Image forming apparatus

Abstract

To provide an image formation device that switches between an image formation conveyance path and a purge conveyance path based upon a quantity of change in conveyance load for a sheet.SOLUTION: Through a conveyance path 23, a sheet S is conveyed. An image formation part 14 forms an image on the sheet S. An image formation conveyance path 24 extends to a conveyance-directional downstream side of the conveyance path 23, and the sheet S is conveyed to the image formation part 14. A purge conveyance path 25 extends to a conveyance-directional downstream side of the conveyance path 23, branches off from the image formation conveyance path 24, and conveys the sheet S to be purged. A detection part 22 detects a quantity of change in conveyance load depending upon a sheet type. A determination part 43 determines whether the sheet S can be conveyed to the image formation path 24 based upon the quantity of change in conveyance load, and outputs determination information. A switching part 27 switches between the image formation conveyance path 24 and the purge conveyance path 25 based upon the determination information.SELECTED DRAWING: Figure 3

Description

Technical Field

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

Background Art

[0002] Patent Document 1 discloses a paper transport device that suppresses contact between paper and a guide member and can configure a desired transport path.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, Patent Document 1 does not disclose an invention that switches a transport path based on the amount of change in transport load according to the type of sheet.

[0005] An object of the present invention is to provide an image forming apparatus that switches an image forming transport path for forming an image on a sheet and a purge transport path for purging the sheet based on the amount of change in transport load according to the type of sheet.

Means for Solving the Problems

[0006] The image forming apparatus according to the present invention includes a conveyance path, an image forming unit, an image forming conveyance path, a purge conveyance path, a detection unit, a determination unit, and a switching unit. The conveyance path conveys a sheet. The image forming unit forms an image on the sheet. The image forming conveyance path extends downstream in the conveyance direction of the conveyance path and conveys the sheet to the image forming unit. The purge conveyance path extends downstream in the conveyance direction of the conveyance path, branches off from the image forming conveyance path, and conveys a sheet to be purged. The detection unit detects a change amount of the conveyance load based on the sheet type. The determination unit determines whether or not the sheet can be conveyed to the image forming conveyance path based on the change amount and outputs determination information. The switching unit switches between the image forming conveyance path and the purge conveyance path based on the determination information.

Effect of the Invention

[0007] According to the image forming apparatus of the present invention, it is possible to switch between an image forming conveyance path for forming an image on a sheet and a purge conveyance path for purging the sheet based on a change amount of the conveyance load based on the sheet type.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Best Mode for Carrying Out the Invention

[0009] Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals and description thereof will not be repeated. Also, in the present embodiment, the X-axis, Y-axis, and Z-axis orthogonal to each other are shown in the drawings. The Z-axis is parallel to the vertical plane, and the X-axis and Y-axis are parallel to the horizontal plane.

[0010] In the present embodiment, in the image forming unit 14, the Z-axis direction, which is the conveyance direction of the sheet S, may be described as the main scanning direction. The Y-axis direction may be described as the sub-scanning direction. The X-axis direction may be described as the direction intersecting the main inspection direction and the sub-scanning direction.

[0011] With reference to FIGS. 1 to 6, the multifunction machine 1 (image forming apparatus 3) according to the embodiment of the present invention will be described. FIG. 1 is a diagram showing the multifunction machine 1 (image forming apparatus 3) according to the embodiment of the present invention. FIG. 2 is a diagram showing the conveyance path 23 of the image forming apparatus 3 according to the present embodiment. FIG. 3 is a diagram showing the image forming conveyance path 24 and the purge conveyance path 25 of the image forming apparatus 3 according to the present embodiment. FIGS. 4(a) and (b) are diagrams showing the phase difference detection unit 42 of the image forming apparatus 3 according to the present embodiment. FIG. 5 is a diagram showing the control unit 17 of the image forming apparatus 3 according to the present embodiment. FIGS. 6(a) and (b) are diagrams showing the processing of the phase difference detection unit 42 of the image forming apparatus 3 according to the present embodiment.

