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JP2005194089A - Image forming apparatus - Google Patents

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JP2005194089A
JP2005194089A JP2004004630A JP2004004630A JP2005194089A JP 2005194089 A JP2005194089 A JP 2005194089A JP 2004004630 A JP2004004630 A JP 2004004630A JP 2004004630 A JP2004004630 A JP 2004004630A JP 2005194089 A JP2005194089 A JP 2005194089A
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recording paper
branching
stepping motor
image forming
forming apparatus
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JP4244191B2 (en
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Chikashi Tanabe
史 田鍋
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Ricoh Co Ltd
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Ricoh Co Ltd
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Abstract

【課題】 分岐装置の分岐爪切り換え精度を向上することによって、記録紙間隔を狭めて高い印刷生産性を達成する画像形成装置を提供する。
【解決手段】 複数の経路に分岐する記録紙搬送経路１５、１６を有する画像形成装置において、前記記録紙搬送経路１５、１６の分岐点で記録紙搬送方向を切り換える分岐手段９、１２と、この分岐手段９、１２が基点となる位置にあることを検知する位置検知手段２１と、前記分岐手段９、１２を制御するために駆動連結されたステッピングモータ２０とからなる。
【選択図】 図２PROBLEM TO BE SOLVED: To provide an image forming apparatus which achieves high printing productivity by narrowing a recording paper interval by improving the branching claw switching accuracy of a branching device.
In an image forming apparatus having recording paper transport paths 15 and 16 branched into a plurality of paths, branch means 9 and 12 for switching a recording paper transport direction at a branch point of the recording paper transport paths 15 and 16; It comprises a position detecting means 21 for detecting that the branching means 9 and 12 are at the base position, and a stepping motor 20 that is drivingly connected to control the branching means 9 and 12.
[Selection] Figure 2

Description

本発明は、分岐装置を有する複写機、ファクシミリ等の画像形成装置に関するものである。   The present invention relates to an image forming apparatus such as a copying machine or a facsimile having a branching device.

従来の両面搬送手段を有する画像形成装置は、いずれの画像面にも画像を形成していない記録紙を画像形成部に搬送させ片面を画像形成してから両面搬送手段に案内する搬送動作と、一面に画像が形成されて両面搬送手段を通して記録紙を反転させて他面を画像形成して排紙トレイ側に案内する搬送動作を交互に行うノンスタックインターリーフ方式を採用するものが多かった（例えば特許文献１および２参照）。
特許第２８４９４８５号 特開平１０−１８１９７８号公報 A conventional image forming apparatus having a double-sided conveying unit conveys a recording sheet that does not form an image on any image surface to an image forming unit, forms one side of the image, and then guides the recording sheet to the double-sided conveying unit; Many have adopted a non-stack interleaf system in which an image is formed on one side, the recording paper is reversed through a double-sided conveyance means, the other side is imaged, and the conveyance operation is alternately guided to the discharge tray side ( For example, see Patent Documents 1 and 2.)
Japanese Patent No. 2849485 Japanese Patent Laid-Open No. 10-181978

