JP2006069704A - Image forming device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming device capable of preventing mutual sticking of paper loaded on an FD tray. <P>SOLUTION: The temperature of a transfer material is detected by using a full load detecting lever 19 provided with a heat collecting plate 30. The heat collecting plate 30 is made of metal having smaller thermal capacity as compared with other members and is provided on a paper passing face of the full load detecting lever 19. A temperature detecting sensor 31 is adhered to a rear face of the heat collecting plate 30. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus, and more particularly to a heat fixing apparatus used in a copying machine, a printer, a facsimile machine, etc. The present invention is suitable for application to an apparatus having this heat fixing device.

  A schematic cross-sectional view of a typical image forming apparatus according to the prior art is shown in FIG. As shown in FIG. 7, the image forming apparatus according to the prior art has a sheet feeding apparatus including a sheet feeding tray 1, a sheet stacking table 2, and a sheet feeding roller 3.

  Further, the transfer material P loaded on the sheet stacking table 2 in the paper feed tray 1 is picked up one by one from the uppermost recording material by the paper feed roller 3 and supplied to the registration unit by the transport roller 4 and the transport roller 5. Is done. The transfer material P is fed to the image forming unit after the conveyance direction is aligned by a registration unit including the registration roller 6 and the registration roller 7.

  The image forming unit includes a photosensitive drum 8, a charger that charges the photosensitive drum, a developing unit that develops the latent image on the photosensitive drum with toner, a residual toner on the photosensitive drum, and a cleaner that accommodates the toner cartridge 9. As a unit. The laser scanner unit 10 is configured by unitizing a polyhedral mirror 11, a polyhedral mirror rotating motor, a laser unit, and the like.

  A laser beam L based on the image information is emitted from the laser scanner unit 10 and exposed on the photosensitive drum 8 to form a latent image by an electrophotographic method. The latent image is developed with toner as a developer by the developing means, and the developed toner image is transferred to the transfer material P conveyed from the photosensitive drum 8 by the transfer roller 12.

  After the transfer of the toner image, the transfer material P is conveyed to a fixing unit including a heating unit 13 and a pressure roller 14, and the transferred toner image is heated and fixed. Thereafter, the sheet is discharged onto the FD discharge tray 18 by a discharge unit including an FD discharge roller 16, an FD discharge roller 17, and a full load detection lever. This FD paper discharge unit is shown in FIG. The transfer material P on which the toner image is fixed by the heating unit 13 and the pressure roller 14 is also discharged onto the FU discharge tray 166.

  As shown in FIG. 8, a full load detection sensor for detecting the load amount of the transfer material P discharged from the image forming apparatus is installed on the FD discharge tray 18. The full load detection sensor includes a full load detection lever 19 and a photo interrupter 20.

When the loading amount of the transfer material P on the FD discharge tray 18 exceeds a certain amount, the loading surface of the transfer material P contacts the full load detection lever 19 and starts rotating, and the loading amount of the transfer material P reaches a predetermined amount. At this point, the shielding portion of the full load detection lever 19 blocks the infrared light of the photo interrupter 20 and detects that the FD paper discharge tray 18 is full.
JP 2001-106426 A

However, the conventional image forming apparatus described above has the following problems.
That is, in recent image forming apparatuses, the speedup is remarkable, and the time from when the transfer material P leaves the heat fixing apparatus to when it is stacked on the paper discharge tray is very short. For this reason, the transfer material P on which the toner image is heat-fixed is stacked on the paper discharge tray without being sufficiently cooled. Therefore, depending on the type of paper, there is a possibility that the toner image will stick to the transfer material P stacked in front and back.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an image forming apparatus capable of preventing toner images of transfer materials stacked on the front and back on the discharge tray from sticking to the transfer material.

