Image forming apparatus

Abstract

To improve the quality of images printed on the medium. [Solution] In the ID unit 32 of the image forming section 30, the image forming apparatus 1 is provided with a guide film 75 on the first guide surface 72 of the base frame 40, and the lower end 75L of the guide film protrudes beyond the first guide surface 72 toward the upper part 23U of the conveyor belt. As a result, even if the conveyed paper P is curved and its leading edge is away from the upper part 23U of the conveyor belt, the image forming apparatus 1 can slide the leading edge along the guide film 75 to bring it closer to the upper part 23U of the conveyor belt, and further, the lower end 75L of the guide film can bring the paper P closer to or in contact with the upper part 23U of the conveyor belt. This prevents the leading edge of the paper P from contacting the peripheral surface of the photoreceptor drum 45 and scraping off the toner image TC, and enables the printing of a high-quality image on the paper P.

Description

Technical Field

[0001] The present invention relates to an image forming apparatus, and is suitable for application to, for example, an electrophotographic printer.

Background Art

[0002] Conventionally, as an image forming apparatus, for example, a toner image is formed using toner by an image forming unit, the toner image is transferred onto a sheet of paper (also referred to as a medium) conveyed by a conveying unit, and heat or pressure is applied to this sheet of paper by a fixing unit to fix it, thereby printing an image, and such apparatuses are widely popular.

[0003] Among these, as the conveying unit, for example, there is one in which belt rollers are arranged at two locations along the paper conveyance path, and a conveyance belt is stretched so as to go around the peripheries of the two belt rollers. In a conveying unit having such a configuration, the paper can be sandwiched between the conveyance belt and a predetermined roller or the like, and the paper can be conveyed along the conveyance path as the conveyance belt runs (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] Incidentally, as an image forming unit of the image forming apparatus described above, for example, there is an image carrier such as a cylindrical photoreceptor drum, and an electrostatic latent image is formed on the image carrier by exposure processing, and a toner image is formed by attaching a thin film of toner to this electrostatic latent image. Furthermore, the image forming apparatus described in Patent Document 1 is a so-called direct transfer method, in which a transfer area is formed by sandwiching a transport belt stretched along a transport path between a predetermined transfer roller and the image carrier (photoreceptor drum) of the image forming unit. In this image forming apparatus, a transfer process is performed at the transfer area to transfer a toner image from the image carrier of the image forming unit to a medium such as paper that is being transported by the transport belt of the transport unit.

[0006] However, in image forming apparatuses, for example, when printing the first side in double-sided printing, the media may be warped. In particular, in image forming apparatuses, if the area near the leading edge of the media being transported by the transport unit is warped away from the transport belt, the position of the media relative to the transport belt becomes unstable, which may cause misalignment in the transfer of the toner image or result in poor image transfer to the leading edge of the media. In such cases, image forming apparatuses have the problem of reduced image quality printed on the media.

[0007] This invention was made with the above points in mind, and aims to propose an image forming apparatus that can improve the quality of images printed on a medium. [Means for solving the problem]

[0008] To solve these problems, the present invention provides an image forming apparatus for forming an image on a medium, comprising: a medium supply unit for supplying the medium; a transport belt for transporting the medium supplied from the medium supply unit toward a fixing unit along the transport direction; an image forming transfer unit for transferring the image formed on an image carrier to the medium being transported by the transport belt at a transfer location; and a guide member provided upstream of the transfer location in the transport direction from the transfer location in the image forming transfer unit, having flexibility, and positioned to approach the transport belt as it moves downstream in the transport direction, wherein the shortest distance from the guide member end, which is the end of the guide member that is close to the transport belt, to the transport belt is greater than the maximum thickness in the specifications of the image forming apparatus.

[0009] Furthermore, the image forming apparatus of the present invention includes a medium supply unit for supplying a medium, a transport belt for transporting the medium supplied from the medium supply unit toward a fixing unit along the transport direction, an image forming transfer unit for transferring an image formed on an image carrier onto the medium being transported by the transport belt at a transfer location, and a guide member provided upstream of the transfer location in the transport direction from the transfer location in the image forming transfer unit, having flexibility, and positioned to approach the transport belt as it moves downstream in the transport direction, wherein the first distance, which is the shortest distance from the guide member end (the end of the guide member that is close to the transport belt) to the transport belt, is smaller than the second distance, which is the shortest distance from the guide member end to the image carrier.

[0010] In this invention, even if the leading edge of a medium being transported by a conveyor belt is lifted off the conveyor belt, the leading edge can be brought into contact with a guide member and then slid along the guide member to guide it to the end of the guide member, thereby bringing it closer to the conveyor belt. As a result, this invention enables stable transport of the medium along the conveyor belt and prevents the leading edge of the medium from contacting the image carrier and scraping off the image. [Effects of the Invention]

[0011] According to the present invention, an image forming apparatus capable of enhancing the quality of an image printed on a medium can be realized.

Brief Description of the Drawings

[0012] [Figure 1] It is a schematic side view showing the overall configuration of the image forming apparatus. [Figure 2] It is a schematic side view showing the configuration of the image forming section. [Figure 3] It is a schematic perspective view showing the configuration of the image forming section. [Figure 4] It is a schematic perspective view showing the configuration of the ID unit. [Figure 5] It is a schematic enlarged view showing the configuration of the ID unit. [Figure 6] It is a schematic enlarged view showing the configuration of the ID unit. [Figure 7] It is a schematic diagram showing the state of measuring the lower belt distance. [Figure 8] It is a schematic diagram showing the state of paper conveyance (1). [Figure 9] It is a schematic diagram showing the state of paper conveyance (2). [Figure 10] It is a schematic diagram showing the state of paper conveyance (3). [Figure 11] It is a schematic diagram showing the state of paper conveyance (4).

Embodiments for Carrying Out the Invention

[0013] Hereinafter, embodiments for carrying out the invention (hereinafter referred to as embodiments) will be described with reference to the drawings.

[0014] [1. Configuration of Image Forming Apparatus] As shown in FIG. 1, the image forming apparatus 1 according to the present embodiment is an electrophotographic printer and can form, i.e., print, a color image on a sheet P (also referred to as a medium) such as plain paper or coated paper. Incidentally, the image forming apparatus 1 does not have an image scanner function for reading a document or a communication function using a telephone line, etc., and is a single-function SFP (Single Function Printer) having only a printer function.