上述したような画像形成装置における分岐装置は、記録紙と記録紙の間隔で一回ずつ分岐爪を切り換える必要があった。また、従来の分岐装置は分岐爪にソレノイドと戻しばねを組み合わせる構成であった。
しかしながら、ソレノイドは作動に伴う遅延時間が通常５０から１００ｍ秒程度ある。また、切り換え途中の動作位置は制御できないので、分岐爪の高精度な制御は不可能であった。
さらに、ソレノイドがオフするとき、戻しばねの戻し力のみに頼っているので、切り換え途中の分岐爪の高精度な位置制御は不可能であった。
そのため、従来機の分岐装置においては分岐爪の切り換え精度が悪いため記録紙と記録紙の紙間隔を広く取り分岐部のジャムを回避していた。したがって、紙間隔が広がることで印刷の生産性が低くなるという問題点があった。
そこで本発明の目的は、上述した実情を考慮してなされたもので、分岐装置の分岐爪切り換え精度を向上することによって、記録紙間隔を狭めて高い印刷生産性を達成する画像形成装置を提供することにある。 The branching device in the image forming apparatus as described above has to switch the branching claw once every time between recording sheets. Further, the conventional branching device has a structure in which a solenoid and a return spring are combined with a branching claw.
However, solenoids usually have a delay time associated with operation of about 50 to 100 milliseconds. Further, since the operation position during switching cannot be controlled, it is impossible to control the branching claw with high accuracy.
Furthermore, when the solenoid is turned off, only the return force of the return spring is relied on, so that it is impossible to control the position of the branching claw during switching with high accuracy.
For this reason, in the conventional branching device, the switching accuracy of the branching claw is poor, and therefore, the gap between the recording paper and the recording paper is widened to avoid the jamming of the branching portion. Therefore, there has been a problem that the productivity of printing is lowered due to an increase in the paper interval.
SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an image forming apparatus that achieves high printing productivity by narrowing the recording paper interval by improving the branching claw switching accuracy of the branching device in consideration of the above situation. There is to do.

上記の課題を解決するために、請求項１に記載の発明は、複数の経路に分岐する記録紙搬送経路を有する画像形成装置において、前記記録紙搬送経路の分岐点で記録紙搬送方向を切り換える分岐手段と、この分岐手段が基点となる位置にあることを検知する位置検知手段と、前記分岐手段を制御するために駆動連結されたステッピングモータとを備えた画像形成装置を特徴とする。
また、請求項２に記載の発明は、記録紙の先端が前記分岐手段の記録紙ガイド部に衝突するタイミングでは前記ステッピングモータの励磁電流値を上げておき、前記記録紙の先端が前記分岐手段の前記記録紙ガイド部を過ぎた時点で前記ステッピングモータの励磁電流値を下げる請求項１記載の画像形成装置を特徴とする。
また、請求項３に記載の発明は、通紙する記録紙が厚紙であることがプリント信号により判別された場合は、前記分岐手段と記録紙が接触している間は前記ステッピングモータの励磁電流を上げ続ける請求項２記載の画像形成装置を特徴とする。 In order to solve the above-described problem, the invention according to claim 1 is an image forming apparatus having a recording paper conveyance path that branches into a plurality of paths, and switches the recording paper conveyance direction at a branch point of the recording paper conveyance path. The image forming apparatus includes a branching unit, a position detection unit that detects that the branching unit is located at a base point, and a stepping motor that is drivingly connected to control the branching unit.
According to a second aspect of the present invention, the exciting current value of the stepping motor is increased at the timing when the leading edge of the recording paper collides with the recording paper guide portion of the branching means, and the leading edge of the recording paper is the branching means. The image forming apparatus according to claim 1, wherein an excitation current value of the stepping motor is lowered when the recording paper guide portion is passed.
According to a third aspect of the present invention, when it is determined from the print signal that the recording paper to be passed is a thick paper, the exciting current of the stepping motor is in contact with the branching means and the recording paper. The image forming apparatus according to claim 2, wherein

本発明によれば、ステッピングモータはステップ角度毎の位置制御および回転スピード制御が可能なので、分岐爪の切り換え精度が向上し、延いては、記録紙間隔を狭めた高い印刷生産性を達成できる。   According to the present invention, since the stepping motor can perform position control and rotation speed control for each step angle, the switching accuracy of the branching claw is improved, and as a result, high printing productivity with a narrow recording paper interval can be achieved.

