JP2008286923A - Image forming apparatus - Google Patents

Image forming apparatus Download PDF

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JP2008286923A
JP2008286923A JP2007130392A JP2007130392A JP2008286923A JP 2008286923 A JP2008286923 A JP 2008286923A JP 2007130392 A JP2007130392 A JP 2007130392A JP 2007130392 A JP2007130392 A JP 2007130392A JP 2008286923 A JP2008286923 A JP 2008286923A
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transfer
image forming
transfer belt
forming apparatus
transfer member
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Masataka Yagi
昌隆 八木
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Konica Minolta Business Technologies Inc
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Konica Minolta Business Technologies Inc
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Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrophotographic image forming apparatus capable of reducing its cost and maintaining predetermined transfer performance against an environmental change or the like. <P>SOLUTION: The image forming apparatus has a plurality of image forming units including: a transfer belt 1 conveying a transfer medium in the direction of the arrow A while attracting it to its conveying face 1a; and photoreceptor drums 11 arranged opposite the transfer belt 1 so as to be parallel to one another in the direction of the arrow A. Transfer members 15 are disposed in firm contact with the internal face of the transfer belt 1 and downstream of the corresponding photoreceptor drums 11 in the direction of conveyance, and apply charges of opposite polarity to toner to the transfer medium via the transfer belt 1. Each of the transfer members 15 is made from a conductive material and is reciprocative so as to hold the distance L1, L2 between the corresponding photoreceptor drum 11 and the transfer member 15. When the environment has high humidity and regular paper is supplied, the transfer member 15 is set to the distance L1. When the environment has low humidity and cardboard paper is supplied, the transfer member 15 is set into the distance L2. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

本発明は、画像形成装置、特に、電子写真法によって転写媒体上にトナー画像を形成する画像形成装置に関する。   The present invention relates to an image forming apparatus, and more particularly to an image forming apparatus that forms a toner image on a transfer medium by electrophotography.

従来、複写機やプリンタなどの電子写真法によって紙などの転写媒体上にトナー画像を形成する画像形成装置においては、転写媒体を転写ベルトに吸着させて搬送しつつ、該転写媒体に転写ベルトを介してトナーとは逆極性の電荷を付与し、感光体上に形成されたトナー画像を転写媒体に転写する方式が知られている(例えば、特許文献1,2,3参照)。   2. Description of the Related Art Conventionally, in an image forming apparatus that forms a toner image on a transfer medium such as paper by electrophotography such as a copying machine or a printer, the transfer medium is attracted to the transfer belt and conveyed, and the transfer belt is attached to the transfer medium. There is known a method of applying a charge having a polarity opposite to that of the toner and transferring the toner image formed on the photosensitive member to a transfer medium (see, for example, Patent Documents 1, 2, and 3).

この種の転写方式においては、トナーとは逆極性の電荷を転写ベルトを介して転写媒体に付与する転写部材として、ゴムローラを用いるのが一般的である。しかし、ゴムローラは、金属シャフトに1×106オーム以上の抵抗値を有する発泡ウレタン製のローラを取り付けているため、高価につくという問題点を有していた。また、カラー画像を形成するタンデム方式では、複数の転写部材を設置しているが、転写部材それぞれに電気抵抗値にばらつきを有するため、それぞれの転写部材ごとに高圧電源を設けて印加電圧値を調整する必要があり、電源部のコストも上昇するという問題点を有していた。 In this type of transfer system, a rubber roller is generally used as a transfer member that applies a charge having a polarity opposite to that of toner to a transfer medium via a transfer belt. However, the rubber roller has a problem that it is expensive because a roller made of urethane foam having a resistance value of 1 × 10 6 ohms or more is attached to the metal shaft. In addition, in the tandem method for forming a color image, a plurality of transfer members are installed. However, since each transfer member has a variation in electric resistance value, a high voltage power source is provided for each transfer member to set an applied voltage value. It has to be adjusted, and the cost of the power supply unit also increases.

一方、半導電性の転写ベルトの電気抵抗を利用して転写部材から転写ベルトを介して転写バイアス電圧を印加する場合、転写部材は転写放電を安定させるために感光体と転写ベルトとのニップ部に対して転写ベルトの移動方向上流側近傍又は下流側近傍のいずれかに所定の距離を置いて配置していた。特許文献2,3に記載の転写装置のように、ニップ部と転写部材との間の距離を一定に設定すると、環境湿度の変化や転写媒体の厚さなどで電流値が異なり転写性能にばらつきを生じてしまう。例えば、高湿環境下での転写放電安定性から決めた距離では、低湿環境に変化すると、電流が流れすぎて転写性能が低下してしまう。逆の場合は電流量が少なくなって転写性能が低下してしまう。
特開平10−228186号公報 特開平11−249460号公報 特開平9−212001号公報
On the other hand, when a transfer bias voltage is applied from the transfer member via the transfer belt by utilizing the electrical resistance of the semiconductive transfer belt, the transfer member has a nip portion between the photoreceptor and the transfer belt to stabilize the transfer discharge. On the other hand, the transfer belt is disposed at a predetermined distance in the vicinity of the upstream side or the downstream side in the moving direction. If the distance between the nip part and the transfer member is set to a constant value as in the transfer devices described in Patent Documents 2 and 3, the current value varies depending on changes in the environmental humidity, the thickness of the transfer medium, etc., and the transfer performance varies. Will occur. For example, at a distance determined from the stability of transfer discharge in a high humidity environment, if the environment changes to a low humidity environment, current will flow too much and transfer performance will deteriorate. In the opposite case, the amount of current decreases and the transfer performance deteriorates.
JP-A-10-228186 JP-A-11-249460 JP 9-21001 A

そこで、本発明の目的は、低コスト化を達成するとともに、環境変化などに対して所定の転写性能を保持できる電子写真法による画像形成装置を提供することにある。   SUMMARY OF THE INVENTION An object of the present invention is to provide an image forming apparatus by electrophotography that can achieve cost reduction and can maintain a predetermined transfer performance against environmental changes.

