Image forming apparatus

Abstract

To prevent a guide member from getting dirty with toner when clearing a jam of the recording medium.SOLUTION: When a fixing unit is located at a first position, a moving member is located on a side of a first rotating body with respect to a virtual line connecting an end on a recording material entrance side of a fixing nip part and an end on the upstream side in a recording material conveyance direction of a guide member to each other when seen in a rotation axis direction, and when the fixing unit is located at a second position, the moving member is located at a position where at least part of the moving member projects toward a second rotating body beyond the virtual line.SELECTED DRAWING: Figure 11

Description

[Technical Field]

[0001] The present invention relates to a toner image forming apparatus that forms a toner image on a recording material using electrophotographic recording technology. [Background technology]

[0002] Toner image forming devices using electrophotographic recording technology, such as printers, copiers, and multifunction devices, are equipped with a fixing unit that fixes a toner image formed on a recording material to the recording material. It has also been considered to make it easier to replace the fixing unit in the main body of the image forming device by moving the fixing unit from a first position to a second position during printing (Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2012-47806 Summary of the Invention [Problem to be solved by the invention]

[0004] However, if the fixing unit is moved to the second position while a recording material is still caught in the fixing unit to clear a jammed recording material, it is conceivable that the unfixed toner on the recording material will come into contact with and contaminate the guide member that guides the recording material.If the fixing unit is returned to the first position and printing is resumed while the guide member is still contaminated with toner, the toner adhering to the guide member will contaminate the next recording material.

[0005] SUMMARY OF THE INVENTION An object of the present invention is to prevent a guide member from being soiled with toner when a jammed recording material is cleared. [Means for solving the problem]

[0006] In order to solve the above-mentioned problems, the present invention provides an image forming apparatus having an image forming section having a transfer section that transfers an unfixed toner image onto a recording material, a first rotating body with which the unfixed toner image formed on the recording material comes into contact, a second rotating body that comes into contact with the outer circumferential surface of the first rotating body to form a fixing nip section between the first rotating body and the second rotating body, and a fixing unit that fixes the unfixed toner image formed on the recording material at the fixing nip section to the recording material, the image forming apparatus comprising: a first position when the unfixed toner image is fixed at the fixing nip section; and a support mechanism capable of moving the fixing unit while supporting it at a first position and a second position, the support mechanism being provided with a moving member that moves relative to the guide member when the fixing unit moves between the first position and the second position, and when the fixing unit is located at the first position, the moving member is located closer to the first rotating body than an imaginary line connecting an end of the fixing nip portion on the recording material entrance side when viewed in the direction of the rotation axis and an end of the guide member on the upstream side in the recording material transport direction, and when the fixing unit is located at the second position, the moving member is located at a position where at least a part of the moving member protrudes closer to the second rotating body than the imaginary line. [Effects of the Invention]

[0007] As described above, according to the present invention, it is possible to prevent the guide member from being soiled with toner when clearing a jammed recording material. [Brief explanation of the drawings]

[0008] [Figure 1] Cross-sectional view of an image forming apparatus [Figure 2] 1 is a cross-sectional view of an image forming apparatus showing a state in which a fixing unit has moved to a second position; [Figure 3] FIG. 1 is a perspective view of an image forming apparatus with a door open. [Figure 4]FIG. 1 is a perspective view of an image forming apparatus showing a state in which a fixing unit has moved to a second position; [Figure 5] FIG. 10 is a cross-sectional view illustrating a state in which the fixing unit has moved to the second position while the recording material is still caught in the fixing nip portion. [Figure 6] A perspective view of a guide member when retracting [Figure 7] Cross-sectional view of the fixing unit when it is located at the first position [Figure 8] Cross-sectional view of the fixing unit when it is located at the second position [Figure 9] A perspective view of a guide member [Figure 10] FIG. [Figure 11] Comparison of guide member positions when retracting DETAILED DESCRIPTION OF THE INVENTION

[0009] [Example 1] (Overall composition) A printer 1 as an image forming apparatus will be described with reference to Fig. 1. Fig. 1 is a diagram illustrating the overall configuration of the printer 1 according to this embodiment. The printer 1 is an electrophotographic color laser beam printer that forms a toner image on a sheet S as a recording material.

