JP7516792B2 - Image forming apparatus and method - Google Patents

Description

The present invention relates to an image forming apparatus and method.

One technique for removing skew when setting a roll-shaped recording medium in an image forming device is to clamp the recording medium between a conveying roller and a pressure driven roller, and then to remove the skew by simultaneously rotating a mechanism that holds the roll-shaped recording medium from both ends and the conveying roller to apply a certain tension to the recording medium while conveying it in the rewinding direction.

In conventional skew removal mechanisms, the tension applied to the recording medium during skew removal is the same as that during transport, which can lead to problems such as the recording medium having to be transported for a long time until the skew is completely removed, or a deterioration in image quality.

The present invention was made in consideration of the above-mentioned problems, and aims to more quickly remove skew when a recording medium is set without deteriorating the image quality during image formation.

In order to solve the above-mentioned problems and achieve the object, the image forming apparatus of the present invention comprises a holding unit that holds a recording medium, an image forming unit that forms an image on the recording medium, a drive mechanism that rotates the holding unit in a direction in which the holding unit rewinds the recording medium , a torque change unit that changes the torque of the drive mechanism that rotates the holding unit in the above direction , a control unit that controls the torque change unit so that the torque of the drive mechanism before image formation is greater than the torque of the drive mechanism during image formation by the image forming unit, and a setting unit, wherein the control unit has a skew removal mode for removing skew during transport that occurs due to variations in the posture of the recording medium when the recording medium is set in the holding unit by a user, and controls the torque change unit so that the torque of the drive mechanism in the skew removal mode is greater than the torque of the drive mechanism during image formation, and the setting unit accepts a setting by the user of the amount of transport of the recording medium during the skew removal mode in the skew removal mode .

The present invention has the effect of being able to quickly remove skew when setting a recording medium without deteriorating the image quality during image formation.

FIG. 1 is a perspective view showing the external appearance of an image forming apparatus according to an embodiment of the present invention. FIG. 2 is a top view of the carriage scanning mechanism of the image forming apparatus according to the embodiment. FIG. 3 is a diagram for explaining a conveying mechanism for the recording medium. FIG. 4 is a diagram for explaining the take-up paper tube and the peripheral mechanism of the take-up paper tube. FIG. 5 is a block diagram of an image forming apparatus according to an embodiment of the present invention. FIG. 6 is a functional block diagram of a control unit of the image forming apparatus according to the embodiment. FIG. 7 is a top view of an example of when a recording medium is set in the image forming apparatus according to the embodiment (an example in which skew occurs). FIG. 8 is a top view of an example of skew during transport after a recording medium is set in the image forming apparatus according to the embodiment. FIG. 9 is a top view of the sheet during transportation after the skew has been removed. FIG. 10 is a schematic diagram of an example of a torque change unit of the image forming apparatus according to the embodiment. FIG. 11 is a diagram illustrating an example of a control flowchart of the skew removal mode (automatic removal mode) of the image forming apparatus according to the embodiment. FIG. 12 is a diagram illustrating an example of a control flowchart of the skew removal mode (manual removal mode) of the image forming apparatus according to the embodiment. FIG. 13 is a diagram showing the results (approximation lines) of evaluation of the transport amount until the skew is actually removed with different idling torques in the embodiment. FIG. 14 is a block diagram of an image forming apparatus according to a modified example of the embodiment.

Below, an image forming apparatus according to an embodiment will be described with reference to the attached drawings, which is an example of an image forming apparatus, a winding control method, and a winding control program.

(External appearance)
1 is a perspective view showing the exterior of an image forming apparatus 100 according to an embodiment. As an example, the image forming apparatus 100 according to the embodiment is a so-called inkjet type image forming apparatus. Inside the main body 1, a guide rod 3 and a sub-guide rail 4 are suspended between both side plates. A carriage 5 is held by the guide rod 3 and the sub-guide rail 4 so as to be movable in the direction of arrow A (main scanning direction).

