JP4498328B2 - Conveying roller structure and image forming apparatus using the same - Google Patents

Description

  The present invention relates to a conveying roller structure and an image forming apparatus using the same, and in particular, image information formed by an electrophotographic method is visualized by a developer, and a recording medium on which the developer image is formed is conveyed by a roller. The present invention relates to a transport roller structure for transporting by an image forming apparatus and an image forming apparatus using the same.

Conventionally, in an image forming apparatus, image formation by electrophotography is performed using toner as a material for visualizing image information on a sheet.
The toner is usually composed of a transparent resin component (approximately 80%), an internal additive such as a colorant, a charge control agent, and a lubricant (improving slipperiness), and an external additive such as Sio ₂ . .

  The toner configured in this manner is electrostatically adsorbed onto the recording medium at the transfer portion in the printing process, and is melted and fixed on the recording medium with heat and pressure in the fixing process and is discharged outside the apparatus. However, when the toner immediately after passing through the fixing step is in a high heat state immediately after melting, the lubricant or the like in the toner component immediately after melting is deposited on the surface of the toner and is in a softened state. When the toner on the recording medium is in the state as described above, if it is rubbed in contact with the conveying roller disposed in the recording medium conveying path of the apparatus, colorant, lubricant, etc. may adhere to the conveying roller. Become.

  On the other hand, the conveyance roller is arranged to convey the recording medium to the next process, and its configuration is mainly in contact with the driving roller connected to the driving source, the rotational force of the driving roller and the driving roller. And a driven roller that is driven to rotate by the driving roller by the pressure contact force (nip pressure).

Generally, the drive roller often uses a hard material (metal, hard resin, etc.) in order to stably transmit the drive force from the drive source to the driven roller. On the other hand, the driven roller is a softer material than the drive roller in order to ensure a nip width with a predetermined pressure with respect to the drive roller and to reliably guide the conveyed recording medium to the transport roller and transport it to the next process. It is often composed of (a rubber or the like having a low hardness).
Further, the surface roughness of the driven roller and the driven roller is generally configured such that the surface of the driven roller is rougher than the driving roller due to the difference in the material constituting each (see Patent Document 1).
JP-A-8-108953

  However, when the toner image formed on the recording medium passes through the thus configured conveying roller while being heated and softened, a problem arises in that a toner component adheres to the surface of the conveying roller. The adhering toner is likely to be adsorbed to the uneven portions on the surface of the driven roller having a “rough” surface due to the surface roughness relationship between the driving roller and the driven roller before the toner temperature is lowered.

  Then, as shown in FIG. 6, the toner adhering to the driven roller adheres to the print surface of the recording medium P0 conveyed by the driven roller as “streaks P3” along the recording medium conveying direction as dirt. Detected.

  Since the lubricant constituting the toner material has a softening temperature lower than that of the colorant and resin, the lubricating component in the toner material adsorbed by the conveyance roller is a high-temperature toner during conveyance of the recording medium in the next process. It is softened by the heat effect of and deposited on the recording medium. In general, since many lubricants used as an internal additive of toner are colorless, it is difficult to confirm “streaks P3” on ordinary recording paper, which is not conspicuous.

  However, when irradiating light onto image information printed like OHP and projecting the image information contents in an enlarged manner, the lubricant deposited on the OHP is projected as a “nigori” component of the image. .

  The present invention has been made in view of the above-described conventional problems, and uses a transport roller structure capable of realizing high-quality image output by preventing toner from adhering to a transport roller for transporting a recording medium. An object of the present invention is to provide an image forming apparatus.

In order to solve the above-described problems, the structure of the conveying roller structure and the image forming apparatus using the same according to the present invention are as follows.
Conveying roller structure as claimed in claim 1 is drive moving roller and a driven roller and by Ri conveying roller configuration, the driving roller is disposed at the position opposite the printing surface of the recording medium, the driven roller is the recording The drive roller is disposed at a position facing the back surface of the printing surface of the medium, and the driving roller has a surface roughness finer than that of the driven roller, and a toner image is formed by the driving roller and the driven roller. In the conveying roller structure for nipping and conveying the formed recording medium , the driven roller is configured by a soft member including a soft resin material, a hard rubber material, or a foaming elastic member, and the driving roller is configured as the driven roller. It is characterized in that it is formed of a hard metal member as compared with the above.

According to a second aspect of the present invention, there is provided an image forming apparatus including: a recording medium conveying unit that conveys a recording medium; and a developer image that is visualized by using a developer based on input image information. An image forming unit to be formed, a conveyance roller structure for conveying a recording medium on which a developer image is formed by a conveyance roller composed of a driving roller and a driven roller, and an unfixed developer image formed on the recording medium In the image forming apparatus comprising: a fixing unit that melts and fixes the recording medium on the recording medium; and a paper discharge tray as a recording medium discharge unit that discharges the recording medium after the developer image fixing process. The transport roller structure according to claim 1 is provided.

