Static elimination device and image forming system

Abstract

There was a risk that the job would continue without detecting whether maintenance of the non-contact static elimination unit was needed at the appropriate time. [Solution] A static elimination device comprising: an electrode unit that generates ions and a non-contact static elimination unit that removes static electricity from a sheet without contact with the sheet on which an image has been formed in an image forming unit; a static elimination process that removes static electricity from a plurality of sheets transported from the image forming unit by the non-contact static elimination unit; and a control unit that performs a detection process after the static elimination process to detect whether or not maintenance of the electrode unit is required, wherein the control unit performs the detection process when the cumulative operating time, which is the accumulated operating time of the non-contact static elimination unit over multiple static elimination processes, is equal to or greater than a first threshold, and the control unit performs the detection process when the operating time of the non-contact static elimination unit over a single static elimination process is equal to or greater than a second threshold which is less than the first threshold.

Description

[Technical Field]

[0001] This invention relates to an anti-static device and an image forming system. [Background technology]

[0002] In image forming apparatuses that form images on sheets, the sheets can become electrically charged during image formation, causing them to stick together after being discharged, resulting in loading problems. Therefore, an image forming system equipped with a non-contact static elimination unit that removes static electricity from the sheets without contact has been proposed. However, continuous use of a non-contact static elimination unit can lead to a decrease in its static elimination performance due to the deposition of dust and organic matter from the air onto the electrodes of the unit. For this reason, it is desirable for the non-contact static elimination unit to be maintained at appropriate intervals. Reference 1 describes a detection process that determines whether maintenance of the non-contact static elimination unit is necessary when the number of sheets that have been statically eliminated by the unit reaches a threshold. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2024-107617 [Overview of the project] [Problems that the invention aims to solve]

[0004] However, depending on the length of the job, there is a risk that the detection process may not be executed at the appropriate time, causing the job to continue with reduced static elimination capabilities in the non-contact static elimination unit. Therefore, the present invention aims to provide a static elimination device and an image forming system that can execute a detection process to determine whether or not maintenance is required at the appropriate time. [Means for solving the problem]

[0005] One aspect of the present invention is a static elimination device comprising: an electrode section for generating ions, a non-contact static elimination section for removing static electricity from a sheet that has been image-formed in an image-forming section without contact; a static elimination process for removing static electricity from a plurality of sheets transported from the image-forming section by the non-contact static elimination section; and a control unit which performs a detection process to detect whether or not maintenance of the electrode section is required after the static elimination process, wherein the control unit performs the detection process when the cumulative operating time, which is the accumulated operating time of the non-contact static elimination section over multiple static elimination processes, is equal to or greater than a first threshold; and even if the cumulative operating time is less than the first threshold, the control unit performs the detection process when the operating time of the non-contact static elimination section over a single static elimination process is equal to or greater than a second threshold which is less than the first threshold.

[0006] Another embodiment of the present invention is a static elimination device comprising: an electrode section for generating ions, a non-contact static elimination section for eliminating static electricity from a sheet that has been image-formed in an image-forming section without contact; a static elimination process for eliminating static electricity from a plurality of sheets transported to the non-contact static elimination section by the non-contact static elimination section; and a control section which performs a detection process after the static elimination process to detect whether or not maintenance of the electrode section is required, wherein the control section performs the detection process when the cumulative number of sheets that have passed through the non-contact static elimination section in multiple static elimination processes is equal to or greater than the first threshold, and even if the cumulative number is less than the first threshold, the control section performs the detection process when the number of sheets that have passed through in one static elimination process is equal to or greater than the second threshold which is smaller than the first threshold. [Effects of the Invention]

[0007] According to the present invention, it is possible to perform a detection process to determine whether or not maintenance of the non-contact static elimination unit is required at an appropriate time. [Brief explanation of the drawing]

[0008] [Figure 1] Schematic diagram of an image forming system. [Figure 2]Schematic diagram of an anti-static device. [Figure 3] A diagram illustrating an image formation system. [Figure 4] Perspective views of the upper and lower units with the upper unit closed. [Figure 5] A perspective view of the upper and lower units with the upper unit in the open position. [Figure 6] Perspective view of the transport guide for the non-contact static elimination unit. [Figure 7] Control block diagram of the image forming apparatus and static elimination apparatus. [Figure 8] Screen display of the user control panel. [Figure 9] Control flowchart for the static elimination control unit. [Figure 10] A modified example of the control flowchart for the static elimination control unit. [Modes for carrying out the invention]

[0009] Embodiments of the present invention will be described below with reference to the figures. Unless otherwise specifically stated, the dimensions, materials, and relative positions of the components of the image forming apparatus and static eliminator are not intended to limit the scope of the present invention to those components alone. Furthermore, components denoted by the same reference numerals in each figure have the same configuration or function, and redundant explanations of these components have been omitted as appropriate.

[0010] (Example 1) <Schematic configuration of an image forming apparatus> Figure 1 is a diagram of the configuration of the image forming system 300 in this embodiment. The image forming system 300 comprises an image forming apparatus 100 for forming an image on a sheet S, and a static elimination apparatus 200 for eliminating the electric charge on the sheet surface. Details of the static elimination apparatus 200 are omitted in the schematic diagram of the image forming system 300 in Figure 1. The configuration of the static elimination apparatus 200 will be described later (see Figure 2).

[0011] First, the schematic configuration of the image forming apparatus 100 will be described. The image forming apparatus 100 forms an image on a sheet using an electrophotographic process. The image forming apparatus 100 has four image forming units 11Y, 11M, 11C, and 11K that form images of yellow (Y), magenta (M), cyan (C), and black (K), respectively, as a plurality of image forming units. These image forming units 11Y, 11M, 11C, and 11K are arranged in a row along the moving direction of the image transfer surface disposed substantially horizontally on the intermediate transfer belt 6 described later. The image forming unit 11 has a photosensitive drum 1 (1Y, 1M, 1C, 1K), a charging device 2 (2Y, 2M, 2C, 2K), an exposure device 3 (3Y, 3M, 3C, 3K), a developing device 4 (4Y, 4M, 4C, 4K), and a primary transfer roller 5 (5Y, 5M, 5C, 5K).

[0012] As shown in FIG. 1, the photosensitive drums (latent image carriers) 1Y, 1M, 1C, and 1K rotate in the direction of arrow A. The surfaces of the photosensitive drums 1Y, 1M, 1C, and 1K are uniformly charged by the charging devices 2Y, 2M, 2C, and 2K. The exposure devices 3Y, 3M, 3C, and 3K perform exposure based on image information to form an electrostatic latent image on the surfaces of the photosensitive drums 1Y, 1M, 1C, and 1K. The developing devices 4Y, 4M, 4C, and 4K contain toners of yellow (Y), magenta (M), cyan (C), and black (K) colors, respectively. The developing devices 4Y, 4M, 4C, and 4K develop the electrostatic latent image with their respective toners, and toner images are formed on the surfaces of the respective photosensitive drums 1Y, 1M, 1C, and 1K. In this embodiment, the image forming apparatus 100 uses a reversal development method in which toner is attached to the exposure portion of the electrostatic latent image for development.