[0015] Various components are arranged inside a housing 2 formed in a substantially box shape in the image forming apparatus 1. Incidentally, hereinafter, with the right end portion in FIG. 1 being defined as the front of the image forming apparatus 1, the following description will be given after defining the vertical direction, the horizontal direction, and the front-rear direction when viewed facing this front.

[0016] The image forming apparatus 1 is configured to be overall controlled by a control unit 3. This control unit 3 is connected to a host device such as a computer device (not shown), and when receiving a print instruction or print data from this host device, executes an image forming process (also referred to as a printing process) for forming a printed image on the surface of the sheet P.

[0017] An operation panel 4 for displaying various information and receiving operation inputs is provided near the front of the upper surface of the housing 2. This operation panel 4 has, for example, a display panel such as a liquid crystal panel and a touch sensor combined into a touch panel, or LEDs (Light Emitting Diodes), etc., and displays various information based on the control of the control unit 3, and also receives operation inputs from the user.

[0018] A tray 5 for accommodating the sheet P is provided at the lowermost part inside the housing 2. This tray 5 can accommodate the sheet P of up to A3 size with its short side along the horizontal direction. A paper feeding and conveying unit 10 is provided above the front of the tray 5. The paper feeding and conveying unit 10 forms a paper feeding and conveying path W1, which is a path for conveying the sheet P, by conveying guides 11 facing each other at a predetermined interval.

[0019] The paper feeding and transport section 10 also has a pickup roller 12, a paper feeding roller 13, a separation roller 14, a registration roller 15, a pressure roller 16, and a pair of transport rollers 17 arranged along the paper feeding and transport path W1. Each roller is formed in a cylindrical shape with its central axis aligned in the left-right direction and is supported so as to be rotatable. Some of the rollers are also driven by a paper feeding motor (not shown). The transport roller pairs 17 have transport rollers positioned opposite each other across the paper feeding and transport path W1.

[0020] The paper feed and transport unit 10 picks up and transports the paper P stored in the tray 5 one sheet at a time, separating them as it rotates each roller appropriately based on the control of the control unit 3. Specifically, the pickup roller 12 pulls the paper P out of the tray 5. The paper feed roller 13 moves the paper P pulled out of the tray 5 by the pickup roller 12 along the paper feed transport path W1. When multiple sheets of paper P are removed from the tray 5, the separation roller 14 separates the uppermost sheet of paper P from the other sheets of paper P. The registration roller 15 and pressure roller 16 correct the orientation (the orientation of each side relative to the direction of travel) of the paper P if it is skewed relative to the paper feed transport path W1, allowing it to move correctly. The transport roller pair 17 transports the paper P along the paper feed transport path W1 and then feeds it diagonally upward and backward.

[0021] In the paper feed transport unit 10, a transport unit 20 is positioned below the transport roller pair 17, and four image forming units 30 are positioned above it. A transfer transport path W2 is formed between the transport unit 20 and each image forming unit 30. This transfer transport path W2 is connected to the paper feed transport path W1 and is in a straight line extending diagonally upwards and backwards.

[0022] The conveying section 20 is composed of a drive roller 21, an idler roller 22, and a conveyor belt 23, etc. Both the drive roller 21 and the idler roller 22 are formed in a cylindrical shape with their central axis aligned in the left-right direction, and are each supported so as to be rotatable.

[0023] The drive roller 21 is positioned relatively far to the rear and can be rotated by a driving force supplied from a power source (not shown). The idler roller 22 is positioned slightly in front of and below the drive roller 21, in the vicinity of the conveyor roller pair 17.

[0024] The conveyor belt 23 is a flexible, endless belt that is stretched around the drive roller 21 and the idler roller 22. The upper portion of this conveyor belt 23 (hereinafter referred to as the upper conveyor belt 23U) is stretched in a straight line connecting the vicinity of the upper end of the drive roller 21 and the vicinity of the upper end of the idler roller 22, and is in a straight line along the transfer conveyor path W2.

[0025] With this configuration, in the conveying unit 20, when the drive roller 21 rotates counterclockwise in Figure 1, the conveying belt 23 is driven, and the idler roller 22 is rotated accordingly. At this time, the upper part 23U of the conveying belt travels diagonally upward and backward along the transfer conveying path W2.

[0026] The four image forming units 30 (30K, 30Y, 30M, and 30C) are arranged mainly above the transport unit 20, aligned along the transfer transport path W2, that is, in an oblique direction from the front lower side to the rear upper side. Each image forming unit 30 corresponds to a respective color, black (K), yellow (Y), magenta (M), and cyan (C), but differs only in color; they are all configured similarly.

[0027] Each image forming unit 30 includes a toner cartridge 31, an image drum (ID) unit 32, an exposure head 33, and a transfer roller 34, as shown in the schematic enlarged view in Figure 2. Of these, the toner cartridge 31 and the ID unit 32 are configured to be detachable from the housing 2. Furthermore, the toner cartridge 31 is configured to be detachable from the ID unit 32.

[0028] The toner cartridge 31, which serves as the developer storage unit, has a space inside for storing toner (also called developer), and supplies the toner into the ID unit 32 through a supply port formed on its lower side.

[0029] The ID unit 32 has a toner storage space 41 for storing toner inside the base frame 40, which is a holding part that constitutes the outer shell, and a supply roller 42, a developing roller 43, a developing blade 44, a photoreceptor drum 45, a charging roller 46, a charging cleaning roller 47, a cleaning member 48, etc. are appropriately arranged below or behind it.

[0030] The toner storage space 41 houses the toner supplied from the toner cartridge 31 when the toner cartridge 31 is mounted on the upper side of the base frame 40. The toner storage space 41 is provided with a toner stirring unit (not shown) that appropriately stirs the stored toner to prevent aggregation of the toner and to smoothly supply the toner to the supply roller 42, etc.

[0031] The supply roller 42, developing roller 43, photoreceptor drum 45, charging roller 46, and charging cleaning roller 47 are all cylindrical or cylindrical in shape with their central axis aligned in the left-right direction, and are rotatably supported. These rollers and drums are rotated by a driving force supplied from a predetermined drum motor (not shown).

[0032] The supply roller 42, which serves as a developer supply unit, is located at the bottom of the toner storage space 41. The developing roller 43 is positioned diagonally above and behind the supply roller 42, in contact with both the supply roller 42 and the photoreceptor drum 45. Both the supply roller 42 and the developing roller 43 are formed in a cylindrical shape with their central axis aligned in the left-right direction, and are rotatably supported by the base frame 40 around their respective central axes. A predetermined high voltage, which is the supply voltage and developing voltage, is applied to the supply roller 42 and the developing roller 43, respectively. The developing blade 44 is formed in a thin plate shape, with one end fixed to the base frame 40 and the other end in contact with the circumferential surface of the developing roller 43, and further applies an elastic force to the developing roller 43.

