Image forming device

Abstract

To prevent, with a simple configuration, a rear end of a recording material from moving toward a fixing film when the recording material passes through a fixing device.SOLUTION: Before a rear end of a recording material passes through a fixing nip part, a control unit decreases a rear conveyance speed Ve of a conveying device compared with a fixing conveyance speed Vf of a fixing device (S3) to make a relative speed difference ΔV smaller than 0 (ΔV<0). This makes it possible to convey the recording material while bending it toward a pressure roller between the fixing device and the conveying device in a state in which the recording material is sandwiched by both the fixing device and the conveying device. When the recording material is conveyed while bending it toward the pressure roller in this way, the rear end of the recording material can be prevented from moving toward a fixing film when the recording material passes through the fixing nip part. Consequently, the rear end of the recording material does not come too close to the fixing film, and thus spark discharge does not occur in part of a surface of the fixing film.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to an image forming apparatus using electrophotographic technology, such as a printer, a copying machine, a facsimile machine, or a multifunction machine. [Background technology]

[0002] Image forming apparatuses using electrophotography are equipped with a fixing device that applies heat and pressure to a recording material on which an unfixed toner image has been formed, thereby fixing the toner image to the recording material. A pressure-heating fixing device has been proposed (Patent Document 1). The fixing film is disposed on one side of the recording material on which the unfixed toner image is formed, and the pressure roller is disposed on the opposite side of the recording material. In this fixing device, when the recording material on which the unfixed toner image has been formed passes through a fixing nip formed between the fixing film and the pressure roller, heat and pressure are applied to the recording material, thereby fixing the toner image to the recording material. A conveying device having a pair of conveying rollers is provided downstream of the fixing device in the conveying direction of the recording material. The pair of conveying rollers abut against each other to form a conveying nip that sandwiches and conveys the recording material that has passed through the fixing device.

[0003] When a recording material passes through the fixing device, the trailing edge of the recording material may move toward the fixing film and approach the fixing film. If the trailing edge of the recording material gets too close to the fixing film, the potential difference between the recording material and the fixing film may cause a discharge (a spark discharge) on a portion of the surface of the fixing film, which has been negatively charged for toner image fixing, and the area where the discharge occurred may become positive. If this happens, when the next recording material is conveyed successively and passes through the fixing nip, the toner on the recording material may move to the fixing film and adhere to it at the area that has become positive, causing image distortion.

[0004] Therefore, the device described in Patent Document 1 is designed to apply a bias voltage to the fixing film or pressure roller to separate the toner adhering to the fixing film. Also, a device has been proposed (Patent Document 2) that blows air toward the recording material passing through the fixing nip to prevent the trailing edge of the recording material from moving toward the fixing film. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 10-221983 [Patent Document 2] Japanese Patent Application Laid-Open No. 2015-4833 Summary of the Invention [Problem to be solved by the invention]

[0006] However, the above-mentioned conventional devices require a separate power supply to apply a bias voltage to the fixing film or pressure roller to separate the toner, an air blower to blow gas onto the recording material, etc., which makes the device configuration complicated and costly. Therefore, in recent years, it has become difficult to adopt such devices from the perspective of reducing the size and cost of the device.

[0007] The present invention has been made in consideration of the above-mentioned problems, and aims to provide an image forming apparatus that can suppress, with a simple configuration, the movement of the trailing end of the recording material toward the fixing film when the recording material passes through the fixing device. [Means for solving the problem]

[0008] An image forming apparatus according to one embodiment of the present invention includes a fixing device having an image forming section that forms a toner image on a recording material, a fixing member that fixes the toner image on the recording material, and a pressure member that contacts the fixing member and forms a first nip portion that nip-conveys the recording material, a first drive section that rotates the fixing member, and a pressure member that is provided downstream of the first nip portion in the conveying direction of the recording material, Next to the first nip portiona conveying section that forms a second nip section that nip-conveys a recording material, the second nip section having a distance from the first nip section that is shorter than the length of the recording material being conveyed; a second driving section that rotates the conveying section; and a control section that can execute a conveying mode in which the recording material is conveyed, wherein in the conveying mode, there is a period in which the recording material is nipped between the first nip section and the second nip section, and the period is , including the period during which the leading edge of the recording material passes through the second nip portion The control unit has a first period and a second period following the first period, and when executing the conveying mode, the control unit controls at least one of the first drive unit and the second drive unit during the first period so that the circumferential speed of the conveying unit is greater than the circumferential speed of the fixing member, and controls at least one of the first drive unit and the second drive unit during the second period so that the circumferential speed of the conveying unit is less than the circumferential speed of the fixing member. [Effects of the Invention]

[0009] According to the present invention, when the recording material passes through the fixing means, it is possible to prevent the rear end of the recording material from moving toward the first rotating body arranged on one side of the recording material on which the toner image is formed, using a simple configuration. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a schematic diagram showing a configuration of an image forming apparatus according to an embodiment of the present invention. [Figure 2] FIG. 2 is a schematic diagram showing a fixing device and a conveying device according to the third embodiment. [Figure 3] FIG. 3 is a control block diagram illustrating a control unit. [Figure 4] 10 is a flowchart showing a conveying speed control process according to the first embodiment. [Figure 5] 5 is a timing chart of the conveying speed control per sheet of recording material in the first embodiment. [Figure 6] FIG. 3 is a diagram showing a conveyance state of a recording material in the first embodiment. [Figure 7] 10 is a timing chart showing the control of the conveying speed per sheet of recording material in a conventional example. [Figure 8]FIG. 10 is a diagram showing a conveyance state of a recording material in a conventional example. [Figure 9] FIG. 10 is a schematic diagram showing a fixing device and a conveying device that can be moved by a moving mechanism according to a second embodiment. [Figure 10] FIG. 11 is a schematic diagram showing a fixing device, a conveying device, and an auxiliary conveying device according to a third embodiment. [Figure 11] 10 is a timing chart of the conveying speed control per sheet of recording material in the third embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0011] First Embodiment The present embodiment will be described below. First, the configuration of the image forming apparatus of the present embodiment will be described with reference to Fig. 1. The image forming apparatus 1 shown in Fig. 1 is a full-color printer of an intermediate transfer type that includes multiple image forming units PY, PM, PC, and PK for yellow, magenta, cyan, and black along an intermediate transfer belt 8.

