JP4130898B2 - Fixing device - Google Patents

Description

【００８０】
表１の場合、普通紙Ａ４用紙の縦使用時には、総ての開口部Ａ，Ｂ，Ｃが全開状態であり、Ａ４用紙の横使用（Ａ４Ｒ）および葉書使用時には、前記開口部Ａ，Ｃは全閉状態となり、前記Ａ４用紙の横幅よりも広いＢ５用紙の縦使用時には、前記開口部Ａ，Ｃの開口率は５０％となっている。
【００８１】
【表２】

【００８２】
表２の場合、厚紙使用時であり、用紙による吸熱が大きく、用紙幅領域内と用紙幅領域外とで温度差が大きくなるので、Ａ４用紙の縦使用時には、総ての開口部Ａ，Ｂ，Ｃが全開状態であり、Ａ４用紙の横使用（Ａ４Ｒ）時には、前記開口部Ａ，Ｃは全閉状態となるのは前記表１と同様であるけれども、Ｂ５用紙の縦使用時には、前記開口部Ａ，Ｃの開口率は４０％となっている。
【００８３】
【表３】

【００８４】
表３の場合、連続プリント枚数が５０枚を超えた場合、用紙幅領域外に蓄積される熱量が増加し、該用紙幅領域外と用紙幅領域内とで温度差が大きくなるので、Ａ４用紙の縦使用時には、中央部の開口部Ｂのみが全開状態であり、開口部Ａ，Ｃは９０％となり、Ａ４用紙の横使用（Ａ４Ｒ）時には、前記開口部Ａ，Ｃは全閉状態となり、Ｂ５用紙の縦使用時には、前記開口部Ａ，Ｃの開口率３０％となっている。
【００８５】
このように、印字要求に合わせて可動リフレクタ３７３の角度を適切に変化させることができ、これにより、ヒートローラの温度ムラの発生を効果的に防ぐことができる。なお、本発明は、以上説明した実施の形態に限定されることなく、発明の要旨を逸脱しない限りにおいて、必要に応じて、適宜、設計変更や改良等は自由である。
【００８６】
【発明の効果】
以上の説明から明らかなように、本発明は、以下の効果を奏する。
【００８７】
（１）ヒートローラの加熱効率を高めるために設けられるリフレクタを複数枚設け、その相互の重なりを変えることによってヒーターランプからヒートローラへの照射光量（照射熱量）を制御するので、ヒートローラの定着位置での温度分布を適切に調整することができ、温度ムラの発生を効果的に防ぐことができる。
【００８８】
また、ヒーターランプは１本で済み、高効率化を図ることができ、装置を低コストで提供することができ、かつ、ヒートローラの径も小さくて済むため、装置のコンパクト化を実現することもできる。さらに、温度ムラが防止されるため、ヒートローラ内で発生する熱応力を少なくすることができるため、ヒートローラの長寿命化が可能となる。
【００８９】
（２）複数枚で構成したリフレクタを、ロッド状のヒーターランプを略中心として、周方向に相対的に変位させることで、開口部の重なり具合を変化させて、前記ヒーターランプからヒートローラへの照射光量（照射熱量）を制御するので、プリント条件（用紙サイズ、用紙厚さ、連続プリント枚数）などに応じて、ヒートローラへの照射条件を適切に調整し、温度ムラを抑えることができる。また、ヒーターランプは１本で済み、低コストに実現することができると共に、ヒートローラの径も小さくてよく、装置のコンパクト化が可能となり、高効率化を図ることもできる。
【００９０】
（３）駆動源の回転駆動力が、回転機構を介して、複数枚のリフレクタの中の少なくとも一つのリフレクタに正逆方向に可逆的に伝達されるので、プリント条件（用紙サイズ、用紙厚さ、連続プリント枚数）などに応じて、ヒートローラへの照射条件を容易かつ適切に変化させることができる。
【００９１】
（４）被動ギヤに対して遊離ギヤを選択的に噛み合わせることで、駆動源を一方向に回転させておいても、駆動源からの駆動力を、少なくとも一つのリフレクタ（可動リフレクタ）に対して正逆方向に伝達することができるので、照射光量を可逆的に調整することが可能となる。
【００９２】
（５）互いに重なり合う前記リフレクタ同士の内壁径と外壁径を、ヒーターランプからの照射熱による熱膨張を許容できる程度の径差に設定しているので、各リフレクタの各部の温度が変化し、膨張、収縮しても、リフレクタ同士の接触を確実に避けることができる。
【００９３】
（６）リフレクタを、熱膨張率の低い材料で形成するので、リフレクタの熱による変形を少なくし、リフレクタ同士の接触によるトラブルを回避することができる。
【００９４】
（７）リフレクタの反射面に光拡散性を具備させたので、ヒートローラへの照射光を分散させることができ、部分的に高温になったり、温度分布が急激に変化するのを防ぐことができ、ヒートローラの劣化を防止することができる。
【００９５】
（８）ヒートローラのニップ部が、予め定められる定着温度になるように、複数のリフレクタの開口位置および開口サイズを設定するので、トナー画像を良好に定着させることができ、画像品位の向上を図ることができる。
【００９６】
（９）リフレクタの開口部の形成位置を、定型の用紙サイズを合わせて設定するので、ヒーターランプからの光がヒートローラに照射される範囲と用紙幅とを一致させることができ、ヒートローラの温度ムラを効果的に抑制することができる。
【００９７】
（１０）リフレクタのヒートローラ回転軸に対して垂直な断面形状を、円弧状とするので、リフレクタ同士の周方向の相対変位を容易に行うことができる。また、リフレクタを１回転以上回転させても、互いに径が異なるため、リフレクタ同士が衝突することもない。
【００９８】
（１１）温度検出手段を、それぞれ各開口部に対応した位置に設けるので、定着温度を精度よく制御することができる。
【図面の簡単な説明】
【図１】従来の定着装置の構成説明図である。
【図２】本発明の実施の一形態に係る定着装置の要部構成を示す透視斜視図である。
【図３】同リフレクタの開閉状態の説明図である。
【図４】同回転機構の動作説明図である。
【図５】同回転機構におけるギヤトレインの支持部の説明図である。
【図６】同回転機構の分解斜視図である。
【図７】同回転機構の組み付け状態の斜視図である。
【図８】同定着装置を具備した画像形成装置の構成説明図である。
【図９】同ヒートローラの温度分布を従来と比較して示したグラフである。
【符号の説明】
３７Ａ−ヒートローラ
３７１−ヒーターランプ
３７２，３７３−リフレクタ
３７５−被動ギヤ
５１，５２，５３，５４−ギヤトレイン
５３，５４−遊離ギヤ
Ａ，Ｂ，Ｃ，Ｄ−開口部
Ｎ−ニップ部[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a fixing device provided in an electrophotographic image forming apparatus such as a copying machine or a printer, and more particularly to a fixing device in which a heat roller is heated by a rod-shaped heater lamp provided therein.
[0002]
[Prior art]
In a fixing device in which a heat roller (heating roller) that is rotationally driven by forming a nip portion with a pressure roller is heated by a heater lamp provided therein, in order to increase its thermal efficiency, A configuration in which light from the heater lamp is collected by a reflector has been conventionally employed (see, for example, Patent Document 1).
[0003]
The configuration is shown in FIG. The fixing device 100 is used in an electrophotographic image forming apparatus, and a toner image formed on a sheet is fixed by passing through a nip portion N between a heat roller 101 and a pressure roller 102. At that time, the light irradiated from the heater lamp 103 is condensed by the inner reflector 104 upstream of the nip portion N between the heat roller 101 and the pressure roller 102, so that the surface temperature of the heat roller 101 is increased. However, the maximum temperature is reached at the nip portion N, and the thermal efficiency is excellent.
