JP2008015313A - Image forming apparatus and transfer device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus capable of preventing a trouble caused by heat released by a fixing device. <P>SOLUTION: A heat shield cover 24 is disposed downstream of a transfer unit 20 that transfers a toner image to recording paper P from the photoreceptor drum 10 of the image forming apparatus 1. The heat shield cover 24 has a U-shaped cross-section and forms a cooling air passage 25 between the transfer unit 20 and the fixing device 50. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an electrophotographic image forming apparatus such as a copying machine, a printer, and a facsimile.

  In an image forming apparatus using an electrophotographic method, a photosensitive member on the surface of a photosensitive drum is charged by a charging device, and then an electrostatic latent image with reduced charge is formed by exposure by an exposure device. A toner image is formed by adhering toner charged by the developing device to the image. Then, the toner image on the photosensitive drum is transferred to a recording medium such as recording paper by a transfer device, and the toner image is fixed on the recording paper by a fixing device and discharged.

As a fixing device in such an image forming apparatus, a so-called thermal fixing method in which toner is melted by heat and pressed and fixed to a recording sheet is often employed.
A general fixing device using a thermal fixing system is configured by pressing a pressure roll, which is formed of a heat-resistant elastic material, onto a heating roll heated to a predetermined temperature at a predetermined pressure. Then, a recording sheet holding an unfixed toner image is sandwiched between both rolls, and the toner image is fixed (fixed) to the recording sheet by heating and pressing.

By the way, in an image forming apparatus, in order to prevent malfunction and image quality deterioration due to high temperatures, heat generated by other devices such as a fixing device (a drive motor such as a photosensitive drum or a control device) is quickly generated. It is configured to release to the outside.
In particular, in the case of using a heat fixing type fixing device, a configuration for preventing an adverse effect due to heat on an adjacent mechanism is required.
Patent Document 1 discloses a configuration in which a heat reflecting plate is provided between the fixing device and the intermediate transfer belt, and further a configuration in which an exhaust device that discharges warm air near the fixing device to the outside of the device is installed. .

JP 2002-169350 A

  SUMMARY An advantage of some aspects of the invention is that it provides an image forming apparatus capable of suppressing problems caused by heat released from a fixing device.

For this purpose, the image forming apparatus of the present invention includes an image holding member for holding a toner image, a transfer device for transferring the toner image held by the image holding member to a recording medium, and fixing the toner image on the recording medium. A fixing device, and a shielding member that is provided between the transfer device and the fixing device and shields heat from the fixing device to the transfer device and forms a flow path of cooling air between the fixing device and the transfer device. It is characterized by that.
Here, the shielding member includes a shielding portion interposed between the transfer device and the fixing device, and a support guide portion that supports the recording medium between the transfer device and the fixing device and guides the movement thereof. It can be characterized by being.
Moreover, it can be provided with the ventilation apparatus which ventilates cooling air to the flow path of the cooling air formed of the shielding member.

Another image forming apparatus of the present invention includes an image carrier that holds a toner image, a transfer device that transfers the toner image held by the image carrier to a recording medium, a fixing device that fixes the toner image on the recording medium, A transfer member that is provided between the transfer device and the fixing device and shields heat from the fixing device to the transfer device. The transfer device circulates and conveys the recording medium; and a transfer carrier belt And a cleaning device for cleaning the transfer conveyance belt provided on the downstream side in the conveyance direction of the recording medium, and the shielding member forms a cooling air flow path between the fixing device and the cleaning device. To do.
Here, the shielding member includes a shielding portion interposed between the fixing device and the cleaning device, and a support guide portion that supports the recording medium between the transfer device and the fixing device and guides the movement thereof. Can be a feature.
The transfer device of the present invention is a transfer device of an image forming apparatus, and is arranged inside the transfer and transport belt member, which is stretched so as to be able to be driven around and transports a recording medium, and is provided with a toner image. A transfer member that presses the transfer conveyance belt member against the image support to be supported; a cleaning device that is provided on the downstream side in the conveyance direction of the recording medium by the transfer conveyance belt member; and a cleaning device that cleans the transfer conveyance belt member; A shielding member provided on the downstream side in the movement direction, the shielding member forming a cooling air flow path with the cleaning device, and a support guide unit for supporting the recording medium and guiding its movement It is characterized by having.

