JP2003295742A - Image forming machine and process unit to be applied to the machine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming machine capable of efficiently removing the discharged from a fixing means after transfer without stagnating the heat on the lower side of a guide plate. <P>SOLUTION: The image forming machine is provided with a photosensitive drum arranged so as to be optionally rotated; an electrifier for electrifying the circumferential surface of the drum to specific polarity; a developing device for developing an electrostatic latent image formed on the circumferential surface of the drum to a toner image; a transfer means for transferring the toner image formed on the circumferential surface of the drum to transfer paper; a fixing means for heat-fixing the toner image transferred to the transfer paper by the transfer means; and a cooling fan for sending cooling air to the periphery of the fixing means, and also provided with a guide plate for guiding the transfer paper to which the toner image is transferred by the transfer means to the fixing means, and a plurality of apertures are formed on the guide plate in the longitudinal direction. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention develops an electrostatic latent image formed on a photosensitive layer of a photosensitive drum such as an electrostatic copying machine or a laser printer into a toner image and transfers the toner image onto a transfer paper. The present invention relates to an image forming machine and a process unit applied to it.

[0002]

2. Description of the Related Art An image forming machine of this kind is arranged rotatably and a photosensitive drum which sequentially passes through a charging area, an electrostatic latent image forming area, a developing area and a transfer area, and is arranged in the charging area. A charger that charges the peripheral surface of the photosensitive drum to a specific polarity, and a developing device that is disposed in the developing area and develops the electrostatic latent image formed on the peripheral surface of the photosensitive drum into a toner image in the electrostatic latent image forming area. The image forming apparatus includes an apparatus and a transfer unit that is arranged in the transfer area and transfers the toner image formed on the peripheral surface of the photosensitive drum to a transfer paper. Further, a fixing means for heating and fixing the toner image transferred onto the transfer paper by the transfer means is disposed downstream of the transfer means in the transfer paper transport direction. In order to prevent the surroundings from being heated by the heat radiation from the fixing means, a cooling fan causes cooling air to flow around the fixing means.

[0003]

A guide plate for guiding the transfer paper having the toner image transferred by the transfer means to the fixing means is provided between the transfer means and the fixing means. The heat radiated from the fixing means stays below the guide plate, which causes overheating.

The present invention has been made in view of the above facts, and its main technical problem is to effectively cool the heat radiated from the fixing means to the lower side of the post-transfer guide plate without delay. An image forming machine and a process unit of the image forming machine.

[0005]

In order to achieve the above main technical problems, according to the present invention, a rotatably arranged photosensitive drum and a peripheral surface of the photosensitive drum are charged to a specific polarity. A charger, a developing device for developing an electrostatic latent image formed on the peripheral surface of the photosensitive drum into a toner image, and a transfer unit for transferring the toner image formed on the peripheral surface of the photosensitive drum onto a transfer paper. In an image forming machine including a fixing unit for heating and fixing the toner image transferred onto the transfer paper by the transfer unit, and a cooling fan for sending cooling air around the fixing unit, the toner image is transferred by the transfer unit. An image forming machine is provided, which comprises a guide plate for guiding the transferred transfer paper to the fixing means, and the guide plate is formed with a plurality of openings in the longitudinal direction.

Further, according to the present invention, a photosensitive drum which is arranged rotatably and sequentially passes through a charging area, an electrostatic latent image forming area, a developing area and a transferring area, and the photosensitive drum which is arranged in the charging area. A charger that charges the peripheral surface of the photosensitive drum to a specific polarity, and an electrostatic latent image formed on the peripheral surface of the photosensitive drum in the electrostatic latent image forming area is developed into a toner image in the developing area. In the process unit of the image forming machine, which is detachably attached to the fuser housing provided with the fixing means and the cooling fan for sending the cooling air around the fixing means, the toner image is formed in the transfer area. Provided is a process unit of an image forming machine, comprising: a guide plate for guiding the transferred transfer paper to the fixing means, wherein the guide plate has a plurality of openings formed in a longitudinal direction. It

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of an image forming machine constructed according to the present invention will be described in detail below with reference to the accompanying drawings. In the illustrated embodiment, a printer will be described as an example of an image forming machine configured according to the present invention.

FIG. 1 schematically shows an embodiment of a printer constructed according to the present invention. Printer 2
Is a small-sized low-speed laser printer used as a printing device such as a word processor in this embodiment, and is a machine housing 20 molded of synthetic resin.
It is equipped with. The machine body housing 20 includes a box-shaped housing body 21 having an open upper side, and a cover 23 rotatably mounted on a shaft 22 arranged at an upper portion of the housing body 21. The process unit 4 is detachably mounted in the central portion of the body housing 20 configured as described above.

