JP4066294B2

JP4066294B2 - Master cylinder

Info

Publication number: JP4066294B2
Application number: JP32910799A
Authority: JP
Inventors: 公雄石原
Original assignee: Bosch Corp
Current assignee: Bosch Corp
Priority date: 1999-11-19
Filing date: 1999-11-19
Publication date: 2008-03-26
Anticipated expiration: 2019-11-19
Also published as: JP2001146157A

Description

【０００１】
【発明の属する技術分野】
本発明は、自動車の各種ブレーキ装置などに使用されるマスタシリンダの改良に関する。
【０００２】
【従来の技術】
従来、この種のマスタシリンダとしては、例えば図４に示すタンデムマスタシリンダがあり、図示しないブレーキ倍力装置の前部に装着されて、該倍力装置の出力部に連結されて使用される。このマスタシリンダのシリンダハウジング１は、一端に開口部を有するボデイ本体２と、該ボデイ本体２の開口部に結合されるキャップ３と、内部にシリンダ８ａが成形されるとともに、一端が該ボデイ本体２内に嵌装されたスリーブ８とによりシリンダハウジング１を構成し、スリーブ８の内部に成形されたシリンダ８ａ内に第１、第２のピストン４、５が直列状に嵌挿され、これらピストン４、５はスリーブ８の中に摺動可能に配設されている。第１のピストン４は、その一端部をブレーキ倍力装置の出力部と当接係合できるように構成されている。
【０００３】
前記第１、第２のピストン４、５と前記シリンダハウジング１とによって第１の圧力室９が画成され、前記第２のピストン５と前記シリンダハウジング１とによって第２の圧力室１０が画成されている。これら第１、第２の圧力室９、１０の各々は、シリンダハウジング１に設けられた連通孔１ａ、１ｂを介してそれぞれのブレーキ装置の配管に接続される。
【０００４】
また、前記第１、第２のピストン４、５の外周と前記シリンダハウジング１とにより第１の給液室２１と、第２の給液室２２をそれぞれ画成している。これら第１、第２の給液室２１、２２の各々は、それぞれの液リザーバ２３に接続される。
【０００５】
前記第１の給液室２１は、前記第１の圧力室９との間及び前記シリンダハウジング１の外部との間を、該シリンダハウジング１に設けられて前記第１のピストン４と係合するそれぞれのシール２４、２５により密封されている。
同様に、前記第２の給液室２２は、前記第２の圧力室１０との間及び前記第１の圧力室９との間を、前記シリンダハウジング１に設けられて前記第２のピストン５と係合するそれぞれのシール２６、２７により密封されている。
【０００６】
前記第１、第２の圧力室９、１０に、前記第１、第２のピストン４、５を後退方向に付勢する戻しばね機構１１、１２がそれぞれ配設されている。特に、前記第１の圧力室９に配設されるばね機構１１は、前記第２のピストン５の後端面に当接するほぼ円筒状のばねリテーナ１７と、該リテーナ１７内に挿通されその頭部が該リテーナ１７に係止するとともに前記第１のピストンの先端側に形成された凹部底面に係着するガイドピン１６と、前記ばねリテーナ１７と前記第１のピストン４との間に縮設される戻しばね１５から成っている。
【０００７】
これらばね機構１１、１２の各々は、非作動時、前記第１のピストン４を、ブレーキ倍力装置の出力部との当接位置により規制される後退限に、前記第２のピストン５を、前記ばねリテーナ１７の位置により規制される後退限にそれぞれ戻すとともに、これらピストン４、５をこの非作動位置に保持する。
【０００８】
前記第１、第２のピストン４、５が非作動位置に在るとき、前記第１、第２の圧力室９、１０は、前記第１、第２のピストン４、５の各々に設けられたリリーフ孔４ｃ、５ｃ（本発明のリリーフ通路に相当）により前記第１、第２の給液室２１、２２とそれぞれ連通するように構成されている。これにより、ブレーキ装置のブレーキ液圧力は、前記第１、第２の圧力室９、１０、前記各リリーフ孔４ｃ、５ｃ及び前記第１、第２の給液室２１、２２をそれぞれ通って液リザーバ２３に解放され、ブレーキ装置は非作動状態に維持される。
【０００９】