[0012] [Image forming equipment] Although not shown, the image forming apparatus 1 is an apparatus that forms an image on a recording material S in accordance with image information from an external device, such as a document reading device connected to the apparatus main body or a personal computer connected to the apparatus main body so as to be able to communicate with the apparatus main body. Examples of the recording material S include various types of recording material, such as plain paper, cardboard, rough paper, textured paper, coated paper, plastic film, and cloth. In this embodiment, the image forming sections PY to PK, primary transfer rollers 6Y to 6K, intermediate transfer belt 8, inner secondary transfer roller 13, outer secondary transfer roller 14, etc., constitute an image forming unit 300 as image forming means that forms a toner image on one side of the recording material S.

[0013] In the conveyance process of the recording material S, for example, the recording materials S are stacked in a cassette 15 and fed one by one to a conveyance path 17 by a paper feed roller 16 in accordance with the image formation timing. Alternatively, the recording materials S stacked in a manual feed tray (not shown) are fed one by one to the conveyance path 17. The recording material S is conveyed to a registration roller 18 arranged midway along the conveyance path 17, where the registration roller 18 corrects skew and timing of the recording material S before sending it to a secondary transfer portion T2. ​​The secondary transfer portion T2 is a transfer nip formed by an opposing inner secondary transfer roller 13 and outer secondary transfer roller 14. At the secondary transfer portion T2, a secondary transfer voltage is applied from a high-voltage power supply (not shown) to the outer secondary transfer roller 14, which serves as a transfer member, thereby secondarily transferring the toner image from the intermediate transfer belt 8 to the recording material S.

[0014] The image forming process for an image sent to the secondary transfer station T2 at the same timing as the process for transporting the recording material S to the secondary transfer station T2 described above will now be described. First, the image forming stations PY, PM, PC, and PK will be described. However, the image forming stations PY, PM, PC, and PK are configured almost identically except that the toner colors used in the developing devices 5Y, 5M, 5C, and 5K are yellow, magenta, cyan, and black. Therefore, the following description will be given using the yellow image forming station PY as a representative example, and descriptions of the other image forming stations PM, PC, and PK will be omitted.

[0015] The image forming unit PY is mainly composed of a photosensitive drum 2Y, a charging device 3Y, an exposure device 4Y, and a developing device 5Y. The photosensitive drum 2Y, rotated by a motor (not shown), is uniformly charged on its surface by the charging device 3Y. An electrostatic latent image is then formed on the photosensitive drum 2Y by the exposure device 4Y, which is driven based on an image information signal. The electrostatic latent image formed on the photosensitive drum 2Y is then developed into a toner image using a developer by the developing device 5Y. Thereafter, a predetermined pressure and a primary transfer bias are applied by a primary transfer roller 6Y, which is disposed opposite the image forming unit PY with the intermediate transfer belt 8 sandwiched therebetween, to primarily transfer the toner image formed on the photosensitive drum 2Y to the intermediate transfer belt 8. The intermediate transfer belt 8, which serves as an image carrier, rotates while carrying the toner image.

[0016] The intermediate transfer belt 8 is stretched over a tension roller 7, a secondary transfer inner roller 13, and a tension roller 10, and is driven to move in the direction of arrow R2. In this embodiment, the tension roller 7 also serves as a drive roller that drives the intermediate transfer belt 8. The image formation process for each color performed by the image forming units PY to PK described above is performed at a timing to sequentially superimpose the toner image of the color upstream in the movement direction that has been primarily transferred onto the intermediate transfer belt 8. As a result, a full-color toner image is finally formed on the intermediate transfer belt 8 and is transported to the secondary transfer unit T2.

[0017] Through the conveying process and image forming process described above, the timing of the recording material S and the full-color toner image coincides at the secondary transfer portion T2, and the toner image is secondarily transferred from the intermediate transfer belt 8 to the recording material S. Thereafter, the recording material S onto which the toner image has been transferred is conveyed to the fixing device 100, which applies heat and pressure to fix the toner image to the recording material S (pressure and heat method). The recording material S onto which the toner image has been fixed by the fixing device 100 is conveyed by the conveying device 150 towards the discharge roller pair 20, and is discharged by the discharge roller pair 20 onto a discharge tray 21 provided outside the apparatus. The discharged recording material S is stacked on the discharge tray 21.

[0018] [Fixing device] Next, a pressure and heat type fixing device 100 will be described with reference to FIG. 2. As shown in FIG. 2, the fixing device 100 includes a fixing film unit 101 and a pressure roller 120. In this embodiment, the fixing film unit 101 is provided so as to be movable toward the pressure roller 120. The fixing film unit 101 includes a fixing film 102, a heater holder 103, a stay 104, a heater 105, and a temperature sensor 106. In the following description, unless otherwise specified, "upstream" refers to the upstream side in the conveyance direction (direction of arrow X) of the recording material S, and "downstream" refers to the downstream side in the conveyance direction of the recording material S.

[0019] [Fixing film] The fixing film 102 as the first rotating body is a flexible endless belt member (endless belt). The fixing film 102 has an elastic layer formed on a substrate, and a release layer further formed on the elastic layer. The substrate is, for example, a cylindrical metal film made of stainless steel with a thickness of 30 to 35 μm. The elastic layer is, for example, a silicone rubber layer with a thickness of 200 μm, and the release layer is, for example, a perfluoroalkoxyalkane (PFA) resin tube with a thickness of 30 μm. Grease is applied to the inner surface of the fixing film 102 as a lubricant to improve the sliding properties between the inner surface of the fixing film 102 and the heater holder 103 and heater 105 (described later) that contact the inner surface of the fixing film 102. Note that the substrate of the fixing film 102 may be made of an alloy made of a metal material such as nickel, copper, or aluminum, or a heat-resistant resin such as polyimide, in addition to stainless steel.

[0020] [Stay] The stay 104 is made of a highly rigid metal plate or the like, and is disposed inside the fixing film 102 so as not to rotate. The stay 104 is pressed against the pressure roller 120 with a predetermined pressure (for example, 90 to 320 N) by a pressure mechanism (not shown). This causes the fixing film 102 and the pressure roller 120 to be pressed against each other, forming a fixing nip N1 that sandwiches and conveys the recording material S while applying heat and pressure. In this embodiment, the fixing nip N1 is formed to have a length (conveyance direction length) of approximately 5.5 to 6.5 mm in the conveyance direction (arrow X direction) of the recording material S.

