Image forming apparatus

Abstract

To suppress occurrence of a failure of an apparatus caused by contact of a print sheet with the apparatus arranged along a conveyance path when printing is restarted after a jam is eliminated.SOLUTION: A controller 74 controls a print engine 10a and a sheet conveyance portion 10b to execute printing, and detects jamming of a print sheet on a conveyance path by using a plurality of sheet sensors 31, 32, and 33 to restart printing after the jamming is eliminated. At this time, the controller 74 (a) causes the sheet conveyance portion 10b to perform conveyance of the print sheet at first linear velocity at the time of printing, and (b) causes the sheet conveyance portion 10b to start conveyance of the print sheet at second linear velocity lower than the first linear velocity at the time of restarting the printing after the jam is eliminated, and returns conveyance speed of the print sheet from the second linear velocity to the first linear velocity when predetermined time elapses after the conveyance of the print sheet is started.SELECTED DRAWING: Figure 2

Description

[Technical Field]

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

[0002] One image forming apparatus is provided with a reflective sensor that optically detects a print sheet being conveyed at a predetermined position on a conveyance path (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2021-169358 Summary of the Invention [Problem to be solved by the invention]

[0004] The image forming apparatus described above prints while conveying a print sheet along a conveyance path at a predetermined conveyance speed, and if a jam occurs in the print sheet, the jam can be detected using a reflective sensor. When the user clears the jam, the apparatus confirms that the reflective sensor no longer detects the print sheet before resuming printing. However, there are cases where the reflective sensor does not detect a print sheet that has shifted position due to the jam and remains on the conveyance path without being removed, and in such cases, printing resumes without removing the print sheet that caused the jam.

[0005] If printing is resumed without removing the print sheet that caused the jam, and the print sheet has become bent or deformed, it may come into contact with devices (such as reflective sensors or dryers) located along the transport path, causing malfunctions in those devices.

[0006] The present invention has been made in consideration of the above-mentioned problems, and aims to provide an image forming apparatus that suppresses the occurrence of malfunctions in such devices arranged along the conveying path caused by contact of a print sheet with the devices when printing is resumed after a jam has been cleared. [Means for solving the problem]

[0007] An image forming apparatus according to the present invention includes a sheet transport unit that transports a print sheet along a transport path, a print engine that is disposed opposite the transport path and ejects ink onto the print sheet to form an image on the print sheet, sheet sensors that are disposed opposite the transport path at a predetermined position on the transport path and optically detect the print sheet passing through that position, and a controller that controls the sheet transport unit and the print engine to perform printing, detects a jam of the print sheet on the transport path using the sheet sensors, and resumes the printing after the jam is cleared. The controller (a) causes the sheet transport unit to transport the print sheet at a first linear speed during the printing, and (b) when the printing is resumed after the jam is cleared, causes the sheet transport unit to start transporting the print sheet at a second linear speed that is lower than the first linear speed, and returns the print sheet transport speed from the second linear speed to the first linear speed after a predetermined time has elapsed since the start of print sheet transport. [Effects of the Invention]

[0008] According to the present invention, an image forming apparatus can be obtained that suppresses the occurrence of malfunctions in devices arranged along the conveying path caused by a print sheet coming into contact with the devices when printing is resumed after a jam has been cleared.

[0009] 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 explanation of the drawings]

[0010] [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. [Figure 2] FIG. 2 is a block diagram showing the electrical configuration of the image forming apparatus 10 according to the embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0012] 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, copier, facsimile machine, or multifunction device, and in this embodiment is equipped with a line-head inkjet color printing mechanism.

[0013] The image forming apparatus 10 shown in FIG. 1 includes a print engine 10a and a sheet transport unit 10b. The print engine 10a is disposed opposite the transport path and ejects ink onto a print sheet to form an image on the print sheet. 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 along the transport path.

[0014] In this embodiment, print engine 10a has line-head inkjet recording units 1a-1d corresponding to four ink colors: cyan, magenta, yellow, and black, and ink is ejected onto a print sheet by inkjet recording units 1a-1d. In this embodiment, each of inkjet recording units 1a, 1b, 1c, and 1d has one or more head units. Each head unit has multiple nozzles arranged in the main scanning direction, and ejects ink from the nozzles onto a print sheet.