[0004]
However, in such a configuration, when only a sheet having the maximum usable width is used, a substantially constant temperature distribution can be obtained with respect to the axial direction of the heat roller 101. A paper having a smaller size than that of the maximum width paper is frequently used, and when a certain number of such small size papers are processed, there is a problem that temperature unevenness occurs in the axial direction.
[0005]
For example, in the case of center reference (processing is performed with the center of the paper width being aligned with the center of the heat roller 101 in the axial direction), as shown by the broken line in FIG. There is a difficulty.
[0006]
In addition, in such a fixing device that does not use a reflector, although illustration is omitted in order to suppress temperature unevenness, for example, there is one in which two heater lamps are provided in a heat roller. In this case, one of the lamps has a length corresponding to the maximum usable paper, and the other lamp has a length corresponding to a small size paper, and is configured to use them properly. .
[0007]
[Patent Document 1]
JP-A-4-221978 (FIGS. 1 and 2, paragraphs “0011” to “0014”)
[0008]
[Problems to be solved by the invention]
However, as described above, in the configuration in which the two heater lamps are provided in the heat roller, there are problems that the cost is increased and the heat roller is increased in diameter and the thermal efficiency is lowered. In addition, when the paper size is large, there is a problem that the temperature unevenness cannot be suppressed with high accuracy.
[0009]
SUMMARY An advantage of some aspects of the invention is that it provides a fixing device that can achieve low cost and high efficiency, and can effectively suppress temperature unevenness.
[0010]
[Means for Solving the Problems]
In the present invention, means for solving the above-described problems are configured as follows.
[0011]
  (1) In a heat roller that is rotationally driven,Rod-shapedWhile providing a heater lamp, between the heater lamp and the heat roller,At different positions in the radial direction about the heater lamp as a center.Provide multiple reflectors,
  Each of the plurality of reflectors has an opening formed therein.
  By relatively displacing the plurality of reflectors in the circumferential direction of the heater lamp,Change the overlapping state of the reflectorsThe open state between the heater lamp and the heat roller at a plurality of positions in the axial direction of the heat roller is changed to a plurality of states including a fully closed state in the circumferential direction. In any case, the circumferential directionAdjust the amount of light emitted from the heater lamp to the heat rollerDoIt is characterized by that.
[0012]
In this configuration, in the fixing device in which a heater lamp is provided inside the heat roller and the heat roller is irradiated with light from the heater lamp to heat the heat roller, the heat roller is provided to increase the heating efficiency. In addition, a plurality of reflectors for collecting the irradiation light from the heater lamp are provided.
[0013]
Then, by changing the overlapping of the plurality of reflectors, the amount of light (irradiation heat) from the heater lamp to the heat roller is controlled, so that the temperature distribution at the fixing position of the heat roller can be adjusted appropriately. it can.
