JP2009163038A - Image forming apparatus - Google Patents

Image forming apparatus Download PDF

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JP2009163038A
JP2009163038A JP2008001192A JP2008001192A JP2009163038A JP 2009163038 A JP2009163038 A JP 2009163038A JP 2008001192 A JP2008001192 A JP 2008001192A JP 2008001192 A JP2008001192 A JP 2008001192A JP 2009163038 A JP2009163038 A JP 2009163038A
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temperature
pressure roller
fixing
roller
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JP5486770B2 (en
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Makoto Egi
誠 江木
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Kyocera Document Solutions Inc
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Kyocera Mita Corp
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Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus, which can accurately correct a nip transport speed of a fixing nip part according to a temperature change of a fixing device in simple apparatus configuration. <P>SOLUTION: The image forming apparatus 1 includes: an endless fixing belt 52 stretched between a heat roller 55 containing a heater lamp 55a and a fixing roller 53; a pressure roller 54 disposed in pressure contact with the fixing belt 52; a thermistor 84 for detecting the temperature of the fixing belt 52; a driving means 57 having a motor for driving the pressure roller 54 in rotation; and a control part 74 for controlling the rotation of the driving means 57, wherein a paper sheet P where an unfixed toner image is supported is passed through a nip part N formed by pressure contact of the fixing belt 52 and the pressure roller 54 to perform heat fixing. The control part 74 controls the rotational frequency of the driving means 57 based on the detected temperature of the thermistor 84, so that the pressure roller 54 achieves a predetermined peripheral speed regardless of the temperature of the heating roller. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

本発明は、電子写真方式を利用した複写機、プリンタ、ファクシミリ、それらの複合機等の画像形成装置に関し、特に、加圧部材等によって用紙を搬送する定着装置を備えた画像形成装置に関するものである。   BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as a copying machine, a printer, a facsimile, or a composite machine using an electrophotographic system, and more particularly to an image forming apparatus including a fixing device that conveys paper by a pressure member. is there.

従来の画像形成装置における定着装置は、所定の温度に維持された加熱ローラと、この加熱ローラに圧接する加圧ローラとを備え、この加圧ローラと加熱ローラとの圧接によって形成されたニップ部により、未定着トナー像を担持した用紙(転写材)を挟持搬送しつつ加熱処理するローラ定着方式が知られている。加えて最近では、加圧ローラに対向配置される定着ローラと、加熱ローラと、定着ローラと加熱ローラとの間に張架される無端状の定着ベルトとを備え、加圧ローラと定着ベルトとの圧接によって形成されたニップ部にて、定着ベルトを介して加熱ローラの熱を転写材に与えることで、未定着トナー像を転写材に加圧定着させるベルト定着方式が実施されている。   A fixing device in a conventional image forming apparatus includes a heating roller maintained at a predetermined temperature, and a pressure roller that is in pressure contact with the heating roller, and a nip portion formed by the pressure contact between the pressure roller and the heating roller. Thus, there is known a roller fixing system in which a sheet (transfer material) carrying an unfixed toner image is heated while being nipped and conveyed. In addition, recently, the apparatus includes a fixing roller disposed opposite to the pressure roller, a heating roller, and an endless fixing belt stretched between the fixing roller and the heating roller. A belt fixing system in which an unfixed toner image is pressure-fixed on a transfer material by applying heat from a heating roller to the transfer material via a fixing belt at a nip portion formed by the pressure contact is performed.

しかしながら、ローラ定着方式やベルト定着方式のように、ニップ部に転写材を導入して転写材を加熱加圧処理すると、加圧ローラや加熱ローラ等の構成部材の温度状態によって、転写部材の挟持搬送速度に変動を生じることがあった。   However, when the transfer material is introduced into the nip portion and heated and pressed as in the roller fixing method and the belt fixing method, the transfer member is sandwiched depending on the temperature state of the constituent members such as the pressure roller and the heating roller. In some cases, the conveyance speed fluctuated.

例えば、ベルト定着方式では、加圧ローラを回転駆動させることで、定着ベルトを従動回転させつつ、転写材をニップ部に挟持搬送させるが、加圧ローラの回転駆動に伴って、加熱された定着ベルトの熱が加圧ローラに伝わることによって、加圧ローラの温度が上昇して、ゴム材等で形成された加圧ローラは、ゴム材が熱膨張し、その外径が大きくなる。これに対し、加圧ローラを一定の回転数で駆動させていた場合には、加圧ローラが高温になるにつれて外径が大きくなることで、この加圧ローラの周速度が増加し、その結果、転写材の挟持搬送速度が速くなる。ローラ定着方式においても同様であり、装置の駆動に伴い、加圧ローラの外径が大きくなることから、転写材を挟持搬送する速度も増加する。   For example, in the belt fixing system, the pressure roller is driven to rotate, the fixing belt is driven to rotate, and the transfer material is nipped and conveyed to the nip portion. When the heat of the belt is transmitted to the pressure roller, the temperature of the pressure roller rises, and the pressure roller formed of a rubber material or the like thermally expands and the outer diameter of the pressure roller increases. On the other hand, when the pressure roller is driven at a constant rotational speed, the outer diameter of the pressure roller increases as the pressure roller becomes higher in temperature, thereby increasing the peripheral speed of the pressure roller. In addition, the nipping and conveying speed of the transfer material is increased. The same applies to the roller fixing method, and as the apparatus is driven, the outer diameter of the pressure roller increases, so the speed at which the transfer material is nipped and conveyed also increases.

一方で、定着装置よりも上流の例えば画像転写部での転写材の搬送は所定の一定速度で制御されているため、転写材が画像転写部と定着装置のニップ部の両方において挟持搬送状態になっている状態では、ニップ部の温度によっては定着装置の搬送速度の方が画像転写部での搬送速度より速くなることから、定着装置が転写材を引っ張ることとなり、画像転写部において転写の画像ズレが生じていた。   On the other hand, since transfer of the transfer material at, for example, the image transfer unit upstream of the fixing device is controlled at a predetermined constant speed, the transfer material is held in a nipped and transported state in both the image transfer unit and the nip portion of the fixing device. In this state, depending on the temperature of the nip portion, the conveyance speed of the fixing device becomes faster than the conveyance speed in the image transfer portion, so that the fixing device pulls the transfer material, and the transfer image is transferred in the image transfer portion. There was a gap.

このような転写の画像ズレを解消するには、画像転写部と定着装置との間を搬送される転写材に、たるみとしてのループを形成するように、定着装置の挟持搬送速度を画像転写部での搬送速度よりも初期から遅く設定すれば、その間で転写材が引っ張られるという現象の発生を未然に防ぐことが可能となる。逆に画像転写部における転写材の搬送速度が定着装置における挟持搬送速度を上回り過ぎると、転写材に必要以上のループが形成されることになるために、定着装置への転写材の入射角等が不安定となって、定着装置でのオフセット等が発生する。従って、画像転写部と定着装置との間では、転写材は適度なループを形成して搬送される事が必要となる。   In order to eliminate such transfer image misalignment, the nipping / conveying speed of the fixing device is set so that a loop as a slack is formed on the transfer material conveyed between the image transferring portion and the fixing device. If the transfer speed is set slower than the initial speed, the occurrence of a phenomenon that the transfer material is pulled during that time can be prevented. On the other hand, if the transfer speed of the transfer material in the image transfer unit exceeds the clamping transfer speed of the fixing device, an unnecessarily loop is formed in the transfer material. Becomes unstable, causing an offset in the fixing device. Therefore, it is necessary that the transfer material is transported in an appropriate loop between the image transfer unit and the fixing device.

そこで、特許文献1では、転写材が画像転写部と定着装置とに同時に保持された状態で画像転写部と定着装置との間に転写材が形成するループの量を検知するループ量検知手段と、このループ量検知手段の検知結果に応じて定着装置のニップ部における転写部材の挟持搬送速度を切り替え制御するために、加圧ローラを回転駆動させる定着モータの回転数を切り替えている。このときに、加圧ローラ表面にサーミスタを配置して、このサーミスタの検知温度によって、定着温度制御状況に応じた各部品の熱膨張を考慮し、定着装置の挟持搬送速度を設定している。また別実施形態では、ニップ部とは反対側面に設置されているサーミスタの温度をモニタして、簡易的に加圧ローラの温度、つまり膨張量を予測している。   Therefore, in Patent Document 1, a loop amount detection unit that detects the amount of loop formed by the transfer material between the image transfer unit and the fixing device in a state where the transfer material is simultaneously held by the image transfer unit and the fixing device. In order to switch and control the nipping and conveying speed of the transfer member at the nip portion of the fixing device in accordance with the detection result of the loop amount detecting means, the rotation speed of the fixing motor that rotates the pressure roller is switched. At this time, a thermistor is disposed on the surface of the pressure roller, and the nipping and conveying speed of the fixing device is set based on the detected temperature of the thermistor in consideration of the thermal expansion of each component in accordance with the fixing temperature control status. In another embodiment, the temperature of the thermistor installed on the side surface opposite to the nip portion is monitored, and the temperature of the pressure roller, that is, the amount of expansion is simply predicted.

しかしながら、上述した従来技術では、熱膨張を算出するための専用サーミスタを加圧ローラに配設しているので、加圧ローラそのものから検知した温度に基づいて、加圧ローラの熱膨張を導き、定着装置のニップ部の挟持搬送速度を正確に設定することができるが、サーミスタとそれに係わる部品数が増えることになり、生産コスト上高くなるという不都合があった。また、ニップ部の反対側面にサーミスタを設置している場合には、簡易的にしか膨張量を予測することができていないで、加熱ベルト等の初期の加熱温度から定着時の温度までの幅広い温度範囲において、熱膨張に伴う加圧ローラ径の変化を正確に予測しづらく、ニップ部の挟持搬送速度を補正することが困難であるという問題があった。
特開2007−72289号公報(段落[0037]〜[0040]、[0055]、図2)
However, in the above-described prior art, the dedicated thermistor for calculating the thermal expansion is arranged in the pressure roller, so that the thermal expansion of the pressure roller is led based on the temperature detected from the pressure roller itself, Although the nipping and conveying speed of the nip portion of the fixing device can be set accurately, there is an inconvenience that the thermistor and the number of parts related to it increase and the production cost increases. In addition, when a thermistor is installed on the opposite side of the nip, the amount of expansion can only be predicted simply, and a wide range from the initial heating temperature of the heating belt etc. to the temperature at the time of fixing. In the temperature range, there is a problem that it is difficult to accurately predict the change in the pressure roller diameter due to thermal expansion, and it is difficult to correct the nipping and conveying speed of the nip portion.
JP 2007-72289 A (paragraphs [0037] to [0040], [0055], FIG. 2)

本発明は、上記のような課題を解決するためになされたものであり、簡単な装置構成で、定着装置の温度変化に応じて、定着ニップ部の挟持搬送速度を正確に補正する画像形成装置を提供することを目的とする。   The present invention has been made to solve the above-described problems, and an image forming apparatus that accurately corrects the nipping / conveying speed of the fixing nip portion according to a temperature change of the fixing apparatus with a simple apparatus configuration. The purpose is to provide.