以下、図面を参照して、本発明の実施形態を詳細に説明する。図１は本発明による両面搬送装置付きの画像形成装置の全体概略図である。図示の画像形成装置は、装置本体１内の給紙カセット２に積載された記録紙３を給紙コロ４により搬送する。
搬送された記録紙３はレジストローラ対５で画像と記録紙の位置合わせを行い、感光体６と転写ベルト７により記録紙３の片面に画像を形成し、その後、定着ローラ対８によって記録紙３の表面のトナー画像をこの記録紙３に溶融定着する。
その後、記録紙３の両面に印刷しない場合は分岐爪９により排紙ローラ対１０に記録紙３を搬送させて排紙トレイ１１に排出するが、記録紙３の両面に印刷する場合は分岐爪９、第２分岐爪１２により記録紙搬送経路を切り換えて、搬送ローラ１３、正逆転ローラ１４を経て記録紙３をスイッチバック搬送路１５に案内する。
スイッチバック搬送路１５に入った記録紙の後端が第２分岐爪１２の先端部を越えたら、正逆転ローラ１４を逆転させると共に第２分岐爪１２を作動させて記録紙を再搬送路１６に案内し、レジストローラ対５を経て記録紙３の逆面に印刷を行う。
上記のような搬送経路を使用することによって両面印刷が可能であるが、１枚毎に上記搬送プロセスを行うと両面印刷の生産性が極端に悪化する。そのため、再搬送路１６からの裏面印刷動作と、給紙カセット２からの表面印刷動作を交互に行う、いわゆるノンスタックインターリーフ方式を採用することで両面印刷の生産性を向上させている。
このインターリーフ方式を採用すると、分岐爪９は１枚毎に搬送路を切り換えることとなるが、さらに高い生産性を確保するためには、記録紙同士の紙間隔が短縮されても、その短い紙間隔の間で精度良く用紙を分岐できる装置が必要となる。 Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is an overall schematic view of an image forming apparatus with a duplex conveying device according to the present invention. The illustrated image forming apparatus conveys a recording sheet 3 loaded on a sheet feeding cassette 2 in the apparatus main body 1 by a sheet feeding roller 4.
The transported recording paper 3 is aligned with the registration roller pair 5, and an image is formed on one side of the recording paper 3 by the photoreceptor 6 and the transfer belt 7. Thereafter, the recording paper 3 is formed by the fixing roller pair 8. The toner image on the surface 3 is melt-fixed on the recording paper 3.
Thereafter, when printing is not performed on both sides of the recording paper 3, the recording paper 3 is conveyed to the paper discharge roller pair 10 by the branching claws 9 and discharged to the paper discharge tray 11. However, when printing is performed on both sides of the recording paper 3, the branching claws 9. The recording paper conveyance path is switched by the second branch claw 12, and the recording paper 3 is guided to the switchback conveyance path 15 through the conveyance roller 13 and the forward / reverse rotation roller 14.
When the trailing edge of the recording paper that has entered the switchback conveyance path 15 exceeds the leading edge of the second branch claw 12, the forward / reverse rotation roller 14 is reversed and the second branch claw 12 is operated to re-record the recording paper 16 Then, printing is performed on the reverse side of the recording paper 3 through the registration roller pair 5.
Double-sided printing is possible by using the above-described transport path. However, when the transport process is performed for each sheet, the productivity of double-sided printing is extremely deteriorated. For this reason, the productivity of double-sided printing is improved by adopting a so-called non-stack interleaf system in which the back surface printing operation from the re-conveying path 16 and the front surface printing operation from the paper feed cassette 2 are alternately performed.
When this interleaf method is adopted, the branching claw 9 switches the conveyance path for each sheet. However, in order to secure even higher productivity, even if the sheet interval between the recording sheets is shortened, the branching claw 9 is short. A device capable of accurately branching paper between the paper intervals is required.

