Image forming device

Abstract

To highly accurately detect a moving amount of a recording medium with no pattern.SOLUTION: An image formation device includes: conveyance means for conveying a recording medium according to a predetermined conveyance amount; image formation means for forming an image on the recording medium conveyed by the conveyance means; mark additional means for adding a periodic mark to the recording medium when the recording medium is conveyed by the conveyance means; detection means for detecting the mark from the recording medium; calculation means for calculating a moving amount of the mark detected by the detection means; and correction means for correcting the conveyance amount of the recording medium by the moving amount.SELECTED DRAWING: Figure 6

Description

[Technical field]

[0001] The present invention relates to an image forming apparatus. [Background technology]

[0002] Conventionally, in inkjet printers, there is a technique for correcting the transport amount before printing because there is variation in the friction resistance between the platen and the recording paper due to differences in the material of the back surface of the recording paper. For example, there is a technique for acquiring the movement amount of the recording paper by photographing the fiber pattern of the recording paper with a camera and performing pattern matching of the photographed image at each cycle.

[0003] Patent Document 1 discloses a technique for capturing an image of a pattern on a print medium to obtain the amount of movement. In this technique, the pattern on the print medium is captured by a high-precision camera and the amount of movement is detected by pattern matching the pattern. Summary of the Invention [Problem to be solved by the invention]

[0004] However, conventional techniques require a high-precision camera to capture the pattern of the fibers of the recording medium, and also require highly accurate assembly to detect fine patterns. Also, there is a problem that the accuracy of detecting the amount of movement decreases when using recording media such as plastic media that have no pattern.

[0005] The present invention has been made in view of the above, and has an object to provide an image forming apparatus that is capable of detecting the amount of movement with high accuracy even for a recording medium that has no pattern. [Means for solving the problem]

[0006] In order to solve the above-mentioned problems and achieve the object, an image forming apparatus of the present invention includes a conveying means for conveying a recording medium according to a predetermined conveying amount, an image forming means for forming an image on the recording medium conveyed by the conveying means, a mark adding means for adding periodic marks to the recording medium when the recording medium is conveyed by the conveying means, a detection means for detecting the marks from the recording medium, and a detection means for detecting the marks detected by the detection means. The vertical pitch of the mark is based on the horizontal pitch of the regular mark. The apparatus includes a calculation unit that calculates a movement amount, and a correction unit that corrects the conveyance amount of the recording medium based on the movement amount. Effect of the Invention

[0007] According to the present invention, it is possible to detect the amount of movement with high accuracy even for a recording medium that has no pattern. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a perspective view of an outer appearance of an inkjet recording apparatus which is an example of an image forming apparatus according to an embodiment. [Diagram 2] FIG. 2 is a plan view of the internal configuration of the inkjet recording apparatus. [Diagram 3] FIG. 3 is a side view of the internal configuration of the inkjet recording apparatus. [Figure 4] FIG. 4 is an explanatory diagram of the mark adding means. [Diagram 5] FIG. 5 is a diagram showing an example of the configuration of a control block of the inkjet recording apparatus. [Figure 6] FIG. 6 is a diagram showing an example of a specific control block configuration of the sub-scanning motor drive unit. [Figure 7] FIG. 7 is a diagram showing an example of a calculation result in which the transport amount is calculated by averaging several transport amounts and movement amounts. [Figure 8] FIG. 8 is a diagram showing an example of a control flow of the inkjet recording apparatus. [Figure 9] FIG. 9 is a detailed flow diagram of the transport amount correction sequence. [Figure 10]FIG. 10 is a diagram showing an example of a change in the pattern of spike marks in an imaging area. [Figure 11] FIG. 11 is a diagram showing the patterns of the imaging area at a certain point in time and the next point in time when the pitch of the spike marks and the transport amount of the recording sheet are the same. [Figure 12] FIG. 12 is an explanatory diagram of a method for calculating the amount of movement. [Figure 13] FIG. 13 is a diagram for explaining detection of skew and meandering of a recording sheet. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an image forming apparatus according to the present invention will be described in detail below with reference to the accompanying drawings. In the following, an example of an application of an image forming apparatus according to the present embodiment to an inkjet recording apparatus will be described.