前記第１のピストン４がブレーキ倍力装置の出力部に押圧されて、前進方向にストロークするとき、第１のピストン４に設けられた前記リリーフ孔４ｃが未だ前記第１の給液室２１と連通する位置に在る初期段階においては、該第１のピストン４により押し出されたブレーキ液は、前記第１の圧力室９から前記第１の給液室２１に流出してしまう。そのため、前記第１の圧力室９内のブレーキ液圧力は自動車の制動に十分な圧力まで上昇することができない。制動開始直後に過渡的に発生するこのストロークは、ブレーキを操作する上でもブレーキの効き遅れとして感じられる無効ストロークで好ましくない。従って、この無効ストロークを短縮すべく、前記リリーフ孔４ｃは、前記第１の圧力室９と前記第１の給液室２１との間に設けられた前記シール２４に対し、極力近接させて開口される。
【００１０】
前記第１のピストン４が更にストロークして、該リリーフ孔４ｃが前記第１の圧力室９と前記第１の給液室２１との間に設けられた前記シール２４と重なって閉塞される位置に達すると、前記第１のピストン４は、前記第１の圧力室９内のブレーキ液をブレーキ配管に吐出し始める。更なる該第１のピストン４のトロークにより、前記第１の圧力室９内にブレーキ液圧力が発生し、このブレーキ液圧力を後端面に受けた前記第２のピストン５は、前進方向にストロークする。該第２のピストン５のストロークの初期においても、前記第１のピストン４の場合と同様な過程で過渡的に無効ストロークが発生する。従って、無効ストロークを短縮すべく、前記第２のピストン５に設けられた前記リリーフ孔５ｃも、前記第２の圧力室１０と前記第２の給液室２２との間に設けられた前記シール２６に対し可能な限り近い位置に開口される。
【００１１】
一方、前記第１、第２のピストン４、５のそれぞれの後退限と前記シリンダハウジング１に設けられた前記シール２４、２６との相対位置は、これに関係する多くの構成部品の寸法の累積により定まるので、距離的に大きなばらつきを持つ。従って、前記ピストン４、５に設けられた前記リリーフ孔４ｃ、５ｃと前記シリンダハウジング１に設けられた前記シール２４、２６との間の距離も、大きなばらつきを持っている。更に、これら関係構成部品に発生する経時的な寸法変化によっても影響を受ける。そのため、ブレーキの戻し時、予期せず、前記リリーフ孔４ｃ、５ｃが前記給液室２１、２２と連通する位置まで戻りきれずに該リリーフ孔４ｃ、５ｃの給液室内開口部４ｄ、５ｄが前記シール２４、２６と重なって閉塞されてしまう可能性がある。結果的にブレーキ装置にブレーキ液圧力が解放されないで残ってしまい、この状態を気付かずに自動車が走行されると大きな事故につながる可能性が高い。これらを考慮すると、前記ピストン４、５に設けられた前記リリーフ孔４ｃ、５ｃと前記シリンダハウジング１に設けられた前記シール２４、２６との間の距離は、余裕をもたせた値にせざるを得ず、また、これらを考慮してしても、部品に予期しない異常な変化が起こった場合には、上述の不具合は回避できない。
【００１２】
【発明が解決しようとする課題】
従って、無効ストローク短縮に対し制約となり、かつ、安全上多くの問題の原因となり、大きな事故につながる可能性の大きいブレーキ液圧力の残圧を発生させることのないマスタシリンダを提供することが、本発明が解決しようとする課題である。
【００１３】
【課題を解決するための手段】
前記課題を解決するために、請求項１の発明のマスタシリンダは、シリンダハウジングの一端にシリンダを開口し、前記シリンダ内に嵌挿されるピストンを摺動可能に設け、前記ピストンと前記シリンダハウジングとによって圧力室を画成するとともに、前記ピストンの外周と前記シリンダハウジングの間には給液室を画成し、かつ前記圧力室と前記給液室との間をシールにより密封し、また、前記圧力室に前記ピストンを後退方向へ付勢するばね機構を配設し、前記ピストンが前記ばね機構より戻されて非作動位置に在るとき、前記圧力室は、前記ピストンに設けられたリリーフ通路により前記給液室と連通するように構成されたマスタシリンダにおいて、前記ピストンには、該ピストンに設けられた前記リリーフ通路の給液室内開口部のやや後方位置に、前記ピストンを貫通して前記圧力室に達する細径のセイフティ孔の開口部を設け、前記セイフティ孔の開口部が、前記ピストンが前記圧力室に配設されたばね機構により戻されて非作動位置に在るときで、前記リリーフ通路の給液室内開口部が前記シールと重なってしまう位置に在っても、前記ピストンに設けられた前記セイフティ孔によって、前記圧力室が前記給液室と連通するように構成されたことを特徴としている。
【００１４】
