JP4079300B2

JP4079300B2 - Surface potential sensor and electrophotographic developing apparatus

Info

Publication number: JP4079300B2
Application number: JP2000005098A
Authority: JP
Inventors: 高志浦野; 隆山本
Original assignee: TDK Corp
Current assignee: TDK Corp
Priority date: 2000-01-13
Filing date: 2000-01-13
Publication date: 2008-04-23
Anticipated expiration: 2020-01-13
Also published as: JP2001194402A

Description

【０００１】
【発明の属する技術分野】
本発明は、表面電位センサ及びこの表面電位センサを組み込んだ電子写真現像装置に関する。
【０００２】
【従来の技術】
電子写真現像装置は複写機やプリンタ等の現像装置として、従来より実用に供せられているが、昨今のカラー化の進展に伴い、事務機分野のみならず、家庭用としても急速に普及しつつある。
【０００３】
電子写真現像装置は静電現象を利用した現像装置であって、感光体上に帯電潜像を形成してトナーを付着させ、このトナーを紙その他の媒体に転写して可視像を得る現像方式である。高品位な可視像を得るためには、感光体の表面電位を高精度で制御することが重要であり、このため、感光体の表面電位を非接触で検知することが必要となる。このことは、電子写真現像装置のカラー化に伴い、益々重要な課題となっている。更に、カラー現像装置では、分解した色毎に感光体の表面電位を検知することが必要である。このため、高速現像を要求される装置には、各色毎の感光体ドラムに対応して、マゼンタ、イエロー、シアン及びブラック用の少なくとも４個のセンサが必要で、しかも相互間に特性ばらつきの少ないセンサが求められている。
【０００４】
感光体の表面電位を非接触で検知する方法として、被測定電位面に対向して検知電極を配置し、被測定電位面と検知電極との対向面積、あるいは被測定電位面と検知電極との間の距離を周期的に変化させて、検知電極に誘導される電荷の周期的な変動を交流信号に変換して出力する表面電位センサが知られている。
【０００５】
実開平７−１８２７８号公報に開示された表面電位センサはこのような表面電位センサであって、被測定電位面と検知電極との対向面積、あるいは被測定電位面と検知電極との間の距離を周期的に変化させるために振動部材を用いる。振動部材は恒弾性金属板を用い、二本のアームを備えた音叉型に形成され、二本のアームの基部寄りに圧電振動子を取り付け振動させる。
【０００６】
このうち、対向面積を可変する方式では、検知電極が取り付けられた基板と、振動部材とを基体で支持する。振動部材は振動端となる二本のアームの先端にチョッピング部を設け、このチョッピング部を被測定電位面と検知電極との間に配置し、チョッピング部を被測定電位面と水平方向に振動させる。検知電極は被測定電位面との対向面積が周期的に変化するため、周期的に変化する誘導電荷を発生する。一般的にアームの振動周波数は７００Ｈｚ、振幅はアームの先端で数１０μｍから１００μｍ程度である。
【０００７】
このような従来の表面電位センサは、コスト及び、製造の容易さから、ガラスエポキシ等の樹脂を主体とした基材に導体パターンを形成したプリント基板を用い、検知電極を導電性接着材で前記導体パターンに接着し、電気的、機械的に接続していた。また、その接続部の周辺には、検知電極取り付け工程での位置決めを容易にするとともに、基板の耐湿性を向上させ、長期間にわたり特性の安定化を図るために、シリコーン樹脂やエポキシ等の樹脂コーティング層を施していた。
【０００８】
このような、樹脂を多用した従来の表面電位センサは、機械的な衝撃を受けると、出力特性が容易に変動してしまうという欠点を有していた。例えば、表面電位センサを数１０ｃｍの高さから落下させたり、物にぶつけたりするだけで、出力特性が変動してしまう。この種の表面電位センサは、複写機やプリンタに多く用いられることから、その製造工程のみならず、保守、点検作業においても、取り扱いに細心の注意が必要であり、電子写真現像装置の性能や、信頼性に影響を与えることから、機械的な衝撃による出力特性変動の防止策が望まれていた。
【０００９】
しかしながら、機械的な衝撃による出力特性の変動は、数時間ないし数日間放置すると、復帰するものが多々あり、その原因究明が極めて困難であった。
【００１０】
【発明が解決しようとする課題】
本発明の課題は、機械的な衝撃が加わっても、出力特性の変動が生じにくく、ばらつきが少ない、特性の安定した表面電位センサを提供することである。
【００１１】
本発明のもう一つの課題は、取り扱いが容易な表面電位センサを提供することである。
【００１２】
本発明の更にもう一つの課題は、取り扱いが容易で、信頼性の高い電子写真現像装置を提供することである。
【００１３】
【課題を解決するための手段】
上述した課題を解決するため、本発明に係る表面電位センサは、基体と、振動部材と、検知電極取り付け基板と、検知電極とを含む。
【００１４】
前記基体は、振動部材支持部と、検知電極取り付け基板支持部とを含む。前記振動部材は、少なくとも一本のアームと、圧電振動子とを含む。前記アームは、弾性金属体で構成され、固定部とチョッピング部とを含み、前記固定部により前記振動部材支持部に取り付けられている。前記圧電振動子は、前記アームに取り付けられている。
【００１５】
前記検知電極取り付け基板は、無機材料で構成され、表面に導体パターンを有し、前記基体の前記検知電極取り付け基板支持部に取り付けられている。
【００１６】
前記検知電極は、金属材料で構成され、前記チョッピング部に対応する位置において、金属間結合により、前記導体パターンに電気的、機械的に接合されている。
【００１７】
上述した本発明に係る表面電位センサにおいて、圧電振動子の振動により、振動部材のアームが振動して振動端に設けられたチョッピング部を被測定電位面と水平方向に振動させる。
【００１８】
チョッピング部は被測定電位面と検知電極との間の電気力線をチョッピングするとともに、被測定電位面と検知電極との対向面積を周期的に変化させる。このため、被測定電位面と検知電極との間の静電結合が周期的に変化し、検知電極は被測定電位面の電位に比例した静電誘導を交番的に発生させる。
【００１９】
上述した構成は、従来より知られている表面電位センサでも採用されていた構成である。本発明の特徴は、検知電極取り付け基板が無機材料で構成され、表面に導体パターンを有しており、検知電極が、金属間結合により、導体パターンに電気的、機械的に接合されていることにある。
【００２０】
樹脂を多用した従来の表面電位センサは、機械的な衝撃を受けると、出力特性が容易に変動してしまうという問題点があったことは、既に述べた通りである。本発明者等は、その原因究明に取り組み、機械的な衝撃による出力特性の変動の原因は、衝撃による摩擦帯電にあると推定するに至った。即ち、表面電位センサに機械的な衝撃が加わると、特に、検知電極取付け基板と検知電極との接合部に微少な変位が生じる。
【００２１】
樹脂を多用した従来の表面電位センサでは、検知電極取付け基板と検知電極との接合部において、この変位による摩擦や周辺の空気との摩擦により、帯電電荷が蓄積される。この帯電電荷は検知電極に検知され、検知信号に重畳するため、センサ出力を変動させると推定される。表面電位センサに上述した帯電電荷を生じた場合、例えば、被測定電位面の電位が０ボルトのとき、検知電極の測定電位が０ボルトであっても、検知電極の周辺がマイナスに帯電していると、表面電位センサには、あたかも、測定電位面がプラスであるかのような出力を生じる。
【００２２】
本発明では、検知電極取付け基板を無機材料で構成するとともに、電検知電極を、金属間結合により、検知電極取付け基板の導体パターンに電気的、機械的に接合したので、表面電位センサが機械的な衝撃を受けても、摩擦による帯電電荷が生じにくい。このため、出力特性の変動が生じにくくなると共に、ばらつきが少なくなり、特性が安定する。また、製造工程及びその後の運搬や保守点検時においても、取り扱いが容易である。
【００２３】
本発明の表面電位センサは、検知電極取り付け基板の材料としてアルミナを用い、はんだ付により検知電極を接合できる。アルミナやはんだ付けは電子部品の製造に通常用いる材料、工法であり、材料の入手性、組立ての容易性の面で工業上有益である。
【００２４】
検知電極取り付け基板の検知電極取り付け部周辺にはガラスコーティング層を形成することができる。このようにすれば、検知電極の取り付け工程での位置決めが容易であり、また、検知電極取り付け基板の耐湿性が向上し、信頼性が向上する。
【００２５】
本発明の表面電位センサは、検知窓を有するシールドカバーでシールドすることができる。シールドカバーの検知窓と検知電極取り付け基板との対向領域内に非有機物を介在させる（有機物を介在させない）ように構成すれば、出力特性の変動を更に低減することができる。
【００２６】
本発明は、更に、上述の表面電位センサを用いた電子写真現像装置についても開示する。
【００２７】
本発明の他の目的、構成及び利点については、添付図面を参照して、更に詳しく説明する。図面は単なる例示に過ぎない。