  In the present invention, the developer includes one using toner, and the developer image includes a toner image formed using toner.

According to a third aspect of the present invention, in addition to the configuration described in the second aspect , the recording medium after the developer image fixing process is discharged to the recording medium discharge portion downstream of the fixing unit in the recording medium conveyance direction. An image forming apparatus provided with a recording medium discharge unit, for example, a discharge roller, wherein the transport roller structure is arranged on a recording medium transport path from the fixing unit to the recording medium discharge unit. To do.

According to the invention described in claim 1, is drive moving roller and a driven roller and by Ri conveying roller configuration, the driving roller is disposed at the position opposite the printing surface of the recording medium, the driven roller is the recording The drive roller is disposed at a position facing the back surface of the printing surface of the medium, and the driving roller has a surface roughness finer than that of the driven roller, and a toner image is formed by the driving roller and the driven roller. In the conveying roller structure for nipping and conveying the formed recording medium , the driven roller is configured by a soft member including a soft resin material, a hard rubber material, or a foaming elastic member, and the driving roller is configured as the driven roller. compared to that formed by a rigid metal member, and prevent the lubricant deposited from the toner and the toner softened by the high temperature heating is attached to the conveying roller and thereby the next step ( Since the lubricating agent deposited from the toner and the toner on the recording medium of the printing process) of transferring it can be suppressed, thereby realizing a high-quality image output without contaminating the recording medium.

Moreover, according to the invention of Claims 2-3 , in addition to the said common effect obtained by the invention of Claim 1, the following effect can be acquired.

According to the second aspect of the present invention, the recording medium conveying means for conveying the recording medium and the developer image (for example, toner image) visualized using the developer based on the input image information are conveyed. Formed on the recording medium, an image forming means for forming on the recording medium, a conveying roller structure for conveying the recording medium on which the developer image is formed by a conveying roller between a driving roller and a driven roller, and formed on the recording medium An image forming apparatus comprising: a fixing unit that melts and fixes an unfixed developer image on the recording medium; and a paper discharge tray as a recording medium discharge unit that discharges the recording medium after the developer image fixing process. next, examples of the conveying roller structure, by providing the conveyance roller structure of claim 1, to prevent the lubricant deposited from the toner and the toner softened by the high temperature heating is attached to the conveying roller, thereby Extent it is possible to suppress the lubricant deposited from the toner and the toner on the recording medium (next printing process) is transferred, it can realize high-quality image output without contaminating the recording medium.

According to the third aspect of the present invention, in addition to the effect obtained by the second aspect of the invention, the recording medium after the developer image fixing process is provided downstream of the fixing unit in the recording medium conveying direction. The image forming apparatus includes a recording medium discharging unit that discharges to a discharging unit, for example, a discharging roller, and the conveying roller structure is disposed on a recording medium conveying path from the fixing unit to the discharging roller. Thus, since the toner image softened by high temperature heating after passing through the fixing means after printing can be cooled until the recording medium reaches the paper discharge roller, the toner and the lubricant deposited from the toner are discharged. Adhering to the roller can be suppressed, and thus the recording medium can be discharged without being contaminated.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
1 and 2 show an example of an embodiment of the present invention. FIG. 1 is a perspective view showing the overall configuration of an image forming apparatus according to an embodiment of the present invention. FIG. 2 shows the inside of the image forming apparatus. It is side surface sectional drawing which shows this structure.

  The image forming apparatus 1 according to the present embodiment includes a document reading device 40A that reads image information of a document G, and a recording medium conveying unit that conveys a predetermined sheet-like recording sheet (hereinafter referred to as a sheet) serving as a recording medium. And a toner image (developer image) visualized using toner (developer) by electrophotography based on the image information of the original G read by the original reading device 40A on the recording medium conveyed. An image forming unit to be formed, a conveyance roller structure for conveying a recording medium on which a developer image is formed by a conveyance roller composed of a driving roller and a driven roller, and an unfixed developer image formed on the recording medium An image forming apparatus comprising: a fixing device (fixing unit) that melts and fixes the recording medium on the recording medium; and a paper discharge tray as a recording medium discharge unit that discharges the recording medium after the developer image fixing process. It is obtained by employing the conveying roller structure according to the invention.

First, the overall configuration of the image forming apparatus 1 according to the present embodiment will be described with reference to the drawings.
As shown in FIGS. 1 and 2, the image forming apparatus 1 is provided with a document placing table 2 made of transparent glass on which a document G is placed on the upper surface of the apparatus main body 1a.