上記目的を達成するために本発明は、熱源を有する加熱部材と、前記加熱部材に圧接して配置された加圧部材と、前記加熱部材の温度を検知する温度検知部材と、前記加圧部材を回転駆動する駆動手段と、前記駆動手段の回転を制御する制御部とを備え、前記加熱部材と前記加圧部材との圧接によって形成されるニップ部に、未定着トナー像を担持した用紙を通紙して加熱定着を行う画像形成装置において、前記制御部は、前記温度検知部材の検知温度に基づいて、前記駆動手段の回転数を制御して、前記加圧部材の温度に係わらずに前記加圧部材を所定の周速度にすることを特徴としている。   To achieve the above object, the present invention provides a heating member having a heat source, a pressure member disposed in pressure contact with the heating member, a temperature detection member for detecting the temperature of the heating member, and the pressure member. And a control unit for controlling the rotation of the driving unit. A sheet carrying an unfixed toner image is formed in a nip formed by the press contact between the heating member and the pressing member. In the image forming apparatus that passes the paper and performs heat fixing, the control unit controls the number of rotations of the driving unit based on the temperature detected by the temperature detecting member, regardless of the temperature of the pressure member. The pressurizing member is set to a predetermined peripheral speed.

この構成によれば、熱源により加熱された加熱部材が加圧部材に圧接すると、加熱部材の熱が加圧部材に伝わり、加熱部材の温度が下降する。この下降温度を温度検知部材によって検知する。制御部は、加熱部材の下降温度に基づいて加圧部材の温度を推定して、加圧部材を所定の周速度で回転させるように、駆動手段の回転数を制御する。   According to this configuration, when the heating member heated by the heat source is pressed against the pressure member, the heat of the heating member is transmitted to the pressure member, and the temperature of the heating member is lowered. This falling temperature is detected by the temperature detection member. The control unit estimates the temperature of the pressure member based on the descending temperature of the heating member, and controls the rotation speed of the driving unit so as to rotate the pressure member at a predetermined peripheral speed.

また、請求項2に記載の発明では、前記制御部は、前記駆動手段の回転開始時に検知する前記温度検知部材の検知温度と、回転開始時から所定時間後に検知する前記温度検知部材の検知温度との加熱部材温度差に基づいて、前記駆動手段の回転数を制御することを特徴としている。この構成によれば、加熱部材から加圧部材に熱が伝わると加熱部材の温度が下降するが、温度検知部材が駆動手段の回転開始時から所定時間までに加熱部材の下降する温度差を検知し、制御部がその温度差に基づいて加圧部材の温度を推定する。   In the invention according to claim 2, the control unit detects the temperature detected by the temperature detecting member at the start of rotation of the driving means and the detected temperature detected by the temperature detecting member after a predetermined time from the start of rotation. The number of rotations of the driving means is controlled based on the difference in temperature of the heating member. According to this configuration, when heat is transmitted from the heating member to the pressure member, the temperature of the heating member decreases, but the temperature detection member detects a temperature difference at which the heating member descends from the start of rotation of the driving means to a predetermined time. Then, the control unit estimates the temperature of the pressure member based on the temperature difference.

また、請求項3に記載の発明では、前記制御部は、前記駆動手段の回転開始時から第1及び第2の所定時間後に検知する前記温度検知部材の検知温度との加熱部材温度差に基づいて、前記駆動手段の回転数を制御することを特徴としている。この構成によれば、加熱部材から加圧部材に熱が伝わると加熱部材の温度が下降するが、熱源により加熱部材が均一に加熱された状態で、温度検知部材が加熱部材の下降する温度差を検知し、制御部がその温度差に基づいて加圧部材の温度を推定する。   According to a third aspect of the present invention, the control unit is based on a heating member temperature difference from a detected temperature of the temperature detecting member that is detected after the first and second predetermined time from the start of rotation of the driving unit. The rotational speed of the driving means is controlled. According to this configuration, when the heat is transmitted from the heating member to the pressure member, the temperature of the heating member decreases. However, the temperature difference between the temperature detection member and the heating member is lowered while the heating member is uniformly heated by the heat source. , And the control unit estimates the temperature of the pressure member based on the temperature difference.

また、請求項4に記載の発明では、前記制御部は、前記加熱部材温度差が所定温度より低い場合には、前記駆動手段の回転数を前記所定温度における前記駆動手段の所定回転数より小さくし、前記加熱部材温度差が前記所定温度より高い場合には、前記駆動手段の回転数を前記所定回転数より大きくすることを特徴としている。この構成によれば、加熱部材温度差が所定温度より低い場合には、駆動手段の回転数を、所定温度における所定の回転数より小さくすることによって、温度が高くなって外径が大きくなった加圧部材の周速度を小さくし、加熱部材温度差が前記所定温度より高い場合には、駆動手段の回転数を所定回転数より大きくすることによって、温度が低くなって外径が小さくなった加圧部材の周速度を大きくしている。   According to a fourth aspect of the present invention, when the temperature difference of the heating member is lower than a predetermined temperature, the control unit reduces the rotational speed of the driving means to be smaller than the predetermined rotational speed of the driving means at the predetermined temperature. And when the said heating member temperature difference is higher than the said predetermined temperature, the rotation speed of the said drive means is made larger than the said predetermined rotation speed. According to this configuration, when the temperature difference of the heating member is lower than the predetermined temperature, the temperature is increased and the outer diameter is increased by making the rotational speed of the driving means smaller than the predetermined rotational speed at the predetermined temperature. When the peripheral speed of the pressure member is reduced and the temperature difference of the heating member is higher than the predetermined temperature, the temperature is lowered and the outer diameter is reduced by increasing the rotational speed of the driving means above the predetermined rotational speed. The peripheral speed of the pressure member is increased.

また、請求項5に記載の発明では、用紙が前記ニップ部を連続して通紙されるときに、前記制御部は、通紙枚数が増えると、前記駆動手段の回転数を前記所定回転数に近づけることを特徴としている。   According to a fifth aspect of the present invention, when the sheet is continuously passed through the nip portion, the control unit sets the number of rotations of the driving unit to the predetermined number of rotations when the number of sheets to be passed increases. It is characterized by being close to.

また、請求項6に記載の発明では、前記駆動手段が前記加圧部材を連続して回転駆動させるときに、前記制御部は、前記駆動手段の回転駆動時間が長くなると、前記駆動手段の回転数を前記所定回転数に近づけることを特徴としている。   According to a sixth aspect of the present invention, when the driving unit continuously drives the pressure member to rotate, the control unit rotates the driving unit when the rotation driving time of the driving unit becomes longer. The number is made close to the predetermined number of rotations.

請求項1に記載の発明によれば、熱源により加熱された加熱部材が加圧部材に圧接すると、加熱部材の熱が加圧部材に伝わり、加熱部材の温度が下降する。この下降温度を温度検知部材によって検知する。制御部は、加熱部材の下降温度に基づいて加圧部材の温度を推定して、加圧部材を所定の周速度で回転させるように、駆動手段の回転数を制御するので、加圧部材に温度検知部材等を設けなくとも、加圧部材の温度に係わらずに、ニップ部の用紙の挟持搬送速度が一定になり、用紙の転写画像ズレや用紙シワの発生を抑制した用紙搬送をニップ部で行うことができる。   According to the first aspect of the present invention, when the heating member heated by the heat source is pressed against the pressure member, the heat of the heating member is transmitted to the pressure member, and the temperature of the heating member is lowered. This falling temperature is detected by the temperature detection member. The control unit estimates the temperature of the pressure member based on the descending temperature of the heating member, and controls the rotation speed of the driving means so as to rotate the pressure member at a predetermined peripheral speed. Regardless of the temperature of the pressure member, even if a temperature detection member or the like is not provided, the nipping / conveying speed of the paper in the nip is constant, and the paper conveyance that suppresses the transfer image misalignment and paper wrinkles is suppressed. Can be done.

また、請求項2に記載の発明によれば、加熱部材から加圧部材に熱が伝わると加熱部材の温度が下降するが、温度検知部材が駆動手段の回転開始時から所定時間までに加熱部材の下降する温度差を検知し、制御部がその温度差に基づいて、加圧部材の温度を推定し、加圧部材を所定の周速度で回転させるので、ニップ部の挟持搬送速度が正確に補正される。   According to the second aspect of the present invention, when heat is transmitted from the heating member to the pressurizing member, the temperature of the heating member decreases. Is detected, and the controller estimates the temperature of the pressure member based on the temperature difference and rotates the pressure member at a predetermined peripheral speed. It is corrected.

また、請求項3に記載の発明によれば、加熱部材から加圧部材に熱が伝わると加熱部材の温度が下降するが、熱源により加熱部材が均一に加熱された状態で、温度検知部材が加熱部材の下降する温度差を検知し、制御部がその温度差に基づいて、加圧部材の温度を推定し、加圧部材を所定の周速度で回転させるので、ニップ部の挟持搬送速度が正確に補正される。   According to the invention described in claim 3, when the heat is transmitted from the heating member to the pressure member, the temperature of the heating member is lowered, but the temperature detection member is in a state where the heating member is uniformly heated by the heat source. The temperature difference that the heating member descends is detected, the control unit estimates the temperature of the pressure member based on the temperature difference, and rotates the pressure member at a predetermined peripheral speed. Corrected accurately.

また、請求項4に記載の発明によれば、加熱部材温度差が所定温度より低い場合には、駆動手段の回転数を、所定温度における所定の回転数より小さくすることによって、温度が高くなって外径が大きくなった加圧部材の周速度を小さくしているので、加圧部材の温度に係わらずに、ニップ部の挟持搬送速度を一定にすることができる。また、加熱部材温度差が前記所定温度より高い場合には、駆動手段の回転数を、所定回転数より大きくすることによって、温度が低くなって外径が小さくなった部材の周速度を大きくしているので、加圧部材の温度に係わらずに、ニップ部の挟持搬送速度を一定にすることができる。   According to the fourth aspect of the present invention, when the temperature difference of the heating member is lower than the predetermined temperature, the temperature is increased by making the rotational speed of the driving means smaller than the predetermined rotational speed at the predetermined temperature. Since the peripheral speed of the pressure member whose outer diameter is increased is reduced, the nipping and conveying speed of the nip portion can be made constant regardless of the temperature of the pressure member. In addition, when the temperature difference of the heating member is higher than the predetermined temperature, the peripheral speed of the member whose temperature is lowered and the outer diameter is reduced is increased by increasing the rotational speed of the driving means to be higher than the predetermined rotational speed. Therefore, the nipping and conveying speed of the nip portion can be made constant regardless of the temperature of the pressure member.

また、請求項5に記載の発明によれば、通紙枚数が増えると、加圧部材は所定温度に対応する温度に近づくために、駆動手段の回転数を所定回転数に近づけて、通紙枚数に係わらずにニップ部の挟持搬送速度を一定にすることができる。   According to the invention described in claim 5, when the number of sheets to be passed increases, the pressure member approaches the temperature corresponding to the predetermined temperature. Regardless of the number of sheets, the nipping and conveying speed of the nip portion can be made constant.

また、請求項6に記載の発明によれば、加圧部材の回転駆動時間が増えると、加圧部材は所定温度に対応する温度に近づくために、駆動手段の回転数を所定回転数に近づけて、回転駆動時間に係わらずにニップ部の挟持搬送速度を一定にすることができる。   According to the sixth aspect of the present invention, when the rotation driving time of the pressure member increases, the pressure member approaches the temperature corresponding to the predetermined temperature, so that the rotation speed of the driving means approaches the predetermined rotation speed. Thus, the nipping and conveying speed of the nip portion can be made constant regardless of the rotational drive time.