[0033] The photoreceptor drum 45, which serves as the image carrier, is formed in a cylindrical shape with its central axis aligned in the left-right direction, and is rotatably supported by the base frame 40 around this central axis. The photoreceptor drum 45 is also made capable of being charged by sequentially forming thin film charge generation layers and charge transport layers on its circumferential surface. The charging roller 46, which serves as the charging part, is formed in a cylindrical shape with its central axis aligned in the left-right direction, is rotatably supported by the base frame 40, and is positioned to abut the front upper side of the photoreceptor drum 45. The charging cleaning roller 47 is positioned above the charging roller 46 and in contact with it. The charging cleaning roller 47 moves in conjunction with the rotation of the charging roller 46, or rotates with a difference in peripheral speed.

[0034] The exposure head 33, also called the exposure unit, is formed in a long, slender rod shape along the left-right direction and is located above the photoreceptor drum 45. This exposure head 33 has multiple LED (Light Emitting Diode) elements, which are light-emitting elements, arranged along the main scanning direction (i.e., the left-right direction), as well as a rod lens array. Based on the control of the exposure control unit 67 (Figure 3), which will be described later, the exposure head 33 appropriately emits light from each LED element, focusing the light downwards and irradiating it, thereby forming an image near the upper end of the peripheral surface of the photoreceptor drum 45, and thereby exposing the surface of the photoreceptor drum 45 and forming an electrostatic latent image.

[0035] The cleaning member 48 is provided on the front side of the photoreceptor drum 45 and is made of a flexible resin material in the shape of a thin plate. The front end of the cleaning member 48 is fixed to the base frame 40 and the area near the rear end is in contact with the circumferential surface of the photoreceptor drum 45.

[0036] The transfer roller 34 is formed in a cylindrical shape with its central axis aligned in the left-right direction, and is positioned below the conveyor belt 23, facing the photoreceptor drum 45. This transfer roller 34 is biased diagonally upward and forward by a biasing member (not shown), that is, toward the photoreceptor drum 45. As a result, the transfer roller 34 can grip the conveyor belt 23 between itself and the photoreceptor drum 45, and when paper P is being conveyed along the transfer conveyor path W2, it can grip the paper P together with the conveyor belt 23.

[0037] In the following, the upper part of the conveyor belt 23, which lies along the transfer conveyor path W2, will be referred to as the upper conveyor belt 23U, and the direction in which the upper conveyor belt 23U travels, diagonally upward and backward, will also be referred to as the conveying direction. Furthermore, in the following, the points where the conveyor belt 23 is gripped (i.e., nipped) by the photoreceptor drum 45 and the transfer roller 34 will be referred to as the transfer points QC.

[0038] In this configuration, when performing printing, each image forming unit 30 rotates the developing roller 43, charging roller 46, and transfer roller 34 of the ID unit 32 in the direction of arrow R2, based on the control of the control unit 3, and rotates the photoreceptor drum 45 and supply roller 42 in the direction of arrow R1. At the same time, the image forming unit 30 supplies a predetermined high voltage to the developing roller 43, supply roller 42, developing blade 44, charging roller 46, and transfer roller 34, based on the control of the control unit 3.

[0039] The supply roller 42, by charging, causes toner in the toner storage space 41 to adhere to its circumferential surface, and by rotating, this toner adheres to the circumferential surface of the developing roller 43. After the developing blade 44 removes excess toner from the circumferential surface of the developing roller 43 and a thin layer of toner is formed, this thin layer of toner comes into contact with the circumferential surface of the photoreceptor drum 45.

[0040] Furthermore, the charging roller 46, while charged, comes into contact with the photoreceptor drum 45, thereby uniformly charging the peripheral surface of the photoreceptor drum 45. At this time, the charging cleaning roller 47 scrapes off toner and external additives of the toner that are adhering to the charging roller 46.

[0041] Meanwhile, the control unit 3 generates print data based on a print job acquired from a higher-level device (not shown) and supplies this print data to the exposure head 33 as dot data for each line. The exposure head 33 emits light according to a light emission pattern based on the supplied dot data, exposing the photoreceptor drum 45. As a result, an electrostatic latent image is formed on the peripheral surface of the photoreceptor drum 45 near its upper end.

[0042] Next, the photoreceptor drum 45 rotates in the direction of arrow R1, bringing the area where the electrostatic latent image was formed into contact with the developing roller 43. As a result, toner adheres to the circumferential surface of the photoreceptor drum 45 based on the electrostatic latent image, and a toner image based on the image data is developed. The developed toner image, due to the rotation of the photoreceptor drum 45, reaches the point where it is clamped with the transfer roller 34, i.e., the transfer point QC on the transfer transport path W2.

[0043] At this time, if the paper P is being transported along the transfer transport path W2, the image forming unit 30 (Figure 1) charges the paper P with a high voltage applied to the transfer roller 34, and the toner image is transferred from the peripheral surface of the photoreceptor drum 45 to the paper P at the transfer location QC due to the potential difference in each part. Incidentally, if toner remains on the peripheral surface of the photoreceptor drum 45 after passing through the transfer location QC, the image forming unit 30 scrapes off the toner with the cleaning member 48.

[0044] In this way, the image forming unit 30 forms a toner image based on the print data and can transfer the toner image to the paper P being transported from the front along the transfer transport path W2 at the transfer location QC.

[0045] A fixing unit 50 is located behind the image forming unit 30C, which is the rearmost part of the transport unit 20. The fixing unit 50 includes a fixing roller 51, a pressure roller 52, and a heater 53, etc. The fixing roller 51 and the pressure roller 52 are rotatably supported in positions that sandwich the fixing transport path W3 from above and below each other. The pressure roller 52 is biased against the fixing roller 51 by a predetermined biasing member.

[0046] When printing is to be performed, the fuser unit 50 rotates the fuser roller 51 and the pressure roller 52 in advance and heats up the heater 53. When the paper P is transported along the fuser transport path W3, the fuser unit 50 grips the paper with the fuser roller 51 and the pressure roller 52, applies heat and pressure to fix the toner to the paper P, and then feeds the paper P diagonally upward and backward.