  An automatic document processor 40 is provided above the document table 2, while a scanner unit 3 serving as a document reading unit for reading image information of the document G is disposed below the document table 2. Yes.

  A document reading device 40A is constituted by the document placing table 2, the scanner unit 3, the automatic document processing device 40, and the like.

  Below the scanner unit 3, an image forming unit 10, a fixing device (fixing unit) 30 and a paper discharge unit 22 are configured, and below that, a paper feed cassette 23 containing paper P as a recording medium is stored. It is arranged.

As shown in FIG. 2, the scanner unit 3 includes a first scanning unit 4 and a second scanning unit 5 which are arranged below the document table 2 and reciprocate in parallel, an optical lens body 6, and photoelectric conversion. The document image reading unit is provided with an element (CCD) 7.
In FIG. 2, the optical path of the scanner unit 3 is indicated by a one-dot chain line.

  The first scanning unit 4 has an exposure lamp 4A, a reflector 4B that exposes light from the exposure lamp 4A on the surface of the original image, and a reflected light image from the original that is exposed and reflected through the reflector 4B. And a first mirror 4C for guiding in the direction toward the direction, and is controlled to reciprocate in parallel at a predetermined scanning speed while maintaining a certain distance from the lower surface of the document table 2. .

  The second scanning unit 5 includes a second mirror 5A and a third mirror for guiding the reflected light image from the document guided by the first mirror 4C of the first scanning unit 4 further in a predetermined direction. The mirror 5B is provided and is controlled to reciprocate in parallel with the first scanning unit 4 while maintaining a constant speed relationship.

  The optical lens body 6 is arranged on the optical path of the reflected light of the document image guided by the third mirror 5B of the second scanning unit 5 and forms the optical image on the photoelectric conversion element 7.

  A photoelectric conversion element (for example, a CCD (charge coupled device)) 7 reads a light image of a document image formed by the optical lens body 6 and photoelectrically converts it into an electrical signal to create document image information (document image data). The document image information is output to an image processing unit 57 (see FIG. 5) described later.

  The image processing unit 57 processes the document image information output from the photoelectric conversion element 7 into printing image information (printing image data) whose resolution, density, and the like are suitable for printing. The image information for printing after image processing is transferred to an image data input unit of a laser scanning unit (LSU) 8.

  The laser scanning unit 8 irradiates the surface of the photosensitive drum 11 constituting the image forming unit (image forming unit) 10 with laser light corresponding to the printing image information output from the image processing unit 57. Thereby, an electrostatic latent image of image information for printing is written and formed on the photosensitive drum 11.

  As shown in FIG. 2, the image forming unit 10 mainly includes a photosensitive drum 11 that is rotationally driven in the direction of an arrow, a main charger 12 that charges the surface of the photosensitive drum 11 to a predetermined potential, and a photosensitive member. A laser scanning unit 8 that irradiates the surface of the drum 11 with laser light for forming an electrostatic latent image, and the electrostatic latent image resulting from the laser light irradiation from the laser scanning unit 8 is developed with toner and visualized. Developing device 13 and a paper (corresponding to a “recording medium”) on which a toner image of a document image visualized by the developing device 13 is fed from a paper feed cassette 23 to be described later via a paper feed path 25. (Also referred to as “transfer sheet”) and a cleaning roller 15 for cleaning residual toner remaining on the photosensitive drum 11 after transfer by the transfer roller 14 and the transfer roller 14. They are arranged in order along a rotational direction of the body drum 11.

  The main charger 12 of the image forming unit 10 has a function of a static elimination device (not shown) that neutralizes charges on the surface of the photosensitive drum 11 after being cleaned by the cleaning device 15.

  As shown in FIG. 2, the fixing device 30 includes a heating roller 31 and a pressure roller 32, and rotates the heating roller 31 while the paper P is sandwiched between the heating roller 31 and the pressure roller 32. By passing between the heating roller 31 and the pressure roller 32, the toner image transferred onto the paper P is melted and fixed on the paper P.

Next, the paper conveyance path of the image forming apparatus will be described.
As shown in FIG. 2, the sheet conveyance path of the image forming apparatus 1 mainly includes a sheet feeding conveyance path 25 that conveys the sheet P from the sheet feeding cassette 23 provided in the lower part of the apparatus upward to the image forming unit 10. The main conveyance path 16 conveys the sheet P from the image forming unit 10 through the fixing device 30 to the sheet discharge conveyance roller (conveyance roller) 18 and conveys the sheet P from the sheet discharge conveyance roller 18 to the sheet discharge roller 19. A paper discharge conveyance path (recording medium conveyance path) 17 to be performed, and a reverse conveyance path 28 that reversely drives the paper discharge roller 19 and reverses the paper P by switching back the paper P by the reverse roller 29.