図２は本発明の画像形成装置に使用する分岐装置を示す斜視図である。図２の斜視図においては説明をし易くするために、上ガイド板２２、排紙ローラ１０と搬送ローラ１３の上側のローラは省略している。
分岐爪９は軸９−２上に複数の爪部材９−１が配置された構成になっている。爪部材９−１の先端は左下ガイド板１８と右下ガイド板１９にあいた穴（凹形状でも可）１８−１、１９−１に嵌合可能であり、それによって記録紙の搬送方向を分岐する。
軸９−２には回転位置を検知するシャッタ部９−３が固定され、そのシャッタ部９−３のエッジをフォトセンサ２１で検知することにより分岐爪９が記録紙を排紙トレイ１１側に案内する第１姿勢を検知できる。
軸９−２にはプーリ９−４が固定されていて、タイミングベルト２３を介してステッピングモータ２０に駆動連結されている。分岐爪９はこのステッピングモータ２１の駆動力で動作している。 FIG. 2 is a perspective view showing a branching device used in the image forming apparatus of the present invention. In the perspective view of FIG. 2, the upper guide plate 22, the paper discharge roller 10, and the upper roller of the transport roller 13 are omitted for easy explanation.
The branch claw 9 has a configuration in which a plurality of claw members 9-1 are arranged on a shaft 9-2. The tip of the claw member 9-1 can be fitted into holes (can be concave) 18-1 and 19-1 in the lower left guide plate 18 and the lower right guide plate 19, thereby branching the recording paper conveyance direction. To do.
A shutter unit 9-3 for detecting the rotational position is fixed to the shaft 9-2. When the photosensor 21 detects the edge of the shutter unit 9-3, the branch claw 9 moves the recording paper to the discharge tray 11 side. The first posture to be guided can be detected.
A pulley 9-4 is fixed to the shaft 9-2 and is drivingly connected to the stepping motor 20 via the timing belt 23. The branching claw 9 is operated by the driving force of the stepping motor 21.

図３は分岐爪を初期設定する動作を説明するフローチャートである。印刷指令が入力されると、フォトセンサ２１の検知状態を確認し（Ｓ１）、オンならばオフになるまでステッピングモータ２０を逆転する（Ｓ２）。
但し、所定時間内にオフ検知しない場合（Ｓ５）は、部品の故障の可能性があるので装置を停止し、故障表示とする（Ｓ６）。無事にオフ検知となったらオン検知になるまでステッピングモータ２０を正転させる（Ｓ７）。
先ほどと同様に所定時間内にオン検知しない場合は部品の故障の可能性があるので装置を停止し、故障表示とする（Ｓ１１）。無事にオン検知となったらステッピングモータ２０を無回転状態にて励磁させ（Ｓ１２）、待機状態とする。もし、プリントジョブが片面印刷の場合、このまま印刷動作を始める。
プリントジョブが両面印刷ならば（Ｓ１３）、ステッピングモータ２０を所定パルス数逆転させ（Ｓ１４）、記録紙を両面搬送手段側に案内する第２姿勢まで駆動した後、停止し励磁させ（Ｓ１５）、待機状態とする。
この制御で印刷前の分岐爪９の位置がどこにあっても、精度良くシャッタ部９−３のエッジを検知することにより、基点である第１姿勢もしくは第１姿勢より所定のパルス分移動した第２姿勢を保持した状態で印刷待機できる。 FIG. 3 is a flowchart for explaining the operation of initially setting the branching claw. When a print command is input, the detection state of the photosensor 21 is confirmed (S1), and if it is on, the stepping motor 20 is reversed until it is turned off (S2).
However, if OFF detection is not performed within a predetermined time (S5), there is a possibility of component failure, so the device is stopped and a failure display is made (S6). If the off detection is successfully detected, the stepping motor 20 is rotated forward until the on detection is detected (S7).
Similarly to the previous case, if the on-state is not detected within a predetermined time, there is a possibility of a component failure, so the device is stopped and a failure display is made (S11). When the on-state is successfully detected, the stepping motor 20 is excited in the non-rotating state (S12) and is set in a standby state. If the print job is single-sided printing, the printing operation is started as it is.
If the print job is double-sided printing (S13), the stepping motor 20 is reversed by a predetermined number of pulses (S14), driven to the second posture for guiding the recording paper to the double-sided conveying means side, then stopped and excited (S15), Set to the standby state.
By this control, the edge of the shutter portion 9-3 is accurately detected wherever the position of the branching claw 9 before printing is, so that the first position or the first position that is the base point is moved by a predetermined pulse. It is possible to wait for printing while maintaining two postures.

