printer

Abstract

To form a proper image even if a surface of a carrier roller wears and a diameter thereof is reduced.SOLUTION: A printer 1 comprises: a recording head 151 that discharges an ink onto a printing medium P and forms an image thereon; a carrier roller 153 that carries the printing medium P toward the recording head 151; a photosensor SP which detects marks M formed on the printing medium P at prescribed intervals LP; and a control part 11 that controls the recording head 151 and the carrier roller 153. The control part 11 acquires at least one of a rotation amount of the carrier roller 153 and a carrying time of the printing medium P during a period from detection of a first mark M1, which is the first of the marks M, by the photosensor SP to detection of a second mark M2, which is a mark next to the first mark M1, by the photosensor SP as a measured value, and corrects an impact position of the ink discharged from the recording head 151 on the basis of the measured value and a reference value indicating the standard of the measured value.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to printing devices. [Background technology]

[0002] Patent Document 1 discloses that in a line head inkjet printer, when the drive roller is eccentric, landing errors occur, resulting in a deterioration in image quality. In order to solve this problem, the ejection timing is corrected in accordance with the period of the eccentricity of the drive roller, thereby eliminating landing errors caused by eccentricity. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2008-23943 Summary of the Invention [Problem to be solved by the invention]

[0004] However, the technology described in Patent Document 1 was not always sufficient to reduce degradation in image quality. For example, when a printer is used over a long period of time, the surface of the transport roller wears and the diameter of the transport roller becomes smaller. This causes the transport distance of the print medium to become shorter than when the transport roller was new, such as when the printer was purchased, and the printed image may become smaller in size in the transport direction. [Means for solving the problem]

[0005] A printing device according to one aspect of the present invention that solves the above problem includes a recording head that ejects ink onto a printing medium to form an image, a transport roller that transports the printing medium toward the recording head, a detection sensor that detects feature points formed at predetermined intervals on the printing medium, and a control unit that controls the recording head and the transport roller. The control unit acquires, as a measurement value, at least one of the amount of rotation of the transport roller and the transport time of the printing medium from the time when the detection sensor detects a first feature point, which is the first feature point, to the time when the detection sensor detects a second feature point, which is the feature point next to the first feature point, and corrects the landing position of the ink ejected from the recording head based on the measurement value and a reference value that indicates a standard for the measurement value. [Brief explanation of the drawings]

[0006] [Figure 1] FIG. 1 is a diagram illustrating an example of the configuration of a printer according to an embodiment. [Figure 2] FIG. 4 is a right side view showing an example of the arrangement of photosensors in the printer. [Figure 3] FIG. 4 is a left side view showing an example of the arrangement of encoders in the printer. [Figure 4] FIG. 10 is a diagram showing an example of a mark formed on a specific print medium. [Figure 5] 10 is a diagram showing an example of the relationship between the rotation amount increase rate and the ejection delay rate. [Figure 6] 10 is a diagram showing an example of the relationship between the rate of increase in transport time and the rate of increase in rotation speed. [Figure 7] 10 is a flowchart showing an example of main processing of a control unit. [Figure 8] 10 is a table showing an example of the relationship between the cumulative conveyance amount and the ejection delay rate. DETAILED DESCRIPTION OF THE INVENTION

[0007] The present embodiment will be described below with reference to the drawings. The present embodiment includes a first embodiment which will be described with reference to Figures 1 to 7, and a second embodiment which will be described mainly with reference to Figure 8.

[0008] [1. First embodiment] First, the configuration of the printer 1 will be described with reference to Fig. 1. Fig. 1 is a diagram showing an example of the configuration of the printer 1 according to the first embodiment. As shown in FIG. 1, the printer 1 includes a control unit 11, an operation mechanism 12, a display mechanism 13, a communication interface 14, a printing mechanism 15, an ink supply unit 16, and a printing medium storage unit 17. The control unit 11 controls the operation of each unit of the printer 1. The operation mechanism 12, the display mechanism 13, the communication interface 14, and the printing mechanism 15 are each configured to be able to communicate with the control unit 11. The printer 1 corresponds to an example of a "printing device."

[0009] The control unit 11 includes a processor 11A such as a CPU (Central Processing Unit) and a memory 11B such as a ROM (Read Only Memory). The memory 11B stores a control program PG.

[0010] The processor 11A may be configured with multiple processors or may be configured with a single processor. The processor 11A may be hardware programmed to implement the functions of each unit described below. That is, the processor 11A may be configured with the control program PG installed as a hardware circuit. In this case, the processor 11A may be configured with, for example, an ASIC (Application Specific Integrated Circuit), an FPGA (Field-Programmable Gate Array), or the like. In the following description, the processor 11A executes the control program PG to realize various functions of the control unit 11.

[0011] The memory 11B has a nonvolatile storage area that stores programs and data in a nonvolatile manner. The memory 11B may include, for example, a ROM, a hard disk drive (HDD), or a solid state drive (SSD) as the nonvolatile storage area. The memory 11B may also include a volatile storage area that constitutes a work area that temporarily stores programs executed by the processor 11A and data to be processed. The memory 11B may also include, for example, a random access memory (RAM) as the volatile storage area.

[0012] In the first embodiment, the processor 11A executes the control program PG to control each part of the printer 1, but this is not limiting. The control unit 11 may include, for example, an ASIC, and the ASIC may execute processing using implemented functions. The control unit 11 may also include, for example, a signal processing circuit, and the signal processing circuit may execute processing by performing signal processing.

[0013] The operation mechanism 12 includes input means such as operation switches and a touch panel provided on the printer 1, detects user operations on the input means, and outputs a detection signal corresponding to the operation to the control unit 11. Based on the input from the operation mechanism 12, the control unit 11 executes processing corresponding to the user operation.

[0014] The display mechanism 13 includes a display panel such as a plurality of LEDs (Light Emitting Diodes) and an LCD (Liquid Crystal Display), and, under the control of the control unit 11, turns on, turns off, and blinks the LEDs in a predetermined manner, displays information on the display panel, and so on.

