JP7183695B2 - Image forming apparatus and transport control method - Google Patents

Description

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

2. Description of the Related Art There is an image forming apparatus that performs a recording operation on a recording medium to form an image. In recent years, in accordance with the demand for higher resolution, the frequency of operation of the printing operation unit has increased relative to the moving distance of the printing operation unit that performs the printing operation and the conveying distance of the printing medium.

The image forming apparatus can form images with a plurality of resolutions by adjusting the operation frequency of the recording operation unit. However, there is an upper limit to the number of times (maximum frequency) that the recording operation section can operate per unit time. In Japanese Patent Laid-Open No. 2002-200015, the transport speed is determined so that the recording operation can be performed at the maximum resolution that can be set by combining the transport speed and the maximum frequency, and the operating frequency of the recording operation unit is changed according to the resolution of the formed image. A technique for doing so is disclosed.

JP-A-2003-48344

However, in an image forming apparatus that forms an image while switching between a plurality of resolutions, there is a problem that the image forming speed becomes slower than necessary when forming an image with a resolution other than the maximum resolution, resulting in poor efficiency.

SUMMARY OF THE INVENTION An object of the present invention is to provide an image forming apparatus and a transport control method capable of forming images more efficiently.

In order to achieve the above object, the invention according to claim 1,
a transport unit that moves the recording medium along a predetermined transport path;
a recording operation unit that performs a recording operation on the recording medium over a recordable width of the recording medium in a direction that intersects the direction along the transportation path at a predetermined position on the transportation path;
a control unit that controls a recording medium conveying operation by the conveying unit and the recording operation;
with
The control unit causes the conveying unit to perform the conveying operation at a conveying speed determined according to the resolution of the image to be formed so as to form a plurality of images having different resolutions. When the second resolution of the second image to be formed next is higher than the first resolution of the image, before the recording operation for the second image is started, the first image is processed. Decrease the transport speed determined according to the second resolution during the recording operation
,
When a command to form a plurality of images with different resolutions is acquired, the recording operation unit forms the plurality of images in descending order of resolution.
This image forming apparatus is characterized by:

Further, according to the invention of claim 2, in the image forming apparatus of claim 1,
The control section is characterized in that the start timing of the reduction of the conveying speed is determined such that the reduction of the conveying speed is finished at the timing of starting the recording operation related to the second image.

Further, according to the invention of claim 3, in the image forming apparatus of claim 1 or 2,
The conveying speed is determined to be the maximum speed at which the resolution of the image to be formed can be obtained at the maximum driving frequency of the recording operation section.

Further, the invention according to claim 4 is the image forming apparatus according to any one of claims 1 to 3,
The recording operation section has a plurality of recording units each having a different predetermined position,
The controller reduces the conveying speed before starting the recording operation for the second image by a recording unit whose predetermined position is the most upstream of the conveying path among the plurality of recording units. It is characterized by

Further, the invention according to claim 5 is the image forming apparatus according to any one of claims 1 to 4 ,
The controller changes the transport speed so that an acceleration associated with the change of the transport speed is equal to or less than a predetermined reference value.

Further, according to the invention of claim 6 , in the image forming apparatus of claim 5 ,
The control unit controls that the acceleration during a first predetermined period from the start of the change of the conveying speed and a second predetermined period until the end of the change is The conveying speed is changed so as to be smaller than the acceleration in front.

Further, the invention according to claim 7 is the image forming apparatus according to claim 6 ,
The controller changes the conveying speed so that the magnitude of the acceleration gradually increases during the first predetermined period and the magnitude of the acceleration gradually decreases during the second predetermined period.

Further, the invention according to claim 8 is the image forming apparatus according to any one of claims 1 to 7 ,
A drying unit is provided downstream of the recording operation unit in a direction along the conveying path,
The recording operation unit performs the recording operation by ejecting ink,
The drying section is characterized by drying the ink on the recording medium.

Further, the invention according to claim 9 is the image forming apparatus according to any one of claims 1 to 8 ,
It is characterized by comprising a medium delivery section that delivers the recording medium to the transport path.

Further, the invention according to claim 10 ,
a transport unit for moving a recording medium along a predetermined transport path; and a recordable width of the recording medium in a direction intersecting the direction along the transport path at a predetermined position on the transport path with respect to the recording medium. A conveyance control method for an image forming apparatus, comprising:
a conveying operation step of causing the conveying unit to convey the recording medium at a conveying speed determined according to the resolution of the image to be formed;
When forming a plurality of images having different resolutions, the second resolution of the second image to be formed next to the first image is higher than the first resolution of the first image to be formed. is lower, after the recording operation for the first image is completed, the speed change is performed to increase the conveying speed to the transport speed determined according to the second resolution during the recording operation for the second image. step,
an order change step of causing the recording operation unit to form the plurality of images in descending order of resolution when a command to form a plurality of images having different resolutions is acquired;
characterized by comprising

According to the present invention, there is an effect that an image can be formed more efficiently in the image forming apparatus.