また、請求項２の発明は、シリンダハウジングの一端にシリンダを開口し、前記シリンダ内に嵌挿される第１、第２のピストンを摺動可能に設け、前記第１、第２のピストンと前記シリンダハウジングとによって第１の圧力室を、前記第２のピストンと前記シリンダハウジングとによって第２の圧力室をそれぞれ画成するとともに、前記第１、第２のピストンの外周と前記シリンダハウジングの間には第１、第２の給液室をそれぞれ画成し、かつ前記第１の圧力室と前記第１の給液室との間、および前記第２の圧力室と前記第２の給液室との間をそれぞれ第１、第２のシールにより密封し、前記第１、第２の圧力室内に前記第１、第２のピストンを後退方向へ付勢するばね機構をそれぞれ配設し、前記第１、第２のピストンが前記ばね機構の各々によりそれぞれ戻されて非作動位置に在るとき、前記第１、第２の圧力室は、前記第１、第２のピストンの各々に設けられたリリーフ通路により前記第１、第２の給液室とそれぞれ連通するように構成されたマスタシリンダにおいて、少なくとも、前記第１のピストンには、該第１のピストンに設けられた前記リリーフ通路の給液室内開口部のやや後方位置に、前記第１のピストンを貫通して前記第１の圧力室に達する細径のセイフティ孔の開口部を設け、前記セイフティ孔の開口部が、前記第１のピストンが前記第１の圧力室に配設されたばね機構により戻されて非作動位置に在るときで、前記第１のピストンのリリーフ通路の給液室内開口部が前記第１のシールと重なってしまう位置に在っても、前記第１のピストンに設けられた前記セイフティ孔によって、前記第１の圧力室が前記第１の給液室と連通するように構成されたことを特徴としている。
【００１５】
更に、請求項３の発明は、一端に開口部を有するボデイ本体と、該ボデイ本体の開口部に結合されるキャップと、内部にシリンダが成形されるとともに、一端が該ボデイ本体内に嵌装されたスリーブとによってシリンダハウジングを構成し、前記シリンダ内に嵌挿される第１、第２のピストンを摺動可能に設け、該第１、第２のピストンと前記シリンダハウジングとによって第１の圧力室を、前記第２のピストンと前記シリンダハウジングとによって第２の圧力室をそれぞれ画成するとともに、前記第１、第２のピストンの外周と前記シリンダハウジングの間には第１、第２の給液室をそれぞれ画成し、かつ前記第１の圧力室と前記第１の給液室との間、および前記第２の圧力室と前記第２の給液室との間をそれぞれ第１、第２のシールにより密封し、前記１、第２の圧力室に前記第１、第２のピストンを後退方向へ付勢するばね機構をそれぞれ配設し、前記第１、第２のピストンが前記ばね機構の各々によりそれぞれ戻されて非作動位置に在るとき、前記第１、第２の圧力室は、前記第１、第２のピストンの各々に設けられたリリーフ通路により前記第１、第２の給液室とそれぞれ連通するように構成されたマスタシリンダにおいて、前記第１、第２のピストンには、該第１、２のピストンに設けられた前記リリーフ通路の給液室内開口部のやや後方位置に、前記第１、第２のピストンを貫通して前記第１、２の圧力室に達するように設けられた細径の第１、第２のセイフティ孔の開口部をそれぞれ設け、前記第１、第２のセイフティ孔の開口部が、それぞれ、前記第１、第２のピストンが前記ばね機構の各々によりそれぞれ戻されて非作動位置に在るときで、前記第１、第２のピストンの各リリーフ通路の給液室内開口部が、それぞれ、前記第１、第２のシールと重なってしまう位置に在っても、前記第１、第２のピストンの各々に設けられた前記第１、第２セイフティ孔によって、前記第１、第２の圧力室が前記第１、第２の給液室とそれぞれ連通するように構成されたことを特徴としている。
【００１６】
【作用】
このような構成をしたマスタシリンダにおいては、前記ピストンの後退限が変化し、リリーフ通路が前記給液室と連通する位置まで戻りきれず、リリーフ通路の給液室内開口部がシールと重なって閉塞されてしまった場合、前記ピストンは、その後退限をブレーキ倍力装置により規制されているので、前記第１の圧力室内のブレーキ液圧力により押圧されても後退することはできない。従って、従来の構成においては、圧力室内のブレーキ液圧は残圧となり、この残圧は、前記圧力室内に高い圧力のまま保持されてしまう。しかし、本発明の構成によれば、前記ピストンの後退限が変化し、リリーフ通路が前記給液室と連通する位置まで戻りきれず、リリーフ通路の給液室内開口部がシールと重なって閉塞されてしまった場合でも、リリーフ通路より後方に位置するセイフティ孔が前記給液室に連通するので、この残圧は該セイフティ孔を介して給液室に解放される。
【００１７】
また、請求項２のマスタシリンダにおいても、前記第１のピストンの後退限が変化したため第１のピストンのリリーフ通路が前記第１の給液室に戻りきれず、このリリーフ通路の給液室内開口部がシールと重なって閉塞されてしまった場合、前記第１のピストンは、その後退限をブレーキ倍力装置により規制されているので、前記第１の圧力室内のブレーキ液圧力により押圧されても後退することはできない。従って、従来の構成においては、第１の圧力室内のブレーキ液圧は残圧となり、この残圧は、前記第１の圧力室内に高い圧力のまま保持されてしまう。しかし、本発明の構成によれば、前記第１のピストンの後退限が変化したため第１のピストンのリリーフ通路が前記第１の給液室に戻りきれず、リリーフ通路の給液室内開口部がシールと重なって閉塞されてしまった場合でも、リリーフ通路より後方に位置するセイフティ孔が前記第１の給液室内に連通するので、この残圧は該セイフティ孔を介して第１の給液室に解放される。