[0012] With reference to FIG. 1, the multifunction machine 1 will be described. The multifunction machine 1 is, for example, an MFP (Multi Function Printer) that combines functions such as a scanner, a copier, a printer, a duplicator, a facsimile, and others. The multifunction machine 1 is, for example, a copier, a facsimile, or a multifunction machine having these functions.

[0013] As shown in FIG. 1, the multifunction machine 1 includes a document reading device 2 and an image forming device 3.

[0014] The original document reading device 2 includes, for example, an original document feeding device 10 and an image reading device 11. The original document feeding device 10 includes, for example, an original document tray, an original document feeding unit, an original document sensor, and an original document discharging unit. An example of the original document feeding device 10 is an ADF (Auto Document Feeder).

[0015] The image reading device 11 has an optical system. The optical system includes, for example, a light emitting unit, a lens, a mirror, and a light receiving unit.

[0016] The image reading device 11 reads an image from the original document G conveyed by the original document feeding device 10. The image reading device 11 generates image data from the read image. An example of the image reading device 11 is a scanner using the CIS (Contact Image Sensor) method or the CCD (Charge Coupled Devices) method.

[0017] Next, for example, in the case of an electrophotographic image forming device 3, it includes a sheet feeding device 12, a sheet conveying device 13, an image forming unit 14 (image forming device 14), a fixing device 15, and a sheet discharging device 16.

[0018] When the image forming device 3 is, for example, an inkjet printer, the image forming unit 14 includes at least an ink tank (not shown), an ink cartridge, and an ink head.

[0019] When the image forming device 3 is, for example, an inkjet printer, the fixing unit 15 may not be provided.

[0020] The sheet feeding device 12 includes, for example, a sheet tray and a pickup roller.

[0021] The sheet conveying device 13 includes a conveying roller 20, a conveying motor 21, a detection unit 22, a conveying path 23 (bent conveying path 23), an image forming conveying path 24, a purge conveying path 25, a purge tray 26, and a switching unit 27.

[0022] The conveying roller 20 is disposed in the conveying path 23 and conveys the sheet S. The conveying roller 20 conveys the sheet S to the conveying path 23 while rotating. A plurality of conveying rollers 20 may be arranged in the conveying path 23.

[0023] The conveying motor 21 rotationally drives the conveying roller 20.

[0024] As shown in FIGS. 4(a) and (b), the detection unit 22 detects the change amount of the conveying load based on the sheet type. The detection unit 22 includes a light emitting unit 30, an encoder 31, a light receiving unit 32, and a sheet thickness detection unit 33.

[0025] The light emitting unit 30 emits light. An example of the light emitting unit 30 is a light emitting diode (LED).

[0026] The encoder 31 has a transmission part that transmits the light emitted from the light emitting unit 30 and a shielding part that shields the light, which are alternately arranged in an annular shape and rotate in synchronization with the conveying motor 21. The encoder 31 may be arranged coaxially with the conveying motor 21.

[0027] The light receiving unit 32 receives the transmitted light that has passed through the encoder 31 and outputs light receiving information based on the amount of received light. An example of the light receiving unit 32 is a CCD (Charged Coupled Device).

[0028] As shown in FIG. 4(b), the sheet thickness detection unit 33 biases the conveying roller 20 with an elastic member, detects the sheet thickness based on the amount of expansion and contraction of the elastic member, and outputs sheet thickness information. The sheet thickness detection unit 33 will be described later.

[0029] As shown in FIG. 3, the conveying path 23 conveys the sheet S fed from the sheet feeding device 12. The conveying path 23 extends at least to the image forming conveying path 24 and the purge conveying path 25 starting from the sheet feeding device 12.

[0030] The conveyance path 23 may be a bent conveyance path 23 formed in a bent shape. The bent conveyance path 23 may be formed such that the radius of curvature becomes smaller toward the downstream side in the conveyance direction. The sheet S conveyed through the bent conveyance path 23 increases in friction with the bent conveyance path 23 as it is conveyed toward the downstream side in the conveyance direction, imposing a load on the conveyance motor 21. Hereinafter, the conveyance path 23 may be the bent conveyance path 23. Therefore, the description of the conveyance path 23 may be a description regarding the bent conveyance path 23.