[0014]
Therefore, the irradiation condition to the heat roller can be changed according to printing conditions (paper size, paper thickness, number of continuous prints), environmental conditions, etc., and temperature unevenness can be suppressed with high accuracy. Further, only one heater lamp is required, and the apparatus can be provided at low cost, and the diameter of the heat roller can be small, so that the apparatus can be made compact. Also, high efficiency can be achieved.
[0015]
When the sheet passes through the fixing device, heat is taken away by the sheet, so that the heat roller becomes hot outside the area in contact with the sheet. That is, when the paper size is small, the temperature increases because the high temperature range is widened. Therefore, as described above, by changing the overlapping state of the plurality of reflectors, the temperature distribution at the fixing position can be made appropriate, and further, high temperature outside the paper area can be prevented, and the heat roller Long service life is possible.
[0016]
  (2) The plurality of reflectorsConsists of a first reflector and a second reflector,
  The first reflector includes a first opening over the entire area in the axial direction,
  The second reflector includes a second opening at a position facing the passing range of the small size paper and a third opening at a position facing the outside of the passing range of the small size paper,
  Regarding the circumferential direction, the opening range of the second opening includes the opening range of the third opening, and is wider than the opening range of the third opening,
  About the said circumferential direction, the opening range of the said 3rd opening part is narrower than the range except the said 1st opening part in a said 1st reflector.It is characterized by that.
[0017]
In this configuration, in the fixing device in which a heater lamp is provided inside the heat roller and the heat roller is irradiated with light from the heater lamp to heat the heat roller, the heat roller is provided to increase the heating efficiency. A plurality of reflectors that collect the irradiation light from the heater lamp, and the plurality of reflectors are relatively displaced in the circumferential direction around the rod-shaped heater lamp as a center. The amount of irradiation (amount of irradiation heat) from the heater lamp to the heat roller is controlled by changing the overlapping of the reflectors and changing the communication state (overlap state) of the opening.
[0018]
Therefore, the irradiation condition to the heat roller can be changed according to the printing conditions (paper size, paper thickness, number of continuous prints), etc., and temperature unevenness can be suppressed with high accuracy. Further, the number of heater lamps is one, which can be realized at a low cost, and the diameter of the heat roller may be small, the apparatus can be made compact, and high efficiency can be achieved.
[0019]
  (3) The aboveThe first reflector and the second reflector are relatively displaced in the circumferential direction in accordance with the type of paper passing through the heat roller and the number of continuous passes.It is characterized by that.
[0020]
In this configuration, the rotational driving force of the driving source is reversibly transmitted in the forward and reverse directions to at least one of the plurality of reflectors via the rotation mechanism, so that the printing conditions (paper size, paper The irradiation conditions to the heat roller can be easily and appropriately changed according to the thickness, the number of continuous prints), and the like.
[0021]
  (4)A rotation mechanism for reversibly transmitting a rotational driving force from a driving source of the heat roller to the second reflector in a forward and reverse direction;A gear train comprising a plurality of gears, andSecondAnd a driven gear attached to the reflector.Equipped with a rotating mechanism
  The driven gear is a chipped gear in which teeth are formed only in the opening range of the third opening in the circumferential direction,
  During the gear train,A pair of free gears rotating in opposite directions by a rotational driving force from a drive source,Driven gearInSelectiveMesh withA pair of free gears is provided.
[0022]
In this configuration, by selectively changing the meshing state of the disengaged gear with the driven gear, the driving force from the driving source can be transmitted to at least one reflector (movable reflector) even if the driving source is rotated in one direction. ) Can be transmitted in the forward and reverse directions, so that the amount of irradiation light can be adjusted reversibly.
[0023]
(5) The inner wall diameter and the outer wall diameter of the reflectors that overlap each other are set to a diameter difference that allows thermal expansion due to heat applied from the heater lamp.
[0024]
  In this configuration, the temperature of each part of each reflector changes due to the turning on and off of the heater lamp, the overlapping state of the wall surfaces of the reflector, and the like, and it deforms due to expansion and contraction. Therefore, by setting an interval (diameter) between the reflectors including a margin for the deformation, it is possible to reliably avoid contact between the reflectors..
  (6) The reflector is formed of a material having a low coefficient of thermal expansion.
[0025]
In this configuration, the temperature of each part of each reflector changes due to the turning on and off of the heater lamp, the overlapping state of the wall surfaces of the reflector, and the like, and it deforms due to expansion and contraction. Therefore, by using a material having a low coefficient of thermal expansion, the deformation can be reduced, and troubles due to contact between reflectors can be avoided.
[0026]
(7) A light diffusivity is provided on an inner wall surface serving as a reflection surface of the reflector.
[0027]
When the light diffusibility of the reflecting surface of the reflector is low, the irradiation light to the heat roller is concentrated on a part and partially becomes high temperature. Therefore, the heat roller is easily deteriorated due to a rapid change in temperature distribution or high temperature.
[0028]
In this configuration, by imparting light diffusibility to the reflecting surface of the reflector, it is possible to disperse the irradiation light to the heat roller and prevent such a problem.
[0029]
(8) The opening positions and the opening sizes of the plurality of reflectors are set so that the nip portion of the heat roller has a predetermined fixing temperature.
[0030]
When heating the heat roller from the inside, it takes time for the heat to propagate to the outside of the heat roller in contact with the paper. Further, the amount of irradiation light varies depending on the opening size of the reflector. Therefore, in this configuration, by appropriately setting the opening position and opening size of each reflector, the nip portion of the heat roller can be made to reach a predetermined fixing temperature, and the toner image Can be fixed satisfactorily, and the image quality can be improved.