[0010] The printer 1 has a housing 1A, a laser scanner 2, a control unit 3, and a door (opening / closing member) 20 that can be opened and closed relative to the housing 1A. The printer 1 also has a sheet feeding unit 30, a transfer unit 40, a tray unit (moving unit, supporting unit) 50, and a fixing unit 80.

[0011] The housing 1A accommodates the scanner 2, the control unit 3, the sheet feeding unit 30, the transfer unit 40, the tray unit 50, and the fixing unit 80.

[0012] The sheet feeding section 30 has a stacking tray 31 for stacking sheets S, and a supply roller 32. The stacking tray 31 can be pulled out toward the door 20 to replenish the sheets S.

[0013] The tray unit 50 has a tray (support member) 51 and the cartridges PY, PM, PC, and PK. The tray 51 has a tray handle 52. The cartridges PY, PM, PC, and PK are removably attached to the tray 51.

[0014] The cartridges PY, PM, PC, and PK are each independently attachable to and detachable from the tray 51. The cartridges PY, PM, PC, and PK contain yellow (Y), magenta (M), cyan (C), and black (K) toner (developers), respectively. The cartridges PY, PM, PC, and PK have the same configuration except for the toner colors they contain. Therefore, the configuration and operation of only one of the cartridges PY, PM, PC, and PK will be described, and descriptions of the others will be omitted. Furthermore, when there is no need to distinguish between the cartridges PY, PM, PC, and PK, the cartridges PY, PM, PC, and PK may be simply referred to as cartridges.

[0015] Each cartridge has a photosensitive drum (image carrier) 61, a charging roller 62 (charging member), and a developing roller (developer carrier) 71. The rotational axes of the photosensitive drum 61, the developing roller 71, and the charging roller 62 are parallel to each other.

[0016] The portion where a black (K) toner image is formed is called the black station (first station), the photosensitive drum 61 of the first station is called the first photosensitive drum, the developing roller 71 is called the first developing roller, and the charging roller 62 is called the first charging roller.

[0017] The portion where a cyan (C) toner image is formed is called a cyan station (second station), the photosensitive drum 61 of the second station is called a second photosensitive drum, the developing roller 71 is called a second developing roller, and the charging roller 62 is called a second charging roller.

[0018] The portion where a magenta (M) toner image is formed is called the magenta station (third station), the photosensitive drum 61 of the third station is called the third photosensitive drum, the developing roller 71 is called the third developing roller, and the charging roller 62 is called the third charging roller.

[0019] The portion where a yellow (Y) toner image is formed is called the yellow station (fourth station), the photosensitive drum 61 of the fourth station is called the fourth photosensitive drum, the developing roller 71 is called the fourth developing roller, and the charging roller 62 is called the fourth charging roller.

[0020] The cartridge PK is installed in the black station, the cartridge PC in the cyan station, the cartridge PM in the magenta station, and the cartridge PY in the yellow station. The numbers 1, 2, 3, and 4 are used for convenience of explanation. In this embodiment, the cartridge includes the photosensitive drum 61, the charging roller 62, and the developing roller 71, but these components may also be provided on the tray 51.

[0021] The transfer unit 40 includes a belt 41, a primary transfer roller 42, a cleaning unit 43, a drive roller 46 that drives the belt 41, and a tension roller (driven roller) 47. The printer 1 is also provided with an optical sensor 44 that detects the toner image transferred to the belt 41. The belt 41 is disposed below the photosensitive drum 61, and the primary transfer roller 42 allows the belt 41 to contact the photosensitive drum 61 so that a primary transfer section is formed between the belt 41 and the photosensitive drum 61. The printer 1 also includes a secondary transfer roller 45 that contacts the belt 41 so as to form a secondary transfer section. The secondary transfer section is formed between the belt 41 and the secondary transfer roller 45. The rotation axes of the primary transfer roller 42, drive roller 46, tension roller 47, and secondary transfer roller 45 are parallel to one another. A registration roller pair 4 is disposed below the secondary transfer section. In the printer 1 of this embodiment, the laser scanner 2, the first to fourth stations, the belt 41, the primary transfer roller 42, the secondary transfer roller 45, etc. correspond to the image forming section, and the secondary transfer section corresponds to the transfer section that transfers the unfixed toner image onto the sheet S.