  The paper feed conveyance path 25 is provided with a roller (not shown) for separating the paper one by one when the paper is double-fed in the paper conveyance direction downstream of the paper pickup roller 24 in the paper conveyance direction. The resist roller 26 provided close to the lower side (upstream side in the paper conveyance direction) of the photosensitive drum 11 is gently curved and provided substantially linearly.

  The main conveyance path 16 is formed substantially linearly from the downstream side of the registration roller 26 through the image forming unit 10 to the fixing device 30, and is discharged from the outlet side (downstream side in the paper conveyance direction) of the fixing device 30 substantially upward. It is formed curved toward the paper conveying roller 18 (left direction in the figure).

  The paper discharge conveyance path 17 is provided substantially linearly between the paper discharge conveyance roller 18 and the paper discharge roller 19.

  The sub-conveying path 28 communicates with the upper part of the main conveying path 16 (upstream in the sheet conveying direction) to switch the sheet so that the sheet P is switched back by the reverse rotation driving of the sheet discharge roller 19 to be reversed and conveyed. By switching the gate 27, the sheet P is conveyed to the lower side of the apparatus by the reverse roller 29 and is conveyed again to the registration roller 26.

  Specifically, the sub-conveying path 28 is directed from the upper side of the apparatus to the lower side of the apparatus and from the lower side of the apparatus in order to change the direction of the paper P conveyed in the reverse direction from the discharge conveying path 17 to the lower side of the apparatus. It is curved toward the registration roller 26 side.

  The sheet P after the toner image is transferred between the photosensitive drum 11 and the transfer roller 14 is peeled off from the photosensitive drum 11 to connect the photosensitive drum 11 and the fixing device 30 to each other. The toner enters between the heating roller 31 and the pressure roller 32 of the fixing device 30 via the conveyance path 16. A nip portion is formed at a contact portion between the heating roller 31 and the pressure roller 32 by a predetermined pressing force.

  In the fixing device 30, the sheet P sandwiched between the heating roller 31 and the pressure roller 32, that is, the nip portion, is heated on the sheet P by the heating roller 31 and the pressure applied by the pressure roller 32. The unfixed toner image transferred from the drum 11 is fixed.

  The paper P after being fixed by the fixing device 30 is transported to the paper discharge transport path 17 and is transported by the paper discharge transport roller 18 toward the paper discharge roller 19 on the paper discharge outlet 20 side.

  The sheet P conveyed to the paper discharge conveyance path 17 is detected by the fixing detection switch 21A in a state where the sheet P passes between the heating roller 31 and the pressure roller 32 provided on the downstream side of the fixing device 30. The

  In the case of normal single-sided printing, the paper is discharged from the paper discharge port 20 onto the paper discharge tray 22a installed in the lower space of the scanner unit 3 by the rotational drive of the paper discharge transport roller 18 and paper discharge roller 19 as it is. Thus, the passage state of the paper P by the paper discharge roller 19 is detected by a paper discharge detection switch 21B provided on the upstream side of the paper discharge roller 19.

  The paper P is discharged in the lateral direction of the image forming unit 10 and is discharged to the paper discharge unit 22 above the paper feed cassette 23 and below the scanner unit 3.

  The paper discharge unit 22 mainly includes a paper discharge conveyance path 17, a paper discharge conveyance roller 18, a paper discharge roller 19, a paper discharge port 20, and a paper discharge tray 22a.

A paper stacking amount detection sensor 21D, also called a full detection sensor, is provided outside the paper discharge port 20 (on the paper discharge tray 22a side).
The sheet stacking amount detection sensor 21D is mainly configured by a detection body 21D1 that operates when discharged and stacked sheets abut and a sensor body 21D2 that outputs a signal in accordance with the operation of the detection body 21D1. Yes.

  The detection body 21D1 has a rod shape, one end is engaged with the sensor body 21D2, the other end is swingably provided with the one end serving as a fulcrum, and the outer side from the apparatus side (the discharge port 20 side). It is arranged so as to be opposed and inclined obliquely downward.

  The sheet stacking amount detection sensor 21D receives a detection signal from the sensor body 21D2 by pushing up the other end of the detection body 21D1 when the discharged sheet is stacked and reaches a predetermined amount (height). It is designed to output.

  On the inner bottom side of the apparatus main body 1a, a replaceable sheet cassette 23 in which sheets P are stacked and stored for each predetermined sheet size is disposed. A half-moon-shaped paper pick-up roller 24 is disposed on the paper discharge side upper portion of the paper feed cassette 23.

