JP2007225913A - Fixing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fixing device that reduces damage to a rotary body of the fixing device and hardly deforms a temperature detection section or cavses positional deviation. <P>SOLUTION: The fixing device has a heating section which heats at least one of a pair of rotary bodies conveying a recording medium to between nips pressed against each other and a noncontact temperature detection section detecting the temperature of the rotary body, and is equipped with a protection member disposed upstream from the temperature detection section in the rotating direction of the rotary body without contacting to stop a recording paper from enternig. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a fixing device used in an image forming apparatus such as a copying machine, a printer, a facsimile machine, and a multifunction machine having a plurality of these functions, and more particularly to a fixing device that prevents a non-contact temperature detection unit from being damaged by jammed paper.

In recent years, the speed of image forming apparatuses has been increased more and more, recording sheets are inevitably conveyed at high speed, and the interval between recording sheets is narrowed. For example, an image forming apparatus of 80 sheets / min or more and an image forming apparatus of 100 sheets / min or more have been developed. In the fixing device of such a high-speed image forming apparatus, a non-contact temperature detecting unit is used as a temperature detecting unit for controlling the rotating roller to the fixing temperature so as not to damage the rotating roller.
In addition, the separation claw for separating the recording paper from the rotation roller also comes into contact with the rotation roller only just before the leading edge of the recording paper reaches the separation claw so that the rotation roller is not damaged, and after the recording paper is separated from the rotation roller, The swinging is controlled so as to be separated from the rotating roller. Accordingly, the swing control of the separation claw is extremely short and requires high speed control.
However, when the recording paper is attracted to the rotating roller and the separation claw is poorly controlled, the recording paper may rub through the separation claw. Then, the recording paper may collide with the temperature detection unit, and the temperature detection unit may be damaged or misaligned. Alternatively, a member other than the temperature detection unit forming the fixing device, for example, a cleaning member or a support structure thereof is damaged to cause a positional shift.
Patent Document 1 discloses that an intrusion prevention material for preventing intrusion of a recording sheet or a regulating member for restricting deformation of the temperature detection unit is provided upstream of the temperature detection unit.
JP 2005-345687 A

According to this Patent Document 1, it is possible to prevent the recording paper from entering, or to regulate the deformation of the temperature detection unit. However, in Patent Document 1, the separation claw is pressed against the rotating roller by a spring. When the tip of the separation claw is sharply processed and pressed against the rotating roller, the surface of the rotating roller is scratched. In particular, in a high-speed image forming apparatus, the rotation speed of the rotation roller is high, and therefore the surface abrasion of the rotation roller tends to be deep, and the life of the rotation roller is shortened. In addition, image defects occur due to scratches on the rotating roller. Moreover, the temperature detection part of this patent document 1 is a contact-type temperature detection part which contacts a rotary body, and does not respond to a high-speed image forming apparatus.
The present invention solves the above-described problems, and provides a fixing device that reduces damage to a rotating body of a fixing device and prevents deformation and displacement of a temperature detection unit in a high-speed image forming apparatus. Is.

  In order to solve the above problems, a fixing device of the present invention includes a pair of rotating bodies that convey a recording medium between nips that are pressed against each other, a heating unit that heats at least one of the rotating bodies, A non-contact temperature detecting unit that detects at least one temperature, and a defense member that is arranged in a non-contact manner on the rotating body on the upstream side in the rotation direction of the rotating body from the temperature detecting unit. According to this configuration, since the recording paper wound around the rotating body comes into contact with the protective member, further intrusion can be prevented. Therefore, it does not reach the temperature detection unit. As a result, damage or misalignment of the temperature detection unit can be prevented.