The carriage 5 is connected to a timing belt 11 that is stretched across a drive pulley 9 and a pressure pulley 10. This timing belt 11 is driven by the main scanning motor 8 via the drive pulley 9, causing the carriage 5 to move back and forth along the main scanning direction A. Tension is applied to the timing belt 11 by the pressure pulley 10. Therefore, the carriage 5 is driven without slack.

(Carriage Scanning Mechanism)
FIG. 2 is a plan view of the carriage scanning mechanism. In FIG. 2, the recording medium M is intermittently transported in the direction of the arrow B (sub-scanning direction) below the carriage 5 that moves back and forth. The recording heads 6k, 6c, 6m, and 6y eject ink from a plurality of nozzles onto the recording medium M. This causes a predetermined image or character to be printed on the recording medium M. Note that "k" stands for black or key plate, "c" for cyan, "m" for magenta, and "y" for yellow. In addition, the ink is an example of a liquid. As an example, the ink may be, for example, a water-based ink, a UV (ultraviolet) curable ink, an electron beam curable ink, or a solvent ink.

The main body 1 of the image forming apparatus 100 is also provided with a cartridge 7 that supplies ink to the recording head 6, and a maintenance mechanism 15 that performs maintenance on the recording head 6 provided on the carriage 5. An encoder sensor 13 is provided inside the carriage 5. The encoder sensor 13 detects the main scanning direction position of the carriage 5 by continuously reading an encoder sheet 14 that is hung between both side plates. The carriage 5 is controlled to move between the two side plates based on the main scanning direction position detected by the encoder sensor 13. The carriage 5 is also provided with an imaging unit 101 that moves together with the carriage 5. The imaging unit 101 reads the color patches of the reference chart and performs color measurement processing for each paper type.

(Transportation configuration)
FIG. 3 is a diagram for explaining the transport mechanism of a recording medium M (image forming medium). The recording medium M is a roll type medium. For example, a paper medium or a polyvinyl chloride medium can be used as the recording medium M. In FIG. 3, a recording head 6 is provided on a carriage 5, and image formation such as printing is performed on a platen 25. The recording medium M is set in a paper feed unit while being wound around a paper feed tube 52, and is pulled around in the direction of the arrow. As a result, the recording medium M passes through the image forming area on the platen 25 via a transport roller 35 of the transport unit, and is taken up around a take-up paper tube 44 set in a take-up unit.

The winding unit has a winding encoder sheet 45 that detects the amount of rotation of the winding tube 44, a winding encoder sensor 39, and a torque limiter 40 that is drivingly connected to the winding tube 44 and manages the upper limit of the torque applied to the recording medium M. The winding unit also has a winding motor 41 that serves as the driving source when performing winding and loosening operations, a winding motor encoder sheet 42 attached to the motor shaft to detect the rotation speed and amount of rotation of the winding motor 41, and a winding motor encoder sensor 43.

The paper feed unit has a paper remaining amount encoder sheet 51 for detecting the amount of rotation of the paper feed tube 52, a paper remaining amount encoder sensor 46, and a torque change unit 110 for determining the tension to be applied to the recording medium M. The paper feed unit also has a paper feed motor 49, which serves as a drive source for generating tension on the paper feed side, a paper feed motor encoder sheet 48 attached to the motor shaft for detecting the rotation speed and amount of rotation of the paper feed motor 49, and a paper feed motor encoder sensor 50. The paper feed motor 49 constitutes a drive mechanism 91.

During image formation, when the paper feed motor 49 is rotated and a force is applied in the direction opposite to the conveying direction shown by the arrow in FIG. 3, tension is applied to the recording medium M held by the conveying roller 35 and the pressure roller 34, and the torque change unit 110 starts to slide. This allows the paper feed tension created by the torque change unit 110 to be applied to the recording medium M.

The transport unit has a transport motor 37 that serves as a drive source for rotating the transport roller 35, a transport motor encoder sheet 38 attached to the shaft of the transport roller 35 for detecting the rotation speed and amount of rotation of the transport motor 37, and a transport motor encoder sensor 36.