【００２８】
【発明の実施の形態】
図１は本発明の表面電位センサの一実施例を示す分解斜視図である。図２は図１に示した本発明の表面電位センサの断面図である。図３は図１に示した本発明の表面電位センサに用いる検知電極とその取り付け基板の斜視図である。図４は図３の４ー４線に沿った拡大断面図である。図５は図１に示した本発明の表面電位センサの底板部を除いた部分底面図である。
【００２９】
図示された表面電位センサは、検知電極１と、振動部材２と、検知電極取り付け基板３と、中継基板４と、配線６１、６２、６３と、シールドカバー７と、底板８と、基体９とを含む。
【００３０】
検知電極１は、方形の平面状電極面と、三本の足を含み、金属板材を打ち抜いて、足となる部分を直角に折り曲げて構成され、後述する検知電極取り付け基板３に取り付けられる。平面状電極面が電位測定面となる。検知電極１の足は本数を問わず、基板３に安定して取り付けられれば良く、また、足を用いず、検知電極取り付け基板３に直接取り付ける構成であってもよい。
【００３１】
振動部材２は、二本のアーム２１と、固定部２２と、チョッピング部２４とを含み、恒弾性金属板材を打ち抜き、折り曲げて音叉型に構成され、更に、圧電振動子２５を含んでいる。
【００３２】
二本のアーム２１は、それぞれ基部側が固定部２２と連続し、先端側が振動端とされ、振動端にチョッピング部２４が形成されている。固定部２２は二個の取り付け孔２３を有する。圧電振動子２５はその振動方向をアーム２１の振動方向と合わせ、二本のアーム２１のそれぞれ基部寄りに導電性接着材で貼着されている。
【００３３】
振動部材２は、必ずしも音叉型に構成する必要はなく、一本のアーム２１と、アーム２１に連続した固定部２２と、チョッピング部２４と、アーム２１の固定部２２寄りに貼着された圧電振動子２５とを含み、チョッピング部２４の振動により、検知電極と被測定電位面との対向面積が周期的に変化するよう構成してもよい。
【００３４】
検知電極取り付け基板３は無機材料で構成される。中継基板４は特に材質を問わず、無機材料あるいは有機材料を主体とするものであってもよい。本実施例では検知電極取り付け基板３及び中継基板４の両者ともアルミナで構成されている。検知電極取り付け基板３は、一方の面に、検知電極１を電気的、機械的に接続する導体パターン３１を備え、更に、図３に示す如く、検知電極１の足と導体パターン３１との接合部３６を除くその周辺にガラスコーティング層３５が形成されている。
【００３５】
検知電極１は、その足を利用して、上述の如く構成された検知電極取り付け基板３の導体パターン３１に、金属間結合３７により、電気的、機械的に接合される。接合手段は、金や、はんだ等の金属ボールやバンプ等を用いた超音波接合やダイボンディング、クリームはんだやその他のはんだを用いたはんだ付け等、最終的に有機物が介在しない金属間結合による接合手段であれば手段を問わない。本実施例では、後述するインピーダンス変換回路を構成する部品と同一工程で接合できるよう、はんだ付けにより接合される。
【００３６】
検知電極取り付け基板３は他方の面に、インピーダンス変換回路５を構成する回路部品５１が取り付けられる導体パターンや印刷抵抗パターン、信号出力用導体ランド３２（図５参照）、グランドパターン３３等を備え、更に、両面の導体パターンを接続する貫通導体を備えている。これらの導体パターンは、例えば銀やパラジウムを主成分とする導体ペーストを基板とともに焼成するか、焼き付けることにより形成される。
【００３７】
インピーダンス変換回路は電界効果トランジスタや抵抗等の回路部品５１、印刷抵抗パターン等で構成され、検知電極取り付け基板３の他方の面の導体パターンに取り付けられ、貫通導体を介して、検知電極取り付け基板３の一方の面の導体パターン３１と接続されている。中継基板４は、圧電振動子駆動用配線６１と外部接続用駆動配線６２の接続を中継する基板であって、両配線を接続する導体パターン４１を備えている。
【００３８】
配線は、圧電振動子駆動用配線６１と、外部接続用駆動配線６２と、信号用配線６３とを含む。圧電振動子駆動用配線６１は圧電振動子２５に駆動電力を供給する配線であって、振動部材２の振動に対する負荷とならないように例えば１０μｍφ程度の極めて細いウレタン被覆線が用いられる。外部接続用駆動配線６２は中継基板４を介して圧電振動子駆動用配線６１と接続されるため、振動部材２の振動に対する負荷とならないので、例えば１ｍｍφ程度の比較的太い樹脂被覆線が用いられる。信号用配線６３はセンサ出力信号をセンサ外部に取り出すために設けられ、微弱なセンサ出力信号を外部ノイズから保護するため、本実施例ではシールド線が用いられる。
【００３９】
シールドカバー７はセンサ内部を保護し、外部ノイズを遮断する機能を備え、測定個所を特定するための検知窓７１と、基体９に固定するための取り付け片７２を備え、金属板材を打ち抜き、断面コ字状に折り曲げて形成される。
【００４０】
底板８は同様に、センサ内部を保護し、外部ノイズを遮断する機能を備え、金属板材を打ち抜き形成される。
【００４１】
基体９は、検知電極取り付け基板支持部９１と、振動部材支持部９２と、中継基板支持部９３と、シールドカバー支持部９６と、配線挿通孔９５とを含む。基体９は、振動部材を安定して動作させ、かつ、複雑な立体構造を可能とするため、例えば亜鉛合金のダイキャストで形成される。
【００４２】
検知電極取り付け基板支持部９１は、センサ長手方向において、振動部材支持部９２の一方側に連続して形成された方形の枠体９１１と、枠体９１１の内側に形成された段差部９１２とで構成され、図において、段差部９１２の上面で検知電極取り付け基板３を支持し、段差部９１２の下方に形成される空間を回路部品５１および信号用配線６３等の収容部９１３としている。
【００４３】
中継基板支持部９３は、センサ長手方向において、振動部材支持部９２の他方側に連続して形成された方形の枠体９３１と、図において、枠体９３１の内側の上下方向中間に形成された仕切９３２とで構成され、仕切９３２の上面で中継基板４を支持し、仕切９３２の下部に形成される空間を信号用配線６３の収容部９３３としている（図５参照）。収容部９３３は仕切９３２の下部から突出した信号配線分離体９３４を備えている。収容部９３３は収容部９１３と連続して形成される。
【００４４】
振動部材支持部９２は、検知電極取り付け基板支持部９１および中継基板支持部９３より上方に突出した台状に形成され、上面に形成された平面でなる振動部材受け部９２１と、平面から突出した二個の振動部材固定用突起９２２とを含む。
【００４５】
駆動用配線支持部９４は、振動部材支持部９２のセンサ長手方向側面に形成された段差部９４１で構成される。段差部９４１は、振動部材支持部９２側面の圧電振動子側の端面を駆動用配線支持部始端９４２としてセンサ長手方向に沿って形成される。駆動用配線支持部始端９４２は振動部材２が振動部材支持部９２に取り付けられたとき、その振動方向において、振動部材２より外側に位置している。
【００４６】
配線挿通孔９５は、センサ長手方向の中継基板支持部９３側の端面に外部接続用駆動配線６２と信号用配線６３に対し、それぞれ独立して設けられている。センサ長手方向の検知電極取付け基板支持部９１側の端面９１４は枠体９１１の一部が大きく立ち上がって、シールドカバー７が取り付けられたときセンサ端面を閉塞するよう構成されている。
【００４７】
シールドカバー支持部９６は基体９の長手方向の側面下部が膨出して形成された段部で構成され、膨出部が一部切欠かれ、取り付け片挿通溝９６１が形成されている。
【００４８】
このように構成された基体９には、検知電極１と、回路部品５１が取り付けられた検知電極取り付け基板３と、中継基板４と、振動部材２と、配線６１、６２、６３と、シールドカバー７と、底板８とが取り付けられる。
【００４９】
検知電極１と回路部品５１が取り付けられた検知電極取り付け基板３は、回路部品５１が収容部９１３に収容されるように、検知電極１を上側にして段差部９１２に載置され、接着材で段差部９１２に接着され基体９に固定される。
【００５０】
中継基板４は導体パターン４１を上側にして仕切９３２上に載置され、接着材で基体９に固定される。
【００５１】
振動部材２はチョッピング部２４が検知電極１の電極面（電位測定面）と対向するようにその固定部２２を振動部材受け部９２１に配置し、固定部２２に設けられた取り付け孔２３に突起９２２をはめ込み、突起９２２をかしめることにより取り付けられる。振動部材２の取り付けは、かしめ以外にねじ止めや接着により行ってもよいが、かしめによれば、ねじや接着材等の補助部材が不要であり、また、作業性も良く、更に、経時的なねじのゆるみや、接着材の劣化に起因するセンサ特性の変動を防止できる。
【００５２】
圧電振動子駆動用配線６１は、一端が圧電振動子に接続され、中間部が振動部材支持部９２側面に設けられた配線支持部９４に沿って引き回され、他端が中継基板４に形成された導体パターン４１の一端にはんだ付けされる。圧電振動子駆動用配線６１の一端と配線支持部始端９４２との間の配線は、圧電振動子駆動用配線６１の一端と配線支持部始端９４２とを結ぶ直線に略沿い、かつ、振動部材２が振動したときテンションが加わらないように配線される。
【００５３】
外部接続用駆動配線６２は、一端が中継基板４に形成された導体パターン４１の他端にはんだ付けされ、基体９に設けられた配線挿通孔９５を介して外部に導出される。
【００５４】