【００１８】
また、請求項３のマスタシリンダにおいても、前記第１、第２のピストンの後退限が変化したためこれらの第１、第２のピストンのリリーフ通路が、それぞれ前記第１、第２の給液室に戻りきれず、それぞれのリリーフ通路の給液室内開口部がそれぞれ第１、第２のシールと重なって閉塞されてしまった場合、従来の構成においては、前記第１、第２の圧力室内のブレーキ液圧力は残圧となり、これらの残圧は、前記第１、第２の圧力室内に保持されてしまう。しかし、本発明の構成によれば、前記第１、第２のピストンの後退限が変化したためそれぞれのリリーフ通路が前記第１、第２の給液室に戻りきれず、それぞれのリリーフ孔の給液室内開口部がそれぞれ第１、第２のシールと重なって閉塞されてしまった場合でも、それぞれのリリーフ孔より後方に位置する各セイフティ孔がそれぞれ前記第１、第２の給液室に連通するので、これらの残圧はそれぞれのセイフティ孔を介して第１、第２の給液室に解放される。
【００１９】
【発明の実施の形態】
以下、図面に基づいて本発明の好適な実施の形態を例示的に詳しく説明する。図１は、本発明のマスタシリンダの実施例を示す縦断面図であり、図２及び図３は、それぞれ、図１のA部及びＢ部の拡大図である。
【００２０】
図１において、一端に開口部を有するボデイ本体２と、該ボデイ本体２の開口部に結合されるキャップ３と、内部にシリンダ８ａが成形されるとともに、一端が該ボデイ本体２内に嵌装されたスリーブ８とによりシリンダハウジング１を構成し、スリーブ８の内部に成形されたシリンダ８ａ内に第１、第２のピストン４、５が直列状に嵌挿され、これらピストン４、５はスリーブ８の中に摺動可能に配設されている。第１のピストン４は、その一端部をシリンダハウジング１の外部に突出させて、該突出端にブレーキ倍力装置の出力部（例えば、プッシュロッド）と当接係合することができるように球状凹部４ａが設けられている。該第１、第２のピストン４、５とシリンダハウジング１とによって第１の圧力室９を、第２のピストン５とシリンダハウジング１とによって第２の圧力室１０をそれぞれ画成し、これら第１、第２の圧力室９、１０は、シリンダハウジング１に設けられた連通孔１ａ、１ｂを介してブレーキ装置の配管にそれぞれ接続される。また、第１、第２のピストン４、５のそれぞれの外周とシリンダハウジング１の間には第１、第２の給液室２１、２２をそれぞれ画成し、これら第１、第２の給液室２１、２２は、シリンダハウジング１に設けられた連通孔１ｃ、１ｄを介して液リザーバ２３にそれぞれ接続される。第１の給液室２１は、第１の圧力室９との間及びシリンダハウジング１の外部との間を、シリンダハウジング１に設けられたそれぞれのシール２４、２５により密封されている。同様に、第２の給液室２２は、第２の圧力室１０との間及び第１の圧力室９との間を、シリンダハウジング１に設けられたそれぞれのシール２６、２７により密封されている。第１、第２の圧力室９、１０に、第１、第２のピストン４、５を後退方向へ付勢するばね機構１１、１２がそれぞれ配設され、特に、第１の圧力室９に配設されるばね機構１１は、第２のピストン５の後端面に当接するとともに、該後端面の突出部５ｂに案内されるほぼ円筒状のばねリテーナ１７と、該リテーナ１７内に挿通されその頭部１６ａが該リテーナ１７に係止するとともに第１のピストン４の先端側に形成された凹部底面４ｂに係着するガイドピン１６と、ばねリテーナ１７とガイドピン係着部材１８との間に縮設される戻しばね１５から成っている。これらばね機構１１、１２の各々は、非作動時、第１のピストン４を、ブレーキ倍力装置の出力部が戻りきったときの該出力部の位置により規制される後退限に、第２のピストン５を、ばねリテーナ１７により規制される後退限にそれぞれ戻すとともに、これらピストン４、５をこの非作動位置に保持する。第１、第２のピストン４、５が非作動位置に在るとき、第１、第２の圧力室９、１０は、第１、第２のピストン４、５の各々に設けられたリリーフ孔４ｃ、５ｃにより第１、第２の給液室２１、２２とそれぞれ連通するように構成されている。これにより、ブレーキ装置のブレーキ液圧は連通孔１ａ、１ｂ、第１、第２の圧力室９、１０、リリーフ孔４ｃ、５ｃ、第１、第２の給液室２１、２２及び連通孔１ｃ、１ｄを通って液リザーバ２３に開放されて、ブレーキ装置は非作動状態に維持される。ばねリテーナの周縁部１７ａに、半径方向突出部１７ｂを成形し、スリーブ８には、突出部１７ｂが挿通して係合する軸方向に延びたガイド溝２０と、その後退限を若干超える位置に、該突出部１７ｂを当接させる係止部２０ａとを成形して、第２のピストン５が第２の圧力室１０の液圧力によりその後退限より大きくは後退できないように、また、第１ピストン４が外部へ容易に抜き出すことができないように構成されている。