[0047] A double-sided printing section 55 is provided on the rear and underside of the fixing section 50. The double-sided printing section 55 forms a circulating transport path W4 and a temporary retraction transport path W5, etc., using a switch 56 provided on the rear side of the fixing section 50, as well as multiple transport guides and multiple transport roller pairs. Of these, the circulating transport path W4 is formed to connect the switch 56 and the transport roller pair 17 of the paper feed transport section 10.

[0048] When performing double-sided printing, the double-sided printing unit 55 switches the switch 56 based on the control of the control unit 3 to move the paper P to the temporary retraction transport path W5. Subsequently, after the end of the paper P has passed the switch 56, the double-sided printing unit 55 reverses the direction of travel of the paper P and moves it along the circulating transport path W4, where it merges with the paper feed transport path W1 of the paper feed transport unit 10 near the transport roller pair 17. As a result, the double-sided printing unit 55 moves the paper P from the paper feed transport path W1 to the transfer transport path W2 again with the front and back sides reversed, and transfers the image to the back side of the paper P. Incidentally, when the double-sided printing unit 55 does not perform double-sided printing on the paper P, and when an image has been transferred to the back side of the paper P, it moves the paper P diagonally upward and backward.

[0049] A paper discharge and transport unit 60 is located behind or above the switch 56. The paper discharge and transport unit 60 has a configuration similar to a part of the paper feed and transport unit 10, and a paper discharge transport path W6, which is the path for transporting the paper P, is formed by transport guides 61 that are opposite each other at a predetermined distance, and an outlet 62 is formed at the end of the path. In addition, transport roller pairs 63 and 64, etc. are sequentially arranged in the paper discharge and transport unit 60 along this paper discharge transport path W6.

[0050] The paper discharge and transport unit 60 rotates the transport roller pair 63 and 64 according to the control of the control unit 3, thereby transporting the paper P received from the fuser unit 50 via the switch 56 along the paper discharge and transport path W6 and discharging it from the discharge port 62, placing it on the discharge tray 6 formed on the upper surface of the housing 2.

[0051] In this way, the image forming apparatus 1 sequentially transports the paper P along each transport path W, transfers the toner image formed by each image forming unit 30 to the paper P, and fixes it in the fixing unit 50, thereby forming an image, that is, printing.

[0052] [2. ID Unit Configuration] As shown in the schematic perspective view in Figure 3, the image forming unit 30 is configured to allow the toner cartridge 31 to be attached to and detached from the upper side of the ID unit 32. Incidentally, Figure 3(A) shows the state with the toner cartridge 31 installed, and Figure 3(B) shows the state with the toner cartridge 31 separated.

[0053] As shown in Figure 3(B), the ID unit 32 is formed in the shape of a rectangular parallelepiped, with its lower portion elongated in the left-right direction, and a plate-like portion formed on the upper side near its left end. Furthermore, as shown in Figure 4, a perspective view of the ID unit 32 from a different direction than that of Figure 3(B), and also in the cross-sectional view of Figure 2, the portion near the lower end of the photoreceptor drum 45 is exposed through a drum exposure hole 71 formed in the bottom of the base frame 40.

[0054] On the front side of the drum exposure hole 71 in the base frame 40, the front lower side or lower surface of the base frame 40 is formed with a first guide surface 72, a connecting guide surface 73, and a second guide surface 74.

[0055] As shown in the enlarged side view in Figure 5, the first guide surface 72 is a flat plane connecting the front diagonal upper side and the rear diagonal lower side, and is inclined at an angle of approximately 23 degrees with respect to the upper part 23U of the conveyor belt. The second guide surface 74 is located downstream of the first guide surface 72 in the conveying direction and is a plane that is generally parallel to the upper part 23U of the conveyor belt. That is, the angle of the second guide surface 74 with respect to the upper part 23U of the conveyor belt is different from that of the first guide surface 72. For the sake of explanation, below, the direction parallel to the first guide surface 72, the front diagonal upper direction will be called the guide upward direction G1, and the opposite direction, the rear diagonal lower direction, will be called the guide downward direction G2. Furthermore, the guide upward direction G1 and the guide downward direction G2 will be collectively called the guide direction G.

[0056] As shown in Figure 6, which is an enlarged view of the area corresponding to the range frame F1 in Figure 5, the connecting guide surface 73 is located between the first guide surface 72 and the second guide surface 74, and is a curved surface that smoothly connects the two. That is, when viewed from the left and right directions, the connecting guide surface 73 is curved in an arc shape that protrudes in the direction approaching the upper part 23U of the conveyor belt, and forms a curved surface that is continuous with the first guide surface 72 and the second guide surface 74, respectively. From another viewpoint, when viewed from the left and right directions, no apex angle is formed within the range of the connecting guide surface 73 and at the connection points with the first guide surface 72 and the second guide surface 74.

[0057] In addition to the above configuration, a guide film 75 is provided on the base frame 40. The guide film 75 is formed from a resin material with sufficient light-shielding properties and is extremely thin in the form of a plate, i.e., a film, with a thickness of 0.188 [mm]. Furthermore, as shown in Figure 4, the guide film 75 is formed in a rectangular shape overall. In addition, the guide film 75 has a basis weight (grammage) of 120 [g / m²]. 2 It has higher rigidity than paper P.

[0058] As shown in Figure 6, the guide film 75 is attached to the first guide surface 72 by double-sided adhesive tape 76. Therefore, as shown in Figure 5, the surface of the guide film 75 is parallel to the first guide surface 72 and inclined at an angle of approximately 23 degrees with respect to the upper part 23U of the conveyor belt.

[0059] Furthermore, as shown in Figure 4, the length of the guide film 75 in the left-right direction (i.e., the width direction or the main scanning direction) is slightly shorter than that of the base frame 40. Specifically, the length of the guide film 75 in the left-right direction is approximately 81% of the maximum length of the paper P transported by the transport unit 20 (hereinafter referred to as the maximum paper width).

[0060] Furthermore, as shown in Figure 5, the length of the guide film 75 in the guiding direction G is longer than that of the first guide surface 72, and the end on the upward guiding direction G1 side is approximately aligned with the end of the first guide surface 72. On the other hand, a portion of the guide film 75, including the end on the downward guiding direction G2 side (hereinafter referred to as the lower end of the guide film 75L or the end of the guide member), protrudes further in the downward guiding direction G2 than the end of the first guide surface 72.