信号用配線６３は、基体９に設けられた配線挿通孔９５を介してセンサ外部から基体９の下部に設けられた収容部９１３、９３３（図５参照）に導かれ、収容部９３３において芯線部６３１とシールド被覆線部６３２とが分離され、信号線分離体９３４の一方の側に芯線部６３１が配置され、他方の側にシールド被覆線部６３２が配置される。芯線部６３１の先端は被覆が剥がされ、検知電極取り付け基板３の部品取り付け面側に形成された信号用導体ランド３２にはんだ付けされる。シールド被覆線部６３２はその先端が検知電極取付け基板３の他方の面に形成されたグランドパターン３３にはんだ付けされる。
【００５５】
上述の配線において、圧電振動子駆動用配線６１は、その中間部が振動部材支持部９２の側面に設けられた配線支持部９４に沿って引き回され、弾性接着材６５により、駆動用配線支持部９４に弾性をもって保持される。
【００５６】
このため、本実施例の表面電位センサは圧電振動子駆動用配線６１の引き回しにあたって、引き回し位置が特定されるので、作業性が良く、特性のばらつきを少なくする事ができる。また、圧電振動子駆動用配線６１は極めて細い絶縁被覆線が用いられ、振動部材支持部９２の側面に形成された配線支持部９４に弾性をもって保持されるため、振動部材２の振動に対する負荷とならず、振動部材２の振動により、圧電振動子駆動用配線６１と振動部材２あるいはシールドカバー７や基体９等のその他の金属部分と擦れ合い、絶縁被覆が削り取られ短絡状態に至ったり、断線する事が無い。更に、シールドカバー７を組み付ける際にも配線を噛んでしまったり、傷つけることが無い。
【００５７】
本実施例では、駆動用配線支持部始端９４２は振動部材２が振動部材支持部９２に取り付けられたとき、その振動方向において、振動部材２より外側に位置している。圧電振動子駆動用配線６１の一端と配線支持部始端９４２との間の配線は、圧電振動子駆動用配線６１の一端と配線支持部始端９４２とを結ぶ直線に略沿い、かつ、振動部材２が振動したときテンションが加わらないように配線される。この構成は、上述の振動部材２の振動に起因するショートや断線の発生を更に確実に防止する。
【００５８】
また更に、配線支持部始端９４２に振動部材方向に傾斜するテーパー部や面取り部を形成すれば、配線支持部始端９４２における配線の周囲が確実に弾性接着材６５で囲まれ、この部分での断線発生の防止効果を高めることが出来る。
【００５９】
駆動用配線支持部９４は段差部９４１で構成する以外に、例えば、断面Ｕ字状ないしＶ字状等の溝で構成することもできる。弾性接着材６５はこの溝を埋めるように注入される。
【００６０】
このように、駆動用配線支持部９４を溝状に形成すれば、配線の引き回し位置及び弾性接着材の注入位置がより正確に特定できる。このため、弾性接着材６５の使用量が少量となり、有機樹脂を主体とする弾性接着材６５が検知電極取り付け基板３上に広がったり、検知電極周辺に付着するのを防止できる。弾性接着材６５の種類は特に限定されないが、シリコーン系の絶縁性接着材が通常用いられる。
【００６１】
また更に、本実施例では圧電振動子駆動用配線６１の他端および外部接続用駆動配線６２の一端も同様の弾性接着材６５により、中継基板４の上面に弾性をもって保持される。このように、外部接続用駆動配線６２を中継基板４に接着すれば、電子写真現像装置へのセンサ取り付け作業時や、その他のセンサ取り扱い中に外部接続用駆動配線６２に加わるテンションによる断線事故を低減できる。
【００６２】
信号用配線６３はそのシールド被覆線部６３２が弾性導電性接着材６６により、基体９に弾性をもって固定されるとともに、電気的に接続される。また、シールド被覆線部６３２がはんだ付けされたグランドパターン３３も、同様に弾性導電性接着材６６により基体９に弾性をもって固定されるとともに、電気的に接続される。このため、シールド被覆線部６３２と、グランドパターン３３と、基体９とが同電位とされる。
【００６３】
弾性導電性接着材は接着材中に銀等の良導電性フィラーが混入され、粘度が２０Ｋ〜２５Ｋ（ＣＰＳ）程度に調整されたもので、種類は特に限定されないが、例えば、米国エポキシ・テクノロジー社製のエポテック（商標）がフレキシブル性、硬化時の残留応力吸収特性の面で適している。
【００６４】
上述の構成は、本発明の表面電位センサの基板材料として、アルミナを用いることを可能にした手段の一つであり、表面電位センサの温度変化に対する長期間の信頼性を高める。すなわち、本実施例において、検知電極取り付け基板３はアルミナで形成され、基体９は亜鉛合金のダイキャストで形成される。アルミナの線膨張係数は５×１０^-6／℃程度、ダイキャストに用いられる亜鉛合金のそれは３×１０^-5／℃程度であり、両者間には６倍程度の相違がある。検知電極取り付け基板３及び基体９は周囲の温度変動に応じて収縮、膨張を繰り返すが、弾性導電性接着材６６は線膨張係数の相違を吸収し、長期間にわたって検知電極取り付け基板３のグランドパターン３３と、シールド被覆線部６３２と、基体９との電気的接続を維持する。
【００６５】
検知電極１、検知電極取り付け基板３、中継基板４、振動部材２および配線６１、６２、６３とが取り付けられた基体９は、その上面側からシールドカバー７がかぶせられ、シールドカバー７の検知窓７１と検知電極１とが対向するように、シールドカバー７の縁辺７３をシールドカバー支持部９６で支持し、下面側からは、収容部９１３、９３３を閉塞するように底板８があてがわれる。
【００６６】
基体９とシールドカバー７と底板８とは、シールドカバー７の縁辺７３から下方に突出した取り付け片７２を取り付け片挿通溝９６１に挿通して底板面で折り曲げることにより一体化される。これにより、基体９とシールドカバー７と底板８とは、検知電極取り付け基板３のグランドパターン３３及びシールド被覆線部６３２とを含み、電気的に同電位に接続される。
【００６７】
このように構成された表面電位センサは、シールドカバー７の検知窓７１を被測定電位面に向けて取り付けることにより、検知電極１の電位測定面が振動部材２のチョッピング部２４を介して被測定電位面に対向して配置される。
【００６８】
外部接続用駆動配線６２から中継基板４および圧電振動子駆動用配線６１を介して駆動電力が供給されると圧電振動子２５が振動する。圧電振動子２５の振動により、振動部材２の二本のアーム２１が振動して振動端に設けられたチョッピング部２４を被測定電位面と水平方向に振動させる。
【００６９】
チョッピング部２４は被測定電位面と検知電極１との間の電気力線をチョッピングするとともに、被測定電位面と検知電極１との対向面積を周期的に変化させる。このため、被測定電位面と検知電極１との間の静電結合が周期的に変化し、検知電極１は被測定電位面の電位に比例した静電誘導を交番的に発生させる。インピーダンス変換回路は検知電極１で検知した交流信号をインピーダンス変換して信号用配線６３を介して出力する。
【００７０】
上述の実施例の如く構成された、本発明の表面電位センサは、検知電極取り付け基板が無機材料で構成され、検知電極が無機材料基板の表面に形成された導体パターンに、金属間結合により電気的、機械的に接合する。このため、検知電極周辺に有機物が介在しないので、表面電位センサに機械的な衝撃が加わっても摩擦による帯電が発生しにくい。このような理由により、本発明の表面電位センサは、機械的な衝撃が加わっても出力特性が変動しないと推定される。以下、この点について回路図を参照して説明する。
【００７１】
図６は本発明の表面電位センサの信号処理回路の一実施例を示す回路図である。本実施例の回路は、インピーダンス変換回路５と、直流カットコンデンサ５４と、増幅器５３とを含む。
【００７２】
インピーダンス変換回路５は検知電極取り付け基板の他方の面に構成され、例えば１００ＭΩ程度の高抵抗値の印刷抵抗ＲＧと、検知電極取り付け基板の他方の面に取り付けられた電界効果トランジスタ５２と、低抵抗値のチップ抵抗ＲＤ、ＲＳとを含む。抵抗ＲＧは、その一端が検知電極取り付け基板の貫通導体を介して検知電極１に接続されるとともに、電界効果トランジスタ５２のゲート５２Ｇに接続され、他端が接地される。電界効果トランジスタ５２のドレイン５２Ｄは直流カットコンデンサ５４を介して増幅器５３の入力端に接続されるとともに、抵抗ＲＤを介して直流電圧源ＶＤＤに接続される。電界効果トランジスタ５２のソース５２Ｓは抵抗ＲＳを介して接地される。Ａ１は感光ドラム等の被測定電位面である。
【００７３】
検知電極１はチョッピング部２４及びシールドカバー７の検知窓７１を介して被測定電位面Ａ１と対向して配置される。被測定電位面Ａ１と検知電極１とは空気を媒体とした静電結合Ｃ＝ε（ａ／Ｌ）を構成する。ここで、εは空気の誘電率、ａは被測定電位面Ａ１と検知電極１の電極面との対向面積、Ｌは被測定電位面Ａ１と検知電極１との距離である。
【００７４】
被測定電位面Ａ１と、検知電極１の電極面との対向面積ａは、チョッピング部２４の振動により周期的に変化する。このため、検知電極１には被測定電位面Ａ１の電位に対応し、周期的に変化する誘導電荷Ｑが発生する。誘導電荷Ｑは微少変位電流ｉ＝ｄＱ／ｄｔを抵抗ＲＧに供給するとともに、抵抗ＲＧにより電圧信号に変換され、電界効果トランジスタ５２のゲート５２Ｇに電圧信号として印加される。電界効果トランジスタ５２に印加された電圧信号は、ドレイン５２Ｄから直流カットコンデンサ５４を介して増幅器５３に入力され、増幅された正弦波状のセンサ出力信号に変換される。正弦波の１サイクルはチョッピング部２４の振動周期と一致する。