以下に本発明の実施形態について図面を参照して説明するが、本発明は、この実施形態に限定されない。本発明の実施形態は発明の最も好ましい形態を示すものであり、また発明の用途やここで示す用語等はこれに限定されるものではない。   Embodiments of the present invention will be described below with reference to the drawings, but the present invention is not limited to these embodiments. The embodiment of the present invention shows the most preferable form of the invention, and the use of the invention and the terms shown here are not limited thereto.

(第1実施形態)
図1は、本発明の実施形態に係る画像形成装置の内部構成を概略的に示す断面正面図である。画像形成装置1はタンデム型のカラープリンタであり、回転自在である感光体11a〜11dは、感光層を形成する感光材料として、有機感光体(OPC感光体)が用いられ、ブラック(B)、イエロー(Y)、シアン(C)及びマゼンタ(M)の各色に対応させて配される。感光層はアモルファスシリコンでもよい。各感光体11a〜11dの周囲に、現像装置2a〜2d、露光ユニット12、帯電器13a〜13d及び除電器14a〜14dが配設される。
(First embodiment)
FIG. 1 is a cross-sectional front view schematically showing an internal configuration of an image forming apparatus according to an embodiment of the present invention. The image forming apparatus 1 is a tandem type color printer. As the photosensitive members 11a to 11d that are rotatable, an organic photosensitive member (OPC photosensitive member) is used as a photosensitive material for forming a photosensitive layer, and black (B), It is arranged corresponding to each color of yellow (Y), cyan (C) and magenta (M). The photosensitive layer may be amorphous silicon. Around each of the photoreceptors 11a to 11d, developing devices 2a to 2d, an exposure unit 12, chargers 13a to 13d, and static eliminators 14a to 14d are disposed.

現像装置2a〜2dは、感光体11a〜11dの右斜め下方に対向して配置され、感光体11a〜11dにトナーを供給する。帯電器13a〜13dは、現像装置2a〜2dの感光体回転方向上流側であって感光体11a〜11dの表面に対向して配置され、感光体11a〜11d表面を一様に帯電させ、また、除電器14a〜14dは、現像装置2a〜2dの感光体回転方向下流側であって感光体11a〜11dの表面に対向して配置され、感光体11a〜11d表面に現像後に残った電荷を除電する。   The developing devices 2a to 2d are arranged opposite to the lower right of the photoconductors 11a to 11d and supply toner to the photoconductors 11a to 11d. The chargers 13a to 13d are arranged on the upstream side of the developing device 2a to 2d in the rotation direction of the photosensitive member and opposed to the surfaces of the photosensitive members 11a to 11d, and uniformly charge the surfaces of the photosensitive members 11a to 11d. The static eliminators 14a to 14d are arranged on the downstream side of the photoconductor rotation direction of the developing devices 2a to 2d and to face the surfaces of the photoconductors 11a to 11d, and charge remaining on the surfaces of the photoconductors 11a to 11d after development. Remove static electricity.

露光ユニット12は、パーソナルコンピュータ等から画像入力部(図略)に入力された文字や絵柄などの画像データに基づいて、各感光体11a〜11dを走査露光するためのものであり、現像装置2a〜2dの下方で帯電器13a〜13dの感光体回転方向下流側に設けられる。露光ユニット12には、レーザ光源、ポリゴンミラーが設けられ、各感光体11a〜11dに対応して反射ミラー及びレンズが設けられる。レーザ光源から出射されたレーザ光が、ポリゴンミラー、反射ミラー及びレンズを介して各感光体11a〜11dの表面に照射され、照射されたレーザ光により、各感光体11a〜11d表面には静電潜像が形成される。この静電潜像が各現像装置2a〜2dによりトナー像に現像される。   The exposure unit 12 scans and exposes each of the photoconductors 11a to 11d based on image data such as characters and patterns input from a personal computer or the like to an image input unit (not shown). The developing device 2a Is provided downstream of the chargers 13a to 13d in the rotation direction of the photosensitive member. The exposure unit 12 is provided with a laser light source and a polygon mirror, and a reflection mirror and a lens are provided corresponding to each of the photoreceptors 11a to 11d. Laser light emitted from the laser light source is applied to the surfaces of the photoconductors 11a to 11d via a polygon mirror, a reflection mirror, and a lens, and the surfaces of the photoconductors 11a to 11d are electrostatically applied to the surfaces of the photoconductors 11a to 11d. A latent image is formed. The electrostatic latent images are developed into toner images by the developing devices 2a to 2d.

中間転写ベルト17は、テンションローラ6、駆動ローラ25及び従動ローラ27に張架されている。この中間転写ベルト17に接触するように各感光体11a〜11dが中間転写ベルト17の下方で搬送方向(図1の矢印方向)に沿って上流側から隣り合うように対向して配列されている。各1次転写ローラ26a〜26dは、中間転写ベルト17を挟んで各感光体11a〜11dと対向して中間転写ベルト17に接触するよう配置され、図1における上下方向に移動可能であって、必要に応じて中間転写ベルト17を介して各感光体11a〜11dに圧接して1次転写ニップ部を形成し、また離間する。この1次転写ニップ部において、各感光体11a〜11dで形成されたトナー像が中間転写ベルト17表面に転写される。そして、中間転写ベルト17の回転とともに所定のタイミングで各感光体11a〜11dのトナー像が中間転写ベルト17に順次転写されることにより、中間転写ベルト17表面にはシアン、マゼンタ、イエロー、ブラックの4色のトナー像が重ね合わされたフルカラートナー像が形成される。ベルトクリーニング31が転写後に中間転写ベルト17に残存するトナーを清掃する。   The intermediate transfer belt 17 is stretched around the tension roller 6, the driving roller 25, and the driven roller 27. The photoreceptors 11a to 11d are arranged below the intermediate transfer belt 17 so as to be in contact with the intermediate transfer belt 17 so as to be adjacent to each other from the upstream side in the transport direction (arrow direction in FIG. 1). . The primary transfer rollers 26a to 26d are arranged so as to face the photoreceptors 11a to 11d and contact the intermediate transfer belt 17 with the intermediate transfer belt 17 interposed therebetween, and are movable in the vertical direction in FIG. If necessary, a primary transfer nip portion is formed by being pressed against each of the photoreceptors 11a to 11d via the intermediate transfer belt 17, and is separated. In the primary transfer nip portion, the toner images formed by the photoconductors 11a to 11d are transferred to the surface of the intermediate transfer belt 17. The toner images on the photoconductors 11a to 11d are sequentially transferred to the intermediate transfer belt 17 at a predetermined timing along with the rotation of the intermediate transfer belt 17, whereby cyan, magenta, yellow, and black are transferred onto the surface of the intermediate transfer belt 17. A full color toner image is formed by superimposing the four color toner images. The belt cleaning 31 cleans the toner remaining on the intermediate transfer belt 17 after the transfer.

2次転写ローラ34は、中間転写ベルト17を挟んで駆動ローラ25と対向し、中間転写ベルト17に圧接して2次転写ニップ部を形成して、この2次転写ニップ部において、中間転写ベルト17表面のトナー像を用紙Pに転写する。   The secondary transfer roller 34 is opposed to the driving roller 25 with the intermediate transfer belt 17 interposed therebetween, and presses against the intermediate transfer belt 17 to form a secondary transfer nip portion. In the secondary transfer nip portion, the intermediate transfer belt The toner image on the surface 17 is transferred to the paper P.

画像形成装置1内の下方には、用紙Pを収納する給紙カセット32が配設され、画像形成装置1の中間部には、手差しの用紙を供給するスタックトレイ35が配設される。画像形成装置1の左部には、給紙カセット32から繰り出された用紙Pを中間転写ベルト17で形成される2次転写ニップ部に搬送する第1搬送路33が配設され、右部から左部にかけては、スタックトレイ35から繰り出された用紙を2次転写ニップ部に搬送する第2搬送路36が配設される。また、画像形成装置1の左上部には、画像が形成された用紙Pに対して定着処理を行う定着装置18と、定着処理の行われた用紙を用紙排出部37に搬送する第3搬送路39とが配設される。   A paper feed cassette 32 that stores paper P is disposed below the image forming apparatus 1, and a stack tray 35 that supplies manual paper is disposed in the middle of the image forming apparatus 1. On the left side of the image forming apparatus 1, a first conveyance path 33 that conveys the paper P fed from the paper feed cassette 32 to the secondary transfer nip portion formed by the intermediate transfer belt 17 is disposed. On the left side, a second transport path 36 for transporting the sheet fed from the stack tray 35 to the secondary transfer nip portion is provided. In the upper left part of the image forming apparatus 1, a fixing device 18 that performs a fixing process on the paper P on which an image has been formed, and a third transport path that transports the paper on which the fixing process has been performed to the paper discharge unit 37. 39 is disposed.

給紙カセット32は、装置の外部(図1において手前側)に引き出すことにより用紙の補充を可能にしたもので、収納されている用紙Pがピックアップローラ33b及び捌きローラ33aにより1枚ずつ第1搬送路33側に繰り出される。   The paper feed cassette 32 can be replenished by pulling it out of the apparatus (front side in FIG. 1), and the stored paper P is first fed one by one by the pick-up roller 33b and the separating roller 33a. It is fed out to the conveyance path 33 side.

第1搬送路33と第2搬送路36とはレジストローラ33cの手前で合流しており、レジストローラ33cにより、中間転写ベルト17における画像形成動作と給紙動作とのタイミングを取って、用紙Pが2次転写ニップ部に搬送される。2次転写ニップ部に搬送された用紙Pは、バイアス電位(トナーの帯電極性と逆極性)が印加された2次転写ローラ34によって、中間転写ベルト17上のフルカラーのトナー画像を2次転写されて、定着装置18に搬送される。   The first conveyance path 33 and the second conveyance path 36 are merged before the registration roller 33c, and the registration roller 33c takes the timing of the image forming operation and the paper feeding operation in the intermediate transfer belt 17 to form the sheet P. Is conveyed to the secondary transfer nip portion. The full color toner image on the intermediate transfer belt 17 is secondarily transferred to the sheet P conveyed to the secondary transfer nip portion by the secondary transfer roller 34 to which a bias potential (a polarity opposite to the toner charging polarity) is applied. Then, it is conveyed to the fixing device 18.

定着装置18は、ヒータにより加熱される定着ベルトと、定着ベルトに圧接して配設された加圧ローラ等とを備え、転写材としてのトナー像が転写された用紙Pを加熱及び加圧することにより定着処理を行う。用紙Pは、定着装置18で定着された後、必要に応じて第4搬送路40で反転されて用紙の裏面にも2次転写ローラ34でフルカラーのトナー画像が2次転写され、定着装置18で定着されて、第3搬送路39を通って、排出ローラ19aにより用紙排出部37に排出される。   The fixing device 18 includes a fixing belt heated by a heater, a pressure roller disposed in pressure contact with the fixing belt, and the like, and heats and presses the paper P on which the toner image as a transfer material is transferred. The fixing process is performed by the above. After the sheet P is fixed by the fixing device 18, the sheet P is reversed by the fourth conveyance path 40 as necessary, and the full-color toner image is secondarily transferred to the back surface of the sheet by the secondary transfer roller 34. And is discharged to the paper discharge portion 37 by the discharge roller 19a through the third conveyance path 39.