[0015] The communication interface 14 is a communication interface that communicates with the personal computer 2 in accordance with the Ethernet (registered trademark) standard. The communication interface 14 includes a connector for connecting an Ethernet (registered trademark) cable and an interface circuit for processing signals transmitted through the connector. The communication interface 14 is an interface board having a connector and an interface circuit, and is connected to a main board on which the processor 11A and the like of the control unit 11 are mounted. Alternatively, the connector and interface circuit that constitute the communication interface 14 are mounted on the main board of the control unit 11.

[0016] The printing mechanism 15 executes a printing function under the control of the control unit 11. Under the control of the control unit 11, the printing mechanism 15 prints characters, images, etc. on a printing medium P such as printing paper using ink. The printing mechanism 15 includes a recording head 151, a transport motor 152, and a transport roller 153 as components related to printing.

[0017] The recording head 151 is of an inkjet type and ejects ink supplied from the ink supply unit 16 toward the printing medium P. The recording head 151 is composed of, for example, four line heads. Each of the four line heads ejects ink of one of the colors: black (K), cyan (C), magenta (M), and yellow (Y). Each of the four line heads extends in a direction perpendicular to the transport direction of the printing medium P. The four line heads are arranged along the transport direction of the printing medium P. The recording head 151 is further described with reference to FIG.

[0018] The transport motor 152 drives the transport roller 153. The transport roller 153 is made up of a pair of upper and lower rollers, and transports the print medium P toward the recording head 151. The transport roller 153 will be further described with reference to FIGS.

[0019] The ink supply unit 16 houses an ink tank that stores ink, and supplies ink from the ink tank to the print head 351 of the printing mechanism 15. The ink supplied by the ink supply unit 16 is, for example, ink of each color of cyan (C), magenta (M), yellow (Y), and black (K).

[0020] The print medium storage unit 17 is configured to be able to store print medium P. If the print medium P is cut paper, the print medium storage unit 17 feeds the stored cut paper to a transport path not shown by transport motor 152. If the print medium P is long paper, a roll of long paper wound into a roll is stored in the print medium storage unit 17, and the print medium P is pulled out from the roll and fed to a transport path not shown by transport motor 152. The print medium storage unit 17 may also be configured to collect printed matter, which is the print medium P after printing. The configuration for collecting printed matter may be a configuration in which cut paper is stacked and placed on top of each other.

[0021] The printer 1 further includes a photosensor SP and an encoder SE. The photosensor SP detects characteristic points formed at a predetermined interval LP on the printing medium P. The characteristic points are, for example, marks M formed at a predetermined interval LP on the back surface of the printing medium P. The marks M are, for example, black solid images. The marks M include a first mark M1 and a second mark M2. The second mark M2 is formed upstream of the first mark M1 in the transport direction. The predetermined interval LP is, for example, 1 m. When the printing medium P is cut paper, the printing medium P on which the marks M are formed is a specific printing medium PT. The specific printing medium PT has a length of, for example, 1.2 m. The specific printing medium PT has a width of, for example, the width of an A4 size according to JIS (Japanese Industrial Standards), that is, 210 mm. When the printing medium P is long paper, no specific printing medium PT is prepared, and the first marks M1 and the second marks M2 are formed on a roll stored in the printing medium storage section 17. The mark M corresponds to an example of a "feature point." The first mark M1 corresponds to an example of a "first feature point." The second mark M2 corresponds to an example of a "second feature point." As a characteristic point, marks M may be used that indicate the print start positions of a plurality of print areas provided in the transport direction of the print medium P. The particular print medium PT is further described with reference to FIG.

[0022] The printer 1 is provided with, for example, a paper feed port for mail merge printing so that a specific print medium PT can be transported by transport rollers 153 toward the recording head 151. The printer 1 is also provided with a paper feed tray on which the print medium P to be supplied to the paper feed port for mail merge printing, for example, the specific print medium PT, can be placed.

[0023] The encoder SE detects the rotation angle of the transport roller 153. There are four types of encoder SE: mechanical, optical, magnetic, and electromagnetic induction. In the first embodiment, a case where the encoder SE is, for example, an optical type will be described. The encoder SE counts the number of approximately rectangular notches formed around the periphery of the scale 153S. The scale 153S rotates integrally with the shaft of the transport roller 153. The scale 153S is formed in a disk shape, with approximately rectangular notches formed around the periphery. For example, the scale 153S has 760 notches formed at equal intervals. The encoder SE and the scale 153S are further described with reference to FIG.

[0024] Next, the functional blocks of the control unit 11 of the printer 1 will be described. The control unit 11 includes a measurement unit 111, a determination unit 112, a correction unit 113, a print control unit 114, a communication control unit 115, and a reference value storage unit 316. When the processor 11A executes the control program PG, the processor 11A functions as the measurement unit 111, the determination unit 112, the correction unit 113, the print control unit 114, and the communication control unit 115. When the processor 11A executes the control program PG, the memory 11B also functions as the reference value storage unit 316.

[0025] The reference value storage unit 316 stores the rotation amount reference value NS. The rotation amount reference value NS indicates the reference amount of rotation of the transport roller 153 from the time when the photosensor SP detects the first mark M1 to the time when the photosensor SP detects the second mark M2. The rotation amount reference value NS is measured by the measurement unit 111 based on the detection value of the encoder SE when the transport roller 153 transports a specific print medium PT toward the recording head 151. The rotation amount reference value NS is the amount of rotation of the transport roller 153 when there is no wear on the transport roller 153. When there is no wear on the transport roller 153, for example, the transport roller 153 is brand new. The rotation amount reference value NS corresponds to an example of a "reference value."

[0026] The reference value storage unit 316 also stores a transport time reference value TS. The transport time reference value TS indicates a reference transport time for a specific printing medium PT from the time when the photosensor SP detects the first mark M1 to the time when the photosensor SP detects the second mark M2. The transport time reference value TS is measured by the measurement unit 111 when the transport roller 153 transports the specific printing medium PT toward the recording head 151. The transport time reference value TS is the transport time for a specific print medium PT when there is no wear on the transport roller 153. When there is no wear on the transport roller 153, for example, the transport roller 153 is brand new. The transport time reference value TS corresponds to an example of a "reference value."