As shown in FIG. 2, the process unit 4 includes a photoconductor unit 40 and a developing unit 50 which is swingably supported by the photoconductor unit 40 via a support shaft 5.
It has and. The photoconductor unit 40 includes a photoconductor support means 41. The photoconductor support means 41 has a pair of side wall members 411 (only the back side wall member in FIG. 2 is spaced apart in the front-rear direction). Shown), and a connecting member 412 for connecting the lower portions of the pair of side wall members 411, respectively.
a, 412b. The connecting members 412a and 412b have inner surfaces facing each other arranged in parallel with each other to form a charging means mounting space 412c in which a charging means described later is arranged. This charging means mounting space 412
c is located opposite to the charging area described later. The photoconductor supporting means 41 configured as described above is integrally formed of synthetic resin. Supporting portions 413 each having a mounting hole 414 are provided at the upper ends of the pair of side wall members 411 forming the photosensitive member supporting means 41 on the developing unit 50 side. By inserting the support shaft 5 made of a metal rod disposed in the developing housing of the developing unit 50, which will be described later, into the mounting hole 414 provided in the supporting portion 413, the photoconductor unit 40 and the developing unit 50 are mutually connected. It is swingably supported by.

The photoconductor unit 40 includes a photoconductor drum 42 having a photoconductive layer formed on its peripheral surface. The photosensitive drum 42 is provided with a rotating shaft 421, which is rotatably supported by a pair of side wall members 411 forming the photosensitive member supporting means 41, and is driven by a driving means (not shown) in a direction indicated by an arrow. That is, the charging area 422, the electrostatic latent image forming area 423, the developing area 424, and the transfer area 425 are sequentially driven to rotate. Charged area 422
In the charging means mounting space 412c located at, the charging means 43 is mounted so as to face the lower peripheral surface of the photosensitive drum 42. The charging means 43 includes a charging corona discharger 431 as a charging device arranged along the axial direction in parallel with the photoconductor drum 42, and a charger holding device made of synthetic resin for mounting and holding the charging corona discharger. Member 43
2, the charger holding member 432 is fitted in the charging means mounting space 412c and is positioned at a predetermined position. In addition, the foreign matter collecting brush 4 that contacts the peripheral surface of the photosensitive drum 42 between the charging area 422 and the transfer area 425.
4 are arranged along the axial direction of the photosensitive drum 42. The paper dust collecting brush 44 is made of acrylic fiber or the like and has a length substantially the same as the axial length of the photosensitive drum 42. The paper dust collecting brush 44 is integrally molded with the charger holding member 432 and is arranged in the axial direction of the photosensitive drum 42. It is attached to a brush support member 440 arranged along the line. The upper end of the charger holding member 432 is formed so as to be close to the peripheral surface of the photoconductor drum 42 between the charging corona discharger 431 disposed in the charging area 422 and the foreign matter collecting brush 44. And constitutes a toner intrusion prevention wall 47. The toner intrusion prevention wall 47 is provided on the photosensitive drum 4
When the residual toner attached to the peripheral surface of No. 2 and removed by the foreign matter collecting brush 44 along with the foreign matter such as paper dust falls without being reliably captured by the foreign matter collecting brush 44, it enters the charging corona discharger 431. It has a function to prevent it.

Between the pair of side wall members 411 constituting the photosensitive member supporting means 41, the transfer paper fed obliquely from the upper left in FIG. 2 is directed to the transfer area 425 on the peripheral surface of the photosensitive drum 42. A lower guide plate 451 that constitutes one of the pre-transfer guide plate pair 45 that guides by means of is provided. The lower guide plate 451 is integrally formed with the pair of side wall members 411. As shown in FIG. 3, a plurality of guide ribs 451a are integrally formed on the upper surface of the lower guide plate 451 at intervals in the longitudinal direction (direction perpendicular to the paper surface in FIG. 2). Further, the lower guide plate 451 is integrally formed with a plurality of reinforcing ribs 451b on the lower surface at intervals in the longitudinal direction (direction perpendicular to the paper surface in FIG. 2). 5 is abutted. Therefore, in the lower guide plate 451, even if the upper surface of the lower guide plate 451 tries to bend due to the pressing force, the reinforcing rib 451b is not supported.
It is possible to prevent the occurrence of bending by abutting against. Also,
The lower guide plate 451 functions as a connecting member that connects the upper portions of the pair of side wall members 411 forming the photoconductor supporting unit 41 to each other, and can improve the rigidity strength of the photoconductor supporting unit 41. Further, in the illustrated embodiment, since the lower guide plate 451 is integrally formed with the pair of side wall members 411, the positional relationship with respect to the photosensitive drum 42 rotatably supported by the pair of side wall members 411 is highly accurate. Can be maintained at. The lower guide plate 451 in the illustrated embodiment functions as a member for preventing contact with the photosensitive layer of the photosensitive drum 42 when the process unit 4 is attached or detached, and prevents the developing unit 50 from touching a developing roller described later. It also functions as a member,
It also has a function of preventing scattered toner from the surface of the developing roller, which will be described later, from adhering to the transfer paper or the transfer paper transport path.

