JP5125744B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus.

  2. Description of the Related Art There is known a printing machine configured to print on a sheet while holding the sheet on the outer peripheral surface of the cylinder (conveying drum) and sequentially delivering and conveying the sheet to the cylinder on the downstream side.

In addition, in such a printing machine, a printing machine that attenuates mechanical vibration by providing an operation member on the cylinder has been proposed (for example, see Patent Document 1).
JP-A-6-198855

  Here, in the case of an image forming apparatus having a configuration in which droplets are ejected from a droplet ejection head onto a recording medium that is held and conveyed on the outer peripheral surface of a conveyance body (conveyance drum), conveyance is performed. The fluctuation of the rotational speed of the body, that is, the fluctuation of the conveyance speed of the recording medium has a great influence on the image quality of the image formed on the recording medium.

  The present invention has been made to solve the above-described problems, and it is an object to effectively suppress fluctuations in the conveyance speed of a recording medium on which an image is formed by droplets ejected from a droplet ejection head. It is.

  The image forming apparatus according to claim 1 is installed side by side in the conveyance direction of the recording medium, and rotates when the rotational driving force is transmitted to each other, holds the recording medium on the outer peripheral surface, and delivers it downstream in the conveyance direction. An image is formed by droplets ejected from one or a plurality of droplet ejection heads on a plurality of conveyance bodies to be conveyed and one of the conveyance bodies and the recording medium held on the outer peripheral surface. Between the image forming transport body and one of the transport bodies installed on the downstream side in the transport direction from the image forming transport body, and press-contacted with the outer peripheral surface and rotated. When the recording medium is sandwiched and conveyed, a fixing conveyance body for fixing an image on the recording medium, and a pressure contact provided on the fixing conveyance body, and the fixing member is in pressure contact with the fixing conveyance body The pressure-contact force fluctuation part in which the state fluctuates, and Rotational speed fluctuation suppressing means for suppressing fluctuations in rotational speed of the image forming transport body or the fixing transport body, or at least one transport body installed between the image forming transport body and the fixing transport body It is characterized by providing these.

  The image forming apparatus according to claim 2 is characterized in that the rotational speed fluctuation suppressing means is a brake.

  The image forming apparatus according to claim 3 is characterized in that the brake is a magnetic powder braking device.

  5. The image forming apparatus according to claim 4, wherein when the fixing conveyance body is stopped for a predetermined time or more, the fixing conveyance body is rotated for a predetermined time or more, and then an image is formed on the recording medium. It is characterized by that.

  The image forming apparatus according to claim 5 is characterized in that the rotational speed fluctuation suppressing means is a flywheel.

  The image forming apparatus according to claim 6, wherein the droplet discharge head is provided with a main scanning direction which is a rotation axis direction of the image forming transport body as a longitudinal direction, and is provided on the outer peripheral surface of the image forming transport body. A plurality of nozzles for ejecting the droplets are two-dimensionally arranged on the nozzle surfaces arranged to face each other.

  The image forming apparatus according to claim 7 is characterized in that the rotational speed fluctuation suppressing means suppresses the rotational speed fluctuation of the fixing conveyance body.

  9. The image forming apparatus according to claim 8, further comprising a reading unit that reads an image of the recording medium held on the fixing conveyance body or the conveyance body on the downstream side of the fixing conveyance body. It is characterized by.

  As described above, according to the image forming apparatus of the first aspect, even when the pressure contact state in which the fixing member is pressed against the fixing conveyance body changes and an impact is applied to the fixing conveyance body, the image forming conveyance body or Rotational speed fluctuations of the image forming transport body are suppressed by suppressing rotational speed fluctuations of the fixing transport body or at least one transport body installed between the image forming transport body and the fixing transport body. As a result, there is an excellent effect that fluctuations in the conveyance speed of the recording medium on which an image is formed by droplets ejected from the droplet ejection head can be effectively suppressed.

  According to the image forming apparatus of the second aspect, it is possible to effectively suppress, at a low cost, fluctuations in the conveyance speed of the recording medium on which the image is formed by the droplets ejected from the droplet ejection head. It has an excellent effect.

  According to the image forming apparatus of the third aspect, it is possible to effectively suppress the fluctuation in the conveyance speed of the recording medium on which the image is formed by the droplets ejected from the droplet ejection head at a low cost. It has an excellent effect.

  According to the image forming apparatus of the fourth aspect, it is possible to stably suppress the fluctuation in the conveyance speed of the recording medium on which the image is formed by the droplets ejected from the droplet ejection head. It has the effect.

  According to the image forming apparatus of the fifth aspect, it is possible to effectively suppress the fluctuation in the conveyance speed of the recording medium on which the image is formed by the droplets ejected from the droplet ejection head at a low cost. , Has an excellent effect.

  According to the image forming apparatus of the sixth aspect, the nozzle interval in the main scanning direction as viewed in the rotation direction can be easily narrowed (high resolution can be easily achieved), and the fixing conveyance body. Even if the pressure contact state where the fixing member is pressed against the sheet fluctuates and an impact is applied to the fixing carrier, fluctuations in the conveyance speed of the recording medium on which the image is formed by the droplets ejected from the droplet ejection head are suppressed or prevented Therefore, it has an excellent effect that the landing accuracy of the droplets discharged from the nozzle can be maintained with high accuracy.