[0015] In this embodiment, the sheet conveying section 10b includes a circular conveying belt 2 that is arranged opposite the print engine 10a and rotates to convey the print sheet, a drive roller 3, a driven roller 4, and a tension roller 4a that suspend the conveying belt 2, an adsorption roller 5 that nips the print sheet together with the conveying belt 2, a subsequent conveying belt 6, and a dryer 7.

[0016] A drive roller 3, a driven roller 4, and a tension roller 4a rotate the conveyor belt 2. Then, an attraction roller 5 nips a print sheet conveyed from a 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, where an image of each color is printed by the inkjet recording units 1a to 1d. After printing is complete, the print sheet is discharged onto a discharge tray 10c or the like by a subsequent conveyor belt 6. At this time, a dryer 7 dries the print sheet on which the ink has been ejected.

[0017] The conveyor belt 2 has a plurality of sheet suction holes formed therein, and a sheet suction fan 8 applies negative pressure to the print sheet on the conveyor belt 2, causing the print sheet to adhere to the conveyor belt 2 through the sheet suction holes.

[0018] The conveyor belt 2 is also provided with cleaning members 9 (blades, brushes, etc.) for cleaning the conveyor belt 2. The cleaning members 9 remove ink and the like that has accidentally adhered to the conveyor belt 2.

[0019] Furthermore, the sheet transport unit 10b is equipped with a paper feed cassette 20 as a paper feed source. The paper feed cassette 20 stores 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. Transport rollers 27 are rollers that transport the print sheets 101 along a predetermined transport path.

[0020] The sheet sensors 31, 32, and 33 are each positioned facing the conveyance path at a predetermined position on the conveyance path and optically detect print sheets passing through that position. Here, the sheet sensors 31, 32, and 33 are reflective sensors that detect print sheets without contact. These reflective sensors irradiate the sheet detection position with light, detect the reflected light, and output a sensor signal corresponding to the amount of reflected light. Therefore, the sensor signal changes depending on whether a print sheet is present at the sheet detection position. For example, these reflective sensors separately detect the specular reflection component and the diffuse reflection component of the reflected light and output a sensor signal corresponding to the difference or ratio between them. Because these differences or ratios differ between the conveyance belt 2 and the print sheet, the presence or absence of a print sheet at the sheet detection position can be determined based on the sensor signal.

[0021] The sheet sensor 31 is disposed at a position facing the conveyor belt 2 inside the print engine 10a (here, between the inkjet recording units 1b and 1c).

[0022] The sheet sensor 32 is an upstream sheet sensor that optically detects a print sheet at a predetermined position on the upstream side of the conveyance path relative to the sheet sensor 31. The sheet sensor 33 is a downstream sheet sensor that optically detects a print sheet at a predetermined position on the downstream side of the conveyance path relative to the sheet sensor 31.

[0023] Fig. 2 is a block diagram showing the electrical configuration of image forming apparatus 10 according to an embodiment of the present invention. As shown in Fig. 2, image forming apparatus 10 includes a printing device 71 having the mechanical configuration shown in Figs. 1 and 2, as well as an operation panel 72, a storage device 73, and a controller 74.

[0024] The operation panel 72 is arranged on the surface of the housing of the image forming device 10 and is equipped with a display device 72a such as an LCD display and an input device 72b such as hard keys or a touch panel, and displays various messages to the user on the display device 72a and accepts user operations on the input device 72b.

[0025] 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.

[0026] The controller 74 includes a computer that operates according to a program, an ASIC (Application Specific Integrated Circuit) that executes predetermined operations, and the like, and executes various processes. The computer includes a CPU (Central Processing Unit), ROM (Read Only Memory), RAM (Random Access Memory), and the like, and executes various processes (together with the ASIC, if necessary) by loading programs stored in the ROM, storage device 73, etc. into the RAM and executing them on the CPU.