図2は、上述の画像形成装置1に用いられる定着装置18の概略の構成を示す断面正面図である。定着装置18は、ベルト定着方式であり、加熱部材としての定着ベルト52と、定着ローラ53と、加圧部材としての加圧ローラ54と、熱ローラ55と、モータと減速ギアを有する駆動手段57と、サーモスタットユニット60、及びサーミスタ84とを備えている。そして、熱ローラ55の中空内には、定着装置18の熱源としてヒータランプ55aが設けられている。定着ローラ53、加圧ローラ54及び熱ローラ55は、定着装置18の筐体(図略)の長手方向に回転可能に軸支され、駆動手段57、ヒータランプ55a、サーモスタットユニット60、及びサーミスタ84は、筐体(図略)に固定保持されている。   FIG. 2 is a cross-sectional front view showing a schematic configuration of the fixing device 18 used in the image forming apparatus 1 described above. The fixing device 18 is a belt fixing method, and includes a fixing belt 52 as a heating member, a fixing roller 53, a pressure roller 54 as a pressure member, a heat roller 55, a driving means 57 having a motor and a reduction gear. And a thermostat unit 60 and a thermistor 84. In the hollow of the heat roller 55, a heater lamp 55 a is provided as a heat source for the fixing device 18. The fixing roller 53, the pressure roller 54, and the heat roller 55 are rotatably supported in the longitudinal direction of the casing (not shown) of the fixing device 18, and drive means 57, a heater lamp 55a, a thermostat unit 60, and a thermistor 84. Is fixedly held in a housing (not shown).

定着ベルト52は、定着ローラ53及び熱ローラ55に掛け回され、駆動手段57によって加圧ローラ54を介して、図2に示す矢印x方向に回転駆動される。この定着ベルト52は、厚さ40μmのニッケル薄板で形成される無端ベルトであって、外周表面にシリコンゴム膜等のオフセット防止剤がコーティングされたものである。   The fixing belt 52 is wound around the fixing roller 53 and the heat roller 55, and is driven to rotate in the direction of the arrow x shown in FIG. The fixing belt 52 is an endless belt formed of a nickel thin plate having a thickness of 40 μm, and has an outer peripheral surface coated with an offset preventive agent such as a silicone rubber film.

定着ローラ53と加圧ローラ54とは、対向して配置されるゴムローラであり、加圧ローラ54が定着ベルト52を介して定着ローラ53の中心方向に加圧されることにより、加圧ローラ54と定着ベルト52との間でニップ部Nが形成される。熱ローラ55は、定着ベルト52にテンションを与えるものであり、円筒形をしたアルミ管で形成される。定着ローラ53と加圧ローラ54が長手方向で定着ベルト52より長く形成されているために、加圧ローラ54は定着ベルト52とともに定着ローラ53にも圧接している。   The fixing roller 53 and the pressure roller 54 are rubber rollers arranged to face each other. When the pressure roller 54 is pressed toward the center of the fixing roller 53 via the fixing belt 52, the pressure roller 54. A nip portion N is formed between the fixing belt 52 and the fixing belt 52. The heat roller 55 applies tension to the fixing belt 52 and is formed of a cylindrical aluminum tube. Since the fixing roller 53 and the pressure roller 54 are formed longer than the fixing belt 52 in the longitudinal direction, the pressure roller 54 is in pressure contact with the fixing roller 53 together with the fixing belt 52.

駆動手段57は、モータと減速ギア列を備えて、加圧ローラ54にギア接続され、図2に示す矢印方向に回転駆動すると、加圧ローラ54が矢印方向に回転する。加圧ローラ54の回転により、加圧ローラ54に圧接する定着ローラ53と定着ベルト52が同速で図2示す矢印方向に回転し、さらに熱ローラ55が定着ベルト52に従動回転する。熱ローラ55の中空内に配設されたヒータランプ55aからの熱が、熱ローラ55を介して定着ベルト52に伝わり、定着ベルト52が加熱される。加圧ローラ54と定着ベルト52の互いの逆回転により、用紙Pのトナー像Tをニップ部Nで加熱溶融させながら、用紙Pが装置の上方に搬送される。   The drive unit 57 includes a motor and a reduction gear train, and is gear-connected to the pressure roller 54. When the drive unit 57 is rotationally driven in the arrow direction shown in FIG. 2, the pressure roller 54 rotates in the arrow direction. The rotation of the pressure roller 54 causes the fixing roller 53 and the fixing belt 52 that are in pressure contact with the pressure roller 54 to rotate at the same speed in the direction of the arrow shown in FIG. Heat from the heater lamp 55a disposed in the hollow of the heat roller 55 is transmitted to the fixing belt 52 through the heat roller 55, and the fixing belt 52 is heated. By the reverse rotation of the pressure roller 54 and the fixing belt 52, the paper P is conveyed upward of the apparatus while the toner image T of the paper P is heated and melted at the nip portion N.

上記構成の定着装置18においては、トナー像Tを形成された用紙Pは、定着ベルト52の用紙搬送方向の上流側に配された定着前ガイド21から、図2に示す矢印y方向に搬送され、用紙Pのトナー像がニップ部Nで加熱溶融されることによって、トナー像Tが定着される。その後、用紙Pは、用紙搬送方向下流側に配された定着後ガイド22及び搬送ローラ23a、23bにより、用紙排出部37(図1参照)に排出される。   In the fixing device 18 configured as described above, the paper P on which the toner image T is formed is conveyed in the direction of the arrow y shown in FIG. 2 from the pre-fixing guide 21 arranged on the upstream side of the fixing belt 52 in the paper conveying direction. The toner image on the paper P is heated and melted at the nip portion N, whereby the toner image T is fixed. Thereafter, the paper P is discharged to the paper discharge unit 37 (see FIG. 1) by the post-fixing guide 22 and the transport rollers 23a and 23b arranged on the downstream side in the paper transport direction.

次に、サーモスタットユニット60とサーミスタ84について説明する。サーモスタットユニット60は、熱ローラ55の周面に向けて配設され、熱ローラ55の温度を逐一検知し、熱ローラ55の温度が予め設定された温度範囲を超えた場合には、ヒータランプ55aへの通電を遮断して、ローラの過加熱を防止するものである。サーモスタットユニット60は、定着ベルト52の内側に形成される中空部に配され、サーモスタット62、サーモスタット支持部材63、コイルバネ64、及びそれらを内部に保持する保持部材61を備え、サーモスタット62が、コイルバネ64の付勢力により、保持部材61から熱ローラ55方向に移動自在に突出して、サーモスタット62の検知面は熱ローラ55周面に常に接触して温度検知することができるようになっている。   Next, the thermostat unit 60 and the thermistor 84 will be described. The thermostat unit 60 is arranged toward the peripheral surface of the heat roller 55, detects the temperature of the heat roller 55 one by one, and when the temperature of the heat roller 55 exceeds a preset temperature range, the heater lamp 55a. This prevents the roller from being overheated by interrupting energization of the roller. The thermostat unit 60 is disposed in a hollow portion formed inside the fixing belt 52, and includes a thermostat 62, a thermostat support member 63, a coil spring 64, and a holding member 61 that holds them inside, and the thermostat 62 includes the coil spring 64. Due to this urging force, the thermostat 62 protrudes from the holding member 61 in the direction of the heat roller 55 so that the detection surface of the thermostat 62 is always in contact with the circumferential surface of the heat roller 55 and can detect the temperature.

温度検知手段としてのサーミスタ84は、定着ベルト52の外側でかつ熱ローラ55により張架される部分に配され、接触している定着ベルト52の温度を検知している。この検知温度に基づいて、トナー像Tの定着に関わるニップ部Nの温度が制御され、また、後述するように、駆動手段57の回転数が制御され、ニップ部Nの定着時の温度変化に係らずに、常に一定の挟持搬送速度にて、用紙Pがニップ部Nを通過することができるようになっている。   The thermistor 84 as temperature detecting means is disposed outside the fixing belt 52 and in a portion stretched by the heat roller 55, and detects the temperature of the fixing belt 52 that is in contact therewith. Based on this detected temperature, the temperature of the nip portion N related to the fixing of the toner image T is controlled, and as will be described later, the rotational speed of the driving means 57 is controlled to change the temperature of the nip portion N at the time of fixing. Regardless, the sheet P can always pass through the nip portion N at a constant nipping and conveying speed.

次に、制御部による画像形成装置の要部の制御について図3に基づいて説明する。図3は、制御部を備える画像形成装置の構成を示すブロック図である。   Next, control of the main part of the image forming apparatus by the control unit will be described with reference to FIG. FIG. 3 is a block diagram illustrating a configuration of an image forming apparatus including a control unit.

画像形成装置1は、帯電部13、現像装置2、感光体11、中間転写ベルト等の転写部72を含む画像形成部71と、加圧ローラ54、ヒートランプ55a、サーモスタット62及びサーミスタ84を含む定着装置18と、加圧ローラ54等の装置各部を駆動する駆動手段57、及び給紙カセット32の他に、制御部74と、記憶部75と、操作パネル79と、主電源83と、現像モータ81、及び給紙モータ82を備えて構成されている。   The image forming apparatus 1 includes an image forming unit 71 including a charging unit 13, a developing device 2, a photoconductor 11, a transfer unit 72 such as an intermediate transfer belt, a pressure roller 54, a heat lamp 55a, a thermostat 62, and a thermistor 84. In addition to the fixing device 18, driving means 57 for driving each part of the device such as the pressure roller 54, and the paper feed cassette 32, a control unit 74, a storage unit 75, an operation panel 79, a main power supply 83, and development A motor 81 and a paper feed motor 82 are provided.

記憶部75は、RAM76、ROM77、及び画像メモリ78を備えており、RAM76及びROM77は制御部74の処理プログラムや処理内容等を記憶して、画像メモリ78はパーソナルコンピュータ等から画像入力部(図略)に入力された文字や絵柄などの画像データを記憶している。   The storage unit 75 includes a RAM 76, a ROM 77, and an image memory 78. The RAM 76 and the ROM 77 store processing programs and processing contents of the control unit 74, and the image memory 78 receives an image input unit (see FIG. Image data such as characters and designs input in (Omitted) is stored.

操作パネル79は、複数の操作キーからなる操作部と、設定条件や装置の状態等を表示する表示部(いずれも図略)とから構成されており、ユーザが装置の主電源83のオン・オフや、用紙のサイズ・種類、印刷枚数等の印刷条件等の設定を行う他、画像形成装置1がファクシミリ機能を有する場合には、記憶部75にファクシミリ送信先を登録し、さらに登録された送信先の読み出しや書き換えを行う等の種々の設定にも使用される。   The operation panel 79 includes an operation unit composed of a plurality of operation keys, and a display unit (all of which is not shown) that displays setting conditions, device statuses, and the like. The user can turn on / off the main power supply 83 of the device. When the image forming apparatus 1 has a facsimile function, the facsimile transmission destination is registered in the storage unit 75 in addition to setting the printing conditions such as OFF, the paper size / type, and the number of printed sheets. It is also used for various settings such as reading and rewriting the transmission destination.

