JP2001315314A - Ink jet imaging apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ink jet imaging apparatus in which image quality is prevented from lowering due to abrupt bending of a recording medium. SOLUTION: In the way of imaging on a sheet of recording medium 12, the number of print passes is altered at a specified timing. Bands (12-1) and (12-2) are subjected to one pass printing. When a band (12-4) is under imaging, a discharged part of the recording medium 12 has been predicted to bend due to its self-weight. Consequently, bands (12-3) and (12-4) are subjected to two pass printing. After the recording medium 12 has bent slowly, it is guided downward while touching a guide plate. Consequently, bands (12-5) and (12-6) are subjected to one pass printing.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an ink jet type image forming apparatus for forming an image by discharging ink onto a recording medium.

[0002]

2. Description of the Related Art As one of output devices of computers and workstations, there is known an ink jet type image forming apparatus which forms an image by discharging ink onto a recording medium such as recording paper. In general, the inkjet type image forming apparatus is provided with a print head for discharging ink, and a scanning (reciprocating) in a predetermined main scanning direction by mounting the print head.
And a recording medium transport device that transports the recording medium in a sub-scanning direction (recording medium transport direction) orthogonal to the predetermined direction.

In forming an image on a recording medium,
A plurality of bands extending in the main scanning direction and arranged in the sub-scanning direction are assumed in the recording medium in advance. Each band is elongated, and the length of one band means the length of this band in the main scanning direction. The width of one band refers to the length of this band in the sub-scanning direction, which is much shorter than the length of the recording medium in the sub-scanning direction.

When forming an image on a recording medium in which a plurality of bands are assumed as described above, the recording medium being transported by the recording medium transport device is temporarily stopped, and the carriage is scanned in the main scanning direction. In this manner, ink is ejected from the print head based on an image signal carrying image information, and an image is formed on a portion (corresponding to one band) of a recording medium located in an image forming area facing the print head. Thereafter, the recording medium is conveyed by the width of one band and stopped, and again, while the carriage is reciprocated in the above-described predetermined direction, ink is ejected from the nozzles based on the image signal, and the next band (the recording medium An image is formed on the portion newly located in the image forming area. By repeating such an operation, an image is formed on the recording medium. The recording medium on which the image is formed is usually discharged, hangs down, and is stored in a basket or the like.

[0005]

In an image forming apparatus using ink, such as the above-mentioned ink jet type image forming apparatus, when the ink is ejected on a recording medium, the ink is absorbed by the recording medium and the recording is performed. The medium may be wavy (partially raised). Such a recording medium absorbing ink and waving is called cockling.

When cockling occurs in a recording medium, the "waist" of the portion where the cockling occurs may be strengthened. When the “stiffness” of the recording medium increases, the discharged recording medium becomes difficult to bend. When the recording medium is hardly bent as described above, even if the discharged portion (discharge portion) of the recording medium becomes considerably long, the discharged portion remains straight without being bent. However, when the discharge portion has reached a certain length, the discharge portion sharply bends under its own weight and hangs down.

[0007] When the discharge portion is sharply bent as described above, the recording medium vibrates. This vibration is also transmitted to a portion of the recording medium located in the image forming area (a portion where an image is being formed), and this portion vibrates. The portion where the image is being formed is where ink ejected from the print head lands. For this reason, when the portion where the image is being formed vibrates, there is a problem that the ink landing position deviates from the normal position and the image quality (print quality) is reduced.

SUMMARY OF THE INVENTION In view of the above circumstances, it is an object of the present invention to provide an ink jet type image forming apparatus which prevents deterioration of image quality due to sharp bending of a recording medium.

[0009]

According to the first aspect of the present invention, there is provided an ink-jet image forming apparatus according to the present invention.
A plurality of bands extending in a predetermined main scanning direction and arranged in a sub-scanning direction orthogonal to the main scanning direction are assumed on a recording medium in advance, and a print head that ejects ink is scanned in the main scanning direction. An ink-jet that forms an image on a recording medium by sequentially forming images on the plurality of bands by repeatedly performing an operation of ejecting ink from the print head to one of the plurality of bands to form an image. (1) The number of times that the print head scans in the main scanning direction is changed at a predetermined timing in order to finish forming an image on the one band.