[0031]
(9) The position where the reflector opening is formed in the axial direction is set in accordance with a plurality of standard paper sizes.
[0032]
When the paper size is smaller than the irradiation range in the axial direction of the heat roller, the temperature of the surface of the heat roller becomes higher in a region outside the paper size, and temperature unevenness occurs. In order to reduce such temperature unevenness, the irradiation range may be adjusted according to the standard paper size.
[0033]
In this configuration, by setting the opening formation position according to the standard paper size, the communication state of the opening can be changed. The widths of the various papers to be matched can be matched, and temperature unevenness of the heat roller can be effectively suppressed.
[0034]
(10) A cross-sectional shape perpendicular to the heat roller rotation axis of the reflector is an arc shape.
[0035]
In this configuration, the relative displacement in the circumferential direction between the reflectors can be easily performed. Further, even if the reflectors are rotated one or more times, the diameters are different from each other, so that the reflectors do not collide with each other.
[0036]
(11) A plurality of temperature detection means provided for controlling the fixing temperature are provided, and each temperature detection means is provided at a position corresponding to each opening.
[0037]
Since a plurality of temperature regions are generated by a plurality of openings, in this configuration, the temperature can be detected by a temperature detecting unit provided individually and used for temperature control, thereby realizing high-precision fixing temperature control. Can do.
[0038]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, a fixing device according to an embodiment of the present invention will be described in detail with reference to the drawings.
[0039]
<Image forming apparatus>
FIG. 8 shows a configuration of the image forming apparatus G. The image forming apparatus G includes an image reading unit 10, a laser writing unit 20, an image forming unit 30, and a paper feeding unit 40, and a paper conveyance direction of the image forming unit 30. A fixing device (fixing device) 37 that heats and fixes a toner image formed on the sheet by the image forming unit 30 under pressure is provided on the downstream side of the image forming unit 30.
[0040]
The image reading unit 10 includes an optical unit U including a first mirror unit 11 including a rod-shaped illumination lamp 11A and a mirror 11B, and a second mirror unit 12 in which a pair of mirrors 12A are arranged to face each other. The optical unit U exposes and scans the image of the document D placed on the document table provided at the top of the apparatus main body.
[0041]
The exposure scanning includes a parallel movement of the first mirror unit 11 of the optical unit U from a solid line to a position indicated by a broken line, and a follow-up movement of the second mirror unit 12 with respect to the first mirror unit 11 at a speed of 1/2. Is done. An image obtained by exposure scanning is imaged on the image sensor 14 via the projection lens 13, and the photoelectrically converted electric signal is temporarily stored in the memory as an image signal through image processing in an image processing unit (not shown). The
[0042]
Next, when the image signal is input to the laser writing unit 20, the laser beam generated by the semiconductor laser is rotationally scanned by the polygon mirror 22 rotated by the drive motor 21. Thereafter, the laser beam scans and exposes the photosensitive surface of the photosensitive drum 32 that has been charged to a predetermined potential in advance by the charger 31 through the reflection optical system including the fθ lens 23 and the mirrors 24 to 26.
[0043]
Thereby, an electrostatic latent image of the original image is formed. As described above, an electrostatic latent image of the original image is formed on the peripheral surface of the photosensitive drum 32 by the main scanning by the laser beam and the sub-scanning accompanying the rotation of the photosensitive drum 32. This electrostatic latent image is reversely developed with toner carried by the developing sleeve 33A of the developing device 33 to become a toner image.
[0044]
On the other hand, from each paper feed cassette 41 loaded in the paper feed unit 40, the recording paper P of a specified size is carried out by the operation of the carry-out roller 41A of the paper feed cassette 41 that stores it. Thereafter, the sheet is fed toward the image transfer unit via the conveyance roller 43. The fed recording paper P is fed to the toner image on the peripheral surface of the photosensitive drum 32 by the registration roller 44, the timing is adjusted, and the paper is synchronously fed to the transfer unit. The toner image is transferred by being charged by the device 34.
[0045]
Further, the recording paper P onto which the toner image has been transferred is separated from the peripheral surface of the photosensitive drum 32 by the charge eliminating action of the separator 35, and is conveyed to the fixing device 37 via the conveying belt 36, and is pressed against the heat roller 37A. After the toner is fused and fixed by heating under pressure nipping at the nip portion N by the roller 37B, the toner is discharged from the fixing device 37 by the conveying roller 38. The discharged recording paper P is finally discharged onto the tray 50 via the paper discharge roller 45.
[0046]
On the other hand, the photosensitive drum 32 from which the transfer paper P has been separated is subjected to removal of residual toner and cleaning by a blade 39A that is pressed by a cleaning device 39, and then charged again by the charger 31 for the next image forming process. enter.
[0047]
<Fixing device>
FIG. 2 is a see-through perspective view showing the main configuration of the fixing device 37. The fixing device 37 has a heater lamp 371 (for example, a halogen lamp) for heating the heat roller 37A at the axial center portion of the rotationally driven heat roller 37A, and the heat roller 37A and Two reflectors of an inner reflector 372 and a movable reflector 373 are provided concentrically with the heater lamp 371.