【００７５】
本発明の表面電位センサは、検知電極の周辺が摩擦帯電しにくいので、表面電位センサに機械的衝撃が加わっても微少変位電流に誤差は生じない。
【００７６】
このため、本実施例の表面電位センサにおいて、ｉ＝ｄＱ／ｄｔで与えられる微少変位電流は、被測定電位面Ａ１の電位が０ボルトのときｉ＝ｄＱ／ｄｔ＝０となる。
【００７７】
これに対し、従来の、樹脂を多用した表面電位センサは、機械的衝撃が加わると、摩擦により検知電極周辺の樹脂が帯電し｜Ｑ｜＞０の帯電電荷が生じる。このため、ｉ＝ｄＱ／ｄｔ≠０となり、微少変位電流が発生して測定誤差を生じる。
【００７８】
図７はこのような機械的衝撃が加わったときの表面電位センサの出力波形の比較図である。図７は、理想の表面電位センサと、樹脂を多用した従来型の表面電位センサと、本発明の表面電位センサとのそれぞれについて、被測定電位面Ａ１の電位が０Ｖのときと、−５００Ｖのときのそれぞれの出力波形を示している。
【００７９】
理想の表面電位センサの出力波形は被測定電位面の電位に比例した電圧Ｖｅを出力するが、従来型の表面電位センサでは、被測定電位面の電位が−５００Ｖのとき、検知電極１の周辺がプラスに帯電していると、検知電極と被測定電位面間の電位差が増大し、実線の如く電圧Ｖｅを大きく上回り、検知電極１の周辺がマイナスに帯電していると、逆に破線の如く電圧Ｖｅを大きく下回り、０Ｖ、−５００Ｖのいずれにおいても理想の表面電位センサの出力波形と比較して大きな誤差を有している。
【００８０】
これに対し、本発明の表面電位センサの出力波形は０Ｖ、−５００Ｖのいずれにおいても理想の表面電位センサの出力波形と極めて近似している。
【００８１】
図８〜図１０は従来型の表面電位センサと、本実施例の表面電位センサとの落下衝撃試験の結果を示すグラフである。落下衝撃試験は従来型の表面電位センサ（No.１ａ〜No.１５ａ）と、本実施例の表面電位センサ（No.１ｂ〜No.１５ｂ）とをそれぞれ１５個用意して行った。それぞれのセンサについて、被測定電位面の電位が０Ｖ、−５００Ｖ、−９００Ｖにおける出力電圧を落下直前に測定した。測定したセンサはそれぞれ５個づつの組みに分けられ、各組毎に３０ｃｍ、５０ｃｍ、７０ｃｍの高さから木製の机の上に落下させ、その直後に落下直前の測定と同様の測定を行った。図８は３０ｃｍの高さから落下させたときのデータを示している。図８（ａ）は従来型の表面電位センサのデータ、図８（ｂ）は本発明に係る実施例のデータである。
【００８２】
図９は５０ｃｍの高さから落下させたときのデータを示している。図９（ａ）は従来型の表面電位センサのデータ、図９（ｂ）は本発明に係る実施例のデータである。
【００８３】
図１０は７０ｃｍの高さから落下させたときのデータを示している。図１０（ａ）は従来型の表面電位センサのデータ、図１０（ｂ）は本発明に係る実施例のデータである。図８〜図１０のいずれにおいても、横軸が被測定電位面の電位を示し、縦軸が落下直前の測定結果と落下直後の測定結果の電圧変化量を示している。
【００８４】
図から判るように、従来型のセンサNo.１ａ〜１５ａは、被測定電位面の電位が０Ｖのときはいずれも、落下直前と落下直後の測定電位変化量に大きな変化はない。しかし、被測定電位面の電位が−５００Ｖ、−９００Ｖになると、３０ｃｍの高さから落下させたNo.１ａ〜No.５ａの組みでは、測定電位はわずかに変化（図８（ａ）参照）し、５０ｃｍの高さから落下させたNo.６ａ〜No.１０ａの組みでは０．２Ｖの変化量を越えるものが発生（図９（ａ）参照）し、７０ｃｍの高さから落下させたNo.１１ａ〜No.１５ａの組みでは０．４Ｖの変化量を越えるものが発生し、個々のセンサ間のばらつきも大きくなっている。
【００８５】
これに対し、本実施例の表面電位センサNo.１ｂ〜No.１５ｂは、図８（ｂ）、図９（ｂ）及び図１０（ｂ）に示す通り、いずれの高さにおいても、測定電位に変化量がほとんど発生せず、かつ、個々のセンサ間でのばらつきも極めて小さく、特性が安定している。
【００８６】
本発明に係る表面電位センサは電子写真現像装置の感光ドラム表面の電位を検出するセンサとして用いることもできるし、フィルムやその他の媒体の表面の電位を検出するセンサとしても用いることができる。
【００８７】
図１１は本発明の表面電位センサを用いた電子写真現像装置の感光ドラム周辺の概念図である。感光ドラムＡの周辺には、帯電器Ｂ、表面電位センサＣ、露光器Ｄ、トナータンクＥ、回転ローラＦ、及び、可視像が転写される紙等の媒体Ｇを含む。感光ドラムＡは、矢印方向に回転する。表面電位センサＣは被測定電位面である感光ドラムＡの表面に対向して配置される。帯電器Ｂは高電圧発生器Ｈから高電圧が印加され、コロナ放電によって、感光ドラムＡの表面を一様に帯電する。露光器Ｄは写真像に従い感光ドラムＡの表面を露光する。感光ドラムＡの表面は露光した部分が導電性となり、その露光量に応じて電荷が消失し写真像に対応した帯電潜像が形成される。感光ドラムＡはトナータンクＥからトナーの供給を受け、帯電潜像にトナーが付着する。
【００８８】
付着したトナーは、回転ローラＦにより、感光ドラムＡに接触して移送される紙その他の媒体Ｇに可視像として転写される。
【００８９】
上述の転写サイクルで、表面電位センサＣは適時感光ドラムＡの表面電位を検知し、その出力を信号処理装置Ｊを介して制御装置Ｋに送出する。
【００９０】
カラーの電子写真現像装置の場合、表面電位センサＣは少なくとも４個用いられ、それぞれの特性を揃える必要があり、保守、点検作業も頻繁に発生する。本発明の表面電位センサは特性のばらつきを低減でき、保守、点検作業時の取り扱いも容易なため、特にカラーの電子写真現像装置に用いて好適である。
【００９１】
また、電子写真現像装置は、その稼働時に表面電位センサの周囲温度が５０℃から６０℃程度迄上昇する。従って、電子写真現像装置の稼働、停止に伴い表面電位センサは温度サイクルが加えられる。本実施例に示した表面電位センサは温度変動に対する信頼性が高い。このため、本実施例の表面電位センサは温度変動が頻繁に発生する複写機やプリンタに用いて好適である。
【００９２】
以上、好ましい実施例を参照して本発明の内容を詳細に説明したが、本発明はこれらに限定されるものではなく、当業者であれば、その基本的技術思想及び教示に基づき、種々の変形例を想到できることは自明である。
【００９３】
【発明の効果】
以上述べたように、本発明によれば、次のような効果を得ることができる。
（ａ）機械的な衝撃が加わっても、出力特性の変動が生じにくく、ばらつきが少ない、特性の安定した表面電位センサを提供することができる。
（ｂ）取り扱いが容易な表面電位センサを提供することができる。
（ｃ）取り扱いが容易で、信頼性の高い電子写真現像装置を提供することができる。
【図面の簡単な説明】
【図１】本発明に係る表面電位センサの一実施例を示す分解斜視図である。
【図２】図１に示した表面電位センサの断面図である。
【図３】図１に示した表面電位センサに用いる検知電極とその取り付け基板の斜視図である。
【図４】図３の４ー４線に沿った拡大断面図である。
【図５】図１に示した表面電位センサの底板部を除いた部分底面図である。
【図６】本発明に係る表面電位センサの信号処理回路の一実施例を示す回路図である。
【図７】機械的衝撃が加わったときの表面電位センサの出力波形の比較図である。
【図８】従来型の表面電位センサを３０ｃｍの高さから落下させたときの落下衝撃試験の結果（図８（ａ））、及び、本発明に係る表面電位センサを３０ｃｍの高さから落下させたときの落下衝撃試験の結果（図８（ｂ））を示すグラフである。
【図９】従来型の表面電位センサを５０ｃｍの高さから落下させたときの落下衝撃試験の結果（図９（ａ））、及び、本発明に係る表面電位センサを５０ｃｍの高さから落下させたときの落下衝撃試験の結果（図９（ｂ））を示すグラフである。
【図１０】従来型の表面電位センサを７０ｃｍの高さから落下させたときの落下衝撃試験の結果（図９（ａ））、及び、本発明に係る表面電位センサを７０ｃｍの高さから落下させたときの落下衝撃試験の結果（図９（ｂ））を示すグラフである。
【図１１】本発明に係る表面電位センサを用いた電子写真現像装置の感光ドラム周辺の概念図である。
【符号の説明】
１検知電極
２振動部材
２１アーム
２２固定部
２５圧電振動子
３検知電極取り付け基板
３６接合部
９基体
９２振動部材支持部[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a surface potential sensor and an electrophotographic developing apparatus incorporating the surface potential sensor.
[0002]
[Prior art]
Electrophotographic developing devices have been put to practical use as developing devices such as copying machines and printers, but with the recent progress in colorization, they have rapidly spread not only in the office machine field but also for home use. It's getting on.