[0027] For example, the controller 74 controls the printing device 71 (print engine 10a, sheet transport unit 10b, etc.) to execute a print job requested by a user. In this embodiment, the controller 74 executes predetermined image processing (RIP (Raster Image Processing), color conversion, halftoning, etc.) on the image to be printed, and controls the print engine 10a to eject ink to form a print image on a print sheet.

[0028] Furthermore, the controller 74 detects a jam of the print sheet on the conveying path using the sheet sensors 31, 32, and 33, and resumes printing after the jam is cleared.

[0029] When a jam occurs, the sheet sensors 31, 32, and 33 do not detect the print sheet at a predetermined timing, or the sheet sensors 31, 32, and 33 continue to detect the print sheet for more than a predetermined time, and the controller 74 detects the jam based on the sensor signals of the sheet sensors 31, 32, and 33. After the user performs an operation to clear the jam, the controller 74 confirms that the sheet sensors 31, 32, and 33 are no longer detecting the print sheet, and then resumes printing.

[0030] At this time, the controller 74 (a) causes the sheet conveying section 10b to convey the print sheet at a predetermined first linear speed during printing, and (b) when printing is resumed after the jam is cleared, causes the sheet conveying section 10b to start conveying the print sheet at a second linear speed lower than the first linear speed, and when a predetermined time has elapsed since the start of conveying the print sheet, returns the conveying speed of the print sheet from the second linear speed to the first linear speed.

[0031] For example, the controller 74 controls a belt driving unit 81 such as a motor to adjust the rotation speed of the conveyor belt 2, thereby setting the conveying speed of the print sheet to the first linear velocity or the second linear velocity.

[0032] In this embodiment, the predetermined time is set based on the longer distance L between the distance from the sheet detection position of sheet sensor 31 to the sheet detection position of upstream sheet sensor 32 and the distance from the sheet detection position of sheet sensor 31 to the sheet detection position of downstream sheet sensor 33, and the second linear speed V. Specifically, the predetermined time is set to a value equal to or greater than the value obtained by dividing the distance L by the second linear speed V.

[0033] Furthermore, if the sheet sensors 31, 32, and 33 do not detect a print sheet before the specified time has elapsed after printing resumes, the controller 74 determines that the jam has not been resolved and stops printing again without returning the conveying speed to the first linear speed.

[0034] In addition, if there are multiple sheet sensors upstream and downstream of sheet sensor 31, the above-mentioned specified time is similarly set based on the longer of the distance from the sheet detection position of sheet sensor 31 to the sheet detection position of the upstream sheet sensor closest to sheet sensor 31 on the conveying path and the distance from the sheet detection position of sheet sensor 31 to the sheet detection position of the downstream sheet sensor closest to sheet sensor 31 on the conveying path, and the second linear speed.

[0035] Next, the operation of the image forming apparatus 10 will be described.

[0036] When the controller 74 receives a job request, it controls the printing device 71 to execute the print job requested by the user. At that time, the controller 74 causes the sheet conveying unit 10b to convey the print sheet at a predetermined first linear velocity, and causes the print engine 10a to form an image on the print sheet.

[0037] At this time, the controller 74 monitors the sensor signals of the sheet sensors 31, 32, and 33, and if a print sheet jam occurs on the conveying path, the controller 74 detects the jam based on the sensor signals, stops the conveyance of the print sheet by the sheet conveying unit 10b and the image formation on the print sheet by the print engine 10a, and notifies the user of the jam.

[0038] Thereafter, when the user performs an operation to clear the jam, the controller 74 confirms that the sheet sensors 31, 32, and 33 do not detect the print sheet, and resumes printing. When resuming printing after the jam has been cleared, the controller 74 causes the sheet transport unit 10b to start transporting the print sheet at a second linear speed that is lower than the first linear speed, and when a predetermined time has elapsed since the start of print sheet transport (when the sheet sensors 31, 32, and 33 do not detect the print sheet), the controller 74 returns the print sheet transport speed from the second linear speed to the first linear speed. When returning the print sheet transport speed from the second linear speed to the first linear speed, the controller 74 gradually increases the print sheet transport speed at a predetermined acceleration.