The take-up paper tube 44 is held by being sandwiched between flanges 54 (Figure 4) on the left and right. The take-up paper tube 44 rotates when the take-up motor 41 rotates the flanges 54 via the torque limiter 40. An encoder sheet 45 is provided on the axis of the flange 54. The take-up encoder sensor 39 outputs an encoding pulse according to the rotation speed of the encoder sheet 45. The amount of rotation, rotation position, rotation speed, etc. of the take-up paper tube 44 are calculated based on the number of pulses of this encoding pulse. The take-up paper tube 44 is also called the paper discharge flange.

The configuration of the winding paper tube 44 has been explained using Figure 4, but the paper feed paper tube 52 has a similar configuration. For details, please refer to the explanation of Figure 4.

(Main and auxiliary drive control section)
Fig. 5 is a block diagram of the main/sub-drive control unit 105 of the image forming apparatus 100. As shown in Fig. 5, the image forming apparatus 100 has, as the main/sub-drive control unit 105, a control unit 61 (an example of a rotation control unit), a main scanning unit 62, a conveying unit 63, a paper feed unit 64, a winding unit 65, a torque change unit 110, and a skew amount detection unit 120.

The main scanning unit 62 has a main scanning motor 8, a carriage 5 driven by the main scanning motor 8, a recording head 6 provided on the carriage 5, and a main scanning encoder sensor 71.

The conveying unit 63 has a conveying roller 35 driven by a conveying motor 37 and a conveying encoder sensor 73 that outputs an encoding pulse that changes as the conveying roller 35 rotates.

The paper feed unit 64 has a paper feed paper tube flange 78 (an example of a holding unit) driven by a paper feed motor 49 (an example of a drive mechanism), a paper feed motor encoder sensor 50 that outputs an encoding pulse that changes as the paper feed motor 49 rotates, and a paper remaining amount encoder sensor 46 that outputs an encoding pulse that changes as the paper feed paper tube 52 rotates.

The winding unit 65 has a winding paper tube flange 82 driven by the winding motor 41, and a winding motor encoder sensor 43 that outputs an encoding pulse that changes as the winding motor 41 rotates. The winding unit 65 also has a winding amount encoder sensor 81 that outputs an encoding pulse that changes as the winding paper tube 44 rotates.

That is, the winding unit 65 has two encoders: a winding motor encoder sensor 43 that detects the rotation of the motor shaft, and a winding amount encoder sensor 81 that detects the rotation of the paper tube (flange). Therefore, two encoder values can be obtained from the winding unit 65.

The skew amount detection unit 120 has a control unit 121 and a sensor 122. Note that the sensor 122 is actually mounted on the carriage 5.

(Functions of the control unit)
Fig. 6 is a functional block diagram of the control unit 61. The control unit 61 executes a control program stored in the memory 84 shown in Fig. 5 to realize the functions of an image formation control unit 85, a setting unit 86, and a skew removal unit 87, as shown in Fig. 6.

In this example, the image formation control unit 85 to the skew removal unit 87 are implemented as software, but some or all of these may be implemented as hardware such as an integrated circuit (IC). The functions implemented by the image formation control unit 85 to the skew removal unit 87 may be implemented as a stand-alone control program, or some of the processing may be executed by another program, or the processing may be executed indirectly using another program.

The control program may be provided by recording it in an installable or executable file format on a computer-readable recording medium such as a CD-ROM or a flexible disk (FD). The control program may be provided by recording it in a computer-readable recording medium such as a CD-R, a DVD (Digital Versatile Disk), a Blu-ray Disc (registered trademark), or a semiconductor memory. The control program may be provided by installing it via a network such as the Internet, or may be provided by being pre-installed in a ROM or the like within the device.

The image forming control unit 85 issues drive instructions to each of the main scanning motor 8, the transport motor 37, the paper feed motor 49, and the winding motor 41. Each of the motors 8, 37, 49, and 41 can be, for example, a DC motor (direct current motor).