[0022] The fixing unit 80 is a unit that fixes an unfixed toner image formed on the sheet S to the sheet S at the fixing nip FN. The fixing unit 80 has a heating roller (first rotating body) 82 that comes into contact with the unfixed toner image formed on the sheet S, and a pressure roller (second rotating body) 81 that comes into contact with the outer circumferential surface of the heating roller 82 to form the fixing nip FN between the heating roller 82 and the heating roller 82. The fixing unit 80 also has a guide member 99 that is positioned closer to the heating roller 82 than the pressure roller 81 when viewed in the direction of the rotation axis of the pressure roller 81, and that guides the sheet S to the fixing nip FN. The guide member 99 is made of resin. When fixing an unfixed toner image at the fixing nip FN, the fixing unit 80 is located in the first position shown in FIG. 1.

[0023] 1 and 2, the movement of the transfer unit 40 and the tray unit 50 will be described. Fig. 2 is a cross-sectional view showing a state in which the door 20 is open and the fixing unit 80 has retreated to the second position.

[0024] The transfer unit 40 and the tray unit 50 can be moved from inside to outside the housing 1A through an opening 1A1 created by opening the door 20. The movement direction of the transfer unit 40 and the tray unit 50 is a direction that intersects with the rotation axis direction of the photosensitive drum 61.

[0025] In the horizontal direction X, the fixing unit 80 is disposed on the side of the opening 1A1 of the housing 1A. The door 20 attached to the housing 1A is rotatable between a closed position and an open position. As shown in FIG. 2, when the door 20 is in the open position, the opening 1A1 is formed. As shown in FIG. 1, when the door 20 is in the closed position, the door 20 covers the fixing unit 80 attached to the housing 1A. More specifically, when the door 20 is in the closed position, the upper cover portion 20b of the door 20 is located above the fixing unit 80.

[0026] As will be described later, the fixing unit 80 can be retracted toward the opening 1A1 side, moving from the state shown in Figure 1 to the state shown in Figure 2. That is, the fixing unit 80 can be moved between a first position where an unfixed toner image is fixed at the fixing nip FN, and a second position that is farther away from the transfer unit than the first position. With the door 20 and fixing unit 80 moved as shown in Figure 2, the transfer unit 40 and tray unit 50 can be moved from an inside position to an outside position of the housing 1A through the opening 1A1.

[0027] (Image formation operation) 1, the image forming operation of the printer 1 will be described. The control unit 3 of the printer 1 starts the image forming operation on the sheet S based on an image signal received from an external host device such as a personal computer or an image reader.

[0028] 1, the tray unit 50 and the transfer unit 40 are located inside the housing 1A, and the door 20 is located in the closed position. With the transfer unit 40 located inside the housing 1A, the belt 41 can contact the photosensitive drum 61.

[0029] While a charging voltage is applied to the charging roller 62 and the photosensitive drum 61 is rotating, the scanner 2 irradiates the photosensitive drum 61 with laser light corresponding to image information, exposing the surface of the photosensitive drum 61 charged by the charging roller 62. As a result, an electrostatic latent image corresponding to the image information is formed on the surface of the photosensitive drum 61.

[0030] A developing voltage is applied to the developing roller 71 that carries the toner, and the electrostatic latent image formed on the photosensitive drum 61 is developed with the toner supplied from the developing roller 71. In this way, a toner image is formed on the surface of the photosensitive drum 61. When a full-color toner image is formed, a toner image of each color is formed on each photosensitive drum 61.

[0031] The toner images formed on the respective photosensitive drums 61 are transferred onto the belt 41 by the primary transfer roller 42 at the primary transfer portion, and then move toward the secondary transfer portion formed by the belt 41 and the secondary transfer roller 45.

[0032] Meanwhile, the housing 1A is provided with a conveying path 1c through which the sheet S passes toward the fixing unit 80, and inside the door 20 is formed a double-sided conveying path 20a through which the sheet S passes after passing through the fixing unit 80. When the door 20 is opened, the conveying path 1c and a part of the double-sided conveying path 20a are exposed.

[0033] Sheets S stacked on stacking tray 31 are fed by supply roller 32 at a predetermined timing and conveyed through sheet feed conveyance path 1a toward the secondary transfer unit. At the secondary transfer unit, a toner image is transferred from belt 41 to sheet S. Toner that has not been transferred to sheet S is removed from belt 41 by a cleaning blade (cleaning member) 43A provided in cleaning unit 43.