[0010] (Embodiment) FIG. 1 is an external perspective view of an inkjet recording apparatus (a wide-format printer is an example of an image forming apparatus according to an embodiment). FIG. 1 shows a perspective view of part of the internal configuration of the inkjet recording apparatus. FIG. 2 is a plan view of the internal configuration of the inkjet recording apparatus. FIG. 3 is a side view of the internal configuration of the inkjet recording apparatus. FIG. 3 shows a schematic diagram of the internal configuration of a conveying means that is mainly hidden in the plan view of FIG. 2. First, the configuration of the inkjet recording apparatus, an example of an image forming apparatus according to an embodiment, will be described with reference to FIGS. 1 to 3.

[0011] The inkjet recording device 1 is provided with a carriage 11, an ejection head 12 mounted on the carriage 11, ink cartridges 13 that supply ink of each color to the ejection head 12, and a driving means 10 that drives the carriage 11 in a direction A, which are arranged on the upper part of the device body. These correspond to "image forming means." Note that the image forming means is not limited to this configuration, and any means that forms an image on a recording medium is included in the image forming means.

[0012] A conveying means 20 that intermittently drives in a direction B to convey a recording medium (for example, a long recording sheet 100) set on a roll mounting portion is provided at the bottom of the device main body.

[0013] The driving means 10 includes a main guide rod 14 and a secondary guide rod 15, which are guide members horizontally mounted on the left and right side plates of the main body of the apparatus.

[0014] The carriage 11 is fixed to a timing belt 18 stretched between a drive pulley 16 and a driven pulley 17. The drive pulley 16 is driven by the control of a main scanning motor 19, and the carriage 11 moves in the A direction.

[0015] The carriage 11 includes an encoder sensor 31, and detects the position of the carriage 11 by reading an encoder sheet (linear scale) 32 provided along the movement direction of the carriage 11 (direction A) with the encoder sensor 31.

[0016] In this example, ink of each color is supplied from ink cartridges 13 of yellow (Y), magenta (M), cyan (C), and black (Bk), and ink droplets of each color are ejected from the ejection nozzle rows of the ejection head 12.

[0017] The recording sheet 100 is fed from a roll mounting section at the rear of the device body by the rotation of a paper feed unit 21 composed of a motor and an encoder sensor. The fed recording sheet 100 is sandwiched between a registration roller 22 and a pinch roller 23, which are rotating rollers, and is sent in a direction B along the peripheral surface of a platen 24, and is wound up and collected on a paper tube of a paper discharge unit 25 on the paper discharge side. In this example, the registration roller 22 is driven to rotate intermittently, and at this time, the pinch roller 23 presses the recording sheet 100 against the registration roller 22 so that the recording sheet 100 is always in contact with the rotating surface of the registration roller 22 under pressure. Therefore, the power of the registration roller 22 is appropriately transmitted to the recording sheet 100, and the tension of the recording sheet 100 between the paper feed unit 21 and the registration roller 22 is kept constant during rotation.

[0018] When the registration rollers 22 operate intermittently, the recording sheet 100 is intermittently sent to the discharge side by a predetermined amount.

[0019] The platen 24 is equipped with an adsorption means for preventing the recording sheet 100 from floating. In this example, many small suction holes are provided, and the recording sheet 100 is adsorbed to the outer circumferential surface of the platen 24 by rotation of a fan, preventing the recording sheet 100 from floating. The platen 24 also has heaters such as a cure heater 26 and a post heater 27. These heaters harden the ink dropped onto the recording sheet 100 to fix the image.

[0020] As shown in Fig. 3, the ejection head 12 ejects ink of each color from the ejection surface of the ejection head 12 to form an image within an imaging area. The ejection surface of the ejection head 12 is provided with multiple rows of ejection nozzles in the A direction (main scanning direction). In the example shown in Fig. 3, three rows of ejection nozzles are provided for each of the colors yellow (Y), magenta (M), cyan (C), and black (Bk).