[0021] [Heater holder] The heater holder 103 is formed, for example, from a resin member having high heat resistance and heat insulation properties, and, like the stay 104, is non-rotatably disposed inside the fixing film 102. The heater holder 103 holds a heater 105 as a heating means and guides the fixing film 102. The heater holder 103 holds the heater 105 on the side opposite the stay 104 (i.e., the fixing nip N1 side) so that the heater 105 can contact the inner circumferential surface of the fixing film 102 and heat the fixing film 102. As a result, when the recording material S passes through the fixing nip N1, the heat of the heater 105 is conducted to the recording material S via the fixing film 102, and the toner image is fixed to the recording material S. The heater 105 is, for example, a ceramic heater with low heat capacity.

[0022] A polyimide layer having a thickness of, for example, about 10 μm is formed as a friction layer on the surface side of the heater 105 that contacts the inner circumferential surface of the fixing film 102. By forming a polyimide layer on the heater 105, it is possible to reduce friction resistance between the fixing film 102 and the heater 105, thereby reducing the drive torque for rotating the fixing film 102 and reducing wear of the fixing film 102 due to friction. In this embodiment, the length of the heater 105 in the conveying direction is "about 8.75 mm," while the length in the conveying direction over which the inner circumferential surface of the fixing film 102 and the heater 105 rub against each other is set to about "about 3 to 4 mm."

[0023] [Temperature sensor] In this embodiment, a temperature sensor 106 is provided to detect the temperature of the heater 105 in order to manage the temperature of the fixing film 102. In this embodiment, a contact-type temperature sensor 106 such as a thermistor sensor is used. However, the temperature sensor 106 may also be a non-contact type. The temperature sensor 106 is arranged inside the heater holder 103 so that a heat-sensitive portion is in contact with the rear surface of the heater 105 opposite the fixing film 102. Note that the number of temperature sensors 106 is not limited to one, and multiple sensors may be arranged across the width direction of the fixing film 102 (the direction of the rotation axis of the pressure roller 120).

[0024] [Pressure roller] The pressure roller 120, which serves as a second rotating body, is rotatably supported by the apparatus body. The pressure roller 120 is provided so as to be in pressure contact with the fixing film 102. The pressure roller 120 has an elastic layer 122 made of silicone rubber or the like having a thickness of approximately 3.5 mm on the outer periphery of a stainless steel core 121, for example, and a release layer 123 made of a fluororesin such as PTFE, PFA, or FEP having a thickness of approximately 45 to 65 μm on the outer periphery of the elastic layer 122. The Asker-C hardness of the pressure roller 120 is, for example, approximately 60 degrees.

[0025] As described above, the fixing film 102 and the pressure roller 120 are pressed against each other to form the fixing nip N1. Therefore, when the pressure roller 120 is rotated by the drive motor 124, the frictional force generated in the fixing nip N1 transmits the rotational force of the pressure roller 120 to the fixing film 102. In this way, the fixing film 102 is driven to rotate by the pressure roller 120 (a so-called pressure roller drive method). The recording material S is nipped and conveyed in the fixing nip N1 formed by the rotating pressure roller 120 and the fixing film 102.

[0026] In the fixing device 100 described above, the recording material S is guided to the fixing nip portion N1 with the temperature of the heater 105 adjusted to a target temperature. The recording material S enters the fixing nip portion N1 with one side on which a toner image has been formed by the image forming unit 300 (see FIG. 1) facing the fixing film 102. As the recording material S passes through the fixing nip portion N1, heat from the heater 105 is applied to the recording material S via the fixing film 102, and the toner image is fixed to the recording material S.

[0027] The fixing device 100 is disposed downstream of the secondary transfer portion T2 so that, for example, the most upstream portion of the fixing nip portion N1 is located at a position "approximately 90 mm" away from the most downstream portion of the secondary transfer portion T2. ​​In this embodiment, the leading end (downstream end) of the recording material S reaches the fixing nip portion N1 before the trailing end (upstream end) of the recording material S passes through the secondary transfer portion T2. ​​In this embodiment, a post-secondary transfer sensor 191 capable of detecting the trailing end of the recording material S is disposed downstream of the outer secondary transfer roller 14 and upstream of the fixing device 100 to detect whether the recording material S has passed through the secondary transfer portion T2.

[0028] [Transportation equipment] Next, the conveying device 150 will be described with reference to FIG. 2. The conveying device 150, which serves as a conveying means, is provided downstream of the fixing device 100 in the conveying direction (the direction of the arrow X), and has a pair of rotatable conveying rollers 151 and 152. The conveying rollers 151 and 152, which serve as conveying rotating bodies, come into contact with each other and form a conveying nip N2 that sandwiches and conveys the recording material S. In this embodiment, the conveying roller 151 is rotated by a drive motor 153, and the conveying roller 152 is rotated following the rotation of the conveying roller 151. The recording material S is sandwiched and conveyed by the conveying nip N2 formed by these rotating conveying rollers 151 and 152.

[0029] The conveying device 150 is disposed downstream of the fixing device 100 at a distance from the fixing device 100 so as to be able to nip and convey the recording material S before the trailing edge of the recording material S passes through the fixing nip N1. In other words, when the leading edge of the recording material S reaches the most upstream portion of the conveying nip N2, the trailing edge of the recording material S is still being nipped and conveyed by the fixing nip N1. That is, in this embodiment, the recording material S being conveyed can be nipped by both the fixing device 100 (specifically, the fixing nip N1) and the conveying device 150 (specifically, the conveying nip N2). For example, the conveying device 150 is disposed downstream of the fixing device 100 so that the most upstream portion of the conveying nip N2 is located approximately 50 mm away from the most downstream portion of the fixing nip N1.

[0030] 2, dotted line a indicates a line passing through the fixing nip portion N1 of the fixing device 100, and dotted line b indicates a line connecting the most downstream portion of the fixing nip portion N1 and the most upstream portion of the conveying nip portion N2. As shown in Fig. 2, the conveying device 150 is disposed so that dotted line b is located closer to the fixing film 102 than dotted line a when viewed from the direction of the rotation axes of the pair of conveying rollers 151 and 152. In other words, the conveying device 150 is positioned relative to the fixing device 100 so that the conveying nip portion N2 is located closer to the fixing film 102 than the fixing nip portion N1.