According to the image forming apparatus of the first aspect of the present invention, the shielding member can suppress problems caused by heat released from the fixing device.
According to the image forming apparatus of the second aspect of the present invention, the shielding portion of the shielding member can suppress a problem due to heat released from the fixing device, and the recording medium from the transfer device to the fixing device can be supported by the support guide portion. I can guide you.
According to the image forming apparatus of the third aspect of the present invention, the effect of suppressing defects due to heat released from the fixing device is further improved by causing the cooling air to flow through the flow path of the cooling air.
According to the image forming apparatus of the fourth aspect of the present invention, the shielding member can suppress problems of the cleaning device due to heat released from the fixing device.
According to the image forming apparatus of the fifth aspect of the invention, the shielding portion of the shielding member can suppress problems of the cleaning device due to heat released from the fixing device, and the support guide portion extends from the transfer device to the fixing device. A recording medium can be guided.
According to the transfer device of the sixth aspect of the present invention, the shielding member can suppress problems caused by heat released from the fixing device located downstream in the recording sheet conveyance direction.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 is a diagram showing a schematic configuration of an image forming apparatus 1 according to the present embodiment. The figure is a view of the image forming apparatus 1 as viewed from the side on which the user operates. Hereinafter, the front side surface is referred to as a front surface, and the rear surface in the drawing is referred to as a back surface.
In the image forming apparatus 1, a photosensitive drum 10 as an example of an image holding body that rotates in a direction indicated by an arrow A in the figure is provided inside the housing frame 1 </ b> A. Along the direction, a charger 11, a laser exposure device 12, a developing device 13 as a developing device, a pre-transfer charger 14, a transfer unit 20 as a transfer device constituting a transfer portion 15, a pre-cleaning charger 16, a drum cleaner Various devices such as 17 are arranged.
The image forming apparatus 1 also includes a recording paper transport mechanism 40 that transports the recording paper P, and a fixing device 50 that fixes the unfixed toner image transferred to the recording paper P.
Further, an intake fan 2A is provided on the front side of the housing frame 1A, and an exhaust fan 2B is provided on the back side. These intake fan 2A and exhaust fan 2B are the ventilation device in the present embodiment. A paper discharge tray 2C is provided outside the housing frame 1A.

In the photosensitive drum 10, an organic photosensitive layer made of a negatively charged material is formed on the surface of a metal thin cylindrical drum. And it is rotationally driven by a drum drive motor (not shown).
The charger 11 is a scorotron charger in which two charging wires are stretched in a shield case that opens toward the photosensitive drum 10 and a grid is provided in the opening, and is charged from a high-voltage power source (not shown). A predetermined negative voltage is applied to the wire and the grid to charge the surface of the photoreceptor negatively.

The laser exposure device 12 irradiates the photosensitive drum 10 with, for example, an exposure beam Bm emitted from a semiconductor laser according to the input image data, and forms an electrostatic latent image on the photosensitive member on the peripheral surface.
The developing device 13 includes a developing sleeve 13A in which an image electric field is formed between the developing drum 13 and the photosensitive drum 10 when a developing bias is applied. The developing device 13 is formed on the photosensitive drum 10 using negatively charged toner. The electrostatic latent image is developed by a reversal development method.
The pre-transfer charger 14 is constituted by a corotron charger disposed in a non-contact manner with respect to the photosensitive drum 10, and performs a negative discharge to form a toner image on the photosensitive drum 10. Is adjusted before transfer.

The transfer unit 20 includes a transfer conveyance belt 21A as a transfer conveyance belt member, and a transfer roll 23 as a transfer member disposed inside the transfer conveyance belt 21A.
The transfer roll 23 presses the transfer conveyance belt 21 </ b> A from the inner side toward the photosensitive drum 10 to be in pressure contact therewith. Further, a high voltage power source (not shown) is connected to the transfer roll 23 so that a charge having a polarity opposite to the toner charging polarity on the photosensitive drum 10 is applied to the transfer conveyance belt 21A.
A pressure contact portion of the transfer conveyance belt 21 </ b> A to the photosensitive drum 10 by the transfer roll 23 is a transfer portion 15 that transfers the toner image formed on the photosensitive drum 10 to the recording paper P.
The transfer unit 20 will be described in detail later.