A guide plate 46 is disposed between the pair of side wall members 411 constituting the photoconductor supporting means 41 to guide the transfer paper on which the toner image has been transferred in the transfer area 425 to a fixing means which will be described later. The guide plate 46 is integrally formed with the pair of side wall members 411. Therefore, the guide plate 46 functions as a connecting member that connects the pair of side wall members 411 forming the photoconductor supporting unit 41 to each other, and the rigidity strength of the photoconductor supporting unit 41 can be improved. The guide plate 46 in the illustrated embodiment has a transfer paper guide portion 461 whose lower surface functions as a transfer paper guide surface, and is formed substantially vertically on the upper surface of the transfer paper guide portion 461 and is provided over the entire length in the longitudinal direction. And a reinforcing portion 462. As shown in FIG. 3, the transfer paper guide portion 461 is provided with a plurality of openings 463 in the longitudinal direction (direction perpendicular to the paper surface in FIG. 2), and the plurality of openings 463 are downstream in the transfer paper transport direction. The side end reaches the downstream end of the transfer paper guide portion 461 in the transfer paper conveyance direction and is opened. A plurality of openings 463 provided in the transfer paper guide portion 461 which constitutes the guide plate 46.
Has a function of letting out hot air warmed by heat radiation from a fixing unit described later. Further, since the plurality of openings 463 are open at the downstream end in the transfer paper transport direction and have no opening edge, the tip of the transfer paper guided by the lower surface of the transfer paper guide portion 461 is not caught by the opening edge. The transfer paper can be smoothly guided. Therefore, it is possible to prevent the occurrence of paper jam (jam) due to the leading edge of the transfer paper being caught by the opening edge.

Next, another embodiment of the guide plate 46 which guides the transfer paper on which the toner image is transferred to the fixing means will be described with reference to FIG. In the illustrated embodiment, a plurality of ribs 464 are provided at intervals in the longitudinal direction on the upper surface of the transfer paper guide portion 461 forming the guide plate 46. The plurality of ribs 464 are provided between the openings 463, and are formed in a triangular shape from the reinforcing portion 462 to the downstream side end in the transfer paper conveyance direction. In this way, the guide plate 4
Since a plurality of ribs 464 are provided on the upper surface of the transfer paper guide portion 461 which constitutes No. 6, the plurality of openings 463 are formed as described above.
It is possible to compensate for the decrease in the rigidity of the transfer paper guide portion 461 due to the provision of the. Therefore, since the rigidity of the transfer paper guide portion 461 can be ensured, the guide accuracy of the transfer paper is ensured and the deformation due to heat is prevented.

Next, the developing unit 50 as an electrostatic latent image developing device will be described. The developing unit 50 in the illustrated embodiment includes a developing housing 51 that accommodates a developer including one-component toner. The developing housing 51 includes a bottom wall 511 and front and rear side walls 512 (see FIG. 2) which are formed to stand upright from the front and rear ends of the bottom wall 511 (ends in the direction perpendicular to the paper surface in FIG. 2).
(Only the rear side wall is shown in FIG. 3) and a left side wall 513, which are integrally molded of synthetic resin and define a stirring chamber 514 and a developing chamber 515. The bottom wall 511 forming the developing housing 51 has a stirring chamber 51.
4 and the developing chamber 515 are integrally formed with a partition wall 516 provided in the front-rear direction (direction perpendicular to the paper surface in FIG. 2). Both left and right sides of the partition wall 516 are formed into arc-shaped guide surfaces 516a and 516b. Between the front and rear side walls 512 constituting the developing housing 51, a connecting member 517 disposed on the upper side of the developing chamber 515 side is provided, and is integrally formed on the front and rear side walls 512. A toner supply hole 518 is formed in the rear side wall 512 which constitutes the developing housing 51.
8 is fitted with a cap 519. The support shaft 5 is disposed at the upper end of the developing housing 51 on the side of the developing chamber 515 having the above-described structure so as to pass through the front and rear side walls 512, and the photoconductor unit 4 is provided at both ends of the support shaft 5.
0 of the pair of side wall members 41 constituting the photosensitive member support means 41
By fitting the mounting hole 414 provided in the first supporting portion 413, the photoconductor unit 40 and the developing unit 50 are swingably supported with respect to each other. The photoconductor unit 4
0 lower end of the photoconductor supporting means 41 and the developing housing 51
A coil spring 52, which is a spring means, is interposed between the lower end of the photoconductor and the front end and the rear end of the photoconductor support means 41 and the developing housing 5.
1 are urged so that they are pulled toward each other with the support shaft 5 as a fulcrum. The developing housing 51 is open above and to the right, that is, on the side of the photoconductor unit 40.