前記目的を達成するため、本発明に係る画像形成装置は、
所定速度で回転駆動される半導電性の転写ベルトと、
前記転写ベルトの外側面に対向して配置された作像ユニットと、
前記作像ユニットに含まれる感光体と前記転写ベルトとのニップ部に対して転写ベルトの移動方向上流側近傍又は下流側近傍のいずれかに配置されて該転写ベルトの内側面に圧接し、トナーとは逆極性の電荷を転写ベルトを介して付与する導電性材料からなる転写部材と、
前記転写部材を前記転写ベルトの移動方向にほぼ沿って往復移動させる移動手段と、
少なくとも環境条件又は転写媒体の種類に応じて前記移動手段にて前記転写部材を移動させる制御手段と、
を備えたことを特徴とする。
In order to achieve the above object, an image forming apparatus according to the present invention includes:
A semiconductive transfer belt that is rotationally driven at a predetermined speed;
An image forming unit disposed to face the outer surface of the transfer belt;
A toner that is disposed in the vicinity of the upstream side or the downstream side of the transfer belt in the moving direction of the transfer belt with respect to the nip portion between the photoconductor included in the image forming unit and the transfer belt, and presses the inner surface of the transfer belt. A transfer member made of a conductive material that imparts a charge of opposite polarity to the transfer belt via a transfer belt;
Moving means for reciprocating the transfer member substantially along the moving direction of the transfer belt;
Control means for moving the transfer member by the moving means according to at least the environmental conditions or the type of transfer medium;
It is provided with.

本発明に係る画像形成装置において、転写部材は導電性材料からなるため、転写部材を例えば金属製ローラにて安価に製作できる。そして、少なくとも環境条件又は転写媒体の種類に応じて移動手段にて転写部材を転写ベルトの移動方向にほぼ沿って往復移動させるようにしたため、環境条件の変化などに対応した最適な転写電流を供給することができ、転写性能の低下を解消することができる。   In the image forming apparatus according to the present invention, since the transfer member is made of a conductive material, the transfer member can be manufactured at a low cost using, for example, a metal roller. Since the transfer member is reciprocated substantially along the moving direction of the transfer belt by the moving means according to at least the environmental conditions or the type of transfer medium, an optimum transfer current corresponding to changes in environmental conditions is supplied. And a decrease in transfer performance can be eliminated.

本発明に係る画像形成装置において、転写部材は、導電性金属材料からなるローラ又は導電性樹脂材料からなるローラであってもよく、あるいは、転写ベルトに接触する導電性フィルムであってもよい。   In the image forming apparatus according to the present invention, the transfer member may be a roller made of a conductive metal material or a roller made of a conductive resin material, or may be a conductive film in contact with the transfer belt.

また、本発明に係る画像形成装置は、各色のトナー画像を形成する複数の作像装置が転写ベルトの移動方向に沿って並置され、複数の転写部材が各作像ユニットに含まれる感光体に対向して配置されている、いわゆるタンデム方式でカラー画像を形成するように構成してもよい。この場合、転写ベルトはその外側面に転写媒体を吸着保持して搬送し、転写部材は転写ベルトを介して転写媒体に転写バイアス電圧を印加する。   In the image forming apparatus according to the present invention, a plurality of image forming apparatuses that form toner images of the respective colors are juxtaposed along the moving direction of the transfer belt, and a plurality of transfer members are provided on the photoconductor included in each image forming unit. You may comprise so that a color image may be formed in what is called a tandem system arrange | positioned facing. In this case, the transfer belt attracts and holds the transfer medium on its outer surface, and the transfer member applies a transfer bias voltage to the transfer medium via the transfer belt.

タンデム方式の画像形成装置にあっては、転写部材のそれぞれに転写バイアス電圧を印加する一つの高圧電源を備えていればよい。導電性材料かならなる転写部材は電気抵抗値はほぼ0であるため、個々の転写部材に対して転写バイアス電圧を微調整する必要はなく、転写部材のそれぞれに一つの高圧電源から転写バイアス電圧を印加すれば、電源部のコストを低減することができる。   In the tandem image forming apparatus, it is only necessary to have one high-voltage power supply for applying a transfer bias voltage to each of the transfer members. Since the transfer member made of a conductive material has an electric resistance value of almost zero, it is not necessary to finely adjust the transfer bias voltage for each transfer member. If is applied, the cost of the power supply unit can be reduced.

また、移動手段は、転写ベルトが感光体から離間する位置に転写部材を移動させるベルト接離手段を兼ねていてもよい。タンデム方式では、モノクロ画像形成時などでは黒色の画像を形成する作像ユニットのみを動作させる。この場合、転写ベルトを他の作像装置の感光体から離間させる接離手段が設置されており、移動手段がこの接離手段を兼ねることにより、構成が簡略化される。   The moving unit may also serve as a belt contacting / separating unit that moves the transfer member to a position where the transfer belt is separated from the photosensitive member. In the tandem system, only the image forming unit that forms a black image is operated when a monochrome image is formed. In this case, contact / separation means for separating the transfer belt from the photoconductor of another image forming apparatus is provided, and the configuration is simplified by the moving means also serving as the contact / separation means.