It is desirable that the protection member be arranged in a non-contact manner with respect to the rotating body with an interval less than the thickness of the recording paper. Thereby, the recording paper wound around the rotating body does not enter more than the protective member.
Preferably, a recording paper separation claw is provided between the nip portion and the defense member, and a cleaning member for the rotating body is provided between the defense member and the non-contact temperature detection portion. As a result, the recording sheet can be normally guided to the conveyance path. In addition, the cleaning member can be protected.
The recording paper separating claw is preferably in contact with the rotating body immediately before the recording paper leading edge reaches the recording paper separating claw and swings away from the rotating body after the recording paper is separated from the rotating body. . According to this configuration, scratches on the rotating body can be minimized and a high-speed image forming apparatus can be realized.
The defense member may be disposed within 135 ° in the rotation direction of the rotating body from the nip portion when the nip portion is at the lowest position of the rotating body. Thereby, it can peel from a rotary body using the gravity of a recording paper.
The said defense member is good to arrange | position within 45 degrees-135 degrees in the rotation direction of the said rotary body from the said nip part. Thereby, the recording paper can be effectively peeled from the rotating body.
The defense member may be arranged within 90 ° from the front to the rear in the rotation direction of the rotating body from the nip portion. Thereby, the recording paper can be more effectively peeled from the rotating body.

  According to the present invention, it is possible to reduce damage to the rotating body of the fixing device, and it is possible to prevent deformation and displacement of the temperature detection unit. Thereby, a high-speed image forming apparatus can be realized.

An embodiment of the present invention will be described with reference to FIG. FIG. 1 is a diagram illustrating a configuration of an image forming apparatus according to the present embodiment.
This image forming apparatus forms a monochrome image on a predetermined sheet (recording paper) in accordance with image data transmitted from the outside. As shown in the figure, the image forming apparatus includes an exposure unit 1, a paper feed tray 2, a paper transport path 3, a developing device 4, a photoconductor 5, a charger 6, a cleaner unit 7, a transfer mechanism 8, a fixing unit 9 and A paper discharge tray 10 and others are provided, and these are configured.

The exposure unit 1 includes, for example, an EL or LED writing head in which light emitting elements are arranged in an array in addition to a method using a laser scanning unit (LSU) including a laser irradiation unit 11 and a reflection mirror 12 as shown in FIG. There is also a method using. In addition, this image forming apparatus employs a technique of using a plurality of laser beams to reduce the speed of irradiation timing and adopting a two-beam technique in order to perform high-speed printing processing. The exposure unit 1 exposes the photoconductor 5 uniformly charged by the charger 6 according to the input image data, thereby forming an electrostatic latent image according to the image data on the surface of the photoconductor 5. It has a function to form.
The developing device 4 visualizes the electrostatic latent image with toner. A toner tank 13 is provided behind the developing unit 4 to supply toner to the developing unit 4. A toner bottle 14 is provided to supply toner to the toner tank 13. The developing device 4 of this embodiment visualizes the electrostatic latent image formed on the photoconductor 5 with black toner, but in the case of a color image forming apparatus, color toner is prepared.

The charger 6 is a charging means for uniformly charging the surface of the drum forming the photoreceptor 5 to a predetermined potential, and a charger-type charger is used as shown in FIG. Instead of this, a contact type roller type or brush type charger may be used.
The cleaner unit 7 removes and collects toner remaining on the surface of the photoreceptor 3 after development and image transfer.
The electrostatic image visualized on the photoreceptor 5 as described above is applied from the transfer mechanism 8 to the recording paper to be transported by the transfer mechanism 8, and an electric field having a reverse polarity to the charge of the electrostatic image is applied. It is transferred onto the paper. For example, when the electrostatic image has a charge of (−) polarity, the applied polarity of the transfer mechanism 8 is (+) polarity. The transfer mechanism 8 of this image forming apparatus is constituted by a transfer belt unit, which is bridged by a driving roller 15, a driven roller 16, and other rollers, and has a predetermined resistance value (1 × 10 ⁹ to 1 × 10 ¹³ Ω · cm). A transfer belt 17 having a range) is disposed. An elastic conductive roller 19 capable of applying a transfer electric field with a conductivity different from that of the driving roller 15 and the driven roller 16 is disposed at a contact portion 18 between the photosensitive member 5 and the transfer belt 17. Since the elastic conductive roller 19 has elasticity, the photosensitive member 5 and the transfer belt 17 are not in line contact but form a transfer nip portion 20 having a predetermined width. The transfer nip portion 20 is in surface contact with a predetermined width, thereby improving the transfer efficiency to the conveyed recording paper.