  According to the image forming apparatus of the seventh aspect, even when the pressure contact state in which the fixing member is pressed against the fixing conveyance body fluctuates and an impact is applied to the fixing conveyance body, fluctuations in the rotational speed of the fixing conveyance body are suppressed. Therefore, it is possible to suppress fluctuations in the rotation speed of the conveyance body over the entire apparatus, and as a result, fluctuations in the conveyance speed of the recording medium on which an image is formed by droplets ejected from the droplet ejection head, It has an excellent effect that it can be effectively suppressed at a low cost.

  According to the image forming apparatus of the eighth aspect, since the fluctuation in the rotational speed of the fixing conveyance body or the conveyance body installed on the downstream side in the conveyance direction with respect to the fixing conveyance body is suppressed, the image is fixed on the recording medium. It has an excellent effect that an image can be read accurately.

  The image forming apparatus according to the embodiment of the present invention will be described below. FIG. 1 shows a schematic configuration of an image recording apparatus according to the present invention. Further, the conveyance direction of the recording paper P is indicated by an arrow S, and the rotation direction of each conveyance drum is indicated by an arrow K.

[Image forming apparatus]
First, the overall configuration of the image forming apparatus 10 will be described. As shown in FIG. 1, in the image forming apparatus 10 according to the present embodiment, a plurality of processing units are arranged side by side along the transport direction S of a recording paper P as a recording medium. Each processing unit is provided with two cylindrical transfer drums as transfer bodies. In the present embodiment, all the transport drums have the same size (diameter and length). The recording paper P is held on the outer peripheral surface of the transport drum, and the recording paper P is sequentially transferred to the downstream transport drum and transported (see FIG. 3, details will be described later).

  Specifically, in order from the upstream side in the transport direction, the recording paper P is stacked and stored, and the paper supply unit 20 that feeds the stored recording paper P and the recording surface PA of the recording paper P (see FIG. 3). A pre-processing unit 30 for applying a pre-treatment by applying a treatment liquid, ink droplets TY, TM, TC, TK (each color from an ink jet device 44 onto a recording surface PA of a pre-processed recording paper P (with a treatment liquid applied) 3), an image forming unit 40 for forming an image, a drying unit 50 for drying the image formed on the recording surface PA of the recording paper P, and an image that fixes and fixes the dried image on the recording paper P. A fixing inspection unit 60 for discharging the recording paper P, and a discharge unit 70 for loading and storing the recording paper P on which the discharged recording paper P is discharged.

  Next, each processing unit will be described in detail.

[Paper Feed Unit]
The paper supply unit 20 is provided with a storage unit 22 in which recording paper P is stacked and stored. Then, the recording paper P stored in the storage unit 22 is fed to the preprocessing unit 30 one by one.

  The paper feeding unit 20 is provided with a control unit 24 that controls the entire image forming apparatus 10. The control unit 24 includes a control circuit (not shown) including, for example, a CPU, RAM, ROM, and the like. Various programs and various information (various data) are stored in advance in the ROM.

  Further, the paper feed unit 20 is provided with a drive motor 26 as drive means. The drive motor 26 drives and rotates the transport drum of each processing unit (details will be described later).

[Preprocessing unit]
In the pre-treatment liquid unit 30, a delivery transport drum 130 and a pretreatment transport drum 132 are rotatably provided. Above the pretreatment transport drum 132, a treatment liquid coating device 32 is provided in which the rotational axis direction of the pretreatment transport drum 132 is the longitudinal direction. Then, the processing liquid is applied to the recording surface PA of the recording paper P by the processing liquid coating device 32 (the processing liquid will be described later).

[Image unit]
In the image forming unit 40, a delivery transport drum 140 and an image formation transport drum 142 are rotatably provided.

  An ink jet device 44 is provided above the image forming conveyance drum 142. The ink jet device 44 includes ink jet recording heads 42Y, 42M, 42C, and 42K corresponding to yellow (Y), magenta (M), cyan (C), and black (K) colors.

  In the following, when distinguishing yellow (Y), magenta (M), cyan (C), and black (K), Y, M, C, and K are added after the code, and it is not necessary to distinguish between them. Omits Y, M, C, and K after the symbol.

  The nozzle surface 42A (see FIG. 6) of the ink jet recording head 42 has an image formable area (ink droplet) that is equal to or larger than the maximum width (width in the main scanning direction) of the recording paper P on which image formation is assumed. Discharge region).

  The ink jet recording heads 42Y, 42M, 42C, and 42K are arranged with the rotation axis direction (main scanning direction) of the image forming transport drum 142 as the longitudinal direction, and are arranged side by side along the circumferential direction.

  The nozzle surface 42 </ b> A (see FIG. 6) of the inkjet recording head 42 is disposed so as to face the outer peripheral surface 142 </ b> A of the image forming conveyance drum 142. A plurality of nozzles 46 (see FIG. 6) are formed on the nozzle surface 42A, and ink droplets T (see FIG. 3) are ejected from the nozzles 46 by known means such as a thermal method or a piezoelectric method. . Then, when the ink droplets T land on the recording surface PA of the recording paper P, a color image is formed.