駆動手段57は、制御部74からの制御信号に応じて、感光体11、転写部72の駆動ローラ25(図1参照)、定着装置18の加圧ローラ54を回転駆動させる。現像モータ81は、制御部74からの制御信号に応じて現像装置2内のトナー撹拌スクリューと現像ローラを駆動させる。給紙モータ82は、制御部74からの制御信号に応じて給紙カセット32内の給紙ローラを駆動させる。   The driving unit 57 drives the photosensitive member 11, the driving roller 25 (see FIG. 1) of the transfer unit 72, and the pressure roller 54 of the fixing device 18 in response to a control signal from the control unit 74. The developing motor 81 drives the toner stirring screw and the developing roller in the developing device 2 in accordance with a control signal from the control unit 74. The paper feed motor 82 drives the paper feed roller in the paper feed cassette 32 in accordance with a control signal from the control unit 74.

サーモスタット62は、熱ローラ55(図2参照)の温度を検知する。検知された温度に応じて、熱ローラ55が予め設定された上限温度を超えるとサーモスタット62の接点が開止されてヒートランプ55aへの電力の供給が停止される。サーミスタ84は、定着ベルト52の表面温度を検知して、検知された温度信号が制御部74に送出される。制御部74がその温度信号に基づいて、定着ベルト52が定着を良好に行える定着可能温度を維持するように、ヒートランプ55aのオン・オフを制御し、また、定着時の温度にかかわらず、加圧ローラ54の周速度が一定になるように、駆動手段57のモータの回転数を制御する。   The thermostat 62 detects the temperature of the heat roller 55 (see FIG. 2). When the heat roller 55 exceeds a preset upper limit temperature in accordance with the detected temperature, the contact of the thermostat 62 is opened and the supply of power to the heat lamp 55a is stopped. The thermistor 84 detects the surface temperature of the fixing belt 52 and sends the detected temperature signal to the controller 74. Based on the temperature signal, the control unit 74 controls on / off of the heat lamp 55a so as to maintain a fixing temperature at which the fixing belt 52 can perform the fixing satisfactorily. The number of rotations of the motor of the drive unit 57 is controlled so that the peripheral speed of the pressure roller 54 is constant.

制御部74は、マイクロコンピュータ等で構成され、RAM76及びROM77に設定されたプログラムに従って、画像形成部71、給紙カセット32、定着装置18、モータ81、82、及び駆動手段57を全般的に制御する。また、制御部74は、サーミスタ84の検知温度と、ROM77に記憶された回転数補正テーブルとに基づいて、駆動手段57のモータの回転数を制御する。   The control unit 74 is constituted by a microcomputer or the like, and generally controls the image forming unit 71, the paper feed cassette 32, the fixing device 18, the motors 81 and 82, and the driving unit 57 in accordance with programs set in the RAM 76 and the ROM 77. To do. Further, the control unit 74 controls the rotational speed of the motor of the driving unit 57 based on the temperature detected by the thermistor 84 and the rotational speed correction table stored in the ROM 77.

回転数補正テーブルは、定着ベルト52の温度と駆動手段57の回転数とに関するものであり、図2、図3とともに、図4及び図5に基づいて説明する。図4は、先回の定着から所定時間放置後に、駆動手段57を駆動させて加圧ローラ54と定着ベルト52を回転させたときの、加圧ローラ54と定着ベルト52の温度変化を示す図であり、縦軸は温度(単位は℃)、横軸は時間(単位は秒)を示す。図4は、1時間放置した後、駆動手段57のモータを駆動させた状態を示し、図5は、1分間放置した後、駆動手段57のモータを駆動させた状態を示す。   The rotation speed correction table relates to the temperature of the fixing belt 52 and the rotation speed of the driving unit 57, and will be described based on FIGS. 4 and 5 together with FIGS. FIG. 4 is a diagram showing temperature changes of the pressure roller 54 and the fixing belt 52 when the driving unit 57 is driven to rotate the pressure roller 54 and the fixing belt 52 after being left for a predetermined time after the previous fixing. The vertical axis indicates temperature (unit: ° C.), and the horizontal axis indicates time (unit: seconds). 4 shows a state in which the motor of the driving unit 57 is driven after being left for one hour, and FIG. 5 shows a state in which the motor of the driving unit 57 is driven after being left for one minute.

尚、回転数補正テーブルを作成する装置モデルには、本実施形態の加圧ローラ54の外周にサーミスタ84を配設して、加圧ローラ54の外周温度を測定しているが、本実施形態では、加圧ローラ用のサーミスタが配設されておらず、この装置モデルで作成された回転数補正テーブルが搭載されている。   In the apparatus model for creating the rotation speed correction table, the thermistor 84 is disposed on the outer periphery of the pressure roller 54 of the present embodiment, and the outer peripheral temperature of the pressure roller 54 is measured. However, a thermistor for the pressure roller is not provided, and a rotation speed correction table created by this apparatus model is mounted.

図4に示すように、定着ベルト52が定着可能温度(180〜190℃)を維持し、定着ベルト52から熱が伝わり、加圧ローラ54が略一定の温度(60℃)を維持した状態で、駆動手段57が駆動開始される。駆動手段57の回転駆動によって、加圧ローラ54が回転し、定着ベルト52が回転すると、定着ベルト52の熱が加圧ローラ54に伝わって、その伝熱分だけ伝達定着ベルト52の温度が下がる。同様に、定着ベルト52を定着可能温度(180〜190℃)に維持して、加圧ローラ54の他の温度においても、定着ベルト52の加圧ローラ54への伝熱による下降温度を調べる。このとき、定着ベルト52と加圧ローラ54の温度差が大きいと、定着ベルト52の温度が急速に下降し、この温度差が小さいと、定着ベルト52の温度がゆっくりと下降する。定着ベルト52の時間当たりのこの下降温度から加圧ローラ54の温度を推定して、この下降温度に対応させて、駆動手段57のモータの回転数を決定する。   As shown in FIG. 4, the fixing belt 52 maintains a fixing possible temperature (180 to 190 ° C.), heat is transferred from the fixing belt 52, and the pressure roller 54 maintains a substantially constant temperature (60 ° C.). Then, driving of the driving means 57 is started. When the pressure roller 54 is rotated by the rotation of the driving unit 57 and the fixing belt 52 is rotated, the heat of the fixing belt 52 is transmitted to the pressure roller 54 and the temperature of the transmission fixing belt 52 is lowered by the amount of the heat transfer. . Similarly, the fixing belt 52 is maintained at a fixing temperature (180 to 190 ° C.), and the temperature at which the fixing belt 52 is lowered due to heat transfer to the pressure roller 54 is also examined at other temperatures of the pressure roller 54. At this time, if the temperature difference between the fixing belt 52 and the pressure roller 54 is large, the temperature of the fixing belt 52 rapidly decreases. If the temperature difference is small, the temperature of the fixing belt 52 slowly decreases. The temperature of the pressure roller 54 is estimated from the descending temperature per time of the fixing belt 52, and the number of rotations of the motor of the driving unit 57 is determined in accordance with the descending temperature.

具体的には、図4において、駆動手段57の駆動開始から1秒後と2秒後において、定着ベルト52のサーミスタ84による各検知温度は、169℃と154℃であり、加圧ローラ54の検知温度は60℃である。1秒後と2秒後の温度差は15°あり、加圧ローラ54が60℃である場合には、定着ベルト52から15°相当の熱が伝わることがわかる。次に、図5に示すように、駆動手段57の先回の駆動から1分間後では、加圧ローラ54の検知温度が120℃になっていて、駆動手段57の駆動開始から1秒後と2秒後の定着ベルト52のサーミスタ84による各検知温度は、176℃と167℃である。1秒後と2秒後の温度差は9°あり、加圧ローラ54が120℃である場合には、定着ベルト52から9°相当の熱が伝わることがわかる。尚、ここで駆動開始から1秒後と2秒後に温度を検知しているのは、定着ベルト52が駆動開始から1回移転して、定着ベルト52全周にヒータランプ55aからの熱が均一に加熱された状態で、加圧ローラ54の回転に伴う定着ベルト52の下降温度を検知するためである。   Specifically, in FIG. 4, the detected temperatures by the thermistor 84 of the fixing belt 52 are 169 ° C. and 154 ° C. after 1 second and 2 seconds from the start of driving of the driving unit 57, respectively. The detected temperature is 60 ° C. The difference in temperature between 1 second and 2 seconds is 15 °, and it can be seen that when the pressure roller 54 is 60 ° C., heat corresponding to 15 ° is transmitted from the fixing belt 52. Next, as shown in FIG. 5, the detected temperature of the pressure roller 54 is 120 ° C. after 1 minute from the previous drive of the drive unit 57, and 1 second after the drive start of the drive unit 57. The detected temperatures by the thermistor 84 of the fixing belt 52 after 2 seconds are 176 ° C. and 167 ° C., respectively. The difference in temperature between 1 second and 2 seconds is 9 °, and when the pressure roller 54 is 120 ° C., it can be seen that heat corresponding to 9 ° is transmitted from the fixing belt 52. Here, the temperature is detected 1 second and 2 seconds after the start of driving because the fixing belt 52 is moved once from the start of driving and the heat from the heater lamp 55a is uniformly distributed on the entire circumference of the fixing belt 52. This is for detecting the descending temperature of the fixing belt 52 accompanying the rotation of the pressure roller 54 in a state where the pressure roller 54 is heated.

同様に、60℃〜120℃における加圧ローラ54の検知温度においても、定着ベルト52の下降温度を調べると、加圧ローラ54の検知温度が80℃では温度差が13°あり、加圧ローラ54の検知温度が100℃では、温度差が10°あり、以上の加圧ローラ54の温度と定着ベルト52の温度差は、表1のような結果になる。

Figure 2009163038
Similarly, when the temperature detected by the pressure roller 54 at 60 ° C. to 120 ° C. is checked, the temperature difference between the pressure roller 54 and the detected temperature of the pressure roller 54 is 13 ° when the temperature detected by the pressure roller 54 is 80 ° C. When the detected temperature of 54 is 100 ° C., the temperature difference is 10 °, and the temperature difference between the pressure roller 54 and the fixing belt 52 is as shown in Table 1.
Figure 2009163038

本実施形態では、加圧ローラ54は外径35mmのゴムローラであり、加圧ローラ54の周面の変動温度範囲は上記の60〜120℃であり、この範囲の温度変化では、熱膨張により、加圧ローラ54の外径が略0.4mm変化することになる。そこで、この外径が変化しても加圧ローラ54の周速度を略一定にするために、表1に示す定着ベルト52の温度差と加圧ローラ54の温度に基づいて、駆動手段57の回転数を補正する。この回転数補正テーブルが表2である。

Figure 2009163038
In the present embodiment, the pressure roller 54 is a rubber roller having an outer diameter of 35 mm, and the fluctuation temperature range of the peripheral surface of the pressure roller 54 is 60 to 120 ° C. The temperature change in this range causes thermal expansion, The outer diameter of the pressure roller 54 changes by about 0.4 mm. Therefore, in order to make the peripheral speed of the pressure roller 54 substantially constant even when the outer diameter changes, the temperature of the fixing belt 52 shown in Table 1 and the temperature of the pressure roller 54 are changed based on the temperature of the driving means 57. Correct the rotation speed. This rotation speed correction table is shown in Table 2.
Figure 2009163038

この表2では、定着ベルト52の温度差が10<ΔX≦13にあるエリアCでは、加圧
ローラ54の温度が80〜100℃(基準温度とする)の範囲にある。通常、連続通紙時には、この基準温度を維持して、この基準温度において駆動手段57の回転数が設定されているので、エリアCにおける駆動手段57の回転数を基準回転数として、各エリアの温度差に応じて、駆動手段57の回転数を補正することになる。
In Table 2, in the area C where the temperature difference of the fixing belt 52 is 10 <ΔX ≦ 13, the temperature of the pressure roller 54 is in the range of 80 to 100 ° C. (reference temperature). Normally, during continuous paper feeding, the reference temperature is maintained, and the rotation speed of the drive means 57 is set at the reference temperature. Therefore, the rotation speed of the drive means 57 in the area C is set as the reference rotation speed, The rotational speed of the drive means 57 is corrected according to the temperature difference.