  Further, on the downstream side of the transfer area of the transfer belt 17, the recording paper to be conveyed neutralizes the electric field applied in the transfer area, and a neutralizing roller 21 is provided on the back surface of the transfer belt 17 for smooth conveyance to the next process. Is arranged. In addition, the transfer mechanism 8 is provided with a charge removal mechanism 22 that performs cleaning to remove toner contamination on the transfer belt 17 and performs charge removal. The neutralization mechanism 22 may be grounded via an image forming apparatus, or may be positively applied with a polarity opposite to the polarity of the transfer electric field.

The electrostatic image (unfixed toner) transferred onto the paper by the transfer mechanism 8 is conveyed to the fixing unit 9, where the unfixed toner is melted and fixed on the paper. The fixing unit 9 includes a heating roller 23 and a pressure roller 24. As shown in FIG. 3, a sheet separation claw 25, a roller surface temperature detection member 26 (thermistor), a web cleaning type are provided on the outer periphery of the heating roller 23. A roller surface cleaning member 27 is disposed and has a heater 28 for heating the surface of the heating roller 23 to a predetermined temperature (fixing set temperature: approximately 160 to 200 ° C.).
On the other hand, the pressure roller 24 is provided with a pressure member (not shown) that allows the pressure roller 24 to come into pressure contact with the heating roller 23 at a predetermined pressure amount at both ends of the roller. Further, a paper separation claw 29 and a roller surface cleaning member (not shown) are disposed on the outer periphery of the pressure roller 24 as in the outer periphery of the heating roller 23.
In such a fixing unit 9, unfixed toner on a recording sheet conveyed at the pressure contact portion 30 (referred to as a fixing nip portion) between the heating roller 23 and the pressure roller 24 at the surface temperature of the heating roller 23. The unfixed toner is fixed on the paper by melting and the pressing action on the recording paper by the pressure contact force.

The sheet feed tray 2 is a tray for storing sheets (recording sheets) used for image formation, and is provided below the image forming unit in this image forming apparatus. Since this image forming apparatus is intended to perform high-speed printing processing, the paper feed tray 2 disposed below the image forming unit has a plurality of paper feeds capable of storing 500 to 1500 standard sizes in each tray. The trays 2a, 2b and 2c are arranged. The paper feed tray 2a stores A4 size recording paper. The paper feed tray 2b accommodates B5 size recording paper, and the paper feed tray 2c accommodates B4 size recording paper. On the other hand, on the side surface of the image forming apparatus, a large-capacity paper feed cassette 31 capable of storing a large amount of a plurality of paper types and a manual feed tray 32 mainly used for printing an irregular size such as a postcard or letter size paper are arranged. ing.
The paper discharge tray 10 is disposed on the side surface opposite to the manual feed tray 32 of the image forming apparatus. However, instead of the paper discharge tray 10, a post-processing device for paper discharge (such as stapling and punching processing), a plurality of paper discharge trays are provided. A staged paper discharge tray can also be arranged as an option.

  In addition to the above-described configuration, the image forming apparatus includes an automatic document feeding mechanism and document presser foot 33 on the upper side. The document holder 33 presses the document placed on the document table 34 against the document reading surface. A laser scanning mechanism 35 is provided below the document table 34 to read the document placed on the document table 34 and convert it into an electrical signal. The automatic document feeder and document presser foot 33 automatically feeds the document placed on the document tray 36 to the document reading unit 37 and conveys it to the paper discharge tray 38. The automatic document feed mechanism includes a document reverse feed unit 39 for reading the back side of the document.