【００２１】
以下、図２において説明すると、第１のピストン４に、リリーフ孔４ｃの給液室内開口部４ｄのやや後方位置に、該第１のピストン４を貫通して第１の圧力室９に達するように設けられた細径のセイフティ孔４ｅが開口されている。ここで、リリーフ孔４ｃの給液室内開口部４ｄとセイフテイ孔４ｅとの間の距離は、リリーフ孔４ｃの給液室内開口部４ｄがシール２４と重なってしまう位置に在ってもセイフティ孔４ｅはまだ第１の給液室２１に連通できる距離であり、また、リリーフ孔４ｃは第１の圧力室９と第１の給液室２１との間のブレーキ液の移動が瞬間的に行われ得る程度に比較的大きな通路面積を持つのに対し、該セイフティ孔４ｅは、第１の圧力室９と第１の給液室２１との間のブレーキ液の移動が数秒程度時間をかけて行われるように細径の孔となっている。尚、シール２４が圧力により第１の圧力室側に異常な変形をするのを防止するため、シールリテーナ２８がシール２４を背後から支えている。第１のピストン４がばね機構１１によりブレーキ倍力装置の出力部の位置により規制される後退限に戻されて非作動位置に在るとき、該セイフティ孔４ｅは第１の給液室２１に連通し、第１の圧力室９は、第１のピストン４に設けられた該セイフティ孔４ｅによっても第１の給液室２１と連通するように構成されている。
【００２２】
以下、図３において説明すると、第２のピストン５に、リリーフ孔５ｃの給液室内開口部５ｄのやや後方位置に、該第２のピストン５を貫通して第２の圧力室１０に達するように設けられた細径のセイフティ孔５ｅが開口されている。ここで、リリーフ孔５ｃの給液室内開口部５ｄとセイフティ孔５ｅとの間の距離は、リリーフ孔５ｃの給液室内開口部５ｄがシール２６と重なってしまう位置に在ってもセイフティ孔５ｅはまだ第２の給液室２２に連通できる距離であり、また、リリーフ孔５ｃは第２の圧力室１０と第２の給液室２２との間のブレーキ液の移動が瞬間的に行われ得る程度に比較的大きな通路面積を持つのに対し、該セイフティ孔５ｅは、第２の圧力室１０と第２の給液室２２との間のブレーキ液の移動が数秒程度時間をかけて行われるように細径の孔となっている。尚、シール２６が圧力により第１の圧力室側に異常な変形をするのを防止するため、シールリテーナ２９がシール２６を背後から支えている。第２のピストン５がばね機構１２により第１の圧力室９内に配設されたばねリテーナ１７により規制される後退限に戻されて非作動位置に在るとき、該セイフティ孔５ｅは第２の給液室２２に連通し、第２の圧力室１０は、第２のピストン５に設けられた該セイフティ孔５ｅによっても第２の給液室２２と連通するように構成されている。
【００２３】
無効ストロークを短縮すべく、初期的に、リリーフ孔４ｃ、５ｃをシール２４、２６に接近させ組立てた場合、関係部品寸法に予期せず発生した経時変化がピストン４、５の後退限を前進方向に移動させるものであると、ピストン４、５が正規の非作動位置に戻りきれずにリリーフ孔４ｃ、５ｃの給液室内開口部４ｄ、５ｄがシール２４、２６と重なって閉塞されことが起こる。この場合、従来のマスタシリンダにおいては、圧力室９、１０内のブレーキ液圧力は給液室２１、２２に流出できずに残圧となるが、本発明のマスタシリンダにおいては、セイフティ孔４ｅ、５ｅをリリーフ孔４ｃ、５ｃの後方に位置させて設けてあるので、該セイフテイ孔４ｅ、５ｅは給液室９、１０内に在る。従って走行中でもこの残圧は該セイフテイ孔４ｅ、５ｅを介して給液室９、１０内に解放する。また、該セイフティ孔４ｅ、５ｅは、無効ストロークを拡大することにならないように、リリーフ孔４ｃ、５ｃに比較して通路面積を極端に少なくすべく細径の孔とした。
【００２４】
なお、本発明の技術は前記実施例における技術に限定されるものではなく、同様な機能を果たす他の態様の手段によってもよく、また、本発明の技術は前記構成の範囲内において種々の変更、附加が可能である。
【００２５】
【発明の効果】