[0013] The intermediate transfer belt 6 is arranged so as to abut on the surfaces of the photosensitive drums 1Y, 1M, 1C, and 1K. The intermediate transfer belt 6 is stretched over a plurality of stretching rollers 20, 21, 22, 23, 24, and 25 and rotates in the direction of arrow G at a rotational speed of 150 to 470 mm / sec. In this embodiment, the stretching roller 20 is a tension roller configured to control the tension of the intermediate transfer belt 6 to be constant. The stretching roller 22 is a driving roller of the intermediate transfer belt 6. The stretching roller 21 is an inner roller for secondary transfer. The outer roller 9 for secondary transfer sandwiches and conveys the sheet S at the secondary transfer nip (secondary transfer section) between the outer roller 9 and the intermediate transfer belt 6.

[0014] The primary transfer rollers 5Y, 5M, 5C, and 5K are arranged opposite to the respective photosensitive drums 1Y, 1M, 1C, and 1K via the intermediate transfer belt 6, and form a primary transfer nip (primary transfer section) between the respective photosensitive drums 1Y, 1M, 1C, and 1K. In synchronization with the conveyance of the respective color toner images on the surfaces of the photosensitive drums 1Y, 1M, 1C, and 1K to the primary transfer nip section, a transfer bias controlled at a constant voltage with a polarity opposite to that of the toner image is applied to the primary transfer rollers 5Y, 5M, 5C, and 5K. Thereby, the toner images on the respective photosensitive drums 1Y, 1M, 1C, and 1K are transferred onto the intermediate transfer belt 6 (primary transfer).

[0015] A belt surface reading sensor 17 is provided near the intermediate transfer belt 6. The belt surface reading sensor 17 reads the image transferred onto the intermediate transfer belt 6. The belt surface reading sensor 17 is, for example, an optical sensor, and reads the image by irradiating light onto the image on the intermediate transfer belt 6 and receiving the reflected light. For example, the belt surface reading sensor 17 reads an adjustment image for adjusting the image forming conditions formed on the intermediate transfer belt 6. The main body CPU 61 described later analyzes the reading result of the adjustment image by the belt surface reading sensor 17 and performs calibration by feeding back to the image forming conditions.

[0016] The sheet S stored in the cassette 28 is transported to the register roller 8 by the feed roller and the like, and temporarily stopped. The register roller 8 then transports the sheet S to the secondary transfer section in synchronization with the toner image on the intermediate transfer belt 6 being transported to the secondary transfer nip. The pre-secondary transfer transport guide 14 improves the transport accuracy when transporting the sheet S to the secondary transfer section. The high-voltage application unit 10 applies a constant-voltage controlled transfer bias with the opposite polarity to the toner image to the outer roller 9 for secondary transfer. As a result, the toner image on the intermediate transfer belt 6 is transferred to the sheet S (secondary transfer). In this embodiment, since the toner has a negative polarity, a positive voltage is applied to the outer roller 9 for secondary transfer. On the other hand, the tension roller 21, which is the inner roller for secondary transfer, is electrically grounded. However, the high-voltage application unit 10 may apply a constant-voltage controlled transfer bias with the same polarity as the toner to the tension roller 21, which is the inner roller for secondary transfer, and the outer roller 9 for secondary transfer may be electrically grounded.

[0017] The sheet S onto which the toner image has been transferred is transported by the pre-fixing transport device 31, which has a rotating belt. The fixing device 30 heats and pressurizes the sheet S to fix the toner image onto the sheet S. The belt cleaning device 12 electrostatically collects and cleans the residual secondary transfer toner that remains on the intermediate transfer belt 6 without being transferred to the sheet S. The cleaned intermediate transfer belt 6 is repeatedly used for image formation.

[0018] The main display unit 66 is located on the exterior of the image forming system 300. The main display unit 66 may be directly fixed to the exterior, or it may be connected to the device by a cable and placed on top of the device. Alternatively, the main display unit 66 may not be connected to the main device by a cable and may communicate wirelessly using Bluetooth®.

[0019] <Outline configuration of a static elimination device> Figure 2 shows a schematic configuration of the static elimination device 200. Figure 3 shows the image forming system 300. The static elimination device 200 is located downstream of the image forming apparatus 100 with respect to the sheet transport direction. In the secondary transfer described above, a high voltage of positive polarity is applied to the outer roller 9 for secondary transfer (see Figure 1). As a result, the sheet S that has passed through the secondary transfer section has a positive charge on its lower surface and a negative charge on its upper surface due to dielectric polarization. Therefore, if the sheets are loaded onto the discharge tray 60 without static elimination treatment, the contact surfaces of the loaded sheets will have opposite polarities, and there is a risk that the sheets will stick together due to electrostatic force. In this embodiment, the static elimination device 200 removes the charge from the sheet surface (upper and lower surface) using a contact static elimination unit 57 and a non-contact static elimination unit 58 to prevent the sheets from sticking together due to electrostatic force.

[0020] The static eliminator 200 may be directly connected to the image forming apparatus 100, or it may be connected to the image forming apparatus 100 via a sheet processing device such as an inserter. The image forming apparatus 100 and the static eliminator 200 may be integrally formed to constitute the image forming apparatus 100. Alternatively, the image forming apparatus 100 and the static eliminator 200 may be integrally formed to constitute the static eliminator 200. In other words, the housings of the image forming apparatus 100 and the static eliminator 200 may be the same, or they may be separate.

[0021] The static elimination device 200 consists of a housing 59, a contact static elimination unit 57, a non-contact static elimination unit 58, a transport guide 53, and a control unit (not shown) that controls the entire static elimination device 200. Furthermore, the static elimination device 200 includes a static elimination operation unit 54 and a static elimination display unit 56. The sheet S transported from the image forming apparatus 100 has its charge roughly removed by the contact static elimination unit 57, which removes static charge from the sheet while in contact with the sheet. Next, the sheet S has any remaining charge that could not be removed by the contact static elimination unit 58 removed by the non-contact static elimination unit 58, and is discharged outside the static elimination device 200. Details of the contact static elimination unit 57, the non-contact static elimination unit 58, and the static elimination operation unit 54 will be described later.

[0022] The static elimination indicator unit 56 has an LED and, as shown in Figure 3, is located on the top surface 200a (top surface of the device) of the exterior covering the housing 59. Alternatively, the static elimination indicator unit 56 may be located on the front surface 200b (front of the device) of the exterior of the static elimination device 200. The front surface 200b is the surface of the static elimination device 200 facing the front of the device, and the front surface 200b includes inclined surfaces that intersect with the vertical direction. By positioning the static elimination indicator unit 56 on the top surface 200a or the front surface 200b of the exterior of the static elimination device 200, the user can check the display content when using the static elimination device 200. In other words, the static elimination indicator unit 56 only needs to be located on the outside of the exterior. For example, the static elimination indicator unit 56 may be directly fixed to the exterior, or it may be connected to the device by a cable and placed on top of the device. Furthermore, the static elimination indicator unit 56 may not be connected to the main body of the device by a cable, and wireless communication via Bluetooth may be used. The static elimination indicator unit 56 switches between being lit and unlit depending on the state of the ionizer 52 of the non-contact static elimination unit 58.

[0023] In this embodiment, the static elimination indicator unit 56 has an LED, but it is not limited to this and may be a display such as a liquid crystal. Furthermore, the static elimination indicator unit 56 may display information not only about the non-contact static elimination unit 58, but also about the contact static elimination unit 57.