図４は分岐装置の詳細断面図である。図４では分岐爪９が記録紙を排紙トレイ１１側にガイドする第１姿勢を示している。図５は図４の分岐装置の詳細断面図である。図５では記録紙を両面搬送手段側に案内する第２姿勢を示している。
図４および図５において、分岐爪９の第１姿勢と第２姿勢とのなす角をθ°、分岐爪９とガイド板２２のオーバーラップ量をＬ（ｍｍ）、用紙の線速をＶ（ｍｍ／秒）、記録紙と記録紙の紙間隔をｌｐ（ｍｍ）としている。
図４において先行の記録紙の後端が分岐爪９の先端位置に位置したときに、図示していないステッピングモータ２０を駆動開始する。分岐爪９の回転スピードをおよそＶ・θ／Ｌ（°／秒）となるようにステッピングモータ２０を駆動制御すれば、分岐爪９と先行の記録紙の後端が接触せずに切り換えが可能である。 FIG. 4 is a detailed sectional view of the branching device. FIG. 4 shows a first posture in which the branching claw 9 guides the recording paper to the discharge tray 11 side. FIG. 5 is a detailed sectional view of the branching device of FIG. FIG. 5 shows a second posture for guiding the recording paper to the double-sided conveying means side.
4 and 5, the angle between the first posture and the second posture of the branch claw 9 is θ °, the overlap amount of the branch claw 9 and the guide plate 22 is L (mm), and the linear velocity of the paper is V ( mm / second), and the interval between the recording paper and the recording paper is lp (mm).
In FIG. 4, when the trailing edge of the preceding recording sheet is located at the leading edge of the branching claw 9, the driving of the stepping motor 20 (not shown) is started. If the stepping motor 20 is driven and controlled so that the rotation speed of the branching claw 9 is approximately V · θ / L (° / second), the branching claw 9 and the trailing edge of the preceding recording paper can be switched without contact. It is.

