JP2007264551A - Medium transport apparatus and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus which can stably transport a recording medium, thereby surely preventing the occurrence of color shift of a toner image or a jamming in the recording medium, etc.. <P>SOLUTION: An image forming system is provided with a first medium transport part 102 for transporting the recording medium P to an image forming part, where an image is formed to the recording medium P; a second medium transport part 132, provided upstream from the first medium transport part 102 in a medium transport direction; a slack detecting part 104 for detecting the existence of slack in the recording medium P between the first medium transport part 102 and the image forming part; and a control part for controlling the transport speed of the first medium transport part 102 and the second medium transport part 132, based on the detected result by the slack detecting part 104. The control part performs control so that the second medium transport part 132 is driven, before the start of the first medium transport part 102 drive, at the transport start of the recording medium P. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a medium conveying apparatus that conveys a medium, and an image forming apparatus that forms an image on a recording medium conveyed by the medium conveying apparatus.

  2. Description of the Related Art Conventionally, an image forming apparatus using an electrophotographic process for forming an image by fixing toner on a predetermined recording medium is known. In such an image forming apparatus, the recording medium is fed from a medium transport unit located upstream in the medium transport direction as viewed from a transfer unit that transfers the toner image formed by the image forming unit to the recording medium. In this type of image forming apparatus, if the recording medium is excessively stretched before the recording medium fed from the medium conveying unit is conveyed to the image forming unit or the transfer unit, the recording medium is added. Due to the influence of the transport load, the transport speed changes instantaneously, which causes a change in the recording pitch of the toner image, the occurrence of horizontal stripes, etc., and in some cases also causes a jam in the recording medium. . In view of this, an image recording apparatus has been proposed in which a slack relief section for forming slack in a recording medium is provided between the medium transport section and the image forming section or transfer section (see Patent Document 1). Specifically, in this image recording apparatus, the slack relief unit has a slack state detection unit that detects a slack state of the recording medium. Based on the detection result of the slack state detection unit, the motor speed of the medium transport unit Is controlled to keep the recording medium slack.

JP 9-325544 A

  However, in the conventional techniques including the above-described Patent Document 1, when a super-long recording medium made of roll paper or the like is used, the medium transport unit and the image forming unit and the transfer unit are driven separately. Since these are driven by the system, errors in the transport amount of the recording medium accumulate due to various factors such as the driving timing and driving speed of these driving systems, and the recording medium is stretched between the driving systems. There is still the problem of inducing a situation where slackness occurs.

  The present invention has been made in view of such circumstances, can stably convey a recording medium, and can surely prevent occurrence of color misregistration of a toner image, jamming of a recording medium, and the like. It is an object of the present invention to provide a medium conveying device and an image forming apparatus.

  A medium transport apparatus according to the present invention that achieves the above-described object is a medium transport apparatus that transports a medium, and a first medium transport section that transports the medium to an image processing section that performs image processing on the medium. And whether the medium is slack between the second medium transport unit provided upstream of the first medium transport unit in the medium transport direction, and between the first medium transport unit and the image processing unit. And a control unit for controlling the conveyance speed by the first medium conveyance unit and the second medium conveyance unit based on a detection result by the slack detection unit. Yes.

  An image forming apparatus according to the present invention that achieves the above-described object is an image forming apparatus that forms an image on a recording medium based on input image data. The image forming apparatus forms an image on the recording medium. A first medium conveying unit that conveys the recording medium to the image forming unit, a second medium conveying unit that conveys the recording medium to the first medium conveying unit, and the first medium conveying unit. A slack detection unit that detects whether the recording medium is slack between the medium transport unit and the image forming unit, and the first medium transport unit and the second medium based on a detection result of the slack detection unit. And a control unit for controlling the conveyance speed of the medium conveyance unit.

  In such a medium conveyance device and image forming apparatus according to the present invention, the medium can be loosened by controlling the conveyance speeds of the first medium conveyance unit and the second medium conveyance unit. Therefore, in the medium conveying apparatus and the image forming apparatus according to the present invention, when the tension of the medium is detected between the image forming unit and the first medium conveying unit, the first medium is loosened. Even if the conveyance speed by the medium conveyance unit is increased, the medium can be conveyed stably.

  In the present invention, the recording medium can be stably conveyed, and the occurrence of color misregistration of the toner image and jamming of the recording medium can be reliably prevented.

  Hereinafter, specific embodiments to which the present invention is applied will be described in detail with reference to the drawings.

  In this embodiment, charging and exposure of a photosensitive drum as an electrostatic latent image carrier, development of the electrostatic latent image formed on the photosensitive drum with toner, and onto the recording medium of the obtained toner image An image forming apparatus of an electrophotographic recording system that forms an image on the recording medium based on input image data through a process such as transfer of toner and fixing of a toner image on the recording medium. An image forming system includes a medium conveying apparatus that conveys a recording medium to the apparatus. In particular, when the image forming system forms an image on a recording medium fed from a medium conveying device provided on the upstream side in the medium conveying direction and conveyed to the image forming device, the image forming system By appropriately operating the drive system and the drive system on the image forming apparatus side, extremely stable conveyance of the recording medium can be realized.

  In the present embodiment, an image forming system including an image forming apparatus and a medium conveying apparatus that conveys a recording medium to the image forming apparatus will be described. The present invention includes a medium conveying apparatus therein. The present invention can be similarly applied to the image forming apparatus.

  First, an image forming system shown as the first embodiment of the present invention will be described.

  As shown in FIG. 1, the image forming apparatus 100 includes a paper feed detection unit 101 that detects that the recording medium P is fed in the order of passage of the recording medium P transported from a medium transporting device 130 described below. A first medium transport unit 102 that transports the recording medium P to an image forming unit provided on the downstream side in the medium transport direction, and the leading end of the recording medium P is the first medium transport to start writing image data. A write start detection unit 103 that detects that the recording medium P has passed, and a slack detection unit 104 that detects whether the recording medium P is slack between the first medium transport unit 102 and the image forming unit.

  The paper feed detection unit 101 includes, for example, a lever type sensor that detects passage of the recording medium P by detecting a part of a lever arm that rotates as the recording medium P passes by a photocoupler sensor. The In the paper feed detection unit 101, when the recording medium P is not passing, the lever arm is biased in an inverted state, and the output from the photocoupler sensor is at a low level. On the other hand, in the paper feed detection unit 101, as the recording medium P conveyed from the medium conveyance device 130 reaches the paper supply port of the image forming apparatus 100 and the recording medium P passes, the lever arm is substantially horizontal. The output from the photocoupler sensor switches to high level. Accordingly, the paper feed detection unit 101 detects that the recording medium P has been fed.

  The first medium transport unit 102 includes, for example, a pair of rollers that are rotationally driven by a stepping motor, and transports the recording medium P to an image forming unit provided on the downstream side in the medium transport direction. Specifically, the first medium transport unit 102 is driven to rotate in response to the feed detection of the recording medium P detected by the paper feed detection unit 101. The first medium transport unit 102 is driven by a stepping motor that is separate from a stepping motor that drives a second medium transport unit 132 (described later) in the medium transport device 130.