[0031] The image formation conveyance path 24 extends to the downstream side in the conveyance direction of the conveyance path 23 and conveys the sheet S to the image forming unit 14.

[0032] The purge conveyance path 25 extends to the downstream side in the conveyance direction of the bent conveyance path 23 and conveys the sheet S to be purged. The purge conveyance path 25 conveys the sheet S determined to be non-conveyable (having high rigidity).

[0033] The purge tray 26 stacks the sheet S conveyed through the purge conveyance path 25 and discharged. As shown in FIG. 3, as an example, a resin tray is disposed outside the machine for the purge tray 26. The purge tray 26 stacks the sheet S conveyed through the purge conveyance path 25 and discharged outside the machine.

[0034] Sheets may have different stiffnesses depending on the type of sheet. Generally, soft sheets or thin sheets have low stiffness. Generally, hard sheets or thick sheets have high stiffness.

[0035] In addition, in order to support the double-sided printing mode, the image forming apparatus 3 may have an inversion unit (not shown) for inverting the sheet surface. Additionally, the image forming apparatus 3 may have a conveyance path 23 with a small radius of curvature.

[0036] When a sheet S with high stiffness enters the inversion section, it is subjected to a large bending stress at the sharp curve (curve with a small radius of curvature) in the inversion section, increasing the conveyance load. Therefore, the sheet S with high stiffness cannot pass through the inversion section and may cause a jam. Accordingly, in the duplex printing mode, when a sheet S with high stiffness that cannot be inverted at the inversion section is conveyed by the conveyance motor 21, it is preferable that the sheet S is not conveyed to the inversion section but is conveyed through the purge conveyance path 25.

[0037] The purge conveyance path 25 is preferably arranged to extend in the same direction as the conveyance motor 21. This is because the sheet S with high stiffness can be easily conveyed from the conveyance motor 21 to the purge conveyance path 25.

[0038] The switching unit 27 switches between the image forming conveyance path 24 and the purge conveyance path 25 based on the determination information output by a determination unit 43 described later. As an example, the switching unit 27 can be realized by a branch plate that is pivotally supported and can pivot in the direction extending to the image forming conveyance path 24 and the direction extending to the purge conveyance path 25.

[0039] Next, as shown in FIG. 1, in the case of an electrophotographic system, the image forming unit 14 forms a toner image (not shown) on the sheet S based on document image data. When the image forming unit 14 is an inkjet printer, an ink image (not shown) is formed on the sheet S based on document image data.

[0040] In the present embodiment, unless otherwise particularly described as an inkjet printer, in principle, the electrophotographic image forming unit 14 will be described.

[0041] The image forming unit 14 includes, for example, an image data input unit (not shown), a charging unit, an exposure unit, a developing unit, a transfer unit, and a cleaning unit.

[0042] The fixing device 15 heats and presses the toner image developed on the sheet S to fix the toner image on the sheet S. The fixing device 15 includes, for example, a fixing belt, a pressure roller, and a heater.

[0043] The fixing belt is a hollow cylindrical belt. The pressure roller is pressed against the fixing belt to form a nip portion with the fixing belt. The pressure roller is rotationally driven by a driving unit (not shown), and rotates the fixing belt by forming a nip portion with the fixing belt.

[0044] The heater is supplied with power from a power source (not shown) to heat the fixing belt. The heater is disposed close to the inner peripheral surface of the fixing belt. The sheet S conveyed to the sheet conveying device 13 passes through the nip portion, is heated by the heater, and the toner image is fixed.

[0045] The sheet discharging unit 16 discharges the sheet S to the outside of the housing of the multifunction machine 1. The sheet discharging unit 16 may include a discharging roller and a discharging tray. The discharging roller discharges the sheet S conveyed by the conveying motor 21 from the fixing device 15 to the discharging tray. The discharging tray stacks the discharged sheets S.