[0048]
The inner reflector 372 is formed in a semi-cylindrical shape in which the longitudinal half of the cylindrical body is broken and removed, so that the condensing position of the heater lamp 371 is a position on the front side of the nip portion N (upstream side in the sheet conveyance direction). It is provided in a fixed state. On the other hand, the movable reflector 373 is formed to have a larger diameter than the inner reflector 372 and has three openings A, B, and C corresponding to the standard paper size as will be described later.
[0049]
  Both ends of the heat roller 37A are rotatably supported by a support member (not shown), and one end of the heat roller 37A receives a rotational driving force from a power source (not shown). Heat rollerYa374 is fixed. As will be described later, power for changing the angle of the movable reflector 373 is applied to one end of the movable reflector 373 as a heat roller gear.YaReflector for receiving from 374Ya(Driven gear of the present invention) 375 is fixed. In addition, this reflectorYaIn 375, a toothless area that is in a missing tooth state over a substantially half circumference is formed (see FIGS. 4A and 4B).
[0050]
  The other end of the movable reflector 373 is rotatably supported by an end plate (not shown). Free insertion holes and reflector gigs formed in the center of the end plateYaThe terminal portions at both ends of the heater lamp 371 are inserted into the loose holes formed in the central portion of 375 in a loosely fitted state, and are connected to terminals 278 and 279 connected to a heater power source (not shown).
[0051]
  ReflectoragiYaA groove that supports one end of the inner reflector 372 is formed on the inner periphery of the 375, and a groove that supports the other end of the inner reflector 372 is formed on the end plate. By these grooves, the inner reflector 372 is fixed toward the front side of the nip portion N as described above.
[0052]
In the inner reflector 372 and the movable reflector 373, at least the inner peripheral surface of the inner reflector 372 is subjected to, for example, a satin finish, and the reflecting surface is provided with diffusibility. As a result, even if the light from the heater lamp 371 is condensed before the nip portion N, it is possible to prevent excessive condensing and non-uniform light collecting, suppress deterioration of the heat roller 37A, and extend the life. Can do.
[0053]
The inner reflector 372 and the movable reflector 373 are made of a material having a low coefficient of thermal expansion. On the other hand, the temperature of each part of the reflectors 372 and 373 changes due to the lighting and extinguishing of the heater lamp 371 and the overlapping state of the wall surfaces of the two reflectors 372 and 373 and deforms due to expansion and contraction. Therefore, by using a material having a low coefficient of thermal expansion, the deformation can be suppressed to be small, and contact between the reflectors 372 and 373 can be avoided.
[0054]
Furthermore, in addition to using a material having a low coefficient of thermal expansion as described above, the interval between the reflectors 372 and 373 is set in consideration of a margin for deformation of the reflectors 372 and 373 due to heat irradiated from the heater lamp 371. ing. Accordingly, as described above, even if the temperature of each part of each reflector 372, 373 changes due to the lighting and extinguishing of the heater lamp 371 and the overlapping state of the wall surfaces of the reflectors 372, 373, and the like, Contact between the reflectors 372 and 373 can be surely avoided.
[0055]
FIG. 3 is a longitudinal sectional view for explaining the operation of the movable reflector 373. 3A, 3B, and 3C are cross-sectional views taken along section line A1-A2, B1-B2, and C1-C2 in FIG. 2, that is, the three openings A and B. , C is a sectional view of each. (D), (e), and (f) are cross-sectional views of the openings A, B, and C, respectively, showing a state where the movable reflector 373 is rotated by 170 ° from the state shown in FIG.
[0056]
In contrast to the inner reflector 372 formed in the semi-cylindrical shape, that is, opened 180 °, the movable reflector 373 is located at the center in the axial direction, and the heater lamps 371 receive all the paper from the heater lamp 371. In FIG. 3, the central opening B that needs to transmit light has 20 ° of the cylindrical wall surface remaining, and the remaining 340 ° (white background portion) is open.
[0057]
On the other hand, the openings A and C, which are located on both sides in the axial direction and need to transmit light from the heater lamp 371 only to large-size paper, remain at 200 ° of the cylindrical wall surface. The remaining 160 ° (white background portion) is open.
[0058]
3A, 3B, and 3C show a state when the large-size paper is fixed, and in this case, all the openings A, B, and C are fully opened. On the other hand, FIGS. 3D, 3E and 3F show the state when the small-size paper is fixed, and only the opening B is in an open state in which the width hardly changes, and the rest The openings A and C are fully closed.
[0059]
In the example of FIG. 3, as described above, the opening portions A and C are 160 ° opening portions, and both ends in the circumferential direction are evenly (10 ° each) so as to cover the inner reflector 372 when fully opened. And the opening of the inner reflector 372 is completely covered by rotating by 170 ° from that state.
[0060]
In this way, it is possible to change only the light amount to the peripheral portion without changing the light amount irradiated to the central portion of the heat roller 37A. Accordingly, in FIG. 9 described in the above prior art, the temperature distribution at both sides in the direction perpendicular to the transport direction can be changed as indicated by the solid line. Temperature rise on both sides can be suppressed.
[0061]
The opening positions and the opening sizes of the openings A, B, and C are set in this way so that the nip portion N has a predetermined fixing temperature. Therefore, when the heat roller 37A is heated from the inside, it takes time for heat to propagate to the outside in contact with the paper, and the amount of irradiation varies depending on the opening size of the openings A, B, C. With this setting, a predetermined fixing temperature can be maintained in the nip portion N of the heat roller 37A.