  The direction orthogonal to the conveyance direction of the recording paper P, that is, the rotation axis direction of the image forming conveyance drum 142 is the main scanning direction W, and the conveyance direction S is the sub-scanning direction.

  FIG. 6 shows the nozzle surface 42 </ b> A of the inkjet recording head 42. As shown in FIG. 6, the nozzles 46 are two-dimensionally arranged in a plane (matrix arrangement). More specifically, the nozzle row in which the nozzles 46 are arranged in the main scanning direction W (the rotation axis direction of the image forming conveyance drum 142) is shifted in the main scanning direction W and the sub scanning direction S (image forming conveyance). The drum 142 is arranged in the rotation direction of the drum 142 and the conveyance direction of the recording paper P. When viewed in the sub-scanning direction S, the nozzles 46 are arranged in the main scanning direction W at equal intervals.

  Then, by arranging these two-dimensionally in a matrix, the interval between the nozzles 46 in the main scanning direction W can be substantially reduced.

  The control unit 24 (see FIG. 1) described above determines the ejection timing and the nozzle 44 to be used according to the image signal, and ejects ink droplets TY, TM, TC, TK (see FIG. 3). The In addition, the landing position can be determined with high accuracy by ejecting ink droplets TY, TM, TC, and TK in synchronization with an encoder (not shown) that detects the rotational speed of the image forming conveyance drum 142. it can.

  The inkjet device 44 shown in FIG. 1 is provided with a maintenance device (not shown) that performs various maintenance such as cleaning of the nozzle surface 42A of the inkjet recording head 42 and discharging of the thickened ink. The ink jet recording heads 42Y, 42M, 42C, and 42K are movable, and the nozzle surface 42A of the ink jet recording head 42 is retracted from the state close to the outer peripheral surface 42A of the image forming conveyance drum 142. Thus, the maintenance by the maintenance device described above is performed.

  In addition, the ink jet device 44 is provided with ink tanks (not shown) for replenishing the ink jet recording heads 42Y, 42M, 42C, and 42K with the respective color inks.

  Here, the processing liquid applied to the recording surface PA of the recording paper P in the pretreatment unit 30 described above aggregates due to the reaction of the color material (pigment) dispersed in the ink, and the color material (pigment). ) And the solvent. Therefore, when the ink droplet T (FIG. 3) lands, an aggregate is formed so that a color material flow or the like does not occur on the recording surface PA of the recording paper P.

[Ink drying unit]
In the drying unit 50, a delivery transport drum 150 and an ink drying transport drum 152 are rotatably provided. Above the ink drying transport drum 152, a hot air nozzle 52 and an IR heater 54 are provided so as to be close to the outer peripheral surface 452A. The hot air nozzle 52 and the IR heater 54 dry the solvent in the ink separated by the color material aggregating action by the processing liquid on the recording surface PA of the recording paper P, thereby forming a thin image layer.

[Image fixing inspection unit]
The image fixing inspection unit 60 is rotatably provided with a delivery transport drum 160 and a fixing inspection transport drum 162. Further, the image fixing inspection unit 60 is provided with a fixing roll 62 that is in pressure contact with the outer peripheral surface 162A of the fixing inspection transport drum 162.

  FIG. 4 schematically shows a main part of the image fixing inspection unit 60. As shown in FIG. 4, the fixing roll 62 rotates following the rotation of the fixing inspection transport drum 162 about the rotation shaft 64.

  The fixing roll 62 has a structure in which an elastic layer 63 is formed on the surface. The rotating shaft 64 of the fixing roll 62 is pressed in the normal direction of the fixing inspection conveyance drum 162 by a coil spring 66 as a pressing means via a bearing 65. That is, the fixing roll 62 is in pressure contact with the outer peripheral surface 162A of the fixing inspection conveyance drum 162. Then, the recording paper P is sandwiched and conveyed between the fixing roll 62 and the nip portion 62 (nip portion), whereby the image is fixed and fixed on the recording paper P.

  Further, as shown in FIGS. 1 and 4, an image reading sensor 68 (this embodiment) as a reading unit arranged with the rotation axis direction as a longitudinal direction downstream of the conveyance direction (rotation direction) of the fixing roll 62. In the form, an inline sensor is used). Then, when the recording paper P is conveyed and passes below the image reading sensor 68, the fixed image is read. The read information thus read is sent to the control unit 24 (see FIG. 1) and analyzed to check whether there is any abnormality. If there is any abnormality in the image, the control unit 24 issues a warning to a control panel (not shown), for example.

  Further, an electromagnetic powder brake 200 is provided on the conveyance drum 162 for fixing inspection. Therefore, a predetermined load (rotational resistance) is applied to the fixing inspection transport drum 162 by the electromagnetic powder brake 200. The electromagnetic powder brake 200 is an electromagnetic brake (brake) using a magnetic powder (powder) sealed in a gap as a torque transmission medium. Note that the fixing inspection transport drum 162 is applied with a predetermined load (rotational resistance) by the electromagnetic powder brake 200, but is configured to rotate at a predetermined rotational speed.