In order to achieve the above object, the present invention provides:
A paper feeding unit for supplying a transfer material;
An image forming unit for forming an image on a transfer material;
A heat fixing unit for fixing the image formed on the transfer material by the image forming unit;
A paper discharge unit for discharging the transfer material;
A paper discharge tray for stacking transfer materials discharged by the paper discharge unit;
A full load detection lever arranged above the paper discharge tray and configured to be able to detect the full state of the transfer material by contacting the transfer material stacked surface loaded on the paper discharge tray;
A heat collecting plate provided on the transfer material passing surface side of the full load detection lever and in contact with the transfer material discharged to the paper discharge tray;
A temperature detecting means for detecting the temperature provided on the back side of the heat collecting plate;
An image forming apparatus configured to be able to detect a temperature of a transfer material discharged to a paper discharge tray by a paper discharge unit.

  In the present invention, typically, only the heat collecting plate on which the full load detection lever slides with the transfer material is composed of a member having a small heat capacity, and the other portions are composed of plastic. In the present invention, typically, the contact portion of the full load detection lever with the leading end portion of the transfer material is made of plastic.

  In this way, the heat collecting plate of the full load detection lever is made of a member having a smaller heat capacity than other members, and the other members are made of plastic so that the temperature of the heat collecting plate can be reduced in a short time. It becomes possible to make it substantially the same as the temperature of the transfer material.

  In the present invention, typically, when the full load detection lever is rotated by the transfer material, the temperature detection means is disposed immediately above the position where the heat collecting plate and the transfer material slide.

  In this way, temperature detection means is placed directly above the position where the heat collecting plate and the transfer material slide when the full load detection lever is rotated by the transfer material, minimizing the influence of the temperature gradient in the heat collecting plate. By limiting the temperature, the accuracy of temperature detection of the transfer material can be increased. Further, by using a metal member for the sliding portion with the transfer material, it is possible to prevent the sliding portion from being worn and to improve the durability of the full load detection lever.

  In the present invention, typically, the back surface of the heat collecting plate is hollow except for the joint with the full load detection lever.

In this way, by making the back surface of the heat collecting plate hollow except for the joint with the full load detection lever portion, the heat capacity near the heat collection portion is reduced, and the heat collection plate and the full load detection lever are insulated. It is possible to prevent the heat collected in the temperature detecting means from escaping, and it is possible to improve the responsiveness of the temperature detecting means, and the charge of the heat collecting plate is brought into contact with the heat collecting plate and the neutralizing brush. , And electrostatic breakdown of the temperature detecting means can be prevented.

  As described above, according to the present invention, the temperature of the transfer material discharged to the paper discharge tray can be detected by detecting the temperature of the transfer material discharged to the paper discharge tray by the paper discharge unit. Detection and control based on this temperature, for example, the throughput of the image forming apparatus can be changed, so that it is possible to prevent sticking of the transfer materials stacked on the paper discharge tray and to detect full load. Even after the mechanism detects that the discharge tray is full, it can be determined to which discharge tray the transfer material being passed is discharged.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In all the drawings of the following embodiments, the same or corresponding parts are denoted by the same reference numerals.

(First embodiment)
First, an image forming apparatus according to a first embodiment of the present invention will be described. FIG. 1 shows an image forming apparatus according to a first embodiment of the present invention. Note that the paper feeding / conveying process and the image forming process in the image forming apparatus are the same as those in the prior art, and thus description thereof is omitted.

  In the first embodiment, a case where the present invention is applied to a film heating type heating fixing device (on-demand fixing device) that heats a sheet through a thin film will be described. The apparatus is not limited to the apparatus, and is a so-called heat roller that heats paper while nipping and conveying it using a heat roller maintained at a predetermined temperature and a pressure roller that presses the heat roller through an elastic layer. The present invention can be applied to any image fixing method such as a method.

  The transfer material P is developed and transferred by an image forming unit composed of a photosensitive drum, a transfer roller, and the like, and then sent to a heat fixing unit. At this time, the leading edge of the transfer material P is guided by a fixing inlet guide 21 to a pressure nip N including a heating body 23 and a pressure roller 24 with a fixing film 22 interposed therebetween.