従来、シールとリリーフ通路と間の距離は、これに関係する部品の寸法ばらつきを考慮して、ピストンが正規の非作動位置に在るときはシールがリリーフ通路を絶対に閉塞することのない値にすることが必要で、更に経時的な寸法変化をも配慮すると、これに余裕を附加しなければならなかった。従って無効ストロークを短縮するにあたって限界があった。しかし、本発明によれば、細径のセイフティ孔をリリーフ通路の後方位置に設けたことにより、シールとリリーフ通路と間の距離に余裕を持たせる必要はなくなり、その分、無効ストロークの短縮が可能となる。また、従来、関係部品の寸法ばらつきや経時的な寸法変化を考慮してシールとリリーフ通路と間の距離を設定しても、予期しないような異常な変化が部品等に起こってシールがリリーフ通路を閉塞してしまうことはあり得る。しかし、本発明によれば、細径のセイフティ孔をリリーフ通路の後方位置に設けたことにより、圧力室にブレーキ液圧力が残ることを回避できる。
【図面の簡単な説明】
【図１】本発明のマスタシリンダの実施例を示す縦断面図である。
【図２】図１のＡ部の拡大図である。
【図３】図１のＢ部の拡大図である。
【図４】従来のマスタシリンダを示す縦断面図である。
【符号の説明】
１シリンダハウジング
２ボデイ本体
３キャップ
４第１のピストン
４ｂ凹部底面
４ｃリリーフ孔
４ｄ給液室内開口部
４ｅセイフティ孔
５第２のピストン
５ｃリリーフ孔
５ｄ給液室内開口部
５ｅセイフティ孔
８スリーブ
８ａシリンダ
９第１の圧力室
１０第２の圧力室
１１ばね機構
１２ばね機構
１５戻しばね
１６ガイドピン
１６ａ頭部
１７ばねリテーナ
１７ａ周縁部
１７ｂ半径方向突出部
２０ガイド溝
２０ａ係止部
２１第１の給液室
２２第２の給液室
２４シール
２５シール[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an improvement of a master cylinder used for various brake devices of an automobile.
[0002]
[Prior art]
Conventionally, as this type of master cylinder, for example, there is a tandem master cylinder shown in FIG. 4, which is mounted on the front of a brake booster (not shown) and connected to the output of the booster. The cylinder housing 1 of the master cylinder includes a body main body 2 having an opening at one end, a cap 3 coupled to the opening of the body main body 2, a cylinder 8a formed therein, and one end at the body main body. The cylinder housing 1 is constituted by the sleeve 8 fitted in the cylinder 2, and the first and second pistons 4 and 5 are fitted and inserted in a cylinder 8a formed in the sleeve 8 in series. 4 and 5 are slidably disposed in the sleeve 8. The first piston 4 is configured such that one end thereof can be brought into contact with and engaged with the output portion of the brake booster.
[0003]
A first pressure chamber 9 is defined by the first and second pistons 4 and 5 and the cylinder housing 1, and a second pressure chamber 10 is defined by the second piston 5 and the cylinder housing 1. It is made. Each of the first and second pressure chambers 9, 10 is connected to the piping of each brake device via communication holes 1 a, 1 b provided in the cylinder housing 1.