In order to achieve the above object, a second ink jet type image forming apparatus according to the present invention (an ink jet type image forming apparatus according to the second aspect) extends in a predetermined main scanning direction and has a main scanning direction. A plurality of bands arranged in the sub-scanning direction perpendicular to the direction are assumed in advance on the recording medium, and the print head for ejecting ink is scanned in the main scanning direction while one of the plurality of bands is scanned. In an ink jet type image forming apparatus for forming an image on a recording medium by sequentially forming an image on the plurality of bands by repeatedly performing an operation of forming an image by discharging ink from a print head, ,
The number of times of scanning in the main scanning direction in order to finish forming an image in the one band is changed at a predetermined timing.

Here, the above-mentioned ink jet type image forming apparatus comprises (3) a memory which stores a plurality of types of recording media, and the number of times and the predetermined timing corresponding to each of the plurality of types, 4) The user may determine the type of recording medium on which an image is formed, and select the number of times and the predetermined timing from the memory based on the determined type.

Further, the above-mentioned ink jet type image forming apparatus comprises: (5) a memory storing a plurality of types of recording media, and the number of times and the predetermined timing corresponding to each of the plurality of types; A determination sensor for determining the type of the recording medium may be provided, and (7) the number of times and the predetermined timing may be selected from the memory based on the type of the recording medium determined by the determination sensor.

Further, the above-mentioned ink jet type image forming apparatus is provided with (8) a memory which stores the number of times corresponding to the humidity and the predetermined timing, and (9) a humidity detecting sensor which detects the humidity. The number of times and the predetermined timing may be selected from the memory based on the humidity detected by the humidity detection sensor.

According to a third aspect of the present invention, there is provided an ink-jet type image forming apparatus according to the present invention, which extends in a predetermined main-scanning direction. A plurality of bands arranged in the sub-scanning direction perpendicular to the direction are assumed in advance on the recording medium, and the print head for ejecting ink is scanned in the main scanning direction while one of the plurality of bands is scanned. The ink is ejected from the print head to form an image,
Thereafter, the recording medium is conveyed in the sub-scanning direction by the width of the one band at a predetermined conveying speed, and the operation of forming an image by discharging ink from the print head to the next one band is repeated. In an ink jet image forming apparatus for forming an image on a recording medium by sequentially forming images on a plurality of bands, (11) the transport speed is changed at a predetermined timing.

Here, the above-mentioned ink jet type image forming apparatus comprises (12) a memory for storing a plurality of types of recording media, and the above-mentioned transport speed and timing corresponding to each of the plurality of types. The user may determine the type of the recording medium on which the image is formed, and select the transport speed and the timing from the memory based on the determined type.

Further, the above-mentioned ink jet type image forming apparatus comprises: (14) a memory which stores a plurality of types of recording media, and the transport speed and the predetermined timing corresponding to each of the plurality of types; And (16) a discrimination sensor for discriminating the type of the recording medium, and (16) the transport speed and the predetermined timing are selected from the memory based on the type of the recording medium determined by the discrimination sensor. Good.

Further, the above-mentioned ink jet type image forming apparatus is provided with (17) a memory which stores the above-mentioned conveying speed and the above-mentioned predetermined timing corresponding to humidity, and (18) a humidity detecting sensor which detects humidity. 19) The transport speed and the predetermined timing may be selected from the memory based on the humidity detected by the humidity detection sensor.

[0018]

Embodiments of the present invention will be described below with reference to the drawings.

Referring to FIG. 1 and FIG. 2, a plotter as an example of the ink jet type image forming apparatus of the present invention will be described.

FIG. 1 is a perspective view schematically showing a plotter. FIG. 2 is a block diagram showing a part of the configuration of the plotter of FIG.

The plotter 10 has a platen 14 on which a recording medium 12 conveyed in the direction of arrow A is placed.
Above the platen 14, two guide shafts 16 are extended in parallel with the platen 14. The guide shaft 16 is provided with a carriage 18 (not shown) that reciprocates freely in directions indicated by arrows B and C (a direction orthogonal to the direction of arrow A) by a motor (not shown) and a belt (not shown). Attached via).