図５は分岐爪９が第２姿勢になった瞬間の図である。図からも分かるように、スリップなどを考えずに理想値だけを考慮すると、記録紙と記録紙の紙間隔ｌｐ（ｍｍ）が分岐爪９とガイド板２２のオーバーラップ量Ｌ（ｍｍ）よりも大きければ記録紙の分岐は可能である。
なお、第２姿勢を検知する検知手段は不要であり、第１姿勢から所定のパルス数をステッピングモータ２０に入力することによって第２姿勢の位置決めを行う。装置全体の制御手段は画像形成装置本体に組み込まれている。
所定のパルス数とは分岐爪９の第１姿勢と第２姿勢とのなす角θ°をステッピングモータ２０の分解能角度および駆動部分の減速比で簡単に求めることができる。分岐点でもステッピングモータを使うことは可能である。
上記のような制御にてステッピングモータ２０を制御すると、このステッピングモータ２０は無回転状態でも励磁する必要があり、１００％の電流値が付与されてしまい、長い時間プリントが続くとステッピングモータ２０の温度がどんどん上昇してしまう。
そこで、記録紙から分岐爪９への負荷力がピークになるときだけ１００％電流値を付与し、その他のタイミングでは電流値を下げてステッピングモータ２０の温度上昇を抑える必要がある。
記録紙から分岐爪９への負荷力がピークになるときは記録紙の先端が分岐爪９の記録紙案内面に衝突するときであり、衝突が予想される時間帯のみステッピングモータ２０への励磁電流を１００％とする。
そのとき以外のタイミング、つまり分岐爪９の姿勢移動中や、記録紙の先端が分岐爪９を通り越した以降の時間は電流値を２０〜５０％下げる制御にしてステッピングモータ２０の温度上昇を抑制する。 FIG. 5 shows the moment when the branching claw 9 is in the second posture. As can be seen from the figure, when only the ideal value is considered without considering slip or the like, the sheet interval lp (mm) between the recording paper and the recording paper is larger than the overlap amount L (mm) between the branch claw 9 and the guide plate 22. If it is larger, the recording paper can be branched.
In addition, the detection means for detecting the second posture is not necessary, and the second posture is positioned by inputting a predetermined number of pulses from the first posture to the stepping motor 20. Control means for the entire apparatus is incorporated in the main body of the image forming apparatus.
With the predetermined number of pulses, the angle θ ° formed by the first posture and the second posture of the branching claw 9 can be easily obtained from the resolution angle of the stepping motor 20 and the reduction ratio of the drive portion. It is possible to use a stepping motor even at a branch point.
When the stepping motor 20 is controlled by the control as described above, the stepping motor 20 needs to be excited even in a non-rotating state, and a current value of 100% is applied. If printing is continued for a long time, the stepping motor 20 The temperature will continue to rise.
Therefore, it is necessary to give a 100% current value only when the load force from the recording paper to the branching claw 9 reaches a peak, and to reduce the current value at other timings to suppress the temperature rise of the stepping motor 20.
When the load force from the recording paper to the branching claw 9 reaches a peak, the leading edge of the recording paper collides with the recording paper guide surface of the branching claw 9, and the stepping motor 20 is excited only in a time zone where a collision is expected. The current is 100%.
At other times, that is, during the movement of the position of the branching claw 9 or the time after the leading edge of the recording paper passes over the branching claw 9, the current value is controlled to decrease by 20 to 50% to suppress the temperature rise of the stepping motor 20. To do.

しかしながら、上記のような電流値制御は普通紙、いわゆる坪量１５７ｇ／ｍ２未満の記録紙に最適な制御手段である。これ以上の重さの記録紙いわゆる厚紙は記録紙の先端が分岐爪９に衝突するときはもちろんのこと、記録紙が通過している最中に分岐爪９へ負荷を与える。
したがって、プリントジョブが厚紙指定のとき、分岐爪９と記録紙が接触している間は励磁電流を１００％とし、記録紙と接触していないときもしくは分岐爪９が回転駆動するときのみ電流値を２０〜５０％下げる制御とする。これにより、厚紙通紙途中での分岐爪９の姿勢がずれることなく良好な搬送性能を確保できる。
ステッピングモータ２０はステップ角度毎の位置制御および回転スピード制御が可能なので、分岐爪９の切り換え精度が向上し、延いては、記録紙間隔を狭めた高い印刷生産性を達成できる。
ホームポジションセンサは分岐爪９が記録紙を排紙トレイ１１側に案内する第１姿勢を検知できるので、ステッピングモータ２０の往復動作の基点が狂うことが無く、分岐爪９の切り換え精度が向上し、延いては、記録紙間隔を狭めた高い印刷生産性を達成できる。
制御手段はプリントジョブの内容を判断して両面ジョブと判断したら、分岐爪９を事前に両面搬送手段側に案内する第２姿勢に切り換えた位置で分岐爪９を待機することができるので、両面プリント１枚目の動作が速く行える。 However, the current value control as described above is optimal control means for plain paper, so-called recording paper having a basis weight of less than 157 g / m 2 . A so-called thick paper having a weight more than this applies a load to the branching claw 9 while the recording paper is passing, as well as when the leading edge of the recording paper collides with the branching claw 9.
Therefore, when the print job is designated as thick paper, the excitation current is set to 100% while the branching claw 9 and the recording paper are in contact, and the current value is only when the recording paper is not in contact or when the branching claw 9 is driven to rotate. Is controlled to lower by 20 to 50%. As a result, it is possible to ensure a good conveyance performance without shifting the posture of the branching claw 9 during the cardboard feeding.
Since the stepping motor 20 can perform position control and rotation speed control for each step angle, the switching accuracy of the branching claw 9 is improved, and as a result, high printing productivity with a narrow recording paper interval can be achieved.
Since the home position sensor can detect the first posture in which the branching claw 9 guides the recording paper to the paper discharge tray 11 side, the base point of the reciprocating operation of the stepping motor 20 does not go wrong, and the switching accuracy of the branching claw 9 is improved. As a result, it is possible to achieve high printing productivity by narrowing the recording paper interval.
When the control means determines the contents of the print job and determines that the job is a double-sided job, the branching claw 9 can wait in a position where the branching claw 9 is switched to the second posture in advance to guide the double-sided conveyance means. The first print can be performed quickly.