2 is a transverse sectional view showing the detailed structure of the fixing unit 9, FIG. 3 is a longitudinal sectional view, and FIG. 3 (a) is a central portion where the non-contact thermistor 26 is arranged in FIG. It is sectional drawing. FIG. 3B is a cross-sectional view of the end where the contact thermistor 41 is disposed in FIG. As shown in FIGS. 2 and 3, the main heater 28 and the sub heater 42 are inserted into the heating roller 23 in a non-rotating manner. As shown in FIG. 2, the main heater 28 heats the central portion of the heating roller 23, and the sub heater 42 heats the end portion. The heating roller 23 is heated from the inside by the main heater 28 and the sub heater 42, and is heated by an external heating roller 43 disposed so as to be in contact with the outer surface of the heating roller 23. An external heating heater 44 is inserted into the external heating roller 43 in a non-rotating manner.
The heating roller 23 is made of a metal such as iron in a monochrome image forming apparatus, and the surface thereof is coated with titanium or fluorine as necessary. In a color image forming apparatus, a metal body such as iron is coated with silicon rubber and further coated with titanium or fluorine. The external heating roller 43 is a thin roller and is disposed in the vicinity of the recording paper conveyance inlet side, and heats up the heating roller 23 from the surface, thereby speeding up the image forming apparatus.

The pressure roller 24 is formed, for example, by coating silicon rubber with a surface as necessary, and a pressure roller heater 45 is inserted in the inside thereof in a non-rotating manner. The pressure roller heater 45 heats the pressure roller 24 from the inside, keeps the temperature of the back side of the recording sheet at the nip constant, enhances the toner throwing action, and fixes the unfixed toner on the recording sheet. .
3A and 3B, the recording sheet is conveyed from the transfer mechanism 8 to the nip portion 30 of the fixing unit 9 by the paper guide 46. After the recording paper passes through the nip portion 30 of the fixing unit 9, the recording paper is separated from the heating roller 23 by the paper separation claw 25 and separated from the pressure roller 24 by the paper separation claw 29. Then, the paper is guided by the upper paper guide 47 and the lower paper guide 48 and is conveyed toward the paper discharge tray 10 in the direction of arrow A.

As shown in FIG. 4, the sheet separation claw 25 is integrally formed with a separation claw portion 25 a and a separation claw shaft portion 25 b and is attached to a plurality of separation claw support shafts 51 arranged in parallel with the heating roller 23. As shown in FIG. 5, when the image forming apparatus conveys the recording sheet by the center conveyance method, the sheet separation claw 25 has a minimum sheet width (for example, Paper separation pawls 251 and 252 arranged at slightly narrower intervals than the postcard), paper separation claws 253 and 254 arranged at slightly smaller intervals than the maximum paper width (for example, A3 size), and the most commonly used paper width (for example, , A4 size) paper separating claws 255, 256 arranged at a slightly narrower interval than the A4 size).
As shown in FIG. 6, these paper separation claws 25 are normally biased in a direction away from the heating roller 23 by a spring 25 c, and are peeled off when the peeling claw support shaft 51 rotates in a direction in contact with the heating roller 23. It is attached so as to rotate together with the claw support shaft 51. The distance at which the tip of the peeling claw 25a is separated from the surface of the heating roller 23 is the variation in the length of the peeling claw 25a, the eccentricity of the rotating roller 23, and the variation in the location where the peeling claw support shaft 51 and the paper separation claw 25 are joined. In consideration of the above, it is desirable that the tip of the peeling claw portion 25a is set to be separated from the surface of the heating roller 23 so as to be surely non-contact, and the interval is preferably small.

