Image formation device

Abstract

To provide an image formation device that accurately detects a speed of a conveyance belt even though the number of opening parts provided in the conveyance belt is small.SOLUTION: A conveyance belt 2 conveys a print sheet. The conveyance belt 2 is formed with an opening part 63. A line sensor 42 reads the opening part 63. A belt speed detection part (a) causes the line sensor 42 to read the opening part 63 with a predetermined time interval, (b) identifies a movement distance of the opening part 63 on the basis of a pixel position of the line sensor 42 at which the opening part 63 has been detected, and (b) detects a surface speed of the conveyance belt 2 on the basis of the time interval and the identified movement distance.SELECTED DRAWING: Figure 3

Description

[Technical field]

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

[0002] One image reading device includes a conveyor belt having multiple through holes formed at predetermined intervals, a reflective sensor, and a speed measuring unit that measures the speed of the conveyor belt based on the timing of the through holes passing through the detection position of the reflective sensor (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2006-246253 A Summary of the Invention [Problem to be solved by the invention]

[0004] In the above-mentioned image reading device, the accuracy of measuring the speed of the conveyor belt can be improved by increasing the number of through holes. However, increasing the number of through holes reduces the strength of the conveyor belt.

[0005] The present invention has been made in consideration of the above problems, and has an object to provide an image forming apparatus that is capable of detecting the speed of a conveyor belt with high accuracy even if the conveyor belt has few openings. [Means for solving the problem]

[0006] The image forming apparatus of the present invention includes a conveyor belt for conveying a print sheet, an opening formed in the conveyor belt, a line sensor for reading the opening, and a belt speed detection unit that (a) causes the line sensor to read the opening at predetermined time intervals, (b) determines a movement distance of the opening based on a pixel position of the line sensor where the opening is detected, and (b) detects a surface speed of the conveyor belt based on the time interval and the determined movement distance. Effect of the Invention

[0007] According to the present invention, an image forming apparatus is obtained that is capable of detecting the speed of a transport belt with high accuracy even if the transport belt has few openings.

[0008] The above and other objects, features and advantages of the present invention will become more apparent from the following detailed description taken in conjunction with the accompanying drawings. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a side view illustrating the mechanical internal configuration of an image forming apparatus according to an embodiment of the present invention. [Diagram 2] FIG. 2 is a front view showing an example of the configuration of the inkjet recording units 1a, 1b, 1c, and 1d in FIG. [Diagram 3] FIG. 3 is a diagram showing an example of the conveyor belt 2 in FIG. [Figure 4] FIG. 4 is a block diagram showing an electrical configuration of the image forming apparatus 10 according to the embodiment of the present invention. [Diagram 5] FIG. 5 is a diagram showing an example of a series of detection results in chronological order regarding the pixel positions and movement distances of three openings 63 (marks #1, #2, and #3). DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0011] 1 is a side view illustrating the internal mechanical configuration of an image forming apparatus according to an embodiment of the present invention. The image forming apparatus 10 according to this embodiment is a device such as a printer, a copier, a facsimile machine, or a multifunction machine, and in this embodiment, is equipped with a line-head type inkjet color printing mechanism.

[0012] The image forming apparatus 10 shown in Fig. 1 includes a print engine 10a and a sheet transport unit 10b. The print engine 10a physically prints an image to be printed on a print sheet (such as print paper). An ink cartridge is detachably attached to the print engine 10a, and the print engine 10a performs printing using ink supplied from the ink cartridge. The sheet transport unit 10b transports the print sheet to the print engine 10a.

[0013] In this embodiment, the print engine 10a is equipped with line-head type inkjet recording units (hereinafter, simply referred to as recording units) 1a-1d corresponding to four ink colors: cyan, magenta, yellow, and black. Each of the inkjet recording units 1a-1d ejects ink onto a print sheet 101 using an array of nozzles to perform printing.

[0014] Fig. 2 is a front view showing an example of the configuration of the inkjet recording units 1a, 1b, 1c, and 1d in Fig. 1. For example, as shown in Fig. 2, each of the inkjet recording units 1a to 1d includes a head unit 41 having a plurality of nozzles arranged along the main scanning direction, and a line sensor 42.

[0015] Here, the line sensor 42 is a CIS (Contact Image Sensor) and includes a plurality of sensor pixels (light receiving elements) arranged in a predetermined direction. The plurality of sensor pixels are arranged at a predetermined physical resolution. For example, the line sensor 42 is an A4-sized CIS with 600 dpi and includes 5184 sensor pixels arranged one-dimensionally (i.e., there are pixel numbers (pixel positions) from 1 to 5184). The line sensor 42 is also disposed along the conveying direction of the print sheet (the moving direction of the conveyor belt 2). In other words, the sensor pixels are arranged along the moving direction of the conveyor belt 2.