以下、本発明に係る画像形成装置の実施例について添付図面を参照して説明する。なお、各実施例において共通する部材には同じ符号を付し、重複する説明は省略する。   Embodiments of an image forming apparatus according to the present invention will be described below with reference to the accompanying drawings. In addition, the same code | symbol is attached | subjected to the member which is common in each Example, and the overlapping description is abbreviate | omitted.

(画像形成装置の基本構成、図1参照)
図1に本発明に係る画像形成装置の基本構成の要部を示す。この画像形成装置は、周知の電子写真法を用いたタンデム方式でかつ直接転写式によってカラーのトナー画像を形成するものである。具体的には、駆動ローラ2と従動ローラ3とに無端状に巻回保持された転写ベルト1と、4色(Y,M,C,K)のトナー画像を形成する作像ユニット10(10Y,10M,10C,10K)とを備えている。
(Basic configuration of image forming apparatus, see FIG. 1)
FIG. 1 shows a main part of a basic configuration of an image forming apparatus according to the present invention. This image forming apparatus forms a color toner image by a tandem method using a well-known electrophotographic method and by a direct transfer method. Specifically, the transfer belt 1 wound and held endlessly around the driving roller 2 and the driven roller 3 and an image forming unit 10 (10Y) that forms toner images of four colors (Y, M, C, K). , 10M, 10C, 10K).

転写ベルト1は駆動ローラ2によって矢印A方向に定速度で回転駆動され、紙などの転写媒体Mは矢印B方向から1枚ずつ供給され、吸着ローラ4から付与される電界にて下側面に静電的に吸着保持され、矢印A方向に搬送される。以下、この下側面を転写媒体Mに対する吸着搬送面1aと称する。また、転写ベルト1は従動ローラ3がコイルばね5にて弾性的に付勢されることで一定の張力を保持している。   The transfer belt 1 is driven to rotate at a constant speed in the direction of arrow A by a driving roller 2, and a transfer medium M such as paper is supplied one by one from the direction of arrow B and statically applied to the lower surface by an electric field applied from the suction roller 4. It is electrically attracted and held and conveyed in the direction of arrow A. Hereinafter, this lower side surface is referred to as a suction conveyance surface 1a for the transfer medium M. Further, the transfer belt 1 maintains a constant tension by the driven roller 3 being elastically biased by the coil spring 5.

各作像ユニット10は、それぞれ、感光体ドラム11や図示しない帯電器、現像器、画像露光ユニット(光走査ユニット)などを備え、各感光体ドラム11の表面にY,M,C,Kのトナー画像を形成する。トナー画像を形成するプロセスは周知であり、その説明は省略する。   Each image forming unit 10 includes a photosensitive drum 11, a charger, a developing device, an image exposure unit (optical scanning unit) (not shown), and the like, and Y, M, C, and K on the surface of each photosensitive drum 11. A toner image is formed. The process of forming a toner image is well known and will not be described.

転写ベルト1の吸着搬送面1aの内側には、各感光体ドラム11にほぼ対向する位置に転写部材15が弾性的に圧接されている。この転写部材15は、以下に詳述する構成からなる導電性材料からなり、感光体ドラム11と転写ベルト1とのニップ部に対して転写ベルト1の移動方向(矢印A方向)の下流側近傍に配置されている。各転写部材15に対しては、一つの高圧電源20により所定値の転写バイアス電圧が印加される。   On the inner side of the suction conveyance surface 1 a of the transfer belt 1, a transfer member 15 is elastically pressed to a position almost opposite to each photosensitive drum 11. The transfer member 15 is made of a conductive material having a configuration described in detail below, and is near the downstream side of the transfer belt 1 in the moving direction (arrow A direction) with respect to the nip portion between the photosensitive drum 11 and the transfer belt 1. Is arranged. A transfer bias voltage of a predetermined value is applied to each transfer member 15 by one high-voltage power supply 20.

各感光体ドラム11の表面に形成されたトナー画像は、転写ベルト1の吸着搬送面1aに吸着されて搬送される転写媒体に、転写部材15からトナーとは逆極性の電荷が転写ベルト1を介して付与されることにより転写される。このように、各感光体ドラム11上に形成されたトナー画像は転写媒体の表面に転写されて合成され、後段に設置された定着ユニット21により加熱定着される。   The toner image formed on the surface of each photosensitive drum 11 is transferred from the transfer member 15 to the transfer medium that is attracted to and transported by the suction transport surface 1a of the transfer belt 1. It is transcribed by being applied via. As described above, the toner images formed on the respective photoconductive drums 11 are transferred to the surface of the transfer medium, synthesized, and heated and fixed by the fixing unit 21 installed in the subsequent stage.

転写ベルト1はローラ2,3や転写部材15を含めて図示しないフレームに取り付けて一つのユニットとして構成され、この転写ユニットは矢印C方向に回動させることで、転写媒体の搬送経路を大きく上方に開放することができる。従って、搬送途中で転写媒体がジャムした場合、転写ユニットを矢印C方向に回動させることにより搬送経路を開放してジャムした転写媒体を容易に排除することができる。   The transfer belt 1 includes a roller 2 and 3 and a transfer member 15 and is attached to a frame (not shown) to form a unit. Can be opened. Therefore, when the transfer medium is jammed during conveyance, the jammed transfer medium can be easily removed by opening the conveyance path by rotating the transfer unit in the direction of arrow C.