  Similar to the paper feed detection unit 101, the write start detection unit 103 includes, for example, a lever type sensor. In other words, in the state where the recording medium P has not passed, the writing detection unit 103 is biased to the inverted state, and the output from the photocoupler sensor is set to the low level. On the other hand, in the writing detection unit 103, as the leading end of the recording medium P passes through the first medium transport unit 102, the lever arm is tilted in the substantially horizontal direction, and the output from the photocoupler sensor is switched to a high level. In the image forming apparatus 100, the writing of image data is started in response to the output of the writing detection unit 103 switching to a high level.

  Similar to the paper feed detection unit 101 and the write start detection unit 103, the slack detection unit 104 is configured by, for example, a lever sensor, and whether the recording medium P is slack between the first medium transport unit 102 and the image forming unit. Detects whether the amount of slack is decreasing and stretching. Specifically, as shown in FIG. 2A, the slack detection unit 104 has the lever arm in a substantially horizontal direction when the recording medium P is stretched between the recording medium reel 131 and the image forming unit. In this state, the output from the photocoupler sensor is at a high level. Further, as shown in FIG. 2B, the slackness detection unit 104 has a recording medium P between the second medium conveyance unit 132 in the medium conveyance device 130 and the first medium conveyance unit 102 in the image forming apparatus 100. In the slack state, the lever arm remains in a tilted state, and the output from the photocoupler sensor is also kept at the high level. On the other hand, as shown in FIG. 2C, the slack detection unit 104 is configured such that the lever arm is inverted when the recording medium P is slackened by a predetermined amount between the first medium transport unit 102 and the image forming unit. The output from the photocoupler sensor is set to a low level. FIG. 2C shows a state in which the recording medium P is loose even between the second medium transport unit 132 and the first medium transport unit 102. In this way, the slack detection unit 104 detects whether the recording medium P is slack between the first medium transport unit 102 and the image forming unit.

  Further, as shown in FIG. 1, the image forming apparatus 100 has four colors of black (k), yellow (y), magenta (m), and cyan (c) on the downstream side of the slack detecting unit 104 in the medium conveyance direction. Four image forming units each composed of various members corresponding to each of them, and a toner image formed by these image forming units are fed from a medium conveying device 130 to be described later and conveyed in the direction indicated by arrow a in FIG. And a transfer section that transfers to the recorded recording medium P.

  Each of the image forming units includes photoreceptor drums 110k, 110y, 110m, and 110c that form an electrostatic latent image on a surface layer made of a conductive base layer made of, for example, aluminum or the like and an organic photoreceptor. Around each of the photosensitive drums 110k, 110y, 110m, and 110c, charging rollers 111k, 111y, 111m, and 111c are disposed in contact with the photosensitive drums 110k, 110y, 110m, and 110c. Each of these charging rollers 111k, 111y, 111m, and 111c is formed by forming a semiconductive rubber material such as epichlorohydrin rubber in a roll shape on a conductive metal shaft, for example. When a positive voltage or a negative voltage is applied by a predetermined power source that operates under control, the surfaces of the photosensitive drums 110k, 110y, 110m, and 110c that are in contact with each other are charged to a uniform voltage. In this embodiment, a reversal development method is adopted, and negative voltages are applied to the charging rollers 111k, 111y, 111m, and 111c, respectively, and the photosensitive drums 110k, 110y, 110m, and 110c are set to negative voltages. It shall be charged.

  In the image forming unit, exposure units 112k, 112y, 112m, and 112c having LED (Light Emitting Diode) heads that perform exposure are disposed around the photosensitive drums 110k, 110y, 110m, and 110c, respectively. . Each of these exposure units 112k, 112y, 112m, and 112c irradiates the surfaces of the photosensitive drums 110k, 110y, 110m, and 110c with light that has been image-modulated based on image data received from the host device, and exposes the light. Electrostatic latent images are formed on the photosensitive drums 110k, 110y, 110m, and 110c.

  Further, in the image forming units, developing rollers 113k, 113y, 113m, and 113c are disposed around the photosensitive drums 110k, 110y, 110m, and 110c, in contact with the photosensitive drums 110k, 110y, 110m, and 110c, respectively. Has been. Each of these developing rollers 113k, 113y, 113m, and 113c is formed by forming a semiconductive rubber such as silicon on a conductive metal shaft in a roll shape, and operates under the control of a process control unit. By applying a positive voltage or a negative voltage by the power source, the electrostatic latent images formed on the contacted photosensitive drums 110k, 110y, 110m, and 110c are developed with toner of each color. Further, around each of the developing rollers 113k, 113y, 113m, and 113c, toner supply rollers 114k, 114y, 114m, and 114c for supplying toner to the developing rollers 113k, 113y, 113m, and 113c are the developing rollers 113k, It arrange | positions in the state which contacted 113y, 113m, and 113c. Each of the toner supply rollers 114k, 114y, 114m, and 114c is formed with a roll-like rubber formed by adding a foaming agent to the conductive metal shaft during rubber kneading in order to improve toner conveyance. Is. A positive voltage or a negative voltage is applied to the toner supply rollers 114k, 114y, 114m, and 114c by a predetermined power source. In the present embodiment, toner charged to a negative voltage is used. During development, negative voltages are applied to the developing rollers 113k, 113y, 113m, and 113c and the toner supply rollers 114k, 114y, 114m, and 114c, respectively. Shall be applied.

  Furthermore, in the image forming unit, cleaning blades 115k, 115y, 115m, and 115c are arranged around the photosensitive drums 110k, 110y, 110m, and 110c, in contact with the photosensitive drums 110k, 110y, 110m, and 110c, respectively. It is installed. These cleaning blades 115k, 115y, 115m, and 115c remove transfer residual toner remaining on the surfaces of the photosensitive drums 110k, 110y, 110m, and 110c, respectively, and are disposed in the attached waste toner boxes 116k, 116y, 116m, and 116c, respectively. to recover.

  On the other hand, the transfer unit includes a transfer belt 107, a driving roller 108 driven by a belt motor (not shown), and a belt idle roller that rotates according to the movement of the transfer belt 107 and applies tension so that the transfer belt 107 does not relax. 109, and transfer rollers 117k, 117y, 117m, and 117c for applying a transfer voltage to the image forming unit. The image forming unit is arranged in parallel with the transfer rollers 117k, 117y, 117m, and 117c so as to sandwich the transfer belt 107, and the rotational force of the photosensitive drums 110k, 110y, 110m, and 110c, While the recording medium P is conveyed by the driving and conveying force of the transfer belt 107, image formation using toner of each color is performed on the recording medium P placed on the transfer belt 107.

