Image forming apparatus

Abstract

To detect multi-feed of recording media to which images are transferred without providing a sensor dedicated to detect multi-feed.SOLUTION: An image forming apparatus comprises: a conveying unit that sequentially conveys a plurality of recording media; a transfer member that transfers, by potential difference, an image formed on an image holding body to the recording medium conveyed by the conveying unit; a detection unit that detects the electrical characteristic value of the transfer member when it transfers the image to the recording medium; and a determination unit that compares the electrical characteristic value when the image is transferred to the recording medium earlier with the electrical characteristic value when the image is transferred to the recording medium later to determine multi-feed of the recording media.SELECTED DRAWING: Figure 3

Description

Technical Field

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

Background Art

[0002] The image forming apparatus described in Patent Document 1 includes a transfer belt that carries a toner image, a secondary transfer roll that nips a sheet between the transfer belt and transfers the toner image on the transfer belt to the sheet at the nip position, a current detection unit that detects a current flowing through the secondary transfer roll when a transfer voltage is applied to the secondary transfer roll by a high-voltage power source to transfer the toner image on the transfer belt to the sheet, an arithmetic unit that calculates the electrical resistance during transfer using the current value detected by the current detection unit and the transfer voltage applied to the secondary transfer roll, a comparison determination unit that compares the electrical resistance during transfer calculated by the arithmetic unit with a preset threshold resistance, and determines whether there is an abnormality in the sheet conveyance at the nip position based on the comparison result.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The problem of the present disclosure is to detect double feeding of a recording medium on which an image is transferred without providing a dedicated sensor for detecting double feeding.

Means for Solving the Problems

[0005] An image forming apparatus according to a first aspect of the present disclosure is characterized by comprising: a transport unit that sequentially transports a plurality of recording media; a transfer member that transfers an image formed on an image holder to a recording media transported by the transport unit by a potential difference; a detection unit that detects the electrical characteristic value of the transfer member when transferring an image to a recording media; and a determination unit that determines double feeding of a recording media by comparing the electrical characteristic value when the image is first transferred to the recording media with the electrical characteristic value when the image is later transferred to the recording media.

[0006] An image forming apparatus according to a second aspect of the present disclosure is characterized in that, in the image forming apparatus described in the first aspect, the determination unit determines that a double feed has occurred when the rate of change of the electrical characteristic value sequentially detected by the detection unit exceeds a threshold.

[0007] An image forming apparatus according to a third aspect of this disclosure is characterized in that, in the image forming apparatus described in the second aspect, the determination unit determines double feeding using the rate of change between an electrical characteristic value detected earlier with respect to the electrical characteristic value determined to be double feeding and an electrical characteristic value detected after the electrical characteristic value determined to be double feeding.

[0008] The image forming apparatus according to the fourth aspect of this disclosure is characterized in that, in the image forming apparatus according to any one of the first to third aspects, a notification unit is provided that notifies the user of a double feed when the determination unit determines that a double feed has occurred.

[0009] An image forming apparatus according to a fifth aspect of this disclosure is an image forming apparatus according to a fourth aspect, further comprising a display unit for displaying information about image forming, wherein the notification unit displays a double feed on the display unit. [Effects of the Invention]

[0010] The image forming apparatus according to the first aspect of this disclosure can detect double feeding of the recording medium on which an image is transferred without providing a dedicated sensor for detecting double feeding.

[0011] The image forming apparatus according to the second aspect of this disclosure can suppress the decrease in accuracy of double feeding detection when different types of paper are used, compared to the case in which double feeding is determined when the difference in the absolute values ​​of the sequentially detected electrical characteristic values ​​exceeds a threshold.

[0012] The image forming apparatus according to the third aspect of this disclosure can suppress the occurrence of misjudgments compared to a method in which double feeding is determined using the rate of change between the electrical characteristic value when double feeding is determined and the electrical characteristic value detected after the electrical characteristic value when double feeding is determined.

[0013] The image forming apparatus according to the fourth aspect of this disclosure can notify the user of a double feed.