  The fixing film 22 has a thin and flexible endless belt shape as a rotating body for heating, and a release layer is provided on the surface layer. The endless belt-shaped fixing film 22 is externally fitted to the semicircular arc-shaped film guide member 25 with a margin in the circumference.

  The fixing film 22 has a total thickness of 100 μm or less, preferably 20 μm or more and 60 μm or less in order to reduce the heat capacity and improve the quick start property. In addition, as the fixing film 22, a heat-resistant resin film such as polyimide or polyetheretherketone (PEEK), or a metal film such as a Ni electroformed film or a stainless seamless film is used. Thus, in the case of a metal film, since heat conductivity is favorable, the thickness should just be 150 micrometers or less, and it becomes fully practical.

  The pressure roller 24 is a pressure rotating body. A silicone rubber layer is formed on the surface of a metal core such as iron or aluminum, and a perfluoroalkoxy layer made of a fluororesin is formed thereon as a release layer. An alkane (PFA) tube layer is provided.

The fixing film 22 is brought into close contact with the surface of the heating body 23 (heating heater) in the clockwise direction indicated by an arrow in FIG. 23, while sliding on the surface 23, at a predetermined peripheral speed, that is, substantially the same peripheral speed as the transfer speed of the transfer material P carrying the unfixed toner image T conveyed from the image forming unit (not shown) side, It is rotationally driven without wrinkles.

  The heating body 23 is, for example, a ceramic heater. The heating element 23 has an energization heating element (resistance heating element) as a heat generation source that generates heat by power supply, and is configured to increase the temperature by the heat generation of the energization heating element.

In the heating body 23, alumina (Al ₂ O ₃ ) or aluminum nitride (AlN) is used for the substrate. Then, a resistor made of silver / palladium is printed on the surface of the substrate with a thick film to form a heating element pattern having a desired resistance value. Further, a glass layer as a sliding layer with the protective layer / fixing film 22 is provided on the heating element.

  A thermistor as a temperature detection element is bonded and fixed to the back side of the heating element forming surface. The thermistor is configured to be able to monitor the heater temperature, and supplies the monitored temperature information to the control circuit unit. The control circuit unit controls the AC driver in order to maintain the heater temperature (fixing nip temperature) at a predetermined temperature, and controls the amount of power supplied from the AC power source to the heating element of the heating element 23.

  The heating element 23 is heated by the power supply to the energizing heating element, and in the state where the fixing film 22 is rotationally driven, the elastic force generated by the deformation of the elastic layer of the pressure roller 24 causes a gap between the heating element 23 and the heating element 23. When the transfer material P is introduced into the pressure nip portion N (fixing nip portion) formed on the fixing nip portion N, the transfer material P is in close contact with the fixing film 22 and overlaps with the fixing film 22. Going through.

  In the process in which the transfer material P passes through the fixing nip portion, thermal energy is applied to the transfer material P from the heating body 23 through the fixing film 22, and the unfixed toner image T on the transfer material P is heated, melted and fixed. The Thereafter, the transfer material P passes through the fixing nip portion N, is separated and discharged from the fixing film 22, and is sent to the FD paper discharge portion by the fixing paper discharge roller 26 and the fixing paper discharge roller 27. The paper is stacked on the FD paper discharge tray 18 by the FD paper discharge roller 29.

  Above the FD discharge tray 18, a full load detection sensor including a full load detection lever 19 and a photo interrupter 20 is installed to detect that the load amount of the transfer material P on the FD discharge tray reaches a certain height. To do.

(Temperature detection means)
In the image forming apparatus according to the first embodiment, as shown in FIG. 4, a heat collecting plate 30 and a temperature detection sensor 31 as temperature detection means are provided on the full load detection lever 19. The heat collecting plate 30 and the temperature detection sensor 31 can detect the temperature of the transfer material P after image fixing discharged from the image forming apparatus onto the FD discharge tray 18.