[0039] As described above, according to the above embodiment, the controller 74 controls the print engine 10a and the sheet transport unit 10b to perform printing, and also detects a print sheet jam on the transport path using the multiple sheet sensors 31, 32, and 33, and resumes printing after the jam is cleared. In this case, the controller 74 (a) causes the sheet transport unit 10b to transport the print sheet at a first linear speed during printing, and (b) when printing is resumed after the jam is cleared, causes the sheet transport unit 10b to start transporting the print sheet at a second linear speed that is lower than the first linear speed, and when a predetermined time has elapsed since the start of print sheet transport, returns the print sheet transport speed from the second linear speed to the first linear speed.

[0040] As a result, even if the print sheet accidentally remains on the transport path when printing resumes and comes into contact with devices arranged along the transport path (print engine 10a, sheet sensors 31, 32, 33, dryer 7, etc.), the speed of the print sheet when it comes into contact is low, so the occurrence of problems with such devices due to the print sheet coming into contact with them is suppressed. Also, because the transport of the print sheet is resumed at a low speed when printing resumes after a jam is cleared, even if the jam is not completely cleared and the transport of the print sheet is stopped again, the print sheet is stopped in a relatively short time because it is being transported at a low speed, and further damage to the print sheet is suppressed even if it comes into contact with such devices again.

[0041] 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, it is intended that such changes and modifications be included within the scope of the claims. [Industrial Applicability]

[0042] The present invention is applicable to, for example, an inkjet type image forming apparatus. [Explanation of symbols]

[0043] 9 Cleaning materials 10 Image forming device 10a Print Engine 10b Sheet transport section 31 Sheet Sensor 32 Sheet sensor (an example of an upstream sheet sensor) 33 Sheet sensor (an example of a downstream sheet sensor) 74 Controller

Claims

1. a sheet conveying section that conveys a print sheet along a conveying path; a print engine disposed opposite the transport path and ejecting ink onto the print sheet to form an image on the print sheet; a sheet sensor disposed at a predetermined position on the conveying path so as to face the conveying path and optically detects the print sheet passing through that position; a controller that controls the sheet transport unit and the print engine to perform printing, detects jamming of the print sheet on the transport path using the plurality of sheet sensors, and resumes the printing after the jam is cleared; the controller (a) causes the sheet transport unit to transport the print sheet at a first linear speed during the printing, and (b) causes the sheet transport unit to start transporting the print sheet at a second linear speed lower than the first linear speed when the printing is resumed after the jam is cleared, and returns the transport speed of the print sheet from the second linear speed to the first linear speed after a predetermined time has elapsed since the start of transport of the print sheet; An image forming apparatus comprising:

2. an upstream sheet sensor disposed opposite the conveyance path at a predetermined position upstream of the sheet sensor, and configured to optically detect the print sheet passing through that position; a downstream sheet sensor that is disposed opposite the conveyance path at a predetermined position downstream of the sheet sensor and that optically detects the print sheet passing through that position; the sheet conveying unit includes a conveying belt that is disposed opposite the print engine and rotates; the sheet sensor is disposed at a position facing the conveyor belt, the predetermined time is set based on the second linear velocity and a longer distance between a distance from the sheet detection position of the sheet sensor to the sheet detection position of the upstream sheet sensor and a distance from the sheet detection position of the sheet sensor to the sheet detection position of the downstream sheet sensor; 2. The image forming apparatus according to claim 1, wherein:

3. An image forming apparatus as described in claim 2, characterized in that when there are multiple upstream sheet sensors and multiple downstream sheet sensors, the specified time is set based on the longer of the distance from the sheet detection position of the sheet sensor to the sheet detection position of the upstream sheet sensor that is closest to the sheet sensor on the conveying path and the distance from the sheet detection position of the sheet sensor to the sheet detection position of the downstream sheet sensor that is closest to the sheet sensor on the conveying path, and the second linear speed.

4. 4. The image forming apparatus according to claim 1, wherein the sheet sensor is a reflective sensor that detects the print sheet in a non-contact manner.

5. 4. The image forming apparatus according to claim 1, further comprising a cleaning member for cleaning the conveyor belt.

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