[0024] The static elimination device 200 is provided with a door 250 (Figure 3) that forms the front of the device, and the door 250 is configured to be openable and closable relative to the housing 59 by an opening and closing mechanism (not shown). The opening and closing of the door 250 of the static elimination device 200 is detected by a door sensor 202. By opening the door 250, the user can access the upper unit 401 and the lower unit 402. Specifically, as shown in Figure 2, the upper unit 401 is equipped with a static elimination opposing roller 51 and an ionizer 52a. The lower unit 402 is equipped with a static elimination roller 50, an ionizer 52b and a transport guide 53. The upper unit 401 is also configured to be openable and closable relative to the lower unit 402.

[0025] Figure 4 shows a perspective view of the upper unit 401 and lower unit 402 in the closed state. Figure 5 shows a perspective view of the upper unit 401 and lower unit 402 in the open state. The upper unit 401 has an upper housing 401a made of sheet metal, and the ionizer 52a is fixed to the upper housing 401a. The lower unit 402 has a lower housing 402a made of sheet metal, and the ionizer 52b is fixed to the lower housing 402a. The lower unit 402 is fixed to the housing 59 of the static elimination device 200 so as not to move. On the other hand, the upper unit 401 is provided so as to be rotatable around a pivot axis 405 relative to the lower unit 402. The upper unit 401 is provided with a handle 406. Since the upper unit 401 rotates inside the housing 59, the range in which the upper unit 401 can rotate is restricted by the height of the top surface of the housing 59. In other words, the upper unit 401 is rotatable from a closed position until it contacts the top surface of the housing 59.

[0026] To maintain the static elimination capability of the ionizer 52, the user must perform maintenance on the electrode section of the ionizer 52. Since the upper unit 401 is configured to rotate relative to the lower unit 402, the user can access the electrode section.

[0027] Figure 6 is a perspective view of the conveyor guide 53 that guides the sheet. The conveyor guide 53 has two interlocking holes 532 that interlock with the protrusions 407, described later, located outside the conveyor path in the width direction perpendicular to the sheet conveying direction. On the other hand, as shown in Figure 5, the lower unit 402 has two protrusions 407 that protrude upward outward from the conveyor path in the width direction perpendicular to the sheet conveying direction. The conveyor guide 53 is positioned on the lower unit 402 by interlocking each of the two interlocking holes 532 of the conveyor guide 53 with the protrusions 407 of the lower unit 402. The positioned conveyor guide 53 is then detachably attached to the lower housing 402a of the lower unit 402 by screws 408, which are fixing members located on the front side of the device. However, the conveyor guide 53 may also be configured to be rotatable relative to the lower unit 402 and may be fixed to the lower unit 402 by engaging members, not limited to screw fastening.

[0028] In the configuration described above, when cleaning the static elimination needle 520 of the ionizer 52a, the user first opens the door 250 and rotates the upper unit 401 upward using the handle 406. This allows the user to access the static elimination needle 520 of the ionizer 52a. When cleaning the static elimination needle of the ionizer 52b, after rotating the upper unit 401 upward, the transport guide 53 is removed from the lower unit 402. This allows the user to access the static elimination needle 520 of the ionizer 52b and perform maintenance (cleaning) on ​​the ionizer 52 of the non-contact static elimination unit 58.

[0029] Furthermore, when the user rotates the upper unit 401 upward, the static elimination roller 50 and the static elimination opposing roller 51 are separated. Therefore, when a sheet gets jammed inside the static elimination device, the user can remove the jammed sheet by rotating the upper unit 401.

[0030] <Contact Static Elimination Unit> As shown in Figure 2, the contact static elimination unit 57 includes a static elimination roller 50 and a static elimination opposing roller 51, which are contact static elimination means, and a high-voltage substrate 55 that generates high voltage applied to the static elimination roller 50. The static elimination roller 50 consists of an elastic layer of ion-conductive foamed rubber and a core metal. The static elimination roller 50 has an outer diameter of 20-25 mm, and when measured in a 23°C, 50% RH environment with a voltage of 2 kV applied, the resistance value of the static elimination roller 50 is 1 × 10⁻¹⁶. 5 ~1 × 10 8 It is Ω and is the same material as the outer roller 9 for secondary transfer. The static elimination roller 50 is subjected to a static elimination voltage, which is a DC voltage controlled by a constant voltage by the high-voltage substrate 55. In this embodiment, as described above, the sheet S is transported to the static elimination device 200 with the upper surface of the sheet negatively charged and the lower surface of the sheet positively charged. Therefore, the high-voltage substrate 55 applies a negative voltage to the static elimination roller 50 which is positioned on the lower side of the sheet.

[0031] The static elimination opposing roller 51 is made of stainless steel (SUS) and is electrically grounded (connected to ground). The static elimination opposing roller 51 uses a roller with an outer diameter of 20 to 25 mm and is positioned opposite the static elimination roller 50.

[0032] The static elimination roller 50 and the static elimination opposing roller 51 form a static elimination nip section. The static elimination roller pair, consisting of the static elimination roller 50 and the static elimination opposing roller 51, is in contact with the sheet S and roughly removes the static charge from the sheet. The contact static elimination section 57 in this embodiment has a high static elimination effect because it is in contact with the sheet S and applies voltage directly. On the other hand, the contact static elimination section 57 has the characteristic that the surface potential of the sheet S after static elimination varies greatly, and static elimination tends to be uneven. Therefore, in the static elimination device 200 of this embodiment, a non-contact static elimination section 58 is provided downstream of the contact static elimination section 57 in the sheet transport direction.

[0033] In this embodiment, the static elimination opposing roller 51 rotates by being driven by a static elimination drive motor (not shown) and conveys the sheet S held by the static elimination nip. In this embodiment, the static elimination roller 50 is subjected to a negative voltage by the high-voltage substrate 55 and the static elimination opposing roller 51 is electrically grounded, but this is not limited to this. The static elimination opposing roller 51 may be subjected to a positive voltage by the high-voltage substrate 55 and the static elimination roller 50 may be electrically grounded.

[0034] <Non-contact static elimination unit> The non-contact static elimination unit 58 is composed of ionizers 52 (52a, 52b), which are non-contact static elimination means. In this embodiment, the ionizer 52a is a bar type that extends in the width direction perpendicular to the sheet transport direction, and the ionizer 52a is equipped with a static elimination needle 520 that generates ions and an ionizer control unit 521 that controls the ionizer. The ionizer 52b has the same configuration as the ionizer 52a. The ionizers 52 are positioned above and below the transport guide 53. The ionizer 52a is positioned above the transport guide 53, and the ionizer 52b is positioned below the transport guide 53. An AC bias is applied to the ionizer 52, and positive and negative ions are alternately emitted by corona discharge. Therefore, it is possible to simultaneously eliminate residual charge on both sides of the sheet S at the contact static elimination unit 57, regardless of the polarity direction of the residual charge on the sheet S. The static elimination effect of the sheet S by the non-contact static elimination unit 58 in this embodiment is smaller than that of the contact static elimination unit 57, but the surface potential of the sheet S after static elimination treatment has less variation. Therefore, the non-contact static elimination unit 58 can equalize the surface potential of the sheet S, which has become uneven due to the contact static elimination unit 57. The static elimination needle 520 in this embodiment is an example of an electrode part.

