

14. The image forming system according to any one of claims 1 to 13, further comprising a rotation speed detection means for detecting the rotation speed of the drive source of the second transport means.

15. A control method for an image forming system comprising: an image forming means for forming an image on a recording medium consisting of a continuous sheet or a long sheet; a first transport means for transporting the recording medium along a first transport path on which the image forming means is arranged; an image reading means for reading the image on the recording medium along a second transport path downstream of the first transport path in the transport direction of the recording medium; and a second transport means for transporting the recording medium along the second transport path, wherein A control method for an image forming system, characterized by performing speed control on the drive source of the first transport means to maintain a target speed, and performing torque control on the drive source of the second transport means to maintain a target torque that can always apply tension to the recording medium downstream.

Images