[0046] Next, as shown in FIG. 5, the control unit 17 includes a drive pulse transmitting unit 40, an encoder pulse generating unit 41, a phase difference detecting unit 42, a determination unit 43, and a setting unit 44. Each component of the control unit 17 can be realized by, for example, an ASIC (Application Specific Integrated Circuit).

[0047] As shown in FIG. 6(a), the drive pulse transmitting unit 40 transmits drive pulses for rotating the conveying motor 21.

[0048] As shown in FIG. 6(a), the encoder pulse generating unit 41 generates encoder pulses based on the received light information.

[0049] As shown in FIG. 6(a), the phase difference detecting unit 42 detects the phase difference (delay time) of the encoder pulses with respect to the drive pulses, which is generated when the sheet S is conveyed through the bending conveying path 23.

[0050] Based on the phase difference, the determination unit 43 determines whether the sheet S can be conveyed and outputs determination information indicating the result.

[0051] According to the present embodiment, by using the encoder 31, based on the phase difference between the drive pulse of the conveyance motor 21 transmitted by the drive pulse transmission unit 40 and the encoder pulse generated by the encoder pulse generation unit 41, it is possible to determine whether the sheet S can be conveyed.

[0052] As shown in FIG. 6(b), the determination unit 43 may determine whether the sheet S can be conveyed based on the peak value of the phase difference and output determination information indicating the result.

[0053] In FIG. 6(b), the horizontal axis represents the conveyance time and the vertical axis represents the phase difference. As shown in FIG. 6(b), when the sheet S approaches the conveyance roller 20, a phase difference occurs between the drive pulse of the conveyance motor 21 transmitted by the drive pulse transmission unit 40 and the encoder pulse generated by the encoder pulse generation unit 41.

[0054] That is, due to the conveyance load of the sheet S, a load is applied to the conveyance motor 21, and the encoder pulse output from the detection unit 22 having the encoder 31 is delayed. Therefore, the encoder pulse is delayed with respect to the drive pulse, and a phase difference occurs between the drive pulse and the encoder pulse.

[0055] When the sheet S is further conveyed, the sheet S receives bending stress in the bending conveyance path 23. Therefore, as shown in FIG. 6(b), the conveyance load applied to the conveyance motor 21 increases and reaches the peak value.

[0056] According to the present embodiment, by using the peak value of the phase difference between the drive pulse and the encoder pulse, it is possible to more suitably determine whether the sheet S can be conveyed.

[0057] Based on the change amount of the conveyance load, the determination unit 43 determines whether the sheet S can be conveyed to the image formation conveyance path 24 and outputs determination information.

[0058] An example of the change amount of the conveyance load is the phase difference between the drive pulse and the encoder pulse. An example of the change amount may be the peak value of the phase difference between the drive pulse and the encoder pulse.

[0059] According to the present embodiment, based on the change amount of the conveyance load according to the type of the sheet S, the image formation conveyance path 24 for forming an image on the sheet S and the purge conveyance path 25 for purging the sheet S can be switched.

[0060] The setting unit 44 may set the power supplied to the conveyance motor 21 based on the phase difference. That is, the setting unit 44 may be set to increase the power supplied to the conveyance motor 21 as the phase difference increases.

[0061] According to the present embodiment, even when a sheet S with high stiffness is conveyed, the sheet S can be suitably conveyed by increasing the power supplied to the conveyance motor 21.

[0062] The setting unit 44 may set the power supplied to the conveyance motor 21 based on the peak value of the phase difference. That is, the setting unit 44 may be set to increase the power supplied to the conveyance motor 21 based on the peak value of the phase difference.

[0063] According to the present embodiment, even when a sheet S with high stiffness is conveyed, the sheet S can be conveyed more suitably.

[0064] The setting unit 44 may set the temperature of the heater of the fixing device 15 based on the phase difference.

[0065] The setting unit 44 may set the temperature of the heater of the fixing device 15 based on the peak value of the phase difference.

[0066] According to the present embodiment, even when a sheet S with high stiffness is conveyed, the fixing of the sheet S can be performed more suitably.

[0067] Next, an embodiment in the case where the image forming apparatus 3 is an inkjet printer will be described.