  In the image forming apparatus 100 including such an image forming unit and a transfer unit, each of the photosensitive drums 110k, 110y, 110m, and 110c converts the developed toner images of each color under the control of the process control unit. Along with the rotation, the images are sequentially superimposed and transferred onto the recording medium P by the transfer rollers 117k, 117y, 117m, and 117c. In the image forming apparatus 100, the recording medium P is conveyed to a fixing unit provided on the downstream side of the image forming unit while being electrostatically adsorbed to the transfer belt 107.

  The fixing unit includes, for example, a fixing roller 121 configured by adhering an elastic member to the outer periphery of a metal hollow roller, and a pressure roller 122 that presses the recording medium P together with the fixing roller 121. The pressure roller 122 is disposed so as to face and contact the fixing roller 121, and forms a nip portion that sandwiches the recording medium P. A halogen lamp that emits light from a power source (not shown) is embedded in the fixing roller 121. In the fixing unit, the fixing roller 121 is heated by causing a halogen lamp to emit light under the control of the process control unit. Such a fixing unit rotates the fixing roller 121 and the pressure roller 122 to pass the recording medium P through the nip portion, and heats and presses the recording medium P, whereby the toner on the recording medium P is removed. The toner image is melted and thermally fixed. In the image forming apparatus 100, when an image is fixed on a recording medium by such a fixing unit, the recording medium P is conveyed in a direction indicated by an arrow b in the figure by a discharge roller (not shown) and discharged to the outside. Paper is loaded on a stacker.

  The image forming apparatus 100 includes a paper discharge detection unit 123 that detects that the recording medium P has been discharged downstream of the fixing unit in the medium conveyance direction. The paper discharge detection unit 123 includes, for example, a lever-type sensor, like the paper feed detection unit 101, the writing start detection unit 103, and the slack detection unit 104. In the paper discharge detection unit 123, the lever arm is biased in an inverted state when the recording medium P is not passing, and the output from the photocoupler sensor is set to a low level. On the other hand, in the paper discharge detection unit 123, as the recording medium P discharged from the fixing unit passes, the lever arm is tilted in a substantially horizontal direction, and the output from the photocoupler sensor is switched to a high level. Accordingly, the paper discharge detection unit 123 detects that the recording medium P has been discharged.

  In addition, the medium transport device 130 that transports the recording medium P to the image forming apparatus 100 has a recording medium reel 131 around which the recording medium P is wound, and a recording medium P that is wound around the recording medium reel 131. A second medium conveying unit 132 that conveys the image to the image forming apparatus 100.

  The second medium transport unit 132 includes a pair of rollers that are rotationally driven by a stepping motor that is separate from the stepping motor that drives the first medium transport unit 102 in the image forming apparatus 100, and the recording medium P is transferred to the image forming apparatus 100. Transport to. Specifically, the second medium transport unit 132 is driven to rotate according to an instruction given from the image forming apparatus 100 side via the communication cable 140, and the recording medium P wound around the recording medium reel 131. Is conveyed in the direction indicated by arrow a in FIG. Then, the second medium transport unit 132 stops its rotation drive in response to the output of the paper feed detection unit 101 switching to a high level. Note that the second medium transport unit 132 does not stop completely when the first medium transport unit 102 is rotationally driven, even when the rotational drive by the stepping motor is stopped. As the first medium transport unit 102 is driven to rotate and the recording medium P is transported, the recording medium P is rotated in accordance with the transport speed and acts as a transport load for the recording medium P.

  The image forming apparatus 100 and the medium transport apparatus 130 are electrically connected to each other via the communication cable 140, and supply a control signal or the like given from the host apparatus to the image forming apparatus 100 to the medium transport apparatus 130. It is configured to be able to.

  A control system in the image forming system including the image forming apparatus 100 and the medium conveying apparatus 130 is configured as shown in FIG. That is, the image forming system includes a central control unit 201 that comprehensively controls each unit, a first motor control unit 202 that controls a stepping motor 102a that rotationally drives the first medium transport unit 102, and a second medium. A second motor control unit 203 that controls a stepping motor 132a that rotationally drives the conveyance unit 132, an interface unit 204 that receives image data and control signals transmitted from the host device, and an image forming process performed by the image forming apparatus 100. And a process control unit 205 for controlling.

  The central control unit 201 includes, for example, a microprocessor, a ROM (Read Only Memory), a RAM (Random Access Memory), a timer, and the like, and controls each unit. Specifically, when the central control unit 201 receives image data, control signals, and the like from the host device via the interface unit 204, the central control unit 201 supplies the image data, control signals, and the like to the process control unit 205. Further, the central control unit 201 controls the first motor control unit 202 and the second motor control unit 203 based on the presence or absence of the slack of the recording medium P detected by the slack detection unit 104. For example, the central control unit 201 determines the rotational drive start timing of the stepping motors 102a and 132a based on the detection result by the looseness detection unit 104, and refers to a table stored in a ROM or the like (not shown). Information indicating the number and period of pulse signals corresponding to the rotation angles and rotation speeds of the stepping motors 102 a and 132 a is acquired and supplied to the first motor control unit 202 and the second motor control unit 203.

  The first motor control unit 202 and the second motor control unit 203 control a stepping motor 102a that rotates the first medium transport unit 102 and a stepping motor 132a that rotates the second medium transport unit 132, respectively. Drive circuit. That is, each of the first motor control unit 202 and the second motor control unit 203 outputs a pulse signal to a terminal corresponding to each phase of the stepping motors 102a and 132a based on the information supplied from the central control unit 201. By applying a current in the form, the rotational driving and stopping operations of these stepping motors 102a and 132a are controlled. Note that the first motor control unit 202 can supply three-phase signals of low, medium, and high to terminals corresponding to the respective phases of the stepping motor 102a, and the stepping cycle is changed according to the phase switching period. The rotation speed of the motor 102a is changed. That is, the first motor control unit 202 gives a signal having a long phase switching cycle as a low-level phase signal, and gives a signal having a short phase switching cycle as the level becomes high. As a matter of course, the first motor control unit 202 gradually changes the switching cycle when switching the phase when driving the stepping motor 102a, and determines the rotation speed of the stepping motor 102a from acceleration. Control from speed and constant speed to deceleration. Such a first motor control unit 202 turns off the phase signal applied to the stepping motor 102a, thereby setting the conveyance speed V1 by the first medium conveyance unit 102 to 0 and setting the phase signal to a low level. The transport speed V1 is set to the low speed Vl, the phase signal is set to the medium level, the transport speed V1 is set to the standard speed Vm (> Vl), and the phase signal is set to the high level to set the transport speed V1 to the high speed Vh. (> Vm). On the other hand, the second motor control unit 203 can apply a one-phase signal to terminals corresponding to the respective phases of the stepping motor 132a. Then, the second motor control unit 203 turns off the phase signal given to the stepping motor 132a, thereby setting the conveyance speed V2 by the second medium conveyance unit 32 to 0, and turning on the phase signal, thereby conveying the phase signal. The speed V2 is a high speed Vh by the first medium transport unit 102.