In the developing housing 51, a developing roller 53, a replenishing roller 54, a stirring means 55 and a developer regulating means 56 are arranged. The developing roller 53 is
A rotary shaft 531 arranged in the developing chamber 515 of the developing housing 51 and rotatably mounted on the front and rear side walls 512 constituting the developing housing 51, and a solid synthetic rubber roller fixed to the outer peripheral surface of the rotating shaft 531. And 532 are included. The rotating shaft 531 can be formed of a suitable metal material such as stainless steel. Solid synthetic rubber roller 53
Reference numeral 2 is made of a relatively flexible and conductive material, for example, a conductive solid synthetic rubber such as urethane rubber. In the illustrated embodiment, a solid synthetic rubber roller 5
The surface roughness of the peripheral surface of 32, that is, the ten-point average roughness Rz specified in JIS B 0601 is set to 5.0 to 12.0. The volume resistance of the solid synthetic rubber roller 532 is set to about 104 to 109 Ω · cm. The roller hardness of the solid synthetic rubber roller 532 is
In the illustrated embodiment, the Asker C hardness is 60 to 80.
Is set to. Developing roller 5 configured in this way
The third roller 532 is exposed through the right side opening formed in the developing housing 51 and is positioned so as to face the photosensitive drum 42. The peripheral surface of the roller 532 that constitutes the developing roller 53 is brought into pressure contact with the peripheral surface of the photosensitive drum 42 in the developing area, and the peripheral surface of the roller 532 is slightly elastically compressed in the pressed nip portion. ing. The rotation shaft 531 of the developing roller 53 is driven to rotate from the lower side to the upper side in the direction indicated by the arrow by a driving unit (not shown), that is, in the developing area where the roller 532 contacts the photosensitive drum 42. The roller 532 is also driven to rotate in the direction indicated by the arrow by the above rotation of the rotary shaft 531.
The peripheral surface of No. 2 has a developer holding area 533 and a developer regulation area 534.
And the developing area 424 can be moved sequentially. In addition,
In the illustrated embodiment, the rotary shaft 5 of the developing roller 53.
A constant voltage of 300 V is applied to 31.

The replenishing roller 54 is disposed in the developing chamber 515 of the developing housing 51 in parallel with the developing roller 53, and is rotatably mounted on the front and rear side walls 512 constituting the developing housing 51. Axis 541,
It includes a roller 542 fixed to the outer peripheral surface of the rotating shaft 541. The rotary shaft 541 can be formed of an appropriate metal material such as stainless steel, like the rotary shaft 531 of the developing roller 53. The roller 542 is made of foam such as foam silicon or foam urethane. The roller 542 is the roller 5 of the developing roller 53 in the developer holding area 533 which is a nip portion with the developing roller 53.
It is pressed against 32. Roller 54 of supply roller 54
The hardness of the foam forming 2 is considerably smaller than the hardness of the roller 532 forming the developing roller 53 (for example, Asker C hardness is about 35), and the roller 542 is pressed against the roller 532 of the developing roller 53. It is desirable that the roller 542 be elastically compressed by about 0.1 to 0.6 mm in the nip region. Also, the roller 5
42 also has conductivity, and its volume resistance is 102-1.
It is set to about 06 Ω · cm. Supply roller 54
The rotating shaft 541 is driven to rotate from the upper side to the lower side in a developer holding area 533 which is a nip portion between the roller 542 and the roller 532 of the developing roller 53 by a driving means (not shown). The roller 542 is also rotationally driven in the direction indicated by the arrow by the above rotation of the rotary shaft 541. In the illustrated embodiment, a constant voltage of 450 V, which is higher than the applied voltage to the developing roller 53, is applied to the rotating shaft 541 of the replenishing roller 54.

The peripheral speed V1 of the photosensitive drum 42, the peripheral speed V2 of the developing roller 53, and the peripheral speed V3 of the replenishing roller 54 are set to have a relationship of V1 <V2 <V3.
In the illustrated embodiment, the relationship between the peripheral speed V1 of the photosensitive drum 42 and the peripheral speed V2 of the developing roller 53 is
1.2V1 ≦ V2 ≦ 2.5V1 is set, and the peripheral speed V2 of the developing roller 53 and the peripheral speed V3 of the supply roller 54 are set.
The relationship with is set to 1.0V2 ≦ V3 ≦ 2.0V2. When the peripheral speed V2 of the developing roller 53 becomes 1.2 V1 or less, the supply of the developer to the photosensitive drum 42 becomes insufficient, which causes a decrease in image density. Further, when the peripheral speed V2 of the developing roller 53 becomes 1.2 V1 or less, the scraping action of the developing roller 53 on the non-transfer developer adhering to the photosensitive drum 42 after transfer is reduced, so that the non-transfer developer is removed. This causes so-called offset fogging that occurs because the toner cannot be removed from the photoconductor drum 42. On the other hand, when the peripheral speed V2 of the developing roller 53 is 2.5 V1 or more, the driving torque of the developing roller 53 increases and the developer scatters due to the centrifugal force. Further, when the peripheral speed V3 of the supply roller 54 becomes 1.0 V2 or less, the supply of the developer to the developing roller 53 becomes insufficient, which causes a decrease in image density. Also, the peripheral speed V of the supply roller 54
When 3 is 1.0 V2 or less, the replenishing roller 54 has a weak scraping effect on the peripheral surface of the developing roller 53, and therefore, when the non-transferred developer adhering to the photosensitive drum 42 adheres to the developing roller 53 after transfer, It becomes difficult to remove the adhering developer, and the adhering developer causes a so-called ghost phenomenon that appears during the next development. On the other hand, when the peripheral speed V3 of the supply roller 54 becomes 2.0 V2 or more, the supply roller 54
As the driving torque of the developer increases, the tendency of the developer to stay above the nip portion between the replenishing roller 54 and the developing roller 53 becomes strong, which causes insufficient supply of the developer to the developing roller 53.