[0068] When the image forming apparatus 3 is an inkjet printer, the configurations different from the electrophotographic method are the image forming unit 14, the sheet thickness detection unit 33, and the setting unit 44.

[0069] The image forming unit 14 has, for example, an ink tank, a conveyance belt, and an inkjet head.

[0070] The ink tank is, as an example, a tank for each color of cyan, magenta, yellow, and black. The ink tank is connected to the inkjet head.

[0071] As described above with reference to FIG. 4(b), the sheet thickness detection unit 33 biases the conveyance roller 20 with an elastic member, detects the sheet thickness based on the amount of expansion and contraction of the elastic member, and outputs sheet thickness information. An example of the elastic member is a spring.

[0072] The conveyance belt conveys the sheet S. The conveyance belt is disposed to face the inkjet head. The inkjet head ejects ink onto the sheet S conveyed by the conveyance belt based on the image data, and forms an image with the ink. An ink image based on the image data is formed on the sheet S.

[0073] The setting unit 44 sets the distance between the conveyance belt and the ink head based on the sheet thickness information.

[0074] A driving device (not shown) can move the conveyance belt relative to the ink head. The driving device can move the conveyance belt closer to the ink head. The driving device can move the conveyance belt farther away from the ink head.

[0075] The setting unit 44 may be set to reduce the distance between the conveyance belt and the ink head based on the sheet thickness information indicating that the sheet thickness is thin. The setting unit 44 may be set to increase the distance between the conveyance belt and the ink head based on the sheet thickness information indicating that the sheet thickness is thick.

[0076] When the setting unit 44 is set to reduce the distance between the conveyance belt and the ink head based on the sheet thickness information indicating that the sheet thickness is thin, the driving device can move the conveyance belt closer to the ink head so as to achieve the set distance.

[0077] When the setting unit 44 is set to increase the distance between the conveyance belt and the ink head based on the sheet thickness information indicating that the sheet thickness is thick, the driving device can move the conveyance belt away from the ink head so as to achieve the set distance.

[0078] According to the present embodiment, the sheet thickness can be measured with a simple configuration.

[0079] Further, according to the present embodiment, the distance between the conveyance belt and the ink head can be set or adjusted based on the sheet thickness, and a suitable distance from the inkjet head to the sheet S can be set or adjusted. Therefore, a stable ink image can be formed regardless of the sheet thickness.

[0080] Next, with reference to FIG. 7, the processing by the image forming apparatus 3 according to the present embodiment will be described. FIG. 7 is a flowchart showing the processing of the image forming apparatus 3 according to the present embodiment.

[0081] As shown in FIG. 7, the flowchart includes steps S10 to S22. Specifically, it is as follows.

[0082] In step S10, the conveyance path 23 conveys the sheet S. The process proceeds to step S12.

[0083] In step S12, the detection unit 22 detects the amount of change in the conveyance load based on the sheet type. The process proceeds to step S14.

[0084] In step S14, the determination unit 43 determines whether the sheet S can be conveyed to the image formation conveyance path 24 based on the amount of change in the conveyance load and outputs determination information.

[0085] If it is determined that conveyance is possible (Yes in step S14), the process proceeds to step S16.

[0086] If it is determined that conveyance is not possible (No in step S14), the process proceeds to step S22.

[0087] In step S14, if Yes, in step S16, the switching unit 27 switches to the image formation conveyance path 24 based on the determination information. The process proceeds to step S18.

[0088] In step S18, the image forming unit 14 forms an image on the sheet S. The process proceeds to step S20.

[0089] In step S20, the control unit 17 determines whether the job has ended.

[0090] If the job has not ended, the process returns to step S12 and the process is repeated.

[0091] When the job ends, the process ends.

[0092] In step S14, if No, in step S22, the switching unit 27 switches to the purge conveyance path 25. Then the process ends.

[0093] The embodiments of the present invention have been described above with reference to the drawings. However, the present invention is not limited to the above-described embodiments, and can be implemented in various forms without departing from the gist thereof. The drawings schematically show each component mainly for easy understanding, and the number of each illustrated component, etc. is different from the actual one for convenience of drawing creation. Also, each component shown in the above embodiments is an example and is not particularly limited, and various changes can be made without substantially departing from the effects of the present invention.