[0061] Here, the lower end belt distance L1, which is the shortest distance from the lower end 75L of the guide film to the upper end 23U of the transport belt, is greater than the maximum thickness of paper P that can be printed on, as defined in the specifications of the image forming apparatus 1 (hereinafter referred to as the maximum paper thickness). Also, this lower end belt distance L1 is smaller than the lower end drum distance L2, which is the shortest distance from the lower end 75L of the guide film to the photosensitive drum 45. Incidentally, the lower end belt distance L1 is smaller than the frame belt distance L3, which is the shortest distance from the second guide surface 74 to the upper end 23U of the transport belt. For the sake of explanation, below we will also refer to the lower end belt distance L1 as the first distance, the lower end drum distance L2 as the second distance, and the frame belt distance L3 as the third distance.

[0062] However, in the image forming apparatus 1, when the photoreceptor drum 45 of the ID unit 32 and the transport belt 23 come into contact, the photoreceptor drum 45 is harder than the transport belt 23, causing the transport belt 23 to bend and deform. For this reason, it is extremely difficult to accurately measure the lower end belt distance L1 etc. with respect to the upper part 23U of the transport belt in an actual image forming apparatus 1.

[0063] Therefore, in this embodiment, instead of the actual upper part 23U of the conveyor belt, a virtual straight line aligned with the conveying direction when viewed from the left and right is used as the reference for defining the lower end of the lower end belt distance L1. This virtual straight line is a line obtained by shifting the virtual tangents that contact the drive roller 21 and idler roller 22, respectively, by a distance equivalent to the thickness of the conveyor belt 23.

[0064] Furthermore, when measuring the lower end belt distance L1, etc., based on the upper part 23U of the conveyor belt, measurement processes using laser light or CAD applications executed on a computer can be used as appropriate. Below, an example of a specific process for actually measuring the lower end belt distance L1 will be described.

[0065] In this measurement process, first, a laser measuring instrument LJ-X8080 (manufactured by Keyence Corporation) is used to measure the shape (so-called profile) of the lower part of the ID unit 32 alone, as shown in the schematic cross-sectional view in Figure 7(A). At this time, in the left-right direction, the shape of the central part of the ID unit 32 (Figure 4), that is, the part where the guide film 75 is provided, is measured. This generates shape data as shown in Figure 7(B). This shape data accurately represents the outer shape (contour) of the ID unit 32 when viewed from the left-right direction, and represents parts of the base frame 40, photoreceptor drum 45, and guide film 75 of the ID unit 32.

[0066] Next, a CAD (Computer Aided Design) application is executed on a designated computer device, and the shape data is imported using the data import function of the CAD application. In the following, the line representing the outline (contour) of the ID unit 32 in the shape data imported at this time will be called the outline line OW.

[0067] Incidentally, as shown in Figure 7(A), the ID unit 32 has a flat base frame rear bottom surface 40RB formed behind the drum exposure hole 71 in the base frame 40. This base frame rear bottom surface 40RB is designed to be a plane parallel to the upper part 23U of the conveyor belt when the ID unit 32 is mounted on the image forming apparatus 1, as shown in Figure 5, etc.

[0068] Therefore, as shown in Figure 7(C), by rotating the entire shape data in the CAD application, the base frame rear bottom surface outline OW40RB, which corresponds to the base frame rear bottom surface 40RB in the outline line OW, is made to align with the horizontal direction. As a result, the horizontal direction in the CAD application represents the direction parallel to the transport direction in the image forming apparatus 1.

[0069] Next, as shown in Figure 7(D), in the CAD application, three distant points are selected on the photoreceptor drum outline OW45, which is the arc-shaped portion corresponding to the photoreceptor drum 45. A circle passing through these three points (hereinafter referred to as drum circle C45) is created, and its center point, drum center point Q45, is identified. At this time, the radius of drum circle C45, drum circle radius R45, is calculated.

[0070] Next, as shown in Figure 7(E), a horizontal line X1 is created passing through the drum center point Q45, and a line X2 is created by moving this line X1 downward by the drum circle radius R45. This line X2 is a line that abuts the drum circle C45, i.e., it is a tangent line. Furthermore, line X2 corresponds to the surface of the upper part 23U of the conveyor belt (Figure 5, etc.) if the conveyor belt upper part 23U were straight and not deflected. For this reason, this line X2 can be considered a reference when measuring the lower end belt distance L1, etc.

[0071] Finally, as shown in the enlarged view in Figure 7(F), in the CAD application, the distance in the vertical direction between the film lower edge outer shape point OW75L, which corresponds to the lower edge 75L of the guide film on the outline line OW, and the straight line X2 is calculated as the lower edge belt distance L1.

[0072] Furthermore, as shown in Figure 7(E), by creating an auxiliary line S1 in the CAD application that connects the drum center point Q45 and the film lower edge outline point OW75L, the distance from the intersection point with the drum circle C45 on the auxiliary line S1 to the film lower edge outline point OW75L can be calculated as the lower drum distance L2.

[0073] Furthermore, regarding the frame belt distance L3, for example, the shape of the parts near both ends in the left-right direction of the ID unit 32, i.e., the parts where the guide film 75 is not provided, can be measured using the laser measuring instrument LJ-X8080. In other words, the shape data generated in this way will form an outline (not shown) that is partially different in shape from the outline OW. On this outline, parts corresponding to the photoreceptor drum 45 and parts corresponding to the second guide surface 74 will appear. Therefore, in the CAD application, by creating a straight line X2 in the same way as described above, the distance in the perpendicular direction between the part of the outline corresponding to the second guide surface 74 and the straight line X2 can be calculated as the frame belt distance L3.

[0074] [3. Printing Process] Next, we will explain the parts of the printing process performed by the image forming apparatus 1 that relate to the transport of the paper P and the transfer of the toner image. Here, we will assume that the image forming apparatus 1 is performing double-sided printing, sequentially printing on both sides of the paper P based on a print job supplied from a higher-level device (not shown), and that the printing process on the first side (front) has been completed and printing on the second side (back) has begun.

[0075] At this time, the paper P may bend around a virtual axis along its width due to various factors in the printing process, such as being bent along the transport path W while heat is applied by the fixing unit 50 during the printing process of the first side. In the following, we will assume that the paper P is curved with the second side facing inward.

[0076] Figures 8, 9, 10, and 11 are all schematic diagrams that enlarge the area corresponding to the range frame F2 in Figure 5. Figures 8 to 11 show, in stages, how the paper P is transported by the transport roller pair 17 (Figure 1) and the transport belt 23, etc., toward the transfer area QC of the image forming unit 30K, which is located furthest upstream in the transport direction.