  The interface unit 204 receives image data, control signals, and the like from a host device such as a personal computer provided outside the image forming apparatus 100 and the medium conveyance device 130 and supplies the image data and control signals to the central control unit 201.

  The process control unit 205 performs drive control of the image forming apparatus 100 based on image data, control signals, and the like received from the host device via the central control unit 201.

  In such an image forming system including the image forming apparatus 100 and the medium transport apparatus 130, when the recording medium P is transported, the recording medium P is stretched or excessively loosened under the control of the central control unit 201. As shown in FIG. 2C, the drive operation of the first medium transport unit 102 and the second medium transport unit 132 is maintained so as to maintain the slackened state by an appropriate amount. To control.

  Here, a state where the recording medium is stretched or excessively loosened will be described.

  First, the case where the recording medium is stretched can be considered as follows.

  As a first example of causing a state in which the recording medium is stretched, there is a case where the drawing load of the long recording medium wound around a reel or the like is large. In this case, in the image forming apparatus, a large load is applied to the shaft of the reel. Therefore, in an existing image forming system, when an attempt is made to feed the recording medium to the image forming apparatus to feed the recording medium in this state, the upstream side in the medium conveying direction is moved to the drive system that conveys the recording medium. A large load is applied in the pulling direction, and the recording medium is stretched.

  As a second example in which the recording medium is stretched, there is a case where the conveyance speed by the medium conveyance unit provided in the image forming apparatus is set close to the lower limit of the specification and is slow. This occurs when the difference between the conveyance speed by the medium conveyance unit and the conveyance speed by the image forming unit or the transfer unit is small, or these conveyance speeds are the same. In addition, since the angular speed of the roller pair constituting the medium transport unit is constant, the transport speed of the medium transport unit is slow even when the peripheral speed of the roller pair is reduced. In such an image forming system, the recording medium is stretched even in such a case.

  On the other hand, the case where the recording medium is excessively loosened can be considered as follows.

  First, as a first example in which a recording medium is excessively slackened, there is a case where a conveyance speed by a medium conveyance unit provided in the image forming apparatus is high. This occurs when the diameter of the roller pair constituting the medium transport unit is expanded due to thermal expansion and the peripheral speed is increased due to this. Also, due to variations in the motor that rotationally drives the medium transport unit, the transport speed is increased even when a product near the upper limit of the specification is used. In such an image forming system, in such a case, the recording medium is excessively loosened.

  Further, as a second example in which the recording medium is excessively slackened, there is a case where the conveyance speed by the image forming unit or the transfer unit is set near the lower limit of the specification and is slow. This occurs when the difference between the conveyance speed by the medium conveyance unit and the conveyance speed by the image forming unit or the transfer unit is large. In such an image forming system, the recording medium is excessively loosened even in such a case.

  As described above, in the existing image forming system, due to various factors, there is a problem that the recording medium is stretched or excessively slacked between the drive systems, and the stable medium conveyance cannot be performed. .

  On the other hand, in an image forming system including the image forming apparatus 100 and the medium transport apparatus 130, the first medium transport section 102 and the second medium transport section 132 are driven under the control of the central control section 201. By controlling the operation, the recording medium P is prevented from being stretched or excessively slackened. Specifically, in the image forming system, the recording medium P is conveyed according to a series of procedures as shown in FIG. Here, FIG. 5A to FIG. 5E are used to explain the state of the recording medium P, and FIG. 6 is used to explain the slack control sequence of the recording medium P. .

  First, as shown in FIG. 4, when the central control unit 201 receives a paper feed start instruction from the host apparatus in step S1 in step S1, the central control unit 201 controls the second motor control unit 203 in step S2. Then, the second medium transport unit 132 is rotationally driven to transport the recording medium P to the paper feed port of the image forming apparatus 100, for example, as shown in FIG. 5A (time t1 in FIG. 6). Here, the second medium transport unit 132 is rotationally driven under the control of the second motor control unit 203 only when a drive instruction is issued from the central control unit 201 via the communication cable 140. Otherwise, the recording medium P is transported as described above. Note that the second medium transport unit 132 operates to accelerate the transport speed V2 to the high speed Vh in order to feed the recording medium P while slackening it when a drive instruction is given.

  Further, the central control unit 201 determines in step S3 in FIG. 4 whether or not the recording medium P has been fed to the paper feed port of the image forming apparatus 100 based on the detection result by the paper feed detection unit 101. Here, when the central control unit 201 confirms that the output of the paper feed detection unit 101 is at a high level and the recording medium P is fed to the paper feed port of the image forming apparatus 100 (time in FIG. 6). t2) In step S4 in FIG. 4, the first motor control unit 202 is controlled to start rotation of the first medium transport unit 102, and the second motor control unit 203 is controlled to perform the second operation. The drive of the medium transport unit 132 is stopped. Specifically, for example, as shown in FIG. 5B, the central control unit 201 confirms that the recording medium P has been fed to the paper feeding port of the image forming apparatus 100, and the recording medium P is At the timing (time t3 in FIG. 6) immediately before reaching the first medium transport unit 102, the first medium transport unit 102 starts to rotate, and the transport speed V1 is set to the medium level as shown in FIG. An instruction is given to the first motor control unit 202 so as to accelerate to the standard speed Vm corresponding to. Then, the central control unit 201 performs the second medium conveyance at the timing (time t4 in FIG. 6) when the conveyance speed V1 by the first medium conveyance unit 102 is accelerated to the standard speed Vm at time t4 in FIG. An instruction is given to the second motor control unit 203 so as to stop the driving of the unit 132. As a result, the recording medium P is fed out from the first medium transport unit 102 and the leading end of the recording medium P is positioned in front of the looseness detection unit 104, as shown in FIG. Note that, as described above, the second medium transport unit 132 does not stop completely but is driven at the same transport speed as the transport speed Vm by the first medium transport unit 102 and acts as a transport load.

  Here, at time t5 in FIG. 6, for example, as shown in FIG. 5D, it is assumed that the leading edge of the recording medium P reaches the slackness detection unit 104 via the write start detection unit 103. At this time, the slack detection unit 104 outputs detection information indicating that the recording medium P is stretched, but the central control unit 201 does not perform slack control at this timing. Then, in step S5 in FIG. 4, the central control unit 201 determines whether or not a predetermined time T1 has elapsed after the start of driving of the first medium transport unit 102, and after the predetermined time T1 has elapsed, In S6, the slack control is started (time t6 in FIG. 6). Here, the reason why the slack control is not started immediately after confirming that the recording medium P is stretched is as follows. That is, since the recording medium P has a higher conveying speed by the first medium conveying unit 102 than a conveying speed by the transfer belt 107, for example, as shown in FIG. This is because looseness occurs by reaching the formation portion, and the looseness detection portion 104 detects the occurrence of looseness.