[0034] The sheet S onto which the toner image has been transferred in the secondary transfer unit is transported toward the fixing unit 80. In the fixing unit 80, the toner image is fixed to the sheet S. The sheet S onto which the toner image has been fixed is transported toward a flapper 5, which serves as a transport path switching unit. The flapper 5 is movable between a paper discharge position where the sheet S that has passed through the fixing unit 80 is guided toward a paper discharge path 1d, and a reversing position where the sheet S is guided toward a reversing path 1e.

[0035] When printing on only one side, the sheet S is guided by the flapper 5 to the discharge path 1d and discharged onto the discharge tray 1f formed at the top of the housing 1A. On the other hand, when printing on both sides, the sheet S is guided by the flapper 5 to the reversal path 1e. After the sheet S is guided to the reversal path 1e, the conveying direction of the sheet S is reversed, and the sheet S is conveyed again toward the secondary transfer unit through the double-sided conveying path 20a formed inside the door 20. Thereafter, at the secondary transfer unit, a toner image is transferred onto the back side of the sheet S, and the sheet S passes through the fixing unit 80 again, is guided by the flapper 5 to the discharge path 1d, and is discharged onto the discharge tray 1f.

[0036] (Support structure of the fixing unit) 2 and 6(a), a detailed description will be given of the support mechanism 90M of the fixing unit 80. The support mechanism 90M can move the fixing unit 80, while supporting it, between a first position (position in FIG. 1) for fixing an unfixed toner image at the fixing nip FN, and a second position (position in FIG. 2) that is farther from the transfer section than the first position.

[0037] The fixing unit 80 is mounted on a mounting portion 91 that supports the bottom surface of the fixing unit 80. The mounting portion 91 is connected to two support members 90c that are provided on one end side and the other end side of the printer 1 in the Y-axis direction (the direction of the rotation axis of the pressure roller 81). Support members 90a and 90b are connected to the two support members 90c, respectively. Lift springs 97a are provided on the two support members 90a, and lift springs 97b are provided on the two support members 90b, respectively. The lift springs 97a and 97b urge the fixing unit 80 in a lifting direction that lifts the fixing unit 80 from the first position to the second position.

[0038] 3 and 4 are perspective views of the printer 1 with the door 20 open. The release lever 96 is a lever that releases the lock that prevents the movement of the fixing unit 80. By pressing the release lever 96, the fixing unit 80 attached to the attachment portion 91 moves from the position shown in FIG. 3 to the position shown in FIG. 4 by the force of the lift springs 97a and 97b without the user having to apply any force. The position of the fixing unit 80 in FIG. 3 is the first position, and the position of the fixing unit 80 in FIG. 4 is the second position.

[0039] (Configuration of guide member during evacuation) 5 is a cross-sectional view of the state in which the sheet S has become stuck in the fixing nip FN due to a jam or the like, and the fixing unit 80 has been moved to the second position in this state. As shown in the figure, if a user attempts to remove the sheet S in this state, it is possible that the sheet S may accidentally come into contact with the guide member 99 of the fixing unit 80, causing the guide member 99 to become soiled with unfixed toner on the sheet S. If printing is resumed with the guide member 99 still soiled, the leading edge of the sheet S will become soiled.

[0040] Therefore, the support mechanism 90M is provided with a retraction guide member (moving member) 98 that moves relative to the guide member 99 when the fixing unit 80 moves between the first position and the second position. The retraction guide member 98 serves to prevent the guide member 99 from being soiled with toner when it is at the second position.

[0041] 6A and 6B are perspective views illustrating the configuration of the retraction guide member 98, with FIG. 6A showing the fixing unit 80 in the first position and FIG. 6B showing the fixing unit 80 in the second position. The retraction guide member 98 is a metal rod that is attached to the two support members 90a so as to connect them. The length of the retraction guide member 98 in the Y-axis direction is equal to or greater than the width of the widest recording material that can be used in the printer 1.

[0042] When moving from the first position in FIG. 6(a) to the second position in FIG. 6(b), the retracting guide member 98 moves in the vertical direction (Z-axis direction) and also in the horizontal direction (X-axis direction).