つまり、エリアA、Bでは、定着ベルト52の温度差がエリアCに比べると小さい、つまり加圧ローラ54の温度がエリアCの加圧ローラ54の基準温度より高くなっているので、加圧ローラ径がエリアCのものより大きくなっている。従って駆動手段57の回転数を、エリアAでは、基準回転数に対して0.8%小さくし、エリアBでは、基準回転数に対して0.4%小さくする。ここで、エリアAは、エリアBより加圧ローラ54の温度が高くなっているので、エリアBよりさらに駆動手段57の回転数を小さくしている。一方、エリアD、Eでは、定着ベルト52の温度差がエリアCに比べると大きい、つまり加圧ローラ54の基準温度より高くなっているので、加圧ローラ径がエリアCのものより小さくなっている。従って駆動手段57の回転数を、エリアDでは、基準回転数に対して0.4%大きくし、エリアEでは、基準回転数に対して0.8%大きくする。ここでエリアEは、エリアDより加圧ローラ54の温度が低くなっているので、エリアDよりさらに駆動手段57の回転数を大きくしている。   That is, in the areas A and B, the temperature difference of the fixing belt 52 is smaller than that of the area C, that is, the temperature of the pressure roller 54 is higher than the reference temperature of the pressure roller 54 in the area C. The diameter is larger than that of area C. Therefore, the rotation speed of the driving means 57 is reduced by 0.8% with respect to the reference rotation speed in the area A, and is reduced by 0.4% with respect to the reference rotation speed in the area B. Here, since the temperature of the pressure roller 54 is higher in the area A than in the area B, the number of rotations of the driving unit 57 is made smaller than that in the area B. On the other hand, in the areas D and E, the temperature difference of the fixing belt 52 is larger than that of the area C, that is, higher than the reference temperature of the pressure roller 54, so that the pressure roller diameter is smaller than that of the area C. Yes. Accordingly, the rotation speed of the driving means 57 is increased by 0.4% with respect to the reference rotation speed in the area D, and is increased by 0.8% with respect to the reference rotation speed in the area E. Here, since the temperature of the pressure roller 54 is lower in the area E than in the area D, the rotational speed of the driving unit 57 is made larger than that in the area D.

このように、表2に示す回転数補正テーブルは、基準回転数に回転数補正係数を掛け算して、駆動手段57の回転数を補正して、定着時の温度にかかわらず、加圧ローラ54の周速度を一定にするものであり、ROM77に記憶されている。   In this manner, the rotation speed correction table shown in Table 2 multiplies the reference rotation speed by the rotation speed correction coefficient to correct the rotation speed of the driving unit 57, so that the pressure roller 54 can be used regardless of the fixing temperature. Is stored in the ROM 77.

次に、定着装置の駆動手段57の駆動制御について、図2とともに図3に基づいて説明する。   Next, driving control of the driving unit 57 of the fixing device will be described based on FIG. 3 together with FIG.

制御部74は熱ローラ55(図2参照)のヒートランプ66aを制御する。ヒートランプ55aが通電オンされて、定着ベルト52(図2参照)が定着可能温度に上昇するまで、通電オン状態を維持する(ウォームアップする)ように制御が行われる。サーミスタ84の温度検知により、定着ベルト52の表面温度が定着可能温度に到達すると、ヒートランプ55aへの通電はそのまま継続され、その定着可能温度を安定して維持するように、サーミスタ84の検知温度に基づいて、ヒートランプ55aのオン・オフ制御が行われる。   The controller 74 controls the heat lamp 66a of the heat roller 55 (see FIG. 2). Control is performed so that the energization-on state is maintained (warm-up) until the heat lamp 55a is energized and the fixing belt 52 (see FIG. 2) rises to a fixable temperature. When the surface temperature of the fixing belt 52 reaches the fixable temperature by detecting the temperature of the thermistor 84, the energization of the heat lamp 55a is continued as it is, and the detected temperature of the thermistor 84 is maintained so as to stably maintain the fixable temperature. On / off control of the heat lamp 55a is performed based on the above.

画像形成動作の開始信号が制御部74に入力されると、制御部74は駆動手段57を制御する。開始信号の入力が定着ベルトのウォームアップ中であるなら、定着可能温度になるまで待機し、定着可能温度になると、駆動手段57を基準回転数で回転駆動させ、この駆動手段57によって加圧ローラ54が回転させられる。   When the start signal of the image forming operation is input to the control unit 74, the control unit 74 controls the driving unit 57. If the input of the start signal is during the warming up of the fixing belt, the process waits until the fixing temperature is reached. When the fixing temperature is reached, the driving means 57 is driven to rotate at the reference rotational speed, and the driving means 57 rotates the pressure roller. 54 is rotated.

加圧ローラ54の回転により、図2に示すように、定着ベルト52が回転すると、制御部74は、駆動手段57の駆動開始から1秒後と2秒後に入力されるサーミスタ84の検知温度に基づいて、1秒後と2秒後との温度差を算出する。ROM77の回転数補正テーブル(表2)を参照して、この温度差に対応する回転数補正係数を割り出し、駆動手段57の回転数を補正する。この回転数の補正によって、加圧ローラ54の周速度も補正されると、図2に示す矢印y方向に搬送された用紙Pがニップ部Nに突入し、ニップ部Nにおいて加熱加圧されることによって、トナー像Tが定着されながら、所定の挟持搬送速度で定着後ガイド22に搬送される。   When the fixing belt 52 rotates as shown in FIG. 2 by the rotation of the pressure roller 54, the control unit 74 sets the detected temperature of the thermistor 84 that is input 1 second and 2 seconds after the drive of the drive unit 57 starts. Based on this, the temperature difference between 1 second and 2 seconds is calculated. With reference to the rotational speed correction table (Table 2) in the ROM 77, the rotational speed correction coefficient corresponding to this temperature difference is determined, and the rotational speed of the driving means 57 is corrected. When the peripheral speed of the pressure roller 54 is also corrected by correcting the rotation speed, the paper P conveyed in the direction of the arrow y shown in FIG. 2 enters the nip portion N and is heated and pressurized in the nip portion N. As a result, the toner image T is conveyed to the post-fixing guide 22 at a predetermined nipping and conveying speed while being fixed.

トナー像を形成した用紙Pを連続通紙するときには、制御部74は、ニップ部Nを通過する用紙枚数を計数して、その計数値が所定枚数(例えば25枚)を超えると、駆動手段57の回転数を回転数補正テーブル(表2)の基準回転数に近づけるように補正(回転数がエリアAにあると、エリアBに補正、またはエリアEにあるとエリアDに補正)する。さらに、用紙枚数の計数値が大きくなると(例えば50枚)、駆動手段57を基準回転数に補正(エリアBまたはエリアDをエリアCに補正)して回転駆動させる。   When the paper P on which the toner image is formed is continuously passed, the control unit 74 counts the number of sheets passing through the nip portion N, and when the counted value exceeds a predetermined number (for example, 25), the driving unit 57. Is corrected so as to approach the reference rotation speed of the rotation speed correction table (Table 2) (if the rotation speed is in area A, it is corrected in area B, or if it is in area E, it is corrected in area D). Further, when the count value of the number of sheets becomes large (for example, 50 sheets), the driving means 57 is corrected to the reference rotation number (area B or area D is corrected to area C) and driven to rotate.

また、駆動手段57を連続駆動するときには、駆動手段57の駆動開始から時間を係数して、所定時間(例えば、1分)経過すると、駆動手段57の回転数を基準回転数に近づけるように補正(エリアAからエリアBに補正、またはエリアEからエリアDに補正)して、さらに時間(例えば、2分)が経過すると、駆動手段57を基準回転数に補正(エリアBまたはエリアDからエリアCに補正)して回転駆動させる。   Further, when the driving unit 57 is continuously driven, the time is calculated from the start of driving of the driving unit 57, and when a predetermined time (for example, 1 minute) elapses, the rotational speed of the driving unit 57 is corrected to approach the reference rotational speed. (Correct from area A to area B or from area E to area D), and when the time (for example, 2 minutes) elapses, the drive means 57 is corrected to the reference rotational speed (from area B or area D to area C) and rotationally drive.

上記第1実施形態によれば、画像形成装置1は、ヒータランプ55aを内蔵する熱ローラ55と定着ローラ53との間に張架される無端状の定着ベルト52と、この定着ベルト52に圧接して配置された加圧ローラ54と、定着ベルト52の温度を検知するサーミスタ84と、加圧ローラ54を回転駆動するモータを有する駆動手段57と、この駆動手段57の回転を制御する制御部74とを備え、定着ベルト52と加圧ローラ54との圧接によって形成されるニップ部Nに、未定着トナー像を担持した用紙Pを通紙して加熱定着を行う。制御部74は、サーミスタ84の検知温度に基づいて、駆動手段57の回転数を制御して、加圧ローラ54の温度に係わらずに加圧ローラ54を所定の周速度にする。   According to the first embodiment, the image forming apparatus 1 includes the endless fixing belt 52 stretched between the heat roller 55 including the heater lamp 55 a and the fixing roller 53, and the pressure contact with the fixing belt 52. The pressure roller 54 arranged in this manner, the thermistor 84 for detecting the temperature of the fixing belt 52, drive means 57 having a motor for rotating the pressure roller 54, and a control unit for controlling the rotation of the drive means 57. 74, a sheet P carrying an unfixed toner image is passed through a nip portion N formed by pressure contact between the fixing belt 52 and the pressure roller 54, and heat fixing is performed. Based on the temperature detected by the thermistor 84, the control unit 74 controls the rotational speed of the driving unit 57 so that the pressure roller 54 has a predetermined peripheral speed regardless of the temperature of the pressure roller 54.

この構成によると、加熱された定着ベルト52が加圧ローラ54に圧接すると、定着ベルト52の熱が加圧ローラ54に伝わり、定着ベルト52の温度が下降する。この下降した温度をサーミスタ84によって検知する。制御部74は、定着ベルト52の下降温度に基づいて、加圧ローラ54の温度を推定して、加圧ローラ54を所定の周速度で回転させるように、駆動手段の回転数を制御する。このことによって、加圧ローラに専用のサーミスタを設けることなく、加圧ローラ54の温度に係わらずに、ニップ部Nの用紙Pの挟持搬送速度が一定になり、用紙の転写画像ズレや用紙シワの発生を抑制した用紙搬送をニップ部で行うことができる。   According to this configuration, when the heated fixing belt 52 is pressed against the pressure roller 54, the heat of the fixing belt 52 is transmitted to the pressure roller 54, and the temperature of the fixing belt 52 decreases. This lowered temperature is detected by the thermistor 84. The control unit 74 estimates the temperature of the pressure roller 54 based on the descending temperature of the fixing belt 52 and controls the rotation speed of the driving unit so as to rotate the pressure roller 54 at a predetermined peripheral speed. As a result, without providing a dedicated thermistor to the pressure roller, the nipping and conveying speed of the paper P in the nip portion N becomes constant regardless of the temperature of the pressure roller 54, and the transfer image deviation and paper wrinkle of the paper are constant. Thus, the sheet conveyance with the occurrence of the occurrence of the ink can be performed at the nip portion.