[0003]
An electrophotographic developing device is a developing device that uses an electrostatic phenomenon, and forms a charged latent image on a photosensitive member, attaches toner, and transfers the toner onto paper or other media to obtain a visible image. It is a method. In order to obtain a high-quality visible image, it is important to control the surface potential of the photoconductor with high accuracy. For this reason, it is necessary to detect the surface potential of the photoconductor in a non-contact manner. This has become an increasingly important issue with the colorization of electrophotographic developing devices. Further, in the color developing device, it is necessary to detect the surface potential of the photoreceptor for each separated color. For this reason, an apparatus that requires high-speed development requires at least four sensors for magenta, yellow, cyan, and black corresponding to the photosensitive drum for each color, and there is little variation in characteristics between them. A sensor is needed.
[0004]
As a method for detecting the surface potential of the photoconductor in a non-contact manner, a detection electrode is arranged opposite to the potential surface to be measured, and the area where the potential surface to be measured and the detection electrode are opposed to each other, or between the measurement potential surface and the detection electrode A surface potential sensor is known that periodically changes the distance between them and converts periodic fluctuations in the charge induced in the sensing electrode into an alternating current signal and outputs it.
[0005]
The surface potential sensor disclosed in Japanese Utility Model Laid-Open No. 7-18278 is such a surface potential sensor, and is a facing area between the measured potential surface and the detection electrode, or a distance between the measured potential surface and the detection electrode. A vibration member is used to change the frequency periodically. The vibration member uses a constant elastic metal plate and is formed in a tuning fork type having two arms, and a piezoelectric vibrator is attached and vibrated near the base of the two arms.
[0006]
Among these, in the method of changing the facing area, the substrate on which the detection electrode is attached and the vibration member are supported by the base. The vibration member is provided with a chopping portion at the tip of two arms serving as vibration ends, and this chopping portion is disposed between the measured potential surface and the detection electrode, and the chopping portion is vibrated in the horizontal direction with the measured potential surface. . The sensing electrode generates an inductive charge that changes periodically because the area facing the potential surface to be measured changes periodically. In general, the vibration frequency of the arm is 700 Hz, and the amplitude is about several tens to 100 μm at the tip of the arm.
[0007]
Such a conventional surface potential sensor uses a printed circuit board in which a conductor pattern is formed on a base material mainly made of resin such as glass epoxy, and the detection electrode is made of a conductive adhesive because of cost and ease of manufacture. It was bonded to the conductor pattern and connected electrically and mechanically. In addition, in order to facilitate positioning in the detection electrode mounting process, improve the moisture resistance of the substrate, and stabilize the characteristics over a long period of time, there is a resin such as a silicone resin or an epoxy around the connection part. A coating layer was applied.
[0008]
Such a conventional surface potential sensor using a large amount of resin has a drawback that output characteristics easily fluctuate when subjected to a mechanical impact. For example, output characteristics fluctuate simply by dropping the surface potential sensor from a height of several tens of centimeters or hitting it against an object. Since this type of surface potential sensor is often used in copiers and printers, it must be handled with great care not only in the manufacturing process but also in maintenance and inspection work. Therefore, since it affects the reliability, a countermeasure for preventing fluctuations in output characteristics due to mechanical shocks has been desired.
[0009]
However, the change in output characteristics due to mechanical shock often returns when left for several hours to several days, and it has been extremely difficult to investigate the cause.
[0010]
[Problems to be solved by the invention]
SUMMARY OF THE INVENTION An object of the present invention is to provide a surface potential sensor having stable characteristics, in which output characteristics do not easily change even when a mechanical shock is applied, and variations are small.
[0011]
Another object of the present invention is to provide a surface potential sensor that is easy to handle.
[0012]
Yet another object of the present invention is to provide an electrophotographic developing apparatus that is easy to handle and highly reliable.
[0013]
[Means for Solving the Problems]
In order to solve the above-described problem, a surface potential sensor according to the present invention includes a base, a vibrating member, a detection electrode mounting substrate, and a detection electrode.
[0014]
The base includes a vibrating member support and a detection electrode mounting substrate support. The vibration member includes at least one arm and a piezoelectric vibrator. The arm is made of an elastic metal body, includes a fixed portion and a chopping portion, and is attached to the vibration member support portion by the fixed portion. The piezoelectric vibrator is attached to the arm.
[0015]
The detection electrode mounting substrate is made of an inorganic material, has a conductor pattern on the surface, and is mounted on the detection electrode mounting substrate support portion of the base.
[0016]
The detection electrode is made of a metal material, and is electrically and mechanically joined to the conductor pattern by metal-to-metal bonding at a position corresponding to the chopping portion.
[0017]
In the above-described surface potential sensor according to the present invention, the arm of the vibration member vibrates due to the vibration of the piezoelectric vibrator, and the chopping portion provided at the vibration end is vibrated in the horizontal direction with the potential surface to be measured.
[0018]
The chopping unit chops electric lines of force between the measured potential surface and the detection electrode, and periodically changes the facing area between the measured potential surface and the detection electrode. For this reason, the electrostatic coupling between the measured potential surface and the detection electrode periodically changes, and the detection electrode alternately generates electrostatic induction proportional to the potential of the measured potential surface.
[0019]
The above-described configuration is a configuration that has been employed in conventionally known surface potential sensors. The feature of the present invention is that the detection electrode mounting substrate is made of an inorganic material, has a conductor pattern on the surface, and the detection electrode is electrically and mechanically joined to the conductor pattern by metal-to-metal bonding. It is in.
[0020]
As described above, the conventional surface potential sensor using a lot of resin has a problem that the output characteristics easily fluctuate when subjected to a mechanical shock. The inventors of the present invention have investigated the cause, and have come to estimate that the cause of fluctuation in output characteristics due to mechanical impact is frictional charging due to impact. That is, when a mechanical impact is applied to the surface potential sensor, in particular, a slight displacement occurs at the joint between the detection electrode mounting substrate and the detection electrode.
[0021]
In the conventional surface potential sensor using a lot of resin, charged charges are accumulated at the joint between the detection electrode mounting substrate and the detection electrode due to friction due to this displacement and friction with surrounding air. This charged charge is detected by the detection electrode and is superimposed on the detection signal, so that it is estimated that the sensor output fluctuates. When the above-described charged charge is generated in the surface potential sensor, for example, when the potential of the surface to be measured is 0 volt, the periphery of the detection electrode is negatively charged even if the measurement potential of the detection electrode is 0 volt. The surface potential sensor produces an output as if the measured potential surface is positive.
[0022]
In the present invention, the detection electrode mounting substrate is made of an inorganic material, and the electric detection electrode is electrically and mechanically joined to the conductor pattern of the detection electrode mounting substrate by metal-to-metal bonding. Even when subjected to a strong impact, charged charges due to friction are unlikely to occur. For this reason, fluctuations in output characteristics are less likely to occur, variations are reduced, and characteristics are stabilized. In addition, it is easy to handle during the manufacturing process and during subsequent transportation and maintenance.
[0023]
In the surface potential sensor of the present invention, alumina is used as the material of the detection electrode mounting substrate, and the detection electrodes can be joined by soldering. Alumina and soldering are materials and methods usually used in the manufacture of electronic components, and are industrially beneficial in terms of material availability and ease of assembly.
[0024]
A glass coating layer can be formed around the detection electrode mounting portion of the detection electrode mounting substrate. If it does in this way, positioning in the attachment process of a detection electrode will be easy, and the moisture resistance of a detection electrode attachment board will improve, and reliability will improve.
[0025]
The surface potential sensor of the present invention can be shielded by a shield cover having a detection window. If a non-organic substance is interposed in the region where the detection window of the shield cover and the detection electrode mounting substrate are opposed to each other (no organic substance is interposed), fluctuations in output characteristics can be further reduced.
[0026]
The present invention further discloses an electrophotographic developing apparatus using the above-described surface potential sensor.
[0027]
Other objects, configurations and advantages of the present invention will be described in more detail with reference to the accompanying drawings. The drawings are merely examples.
[0028]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is an exploded perspective view showing an embodiment of the surface potential sensor of the present invention. FIG. 2 is a sectional view of the surface potential sensor of the present invention shown in FIG. FIG. 3 is a perspective view of the detection electrode and its mounting substrate used in the surface potential sensor of the present invention shown in FIG. 4 is an enlarged sectional view taken along line 4-4 of FIG. FIG. 5 is a partial bottom view of the surface potential sensor of the present invention shown in FIG.
[0029]
The illustrated surface potential sensor includes a detection electrode 1, a vibrating member 2, a detection electrode mounting substrate 3, a relay substrate 4, wirings 61, 62, 63, a shield cover 7, a bottom plate 8, and a base 9. including.
[0030]
The detection electrode 1 includes a square planar electrode surface and three legs, is formed by punching out a metal plate material, and bends a leg portion at a right angle, and is attached to a detection electrode mounting substrate 3 described later. The planar electrode surface becomes the potential measurement surface. Regardless of the number of legs of the detection electrode 1, it is sufficient that the legs are stably attached to the substrate 3, and a structure in which the legs are directly attached to the detection electrode attachment board 3 without using the legs may be employed.
[0031]
The vibration member 2 includes two arms 21, a fixing portion 22, and a chopping portion 24, is formed into a tuning fork type by punching and bending a constant elastic metal plate material, and further includes a piezoelectric vibrator 25.
[0032]
Each of the two arms 21 has a base portion continuous with the fixed portion 22, a distal end side serving as a vibration end, and a chopping portion 24 formed at the vibration end. The fixing portion 22 has two attachment holes 23. The piezoelectric vibrator 25 has its vibration direction aligned with the vibration direction of the arm 21, and is attached to each of the two arms 21 with a conductive adhesive near the base.