A stirring means 55 is disposed in the stirring chamber 514 of the developing housing 51. The stirring means 55
Is disposed in parallel with the replenishing roller 54, is rotatably mounted on the front and rear side walls 512 constituting the developing housing 51, and a stirring member 552 fixed to the rotating shaft 551. It includes an elastic stirring sheet member 553 attached to the stirring member 552.
The stirring member 552 is made of synthetic resin,
A plurality of openings are provided in the longitudinal direction (direction perpendicular to the paper surface in FIG. 2). The stirring sheet member 553 is made of, for example, polyethylene terephthalate (PET) having flexibility and elasticity.
P) is made of resin, and is fixed to the tip edge of the stirring member 552 with an adhesive or the like. The stirring means 55 configured in this manner is continuously driven to rotate in the direction indicated by the arrow in FIG. 2 by a driving means (not shown).

The developer regulating means 56 is provided with a flexible elastic blade 561 which is brought into pressure contact with the peripheral surface of the roller 532 constituting the developing roller 32.
The blade 561 has a thickness of 0.1 to 0.2 mm, for example.
The developing roller 53 is made of a stainless steel plate or a spring steel plate, and has substantially the same longitudinal dimension as the length of the roller 532 forming the developing roller 53. Blade 561
Is a bottom wall 5 whose base end constitutes the developing housing 51.
11 is attached to the blade attachment portion 511a provided at the open end of the photoreceptor unit 40 side. That is, the blade 561
The base end portion of the blade mounting portion 511a and the pressing plate 562
It is clamped by and fixed by a screw 563. The tip of the blade 561 is formed in a bent shape, and this bent portion is configured to be pressed against the peripheral surface of the roller 532 forming the developing roller 53 in the developer regulation area 534.

A lid 57 is attached to the developing housing 51 to cover the opened upper portion. The lid 57 is made of synthetic resin, and is fixed to the upper surfaces of the front and rear side walls 512, the left side wall 513, and the connecting member 517, which form the developing housing 51, with an adhesive. A regulating portion 571 is integrally formed on the inner surface of the lid 57 at a position facing the replenishing roller 54, extending in the front-rear direction (direction perpendicular to the paper surface in FIG. 2) and projecting to the developing chamber 515 side. A predetermined gap is provided between the lower end of the restriction portion 571 and the outer peripheral surface of the roller 542 that constitutes the replenishing roller 54. In the illustrated embodiment, the sheet-shaped sealing member 58 is attached to the connecting member 517 that constitutes the developing housing 51. The sheet-shaped sealing member 58 is made of, for example, polyethylene terephthalate (P
It is made of a flexible elastic sheet member such as ETP resin and has a length substantially the same as the axial length of the roller 532 constituting the developing roller 53. The sheet-like seal member 58 has one end portion thereof connected to the connecting member 517.
The roller 53 is fixed to the developing roller 53 by a fixing means such as an adhesive, and the other end is curved to form the developing roller 53.
It is elastically brought into contact with the peripheral surface of 2. The sheet-like seal member 58 thus configured is provided with the blade 561 of the developer regulating means 56 together with the developing housing 5.
The developer is prevented from scattering from the opening of the first photosensitive member unit 40 side.

The process unit 4 configured as described above is detachably mounted on the machine housing 20 of the printer 2 as shown in FIG. That is, by turning the cover 23 constituting the machine housing 20 of the printer 2 around the shaft 22 in the counterclockwise direction in FIG. 1, the upper part of the housing main body 21 constituting the machine housing 20 is opened. Next, the process unit 4 is mounted in the housing body 21 from above. The housing body 21
Positioning means (not shown) for mounting the photoconductor unit 40 of the process unit 4 at a predetermined position is provided therein. The process unit 4 in the body housing 20
Once installed on the housing body 21 of the
By turning clockwise two times in FIG. 1, the upper part is closed.

As shown in FIG. 1, at the bottom of the housing body 21 which constitutes the machine housing 20 of the printer 2,
A laser unit 24 is provided. The laser unit 24 irradiates the photosensitive layer of the photosensitive drum 42 with a laser beam corresponding to print data from, for example, a word processor connected to the printer 2 in the electrostatic latent image forming area 423 of the process unit 4 to electrostatically discharge the photosensitive layer. Form a latent image.

Further, a fixing roller pair 25, which constitutes a fixing means, is arranged downstream of the guide plate 46 in the housing body 21 which constitutes the machine housing 20 of the printer 2. The fixing roller pair 25 is composed of a heating roller 251 having a built-in heating unit, and a pressure roller 252 arranged in contact with the peripheral surface of the heating roller 251.
The pressure roller 252 is a heating roller 25 as shown in FIG.
The heating roller 251 is arranged in contact with the heating roller 251 on the downstream side of the vertical line passing through the axis 1 of the transfer sheet, and thus a space is formed above the heating roller 251. The guide plate 46 is arranged so as to extend to the space formed above the heating roller 251. Thus, in the illustrated embodiment, the pressure roller 252 is replaced by the heating roller 251.
Since the guide plate 46 is disposed downstream of the vertical line passing through the axis of the transfer paper in the transfer paper conveyance direction and extends to the space formed above the heating roller 251, the heating roller 251.
The space formed above can be used as a space for disposing the guide plate 46, and the size of the image forming machine in the front-rear direction (the left-right direction in FIG. 1) can be reduced. On the other hand, when the guide plate 46 is arranged so as to extend above the heating roller 251,
The hot air warmed by the heat radiation from the heating roller 251 tends to stay between the heating roller 251 and the guide plate 46. However, in the illustrated embodiment, a plurality of transfer paper guide portions 461 forming the guide plate 46 are provided. Since the individual openings 463 are provided, the hot air can be smoothly released.