BRIEF DESCRIPTION OF THE DRAWINGS It is a front view explaining the outline of the whole structure of an inkjet recording device. 4 is a bottom view showing an ink ejection surface of the head unit; FIG. 1 is a block diagram showing the functional configuration of an inkjet recording apparatus; FIG. FIG. 5 is a diagram schematically showing temporal changes in resolution and transport speed; 4 is a flowchart showing a control procedure of image recording control processing; FIG. 10 is a diagram showing a modification of the relationship between resolution and conveying speed for image formation; FIG. 11 is a modified example of the flowchart showing the control procedure of the image recording control process; FIG.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a front view for explaining the outline of the overall configuration of an inkjet recording apparatus 100, which is an image forming apparatus according to this embodiment.

The inkjet recording apparatus 100 includes a medium dispensing section 10, a recording operation section 20, a drying section 30, a medium discharging section 40, and the like.

The medium supply unit 10 includes a medium roll 11, a delivery roller 12, and the like. A continuous recording medium M such as roll paper or cloth is wound around the medium roll 11 . The medium roll 11 rotates at a speed corresponding to the transport speed of the transport unit and delivers the recording medium M to the transport path of the transport unit 70 . The delivery roller 12 delivers the recording medium M to the transport section 70 (recording operation section 20) while stretching the recording medium M with an appropriate tension. The recording medium M is horizontally sent to the recording operation section 20 after smoothing wrinkles and slack.

The recording operation unit 20 includes a driving roller 21, a driven roller 22, a conveying belt 23, an encoder 24, a head unit 25 (recording unit), and the like.

The drive roller 21 rotates according to the operation of a drive motor (not shown), and rotates the conveying belt 23 at a predetermined speed. The conveying belt 23 is an endless (annular) belt member and is stretched between the driving roller 21 and the driven roller 22 . The conveying belt 23 circulates according to the rotation of the drive roller 21 . Along with this, the recording medium M placed on the outer peripheral surface (conveying surface) of the conveying belt 23 within a predetermined range is conveyed and moved. The outer peripheral surface of the conveying belt 23 may be coated with an adhesive or the like so that the recording medium M can adhere thereto. Further, a pressure roller (not shown) may be provided for adhering the recording medium M to the outer peripheral surface. The driven roller 22 rotates according to the circular movement of the conveying belt 23 .

The encoder 24 is a rotary encoder and detects rotation of the drive roller 21 . The encoder 24 outputs a detection signal corresponding to the direction of rotation to the controller 50 (see FIG. 3) for each rotation of a predetermined angle.

The head unit 25 moves the recording medium M placed on the transport belt 23 in the width direction perpendicular to (intersecting) the transport direction of the recording medium M (the direction along the transport path). It has a line head provided with recording elements 20a (see FIG. 3) over a recordable width (full width or including predetermined margins at both ends). The recording elements 20a each eject ink to perform a belt-like (linear) recording operation, and form an image (two-dimensional image) to be formed in combination with a conveying operation. A plurality of head units 25, four here, may be provided in order at different positions (predetermined positions) in the transport direction. These head units 25 may be set to eject inks of different colors. For example, inks of C (cyan), M (magenta), Y (yellow), and K (black) may be ejected. be done.

The drying section 30 dries and fixes the ink on the recording medium M downstream of the head unit 25 (recording operation section 20) in the transport direction. The drying section 30 includes transport rollers 31 and 32, a drying operation section 35, and the like.

The transport rollers 31 and 32 move the recording medium M delivered from the recording operation section 20 within the drying section 30 . The transport rollers 32 are two transport rollers that sandwich the recording medium M after drying the ink. The conveying roller 32 generates a force to pull the recording medium M, and the recording medium M placed on the conveying belt 23 , especially the sticking recording medium M, is peeled off from the conveying belt 23 and pulled into the drying section 30 .

The drying operation unit 35 performs an operation for drying and fixing the ink on the recording medium M. FIG. Here, the drying operation unit 35 performs heating and/or air blowing for evaporating the water content of the water-based ink. Although not particularly limited, the drying section 30 has a housing, and the drying operation section 35 is provided inside the housing and has a structure in which the heat generated by the drying operation section 35 is easily maintained. . The internal air containing water vapor may be naturally discharged from the gap of the housing (including air blown by the movement of the recording medium M or the conveying belt 23), or may be forcibly discharged by an exhaust fan or the like. good.

The medium discharge section 40 includes a discharge roller 41, and shakes off the recording medium M, which has dried and adhered ink and is sent from the drying section 30, onto a tray or the like at the bottom (not shown). The ejected recording medium M may be appropriately sent to a post-processing device or the like to be cut or the like.