[0031] <Control unit> As shown in Fig. 1, the image forming apparatus 1 includes a control unit 500. The control unit 500 will be described using Fig. 3 while referring to Fig. 1. In addition to those shown in the figure, the control unit 500 is also connected to various motors that drive the components of the image forming unit 300 and various power sources that apply voltage. However, as this is not the main focus of the invention, illustration and description of these components will be omitted here.

[0032] The control unit 500, which serves as a control means, performs various controls of the image forming apparatus 1, such as the image forming operation, and includes, for example, a CPU (Central Processing Unit) 501 and a memory 502. The memory 502 is configured with a ROM (Read Only Memory) and a RAM (Random Access Memory), and stores various programs and data for controlling the image forming apparatus 1. The CPU 501 can execute, for example, an image formation job (not shown) and conveyance speed control (see FIG. 4, described later) stored in the memory 502, and can operate the image forming apparatus 1 to form an image on the recording material S. The memory 502 can temporarily store the results of calculations and the like associated with the execution of the various programs.

[0033] An operation unit 400 is connected to the control unit 500 via an input / output interface. The operation unit 400 is, for example, an operation panel that accepts inputs (start instructions, etc.) of various programs such as image forming jobs and inputs of various data by the user. Using the operation unit 400, the user can input, for example, the type and size of the recording material S as information about the recording material S, or instruct the start of an image forming job. In addition, the execution of a conveying speed control (conveying mode), which will be described later, may be selectable.

[0034] An image forming job is a series of operations from the start of an image forming operation to the completion of the image forming operation based on a print signal for forming an image on a recording material S. That is, it is a series of operations from the start of a preparatory operation (so-called pre-rotation) required for image formation, through the image forming process, to the completion of a preparatory operation (so-called post-rotation) required for completing the image formation. Specifically, it refers to the period from the pre-rotation (preparatory operation before image formation) after receiving a print signal (input of an image forming job) to the post-rotation (operation after image formation), and includes the image formation period and the paper interval.

[0035] Furthermore, the control unit 500 is connected to the above-mentioned drive motor 124, drive motor 153, post-second transfer sensor 191, heater 105, temperature sensor 106, temperature and humidity sensor 250, etc. via an input / output interface. The control unit 500 can maintain the surface temperature of the fixing film 102 at a predetermined temperature during an image formation job by controlling the heater 105 based on the detection result of the temperature sensor 106. The temperature and humidity sensor 250, which serves as humidity detection means, can detect the temperature and humidity of the location where the image forming apparatus 1 is installed, and the control unit 500 can acquire the detection result of the temperature and humidity sensor 250.

[0036] The control unit 500 can change the peripheral speed of the pressure roller 120 by controlling the drive motor 124 as a first drive means. This adjusts the conveyance speed of the recording material S by the fixing device 100 (for convenience, referred to as the fixing conveyance speed (first conveyance speed)). The control unit 500 can also change the peripheral speed of the conveyance roller 151 by controlling the drive motor 153 as a second drive means. This adjusts the conveyance speed of the recording material S by the conveyance device 150 (for convenience, referred to as the post-conveyance speed (second conveyance speed)). In other words, the control unit 500 can make the conveyance speed of the recording material S different between the fixing device 100 and the conveyance device 150. The control unit 500 can identify the position of the recording material S being conveyed from the secondary transfer unit T2 to the conveyance device 150 based on the detection result of the post-second transfer sensor 191 as a conveyance detection means, and can adjust the conveyance speed of the recording material S by each of the fixing device 100 and the conveyance device 150 accordingly. By adjusting the conveying speed of the recording material S in this way, the posture (conveying state) of the recording material S being conveyed between the fixing device 100 and the conveying device 150 changes.

[0037] Incidentally, this is particularly noticeable when the conveying nip N2 is located closer to the fixing film 102 than the fixing nip N1 (see FIG. 2), but as the trailing end of the recording material S passes through the fixing nip N1, the trailing end of the recording material S may move closer to the fixing film 102. If the trailing end of the recording material S gets too close to the fixing film 102 at this time, a spark discharge occurs on part of the surface of the fixing film 102. If a spark discharge occurs, when the next recording material S being continuously conveyed passes through the fixing nip N1, the toner on the recording material S may adhere to the fixing film 102, causing image distortion.

[0038] In view of the above problem, in this embodiment, in order to prevent spark discharge from occurring between the trailing edge of the recording material S and the fixing film 102, the conveying speed of the recording material S of each of the fixing device 100 and the conveying device 150 is adjusted to prevent the trailing edge of the recording material S from approaching the fixing film 102. Below, the conveying speed control process (conveying mode) of the first embodiment that achieves this will be described using FIGS. 4 to 6 with reference to FIGS. 2 and 3.

[0039] <Transport speed control process> 4 is a flowchart showing the conveying speed control process of the first embodiment. The conveying speed control process of the present embodiment is executed by the control unit 500 during an image forming job in response to input of an instruction to start the image forming job.

[0040] 4, the control unit 500 controls the drive motor 124 and the drive motor 153 so that the peripheral speed of the pressure roller 120 and the peripheral speed of the conveying roller 151 are set to different initial speeds according to the process speed of the image forming unit 300 (see FIG. 1) (S1). At this time, the control unit 500 controls the drive motor 124 and the drive motor 153 so that the post-conveying speed of the conveying device 150 is faster than the fixing and conveying speed of the fixing device 100 before the leading edge of the recording material S reaches the fixing nip N1. In other words, when the fixing and conveying speed of the fixing device 100 is Vf and the post-conveying speed of the conveying device 150 is Ve, the control unit 500 controls the relative speed difference ΔV (Ve-Vf) to be greater than 0 (ΔV>0).

[0041] Thereafter, the control unit 500 determines whether or not the trailing edge of the recording material S has passed through the secondary transfer portion T2 based on the detection result of the post-secondary transfer sensor 191 (S2). Here, it is deemed that the trailing edge of the recording material S has passed through the secondary transfer portion T2 in response to the trailing edge of the recording material S being detected by the post-secondary transfer sensor 191. If the trailing edge of the recording material S has not passed through the secondary transfer portion T2 (NO in S2), the control unit 500 maintains the state in which the post-conveying speed of the conveying device 150 is faster than the fixing conveying speed of the fixing device 100 (ΔV>0).