The carriage 18 is provided with a print head 20 having ink discharge ports (nozzle outlets, not shown) for discharging ink. An image forming area 22 on which an image is formed is located in front of the ink ejection port. Ink is ejected from the ink ejection port to a portion of the recording medium 12 located in the image forming area 22 to form an image. The portion of the recording medium 12 where the image is formed is a platen 14
Is guided by the guide plate 28 which is continuous with the second direction.

At a position on one side of the movable range of the carriage 18 distant from the image forming area 22, ink is forcibly sucked from the nozzles to clean the ink supply paths and nozzles formed on the print head 20. A recovery device 30 is provided for setting the ink discharge state of the print head 20 to the initial discharge state. A waste ink recovery device (not shown) is disposed below the recovery device 30.

In forming an image on the recording medium 12, the recording medium 12 is placed on a platen 14, and the recording medium 12 is moved from an opening (not shown) formed in the platen 14 to an outer peripheral surface. A transport roller 24 partially exposed, and a pinch roller 26 for pressing both ends of the recording medium 12 from above.
And transport by rotating the transport roller 24 by a motor (not shown). The carriage 18 is reciprocated in the directions of arrows B and C above the recording medium 12, and ink is ejected from the nozzles based on an image signal carrying image information transmitted from the control device 40 to the print head 20. 12, an image is formed in a portion located in the image forming area 22. During the image forming operation, when it becomes necessary to suck ink from the nozzles to clean the nozzles, the carriage 18 is moved above the recovery device 30.

As shown in FIG. 2, the control device 40 includes an image controller 42 for controlling print data (image data) carrying image information and the like, and an engine for controlling conveyance of the recording medium 12 and movement of the carriage 18. The controller 50 includes a controller 50 and a print head controller 44 that controls an ejection signal of ink ejected from the print head 20. The engine controller 50 includes a data rasterizing unit 52 for dividing print data sent from the image controller 42, and a print parameter changing unit 5 for changing print parameters according to the type of recording medium.
4, and a transport motor 46 for rotating the transport roller 24
And a transport control unit 56 that controls

Various print data and the like are sent to the image controller 42 from a host computer 48 having a large number of memories and the like. These various print data and the like are sent to the data rasterizing unit 52, where the print data is divided according to the nozzle width of the print head 20 and the number of print passes described later. Further, a signal carrying the type of the recording medium input by the user from the operation unit 58 and a signal carrying the type of the recording medium determined by the paper type automatic discriminator 60 are sent to the print parameter changing unit 54. Come. Such a signal is sent to the transport control unit 56 via the print parameter changing unit 54, and the transport control unit 56 controls the transport motor 46 based on the transmitted signal.

The recording medium 12 in which cockling has occurred will be described with reference to FIGS.

FIG. 3 is a schematic diagram showing a recording medium in which cockling has occurred. FIG. 4A is a schematic diagram illustrating a recording medium guided by a guide plate after being bent, and FIG. 4B is a schematic diagram illustrating a recording medium that is discharged straight to be bent. In these figures, FIG.
Are denoted by the same reference numerals.

The recording medium 12 that easily absorbs ink is
When used as, the ink ejected to the recording medium 12 is absorbed by the recording medium 12. Cockling occurs in the recording medium 12 due to the ink absorption. As shown in FIG. 3, when the cockling repeats the irregularities in the directions of arrows B and C, the “stiffness” of the recording medium 12 increases. As a result, the recording medium 12 is conveyed straight as shown in FIG. 4B without hanging down as shown in FIG.

When the recording medium 12 is ejected straight as shown in FIG. 4B, the ejected portion 12a is bent sharply by its own weight. As described above, due to the sharp bend, vibration occurs and the landing position of the ink deviates from the normal position, thereby deteriorating the image quality.

In order to prevent the recording medium 12 from being sharply bent as described above, the number of printing passes or the transport speed of the recording medium 12 was changed. Such a change will be described with reference to first to fourth examples.
[First Example] An example in which the number of print passes is changed will be described with reference to FIGS.

FIG. 5 is a flowchart showing a procedure for changing the number of print passes. FIG. 6 is a schematic diagram illustrating an example in which the number of print passes is changed.

