JP5332915B2 - Image forming apparatus - Google Patents

Image forming apparatus Download PDF

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JP5332915B2
JP5332915B2 JP2009131683A JP2009131683A JP5332915B2 JP 5332915 B2 JP5332915 B2 JP 5332915B2 JP 2009131683 A JP2009131683 A JP 2009131683A JP 2009131683 A JP2009131683 A JP 2009131683A JP 5332915 B2 JP5332915 B2 JP 5332915B2
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transfer bias
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一矢 北村
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Konica Minolta Inc
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Description

本発明は、複写機，プリンタ，ファクシミリ及びこれらの複合機などの電子写真方式を利用した画像形成装置に関するものである。特に、回転駆動される中間転写ベルトを介して対向するように複数の感光体と複数の転写部材とが設けられ、複数の転写部材に一つの転写バイアス電源から転写バイアス電圧を印加させて、各感光体の表面に形成されたトナー像を中間転写ベルトに順々に転写させるようにした画像形成装置や、回転駆動される搬送ベルトを介して対向するように複数の感光体と複数の転写部材とが設けられ、上記の搬送ベルトによって記録媒体を搬送させると共に、複数の転写部材に一つの転写バイアス電源から転写バイアス電圧を印加させて、対応する各感光体の表面に形成されたトナー像を上記の搬送ベルトによって搬送される記録媒体に順々に転写させるようにした画像形成装置において、転写バイアス電源から上記の各転写部材に印加させる転写バイアス電圧を決定する際に、多くの感光体の表面が不要に摩耗されるのを防止すると共に、一つの転写バイアス電源から上記の各転写部材に印加させる転写バイアス電圧を適切に設定できるようにした点に特徴を有するものである。   The present invention relates to an image forming apparatus using an electrophotographic system such as a copying machine, a printer, a facsimile machine, and a multifunction machine of these. In particular, a plurality of photoconductors and a plurality of transfer members are provided so as to face each other via a rotationally driven intermediate transfer belt, and a transfer bias voltage is applied from a single transfer bias power source to each of the plurality of transfer members. An image forming apparatus that sequentially transfers toner images formed on the surface of the photosensitive member to an intermediate transfer belt, and a plurality of photosensitive members and a plurality of transfer members that face each other via a rotationally driven conveyance belt And a transfer bias voltage is applied from a single transfer bias power source to a plurality of transfer members to transfer toner images formed on the surfaces of the corresponding photoreceptors. In the image forming apparatus in which transfer is sequentially performed on the recording medium transported by the transport belt, a transfer bar applied from the transfer bias power source to each of the transfer members. When determining the bias voltage, the surface of many photoconductors is prevented from being unnecessarily worn, and the transfer bias voltage applied to each of the transfer members from one transfer bias power source can be set appropriately. It has the characteristics in the point.

複写機，プリンタ，ファクシミリ及びこれらの複合機などの電子写真方式を利用した画像形成装置の一つとして、近年、フルカラーの画像形成を行う画像形成装置が広く利用されている。   2. Description of the Related Art In recent years, image forming apparatuses that form full-color images have been widely used as one of image forming apparatuses using an electrophotographic system such as a copying machine, a printer, a facsimile machine, and a combination machine thereof.

そして、このようにフルカラーの画像形成を行う画像形成装置の一つとして、各色彩のトナー像が形成される複数の感光体と回転駆動される中間転写ベルトを介して対向するように複数の転写部材とを設け、上記の各転写部材に転写バイアス電圧を印加させて、各感光体の表面に形成されたトナー像を中間転写ベルトに順々に転写させ、この中間転写ベルトにフルカラーのトナー像を形成し、このトナー像を中間転写ベルトから記録紙等の記録媒体に転写させるようにしたものが用いられている。   As one of the image forming apparatuses that perform full-color image formation in this way, a plurality of transfer units are opposed to a plurality of photoconductors on which toner images of various colors are formed via an intermediate transfer belt that is rotationally driven. A transfer bias voltage is applied to each of the transfer members, and the toner images formed on the surfaces of the photosensitive members are sequentially transferred to the intermediate transfer belt, and a full-color toner image is transferred to the intermediate transfer belt. And the toner image is transferred from an intermediate transfer belt to a recording medium such as recording paper.

ここで、上記のように各転写部材にそれぞれ転写バイアス電圧を印加させて、各感光体の表面に形成されたトナー像を中間転写ベルトに順々に転写させるにあたり、従来においては、一般に、特許文献１に示されるように、各転写部材に対応させてそれぞれ転写バイアス電源を設け、各転写バイアス電源からそれぞれの転写部材に印加させる転写バイアス電圧の適正値を求め、それぞれの転写部材に適切な転写バイアス電圧を印加させるようにしたものが提案されている。   Here, as described above, a transfer bias voltage is applied to each transfer member, and the toner images formed on the surface of each photoconductor are sequentially transferred onto the intermediate transfer belt. As shown in Document 1, a transfer bias power source is provided corresponding to each transfer member, and an appropriate value of the transfer bias voltage to be applied to each transfer member from each transfer bias power source is obtained, and an appropriate value is applied to each transfer member. There has been proposed one in which a transfer bias voltage is applied.

しかし、このように各転写部材に対応させてそれぞれ転写バイアス電源を設けるようにした場合、複数の転写バイアス電源が必要になってコストが高くつくと共に、設置スペースも必要になって装置が大型化するという問題があり、さらに各転写バイアス電源からそれぞれの転写部材に印加させる転写バイアス電圧の適正値を求めて、それぞれの転写部材に適切な転写バイアス電圧を印加させることが必要になり、その制御も面倒になるという問題があった。   However, when a transfer bias power supply is provided corresponding to each transfer member in this way, a plurality of transfer bias power supplies are required, resulting in high costs and a large installation space. In addition, it is necessary to obtain an appropriate value of the transfer bias voltage to be applied to each transfer member from each transfer bias power source, and to apply an appropriate transfer bias voltage to each transfer member. There was also the problem of becoming troublesome.

このため、従来においては、図１に示すように、複数の感光体１１ａ〜１１ｄと回転駆動される中間転写ベルト２１を介して対向するように設けられた複数の転写部材２３ａ〜２３ｄに対して、一つの転写バイアス電源２４から転写バイアス電圧を印加させるようにしたものも提案されている。   For this reason, conventionally, as shown in FIG. 1, the plurality of transfer members 23a to 23d provided to face the plurality of photoconductors 11a to 11d via the intermediate transfer belt 21 that is rotationally driven. A transfer bias voltage applied from a single transfer bias power supply 24 has also been proposed.