The setting unit 86 sets a skew removal mode to remove skew during transport caused by variations in the position of the recording medium M when the recording medium M is set by the user on the paper feed tube flange 78. In addition, in the skew removal mode, the setting unit 86 accepts a user setting, via the operation panel (operation unit), of the amount of transport of the recording medium M during the skew removal mode.

The skew removal unit 87 controls the torque change unit 110 so that the torque of the drive mechanism 91 before image formation is greater than the torque of the drive mechanism 91 during image formation in the main scanning unit 62. The skew removal unit 87 also controls the torque change unit 110 so that the torque of the drive mechanism 91 in the skew removal mode is greater than the torque of the drive mechanism 91 during image formation.

In addition, in the skew removal mode, when removing skew, the skew removal unit 87 drives the transport roller 35 of the transport unit 63 in the transport direction and drives the paper feed tube flange 78 in the rewinding direction.

In addition, in the skew removal mode, the skew removal unit 87 and the control unit 61 transport the recording medium M, and then rewind the recording medium M by a length equal to the amount of transport.

Here, in the skew removal mode, the skew amount detection unit 120 (Figure 5) detects the amount of skew of the recording medium M when the recording medium M is transported in the skew removal mode and when the recording medium M is rewound. The control unit 121 of the skew amount detection unit 120 automatically detects the amount of skew each time the recording medium M is transported a certain amount, and determines whether to continue transporting the recording medium M based on the detected amount of skew. In addition, the sensor 122 of the skew amount detection unit 120 is mounted on the carriage 5 and detects the amount of skew.

In the above configuration, the recording medium M sent from the paper feed tube 52 that holds the paper feed roll M1 on the recording medium M before image formation passes over the paper feed guide plate 108 and is sandwiched between the transport roller 35 and the pressure roller 34. The recording medium M transported by the transport roller 35 reaches the platen 25 facing the recording head 6 arranged in the carriage 5, where an image is formed. The recording medium M with the image formed is further transported, passes over the paper discharge guide plate 109, and is stored in the paper discharge roll M2 held by the take-up paper tube 44.

If the tension applied to the recording medium M is not uniform in the main scanning direction, there is a concern that the recording medium M may become skewed during transport, resulting in a deterioration in image quality. Therefore, a certain amount of tension is applied between the feed roll M1 and the transport roller 35 during transport. The tension application means, for example, rotates the feed paper tube 52 in the opposite direction to the transport direction during transport, and further applies tension to the recording medium M using torque limiters 111, 112 in the drive configuration of the feed paper tube 52.

Figure 7 is a top view of an example of when a recording medium is set in an image forming device according to an embodiment (an example in which skew occurs).

As mentioned above, if the tension applied to the recording medium M is not uniform in the main scanning direction, the recording medium M will become skewed during transport. This is most likely to occur immediately after the user sets the recording medium M in the image forming device. The user pulls the recording medium M from the feed roll M1 to a position where it can be held by the transport roller 35 and the pressure roller 34, and then holds it between the transport roller 35 and the pressure roller 34. At this time, the recording medium M needs to be pulled straight out from the feed roll M1, but it is difficult for the user to set it accurately, and in the worst case, it will be set in an oblique position as shown in Figure 7. In order to reduce variation when setting, scales 130 are sometimes placed on the feed guide plate 108, platen 25, and discharge guide plate 109 to align the end positions of the recording medium M on the feed side and discharge side, but even with this, the skew after setting cannot be completely eliminated.

Figure 8 is a top view of an example of skew during transport after a recording medium is set in an image forming device in an embodiment, and Figure 9 is a top view of transport after the skew is removed.

After the recording medium M is set, the conveying roller 35 is driven to convey it. At this time, the paper feed tube 52 rotates in the opposite direction to the conveying direction (opposite to the arrow in FIG. 3), and tension is applied to the recording medium M by the idling torque of the drive unit of the paper feed tube 52. If the setting is not accurate, a left-right difference in tension will occur in the main scanning direction as shown in FIG. 8. If a stronger tension is applied to the right side of the recording medium M as shown in FIG. 8, a slight slippage will occur in the recording medium M at the portion of the recording medium M held between the conveying roller 35 and the pressure roller 34. Therefore, the left side of the recording medium M in FIG. 8 will be conveyed more, and skew will occur. However, if conveyance is continued even after skew occurs, the tension on the paper feed side will gradually become uniform in the main scanning direction, and will stabilize when the tension becomes uniform as shown in FIG. 9. Therefore, in order to maintain a stable and good image quality, it is necessary to continue conveying the recording medium M until no skew occurs and to remove the skew.