[0021] The platen 24 is pre-warmed by the heater 27, so that the ink discharged from the discharge surface of the discharge head 12 adheres to the recording sheet 100 and hardens immediately.

[0022] The ejection head 12 forms an image in the main scanning direction on the recording sheet 100 by driving means 10 reciprocatingly driving the carriage 11 in direction A. After completing image formation in the main scanning direction, the transport means 20 feeds the recording sheet 100 a predetermined amount in direction B. Then, the drive means 10 again drives the carriage 11 reciprocally in direction A to form an image in the main scanning direction. In this way, the inkjet recording device 1 repeats image formation in the main scanning direction by the ejection head 12 and transport of the recording sheet 100 in the sub-scanning direction by the transport means 20, forming an image on the recording sheet 100.

[0023] The inkjet recording apparatus 1 according to this embodiment has a configuration for detecting the movement amount (feed amount) of the recording sheet 100. The configuration includes a mark adding means for adding periodic marks to the recording sheet 100 when the recording sheet 100 is transported by the transport means 20, and a detection means for detecting the marks from the recording sheet 100. The registration rollers 22 shown in Fig. 3 include a spike mark forming means for forming spike marks on the recording sheet 100 as the mark adding means. A detection sensor 28 provided on the platen 24 corresponds to the detection means, and detects the movement amount of the recording sheet 100 from the spike marks on the recording sheet 100.

[0024] FIG. 4 is an explanatory diagram of the mark adding means. FIG. 4(a) and FIG. 4(b) show an example in which spike marks are formed on the recording sheet 100 by a spike mark forming means provided on the registration roller 22. As shown in FIG. 4(a) and FIG. 4(b), a plurality of protrusions are provided at a predetermined interval along the circumferential direction of the rotation surface of the registration roller 22 (the rotation surface that contacts the recording sheet 100). A plurality of protrusions are provided at a predetermined pitch in a direction perpendicular to the circumferential direction (called the lateral direction). Here, as an example, a number of spikes 22-1 are provided in a regular arrangement. When the registration roller 22 rotates in the direction of the rotation arrow, the rotation sends the recording sheet 100 in the B direction (the discharge side), and each spike 22-1 pierces the back side of the recording sheet 100 at a predetermined interval according to the movement amount of the recording sheet 100, forming regular spike marks 100-1 on the back side of the recording sheet 100.

[0025] The spike marks 100-1 formed on the back surface of the recording sheet 100 are read in a predetermined imaging area set by the detection sensor 28 provided on the platen 24. FIG. 4(a) shows an example of the imaging area of ​​the detection sensor 28. The detection sensor 28 captures an image of the imaging area shown in the dotted rectangular frame in FIG. 4(a) using an imaging means (e.g., a CCD (Charge Coupled Device) sensor, etc.), and uses the captured spike marks 100-1 as marks to calculate the amount of movement from the regular pattern of the marks and feeds it back. For example, the detection sensor 28 tracks the same mark (spike mark 100-1) in the imaging area before and after the recording sheet 100 is conveyed, calculates the amount of movement from the interval, and feeds it back to the control unit.

[0026] Furthermore, when the spikes 22-1 are provided in this manner, the spikes 22-1 pierce the back side of the recording sheet 100, so it becomes possible to transport the recording sheet 100 without slipping. Here, the spikes 22-1 are protrusions that are large enough to leave spike marks 100-1 on the recording sheet 100, but are large enough not to affect the front side of the recording sheet 100.

[0027] Fig. 5 is a diagram showing an example of the configuration of a control block of the inkjet recording apparatus 1. A control unit 40 shown in Fig. 5 has a CPU (Central Processing Unit) 41, a ROM (Read Only Memory) 42, a RAM (Random Access Memory) 43, a NVLAM 44, an ASIC (Application Specific Integrated Circuit) 45, and the like.

[0028] The CPU 41 controls the entire device. The ROM 42 stores control programs and data. The RAM 43 is used as a work area for the CPU 41. The NVRAM 44 holds data even when the power to the device is cut off. The ASIC 45 performs image processing and the like.