[0035] The transport guide 53 is a member for guiding the sheet and consists of an upper transport guide 53a positioned opposite the upper surface of the sheet and a lower transport guide 53b positioned opposite the lower surface of the sheet. In the vertical direction, the transport guide 53 is positioned below the ionizer 52a located in the upper unit 401 and above the ionizer 52b located in the lower unit 402. That is, in the vertical direction, the transport guide 53 is positioned between the ionizer 52a and the ionizer 52b. The sheet that has passed through the static elimination roller pair, which consists of a static elimination roller 50 and a static elimination opposing roller 51, is transported between the upper transport guide 53a and the lower transport guide 53b. The upper transport guide 53a and the lower transport guide 53b are made of an insulating resin synthesized from PC (polycarbonate) and ABS (acrylonitrile-butadiene-styrene). The volume resistivity of the transport guide in this embodiment is 1 × 10⁻⁶ 14 It is Ω·cm.

[0036] Figure 6 shows a perspective view of the transport guide 53. The transport guide 53a is provided with openings 53c so that ions generated from the static elimination needle 520, which is the ion emission part, are not physically shielded by the transport guide 53. Specifically, the upper transport guide 53a has multiple openings 53c arranged in the width direction perpendicular to the sheet transport direction. The lower transport guide 53b is similarly provided with multiple openings. The upper transport guide 53a and the lower transport guide 53b are fixed to each other by multiple screws 531 provided at both ends in the width direction, forming a single guide unit (transport guide 53).

[0037] In this embodiment, an ionizer 52 is used as the non-contact static elimination unit, but this is not the only option. For example, an AC Corotron method that applies high voltage to a wire may be used as the non-contact static elimination unit. Also, in this embodiment, the ionizer 52 is positioned on the upper and lower sides of the sheet, but this is not the only option. For example, the ionizer 52 may be positioned on only one side of the sheet, either the upper or lower side. Furthermore, the applied high voltage may be a DC voltage instead of an AC voltage.

[0038] <Configuration of the static elimination operation unit> In this embodiment, the static elimination device 200 is equipped with two static elimination units: a contact static elimination unit 57 and a non-contact static elimination unit 58. These two units eliminate static electricity from the sheet. However, the static elimination device 200 can also eliminate static electricity from the sheet by operating only the non-contact static elimination unit 58 without operating the contact static elimination unit 57. For example, for sheets such as plain paper with low electrical resistance, it is possible to sufficiently eliminate static electricity from the sheet by performing static elimination using only the non-contact static elimination unit 58 without using the contact static elimination unit 57. On the other hand, for sheets such as synthetic paper with high electrical resistance, it is preferable to eliminate static electricity from the sheet using both the contact static elimination unit 57 and the non-contact static elimination unit 58. Therefore, the user can arbitrarily change the settings of the static elimination device 200 using the static elimination operation unit 54 according to the type of sheet to be printed in the job.

[0039] The static elimination operation unit 54 is located on the top surface 200a (top surface of the device) of the housing of the static elimination device 200. Alternatively, the static elimination operation unit 54 may be located on the front surface 200b (front surface of the device) of the housing of the static elimination device 200. In this embodiment, the static elimination operation unit 54 includes a mode lever 54a and a dial 54b. The mode lever 54a is a selector switch for manually switching between "ON" and "OFF" (enabled and disabled) the voltage application to the static elimination roller 50 by the high-voltage substrate 55. The sheet is transported even when the mode lever 54a is in the OFF position. Furthermore, the non-contact static elimination unit 58 performs static elimination even when the mode lever 54a is set to OFF.

[0040] The dial 54b is a thumb rotary switch for manually setting the voltage value applied to the static elimination roller 50 by the high-voltage substrate 55. In this embodiment, the static elimination operation unit is equipped with two manual setting units, the mode lever 54a and the dial 54b, so that the user can change the setting of the mode lever without changing the setting of the dial 54b.

[0041] However, the voltage value applied to the static elimination roller 50 is not limited to manual setting by the user. The image forming apparatus 100 may transmit the sheet type to the static elimination device 200, and the static elimination CPU 82 (Figure 7) of the static elimination device 200 may determine the voltage value applied to the static elimination roller 50 based on the sheet type. Alternatively, the static elimination device 200 may be equipped with a detection roller or surface potential sensor to detect the amount of charge on the sheet, measure the amount of charge on the sheet after image formation, and the static elimination CPU 82 may determine the voltage value applied to the static elimination roller 50 according to the measured amount of charge on the sheet. Furthermore, the method for setting the voltage value applied to the static elimination roller 50 may be selectable between manual setting by the user and automatic setting by measuring the amount of charge on the sheet using a detection roller or the like.

[0042] <Image Forming System Block Diagram> Figure 7 is a block diagram showing the electrical configuration of the image forming apparatus 100 and the static elimination device 200. First, the configuration of the image forming apparatus 100 will be described. The image forming apparatus 100 consists of a main CPU 61, ROM 62, RAM 63, EEPROM 64, timer 65, main display unit 66, operation unit 67, communication I / F 68, laser scanner control unit 69, PWM control unit 70, A / D converter 76, and input port 79. These components are connected via a system bus. Furthermore, the PWM control unit 70 is connected to a heater control unit 71, a transport motor 72, a drum motor 73, a fuser motor 74, and a high-voltage generation unit 75. The A / D converter 76 is connected to a temperature sensor 77 and a humidity sensor 78. The input port 79 is connected to a paper feed transport sensor 80 and a paper discharge transport sensor 81.

[0043] The main CPU 61 comprehensively controls image processing and printing based on saved programs and other data.

[0044] ROM 62 and EEPROM 64 store programs and data necessary for the main CPU 61 to perform various processes, and RAM 63 operates as a work area. Timer 65 is used for various timing control by the main CPU 61. The main display unit 66 displays setting information of the image forming apparatus 100 and the processing status of print jobs. The operation unit 67 accepts input of various settings and operation instructions from the user. The communication interface 68 is connected to the static elimination device 200 via a communication cable, and communication for the control of each device takes place.

[0045] The laser scanner control unit 69 is a device that irradiates a photosensitive drum 1, which is charged to form an electrostatic latent image, with laser light modulated according to the image data. In the laser scanner control unit 69, the photosensitive drum 1 is charged to a uniform negative potential by the high-voltage generation unit 75 (described later), and the laser light is deflected by a polygon mirror while irradiating the photosensitive drum. As a result, the negative charge in the area of ​​the photosensitive drum 1 irradiated with laser light is neutralized, and an electrostatic latent image is formed.

[0046] The PWM control unit 70 controls the heater control unit 71, the transport motor 72, the drum motor 73, the fuser motor 74, and the high-pressure generation unit 75. The heater control unit 71 controls the temperature of the fuser device 30. The transport motor 72 drives the transport rollers for transporting the sheets and the pre-fusing transport device 31. The drum motor 73 rotates the photosensitive drum 1. The fuser motor 74 drives the fuser belt and other components of the fuser device 30. The A / D converter 76 performs A / D conversion, converting the analog signals output from the temperature sensor 77 and humidity sensor 78 into digital signals. The input port 79 receives the output signals from the paper feed sensor 80 and the paper discharge sensor 81.