[0062]
In short, the formation positions of the openings A, B, and C are set in consideration of the standard paper size, and all the openings A, B, and C are opened when the maximum width recording paper is used. When the recording paper having a narrow width is used, the opening B on the inner side than the width of the recording paper is set in the open state, and the outer openings A and C are set in the shielding state. The temperature rise in the outside region can be suppressed.
[0063]
Accordingly, for example, the temperature distribution of the heat roller 37A when the A4 sheet is used in the horizontal direction (A4R) is appropriately set by substantially matching the both ends of the opening B and the width (edge) of the A4 sheet. Can be controlled. As a result, the range irradiated with light from the heater lamp 37A matches the sheet width, and the temperature unevenness can be suppressed with high accuracy.
[0064]
Furthermore, normally, the fixing device 37 is provided with temperature detection means such as a thermistor in order to control the fixing temperature. A plurality of temperature detecting means are provided corresponding to the openings A, B, and C, respectively. Therefore, even if a plurality of temperature regions are generated by the plurality of openings A, B, and C, accurate temperature control can be realized by detecting them by temperature detecting means provided individually and using them for temperature control. Can do.
[0065]
4 to 7 are views for explaining the rotation mechanism R of the movable reflector 373, FIG. 4 is a side view for explaining the operation of the rotation mechanism R, and FIG. FIG. 6 is a side view showing a state of switching of the rotation direction, FIG. 6 is an exploded perspective view of the rotation mechanism R, and FIG. 7 is a perspective view of the rotation mechanism R.
[0066]
As described above, the heat roller 37A is rotationally driven when power from a power source (not shown) is transmitted to the heat roller gear 374 fixed to one end thereof. As shown in FIGS. 4 (a) and 4 (b), the rotating mechanism R transmits the power of the heat roller gear 374 to one of the movable reflectors 373 via gears 51, 52, 53, and 54 constituting a gear train. It is transmitted to the reflector gear 375 fixed to the end portion, and is rotated in both forward and reverse directions to change the angle of the movable reflector 373.
[0067]
The support shafts 51a, 52b, 53c, 54d of the gears 51, 52, 53, 54 are rotatably supported by a gear frame 376 as shown in FIGS. Is supported so as to be swingable about the axis of the support shaft 51 a of the gear 51. One end of the gear frame 376 is connected to an output shaft 377a of a solenoid 377 provided at a fixed position via a spring s.
[0068]
  As shown in FIGS. 6 and 7, the gear 51 is a heat roller gear.YaThis is a gear that takes in power from 374, and when this gear 51 rotates, the two gears 52, 54 meshing with it also rotate in conjunction with each other. Another gear 53 is engaged with the gear 52. Therefore, the two gears (free gears of the present invention) 53 and 54 rotate in opposite directions with each other by the power taken in by the gear 51.
[0069]
  Then, when the gear frame 376 is swung, one of the gear 53 and the gear 54 is reflected by the reflector gear.YaIt meshes with 375 and transmits power. In this way, as described above,Ya375 can be rotated in both forward and reverse directions. Since one end of the gear frame 376 is connected to the solenoid 377 provided at the fixed position as described above, when the solenoid 377 is turned on / off, the gear frame 376 is oscillated and displaced. The gear 54 is switched.
[0070]
  FIG. 5A shows a state where the solenoid 377 is ON. In this case, since the solenoid 377 pulls the output shaft 377a, the gear frame 376 is rotated and displaced clockwise, and the gear 53 is connected to the reflector gear as shown in FIG.Ya375 meshed with the reflectorYa375 rotates counterclockwise.
[0071]
  On the other hand, FIG. 5B shows a state where the solenoid 377 is OFF. In this case, since the solenoid 377 protrudes the output shaft 377a, the gear frame 376 is displaced counterclockwise, and the gear 54 is connected to the reflector gear as shown in FIG.Ya375 (gear 53 disengages) and the reflector gearYa375 rotates clockwise.
[0072]
  Where ReflectagiYa375 is formed with a toothless area 375a that is in a missing tooth state over a substantially half circumference, and as described above, when the movable reflector 373 rotates 170 °, the gears 51, 52, 53 are rotated by the rotation of the heat roller 37A. , 54 does not rotate any more, and the openings A and C can be switched to either the fully open state or the fully closed state.
[0073]
As described above, in the fixing device of the present invention, the heater lamp 371 is provided inside the heat roller 37A, and the heat roller 37A is heated by irradiating the inner wall of the heat roller 37A with the light of the heater lamp 371. In the fixing device, the two reflectors 372 and 373 having different outer diameters are formed of a cylindrical body having an opening, and are arranged concentrically with the rod-shaped heater lamp 371 as a substantial center. By relatively displacing these cylindrical bodies in the circumferential direction, the communication state (overlapping condition) of the opening is changed, and the irradiation light amount (irradiation heat amount) from the heater lamp 371 to the heat roller 37A is controlled. be able to.
[0074]
Accordingly, the heat roller 37A is driven by controlling the drive source of the rotation mechanism R via the control means (not shown) according to the detection information such as the print conditions (paper size, paper thickness, number of continuous prints). By appropriately changing the irradiation conditions, temperature unevenness can be suppressed with high accuracy.