また、上記第1実施形態によると、制御部74は、駆動手段57の回転開始時から第1及び第2の所定時間(1秒と2秒)後に検知するサーミスタ84の検知温度との温度差に基づいて、駆動手段57の回転数を制御する。定着ベルト52から加圧ローラ54に熱が伝わると定着ベルト52の温度が下降するが、ヒータランプ55aにより定着ベルト52全周が均一に加熱された状態で、サーミスタ84が定着ベルト52の下降温度を検知し、その下降温度に基づいて、加圧ローラ54の温度を推定し、加圧ローラ54を所定の周速度で回転させるために、ニップ部Nの挟持搬送速度が正確に補正される。   Further, according to the first embodiment, the control unit 74 detects the temperature difference from the detected temperature of the thermistor 84 detected after the first and second predetermined times (1 second and 2 seconds) from the start of rotation of the driving unit 57. Based on the above, the rotational speed of the drive means 57 is controlled. When heat is transmitted from the fixing belt 52 to the pressure roller 54, the temperature of the fixing belt 52 decreases. However, the thermistor 84 decreases the temperature of the fixing belt 52 while the entire circumference of the fixing belt 52 is uniformly heated by the heater lamp 55a. In order to estimate the temperature of the pressure roller 54 based on the descending temperature and rotate the pressure roller 54 at a predetermined peripheral speed, the nipping and conveying speed of the nip portion N is accurately corrected.

また、上記第1実施形態によると、制御部74は、第1及び第2の所定時間後(1秒後と2秒後)の温度差が所定温度(回転数補正テーブルのエリアC)より低い場合には、駆動手段57の回転数を、所定温度における所定の回転数(基準回転数)より小さくすることによって、温度が高くなって外径が大きくなった加圧ローラ54の周速度を小さくしているので、加圧ローラ54の温度に係わらずに、ニップ部Nの用紙Pの挟持搬送速度を一定にすることができる。また、ニップ部Nの挟持搬送速度が正確に補正される。また、第1及び第2の所定時間後(1秒後と2秒後)の温度差が所定温度より高い場合には、駆動手段57の回転数を、所定回転数(基準回転数)より大きくことによって、温度が低くなって外径が小さくなった加圧ローラ54の周速度を大きくしているので、加圧ローラ54の温度に係わらずに、ニップ部Nの用紙Pの挟持搬送速度を一定にすることができる。   Further, according to the first embodiment, the controller 74 determines that the temperature difference after the first and second predetermined times (after 1 second and after 2 seconds) is lower than the predetermined temperature (area C of the rotation speed correction table). In this case, the peripheral speed of the pressure roller 54 whose temperature is increased and the outer diameter is increased is reduced by making the rotational speed of the driving means 57 smaller than a predetermined rotational speed (reference rotational speed) at a predetermined temperature. Therefore, regardless of the temperature of the pressure roller 54, the nipping and conveying speed of the paper P in the nip portion N can be made constant. Further, the nipping and conveying speed of the nip portion N is accurately corrected. In addition, when the temperature difference between the first and second predetermined times (after 1 second and 2 seconds) is higher than the predetermined temperature, the rotational speed of the driving unit 57 is set larger than the predetermined rotational speed (reference rotational speed). As a result, the peripheral speed of the pressure roller 54 whose temperature is lowered and the outer diameter is reduced is increased, so that the nipping and conveying speed of the paper P in the nip portion N is increased regardless of the temperature of the pressure roller 54. Can be constant.

また、上記第1実施形態によると、用紙Pがニップ部Nを連続して通紙されるときには、制御部74は、通紙枚数が増えると、駆動手段57の回転数を所定回転数(基準回転数)に近づけることによって、通紙枚数が増えると、加圧ローラ54は基準温度対応する温度に近づくために、駆動手段57の回転数を所定回転数(基準回転数)に近づけて、通紙枚数に係わらずにニップ部Nの用紙Pの挟持搬送速度を一定にすることができる。   Further, according to the first embodiment, when the paper P is continuously passed through the nip portion N, the controller 74 sets the rotational speed of the driving unit 57 to a predetermined rotational speed (reference speed) when the number of paper passes increases. When the number of sheets to be passed increases by approaching the number of revolutions), the pressure roller 54 approaches the temperature corresponding to the reference temperature, so that the number of revolutions of the driving unit 57 is brought close to the predetermined number of revolutions (reference number of revolutions). Regardless of the number of sheets, the nipping and conveying speed of the sheet P in the nip portion N can be made constant.

また、上記第1実施形態によると、駆動手段57が加圧ローラ54を連続して回転駆動させるときには、制御部74は、回転駆動時間が長くなると、駆動手段57の回転数を所定回転数(基準回転数)に近づけることによって、加圧ローラ54の回転駆動時間が増えると、加圧ローラ54は基準温度に対応する温度に近づくために、駆動手段57の回転数を所定回転数(基準回転数)に近づけて、回転駆動時間に係わらずにニップ部Nの用紙Pの挟持搬送速度を一定にすることができる。   Further, according to the first embodiment, when the driving unit 57 continuously drives the pressure roller 54 to rotate, the control unit 74 sets the rotational speed of the driving unit 57 to a predetermined rotational speed (when the rotational driving time becomes longer). When the rotation driving time of the pressure roller 54 increases by approaching the reference rotation speed), the pressure roller 54 approaches the temperature corresponding to the reference temperature, so that the rotation speed of the driving unit 57 is set to a predetermined rotation speed (reference rotation). The holding and conveying speed of the paper P in the nip portion N can be made constant regardless of the rotational drive time.

(第2実施形態)
本発明は上記の第1実施形態に限らず、第1実施形態と同じ構成の定着ベルト方式において、駆動開始時から所定時間における定着ベルト52の下降温度に基づいて、回転数補正テーブルを作成して、回転数補正テーブルをROM77に記憶させてもよい。図2、図4及び図5に基づいて説明する。
(Second Embodiment)
The present invention is not limited to the first embodiment described above, and in the fixing belt system having the same configuration as that of the first embodiment, a rotation speed correction table is created based on the descending temperature of the fixing belt 52 for a predetermined time from the start of driving. Thus, the rotation speed correction table may be stored in the ROM 77. This will be described with reference to FIGS. 2, 4 and 5.

図4において、駆動手段57の駆動開始時と駆動開始から1秒後において、定着ベルト52のサーミスタ84による各検知温度は、191℃と169℃であり、加圧ローラ54の検知温度は60℃である。駆動開始時とその1秒後の温度差は22°あり、加圧ローラ54が60℃である場合には、定着ベルト52から22°相当の熱が伝わることがわかる。次に、図5において、加圧ローラ54の検知温度が120℃になっていて、駆動手段57の駆動開始時とその1秒後との定着ベルト52のサーミスタ84による各検知温度は、189℃と176℃である。駆動開始時とその1秒後の温度差は13°あり、加圧ローラ54が120℃である場合には、定着ベルト52から13°相当の熱が伝わることがわかる。   In FIG. 4, the detected temperatures of the fixing belt 52 by the thermistor 84 are 191 ° C. and 169 ° C. at the start of driving of the driving means 57 and one second after the start of driving, and the detected temperatures of the pressure roller 54 are 60 ° C. It is. The temperature difference between the start of driving and one second after that is 22 °, and it can be seen that when the pressure roller 54 is 60 ° C., heat corresponding to 22 ° is transmitted from the fixing belt 52. Next, in FIG. 5, the detected temperature of the pressure roller 54 is 120 ° C., and the detected temperatures by the thermistor 84 of the fixing belt 52 at the start of driving of the driving means 57 and after 1 second are 189 ° C. And 176 ° C. The temperature difference between the start of driving and one second after that is 13 °, and it can be seen that when the pressure roller 54 is 120 ° C., heat corresponding to 13 ° is transmitted from the fixing belt 52.

同様に、60℃〜120℃における加圧ローラ54の検知温度においても、定着ベルト52の下降温度を調べると、加圧ローラ54の検知温度が80℃では温度差が21°あり、加圧ローラ54の検知温度が100℃では、温度差が17°あり、以上の加圧ローラ54の温度と定着ベルト52の温度差は、表3のような結果になる。

Figure 2009163038
Similarly, when the detected temperature of the pressure belt 54 at 60 to 120 ° C. is examined, the temperature difference of the pressure roller 54 is 21 ° when the detected temperature of the pressure roller 54 is 80 ° C. When the detected temperature of 54 is 100 ° C., the temperature difference is 17 °, and the temperature difference between the pressure roller 54 and the fixing belt 52 is as shown in Table 3.
Figure 2009163038

本実施形態では、加圧ローラ54のサイズ、材料を勘案して、上記の変動温度範囲60〜120℃において、熱膨張により、加圧ローラ54の外径が変化しても加圧ローラ54の周速度を略一定にするために、表3に示す定着ベルト52の温度差と加圧ローラ54の温度に基づいて、駆動手段57の回転数を補正すると、表4に示す回転数補正テーブルになる。

Figure 2009163038
In the present embodiment, in consideration of the size and material of the pressure roller 54, even if the outer diameter of the pressure roller 54 changes due to thermal expansion in the above-described variable temperature range of 60 to 120 ° C., If the rotational speed of the driving unit 57 is corrected based on the temperature difference of the fixing belt 52 and the temperature of the pressure roller 54 shown in Table 3 to make the peripheral speed substantially constant, the rotational speed correction table shown in Table 4 is obtained. Become.
Figure 2009163038

この表4では、定着ベルト52の温度差が17<ΔX≦21にあるエリアCでは、加圧
ローラ54の温度が80〜100℃(基準温度とする)の範囲にある。通常、連続通紙時には、この基準温度を維持して、この基準温度において駆動手段57の回転数が設定されているので、エリアCにおける駆動手段57の回転数を基準回転数として、各エリアの温度差に応じて、駆動手段57の回転数を補正することになる。
In Table 4, in area C where the temperature difference of the fixing belt 52 is 17 <ΔX ≦ 21, the temperature of the pressure roller 54 is in the range of 80 to 100 ° C. (reference temperature). Normally, during continuous paper feeding, the reference temperature is maintained, and the rotation speed of the drive means 57 is set at the reference temperature. Therefore, the rotation speed of the drive means 57 in the area C is set as the reference rotation speed, The rotational speed of the drive means 57 is corrected according to the temperature difference.

(第3実施形態)
第3実施形態は、第2実施形態と同様に、駆動開始時から所定時間までの定着ベルト52の下降温度に基づいて、回転数補正テーブルを作成して、回転数補正テーブルをROM77に記憶させているが、所定時間が第2実施形態と異なる。図2、図4及び図5を基づいて説明する。
(Third embodiment)
As in the second embodiment, the third embodiment creates a rotation speed correction table based on the temperature drop of the fixing belt 52 from the start of driving to a predetermined time, and stores the rotation speed correction table in the ROM 77. However, the predetermined time is different from that of the second embodiment. This will be described with reference to FIGS. 2, 4 and 5.