本発明によれば、画像形成装置は画像形成された記録紙を排出する排紙トレイ１１と、一面側に画像が形成された用紙を他面側に画像を形成させるために反転させて再度画像形成手段に搬送する両面搬送手段とを有し、記録紙を排紙トレイ１１側もしくは該両面搬送手段側へと搬送方向を切り換える分岐手段を有する。
また、画像形成装置は、分岐手段が同軸上に設けた複数の分岐爪９と、これらの分岐爪近傍のガイド板１８上にあいた分岐爪９がはまる穴と、分岐爪９に駆動連結されたステッピングモータ２０と、分岐爪９が記録紙を排紙トレイ１１側に案内する第１姿勢にあることを検知できるホームポジションセンサとを有する。
プリントジョブの信号を検知したら片面ジョブか両面ジョブかを判断し、両面ジョブと判別されたら、ステッピングモータ２０を所定のパルス数にわたって駆動して分岐爪９が第１姿勢から記録紙を両面搬送手段側に案内する第２姿勢に切り換えた位置でステッピングモータ２０を励磁して記録紙の到着を待機する制御手段を有している。
制御手段は記録紙の先端が分岐爪９の記録紙ガイド部に衝突するタイミングはステッピングモータ２０の励磁電流値を上げておくことができるので、記録紙衝突の負荷で分岐爪９のガイド位置がずれることによる記録紙ジャムを回避できる。
制御手段は記録紙の先端が分岐爪９の記録紙ガイド部を過ぎたらステッピングモータ２０の励磁電流値を下げることができるので、ステッピングモータ２０自体の発熱を低く抑えることができる。
制御手段は通紙する記録紙が厚紙であることがプリント信号により判別された場合は、分岐爪９と記録紙が接触している間はステッピングモータ２０の励磁電流を上げ続けることができるので、厚紙通紙による負荷に分岐爪９の位置保持力が確保でき、厚紙通紙時のジャムを回避できる。
制御手段は通紙する紙種に見合ったステッピングモータ２０の電流値を変化することができるので、省エネルギを達成できる。ステッピングモータで制御する分岐手段は分岐爪以外でもよい。 According to the present invention, the image forming apparatus reverses the paper discharge tray 11 for discharging the recording paper on which the image has been formed, and the paper on which the image is formed on one side to invert the image to form the image on the other side. A double-sided conveyance unit that conveys the recording sheet to the forming unit, and a branching unit that switches the conveyance direction of the recording paper to the discharge tray 11 side or the double-sided conveyance unit side.
The image forming apparatus is connected to the branching claws 9 by a plurality of branching claws 9 provided with branching means on the same axis, a hole in which the branching claws 9 on the guide plate 18 near the branching claws fit. It has a stepping motor 20 and a home position sensor that can detect that the branching claw 9 is in the first posture for guiding the recording paper to the discharge tray 11 side.
When a print job signal is detected, it is determined whether the job is a single-sided job or a double-sided job. Control means for exciting the stepping motor 20 and waiting for the arrival of the recording paper at the position switched to the second posture guided to the side.
The control means can raise the exciting current value of the stepping motor 20 at the timing when the leading edge of the recording paper collides with the recording paper guide portion of the branching claw 9, so that the guide position of the branching claw 9 is adjusted by the load of the recording paper. It is possible to avoid recording paper jam due to deviation.
Since the control means can lower the exciting current value of the stepping motor 20 when the leading edge of the recording paper passes the recording paper guide portion of the branching claw 9, it is possible to suppress the heat generation of the stepping motor 20 itself.
When it is determined from the print signal that the recording paper to be passed is a thick paper, the control means can continue to increase the excitation current of the stepping motor 20 while the branching claw 9 and the recording paper are in contact with each other. The position holding force of the branching claw 9 can be secured against the load caused by the thick paper passing, and the jam during the thick paper passing can be avoided.
Since the control means can change the current value of the stepping motor 20 corresponding to the type of paper to be passed, energy saving can be achieved. The branching means controlled by the stepping motor may be other than the branching claw.

