JP2000047443A - Electrophotographic device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrophotographic device capable of satisfactorily carrying a recording medium even regardless of thickness. SOLUTION: A guide member 25 for branching the route of a recording medium 14 to a re-carrying passage and a discharge passage is fixed to the inner wall of a casing. Two struts 7a, 23a are fixed to the inner wall of the casing, and a route switching member 7 for selectively closing either one of the re-carrying passage and the discharge passage is rockably mounted on one strut 7a, and a guide member 23 for guiding the recording medium 14 passed through fixing rollers 18a, 18b to the branch point between the re-carrying passage and the discharge passage is rockably mounted on the other strut 23a. A controller inclines the guide member 23 by an angle θaccording to the thickness of the recording medium 13 by controlling a solenoid for rocking the route switching member 7 around the strut 7a.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic apparatus capable of printing an image on both sides of a recording medium, such as an electronic copier and a printer.

[0002]

2. Description of the Related Art When a normal electrophotographic apparatus is used in a double-sided printing mode, a recording sheet on which one side of a recording process (hereinafter referred to as a front side recording process) has been completed is transported while the other side is being conveyed. (Hereinafter referred to as a backside recording process). The reversing method of the recording paper at this time includes (1) returning the recording paper to the paper feed tray after reversing, (2) switching back the recording paper, and (3) winding the recording paper around the reversing roller. Either one is often adopted.

[0003]

However, in the above-mentioned conventional electrophotographic apparatus, the recording paper being conveyed is curled due to the influence of heat from the two fixing rollers and a conveyed path which is bent to reduce the size of the apparatus. It has factors to cause. In particular,
As shown in FIG. 5, if the recording paper is guided to a straight path B after passing between the two fixing rollers, the recording paper does not curl (b), but the curved path A , C, the recording paper undergoes curls following the curves of paths A and C (a) and (c). When the recording paper being conveyed is curled, the recording paper is often not smoothly conveyed thereafter. Abnormal conditions that are likely to occur in the two-sided printing mode in which the recording medium transport distance is long,
Skew, broken ears, and the like are often caused by curling of recording paper during conveyance. More specifically, if the recording medium curls to the back side in the front side recording process, a jam or the like in the resist portion for correcting skew is likely to occur, or as shown in FIG. The recording paper hardly peels off from the body (transfer drum, transfer belt, etc.), and the jam around the transfer body is liable to occur. In addition, winding of the recording paper around the transfer body may cause a transfer failure or the like due to excessive supply of the transfer voltage.

Therefore, it is necessary to suppress the curl generated on the recording paper being conveyed. However, the fact that the thickness of the recording paper distributed in the market is various makes it difficult. This is because various curls occur on the recording paper depending on its thickness.

Accordingly, it is a first object of the present invention to provide an electrophotographic apparatus capable of smoothly conveying a recording medium. It is a second object of the present invention to provide an electrophotographic apparatus capable of smoothly transporting a recording medium of any thickness.

[0006]

In order to solve the above-mentioned problems, the present invention is directed to an electrophotographic apparatus having a re-sending mechanism for reversing the front and back of a recording medium discharged from a fixing device and re-sending the recording medium to a photosensitive member. An apparatus, comprising: a curl suppressing unit that curves a recording medium discharged from the fixing device in a direction opposite to a curve of a path through which the recording medium is guided; and a control unit that controls the curl suppressing unit. An electrophotographic apparatus is provided.

According to the electrophotographic apparatus, since the curl suppressing means deforms the recording medium, curling of the recording medium due to the influence of heat from the fixing device is suppressed.
The recording medium can be transported smoothly.

In this electrophotographic apparatus, if the control means controls the amount of deformation of the recording medium in accordance with the thickness of the recording medium, the recording medium is suitable for the thickness. Since the recording medium is deformed, the recording medium having any thickness can be conveyed smoothly.

[0009]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

First, the overall configuration of the electrophotographic apparatus according to the present embodiment will be schematically described with reference to FIG. However, here, an electrophotographic apparatus for color printing will be described as an example.

The housing 5 of the electrophotographic apparatus includes a detachable cassette 12 for storing a recording medium 14 such as recording paper, and a discharge tray 20 on which the recording medium 14 after image recording is stacked.
Is provided.

A controller (not shown) for controlling the entire apparatus, a recording medium transport mechanism for transporting the recording medium 14 from the cassette 12 to the discharge tray 20, and a recording medium 14 being transported are provided inside the housing 5. And a recording unit for executing image forming processing.