Industrial Applicability

[0094] The present invention can be used in the field of image forming apparatuses.

Explanation of Signs

[0095] 1 Multifunction device 2 Document reading device 3 Image forming device 10 Document feeding device 11 Image reading device 12 Sheet feeding device 13 Sheet conveying device 14 Image forming unit 15 Fixing device 16 Sheet discharging unit 17 Control unit 20 Conveying roller 21 Conveying motor 22 Detection unit 23 Bending conveying path 24 Image forming conveying path 25 Purge conveying path 26 Purge tray 27 Switching unit 30 Light emitting unit 31 Encoder 32 Light receiving unit 33 Sheet thickness detection unit 40 Driving pulse transmitting unit 41 Encoder pulse generation unit 42 Phase difference detection unit 43 Determination unit 44 Setting unit

Claims

1. A conveyance path through which a sheet is conveyed, An image forming unit that forms an image on the sheet, An image forming conveyance path that extends downstream in the conveyance direction of the conveyance path and through which the sheet is conveyed to the image forming unit, A purge conveyance path that extends downstream in the conveyance direction of the conveyance path, branches off from the image forming conveyance path, and through which a sheet to be purged is conveyed, A detection unit that detects a change amount of the conveyance load based on the sheet type, A determination unit that determines whether the sheet can be conveyed to the image forming conveyance path based on the change amount and outputs determination information, A switching unit that switches between the image forming conveyance path and the purge conveyance path based on the determination information An image forming apparatus comprising the above.

2. A conveyance roller disposed in the conveyance path for conveying the sheet, A conveyance motor that rotationally drives the conveyance roller, further comprising The detection unit A light emitting unit that emits light, A transmission unit that transmits the light emitted from the light emitting unit, and a shielding unit that shields light, are alternately arranged, and an encoder that rotates in synchronization with the conveyance motor, A light receiving unit that receives the transmitted light that has passed through the encoder and outputs light receiving information based on the light receiving amount The image forming apparatus according to claim 1, having the above.

3. The conveyance path is a bent conveyance path formed in a bent shape, A drive pulse transmitting unit that transmits a drive pulse for rotating the conveyance motor, An encoder pulse generating unit that generates encoder pulses based on the light receiving information, A phase difference detection unit that detects a phase difference between the encoder pulses with respect to the drive pulse caused by the conveyance of the sheet through the bent conveyance path Further comprising The determination unit determines whether the sheet can be conveyed based on the phase difference, and outputs the determination information indicating whether it is possible, for the image forming apparatus according to claim 2.

4. The determination unit determines whether the sheet can be conveyed based on the peak value of the phase difference, and outputs the determination information indicating whether it is possible, for the image forming apparatus according to claim 3.

5. The image forming apparatus according to claim 3 or claim 4, further comprising a setting unit that sets the power supplied to the conveyance motor based on the phase difference.

6. The image forming apparatus according to claim 3 or claim 4, further comprising a setting unit that sets the power supplied to the conveyance motor based on the peak value of the phase difference.

7. The image forming apparatus according to claim 3 or claim 4, further comprising a setting unit that sets the temperature of the heater of the fixing device based on the phase difference. The image forming apparatus according to claim 3 or claim 4.

8. The image forming apparatus according to claim 3 or claim 4, further comprising a setting unit that sets the temperature of the heater of the fixing device based on the peak value of the phase difference.

9. The detection unit The image forming apparatus according to any one of claims 2 to 8, further comprising a sheet thickness detection unit that biases the conveyance roller with an elastic member, detects the sheet thickness based on the amount of expansion and contraction of the elastic member, and outputs sheet thickness information.

10. The image forming unit has a conveyance belt for conveying a sheet, and an ink head that forms an image on the sheet conveyed by the conveyance belt with ink and, The image forming apparatus according to claim 9, further comprising a setting unit that sets the distance between the conveyance belt and the ink head based on the sheet thickness information.

Images