The paper pick-up roller 24 picks up the paper P stacked and accommodated in the paper feed cassette 23 one by one from the uppermost layer, toward the downstream side (for convenience, the paper P flow-out side (cassette side) is discharged upstream. The sheet is conveyed to a registration roller (also referred to as an “idle roller”) 26 in the sheet feeding / conveying path 25.
In the drawing, symbol Pa indicates a front end portion of the paper P, and Pb indicates a rear end portion of the paper P.

  A pre-registration detection switch 21 </ b> C is provided on the upstream side of the registration roller 26, and this pre-registration detection switch 21 </ b> C detects the paper P conveyed and fed from the paper feed cassette 23. The paper is fed to the above-described image forming unit 10 while timing the paper feeding based on the signal.

  In the case of performing double-sided printing, after the single-sided printing of the paper P by the image forming unit 10, the paper P after passing from the fixing device 30 conveyed to the paper discharge conveyance path 17 is temporarily disposed on the paper discharge roller 19 side. In this state, the sheet switching gate 27 disposed in the vicinity of the fixing device 30 is controlled to be switched, and the sheet P is switched back by the reverse rotation driving of the sheet discharge roller 19 and introduced into the sub-conveying path 28 where the sheet is reversed. Then, by rotating the sub drive roller (reversing roller) 29 provided in the sub transport path 28, the paper P is transported again to the upstream side of the registration roller 26, whereby the other side printing of the paper P is performed. ing.

  On the document table 2 of the apparatus main body 1a, an automatic document processing device 40 integrated with a document pressing portion (document pressing cover) 51a composed of a double-sided document automatic reading device (R-SPF) by a document moving method can be opened and closed. The document reading device 40A is configured together with the scanner unit 3.

  The document reading device 40A can perform document reading processing for each sheet by the same operation as that of the conventional machine. By installing the automatic document processing device 40, both sides of the document G can be read. Automatic continuous reading processing of a plurality of documents G is possible.

  As shown in FIG. 2, the automatic document processing apparatus 40 has a document tray 41 on which the document G is placed. When reading a plurality of documents G continuously, the automatic document processing device 40 is placed on the document tray 41. The original G is picked up by the original pickup roller 42, and the original G is introduced into the original conveyance path 44 via the original driving roller 43 so as to be guided and conveyed upstream of the registration roller (PS roller) 45. It has become.

  An upstream side of the registration roller 45 is provided with a document insertion sensor 46 for detecting the document size of the document G. The document insertion sensor 46 detects the leading edge and the trailing edge of the document G, and While controlling the conveyance timing based on the signal, conveyance of the document G is controlled toward the document reading table 9 made of slit glass disposed adjacent to one side of the document table 2.

  In this case, the first scanning unit 4 of the scanner unit 3 is controlled to move so as to stand by below the original reading table 9.

  As the document G conveyed on the document reading table 9 is moved, the first image reading surface G1 on one side is scanned by the first scanning unit 4 of the scanner unit 3. Other image forming processes such as reading by the photoelectric conversion element 7, image processing of image information, and printing are the same as described above.

  Then, the original G after the image reading on the original reading table 9 is conveyed to the original discharge roller 49 side of the original discharge path 48 via the conveyance roller 47. Paper is discharged onto the document discharge tray 51 by switching control.

  When performing double-sided document reading, the document G is once discharged onto an intermediate tray 52 disposed between the document tray 41 and the document discharge tray 51 by switching control of the document switching gate 50. Then, the document discharge roller 49 is reversely driven to be switched back so as to be introduced into the document reversing path 53, and again, the document G is transported to the document transport path 44, so that the image reading surface G 2 on the back side of the document G is The original image is read, and the original image on the back side of the original G is printed on the first print surface P1 of the paper P in the same manner as the single-side printing process described above.

  When the printing process of the paper P on the first printing surface P1 is completed, the paper P is reversed by the paper reversing mechanism described above, and is conveyed again to the image forming unit 10, and the second printing surface (printing surface). The original image on the front side of the original G stored in the memory in advance is printed on the back surface P2.

  As shown in FIG. 1, on the front side of the upper part of the apparatus main body 1a in the image forming apparatus 1, the user can select the type of the paper P (paper size, paper thickness, etc.), the number of printed sheets, the magnification, and the density. Operation switches 76 for setting image forming conditions such as these are provided.

Next, a characteristic conveyance roller structure constituting the image forming apparatus 1 according to the present embodiment will be described with reference to the drawings.
FIG. 3 is a schematic explanatory view showing a positional relationship in which the paper discharge transport rollers constituting the transport roller structure according to this embodiment are arranged on the paper transport path, and FIG. 4 is an explanatory diagram showing the configuration of the paper discharge transport rollers. is there.