FIG. 2 is a bottom view showing the ink ejection surface of the head unit 25. As shown in FIG.
Here, the head unit 25 has 16 recording heads 251, and a set of two heads discharges ink to a predetermined range in the width direction. Each recording head 251 is provided with an array of nozzle openings 27a extending in the width direction at two locations in the transport direction. The four arrayed nozzle openings 27a in each set of recording heads 251 are provided with uniform width shifts in the width direction, and as a whole form an array with a predetermined nozzle pitch. It should be noted that the number, size and positional relationship of the nozzle openings 27a shown here are exemplary for explanation, and do not reflect the actual number, size and positional relationship.

FIG. 3 is a block diagram showing the functional configuration of the inkjet recording apparatus 100. As shown in FIG.
In addition to the recording operation unit 20 and the drying unit 30 described above, the inkjet recording apparatus 100 includes a control unit 50, a storage unit 60, a transport unit 70, a communication unit 81, a display unit 82, and an operation reception unit 83. , bus 90 and the like.

The recording operation section 20 includes a head drive section 26 . The head drive section 26 outputs a drive signal for ejecting ink from each nozzle 27 of the head unit 25 . The drive signal is output to, for example, an electromechanical conversion element 28 (piezoelectric element) that deforms an ink flow path (particularly an ink chamber) communicating with the nozzle 27 . The electromechanical conversion element 28 to which the voltage of the drive signal is applied is deformed, and the ink flow path is deformed in accordance with the deformation. is discharged. The output frequency of the drive signal can be adjusted within a range equal to or lower than a predetermined maximum drive frequency. Each nozzle 27 and corresponding ink flow path and electromechanical conversion element 28 constitute a recording element 20a. Note that the recording elements 20a do not have to be arranged in a single row in the width direction, and it is sufficient if the ink can be ejected over the width of the width that can be recorded.

The drying section 30 includes a drying operation drive section 36 . The drying operation drive unit 36 outputs a drive signal to the drying operation unit 35 to cause the drying operation unit 35 to perform a heating operation, an air blowing operation, and the like. The presence or absence of the heat generating operation may be controlled by the control unit 50 according to the temperature inside the housing measured by a temperature sensor (not shown).

The transport unit 70 includes a transport driving unit 76, an encoder 24, and the like. The transport drive unit 76 rotates the medium roll 11, the delivery roller 12, the drive roller 21, the transport roller 32, the discharge roller 41, and the like. Thereby, the transport unit 70 performs a transport operation for moving the recording medium M along a predetermined transport path. The rotation speed of each roller is synchronized according to the set transport speed, but may be finely adjusted under the control of the controller 50 . For example, the rotational speed of the medium roll 11 changes according to the radius of the wound recording medium M and the like. Further, these speeds can be changed according to the image quality accuracy of the image recorded by the head unit 25 and the like. Rewinding the recording medium M by synchronizing them and rotating them in the reverse direction (setting the rotation speed to a negative value) is usually troublesome and not easy. In particular, when an adhesive is applied to the outer peripheral surface of the conveying belt 23, it is difficult to separate the recording medium M from the conveying belt 23 and rewind the recording medium M on the upstream side in the conveying direction. Moreover, the change of the transport speed cannot be performed instantaneously, and a predetermined change time is required.

The control unit 50 has a CPU 51 (Central Processing Unit), a RAM 52 (Random Access Memory), etc., performs various arithmetic processing, and controls the operation of each unit of the inkjet recording apparatus 100 in an integrated manner. The control unit 50 reads out and executes control programs stored in the storage unit 60, and controls the conveying operation, the recording operation, the drying operation, and the like. The controller 50 appropriately adjusts the transport speed particularly according to the resolution of the formed image.

The storage unit 60 stores various programs, setting data, image data related to image formation commands, and the like. The storage unit 60 may include a volatile memory such as a DRAM, a nonvolatile memory such as a flash memory, and an auxiliary storage device such as a HDD (Hard Disk Drive). Image data of an image to be formed is stored in a volatile memory, subjected to high-speed processing, and erased after the processing is completed. Programs, setting data, and the like are stored in a nonvolatile memory and held regardless of whether power is supplied to the inkjet recording apparatus 100 . The program includes a transport control program 61, and the setting data includes a speed table 62 corresponding to resolution. The resolution corresponding speed table 62 stores the conveying speed of the recording medium M by the conveying unit 70, which is predetermined corresponding to the resolution of the image to be formed.

A communication unit 81 controls communication with an external device via a network. The communication unit 81 has, for example, a network card, and controls communication via a LAN (Local Area Network) or the like. The external device includes a computer such as a PC (Personal Computer) and an image forming server (print server), and receives image data of an image to be formed and setting data as job data together with an image forming command from these computers. . In addition, the communication unit 81 transmits status information of image formation (recording operation) under the control of the control unit 50 .

The display unit 82 performs display on the display screen under the control of the control unit 50 . The display screen is not particularly limited, but for example, a liquid crystal display screen or the like is used. The display screen displays an operation reception menu, status, and the like. Further, the display unit 82 may have an LED lamp or the like to indicate the presence or absence of power supply, the presence or absence of an abnormality, and the like.