[0077] Figure 8 shows the leading edge of the paper P approaching the front lower side of the base frame 40 in the ID unit 32 of the image forming unit 30. If the paper P were not curved and was being transported in contact with the upper part 23U of the transport belt, it would move in the transport direction between the lower end 75L of the guide film and the upper part 23U of the transport belt, without coming into contact with the guide film 75, while remaining aligned with the upper part 23U of the transport belt.

[0078] However, as described above, the paper P is curved and warped due to the printing process on the first surface. As a result, the leading edge of the paper P is lifted up and far away from the upper part 23U of the transport belt, and this leading edge comes into contact with the guide film 75. At this time, in the image forming unit 30, the toner image TC to be printed on the second surface of the paper P is formed on the surface of the photoreceptor drum 45, and as the photoreceptor drum 45 rotates, the toner image TC moves closer to the transfer area QC.

[0079] Figure 9 shows the state from Figure 8, where the paper P moves in the transport direction (i.e., diagonally upward and backward along the upper part 23U of the transport belt) and the photoreceptor drum 45 rotates in the direction of arrow R1.

[0080] Incidentally, in the image forming apparatus 1, after performing predetermined verifications, it was found that not all sheets of paper P warped after the printing process was completed, and in most cases the weight of the paper P was within a predetermined range. Upon detailed verification, it was found that the upper limit of the weight (basis weight) value at which this warping is likely to occur is approximately 120 g / m². 2 ]. Therefore, as mentioned above, the guide film 75 had a weighing capacity of 120 [g / m²]. 2 We selected a material with higher rigidity than paper P.

[0081] In other words, in the image forming apparatus 1, even if the paper P is curved due to the printing process on the first surface, its weight is 120 g / m². 2Since the rigidity of the paper P is less than or equal to that of the guide film 75, the leading edge of the paper P slides along the guide film 75 in the image forming apparatus 1 without the guide film 75 being bent by the paper P at all.

[0082] The paper P is slid diagonally downward and backward while its leading edge remains in contact with the guide film 75, and is guided by the guide film 75 so that its leading edge gradually approaches the upper part 23U of the conveyor belt. Furthermore, because the guide film 75 has higher rigidity than the paper P, it can guide the leading edge of the paper P while maintaining its shape almost entirely.

[0083] Figure 10 shows the state in Figure 9, with the paper P moving further in the transport direction and the photoreceptor drum 45 rotating further in the direction of arrow R1. The leading edge of the paper P has reached the transport direction side of the guide film 75's lower end 75L. Also, the lower end 75L of the guide film contacts the paper P slightly towards the tail end, causing a wide area including the leading edge to be close to or in contact with the upper part 23U of the transport belt. In other words, the guide film 75 can prevent the leading edge of the paper P from contacting the circumferential surface of the photoreceptor drum 45.

[0084] Figure 11 shows the state after which the paper P has progressed further in the transport direction from the state in Figure 10, and the photoreceptor drum 45 has rotated further in the direction of arrow R1. The leading edge of the paper P has reached a position close to the transfer area QC, and at this leading edge, it is in contact with the leading edge of the toner image TC formed on the circumferential surface of the photoreceptor drum 45. Furthermore, the paper P is hardly in contact with the lower end 75L of the guide film, and is transported smoothly with reduced sliding resistance.

[0085] Subsequently, in the transfer area QC, the toner image TC is transferred from the circumferential surface of the photoreceptor drum 45 to the paper P, starting from the leading edge and moving towards the trailing edge. Then, in the image forming apparatus 1, the toner image TC of each color is sequentially transferred to the paper P in the image forming section 30 for each color, and the toner image TC is fixed to the paper P by the fixing section 50, thereby completing the printing process.

[0086] [4. Effects, etc.] In the above configuration, the image forming apparatus 1 according to this embodiment is provided with a guide film 75 on the base frame 40 of the ID unit 32 in the image forming section 30 (Figures 4 and 5, etc.). The guide film 75 is attached so that most of it overlaps the first guide surface 72 of the base frame 40, and on the downward direction G2 side, the lower end 75L of the guide film and its vicinity protrude beyond the edge of the first guide surface 72.

[0087] Therefore, when the paper P being transported along the transport path W is being transported toward the transfer location QC of the image forming unit 30, the image forming apparatus 1 can bring the leading edge of the paper P into contact with the guide film 75 and bring it closer to the upper part 23U of the transport belt. Furthermore, even after the leading edge of the paper P has been transported beyond the lower end 75L of the guide film toward the transfer location QC, the image forming apparatus 1 can still bring the paper P closer to or into contact with the upper part 23U of the transport belt using the lower end 75L of the guide film.

[0088] As a result, the image forming apparatus 1 can stably transport the paper P by the transport belt 23 and transfer the toner image of each color to the appropriate position using the image forming unit 30 for each color. Furthermore, the image forming apparatus 1 can prevent the leading edge of the paper P from unnecessarily coming into contact with the peripheral surface of the photoreceptor drum 45, thereby avoiding scraping off the toner image TC adhering to the peripheral surface of the photoreceptor drum 45. As a result, the image forming apparatus 1 can print high-quality images on the paper P.

[0089] Incidentally, in the image forming apparatus 1 (Figure 1), since the photoreceptor drum 45 is a consumable item, the ID unit 32 of the image forming section 30 is configured to be easily attached to and detached from the housing 2. For this reason, the image forming apparatus 1 needs to create a relatively large gap between the mounted ID unit 32 and surrounding parts, etc., that can absorb manufacturing errors and the like.

[0090] For example, the base frame 40 of the ID unit 32 is made of a relatively strong material because it needs to be able to rotate while maintaining the relative positions of the photoreceptor drum 45 and various rollers. On the other hand, the conveyor belt 23 that contacts the photoreceptor drum 45 has a sufficiently flexible structure because it circulates around the drive roller 21 and idler roller 22 in the conveyor section 20, and is therefore relatively easily damaged when it comes into contact with high-strength components.

[0091] Therefore, as shown in Figure 5, the ID unit 32 forms a relatively large gap of frame belt distance L3 between the lower surface of the base frame 40 and the upper part of the conveyor belt 23U, thereby preventing damage caused by contact with the upper part of the conveyor belt 23U. In addition, the ID unit 32 has a first guide surface 72, a connecting guide surface 73, and a second guide surface 74 formed on the front side (i.e., upstream side) of the drum exposure hole 71 on the lower part of the base frame 40. As a result, the ID unit 32 can guide the paper P being conveyed by the conveyor unit 20 towards the upper part of the conveyor belt 23U if the paper curves and its leading edge is lifted above the upper part of the conveyor belt 23U.