  As shown in FIG. 3, the paper discharge transport roller 18 constituting the transport roller structure according to the present embodiment is mainly composed of a driving roller 18a and a driven roller 18b, and is downstream of the fixing device 30 in the paper transport direction. Is disposed in a paper discharge conveyance path (recording medium conveyance path) 17 configured as described above. The drive roller 18a and the driven roller 18b sandwich the paper P after the fixing process and convey it to the paper discharge roller 19 side.

  As shown in FIG. 4, the driving roller 18a and the driven roller 18b mainly include shaft bodies 18a1 and 18b1 arranged substantially in parallel so that the driving roller 18a is positioned on the lower side of the driven roller 18b. The plurality of roller bodies 18a2 and 18b2 are arranged on the shaft bodies 18a1 and 18b1.

  The plurality of roller bodies 18a2 and 18b2 are integrally disposed with respect to the shaft bodies 18a1 and 18b1 at substantially equal intervals at positions facing each other on the shaft bodies 18a1 and 18b1.

The drive roller 18a is disposed at a position facing the first print surface (print surface) P1 of the paper P. The drive roller 18a is rotationally driven by a drive motor 18c serving as a drive source via a drive gear 18c1 and a driven gear 18c2.
On the other hand, the driven roller 18b is rotatably disposed at a position facing the second printing surface (back surface) P2 of the paper P, and rotates in a so-called rotation as the driving roller 18a rotates. ing.

The roller body 18a2 of the driving roller 18a is formed of a hard member, for example, a metal member, compared to the roller body b2 of the driven roller 18b. Further, the surface of the roller body 18a2 is formed finer than the roughness of the surface of the roller body b2 of the driven roller 18b.
On the other hand, the roller body b2 of the driven roller 18b is formed of a soft member, for example, a hard rubber material, compared with the roller body a2 of the driving roller 18a.

  In the present embodiment, the roller body 18a2 of the drive roller 18a is described as an example of a metal member, but may be formed of a hard rubber material, for example. In this case, the roller body 18b2 of the driven roller 18b is preferably formed of a hard rubber material, a soft resin material, or a foaming elastic member that is softer than the roller body 18a2 of the driving roller 18a.

Next, a control system of the image forming apparatus 1 according to the embodiment will be described with reference to FIG.
FIG. 5 is a block diagram showing the configuration of the electric control unit of the image forming apparatus according to the present embodiment.
As shown in FIG. 5, the image forming apparatus 1 according to the embodiment includes a program stored in advance in a ROM (Read Only Memory) 55 such as an image reading process, an image process, an image forming process, and a paper P transport process. Accordingly, the central processing unit (CPU) 54 executes processing using temporary storage means such as a RAM (Random access Memory) 56. Note that storage means such as an HDD (hard disk drive) can be used in place of the ROM 55 and the RAM 56.

  In the image forming apparatus 1, document image information (document image data) read by the scanner unit (document reading unit) 3 or document image information transmitted from each terminal device connected to a communication network (not shown) The image data is input to the image processing unit 57 via the processing unit 58.

  The image processing unit 57 processes the document image information stored in the storage unit such as the RAM 56 into a print image suitable for printing (image formation on paper) by the above program.

The image information for printing is input to the image forming unit 10.
Image forming unit 10, paper transport unit (feeding transport path 25, main transport path 16, sub transport path 28 (which are also referred to as paper guides) (various detection / control of paper P) 59, fixing device 30, a paper discharge processing unit (which performs various detections and controls of the paper P in the paper discharge conveyance path 17) 60 is linked to each drive control unit 62.

Paper is discharged through a printing process (image information printing process in the image forming unit 10) on the paper P conveyed by the paper conveyance unit 59, and then a fixing process (fixing device 30) for the printed paper P. The sheet is discharged to a sheet discharge tray 22a.
Note that detection signals from the fixing detection switch 21A, the paper discharge detection switch 21B, the pre-registration detection switch 21C, and the like are input to the paper transport unit 59.

  The image forming apparatus 1 is provided with an operating condition setting unit 77. The operation condition setting unit 77 is set by the user using the operation switches 76 and the operation conditions such as image formation or conveyance conditions of the image forming apparatus 1 according to the image formation conditions such as the image formation request or the type of the recording medium. Is set.

  In addition, the image forming apparatus 1 includes driving actuators such as the reading unit (scanner unit 3), the sheet conveying unit 59, the image forming unit 10, the fixing device 30, and the paper discharge processing unit 60 according to the set operating conditions. The document reading drive unit 64, the paper conveyance drive unit 66, the print processing drive unit 68, the fixing drive unit 70, and the paper discharge drive unit 72 are synchronized operations in accordance with instructions from the CPU 54 based on a program stored in the ROM 55. Is performed under the control of the drive control unit 62.