転写部材15は、導電性材料からなり、例えば以下に説明するように金属製ローラなどで構成すれば安価に製作できる。また、転写部材15の電気抵抗値はほぼ0であるため、それぞれの転写部材15に対して転写バイアス電圧を微調整する必要はなく、一つの高圧電源20から一定値の電圧を印加すればよく、電源部のコストを低減できる。   The transfer member 15 is made of a conductive material, and can be manufactured at low cost if it is made of, for example, a metal roller as described below. Further, since the electric resistance value of the transfer member 15 is almost zero, it is not necessary to finely adjust the transfer bias voltage for each transfer member 15, and a constant voltage may be applied from one high-voltage power supply 20. The cost of the power supply unit can be reduced.

(転写部材の具体例、図2〜図5参照)
図2に転写部材の第1例を示す。この転写部材は、金属製のシャフト16をそのまま転写ローラとして構成したもので、極めて安価に製作できる。金属材料としては、ステンレス、アルミニウムが適している。直径8mm程度の細い中実シャフトで構成するのが、強度的にもコスト的にも好ましい。金属製のパイプとすれば軽量化を図ることができる。
(Specific examples of transfer member, see FIGS. 2 to 5)
FIG. 2 shows a first example of the transfer member. This transfer member is constructed by using the metal shaft 16 as a transfer roller as it is, and can be manufactured at a very low cost. As the metal material, stainless steel and aluminum are suitable. A thin solid shaft having a diameter of about 8 mm is preferable in terms of strength and cost. If the pipe is made of metal, the weight can be reduced.

なお、細い転写ローラでは、転写ベルト1が転写ローラに巻きかかる部分で転写ベルトにクリープが生じ、転写不良(画像ノイズ)を引き起こす可能性がある。しかし、図3及び図4に示す大径の転写ローラを使用すれば、このような不具合が発生するおそれを回避できる。   In the case of a thin transfer roller, creep may occur in the transfer belt at a portion where the transfer belt 1 is wound around the transfer roller, which may cause transfer failure (image noise). However, if the large-diameter transfer roller shown in FIGS. 3 and 4 is used, it is possible to avoid such a problem.

図3に示す転写部材の第2例は、金属製のパイプ17aの両端に金属製のフランジ17bを取り付けたもので、パイプ17aの直径は12mm以上である。また、図4に示す転写部材の第3例は、導電性ポリアセタールなどからなる複数の導電性樹脂スリーブ18aを金属製のシャフト18bに被せてローラ体としたもので、スリーブ18aの直径は12mm以上である。導電性樹脂スリーブ18aの電気抵抗値が1kΩ以下であれば、ローラ体を構成するそれぞれのスリーブ相互の抵抗のばらつきを無視でき、さらに、各感光体ドラム11に対向して配置されたそれぞれのローラ体相互の抵抗のばらつきを無視でき、一つの高圧電源20から一定値の電圧を印加することで、所定の電荷を転写媒体に付与できる。   The second example of the transfer member shown in FIG. 3 is obtained by attaching metal flanges 17b to both ends of a metal pipe 17a, and the diameter of the pipe 17a is 12 mm or more. A third example of the transfer member shown in FIG. 4 is a roller body in which a plurality of conductive resin sleeves 18a made of conductive polyacetal or the like are covered with a metal shaft 18b, and the diameter of the sleeve 18a is 12 mm or more. It is. If the electrical resistance value of the conductive resin sleeve 18a is 1 kΩ or less, variation in resistance between the sleeves constituting the roller body can be ignored, and each roller disposed opposite to each photosensitive drum 11 can be ignored. Variations in resistance between bodies can be ignored, and a predetermined charge can be applied to the transfer medium by applying a constant voltage from one high-voltage power supply 20.

図5に転写部材の第4例を備えた画像形成装置を示す。図5に示す転写部材は導電性フィルム19を用いたものである。例えば、表面抵抗率が約100Ωのフッ素系樹脂又はポリアミド系樹脂からなる。この導電性フィルム19の先端部を感光体ドラム11と転写ベルト1とのニップ部から矢印Aで示す搬送方向下流側で転写ベルト1の内側面に押し当てる。これにて転写ベルト1を撓ませ、転写ベルト1を感光体ドラム11に対して周方向に1〜2mm程度接触させる。   FIG. 5 shows an image forming apparatus provided with a fourth example of a transfer member. The transfer member shown in FIG. 5 uses a conductive film 19. For example, it is made of a fluorine resin or a polyamide resin having a surface resistivity of about 100Ω. The leading end portion of the conductive film 19 is pressed against the inner surface of the transfer belt 1 on the downstream side in the conveying direction indicated by the arrow A from the nip portion between the photosensitive drum 11 and the transfer belt 1. Thus, the transfer belt 1 is bent, and the transfer belt 1 is brought into contact with the photosensitive drum 11 in the circumferential direction by about 1 to 2 mm.

なお、フッ素系樹脂などの導電性フィルム19は、厚さ100μm程度であり、剛性が低い。それゆえ、転写ベルト1を撓ませて必要なニップ幅を得るには、フィルム19をポリフェニレンサルファイド樹脂などでバックアップすることが必要となる。   Note that the conductive film 19 such as a fluorine-based resin has a thickness of about 100 μm and low rigidity. Therefore, in order to obtain the required nip width by bending the transfer belt 1, it is necessary to back up the film 19 with polyphenylene sulfide resin or the like.