[Discharge unit]
As shown in FIG. 1, the recording paper P on which the image is fixed is discharged to the discharge unit 70, stacked, and stored.

[Drive system]
Next, the drive system of the image forming apparatus 10 will be described. In addition, since it is the same for each conveyance drum, the conveyance drums 130, 132, and 140 are illustrated and described as representatives.

  FIG. 2 is an explanatory diagram for explaining a drive system of the image forming apparatus 10. As shown in FIG. 2, gears 131, 133, and 141 serving as driving force transmitting means are provided at the ends of the transport drums 130, 132, and 140 in the rotation axis direction. These gears 131, 133, 141 are meshed with each other, and the rotational driving force is transmitted.

  A pulley 134 is provided outside the delivery conveyance drum 130. A belt 138 is wound around the pulley 134 and a pulley 136 provided on the rotation shaft of the drive motor 26. When the rotation shaft of the drive motor 26 rotates, the rotational driving force is transmitted via the pulleys 136 and 134 and the belt 138, and the delivery transport drum 130 rotates.

  When the delivery transport drum 130 rotates, the rotational drive force is transmitted by the gears 131, 133, 141 serving as the drive force transmission means described above, and the pretreatment transport drum 132 and the delivery transport drum 140 rotate. The transport drums 142 to 162 installed on the downstream side in the transport direction with respect to the delivery transport drum 140 also have gears at the end portions in the rotational axis direction and similarly rotate by receiving a rotational driving force. Since the gears of the respective conveying drums have the same size and the same number of teeth, the respective conveying drums rotate at the same rotational speed. Further, as described above, a predetermined load (rotational resistance) is applied to the conveyance drum 162 for fixing inspection by the electromagnetic powder brake 200, but the rotational driving force applied by the drive motor 26 is the same. Therefore, each conveyance drum rotates at a predetermined rotational speed.

  In the drawings other than FIG. 2, the illustration of gears is omitted in order to avoid complication (to avoid difficulty in viewing).

[Recording paper transport system (holding and delivering recording paper)]
Next, the conveyance of the recording paper P, that is, the mechanism in which the outer peripheral surface of each conveyance drum holds the recording paper P and the delivery of the recording paper P to the downstream conveyance drum will be described. Since all the transport drums are the same, the transport drums 140, 142, and 150 are illustrated and described as representatives.

  FIG. 3 is an explanatory diagram for explaining the conveyance system of the recording paper P, that is, the holding and delivery of the recording paper P. As shown in FIG. 3, the outer circumferential surfaces 140A, 142A, and 150A of the transport drums 140, 142, and 150 have concave grooves 140D and 140F, concave grooves 142D and 142F, and concave grooves 150D and 150F that have the rotation axis direction as the groove direction. Is formed. The concave groove 140D and the concave groove 140F are formed on opposite sides (positions facing each other) across the rotation axis (circular center). Similarly, the concave groove 142D and the concave groove 142F, and the concave groove 150D and the concave groove 150F are also formed on the opposite side (opposite positions) across the rotation axis.

  In the concave grooves 140D and 140F, the concave grooves 142D and 142F, and the concave grooves 150D and 150F, a rotation shaft 252 disposed in parallel with the rotation axis direction is provided. A plurality of grippers 250 are fixed to the rotating shaft 252 at predetermined intervals in the axial direction (for example, at equal intervals). The front end of the gripper 250 slightly protrudes from the outer peripheral surfaces 140A, 142A, 150A of the transport drums 140, 142, 150.

  Then, the rotation shaft 252 is rotated in both forward and reverse directions by an actuator (not shown), whereby the gripper 250 is rotated in both forward and reverse directions along the substantially circumferential direction of the transport drums 140, 142, 150, and the recording paper P is transported downstream in the transport direction. The side end portion can be held and separated.

  Further, as shown in the drawing, at the transfer position where the outer peripheral surface 140A of the delivery transport drum 140 and the outer peripheral surface 142A of the transport drum 142 face each other, the gripper 250 of the image formation transport drum 142 is changed from the gripper 250 of the delivery transport drum 140. The recording paper P can be delivered to the camera. Similarly, from the gripper 250 of the image forming transport drum 142 to the gripper 250 of the transfer transport drum 150 at the transfer position where the outer peripheral surface 142A of the image forming transport drum 142 and the outer peripheral surface 150A of the delivery transport drum 150 face each other. The recording paper P can be delivered.

  Note that the illustration of the grooves and grippers is omitted in FIG. 3 and drawings other than FIGS. 4 and 5 described later in order to avoid complication (to avoid difficulty in viewing).

[Jump stand (pressure contact variation part)]
FIG. 4 is a side view schematically showing a main part of the fixing inspection unit 60. FIG. 5 shows an enlarged view in which the main part of FIG. 4 is enlarged.