A discharge roller pair 26 is disposed downstream of the fixing roller pair 25, and further, the discharge roller pair 26 is provided.
A paper discharge tray 27 is arranged on the downstream side of. In addition,
In the illustrated embodiment, as shown in FIG. 4, a cooling fan 33 is arranged on the front side of the housing body 21 beside the fixing roller pair 25 (right side in FIG. 4). The cooling fan 33 sends cooling air from the front side of the fixing roller pair 25 toward the inner side thereof, so that the fixing roller pair 25 receives the cooling air.
Cool around.

A cover 23, which constitutes the machine housing 20 of the printer 2, is provided with a paper feed tray 28 on the upper left side in FIG. A paper feed roller 29 is disposed on the downstream side of the paper feed tray 28,
The paper feed roller 29 is rotationally driven in the direction shown by the arrow in FIG. A friction pad 30 for separating the sheet is arranged so as to face the sheet feeding roller 29. Further, in the transfer area 422, a non-contact type transfer roller 31 is arranged so as to face the photosensitive drum 42. The transfer roller 31 is made of conductive urethane foam and is rotatably supported by the cover 23. The transfer roller 31 is provided with collars (not shown) made of an insulating material such as synthetic resin having an outer diameter larger than that of the transfer roller 31 at both ends thereof, and the collars are arranged in contact with the peripheral surface of the photosensitive drum 42. Has been done,
Therefore, the transfer roller 31 is slid and driven by the rotation of the photosensitive drum 42. The gap between the peripheral surface of the transfer roller 31 and the peripheral surface of the photosensitive drum 42 is 0.5 m.
It is set to about m. A constant current of, for example, 10 μA is applied to the transfer roller 31 thus configured.
The cover 23 is provided with an upper guide plate 452 which constitutes the other of the pre-transfer guide plate pair 45.

The printer 2 in the illustrated embodiment is configured as described above, and its operation will be described below. The above-mentioned members start operating based on a print command from a word processor (not shown) or the like, and the charging corona discharger 4
By 3, the surface photosensitive layer of the photosensitive drum 42 is substantially uniformly charged to a specific polarity. Next, the surface of the charged photosensitive layer of the photosensitive drum 42 is irradiated with laser light corresponding to print data from a word processor or the like from the laser unit 24, and an electrostatic latent image is formed. The electrostatic latent image thus formed on the photosensitive layer of the photosensitive drum 42 is developed into a toner image by the developing action of the developing unit 50. Regarding the developing action of the developing unit 50,
It will be described in detail later. On the other hand, the transfer papers placed on the paper feed tray 28 are fed one by one by the action of the paper feed roller 29 and the friction pad 30. Then, the transfer paper is guided by the pre-transfer guide plate pair 45 and the photosensitive drum 42 and the transfer roller 3
The toner image formed on the photosensitive drum 42 is transferred onto the surface of the photosensitive drum 42.

The transfer paper on which the toner image is transferred is the guide plate 4
6 is conveyed to the fixing roller pair 25. The transfer paper on which the toner image is heated and fixed by the fixing roller pair 25 is
The sheet is discharged onto the sheet discharge tray 27 by the pair of discharge rollers 26. The heat radiated from the heating roller 251 for heating and fixing the toner image transferred onto the transfer paper as described above is taken away by the cooling air from the cooling fan 33 and the housing main body 2
It is released from a vent provided on the back side of 1. As described above, the cooling air is sent from the cooling fan 33 to remove the heat radiated from the heating roller 251 to the outside and discharge the heat to the outside of the housing main body 21. Although it prevents overheating, if the cooling fan 33 does not have a considerably large capacity, the heating roller 2
The heat trapped in the lower side of the guide plate 46 disposed above 51 cannot always be sufficiently removed by the cooling air. However, according to the present invention, the transfer paper guide portion 461 forming the guide plate 46 has a plurality of openings 46 in the width direction.
1 is provided, the heat trapped in the lower side of the guide plate 46 escapes upward through the plurality of openings 461 and is taken away by the cooling air to be discharged to the outside of the housing main body 21.
The lower side of the post-transfer guide plate 46 can also be effectively cooled. As a result, even in the configuration in which the photoconductor drum and the fixing unit are arranged close to each other as in the illustrated embodiment,
It is possible to prevent the deterioration of the characteristics of the photoconductor due to the temperature rise of the photoconductor drum and the fusion of the toner on the drum surface. Further, it is possible to prevent the occurrence of a situation in which the housing, the guide plate, and the like are thermally deformed, the positional accuracy cannot be maintained, and the transfer sheet is caught. In addition, since the plurality of openings 463 are open at the downstream end in the transfer paper conveyance direction and have no opening edge, the leading edge of the transfer paper guided by the lower surface of the transfer paper guide portion 461 may be caught on the opening edge. Instead, the transfer paper can be smoothly guided.
Therefore, it is possible to prevent the occurrence of paper jam (jam) due to the leading edge of the transfer paper being caught by the opening edge.