The operation reception unit 83 receives an input operation from the outside and outputs an input signal according to the content of the operation. The operation reception unit 83 has a touch sensor, for example, and operates as a touch panel by being superimposed on the display screen. Further, the operation reception unit 83 may have a push button switch, a rocker switch, or the like for turning on/off the main power supply.

Next, a recording operation and a conveying operation in the inkjet recording apparatus 100 will be described.
The inkjet recording apparatus 100 forms an image in a single pass by ejecting ink from each head unit 25 onto the recording medium M while moving the recording medium M along the transport path. The resolution in the width direction of the image depends on the nozzle pitch of each head unit 25, and the resolution in the transport direction is the interval in the transport direction on the recording medium M on which the head unit 25 performs the recording operation in a strip shape. Therefore, it depends on the relationship between the transport speed of the recording medium M and the ink ejection frequency (that is, the output frequency of the drive signal). In the inkjet recording apparatus 100, as described above, the resolution-corresponding speed table 62 defines the transport speed with respect to the resolution. Image formation (recording operation) is performed at regular intervals.

In order to increase the efficiency of image formation without lowering the image formation speed, the conveying speed should be high. On the other hand, the ejection frequency has an upper limit (maximum drive frequency) at which a pressure wave capable of appropriately ejecting ink can be generated according to the characteristics of the ink and the shape of the ink flow path. If it is too high, an image with a resolution higher than that corresponding to the maximum drive frequency cannot be obtained. Here, the ejection frequency is the maximum drive frequency (if the frequencies that can be set are discrete values, the maximum frequency among them may be used). The maximum frequency that does not exceed the theoretical maximum drive frequency is acceptable considering the blur, error, margin, etc. that can be obtained), or an image with the desired resolution can be obtained while maintaining the transport speed at a slightly lower level. Maximum speed (If the speed that can be set is a discrete value, the maximum speed is acceptable. If it can be set continuously, consider the blur, error, margin, etc. that can actually occur for the setting.) The maximum speed that is unlikely to exceed the theoretical maximum speed is acceptable) or the speed is adjusted to a slightly lower speed. That is, the higher the resolution, the lower the conveying speed.

FIG. 4 is a diagram schematically showing temporal changes in resolution and transport speed.
When a plurality of images with different resolutions, here, a high-resolution image, a low-resolution image, and a medium-resolution image are formed in order as shown in FIG. Therefore, the image formation period of each image is shifted among the plurality of head units 25 . That is, the formation start timing ul of each image by the head unit 25 on the most downstream side is delayed with respect to the formation start timing uf of each image by the head unit 25 on the most upstream side in accordance with the transport speed.

In this inkjet recording apparatus 100, as shown in FIG. 4B, when shifting from relatively high-resolution image formation to low-resolution image formation, the head unit 25 on the most downstream side becomes the object of formation first. After the formation of the image on the high resolution side (first image) is completed, the conveyance that enables the formation of the second image while forming the next image on the low resolution side (second image) to be formed. Increase speed. On the other hand, when shifting from image formation on the relatively low-resolution side to image formation on the high-resolution side, before the head unit 25 on the most upstream side shifts to image formation on the high-resolution side, the image formation on the high-resolution side is performed. The conveying speed is changed in advance during image formation on the low-resolution side so as to complete the reduction to the conveying speed capable of forming the next image.

The time tp required for speed change depends on the speed difference. Also, since the transport speed during image formation on the low-resolution side differs depending on the resolution, the length of the remaining image (predetermined distance) according to the remaining time tp until the image formation by the head unit 25 on the upstream side is completed. is of course different. Therefore, when the timing for starting the reduction of the transport speed is acquired at the position on the recording medium M, the length of the remaining image may be calculated in advance based on these conditions. As a result, it is not necessary to provide a margin between the first image and the second image on the recording medium M (a necessary minute space may be provided), and the margin is removed. There is no need for waiting time in between. By calculating the start timing of lowering the conveying speed, that is, the time tp and the length of the remaining image corresponding to this so that the lowering of the conveying speed ends at the timing of starting high-resolution image formation, the conveying speed is reduced. It is also possible to prevent the throughput from decreasing due to lowering it more than necessary.

At this time, if the speed change (acceleration) per hour is too large, a large force is applied to each part of the inkjet recording apparatus 100, and problems such as blurring of the formed image tend to occur. In addition, since the ink ejection timing is determined based on the detection signal (that is, the transport speed) of the encoder 24, if there is a speed change (acceleration) after the most recent detection signal, the ink ejection timing corresponding to the Positional deviation occurs. Therefore, the conveying speed is not changed abruptly in a short period of time, but is changed gradually. That is, the acceleration (the amount of change in speed within the unit time when the speed change is performed discretely for each unit time) is kept within a predetermined upper limit value (below the reference value). The reference value may be determined according to the permissible amount of displacement of the landing positions (such as the upper limit of the amount of displacement with respect to the original transport direction). As a result, the impact position is not shifted beyond the distance corresponding to the upper limit value. Further, by setting the upper limit value based on the permissible amount of deviation of the landing position, the image quality is not adversely affected.