  As shown in FIG. 4, concave grooves 162D and 162F having the rotation axis direction as the groove direction are also formed on the outer peripheral surface 162A of the fixing inspection conveyance drum 162, and the gripper 250 is fixed to the concave grooves 162D and 162F. A rotating shaft 252 is provided.

  As in the present embodiment, in a configuration in which the fixing roll 62 is pressed against the outer peripheral surface 162A of the fixing inspection transport drum 162 and the image is fixed, the fixing roll 62 is kept in constant contact with the outer peripheral surface 162A. Will interfere with the concave grooves 162D and 162F and the gripper 250 provided on the outer peripheral surface 162A. Therefore, in the present embodiment, in order to prevent interference, the fixing roll 62 is moved in the normal direction from the upstream side in the transport direction to the downstream side in the transport direction of the concave grooves 162D and 162F to avoid the interference by moving away from the outer peripheral surface 162A. A jump base 280 is provided.

  The jump base 280 is a convex part having a mountain shape, and is joined to the outer end of the outer peripheral surface 162A of the fixing inspection transport drum 162 in the rotation axis direction. An end portion 280A on the upstream side in the conveyance direction of the jump table 280 is located upstream of the concave grooves 162D and 162F and the gripper 250, and an end portion 280B on the downstream side in the conveyance direction of the jump table 280 is from the concave grooves 162D and 162F. Is also located downstream.

  Then, as shown in FIG. 5, the fixing roll 62 moves along the outer peripheral surface 280 </ b> C of the jump base 280 instead of the outer peripheral surface 162 </ b> A. In other words, the fixing roll 62 moves from the upstream side in the transport direction to the normal direction outside the concave grooves 162D and 162F and the gripper 250 and moves away from the outer peripheral surface 162A, and then on the downstream side in the transport direction from the concave grooves 162D and 162. Land on the outer peripheral surface 162A again and press contact.

  Here, with the movement of the fixing roll 62 along the outer peripheral surface 280C of the jump base 280, that is, the movement of the fixing roll 62 in the normal direction, the pressure contact state of the fixing roll 62 changes abruptly. Then, due to the sudden change in the pressure contact state, the fixing inspection conveyance drum 162 is subjected to an impact (impact is generated). Particularly, the impact at the moment when the fixing roll 62 rides on the end 280B of the jumping base 280 and the moment when the fixing roll 62 reaches the outer peripheral surface 162A from the end 280C of the jumping base 280 is large. In the present embodiment, the jump base 280 corresponds to the pressure contact force variation portion.

[Run-in operation]
Next, a break-in operation of the electromagnetic powder brake 200 will be described.
When the powder brake 200 has been stopped for a long time (long time), the magnetic powder (powder) inside the powder brake 200 may settle due to gravity and may be biased. When the magnetic powder (powder) is biased in this way, the brake performance (addition of rotational resistance) is not stable. Therefore, in the image forming apparatus 10 of the present embodiment, in order to stabilize the brake performance when it has been stopped for a long time, the powder brake 200, that is, the conveying drum 162 is rotated for a predetermined time to stabilize the magnetic performance (powder). Image formation is performed after a break-in operation to eliminate the bias.

  Therefore, the operation when the image forming apparatus 10 (see FIG. 1) is turned on and started up, that is, when the apparatus is started, will be described below with reference to the flowchart shown in FIG.

  As shown in FIG. 7, when the image forming apparatus 10 (see FIG. 1) is turned on in step 300, the operation at the time of starting the apparatus is started. In step 302, the operation record of the apparatus stored in the control unit 24 (see FIG. 1) is read. In step 304, a stop period (stop time) T1 is calculated from the operation record. In step 306, it is determined whether the stop period T1 is longer than a preset threshold period (threshold time) T2. That is, it is determined whether the image forming apparatus 10 (see FIG. 1) has been idle for a long time.

  If the stop period T1 is shorter than the threshold period T2, that is, if it has not been suspended for a long time, the process proceeds to step 308 and performs a normal start-up operation, and then proceeds to step 310 to start image formation and ends image formation. Go to 312 and finish.

  When the stop period T1 is longer than the threshold period T2, that is, when the stop period is long, the process proceeds to step 314, performs a break-in operation for a predetermined time stored in advance, and then proceeds to step 308.

  The above is based on the assumption that the power is turned off during a long vacation (summer vacation or year-end and New Year holidays). However, in the case where the apparatus may pause for a long time even when the power is kept on, the running-in operation may be similarly performed before image formation.

  The threshold period T2 and the running-in time vary depending on the powder brake to be used, the rotation speed of the transport drum 162, and the like. Therefore, the threshold period T2 and the running-in time are determined by conducting an experiment in advance.

[Action and effect]
Next, functions and effects of the present embodiment will be described.

  As shown in FIG. 5, as the fixing roll 62 moves along the outer peripheral surface 280 </ b> C of the jump base 280, that is, in the normal direction of the fixing roll 62, the pressure contact state of the fixing roll 62 changes abruptly. An impact is applied to the conveyance drum 162 for fixing inspection due to the rapid change in the pressure contact state. In particular, the impact at the moment when the fixing roll 62 rides on the end 280B of the jumping base 280 and the moment when the fixing roll 62 lands on the outer peripheral surface 162A from the end 280A of the jumping base 280 is large.