The pre-cleaning charger 16 is constituted by a corotron charger disposed in a non-contact manner with respect to the photosensitive drum 10, and performs a negative discharge and charges (transfer electric field) remaining on the photosensitive drum 10 after transfer. Is removed).
The drum cleaner 17 includes a cleaning blade 17A that is disposed in pressure contact with the photosensitive drum 10 in the counter direction. The cleaning blade 17A scrapes and removes toner remaining on the surface of the photosensitive drum 10.

The recording paper transport mechanism 40 includes a paper tray 41 for storing the recording paper P and a plurality of transport rolls 42, and transports the recording paper P stored in the paper tray 41 along a predetermined path by the transport roll 42. To do.
The fixing device 50 includes a heating roll 51 having a heating source therein, and a pressure roll 52 disposed in pressure contact with the lower side of the heating roll 51. In addition, an introduction guide 53 for guiding the recording paper P toward the press contact portion of both the rolls 51 and 52 is provided. Then, the recording paper P on which the toner image is transferred is sandwiched between the heating roll 51 and the pressure roll 52 and heated and pressed to fix the toner image to the recording paper P.

The image forming apparatus 1 configured as described above performs image formation by acting as follows.
That is, the photosensitive drum 10 is rotationally driven, the photosensitive member on the surface thereof is charged by the charger 11, and the charged photosensitive drum 10 is scanned by the exposure beam Bm of the laser exposure unit 12 to electrostatically charge the photosensitive drum 10. A latent image is formed. Next, the electrostatic latent image formed on the photosensitive drum 10 is developed by the developing device 13 to be visualized (toner image), and the charging polarity of the toner image is made uniform by the pre-transfer charger 14.
In the transfer unit 15, the recording paper P transported by the recording paper transport mechanism 40 is a toner image formed on the photosensitive drum 10 by a transfer bias applied between the photoconductor drum 10 and the transfer roll 23. Transcript to.

The recording paper P onto which the toner image has been transferred is conveyed to the fixing device 50 by the transfer conveying belt 21A, and the toner image is fixed by the fixing device 50 and discharged onto the paper discharge tray 2C.
On the other hand, residual toner remaining on the photosensitive drum 10 after transfer is charged by the pre-cleaning charger 16 and then removed by the drum cleaner 17. Thereby, a series of image forming steps is completed.
Further, when performing this image forming action, the intake fan 2A provided on the front side sucks outside air into the apparatus, and the exhaust fan 2B provided on the back side discharges the air inside the apparatus to the outside. This prevents overheating of each internal working mechanism.

Next, the transfer unit 20 will be described in detail with reference to FIGS.
FIG. 2 is an enlarged view of the transfer unit 20, and FIG. 3 is a perspective view of the transfer unit 20. The recording paper P is conveyed from the left side to the right side in the drawing by the transfer unit 20. For this reason, hereinafter, the left side is referred to as the upstream side, and the right side is referred to as the downstream side. A direction orthogonal to the moving direction of the recording paper P is referred to as a front-rear direction.
The transfer unit 20 includes a transfer conveyance unit 21, a cleaning unit 22 as a cleaning device, and a heat shielding cover 24 as a shielding member. Then, the transfer unit 15 transfers the toner image on the photosensitive drum 10 to the recording paper P conveyed and supplied by the recording paper conveyance mechanism 40, and conveys the recording paper P onto which the toner image has been transferred to the fixing device 50.

  In the transfer conveyance unit 21, a transfer conveyance belt 21 </ b> A having a predetermined circumferential length is wound around a driving roll 21 </ b> B and a driven roll 21 </ b> C that are arranged in parallel with the photosensitive drum 10. Inside the circulation path, a transfer roll 23 for transferring a toner image to the recording paper P by forming a transfer electric field with the photosensitive drum 10 as described above is disposed. Note that a high-voltage power source is connected to each of the driven roll 21C and the transfer roll 23, and a bias can be applied independently.