As mentioned above, the tension on the paper feed side causes the recording medium M to slip and become skewed at the portion where the recording medium M is held between the transport roller 35 and the pressure roller 34, but the stronger the tension, the easier it is for slippage to occur, and the easier it is to remove the skew. However, in conventional transport mechanisms, the tension applied to the recording medium M when removing the skew is the same as when it is being transported during image formation, and if the tension is set to be greater to remove the skew, the greater the tension, the easier it is for the recording medium M to slip on the transport roller 35, which, as a side effect, worsens the transport accuracy during image formation. This is undesirable as it degrades the image quality.

Conversely, if the tension applied to the recording medium M is small, it will need to be transported a long distance until the skew is completely removed. If a portion of the recording medium M that has been transported once and then rewound is transported again, the transport distance will change for some types of recording medium M (e.g. PVC), and there is a problem that if that portion is used to form an image or adjust the feed distance, the image quality will deteriorate. Therefore, the shorter the transport distance until the skew is removed, the lower the risk of image quality deterioration and the less paper waste, making it preferable.

Therefore, in this embodiment, the idling torque of the paper feed tube 52 is provided with at least two types of idling torque τ1 and τ2 (τ1 < τ2), and a skew removal mode is provided after the recording medium M is set. In addition, the idling torque is switched between during image formation and during the skew removal mode, providing an optimal skew removal method.

Figure 10 is a schematic diagram of an example of a torque change unit (idling torque switching drive mechanism) of an image forming apparatus according to an embodiment.

The torque change unit 110 has two torque limiters 111 and 112 and an electromagnetic clutch 113. The idling torque τ1 of the torque limiter 111 is smaller than the idling torque τ2 of the torque limiter 111. The torque limiters 111 and 112 with different idling torques τ1 and τ2 (τ1 < τ2) are arranged in parallel within the drive mechanism from the paper feed motor 49 to the paper feed paper tube flange 78. Furthermore, the electromagnetic clutch 113 is arranged in series only on the side of the torque limiter 112 with the larger idling torque. With this configuration, when the electromagnetic clutch 113 is idling, the idling torque τ1 becomes dominant in the tension on the recording medium M, and when the electromagnetic clutch is locked, the idling torque τ2 becomes dominant in the tension. This allows a simple configuration in which, by turning off the electromagnetic clutch 113 during image formation, a small tension is applied to the recording medium M, stabilizing the transport quality, and by turning on the electromagnetic clutch in skew removal mode, a large tension is applied to the recording medium M, allowing skew removal to be performed with a small transport distance.

Thus, the torque change unit 110 has two torque limiters 111, 112 and an electromagnetic clutch 113. The idling torque τ1 of the torque limiter 111 is smaller than the idling torque τ2 of the torque limiter 111. The torque change unit 110 changes the torque of the drive mechanism 91. The torque change unit 110 variably controls the torque to at least two types of torque. The torque change unit 110 variably controls the torque using an electromagnetic clutch 113 arranged in the drive mechanism 91. The torque change unit 110 controls the torque during drive of the drive mechanism 91 using the torque limiters 111, 112 arranged in the drive mechanism 91.

Figure 11 shows an example of a control flowchart for the skew removal mode (automatic removal mode) of an image forming device according to an embodiment.