Here, a band assumed when an image is formed by discharging ink on the recording medium 12 will be described. One recording medium 12 has a main scanning direction (arrows B and C).
Direction) and a plurality of elongated bands arranged in a sub-scanning direction (arrow A direction) orthogonal to the main scanning direction are assumed in advance. One band, as shown in FIG.
Length L and width W. Therefore, the recording medium 12 shown in FIG.
Is divided into six bands (six bands). When an image is formed on the recording medium 12, the number of bands is generally larger, but here, six bands are used for explanation.

In forming an image on the recording medium 12, one band (1
Images are formed in order from 2-1). One band (12
After forming the image in -1), the image is formed in the next one band (adjacent band (12-2)). Thus, an image is formed on the recording medium 12 by sequentially forming an image from the band (12-1) to the band (12-6).

In order to form an image in one band,
While selectively discharging ink from a number of nozzles (not shown) of the print head 20 (see FIG. 1), the print head 20 (ie, the carriage 18) is scanned (scanned) in the main scanning direction. In this case, the number of times the print head 20 scans in the main scanning direction to finish forming an image in one band is called the number of print passes. The number of print passes is determined in advance, and the completion of forming an image in one band by the print head 20 performing one scan in the main scanning direction while discharging ink is referred to as one-pass printing. The completion of forming an image in one band by the print head 20 performing two scans in the main scanning direction while discharging ink is referred to as two-pass printing. That is, the end of forming an image in one band by the print head 20 scanning n times in the main scanning direction while discharging ink is called n-pass printing.

In the first example, the number of print passes is changed at a predetermined timing while an image is being formed on one recording medium 12. For example, as shown in FIG. 6, one-pass printing is performed on the band (12-1) and the band (12-2). In this case, when an image is formed on the band (12-4), it is predicted that the discharge portion 12a (see FIG. 4) of the recording medium 12 will be bent by its own weight. Therefore, in band (12-3) and band (12-4), 2
Print the path. As a result, the recording medium 12 is discharged little by little, so that the recording medium 12 is bent slowly and the recording medium 12 can be prevented from being bent sharply downward. As a result, deterioration of the image quality due to the sharp bending of the recording medium 12 is prevented.

After the recording medium 12 is bent slowly, the recording medium 12 is guided by the guide plate 28 (see FIG. 1).
It is guided downward while contacting. Therefore, the band (1
2-5) and the band (12-6) perform one-pass printing.
By reducing the number of printing passes in this manner, the time required to finish forming an image in one band can be shortened, so that the throughput (the number of recording media on which an image can be formed per unit time) can be increased.

The timing for changing the number of print passes is previously programmed in the host computer 48 (see FIG. 2). This program is started at the same time as the start of printing (start of image formation), as shown in FIG. In this program, it is determined whether it is time to change the number of print passes while forming an image (S501). The timing of changing the number of print passes is, for example, in FIG. 6, when an image has been formed in band (12-2). A method for determining this timing will be described.

The distance the recording medium 12 is conveyed each time the print head 20 performs one scan is uniquely determined according to the number of print passes. Therefore, by counting the number of times the recording medium 12 has been scanned, the distance over which the recording medium 12 has been conveyed can be calculated. The distance obtained by this calculation is compared with the distance from the leading end of the recording medium 12 to the position where the number of print passes is changed, and it is determined whether or not it is time to change the number of print passes.

At the timing to change the number of printing passes, for example, the printing is changed from one-pass printing to two-pass printing (S502). Thereafter, it is determined whether or not it is time to return the number of print passes while forming an image with the changed number of print passes (S503). The timing of returning the number of print passes is, for example, in FIG. 6 when the image is formed in the band (12-4). When it is time to return the number of print passes, for example, return from two-pass printing to one-pass printing (S50).
4). Image formation is continued with the returned number of printing passes until printing is completed. In this way, by preprogramming the timing for changing the number of print passes, it is possible to prevent the image quality from being degraded due to the sharp bending of the recording medium 12 without any operation by the user. Here, the printing is changed from one-pass printing to two-pass printing. However, various printing pass numbers are conceivable, such as changing from two-pass printing to four-pass printing according to the type of the recording medium 12 and the environmental humidity.