As shown in FIGS. 5 and 7, a brace 52 is provided at one end of the peeling claw support shaft 51, and a solenoid 53 is coupled thereto. The solenoid 53 is turned on / off in accordance with the conveyance timing of the recording paper. That is, immediately before the recording sheet is conveyed, for example, 10 mm before the leading end of the recording sheet reaches the peeling claw portion 25a, the leading end of the peeling claw portion 25a is brought into contact with the surface of the rotating roller 23. When the leading edge of the recording paper advances a certain amount from the peeling claw portion 25a, for example, 10 mm from the peeling claw portion 25a, the recording paper is turned off, and the peeling claw portion 25a is separated from the rotating roller 23 by the spring 25c. Here, the distance between the peeling claw portion 25a and the front end of the recording paper has been described, but in actuality, it is controlled according to the timing in consideration of the traveling speed of the recording paper.
The paper separation claw 29 on the pressure roller 24 side is configured similarly to the paper separation claw 25 on the heating roller 23 side, and operates in the same manner.

  As shown in FIG. 8, the non-contact temperature detection unit 26 of this embodiment is formed by a rectangular case 55 having an opening 56 on a surface facing the heating roller 23. A temperature detection unit 58 made of a thermistor is attached to a surface 57 facing the case 55 through the opening 56. Therefore, the temperature detector 58 can receive the heat 59 from the heating roller 23 through the opening 56. The case 57 is integrally formed with a lead wire storage portion 59 so as to extend from the rectangular portion. The lead wire storage portion 59 is formed by a flat case on the side away from the heating roller 23. Although FIG. 8 shows only a part of the lead wire storage portion 59, the opening 56 is arranged at the center in the length direction of the heating roller 23, so that one end of the heating roller 23 is reached. It is good to extend. A temperature detection unit (not shown) for detecting the temperature near the fixing device is attached to the lead wire storage unit 59. By comparing the detection temperatures of the temperature detection unit attached to the lead wire storage unit 59 and the temperature detection unit 58 for detecting the temperature of the heating roller, the temperature change around the fixing device is offset, and the heating roller 23 The temperature is detected. The tip of the opening 56 of the non-contact temperature detection unit 26 is attached to the heating roller 23 so as to be separated from the thickest recording sheet that can be used in the image forming apparatus of this embodiment. The recording paper that can be normally used in the image forming apparatus is the thickest OHP paper and has a thickness of 200 to 250 μm. However, if the distance is 2 mm or more, the distance to the temperature detection unit 58 increases and the sensitivity of the temperature detection unit 58 decreases. If it is 250 μm or less, when the OHP sheet is wound around the heating roller 23, it collides with the non-contact temperature detection unit 26. Therefore, about 1 mm is desirable.

  The fixing device according to the present invention is characterized in that a defense member 60 is disposed upstream of the non-contact temperature detection unit 26 in the rotation direction of the heating roller 23. Further, the defense member 60 is disposed upstream of the cleaning member 27. The cleaning member 27 is configured by a web-type cleaning member that winds a nonwoven fabric around the supply roller 27a, presses the nonwoven fabric against the heating roller 23 by the pressing roller 27b, and winds the nonwoven fabric around the winding roller 27c. The cleaning member 27 presses the nonwoven fabric against the heating roller 23 to remove residual toner from the heating roller and clean it. The protection member 60 is formed of a strong material such as a stainless steel plate, for example, and is not deformed or displaced even when a recording sheet collides with the protection member 60 and is not in contact with the heating roller 23. Mounted firmly. It is preferable that the defense member 60 has at least the same length as the non-contact temperature detection unit 26 and at least the same length as the heating roller 23. As shown in FIG. 9, the protection member 60 is sharply formed at the tip, and the distance between the tip and the heating roller 23 is set to be smaller than the thinnest recording paper that can be used in the image forming apparatus. . The thinnest recording paper is, for example, a secondary base paper used for diazo and is about 60 μm. However, the heating roller 23 needs to be mounted in consideration of the thermal expansion at the fixing temperature, the eccentricity, the mounting error of the protection member 60, and the like. Therefore, it is attached to be 60 μm or less. When attached at intervals of 60 μm or more, the protection member 60 cannot prevent the passage of the diazo secondary base paper.