[0014] The image forming apparatus according to the fifth aspect of this disclosure can notify the user of a double feed through visual means. [Brief explanation of the drawing]

[0015] [Figure 1] This is a schematic diagram showing an image forming apparatus according to an embodiment of the present disclosure. [Figure 2] This is a configuration diagram showing the image unit of an image forming apparatus according to an embodiment of the present disclosure. [Figure 3] This is a configuration diagram showing the secondary transfer roll and other components of an image forming apparatus according to an embodiment of the present disclosure. [Figure 4] (A)(B) These are block diagrams showing the control unit of an image forming apparatus according to the present disclosure. [Figure 5] This is a flowchart showing the process for detecting double feeding in an image forming apparatus according to an embodiment of the present disclosure. [Figure 6] This diagram shows a table illustrating the transfer voltage when transferring a toner image to a sheet member in an image forming apparatus according to an embodiment of the present disclosure. [Modes for carrying out the invention]

[0016] An example of an image forming apparatus according to an embodiment of the present disclosure will be described with reference to FIGS. 1 to 6. Note that the arrow H shown in each figure is in the vertical direction and indicates the up and down direction of the apparatus, and the arrow W is in the horizontal direction and indicates the width direction of the apparatus.

[0017] (Overall Configuration of Image Forming Apparatus 10) As shown in FIG. 1, the image forming apparatus 10 includes a paper storage unit 12, a main operation unit 14, an original document reading unit 16, and a display unit 40, which are arranged in order from the lower side to the upper side in the up and down direction of the apparatus. Further, the image forming apparatus 10 includes a conveyance unit 18 that conveys a sheet member P as a recording medium, and a management unit 20 that manages the operations of each unit.

[0018] In the paper storage unit 12, the sheet member P is stored. In the main operation unit 14, image formation is performed on the sheet member P conveyed from the paper storage unit 12. In the original document reading unit 16, the image of the original document is read. In the display unit 40, a screen for the user to exchange information with the image forming apparatus 10 and information about image formation are displayed.

[0019] 〔Paper Storage Unit 12〕 As shown in FIG. 1, the paper storage unit 12 includes a first storage unit 22, a second storage unit 24, a third storage unit 26, and a fourth storage unit 28 that can store sheet members P of different sizes. Further, the first storage unit 22, the second storage unit 24, the third storage unit 26, and the fourth storage unit 28 each include a feeding roll 32 that feeds out the stored sheet members P one by one, and an anti-duplication roll 34 that conveys the fed-out sheet members P one by one to the conveyance path 30 in the image forming apparatus 10.

[0020] 〔Conveyance Unit 18〕 As shown in FIG. 1, the conveying unit 18 includes a plurality of conveying rollers 36 that receive the sheet member P from the double-feed prevention roller 34 and convey it one by one along the conveying path 30. Further, the conveying unit 18 is disposed upstream of a transfer position T (hereinafter simply referred to as the "sheet conveying direction") of the sheet member P, stops one end of the sheet member P, and has an alignment roller 38 that feeds out the sheet member P to the secondary transfer position at a determined timing.

[0021] And, the upstream portion in the sheet conveying direction in the conveying path 30 extends upward from below on one side in the apparatus width direction. Further, the downstream portion in the sheet conveying direction in the conveying path 30 extends from one side to the other side in the apparatus width direction and is connected to a discharge portion 80 where the sheet member P is discharged to the outside of the apparatus main body 10a.

[0022] Furthermore, at the downstream end in the sheet conveying direction in the conveying path 30, a duplex conveying path 31 for conveying and inverting the sheet member P to perform an image on the back surface of the sheet member P is connected.

[0023] The duplex conveying path 31 includes a switchback path 31a, and the sheet member P sent out from the switchback path 31a is inverted front and back and is sent into the upper end portion of the upstream portion in the sheet conveying direction in the conveying path 30.

[0024] Also, at the upper end portion of the upstream portion in the sheet conveying direction in the conveying path 30, a manual feed path 33 for conveying the sheet member P supplied from the manual feed portion 82 outside the apparatus main body 10a is connected.