[0027] The measurement unit 111 measures the rotation amount reference value NS and the transport time reference value TS in advance, for example, when the printer 1 is purchased, and stores the rotation amount reference value NS and the transport time reference value TS in the reference value storage unit 316. The measurement unit 111 also measures a rotation amount measurement value NA and a transport time measurement value TA. The rotation amount measurement value NA is a measurement value of the amount of rotation of the transport roller 153 from the time when the photosensor SP detects the first mark M1 to the time when the photosensor SP detects the second mark M2. The transport time measurement value TA is a measurement value of the transport time of the specific printing medium PT from the time when the photosensor SP detects the first mark M1 to the time when the photosensor SP detects the second mark M2. When the measuring unit 111 measures the transport time reference value TS or the transport time measurement value TA, the measuring unit 111 functions as a so-called "timer." The rotation amount measurement value NA corresponds to an example of a "measurement value." The transport time measurement value TA corresponds to an example of a "measurement value." The measuring unit 111 corresponds to an example of a "timer."

[0028] In the first embodiment, a case will be described in which the measurement unit 111 measures a rotation amount measurement value NA and a transport time measurement value TA, but the embodiment is not limited to this. The measurement unit 111 may measure at least one of the rotation amount measurement value NA and the transport time measurement value TA. In the following description, for convenience, a case will be described in which the measurement unit 111 measures the rotation amount measurement value NA.

[0029] Furthermore, in the first embodiment, a case is described in which the measurement unit 111 functions as a "timer," but the embodiment is not limited to this. The printer 1 may also be provided with a timer configured as hardware. In this case, the timer measures the transport time of a specific print medium PT from the time when the photosensor SP detects the first mark M1 to the time when the photosensor SP detects the second mark M2.

[0030] The determination unit 112 calculates a rotation amount increase rate ΔNA that indicates the increase rate of the rotation amount measurement value NA relative to the rotation amount reference value NS. The determination unit 112 calculates the rotation amount increase rate ΔNA, for example, by the following equation (1). ΔNA = (NA - NS) / NS × 100 (1) The determining unit 112 then determines whether the rotation amount increase rate ΔNA is equal to or greater than a first threshold value THN that is set in advance. The first threshold value THN is, for example, 1%. The rotation amount increase rate ΔNA corresponds to an example of a "rate of change."

[0031] In the first embodiment, a case will be described in which the determination unit 112 determines whether the rotation amount increase rate ΔNA is equal to or greater than a first threshold value THN, but the embodiment is not limited to this. The determination unit 112 may also determine whether the transport time increase rate ΔTA is equal to or greater than a second threshold value THT. In this case, the determination unit 112 executes the following process. The determining unit 112 calculates a transport time increase rate ΔTA indicating the increase rate of the transport time measurement value TA relative to the transport time reference value TS. The determining unit 112 calculates the transport time increase rate ΔTA, for example, by the following formula (2). ΔTA=(TA-TS) / TS×100 (2) Then, the determining unit 112 determines whether the transportation time increase rate ΔTA is equal to or greater than a second threshold value THT that is set in advance. The second threshold value THT is, for example, 1%. The transport time increase rate ΔTA corresponds to an example of a "rate of change."

[0032] The correction unit 113 corrects the landing position of ink ejected from the recording head 151 based on the rotation amount measurement value NA and the rotation amount reference value NS. For example, when the determination unit 112 determines that the rotation amount increase rate ΔNA is equal to or greater than the first threshold value THN, the correction unit 113 corrects the ink landing position by correcting the ink ejection timing from the recording head 151. The correction unit 113 calculates an ejection delay rate ΔT, which is a delay rate of the ink ejection timing, based on, for example, the rotation amount increase rate ΔNA. Then, the correction unit 113 delays the ink ejection timing from the print head 151 in accordance with the ejection delay rate ΔT. The rotation amount increase rate ΔNA and the ejection delay rate ΔT will be further described with reference to FIG.

[0033] In the first embodiment, a case will be described in which the correction unit 113 corrects the landing position of ink ejected from the recording head 151 based on the rotation amount measurement value NA and the rotation amount reference value NS, but the embodiment is not limited to this. The correction unit 113 may also correct the landing position of ink ejected from the recording head 151 based on the transport time measurement value TA and the transport time reference value TS. In this case, the correction unit 113 executes the following process. The correction unit 113 corrects the landing position of the ink ejected from the recording head 151 based on the transport time measurement value TA and the transport time reference value TS. For example, when the determination unit 112 determines that the transport time increase rate ΔTA is equal to or greater than the second threshold value THT, the correction unit 113 corrects the ink landing position by correcting the ink ejection timing from the recording head 151. The correction unit 113 calculates an ejection delay rate ΔT, which is a delay rate of the ink ejection timing, based on the transport time increase rate ΔTA, for example. Then, the correction unit 113 delays the ink ejection timing from the recording head 151 in accordance with the ejection delay rate ΔT.

[0034] In the first embodiment, a case will be described in which the correction unit 113 corrects the ink landing position mainly by delaying the timing of ink ejection from the recording head 151, but the embodiment is not limited to this. The correction unit 113 may correct the ink landing position by correcting the rotation speed of the transport roller 153. For example, the correction unit 113 corrects the rotation speed of the transport roller 153 so that the transport time measurement value TA matches the transport time reference value TS. In this case, the correction unit 113 calculates the rotation speed increase rate ΔNC, which is the increase rate of the rotation speed of the transport roller 153, based on the rotation amount increase rate ΔNA or the transport time increase rate ΔTA. Then, the correction unit 113 corrects the ink landing position by correcting the rotation speed of the transport roller 153 in accordance with the rotation speed increase rate ΔNC. In other words, the correction unit 113 corrects the ink landing position by correcting the rotation speed of the transport motor 152 in accordance with the rotation speed increase rate ΔNC. The transport time increase rate ΔTA and the rotational speed increase rate ΔNC will be further described with reference to FIG.

[0035] The print control unit 114 receives and executes a print job from the personal computer 2. The print control unit 114 instructs the printing mechanism 15 to perform an operation corresponding to the print job, and causes the printing mechanism 15 to execute the print job.

[0036] The communication control unit 115 receives a print job from the personal computer 2 via the communication interface 14 .