ここで、このように一つの転写バイアス電源２４から複数の転写部材２３ａ〜２３ｄに対して転写バイアス電圧を印加させる場合において、各転写部材２３ａ〜２３ｄに印加させる転写バイアス電圧を決定するにあたっては、一般に、中間転写ベルト２１を介して対向する上記の各感光体１１ａ〜１１ｄと各転写部材２３ａ〜２３ｄとをそれぞれ中間転写ベルト２に接触させた状態で、各感光体１１ａ〜１１ｄを回転させると共に上記の中間転写ベルト２１を回転駆動させるようにする。そして、上記の転写バイアス電源２４により中間転写ベルト２１を介して対向する各感光体１１ａ〜１１ｄと各転写部材２３ａ〜２３ｄとの間に定電圧や定電流を作用させて、中間転写ベルト２１を介して対向する各感光体１１ａ〜１１ｄと各転写部材３ａ〜３ｄとの間のインピーダンスをインピーダンス検出手段３０によって検出し、これに基づいて、転写バイアス電源４から各転写部材２３ａ〜２３ｄに印加させる転写バイアス電圧を決定するようにしている。   Here, when the transfer bias voltage is applied from the single transfer bias power source 24 to the plurality of transfer members 23a to 23d, the transfer bias voltage to be applied to each of the transfer members 23a to 23d is determined. In general, the photoconductors 11a to 11d are rotated while the photoconductors 11a to 11d and the transfer members 23a to 23d facing each other through the intermediate transfer belt 21 are in contact with the intermediate transfer belt 2, respectively. The intermediate transfer belt 21 is driven to rotate. Then, a constant voltage or a constant current is applied between the respective photoconductors 11a to 11d and the respective transfer members 23a to 23d facing each other via the intermediate transfer belt 21 by the transfer bias power source 24, so that the intermediate transfer belt 21 is moved. The impedance detection means 30 detects the impedance between the photoconductors 11a to 11d and the transfer members 3a to 3d facing each other, and based on this, the transfer bias power source 4 applies the impedance to the transfer members 23a to 23d. The transfer bias voltage is determined.

しかし、このように中間転写ベルト２１を介して対向する各感光体１１ａ〜１１ｄと各転写部材２３ａ〜２３ｄとをそれぞれ中間転写ベルト２１に接触させた状態で、上記の中間転写ベルト２を回転駆動させると共に各感光体１１ａ〜１１ｄを回転させると、各感光体１１ａ〜１１ｄの表面がクリーニング装置（図示せず）等により摩耗されて、各感光体１１ａ〜１１ｄの寿命が短くなるという問題があり、特に、表面に有機感光層が形成された感光体１１ａ〜１１ｄを用いた場合には、その摩耗が多くなって寿命が大きく低下するという問題があった。   However, the intermediate transfer belt 2 is rotationally driven in such a state that the photosensitive members 11a to 11d and the transfer members 23a to 23d opposed to each other through the intermediate transfer belt 21 are in contact with the intermediate transfer belt 21, respectively. If the photoconductors 11a to 11d are rotated, the surfaces of the photoconductors 11a to 11d are worn by a cleaning device (not shown) or the like, and the life of the photoconductors 11a to 11d is shortened. In particular, when the photoconductors 11a to 11d having the organic photosensitive layer formed on the surface are used, there is a problem that the wear is increased and the life is greatly reduced.

ここで、上記のように中間転写ベルト２を介して対向する感光体１１ａ〜１１ｄと転写部材２３ａ〜２３ｄとの間に定電圧や定電流を作用させて、中間転写ベルト２１を介して対向する各感光体１１ａ〜１１ｄと各転写部材３ａ〜３ｄとの間のインピーダンスをインピーダンス検出手段３０によって検出する場合、上記の転写部材２３ａ〜２３ｄに電気抵抗の低い金属ローラ等を用いると、上記のインピーダンスは感光体１１ａ〜１１ｄと中間転写ベルト２１のインピーダンスによって決定され、これらのインピーダンスを適切に検出することが重要になる。   Here, as described above, a constant voltage or a constant current is applied between the photoconductors 11 a to 11 d and the transfer members 23 a to 23 d that are opposed to each other via the intermediate transfer belt 2, and they are opposed to each other via the intermediate transfer belt 21. When the impedance detection means 30 detects the impedance between the photoconductors 11a to 11d and the transfer members 3a to 3d, the impedance described above can be obtained by using a metal roller or the like having a low electrical resistance for the transfer members 23a to 23d. Is determined by the impedances of the photoreceptors 11a to 11d and the intermediate transfer belt 21, and it is important to appropriately detect these impedances.

ここで、上記の各感光体１１ａ〜１１ｄと各転写部材２３ａ〜２３ｄとの間のインピーダンスは必ずしも一定しておらず、例えば、図２に示すように中間転写ベルト２１を介して対向する各感光体１１ａ〜１１ｄと各転写部材２３ａ〜２３ｄとの位置関係が一定していない場合や、図３に示すように転写バイアス電源２４と各転写部材２３ａ〜２３ｄとの間に設けられた抵抗Ｒａ〜Ｒｄの抵抗値が異なる場合や、各感光体１１ａ〜１１ｄの表面の摩耗状態が大きく異なる場合などにおいては、各感光体１１ａ〜１１ｄと各転写部材２３ａ〜２３ｄとの間のインピーダンスに大きな差が生じている。   Here, the impedance between each of the photoconductors 11a to 11d and the transfer members 23a to 23d is not necessarily constant. For example, as shown in FIG. When the positional relationship between the bodies 11a to 11d and the transfer members 23a to 23d is not constant, as shown in FIG. 3, resistors Ra to provided between the transfer bias power source 24 and the transfer members 23a to 23d are used. When the resistance values of Rd are different, or when the wear states of the surfaces of the photoconductors 11a to 11d are greatly different, there is a large difference in impedance between the photoconductors 11a to 11d and the transfer members 23a to 23d. Has occurred.

このため、上記のように中間転写ベルト２１を介して対向する各感光体１１ａ〜１１ｄと各転写部材２３ａ〜２３ｄとの間のインピーダンスをインピーダンス検出手段３０によって検出しても、各感光体１１ａ〜１１ｄと対向する各転写部材２３ａ〜２３ｄとの間の正確なインピーダンスを検出したことにはならず、上記のように重要となる中間転写ベルト２１のインピーダンス等を精度よく検出して、転写バイアス電源２４から各転写部材２３ａ〜２３ｄに印加させる転写バイアス電圧を適切に決定することができないという問題があった。   For this reason, even if the impedance detection means 30 detects the impedance between each photoconductor 11a-11d and each transfer member 23a-23d which opposes via the intermediate transfer belt 21, as described above, each photoconductor 11a- The accurate impedance between each of the transfer members 23a to 23d facing 11d is not detected, but the impedance of the intermediate transfer belt 21, which is important as described above, is accurately detected, and a transfer bias power source is detected. 24, the transfer bias voltage to be applied to the transfer members 23a to 23d cannot be appropriately determined.