(転写部材の配置とその移動、図6参照)
ところで、前述した導電性材料からなる転写部材15は、それ自体が電気抵抗が小さな値であるため、半導電性の転写ベルト1自体の電気抵抗成分(表面抵抗率約1×108〜1×1010Ω)を利用して転写電界を形成する必要がある。具体的には、転写部材15を感光体ドラム11と転写ベルト1とのニップ部に対して2〜6mm程度搬送方向下流側に配置し、その距離に相当する転写ベルト1の電気抵抗を利用することになる。
(Arrangement and transfer of transfer member, see FIG. 6)
Incidentally, since the transfer member 15 made of the conductive material described above has a small electric resistance, the electric resistance component (surface resistivity of about 1 × 10 8 to 1 ×) of the semiconductive transfer belt 1 itself. It is necessary to form a transfer electric field using 10 10 Ω). Specifically, the transfer member 15 is disposed about 2 to 6 mm downstream in the conveyance direction with respect to the nip portion between the photosensitive drum 11 and the transfer belt 1, and the electric resistance of the transfer belt 1 corresponding to the distance is used. It will be.

なお、転写部材15は感光体ドラム11と転写ベルト1とのニップ部に対して2〜6mm程度搬送方向上流側に配置してもよい。但し、転写部材15を上流側に配置すると、トナー画像の転写前に放電が生じやすいため、十分な転写性能を発揮できない場合がある。   Note that the transfer member 15 may be disposed on the upstream side in the transport direction by about 2 to 6 mm with respect to the nip portion between the photosensitive drum 11 and the transfer belt 1. However, if the transfer member 15 is arranged on the upstream side, electric discharge is likely to occur before the transfer of the toner image, so that there are cases where sufficient transfer performance cannot be exhibited.

以上のごとく、導電性材料からなる転写部材15を用いた場合、図6(A),(B)に示すように、感光体ドラム11と転写ベルト1のニップ部から転写部材15と転写ベルト1のニップ部までの距離L1,L2に応じて前記高圧電源20から印加される転写バイアス電圧によって転写媒体に流れる転写電流が変化することになる。   As described above, when the transfer member 15 made of a conductive material is used, as shown in FIGS. 6A and 6B, the transfer member 15 and the transfer belt 1 from the nip portion between the photosensitive drum 11 and the transfer belt 1 are used. The transfer current flowing through the transfer medium is changed by the transfer bias voltage applied from the high-voltage power supply 20 in accordance with the distances L1 and L2 to the nip portion.

一方、同じ距離L1,L2であっても、湿度85%などの高湿環境にあると転写電流が多く流れ、湿度15%などの低湿環境にあると転写電流が少なくなる。仮に、高湿環境下での転写放電安定性から距離L1が最適であると決めた場合、低湿環境に変化すると、同じ距離L1では電流が流れすぎて転写性能が低下してしまう。そこで、低湿環境に変化した場合、転写部材15を搬送方向Aの上流側に若干移動させて距離L2に補正することにする。これにて、低湿環境においても、良好な転写性能を保持することができる。   On the other hand, even if the distances L1 and L2 are the same, a large transfer current flows in a high humidity environment such as a humidity of 85%, and a transfer current decreases in a low humidity environment such as a humidity of 15%. If it is determined that the distance L1 is optimal from the stability of transfer discharge in a high humidity environment, if the distance L1 is changed to a low humidity environment, current flows too much at the same distance L1 and transfer performance deteriorates. Therefore, when the environment changes to a low humidity environment, the transfer member 15 is slightly moved to the upstream side in the transport direction A to correct the distance L2. Thus, good transfer performance can be maintained even in a low humidity environment.

なお、転写ベルト1が湿度だけではなく温度で電気抵抗が変化するものである場合、温度変化を考慮して距離L1,L2を補正することが好ましい。具体的には、イオン導電性のベルトは、低温(10℃以下)で高抵抗になる傾向にあり、高温(30℃以上)で低抵抗になる傾向がある。   When the transfer belt 1 has an electrical resistance that changes not only with humidity but also with temperature, it is preferable to correct the distances L1 and L2 in consideration of temperature changes. Specifically, an ion conductive belt tends to have a high resistance at a low temperature (10 ° C. or lower) and tends to have a low resistance at a high temperature (30 ° C. or higher).

また、転写電流は転写媒体の種類によっても変化する。例えば、厚紙は普通紙に対して転写電流が流れやすい。それゆえ、厚紙が供給される場合には前記距離L1を短くすることが好ましい。環境湿度と転写媒体の種類を勘案し、以下に説明する第1例及び第2例では、高湿環境でかつ普通紙が供給されることを想定して最適な転写電流が得られるように距離L1を設定した。一方、低湿環境でかつ厚紙が供給される場合には転写部材15を移動させて距離L2に変更する。   Also, the transfer current varies depending on the type of transfer medium. For example, a transfer current is more likely to flow with thick paper than with plain paper. Therefore, when the thick paper is supplied, it is preferable to shorten the distance L1. In consideration of the environmental humidity and the type of transfer medium, in the first and second examples described below, the distance is set so that an optimum transfer current can be obtained assuming that plain paper is supplied in a high humidity environment. L1 was set. On the other hand, when thick paper is supplied in a low humidity environment, the transfer member 15 is moved to change the distance L2.