[0037] Next, the arrangement of the photosensor SP will be described with reference to Fig. 2. Fig. 2 is a right side view showing an example of the arrangement of the photosensor SP of the printer 1. The arrow DP indicates the transport direction of the printing medium P. Fig. 2 shows the right side of the printer 1 when viewed from the downstream side in the transport direction of the printing medium P. The photosensor SP is turned on before the transport of the specific print medium PT starts and turned off when the transport of the specific print medium PT ends. In other words, the photosensor SP is turned on only when the specific print medium PT is being transported.

[0038] As shown in FIG. 2, a transport roller 153 is disposed upstream of the recording head 151 in the transport direction of the print medium P. The transport roller 153 transports the print medium P toward the recording head 151. The print medium P includes specific print media PT. Marks M are formed on the back surface of the specific print media PT at predetermined intervals LP. The marks M are, for example, solid black images.

[0039] The specific print medium PT is transported onto the upper surface of a platen 157 by a transport roller 153. The platen 157 supports the specific print medium PT. A first photosensor SP1 is disposed between the transport roller 153 and the platen 157. When the specific print medium PT is transported from the transport roller 153 to the platen 157, the first photosensor SP1 is disposed below the specific print medium PT.

[0040] The first photosensor SP1 is, for example, a reflective photosensor, and detects a mark M formed on the rear surface of a specific print medium PT. The first photosensor SP1 corresponds to an example of a "detection sensor."

[0041] The second photosensor SP2 is disposed upstream of the transport roller 153 in the transport direction of the print medium P. The second photosensor SP2 is, for example, a transmissive photosensor. The second photosensor SP2 has a light-emitting portion SP21 and a light-receiving portion SP22. The light-projecting unit SP21 is disposed below the specific printing medium P when the specific printing medium PT is transported from the upstream side of the transport roller 153 in the transport direction of the printing medium PT toward the transport roller 153. The light-receiving unit SP22 is disposed above the specific printing medium P when the specific printing medium PT is transported from the upstream side of the transport roller 153 in the transport direction of the printing medium PT toward the transport roller 153. The light-receiving unit SP22 is disposed at a position facing the light-projecting unit SP21. The light-projecting unit SP21 emits light toward the light-receiving unit SP22. The light-receiving unit SP22 receives the light emitted from the light-projecting unit SP21. The second photosensor SP2 detects a mark M formed on the back surface of a specific printing medium PT. The second photosensor SP2 corresponds to an example of a "detection sensor."

[0042] 2, two photosensors SP are arranged, but at least one photosensor SP may be arranged. For example, a first photosensor SP1 or a second photosensor SP2 may be arranged.

[0043] 2, the recording head 151 is composed of four line heads. Each of the four line heads ejects ink of a respective color: black (K), cyan (C), magenta (M), and yellow (Y). Each of the four line heads extends in a direction perpendicular to the transport direction of the printing medium P. The four line heads are arranged along the transport direction of the printing medium P in the order of, for example, the black (K) line head, the cyan (C) line head, the magenta (M) line head, and the yellow (Y) line head.

[0044] Next, the arrangement of the encoder SE of the printer 1 will be described with reference to Fig. 3. Fig. 3 is a left side view showing an example of the arrangement of the encoder SE of the printer 1. The arrow DP indicates the transport direction of the print medium P. Fig. 3 shows the left side of the printer 1 when viewed from the downstream side in the transport direction of the print medium P.

[0045] 3, a transport roller 153 is disposed upstream of the recording head 151 in the transport direction of the print medium P. The transport roller 153 transports the print medium P toward the recording head 151. The print medium P includes specific print media PT. Marks M are formed on the back surface of the specific print media PT at predetermined intervals LP.

[0046] The transport roller 153 is composed of a pair of upper and lower rollers. A scale 153S is fixed to the end of the rotation shaft of the lower one of the transport rollers 153. The scale 153S rotates integrally with the lower one of the transport rollers 153. The scale 153S is formed in a disk shape, and has approximately rectangular notches formed around its periphery. For example, the scale 153S has 760 notches formed at equal intervals. The encoder SE is disposed so as to sandwich the lower end of the scale 153S, and counts the number of substantially rectangular notches formed around the periphery of the scale 153S.

[0047] Next, with reference to FIG. 3, the path along which the driving force of the transport motor 152 is transmitted to the transport roller 153 will be described. As shown in FIG. 3, the transport motor 152 is disposed below the recording head 151. A gear 156 is disposed on the drive shaft of the transport motor 152, and rotates integrally with the drive shaft. The gear 156 meshes with a first gear 154A formed on the outer periphery of a reduction gear 154 that reduces the rotational speed. The reduction gear 154 includes a second gear 154B, and the second gear 154B rotates integrally with the first gear 154A. Each of the first gear 154A and the second gear 154B is formed in a disk shape, and teeth are formed on the outer periphery. The second gear 154B is formed with a smaller diameter than the first gear 154A.

[0048] One side (lower right side in FIG. 3) of belt 155 is wound around the outer periphery of second gear 154B. The other side (upper left side in FIG. 3) of belt 155 is wound around third gear 153A. Third gear 153A is formed in a disk shape and has teeth formed on its outer periphery. Third gear 153A is fixed to the rotation shaft of transport roller 153, which is located on the lower side of transport rollers 153, and rotates integrally with the rotation shaft of transport roller 153.

[0049] With this configuration, the driving force of the transport motor 152 is transmitted to the transport roller 153 via the gear 156, the first gear 154A, the second gear 154B, the belt 155, and the third gear 153A in this order.

[0050] Next, the specific printing medium PT will be described with reference to Fig. 4. Fig. 4 is a diagram showing an example of a mark M formed on the specific printing medium PT. Fig. 4 shows the back side of the specific printing medium PT. The mark M includes a first mark M1 and a second mark M2. The mark M is, for example, a solid black image. 4, a first mark M1 and a second mark M2 are formed on the back surface of the specific printing medium PT. Each of the first mark M1 and the second mark M2 is a rectangular mark formed on one side edge in the width direction of the specific printing medium PT. The predetermined distance LP between the first mark M1 and the second mark M2 is, for example, 1 m. The predetermined distance LP indicates, for example, the distance between the left end of the first mark M1 in FIG. 4 and the left end of the second mark M2 in FIG.