[0025] 〔Main operation unit 14〕 As shown in FIG. 1, the main operation unit 14 includes an image forming unit 60 that forms a toner image, a transfer unit 68 that transfers the toner image to the sheet member P, and a fixing device 58 that fixes the toner image formed on the sheet member P to the sheet member P.

[0026] -Image forming unit 60- The image forming unit 60 includes image forming units 64K, 64C, 64M, and 64Y, which form toner images of yellow (Y), magenta (M), cyan (C), and black (K). In the following description, unless otherwise specified, the YMCK at the end of the code may be omitted.

[0027] As shown in Figure 2, the image forming unit 64 is composed of a cylindrical photoreceptor drum 62 that rotates in the direction of arrow A in the figure, a charger 42 that charges the photoreceptor drum 62, a developer 44 that develops the electrostatic latent image (described later) and visualizes it as a toner image, and a cleaning member 46.

[0028] Furthermore, the image forming unit 60 is equipped with exposure devices 66K, 66C, 66M, and 66Y (see Figure 1) that irradiate exposure light onto a photoreceptor drum 62 charged by a charger 42 to form an electrostatic latent image.

[0029] In this configuration, the charger 42 charges the rotating photoreceptor drum 62, and the exposure device 66 irradiates the charged photoreceptor drum 62 with exposure light to form an electrostatic latent image. Furthermore, the developer 44 develops the electrostatic latent image and visualizes it as a toner image.

[0030] -Transfer Unit 68- As shown in Figure 1, the transfer unit 68 comprises an endless transfer belt 48, a primary transfer roll 50 that transfers a toner image from the photoreceptor drum 62 (see Figure 2) to the transfer belt 48, and a secondary transfer roll 52 that transfers the toner image on the transfer belt 48 to the sheet member P. Furthermore, the transfer unit 68 comprises an auxiliary roll 54 positioned on the opposite side of the secondary transfer roll 52 with the transfer belt 48 in between, and a plurality of rolls 56 around which the transfer belt 48 is wound. The transfer belt 48 is an example of an image holder.

[0031] The transfer belt 48 is triangular in shape, with its apex pointing downwards when viewed from the depth direction of the device. The photoreceptor drum 62 and the primary transfer roll 50 sandwich the base portion of the triangular transfer belt 48. The secondary transfer roll 52 and the auxiliary roll 54 sandwich the apex portion of the triangular transfer belt 48.

[0032] Furthermore, of the multiple rolls 56, one roll 56 functions as a drive roll that rotates the transfer belt 48 in the direction of arrow C in the figure.

[0033] Further details regarding the secondary transfer roll 52 and auxiliary roll 54 will be described later.

[0034] (Operation of the image forming apparatus) In the image forming apparatus 10, an image is formed as follows.

[0035] First, the chargers 42 of each color shown in Figure 2 uniformly negatively charge the surface of the rotating photoreceptor drums 62 of each color at a predetermined potential. Subsequently, based on the image data read by the document reading unit 16 (see Figure 1), the exposure devices 66 of each color (see Figure 1) irradiate exposure light onto the charged surface of the photoreceptor drums 62 of each color to form an electrostatic latent image.

[0036] As a result, electrostatic latent images corresponding to the image data are formed on the surface of each color photoreceptor drum 62. Furthermore, each color developer 44 develops these electrostatic latent images and visualizes them as toner images. The toner images formed on the surface of each color photoreceptor drum 62 are then sequentially transferred to the transfer belt 48 by the primary transfer roll 50.

[0037] Therefore, the sheet member P, which is sent to the transport path 30 by the delivery roll 32 from any of the first storage section 22, second storage section 24, third storage section 26, and fourth storage section 28 shown in Figure 1, is sent to the transfer position T where the transfer belt 48 and the secondary transfer roll 52 come into contact. At the transfer position T, the sheet member P is transported between the transfer belt 48 and the secondary transfer roll 52, and the toner image on the transfer belt 48 is transferred to the sheet member P. Specifically, the toner image on the transfer belt 48 is transferred to the sheet member P by the potential difference that occurs between the auxiliary roll 54 and the secondary transfer roll 52.