In this embodiment, the host computer 48 controls the change of the number of print passes.
This control may be performed by the engine controller 50. [Second Example] In this second example, a technique for changing the transport speed of the recording medium 12 in order to prevent the recording medium 12 from being sharply bent will be described.

FIG. 7 is a flowchart showing a procedure for changing the transport speed of the recording medium. FIG. 8 is a schematic diagram illustrating an example in which the conveyance speed of the recording medium is changed.

In the second example, the conveyance speed of the recording medium is changed at a predetermined timing while an image is being formed on one recording medium 12. Note that the number of printing passes is constant and not changed.

The transport speed is changed at a timing based on the number of bands, for example, as shown in FIG. In this case, it is predicted that the ejected portion 12a (see FIG. 4) of the recording medium 12 is bent by its own weight while an image is formed from the eighth band to the thirteenth band. Therefore, when an image is formed on the first to seventh bands, the recording medium 12 is conveyed at a speed of 4 m / sec after forming the image on each band. Thereafter, when images are formed in the eighth to thirteenth bands,
After forming an image on each band, the recording medium 12 is
/ Second speed. As a result, the recording medium 12 is discharged little by little, so that the recording medium 12 is bent slowly and the recording medium 12 can be prevented from being bent sharply downward. As a result, deterioration of the image quality due to the sharp bending of the recording medium 12 is prevented.

After the recording medium 12 is bent slowly, the recording medium 12 is moved to the guide plate 28 (see FIG. 1).
It is guided downward while contacting. Therefore, the recording medium 12 is conveyed at a speed of 4 m / sec from the 14th band. By increasing the transport speed in this manner, the time for completing the formation of an image in one band can be shortened, so that the throughput (the number of recording media on which an image can be formed per unit time) can be increased.

The timing for changing the transport speed is previously programmed in the host computer 48 (see FIG. 2). This program is started at the same time as the start of printing (start of image formation), as shown in FIG. In this program, it is determined whether it is time to change the transport speed while forming an image (S801). The timing at which the transport speed is changed is, for example, when the image has been formed in the seventh band in FIG. 8 and when the image has been formed in the thirteenth band.

At the timing for changing the transport speed, the transport speed is changed, for example, from 4 m / sec to 2 m / sec (S802). Thereafter, while conveying the recording medium at the changed conveyance speed to form an image, it is determined whether it is time to return the conveyance speed (S803). The timing of returning the transport speed is, for example, when the image has been formed in the thirteenth band in FIG. When the timing for returning the transport speed comes, for example, the speed is returned from 2 m / sec to 4 m / sec (S804). Image formation is continued at the returned transport speed until printing is completed. As described above, by preprogramming the timing for changing the transport speed, it is possible to prevent the image quality from being deteriorated due to the sharp bending of the recording medium 12 without any operation by the user. Here, 4m
Although the speed is changed from 2 m / sec to 2 m / sec, various transport speeds can be considered, such as changing from 4 m / sec to 1 m / sec according to the type of the recording medium 12 and the environmental humidity.

In this embodiment, the host computer 48 controls the change of the number of print passes.
This control may be performed by the engine controller 50. [Third Example] As the recording medium 12 (see FIG. 1), a plurality of types (paper quality) such as plain paper and coated paper are known. The timing at which the sharp bend occurs varies depending on the type of recording medium. Also, some recording media do not have this bending.

Therefore, the timing of occurrence of bending for each type of recording medium is checked in advance and stored in the memory 55 in the engine controller 50 (see FIG. 2). In addition, the number of printing passes for preventing the above-described sharp bending is checked in advance and stored in the memory 55. Tables 1 and 2 show examples of the contents stored in the memory 55. By changing the number of print passes and the transport speed according to the type of the recording medium in this way, it is possible to more reliably and easily prevent the image quality from lowering.

The engine controller 50 counts the number of scans, monitors the timing of changing the number of print passes, and changes the feed amount accompanying the change in the number of print passes. The change of the division of the image data according to the change of the number of print passes is performed by the image controller 42.