[0043] 7 and 8 are cross-sectional views showing the positional relationship between the retraction guide member 98 and (the guide member 99 of) the fixing unit 80, with FIG. 7 showing the first position and FIG. 8 showing the second position. The fixing unit 80 attached to the attachment portion 91 is connected to the support member 90c, while the retraction guide member 98 is connected to the support member 90a. Therefore, the relative positions of the retraction guide member 98 and (the guide member 99 of) the fixing unit 80 differ between the first position in FIG. 7 and the second position in FIG. 8. Therefore, the relative positions of the retraction guide member 98 and the guide member 99 attached to the fixing unit 80 also differ between the first position and the second position.

[0044] Fig. 9 is a perspective view of the guide member 99, Fig. 10 is a cross-sectional view of the guide member, and Fig. 11 is a diagram in which the positions of the heat roller 82, pressure roller 81, guide member 99, and retracted guide member 98 are extracted from Figs. 7 and 8, and the position of the sheet S is added. Fig. 11(a) shows the first position, and Fig. 11(b) shows the second position. In Fig. 11, line L is an imaginary line connecting the end of the fixing nip portion FN on the recording material entrance side when viewed in the Y direction to the end of the guide member 99 on the upstream side in the recording material transport direction.

[0045] When the fixing unit 80 is in the first position, the retraction guide member 98 is located on the heating roller 82 side AR1 from the imaginary line L. When the fixing unit 80 is in the second position, the retraction guide member 98 is located at a position protruding from the imaginary line L to the pressure roller 81 side AR2.

[0046] Therefore, even if the user moves the sheet S in the X-axis direction in an attempt to remove the sheet S in the state shown in Figure 11(b), the retracted guide member 98 can prevent the unfixed toner on the sheet S from coming into contact with the guide member 99.

[0047] In this embodiment, when the fixing unit 80 is located at the second position, the entire retraction guide member 98 protrudes toward the side AR2 of the pressure roller 81. However, as shown in Figure 11(c) , when the fixing unit 80 is located at the second position, the retraction guide member 98 may be located at a position where at least a part of the retraction guide member 98 protrudes toward the side AR2 of the pressure roller 81 beyond the imaginary line L. [Explanation of symbols]

[0048] 1. Printer 80 Fuser unit 98 Guide member when retracting 99 Guide member 99x Guide member tip position L Virtual Line S seat

Claims

1. an image forming unit having a transfer unit that transfers an unfixed toner image onto a recording material; a fixing unit including a first rotating body with which an unfixed toner image formed on a recording material comes into contact, a second rotating body that comes into contact with the outer circumferential surface of the first rotating body to form a fixing nip portion between the first rotating body and the second rotating body, and a guide member that is disposed closer to the first rotating body than the second rotating body when viewed in the direction of the rotation axis of the second rotating body and that guides the recording material to the fixing nip portion, and that fixes the unfixed toner image formed on the recording material at the fixing nip portion to the recording material; In an image forming apparatus having a support mechanism capable of moving the fixing unit while supporting it between a first position when fixing an unfixed toner image in the fixing nip portion and a second position that is farther from the transfer portion than the first position; the support mechanism is provided with a moving member that moves relative to the guide member when the fixing unit moves between the first position and the second position, when the fixing unit is located at the first position, the moving member is located closer to the first rotating body than an imaginary line connecting an end of the fixing nip portion on a recording material entrance side and an end of the guide member on an upstream side in a recording material conveyance direction when viewed in the direction of the rotation axis; an image forming apparatus characterized in that, when the fixing unit is located at the second position, the movable member is located at a position where at least a portion of the movable member protrudes toward the second rotating body beyond the virtual line;

2. 2. The image forming apparatus according to claim 1, wherein when the fixing unit is located at the second position, the movable member is located at a position where the entire movable member protrudes toward the second rotating body beyond the virtual line.

3. 2. The image forming apparatus according to claim 1, wherein the length of the moving member in the direction of the rotation axis is equal to or greater than the width of a recording material having a maximum width that can be used in the image forming apparatus.

4. The image forming apparatus according to claim 1, characterized in that the support mechanism has two support members provided at one end side and the other end side of the image forming apparatus in the direction of the rotation axis, and the moving member is attached to the two support members so as to connect the two support members.

5. 5. The image forming apparatus according to claim 4, wherein the moving member is a metal rod.

Images