(移動手段の第1例、図7参照)
図7に転写部材15の移動手段の第1例を示す。なお、図7では、一つの作像ユニットに対する転写部材15の移動手段30を示しているが、他の作像ユニットに対する転写部材15にも同様の移動手段30が設けられている。
(Refer to FIG. 7 as a first example of moving means)
FIG. 7 shows a first example of moving means for the transfer member 15. 7 shows the moving means 30 of the transfer member 15 with respect to one image forming unit, the similar moving means 30 is also provided in the transfer member 15 with respect to other image forming units.

この移動手段30は、ピン32を支点として回動自在に設けたレバー31の下部に転写部材15を装着したもので、レバー31の上部はコイルばね33にて矢印D方向に弾性的に付勢され、スライダ35の凹部36の内壁面36aに当接している。スライダ35の一端はコイルばね37にて矢印D方向に弾性的に付勢され、他端にカム38の外周面が当接している。また、カム38はその支軸39を支点としてモータ40により回転駆動される。   This moving means 30 has a transfer member 15 attached to a lower portion of a lever 31 that is rotatably provided with a pin 32 as a fulcrum. The upper portion of the lever 31 is elastically biased in the direction of arrow D by a coil spring 33. In addition, the slider 35 is in contact with the inner wall surface 36 a of the recess 36. One end of the slider 35 is elastically biased in the direction of arrow D by a coil spring 37, and the outer peripheral surface of the cam 38 is in contact with the other end. The cam 38 is rotationally driven by a motor 40 with the support shaft 39 as a fulcrum.

モータ40は制御部41によって制御される。制御部41には、図示しないセンサから環境湿度情報が入力されるとともに、供給される転写媒体の種類、即ち、普通紙、厚紙(ハガキ、封筒などを含む)が入力される。   The motor 40 is controlled by the control unit 41. The controller 41 receives environmental humidity information from a sensor (not shown) and also inputs the type of transfer medium to be supplied, that is, plain paper and cardboard (including postcards, envelopes, and the like).

以上の構成において、カム38の小径部がスライダ35の他端に当接しているとき、スライダ35はコイルばね37のばね力にて矢印D方向に移動するとともに、レバー31の上部がコイルばね33のばね力にて内壁面36aに押圧され、レバー31はピン32を支点として反時計回り方向に回動する。これにて、転写部材15は図6(A)に示した距離L1に設定される。   In the above configuration, when the small diameter portion of the cam 38 is in contact with the other end of the slider 35, the slider 35 is moved in the direction of arrow D by the spring force of the coil spring 37, and the upper portion of the lever 31 is the coil spring 33. The spring 31 is pressed against the inner wall surface 36a, and the lever 31 rotates counterclockwise with the pin 32 as a fulcrum. Thereby, the transfer member 15 is set to the distance L1 shown in FIG.

一方、制御部41は、環境湿度情報が低湿に変化したこと、かつ、転写媒体として厚紙が供給される場合は、モータ40を駆動してカム38を180°回転させる。これにて、カム38の大径部がスライダ35の他端に当接し、スライダ35がコイルばね37のばね力に抗して矢印Dとは逆方向に移動するとともに、内壁面36aがレバー31の上部を同方向に移動させる。これにて、レバー31がピン32を支点として時計回り方向に回動し、転写部材15は図6(B)に示した距離L2に設定される。   On the other hand, the control unit 41 drives the motor 40 to rotate the cam 38 by 180 ° when the environmental humidity information has changed to low humidity and when thick paper is supplied as the transfer medium. As a result, the large diameter portion of the cam 38 abuts against the other end of the slider 35, the slider 35 moves in the direction opposite to the arrow D against the spring force of the coil spring 37, and the inner wall surface 36 a moves to the lever 31. Move the top of in the same direction. As a result, the lever 31 rotates clockwise with the pin 32 as a fulcrum, and the transfer member 15 is set to the distance L2 shown in FIG. 6B.

なお、カム38の回転角度を制御することにより、転写部材15の移動量を複数段階に調整することも可能である。また、レバー31の回動範囲を反時計回り方向に広げることにより、転写部材15による転写ベルト1への押圧を解除して転写ベルト1を感光体ドラム11から離間させるベルト接離手段を兼ねることもできる。   It should be noted that the movement amount of the transfer member 15 can be adjusted in a plurality of stages by controlling the rotation angle of the cam 38. Further, by expanding the rotation range of the lever 31 in the counterclockwise direction, it also serves as a belt contacting / separating means for releasing the pressure on the transfer belt 1 by the transfer member 15 and separating the transfer belt 1 from the photosensitive drum 11. You can also.

(移動手段の第2例、図8参照)
図8に転写部材15の移動手段の第2例を示す。なお、図8では、一つの作像ユニットに対する転写部材15の移動手段45を示しているが、他の作像ユニットに対する転写部材15にも同様の移動手段45が設けられている。
(Refer to the second example of moving means, FIG. 8)
FIG. 8 shows a second example of moving means for the transfer member 15. 8 shows the moving means 45 of the transfer member 15 with respect to one image forming unit, the same moving means 45 is also provided in the transfer member 15 with respect to other image forming units.