  Then, as the conveyance load of the recording medium P by the second medium conveyance unit 132 increases, the central control unit 201 first displays the result based on the detection result by the looseness detection unit 104 in step S7 in FIG. When it is confirmed that the recording medium P is stretched as in the state shown in 2 (a), the second motor control unit 203 is controlled to rotate the second medium transport unit 132 in step S8. Driving is started (time t7 in FIG. 6), and the recording medium P is placed between the first medium transport unit 102 and the second medium transport unit 132 as shown in FIG. 2B. Causes slack. Specifically, the central control unit 201 accelerates the transport speed V2 by the second medium transport unit 132 to a high speed Vh that is higher than the transport speed Vm by the first medium transport unit 102 at time t7 in FIG. Thus, an instruction is given to the second motor control unit 203. Thereby, the amount of the recording medium P conveyed from the second medium conveying unit 132 to the first medium conveying unit 102 is larger than the amount conveyed from the first medium conveying unit 102 to the image forming unit. There will be more and you will relax.

  Subsequently, in step S9 in FIG. 4, the central control unit 201 determines whether or not a predetermined time T2 has elapsed after the start of driving of the second medium transport unit 132, and after the predetermined time T2 has elapsed, In step S10, the conveyance speed V1 by the first medium conveyance unit 102 is accelerated from the standard speed Vm to the high speed Vh so that the recording medium P is in the state shown in FIG. An instruction is given to the first motor control unit 202 (time t8 in FIG. 6). Here, the predetermined time T2 is less than the time until the recording medium P actually stretches after the output from the slack detection unit 104 is detected to have switched to the direction in which the slack of the recording medium P has been eliminated. Is set.

  Here, the central control unit 201 confirms that the recording medium P has loosened based on the detection result by the looseness detection unit 104 in step S11 in FIG. 4, and the rear end of the recording medium P in step S12. Does not pass through the first medium transport unit 102, the process proceeds to step S13 (time t9 in FIG. 6). In step S13, the central control unit 201 determines whether or not the period during which the slackness detecting unit 104 continuously detects slack is less than the predetermined time T3. The predetermined time T3 is set to discriminate whether or not the detected slack is excessive slack, and the period during which slackness is continuously detected by the slack detection unit 104 is a predetermined time. When it is less than T3, the amount of slack is within the normal range, and when it is equal to or longer than the predetermined time T3, it indicates that the amount of slack exceeds the normal range and is excessive. Here, it is assumed that the period during which slackness is continuously detected by the slackness detection unit 104 is less than the predetermined time T3.

  Then, in step S14, the central control unit 201 returns the conveyance speed V1 by the first medium conveyance unit 102 to the standard speed Vm and stops the driving of the second medium conveyance unit 132 in step S14, as shown in FIG. As described above, an instruction is given to the first motor control unit 202 and the second motor control unit 203. In step S15 in FIG. 4, the central control unit 201 sets the transport speed V1 by the first medium transport unit 102 to the standard speed until it is confirmed that the recording medium P is stretched based on the detection result by the slackness detection unit 104. Continue control to Vm. Then, as a result of continuing such control, the central control unit 201 displays the detection result by the looseness detection unit 104 in step S15 as the conveyance load of the recording medium P by the second medium conveyance unit 132 increases. Based on this, when it is confirmed that the recording medium P has been stretched again, the process proceeds to step S7 via step S12 (time t10 to time t12 in FIG. 6).

  Here, the recording medium P is slackened again, the process proceeds from step S7 or step S15 in FIG. 4 to step S13, and the period in which slackness is continuously detected by the slackness detection unit 104 is equal to or longer than the predetermined time T3. Consider the case of determination (time t13 in FIG. 6). That is, for example, as shown in FIG. 7, the recording medium P is excessively slackened. FIG. 8 shows transition of the conveyance speeds V1 and V2 by the first medium conveyance unit 102 and the second medium conveyance unit 132 from time t10 to time t16 in FIG. In this case, the central control unit 201 shifts the process to step S16 in FIG. 4, and first decelerates the conveyance speed V1 by the first medium conveyance unit 102 to the low speed Vl corresponding to the low level. An instruction is given to the motor control unit 202. At this time, if the second medium transport unit 132 is rotationally driven, the central control unit 201 instructs the second motor control unit 203 to stop the second medium transport unit 132. Give instructions. As a result, the amount of the recording medium P conveyed from the first medium conveying unit 102 to the image forming unit is reduced, and the slack is eliminated.

  In step S <b> 17, the central control unit 201 sets the conveyance speed V <b> 1 by the first medium conveyance unit 102 to the low speed V <b> 1 until it is confirmed that the recording medium P is stretched based on the detection result by the slack detection unit 104. Continue control. Then, as a result of continuing such control, the central control unit 201 eliminates excessive slack, and confirms that the recording medium P has been stretched again based on the detection result by the slack detection unit 104 in step S17. In this case, in step S18, the first motor control unit 202 is instructed to return the conveyance speed V1 by the first medium conveyance unit 102 to the standard speed Vm, and via steps S12 and S7, In step S8, the second motor control unit 203 is controlled to start rotation of the second medium transport unit 132 (time t14 in FIG. 6). Thereafter, in step S10, the central control unit 201 gives an instruction to the first motor control unit 202 to accelerate the conveyance speed V1 by the first medium conveyance unit 102 from the standard speed Vm to the high speed Vh ( At time t15 in FIG. 6, in response to the occurrence of slack, in step S14 in FIG. 4, the transport speed V1 by the first medium transport unit 102 is returned to the standard speed Vm, and the second medium transport unit 132 An instruction is given to the first motor control unit 202 and the second motor control unit 203 to stop driving (time t16 in FIG. 6).

  The central control unit 201 repeatedly performs such control, and the trailing end of the recording medium P passes through the first medium transport unit 102 based on the detection result by the write start detection unit 103 in step S12 in FIG. In response to the determination, the series of processing ends.

  In the image forming system, under the control of the central control unit 201, the recording medium P is conveyed while performing such slackness control.

  As described above, in the image forming system shown as the first embodiment of the present invention, the second medium transport unit 132 provided upstream in the medium transport direction with respect to the first medium transport unit 102 is provided in advance. By driving and loosening the recording medium P, when a tension of the recording medium P is detected between the image forming unit and the first medium transport unit 102, the recording medium P should be loosened. Even if the conveying speed of the first medium conveying unit 102 is increased, the recording medium P can be stably conveyed, and the occurrence of color misregistration of the toner image, jamming of the recording medium P, and the like can be reliably prevented. Can do.

  Next, an image forming system shown as the second embodiment will be described.

  The image forming system shown as the second embodiment is an improvement of the image forming system shown as the first embodiment, and the second image forming system is configured according to the weight of the recording medium wound around the recording medium reel. Drive control of the medium transport unit is performed. Therefore, in the description of the second embodiment, the same components as those in the description of the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.