[0092] However, in the ID unit 32, as described above, the portion represented by the frame belt distance L3, such as the end of the first guide surface 72 on the downward G2 side of the guide and the gap between the second guide surface 74 and the upper part of the conveyor belt 23U, is relatively large.

[0093] Therefore, in the ID unit 32, the leading edge of the paper P cannot reach the vicinity of the upper part 23U of the transport belt with only the first guide surface 72, and there is a risk that stable transport by the transport belt 23 will not be possible. In this case, in the ID unit 32, there is a risk that the leading edge of the paper P will come into contact with the peripheral surface of the photoreceptor drum 45 through the gap of the frame belt distance L3, thereby scraping off the toner image TC from the photoreceptor drum 45.

[0094] Therefore, in the ID unit 32, a thin guide film 75 made of a flexible material is attached to the first guide surface 72, and the lower end 75L of the guide film 75 is positioned closer to the upper part 23U of the conveyor belt than the end on the downward G2 side of the first guide surface 72 (Figure 5, etc.).

[0095] As a result, even if the paper P is curved and its leading edge is lifted above the upper part 23U of the conveyor belt, the guide film 75 can guide the paper P to the vicinity of the upper part 23U of the conveyor belt, that is, to a position closer to the upper part 23U of the conveyor belt than the end of the first guide surface 72 on the downward G2 side. This allows the image forming apparatus 1 to stably convey the paper P along the conveyor belt 23, and prevents the leading edge of the paper P from scraping off the toner image TC from the circumferential surface of the photoreceptor drum 45.

[0096] Furthermore, the guide film 75 is formed in the form of a thin film from a flexible material. Therefore, in the image forming apparatus 1, even if the guide film 75 comes into contact with the conveyor belt 23, the guide film 75 can be appropriately deformed, thereby avoiding damage to the conveyor belt 23. Also, because the connecting guide surface 73 of the guide film 75 is curved, there is no risk of damage from contact with the base frame 40.

[0097] From another perspective, in the image forming apparatus 1, compared to the conventional ID unit 32 which does not have a guide film 75, the ID unit 32 according to this embodiment can be easily constructed simply by providing a guide film 75 on the first guide surface 72 of the base frame 40, thus eliminating the need to change the design of the base frame 40.

[0098] Furthermore, the ID unit 32 is configured with a guide film 75 made of a light-shielding resin material, and is positioned so as to cover a portion of the photoreceptor drum 45 exposed through the drum exposure hole 71 in the base frame 40 with the guide film 75. As a result, when the ID unit 32 is removed from the image forming apparatus 1, the exposure (so-called exposure) of the photoreceptor drum 45 can be reduced.

[0099] With the above configuration, the image forming apparatus 1 has a guide film 75 on the first guide surface 72 of the base frame 40 in the ID unit 32 of the image forming section 30, and the lower end 75L of the guide film protrudes beyond the first guide surface 72 toward the upper part 23U of the conveyor belt. As a result, even if the conveyed paper P is curved and its leading edge is away from the upper part 23U of the conveyor belt, the image forming apparatus 1 can slide the leading edge along the guide film 75 to bring it closer to the upper part 23U of the conveyor belt, and further, the lower end 75L of the guide film can bring the paper P closer to or in contact with the upper part 23U of the conveyor belt. This prevents the leading edge of the paper P from contacting the peripheral surface of the photoreceptor drum 45 and scraping off the toner image TC, and enables the printing of a high-quality image on the paper P.

[0100] [5. Other Embodiments] In the above-described embodiment, the guide film 75 was attached to each ID unit 32 in the four image forming units 30 provided in the image forming apparatus 1. However, the present invention is not limited to this, and the guide film 75 may be attached only to the ID units 32 of some of the image forming units 30, for example, only to the ID unit 32 of the image forming unit 30K located on the upstream side in the transport direction.

[0101] Furthermore, in the embodiment described above, a configuration was described in which the lower end belt distance L1, which is the shortest distance from the lower end 75L of the guide film to the upper part 23U of the conveyor belt in the ID unit 32 (Figure 5), is made larger than the maximum paper thickness. However, the present invention is not limited to this, and the lower end belt distance L1 may be set based on the lengths of various other parts, for example, by making the lower end belt distance L1 1 / 4 or more of the frame belt distance L3, which is the distance between the second guide surface 74 and the upper part 23U of the conveyor belt.

[0102] Furthermore, in the above-described embodiment, we described a configuration in which the lower end belt distance L1 in the ID unit 32 (Figure 5) is smaller than the lower end drum distance L2, which is the shortest distance from the lower end 75L of the guide film to the photoreceptor drum 45. However, the present invention is not limited to this, and for example, the lower end belt distance L1 may be equal to or greater than the lower end drum distance L2.

[0103] Furthermore, in the embodiment described above, a configuration was described in which the length of the guide film 75 in the ID unit 32 (Figure 4) in the main scanning direction (left-right direction) is approximately 81% of the maximum paper width. However, the present invention is not limited to this, and the length of the guide film 75 may be set to various values, such as 90% or 105% of the maximum paper width. In this case, experimental results show that if the length of the guide film 75 is approximately 80% or more of the maximum paper width, it is possible to effectively avoid the paper P coming into contact with the peripheral surface of the photoreceptor drum 45 and scraping off the toner image TC.

[0104] Furthermore, in the above-described embodiment, the rigidity of the guide film 75 is set to a basis weight (grammage) of 120 g / m². 2 The present invention describes a configuration that makes the rigidity higher than that of the paper P. However, the present invention is not limited to this, for example, 100 [g / m²] 2 The rigidity of paper P, and 150 [g / m²] 2 The rigidity of the paper P in the image forming apparatus 1 may be higher than the rigidity of the paper P in other various weighing conditions. In these cases, when printing is performed in the image forming apparatus 1, the rigidity of the guide film 75 should be determined based on the upper limit of the weighing condition in which bending may occur in the paper P after printing.

[0105] Furthermore, in the above-described embodiment, a configuration was described in which, in the base frame 40 of the ID unit 32, a second planar guide surface 74 is formed on the downward-direction G2 side of the first guide surface 72, substantially parallel to the upper part 23U of the conveyor belt, and a connecting guide surface 73 is formed between the first guide surface 72 and the second guide surface 74 (Figure 6, etc.). However, the present invention is not limited to this, and various shapes may be used, for example, by forming a curved guide surface that protrudes downward instead of the second guide surface 74.