[0075]
In addition, since it is possible to control such irradiation conditions with a single heater lamp 37A, the apparatus can be provided at low cost and the diameter of the heat roller 37A can be reduced, so that the compactness of the apparatus can be achieved. And high efficiency can be obtained.
[0076]
In the above example, two reflectors are provided, but three or more reflectors may be provided. For example, it is possible to divide the inner reflector into three parts, rotate them separately, and change the irradiation direction. If the reflector is divided into a large number of sheets, it is possible to more accurately cope with various types of paper sizes. Moreover, although the shape of the cross section perpendicular to the axis of the reflector is an arc shape, other shapes such as an ellipse or a parabola conventionally known as a reflector may be used. Moreover, you may comprise in a polyhedral form.
[0077]
Further, in the embodiment described above, as shown in FIGS. 3A, 3B and 3C, and FIGS. 3D, 3E and 3F, the movable reflector 373 is switched to only two positions. However, by changing the rotation mechanism R, it may be switched in more stages. For example, the solenoid can be switched to three positions, and an encoder or the like is provided on the movable reflector 373 so that the displacement position can be detected, thereby requesting a print request such as the paper quality and the number of prints of the sheet using the movable reflector 373. It is possible to set an optimum angle in accordance with.
[0078]
Tables 1 to 3 show suitable examples in which the opening ratio of each opening is changed by changing the angle of the movable reflector 373 in accordance with the print request. In these Tables 1 to 3, the angle of the movable reflector 373 is represented by an aperture ratio. Table 1 is an example in which the angle of the movable reflector 373 is changed in accordance with the set paper size. Tables 2 and 3 are also examples in which the angle of the movable reflector 373 is changed in accordance with the set paper size, and each shows a case of thick paper and a case where the number of continuous prints is large. ing.
[0079]
[Table 1]

[0080]
In the case of Table 1, all the openings A, B, C are fully open when the plain paper A4 paper is used vertically, and when the A4 paper is used sideways (A4R) and postcards, the openings A, C are When the B5 sheet is used in the fully closed state and wider than the A4 sheet, the opening ratios of the openings A and C are 50%.
[0081]
[Table 2]

[0082]
In the case of Table 2, when thick paper is used, the heat absorption by the paper is large, and the temperature difference between the paper width area and the outside of the paper width area becomes large. Therefore, when A4 paper is used vertically, all openings A and B , C are in the fully open state, and when the A4 sheet is used sideways (A4R), the openings A and C are in the fully closed state as in Table 1, but when the B5 sheet is used vertically, the opening is opened. The aperture ratio of the portions A and C is 40%.
[0083]
[Table 3]

[0084]
In Table 3, when the number of continuous prints exceeds 50, the amount of heat accumulated outside the paper width area increases, and the temperature difference between the outside of the paper width area and the inside of the paper width area increases. In the vertical use, only the central opening B is fully open, the openings A and C are 90%, and when the A4 paper is used sideways (A4R), the openings A and C are fully closed. When the B5 sheet is used vertically, the opening ratio of the openings A and C is 30%.
[0085]
As described above, the angle of the movable reflector 373 can be appropriately changed in accordance with the print request, thereby effectively preventing the temperature unevenness of the heat roller. The present invention is not limited to the embodiment described above, and design changes and improvements can be freely made as necessary without departing from the spirit of the invention.
[0086]
【The invention's effect】
As is clear from the above description, the present invention has the following effects.
[0087]
(1) Since a plurality of reflectors provided to increase the heating efficiency of the heat roller are provided, and the amount of light (irradiation heat) from the heater lamp to the heat roller is controlled by changing the overlap between the reflectors, the heat roller is fixed. The temperature distribution at the position can be adjusted appropriately, and the occurrence of temperature unevenness can be effectively prevented.
[0088]
Also, only one heater lamp is required, so that high efficiency can be achieved, the apparatus can be provided at low cost, and the diameter of the heat roller can be reduced, so that the apparatus can be made compact. You can also. Furthermore, since temperature unevenness is prevented, thermal stress generated in the heat roller can be reduced, and thus the life of the heat roller can be extended.
[0089]
(2) A plurality of reflectors are displaced relative to each other in the circumferential direction with the rod-shaped heater lamp as a substantial center, thereby changing the overlapping state of the openings, so that the heater lamp can be transferred to the heat roller. Since the irradiation light quantity (irradiation heat amount) is controlled, the irradiation condition to the heat roller can be appropriately adjusted according to the printing conditions (paper size, paper thickness, number of continuous prints), etc., and temperature unevenness can be suppressed. Further, only one heater lamp is required, which can be realized at low cost, and the diameter of the heat roller may be small, the apparatus can be made compact, and high efficiency can be achieved.
[0090]
(3) Since the rotational driving force of the driving source is reversibly transmitted to at least one of the plurality of reflectors in the forward and reverse directions via the rotating mechanism, the printing conditions (paper size, paper thickness) , The conditions for irradiating the heat roller can be changed easily and appropriately.
[0091]
(4) By selectively meshing the driven gear with the driven gear, the driving force from the driving source is applied to at least one reflector (movable reflector) even if the driving source is rotated in one direction. Therefore, the amount of irradiation light can be reversibly adjusted.
[0092]
(5) Since the inner wall diameter and the outer wall diameter of the reflectors that overlap each other are set to a diameter difference that allows thermal expansion by irradiation heat from the heater lamp, the temperature of each part of each reflector changes and expands. Even if it shrinks, it is possible to reliably avoid contact between the reflectors.