The recording section includes a photosensitive belt 2, a photosensitive belt feeding mechanism for feeding the photosensitive belt 2 stretched between two driven rollers 1b and the driving roller 1a in a predetermined direction, and a surface of the photosensitive belt 2 to a predetermined position. A charger 3 for charging to a potential, an optical system box 4 for emitting a laser beam 4a for forming an electrostatic latent image of each color component on the charged photosensitive belt 2, and an electrostatic latent image on the photosensitive belt 2. Each color component that attaches toner to
(Black, yellow, magenta, cyan) developing unit 6
(K), 6 (Y), 6 (M), 6 (C), a transfer drum 10a and a transfer roller 10b for electrostatically transferring the toner images of the respective colors on the photosensitive belt 2 to the recording medium 14 in a superimposed manner; Recording medium 14 on which a color toner image has been transferred from drum 10a
An AC neutralizer 17 for removing static electricity from the recording medium, and sandwiching the recording medium after static elimination between the two heat rollers 18a and 18b to remove the recording medium 14
A fixing device 18 for thermally fixing a color toner image on the transfer drum 10a, a cleaning blade 11 for removing toner remaining on the photoreceptor belt 2 after transferring the toner images of each color to the transfer drum 10a, and a color toner image on the recording medium 14. Is provided with a drum cleaner 21 for removing the toner remaining on the transfer drum 10a after the transfer of the toner. The developing units 6 (K), 6 (Y), 6 (M), 6 (C) for the respective color components are provided on the photosensitive belt 2 on which the electrostatic latent images of the corresponding color components are formed. A developing roller 6a to be contacted; a supply roller 6c for supplying a non-magnetic one-component toner on the developing roller 6a; and an elastic blade for forming a uniform toner layer on the developing roller 6a by frictionally charging the toner on the developing roller 6a. 6d, a reset roller 6b for removing the toner layer on the developing roller 6a, and a transport roller 6e for transporting the toner to the supply roller 6c side are provided.

The recording medium transport mechanism includes a transport path for the recording medium 14, a plurality of rollers, a motor (not shown) for rotating each roller under the control of a controller, and the like. That is, a feeding section for feeding the recording medium 14 from the cassette 12 to the recording section, and the recording medium 14 discharged from the recording section (fixing device 18)
0, a re-sending unit that re-sends the recording medium 14 discharged from the recording unit (the fixing unit 18) to the recording unit, and a path switching that switches a path of the recording medium 14 discharged from the recording unit (the fixing unit 18). Divided into parts. In both the double-sided recording mode and the single-sided recording mode, first, the cassette 12
The recording medium 14 stored in the recording medium is sent out onto the conveyance path by the rotation of the delivery roller 13, and is sent to the recording unit while the skew is corrected by the rotation of the registration rollers 15 arranged in the conveyance path (feeding). Part). And
The recording medium 14 discharged from the fixing device 18 is guided by the guide member 23 and the path switching member 7 to the re-sending path only when the back side recording process in the double-sided recording mode is performed. (A path switching unit described later). Then, the recording medium 1 guided to the discharge path side
4 is discharged to a discharge tray 20 by rotation of a discharge roller 19 disposed in the discharge path (discharge unit). On the other hand, the recording medium 14 discharged to the re-sending path is fed into the reversing roller 8 by the rotation of the conveying rollers 24 arranged at a plurality of positions on the re-sending path, and is caught by the reversing roller 8 during normal rotation. Then, the sheet is re-sent to the registration roller 15 of the feeding section by the reverse rotation of the reversing roller 8 and the rotation of the press roller 9 (re-sending section).

Next, referring to FIG. 2, FIG. 3, and FIG. 4, details of the path switching section of the above-described recording medium transport mechanism will be described.

A guide member 22 for branching the path of the recording medium 14 into a re-sending path and a discharging path is fixed to the inner wall of the housing 5. In addition, two support shafts 7a,
23a is fixed, and a path switching member 7 for selectively closing either the re-sending path or the discharging path is swingably attached to one of the support shafts 7a, and the other support shaft 2a.
3a, two heat rollers 18a, 18b of the fixing device 18 are provided.
A guide member 23 for guiding the recording medium 14 that has passed through the recording medium 14 to a branch point between the re-sending path and the discharging path is swingably attached. Then, under the control of the controller, a solenoid (not shown) swings the path switching member 7 around the support shaft 7a. For example, when performing the back side printing process in the double side printing mode, as shown in FIG.
By driving the solenoid, the path switching member 7 closes the discharge path. At this time, the tip of the path switching member 7 is
3, the guide member 23 is inclined by an angle θ corresponding to the displacement of the tip of the path switching member 7.
Therefore, the recording medium 14 that is curved toward the retransmission path side includes:
Immediately after being extruded from between the two heat rollers 18a and 18b (that is, in a state where there is residual heat), a deflection is given in a direction to offset the curvature. As a result, the recording medium 14 is smoothly conveyed on the re-sending path in a proper state without curl, and then sent to the recording unit in a proper state without curl as shown in FIG. On the other hand, in the case of the single-sided recording mode or when the back-side recording process of the double-sided recording mode is completed, as shown in FIG. 2B, the path switching member 7 closes the retransmission path by driving the solenoid. At this time, since the tip of the path switching member 7 engages with the inner wall at the end of the guide member 23, the guide member 23 is inclined by an angle θ corresponding to the displacement of the tip of the path switching member 7. Therefore, immediately after being extruded from between the two heat rollers 18a and 18b (that is, in a state where there is residual heat), the recording medium 14 that is curved toward the discharge path is given a deflection in a direction to cancel the curvature. . Thereby, the recording medium 14
Is smoothly transported on the discharge path in an appropriate state without curling.