[0029] The control unit 40 includes a host I / F 46 for transmitting and receiving signals to and from the host side. The host I / F 46 receives print data transmitted from the host side via a cable or a network such as a LAN (Local Area Network).

[0030] The print control unit 47 includes a data transfer unit and a drive waveform generation unit that generates a drive waveform for controlling the driving of the ejection head 12. The carriage 11 is provided with a head driver (driver IC (Integrated Circuit)) 12-1 for driving the ejection head 12.

[0031] The main scanning motor drive unit 48-1 drives the main scanning motor 19 based on speed detection values ​​and position detection values ​​obtained by sampling detection pulses from the encoder sensor 31 that constitutes the linear encoder, and on speed target values ​​and position target values ​​obtained from a pre-stored speed / position profile.

[0032] The sub-scanning motor drive unit 48-2 drives the sub-scanning motor 29 based on speed detection values ​​and position detection values ​​obtained by sampling detection pulses from an encoder sensor 29-1 that constitutes a rotary encoder, and on speed target values ​​and position target values ​​(target values) obtained from a pre-stored speed-position profile.

[0033] The detection sensor 28 is an imaging sensor such as a CCD, and outputs captured image data, which is detection data, to an I / O (Input / Output) 49 .

[0034] In addition, an operation panel 30 for inputting and displaying necessary information is communicably connected, and a temperature sensor for detecting temperature, a heater control unit, and the like are also provided.

[0035] The CPU 41 reads and analyzes the received print data, performs necessary image processing and data sorting processing in the ASIC 45, and instructs the print control unit 47 to print the image data.

[0036] Fig. 6 is a diagram showing an example of a specific configuration of a control block of the sub-scanning motor driving unit 48-2. In the control block shown in Fig. 6, the transport amount determination unit 402 corresponds to the "correction means", and the movement amount calculation unit 403 corresponds to the "calculation means". In the control block shown in Fig. 6, the image processing unit 401, the transport amount determination unit 402, and the movement amount calculation unit 403 may be configured by hardware such as an ASIC, or may be functionally realized by the CPU 41 executing a control program. Also, only a part of them may be functionally realized. Also, the same numbers are assigned to parts corresponding to the configuration shown in Fig. 5.

[0037] Before image formation, the registration roller 22 is rotated to transport the recording sheet 100 so that the spike marks can be read at the reading position of the detection sensor 28, and spike marks 100-1 are formed in the margin of the recording sheet 100 up to the reading position.

[0038] The image processing unit 401 outputs the transport amount obtained by analyzing the print data or the like to the transport amount determination unit 402. The transport amount is the amount by which the recording sheet 100 is transported in the sub-scanning direction by one intermittent operation of the transport means 20.

[0039] The transport amount determination unit 402 corrects the transport amount input from the image processing unit 401 according to the movement amount calculated by the movement amount calculation unit 403 (i.e., the actual movement amount), and outputs the transport amount determined by the correction to the sub-scanning motor drive unit 48-2 to drive the motor to a target value. For example, the transport amount determination unit 402 determines the transport amount by the following formula 1.

[0040] Previous transport distance + (target transport distance - media movement distance) = next transport distance ...(Formula 1)

[0041] For example, if the previous transport amount was 100 μm, the target transport amount was 90 μm, and the medium movement amount was 80 μm, applying these to formula 1 gives the transport amount of 100 μm + (90 μm - 80 μm) = 110 μm. Here, the medium movement amount refers to the movement amount of the recording sheet 100.

[0042] Note that formula 1 is just an example, and control may be performed so that the carry amount is corrected when the calculation result of (target carry amount - medium movement amount) is equal to or greater than a certain value. In other words, the error in the carry amount is not corrected until a certain error occurs from the target carry amount, and the carry amount is corrected all at once when a certain error occurs. Also, the carry amount may be calculated by averaging several carry amounts and movement amounts.

[0043] Fig. 7 is a diagram showing an example of a calculation result in which the transport amount is calculated by averaging several transport amounts and movement amounts. In the example shown in Fig. 7, an average value is calculated for every three movement amounts including the two previous movement amounts, and the next transport amount is calculated from the difference (error) between the average value of the previous three movement amounts and the average value of the current three movement amounts. In this way, the transport amount may be calculated by averaging several transport amounts and movement amounts.