[0016] Returning to Figure 1, in this embodiment, the sheet conveying section 10b includes a circular conveying belt 2 arranged opposite the print engine 10a and conveying a print sheet, a drive roller 3, a driven roller 4, and a tension roller 4a around which the conveying belt 2 is suspended, an adhesion roller 5 that nips the print sheet together with the conveying belt 2, a subsequent conveying belt 6, and a dryer 7.

[0017] The driving roller 3, the driven roller 4, and the tension roller 4a rotate the conveyor belt 2. Then, the suction roller 5 nips the print sheet conveyed from the paper feed cassette 20 described later, and the nipped print sheet 101 is conveyed by the conveyor belt 2 to the printing positions of the inkjet recording units 1a to 1d in order, and the inkjet recording units 1a to 1d print images of each color. At this time, the sheet sensor 2a detects the passage of the print sheet, and the current position of the print sheet on the conveying path is specified based on the detection timing, so that the image is printed at an appropriate position on the print sheet. Then, the print sheet after printing is discharged to a discharge tray or the like by the rear conveyor belt 6. At this time, the print sheet on which the ink has been discharged is dried by the dryer 7.

[0018] 3 is a diagram showing an example of the conveyor belt 2 in FIG. 1. The conveyor belt 2 includes a flushing opening 61, a sheet suction hole 62, and an opening 63 for detecting the belt speed. In the conveyor belt 2, the opening 63 is formed at a position where the conveyor belt 2 passes through the reading position of the line sensor 42 as the conveyor belt 2 moves (circulates), and the line sensor 42 reads the opening 63 when the conveyor belt 2 moves (circulates). Note that, although only the recording unit 1a among the recording units 1a to 1d is shown in FIG. 3, the same applies to the recording units 1b to 1d.

[0019] A plurality of openings 63 are formed along the sub-scanning direction (transport direction) so that at least one opening 63 is read by the line sensor 42 at any given time.

[0020] Moreover, the line sensor 42 (CIS) is disposed in each of the recording units 1a to 1d so that the height from the conveyor belt 2 is optimized based on the depth of field of the CIS. The height of each of the recording units 1a to 1d from the conveyor belt 2 is individually adjusted by an adjustment mechanism (not shown) according to the ink ejection characteristics of each of the recording units 1a to 1d, and the line sensor 42 is positioned in the height direction so that the conveyor belt 2 is within the depth of field of the line sensor 42 (CIS) of each of the recording units 1a to 1d even after the adjustment.

[0021] Furthermore, as shown in FIG. 1, for example, ink receiving units 8a-8d are provided below the inkjet recording units 1a-1d, and when any of the flushing openings 61 is located directly below the inkjet recording units 1a, 1b, 1c, 1d, flushing (e.g., line flushing) is performed for each nozzle in the inkjet recording units 1a, 1b, 1c, 1d, and ink ejected from the nozzles during flushing is received by the corresponding ink receiving unit 8a, 8b, 8c, 8d through the flushing opening 61 and is collected in a waste ink tank.

[0022] The sheet suction units 9 are arranged along the print sheet transport path at a location other than the ink receiving units 8a to 8d. A negative pressure is applied to the sheet suction units 9, which causes the print sheet to be attracted to the transport belt 2 through the sheet suction holes 62. A negative pressure lower than that applied to the ink receiving units 8a to 8d is applied to the sheet suction units 9.

[0023] Furthermore, the sheet transport section 10b includes a paper feed cassette 20 as a paper feed source. The paper feed cassette 20 contains print sheets 101, and a lift plate 21 pushes the print sheets 101 upward to abut against a pickup roller 22. The print sheets 101 placed in the paper feed cassette 20 are picked up one by one from above by the pickup roller 22 onto a paper feed roller 23. The paper feed roller 23 is a roller that transports the print sheets 101, which have been fed from the paper feed cassette 20 by the pickup roller 22, onto a transport path one by one.

[0024] The transport rollers 27 are rollers that transport the print sheet 101 on a predetermined transport path. When the transported print sheet 101 is detected by the resist sensor 28a, the registration rollers 28 temporarily stop the print sheet 101 and transport the print sheet 101 to the print engine 10a (specifically, to the nip position between the adsorption roller 5 and the transport belt 2) at the secondary feed timing. The secondary feed timing is specified by the control unit 81, which will be described later, so that an image is formed at a specified position on the print sheet 101.

[0025] Furthermore, the sheet transport unit 10b includes a circulating sheet transport unit 31. During double-sided printing or the like, the circulating sheet transport unit 31 returns the print sheet along the transport path by a transport roller from a predetermined position on the downstream side of the print engine 10a to a predetermined position on the upstream side.