[0038] Furthermore, the fixing device 58 fixes the toner image transferred to the sheet member P onto the sheet member P. The sheet member P with the toner image fixed is then discharged to the discharge section 80 outside the main body of the device 10a.

[0039] (Main part configuration) Next, the secondary transfer roll 52 and auxiliary roll 54 will be described.

[0040] The secondary transfer roll 52 is grounded, as shown in Figure 3. Furthermore, the image forming apparatus 10 includes a voltage application unit 72 for applying a secondary transfer voltage to the auxiliary roll 54. The transfer member 84, which transfers the toner image on the transfer belt 48 to the sheet member P, includes the secondary transfer roll 52, the auxiliary roll 54, and the voltage application unit 72.

[0041] Furthermore, the image forming apparatus 10 is equipped with a voltage detection unit 74 that detects the secondary transfer voltage (hereinafter sometimes referred to as "transfer voltage") applied between the auxiliary roll 54 and the secondary transfer roll 52. The transfer voltage detected by this voltage detection unit 74 is managed by the control unit 20. The voltage detection unit 74 is an example of a detection unit, and the transfer voltage is an example of an electrical characteristic value.

[0042] In this configuration, the voltage application unit 72 applies a secondary transfer voltage to the auxiliary roll 54, creating a potential difference at the transfer position T between the auxiliary roll 54 and the secondary transfer roll 52. As the sheet member P is transported while being sandwiched between the transfer belt 48 and the secondary transfer roll 52, the toner image on the transfer belt 48 is transferred to the sheet member P by the potential difference created at the transfer position T. In this embodiment, as an example, the transfer member 84 is controlled by a constant current.

[0043] Next, we will mainly describe the configuration of the part of the control unit 20 that manages the transfer voltage detected by the voltage detection unit 74.

[0044] [Hardware configuration of the management unit 20] As shown in Figure 4(A), the management unit 20 includes a CPU (Central Processing Unit) 20a, a ROM (Read Only Memory) 20b, a RAM (Random Access Memory) 20c, storage 20d, and a communication interface (I / F) 20e. Each component is connected to the others via a bus 21 so that they can communicate with each other.

[0045] The CPU 20a is the central processing unit, which executes various programs and controls various components. Specifically, the CPU 20a reads programs from ROM 20b or storage 20d and executes them using RAM 20c as the working area. The CPU 20a controls each component and performs various calculations according to the programs recorded in ROM 20b or storage 20d.

[0046] In this embodiment, the ROM 20b or storage 20d stores a calculation program that calculates the rate of change of the transfer voltage sequentially detected by the voltage detection unit 74.

[0047] ROM20b stores various programs and data. RAM20c temporarily stores programs or data as a working area. Storage20d consists of an HDD (Hard Disk Drive) or SSD (Solid State Drive) and stores various programs, including the operating system, and various data. Communication interface20e is an interface for the management unit 20 to communicate with each unit.

[0048] When executing the management program described above, the management unit 20 uses the hardware resources described above to implement various functions. The functional configuration implemented by the management unit 20 will be described below.

[0049] [Functional Configuration of Management Department 20] As shown in Figure 4(B), the management unit 20 includes a recording unit 70a that acquires and records the transfer voltage, and a determination unit 70b that compares the rate of change between the previous transfer voltage and the subsequent transfer voltage recorded in the recording unit 70a and determines whether the rate of change is above a predetermined threshold. Furthermore, the management unit 20 includes a notification unit 70c that notifies the information determined by the determination unit 70b. Each functional configuration is realized by the CPU 20a reading and executing a management program stored in the ROM 20b or storage 20d.

[0050] (Function of the main components) Next, the operation of the main components will be explained using the flowchart shown in Figure 5. Specifically, the process of detecting double feeding, where sheet members P are transported in stacks, will be explained using the flowchart shown in Figure 5.

[0051] When the user instructs the image forming apparatus 10 to execute a print job that forms toner images on multiple sheet members P, the process proceeds to step S100. The print job executed is a so-called single-sided print, in which images are formed only on the surface of the sheet members P.