[0047] Next, the configuration of the static elimination device 200 will be described. The static elimination device 200 consists of a static elimination CPU 82, ROM 83, RAM 84, EEPROM 85, timer 86, communication I / F 87, PWM control unit 88, output port 91, and input port 94. In this embodiment, the static elimination control unit 98 includes the static elimination CPU 82, ROM 83, RAM 84, EEPROM 85, and timer 86. These components are connected via a system bus. Furthermore, a static elimination roller motor 89 and a static elimination high-voltage control unit 90 are connected to the PWM control unit 88. An ionizer ON / OFF signal 92 and a maintenance detection mode transition signal 93 are output from the output port 91. Furthermore, a static elimination display unit 56 is connected to the output port 91, and data corresponding to the information to be displayed on the static elimination display unit 56 is output from the output port 91. A maintenance detection signal 95 is input to the input port 94, and a static elimination operation unit 54 is connected to it. The ionizer 52 receives the ionizer ON / OFF signal 92 and the maintenance detection mode transition signal 93 as inputs and outputs the maintenance detection signal 95.

[0048] The static elimination CPU 82 performs various controls necessary for static elimination and ejection of paper based on stored programs, etc. ROM 83 and EEPROM 85 store programs and data necessary for the static elimination CPU 82 to perform various processing. RAM 84 operates as a work area. Timer 86 controls various timings by the static elimination CPU 82 and measures the operating time of the ionizer 52. Communication I / F 87 is connected to the image forming apparatus 100 via a communication cable, and communication for the control of each device takes place.

[0049] The PWM control unit 88 controls the static elimination roller motor 89 and the static elimination high-voltage control unit 90 to eliminate static electricity and transport the paper discharged from the image forming apparatus 100. The output port 91 outputs an ionizer ON / OFF signal 92, a maintenance detection mode transition signal 93, and the ON / OFF status of the static elimination display unit 56. The input port 94 receives a maintenance detection signal 95 and the ON / OFF status of the static elimination operation unit 54.

[0050] The ionizer 52 switches between generating and stopping ions in response to the ionizer ON / OFF signal 92. When the ionizer ON / OFF signal 92 is at the H level, ions are generated; when it is at the L level, ions are stopped. The static elimination CPU 82 controls ion generation and ion stopping by switching the ionizer ON / OFF signal 92 at predetermined timings.

[0051] The maintenance detection mode transition signal 93 is a signal that switches the ionizer to a maintenance detection mode, which determines whether maintenance of the electrode section is necessary. The static elimination CPU 82 switches the maintenance detection mode transition signal 93 from L level to H level at a predetermined timing, thereby switching the ionizer 52 to maintenance detection mode. Note that the maintenance detection mode transition signal 93 switches from H level to L level 100ms after switching from L level to H level.

[0052] The maintenance detection signal 95 is a signal output when the ionizer determines that maintenance of the electrode section is required in the ionizer's maintenance detection mode. Specifically, the ionizer control unit 521 transitions to a maintenance detection mode, triggered by the switching of the maintenance detection mode transition signal 93 from an L level to an H level, in order to determine whether maintenance is required. The ionizer control unit 521 determines whether maintenance is required while in maintenance detection mode. The determination of whether maintenance is required by the ionizer control unit 521 is reflected in the maintenance detection signal 95. Specifically, if the maintenance detection signal 95 remains at an L level for a predetermined time, it indicates that maintenance is not required, and if it is at an H level, it indicates that maintenance is required. The ionizer control unit 521 continues to detect whether maintenance is required in maintenance detection mode until an H-level maintenance detection signal 95 is output or until a predetermined time has elapsed.

[0053] When the static elimination CPU 82 receives a high level output of the maintenance detection signal 95 from the ionizer control unit 521, the static elimination CPU 82 displays a maintenance warning on the main unit display unit 66 via the communication interface 87, recommending that the ionizer 52 be maintained. In the following explanation, the state where the maintenance detection signal 95 is at a high level corresponds to the state where the maintenance detection signal 95 has been output.

[0054] The ionizer 52 includes an ionizer control unit 521, an ion quantity detection sensor 522 for detecting the amount of ions, and an ion balance sensor 523 for detecting the balance between positive and negative ions. During maintenance detection mode, the ionizer control unit 521 uses the ion quantity detection sensor 522 and the ion balance sensor 523 to determine whether the ionizer can output with a normal amount of ions and ion balance.

[0055] <Ionizer maintenance detection and control> When the ionizer 52 detects the maintenance detection mode transition signal 93, the ionizer 52 performs maintenance requirement detection. Specifically, when the ionizer 52 detects the maintenance detection mode transition signal 93, the ionizer 52 starts operating, and the ion quantity detection sensor 522 detects the amount of ions generated per unit time. A predetermined voltage value is applied to the static elimination needle 520, and if the detected amount of ions generated is less than a predetermined amount, the ionizer control unit 521 outputs a maintenance detection signal 95.

[0056] If the detected amount of ions generated exceeds a predetermined amount, the positive or negative voltage applied to the static elimination needle 520 is gradually increased so that the ion balance detected by the ion balance sensor 523 falls within a predetermined range. In this embodiment, a positive voltage (high-voltage pulse of positive polarity) and a negative voltage (high-voltage pulse of negative polarity) are repeatedly applied alternately to the static elimination needle 520. That is, feedback control is performed to adjust the ion balance between positive and negative ions by increasing the amplitude of the positive voltage or the negative voltage. In other words, the positive or negative voltage is controlled so that the ion balance detected by the ion balance sensor 523 approaches 0. Here, an ion balance within a predetermined range means that the difference between the amount of positive and negative ions generated from one of the ionizers 52 in the upper unit 401 and the lower unit 402 is within a predetermined range.

[0057] If the ion balance does not fall within a predetermined range even when the ionizer 52 increases the voltage applied to the static elimination needle 520 to a predetermined upper limit, the ionizer control unit 521 outputs a maintenance detection signal 95. On the other hand, even if the ion balance falls within a predetermined range, the ionizer control unit 521 continues maintenance detection control for 30 seconds after detecting the maintenance detection mode transition signal 93. Maintenance detection control ends 30 seconds after the detection of the maintenance detection mode transition signal 93.

[0058] Specifically, the ionizer control unit 521 outputs a maintenance detection signal 95 when the amount of ions generated by the ionizer 52 is less than a predetermined amount, or when the ion balance is not within a predetermined range. In this embodiment, an ion amount detection sensor 522 and an ion balance sensor 523 are included, but the embodiment is not limited to these. The amount of ions generated and the ion balance may be calculated based on the positive and negative ion currents (return currents) that return to the ionizer circuit via earth.

[0059] In this embodiment, the ionizer detection process detects whether or not maintenance of the ionizer is required, but it is not limited to this. The ionizer detection process may also detect contamination of the ionizer or measure the performance of the ionizer.

[0060] <Screen display of the user control panel> Figure 8 shows the display contents of the main display unit 66 of the image forming apparatus 100. The main display unit 66 displays setting information of the image forming apparatus 100 and the processing status of print jobs. In this embodiment, the main display unit 66 is a touch panel, and in addition to displaying setting information and the processing status of print jobs, it also accepts input of various settings and operation instructions from the user.