As shown in FIG. 9, the defense member 60 has a pressure contact portion (nip portion) with the pressure roller 24 at the lowermost position, and this point is set as a reference point (0 °) to the center of the rotation axis of the heating roller 23. Install within 135 ° to the angle.
In the range of 0 ° to 45 °, the force of dropping from the heating roller 3 due to the weight of the recording paper works, but the force that presses the recording paper against the heating roller 23 at the nip portion is larger, so the winding force is Greater than peel force. Therefore, when the defense member 60 is arranged in the range of 0 ° to 45 °, the action of preventing the recording paper from entering is weak.
In the range of 45 ° to 90 °, the force that drops from the heating roller 23 due to the weight of the recording paper increases as the angle increases, and the wrapping force is greater than or substantially equal to the force that causes the recording paper to drop from the heating roller 23. It is. Therefore, in this range, as the angle increases, the gravity action of the recording paper increases, and the force falling from the heating roller 23 increases. In the range of 90 ° to 135 °, the peeling force is greater than the winding force. In this range, as the angle increases, the gravity action of the recording paper decreases, and the peeling force from the heating roller 23 decreases.
In the range of 135 ° to 180 °, the wrapping force is larger than the peeling force. In this range, as the angle increases, the gravity action of the recording paper decreases, and the peeling force from the heating roller 23 decreases.
As described above, according to the present invention, even when a recording sheet is wound around the heating roller 23, further entry can be prevented by the protection member 60, and the non-contact temperature detection unit 26 and the cleaning unit 27 can be protected. can do.
The above description is summarized in FIG.
From the above results, it is preferable that the protective member 60 is disposed within 135 ° in the rotational direction of the rotating body from the nip portion, more preferably within 45 ° to 135 °, and further within 15 ° before and after 90 °. Good arrangement.

1 is a diagram illustrating a configuration of an image forming apparatus. FIG. 2 is a cross-sectional view showing a structure of a fixing unit. FIG. 2 is a longitudinal sectional view showing a structure of a fixing unit. It is a figure which shows a paper separation nail | claw. FIG. 6 is a diagram for explaining a mounting state of a sheet separation claw. It is a figure explaining a paper separation claw. It is a figure explaining a heating roller, a pressure roller, and a paper separation claw. It is a perspective view which shows a cost contact temperature detection part. It is a figure explaining the winding state of a heating roller and a recording paper. FIG. 4 shows a relationship diagram between a winding force and a peeling force when a recording sheet is wound around a heating roller.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Exposure unit 5 Photoconductor 9 Fixing unit 23 Heating roller 24 Pressure roller 25 Paper separation nail 26 Non-contact thermistor 27 Cleaning unit 41 Contact thermistor 28 Main heater 43 External heating roller 60 Defense member

Claims (7)

A pair of rotating bodies for conveying the recording medium between the nips pressed against each other;
A heating unit for heating at least one of the rotating bodies;
A non-contact temperature detector for detecting the temperature of at least one of the rotating bodies;
A fixing device comprising: a protective member disposed in a non-contact manner on the rotating body on the upstream side in the rotation direction of the rotating body from the temperature detection unit.   The fixing device according to claim 1, wherein the protection member is arranged with an interval equal to or less than a thickness of the recording paper.   The recording sheet separation claw is provided between the nip portion and the defense member, and the cleaning member for the rotating body is provided between the defense member and the non-contact temperature detection unit. Fixing device.   The recording paper separating claw contacts the rotating body immediately before the recording paper leading edge reaches the recording paper separating claw, and swings away from the rotating body after the recording paper is separated from the rotating body. The fixing device according to any one of claims 1 to 3.   The said protection member is arrange | positioned within 135 degrees in the rotation direction of the said rotary body from the said nip part, when the said nip part exists in the lowest part of a rotary body, The any one of Claim 1 thru | or 4 characterized by the above-mentioned. The fixing device according to Item.   The fixing device according to claim 5, wherein the protection member is disposed within 45 ° to 135 ° in a rotation direction of the rotating body from the nip portion.   The fixing device according to claim 6, wherein the protection member is arranged within 90 ° from front to back in the rotation direction of the rotating body from the nip portion.

Images