Furthermore, as shown in FIGS. 4(c) and 4(d), in order to prevent rapid speed switching at the start and end of the speed change, from the start to the predetermined period t1 (first predetermined period) and to the end, Acceleration (velocity change) during the predetermined period t3 (second predetermined period) is changed to acceleration (velocity change) during the period t2 during the speed change other than these (that is, the period after the predetermined period t1 and before the predetermined period t3) By making it smaller than , it is possible to start and end the speed change slowly. Here, the acceleration magnitude (absolute value) is gradually increased during the first predetermined period, and the acceleration magnitude is gradually decreased during the second predetermined period, resulting in a smooth speed change.

FIG. 5 is a flow chart showing a control procedure by the control unit 50 of the image recording control process executed in the inkjet recording apparatus 100. As shown in FIG. This image recording control process is started when an image forming command is acquired from the outside via the communication section 81 or via the operation reception section 83 . Multiple instructions may be obtained. When receiving a command via the operation receiving unit 83, image data of each resolution may be stored in the storage unit 60 in advance.

When the image recording control process is started, the control unit 50 (CPU 51) acquires image data and setting data related to an image formation command (step S101). The control unit 50 acquires the resolution of the image data, acquires the transport speed corresponding to the resolution from the resolution corresponding speed table 62, and causes the transport unit 70 to start transporting the recording medium M at the acquired transport speed. (step S102; transport operation step). The control unit 50 causes the recording operation unit 20 to start the recording operation (step S103).

While operating the transport unit 70 based on the currently set transport speed (resolution), the control unit 50 checks whether image formation based on the last image data in the acquired image formation command is being performed. It is determined (step S104). If it is determined that the image is not being formed based on the last image data ("NO" in step S104), the control unit 50 replaces the image data of the image to be formed next with the image of the current image to be formed. It is determined whether or not the resolution is lower than the data (including the same resolution) (step S105). If it is determined that the resolution is lower ("YES" in step S105), the control unit 50 determines whether or not the image formation of the current target image in the head unit 25 on the most downstream side has been completed. is determined (step S106). If it is determined that the process has not ended ("NO" in step S106), the control unit 50 repeats the process of step S106.

If it is determined that the image formation of the current target image has been completed ("YES" in step S106), the control unit 50 adjusts the transport speed based on the resolution corresponding speed table 62 to that of the next image to be formed. Processing is performed to increase the speed according to the resolution (step S107). The speed change is a gradual change, as described above. The control unit 50 reduces the ink ejection frequency once according to the change in resolution, and then increases it again according to the change (increase) in the transport speed. Note that if there is no change in resolution, the amount of change in the conveying speed is zero, and the control unit 50 immediately ends the processing of step S107. Then, the processing of the control unit 50 returns to step S104.

If it is determined in the determination processing in step S105 that the next image data to be formed does not have a lower resolution than the current image data to be formed (has a higher resolution) (“NO” in step S105). ), the control unit 50 determines whether image formation (recording operation) has been performed at a position a predetermined distance before the position where image formation of the current image to be formed by the most upstream head unit 25 ends (step S116). If it is determined that the recording operation has not yet been performed at the position before the predetermined distance ("NO" in step S116), the control section 50 repeats the processing of step S116.

If it is determined that the image formation (recording operation) is performed at a position a predetermined distance before the position where the formation of the current image to be formed ends (“YES” in step S116), the control unit 50 performs the following Based on the resolution of the image to be formed and the resolution correspondence speed table 62, the processing of lowering the conveying speed to the speed corresponding to the next resolution is performed (step S117; speed change step). By starting the decrease in the transport speed at the position before the predetermined distance, the decrease in the transport speed ends immediately before the head unit 25 on the most upstream side starts forming the next target image. Then, the processing of the control unit 50 returns to step S104.

If it is determined in the determination processing in step S104 that the current image to be formed (image formation) is based on the last image data (“YES” in step S104), the control unit 50 controls the most downstream side It is determined whether or not the head unit 25 has finished forming the target image (step S121). If it is determined that the process has not ended ("NO" in step S121), the control unit 50 repeats the process of step S121. When it is determined that the image formation of the target image by the head unit 25 on the most downstream side is completed ("YES" in step S121), the control section 50 stops the conveying operation by the conveying section 70 (step S122). . If necessary, the control unit 50 may continue to convey the recording medium M after the last image is formed until the image is discharged to the medium discharge unit 40 .

FIG. 6 is a diagram showing a modification of the relationship between the resolution and the transport speed for image formation.
Here, the order of image formation is such that the resolution monotonously increases, and the conveying speed monotonically decreases (reduces) accordingly. When a plurality of image formation commands with different resolutions are acquired, if the images can be formed by rearranging them in ascending order of resolution (in ascending order of resolution), image formation is performed in ascending order. If set, all changes in the transport speed are unified when starting from a predetermined time before the end of image formation by the head unit 25 on the most upstream side.