[0033]
The vibration member 2 is not necessarily configured to be a tuning fork type, and is a single arm 21, a fixing portion 22 that is continuous with the arm 21, a chopping portion 24, and a piezoelectric member that is attached to the arm 21 near the fixing portion 22. The vibrator 25 may be included, and the opposed area between the detection electrode and the potential surface to be measured may be periodically changed by the vibration of the chopping unit 24.
[0034]
The detection electrode mounting substrate 3 is made of an inorganic material. The relay substrate 4 may be mainly composed of an inorganic material or an organic material regardless of the material. In this embodiment, both the detection electrode mounting substrate 3 and the relay substrate 4 are made of alumina. The detection electrode mounting substrate 3 is provided with a conductor pattern 31 for electrically and mechanically connecting the detection electrode 1 on one surface, and further, as shown in FIG. A glass coating layer 35 is formed in the periphery except for the portion 36.
[0035]
The sensing electrode 1 is electrically and mechanically joined to the conductor pattern 31 of the sensing electrode mounting substrate 3 configured as described above by using an intermetallic bond 37 using its legs. Joining means include joining by metal bonding that does not intervene organic matter, such as ultrasonic bonding or die bonding using gold, solder or other metal balls or bumps, or soldering using cream solder or other solder. Any means can be used. In the present embodiment, they are joined by soldering so that they can be joined in the same process as components constituting the impedance conversion circuit described later.
[0036]
The detection electrode mounting substrate 3 includes a conductor pattern, a printed resistance pattern, a signal output conductor land 32 (see FIG. 5), a ground pattern 33, and the like on which the circuit component 51 constituting the impedance conversion circuit 5 is mounted on the other surface. Furthermore, a through conductor for connecting the conductor patterns on both sides is provided. These conductor patterns are formed, for example, by baking or baking a conductor paste mainly composed of silver or palladium together with a substrate.
[0037]
The impedance conversion circuit includes a circuit component 51 such as a field effect transistor and a resistor, a printed resistance pattern, and the like. The impedance conversion circuit is attached to the conductor pattern on the other surface of the detection electrode mounting substrate 3 and is connected to the detection electrode mounting substrate 3 via the through conductor. Is connected to the conductor pattern 31 on one side of the. The relay substrate 4 is a substrate that relays the connection between the piezoelectric vibrator driving wiring 61 and the external connection driving wiring 62, and includes a conductor pattern 41 that connects both the wirings.
[0038]
The wiring includes a piezoelectric vibrator driving wiring 61, an external connection driving wiring 62, and a signal wiring 63. The piezoelectric vibrator driving wiring 61 is a wiring for supplying driving power to the piezoelectric vibrator 25, and an extremely thin urethane-coated wire of about 10 μmφ, for example, is used so as not to be a load with respect to the vibration of the vibration member 2. Since the external connection drive wiring 62 is connected to the piezoelectric vibrator drive wiring 61 via the relay substrate 4, it does not become a load with respect to the vibration of the vibration member 2. Therefore, a relatively thick resin-coated wire of about 1 mmφ is used, for example. . The signal wiring 63 is provided for taking out the sensor output signal outside the sensor, and a shield line is used in this embodiment in order to protect the weak sensor output signal from external noise.
[0039]
The shield cover 7 has a function of protecting the inside of the sensor and blocking external noise. The shield cover 7 includes a detection window 71 for specifying a measurement location and an attachment piece 72 for fixing to the base body 9. It is formed by bending it into a U shape.
[0040]
Similarly, the bottom plate 8 has a function of protecting the inside of the sensor and blocking external noise, and is formed by punching a metal plate material.
[0041]
The base 9 includes a detection electrode mounting substrate support portion 91, a vibration member support portion 92, a relay substrate support portion 93, a shield cover support portion 96, and a wiring insertion hole 95. The base body 9 is formed by, for example, zinc alloy die casting in order to stably operate the vibration member and enable a complicated three-dimensional structure.
[0042]
The detection electrode mounting substrate support 91 includes a rectangular frame 911 formed continuously on one side of the vibration member support 92 in the sensor longitudinal direction, and a step 912 formed inside the frame 911. In the figure, the detection electrode mounting substrate 3 is supported on the upper surface of the stepped portion 912, and a space formed below the stepped portion 912 is used as a housing portion 913 for the circuit component 51, the signal wiring 63, and the like.
[0043]
The relay substrate support portion 93 is formed in the sensor longitudinal direction in a rectangular frame body 931 continuously formed on the other side of the vibration member support portion 92 and in the middle of the frame body 931 in the vertical direction in the figure. The partition 932 is configured to support the relay substrate 4 on the upper surface of the partition 932, and a space formed in the lower portion of the partition 932 serves as a housing portion 933 for the signal wiring 63 (see FIG. 5). The accommodating portion 933 includes a signal wiring separator 934 protruding from the lower portion of the partition 932. The accommodating portion 933 is formed continuously with the accommodating portion 913.
[0044]
The vibration member support portion 92 is formed in a trapezoidal shape that protrudes upward from the detection electrode mounting substrate support portion 91 and the relay substrate support portion 93, and a vibration member receiving portion 921 that is a flat surface formed on the upper surface, and protrudes from the plane. And two vibration member fixing protrusions 922.
[0045]
The drive wiring support portion 94 includes a stepped portion 941 formed on the side surface of the vibration member support portion 92 in the sensor longitudinal direction. The stepped portion 941 is formed along the sensor longitudinal direction with the end face on the piezoelectric vibrator side of the side surface of the vibration member support portion 92 as the drive wiring support portion start end 942. When the vibration member 2 is attached to the vibration member support portion 92, the drive wiring support portion start end 942 is located outside the vibration member 2 in the vibration direction.
[0046]
The wiring insertion holes 95 are provided independently for the external connection drive wiring 62 and the signal wiring 63 on the end surface of the sensor longitudinal direction on the relay substrate support portion 93 side. An end surface 914 on the detection electrode mounting substrate support portion 91 side in the sensor longitudinal direction is configured such that a part of the frame body 911 rises greatly and closes the sensor end surface when the shield cover 7 is mounted.
[0047]
The shield cover support portion 96 is formed of a stepped portion formed by bulging the lower side surface in the longitudinal direction of the base body 9, and the bulging portion is partially cut away to form an attachment piece insertion groove 961.
[0048]
The base 9 configured in this manner has the detection electrode 1, the detection electrode mounting substrate 3 to which the circuit component 51 is mounted, the relay substrate 4, the vibration member 2, the wirings 61, 62, and 63, and the shield cover. 7 and the bottom plate 8 are attached.
[0049]
The detection electrode mounting substrate 3 to which the detection electrode 1 and the circuit component 51 are mounted is placed on the stepped portion 912 with the detection electrode 1 facing upward so that the circuit component 51 is accommodated in the accommodating portion 913. It is bonded to the step portion 912 and fixed to the base 9.
[0050]
The relay substrate 4 is placed on the partition 932 with the conductor pattern 41 facing upward, and is fixed to the base 9 with an adhesive.
[0051]
The vibration member 2 has its fixing portion 22 arranged on the vibration member receiving portion 921 so that the chopping portion 24 faces the electrode surface (potential measurement surface) of the detection electrode 1, and protrudes into the mounting hole 23 provided in the fixing portion 22. It is attached by fitting 922 and caulking the protrusion 922. The vibration member 2 may be attached by screwing or bonding in addition to caulking, but according to caulking, auxiliary members such as screws and adhesives are unnecessary, workability is good, and further, over time. It is possible to prevent fluctuations in sensor characteristics due to loose screws and adhesive deterioration.
[0052]
One end of the piezoelectric vibrator driving wire 61 is connected to the piezoelectric vibrator, an intermediate portion is routed along the wiring support portion 94 provided on the side surface of the vibration member support portion 92, and the other end is formed on the relay substrate 4. The conductor pattern 41 is soldered to one end. The wiring between one end of the piezoelectric vibrator driving wiring 61 and the wiring support portion start end 942 is substantially along a straight line connecting one end of the piezoelectric vibrator driving wiring 61 and the wiring support portion start end 942, and the vibration member 2. It is wired so that tension is not applied when the oscillates.
[0053]
One end of the external connection drive wiring 62 is soldered to the other end of the conductor pattern 41 formed on the relay substrate 4 and led out to the outside through a wiring insertion hole 95 provided in the base 9.
[0054]
The signal wiring 63 is led from the outside of the sensor to the housing portions 913 and 933 (see FIG. 5) provided in the lower portion of the base 9 through the wiring insertion hole 95 provided in the base 9, and the core portion is formed in the housing 933. 631 and the shield covered wire portion 632 are separated, the core wire portion 631 is disposed on one side of the signal line separator 934, and the shield covered wire portion 632 is disposed on the other side. The coating of the tip of the core wire portion 631 is peeled off and soldered to the signal conductor land 32 formed on the component mounting surface side of the detection electrode mounting board 3. The shield covered wire portion 632 is soldered to the ground pattern 33 whose tip is formed on the other surface of the detection electrode mounting substrate 3.
[0055]
In the above-described wiring, the piezoelectric vibrator driving wiring 61 is routed along the wiring support portion 94 provided on the side surface of the vibration member support portion 92, and is driven by the elastic adhesive 65 to support the driving wiring. The portion 94 is held elastically.
[0056]
For this reason, the surface potential sensor according to the present embodiment specifies the routing position when routing the piezoelectric vibrator driving wiring 61, so that the workability is good and the variation in characteristics can be reduced. In addition, the piezoelectric vibrator driving wiring 61 uses an extremely thin insulation-coated wire, and is elastically held by the wiring support portion 94 formed on the side surface of the vibration member support portion 92. Instead, the vibration of the vibration member 2 rubs against the piezoelectric vibrator driving wiring 61 and the vibration member 2 or other metal parts such as the shield cover 7 and the base 9, and the insulation coating is scraped off, resulting in a short circuit state or disconnection. There is nothing to do. Further, when the shield cover 7 is assembled, the wiring is not bitten or damaged.