The control flow chart of FIG. 11 will be described. After the user sets the recording medium M (S1), the electromagnetic clutch in the torque change unit 110 (drive structure of the paper feed tube 52) is turned ON (S2). After that, the sensor 122 that detects the end of the recording medium M mounted on the carriage 5 detects the end position of the recording medium M (S3), and the conveyance of the recording medium M begins (S4). After conveying a certain amount A mm (S5), the end position of the recording medium M is detected again, and the amount of skew is calculated from the value of the end position detected the previous time (S6). Here, the smaller the value of the certain amount A mm, the less paper waste there is, which is preferable. If the detected amount of skew is not equal to or less than a certain value B mm, the recording medium is conveyed again and skew amount detection is repeated (S7: No).

Here, the value Bmm indicates the amount of skew that does not affect image quality. When the detected amount of skew falls below Bmm (S7: Yes), the drive system drives in the rewinding direction (S8), and a rewinding operation is performed the amount of transport in the skew removal mode (S9), and the electromagnetic clutch 113 is turned off (S10). According to this mode, transport can be performed automatically until no more skew occurs, making it possible to remove skew without bothering the user.

Figure 12 shows an example of a control flowchart for the skew removal mode (manual removal mode) of an image forming apparatus according to an embodiment.

The control flow chart of FIG. 12 will be described. After the user sets the recording medium M (S1), the electromagnetic clutch 113 in the torque change unit 110 is turned on (S2). Then, the detection sensor 122 mounted on the carriage detects the end position of the recording medium M (S3), and starts conveying the recording medium M (S4). After conveying a certain amount Cmm (S5), the end position of the recording medium M is detected again, and the amount of skew is calculated from the value of the end position detected the previous time (S6). Here, the smaller the certain amount Cmm, the more the length at which the conveying quality deteriorates can be suppressed. Then, the drive system drives in the rewinding direction (S21), a rewinding operation of Cmm is performed (S22), and the value of the amount of skew is displayed on the operation panel of the image forming apparatus 100 (S23). From that value, the user selects whether to perform the skew removal mode again, and when execution is selected (S24: Yes), conveying is performed again, and skew amount detection is repeated (S24). After the user selects to end the skew removal mode (S24: No), the electromagnetic clutch is turned off (S11).

This mode makes it possible to limit the amount of transport used to remove skew to C mm, minimizing paper waste and removing skew. In addition, because the sensor 122 that detects the edge of the recording medium M is mounted on the carriage 5, it is possible to check whether skew has occurred during image formation even if the skew removal mode is turned OFF.

Figure 13 shows the results (approximation lines) of an evaluation of the amount of transport required until skew is actually removed for different idling torques τ1 and τ2 (τ1 < τ2). τ2 is set to an idling torque twice that of τ1. From this result, it can be seen that the amount of transport required until skew is removed is reduced to half for τ2 compared to τ1. With the above configuration, it is possible to quickly remove skew caused by misalignment when setting the recording medium M with a simple configuration.

(Effects of the embodiment)
As described above, the image forming apparatus 100 includes the paper feed paper tube flange 78 (holding section) that holds the recording medium M, the main scanning section 62 (image forming section) that forms an image on the recording medium M, the drive mechanism 91 that rotates the paper feed paper tube flange 78 (holding section), the torque change section 110 that changes the torque of the drive mechanism 91, and the control section 61 that controls the torque change section 110 so that the torque of the drive mechanism 91 before image formation is greater than the torque of the drive mechanism 91 during image formation by the main scanning section 62. Thus, skew when the recording medium M is set can be removed more quickly without deteriorating the image quality during image formation.

The control unit 61 also has a skew removal mode for removing skew during transport caused by variations in the position of the recording medium M when the recording medium M is set on the paper feed tube flange 78 by the user, and controls the torque change unit 110 to make the torque of the drive mechanism 91 in the skew removal mode greater than the torque of the drive mechanism 91 during image formation. This makes it possible to reduce the amount of transport required to remove skew caused by misalignment when the recording medium M is set on the paper feed tube flange 78 by the user.

The image forming apparatus 100 also includes a transport roller 35 (transport unit) that transports the recording medium M, and in the skew removal mode, the control unit 61 drives the transport roller 35 of the transport unit 63 in the transport direction and drives the paper feed tube flange 78 (holding unit) in the rewinding direction when removing skew. Thus, tension can be applied to the recording medium M.