[0051] Furthermore, the centers of the first mark M1 and the second mark M2 are formed at positions that are a distance BC away from the center position LC in the width direction of the specific printing medium PT. This distance BC corresponds to the position of the photosensor SP in the direction perpendicular to the paper surface of FIG. 3, as described with reference to FIG. 2. In other words, the distance BC matches the distance from the center position in the width direction of the specific printing medium PT to the photosensor SP in the direction perpendicular to the paper surface of FIG. 2 when the printer 1 transports the specific printing medium PT in FIG. 2.

[0052] In the first embodiment, a case will be described in which the mark M is a rectangular black solid image, but the embodiment is not limited to this. For example, the mark M may be a solid image of another color (e.g., red, blue, green, etc.). Note that if the photosensor SP is a reflective photosensor, it is preferable that the mark M be a color with low reflectivity. Also, for example, the mark M may be a hole (or opening).

[0053] Next, the relationship between the rotation amount increase rate ΔNA and the ejection delay rate ΔT will be described with reference to Fig. 5. Fig. 5 is a diagram showing an example of the relationship between the rotation amount increase rate ΔNA and the ejection delay rate ΔT. A first table TBL1 shown in Fig. 5 shows the relationship between the rotation amount increase rate ΔNA and the ejection delay rate ΔT. The rotation amount increase rate ΔNA is calculated by the determination unit 112. The rotation amount increase rate ΔNA indicates the rate of increase of the rotation amount measurement value NA relative to the rotation amount reference value NS. For example, if the transport roller 153 wears and the diameter of the transport roller 153 decreases, the rotation amount increase rate ΔNA increases as the decrease increases.

[0054] The ejection delay rate ΔT indicates the rate at which the correction unit 113 delays the timing of ink ejection from the print head 151. The larger the ejection delay rate ΔT, the longer the time by which the ink ejection timing is delayed. The upper part of the first table TBL1 shows the rotation amount increase rate ΔNA, and the lower part of the first table TBL1 shows the ejection delay rate ΔT.

[0055] The correction unit 113 sets the ejection delay rate ΔT from the rotation amount increase rate ΔNA calculated by the determination unit 112, for example, by referring to the first table TBL1. The first table TBL1 is stored in, for example, the memory 11B. As shown in the first table TBL1, the larger the rotation amount increase rate ΔNA, the larger the ejection delay rate ΔT. For example, when the rotation amount increase rate ΔNA is 1% or more and less than 2%, the correction unit 113 sets the ejection delay rate ΔT to 0.01%. For example, when the rotation amount increase rate ΔNA is 2% or more and less than 3%, the correction unit 113 sets the ejection delay rate ΔT to 0.02%. For example, when the rotation amount increase rate ΔNA is 3% or more and less than 4%, the correction unit 113 sets the ejection delay rate ΔT to 0.03%.

[0056] In the first embodiment, the correction unit 113 sets the ejection delay rate ΔT from the rotation amount increase rate ΔNA by referring to the first table TBL1, for example, but the embodiment is not limited to this. The correction unit 113 may set the ejection delay rate ΔT from the rotation amount increase rate ΔNA, for example, by using the following formula (3): ΔT=ΔNA×K1 (3) The coefficient K1 is a constant, for example, 0.01.

[0057] Next, the relationship between the transport time increase rate ΔTA and the rotation speed increase rate ΔNC will be described with reference to Fig. 6. Fig. 6 is a diagram showing an example of the relationship between the transport time increase rate ΔTA and the rotation speed increase rate ΔNC. A second table TBL2 shown in Fig. 5 shows the relationship between the transport time increase rate ΔTA and the rotation speed increase rate ΔNC. The transport time increase rate ΔTA is calculated by the determination unit 112. The transport time increase rate ΔTA indicates the rate of increase of the transport time measurement value TA relative to the transport time reference value TS. For example, if the transport roller 153 wears out and the diameter of the transport roller 153 decreases, the transport time increase rate ΔTA increases as the decrease increases.

[0058] The rotation speed increase rate ΔNC indicates the rate at which the correction unit 113 increases the rotation speed of the transport roller 153. The rotation speed of the transport roller 153 increases as the rotation speed increase rate ΔNC increases. The upper part of the second table TBL2 shows the transfer time increase rate ΔTA, and the lower part of the second table TBL2 shows the rotation speed increase rate ΔNC.

[0059] The correction unit 113 sets the rotation speed increase rate ΔNC from the transfer time increase rate ΔTA calculated by the determination unit 112, for example, by referring to the second table TBL2. The second table TBL2 is stored in, for example, the memory 11B. As shown in second table TBL2, the larger the transport time increase rate ΔTA, the larger the rotation speed increase rate ΔNC. For example, if the transport time increase rate ΔTA is equal to or greater than 1% and less than 2%, the correction unit 113 sets the rotation speed increase rate ΔNC to 0.01%. For example, if the transport time increase rate ΔTA is equal to or greater than 2% and less than 3%, the correction unit 113 sets the rotation speed increase rate ΔNC to 0.02%. For example, if the transport time increase rate ΔTA is equal to or greater than 3% and less than 4%, the correction unit 113 sets the rotation speed increase rate ΔNC to 0.03%.

[0060] In the first embodiment, the correction unit 113 sets the rotation speed increase rate ΔNC from the transport time increase rate ΔTA by, for example, referring to the second table TBL2, but the embodiment is not limited to this. The correction unit 113 may set the rotation speed increase rate ΔNC from the transport time increase rate ΔTA by, for example, using the following equation (4). ΔNB=ΔTA×K2 (3) The coefficient K2 is a constant, for example, 0.01.

[0061] Next, the main processing of the control unit 11 in the first embodiment will be described with reference to Fig. 7. Fig. 7 is a flowchart showing an example of the main processing of the control unit 11. 7, for example, a case will be described in which the rotation amount reference value NS is measured and stored in the reference value storage unit 316 when the printer 1 is purchased. In step S101, the control unit 11 turns on the photosensor SP, and then causes the transport roller 153 to transport the specific print medium PT toward the recording head 151. Next, in step S103, the measurement unit 111 measures the rotation amount measurement value NA. The rotation amount measurement value NA is a measurement value of the rotation amount of the transport roller 153 from the time when the photosensor SP detects the first mark M1 to the time when the photosensor SP detects the second mark M2.