[0057]
In this embodiment, the driving wiring support portion start end 942 is located outside the vibration member 2 in the vibration direction when the vibration member 2 is attached to the vibration member support portion 92. The wiring between one end of the piezoelectric vibrator driving wiring 61 and the wiring support portion start end 942 is substantially along a straight line connecting one end of the piezoelectric vibrator driving wiring 61 and the wiring support portion start end 942, and the vibration member 2. It is wired so that tension is not applied when the oscillates. This configuration further reliably prevents the occurrence of a short circuit or disconnection due to the vibration of the vibration member 2 described above.
[0058]
Furthermore, if a taper portion or a chamfered portion inclined in the vibration member direction is formed at the wiring support portion start end 942, the periphery of the wiring at the wiring support portion start end 942 is surely surrounded by the elastic adhesive 65, and disconnection at this portion The effect of preventing the occurrence can be enhanced.
[0059]
In addition to the stepped portion 941, the driving wiring support portion 94 can be formed of a groove having a U-shaped section or a V-shaped cross section, for example. The elastic adhesive 65 is injected so as to fill the groove.
[0060]
In this way, if the driving wiring support portion 94 is formed in a groove shape, the wiring routing position and the elastic adhesive injection position can be specified more accurately. For this reason, the usage-amount of the elastic adhesive material 65 becomes small, and it can prevent that the elastic adhesive material 65 which has organic resin as a main component spreads on the detection electrode attachment board | substrate 3, or adheres to a detection electrode periphery. The type of the elastic adhesive 65 is not particularly limited, but a silicone-based insulating adhesive is usually used.
[0061]
Furthermore, in this embodiment, the other end of the piezoelectric vibrator driving wiring 61 and one end of the external connection driving wiring 62 are also elastically held on the upper surface of the relay substrate 4 by the same elastic adhesive material 65. If the external connection drive wiring 62 is bonded to the relay substrate 4 in this way, a disconnection accident due to the tension applied to the external connection drive wiring 62 during the sensor mounting operation to the electrophotographic developing apparatus or during other sensor handling. Can be reduced.
[0062]
The signal wire 63 has its shield covered wire portion 632 elastically fixed to the base 9 by an elastic conductive adhesive 66 and is electrically connected. Similarly, the ground pattern 33 to which the shield covered wire portion 632 is soldered is also elastically fixed to the base 9 by the elastic conductive adhesive 66 and electrically connected thereto. Therefore, the shield covered wire portion 632, the ground pattern 33, and the base body 9 are set to the same potential.
[0063]
The elastic conductive adhesive is a material in which a good conductive filler such as silver is mixed in the adhesive and the viscosity is adjusted to about 20K to 25K (CPS). The type is not particularly limited. Epotech (trademark) made by the company is suitable in terms of flexibility and residual stress absorption characteristics during curing.
[0064]
The above-described configuration is one of the means that makes it possible to use alumina as the substrate material of the surface potential sensor of the present invention, and improves the long-term reliability against the temperature change of the surface potential sensor. That is, in this embodiment, the detection electrode mounting substrate 3 is formed of alumina, and the base 9 is formed of zinc alloy die-cast. The linear expansion coefficient of alumina is 5 × 10 ^-6 / 3 ° C for zinc alloy used for die casting ^-Five There is a difference of about 6 times between the two. Although the detection electrode mounting substrate 3 and the base body 9 repeatedly contract and expand in accordance with ambient temperature fluctuations, the elastic conductive adhesive 66 absorbs the difference in linear expansion coefficient, and the ground pattern of the detection electrode mounting substrate 3 over a long period of time. 33, the shield covered wire portion 632 and the base body 9 are maintained in electrical connection.
[0065]
The base 9 on which the detection electrode 1, the detection electrode mounting substrate 3, the relay substrate 4, the vibration member 2, and the wirings 61, 62, 63 are attached is covered with a shield cover 7 from the upper surface side. The edge plate 73 of the shield cover 7 is supported by the shield cover support portion 96 so that 71 and the detection electrode 1 face each other, and the bottom plate 8 is applied from the lower surface side so as to close the housing portions 913 and 933.
[0066]
The base body 9, the shield cover 7, and the bottom plate 8 are integrated by inserting the attachment piece 72 protruding downward from the edge 73 of the shield cover 7 into the attachment piece insertion groove 961 and bending it at the bottom plate surface. Thereby, the base 9, the shield cover 7, and the bottom plate 8 include the ground pattern 33 and the shield covered wire portion 632 of the detection electrode mounting substrate 3 and are electrically connected to the same potential.
[0067]
In the surface potential sensor configured in this manner, the detection window 71 of the shield cover 7 is attached to the measured potential surface so that the potential measuring surface of the detection electrode 1 is measured via the chopping portion 24 of the vibrating member 2. It is arranged to face the potential surface.
[0068]
When drive power is supplied from the external connection drive wiring 62 through the relay substrate 4 and the piezoelectric vibrator drive wiring 61, the piezoelectric vibrator 25 vibrates. Due to the vibration of the piezoelectric vibrator 25, the two arms 21 of the vibration member 2 vibrate and vibrate the chopping portion 24 provided at the vibration end in the horizontal direction with respect to the potential surface to be measured.
[0069]
The chopping unit 24 chops electric lines of force between the measured potential surface and the detection electrode 1 and periodically changes the facing area between the measured potential surface and the detection electrode 1. For this reason, the electrostatic coupling between the measured potential surface and the detection electrode 1 periodically changes, and the detection electrode 1 alternately generates electrostatic induction proportional to the potential of the measured potential surface. The impedance conversion circuit impedance-converts the AC signal detected by the detection electrode 1 and outputs it through the signal wiring 63.
[0070]
The surface potential sensor of the present invention configured as in the above-described embodiment is configured such that the detection electrode mounting substrate is made of an inorganic material, and the detection electrode is electrically connected to the conductor pattern formed on the surface of the inorganic material substrate by intermetallic bonding. Mechanically and mechanically. For this reason, since no organic substance is present around the detection electrode, charging due to friction is unlikely to occur even when a mechanical impact is applied to the surface potential sensor. For these reasons, it is presumed that the output potential of the surface potential sensor of the present invention does not change even when a mechanical shock is applied. Hereinafter, this point will be described with reference to a circuit diagram.
[0071]
FIG. 6 is a circuit diagram showing an embodiment of the signal processing circuit of the surface potential sensor of the present invention. The circuit of the present embodiment includes an impedance conversion circuit 5, a DC cut capacitor 54, and an amplifier 53.
[0072]
The impedance conversion circuit 5 is configured on the other surface of the detection electrode mounting substrate, for example, a high resistance printing resistor RG of about 100 MΩ, a field effect transistor 52 mounted on the other surface of the detection electrode mounting substrate, and a low resistance Value chip resistors RD, RS. One end of the resistor RG is connected to the detection electrode 1 through the through conductor of the detection electrode mounting substrate, is connected to the gate 52G of the field effect transistor 52, and the other end is grounded. The drain 52D of the field effect transistor 52 is connected to the input terminal of the amplifier 53 via the DC cut capacitor 54, and is connected to the DC voltage source VDD via the resistor RD. A source 52S of the field effect transistor 52 is grounded via a resistor RS. A1 is a measured potential surface such as a photosensitive drum.
[0073]
The detection electrode 1 is disposed so as to face the measured potential surface A <b> 1 through the chopping portion 24 and the detection window 71 of the shield cover 7. The potential surface A1 to be measured and the detection electrode 1 constitute electrostatic coupling C = ε (a / L) using air as a medium. Here, ε is the dielectric constant of air, a is the facing area between the measured potential surface A1 and the electrode surface of the detection electrode 1, and L is the distance between the measured potential surface A1 and the detection electrode 1.
[0074]
The facing area a between the potential surface A1 to be measured and the electrode surface of the detection electrode 1 is periodically changed by the vibration of the chopping unit 24. Therefore, an induced charge Q that periodically changes corresponding to the potential of the potential surface A1 to be measured is generated in the detection electrode 1. The induced charge Q supplies a minute displacement current i = dQ / dt to the resistor RG, is converted into a voltage signal by the resistor RG, and is applied to the gate 52G of the field effect transistor 52 as a voltage signal. The voltage signal applied to the field effect transistor 52 is input from the drain 52D to the amplifier 53 via the DC cut capacitor 54, and is converted into an amplified sine wave sensor output signal. One cycle of the sine wave coincides with the vibration period of the chopping unit 24.
[0075]
In the surface potential sensor of the present invention, since the periphery of the detection electrode is difficult to be frictionally charged, even if a mechanical shock is applied to the surface potential sensor, no error occurs in the minute displacement current.
[0076]
Therefore, in the surface potential sensor of this embodiment, the minute displacement current given by i = dQ / dt is i = dQ / dt = 0 when the potential of the potential surface A1 to be measured is 0 volts.
[0077]
On the other hand, in the conventional surface potential sensor using a lot of resin, when a mechanical impact is applied, the resin around the detection electrode is charged by friction and a charged charge of | Q |> 0 is generated. For this reason, i = dQ / dt ≠ 0, and a minute displacement current is generated, resulting in a measurement error.
[0078]
FIG. 7 is a comparison diagram of output waveforms of the surface potential sensor when such a mechanical impact is applied. FIG. 7 shows an ideal surface potential sensor, a conventional surface potential sensor using a large amount of resin, and the surface potential sensor of the present invention when the potential of the potential surface A1 to be measured is 0 V and −500 V. Each output waveform is shown.