[0042] When the trailing edge of the recording material S has passed the secondary transfer portion T2 (YES in S2), the control portion 500 controls the drive motors 124 and 153 to increase the peripheral speed of the pressure roller 120 while decreasing the peripheral speed of the conveying roller 151 (S3). At this time, the control portion 500 slows the post-conveying speed of the conveying device 150 compared to the fixing and conveying speed of the fixing device 100. In other words, the control portion 500 makes the relative speed difference ΔV between the fixing and conveying speed Vf of the fixing device 100 and the post-conveying speed Ve of the conveying device 150 smaller than 0 (ΔV<0).

[0043] Then, the control unit 500 determines whether the trailing edge of the recording material S has passed through the fixing nip portion N1 (S4). Note that the control unit 500 can determine whether the trailing edge of the recording material S has passed through the fixing nip portion N1 from, for example, the detection result of the post-second transfer sensor 191 (the time when the trailing edge of the recording material S passed through the secondary transfer portion T2), the length of the recording material S in the conveying direction, and the fixing conveying speed of the fixing device 100.

[0044] If the trailing edge of the recording material S has not passed through the fixing nip portion N1 (NO in S4), the control unit 500 maintains the state in which the post-conveying speed Ve of the conveying device 150 is slower than the fixing conveying speed Vf of the fixing device 100 (ΔV<0). On the other hand, if the trailing edge of the recording material S has passed through the fixing nip portion N1 (YES in S4), the control unit 500 controls the drive motor 153 to temporarily make the post-conveying speed Ve of the conveying device 150 faster than the initial speed (S5). In other words, although the post-conveying speed of the conveying device 150 is faster than the fixing conveying speed of the fixing device 100 (ΔV>0), the relative speed difference ΔV is increased compared to when the trailing edge of the recording material S has not passed through the secondary transfer portion T2 (see S1).

[0045] The control unit 500 temporarily sets the rear conveying speed Ve to a speed faster than before the deceleration, and then controls the drive motor 124 to return the fixing conveying speed Vf of the fixing device 100 to the initial speed, and controls the drive motor 153 to return the rear conveying speed Vc of the conveying device 150 to the initial speed (S6). In this way, conveying speed control for one sheet of recording material S is performed. Then, the control unit 500 determines whether or not to end the image forming job being executed (S7). If the image forming job is not to be ended (NO in S7), the control unit 500 returns to the process of step S2 and performs the processes of steps S2 to S7 above, thereby controlling the conveying speed for the next subsequent recording material S. If the image forming job is to be ended (YES in S7), there is no next subsequent recording material S, so the control unit 500 ends the conveying speed control process.

[0046] The conveying speed control process of this embodiment shown in Figure 4 will be described in detail. Figure 5 shows a timing chart of the conveying speed control per sheet of recording material in this embodiment, and Figure 6 shows the conveying mode of recording material S in this embodiment. Here, an example will be described in which the process speed (hereinafter referred to as PS) of image forming unit 300 (see Figure 1) is set to "300 mm / sec." In Figure 5, the circumferential speed of pressure roller 120 is indicated by a solid line, and the circumferential speed of conveying roller 151 is indicated by a dotted line.

[0047] 5, the pressure roller 120 is rotated at a peripheral speed of 300 mm / sec (PS+0.0%) in accordance with the process speed of the image forming unit 300 before the leading edge of the recording material S reaches the fixing nip N1 (see S1). On the other hand, the conveying roller 151 is rotated at a peripheral speed of 305 mm / sec (PS+1.5%) in accordance with the process speed of the image forming unit 300 before the leading edge of the recording material S reaches the fixing nip N1 (see S1). In other words, the relative speed difference ΔV (Ve-Vf) between the fixing conveying speed Vf of the fixing device 100 and the post-conveying speed Ve of the conveying device 150 is greater than 0. This prevents the recording material S from wrapping around the fixing film 102 during conveyance and prevents the recording material S from undulating while being conveyed. Until the trailing edge of the recording material S passes through the secondary transfer portion T2 (time t1), the post-conveying speed of the conveying device 150 is maintained higher than the fixing conveying speed of the fixing device 100 (ΔV>0).

[0048] At the timing (time t1) when the trailing edge of the recording material S passes through the secondary transfer portion T2, i.e., the timing when the trailing edge of the recording material S is detected by the post-secondary transfer sensor 191, the peripheral speed of the pressure roller 120 is increased to 303 mm / sec (PS+1.0%) (see S3). At the same time, the peripheral speed of the conveying roller 151 is decelerated to 300 mm / sec (PS+0.0%) (see S3). That is, the post-conveying speed Ve of the conveying device 150 is slower than the fixing and conveying speed Vf of the fixing device 100, so that the relative speed difference ΔV is less than 0 (ΔV<0). At this time, the recording material S is not sandwiched by the secondary transfer portion T2, but is sandwiched between both the fixing device 100 (specifically, the fixing nip portion N1) and the conveying device 150 (specifically, the conveying nip portion N2).

[0049] Thereafter, when the trailing edge of the recording material S passes through the fixing nip portion N1 (time t2, see S4), the peripheral speed of the conveying roller 151 is temporarily increased to "450 mm / sec (PS+50%)" in order to quickly discharge the recording material S (see S5). Then, the peripheral speed of the pressure roller 120 is returned to "300 mm / sec (PS+0.0%)", and the peripheral speed of the conveying roller 151 is returned to "305 mm / sec (PS+1.5%)" (see S6). At this time, before the leading edge of the next recording material S reaches the fixing nip portion N1, the peripheral speeds of the respective rollers are returned to the above-mentioned "initial speed".

[0050] As described above, in this embodiment, before the trailing edge of the recording material S passes through the fixing nip portion N1, the post-conveying speed Ve of the conveying device 150 is made slower than the fixing conveying speed Vf of the fixing device 100 (ΔV<0). In this way, as shown in FIG. 6, with the recording material S sandwiched between both the fixing device 100 and the conveying device 150, the recording material S can be conveyed while being curved toward the pressure roller 120 (toward the second rotating body) between the fixing device 100 and the conveying device 150. When the recording material S is conveyed while being curved toward the pressure roller 120 in this way, it is possible to prevent the trailing edge of the recording material S from moving toward the fixing film 102 (toward the first rotating body) when the recording material S passes through the fixing nip portion N1.