  The image forming system shown as the second embodiment is provided with a mechanism for detecting the load on the entire recording medium reel 131 in the medium conveying unit 130 around which the recording medium P is wound, and the amount of the recording medium P is small. When the load on the entire medium reel 131 is lighter than a predetermined reference value, the slack control is performed in substantially the same manner as in the first embodiment, while the amount of the recording medium P is large and the load on the entire recording medium reel 131 is large. Is larger than a predetermined reference value, the recording medium P tends to be stretched or excessively loosened, so that the second medium transport unit 132 is controlled to assist the operation of the first medium transport unit 102. To do.

  In order to realize such control, for example, a medium load detection unit 300 having a structure as shown in FIGS. 9A and 9B is provided on the recording medium reel 131. That is, the medium load detection unit 300 detects the load of the entire recording medium reel 131 including the elastic body 301 formed of a spring or the like fixed to the recording medium reel 131 and the wound recording medium P. Sensor 302.

  The elastic body 301 is fixed to the recording medium reel 131 so as to urge the recording medium reel 131 upward, and the recording medium is generated according to consumption of the recording medium P wound around the recording medium reel 131. The vertical movement of the reel 131 is supported.

  The medium load detection sensor 302 includes a micro switch that detects the vertical movement of the recording medium reel 131. Specifically, the medium load detection sensor 302 is in a state where the load of the entire recording medium reel 131 including the recording medium P is heavier than a predetermined reference value, and the recording medium reel 131 pushes the elastic body 301 downward. In this case, the load on the entire recording medium reel 131 is lighter than the reference value, and the recording medium reel 131 is turned off when the recording medium reel 131 is pushed upward by the urging force of the elastic body 301. Thus, the medium load detection sensor 302 detects whether or not the load on the entire recording medium reel 131 has reached a predetermined reference value.

  Such a detection result by the medium load detection unit 300 is supplied to the central control unit 201 as shown in FIG. The central control unit 201 controls the first motor control unit 202 and the second motor control unit 203 based on the detection result. Specifically, when the medium load detection unit 300 is in a state as shown in FIG. 9B, the central control unit 201 performs slack control substantially the same as that of the first embodiment, and detects the medium load. When the unit 300 is in the state shown in FIG. 9A, the slack control described later is performed.

  Here, unlike the first embodiment, the second motor control unit 203 outputs three steps of low, medium, and high phase signals to the stepping motor 132a as in the first motor control unit 202. The rotation speed of the stepping motor 132a is changed according to the phase switching period. That is, the second motor control unit 202 turns off the phase signal given to the stepping motor 132a, thereby setting the transport speed V2 by the second medium transport unit 132 to 0 and setting the phase signal to a low level. By setting the transport speed V2 to the low speed Vl and the phase signal to the medium level, the transport speed V2 is set to the standard speed Vm (> Vl), and by setting the phase signal to the high level, the transport speed V2 is set to the high speed Vh ( > Vm).

  In such an image forming system, the recording medium P is transported under the control of the central control unit 201 in accordance with a series of procedures as shown in FIGS. 11A and 11B, for example. Here, FIG. 12 is used to explain the slack control sequence of the recording medium P.

  First, as shown in FIG. 11A, when the central control unit 201 receives a paper feed start instruction accompanying an image formation instruction from the host apparatus in step S21, the second motor control unit 203 in step S22. And the second medium transport unit 132 is driven to rotate to transport the recording medium P to the paper feed port of the image forming apparatus 100 (time t21 in FIG. 12). At this time, the second medium transport unit 132 operates to accelerate the transport speed V2 to the standard speed Vm corresponding to the medium level.

  Further, the central control unit 201 determines whether or not the recording medium P has been fed to the paper feed port of the image forming apparatus 100 based on the detection result by the paper feed detection unit 101 in step S23 in FIG. judge. Here, when the central control unit 201 confirms that the output of the paper feed detection unit 101 is at a high level and the recording medium P is fed to the paper feed port of the image forming apparatus 100 (time in FIG. 12). t22) In step S24 in FIG. 11A, based on the detection result by the medium load detection unit 300, it is determined whether or not the load on the entire recording medium reel 131 is heavier than a predetermined reference value.

  Here, if the central control unit 201 determines that the load on the entire recording medium reel 131 is lighter than a predetermined reference value, the central control unit 201 proceeds to the processing from step S41 to step S55 in FIG. That is, the central control unit 201 performs substantially the same processing as the processing from step S4 to step S18 in FIG. 4 described in the first embodiment (time t23 to time t32 in FIG. 12). However, the central control unit 201 controls the second medium transport unit 132 to set the transport speed V2 to the standard speed Vm during the period that is not driven in the first embodiment, and performs the first embodiment. During the period of driving in the form, the vehicle is accelerated from the standard speed Vm to the high speed Vh. That is, the central control unit 201 controls the second medium transport unit 132 so as to assist the operation of the first medium transport unit 102.

  On the other hand, if the central control unit 201 determines that the load on the entire recording medium reel 131 is heavier than a predetermined reference value, the central control unit 201 controls the first motor control unit 202 in step S25 in FIG. Then, the rotational driving of the first medium transport unit 102 is started. Specifically, the central control unit 201 confirms that the recording medium P has been fed to the paper feeding port of the image forming apparatus 100 and immediately before the recording medium P reaches the first medium transport unit 102. At the timing (time t23 in FIG. 12), the first medium transport unit 102 is started to rotate, and as shown in FIG. 12, the transport speed V1 is accelerated to the standard speed Vm corresponding to the medium level. An instruction is given to the first motor control unit 202. At this time, the central control unit 201 does not stop the driving of the second medium transport unit 132 but continues the driving at the standard speed Vm.

  Here, it is assumed that the leading edge of the recording medium P reaches the slackness detection unit 104 via the write detection unit 103 at time t25 in FIG. At this time, the slackness detection unit 104 outputs detection information indicating that the recording medium P is stretched, but the central control unit 201 does not perform slackness control at this timing as in the first embodiment. . Then, in step S26 in FIG. 11A, the central control unit 201 determines whether or not a predetermined time T1 has elapsed after the start of driving of the first medium transport unit 102, and this predetermined time T1 has elapsed. Later, in step S27, the slack control is started (time t26 in FIG. 12).

  When the central control unit 201 confirms that the recording medium P is stretched based on the detection result by the looseness detection unit 104 in step S28 in FIG. 11A, in step S29, the second control unit 201 The second motor control unit 203 is instructed to accelerate the conveyance speed V2 by the medium conveyance unit 132 to a high speed Vh that is larger than the conveyance speed Vm by the first medium conveyance unit 102 (at time t27 in FIG. 12). ), The recording medium P is slackened between the first medium transport unit 102 and the second medium transport unit 132.

  Subsequently, in step S30 in FIG. 11A, the central control unit 201 determines whether or not a predetermined time T2 has elapsed after the start of driving of the second medium transport unit 132, and this predetermined time T2 has elapsed. After that, in step S31, an instruction is given to the first motor control unit 202 to accelerate the conveyance speed V1 by the first medium conveyance unit 102 from the standard speed Vm to the high speed Vh (time t28 in FIG. 12). ).