特開平１１−２０２６５１号公報Japanese Patent Laid-Open No. 11-202651

本発明は、回転駆動される中間転写ベルトを介して対向するように複数の感光体と複数の転写部材とが設けられ、各転写部材に一つの転写バイアス電源から転写バイアス電圧を印加させて、各感光体の表面に形成されたトナー像を中間転写ベルトに順々に転写させるようにした画像形成装置における上記のような問題を解決することを課題とするものである。   In the present invention, a plurality of photoconductors and a plurality of transfer members are provided so as to face each other via a rotationally driven intermediate transfer belt, and a transfer bias voltage is applied to each transfer member from one transfer bias power source, An object of the present invention is to solve the above-described problems in an image forming apparatus in which toner images formed on the surface of each photoconductor are sequentially transferred onto an intermediate transfer belt.

すなわち、本発明においては、上記のように一つの転写バイアス電源から上記の各転写部材に印加させる転写バイアス電圧を決定する際に、多くの感光体の表面が不要に摩耗されるのを防止すると共に、転写バイアス電源から上記の各転写部材に印加させる転写バイアス電圧を適切に設定できるようにすることを課題とするものである。   That is, in the present invention, when determining the transfer bias voltage to be applied to each of the transfer members from one transfer bias power source as described above, the surface of many photoconductors is prevented from being unnecessarily worn. At the same time, it is an object of the present invention to be able to appropriately set the transfer bias voltage to be applied to each transfer member from the transfer bias power source.

本発明の第１の画像形成装置においては、上記のような課題を解決するため、回転駆動される中間転写ベルトを介して対向するように複数の感光体と複数の転写部材とが設けられ、複数の転写部材に一つの転写バイアス電源から転写バイアス電圧を印加させて、対応する各感光体の表面に形成されたトナー像を中間転写ベルトに順々に転写させる画像形成装置において、一つの感光体だけを中間転写ベルトに接触させて、この感光体と中間転写ベルトを介して対向する転写部材との間のインピーダンスを検出するインピーダンス検出手段と、このインピーダンス検出手段によって検出されたインピーダンスに基づいて上記の転写バイアス電源から上記の各転写部材に印加させる転写バイアス電圧を決定する転写バイアス電圧決定手段を設け、上記の中間転写ベルトを介して対向する各感光体と各転写部材との位置関係が一定でない場合に、上記の転写バイアス電圧決定手段に、各感光体と各転写部材との位置関係の情報を伝達して、上記の転写バイアス電源から各転写部材に出力する転写バイアス電圧を決定するようにした。 In the first image forming apparatus of the present invention, in order to solve the above-described problems, a plurality of photosensitive members and a plurality of transfer members are provided so as to face each other via an intermediate transfer belt that is rotationally driven. In an image forming apparatus in which a transfer bias voltage is applied from a single transfer bias power source to a plurality of transfer members, and toner images formed on the surfaces of the corresponding photosensitive members are sequentially transferred to an intermediate transfer belt. Based on the impedance detected by the impedance detection unit, the impedance detection unit detects the impedance between the photosensitive member and the transfer member facing the intermediate transfer belt by contacting only the body with the intermediate transfer belt. the transfer bias voltage determining means for determining the transfer bias voltage applied from the transfer bias power source to each of the transfer member of the provided, When the positional relationship between the respective photoconductors and the respective transfer members facing each other through the intermediate transfer belt is not constant, the transfer bias voltage determining means stores information on the positional relationship between the respective photoconductors and the respective transfer members. The transfer bias voltage output from the transfer bias power source to each transfer member is determined .

また、本発明の第２の画像形成装置においては、回転駆動される搬送ベルトを介して対向するように複数の感光体と複数の転写部材とが設けられ、上記の搬送ベルトによって記録媒体を搬送させると共に、複数の転写部材に一つの転写バイアス電源から転写バイアス電圧を印加させて、対応する各感光体の表面に形成されたトナー像を上記の搬送ベルトによって搬送される記録媒体に順々に転写させる画像形成装置において、一つの感光体だけを搬送ベルトに接触させて、この感光体と搬送ベルトを介して対向する転写部材との間のインピーダンスを検出するインピーダンス検出手段と、このインピーダンス検出手段によって検出されたインピーダンスに基づいて上記の転写バイアス電源から上記の各転写部材に印加させる転写バイアス電圧を決定する転写バイアス電圧決定手段を設け、上記の搬送ベルトを介して対向する各感光体と各転写部材との位置関係が一定でない場合に、上記の転写バイアス電圧決定手段に、各感光体と各転写部材との位置関係の情報を伝達して、上記の転写バイアス電源から各転写部材に出力する転写バイアス電圧を決定するようにした。 In the second image forming apparatus of the present invention, a plurality of photosensitive members and a plurality of transfer members are provided so as to face each other via a rotationally driven conveyance belt, and the recording medium is conveyed by the conveyance belt. In addition, a transfer bias voltage is applied to a plurality of transfer members from one transfer bias power source, and the toner images formed on the surfaces of the corresponding photosensitive members are sequentially transferred to the recording medium conveyed by the conveyance belt. In an image forming apparatus to be transferred, an impedance detecting unit that detects an impedance between the photosensitive member and a transfer member opposed to the photosensitive member via the conveying belt by bringing only one photosensitive member into contact with the conveying belt, and the impedance detecting unit Transfer bias voltage applied to each of the transfer members from the transfer bias power source based on the impedance detected by A transfer bias voltage determining means for determining provided, if the positional relationship between the photosensitive member and the transfer member facing via the conveyor belt of the is not constant, the transfer bias voltage determining means described above, each of the respective photoconductors Information on the positional relationship with the transfer member is transmitted, and the transfer bias voltage output from the transfer bias power source to each transfer member is determined .

また、上記の第１及び第２の画像形成装置において、表面に有機感光層が形成された感光体を用いた場合には、上記の転写バイアス電圧決定手段に、この感光体における有機感光層の層厚情報を伝達して、上記の転写バイアス電源から出力する転写バイアス電圧を決定させるようにすることが好ましい。   In the first and second image forming apparatuses described above, when a photosensitive member having an organic photosensitive layer formed on the surface is used, the transfer bias voltage determining unit is configured to transfer the organic photosensitive layer of the photosensitive member. It is preferable to transmit the layer thickness information to determine the transfer bias voltage output from the transfer bias power source.