[0051] The timing for slowing down the rear conveying speed Ve of the conveying device 150 relative to the fixing conveying speed Vf of the fixing device 100 is preferably changed to a time from when the rear end of the recording material S passes through the secondary transfer portion T2 until when it passes through the fixing nip portion N1 (see time t1 to time t2 in FIG. 5). That is, in this embodiment, when the conveying speed control process is being executed (in conveying mode), "ΔV>0" is set until the rear end of the recording material S passes through the secondary transfer portion T2, and "ΔV<0" is set after the rear end of the recording material S has passed through the secondary transfer portion T2. ​​This is for the following reason.

[0052] That is, as shown in FIG. 6, in order to curve the recording material S toward the pressure roller 120, the relative speed difference ΔV needs to be less than 0 (ΔV<0). Here, it is also possible to set "ΔV<0" immediately after the leading edge of the recording material S reaches the conveying nip N2. However, in this case, the recording material S is likely to bend more than necessary toward the pressure roller 120, which may cause the recording material S to wrap around the fixing film 102 during conveyance, or the recording material S to be conveyed while waving. Furthermore, if "ΔV<0" is set while the recording material S is passing through the secondary transfer portion T2, the behavior of the recording material S at the secondary transfer portion T2 may change, which may result in image defects.

[0053] In view of this, in this embodiment, control is performed so that "ΔV<0" is satisfied while the trailing edge of the recording material S passes from the secondary transfer portion T2 to the fixing nip portion N1. In other words, in the conveying speed control of this embodiment, the rear conveying speed Ve of the conveying device 150 and the fixing conveying speed Vf of the fixing device 100 are adjusted so that "ΔV>0" is satisfied when the leading edge of the recording material S passes, and "ΔV<0" is satisfied when the trailing edge of the recording material S passes. This makes it possible to form a loop of the recording material S between the fixing device 100 and the conveying device 150 while preventing the recording material S from wrapping or waviness. By forming a loop of the recording material S, as described above, it is possible to prevent the trailing edge of the recording material S from moving toward the fixing film 102 when the recording material S passes through the fixing nip portion N1.

[0054] <Conventional example> Here, a conventional example will be shown for comparison with the above-described embodiment. Fig. 7 shows a timing chart of the conveying speed control per sheet of recording material in the conventional example, and Fig. 8 shows the conveying mode of the recording material S in the conventional example. In Fig. 7, the circumferential speed of the pressure roller 120 is shown by a solid line, and the circumferential speed of the conveying roller 151 is shown by a dotted line.

[0055] 7, in the conventional example, the rear conveying speed Ve of the conveying device 150 and the fixing conveying speed Vf of the fixing device 100 are adjusted so as to maintain the relative speed difference ΔV greater than 0 (ΔV>0) without making the relative speed difference ΔV smaller than 0 (ΔV<0). In this example, until the rear end of the recording material S passes through the secondary transfer portion T2 (time t1), the pressure roller 120 rotates at a peripheral speed of "300 mm / sec (PS+0.0%)" and the conveying roller 151 rotates at a peripheral speed of "305 mm / sec (PS+1.5%)", as in the present embodiment.

[0056] Then, when the trailing edge of the recording material S passes through the secondary transfer portion T2 (time t1), the peripheral speed of the pressure roller 120 is maintained, while the peripheral speed of the conveying roller 151 is increased to 309 mm / sec (PS+3.0%). In this case, the relative speed difference ΔV is greater than 0 (ΔV>0). Thereafter, when the trailing edge of the recording material S passes through the fixing nip portion N1 (time t2), the peripheral speed of the conveying roller 151 is increased to 450 mm / sec (PS+50%) in order to quickly discharge the recording material S. In this way, in the conventional example, the rear conveying speed Ve of the conveying device 150 and the fixing conveying speed Vf of the fixing device 100 are adjusted to maintain ΔV>0 during the conveyance of the recording material S. As shown in FIG. 7, in the conventional example, the pressure roller 120 is maintained at a peripheral speed of "300 mm / sec (PS+0.0%)", and the peripheral speed of the conveying roller 151 is appropriately changed so as not to fall below "300 mm / sec".

[0057] In the conventional example, the post-conveying speed Ve of the conveying device 150 is always faster (ΔV>0) than the fixing conveying speed Vf of the fixing device 100, so as shown in Figure 8, the recording material S is conveyed along the straight line (dotted line b) connecting the most downstream part of the fixing nip N1 and the most upstream part of the conveying nip N2. This conventional example has the advantage of preventing the recording material S from sagging during conveyance and from rippling. However, if the trailing edge of the recording material S passes through the fixing nip N1 while the post-conveying speed Ve remains faster than the fixing conveying speed Vf, the trailing edge of the recording material S may come too close to the fixing film 102, which may cause a spark discharge on part of the surface of the fixing film 102.

[0058] As described above, in this embodiment, before the trailing edge of the recording material S passes through the fixing nip portion N1, the relative speed difference ΔV between the rear conveying speed Ve of the conveying device 150 and the fixing conveying speed Vf of the fixing device 100 is made smaller than 0 (ΔV<0), and the recording material S is curved toward the pressure roller 120. In other words, while the recording material S is sandwiched between the fixing device 100 and the conveying device 150, the recording material S is conveyed between the fixing device 100 and the conveying device 150 while being curved toward the pressure roller 120. This makes it possible to prevent the trailing edge of the recording material S from moving toward the fixing film 102, which is arranged on one side of the recording material S on which a toner image is formed, as the recording material S passes through the fixing device 100. Therefore, the trailing edge of the recording material S does not get too close to the fixing film 102, and therefore spark discharge does not occur on part of the surface of the fixing film 102.

[0059] In the above-described embodiment, "ΔV<0" is realized by increasing the fixing conveying speed Vf of the fixing device 100 and decreasing the post-conveying speed Ve of the conveying device 150 (see S3 in FIG. 4) at the timing when the rear end of the recording material S passes through the secondary transfer portion T2, but this is not limitative. Since a feature of the present invention is to adjust the relative speed difference (ΔV) between the fixing conveying speed Vf and the post-conveying speed Ve to "ΔV<0", the relative speed difference "ΔV<0" may also be realized by adopting alternative control such as that shown in Table 1 below. [Table 1]

[0060] For example, as in alternative control 1, the fixing conveying speed Vf may be maintained at "300 mm / sec (PS + 0.0%)" (initial speed) and the post-conveying speed Ve may be decelerated to "297 mm / sec (PS - 1.0%)" to achieve a relative speed difference of "ΔV < 0." Alternatively, as in alternative control 2, the post-conveying speed Ve may be maintained at "305 mm / sec (PS + 1.5%)" (initial speed) and the fixing conveying speed Vf may be increased to "308 mm / sec (PS + 2.5%)" to achieve a relative speed difference of "ΔV < 0." While the magnitude of the relative speed difference ΔV is the same (-1.0%) in this example, the magnitude of the relative speed difference ΔV may vary. A larger relative speed difference (ΔV) can result in a larger amount of curvature (loop) of the recording material S compared to a smaller relative speed difference (ΔV).