FIG. 7 is a modification of the flowchart showing the control procedure by the control unit 50 of the image recording control process. This modification corresponds to the one shown in FIG. 6, in which the processing of step S151 is added to the image recording control processing shown in FIG. The order of the processes after step S104 is partly changed. The same reference numerals are assigned to the same processing contents, and detailed description thereof will be omitted.

After the process of step S101, the control unit 50 (CPU 51) sorts the acquired plurality of image data to be formed in descending order of resolution and determines the order of image formation (step S151). Then, the processing of the control unit 50 proceeds to step S102.

After the process of step S103, the control unit 50 shifts to the process of step S106, and determines whether or not the head unit 25 on the most upstream side is a predetermined distance before the end of the current image forming operation of the image forming object. (Step S106). As described above, the control unit 50 can predetermine a variable value as the predetermined distance according to the amount of speed change and the current conveying speed. If it is determined that the image forming operation by the head unit 25 on the most upstream side is completed before the predetermined distance ("YES" in step S106), the process of the control unit 50 proceeds to step S104.

If it is determined in the determination processing in step S104 that the image to be formed for the current image formation corresponds to the last image data ("YES" in step S104), the processing of the control unit proceeds to step The process proceeds to S121. If it is determined not to correspond to the last image data ("NO" in step S104), the processing of the control unit 50 proceeds to step S107. In the process of step S107, the controller 50 increases the conveying speed, and then returns the process to step S106.

As described above, the inkjet recording apparatus 100, which is the present embodiment of the image forming apparatus, includes the conveying unit 70 that moves the recording medium M along a predetermined conveying path, and the recording medium M that moves along the predetermined conveying path. a recording operation unit 20 that performs a recording operation by recording elements 20a provided over a recordable width of the recording medium M in a direction that intersects the direction along the transport path at a position; and a control unit 50 that controls the recording operation. The control unit 50 causes the conveying unit 70 to perform a conveying operation at a conveying speed determined according to the resolution of the image to be formed. When the second resolution of the second image to be formed next is higher than the first resolution of the second image, before starting the recording operation of the second image, during the recording operation of the first image Decrease the conveying speed to
In this way, by changing the conveying speed according to the resolution, it is possible to set the image recording operation to be performed near the upper limit driving frequency, so that the image forming time is not required more than necessary. Therefore, the inkjet recording apparatus 100 can efficiently form an image. Further, by performing the recording operation while changing the conveying speed, there is no need to stop the recording operation while changing the conveying speed, and unnecessary waiting time is not required. In addition, since the recording medium M is not moved unnecessarily during the standby time, unnecessary blank space is not generated on the recording medium M and the recording medium M is not wasted.
In particular, when sample images are formed little by little while switching between multiple resolutions, the time required for switching, the margins of the recording medium at the time of switching, etc., compared to the time required to form the sample images and the amount of consumption of the recording medium. Although they were large conventionally, these can be efficiently suppressed and removed.

Further, the control unit 50 determines the start timing of the decrease in the transport speed so that the decrease in the transport speed is finished at the timing of starting the recording operation related to the second image on the high-resolution side. As a result, a state in which the conveying speed is unnecessarily slow does not occur, so that the conveying speed can be maintained without waste and images can be formed more efficiently.

Further, the transport speed is set to the maximum speed at which the resolution of the image to be formed can be obtained at the maximum driving frequency of the recording operation section 20 . That is, since the conveying speed is set so that an image with a desired resolution can be obtained at the fastest speed in the inkjet recording apparatus 100, image formation can be performed with maximum efficiency.

The recording operation section 20 has a plurality of head units 25 that perform recording operations at different positions on the transport path. The transport speed is reduced before the head unit 25 on the upstream side starts the recording operation for the high-resolution second image. That is, since the conveying speed is lowered before the recording operation starts at the resolution at which the conveying speed needs to be lowered, the image is appropriately formed at the conveying speed that does not cause any problem in image formation at each resolution. . Further, after image formation by the head unit 25 on the most downstream side is completed, if the conveying speed is changed and image formation by the head unit 25 on the most upstream side is started, the time lag is very large. Although the margins of the recording medium also become long, since these can be eliminated, the efficiency of image formation is greatly improved.

Further, when receiving a command to form a plurality of images with different resolutions, the control unit 50 causes the recording operation unit 20 to form a plurality of images in ascending order of resolution.
In this way, since image formation is performed with a plurality of resolutions in order in the direction of increasing resolution, there is only one method for setting the change timing of the conveying speed according to the change in resolution, and control becomes simple.