[0044] As described above, the transport amount determination unit 402 corrects the transport amount based on the actual transport amount calculated by the transport amount calculation unit 403, and outputs the corrected transport amount to the sub-scanning motor drive unit 48-2. The method of calculating the transport amount by the transport amount calculation unit 403 will be described later.

[0045] 8 is a diagram showing an example of a control flow of the inkjet recording apparatus 1 (control unit 40). First, the inkjet recording apparatus 1 (control unit 40) starts up the machine when the user presses the power button (S1).

[0046] After starting up the machine, the inkjet recording apparatus 1 (controller 40) detects that the recording sheet 100 has been set, and then rotates the registration rollers 22 to form spike marks on the recording sheet 100 up to the reading position of the detection sensor 28 (S2). Then, the inkjet recording apparatus 1 (controller 40) executes a transport amount correction sequence (S3).

[0047] Next, the inkjet recording apparatus 1 (controller 40) determines whether the transport amount and skew amount determined in the transport amount correction sequence are OK (S4), and if they are not OK (S4: No), executes the transport amount correction sequence again by resetting the recording sheet, etc. If the determined transport amount and skew amount are OK (S4: Yes), the inkjet recording apparatus 1 (controller 40) starts printing (S5).

[0048] 9 is a detailed flow diagram of the transport distance correction sequence. First, the inkjet recording apparatus 1 (controller 40) starts the Nth (initially N=1st) test feed of the recording sheet 100 (S31), and captures an image of the spike marks 100-1 pattern of the fed length with the detection sensor 28 (S32).

[0049] Next, the inkjet recording apparatus 1 (control unit 40) calculates the actual movement amount based on the captured pattern (S33), and calculates the transport amount from the calculated movement amount (S34).

[0050] Next, the number of times N is incremented (S35), and it is determined whether N has exceeded 5 (S36). If N has not exceeded 5 (S36: No), the test feed is performed again (S31).

[0051] In this way, the transport amount for five times is determined, and when N=6, since it exceeds N=5 (S36: Yes), the process ends. Note that the upper limit of the number of transports N is set to 5, but this is for ease of understanding, and the number of transports is not limited to 5. The number of transports is arbitrary.

[0052] Here, a method for calculating the amount of movement by the movement amount calculation unit 403 will be described. Fig. 10 is a diagram showing an example of a change in the pattern of spike marks 100-1 in an imaging area. Fig. 10 shows a pattern (a) of spike marks 100-1 in an imaging area at a certain time point and a pattern (b) of spike marks 100-1 in an imaging area at a next time point. The time interval between a certain time point and the next time point is a time interval set by movement amount calculation unit 403 so that a captured image is output from detection sensor 28, and is, for example, a time interval for intermittently driving registration rollers 22. At least two captured images are obtained during the time interval for intermittent driving.

[0053] The spike marks 100-1 of the same pattern shown in Figure 10(a) and Figure 10(b) are surrounded by a rectangle. The movement amount calculation unit 403 finds the actual movement amount of the recording sheet 100 by calculating the movement amount of the pattern that has changed from Figure 10(a) to Figure 10(b).

[0054] Here, there is a problem that the detection accuracy decreases if there is variation in the distance between the recording sheet 100 and the detection sensor 28 due to an assembly error of the detection sensor 28. However, even if there is an assembly error, since the pitch a (horizontal pitch) of the spikes 22-1 is known, it is possible to detect the movement amount of the recording sheet 100 with high accuracy by calculating the movement amount b (the movement amount of the spikes 22-1 in the vertical direction) based on the pitch a of the spikes 22-1.