本発明の第１及び第２の画像形成装置においては、上記のように中間転写ベルトや搬送ベルトに一つの感光体だけを接触させて、この感光体と中間転写ベルトや搬送ベルトを介して対向する転写部材との間のインピーダンスをインピーダンス検出手段によって検出するようにしたため、上記の感光体以外の他の感光体は中間転写ベルトや搬送ベルトに接触されず、他の感光体を回転させる必要がなくなり、クリーニング装置等によって他の感光体の表面が摩耗されるのが防止されて、他の感光体の寿命が短くなるのが抑制される。特に、表面に有機感光層が形成された感光体の場合、感光体の表面の摩耗が多くなって、その寿命が大きく低下するということがなくなる。   In the first and second image forming apparatuses of the present invention, as described above, only one photosensitive member is brought into contact with the intermediate transfer belt or the conveyance belt, and the photosensitive member is opposed to the intermediate transfer belt or the conveyance belt through the intermediate transfer belt or the conveyance belt. Since the impedance detection means detects the impedance between the transfer member and the transfer member, the other photoconductors other than the above-described photoconductors are not in contact with the intermediate transfer belt or the conveyance belt, and it is necessary to rotate the other photoconductors. Thus, the surface of the other photoconductor is prevented from being worn by the cleaning device or the like, and the life of the other photoconductor is prevented from being shortened. In particular, in the case of a photoconductor having an organic photosensitive layer formed on the surface, the surface of the photoconductor is not worn so much that its life is not significantly reduced.

また、第１及び第２の画像形成装置においては、上記のようにインピーダンス検出手段により、一つの感光体と中間転写ベルトや搬送ベルトを介して対向する転写部材との間のインピーダンスを検出するようにしたため、前記のように中間転写ベルトや搬送ベルトを介して対向する各感光体と各転写部材との位置関係が一定していない場合や、転写バイアス電源と各転写部材との間に設けられた抵抗の抵抗値が異なる場合や、各感光体の表面の摩耗状態が大きく異なる場合などにおいても、一定した状態でインピーダンスが検出されるようになり、重要となる中間転写ベルトや搬送ベルト等のインピーダンスを精度よく検出できるようになる。そして、上記の中間転写ベルトを介して対向する各感光体と各転写部材との位置関係が一定でない場合や、上記の搬送ベルトを介して対向する各感光体と各転写部材との位置関係が一定でない場合には、上記の転写バイアス電圧決定手段に、各感光体と各転写部材との位置関係の情報を伝達して、上記の転写バイアス電源から各転写部材に印加させる転写バイアス電圧を上記の転写バイアス電圧決定手段によって適切に決定することができるようになる。
In the first and second image forming apparatuses, as described above, the impedance detection unit detects the impedance between one photoconductor and the transfer member facing the intermediate transfer belt or the conveyance belt. Therefore, when the positional relationship between each transfer member and each transfer member facing each other through the intermediate transfer belt or the conveyance belt is not constant as described above, it is provided between the transfer bias power source and each transfer member. Impedance is detected in a constant state even when the resistance value of each resistor is different or when the wear state of the surface of each photoconductor is greatly different, such as an important intermediate transfer belt or conveyor belt. Impedance can be detected accurately . When the positional relationship between the respective photoconductors and the respective transfer members opposed via the intermediate transfer belt is not constant, or the positional relationship between the respective photoconductors and the respective transfer members opposed via the above conveying belt If the transfer bias voltage is not constant, the transfer bias voltage determining means transmits the information on the positional relationship between each photoconductor and each transfer member, and applies the transfer bias voltage applied to each transfer member from the transfer bias power source. The transfer bias voltage determining means can appropriately determine the transfer bias voltage.

この結果、この発明の第１及び第２の画像形成装置においては、一つの転写バイアス電源から各転写部材に適切な転写バイアス電圧を印加させて、各感光体に形成されたトナー像を上記の中間転写ベルトや上記の搬送ベルトによって搬送される記録媒体に適切に転写させて良好な画像形成が行えるようになる。   As a result, in the first and second image forming apparatuses of the present invention, an appropriate transfer bias voltage is applied to each transfer member from one transfer bias power source, and the toner image formed on each photoconductor is transferred to the above-described toner image. A good image can be formed by appropriately transferring to a recording medium conveyed by the intermediate transfer belt or the conveying belt.

従来の画像形成装置において、中間ベルトを介して対向する各感光体と各転写部材との間のインピーダンスを検出する状態を示した概略説明図である。In the conventional image forming apparatus, it is a schematic explanatory view showing a state of detecting the impedance between each photosensitive member and each transfer member facing each other through an intermediate belt. 従来の画像形成装置において、中間転写ベルトを介して対向する各感光体と各転写部材との位置関係が一定していない状態を示した概略説明図である。FIG. 10 is a schematic explanatory view showing a state in which the positional relationship between each photosensitive member and each transfer member facing each other through an intermediate transfer belt is not constant in a conventional image forming apparatus. 従来の画像形成装置において、転写バイアス電源と各転写部材との間に設けられた抵抗の抵抗値が異なる状態を示した概略説明図である。FIG. 10 is a schematic explanatory diagram showing a state in which resistance values of resistors provided between a transfer bias power source and each transfer member are different in a conventional image forming apparatus. 本発明の実施形態１に係る画像形成装置を示した概略説明図である。1 is a schematic explanatory diagram illustrating an image forming apparatus according to a first embodiment of the present invention. 実施形態１の画像形成装置において、一つの感光体を中間転写ベルトに接触させてインピーダンス検出手段により検出したインピーダンスを転写バイアス電圧決定手段に伝えるようにした状態を示した部分説明図である。FIG. 3 is a partial explanatory view showing a state in which, in the image forming apparatus of Embodiment 1, one photoconductor is brought into contact with an intermediate transfer belt and an impedance detected by an impedance detection unit is transmitted to a transfer bias voltage determination unit. 実施形態１の画像形成装置において、ＣＰＵからさらに感光体の層厚の変化を転写バイアス電圧決定手段に伝えるようにした例を示した部分説明図である。FIG. 3 is a partial explanatory diagram illustrating an example in which a change in the layer thickness of a photosensitive member is further transmitted from a CPU to a transfer bias voltage determining unit in the image forming apparatus of Embodiment 1. 本発明の実施形態２に係る画像形成装置において、回転移動される搬送ベルトにより搬送される記録媒体に、各感光体に形成されたトナー像を転写させる状態を示した部分説明図である。FIG. 10 is a partial explanatory diagram illustrating a state in which a toner image formed on each photoconductor is transferred to a recording medium conveyed by a rotationally conveyed conveyance belt in the image forming apparatus according to the second exemplary embodiment of the present invention. 実施形態２の画像形成装置において、一つの感光体を搬送ベルトに接触させてインピーダンス検出手段により検出したインピーダンスと、ＣＰＵにおける記録媒体の情報などを転写バイアス電圧決定手段に伝えるようにした状態を示した部分説明図である。In the image forming apparatus according to the second embodiment, a state where one photoconductor is brought into contact with a conveyance belt and impedance detected by the impedance detection unit and information on a recording medium in the CPU is transmitted to the transfer bias voltage determination unit is shown. FIG.