On the other hand, the peripheral surface of the photoconductor drum 42 which has passed through the transfer area 425 is removed by the foreign material collecting brush 44 when the foreign material such as paper dust adheres to the peripheral surface when passing through the foreign material collecting brush 44. To be done. At this time, the residual toner adhering to the peripheral surface of the photosensitive drum 42 is also removed together with the foreign matter such as paper dust. The removed residual toner may fall without being reliably captured by the foreign matter collection brush 44. The dropped toner is the charging corona discharger 4 described above.
Although the accumulation on the surface 31 causes uneven charging, in the illustrated embodiment, the toner invasion prevention wall 47 prevents the falling toner from invading the charging corona discharger 431 side.

Next, the developing action of the developing unit 50 will be described. By starting the operation of the developing unit 50,
The developing roller 53, the replenishing roller 54 and the stirring means 5
5 are rotationally driven in the directions indicated by arrows by driving means (not shown). Stirring member 55 that constitutes stirring means 55
2 and the stirring sheet member 553 rotate in the direction indicated by the arrow, the developer accommodated in the stirring chamber 514 is stirred and passes over the partition wall 516 to replenish the supply roller 54.
Is supplied into the developing chamber 514 from above. At this time, due to the restriction portion 571 formed on the inner surface of the lid 57,
The amount of developer supplied into the developing chamber 514 is limited so as not to become excessive. The developer thus supplied by the agitating means 55 rides on the roller 542 of the replenishing roller 54 and is conveyed to the nip portion which is the developer holding area 533 with the roller 532 of the developing roller 53. Since the replenishing roller 54 and the developing roller 53 both rotate in the same direction from the upper side to the lower side in the developer holding area 533 which is the nip portion as described above, the replenishing roller 54 and the developing roller 53 move in the same direction.
The developer is sufficiently supplied to the developer, and the shortage of the developer can be prevented. Further, the supply roller 54 and the developing roller 5
3 is the developer holding area 533 which is the nip portion as described above.
Since they rotate in the same direction, they can be surely driven without requiring a large driving force.

As described above, the developer conveyed to the developer holding area 533 which is the nip portion between the replenishing roller 54 and the developing roller 53 is the roller 53 forming the developing roller 53.
It is held on the peripheral surface of No. 2 and conveyed toward the developer regulation area 534. At this time, the supply roller 54 and the developing roller 53
As described above, both rotate in the same direction from the upper side to the lower side in the developer holding area 533 which is the nip portion, so that the developer is held by the developing roller 53 through both the nip portions and is held in the developer regulating area. Since it is transported to the developing area 524 and the developing area 424, it is sufficiently charged by being rubbed against each other when passing through the nip portion, so that so-called fogging is prevented.

In the developer regulation area 534, the blade 561 of the developer regulation means 56 acts on the developer retained on the peripheral surface of the roller 532 of the developing roller 53 to be retained on the peripheral surface of the roller 532. The developer is regulated to the required amount to form a thin layer. The developer regulated by the blade 561 of the developer regulation means 56 in the developer regulation area 534 and scraped off on the bottom wall 511 of the developing housing 51 is rotated by the replenishing roller 54 in the direction indicated by the arrow. The partition wall 516
The sheet is conveyed along the guide surface 516b.

As described above, it is held on the peripheral surface of the roller 532 which constitutes the developing roller 53 in the developer holding area 533, and is formed into a thin layer in the developer controlling area 534 by the action of the blade 561 of the developer controlling means 56. The developer thus developed is rotated in the developing area 424 along with the rotation in the direction of the arrow.
Be transported to. In the developing area 424, a developer is applied to the electrostatic latent image on the electrostatic photoconductor disposed on the peripheral surface of the photoconductor drum 42, and the electrostatic latent image is developed into a toner image. For example, the electrostatic latent image has a non-image area charged to about +600 V and an image area charged to about +120 V, and toner as a developer is attached to the image area (so-called reversal development). The photosensitive drum 42 and the developing roller 53 are driven to rotate in the direction shown by the arrow in FIG. 2, and therefore, in the developing area 424, the peripheral surface of the photosensitive drum 42 and the roller 5 forming the developing roller 53.
Together with the peripheral surface of 32, they are moved in the same direction from below to above. The peripheral speed V2 of the roller 532 and the photosensitive drum 4
Since the peripheral speed V1 of 2 is set to 1.2V1 ≦ V2 ≦ 2.5V1, sufficient developer is conveyed to the developing area 424 by the roller 532 of the developing roller 53, and the peripheral speed of the photosensitive drum 42 is increased. By the rubbing action of the peripheral surface of the roller 532 against the surface, the developer once attached to the non-image portion of the electrostatic latent image is appropriately peeled off, and thus a good toner image having an appropriate developing density and no fog is formed. Obtainable. On the other hand, the roller 532 that constitutes the developing roller 53
The used developer that has been held on the peripheral surface of the developing roller 53 and has passed through the developing area 424 is transferred to the surface of the replenishing roller 54 at the nip portion between the developing roller 53 and the replenishing roller 54. Since the peripheral speed of the replenishing roller 54 is set to be higher than the peripheral speed of the developing roller 53, the developer is moved in the nip portion. It is possible to weaken the adhesive force of the transfer developer and collect it, so that it is possible to prevent the occurrence of so-called ghost caused by the non-transfer developer attached to the developing roller 53.