  On the FD paper discharge tray 18, a full load detection sensor for detecting the load amount of the transfer material P discharged from the image forming apparatus is installed. The full load detection sensor includes a full load detection lever 19 and a photo interrupter 20. The full load detection lever 19 is mainly composed of a highly slidable plastic member such as polyacetal. 2 and 3 show the full load detection lever 19.

That is, as shown in FIG. 2, when the loading amount of the transfer material P on the FD discharge tray 18 reaches a certain amount A or more, the full load detection lever 19 first has the loading surface of the transfer material P loaded on the full load detection lever 19. Touch to start rotating. Subsequently, when the load amount of the transfer material P reaches the predetermined amount B, the infrared light of the photo interrupter 20 is blocked by the shielding portion of the full load detection lever 19 as shown in FIG. It is detected that 18 is full.

  FIG. 4 shows details in the vicinity of the full load detection lever 19. As shown in FIG. 4, a material having a small heat capacity, for example, aluminum, is provided at the passage portion of the transfer material P at the tip of the full load detection lever 19 as compared with at least a member other than the passage portion of the transfer material P at the tip of the full load detection lever 19. A heat collecting plate 30 made of a metal such as stainless steel is provided. The heat collecting plate 30 is made of a thin plate having a thickness of about 0.1 mm, and is configured integrally with the full load detection lever 19 by outsert molding or the like, and the non-transfer material P discharged from the image forming apparatus by the weight of the lever. It comes in contact with the print side.

  Further, as shown in FIG. 5, the heat collecting plate 30 is disposed below the nip line C of the FD paper discharge roller. Then, the tip of the transfer material P that has passed through the nip portion of the FD paper discharge roller first contacts the plastic portion of the full load detection lever 19, and when the transfer material P is conveyed downstream, the full load detection lever 19 is By rotating, the heat collecting plate 30 contacts the non-printing surface side of the transfer material P.

  As described above, by reducing the heat capacity of the heat collecting plate 30 and positively bringing it into contact with the transfer material P, the temperature of the heat collecting plate 30 can be made substantially the same as the temperature of the transfer material P in a short time. It becomes possible. In order to reduce the heat capacity of the heat collecting plate 30 and efficiently perform heat absorption and heat dissipation, the heat collecting plate 30 has a size along the transfer direction of the transfer material P and the transfer direction of the transfer material P. It is desirable to make the width as small as possible along the direction orthogonal to the width and substantially parallel to the width of the transfer material P.

  When performing double-sided printing, the heat collecting plate 30 on the full load detection lever 19 comes into contact with the first printing surface of the transfer material P when the second surface is passed. At this time, there is a concern about toner adhesion on the surface of the heat collecting plate 30. Therefore, as a countermeasure, surface treatment such as Teflon (registered trademark) or UV coating is applied to the surface of the heat collecting plate 30 in a range that does not affect the heat conduction of the heat collecting plate 30. preferable. It is also preferable to coat polyimide (PI) or the like on the surface of the heat collecting plate 30.

  Further, a highly responsive temperature detection sensor 31 such as a thermistor is attached to the back surface of the heat collecting plate 30 at the tip of the full load detection lever 19 by adhesion or the like. When the transfer material P after image fixing is conveyed from the heat fixing device, the full load detection lever 19 is rotated, the heat collecting plate 30 comes into contact with the non-printing surface of the transfer material P, and the heat of the transfer material P is transferred. , And the temperature of the transfer material P is detected by conducting heat to the temperature detection sensor 31 installed on the back surface.

  At this time, the temperature detection sensor 31 is located at a position where the transfer material P contacts the heat collecting plate 30 when the full load detection lever 19 rotates, that is, when the transfer material P is detected by the full load detection lever 19. The temperature detection accuracy of the transfer material P is increased by minimizing the influence of the temperature gradient in the heat collecting plate 30. Further, by using a metal member for the sliding portion with the transfer material P, wear of the sliding portion can be prevented and the durability of the full load detection lever 19 can be improved.