[0061] The display screen includes an upper status area 501 located at the top of the screen that displays the status of the image forming apparatus, and a lower status area 502 located at the bottom of the screen that displays warnings for the image forming apparatus 100 and the static eliminator 200. Furthermore, the display screen includes a job setting area 503 between the upper status area 501 and the lower status area 502 where the user sets the job details. Above the job setting area 503 is a setting display area 503a that displays the settings for when a job is submitted to the image forming apparatus 100, as set by the user. The upper status area 501 mainly displays whether the print job is executable, whether the print job is in progress, or whether the print job is not executable.

[0062] Figure 8(a) shows the display screen of the main unit display unit 66 when the maintenance detection signal 95 is not output. Figure 8(b) shows the display screen of the main unit display unit 66 when the maintenance detection signal 95 is output. Specifically, the screen in Figure 8(a) does not display a message prompting the user to clean the ionizer 52. The screen in Figure 8(b) displays a message prompting the user to clean the ionizer 52. In this embodiment, even when a maintenance warning for the ionizer 52 is issued, the main unit CPU 61 can still accept jobs. Therefore, the screen in Figure 8(b) displays a message prompting the user to clean the ionizer 52 in the lower status area 502, and also displays in the upper status area 501 that it is possible to accept jobs.

[0063] Furthermore, as shown in the screen in Figure 8(b), if a maintenance detection signal 95 is output, a guidance key 663 capable of displaying guidance on the cleaning procedure is displayed in the lower status area 502. When the user presses the guidance key 663, the cleaning procedure guidance is displayed on the display screen. Specifically, the cleaning procedure can be explained using illustrations, messages, videos, etc., showing how the user can access the electrode part of the ionizer 52 and how to clean using each cleaning component. For example, as a way to access the electrode part of the ionizer, it may be shown that the upper unit 401 of the static eliminator 200 should be lifted upwards.

[0064] In this embodiment, the notification prompting the user to clean the ionizer is provided using the main display unit 66 of the image forming apparatus 100. However, the notification is not limited to this, and the notification prompting the user to clean the ionizer may also be provided using the static elimination display unit 56 of the static elimination device 200. For example, the notification may be provided by changing the display color, brightness, or blinking cycle of the LEDs on the static elimination display unit 56. For example, the static elimination display unit 56 may be used to notify the user with text or the like using a display. Alternatively, both the main display unit 66 and the static elimination display unit 56 may be used.

[0065] <Explanation of the flowchart> Continuous use of an ionizer may reduce its static elimination performance. Therefore, it is preferable for the user to maintain the ionizer at appropriate intervals. However, if jobs that are slightly shorter than the threshold for triggering maintenance detection are repeatedly performed, the ionizer may not be able to perform maintenance detection, and the jobs may continue with reduced static elimination capacity.

[0066] Therefore, in this embodiment, a first threshold for the cumulative operating time of the ionizer and a second threshold for the operating time of the ionizer in the immediately preceding job are provided as thresholds for executing maintenance necessity detection. The static elimination CPU 82 executes maintenance necessity detection when the conditions of at least one of the first threshold and the second threshold are met.

[0067] Figure 9 is a flowchart of the control performed by the static elimination CPU 82 of the static elimination control unit 98.

[0068] The static elimination CPU 82 obtains sheet information from the main unit CPU 61 via the communication I / F 87 and determines whether or not to start the job (S1001). If the job is started (S1001-Y), the static elimination CPU 82 switches the ionizer ON / OFF signal 92 from L level to H level, starts the output of the ionizer 52 (S1002), and causes the timer 86 to start measuring the operating time of the ionizer 52 (S1003). When the image-formed sheet S passes through the ionizer 52, the static elimination CPU 82 determines whether the print job is finished (S1004). Specifically, it determines whether or not the last sheet of the print job has passed. If the last sheet has passed (S1004-Y), the static elimination CPU 82 switches the ionizer ON / OFF signal 92 from H level to L level and stops the output of the ionizer 52 (S1005). The static elimination CPU 82 terminates the timer 86's measurement of the ionizer 52's operating time (S1006).

[0069] The static elimination CPU 82 obtains the operating time T1 of the ionizer 52 measured by the timer 86 and stores it in memory (S1007). In addition, the cumulative operating time T1 of the ionizer 52 for each job since the last maintenance requirement detection has been performed is stored in memory as cumulative operating time Ts. The operating time T1 of the ionizer 52 for the current job is added to the cumulative operating time Ts (S1008). The cumulative operating time Ts is stored in non-volatile memory.

[0070] Next, the static elimination CPU 82 has a cumulative operating time T S It is determined whether the first threshold is 600 seconds or more. The static elimination CPU 82 determines the cumulative operating time T S If the cumulative operating time is 600 seconds or more (S1009-Y), the static elimination CPU 82 will be set to the cumulative operating time T S Initialize to 0 (S1011). The static elimination CPU 82 switches the maintenance detection mode transition signal 93 from L level to H level, causing the ionizer 52 to start detecting whether maintenance is required (S1012).

[0071] The static elimination CPU 82 has a cumulative operating time T S If the cumulative operating time T1 is less than 600 seconds, it is determined whether the operating time T1 of the previous job is 300 seconds or more (S1010). If the operating time T1 of the ionizer 52 in the previous job is 300 seconds or more (S1010-Y), the static elimination CPU 82 will determine the cumulative operating time T S Initialize to 0 (S1011). The static elimination CPU 82 switches the maintenance detection mode transition signal 93 from L level to H level, causing the ionizer 52 to start detecting whether maintenance is necessary (S1012). If the operating time T1 of the ionizer 52 in the previous job was less than 300 seconds, the process is terminated (S1010-N).

[0072] When the static elimination CPU 82 receives a maintenance detection signal 95 from the ionizer 52 (S1013), the static elimination CPU 82 notifies the main unit CPU 61 of a maintenance warning via the communication interface 87 (S1014) and terminates processing. When the main unit CPU 61 receives a maintenance warning notification from the static elimination CPU 82, it displays a maintenance warning on the main unit display unit 66 recommending cleaning the ionizer (Figure 8(b)).

[0073] If the static elimination CPU 82 does not receive a maintenance detection signal 95 within 30 seconds after initiating maintenance detection for the ionizer 52 (S1005-Y), the process terminates. In other words, if the maintenance detection signal 95 remains at the L level for a predetermined period of time, it indicates that maintenance detection has been successfully performed for the predetermined period. In this case, cleaning of the ionizer 52 is not required, so the static elimination CPU 82 does not display a maintenance warning recommending cleaning the ionizer on the main unit display unit 66 (the screen shown in Figure 8(a) is displayed).

[0074] In this embodiment, the threshold for determining whether or not the ionizer needs cleaning is 30 seconds after the start of maintenance requirement detection is set. However, the threshold for determining whether or not the ionizer needs cleaning is not limited to this, and can be set as appropriate.

[0075] Furthermore, if a maintenance warning (Figure 8(b)) is displayed on the main unit display unit 66, the user should clean the ionizer 52. The door sensor 202 (Figure 3) detects that the door 250 has been closed, and if the memory contains information indicating that maintenance is required, the static elimination CPU 82 instructs the ionizer 52 to perform a maintenance requirement detection. If the maintenance requirement detection performed after the door 250 has been closed indicates that the ionizer does not require maintenance, the static elimination CPU 82 displays the screen shown in Figure 8(a) on the main unit display unit 66 via the communication interface 87.