Although the present invention has been described above based on the embodiment applied to a printer, the present invention is not limited to the illustrated embodiment and can be applied to an electrostatic copying machine, for example. Various variations or modifications are possible without departing from the scope of the technical idea of.

[0034]

Since the image forming machine and the process unit of the image forming machine according to the present invention are configured as described above, the following operational effects are achieved.

That is, according to the present invention, since a plurality of openings are formed in the longitudinal direction of the post-transfer guide plate for guiding the transfer paper on which the toner image has been transferred to the fixing means, the post-transfer guide is provided. The heat trapped in the lower side of the plate escapes upward through multiple openings and is taken away by the cooling air sent by the cooling fan and discharged outside the machine, so the lower side of the guide plate is also effectively cooled after transfer. can do.

[Brief description of drawings]

FIG. 1 is a front view schematically showing an embodiment of an image forming machine configured according to the present invention.

FIG. 2 is a sectional view of a process unit mounted on the image forming machine shown in FIG.

FIG. 3 is a perspective view of a main part of a photoconductor unit that constitutes the process unit shown in FIG.

FIG. 4 is a plan view of a main part of the image forming machine shown in FIG.

5 is a perspective view of a main part of another embodiment of a photoconductor unit that constitutes the process unit shown in FIG.

[Explanation of symbols]

2: Printer 4: Process unit 5: Support shaft 20: Airframe housing 21: Housing body 23: Cover 24: Laser unit 25: Pair of fixing rollers 26: Ejection roller pair 27: Output tray 28: Paper feed tray 29: Paper feed roller 30: Friction pad 31: Transfer roller 33: Cooling fan 40: Photoconductor unit 41: Photoreceptor support means 42: photoconductor drum 43: charging means 44: Foreign object collection brush 45: Pre-transfer guide plate pair 46: Information board 47: Toner intrusion prevention wall 50: Development unit 51: Development housing 52: Coil spring 53: developing roller 54: Supply roller 55: stirring means 56: developer control means 57: Lid 58: Sheet-shaped sealing member 431: Corona discharger for charging 411: Side wall member of photoconductor supporting means 412: Connection member for photoconductor supporting means 422: charged area 423: electrostatic latent image forming area 424: Development area 425: Transfer area 461: Transfer paper guide section 462: Reinforcement part 463: Opening 464: Rib 470: Toner intrusion prevention wall 514: stirring chamber 515: Development room 517: Connecting member of developing housing 533: developer holding area 534: Developer regulated area 561: blade

Continued front page    (72) Inventor Yuki Terada             Kyocera 1-22-28 Tamatsukuri, Chuo-ku, Osaka-shi             Within Mita Co., Ltd. F-term (reference) 2H027 JA11 JB15 JC08 JC14                 2H072 CB08                 2H171 FA02 FA06 FA09 FA11 FA12                       FA13 FA15 FA19 FA22 GA23                       JA23 JA25 JA27 JA28 JA29                       JA30 JA31 JA33 JA39 JA48                       JA58 KA17 NA03 NA05 QA04                       QA08 QB02 QB15 QB18 QB32                       QB35 QB37 QB41 QB47 QC03                       QC11 QC14 QC23 QC25 QC36                       SA08 SA17 SA21 SA27 TB02                       TB13 UA03 UA12 UA22                 3F101 FB07 FC03 FC19 LA02 LA07                       LB03

Claims (2)

[Claims] 1. A photosensitive drum rotatably arranged,
A charger that charges the peripheral surface of the photosensitive drum to a specific polarity, a developing device that develops an electrostatic latent image formed on the peripheral surface of the photosensitive drum into a toner image, and a peripheral surface of the photosensitive drum. Transfer means for transferring the formed toner image to a transfer paper,
In an image forming machine equipped with a fixing means for heating and fixing the toner image transferred onto the transfer paper by the transfer means, and a cooling fan for sending cooling air around the fixing means, the toner image is transferred by the transfer means. An image forming machine, comprising: a guide plate for guiding the transfer paper to the fixing means, wherein the guide plate is formed with a plurality of openings in the longitudinal direction. 2. A photosensitive drum which is arranged rotatably and sequentially passes through a charging area, an electrostatic latent image forming area, a developing area and a transfer area, and a peripheral surface of the photosensitive drum which is arranged in the charging area. And a developing device for developing the electrostatic latent image formed on the peripheral surface of the photosensitive drum into a toner image in the electrostatic latent image forming region, the charging device being configured to charge the electrostatic latent image to a specific polarity. In a process unit of an image forming machine detachably attached to a fuser housing provided with a fixing unit and a cooling fan for sending a cooling air around the fixing unit, a transfer sheet on which a toner image is transferred in the transfer area. A process unit of an image forming machine, comprising a guide plate for guiding the fixing means, and the guide plate having a plurality of openings formed in the longitudinal direction.