[0062] Next, in step S105, the determination unit 112 calculates the rotation amount increase rate ΔNA, which indicates the increase rate of the rotation amount measurement value NA relative to the rotation amount reference value NS. Next, in step S107, the determination unit 112 determines whether or not the rotation amount increase rate ΔNA is equal to or greater than a preset first threshold value THN. If the determination unit 112 determines that the rotation amount increase rate ΔNA is not equal to or greater than the first threshold value THN (step S107; NO), the process ends. If the determination unit 112 determines that the rotation amount increase rate ΔNA is equal to or greater than the first threshold value THN (step S107; YES), the process proceeds to step S109.

[0063] Then, in step S109, the correction unit 113 calculates an ejection delay rate ΔT, which is a delay rate of the ink ejection timing, based on the rotation amount increase rate ΔNA. Then, the correction unit 113 delays the ink ejection timing from the print head 151 in accordance with the ejection delay rate ΔT. Next, in step S111, the control unit 11 updates the rotation amount reference value NS stored in the reference value storage unit 316 to the rotation amount measurement value NA. In other words, the control unit 11 replaces the rotation amount reference value NS stored in the reference value storage unit 316 with the rotation amount measurement value NA. Thereafter, the process ends.

[0064] [2. Second Embodiment] Next, a printer 1A according to a second embodiment will be described with reference to Fig. 8. First, differences between the printer 1A according to the second embodiment and the printer 1 described with reference to Figs. 1 to 7 will be described. The printer 1A according to the second embodiment differs from the printer 1 according to the first embodiment in that the photosensor SP of the printer 1 shown in FIG. 1 is not used to correct the ink ejection timing. The printer 1A according to the second embodiment also differs from the printer 1 according to the first embodiment in that it does not include the reference value storage unit 316 of the control unit 11 of the printer 1 shown in FIG. The printer 1A according to the second embodiment also differs from the printer 1 according to the first embodiment in that it does not use the specific print medium PT described with reference to FIG. In the printer 1A according to the second embodiment, the processing of the measurement unit 111, determination unit 112, and correction unit 113 of the control unit 11 shown in FIG. 1 differs from that of the printer 1 according to the first embodiment.

[0065] Next, a printer 1A according to a second embodiment will be described with reference to FIG. The measurement unit 111 calculates the accumulated transport amount TR, which is the accumulated value of the transport amount of the printing medium P. The measurement unit 111 calculates the transport amount of the printing medium P, for example, using the output from the encoder SE. Then, the measurement unit 111 calculates the accumulated transport amount TR, which is the accumulated value of the transport amount of the printing medium P. The determination unit 112 determines whether the cumulative transport amount TR is equal to or greater than a preset third threshold value THR. When the determination unit 112 determines that the accumulated carry amount TR is equal to or greater than the third threshold value THR, the correction unit 113 corrects the timing of ink ejection from the print head 151. For example, the correction unit 113 sets an ejection delay rate ΔT based on the accumulated carry amount TR. The ejection delay rate ΔT is the delay rate of the ink ejection timing.

[0066] Next, a printer 1A according to a second embodiment will be described with reference to FIG. 8. FIG. 8 is a chart showing an example of the relationship between the accumulated carry amount TR and the ejection delay rate ΔT. A third table TBL3 shown in FIG. 8 shows the relationship between the accumulated carry amount TR and the ejection delay rate ΔT. The third table TBL3 shown in FIG. 8 is determined, for example, by experiment. The third table TBL3 shown in FIG. 8 is also determined, for example, from the performance values ​​of other printers. The accumulated transport amount TR shown in the upper part of FIG. 8 is calculated by the measurement unit 111. The accumulated transport amount TR is the accumulated value of the transport amount of the printing medium P. The greater the accumulated transport amount TR, the more the transport roller 153 wears, and the smaller the diameter of the transport roller 153 becomes. As a result, the transport amount of the printing medium transported by the transport roller 153 per rotation becomes shorter compared to when the printer 1A was purchased, and the printed image becomes smaller in the transport direction. Therefore, the correction unit 113 corrects the timing of ink ejection from the recording head 151. The correction unit 113 sets the ejection delay rate ΔT based on the accumulated carry amount TR. The correction unit 113 sets the ejection delay rate ΔT shown in the lower part of FIG. 8 by referring to the third table TBL3. The third table TBL3 is stored in, for example, the memory 11B.

[0067] 8, the correction unit 113 increases the ejection delay rate ΔT as the cumulative conveyance amount TR increases. For example, when the cumulative conveyance amount TR is 10 (m×10 4 ) or more, and 25 (m x 10 4 ), the ejection delay rate ΔT is set to 0.01%. 4 ) or more, and 50 (m x 10 4), the ejection delay rate ΔT is set to 0.015%. 4 ) or more, and 75 (m x 10 4 ), the ejection delay rate ΔT is set to 0.02%.

[0068] In this embodiment, the relationship between the accumulated transport amount TR and the ejection delay rate ΔT is used as the third table TBL3, but the accumulated transport time may be used instead of the accumulated transport amount TR, and the rotation speed increase rate may be used instead of the ejection delay rate ΔT. The accumulated transport time is the accumulated value of the transport time of the printing medium P. The rotation speed increase rate is the increase rate of the rotation speed of the transport roller 153.

[0069] [3. Composition and Effects] As described above with reference to Figures 1 to 7, the printer 1 according to the first embodiment comprises a recording head 151 that ejects ink onto a printing medium P to form an image, a transport roller 153 that transports the printing medium P towards the recording head 151, a photosensor SP that detects marks M formed on the printing medium P at predetermined intervals LP, and a control unit 11 that controls the recording head 151 and the transport roller 153. The control unit 11 acquires, as a measurement value, at least one of the amount of rotation of the transport roller 153 and the transport time of the printing medium P from the time when the photosensor SP detects the first mark M1, which is the first mark M, to the time when the photosensor SP detects the second mark M2, which is the mark next to the first mark M1, and corrects the landing position of the ink ejected from the recording head 151 based on the measurement value and a reference value that indicates the reference for the measurement value.