  The thermistor is an element that changes its resistance value according to temperature. The thermistor is enclosed in glass with a dumet wire baked on the electrode of the thermistor chip. Further, the dumet wire is connected to a control circuit unit which is a control unit through a lead wire or the like. The temperature information detected by the thermistor is supplied to the control circuit section through this lead wire.

When the temperature information detected by the thermistor exceeds the set temperature, the control circuit unit that controls the fixing discharge unit and the image forming unit widens the paper interval or reduces the printing speed,
Discharge throughput is reduced. As a result, the temperature of the transfer material P loaded on the paper discharge tray is lowered. That is, when the temperature information exceeds the set temperature, control is performed such that the temperature is lowered by the control circuit unit. As a result, it becomes possible to prevent the toner image from sticking to the transfer material P stacked in front and back.

  In addition, widening the paper space here means widening the interval between the transfer materials conveyed through the image forming unit and the fixing discharge unit, and thereby the interval between the transfer materials discharged by the fixing discharge unit. The paper is enlarged and discharged. In addition, reducing the printing speed means slowing the transfer material conveyance speed in the image forming unit that forms an image while conveying the transfer material. Since the number of transfer materials discharged from the fixing discharge unit per unit time is reduced by widening the sheet space or reducing the printing speed in this way, the toner of the transfer material on the FD discharge tray 18 is reduced. It is possible to prevent the image from sticking to the transfer material stacked in front and back.

  In addition, the sensor for detecting the presence or absence of the transfer material P in the fixing paper discharge unit and the full load detection sensor are interlocked so that the temperature when the rear end of the transfer material P passes over the full load detection sensor Comparison with the temperature at the part is performed. At this time, if there is a difference between the two temperatures, it is determined that the transfer material P is discharged to the FD discharge tray, and if there is no difference, it is determined that the transfer material P is discharged to the FU discharge tray. As described above, even after the full load detection sensor detects the full load of the FD discharge tray, it is possible to determine whether the transfer material P is discharged to the FD discharge tray or the FU discharge tray. It becomes possible.

  That is, in the full load detection according to the prior art, when the FD discharge tray becomes full, the infrared light of the photo interrupter is always cut off by the shielding portion of the full load detection lever. It was not possible to determine which of the FD discharge tray and the FU discharge tray was discharged. On the other hand, according to the above-described embodiment, the temperature when the rear end portion of the transfer material P passes over the full load detection sensor and the inter-paper portion (transfer material discharged by the fixing discharge portion). Based on the comparison with the temperature (when P does not pass over the full load detection sensor), it can be determined which paper discharge tray is discharged.

  Next, the front end portion of the full load detection lever 19 will be described. As described above, the heat collecting plate 30 made of a material having a small heat capacity is provided at the tip of the full load detection lever 19. The heat collecting plate 30 is formed integrally with a plastic full load detection lever 19 having a low thermal conductivity. Here, the back surface of the heat collecting plate 30 is hollow except for the joint portion with the full load detection lever 19. As described above, since the portion other than the joint portion with the full load detection lever 19 is made hollow, the heat capacity near the heat collecting portion can be reduced, and the heat collecting plate 30 and the full load detection lever 19 can be insulated. The escape of heat collected in the detection sensor 31 can be minimized, and the responsiveness of the temperature detection sensor 31 can be improved.

(Second Embodiment)
Next explained is an image forming apparatus according to the second embodiment of the invention. FIG. 6 shows an image forming apparatus according to the second embodiment of the present invention. In FIG. 6, only the characteristic part is shown.

  In the second embodiment, unlike the first embodiment, the static elimination brush 32 is installed above the FD discharge port. The charge eliminating brush 32 is a brush for removing charges from the charged transfer material P. Then, when the charge eliminating brush 32 comes into contact with a part of the heat collecting plate 30 of the full load detection lever 19, the charge charged up to the full load detection lever 19 is dropped to the ground, and processing equivalent to the grounding is performed. Since other configurations are the same as those in the first embodiment, description thereof is omitted.