[0004]
A first liquid supply chamber 21 and a second liquid supply chamber 22 are defined by the outer circumferences of the first and second pistons 4 and 5 and the cylinder housing 1, respectively. Each of the first and second liquid supply chambers 21 and 22 is connected to a respective liquid reservoir 23.
[0005]
The first liquid supply chamber 21 is provided in the cylinder housing 1 to engage with the first piston 4 between the first pressure chamber 9 and the outside of the cylinder housing 1. Sealed by respective seals 24 and 25.
Similarly, the second fluid chamber 22, the between and between the first pressure chamber 9 and the second pressure chamber 10 of the above provided Linda housing 1 second piston Are sealed by respective seals 26, 27 engaging with 5.
[0006]
Return spring mechanisms 11 and 12 for urging the first and second pistons 4 and 5 in the backward direction are disposed in the first and second pressure chambers 9 and 10, respectively. In particular, the spring mechanism 11 disposed in the first pressure chamber 9 includes a substantially cylindrical spring retainer 17 that is in contact with the rear end surface of the second piston 5, and a head that is inserted into the retainer 17. Is fixed between the spring retainer 17 and the first piston 4, and the guide pin 16 that engages with the retainer 17 and engages with the bottom surface of the recess formed on the front end side of the first piston. It consists of a return spring 15.
[0007]
Each of the spring mechanisms 11 and 12 causes the first piston 4 to move to the retreat limit regulated by the contact position with the output portion of the brake booster when not in operation. The pistons 4 and 5 are held in the non-operating positions while returning to the retreat limit regulated by the position of the spring retainer 17.
[0008]
When the first and second pistons 4 and 5 are in the non-operating position, the first and second pressure chambers 9 and 10 are provided in the first and second pistons 4 and 5, respectively. The relief holes 4c and 5c (corresponding to the relief passage of the present invention) communicate with the first and second liquid supply chambers 21 and 22, respectively. As a result, the brake fluid pressure of the brake device passes through the first and second pressure chambers 9 and 10, the relief holes 4c and 5c, and the first and second liquid supply chambers 21 and 22, respectively. The brake device is released to the reservoir 23 and maintained in a non-operating state.
[0009]
When the first piston 4 is pressed by the output portion of the brake booster and strokes in the forward direction, the relief hole 4c provided in the first piston 4 is still in contact with the first liquid supply chamber 21. In an initial stage at the communicating position, the brake fluid pushed out by the first piston 4 flows out from the first pressure chamber 9 into the first liquid supply chamber 21. Therefore, the brake fluid pressure in the first pressure chamber 9 cannot rise to a pressure sufficient for braking the automobile. This stroke that occurs transiently immediately after the start of braking is not preferable as an invalid stroke that can be felt as a delay in braking even when the brake is operated. Therefore, in order to shorten this invalid stroke, the relief hole 4c is opened as close as possible to the seal 24 provided between the first pressure chamber 9 and the first liquid supply chamber 21. Is done.
[0010]
Position where the first piston 4 further strokes and the relief hole 4c overlaps with the seal 24 provided between the first pressure chamber 9 and the first liquid supply chamber 21 and is closed. The first piston 4 starts to discharge the brake fluid in the first pressure chamber 9 to the brake pipe. Further, the brake fluid pressure is generated in the first pressure chamber 9 by the troking of the first piston 4, and the second piston 5 receiving the brake fluid pressure on the rear end surface is stroked in the forward direction. To do. Even in the initial stroke of the second piston 5, an invalid stroke is transiently generated in the same process as that of the first piston 4. Therefore, the relief hole 5c provided in the second piston 5 is also provided between the second pressure chamber 10 and the second liquid supply chamber 22 in order to shorten the invalid stroke. 26 is opened as close as possible to 26.
[0011]
On the other hand, the relative positions of the retreating limits of the first and second pistons 4 and 5 and the seals 24 and 26 provided in the cylinder housing 1 are the cumulative dimensions of many components related thereto. Therefore, there is a large variation in distance. Accordingly, the distances between the relief holes 4c and 5c provided in the pistons 4 and 5 and the seals 24 and 26 provided in the cylinder housing 1 also vary greatly. Furthermore, it is also affected by dimensional changes over time that occur in these related components. Therefore, when the brake is returned, the relief holes 4c and 5c cannot be returned to the position where the relief holes 4c and 5c communicate with the liquid supply chambers 21 and 22, and the liquid supply chamber openings 4d and 5d of the relief holes 4c and 5c are not returned. The seals 24 and 26 may overlap and be blocked. As a result, the brake fluid pressure remains in the brake device without being released, and there is a high possibility that a serious accident will occur if the vehicle is driven without noticing this state. Considering these, the distance between the relief holes 4c and 5c provided in the pistons 4 and 5 and the seals 24 and 26 provided in the cylinder housing 1 must be a value with a margin. In addition, even if these are taken into consideration, the above-mentioned problems cannot be avoided if an unexpected abnormal change occurs in a part.