[0051]

[Table 1]

[0052]

[Table 2] According to Table 1 above, for example, in the case of thick coated paper, the location where the sharp bend occurs is a position about 300 mm away from the predetermined print standby position. Therefore, one-pass printing is performed until thick coated paper is conveyed by about 300 mm.
Change to 4-pass printing before it is conveyed by about 300 mm. As a result, the thick coated paper is bent slowly and not sharply. After the thick coated paper is slowly bent, return to one-pass printing.

Here, when the print head 20 has 144 nozzles and 360 dpi, the feed amount (recording medium transport amount) for one-pass printing is about 10 mm. Therefore, as shown in Table 2, printing is changed to 4-pass printing at the 28th scan. This causes the thick coated paper to bend slowly, as described above. After that, when the paper is conveyed by about 340 mm from the above-described print standby position, the printing is returned to the one-pass printing.
Thereafter, one-pass printing is continued. In addition, the feed amount at the time of four-pass printing is about ｍｍ mm because it is １ ／ of that at the time of one-pass printing. In the above example, the number of print passes is changed, but the transport amount of the recording medium may be changed.

As a method for determining the type of the recording medium, a method in which the user inputs the type of the recording medium from the operation unit 58 (see FIG. 2) and a method for automatically determining the type of the recording medium, And a method of automatically determining the type of the recording medium by using FIG. 2).
An example of the paper type automatic discriminator 60 is a discriminator that measures the reflectance on a recording medium using an optical sensor and determines the type of the recording medium based on the reflectance. As another paper type automatic discriminator 60, there is a discriminator that reads a barcode printed on a part of the surface of a recording medium by an optical sensor and determines the type of the recording medium. [Fourth Example] A plotter 10 (see FIG. 1) is installed in a room under various environments such as temperature and humidity. Plotter 10
The degree (level) of cockling generated in the recording medium 12 changes according to the humidity of the environment in which is installed. The reason for this is that the amount of water contained in the portion of the recording medium where no image is formed (unprinted portion) changes depending on the humidity. In an environment with low humidity, generally, the difference in the water content before and after the ink lands on the recording medium 12 becomes large, so that cockling tends to be severe (the recording medium 12 is largely wavy).

Therefore, the humidity is divided into several ranges, and the occurrence timing of bending and the like are checked in advance for each range, and are stored in the memory 55 in the engine controller 50 (see FIG. 2). In addition, the number of printing passes for preventing the above-described sharp bending is checked in advance and stored in the memory 55. Table 3 shows an example of the contents stored in the memory 55. By changing the number of printing passes and the transport speed in accordance with the humidity of the environment in which the plotter 10 is installed in this manner, it is possible to more reliably and easily prevent a decrease in image quality.

[0056]

[Table 3] The environmental humidity is detected by a humidity detection sensor (not shown) incorporated in the plotter 10. The engine controller 50 counts the number of scans, monitors the timing of changing the number of print passes, and changes the feed amount accompanying the change in the number of print passes. The change of the division of the image data according to the change of the number of print passes is performed by the image controller 42.

According to Table 3 above, for example, when the humidity is 20%
If it is less than 40%, the printing is changed from one-pass printing to four-pass printing at the 20th scan. This causes the recording medium to bend slowly and not sharply. After the recording medium is bent slowly, the printing is returned to one-pass printing. In addition,
In the above example, the number of print passes is changed, but the configuration may be such that the transport amount of the recording medium is changed.

[0058]

As described above, in the first ink jet type image forming apparatus of the present invention (the ink jet type image forming apparatus according to the first aspect), the portion of the recording medium where the image has been formed is discharged. The number of print passes (the number of times the print head scans in the main scanning direction to finish forming an image in one band) can be increased before the sheet is sharply bent downward. By increasing the number of printing passes in this way, the recording medium is ejected little by little, so that the recording medium can be prevented from suddenly bending downward. As a result, a decrease in image quality due to a sharp bend of the recording medium is prevented. Also, by reducing the number of printing passes after the recording medium is bent, the time required to complete the formation of an image in one band can be shortened, so that the throughput (the number of recording media capable of forming an image per unit time) can be increased.