次に、この発明の実施形態に係る画像形成装置を添付図面に基づいて具体的に説明する。なお、本発明に係る画像形成装置は、下記の実施形態に示したものに限定されず、その要旨を変更しない範囲において適宜変更して実施できるものである。   Next, an image forming apparatus according to an embodiment of the present invention will be specifically described with reference to the accompanying drawings. Note that the image forming apparatus according to the present invention is not limited to those shown in the following embodiments, and can be implemented with appropriate modifications within a range not changing the gist thereof.

（実施形態１）
実施形態１の画像形成装置においては、図４に示すように、その装置本体１内に、４つのイメージングカートリッジ１０Ａ〜１０Ｄを装着させるようにしている。 (Embodiment 1)
In the image forming apparatus according to the first embodiment, as shown in FIG. 4, four imaging cartridges 10 </ b> A to 10 </ b> D are mounted in the apparatus main body 1.

ここで、上記の各イメージングカートリッジ１０Ａ〜１０Ｄにおいては、それぞれドラム状の感光体１１ａ〜１１ｄを回転可能に設けると共に、この感光体１１ａ〜１１ｄの表面に接触して感光体１１ａ〜１１ｄの表面を帯電させる帯電ローラ１２と、帯電された感光体１１ａ〜１１ｄの表面に画像情報に応じた露光を行って感光体１１ａ〜１１ｄの表面に静電潜像を形成する露光装置１３と、感光体１１ａ〜１１ｄの表面に形成された静電潜像にトナーを供給してトナー像を形成する現像装置１４と、感光体１１ａ〜１１ｄの表面に形成されたトナー像を中間転写ベルト２１に転写させた後の感光体１１ａ〜１１ｄの表面に残留するトナー等の残留物を除去する第１クリーニング装置１５とを設けている。   Here, in each of the imaging cartridges 10A to 10D, the drum-shaped photoconductors 11a to 11d are rotatably provided, and the surfaces of the photoconductors 11a to 11d are brought into contact with the surfaces of the photoconductors 11a to 11d. A charging roller 12 for charging, an exposure device 13 for performing exposure according to image information on the surfaces of the charged photoconductors 11a to 11d to form electrostatic latent images on the surfaces of the photoconductors 11a to 11d, and the photoconductor 11a. The developing device 14 for supplying toner to the electrostatic latent images formed on the surfaces of ˜11d to form toner images, and the toner images formed on the surfaces of the photoreceptors 11a˜11d were transferred to the intermediate transfer belt 21 A first cleaning device 15 is provided for removing residues such as toner remaining on the surfaces of the subsequent photoreceptors 11a to 11d.

また、上記の各イメージングカートリッジ１０Ａ〜１０Ｄにおける各現像装置１４においては、黒色，黄色，マゼンダ色，シアン色の異なった色彩のトナーを収容させている。   Further, each developing device 14 in each of the imaging cartridges 10A to 10D accommodates toners of different colors such as black, yellow, magenta, and cyan.

ここで、この実施形態に係る画像形成装置において、フルカラーの画像形成を行うにあたっては、上記の各イメージングカートリッジ１０Ａ〜１０Ｄにおける各感光体１１ａ〜１１ｄの表面をそれぞれ帯電ローラ１２によって帯電させ、このように帯電された各感光体１１ａ〜１１ｄの表面にそれぞれ露光装置１３により画像情報に応じた露光を行って、各感光体１１ａ〜１１ｄの表面に静電潜像を形成するようにしている。   Here, in the image forming apparatus according to this embodiment, when full-color image formation is performed, the surfaces of the photoreceptors 11a to 11d in the imaging cartridges 10A to 10D are charged by the charging roller 12, respectively. The surface of each of the photoconductors 11a to 11d charged to the surface is exposed according to the image information by the exposure device 13 to form an electrostatic latent image on the surface of each of the photoconductors 11a to 11d.

そして、このように静電潜像が形成された各感光体１１ａ〜１１ｄに対して、それぞれ対応する現像装置１４からそれぞれの色彩のトナーを供給し、各感光体１１ａ〜１１ｄの表面に、それぞれの色彩のトナー像を形成するようにしている。   Then, toner of each color is supplied from the corresponding developing device 14 to each of the photoconductors 11a to 11d on which the electrostatic latent images are formed in this manner, and the surface of each of the photoconductors 11a to 11d is respectively supplied. A toner image of the color is formed.

次いで、上記のように各色彩のトナー像が形成された各感光体１１ａ〜１１ｄの表面に、回転ローラ２２に架け渡されて回転移動される中間転写ベルト２１を接触させ、この中間転写ベルト２１を介して上記の各感光体１１ａ〜１１ｄと対向するように設けられたローラ状の各転写部材２３ａ〜２３ｄに対して、一つの転写バイアス電源２４から適当な転写バイアス電圧を印加させて、各感光体１１ａ〜１１ｄの表面に形成されたトナー像を中間転写ベルト２１に順々に転写させ、この中間転写ベルト２１の表面にフルカラーのトナー像を形成するようにしている。   Next, the surface of each of the photoconductors 11a to 11d on which the toner images of each color are formed as described above is brought into contact with the intermediate transfer belt 21 that is stretched around the rotation roller 22 and rotated. An appropriate transfer bias voltage is applied from one transfer bias power source 24 to each of the roller-like transfer members 23a to 23d provided so as to face the respective photoreceptors 11a to 11d via The toner images formed on the surfaces of the photoreceptors 11 a to 11 d are sequentially transferred to the intermediate transfer belt 21, and a full-color toner image is formed on the surface of the intermediate transfer belt 21.

そして、このようにフルカラーのトナー像を中間転写ベルト２１に転写させた後における各感光体１１の表面に残留するトナー等の残留物を、それぞれ第１クリーニング装置１６によって各感光体１１の表面から除去するようにしている。   Then, after the full-color toner image is transferred onto the intermediate transfer belt 21 in this way, the residual toner and the like remaining on the surface of each photoconductor 11 is removed from the surface of each photoconductor 11 by the first cleaning device 16. Try to remove.

一方、上記のように中間転写ベルト２１の表面に形成されたフルカラーのトナー像を、上記の回転ローラ２２と２次転写ローラ２とが対向する転写部に導くと共に、記録媒体Ｓを給紙ローラ３により給紙し、この記録媒体Ｓをタイミングローラ４によって適当なタイミングで上記の回転ローラ２２と２次転写ローラ２とが対向する転写部に導き、中間転写ベルト２１の表面におけるフルカラーのトナー像を記録媒体Ｓに転写させるようにしている。   On the other hand, the full-color toner image formed on the surface of the intermediate transfer belt 21 as described above is guided to the transfer portion where the rotary roller 22 and the secondary transfer roller 2 face each other, and the recording medium S is fed to the paper feed roller. 3, the recording medium S is guided by the timing roller 4 to a transfer portion where the rotary roller 22 and the secondary transfer roller 2 face each other at an appropriate timing, and a full-color toner image on the surface of the intermediate transfer belt 21. Is transferred to the recording medium S.