[0052] In step S100, the voltage detection unit 74 detects the transfer voltage for transferring the toner image to the sheet member P at the transfer position T, and the recording unit 70a acquires and records the transfer voltage detected by the voltage detection unit 74. Once the transfer voltage is recorded, the process proceeds to step S200.

[0053] In step S200, the determination unit 70b determines whether there is a previously recorded transfer voltage (hereinafter referred to as "previous transfer voltage") in relation to the recorded transfer voltage (hereinafter referred to as "later transfer voltage"). Here, the previous transfer voltage is the transfer voltage used to transfer the toner image to the previous sheet member P.

[0054] If the previous transfer voltage has been recorded, the process proceeds to step S300. On the other hand, if the previous transfer voltage has not been recorded, the process returns to step S100 and the transfer voltage is recorded again.

[0055] In step S300, the determination unit 70b calculates the rate of change of the subsequent transfer voltage relative to the previous transfer voltage, and proceeds to step S400.

[0056] In step S400, the determination unit 70b determines whether the rate of change calculated in step S300 is equal to or greater than a predetermined threshold set for determining double feeding.

[0057] Figure 6 shows an example in a table of the number of sheet members P transported, the transfer voltage, and the rate of change of the subsequent transfer voltage relative to the previous transfer voltage. The table in Figure 6 shows an example in which six sheet members P of the same paper type are transported from the same storage unit using constant current control. The predetermined threshold for the rate of change is set to +40%.

[0058] In the example shown in this table, the rate of change of the transfer voltage for transferring the toner image to the fifth sheet member P is +57.1% compared to the previous transfer voltage, which is above the threshold.

[0059] Thus, if the rate of change of the transfer voltage is greater than or equal to the threshold, the determination unit 70b determines that a double feed has occurred and proceeds to step S500. On the other hand, if the rate of change of the transfer voltage is less than the threshold, the process returns to step S100 and the transfer voltage is recorded again.

[0060] In this case, when determining the sixth double feed as shown in the table in Figure 6, since the fifth sheet has been determined to be a double feed, the rate of change in the transfer voltage for transferring the toner image to the sixth sheet member P is calculated by comparing it with the transfer voltage for transferring the toner image to the fourth sheet member P. In other words, the determination unit 70b determines a double feed using the rate of change between the transfer voltage detected before the transfer voltage that was determined to be a double feed and the transfer voltage detected after the transfer voltage that was determined to be a double feed.

[0061] In step S500, the notification unit 70c displays the occurrence of a double feed on the display unit 40, and the process proceeds to step S600.

[0062] In step S600, the determination unit 70b determines whether the transfer of toner images performed by the print job has been completed. If the transfer of toner images to the sheet material P has been completed, the series of steps ends. On the other hand, if the transfer of toner images to the sheet material P has not been completed, the process returns to step S100 and the transfer voltage is recorded again.

[0063] (summary) As explained above, the image forming apparatus 10 determines double feeding of the sheet member P by comparing the first transfer voltage with the second transfer voltage. Therefore, double feeding of the sheet member P to which the toner image is transferred can be detected without the need for a dedicated sensor to detect double feeding.

[0064] Furthermore, in the image forming apparatus 10, the determination unit 70b determines that a double feed has occurred when the rate of change of the transfer voltage, which is sequentially detected by the voltage detection unit 74, exceeds a threshold. Therefore, compared to the case where a double feed is determined when the difference in the absolute values ​​of the sequentially detected transfer voltages exceeds a threshold, the decrease in the accuracy of double feed detection when different types of paper are used is suppressed.

[0065] Furthermore, in the image forming apparatus 10, if a double feed is detected, the determination unit 70b determines the double feed using the rate of change between the transfer voltage detected before the transfer voltage that was determined to be a double feed and the transfer voltage detected after the transfer voltage that was determined to be a double feed. Therefore, compared to the case where a double feed is determined using the rate of change between the transfer voltage at the time of the double feed determination and the transfer voltage detected after the transfer voltage that was determined to be a double feed, the occurrence of misdetermination is suppressed.