[0061] Furthermore, in this embodiment, if the timing at which the post-conveying speed Ve is slowed down relative to the fixing conveying speed Vf is delayed between the time when the rear end of the recording material S passes through the secondary transfer portion T2 and the time when it passes through the fixing nip portion N1, the time during which "ΔV<0" is satisfied is shortened. A shorter time during which "ΔV<0" is satisfied can reduce the amount of curvature of the recording material S that is caused to curve between the fixing device 100 and the conveying device 150 compared to a longer time during which "ΔV<0" is satisfied. Therefore, the amount of curvature of the recording material S can be adjusted not only by the magnitude of the above-mentioned relative speed difference ΔV but also by the timing at which the post-conveying speed Ve or the fixing conveying speed Vf is switched to satisfy "ΔV<0."

[0062] Second Embodiment Next, a second embodiment will be described using Fig. 9 with reference to Figs. 1 and 3. As shown in Fig. 9, in the image forming apparatus 1 described above, the conveying device 150 may be provided so as to be movable in the vertical direction by a movement mechanism 600. In this configuration, in the conveying mode described above, the control unit 500 causes the movement mechanism 600, as a movement means, to move the conveying device 150 toward the pressure roller 120 (vertically downward) before the trailing edge of the recording material S passes through the fixing nip N1.

[0063] In particular, when viewed from the direction of the rotation axes of the conveying rollers 151 and 152, if the conveying nip portion N2 is located closer to the fixing film 102 than the straight line (dotted line a) passing through the fixing nip portion N1, the control unit 500 moves the conveying device 150 toward the pressure roller 120 before the trailing end of the recording material S passes through the fixing nip portion N1. Then, after the trailing end of the recording material S has passed through the conveying device 150, the control unit 500 moves the conveying device 150 vertically upward using the moving mechanism 600, and returns it to its original position.

[0064] In this way, by moving the conveying device 150 toward the pressure roller 120, the amount of curvature (loop amount) of the recording material S can be made larger and the recording material S can be curved in a shorter time than by simply adjusting the relative speed difference ΔV. Therefore, even in the case of the above configuration, when the recording material S passes through the fixing device 100, the trailing edge of the recording material S can be prevented from moving toward the fixing film 102 arranged on one side of the recording material S on which a toner image is formed.

[0065] Third Embodiment Next, a third embodiment will be described. As shown in Fig. 10, in this embodiment, an auxiliary conveying device 160 having a pair of auxiliary rollers 161 and 162 that sandwich and convey the recording material S is provided between the fixing device 100 and the conveying device 150 in the conveying direction of the recording material S (the direction of the arrow X). In the auxiliary conveying device 160 as auxiliary conveying means, the auxiliary roller 161 is rotated in conjunction with the pressure roller 120 at a predetermined speed difference by a drive motor 124 that drives the pressure roller 120. In other words, the auxiliary roller 161 and the pressure roller 120 are connected to the drive motor 124 by gears (not shown). The auxiliary roller 162 is rotated following the rotation of the auxiliary roller 161.

[0066] The conveying speed control of this embodiment will be described with reference to FIGS. 1, 3, and 10 and with reference to FIG. 11. As in the first embodiment described above, the control unit 500 controls the drive motors 124 and 153 to reduce the peripheral speed of the pressure roller 120 while increasing the peripheral speed of the conveying roller 151 when the trailing edge of the recording material S passes the post-second rotation sensor 191. Specifically, the drive motor 124 increases the peripheral speed of the pressure roller 120 to 309 mm / sec (PS+3.0%), and the drive motor 153 decreases the peripheral speed of the conveying roller 151 to 300 mm / sec (PS+0.0%). In other words, the peripheral speed of the pressure roller 120 is faster (303 mm / sec (PS+1.0%)) than in the first embodiment described above. In other words, the relative speed difference ΔV (Ve-Vf) between the fixing conveying speed Vf of the fixing device 100 and the post-conveying speed Ve of the conveying device 150 is set to be greater than 0 (ΔV>0), but the relative speed difference ΔV is set to be larger than in the first embodiment described above.

[0067] In this embodiment, auxiliary rollers 161 and 162 serving as auxiliary rotating bodies contact each other to form a nip N3 through which the recording material S is conveyed. The pressure at nip N3 is lower than the pressure at conveyance nip N2. Therefore, by increasing the relative speed difference ΔV compared to the first embodiment, the recording material S curves and forms a first loop between the conveying device 150 and the auxiliary conveying device 160. Furthermore, in response to the formation of the first loop, the recording material S also curves and forms a second loop between the auxiliary conveying device 160 and the fixing device 100. Thus, even if the auxiliary conveying device 160 is located between the fixing device 100 and the conveying device 150, the recording material S can be curved between the fixing device 100 and the auxiliary conveying device 160. Therefore, even with the above configuration, the same effect as in the first embodiment can be obtained, that is, the trailing edge of the recording material S can be prevented from moving toward the fixing film 102, which is disposed on one side of the recording material S on which a toner image is formed, when the recording material S passes through the fixing device 100.

[0068] <Other embodiments> The above-described conveying speed control may be executed during an image forming job only when the user selects its execution. That is, as shown in the above-described conventional example, during an image forming job, as normal conveying speed control, the rear conveying speed Ve of the conveying device 150 is always faster than the fixing conveying speed Vf of the fixing device 100 (ΔV>0), thereby preventing winding or waving of the recording material S. Then, as a mode for avoiding image defects caused by discharge due to the rear end of the recording material S approaching the fixing film 102, the conveying speed control of this embodiment may be executed only when the user selects its execution from the operation unit 400.