Further, according to the second ink jet type image forming apparatus of the present invention (according to the second aspect of the present invention, the portion of the recording medium on which the image has been formed is discharged and is moved downward. Before the sharp bend, the number of times that the print head scans in the main scanning direction (the number of print passes) to finish forming an image in one band can be increased.
Since the recording medium is discharged little by little, it is possible to prevent the recording medium from being sharply bent downward. As a result, a decrease in image quality due to a sharp bend of the recording medium is prevented. Also, by reducing the number of printing passes after the recording medium is bent, the time required to complete the formation of an image in one band can be shortened, so that the throughput (the number of recording media capable of forming an image per unit time) can be increased.

Here, the ink jet type image forming apparatus is provided with a memory storing a plurality of types of recording media and the above-mentioned number of times corresponding to each of the plurality of types and the predetermined timing. When the user determines the type of the print medium and selects the number of times and the predetermined timing from the memory based on the determined type, the number of times (the number of print passes) and the number of the print passes depend on the type of the recording medium. Select when to change the
The image quality can be more reliably prevented from lowering.

Further, a plurality of types of recording media, a memory for storing the number of times corresponding to each of the plurality of types and the predetermined timing, and a discrimination sensor for discriminating the type of recording medium are provided by an ink jet type image forming apparatus. If the number of times and the predetermined timing are selected from the memory based on the type of the recording medium determined by the determination sensor, the number of times (printing pass) is determined according to the type of the recording medium determined by the determination sensor. ) And the timing for changing the number of print passes, the deterioration of the image quality can be more reliably and easily prevented.

Further, the ink jet type image forming apparatus includes a memory storing the number of times and the predetermined timing corresponding to the humidity, and a humidity detecting sensor for detecting the humidity. When the number of times and the predetermined timing are selected from the memory based on the humidity, when the number of times (the number of print passes) and the timing for changing the number of print passes are selected, humidity is also taken into consideration. It can be prevented more reliably.

Further, according to the third ink jet type image forming apparatus of the present invention (the ink jet type image forming apparatus according to the sixth aspect), the portion of the recording medium where the image has been formed is discharged to the lower side. Before the sharp bend, the transport speed is reduced. By delaying the transport speed in this manner, a bent portion of the recording medium is transported slowly, and the recording medium is gradually bent. Therefore, the recording medium is prevented from being sharply bent downward. As a result, it is possible to prevent the image quality from being degraded due to the sharp bending of the recording medium. Also,
Even if vibration occurs due to the bending of the recording medium, the recording medium is conveyed slowly, so that the vibration until the image is started to be formed in the next one band substantially stops. For this reason, it is possible to further prevent a decrease in image quality due to such vibration.

Here, the ink jet type image forming apparatus is provided with a memory in which a plurality of types of recording media and the above-mentioned transport speeds and the timings corresponding to the plurality of types are stored. When the type is determined by the user and the transport speed and the timing are selected from the memory based on the determined type, the transport speed and the timing of changing the transport speed are selected according to the type of the recording medium. Therefore, it is possible to more reliably prevent the image quality from lowering.

Further, a memory storing a plurality of types of recording media and the above-mentioned transport speed and the predetermined timing corresponding to each of the plurality of types, and a discrimination sensor for discriminating the type of the recording medium are provided by an ink jet type image forming apparatus. When the transport speed and the predetermined timing are selected from the memory based on the type of the recording medium determined by the determination sensor provided in the forming device, the transport is performed according to the type of the recording medium determined by the determination sensor. Since the speed and the timing for changing the transport speed are selected, it is possible to more reliably and easily prevent the image quality from deteriorating.

Further, the ink jet type image forming apparatus is provided with a memory storing the above-described transport speed and the predetermined timing corresponding to the humidity, and a humidity detecting sensor for detecting the humidity. When the transport speed and the predetermined timing are selected from the memory based on the humidity, humidity is also taken into consideration when selecting the transport speed and the timing at which the transport speed is changed, so that the deterioration of the image quality is further ensured. Can be prevented.

[Brief description of the drawings]

FIG. 1 is a perspective view schematically showing a plotter which is an embodiment of an inkjet type image forming apparatus of the present invention.

FIG. 2 is a block diagram showing a part of the configuration of the plotter of FIG. 1;

FIG. 3 is a schematic diagram illustrating a recording medium in which cockling has occurred.

FIG. 4A is a schematic diagram illustrating a recording medium guided by a guide plate after being bent, and FIG. 4B is a schematic diagram illustrating a recording medium that is discharged straight to be bent. is there.