The torque change unit 110 also variably controls the torque to at least two different torques. Therefore, the tension of the recording medium M is variable.

The torque change unit 110 also variably controls the torque using an electromagnetic clutch 113 disposed in the drive mechanism 91. This allows the tension of the recording medium M to be varied with a simple configuration.

The torque change unit 110 also controls the torque of the drive mechanism 91 while it is being driven using torque limiters 111, 112 arranged in the drive mechanism 91. This allows the tension of the recording medium M to be varied with a simple configuration.

The image forming apparatus 100 also includes a setting unit 86 that accepts user settings for the amount of transport of the recording medium M during the skew removal mode. This can reduce wasted paper.

In addition, in the skew removal mode, the control unit 61 transports the recording medium M, and then rewinds the recording medium M by a length equal to the amount of transport of the recording medium M. This reduces wasted paper.

In addition, the image forming apparatus 100 includes a skew amount detection unit 120 that detects the amount of skew of the recording medium M when the recording medium M is transported in the skew removal mode and when the recording medium M is rewound in the skew removal mode. Therefore, the amount of skew can be detected.

The skew amount detection unit 120 also includes a control unit 121 that automatically detects the amount of skew each time the recording medium M is transported a certain amount, and determines whether to continue transporting the recording medium M based on the detected amount of skew. This makes it possible to automate skew removal.

The main scanning unit 62 also includes a recording head 6 (inkjet recording head) and a carriage 55 carrying the recording head 6, and the skew amount detection unit 120 includes a sensor 122 that is mounted on the carriage 5 and detects the amount of skew. Therefore, even if the skew removal mode is OFF, it is possible to check whether skew has occurred during image formation.

Next, a modified example will be described. FIG. 14 is a block diagram of an image forming apparatus according to a modified example of the embodiment. In this modified example, the torque change unit 110 controls the torque of the drive mechanism 91 while it is being driven by a motor current value variable control unit 114 disposed in the drive mechanism 91, which variably controls the current value of the feed motor 49. This makes it possible to control the idling torque of the feed motor 49, and to make the tension of the recording medium M variable. In this modified example, the torque limiters 111 and 112 are not used.

Finally, the above-described embodiment is presented as an example and is not intended to limit the scope of the present invention. This new embodiment can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the gist of the invention. Furthermore, the embodiment and modifications of the embodiment are included within the scope and gist of the invention, as well as within the scope of the invention and its equivalents described in the claims. For example, the image forming apparatus is not limited to an inkjet machine, but may be an electrophotographic machine.

6... Recording head (inkjet recording head)
35...conveying roller 49...paper feed motor (motor)
55: Carriage 61: Control unit 62: Main scanning unit (image forming unit)
63: conveying section 78: paper feed tube flange (holding section)
Reference Signs List 86: setting section 91: driving mechanism 100: image forming apparatus 110: torque changing section 111, 112: torque limiter 113: electromagnetic clutch 114: motor current value variable control section 120: skew amount detection section 121: control section 122: sensor M: recording medium

JP 2011-057353 A

Claims (12)