[0079]
The output waveform of an ideal surface potential sensor outputs a voltage Ve proportional to the potential of the potential surface to be measured. However, in the conventional surface potential sensor, when the potential of the potential surface to be measured is −500 V, the periphery of the detection electrode 1 Is positively charged, the potential difference between the detection electrode and the potential surface to be measured is increased and greatly exceeds the voltage Ve as shown by the solid line. If the periphery of the detection electrode 1 is negatively charged, the broken line is reversed. Thus, the voltage Ve is significantly below, and at 0V and -500V, there is a large error compared to the output waveform of the ideal surface potential sensor.
[0080]
On the other hand, the output waveform of the surface potential sensor of the present invention is very close to the output waveform of the ideal surface potential sensor at both 0V and −500V.
[0081]
8 to 10 are graphs showing the results of a drop impact test between the conventional surface potential sensor and the surface potential sensor of this example. The drop impact test was performed by preparing 15 conventional surface potential sensors (No. 1a to No. 15a) and 15 surface potential sensors (No. 1b to No. 15b) of this example. About each sensor, the output voltage in case the electric potential of a to-be-measured potential surface is 0V, -500V, and -900V was measured just before dropping. Each of the measured sensors was divided into 5 groups, and each group was dropped from a height of 30 cm, 50 cm, and 70 cm onto a wooden desk, and immediately after that, the same measurement as that performed immediately before the drop was performed. . FIG. 8 shows data when dropped from a height of 30 cm. FIG. 8A shows data of a conventional surface potential sensor, and FIG. 8B shows data of an example according to the present invention.
[0082]
FIG. 9 shows data when dropped from a height of 50 cm. FIG. 9A shows data of a conventional surface potential sensor, and FIG. 9B shows data of an example according to the present invention.
[0083]
FIG. 10 shows data when dropped from a height of 70 cm. FIG. 10A shows data of a conventional surface potential sensor, and FIG. 10B shows data of an example according to the present invention. 8 to 10, the horizontal axis indicates the potential of the potential surface to be measured, and the vertical axis indicates the voltage change amount between the measurement result immediately before the drop and the measurement result immediately after the drop.
[0084]
As can be seen from the figure, in the conventional sensors No. 1a to 15a, when the potential of the potential surface to be measured is 0 V, there is no significant change in the amount of change in the measured potential immediately before and after the drop. However, when the potential of the potential surface to be measured is -500 V or -900 V, the measured potential slightly changes in the combination of No. 1a to No. 5a dropped from a height of 30 cm (see FIG. 8 (a)). However, in the combination of No. 6a to No. 10a dropped from a height of 50 cm, a change exceeding 0.2 V occurred (see FIG. 9A), and No. dropped from a height of 70 cm. In the combination of .11a to No. 15a, a change exceeding 0.4V occurs, and the variation among individual sensors is also large.
[0085]
On the other hand, the surface potential sensors No. 1b to No. 15b of the present example have measured potentials at any height as shown in FIGS. 8 (b), 9 (b) and 10 (b). The amount of change hardly occurs, and the variation between individual sensors is extremely small, and the characteristics are stable.
[0086]
The surface potential sensor according to the present invention can be used as a sensor for detecting the potential of the surface of the photosensitive drum of the electrophotographic developing apparatus, or can be used as a sensor for detecting the potential of the surface of a film or other medium.
[0087]
FIG. 11 is a conceptual diagram around the photosensitive drum of the electrophotographic developing apparatus using the surface potential sensor of the present invention. The periphery of the photosensitive drum A includes a charger B, a surface potential sensor C, an exposure device D, a toner tank E, a rotating roller F, and a medium G such as paper on which a visible image is transferred. The photosensitive drum A rotates in the arrow direction. The surface potential sensor C is disposed so as to face the surface of the photosensitive drum A that is a measured potential surface. A high voltage is applied to the charger B from the high voltage generator H, and the surface of the photosensitive drum A is uniformly charged by corona discharge. The exposure device D exposes the surface of the photosensitive drum A according to the photographic image. The exposed portion of the surface of the photosensitive drum A becomes conductive, and the charge disappears according to the exposure amount, and a charged latent image corresponding to the photographic image is formed. The photosensitive drum A receives supply of toner from the toner tank E, and the toner adheres to the charged latent image.
[0088]
The adhering toner is transferred as a visible image by the rotating roller F onto a paper or other medium G transferred in contact with the photosensitive drum A.
[0089]
In the transfer cycle described above, the surface potential sensor C detects the surface potential of the photosensitive drum A in a timely manner and sends the output to the control device K via the signal processing device J.
[0090]
In the case of a color electrophotographic developing apparatus, at least four surface potential sensors C are used, and it is necessary to make the respective characteristics uniform, and maintenance and inspection work frequently occur. Since the surface potential sensor of the present invention can reduce variations in characteristics and is easy to handle during maintenance and inspection work, it is particularly suitable for use in a color electrophotographic developing apparatus.
[0091]
In the electrophotographic developing apparatus, the ambient temperature of the surface potential sensor rises from about 50 ° C. to about 60 ° C. during operation. Therefore, the surface potential sensor is subjected to a temperature cycle as the electrophotographic developing apparatus is operated and stopped. The surface potential sensor shown in this embodiment has high reliability against temperature fluctuations. For this reason, the surface potential sensor of this embodiment is suitable for use in a copying machine or printer in which temperature fluctuations frequently occur.
[0092]
The contents of the present invention have been described in detail with reference to the preferred embodiments. However, the present invention is not limited to these, and those skilled in the art will be able to use various techniques based on the basic technical idea and teachings. It is obvious that variations can be conceived.
[0093]
【The invention's effect】
As described above, according to the present invention, the following effects can be obtained.
(A) It is possible to provide a surface potential sensor with stable characteristics, which is less likely to cause fluctuations in output characteristics even when mechanical shock is applied, and has little variation.
(B) A surface potential sensor that is easy to handle can be provided.
(C) An electrophotographic developing device that is easy to handle and highly reliable can be provided.
[Brief description of the drawings]
FIG. 1 is an exploded perspective view showing an embodiment of a surface potential sensor according to the present invention.
2 is a cross-sectional view of the surface potential sensor shown in FIG. 1. FIG.
3 is a perspective view of a detection electrode used for the surface potential sensor shown in FIG. 1 and its mounting substrate. FIG.
4 is an enlarged cross-sectional view taken along line 4-4 of FIG.
FIG. 5 is a partial bottom view of the surface potential sensor shown in FIG. 1 with a bottom plate portion removed.
FIG. 6 is a circuit diagram showing one embodiment of a signal processing circuit of the surface potential sensor according to the present invention.
FIG. 7 is a comparison diagram of output waveforms of a surface potential sensor when a mechanical shock is applied.
FIG. 8 shows a result of a drop impact test when a conventional surface potential sensor is dropped from a height of 30 cm (FIG. 8A), and the surface potential sensor according to the present invention is dropped from a height of 30 cm. It is a graph which shows the result (FIG.8 (b)) of the drop impact test when it was made to do.
FIG. 9 shows the result of a drop impact test when a conventional surface potential sensor is dropped from a height of 50 cm (FIG. 9A), and the surface potential sensor according to the present invention is dropped from a height of 50 cm. It is a graph which shows the result (Drawing 9 (b)) of the drop impact test when it was made to do.
FIG. 10 shows the result of a drop impact test when a conventional surface potential sensor is dropped from a height of 70 cm (FIG. 9A), and the surface potential sensor according to the present invention is dropped from a height of 70 cm. It is a graph which shows the result (Drawing 9 (b)) of the drop impact test when it was made to do.
FIG. 11 is a conceptual diagram around a photosensitive drum of an electrophotographic developing device using a surface potential sensor according to the present invention.
[Explanation of symbols]
1 Detection electrode
2 Vibration member
21 arm
22 fixed part
25 Piezoelectric vibrator
3 Detection electrode mounting board
36 joints
9 Base
92 Vibration member support

Claims

A surface potential sensor including a base, a vibrating member, a detection electrode mounting substrate, and a detection electrode,
The base is composed of a zinc molded body, and includes a vibration member support portion and a detection electrode mounting substrate support portion,
The vibrating member includes at least one arm and a piezoelectric vibrator,
The arm is made of an elastic metal body, includes a fixed portion and a chopping portion, and is attached to the vibration member support portion by the fixed portion,
The piezoelectric vibrator is attached to the arm,
The detection electrode mounting substrate is made of alumina , has a conductor pattern on the surface on the vibration member side, has a glass coating layer formed at least around the detection electrode mounting portion, and supports the detection electrode mounting substrate of the base Attached to the
The detection electrode is a surface potential sensor that is made of a metal material, and is electrically and mechanically joined to the conductor pattern by being faced with solder at a position corresponding to the chopping portion.

The surface potential sensor according to claim 1 ,
Further, a shield cover is included, and the shield cover is made of metal and supported by the base, covers the detection electrode, the vibration member, and the detection electrode mounting substrate, and includes the detection electrode and the chopping portion. A surface potential sensor in which a detection window is provided at a position facing the detection electrode mounting substrate, and a non-organic substance is present in a region facing the detection window and the detection electrode mounting substrate.

The surface potential sensor according to claim 1 or 2 ,
A surface potential sensor that detects the surface potential of a photosensitive drum of an electrophotographic developing device.

An electrophotographic developing apparatus including a surface potential sensor,
4. The electrophotographic developing apparatus according to claim 3 , wherein the surface potential sensor is the one described in claim 3 .