[0106] Furthermore, in the embodiments described above, the first guide surface 72 of the base frame 40 in the ID unit 32 is described as being a flat, planar shape (Figures 4 and 5, etc.). However, the present invention is not limited to this, and the first guide surface 72 may be a curved surface, or it may be a curved surface that is bent in a broken line shape when viewed from the left or right direction, for example, by connecting multiple planes at different angles. In this case, it is sufficient if the guide film 75 can be attached in accordance with the shape of the first guide surface 72.

[0107] Furthermore, in the embodiment described above, a configuration was described in which the angle between the first guide surface 72 of the base frame 40 and the upper part 23U of the conveyor belt is approximately 23 degrees. However, the present invention is not limited to this, and various other angles such as approximately 30 degrees or approximately 15 degrees may be used. The point is that the leading edge of the paper P can be slid and guided to the vicinity of the upper part 23U of the conveyor belt.

[0108] Furthermore, in the above-described embodiment, the guide film 75 is attached to the first guide surface 72 of the base frame 40 in the ID unit 32 using double-sided adhesive tape 76. However, the present invention is not limited to this, and the guide film 75 may be attached using, for example, a well-known adhesive, or the guide film 75 may be attached using mounting screws or the like. Alternatively, for example, a predetermined engaging shape may be formed on the base frame 40 and an engaging shape that engages with it may be formed on a part of the guide film 75, and the two may be engaged.

[0109] Furthermore, in the first embodiment described above, a configuration was described in which the image forming apparatus 1 is provided with four image forming units 30. However, the present invention is not limited to this, and may be provided with three or fewer, or five or more, image forming units 30.

[0110] Furthermore, the embodiments described above describe a configuration in which the image forming apparatus 1 is configured as a single-function printer. However, the present invention is not limited to this, and the image forming apparatus 1 may also be configured as an MFP (Multi-Function Peripheral) having the functions of a copier or a facsimile machine, for example.

[0111] Furthermore, the present invention is not limited to the embodiments described above and other embodiments. That is, the scope of application of the present invention extends to embodiments that arbitrarily combine some or all of the embodiments described above and other embodiments, as well as embodiments that extract some of them.

[0112] Furthermore, in the above-described embodiment, an image forming apparatus 1 was described in which a tray 5 and paper feed transport unit 10 as a media supply unit, a transport belt 23, an ID unit 32 and transfer roller 34 as an image forming transfer unit, and a guide film 75 as a guide member were used to configure the image forming apparatus. However, the present invention is not limited to this, and an image forming apparatus may be configured with a media supply unit, a transport belt, an image forming transfer unit, and a guide member in various other configurations. [Industrial applicability]

[0113] This invention can be used, for example, in an electrophotographic printer. [Explanation of Symbols]

[0114] 1...Image forming apparatus, 3...Control unit, 5...Tray, 10...Paper feed transport unit, 20...Transport unit, 23...Transport belt, 23U...Upper part of transport belt, 30...Image forming unit, 32...ID unit, 34...Transfer roller, 40...Base frame, 45...Photoreceptor drum, 50...Fusing unit, 72...First guide surface, 73...Connection guide surface, 74...Second guide surface, 75...Guide film, 75L...Lower end of guide film, G1...Guide upward direction, G2...Guide downward direction, L1...Lower end belt distance, L2...Lower end drum distance, L3...Distance, P...Paper, QC...Transfer location, TC...Toner image, W...Transport path.

Claims

1. An image forming apparatus for forming an image on a medium, A media supply unit that supplies the aforementioned medium, A conveyor belt that conveys the medium supplied from the medium supply unit toward the fixing unit along the conveying direction, An image forming and transfer unit transfers the image formed on the image carrier to the medium being transported by the conveyor belt at the transfer location, A guide member is provided upstream of the transfer location in the image forming transfer section in the transport direction, is flexible, and is positioned to approach the transport belt as it moves downstream in the transport direction. It has, The shortest distance from the end of the guide member, which is the end closest to the conveyor belt, to the conveyor belt is greater than the maximum thickness specified in the specifications of the image forming apparatus. An image forming apparatus characterized by the following features.

2. The first distance, which is the shortest distance from the end of the guide member to the conveyor belt, is smaller than the second distance, which is the shortest distance from the end of the guide member to the image carrier. The image forming apparatus according to feature 1.

3. The image forming transfer unit has a holding portion that holds the image carrier, and a first guide surface that approaches the conveyor belt as it moves downstream in the conveying direction, The guide member is a flexible member, attached to the first guide surface, with a portion of it protruding from the first guide surface toward the conveyor belt. The image forming apparatus according to feature 1.

4. The image forming transfer unit has a second guide surface on the holding unit, which is located downstream of the first guide surface in the transport direction and has a different angle with respect to the transport belt than the first guide surface, and a connecting guide surface is formed which is a curved surface connecting the first guide surface and the second guide surface. The image forming apparatus according to feature 3.

5. The image forming apparatus is provided with a plurality of image forming transfer units along the transport direction, The guide member is provided in the image forming transfer section located on the upstream side in the transport direction. The image forming apparatus according to feature 1.

6. The rigidity of the guide member is higher than the rigidity of the medium, which may bend after printing. The image forming apparatus according to feature 1.

7. The rigidity of the guide member is such that the weighing capacity is 120 [g / m] ２ Higher than the rigidity of the aforementioned medium The image forming apparatus according to feature 6.

8. The length of the guide member in the width direction perpendicular to the transport direction of the medium transported by the image forming transfer unit is 80% or more of the maximum length in the width direction of the medium supplied from the medium supply unit. The image forming apparatus according to feature 1.

9. A media supply unit that supplies media, A conveyor belt that conveys the medium supplied from the medium supply unit toward the fixing unit along the conveying direction, The image forming and transfer unit transfers the image formed on the image carrier to the medium being transported by the conveyor belt at the transfer location, A guide member is provided upstream of the transfer location in the image forming transfer section in the transport direction, is flexible, and is positioned to approach the transport belt as it moves downstream in the transport direction. It has, The first distance, which is the shortest distance from the end of the guide member (the end closest to the conveyor belt) to the conveyor belt, is smaller than the second distance, which is the shortest distance from the end of the guide member to the image carrier. An image forming apparatus characterized by the following features.

Images