  According to the second embodiment, the same effect as that of the first embodiment can be obtained, and the charge removal brush 32 is brought into contact with the full load detection lever 19 so as to release the charge charged up to the heat collecting plate 30. Thus, electrostatic breakdown of the thermistor can be prevented.

  As mentioned above, although embodiment of this invention was described concretely, this invention is not limited to the above-mentioned embodiment, The various deformation | transformation based on the technical idea of this invention is possible.

1 is a cross-sectional view illustrating an image forming apparatus according to a first embodiment of the present invention. 1 is a cross-sectional view illustrating a paper discharge unit of an image forming apparatus according to a first embodiment of the present invention. 1 is a cross-sectional view illustrating a paper discharge unit of an image forming apparatus according to a first embodiment of the present invention. 1 is a cross-sectional view illustrating a paper discharge unit of an image forming apparatus according to a first embodiment of the present invention. 1 is a cross-sectional view illustrating a paper discharge unit of an image forming apparatus according to a first embodiment of the present invention. It is sectional drawing which shows the paper discharge part of the image forming apparatus by 2nd Embodiment of this invention. It is sectional drawing which shows the outline of the image forming apparatus by a prior art. It is sectional drawing which shows the outline of the paper discharge part of the image forming apparatus by a prior art.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Paper feed tray 2 Sheet stacking table 3 Paper feed roller 4 Transport roller 5 Transport roller 6 Registration roller 7 Registration roller 8 Photosensitive drum 9 Toner cartridge 10 Laser scanner unit 11 Polyhedral mirror 12 Transfer roller 13 Heating unit 14, 24 Pressure roller 16 FD paper discharge roller 17 FD paper discharge roller 18 paper discharge tray 19 full load detection lever 20 photo interrupter 21 fixing inlet guide 22 fixing film 23 heating element 25 film guide member 26 fixing paper discharge roller 27 fixing paper discharge roller 28 FD paper discharge roller 29 FD discharge roller 30 Heat collecting plate 31 Temperature detection sensor 32 Static elimination brush

Claims (6)

A paper feeding unit for supplying a transfer material;
An image forming unit for forming an image on a transfer material;
A heat fixing unit for fixing the image formed on the transfer material by the image forming unit;
A paper discharge unit for discharging the transfer material;
A paper discharge tray for stacking transfer materials discharged by the paper discharge unit;
A full load detection lever arranged above the paper discharge tray and configured to be able to detect a full load state of the transfer material by contacting a load surface of the transfer material stacked on the paper discharge tray;
A heat collecting plate provided on the passing surface side of the transfer material in the full load detection lever and in contact with the transfer material discharged to the paper discharge tray;
A temperature detecting means for detecting the temperature provided on the back side of the heat collecting plate;
An image forming apparatus, wherein the temperature of the transfer material discharged to the paper discharge tray by the paper discharge unit can be detected. The heat collecting plate that slides on the transfer material is made of a member having a smaller heat capacity than the heat collecting plate other than the heat collecting plate of the full load detecting lever, and the members other than the heat collecting plate of the full load detecting lever are made of plastic. The image forming apparatus according to claim 1, comprising: The image forming apparatus according to claim 2, wherein a portion of the full load detection lever that is in contact with the leading end of the transfer material is made of plastic. The temperature detection means is disposed immediately above a position where the heat collecting plate and the transfer material slide when the full load detection lever is rotated by the transfer material. 4. The image forming apparatus according to any one of items 3. 5. The image forming apparatus according to claim 1, wherein the back side of the heat collecting plate is hollow except for a joint portion with the full load detection lever portion. When the temperature detected by the temperature detecting means is equal to or higher than a predetermined temperature, the transfer material discharged by the paper discharge unit is discharged at a larger interval, or an image is formed by the image forming unit. The image forming apparatus according to claim 1, further comprising: a control unit capable of executing control for slowing down the speed.

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