次いで、このようにフルカラーのトナー像が転写された記録媒体Ｓを一対の定着ローラ６，６が設けられた定着部に導き、この一対の定着ローラ６，６間において、上記のフルカラーのトナー像を記録媒体Ｓに定着させた後、この記録媒体Ｓを排紙ローラ７により排紙させるようにしている。   Next, the recording medium S on which the full-color toner image is transferred in this way is guided to a fixing unit provided with a pair of fixing rollers 6 and 6, and the above-described full-color toner image is interposed between the pair of fixing rollers 6 and 6. Is fixed to the recording medium S, and then the recording medium S is discharged by the discharge roller 7.

また、上記のように中間転写ベルト２１の表面に形成されたフルカラーのトナー像を記録媒体Ｓに転写させた後、この中間転写ベルト２１の表面に残ったトナー等の残留物を第２クリーニング装置８により中間転写ベルト２１から除去するようにしている。   Further, after the full-color toner image formed on the surface of the intermediate transfer belt 21 as described above is transferred to the recording medium S, the residue such as toner remaining on the surface of the intermediate transfer belt 21 is removed by the second cleaning device. 8 is removed from the intermediate transfer belt 21.

ここで、この実施形態の画像形成装置において、上記の転写バイアス電源２４から各転写部材２３ａ〜２３ｄに印加させる転写バイアス電圧を決定するにあたっては、図５に示すように、回転駆動される中間転写ベルト２１に一つの感光体１１ｄだけを接触させて回転させるようにする。   Here, in determining the transfer bias voltage to be applied to the transfer members 23a to 23d from the transfer bias power source 24 in the image forming apparatus of this embodiment, as shown in FIG. Only one photoconductor 11d is brought into contact with the belt 21 and rotated.

そして、上記の転写バイアス電源２４からこの感光体１１ｄと中間転写ベルト２１を介して対向する転写部材２３ｄとの間に定電圧や定電流を作用させて、中間転写ベルト２１を介して対向する上記の感光体１１ｄと転写部材２３ｄとの間のインピーダンスをインピーダンス検出手段３０によって検出し、この結果を転写バイアス電圧決定手段３１に伝えるようにする。   Then, a constant voltage or a constant current is applied from the transfer bias power source 24 to the transfer member 23d opposed to the photoconductor 11d via the intermediate transfer belt 21, and the transfer bias power supply 24 is opposed to the transfer member 23d via the intermediate transfer belt 21. The impedance between the photosensitive member 11d and the transfer member 23d is detected by the impedance detection means 30, and the result is transmitted to the transfer bias voltage determination means 31.

そして、上記の結果に基づいて、この転写バイアス電圧決定手段３１により中間転写ベルト２１の抵抗等を算出して、適切な転写バイアス電圧を決定し、このように決定した転写バイアス電圧を上記の転写バイアス電源２４から各転写部材２３ａ〜２３ｄに印加させて、各感光体１１ａ〜１１ｄの表面に形成された各トナー像を、中間転写ベルト２１に順々に転写させるようにする。   Based on the above result, the transfer bias voltage determining means 31 calculates the resistance of the intermediate transfer belt 21 and the like to determine an appropriate transfer bias voltage, and the transfer bias voltage thus determined is used as the transfer bias voltage described above. The toner images formed on the surfaces of the photoconductors 11a to 11d are sequentially transferred to the intermediate transfer belt 21 by applying the bias power source 24 to the transfer members 23a to 23d.

ここで、上記のように回転駆動される中間転写ベルト２１に一つの感光体１１ｄだけを接触させて回転させ、中間転写ベルト２１を介して対向するこの感光体１１ｄと転写部材２３ｄとの間のインピーダンスをインピーダンス検出手段３０によって検出する場合には、この感光体１１ｄ以外の他の感光体１１ａ〜１１ｃの表面が前記の第１クリーニング装置１５等によって摩耗されるのが防止され、他の感光体１１ａ〜１１ｃの寿命が無駄に低下するのが抑制されるようになり、特に、表面に有機感光層が形成された感光体の場合には、寿命が大きく低下するのが防止されるようになる。   Here, only one photoconductor 11d is brought into contact with and rotated by the intermediate transfer belt 21 that is rotationally driven as described above, and between the photoconductor 11d and the transfer member 23d facing each other via the intermediate transfer belt 21. When the impedance is detected by the impedance detection means 30, it is possible to prevent the surfaces of the other photoconductors 11a to 11c other than the photoconductor 11d from being worn by the first cleaning device 15 or the like. It is possible to prevent the lifespan of 11a to 11c from being unnecessarily lowered, and in particular, in the case of a photoreceptor having an organic photosensitive layer formed on the surface, it is possible to prevent the lifespan from being significantly reduced. .

また、このように回転駆動される中間転写ベルト２１に一つの感光体１１ｄだけを接触させて、中間転写ベルト２１を介して対向するこの感光体１１ｄと転写部材２３ｄとの間のインピーダンスだけをインピーダンス検出手段３０によって検出させるようにすると、前記の図２に示すように中間転写ベルト２１を介して対向する各感光体１１ａ〜１１ｄと各転写部材２３ａ〜２３ｄとの位置関係が一定していない場合や、図３に示すように転写バイアス電源２４と各転写部材２３ａ〜２３ｄとの間に設けられた抵抗Ｒａ〜Ｒｄの抵抗値が異なる場合や、各感光体１１ａ〜１１ｄの表面の摩耗状態が大きく異なる場合のように、各感光体１１ａ〜１１ｄと各転写部材２３ａ〜２３ｄとの間のインピーダンスに差が生じていても、上記のように測定したインピーダンスに基づいて、重要となる中間転写ベルト２１のインピーダンスを精度よく検出することができ、上記の転写バイアス電圧決定手段３１により転写バイアス電源２４から各転写部材２３ａ〜２３ｄに印加させる転写バイアス電圧を適切に決定することができるようになる。   Further, only the one photoreceptor 11d is brought into contact with the intermediate transfer belt 21 that is rotationally driven in this way, and only the impedance between the photoreceptor 11d and the transfer member 23d facing each other via the intermediate transfer belt 21 is impedance. When detection is performed by the detection means 30, the positional relationship between the respective photosensitive members 11a to 11d and the respective transfer members 23a to 23d facing each other via the intermediate transfer belt 21 as shown in FIG. 2 is not constant. In addition, as shown in FIG. 3, when the resistance values of the resistors Ra to Rd provided between the transfer bias power source 24 and the transfer members 23a to 23d are different, the wear state of the surfaces of the photoconductors 11a to 11d is different. Even if there is a difference in impedance between each of the photoconductors 11a to 11d and each of the transfer members 23a to 23d as in the case of a large difference, the measurement is performed as described above. Based on the measured impedance, the impedance of the intermediate transfer belt 21 that is important can be detected with high accuracy, and the transfer bias voltage determined by the transfer bias voltage determination unit 31 is applied to the transfer members 23a to 23d from the transfer bias power source 24. Can be determined appropriately.