  Subsequently, the central control unit 201 confirms that the recording medium P has loosened based on the detection result by the looseness detection unit 104 in step S32 in FIG. 11A, and then in step S33, the medium load detection unit. Based on the detection result by 300, it is determined whether or not the load on the entire recording medium reel 131 is heavier than a predetermined reference value. If the central control unit 201 determines that the load on the entire recording medium reel 131 is lighter than a predetermined reference value, the central control unit 201 proceeds to step S44 in FIG. Processes similar to those in steps S7 to S18 in FIG. 4 described in the embodiment are performed. On the other hand, if the central control unit 201 determines that the load on the entire recording medium reel 131 is heavier than a predetermined reference value, the central control unit 201 is based on the detection result by the writing detection unit 103 in step S34 in FIG. Thus, it is determined whether or not the rear end of the recording medium P has passed through the first medium transport unit 102. When the trailing end of the recording medium P has not passed through the first medium transport unit 102, the central control unit 201 proceeds to step S35 via step S28, and the looseness detection unit 104 It is determined whether the period during which slackness is continuously detected is less than a predetermined time T3. Here, it is assumed that the period during which slackness is continuously detected by the slackness detection unit 104 is less than the predetermined time T3.

  Then, in step S36, the central control unit 201 performs the first motor control so as to return both the transport speed V1 by the first medium transport unit 102 and the transport speed V2 by the second medium transport unit 132 to the standard speed Vm. An instruction is given to the unit 202 and the second motor control unit 203 (time t29 in FIG. 12). In step S37 in FIG. 11A, the central control unit 201 confirms that the recording medium P is stretched based on the detection result by the slack detection unit 104, and the conveyance speed V1 by the first medium conveyance unit 102. And the control which made the conveyance speed V2 by the 2nd medium conveyance part 132 the standard speed Vm is continued. Then, as a result of continuing such control, the central control unit 201 confirms in step S37 that the recording medium P has been stretched again based on the detection result by the looseness detection unit 104. The process proceeds to step S28 via step S34 (time t30 to time t32 in FIG. 12).

  Here, excessive slack occurs in the recording medium P, the process proceeds from step S28 or step S37 to step S35 in FIG. 11A, and a period during which slackness is continuously detected by the slackness detection unit 104 is predetermined. Consider a case where it is determined that the time is T3 or more (time t33 in FIG. 12). In this case, the central control unit 201 shifts the processing to step S38 in FIG. 11A, and reduces both the conveyance speed V1 by the first medium conveyance unit 102 and the conveyance speed V2 by the second medium conveyance unit 132. An instruction is given to the first motor control unit 202 and the second motor control unit 203 so as to decelerate to the low speed Vl corresponding to the level. As a result, the amount of the recording medium P conveyed from the first medium conveying unit 102 to the image forming unit is reduced, and the slack is eliminated.

  In step S39, the central control unit 201 sets the conveyance speed V1 by the first medium conveyance unit 102 to the low speed Vl until it is confirmed that the recording medium P is stretched based on the detection result by the looseness detection unit 104. Continue control. Then, as a result of continuing such control, the central control unit 201 eliminates excessive slack, and confirms that the recording medium P has been stretched again based on the detection result by the slack detection unit 104 in step S39. In this case, in step S40, the first motor control unit 202 and the second medium transport unit 102 and the second medium transport unit 132 both return the transport speed V1 by the first medium transport unit 102 and the transport speed V2 by the second medium transport unit 132 to the standard speed Vm. 2 is given (time t34 in FIG. 12). Thereafter, the central control unit 201 accelerates the conveyance speed V2 by the second medium conveyance unit 132 to the high speed Vh in step S29 via step S33 and step S34 to step S28 in FIG. The second motor control unit 203 is instructed, and in step S31, the first motor control is performed so as to accelerate the conveyance speed V1 by the first medium conveyance unit 102 from the standard speed Vm to the high speed Vh. An instruction is given to the section 202 (time t35 in FIG. 12), and in response to the occurrence of slack, the transport speed V1 and the second medium transport by the first medium transport section 102 in step S36 in FIG. An instruction is given to the first motor control unit 202 and the second motor control unit 203 so that the conveyance speed V2 by the unit 132 is returned to the standard speed Vm (in FIG. 12). T36).

  The central control unit 201 repeatedly performs such control. In step S34 in FIG. 11A, the central end of the recording medium P causes the first medium transport unit 102 to be moved based on the detection result by the writing detection unit 103. A series of processes is terminated according to the determination that it has passed.

  In the image forming system, under the control of the central control unit 201, the recording medium P is conveyed while performing such slackness control.

  As described above, in the image forming system shown as the second embodiment of the present invention, the drive control of the second medium transport unit 132 is performed based on the load of the entire recording medium reel 131, and the first By feeding the recording medium P by both the medium transport unit 102 and the second medium transport unit 132, the first medium required for feeding the recording medium P that is heavy as viewed from the image forming apparatus 100 side. The burden on the transport unit 102 can be reduced, and the recording medium P can be transported stably. Further, in this image forming system, the recording medium P is not always fed by both the first medium conveyance unit 102 and the second medium conveyance unit 132, but the amount of the recording medium P is reduced and recording is performed. When the load on the entire medium reel 131 becomes lighter, the second medium transport unit 132 is controlled not to be driven, so that power consumption can be suppressed.

  The present invention is not limited to the embodiment described above. For example, in the above-described embodiment, the first medium transport unit 102 and the second medium transport unit 132 are driven by the stepping motors 102a and 132a. However, the present invention uses a DC motor as a drive source. It can also be applied to cases.

  Further, in the above-described embodiment, it has been described that the long recording medium P wound around the recording medium reel 131 is conveyed. However, the present invention is not limited to the long recording medium, and any recording can be performed. It can be applied to media. In the second embodiment, the medium load detection unit 300 detects the load of the entire recording medium reel 131 including the recording medium P. However, the present invention is not long as the recording medium P. Assuming the case of transporting the object, it is sufficient if it detects at least the weight of the recording medium P.

  Furthermore, the present invention can be applied to any device that processes an image on a predetermined recording medium, such as a printer, a scanner, a facsimile machine, a copying machine, and their functions. It is suitable to be applied to an apparatus having a composite.

  Thus, it goes without saying that the present invention can be modified as appropriate without departing from the spirit of the present invention.