本発明による両面搬送装置付きの画像形成装置の全体概略図である。1 is an overall schematic diagram of an image forming apparatus with a duplex conveying device according to the present invention. 本発明の画像形成装置に使用する分岐装置を示す斜視図である。It is a perspective view which shows the branch apparatus used for the image forming apparatus of this invention. 分岐爪を初期設定する動作を説明するフローチャートである。It is a flowchart explaining the operation | movement which initializes a branch nail | claw. 分岐装置の詳細断面図である。It is a detailed sectional view of a branch device. 図４の分岐装置の詳細断面図である。FIG. 5 is a detailed sectional view of the branching device of FIG. 4.

符号の説明Explanation of symbols

３ 記録紙
９ 分岐手段（分岐爪）
１２ 分岐手段（分岐爪）
１５ 記録紙搬送経路（スイッチバツク搬送経路）
１６ 記録紙搬送経路（再搬送経路）
２０ ステッピングモータ（制御手段）
２１ 位置検知手段（フォトセンサ） 3 Recording paper 9 Branching means (branching claw)
12 Branch means (branch claw)
15 Recording paper transport path (switchback transport path)
16 Recording paper transport path (re-transport path)
20 Stepping motor (control means)
21 Position detection means (photo sensor)

Claims (3)

複数の経路に分岐する記録紙搬送経路を有する画像形成装置において、前記記録紙搬送経路の分岐点で記録紙搬送方向を切り換える分岐手段と、この分岐手段が基点となる位置にあることを検知する位置検知手段と、前記分岐手段を制御するために駆動連結されたステッピングモータと、を備えたことを特徴とする画像形成装置。   In an image forming apparatus having a recording paper conveyance path that branches into a plurality of paths, a branching unit that switches a recording paper conveyance direction at a branching point of the recording paper conveyance path, and detecting that the branching unit is at a base point An image forming apparatus comprising: a position detecting unit; and a stepping motor that is drivingly connected to control the branching unit. 記録紙の先端が前記分岐手段の記録紙ガイド部に衝突するタイミングでは前記ステッピングモータの励磁電流値を上げておき、前記記録紙の先端が前記分岐手段の前記記録紙ガイド部を過ぎた時点で前記ステッピングモータの励磁電流値を下げることを特徴とする請求項１記載の画像形成装置。   At the timing when the leading edge of the recording paper collides with the recording paper guide portion of the branching means, the excitation current value of the stepping motor is increased, and when the leading edge of the recording paper passes the recording paper guide portion of the branching means. 2. The image forming apparatus according to claim 1, wherein an excitation current value of the stepping motor is lowered. 通紙する記録紙が厚紙であることがプリント信号により判別された場合は、前記分岐手段と記録紙が接触している間は前記ステッピングモータの励磁電流を上げ続けることを特徴とする請求項２記載の画像形成装置。   3. When the print signal determines that the recording paper to be passed is a thick paper, the exciting current of the stepping motor is continuously increased while the branching unit and the recording paper are in contact with each other. The image forming apparatus described.
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