ここで、上記の各感光体１１ａ〜１１ｄとして、表面に有機感光層が形成された感光体を用いた場合、その表面に形成された有機感光層が摩耗されてその層厚が変化すると、感光体１１ａ〜１１ｄのインピーダンスが変化し、上記のインピーダンス検出手段３０によって検出される上記の感光体１１ｄと転写部材２３ｄとの間のインピーダンスに影響を与えることになる。   Here, in the case where a photoreceptor having an organic photosensitive layer formed on the surface is used as each of the above-described photoreceptors 11a to 11d, if the organic photosensitive layer formed on the surface is worn and the layer thickness changes, The impedances of the bodies 11a to 11d change and affect the impedance between the photoreceptor 11d and the transfer member 23d detected by the impedance detection means 30.

このため、図６に示すように、感光体１１ａ〜１１ｄの使用状況を装置本体１に設けたＣＰＵ３２に記憶させて感光体１１ａ〜１１ｄの層厚の変化を算出し、感光体１１ａ〜１１ｄの層厚の変化をＣＰＵ３２から上記の転写バイアス電圧決定手段３１に伝え、インピーダンス検出手段３０からの情報と合わせて、上記の転写バイアス電圧決定手段３１により、転写バイアス電源２４から各転写部材２３ａ〜２３ｄに印加させる転写バイアス電圧を適切に決定させるようにすることが好ましい。   For this reason, as shown in FIG. 6, the usage status of the photoconductors 11a to 11d is stored in the CPU 32 provided in the apparatus main body 1, and the change in the layer thickness of the photoconductors 11a to 11d is calculated. The change in the layer thickness is transmitted from the CPU 32 to the transfer bias voltage determining means 31, and together with the information from the impedance detecting means 30, the transfer bias voltage determining means 31 sends the transfer members 23 a to 23 d from the transfer bias power supply 24. It is preferable that the transfer bias voltage to be applied to is appropriately determined.

（実施形態２）
実施形態２の画像形成装置においては、図７に示すように、上記の実施形態１の中間転写ベルト２１に代えて、搬送ベルト２５を回転駆動させるようにしている。 (Embodiment 2)
In the image forming apparatus according to the second embodiment, as shown in FIG. 7, instead of the intermediate transfer belt 21 according to the first embodiment, the conveying belt 25 is driven to rotate.

そして、この実施形態の画像形成装置においては、上記の搬送ベルト２５によって記録媒体Ｓを、各色彩のトナー像が形成された各感光体１１ａ〜１１ｄの表面に接触するようにして、各感光体１１ａ〜１１ｄと各転写部材２３ａ〜２３ｄとの間に導き、各転写部材２３ａ〜２３ｄに一つの転写バイアス電源２４から適当な転写バイアス電圧を印加させて、各感光体１１ａ〜１１ｄの表面に形成されたトナー像を記録媒体Ｓの上に順々に転写させ、この記録媒体Ｓの表面にフルカラーのトナー像を転写させるようにしている。   In the image forming apparatus according to this embodiment, each photosensitive member is brought into contact with the surface of each of the photosensitive members 11a to 11d on which the toner images of the respective colors are formed by the conveying belt 25. 11a to 11d and the transfer members 23a to 23d, each transfer member 23a to 23d is applied with an appropriate transfer bias voltage from one transfer bias power supply 24, and formed on the surface of each photoconductor 11a to 11d. The toner images thus transferred are sequentially transferred onto the recording medium S, and a full-color toner image is transferred onto the surface of the recording medium S.

ここで、この実施形態の画像形成装置において、上記の転写バイアス電源２４から各転写部材２３ａ〜２３ｄに印加させる転写バイアス電圧を決定するにあたっては、図８に示すように、回転駆動される搬送ベルト２５に一つの感光体１１ｄだけを接触させて回転させ、上記の転写バイアス電源２４からこの感光体１１ｄと搬送ベルト２５を介して対向する転写部材２３ｄとの間に定電圧や定電流を作用させて、搬送ベルト２５を介して対向する上記の感光体１１ｄと転写部材２３ｄとの間のインピーダンスをインピーダンス検出手段３０によって検出し、この結果を転写バイアス電圧決定手段３１に伝えると共に、装置本体１に設けたＣＰＵ３２から上記の記録媒体Ｓの抵抗等の各種の情報を転写バイアス電圧決定手段３１に伝え、これに基づいて、転写バイアス電圧決定手段３１により、転写バイアス電源２４から各転写部材２３ａ〜２３ｄに印加させる転写バイアス電圧を適切に決定させるようにしている。   Here, in the image forming apparatus of this embodiment, when determining the transfer bias voltage to be applied to each of the transfer members 23a to 23d from the transfer bias power supply 24, as shown in FIG. 25, only one photoconductor 11d is brought into contact with the photoconductor 11d and rotated, and a constant voltage or a constant current is applied between the photoconductor 11d and the transfer member 23d facing each other via the conveying belt 25 from the transfer bias power source 24. Then, the impedance between the photosensitive member 11d and the transfer member 23d facing each other via the conveying belt 25 is detected by the impedance detecting means 30, and the result is transmitted to the transfer bias voltage determining means 31 and also to the apparatus main body 1. Various information such as the resistance of the recording medium S is transmitted from the provided CPU 32 to the transfer bias voltage determining means 31, and Zui, the transfer by a bias voltage determining means 31, so as to properly determine the transfer bias voltage applied to each transfer member 23a~23d from the transfer bias power source 24.

このようにすると、上記の実施形態１の場合と同様に、インピーダンスの検出に使用する感光体１１ｄ以外の他の感光体１１ａ〜１１ｃの表面が、前記の第１クリーニング装置１５等によって摩耗されるのが防止され、他の感光体１１ａ〜１１ｃの寿命が無駄に低下するのが抑制されるようになる。   In this manner, as in the case of the first embodiment, the surfaces of the other photoconductors 11a to 11c other than the photoconductor 11d used for impedance detection are worn by the first cleaning device 15 and the like. This prevents the life of the other photoconductors 11a to 11c from being unnecessarily reduced.