  Here, in the case of a configuration to which the present invention is not applied, a rotational speed variation occurs in the fixing inspection transport drum 162 due to an impact applied to the fixing inspection transport drum 162. In addition, the rotational speed fluctuation | variation by an impact is made into the rapid rotational speed fluctuation | variation which occurs in a very short time. This rapid rotational speed fluctuation (impact) is also transmitted to the image forming conveyance drum 142, and the rotational speed fluctuation occurs in the image forming conveyance drum 142. As a result, the conveyance speed of the recording paper P held on the outer peripheral surface 142A of the image forming conveyance drum 142 fluctuates, and a positional deviation occurs in the landing position of the ink droplet T.

  In particular, as shown in FIG. 6, when the nozzles 44 are two-dimensionally arranged as in the present embodiment, fluctuations in the transport speed of the recording paper P, that is, speed fluctuations in the sub-scanning direction, Since it also affects W, the image quality is greatly affected by the displacement of the landing position.

  More specifically, as schematically illustrated in FIG. 11A, ink is ejected from the nozzles 46 in the rows V and Z that are shifted in the main scanning direction W by shifting the ejection timing. By ejecting the droplets TV and TZ, the recording surface PA of the recording paper P is controlled to land on the same straight line as shown in FIG.

  However, if the conveyance speed in the sub-scanning direction S varies (if the conveyance speed of the recording paper P varies), it does not land on the same straight line in the main scanning direction W as shown in FIG. In other words, the influence on the image quality due to the positional deviation of the landing position of the ink droplet T caused by the fluctuation in the conveyance speed of the recording paper P is large.

  However, in the present embodiment, as described above, since the load is applied to the fixing inspection transport drum 162 by the powder brake 200, the impact caused by the change in the pressure contact state of the fixing roll 62 causes the fixing inspection transport drum. Even if it adds to 162, the rotational speed fluctuation | variation of the conveyance drum 162 is suppressed. Therefore, the rotational speed fluctuation (impact) transmitted to the image forming conveyance drum 142 is also suppressed. That is, fluctuations in the conveyance speed of the recording paper P are suppressed. As a result, the displacement of the landing position of the ink droplet T is suppressed.

  In particular, even when the nozzles 44 are two-dimensionally arranged as in this embodiment (when the influence of fluctuations in the conveyance speed of the recording paper P is large), the displacement of the landing position is effectively reduced. Since it can suppress, ie, a landing precision can be maintained with high precision, it is suitable.

  As described above, in the present embodiment, ink droplets TY, TM, TC, and T are ejected in synchronization with an encoder (not shown) that detects the rotational speed of the image forming conveyance drum 142. Since such an impact (impulse), that is, a rapid fluctuation in rotational speed that occurs in a very short time, may not follow sufficiently or may not follow enough, the application of the present invention is effective.

  Further, since fluctuations in the rotation speed of the fixing inspection conveyance drum 162 are suppressed, reading noise of a fixed image read by the image reading sensor 68 is suppressed.

  In this way, only by providing the powder brake 200 on the fixing inspection transport drum 162 (by providing only one powder brake 200 only on the fixing transport drum 162), in other words, the rotational speed fluctuation of the fixing inspection transport drum 162 is changed. By suppressing only this, fluctuations in the conveyance speed of the recording paper P on which an image is formed by the ink droplets T ejected from the inkjet recording head 42, and reading noise of the fixed image read by the image reading sensor 68, Both can be suppressed.

  In other words, both fluctuations in the conveyance speed of the recording paper P on which the image is formed by the ink droplets T ejected from the ink jet recording head 42 and reading noise of the fixed image read by the image reading sensor 68 are both. Low cost and effective suppression.

[First modification]
Next, an image forming apparatus according to a first modification of the embodiment of the present invention will be described.

  As shown in FIG. 8, a brake gear 230 is meshed with the gear 163 of the fixing inspection conveyance drum 162, and a powder brake 201 is provided on the brake gear.

  The brake gear 230 has a smaller diameter and a smaller number of teeth than the gear 163 of the transport drum 162. Therefore, the load (brake torque) of the powder brake 201 transmitted to the conveying drum 162 (gear 163) can be increased by the gear ratio.

  As a result, the degree of freedom of design is increased. For example, even if a powder brake 201 having a low brake torque and a low price is used, a load similar to that of the powder brake 200 (FIG. 1) is applied to the transport drum 162. be able to. Therefore, the rotational speed fluctuation of the image forming conveyance drum 142 can be suppressed at a lower cost.

[Second modification]
Next, an image forming apparatus according to a second modification of the embodiment of the present invention will be described.

  As shown in FIG. 9, a disk-shaped flywheel 500 is provided on the rotation shaft 165 of the conveyance drum 162 for fixing inspection. Therefore, the inertia (inertia) of the transport drum 162 is increased.