[0026] 1, the circulating sheet transport unit 31 includes a switchback transport path 32. The switchback transport path 32 reverses the traveling direction of the print sheet in order to switch the side of the print sheet facing the print engine 10a from the first side to the second side.

[0027] Fig. 4 is a block diagram showing the electrical configuration of the image forming apparatus 10 according to the embodiment of the present invention. As shown in Fig. 4, the image forming apparatus 10 includes a printing device 71 having the mechanical configuration as shown in Figs. 1 to 3, and further includes an operation panel 72, a storage device 73, and an arithmetic processing device 74.

[0028] The operation panel 72 is arranged on the surface of the housing of the image forming apparatus 10 and includes a display device 72a such as an LCD display, and an input device 72b such as hard keys or a touch panel. The display device 72a displays various messages to the user, and the input device 72b accepts user operations.

[0029] The storage device 73 is a non-volatile storage device (such as a flash memory or a hard disk drive) that stores data, programs, and the like required for controlling the image forming apparatus 10.

[0030] The arithmetic processing device 74 includes a computer that operates according to a program, an ASIC (Application Specific Integrated Circuit) that executes a predetermined operation, and the like, and operates as various processing units. The computer includes a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), and the like, and operates as various processing units (together with the ASIC as necessary) by loading a program stored in the ROM, storage device 73, etc., into the RAM and executing the program on the CPU.

[0031] Here, the arithmetic processing unit 74 operates as a control unit 81, an image processing unit 82, and a belt speed detection unit 83.

[0032] The control unit 81 controls the image output unit 71 (print engine 10a, sheet conveying unit 10b, etc.) to execute a print job requested by a user. In this embodiment, the control unit 81 causes the image processing unit 82 to execute predetermined image processing, and controls the print engine 10a to eject ink to form a print image on a print sheet. The image processing unit 82 executes predetermined image processing such as RIP (Raster Image Processing), color conversion, and halftoning on the image data of the image to be printed on the print sheet.

[0033] Specifically, the control unit 81 controls the print engine 10a and the sheet conveying unit 10b to cause the print engine 10a to print a user document image based on print image data specified by the user. The print engine 10a forms an image on a print sheet conveyed by a conveyor belt.

[0034] The belt speed detection unit 83 (a) causes the line sensor 42 to read the opening 63 at a predetermined time interval, (b) determines the movement distance of the opening 63 based on the pixel position of the line sensor 42 where the opening 63 is detected, and (b) detects the surface speed of the conveyor belt 2 based on the above-mentioned time interval and the determined movement distance.

[0035] 3, a plurality of openings 63 are formed in the conveyor belt, and the interval between two adjacent openings 63 among the plurality of openings 63 is narrower than the reading width of the line sensor 42. Then, the belt speed detection unit 83 detects the surface speed of the conveyor belt 2 based on the above-mentioned time interval and the movement distance of the plurality of openings 63.

[0036] The control unit 81 causes the print engine 10a to form an image at a timing based on the surface speed of the conveyor belt 2 detected in this manner.

[0037] Furthermore, as described above, the print engine 10a includes a plurality of inkjet recording units 1a-1d corresponding to a plurality of ink colors, and a plurality of line sensors 42 are provided corresponding to the plurality of recording units 1a-1d. In this embodiment, the control unit 81 individually controls the ink discharge of the plurality of recording units 1a-1d corresponding to the plurality of line sensors, at a timing based on the surface speed detected by each of the plurality of line sensors 42. Specifically, for example, the ink discharge control of the recording unit 1a is performed at a timing based on the surface speed detected by the line sensor 42 built in the recording unit 1a. The same applies to the recording units 1b-1d.

[0038] Next, the operation of the image forming apparatus 10 will be described.

[0039] When the control unit 81 receives a print request, the image processing unit 82 executes image processing on the image specified by the print request to obtain image data of the image to be printed, and the image output unit 71 transports a print sheet and prints the image to be printed on the print sheet based on the image data.

[0040] At that time, when the print sheet is transported, the belt speed detection unit 83 periodically acquires the read image (one-dimensional image) of the line sensor 42, identifies the pixel position of the opening 63 in the read image (for example, the center position of the opening 63 in the read image), identifies the moving distance of the opening 63 per period, derives the surface speed of the transport belt 2, and notifies the control unit 81.

[0041] Based on the surface speed of the transport belt 2 thus periodically obtained, the control unit 81 controls the ink ejection from the recording units 1a to 1d so that an image is formed at an appropriate position on the print sheet being transported.

[0042] Here, the operation of the belt speed detection unit 83 will be described in detail.

[0043] 5 is a diagram showing an example of a series of detection results along a time series for the pixel positions and movement distances of three openings 63 (marks #1, #2, #3). Note that here, the values ​​of the pixel positions (pixel numbers) are set to increase along the conveying direction. Also, the openings 63 detected in the read image are marks #1, #2, #3 in order from the smallest pixel position.