[0093]
(6) Since the reflector is formed of a material having a low coefficient of thermal expansion, deformation of the reflector due to heat can be reduced, and troubles due to contact between the reflectors can be avoided.
[0094]
(7) Since the reflecting surface of the reflector is provided with light diffusibility, it is possible to disperse the irradiation light to the heat roller, and it is possible to prevent a partial increase in temperature and a sudden change in temperature distribution. And deterioration of the heat roller can be prevented.
[0095]
(8) Since the opening positions and the opening sizes of the plurality of reflectors are set so that the nip portion of the heat roller has a predetermined fixing temperature, the toner image can be fixed satisfactorily and the image quality can be improved. Can be planned.
[0096]
(9) Since the position where the opening of the reflector is formed is set in accordance with the standard paper size, the range in which the light from the heater lamp is irradiated on the heat roller can be matched with the paper width. Temperature unevenness can be effectively suppressed.
[0097]
(10) Since the cross-sectional shape perpendicular to the heat roller rotation axis of the reflector is an arc, the relative displacement between the reflectors in the circumferential direction can be easily performed. Further, even if the reflectors are rotated one or more times, the diameters are different from each other, so that the reflectors do not collide with each other.
[0098]
(11) Since the temperature detecting means is provided at a position corresponding to each opening, the fixing temperature can be accurately controlled.
[Brief description of the drawings]
FIG. 1 is a diagram illustrating a configuration of a conventional fixing device.
FIG. 2 is a perspective view illustrating a configuration of a main part of a fixing device according to an embodiment of the present invention.
FIG. 3 is an explanatory diagram of an open / close state of the reflector.
FIG. 4 is an operation explanatory diagram of the rotation mechanism.
FIG. 5 is an explanatory diagram of a gear train support in the rotation mechanism.
FIG. 6 is an exploded perspective view of the rotation mechanism.
FIG. 7 is a perspective view of an assembled state of the rotation mechanism.
FIG. 8 is an explanatory diagram illustrating a configuration of an image forming apparatus including an identification wearing device.
FIG. 9 is a graph showing a temperature distribution of the heat roller in comparison with the conventional one.
[Explanation of symbols]
37A-heat roller
371-Heater lamp
372, 373-reflector
375-driven gear
51,52,53,54-Geartrain
53,54-Free gear
A, B, C, D-opening
N-nip part

Claims (11)

A rod-shaped heater lamp is provided in the heat roller that is rotationally driven, and a plurality of reflectors are provided between the heater lamp and the heat roller at different positions in the radial direction with the heater lamp as a substantially center ,
Each of the plurality of reflectors has an opening formed therein.
The plurality of reflectors are displaced relative to each other in the circumferential direction of the heater lamp to change the overlapping state of the reflectors, thereby changing the communication state of the opening, and a plurality of positions in the axial direction of the heat roller. The open state between the heater lamp and the heat roller in any one of a plurality of states including the fully closed state in the circumferential direction, and the amount of light irradiated from the heater lamp in the circumferential direction to the heat roller A fixing device characterized by adjusting. The plurality of reflectors includes a first reflector and a second reflector,
The first reflector includes a first opening over the entire area in the axial direction,
The second reflector includes a second opening at a position facing the passing range of the small size paper and a third opening at a position facing the outside of the passing range of the small size paper,
Regarding the circumferential direction, the opening range of the second opening includes the opening range of the third opening, and is wider than the opening range of the third opening,
The fixing device according to claim 1 , wherein an opening range of the third opening portion is narrower than a range excluding the first opening portion of the first reflector in the circumferential direction . 3. The fixing device according to claim 2 , wherein the first reflector and the second reflector are relatively displaced in a circumferential direction in accordance with a type of paper passing through a heat roller and a number of continuous passes . A rotation mechanism for reversibly transmitting a rotational driving force from a driving source of the heat roller to the second reflector in forward and reverse directions, a gear train including a plurality of gears, and the second reflector A rotation mechanism composed of an attached driven gear, and
The driven gear is a chipped gear in which teeth are formed only in the opening range of the third opening in the circumferential direction,
During the gear train, a pair of free gears rotate in opposite directions by the rotational driving force from the driving source, and characterized in that disposed a pair of free gears selectively meshed with the driven gear The fixing device according to claim 2 .   2. The fixing device according to claim 1, wherein an inner wall diameter and an outer wall diameter of the reflectors that overlap with each other are set to a diameter difference that allows thermal expansion by irradiation heat from the heater lamp.   The fixing device according to claim 1, wherein the reflector is formed of a material having a low coefficient of thermal expansion.   The fixing device according to claim 1, wherein an inner wall surface serving as a reflection surface of the reflector is provided with light diffusibility.   The fixing device according to claim 1, wherein opening positions and opening sizes of the plurality of reflectors are set so that a nip portion of the heat roller has a predetermined fixing temperature.   The fixing device according to claim 2, wherein the formation position in the axial direction of the opening of the reflector is set according to a plurality of standard paper sizes.   The fixing device according to claim 1, wherein a cross-sectional shape perpendicular to the heat roller rotation axis of the reflector is an arc shape.   The fixing device according to claim 2, wherein a plurality of temperature detecting means provided for controlling the fixing temperature are provided, and each temperature detecting means is provided at a position corresponding to each of the openings.

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