また、上記のように測定したインピーダンスに基づいて、重要となる搬送ベルト２５のインピーダンスを精度よく検出することができ、上記の転写バイアス電圧決定手段３１により転写バイアス電源２４から各転写部材２３ａ〜２３ｄに印加させる転写バイアス電圧を適切に決定することができるようになる。   Further, it is possible to accurately detect the impedance of the transport belt 25 that is important based on the impedance measured as described above, and the transfer bias voltage determination unit 31 causes the transfer members 23a to 23d to be transferred from the transfer bias power source 24. The transfer bias voltage to be applied to can be determined appropriately.

１ 装置本体
２ ２次転写ローラ
３ 給紙ローラ
４ タイミングローラ
６ 定着装置
７ 排紙ローラ
８ 第２クリーニング装置
１０Ａ〜１０Ｄ イメージングカートリッジ
１１ａ〜１１ｄ 感光体
１２ 帯電装置
１３ 露光装置
１４ 現像装置
１５ 第１クリーニング装置
２１ 中間転写ベルト
２２ 回転ローラ
２３ａ〜２３ｄ 転写部材
２４ 転写バイアス電源
２５ 搬送ベルト
３０ インピーダンス検出手段
３１ 転写バイアス電圧決定手段
３２ ＣＰＵ
Ｒａ〜Ｒｄ 抵抗
Ｓ 記録媒体 DESCRIPTION OF SYMBOLS 1 Apparatus main body 2 Secondary transfer roller 3 Paper feed roller 4 Timing roller 6 Fixing apparatus 7 Paper discharge roller 8 2nd cleaning apparatus 10A-10D Imaging cartridge 11a-11d Photoconductor 12 Charging apparatus 13 Exposure apparatus 14 Developing apparatus 15 1st cleaning Device 21 Intermediate transfer belt 22 Rotating roller 23a to 23d Transfer member 24 Transfer bias power supply 25 Conveying belt 30 Impedance detecting means 31 Transfer bias voltage determining means 32 CPU
Ra to Rd Resistance S Recording medium

Claims (3)

回転駆動される中間転写ベルトを介して対向するように複数の感光体と複数の転写部材とが設けられ、複数の転写部材に一つの転写バイアス電源から転写バイアス電圧を印加させて、対応する各感光体の表面に形成されたトナー像を中間転写ベルトに順々に転写させる画像形成装置において、一つの感光体だけを中間転写ベルトに接触させて、この感光体と中間転写ベルトを介して対向する転写部材との間のインピーダンスを検出するインピーダンス検出手段と、このインピーダンス検出手段によって検出されたインピーダンスに基づいて上記の転写バイアス電源から上記の各転写部材に印加させる転写バイアス電圧を決定する転写バイアス電圧決定手段を設け、上記の中間転写ベルトを介して対向する各感光体と各転写部材との位置関係が一定でない場合に、上記の転写バイアス電圧決定手段に、各感光体と各転写部材との位置関係の情報を伝達して、上記の転写バイアス電源から各転写部材に出力する転写バイアス電圧を決定することを特徴とする画像形成装置。 A plurality of photoconductors and a plurality of transfer members are provided so as to face each other via a rotationally driven intermediate transfer belt, and a transfer bias voltage is applied to the plurality of transfer members from a single transfer bias power source, and each corresponding In an image forming apparatus that sequentially transfers toner images formed on the surface of a photoconductor onto an intermediate transfer belt, only one photoconductor is brought into contact with the intermediate transfer belt and is opposed to the photoconductor via the intermediate transfer belt. An impedance detection means for detecting an impedance between the transfer member and the transfer bias for determining a transfer bias voltage to be applied to each of the transfer members from the transfer bias power source based on the impedance detected by the impedance detection means a voltage determining means is provided, the positional relationship between the photosensitive member and the transfer member facing via the intermediate transfer belt of the If not constant, the transfer bias voltage determining means described above, by transmitting the information of the positional relationship between the photosensitive member and the transfer member, determining the transfer bias voltage output to each of the transfer member from the transfer bias power supply An image forming apparatus. 回転駆動される搬送ベルトを介して対向するように複数の感光体と複数の転写部材とが設けられ、上記の搬送ベルトによって記録媒体を搬送させると共に、複数の転写部材に一つの転写バイアス電源から転写バイアス電圧を印加させて、対応する各感光体の表面に形成されたトナー像を上記の搬送ベルトによって搬送される記録媒体に順々に転写させる画像形成装置において、一つの感光体だけを搬送ベルトに接触させて、この感光体と搬送ベルトを介して対向する転写部材との間のインピーダンスを検出するインピーダンス検出手段と、このインピーダンス検出手段によって検出されたインピーダンスに基づいて上記の転写バイアス電源から上記の各転写部材に印加させる転写バイアス電圧を決定する転写バイアス電圧決定手段を設け、上記の搬送ベルトを介して対向する各感光体と各転写部材との位置関係が一定でない場合に、上記の転写バイアス電圧決定手段に、各感光体と各転写部材との位置関係の情報を伝達して、上記の転写バイアス電源から各転写部材に出力する転写バイアス電圧を決定することを特徴とする画像形成装置。 A plurality of photosensitive members and a plurality of transfer members are provided so as to face each other via a rotationally driven conveyance belt, and the recording medium is conveyed by the conveyance belt, and a plurality of transfer members are supplied with a single transfer bias power source. In an image forming apparatus that applies a transfer bias voltage to sequentially transfer toner images formed on the surface of each corresponding photosensitive member to a recording medium conveyed by the conveying belt, only one photosensitive member is conveyed. Impedance detection means for detecting an impedance between the photosensitive member and a transfer member opposed via the conveyor belt in contact with the belt, and the transfer bias power source based on the impedance detected by the impedance detection means It provided a transfer bias voltage determining means for determining the transfer bias voltage applied to each transfer member described above, the upper When the positional relationship between each photosensitive member and each transfer member facing each other via the conveyance belt is not constant, information on the positional relationship between each photosensitive member and each transfer member is transmitted to the transfer bias voltage determining means. And determining a transfer bias voltage output from the transfer bias power source to each transfer member . 請求項１又は請求項２に記載の画像形成装置において、上記の感光体として、表面に有機感光層が形成された感光体を用い、上記の転写バイアス電圧決定手段に、この感光体における有機感光層の層厚情報を伝達して、上記の転写バイアス電源から出力する転写バイアス電圧を決定することを特徴とする画像形成装置。 3. The image forming apparatus according to claim 1, wherein a photoconductor having an organic photoconductive layer formed on the surface is used as the photoconductor, and the organic photosensitivity in the photoconductor is used as the transfer bias voltage determining unit. An image forming apparatus , wherein layer thickness information of a layer is transmitted to determine a transfer bias voltage output from the transfer bias power source .
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