この移動手段45は、転写部材15の支軸22をガイド46の傾斜面46a,46b上に転動自在に載置し、コイルばね47にて弾性的に下方に押圧し、該支軸22をスライダ48の規制面48aに当接させたものである。スライダ48の一端はコイルばね49にて矢印E方向に弾性的に付勢され、他端にカム50の外周面が当接している。また、カム50はその支軸51を支点としてモータ40により回転駆動される。モータ40は制御部41によって制御され、制御部41の構成、動作は前記第1例で説明したとおりである。   The moving means 45 places the support shaft 22 of the transfer member 15 on the inclined surfaces 46a and 46b of the guide 46 so as to be freely rollable, and elastically presses the support shaft 22 downward by a coil spring 47. This is in contact with the regulating surface 48 a of the slider 48. One end of the slider 48 is elastically biased in the direction of arrow E by a coil spring 49, and the outer peripheral surface of the cam 50 is in contact with the other end. The cam 50 is rotationally driven by the motor 40 with the support shaft 51 as a fulcrum. The motor 40 is controlled by the control unit 41, and the configuration and operation of the control unit 41 are as described in the first example.

以上の構成において、カム50の小径部がスライダ45の他端に当接しているとき、スライダ48はコイルばね49のばね力にて矢印E方向に移動するとともに、支軸22がコイルばね47のばね力にて規制面48aに押圧されてガイド46の傾斜面46aの下部に位置する。これにて、転写部材15は図6(A)に示した距離L1に設定される。   In the above configuration, when the small diameter portion of the cam 50 is in contact with the other end of the slider 45, the slider 48 moves in the direction of arrow E by the spring force of the coil spring 49, and the support shaft 22 moves to the coil spring 47. It is pressed by the restricting surface 48 a by the spring force and is positioned below the inclined surface 46 a of the guide 46. Thereby, the transfer member 15 is set to the distance L1 shown in FIG.

一方、制御部41は、環境湿度情報が低湿に変化したこと、かつ、転写媒体として厚紙が供給される場合は、モータ40を駆動してカム50をほぼ90°回転させる。これにて、カム50の腹部がスライダ48の他端に当接し、スライダ48がコイルばね49のばね力に抗して矢印Eとは逆方向に移動するとともに、規制面48aが支軸22を同方向に移動させる。支軸22は傾斜面46aに沿って若干上動し、転写部材15は図6(B)に示した距離L2に設定される。   On the other hand, the control unit 41 drives the motor 40 to rotate the cam 50 by approximately 90 ° when the environmental humidity information has changed to low humidity and when thick paper is supplied as a transfer medium. As a result, the abdomen of the cam 50 abuts against the other end of the slider 48, the slider 48 moves in the direction opposite to the arrow E against the spring force of the coil spring 49, and the regulating surface 48 a moves the support shaft 22. Move in the same direction. The support shaft 22 slightly moves along the inclined surface 46a, and the transfer member 15 is set to the distance L2 shown in FIG.

傾斜面46aの傾斜角度を転写ベルト1が感光体ドラム11に巻き架かる角度と一致させることにより、転写部材15が距離L1,L2に往復移動した場合であっても、転写ベルト1の感光体ドラム11に対する巻き架かり量を一定に保つことができる。   By making the inclination angle of the inclined surface 46a coincide with the angle at which the transfer belt 1 is wound around the photosensitive drum 11, even if the transfer member 15 is reciprocated to the distances L1 and L2, the photosensitive drum of the transfer belt 1 is used. 11 can be kept constant.

さらに、カム50を90°回転させると(図8に示す状態からは180°回転させると)、カム50の大径部がスライダ48の他端に当接し、スライダ48が矢印Eとは逆方向に最大距離移動する。これにて、支軸22は傾斜面46bに乗り上げ、転写部材15による転写ベルト1への押圧が解除され、転写ベルト1が感光体ドラム11から離間する。即ち、本第2例はベルト接離手段を兼ねるように構成されている。   Further, when the cam 50 is rotated 90 ° (180 ° from the state shown in FIG. 8), the large diameter portion of the cam 50 contacts the other end of the slider 48, and the slider 48 is in the direction opposite to the arrow E. Move the maximum distance to. As a result, the support shaft 22 rides on the inclined surface 46 b, the pressure on the transfer belt 1 by the transfer member 15 is released, and the transfer belt 1 is separated from the photosensitive drum 11. That is, the second example is configured to also serve as a belt contacting / separating means.

(他の実施例)
なお、本発明に係る画像形成装置は、前記実施例に限定されるものではなく、その要旨の範囲内で種々に変更することができる。
(Other examples)
The image forming apparatus according to the present invention is not limited to the above-described embodiment, and can be variously modified within the scope of the gist thereof.

例えば、本発明は、トナー画像を転写ベルト上に1次転写して合成した後、転写媒体上に2次転写する間接転写式の1次転写部に適用することも可能である。また、単一の作像ユニットを備えたモノクロ画像形成用の装置にも適用することができる。あるいは、転写媒体の吸着面が下方を向いている形式のみならず、上方を向いている形式であってもよい。   For example, the present invention can also be applied to an indirect transfer type primary transfer portion in which a toner image is primarily transferred and synthesized on a transfer belt and then secondarily transferred onto a transfer medium. The present invention can also be applied to a monochrome image forming apparatus having a single image forming unit. Alternatively, not only the type in which the adsorption surface of the transfer medium faces downward but also the type in which the suction surface faces upward may be used.

また、前記実施例では、転写部材を環境湿度や転写媒体の種類に応じて2位置に移動可能に設置したが、3以上の複数位置に移動可能に設置してもよい。   Moreover, in the said Example, although the transfer member was installed so that a movement to two positions was carried out according to environmental humidity or the kind of transfer medium, you may install so that a movement to three or more multiple positions is possible.