A holding unit that holds a recording medium;
an image forming unit that forms an image on the recording medium;
a drive mechanism that rotates the holding unit in a direction in which the holding unit rewinds the recording medium ;
a torque change unit that changes the torque of the drive mechanism that rotates the holding unit in the direction ;
a control unit that controls the torque change unit so that the torque of the drive mechanism before the image formation is larger than the torque of the drive mechanism during the image formation of the image forming unit;
A setting section;
Equipped with
the control unit has a skew removal mode for removing skew during transport caused by variation in the attitude of the recording medium when the recording medium is set on the holding unit by a user, and controls the torque change unit so that the torque of the driving mechanism in the skew removal mode is greater than the torque of the driving mechanism during the image formation;
The image forming apparatus according to claim 1, wherein the setting unit accepts, in the skew removal mode, a setting by the user of an amount by which the recording medium is transported during the skew removal mode . A holding unit that holds a recording medium;
an image forming unit that forms an image on the recording medium;
a drive mechanism that rotates the holding unit in a direction in which the holding unit rewinds the recording medium ;
a torque change unit that changes the torque of the drive mechanism that rotates the holding unit in the direction ;
a control unit that controls the torque change unit so that the torque of the drive mechanism before the image formation is larger than the torque of the drive mechanism during the image formation of the image forming unit;
Equipped with
The control unit has a skew removal mode for removing skew during transport caused by variations in the posture of the recording medium when the recording medium is set in the holding unit by a user, and controls the torque change unit to make the torque of the drive mechanism in the skew removal mode greater than the torque of the drive mechanism during image formation, and in the skew removal mode, after transporting the recording medium, the image forming apparatus rewinds a length equal to the amount of transport of the recording medium . a conveying unit that conveys the recording medium,
2. The image forming apparatus according to claim 1 , wherein, in the skew removal mode, the control section drives the transport rollers of the transport section in the transport direction and drives the holding section in the rewinding direction when removing skew. The image forming device according to claim 1, characterized in that the torque change unit variably controls the torque to at least two types of torque. The image forming apparatus according to claim 1, characterized in that the torque change unit variably controls the torque using an electromagnetic clutch arranged in the drive mechanism. The image forming apparatus according to claim 4, characterized in that the torque change unit controls the torque during operation of the drive mechanism by a torque limiter disposed in the drive mechanism. The drive mechanism includes a motor that rotates the holding portion,
5. The image forming apparatus according to claim 4, wherein the torque changing unit controls the torque during operation of the drive mechanism by a motor current value variable control unit disposed in the drive mechanism for variably controlling a current value of the motor. 2. The image forming apparatus according to claim 1, further comprising a skew amount detection unit that detects an amount of skew of the recording medium when the recording medium is transported and when the recording medium is rewound in the skew removal mode. The image forming apparatus according to claim 8, characterized in that the skew amount detection unit automatically detects the skew amount each time the recording medium is transported a certain amount, and includes a control unit that determines whether to continue transporting the recording medium based on the detected skew amount. the image forming unit includes an inkjet recording head and a carriage carrying the inkjet recording head;
9. The image forming apparatus according to claim 8 , wherein the skew amount detection unit includes a sensor mounted on the carriage for detecting the skew amount. A holding unit that holds a recording medium;
an image forming unit that forms an image on the recording medium;
a drive mechanism that rotates the holding unit in a direction in which the holding unit rewinds the recording medium ;
a torque change unit that changes the torque of the drive mechanism that rotates the holding unit in the direction ;
a control unit that controls the torque change unit so that the torque of the drive mechanism before the image formation is larger than the torque of the drive mechanism during the image formation of the image forming unit ;
A setting section;
A method performed in an image forming apparatus comprising:
the control unit has a skew removal mode for removing skew during transport caused by variation in the attitude of the recording medium when the recording medium is set on the holding unit by a user, and controls the torque change unit so that the torque of the driving mechanism in the skew removal mode is greater than the torque of the driving mechanism during the image formation,
The method according to claim 1, wherein the setting unit accepts, in the skew removal mode, a setting by the user of an amount by which the recording medium is transported during the skew removal mode . A holding unit that holds a recording medium;
an image forming unit that forms an image on the recording medium;
a drive mechanism that rotates the holding unit in a direction in which the holding unit rewinds the recording medium ;
a torque change unit that changes the torque of the drive mechanism that rotates the holding unit in the direction ;
a control unit that controls the torque change unit so that the torque of the drive mechanism before the image formation is greater than the torque of the drive mechanism during the image formation of the image forming unit ;
A method performed in an image forming apparatus comprising:
The control unit has a skew removal mode for removing skew during transport caused by variations in the posture of the recording medium when the recording medium is set in the holding unit by a user, controls the torque change unit so that the torque of the drive mechanism in the skew removal mode is greater than the torque of the drive mechanism during image formation, and in the skew removal mode, after transporting the recording medium, rewinds the recording medium by a length equal to the amount of transport of the recording medium .

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