[0066] Furthermore, in the image forming apparatus 10, if a double feed is detected, the occurrence of a double feed is displayed on the display unit 40. In this way, the user is notified of the double feed.

[0067] Furthermore, in the image forming apparatus 10, if a double feed is detected, the occurrence of a double feed is displayed on the display unit 40. In this way, the user is notified of the double feed visually.

[0068] Although this disclosure has described specific embodiments in detail, it will be apparent to those skilled in the art that this disclosure is not limited to these embodiments, and that various other embodiments are possible within the scope of this disclosure. For example, in the above embodiment, the transfer voltage was used as the electrical characteristic value for detecting double feeding, but instead of the transfer voltage, the transfer current may be used in the case of constant voltage control, or the resistance value of the sheet member P sandwiched between the transfer belt 48 and the secondary transfer roll 52 may be used.

[0069] Furthermore, in the above embodiment, double feeding was determined using the rate of change of the later transfer voltage relative to the earlier transfer voltage. However, for example, double feeding may be determined using the difference between the absolute value of the earlier transfer voltage and the absolute value of the later transfer voltage. Moreover, if toner images have been transferred to multiple sheet members P in advance, double feeding may be determined using the rate of change of the later transfer voltage relative to the average value of their transfer voltages.

[0070] Furthermore, although not specifically described in the above embodiment, in the case of double-sided printing, double feeding is determined using the rate of change between the transfer voltage when transferring the toner image to the surface of the first sheet member P and the transfer voltage when transferring the toner image to the surface of the second sheet member P.

[0071] Furthermore, although not specifically described in the above embodiment, an error such as incorrect paper insertion may be detected when the absolute value of the later transfer voltage becomes smaller than the absolute value of the earlier transfer voltage by a negative rate of change, and when this negative rate of change exceeds a predetermined threshold.

[0072] Furthermore, although not specifically described in the above embodiment, when toner images are sequentially superimposed onto a single sheet member P for each color, the double feeding of the sheet member P is determined using the transfer voltage at the time the toner image is first transferred to the sheet member P.

[0073] Furthermore, although not specifically described in the above embodiment, the transport of the sheet member P may be stopped if double feeding is detected.

[0074] Furthermore, in the above embodiment, the user was notified of the double feed through visual means, but the user may also be notified of the double feed through sense of smell, hearing, etc.

[0075] While preferred embodiments of the present disclosure have been described in detail above with reference to the attached drawings, the present disclosure is not limited to such examples. It is clear to any person with ordinary skill in the art to which the present disclosure pertains that various modifications or alterations may be conceived within the scope of the technical idea set forth in the claims, and these will naturally also be understood to fall within the technical scope of the present disclosure. [Explanation of Symbols]

[0076] 10 Image forming apparatus 18 Conveying section 40 Display section 48 Transfer belt (an example of an image holder) 70b Judgment part 70c notification section 74 Voltage detection unit (an example of a detection unit) 84 Transfer Member

Claims

1. A transport unit that sequentially transports multiple recording media, A transfer member that transfers an image formed on an image holder to a recording medium transported by the transport unit by a potential difference, A detection unit for detecting the electrical characteristic values ​​of the transfer member when transferring an image to a recording medium, A determination unit that determines whether a recording medium is being double-fed by comparing the electrical characteristic values ​​when transferring an image to the first recording medium with the electrical characteristic values ​​when transferring an image to the second recording medium after the image has been transferred to the first recording medium, An image forming apparatus equipped with the following features.

2. The determination unit determines that a double feed has occurred when the rate of change of the electrical characteristic value sequentially detected by the detection unit exceeds a threshold. The image forming apparatus according to claim 1.

3. The determination unit determines a double feed using the rate of change between the electrical characteristic value detected earlier and the electrical characteristic value detected after the electrical characteristic value that was determined to be a double feed. The image forming apparatus according to claim 2.

4. The system includes a notification unit that notifies the user of a double feed when the determination unit determines that a double feed has occurred. An image forming apparatus according to any one of claims 1 to 3.

5. It is equipped with a display unit that shows information about image formation, The notification unit displays a double feed on the display unit. The image forming apparatus according to claim 4.

Images