[0069] Furthermore, image defects caused by the above-described discharge are more likely to occur in lower humidity environments and with recording material S having higher resistance and lower moisture content. Therefore, if there is a possibility of discharge occurring, for example, based on the detection results of the temperature and humidity sensor 250 or the basis weight corresponding to the type of recording material S, the conveyance speed control of this embodiment may be automatically executed during an image formation job. For example, the conveyance speed control of this embodiment is automatically executed when the basis weight of the recording material is greater than a predetermined value. In this way, by enabling the conveyance speed control to be executed automatically, it is possible to prevent the recording material S from wrapping or rippling and to suppress image defects caused by discharge, without causing stress to the user.

[0070] In the above-described embodiment, the heater 105 is shown as an example of a heating means that is in contact with the fixing film 102, but the heating means is not limited to this and may be a halogen lamp (halogen heater) or an infrared heater that can heat the fixing film 102 without being in contact with it.

[0071] In the above embodiment, the image forming apparatus 1 is described as being configured to primarily transfer the toner images of each color from the photosensitive drums 2Y to 2K of each color onto the intermediate transfer belt 8, and then secondary-transfer the toner images of each color collectively onto the recording material S. However, the present invention is not limited to this. For example, the image forming apparatus may be a direct transfer type image forming apparatus in which the toner images are directly transferred from the photosensitive drums 2Y to 2K onto the recording material S. [Explanation of symbols]

[0072] 1...image forming apparatus, 8...image carrier (intermediate transfer belt), 14...transfer member (secondary transfer outer roller), 100...fixing means (fixing device), 102...first rotating body (fixing film), 105...heating means (heater), 120...second rotating body (pressure roller), 124...first driving means (driving motor), 150...conveying means (conveying device), 151 (152)...conveying rotating body (conveying roller), 153...second driving means (driving motor) , 160... auxiliary conveying means (auxiliary conveying device), 161 (162)... auxiliary rotating body (auxiliary roller), 191... conveying detection means (secondary rotation sensor), 250... humidity detection means (temperature and humidity sensor), 300... image forming means (image forming unit), 400... operation section, 500... control means (control section), 600... moving means (moving mechanism), N1... fixing nip section, N2... conveying nip section, S... recording material, T2... transfer nip section (secondary transfer section)

Claims

1. an image forming unit that forms a toner image on a recording material; a fixing device including a fixing member that fixes a toner image onto the recording material, and a pressure member that comes into contact with the fixing member and forms a first nip portion that nip-conveys the recording material; a first drive portion for rotating the fixing member; a conveying section that forms a second nip section that is provided downstream of the first nip section in a conveying direction of the recording material and that nip-conveys the recording material next to the first nip section, the second nip section having a distance from the first nip section that is shorter than a length of the recording material being conveyed; A second drive unit for rotating the conveying unit; a control unit capable of executing a conveying mode in which the recording material is conveyed, In the conveying mode, there is a period during which the recording material is sandwiched between the first nip portion and the second nip portion, and the period includes a first period including a period during which the leading edge of the recording material passes through the second nip portion, and a second period following the first period; When the control unit executes the transport mode, during the first period, at least one of the first driving unit and the second driving unit is controlled so that a peripheral speed of the transport unit is made higher than a peripheral speed of the fixing member; during the second period, at least one of the first driving unit and the second driving unit is controlled so that a peripheral speed of the transport unit is made slower than a peripheral speed of the fixing member; 1. An image forming apparatus comprising:

2. In the transport direction, a line connecting an upstream end of the second nip portion and a downstream end of the first nip portion is located closer to the fixing member than a line connecting an upstream end and a downstream end of the first nip portion.

2. The image forming apparatus according to claim 1,

3. in the conveying mode, a peripheral speed of the conveying portion is higher than a peripheral speed of the fixing member after the leading edge of the recording material reaches the second nip portion until a predetermined timing is reached; 3. The image forming apparatus according to claim 1, wherein the first and second electrodes are arranged in a first direction.

4. in the conveying mode, after the trailing edge of the recording material passes through the first nip portion, from a predetermined timing before the trailing edge of the recording material passes through the second nip portion until the trailing edge of the recording material passes through the second nip portion, a peripheral speed of the conveying portion is higher than a peripheral speed of the fixing member; 3. The image forming apparatus according to claim 1, wherein the first and second electrodes are arranged in a first direction.

5. The image forming unit includes: a transfer member forming a transfer nip portion for transferring a toner image formed in the image forming portion onto a recording material; a conveyance detection unit that is provided downstream of the transfer nip portion and upstream of the first nip portion in the conveyance direction and detects that a trailing edge of the recording material has passed through the transfer nip portion; 5. The image forming apparatus according to claim 1, wherein the first and second electrodes are arranged in a first direction.

6. a distance between the first nip portion and the second nip portion in the conveying direction is shorter than a length of a conveyable recording material of a minimum size; 6. The image forming apparatus according to claim 1, wherein the first and second electrodes are arranged in a first direction.

7. an operation unit capable of selecting execution of the transport mode, the control unit executes the transport mode when execution of the transport mode is selected by the operation unit.

7. The image forming apparatus according to claim 1, wherein the first and second electrodes are arranged in a first direction.

8. A humidity detection unit is provided for detecting humidity, the control unit automatically executes the transport mode based on a detection result of the humidity detection unit during an image forming job.

7. The image forming apparatus according to claim 1, wherein the first and second electrodes are arranged in a first direction.

9. the control unit acquires information about a recording material during an image forming job, and automatically executes the conveying mode based on the information about the recording material.

7. The image forming apparatus according to claim 1, wherein the first and second electrodes are arranged in a first direction.

10. the information about the recording material is a basis weight of the recording material, the control unit executes the conveying mode when a basis weight of the recording material is greater than a predetermined value during an image forming job.

10. The image forming apparatus according to claim 9,

11. the control unit is capable of executing another conveying mode in which, during an image forming job, the recording material is conveyed so as not to loop between the first nip portion and the second nip portion.

11. The image forming apparatus according to claim 1,

12. an operation unit capable of inputting an instruction to set a mode to be executed by the control unit among a plurality of modes including the transport mode and a transport mode different from the transport mode; 12. The image forming apparatus according to claim 1, wherein the first and second electrodes are arranged in a first direction.

13. the fixing member is a film, A plane heater for heating the film is provided, the sheet heater presses the pressure member through the film to form the first nip portion; 13. The image forming apparatus according to claim 1, wherein the image forming apparatus is a multi-layered image forming apparatus.

Images