[0070] According to this configuration, at least one of the amount of rotation of the transport roller 153 and the transport time of the printing medium P from the time when the photosensor SP detects the first mark M1 until the photosensor SP detects the second mark M2 is obtained as a measurement value, and the landing position of the ink ejected from the recording head 151 is corrected based on the measurement value and a reference value indicating the standard for the measurement value. For example, the amount of rotation of the transport roller 153 from the time when the photosensor SP detects the first mark M1 until the photosensor SP detects the second mark M2 is obtained as a rotation amount measurement value NA, and the landing position of the ink ejected from the recording head 151 is corrected based on the rotation amount measurement value NA and a rotation amount reference value NS that indicates the reference for the rotation amount measurement value NA. Furthermore, for example, the transport time of the printing medium P from the time when the photosensor SP detects the first mark M1 until the photosensor SP detects the second mark M2 is obtained as a transport time measurement value TA, and the landing position of the ink ejected from the recording head 151 is corrected based on the transport time measurement value TA and a transport time reference value TS that indicates the reference for the transport time measurement value TA. Therefore, it is possible to properly correct the landing position of ink ejected from the recording head 151 based on the rotation amount measurement value NA and rotation amount reference value NS, or the transport time measurement value TA and transport time reference value TS. Therefore, even if the surface of the transport roller 153 wears out and the diameter of the transport roller 153 becomes smaller, it is possible to form a proper image.

[0071] Furthermore, in the printer 1 according to the first embodiment, the control unit 11 determines whether the rate of change of the measured value relative to the reference value is greater than or equal to a predetermined threshold value, and if it determines that the rate of change is greater than or equal to the threshold value, corrects the landing position of the ink ejected from the recording head 151.

[0072] According to this configuration, if the rate of change of the measurement value relative to the reference value is equal to or greater than a preset threshold value, the landing position of the ink ejected from the recording head 151 is corrected. Therefore, by setting the threshold value to an appropriate value, it is possible to appropriately determine whether or not to correct the landing position of the ink ejected from the recording head 151.

[0073] Furthermore, in the printer 1 according to the first embodiment, the measurement value is the amount of rotation of the transport roller 153, and an encoder SE is provided to detect the amount of rotation of the transport roller 153.

[0074] According to this configuration, since the encoder SE that detects the rotation amount of the transport roller 153 is provided, the rotation amount of the transport roller 153, which is the measurement value, can be accurately detected. In other words, the rotation amount measurement value NA can be accurately detected. Therefore, the landing position of the ink ejected from the recording head 151 can be appropriately corrected based on the rotation amount measurement value NA and the rotation amount reference value NS.

[0075] Furthermore, in the printer 1 according to the first embodiment, the measurement value is the transport time of the print medium P, and the printer 1 includes a measurement unit 111 that measures the transport time of the print medium P.

[0076] According to this configuration, since the measuring unit 111 that measures the transport time of the printing medium P is provided, the measured value can accurately detect the transport time of the printing medium P. In other words, the transport time measurement value TA can be accurately detected. Therefore, the landing position of the ink ejected from the recording head 151 can be appropriately corrected based on the transport time measurement value TA and the transport time reference value TS.

[0077] Furthermore, in the printer 1 according to the first embodiment, the control unit 11 corrects the timing at which ink is ejected from the recording head 151, thereby correcting the landing position.

[0078] According to this configuration, the ink landing position is corrected by correcting the timing of ink ejection from the recording head 151, so the ink landing position can be corrected appropriately.

[0079] Furthermore, in the printer 1 according to the first embodiment, the control unit 11 corrects the rotation speed of the transport roller 153 to correct the landing position.

[0080] According to this configuration, the ink landing position is corrected by correcting the rotation speed of the transport roller 153, so that the ink landing position can be corrected appropriately.

[0081] Furthermore, in the printer 1 according to the first embodiment, the control unit 11 corrects the landing position and then updates the reference value to the measured value.

[0082] According to this configuration, after the impact position is corrected, the reference value is updated to the measured value, so it is easy to determine whether correction is necessary from the second time onwards.

[0083] In the printer 1 according to the first embodiment, the recording head 151 is configured as a line head.

[0084] According to this configuration, the recording head 151 is composed of a line head, which enhances the effect of being able to properly correct the landing position of ink ejected from the recording head 151 compared to, for example, scanning the recording head with a carriage.

[0085] As explained mainly with reference to Figures 1 and 8, the printer 1A according to the second embodiment comprises a recording head 151 that ejects ink onto a printing medium P to form an image, a transport roller 153 that transports the printing medium P toward the recording head 151, and a control unit 11 that controls the recording head 151 and the transport roller 153. The control unit 11 calculates a cumulative transport amount TR, which is the cumulative value of the transport amount of the printing medium P transported by the transport roller 153, and corrects the timing of ink ejection from the recording head 151 based on the cumulative transport amount TR, which is the cumulative value of the transport amount of the printing medium P.

[0086] According to this configuration, the timing of ink ejection from the recording head 151 is corrected based on the cumulative transport amount TR, which is the cumulative value of the transport amount of the printing medium P, so it is possible to properly correct the landing position of the ink ejected from the recording head 151. Therefore, even if the surface of the transport roller 153 wears out and the diameter of the transport roller 153 becomes smaller, a proper image can be formed.

[0087] Furthermore, in the printer 1A according to the second embodiment, the control unit 11 is provided with a memory 11B that stores a cumulative transport amount TR, which is the cumulative value of the transport amount of the printing medium P, in correspondence with an ejection delay rate ΔT, which is the ratio by which the timing of ink ejection from the recording head 151 is delayed, and corrects the timing of ink ejection from the recording head 151 based on the cumulative transport amount TR, which is the cumulative value of the transport amount of the printing medium P, by referring to the memory 11B.