1 is a diagram illustrating a configuration of an image forming system shown as a first embodiment of the present invention. It is a figure for demonstrating operation | movement of a slack detection part, and is a figure explaining the mode of a slack detection part in the state in which the recording medium is stretching between the recording medium reel and the image formation part. FIG. 10 is a diagram for explaining the operation of the slack detection unit, and the slack detection unit in a state where the recording medium is slack between the second medium transport unit in the medium transport device and the first medium transport unit in the image forming apparatus. FIG. It is a figure for demonstrating operation | movement of a slack detection part, and is a figure explaining the mode of a slack detection part in the state in which the recording medium is slacking only the predetermined amount between the 1st medium conveyance part and an image formation part. . FIG. 2 is a block diagram illustrating a configuration of a control system in the image forming system shown as the first embodiment of the present invention. 4 is a flowchart for describing a series of processes when a recording medium is transported in the image forming system shown as the first embodiment of the present invention. FIG. 3 is a diagram for explaining a state of a recording medium, and is a diagram for explaining a state in which the recording medium is conveyed to a paper feed port of the image forming apparatus. FIG. 4 is a diagram for explaining a state of a recording medium, and is a diagram for explaining a state in which the recording medium is fed into a paper feeding port of the image forming apparatus. It is a figure for demonstrating the state of a recording medium, and is a figure explaining a mode that the recording medium was drawn | fed out from the 1st medium conveyance part, and the front-end | tip was located in front of the slack detection part. It is a figure for demonstrating the state of a recording medium, and is a figure explaining a mode that the front-end | tip of a recording medium reached | attained the looseness detection part through the write-out detection part. FIG. 4 is a diagram for explaining a state of a recording medium, and is a diagram for explaining a state in which the recording medium is slackened between a first medium transport unit and an image forming unit. FIG. 3 is a diagram illustrating a recording medium slack control sequence in the image forming system shown as the first embodiment of the present invention. FIG. 6 is a diagram for explaining a state of a recording medium, and is a diagram for explaining a state in which excessive slackening of the recording medium occurs between a first medium conveyance unit and an image forming unit. It is a figure for demonstrating the transition of the conveyance speed by the 1st medium conveyance part and the 2nd medium conveyance part. FIG. 6 is a diagram illustrating a configuration of a medium load detection unit in an image forming system shown as a second embodiment of the present invention, in a case where the amount of recording medium is large and the load on the entire recording medium reel is heavier than a predetermined reference value It is a figure explaining the mode of a medium load detection part. FIG. 6 is a diagram illustrating a configuration of a medium load detection unit in an image forming system shown as a second embodiment of the present invention, in a case where the amount of a recording medium is small and the load on the entire recording medium reel is lighter than a predetermined reference value It is a figure explaining the mode of a medium load detection part. It is a block diagram explaining the structure of the control system in the image forming system shown as the 2nd Embodiment of this invention. 10 is a flowchart illustrating a series of processing when a recording medium is transported in the image forming system shown as the second embodiment of the present invention. FIG. 12 is a flowchart illustrating a series of processes when a recording medium is conveyed in the image forming system shown as the second embodiment of the present invention, and is a diagram illustrating a process following FIG. FIG. 10 is a diagram illustrating a recording medium slack control sequence in an image forming system shown as a second embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 Image forming apparatus 101 Paper feed detection part 102 1st medium conveyance part 102a, 132a Stepping motor 103 Writing start detection part 104 Slack detection part 110k, 110y, 110m, 110c Photosensitive drum 111k, 111y, 111m, 111c Charging roller 112k, 112y, 112m, 112c Exposure unit 113k, 113y, 113m, 113c Developing roller 114k, 114y, 114m, 114c Toner supply roller 115k, 115y, 115m, 115c Cleaning blade 116k, 116y, 116m, 116c Waste toner box 107 Transfer belt 108 Drive Roller 109 Belt idle roller 117k, 117y, 117m, 117c Transfer roller 121 Fixing roller 122 Pressure roller 123 Paper discharge detection unit 1 DESCRIPTION OF SYMBOLS 30 Medium conveyance apparatus 131 Recording medium reel 132 2nd medium conveyance part 140 Communication cable 201 Central control part 202 1st motor control part 203 2nd motor control part 204 Interface part 205 Process control part 300 Medium load detection part 301 Elasticity Body 302 Medium load detection sensor P Recording medium

Claims (10)

In a medium conveying apparatus for conveying a medium,
A first medium transport unit that transports the medium to an image processing unit that performs image processing on the medium;
A second medium transport unit provided upstream of the first medium transport unit in the medium transport direction;
A slack detection unit that detects whether the medium is slack between the first medium transport unit and the image processing unit;
A medium transport apparatus comprising: a control unit that controls a transport speed by the first medium transport unit and the second medium transport unit based on a detection result by the slack detection unit. 2. The medium according to claim 1, wherein the control unit controls to drive the second medium conveyance unit before starting to drive the first medium conveyance unit at the start of conveyance of the medium. Conveying device. When the control unit confirms that the slack amount of the medium is reduced and stretched based on the detection result by the slack detection unit, the control unit accelerates the transport speed by the first medium transport unit, and 2. The control according to claim 1, wherein when the slack amount of the medium exceeds the normal range and it is confirmed that excessive slack has occurred, the transport speed by the first medium transport unit is controlled to be reduced. Media transport device. A medium load detecting unit for detecting the weight of the medium;
The medium conveyance device according to claim 1, wherein the control unit performs drive control of the second medium conveyance unit based on a detection result by the medium load detection unit. The control unit confirms that the weight of the medium is heavier than a predetermined reference value based on the detection result by the medium load detection unit, and based on the detection result by the looseness detection unit, When it is confirmed that the amount of slack has been reduced and stretched, both the transport speeds of the first medium transport unit and the second medium transport unit are accelerated, and the weight of the medium exceeds a predetermined reference value. When it is confirmed that the medium is heavy and the amount of slack of the medium exceeds the normal range and excessive slack is generated, the medium is transported by the first medium transport unit and the second medium transport unit. The medium conveying apparatus according to claim 4, wherein both the speeds are controlled to be reduced. The control unit performs acceleration control of a conveyance speed by the first medium conveyance unit and / or the second medium conveyance unit after a predetermined time has elapsed after the start of driving of the first medium conveyance unit. The medium conveying device according to claim 3 or 5. The medium transport apparatus according to claim 6, wherein the control unit performs acceleration control of the first medium transport unit after driving the second medium transport unit. When the period during which slackness is continuously detected by the slackness detection unit is equal to or longer than a predetermined time, the control unit controls the transport speed of the first medium transporting unit and / or the second medium transporting unit. 6. The medium conveying device according to claim 3, wherein deceleration control is performed. The medium conveying apparatus according to any one of claims 1 to 8, wherein the medium is a long recording medium wound around a predetermined reel. In an image forming apparatus that forms an image on a recording medium based on input image data,
An image forming unit that forms an image on the recording medium;
A first medium transport unit that transports the recording medium to the image forming unit;
A second medium transport unit that transports the recording medium to the first medium transport unit;
A slack detection unit that detects whether the recording medium is slack between the first medium transport unit and the image forming unit;
An image forming apparatus comprising: a control unit that controls a conveyance speed by the first medium conveyance unit and the second medium conveyance unit based on a detection result by the looseness detection unit.