FIG. 5 is a flowchart showing a procedure for changing the number of print passes.

FIG. 6 is a schematic diagram showing an example in which the number of print passes is changed.

FIG. 7 is a flowchart showing a procedure for changing the transport speed of the recording medium.

FIG. 8 is a schematic diagram illustrating an example in which the conveyance speed of a recording medium is changed.

[Explanation of symbols]

 Reference Signs List 20 print head 24 transfer roller 40 control device 42 image controller 46 transfer motor 50 engine controller 52 data rasterize unit 54 print parameter change unit 55 memory 56 transfer control unit

Claims (9)

[Claims] 1. A print head that ejects ink is provided with a plurality of bands extending in a predetermined main scanning direction and arranged in a sub-scanning direction orthogonal to the main scanning direction on a recording medium in advance. An image is sequentially formed on the plurality of bands by repeating the operation of ejecting ink from the print head to one of the plurality of bands to form an image while scanning, and forming an image on a recording medium. In the inkjet type image forming apparatus for forming, the number of times the print head scans in the main scanning direction is changed at a predetermined timing in order to finish forming an image on the one band, wherein the inkjet type image forming apparatus is characterized in that . 2. A printing medium for ejecting ink, wherein a plurality of bands extending in a predetermined main scanning direction and arranged in a sub-scanning direction orthogonal to the main scanning direction are previously assumed on a recording medium. An image is sequentially formed on the plurality of bands by repeating the operation of ejecting ink from the print head to one of the plurality of bands to form an image while scanning, and forming an image on a recording medium. In the inkjet type image forming apparatus to form, the print head changes the number of times of scanning in the main scanning direction at a predetermined timing in order to finish forming an image on the one band. Type image forming apparatus. And a memory for storing a plurality of types of recording media, and the number of times corresponding to each of the plurality of types and the predetermined timing, wherein a user determines a type of the recording medium on which an image is formed. The image forming apparatus according to claim 1, wherein the number and the predetermined timing are selected from the memory based on the determined type. 4. A memory for storing a plurality of types of recording media, the number of times corresponding to each of the plurality of types, and the predetermined timing, and a determination sensor for determining the type of the recording medium. The inkjet image forming apparatus according to claim 1, wherein the number of times and the predetermined timing are selected from the memory based on a type of the recording medium determined by a sensor. 5. A memory for storing the number of times and the predetermined timing corresponding to humidity, and a humidity detection sensor for detecting humidity, wherein the number of times and the predetermined number are determined based on humidity detected by the humidity detection sensor. The inkjet image forming apparatus according to any one of claims 1 to 4, wherein the timing of (i) is selected from the memory. 6. A print head for ejecting ink is provided with a plurality of bands extending in a predetermined main scanning direction and arranged in a sub scanning direction orthogonal to the main scanning direction on a recording medium in advance. Forming an image by ejecting ink from the print head to one of the plurality of bands while scanning the recording medium, and then moving the recording medium at a predetermined conveyance speed by the width of the one band in the sub-scanning direction. The image is formed by ejecting ink from the print head to the next one band to form an image by repeating the operation of forming the image on the recording medium by sequentially forming images on the plurality of bands. An inkjet image forming apparatus, wherein the transport speed is changed at a predetermined timing. 7. A memory for storing a plurality of types of recording media, and the transport speed and the timing corresponding to each of the plurality of types, wherein a user determines the type of recording medium on which an image is formed, 7. The image forming apparatus according to claim 6, wherein the transport speed and the timing are selected from the memory based on the determined type. 8. A memory for storing a plurality of types of recording media, the transport speed and the predetermined timing corresponding to each of the plurality of types, and a determination sensor for determining the type of the recording medium, The inkjet image forming apparatus according to claim 6, wherein the transport speed and the predetermined timing are selected from the memory based on a type of the recording medium determined by the determination sensor. 9. A memory storing the transport speed and the predetermined timing corresponding to humidity, and a humidity detection sensor for detecting humidity, wherein the transport speed and the humidity are detected based on the humidity detected by the humidity detection sensor. 9. The image forming apparatus according to claim 6, wherein the predetermined timing is selected from the memory.