[0076] Furthermore, in order to determine whether or not to perform maintenance necessity detection, a first threshold Tslimit is provided which is compared with the cumulative operating time Ts of the ionizer 52, and a second threshold T1limit is provided which is compared with the operating time T1 of the ionizer 52. The cumulative operating time Ts is the cumulative operating time T1 of the ionizer 52 for each job since the last maintenance necessity detection was performed. In this embodiment, the first threshold Tslimit is set to 600 seconds and the second threshold T1limit is set to 300 seconds, but it is not limited to these values ​​and can be set as appropriate. In other words, the second threshold T1limit should be set to be smaller than the first threshold Tslimit. Furthermore, it is preferable that the second threshold T1limit is less than or equal to half the value of the first threshold Tslimit.

[0077] In this embodiment, the value of timer 86 and the operating time T1 stored in memory are cleared before the start of measurement by timer 86 in S1003. In other words, for each job, the measurement of timer 86 starts from 0.

[0078] In other words, the static elimination control unit 98 performs static elimination processing and maintenance necessity detection processing. Static elimination processing is the process of eliminating static electricity from multiple sheets being transported using the ionizer 52, and maintenance necessity detection processing is the process of detecting whether or not maintenance of the ionizer 52 is required. Note that the static elimination control unit 98 does not perform maintenance necessity detection processing while static elimination processing is being performed on multiple sheets, but performs maintenance necessity detection after the static elimination processing. Specifically, static elimination processing is performed from the start of the job (S1001-Y) until the job ends and the timer is stopped (S1006). Maintenance detection processing is performed from the start of maintenance necessity detection (S1012) until 30 seconds have elapsed since the start of maintenance warning notification (S1004) or maintenance necessity detection (S1015-Y).

[0079] Note that the static elimination control unit 98 and the ionizer control unit 521 are examples of control units. The static elimination process and the maintenance requirement detection process may be performed by either the static elimination control unit 98 or the ionizer control unit 521.

[0080] In other words, the static elimination control unit 98 executes maintenance requirement detection processing when the cumulative operating time Ts, which is the sum of the operating times T1 of the ionizer 52 in multiple static elimination processes, is equal to or greater than a first threshold. Furthermore, even if the cumulative operating time Ts is less than the first threshold, the static elimination control unit 98 also executes maintenance requirement detection processing when the operating time T1 of the ionizer 52 in a single static elimination process is equal to or greater than a second threshold, which is smaller than the first threshold.

[0081] In other words, the static elimination control unit 98 executes maintenance requirement detection processing when the cumulative operating time Ts, which is the sum of the operating times T1 of the ionizer 52 in multiple jobs, is equal to or greater than a first threshold. Furthermore, even if the cumulative operating time Ts is less than the first threshold, the static elimination control unit 98 also executes maintenance requirement detection processing when the operating time T1 of the ionizer 52 in a single job is equal to or greater than a second threshold, which is smaller than the first threshold.

[0082] In this embodiment, the ionizer ON / OFF signal 92 remains at a high level from the start of the job until the job is finished and the ionizer is turned OFF. However, the ON / OFF signal 92 may be switched between a high level and a low level in accordance with the timing of sheet transport. Specifically, the static elimination CPU 82 may set the ON / OFF signal 92 to a low level from the trailing end of the preceding sheet to the leading end of the following sheet, and then set the ON / OFF signal 92 to a high level only when the sheet passes through the ionizer 52. In this case as well, the operating time T1 of the ionizer 52 may be from when the ionizer 52 is turned ON at the start of the job (S1002) until when the ionizer is turned OFF at the end of the job (S1005), as shown in the flowchart in Figure 9. However, the operating time T1 may also be the cumulative time during which the ionizer 52 is ON during one static elimination process. However, immediately after switching the ionizer 52 from the ion-stopped state to the ion-generating state, static electricity removal by the ionizer 52 is unstable. Therefore, it is preferable to keep the ionizer 52 in the ion-generating state from the start to the end of the job.

[0083] The cumulative operation time Ts is the time obtained by accumulating the operation time T1 of the ionizer 52 in the static elimination process. In other words, the operation time of the ionizer in the maintenance necessity detection process is not included in the cumulative operation time Ts.

[0084] FIG. 10 is a modified example of a flowchart of the control performed by the static elimination CPU 82 of the static elimination control unit 98. In this embodiment, when a job is input during the maintenance necessity detection, the maintenance necessity detection is interrupted. When the maintenance necessity detection is interrupted, the cumulative operation time Ts is not cleared. Since S1001 to S1010 in FIG. 10 are the same as S1001 to S1010 in FIG. 9, the description thereof is omitted.

[0085] The static elimination CPU 82 switches the maintenance detection mode transition signal 93 from the L level to the H level, and starts the maintenance necessity detection for the ionizer 52 (S1012'). When the static elimination CPU 82 receives the maintenance detection signal 95 from the ionizer 52 (S1013'-Y), the static elimination CPU 82 notifies the main body CPU 61 of a maintenance warning (S1014'). Thereafter, the static elimination CPU 82 initializes the cumulative operation time T S to 0 (S1016'), and ends the process. Incidentally, in S1014', the static elimination CPU 82 notifies the main body CPU 61 of a maintenance warning via the communication I / F 87. When the main body CPU 61 receives the maintenance warning notification, the main body display unit 66 displays a maintenance warning recommending cleaning of the ionizer (FIG. 8(b)).

[0086] If the static elimination CPU 82 does not receive the maintenance detection signal 95 even after 30 seconds have elapsed since starting the maintenance necessity detection for the ionizer 52 (S1015'-Y), the static elimination CPU 82 initializes the cumulative operation time T S to 0 (S1016'), and ends the process.

[0087] If the next job is submitted while maintenance necessity detection is in progress (S1017'-Y), the static elimination CPU 82 interrupts maintenance necessity detection (S1018') and suspends processing. At this time, the cumulative operating time Ts is not initialized to 0 and is used for the next job.

[0088] In other words, if the ionizer 52 completes the maintenance requirement detection, the cumulative operating time Ts is initialized to 0. If the ionizer 52 does not complete the maintenance requirement detection because the next job is submitted, the cumulative operating time Ts is not initialized.

[0089] Furthermore, in the flowchart of Figure 9, the cumulative operating time Ts may be initialized after the maintenance necessity detection is completed. Specifically, the cumulative operating time Ts may not be initialized in S1011, but rather after the maintenance warning notification (S1014) and after 30 seconds have elapsed since the start of maintenance necessity detection (S1015-Y).