Further, the control unit 50 changes the transport speed so that the acceleration associated with the change of the transport speed is equal to or less than a predetermined reference value. As a result, it is possible to avoid the application of a force that is too strong compared to the structure of the inkjet recording apparatus 100, and to limit the displacement of the ink ejection position due to rapid acceleration/deceleration to a range that does not cause deterioration in image quality. Further, it is easy to interlock the speed changes of the front and rear drying sections 30 and the medium delivery section 10, and the recording medium M can be conveyed stably.

In addition, the control unit 50 controls that the acceleration during the first predetermined period t1 from the start of the change of the conveying speed and the second predetermined period t3 until the end of the change is the second predetermined period after the first predetermined period t1 and the second predetermined period t3. The conveying speed is changed so as to be smaller than the acceleration during the period t2 before the predetermined period t3. In this way, by providing a switching portion with a small speed change at the start and end of the speed change, it is possible to more stably maintain the image quality during the change of the transport speed.

Further, the control unit 50 changes the conveying speed so that the magnitude of the acceleration gradually increases during the first predetermined period and the magnitude of the acceleration gradually decreases during the second predetermined period. That is, since the speed change is performed more smoothly, the inkjet recording apparatus 100 can better maintain the image quality during the change of the conveying speed.

Further, a drying section 30 is provided downstream of the recording operation section 20 in the direction along the transport path. The recording operation section 20 performs a recording operation by ejecting ink from the recording elements 20a. The ink on the recording medium M is dried. As described above, especially when the inkjet recording apparatus 100 has a configuration related to drying after image formation, it is difficult and troublesome to reversely move the continuous recording medium M. By changing the speed and not creating an unnecessary margin, it is possible to easily and efficiently reduce waste of the recording medium. In addition, it is possible to prevent time consumption due to interposing the operation of reversing.

It also includes a medium delivery unit 10 that delivers the recording medium M to the transport path. In this way, especially when the continuous recording medium M is delivered from the medium delivery section 10 separately from the transport section 70, it is difficult and troublesome to reversely move the recording medium M once advanced. By changing the transport speed while transporting and not generating an unnecessary margin, waste of the recording medium can be efficiently eliminated more easily.

Further, the transport control method of the present embodiment includes a transport operation step in which the transport unit 70 transports the recording medium M at a transport speed determined according to the resolution of the image to be formed, and a plurality of images having different resolutions. When forming the first image, if the second resolution of the second image to be formed next to the first image is lower than the first resolution of the first image to be formed, the first image is formed. a speed change step of increasing the conveying speed determined according to the second resolution during the printing operation for the second image after the printing operation for the image is finished.
By using such a transport control method, it is possible to set the image recording operation to be performed in the vicinity of the upper limit driving frequency for images of any resolution, so that the image forming time is not required more than necessary. . Therefore, image formation can be performed efficiently. Further, by performing the recording operation while changing the conveying speed, there is no need to stop the recording operation while changing the conveying speed, and unnecessary waiting time is not required. Moreover, unnecessary movement of the recording medium M during the waiting time can be eliminated, so that unnecessary blank space is not generated on the recording medium M and the recording medium M is not wasted.

It should be noted that the present invention is not limited to the above embodiments, and various modifications are possible.
For example, in the above-described embodiment, control was performed assuming that the ink ejection operation was performed at the maximum drive frequency and that the transport was performed at the maximum speed corresponding to the desired resolution. may For example, an upper limit transport speed may be determined separately according to the structural strength of the inkjet recording apparatus 100, and the transport operation may be performed at or below this transport speed. In addition, when ink ejection at the maximum drive frequency does not provide a certain level of image quality, ink is ejected at a drive frequency lower than the maximum drive frequency depending on the image quality settings when forming high-resolution images. There may be cases where

Further, in the above embodiment, four head units 25 for ejecting four colors of CMYK ink are provided, but the present invention is not limited to this. There may be one, or two or more arbitrary head units 25 may be provided.

Further, in the above embodiment, the timing (position) at which the conveying speed starts to decrease is obtained according to the speed difference and the current conveying speed. may be set to a fixed value calculated by In this case, depending on the speed difference and the current transport speed, the decrease in transport speed ends before image formation on the high-resolution side starts.

Further, in the above-described embodiment, the inkjet recording apparatus 100 is provided with the drying section 30 for drying the recording medium M on which ink has landed by heat and/or air blowing, but the drying section 30 may not be provided. In addition, when using another method, for example, ink that is cured by ultraviolet rays, an irradiation unit for irradiating ultraviolet rays may be provided instead of the drying unit 30 . Also, the arrangement of the drying operation unit 35 inside the housing may be determined as appropriate. Alternatively, the drying operation unit 35 may be provided outside the housing, and heated dry air may be sent into the housing via a pipe by a fan.

Moreover, the configuration related to the supply and ejection of the recording medium M to the transport path is not limited to that described in the above embodiment.

Further, in the above-described embodiment, all images to be formed are acquired first, but image data to be formed next may be added during image formation. In this case, it suffices if the image data is acquired within a range in time for the start of the process of changing the conveying speed. Alternatively, image data set as image forming targets may be re-sorted sequentially in order of resolution.