図4において、駆動手段57の駆動開始時と駆動開始から2秒後における定着ベルト52のサーミスタ84による温度差と、加圧ローラ54の検知温度60℃に基づいて、また図5において、加圧ローラ54の検知温度120℃における定着ベルト52のサーミスタ84による温度差と、さらに、加圧ローラ54の検知温度80℃及び100℃に基づいて、表5のような結果を得る。

Figure 2009163038
In FIG. 4, based on the temperature difference by the thermistor 84 of the fixing belt 52 at the start of driving of the driving means 57 and 2 seconds after the start of driving, and the detected temperature 60 ° C. of the pressure roller 54, and in FIG. Based on the temperature difference by the thermistor 84 of the fixing belt 52 at the detection temperature 120 ° C. of the roller 54 and the detection temperatures 80 ° C. and 100 ° C. of the pressure roller 54, the results shown in Table 5 are obtained.
Figure 2009163038

上表の変動温度範囲において、加圧ローラ54のサイズ、材料を勘案して、熱膨張により、加圧ローラ54の外径が変化しても加圧ローラ54の周速度を略一定にするために、表5に示す定着ベルト52の温度差と加圧ローラ54の温度に基づいて、駆動手段57の回転数を補正すると、表6に示す回転数補正テーブルになる。

Figure 2009163038
In order to make the peripheral speed of the pressure roller 54 substantially constant even if the outer diameter of the pressure roller 54 changes due to thermal expansion in consideration of the size and material of the pressure roller 54 within the fluctuating temperature range in the above table. Further, when the rotational speed of the driving unit 57 is corrected based on the temperature difference of the fixing belt 52 and the temperature of the pressure roller 54 shown in Table 5, the rotational speed correction table shown in Table 6 is obtained.
Figure 2009163038

上記第2及び3実施形態によれば、制御部74は、駆動手段57の回転開始時に検知するサーミスタ84の検知温度と、回転開始時から所定時間(1秒または2秒)後に検知するサーミスタ84の検知温度との温度差に基づいて、駆動手段57の回転数を制御する。定着ベルト52から加圧ローラ54に熱が伝わると定着ベルト52の温度が下降するが、サーミスタ84が回転開始時から所定時間までの定着ベルト52の下降温度を検知し、その下降温度に基づいて、加圧ローラ54の温度を推定し、加圧ローラ54を所定の周速度で回転させるために、ニップ部Nの挟持搬送速度が正確に補正される。   According to the second and third embodiments, the control unit 74 detects the temperature of the thermistor 84 that is detected when the rotation of the driving unit 57 is started, and the thermistor 84 that is detected after a predetermined time (1 second or 2 seconds) from the start of rotation. The rotational speed of the drive means 57 is controlled based on the temperature difference from the detected temperature. When heat is transmitted from the fixing belt 52 to the pressure roller 54, the temperature of the fixing belt 52 decreases. The thermistor 84 detects the temperature at which the fixing belt 52 is lowered from the start of rotation to a predetermined time, and based on the decreasing temperature. In order to estimate the temperature of the pressure roller 54 and rotate the pressure roller 54 at a predetermined peripheral speed, the nipping and conveying speed of the nip portion N is accurately corrected.

本発明は、電子写真方式を利用した複写機、プリンタ、ファクシミリ、それらの複合機等の画像形成装置に利用することができ、特に、加圧部材等によって用紙を搬送する定着装置を備えた画像形成装置に利用することができる。   The present invention can be used in an image forming apparatus such as a copying machine, a printer, a facsimile, or a composite machine using an electrophotographic method, and in particular, an image including a fixing device that conveys paper by a pressure member or the like. It can be used for a forming apparatus.

は、本発明の第1実施形態に係る画像形成装置の概略の構成を示す断面正面図である。1 is a cross-sectional front view illustrating a schematic configuration of an image forming apparatus according to a first embodiment of the present invention. は、本発明の第1実施形態に係る定着装置の概略の構成を示す断面正面図である。1 is a cross-sectional front view showing a schematic configuration of a fixing device according to a first embodiment of the present invention. は、本発明の第1実施形態に係る画像形成装置の構成を示すブロック図である。FIG. 1 is a block diagram illustrating a configuration of an image forming apparatus according to a first embodiment of the present invention. は、本発明の第1〜第3実施形態に係る画像形成装置の先回の定着から1分間放置した後、定着用のモータを駆動させた状態の定着装置の温度変化を示す図である。FIG. 4 is a diagram showing a temperature change of the fixing device in a state where a fixing motor is driven after being left for one minute from the previous fixing of the image forming apparatus according to the first to third embodiments of the present invention. は、本発明の第1〜第3実施形態に係る画像形成装置の先回の定着から1時間放置した後、定着用のモータを駆動させた状態の定着装置の温度変化を示す図である。FIG. 4 is a diagram illustrating a temperature change of the fixing device in a state where a fixing motor is driven after being left for one hour from the previous fixing of the image forming apparatus according to the first to third embodiments of the present invention.

符号の説明Explanation of symbols

1 画像形成装置
2a〜2d 現像装置
11a〜11d 感光体
17 中間転写ベルト
18 定着装置
52 定着ベルト
53 定着ローラ
54 加圧ローラ
55 熱ローラ
55a ヒータランプ(熱源)
57 駆動手段
60 サーモスタットユニット
62 サーモスタット
71 画像形成部
74 制御部
83 主電源
84 サーミスタ(温度検知部材)
N ニップ部
P 用紙(転写材)
T トナー像
DESCRIPTION OF SYMBOLS 1 Image forming apparatus 2a-2d Developing device 11a-11d Photoconductor 17 Intermediate transfer belt 18 Fixing device 52 Fixing belt 53 Fixing roller 54 Pressure roller 55 Heating roller 55a Heater lamp (heat source)
57 driving means 60 thermostat unit 62 thermostat 71 image forming unit 74 control unit 83 main power supply 84 thermistor (temperature detection member)
N Nip part P Paper (transfer material)
T Toner image

Claims (6)

熱源を有する加熱部材と、前記加熱部材に圧接して配置された加圧部材と、前記加熱部材の温度を検知する温度検知部材と、前記加圧部材を回転駆動する駆動手段と、前記駆動手段の回転を制御する制御部とを備え、前記加熱部材と前記加圧部材との圧接によって形成されるニップ部に、未定着トナー像を担持した用紙を通紙して加熱定着を行う画像形成装置において、
前記制御部は、前記温度検知部材の検知温度に基づいて、前記駆動手段の回転数を制御して、前記加圧部材の温度に係わらずに前記加圧部材を所定の周速度にすることを特徴とする画像形成装置。
A heating member having a heat source; a pressure member disposed in pressure contact with the heating member; a temperature detection member that detects a temperature of the heating member; a drive unit that rotationally drives the pressure member; and the drive unit An image forming apparatus for performing heat fixing by passing a sheet carrying an unfixed toner image through a nip formed by pressure contact between the heating member and the pressure member. In
The control unit controls the number of rotations of the driving unit based on the temperature detected by the temperature detecting member so that the pressure member is set to a predetermined peripheral speed regardless of the temperature of the pressure member. An image forming apparatus.
前記制御部は、前記駆動手段の回転開始時に検知する前記温度検知部材の検知温度と、回転開始時から所定時間後に検知する前記温度検知部材の検知温度との加熱部材温度差に基づいて、前記駆動手段の回転数を制御することを特徴とする請求項1に記載の画像形成装置。   The control unit is based on a heating member temperature difference between a detection temperature of the temperature detection member detected at the start of rotation of the drive unit and a detection temperature of the temperature detection member detected after a predetermined time from the start of rotation. The image forming apparatus according to claim 1, wherein the rotational speed of the driving unit is controlled. 前記制御部は、前記駆動手段の回転開始時から第1及び第2の所定時間後に検知する前記温度検知部材の検知温度との加熱部材温度差に基づいて、前記駆動手段の回転数を制御することを特徴とする請求項1に記載の画像形成装置。   The control unit controls the number of rotations of the drive unit based on a heating member temperature difference from a detected temperature of the temperature detection member detected after the first and second predetermined time from the start of rotation of the drive unit. The image forming apparatus according to claim 1. 前記制御部は、前記加熱部材温度差が所定温度より低い場合には、前記駆動手段の回転数を前記所定温度における前記駆動手段の所定回転数より小さくし、前記加熱部材温度差が前記所定温度より高い場合には、前記駆動手段の回転数を前記所定回転数より大きくすることを特徴とする請求項2または請求項3に記載の画像形成装置。   When the heating member temperature difference is lower than a predetermined temperature, the control unit makes the rotation speed of the driving means smaller than the predetermined rotation speed of the driving means at the predetermined temperature, and the heating member temperature difference is the predetermined temperature. 4. The image forming apparatus according to claim 2, wherein when the speed is higher, the rotational speed of the driving unit is made larger than the predetermined rotational speed. 5. 用紙が前記ニップ部を連続して通紙されるときに、前記制御部は、通紙枚数が増えると、前記駆動手段の回転数を前記所定回転数に近づけることを特徴とする請求項4に記載の画像形成装置。   5. The control unit according to claim 4, wherein when the sheet is continuously passed through the nip portion, the control unit causes the rotation speed of the driving unit to approach the predetermined rotation speed when the number of passing sheets increases. The image forming apparatus described. 前記駆動手段が前記加圧部材を連続して回転駆動させるときに、前記制御部は、前記駆動手段の回転駆動時間が長くなると、前記駆動手段の回転数を前記所定回転数に近づけることを特徴とする請求項4に記載の画像形成装置。   When the driving unit continuously rotates and drives the pressure member, the control unit brings the rotational speed of the driving unit closer to the predetermined rotational speed when the rotational driving time of the driving unit becomes longer. The image forming apparatus according to claim 4.
JP2008001192A 2008-01-08 2008-01-08 Image forming apparatus Expired - Fee Related JP5486770B2 (en)

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Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2011112747A (en) * 2009-11-25 2011-06-09 Canon Inc Image heating apparatus
US8666270B2 (en) 2010-06-21 2014-03-04 Ricoh Company, Ltd. Image forming apparatus
JP2016224252A (en) * 2015-05-29 2016-12-28 キヤノン株式会社 Fixing device

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH0713461A (en) * 1993-06-22 1995-01-17 Canon Inc Fixing device
JPH1115302A (en) * 1997-06-19 1999-01-22 Canon Inc Image forming device
JP2003057988A (en) * 2001-08-09 2003-02-28 Konica Corp Image forming apparatus
JP2005234103A (en) * 2004-02-18 2005-09-02 Oki Data Corp Fixing device
JP2007193121A (en) * 2006-01-19 2007-08-02 Fuji Xerox Co Ltd Fixing device and image forming apparatus

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH0713461A (en) * 1993-06-22 1995-01-17 Canon Inc Fixing device
JPH1115302A (en) * 1997-06-19 1999-01-22 Canon Inc Image forming device
JP2003057988A (en) * 2001-08-09 2003-02-28 Konica Corp Image forming apparatus
JP2005234103A (en) * 2004-02-18 2005-09-02 Oki Data Corp Fixing device
JP2007193121A (en) * 2006-01-19 2007-08-02 Fuji Xerox Co Ltd Fixing device and image forming apparatus

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2011112747A (en) * 2009-11-25 2011-06-09 Canon Inc Image heating apparatus
US8666270B2 (en) 2010-06-21 2014-03-04 Ricoh Company, Ltd. Image forming apparatus
JP2016224252A (en) * 2015-05-29 2016-12-28 キヤノン株式会社 Fixing device

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