  The paper discharge processing unit 60 performs control for performing paper discharge processing for discharging the printed paper to the paper discharge tray, and performs paper discharge processing based on a signal output from the paper stacking amount detection sensor 21D. Is.

The document reading drive unit 64 is a drive actuator for the first scanning unit 4 and the second scanning unit 5 of the scanner unit 3.
The paper transport drive unit 66 is a motor for driving the paper transport unit 59, specifically, the paper pick-up roller 24 and the registration roller 26 on the paper feed transport path 25 described above.
The print processing drive unit 68 is a drive motor for the photosensitive drum 11.
The fixing driving unit 70 is a driving motor for the heating roller 31 and the pressure roller 32 of the fixing device 30.

The paper discharge driving unit 72 is a driving motor 18c that drives the paper discharge conveyance roller 18, the paper discharge roller 19, and the like.
The drive motors of these drive units can be appropriately configured through a power transmission mechanism using the same or different motors as drive sources.

  In the image forming apparatus 1, an automatic document processing device (automatic document reading device) 40 or the like can be disposed as an optional configuration 74, and each of these optional configurations 74 is provided separately from the control unit of the image forming apparatus 1. The optional configuration 74 is configured to synchronize timing adjustment with the apparatus via the communication processing unit 58 while having the control unit 74a.

  The recording medium detection unit 78 detects that the leading end of the recording medium reaches the fixing device 30 or the carry-out unit.

  In the embodiment, the recording medium detection unit 78 detects the timing at which the sheet P reaches (enters) each of the fixing device 30 and the discharge conveyance roller 18 by the conveyance timing detection unit 79b described later. Based on the detection.

  Specifically, the recording medium detecting unit 78 includes a conveyance time measuring unit 79a that measures the conveyance time of the paper P after the paper P is sent out from the registration roller 26 that introduces the paper P at the entrance of the paper feeding conveyance path 25. Based on the distance from the registration roller 26 to each of the fixing device 30 to be controlled and the discharge conveyance roller 18 and the conveyance speed of the paper P, the conveyance timing of the paper P in the main conveyance path 16 and the discharge conveyance path 17 is detected. Conveying timing detecting means 79b.

Further, the image forming apparatus 1 controls the fixing temperature by the heating roller 31 in the fixing device 30 by the temperature control unit 80 in accordance with the operation state.
The temperature controller 80 controls the fixing temperature to be set according to the surface temperature of the heating roller 31 detected by the non-contact thermistor 35a and the contact thermistor 35b provided on the heating roller 31. It is.

Next, paper conveyance by the paper discharge conveyance roller 18 constituting the conveyance roller structure according to the present embodiment will be described.
As shown in FIG. 2, the paper P after the fixing process for fixing the toner image on the paper P is conveyed from the fixing device 30 to the paper discharge roller 18, and is conveyed to the paper discharge roller 19 by the paper discharge roller 18. Then, the paper is discharged from the paper discharge port 20 to the paper discharge tray 22a.

  When the paper P is transported by the paper discharge transport roller 18, it is transported on the first printing surface P1 on which the toner image is formed, downward in the drawing, that is, toward the drive roller 18a. At this time, the toner image on the first printing surface P1 of the paper P is heated by the fixing device 30 and is in a softened state.

  In the paper P, the first printing surface P1 in which the toner image is softened contacts the roller body 18a2 of the driving roller 18a, and the second printing surface (back surface of the printing surface) P2 contacts the roller body 18b2 of the driven roller 18b. Thus, the sheet is conveyed while being sandwiched between the driving roller 18a and the driven roller 18b.

  The roller body 18a2 that is in contact with the first print surface P1 conveys the paper P by rotating while being pressed against the first print surface P1. At this time, since the roughness of the surface of the roller body 18a2 is so fine that the toner does not get caught, the paper P is conveyed while suppressing the soft toner from adhering to the surface of the roller body 18a2. Can do.

  On the other hand, the roller body 18b2 that is in contact with the second printing surface P2 is arranged so as to sandwich the paper P together with the roller body 18a2 with a predetermined force, and is configured by a softer member than the roller body 18a2. The paper P can be held by a predetermined nip pressure while being pushed into the roller body 18a2 and deformed, and the paper P can be easily conveyed by the rotation by receiving the rotational force of the roller body 18a2.

In this way, the driving roller 18a can suppress the adhesion of the softened toner and the lubricant deposited from the toner even if it contacts the first print surface P1 on which the toner image of the paper P is formed. Even if the driven paper 18 is brought into contact with the driven roller 18b after the processed paper P is conveyed, the driven roller 18b is not contaminated with toner or the like.
Therefore, even if the paper P is nipped and conveyed by the driving roller 18a and the driven roller 18b in the next process (next printing process), the paper P can be conveyed without being stained.