  As a result, even if an impact caused by a sudden change in the pressure contact state of the fixing roll 62 is applied to the fixing inspection conveyance drum 162, the rotation speed fluctuation of the fixing inspection conveyance drum 162 is suppressed. Therefore, the rotational speed fluctuation (impact) transmitted to the image forming transport drum 142 is also suppressed, the rotational speed fluctuation of the image forming transport drum 142 is suppressed, and the transport speed fluctuation of the recording paper P is suppressed. As a result, the displacement of the landing position of the ink droplet T is suppressed.

  Further, since fluctuations in the rotation speed of the fixing inspection conveyance drum 162 are suppressed, reading noise of a fixed image read by the image reading sensor 68 is suppressed.

  Moreover, although illustration is abbreviate | omitted, brakes (brakes) other than a powder brake may be sufficient. For example, a drum brake or a disc brake may be used.

[Others]
In addition, this invention is not limited to the said embodiment.

  For example, in the above-described embodiment, the pressure contact fluctuation portion where the pressure contact state in which the fixing roll 62 presses against the fixing inspection conveyance drum 162 rapidly changes is the jump table 280, but is not limited thereto. For example, in the configuration in which the jump stand 280 is not provided, when the fixing roll 62 passes through the gripper or the groove (when overriding), the pressure contact state of the fixing roll 62 rapidly changes. It becomes the pressure contact fluctuation part. Further, the pressure contact force variation part may be a part or a structure other than the jump stand, the gripper, and the groove. For example, if a convex portion or a concave portion is formed on the outer peripheral surface of the conveyance drum (conveyance body) for some purpose, the convex portion or the concave portion becomes the pressure contact force varying portion. In short, a portion or structure where the pressure contact state in which the fixing member (fixing roll) is pressed against the fixing conveyance drum (conveyance body) abruptly varies is the pressure variation portion.

  Further, for example, in the image forming apparatus 10 of the above-described embodiment, the image reading sensor 68 reads the image of the recording paper P held on the conveyance drum 162 for fixing inspection. That is, the fixing inspection unit 60 (fixing inspection transport drum 162) performs both the fixing of the image and the reading inspection of the fixed image, but is not limited thereto.

  For example, as shown in FIG. 10, the processing unit disposed on the downstream side in the transport direction of the drying unit 50 is an image fixing unit 61 that performs only fixing, and between the image fixing unit 61 and the discharge unit 70. Alternatively, the image forming apparatus 11 may include an image inspection unit 80 that performs a reading inspection.

  Even in such a configuration, by providing the fixing conveyance drum 163 with the powder brake 200 and the like, fluctuations in the rotation speed of the image forming conveyance drum 142 are suppressed, and the rotation speed of the inspection conveyance drum 182 is suppressed. Variations are also suppressed.

  Further, the image reading sensor 68 as a reading unit is an inline sensor in the above embodiment, but is not limited thereto. It may be configured to read by reading means other than the inline sensor.

  The powder brakes 200 and 201 and the flywheel 500 as the rotational speed fluctuation suppressing means are provided so as to suppress the rotational speed fluctuation of the fixing inspection conveyance drum 162, but are not limited thereto. Any one transport drum from the image forming transport drum 142 to the fixing inspection transport drum 162 (the image forming transport drum 142 or the fixing inspection transport drum 162, or the image forming transport drum 142 to the fixing transport drum 162. The rotation speed fluctuation of at least one transport drum installed between the two may be suppressed.

  For example, it may be provided so as to suppress fluctuations in the rotational speed of the delivery transport drum 160, or may be provided so as to suppress fluctuations in the rotational speed of the image forming transport drum 142. Alternatively, two rotation speed fluctuations of the fixing inspection conveyance drum 162 and the drying conveyance drum 152 may be suppressed. However, in the case where it is not provided so as to suppress fluctuations in the rotation speed of the conveyance drum 162 for fixing inspection, there is no effect of suppressing the reading noise by the image reading sensor 68.

  Further, for example, in the above-described embodiment, the delivery transport drum 130 arranged on the most upstream side in the transport direction is rotationally driven by the drive motor 26 (drive means), but is not limited thereto. Any conveyance drum may be driven to rotate.

  In the above embodiment, the four inkjet recording heads 42Y, 42M, 42C, and 42K corresponding to the respective colors of yellow (Y), magenta (M), cyan (C), and black (K) are provided. It is not limited to. For example, five or more inkjet recording heads may be provided (for example, an inkjet recording head corresponding to light yellow or light magenta may be provided). Alternatively, three or less, for example, only one inkjet recording head may be provided (monochrome).

  The “recording medium” that is the target of image recording in the image forming apparatus of the present invention includes a wide variety of objects as long as the droplet discharge head is an object that discharges droplets. In other words, the dot pattern on the recording medium obtained by attaching the droplet onto the recording medium is widely included in the “image” or “recorded image” obtained by the recording apparatus of the present invention. Therefore, the recording apparatus of the present invention is not limited to that used for recording characters and images on recording paper. In addition, the recording medium includes a recording medium other than the recording paper, such as an OHP sheet, but also includes, for example, a substrate on which a wiring pattern or the like is formed. The “image” includes not only general images (characters, pictures, photographs, etc.) but also the above-described wiring patterns, organic thin films, and the like. The liquid to be ejected is not limited to ink. For example, production of a color filter for display by discharging colored ink on a polymer film or glass, formation of bumps for component mounting by discharging molten solder onto the substrate, and organic EL solution on the substrate For general liquid droplet ejecting devices intended for various industrial applications, such as the formation of EL display panels that are ejected onto the substrate and the formation of bumps for electrical mounting that are performed by ejecting molten solder onto the substrate. The invention can be applied.