[0055] FIG. 11 is a diagram showing the pattern of the imaging area at a certain time and the next time when the pitch of the spike marks 100-1 and the transport amount of the recording sheet 100 are the same. That is, in FIG. 11(a) and FIG. 11(b), the pitch c of the spikes 22-1 coincides with the transport amount b. In this way, when the pitch c of the spikes 22-1 and the transport amount b are the same, the pattern after transport becomes the same as the pattern before transport, and the actual movement amount of the recording sheet 100 may not be detected correctly. Therefore, the movement amount is calculated as follows. FIG. 12 is an explanatory diagram of a method of calculating the movement amount. The movement amount calculation unit 403 recognizes the transport amount b in advance, and calculates the movement amount by photographing the vicinity of the transport amount b as shown in FIG. 12(b) with respect to FIG. 12(a). In this case, since the photograph is taken near the transport amount b, the transport amount b can be shifted from the pitch of the spikes c, and the movement amount can be detected with high accuracy.

[0056] Fig. 13 is a diagram for explaining detection of skew or meandering of the recording sheet 100. When skew or meandering occurs in the recording sheet 100, the spike trace marks move laterally. Therefore, the angle θ of the mark indicating the movement direction with an arrow in Fig. 13 is obtained, and skew or meandering is detected from the amount of lateral movement of the recording sheet 100.

[0057] Skew and meandering are detected before printing and the recording sheet 100 is reset, thereby making it possible to prevent abnormal images from being printed.

[0058] In the present embodiment, the spikes 22-1 are provided on the registration roller 22 as a mark adding means for adding periodic marks to the recording sheet 100, but other methods may be used as long as they are mark adding means for adding periodic marks to the recording sheet 100. For example, regular marks may be transferred from the registration roller 22 using ink or the like. Also, the marks may be formed using ink or the like that cannot be recognized by the human eye.

[0059] As described above, in the image forming apparatus according to the present embodiment, a mark is added to the recording medium when an image is formed on the recording medium, so that the amount of movement of the recording medium can be detected with high accuracy even for recording media without a pattern. In addition, since a mark is added, a camera with as high accuracy as a camera for photographing a fiber pattern is not required, and installation is also easy. Furthermore, since the amount of transport of the recording medium can be corrected at the same time as the image is formed, there are advantages in terms of productivity and running costs.

[0060] The program executed by the image forming apparatus according to this embodiment is provided as a file in an installable or executable format recorded on a computer-readable recording medium such as a CD-ROM, a flexible disk (FD), a CD-R, or a DVD (Digital Versatile Disk).

[0061] The program executed by the image forming apparatus according to the present embodiment may be stored in a computer connected to a network such as the Internet and provided by being downloaded via the network. The program executed by the image forming apparatus according to the present embodiment may be provided or distributed via a network such as the Internet.

[0062] The program for the image forming apparatus according to the present embodiment may be provided by being pre-installed in a ROM or the like. [Explanation of symbols]

[0063] 22 Registration roller 22-1 Spike 28 Detection Sensor 29 Sub-scanning motor 29-2 Encoder sensor 48-2 Sub-scanning motor drive unit 100 Record Sheet 100-1 Spike marks 401 Image Processing Unit 402 Transport amount determination unit 403 Movement Calculation Unit [Prior art documents] [Patent documents]

[0064] [Patent Document 1] JP 2018-83678 A

Claims

1. a conveying means for conveying the recording medium according to a predetermined conveying amount; an image forming means for forming an image on the recording medium conveyed by the conveying means; a mark adding means for adding periodic marks to the recording medium when the recording medium is conveyed by the conveying means; a detection means for detecting the mark from the recording medium; a calculation means for calculating a vertical movement amount of the mark based on a horizontal pitch of the regular mark detected by the detection means; a correction unit that corrects the conveyance amount of the recording medium based on the movement amount; An image forming apparatus comprising:

2. the mark adding means is provided on a rotating roller that rotates in contact with the recording medium as the recording medium is conveyed by the conveying means; The image forming apparatus according to claim 1 .

3. the mark adding means is a plurality of protrusions provided at a predetermined interval on a rotation surface of the rotating roller that contacts the recording medium, the detection means detects a trace formed by the protrusion on the recording medium as the mark; The image forming apparatus according to claim 2 .

4. the calculation means further detects a skew of the recording medium by calculating a regular horizontal shift amount of the marks detected from the recording medium. The image forming apparatus according to claim 1 .

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