As described above, according to the present embodiment, the toner image on the paper P can be obtained by adopting the paper discharge transport roller 18 including the driving roller 18a and the driven roller 18b characteristic of the transport roller structure. When transporting after fixing the toner, it is possible to suppress the toner softened by high-temperature heating and the lubricant deposited from the toner from adhering to the paper discharge transport roller 18, thereby enabling the next process (next printing process). Since the transfer of the toner and the lubricant deposited from the toner on the paper P can be suppressed, high-quality image output can be realized without soiling the paper P.
Therefore, according to the present embodiment, when an image is formed on an OHP sheet, it is possible to suppress the adhesion of the “nigori” component due to the toner, the lubricant deposited from the toner, and the like, so that clear image information can be enlarged and projected.

  Further, according to the present embodiment, since the paper discharge transport roller 18 is disposed in the paper discharge transport path 17 from the fixing device 30 to the paper discharge roller 19, the sheet P after the fixing process reaches the paper discharge roller 19. Since the toner image can be cooled by this time, the paper discharge roller 19 can be prevented from becoming dirty, and the paper P can be discharged without being dirty.

  The place where the conveyance roller structure according to the present invention is configured is not limited to the installation place and orientation (vertical direction) of the paper discharge conveyance roller 18 according to the present embodiment, but the shape and layout of the recording medium conveyance path. The position is determined appropriately according to the above.

Further, in the present embodiment, as the configuration of the paper discharge conveyance roller 18, the roller body 18a2 of the driving roller 18a is formed of a metal member, and the roller body 18b2 of the driven roller 18b is formed of a hard rubber material. As long as the roller facing the printing surface of the paper P has a finer surface as compared with the roller facing the back surface of the paper P, the configuration of the paper discharge roller 18 is described above. For example, the material of the roller body of the driving roller and the roller body of the driven roller may be reversed.
Further, the combination of the surface roughness and material of the roller body is appropriately determined according to the state of the toner, and an optimum condition may be determined experimentally.

1 is a perspective view illustrating an overall configuration of an image forming apparatus according to an embodiment of the present invention. 2 is a side cross-sectional view illustrating an internal configuration of the image forming apparatus. FIG. FIG. 5 is a schematic explanatory diagram illustrating a positional relationship in which a paper discharge transport roller that configures a transport roller structure according to the present embodiment is disposed on a paper transport path. It is explanatory drawing which shows the structure of the said paper discharge conveyance roller. FIG. 2 is a block diagram illustrating a configuration of an electric control unit of the image forming apparatus. FIG. 10 is an explanatory diagram illustrating an example of a stain on a recording medium by a conveyance roller in a conventional image forming apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 10 Image forming part (image forming means)
17 Paper discharge conveyance path 18 Paper discharge conveyance roller (conveyance roller structure)
18a Drive roller 18a1, 18b1 Shaft body 18a2, 18b2 Roller body 18b Driven roller 18c Drive motor 19 Paper discharge roller (recording medium discharge means)
20 Paper discharge port 22a Paper discharge tray (recording medium discharge part)
30 Fixing device (fixing means)
31 Heating roller 32 Pressure roller P Paper (recording medium)
P1 First printing surface (printing surface)
P2 Second printing surface (back)

Claims (3)

Conveying rollers Ri by the driving roller and the driven roller is configured, the driving roller is disposed at the position opposite the printing surface of the recording medium, the driven roller in a position facing the back side of the printing surface of the recording medium The drive roller is arranged and the surface of the drive roller is finer than the follower roller, and the drive roller and the follower roller sandwich the recording medium on which the toner image is formed. In the roller structure,
The driven roller is composed of a soft resin material, a hard rubber material, or a soft member including a foaming elastic member,
The drive roller, conveyor roller structure wherein Rukoto formed of a hard metal member as compared with the driven roller. A recording medium conveying means for conveying a recording medium; an image forming means for forming a developer image visualized using a developer based on input image information on the conveyed recording medium; and a developer image. A conveyance roller structure that conveys the formed recording medium by being nipped by a conveyance roller composed of a driving roller and a driven roller, and fixing that fuses and fixes an unfixed developer image formed on the recording medium onto the recording medium. In an image forming apparatus comprising: a means; and a recording medium discharge unit for discharging a recording medium after the developer image fixing process.
An image forming apparatus comprising the conveyance roller structure according to claim 1 as the conveyance roller structure. An image forming apparatus comprising: a recording medium discharging unit that discharges the recording medium after the developer image fixing process to the recording medium discharging unit downstream of the fixing unit in the recording medium conveyance direction;
The image forming apparatus according to claim 2 , wherein the conveyance roller structure is disposed on a recording medium conveyance path from the fixing unit to the recording medium discharge unit.

Images