[0044] When the belt speed detection unit 83 identifies the pixel position of the opening 63 (marks #1, #2, #3) at a certain detection timing, it performs a pixel position decrease determination. That is, the belt speed detection unit 83 determines whether the pixel position identified this time for any of the openings 63 has decreased (become smaller) than the pixel position one period ago.

[0045] For any opening 63, if at least one pixel position identified this time has not decreased from the pixel position of one period before, the belt speed detection unit 83 calculates the difference between the two for each opening 63 (mark) and derives the average value of the differences for the three openings 63 (marks) as the moving distance of the conveyor belt 2. For example, in Fig. 5, at the detection timing of the period N+2, all pixel positions of marks #1 to #3 have increased from the pixel positions at the detection timing of the previous period N+1, so the average value (=520) of the differences of the pixel positions for marks #1 to #3 is derived as the moving distance of the conveyor belt 2.

[0046] On the other hand, when the pixel position identified this time for at least one opening 63 is decreased from the pixel position of one period before, the belt speed detection unit 83 calculates the difference between the pixel position of the current mark #3 and the pixel position of the previous mark #2, and the difference between the pixel position of the current mark #2 and the pixel position of the previous mark #1, and derives the average value of these differences as the moving distance of the conveyor belt 2. For example, in FIG. 5, at the detection timing of the period N+1, the pixel position of the mark #1 has decreased from the pixel position at the detection timing of the previous period N+1, so for the remaining marks #2 and #3, the average value (=500) of the difference (=500) between the pixel position of the current mark #3 (=3530) and the pixel position of the previous mark #2 (=3030) and the difference (=500) between the pixel position of the current mark #2 (=2150) and the pixel position of the previous mark #1 (=1650) is derived as the moving distance of the conveyor belt 2.

[0047] The belt speed detection unit 83 derives the surface speed of the conveyor belt 2 by dividing the moving distance thus obtained by the above-mentioned period.

[0048] As described above, according to the embodiment, the conveyor belt 2 conveys a print sheet. The openings 63 are formed in the conveyor belt 2. The line sensor 42 reads the openings 63. The belt speed detection unit 83 (a) causes the line sensor 42 to read the openings 63 at a predetermined time interval, (b) specifies the movement distance of the openings 63 based on the pixel position of the line sensor 42 at which the openings 63 are detected, and (b) detects the surface speed of the conveyor belt 2 based on the time interval and the specified movement distance.

[0049] As a result, the positions of the openings 63 are identified as pixel positions of the line sensor 42 at each point in time, so that the speed of the conveyor belt 2 can be detected with high accuracy even if the number of openings 63 provided in the conveyor belt 2 is small.

[0050] It should be noted that various changes and modifications to the above-described embodiments will be apparent to those skilled in the art. Such changes and modifications may be made without departing from the spirit and scope of the subject matter and without diminishing its intended advantages. In other words, such changes and modifications are intended to be included within the scope of the claims. [Industrial Applicability]

[0051] The present invention is applicable to, for example, an image forming apparatus equipped with a conveyor belt. [Explanation of symbols]

[0052] 1a to 1d Inkjet recording unit (example of recording unit) 2 Conveyor belt 10 Image forming device 10a Print Engine 42 Line Sensor 63 Opening 81 Control Unit 83 Belt speed detector

Claims

1. A conveyor belt for conveying a print sheet; An opening formed in the conveyor belt; A line sensor that reads the opening; (a) causing the line sensor to read the opening at a predetermined time interval; (b) determining a moving distance of the opening based on a pixel position of the line sensor where the opening is detected; and (b) detecting a surface speed of the conveyor belt based on the time interval and the determined moving distance. An image forming apparatus comprising:

2. A plurality of openings are formed in the conveyor belt, a distance between two adjacent openings in the plurality of openings is narrower than a reading width of the line sensor; the belt speed detection unit detects a surface speed of the conveyor belt based on the time interval and the moving distance of the plurality of openings; 2. The image forming apparatus according to claim 1,

3. a print engine for forming an image on the print sheet conveyed by the conveyor belt; A control unit that controls the print engine, the control unit causes the print engine to form the image at a timing based on the detected surface speed; 3. The image forming apparatus according to claim 1, wherein:

4. a plurality of line sensors for reading the openings; the print engine includes a plurality of inkjet recording units corresponding to a plurality of ink colors; the plurality of line sensors are provided corresponding to the plurality of recording units, the control unit controls ink ejection of the recording units corresponding to the line sensors individually at timings based on the surface speeds detected by the line sensors; 4. The image forming apparatus according to claim 3,

Images