本発明に係る画像形成装置の基本構成を示す概略構成図である。1 is a schematic configuration diagram illustrating a basic configuration of an image forming apparatus according to the present invention. 転写部材の第1例を示す正面図である。It is a front view which shows the 1st example of a transfer member. 転写部材の第2例を示す断面図である。It is sectional drawing which shows the 2nd example of a transfer member. 転写部材の第3例を示す断面図である。It is sectional drawing which shows the 3rd example of a transfer member. 転写部材の第4例を備えた画像形成装置を示す概略構成図である。It is a schematic block diagram which shows the image forming apparatus provided with the 4th example of the transfer member. 転写部材の移動態様を示す説明図である。It is explanatory drawing which shows the movement aspect of a transfer member. 転写部材移動手段の第1例を示す概略構成図である。It is a schematic block diagram which shows the 1st example of a transfer member moving means. 転写部材移動手段の第2例を示す概略構成図である。It is a schematic block diagram which shows the 2nd example of a transfer member moving means.

符号の説明Explanation of symbols

1…転写ベルト
10(10Y,10M,10C,10K)…作像ユニット
11…感光体ドラム
15…転写部材
20…高圧電源
30,45…移動手段
41…制御部
DESCRIPTION OF SYMBOLS 1 ... Transfer belt 10 (10Y, 10M, 10C, 10K) ... Image forming unit 11 ... Photoconductor drum 15 ... Transfer member 20 ... High voltage power supply 30, 45 ... Moving means 41 ... Control part

Claims (7)

所定速度で回転駆動される半導電性の転写ベルトと、
前記転写ベルトの外側面に対向して配置された作像ユニットと、
前記作像ユニットに含まれる感光体と前記転写ベルトとのニップ部に対して転写ベルトの移動方向上流側近傍又は下流側近傍のいずれかに配置されて該転写ベルトの内側面に圧接し、トナーとは逆極性の電荷を転写ベルトを介して付与する導電性材料からなる転写部材と、
前記転写部材を前記転写ベルトの移動方向にほぼ沿って往復移動させる移動手段と、
少なくとも環境条件又は転写媒体の種類に応じて前記移動手段にて前記転写部材を移動させる制御手段と、
を備えたことを特徴とする画像形成装置。
A semiconductive transfer belt that is rotationally driven at a predetermined speed;
An image forming unit disposed to face the outer surface of the transfer belt;
A toner that is disposed in the vicinity of the upstream side or the downstream side of the transfer belt in the moving direction of the transfer belt with respect to the nip portion between the photoconductor included in the image forming unit and the transfer belt, and presses the inner surface of the transfer belt. A transfer member made of a conductive material that imparts a charge of opposite polarity to the transfer belt via a transfer belt;
Moving means for reciprocating the transfer member substantially along the moving direction of the transfer belt;
Control means for moving the transfer member by the moving means according to at least the environmental conditions or the type of transfer medium;
An image forming apparatus comprising:
前記転写部材は、前記転写ベルトに接触するローラを含み、該ローラは導電性金属材料又は導電性樹脂材料からなること、を特徴とする請求項1に記載の画像形成装置。   The image forming apparatus according to claim 1, wherein the transfer member includes a roller in contact with the transfer belt, and the roller is made of a conductive metal material or a conductive resin material. 前記転写部材は、前記転写ベルトに接触する導電性フィルムを含むこと、を特徴とする請求項1に記載の画像形成装置。   The image forming apparatus according to claim 1, wherein the transfer member includes a conductive film that contacts the transfer belt. 各色のトナー画像を形成する複数の作像装置が前記転写ベルトの移動方向に沿って並置され、
複数の転写部材が各作像ユニットに含まれる感光体に対向して配置されていること、
を特徴とする請求項1ないし請求項3のいずれかに記載の画像形成装置。
A plurality of image forming apparatuses that form toner images of the respective colors are juxtaposed along the moving direction of the transfer belt,
A plurality of transfer members are arranged to face the photoconductor included in each image forming unit;
The image forming apparatus according to claim 1, wherein the image forming apparatus is an image forming apparatus.
前記転写ベルトはその外側面に転写媒体を吸着保持して搬送し、
前記転写部材は前記転写ベルトを介して前記転写媒体に転写バイアス電圧を印加すること、
を特徴とする請求項4に記載の画像形成装置。
The transfer belt sucks and holds the transfer medium on its outer surface, and conveys it,
The transfer member applies a transfer bias voltage to the transfer medium via the transfer belt;
The image forming apparatus according to claim 4.
前記転写部材のそれぞれに転写バイアス電圧を印加する一つの高圧電源を備えていることを特徴とする請求項4又は請求項5に記載の画像形成装置。   6. The image forming apparatus according to claim 4, further comprising one high-voltage power supply that applies a transfer bias voltage to each of the transfer members. 前記移動手段は、前記転写ベルトが前記感光体から離間する位置に前記転写部材を移動させるベルト接離手段を兼ねていることを特徴とする請求項4ないし請求項6のいずれかに記載の画像形成装置。   7. The image according to claim 4, wherein the moving unit also serves as a belt contacting / separating unit that moves the transfer member to a position where the transfer belt is separated from the photosensitive member. Forming equipment.
JP2007130392A 2007-05-16 2007-05-16 Image forming apparatus Pending JP2008286923A (en)

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Application Number Priority Date Filing Date Title
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