Further, in the above embodiment, image data of each resolution has been described as being acquired and held from the outside, but one type of original data (such as vector image data) is acquired and held, and a set of multiple A bitmap image (raster image) corresponding to the resolution may be generated by the control unit 50 respectively.

Further, in the above embodiments, the image forming apparatus that performs the recording operation of ejecting ink has been described, but the present invention is not limited to this. A recording operation is performed within a predetermined maximum driving frequency by arranging other types of recording elements, such as an LED printer, or by another mechanism that forms an image extending in the width direction in units of lines. good too.
In addition, specific details such as the configurations, structures, control contents and procedures shown in the above embodiments can be changed as appropriate without departing from the scope of the present invention.

10 Medium delivery unit 11 Medium roll 12 Feeding roller 20 Recording operation unit 20a Recording element 21 Driving roller 22 Driven roller 23 Conveyor belt 24 Encoder 25 Head unit 251 Recording head 26 Head driving unit 27 Nozzle 27a Nozzle opening 28 Electromechanical conversion element 30 Drying Section 31 Conveyance Roller 32 Conveyance Roller 35 Drying Operation Section 36 Drying Operation Driving Section 40 Medium Discharge Section 41 Discharge Roller 50 Control Section 51 CPU
52 RAMs
60 storage unit 61 transport control program 62 resolution corresponding speed table 70 transport unit 76 transport drive unit 81 communication unit 82 display unit 83 operation reception unit 90 bus 100 inkjet recording device M recording medium

Claims (10)

a transport unit that moves the recording medium along a predetermined transport path;
a recording operation unit that performs a recording operation on the recording medium over a recordable width of the recording medium in a direction that intersects the direction along the transportation path at a predetermined position on the transportation path;
a control unit that controls a recording medium conveying operation by the conveying unit and the recording operation;
with
The control unit
When forming a plurality of images having different resolutions by causing the conveying unit to perform the conveying operation at a conveying speed determined according to the resolution of the image to be formed, the first image of the first image to be formed is formed. When the second resolution of the second image to be formed next is higher than the resolution, the recording operation relating to the first image is performed before starting the recording operation relating to the second image. to the conveying speed determined according to the second resolution ,
When a command to form a plurality of images with different resolutions is acquired, the recording operation unit forms the plurality of images in descending order of resolution.
An image forming apparatus characterized by: 2. The apparatus according to claim 1, wherein the control unit determines the start timing of the reduction of the conveying speed so as to end the reduction of the conveying speed at the timing of starting the recording operation related to the second image. Image forming device. 3. The image forming apparatus according to claim 1, wherein the conveying speed is set to a maximum speed at which resolution of the image to be formed can be obtained at a maximum driving frequency of the recording operation section. The recording operation section has a plurality of recording units each having a different predetermined position,
The controller reduces the conveying speed before starting the recording operation for the second image by a recording unit whose predetermined position is the most upstream of the conveying path among the plurality of recording units. The image forming apparatus according to any one of claims 1 to 3, characterized in that: 5. The image forming apparatus according to any one of claims 1 to 4 , wherein the control unit changes the conveying speed so that an acceleration associated with changing the conveying speed is equal to or less than a predetermined reference value. . The control unit controls that the acceleration during a first predetermined period from the start of the change of the conveying speed and a second predetermined period until the end of the change is 6. The image forming apparatus according to claim 5 , wherein the conveying speed is changed so as to be smaller than the acceleration in front. The controller changes the conveying speed so that the magnitude of the acceleration gradually increases during the first predetermined period and the magnitude of the acceleration gradually decreases during the second predetermined period. Item 7. The image forming apparatus according to item 6 . A drying unit is provided downstream of the recording operation unit in a direction along the conveying path,
The recording operation unit performs the recording operation by ejecting ink,
The image forming apparatus according to any one of claims 1 to 7 , wherein the drying section dries ink on the recording medium. 9. The image forming apparatus according to any one of claims 1 to 8, further comprising a medium delivery section that delivers the recording medium to the transport path. a transport unit for moving a recording medium along a predetermined transport path; and a recordable width of the recording medium in a direction intersecting the direction along the transport path at a predetermined position on the transport path with respect to the recording medium. A conveyance control method for an image forming apparatus, comprising:
a conveying operation step of causing the conveying unit to convey the recording medium at a conveying speed determined according to the resolution of the image to be formed;
When forming a plurality of images having different resolutions, the second resolution of the second image to be formed next to the first image is higher than the first resolution of the first image to be formed. is lower, after the recording operation for the first image is completed, the speed change is performed to increase the conveying speed to the transport speed determined according to the second resolution during the recording operation for the second image. step,
an order change step of causing the recording operation unit to form the plurality of images in descending order of resolution when a command to form a plurality of images having different resolutions is acquired;
A transport control method, comprising:

Images