1 is a schematic configuration diagram schematically showing a configuration of an image recording apparatus according to the present invention. It is explanatory drawing explaining the structure of the drive system of the image recording apparatus which concerns on this invention. FIG. 3 is an explanatory diagram illustrating a recording paper conveyance system in the image recording apparatus according to the present invention. FIG. 3 is a side view schematically showing a main part of a fixing inspection unit. It is the enlarged view to which the principal part of FIG. 4 was expanded. It is explanatory drawing explaining arrangement | positioning of the nozzle of an inkjet recording head. It is a flowchart explaining the running-in operation performed at the time of starting. It is explanatory drawing which shows typically the principal part of a 1st modification. It is explanatory drawing which shows the principal part of a 2nd modification typically. It is a schematic block diagram which shows typically the structure of the image recording apparatus of another structure. (A) is a schematic diagram schematically showing two nozzle rows arranged shifted in the main scanning direction, and (B) is an explanatory diagram for explaining a case where ink droplets land on the same straight line. (C) is an explanatory diagram for explaining a case where ink droplets do not land on the same straight line due to fluctuations in the transport speed in the sub-scanning direction.

Explanation of symbols

10 Image forming apparatus 42Y Inkjet recording head (droplet ejection head)
42M inkjet recording head (droplet ejection head)
42C inkjet recording head (droplet ejection head)
42K inkjet recording head (droplet ejection head)
62 Fixing roll (fixing member)
68 Inline sensor (reading means)
130 Delivery drum for delivery (conveyor)
132 Pretreatment transport drum (transport body)
140 Transport drum for delivery (transport body)
142 Image Forming Conveying Drum (Image Forming Conveying Body)
150 Delivery drum for delivery (conveyance body)
152 Drying transport drum (transport body)
160 Delivery drum for delivery (conveyance body)
162 Fixing inspection transport drum (fixing transport body)
163 Fixing transport drum (fixing transport body)
180 Delivery drum for delivery (conveyance body)
182 Transport drum for inspection (transport body)
200 Powder brake (rotational speed fluctuation suppression means, brake, magnetic powder braking device)
201 Powder brake (rotational speed fluctuation suppressing means, brake, magnetic powder braking device)
230 Brake gear (rotational speed fluctuation suppression means)
280 Jump stand (Pressure force fluctuation part)
500 Handwheel P Recording paper (recording medium)
S Transport direction TY Ink droplet (droplet)
TM ink droplet
TC ink droplet (droplet)
TM ink droplet

Claims (8)

A plurality of conveyance bodies that are installed side by side in the conveyance direction of the recording medium, rotate by transmitting a rotational driving force to each other, hold the recording medium on the outer peripheral surface, and deliver and convey it downstream in the conveyance direction;
An image forming transport body that forms one of the transport bodies and forms an image on the recording medium held on the outer peripheral surface by droplets ejected from one or a plurality of droplet ejection heads; ,
The recording medium is sandwiched between a rotating fixing member that is in pressure contact with the outer peripheral surface and constitutes one of the conveying bodies installed on the downstream side in the conveying direction from the image forming conveying body. A fixing carrier for fixing the image on the recording medium,
A pressure contact force varying portion provided in the fixing transport body, wherein a pressure contact state in which the fixing member is in pressure contact with the fixing transport body varies;
Rotational speed fluctuation suppression that suppresses rotational speed fluctuations of the image forming transport body, the fixing transport body, or at least one transport body disposed between the image forming transport body and the fixing transport body. Means,
An image forming apparatus comprising:   The image forming apparatus according to claim 1, wherein the rotation speed fluctuation suppressing unit is a brake.   The image forming apparatus according to claim 2, wherein the brake is a magnetic powder braking device.   4. The image forming apparatus according to claim 3, wherein when the fixing conveyance body is stopped for a predetermined time or more, the fixing conveyance body is rotated for a predetermined time or more, and then an image is formed on the recording medium. The image forming apparatus described.   The image forming apparatus according to claim 1, wherein the rotation speed fluctuation suppressing unit is a flywheel.   The droplet discharge head is provided with a main scanning direction which is a rotation axis direction of the image forming transport body as a longitudinal direction, and on a nozzle surface disposed to face the outer peripheral surface of the image forming transport body. The image forming apparatus according to claim 1, wherein the plurality of nozzles that discharge the droplets are two-dimensionally arranged.   The image forming apparatus according to claim 1, wherein the rotation speed fluctuation suppressing unit suppresses a rotation speed fluctuation of the fixing conveyance body.   The image forming apparatus includes a reading unit that reads an image of the recording medium held by the fixing conveyance body or the conveyance body installed on the downstream side in the conveyance direction with respect to the fixing conveyance body. The image forming apparatus according to claim 7.

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