In this embodiment, the recording medium is bent by the guide member 23 on the side opposite to the curved path, but the recording medium is bent by the other member on the side opposite to the curved path 14. You can let it go. Further, in the present embodiment, the guide member 23 is moved by the path switching member 7, but may be reversed, or the guide member 23 and the path switching member 7 are moved by separate driving sources. It may be done.

Incidentally, it is known that the curl generated on the recording medium 14 by the influence of heat from the fixing device 18 has a correlation with the thickness of the recording medium 14. Therefore, in the present embodiment, the photo sensor for detecting the thickness of the recording medium 14 is provided at an appropriate position on the feeding path, or the thickness of the recording medium is designated by the user, as described below. As described above, the amount of deformation applied to the recording medium 14 from the guide member 23 is controlled according to the thickness of the recording medium 14. The controller drives the solenoid based on the detection value output from the detection circuit of the photo sensor or the designation from the user, and guides the guide member 23 to the common tangent line of the two heat rollers 18a and 18b.
Is controlled. That is, the controller operates the recording medium 1 according to the relationship shown in FIG.
The solenoid is controlled such that the thinner 4 is, the larger the inclination angle θ of the guide member 23 with respect to the common tangent line of the two heat rollers 18a and 18b is. Accordingly, even if a recording medium having any thickness is used, it is possible to ensure smooth conveyance after passing through the fixing device. It is preferable that the guide member 23 be swingable up to about 30 ° in each of the left and right directions, assuming that various types of recording paper on the market are used.

[0019]

According to the electrophotographic apparatus of the present invention, the curl of the recording medium during conveyance is suppressed, so that the recording medium can be smoothly conveyed. The same effect can be obtained for a recording medium of any thickness.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of a color electrophotographic apparatus according to an embodiment of the present invention.

FIG. 2 is a diagram illustrating a state in which a recording medium passes through a path switching unit of the color electrophotographic apparatus according to one embodiment of the present invention.

FIG. 3 is a diagram illustrating a state in which a recording medium is passing through a recording unit of the color electrophotographic apparatus according to one embodiment of the present invention.

FIG. 4 is a diagram illustrating a correspondence relationship between a thickness of a recording medium and an inclination angle of a guide member.

FIG. 5 is a diagram for explaining a relationship between a traveling direction and a state of a recording medium that has passed through a fixing device of a conventional electrophotographic apparatus.

FIG. 6 is a view showing a state in which a jam around a transfer body (transfer drum) occurs in a conventional electrophotographic apparatus.

[Explanation of symbols]

 1a Drive roller 1b Follower roller 2 Photosensitive belt 3 Charger 4 Optical system box 4a Laser beam 5 Housing 6 (K), 6 (Y), 6 (M), 6 (C) ... Each color Component developing device 6a developing roller 6c supply roller 6d elastic blade 6b reset roller 7 path switching member 7a support shaft of path switching member 8 reversing roller 9 pressing roller 10a transfer drum 10b Transfer roller 11 Cleaning blade 12 Cassette 13 Delivery roller 14 Recording medium such as recording paper 15 Registration roller 17 AC eliminator 18a, 18b Heat roller 18 Fixing device 19 Discharge roller 20 ... Discharge tray 21. Drum cleaner 22. Guide member 23. Guide member 23a.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G03G 15/20 G03G 15/20 (72) Inventor Katsuyoshi Onose 1-1-1, Higashitagacho, Hitachi City, Ibaraki Prefecture F-term (reference) in Hitachi, Ltd.Electrical Equipment Division

Claims (3)

[Claims] An electrophotographic apparatus having a re-sending mechanism for reversing the recording medium discharged from a fixing device and re-sending the recording medium to a photosensitive member, wherein the recording medium discharged from the fixing device is removed. An electrophotographic apparatus, comprising: a curl suppressing unit that curves to a side opposite to a curve of a path through which the recording medium is guided; and a control unit that controls the curl suppressing unit. 2. The electrophotographic apparatus according to claim 1, wherein said control means controls a deformation amount applied to said recording medium by said curl suppressing means according to a thickness of said recording medium. Electrophotographic apparatus. 3. The electrophotographic apparatus according to claim 1, wherein the curl suppressing unit includes a path to a discharge port side of the recording medium discharged from the fixing device and a path to the re-feed mechanism side. A path switching member that is disposed at a branch point and selectively closes one of the two paths; and a recording medium that is discharged from the fixing device is guided to the branch point. A guide member for providing the bending to the recording medium being guided to the branch point in conjunction with the control unit, wherein the control unit controls the movement of at least one of the path switching member and the guide member. Electrophotographic equipment.