[0090] In this embodiment, the operating time of the ionizer 52 and a threshold for the operating time are used to determine whether or not to perform maintenance detection. However, the number of sheets passed through and a threshold for the number of sheets passed may also be used. Specifically, instead of a timer that measures time, a counter that counts the number of sheets passed through is used. The counter counts the number of sheets that pass through the ionizer 52 from the start of the job until the end of the job. The static elimination CPU 82 adds the counted count value C1 to the cumulative count value Cs. The cumulative count value Cs is the cumulative value of the count value C1 for each job since the last time maintenance detection for the ionizer 52 was completed. Subsequently, the static elimination CPU 82 compares the cumulative count value Cs with the first threshold number of sheets Cslimit, and if the cumulative count value Cs is equal to or greater than the first threshold number of sheets Cslimit, it performs maintenance detection. The static elimination CPU 82 performs maintenance requirement detection if the cumulative count value Cs is less than the first threshold number Cslimit, and the count value C1 is equal to or greater than the second threshold number C1limit. In this embodiment, the cumulative count value Cs is an example of the cumulative number of sheets, and the count value C1 is an example of the number of sheets that have passed through.

[0091] In other words, the control unit executes maintenance requirement detection processing when the cumulative number of sheets that have passed through the non-contact static elimination unit in multiple static elimination processes is equal to or greater than a first threshold number. Furthermore, even if the cumulative number is less than the first threshold number, the control unit executes maintenance requirement detection processing if the number of sheets that have passed through in a single static elimination process is equal to or greater than a second threshold number which is less than the first threshold number.

[0092] In other words, the control unit performs maintenance detection processing when the cumulative number of sheets that have passed through the non-contact static elimination unit over multiple jobs is equal to or greater than a first threshold number. Furthermore, even if the cumulative number is less than the first threshold number, the control unit performs maintenance detection processing if the number of sheets that have passed through in a single job is equal to or greater than a second threshold number which is less than the first threshold number.

[0093] In other words, in this embodiment, a first criterion related to the cumulative operation of the ionizer and a second criterion corresponding to the job immediately preceding the maintenance requirement detection are provided for determining whether or not to perform maintenance requirement detection. Time and the number of sheets may be used in combination to determine whether or not to perform maintenance requirement detection. For example, a first threshold Tslimit corresponding to the cumulative operating time Ts may be used as the first criterion, and a second threshold number C1limit corresponding to the count value C1 of the sheets may be used as the second criterion. However, it is preferable to unify the first criterion, which indicates the cumulative operation of the ionizer, and the second criterion, which corresponds to the job immediately preceding, to either the number of sheets or time.

[0094] As explained above, the static elimination control unit compares the cumulative operating time of the ionizer 52 since the last maintenance requirement detection with the first threshold, as well as the operating time of the ionizer 52 immediately prior to the second threshold. Therefore, even when print jobs that continue for a long time are executed consecutively, it is possible to perform maintenance requirement detection at the appropriate timing. This reduces the possibility of defects in the loading of deliverables caused by executing jobs with reduced static elimination capacity of the ionizer 52.

[0095] In this embodiment, an ionizer 52 was used in the non-contact static elimination unit 58, but this is not limited to this; a Corotron may also be used. Also, in this embodiment, the voltage value is set so that the surface potential of the sheet approaches 0 by applying a voltage to the static elimination roller 50 as the contact static elimination unit 57, but this is not limited to this. The static elimination device 200 also functions as a charge adjustment device that adjusts the charged state of the sheet by supplying charge to the sheet via the static elimination roller 50 as a charge supply member. The charge adjustment device does not necessarily reduce the amount of charge on the sheet (does not eliminate static charge). For example, when the sheets are stacked after processing by the charge adjustment device, the amount of charge on each surface of the sheet may be adjusted so that the opposing surfaces of overlapping sheets are charged with the same polarity. Specifically, the charge adjustment device applies a voltage to every other sheet in a plurality of sheets so as to reverse the electrostatic polarity of the sheet surface. In other words, a voltage of a magnitude that reverses the electrostatic polarity of the sheet surface is set, and the voltage is applied to every other sheet. In this case, the opposing surfaces of overlapping sheets are charged with the same polarity, which reduces the sheets from sticking together due to electrostatic force. However, since the sheets have a large charge after being charged by the charge adjustment device described above, they are prone to sticking to the transport path, which may cause transport failures. To reduce sheet transport failures, a non-contact static elimination unit 58 may be placed downstream of the rollers that adjust the charge of the sheets in the charge adjustment device, and the sheets may be statically eliminated by the non-contact static elimination unit 58. In this case as well, it is preferable that the non-contact static elimination unit 58 perform maintenance necessity detection at an appropriate timing, and it is preferable that the determination of whether or not maintenance necessity detection is performed is made according to the cumulative operating time of the ionizer 52 and the operating time in the previous job.

[0096] In the above-described embodiment, the image forming system was explained in the case where it was applied to an electrophotographic image forming system 300, but it is not limited to this, and may also be applied to an inkjet recording system. [Explanation of symbols]

[0097] 52 Ionizer 58 Non-contact static elimination unit 66 Main unit display 98 Static Elimination Control Unit 200 Static eliminator

Claims

1. A non-contact static elimination unit is provided, which has an electrode section that generates ions and removes static electricity from the sheet in which an image has been formed in the image forming section without contacting the sheet. A control unit that performs a static discharge process in which a plurality of sheets transported from the image forming unit are discharged by the non-contact static discharge unit, and a detection process that is performed after the static discharge process to detect whether or not maintenance of the electrode unit is required. It has, The control unit executes the detection process when the cumulative operating time, which is the sum of the operating times of the non-contact static elimination unit in multiple static elimination processes, is equal to or greater than a first threshold. Even if the cumulative operating time is less than the first threshold, the control unit executes the detection process if the operating time of the non-contact static elimination unit in a single static elimination process is greater than or equal to a second threshold which is less than the first threshold. A static elimination device characterized by the following features.

2. The cumulative operating time is initialized when the detection process is executed. The static elimination device according to feature 1.

3. If a job is submitted while the detection process is running, the detection process will be interrupted and the cumulative operating time will not be reset. The static elimination device according to feature 2.

4. A non-contact static elimination unit is provided, which has an electrode section that generates ions and removes static electricity from the sheet in which an image has been formed in the image forming section without contacting the sheet. A control unit that performs a static discharge process in which a plurality of sheets conveyed to the non-contact static discharge unit are discharged by the non-contact static discharge unit, and a detection process that is performed after the static discharge process to detect whether or not maintenance of the electrode unit is required. It has, The control unit executes the detection process when the cumulative number of sheets that have passed through the non-contact static elimination unit in multiple static elimination processes is equal to or greater than a first threshold. The control unit executes the detection process even when the cumulative number of sheets is less than the first threshold, if the number of sheets passing through in one static elimination process is greater than or equal to a second threshold which is less than the first threshold. A static elimination device characterized by the following features.

5. The cumulative number is initialized when the detection process is executed. The static elimination device according to feature 4.

6. If a job is submitted while the detection process is running, the detection process is interrupted and the cumulative count is not reset. The static elimination device according to feature 5.

7. The second threshold is less than or equal to half the value of the first threshold. The static elimination device according to feature 1.

8. It has a display unit that notifies that cleaning of the non-contact static elimination unit is recommended. The static elimination device according to feature 1.

9. The display unit indicates that the detection process is being executed. The static elimination device according to feature 8.

10. In the sheet transport direction, it is positioned downstream of the image forming unit and has a contact static elimination unit that eliminates static electricity from the sheet while in contact with it. The non-contact static elimination unit is located downstream of the contact static elimination unit in the sheet transport direction. The static elimination device according to feature 1.

11. The static elimination device according to claim 1, An image forming system comprising the image forming unit described above.

Images