The transfer conveyance belt 21A is a semiconductive endless belt in which, for example, a rubber layer made of chloroprene rubber is overcoated with a urethane resin in which PTFE (polytetrafluoroethylene) is dispersed.
The drive roll 21B is rotationally driven by a drive motor (not shown), thereby driving the transfer / conveying belt 21A to rotate at a predetermined speed in the direction indicated by the arrow B in FIGS. .

The transfer roll 23 is configured to have a predetermined resistance value by forming a foamed rubber layer with a predetermined thickness on a metal shaft.
A transfer bias having a polarity (positive polarity) opposite to the toner charging polarity (negative polarity) is stably applied to the transfer roll 23 from a high voltage power source (not shown), and the toner on the photosensitive drum 10 is charged to the transfer conveyance belt 21A. A charge having a polarity opposite to the polarity is applied.

The cleaning unit 22 includes a cleaning blade 22B, a cleaning brush 22C, and an auger shaft 22D inside the cleaning box 22A.
The cleaning blade 22B is formed in a plate shape having a predetermined thickness with urethane rubber, and is disposed in pressure contact with the transfer conveyance belt 21A in the counter direction with respect to the moving direction thereof.
The cleaning brush 22 </ b> C is a columnar brush formed by planting bristles having a predetermined electric resistance value on a metal shaft, and the shaft is grounded. Further, it is driven to rotate in a direction opposite to the conveying direction of the transfer conveying belt 21A by a driving source (not shown).
The auger shaft 22D has a feed blade spirally formed around the shaft, and is driven to rotate by a drive source (not shown) so that paper dust, toner, and the like in the cleaning box 22A are provided at the shaft end on the back side. Transport to a collection bottle (not shown).

Then, the cleaning unit 22 wipes off deposits such as paper dust and toner adhering to the surface of the transfer conveyance belt 21A while the cleaning brush 22C rotates, and collects it in the cleaning box 22A. Further, the cleaning blade 22B scrapes off deposits that could not be removed by the cleaning brush 22C and collects them in the cleaning box 22A. The auger shaft 22D conveys paper dust, toner, and the like collected in the cleaning box 22A to a collection bottle.
By such a cleaning unit 22, the so-called inter-image unit between successive recording papers P removes dirt from the toner on the transfer / conveying belt 21 </ b> A from the photosensitive drum 10, and the dirt adheres to the back surface of the recording paper P. To prevent that.

The heat shielding cover 24 is an opaque resin having heat resistance such as polycarbonate having a substantially U-shaped cross-section by an upper surface plate 24A as a support guide portion, a side plate 24B as a shielding portion, and a lower surface plate 24C. Is formed by. The opening side is fixed to the cleaning box 22A at the edge of the upper surface plate 24A with the open side facing the upstream side. The length in the front-rear direction is substantially the same as that of the transfer unit 20.
The upper surface plate 24 </ b> A is formed obliquely so as to connect the downstream end portion of the transfer conveyance belt 21 </ b> A and the introduction guide 53 of the fixing device 50. That is, it is formed along the moving path of the recording paper P from the transfer unit 20 to the fixing device 50, supports the recording paper P on its upper surface, and guides the recording paper P from the transfer unit 20 to the fixing device 50. It is supposed to be.
The side plate 24B is suspended at a predetermined height from the downstream edge of the upper surface plate 24A, and is formed so as to be interposed between the transfer unit 20 and the fixing device 50.
The lower surface plate 24C is extended obliquely downward on the upstream side from the lower edge of the side plate 24B. The leading edge is close to the outer surface of the cleaning box 22 </ b> A of the cleaning unit 22.

The heat shield cover 24 having such a configuration has the side plate 24B positioned between the transfer unit 20 and the fixing device 50 so as to partition the two. In addition, a cooling air flow path 25 whose front and rear end faces are open between the entire heat shield cover 24 having a U-shaped cross section and the outer surface of the cleaning box 22A (that is, between the transfer unit 20 and the fixing device 50). Form.
Thereby, the heat shielding cover 24 shields heat radiation from the fixing device 50 toward the transfer unit 20 (cleaning unit 22). Further, the inside of the cooling air flow path 25 formed by the heat shielding cover 24 is caused by the intake fan 2A and the exhaust fan 2B as shown by arrows in FIG. The air flow to the side is rectified and flows.
That is, the side plate 24 </ b> B of the heat shielding cover 24 blocks heat radiation from the fixing device 50, and the cooling air smoothly flows inside the cooling air flow path 25.