[0088] According to this configuration, the ejection delay rate ΔT, which is the ratio by which the timing of ejecting ink from the recording head 151 is delayed, is set based on the cumulative transport amount TR, which is the cumulative value of the transport amount of the printing medium P. This makes it possible to properly correct the landing position of the ink ejected from the recording head 151. Therefore, even if the surface of the transport roller 153 wears out and the diameter of the transport roller 153 becomes smaller, a proper image can be formed.

[0089] This embodiment shows one mode, and any modifications and applications are possible without departing from the spirit and scope of the present invention.

[0090] In this embodiment, the "image forming apparatus" is a printer 1, but is not limited to this. The "image forming apparatus" may be, for example, a copy machine. The "image forming apparatus" may also be, for example, a so-called multifunction peripheral.

[0091] In this embodiment, a case is described in which the processor 11A included in the printer 1 executes the control program PG stored in the memory 11B, but the embodiment is not limited to this. The control program PG can also be configured as a recording medium on which it is recorded so as to be readable by a computer, or as a transmission medium for transmitting the control program PG. The recording medium may be a magnetic or optical recording medium or a semiconductor memory device, including portable or fixed recording media such as flexible disks, HDDs, CD-ROMs (Compact Disk Read Only Memory), DVDs (Digital Versatile Disks), Blu-ray (registered trademark) Discs, magneto-optical disks, flash memories, and card-type recording media. The recording medium may be a non-volatile storage device such as a RAM, ROM, or HDD that is an internal storage device provided in the printer 1.

[0092] The functions of the control unit 11 of the printer 1 may be realized by one or more processors or semiconductor chips. The control unit 11 may also be configured to further include a co-processor such as an SoC (System-on-a-Chip), MCU (Micro Control Unit), or FPGA. The control unit 11 may perform various controls by using both the CPU and the co-processor in cooperation with each other, or by selectively using one of the two.

[0093] The processing units in the flowchart of FIG. 7 are divided according to the main processing content to make it easier to understand the processing of the control unit 11 of the printer 1, and are not limited by the way in which the processing units are divided or the names of the processing units. The processing units in the flowchart may be divided into more processing units depending on the processing content. One processing unit may also be divided so that it includes more processes. The order of the processing may be changed as appropriate as long as it does not interfere with the intent.

[0094] Each functional unit shown in FIG. 1 indicates a functional configuration, and the specific implementation form is not particularly limited. It is not necessary to implement hardware that corresponds to each functional unit individually; a configuration in which a single processor executes a program to realize the functions of multiple functional units is also possible. Some of the functions realized by software in the above-described embodiment may be implemented by hardware, or some of the functions realized by hardware may be implemented by software. The specific detailed configurations of the other units of the printer 1 may also be changed as desired without departing from the spirit of the invention. [Explanation of symbols]

[0095] 1...printer (printing device), 11...control unit, 11A...processor, 11B...memory, 111...measuring unit (timer), 112...determination unit, 113...correction unit, 114...printing control unit, 115...communication control unit, 116...reference value storage unit, 14...first communication interface, 15...printing mechanism, 151...recording head, 152...conveying motor, 153...conveying roller, 2...personal computer, LP...predetermined interval, M...mark (feature point), M1...first mark (first feature point), M2...second mark (second feature point) point), NA...rotation amount measurement value (measured value), NS...rotation amount reference value (reference value), P...printing medium, PG...control program, PT...specific printing medium, SE...encoder, SP...photosensor, SP1...first photosensor (detection sensor), SP2...second photosensor (detection sensor), TA...transport time measurement value (measured value), TR...cumulative transport amount, TS...transport time reference value (reference value), ΔNA...rotation amount increase rate (rate of change), ΔNC...rotation speed increase rate, ΔT...ejection delay rate, ΔTA...transport time increase rate (rate of change).

Claims

1. a recording head that ejects ink onto a print medium to form an image; a transport roller that transports the print medium toward the recording head; a detection sensor for detecting feature points formed at predetermined intervals on the print medium; a control unit that controls the recording head and the transport roller; Equipped with The control unit acquire, as a measurement value, at least one of the rotation amount of the transport roller and the transport time of the print medium from the time when the detection sensor detects a first feature point, which is the first feature point, until the detection sensor detects a second feature point, which is the feature point next to the first feature point; correcting a landing position of the ink ejected from the recording head based on the measurement value and a reference value indicating a reference for the measurement value; Printing device.

2. The control unit determining whether a rate of change of the measurement value with respect to the reference value is equal to or greater than a preset threshold value; correcting a landing position of the ink ejected from the recording head when it is determined that the rate of change is equal to or greater than the threshold value; The printing device of claim 1 .

3. the measured value is the rotation amount of the transport roller, an encoder for detecting the amount of rotation of the transport roller; 3. The printing device according to claim 1 or 2.

4. the measured value is a transport time of the print medium, a timer for measuring a transport time of the print medium; 3. The printing device according to claim 1 or 2.

5. the control unit corrects the landing position by correcting the ejection timing of the ink from the recording head; The printing device of claim 1 .

6. the control unit corrects the landing position by correcting the rotation speed of the transport roller. The printing device of claim 1 .

7. the control unit corrects the impact position and then updates the reference value to the measured value. The printing device of claim 1 .

8. The recording head is a line head. The printing device of claim 1 .

9. a recording head that ejects ink onto a print medium to form an image; a transport roller that transports the print medium toward the recording head; a control unit that controls the recording head and the transport roller; Equipped with The control unit calculating a cumulative value of the transport distance of the print medium transported by the transport roller or a cumulative value of the transport time of the print medium; correcting the ejection timing of the ink from the recording head or the rotation speed of the transport roller based on the cumulative value of the transport amount of the printing medium or the cumulative value of the transport time of the printing medium; Printing device.

10. The control unit a storage unit that stores a cumulative value of the transport amount of the printing medium or a cumulative value of the transport time of the printing medium in association with a ratio of delaying the timing of ejecting the ink from the recording head or a ratio of increasing the rotation speed of the transport roller; correcting the ink ejection timing from the recording head or the rate at which the rotation speed of the transport roller is increased based on the cumulative value of the transport amount of the printing medium or the cumulative value of the transport time of the printing medium, by referring to the storage unit; The printing device of claim 9.

Images