As a result, heating of the cleaning unit 22 due to heat released from the fixing device 50 is suppressed, and melting and solidification caused by heating of the collected toner accommodated in the cleaning box 22A can be prevented. That is, the toner used for heat fixing is normally in the form of a powder, but melts at, for example, about 50 ° C. to form a nodule. Once the toner inside the cleaning unit 22 is in such a state, problems such as the auger shaft 22D being unable to be transported to the collection container occur, but such a problem is caused by the action of the heat shielding cover 24 described above. It can be prevented.
Further, the upper surface (upper surface plate 24 </ b> A) of the heat shielding cover 24 guides the moving path of the recording paper P from the transfer unit 20 to the fixing device 50. That is, the heat shielding cover 24 also serves as a support guide member for the recording paper P. For this reason, it is not necessary to separately provide a support guide member.

The present invention is not limited to the above embodiment. For example, in the above embodiment, the heat shielding cover 24 is mounted on the transfer unit 20, but may be provided on the fixing device 50 or may be provided independently on the housing frame 1A.
In the above embodiment, the present invention is applied to the monochrome image forming apparatus 1. However, the present invention may be applied to a color image forming apparatus.

1 is a diagram illustrating a schematic configuration of an image forming apparatus according to an exemplary embodiment. It is an enlarged view of a transfer unit. It is a perspective view of a transfer unit.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Image forming apparatus, 2A ... Intake fan (ventilation apparatus), 2B ... Exhaust fan (ventilation apparatus), 10 ... Photosensitive drum (image holding body), 20 ... Transfer unit, 21A ... Transfer conveyance belt (transfer conveyance belt member) ), 23... Transfer roll (transfer member), 24... Heat shield cover, 24 A... Upper plate (support guide portion), 24 B .. side plate (shield portion), 25. )

Claims (6)

An image carrier for holding a toner image;
A transfer device for transferring a toner image held by the image carrier to a recording medium;
A fixing device for fixing the toner image on the recording medium;
A shielding member that is provided between the transfer device and the fixing device, shields heat from the fixing device to the transfer device, and forms a cooling air flow path between the fixing device and the transfer device;
An image forming apparatus comprising: The shielding member is
A shielding part interposed between the transfer device and the fixing device;
A support guide for supporting the recording medium between the transfer device and the fixing device and guiding its movement;
The image forming apparatus according to claim 1, further comprising:   3. The image forming apparatus according to claim 1, further comprising a ventilating device that ventilates cooling air through the cooling air flow path formed by the shielding member. 4. An image carrier for holding a toner image;
A transfer device for transferring a toner image held by the image carrier to a recording medium;
A fixing device for fixing the toner image on the recording medium;
A shielding member that is provided between the transfer device and the fixing device and shields heat from the fixing device to the transfer device;
The transfer device includes a transfer conveyance belt that circulates and conveys the recording medium, and a cleaning device that cleans the transfer conveyance belt provided downstream in the conveyance direction of the recording medium by the transfer conveyance belt. ,
The image forming apparatus, wherein the shielding member forms a flow path of cooling air between the fixing device and the cleaning device. The shielding member is
A shielding part interposed between the fixing device and the cleaning device;
A support guide for supporting the recording medium between the transfer device and the fixing device and guiding its movement;
The image forming apparatus according to claim 4, further comprising: A transfer device for an image forming apparatus,
A transfer conveying belt member that is stretched so as to be capable of circular driving and conveys a recording medium;
A transfer member disposed on the inner side of the transfer conveyance belt member and press-contacting the transfer conveyance belt member to an image support that supports a toner image;
A cleaning device provided on the downstream side in the conveyance direction of the recording medium by the transfer conveyance belt member and cleaning the transfer conveyance belt member;
A shielding member provided on the downstream side in the moving direction of the recording medium of the cleaning device,
The shielding member is
A shielding part for forming a cooling air flow path with the cleaning device;
And a support guide portion for supporting the recording medium and guiding its movement.

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