[0012]
[Problems to be solved by the invention]
Therefore, it is important to provide a master cylinder that is not limited to shortening the invalid stroke and that causes many safety problems and does not generate a residual brake fluid pressure that can lead to a major accident. It is a problem to be solved by the invention.
[0013]
[Means for Solving the Problems]
In order to solve the above problems, the master cylinder of the invention of claim 1 is opened to the cylinder at one end of the cylinder housing is provided with a piston fitted in the cylinder slidably, said piston and said cylinder housing by addition to defining a pressure chamber, between the outer periphery and the cylinder housing of the piston is sealed by a seal between defining a fluid chamber and said pressure chamber and said liquid supply chamber, in addition, the A spring mechanism for urging the piston in the backward direction is disposed in the pressure chamber, and when the piston is returned from the spring mechanism and is in an inoperative position, the pressure chamber is provided in a relief passage provided in the piston. In the master cylinder configured to communicate with the liquid supply chamber, the piston includes a liquid supply chamber opening portion of the relief passage provided in the piston. To and rearward position, setting the opening of the small-diameter safety holes reaching said pressure chamber through said piston only, the opening of the safety hole, return by a spring mechanism in which the piston is disposed in the pressure chamber when located in the inactive position it is, even in a position where the liquid supply chamber opening of the relief passage is overlaps with the seal, by the safety hole provided in the piston, the pressure chamber Is configured to communicate with the liquid supply chamber.
[0014]
Further, the invention of claim 2, opens the cylinder on one end of the cylinder housing, the first is fitted in the cylinder, a second piston slidably, said first and second piston wherein A first pressure chamber is defined by the cylinder housing, and a second pressure chamber is defined by the second piston and the cylinder housing, respectively, and between the outer periphery of the first and second pistons and the cylinder housing. Includes first and second liquid supply chambers, respectively, and between the first pressure chamber and the first liquid supply chamber and between the second pressure chamber and the second liquid supply chamber. And a spring mechanism for urging the first and second pistons in the retreating direction in the first and second pressure chambers, respectively. The first and second pistons of the spring mechanism When the first and second pressure chambers are returned to each other by the relief passages provided in the first and second pistons, respectively, the first and second supply chambers are in the inoperative position. in the produced master cylinder so as to respectively a liquid chamber communicating, at least, in the in the first piston, slightly behind the position of the liquid supply chamber opening of the relief passage provided in the first piston, the setting the opening of the first piston through the small diameter reaching the first pressure chamber safety holes only, the opening of the safety hole, distribution of the first piston within the first pressure chamber Even when the liquid supply chamber opening of the relief passage of the first piston overlaps the first seal when it is returned to the non-operating position by the spring mechanism provided , before provided first piston Depending on the safety hole, it is characterized in that the first pressure chamber is configured to communicate with the first fluid chamber.
[0015]
Further, the invention of claim 3 is characterized in that a body main body having an opening at one end, a cap coupled to the opening of the body main body, a cylinder is formed inside, and one end is fitted in the body main body. A cylinder housing is constituted by the formed sleeve, and first and second pistons fitted into the cylinder are slidably provided, and the first and second pistons and the cylinder housing provide a first pressure. A second pressure chamber is defined by the second piston and the cylinder housing, respectively, and the first and second chambers are defined between the outer circumferences of the first and second pistons and the cylinder housing. A liquid supply chamber is defined, and a first space is formed between the first pressure chamber and the first liquid supply chamber, and a space between the second pressure chamber and the second liquid supply chamber. According to the second seal Sealed, the 1, the first to the second pressure chamber, a spring mechanism for biasing the second piston backward direction are disposed respectively, by each of said first, second piston said spring mechanism When each of the first and second pressure chambers is returned to the non-operating position, the first and second liquid supply chambers are provided by relief passages provided in the first and second pistons, respectively. In each of the master cylinders configured to communicate with the first and second pistons, the first and second pistons are located slightly behind the liquid supply chamber openings of the relief passages provided in the first and second pistons, respectively. the first, the first through the second piston small diameter is provided so as to reach the pressure chambers of the first and second, only respectively set the opening of the second safety hole, the first, opening of the second safety hole, respectively, said first, second When the piston is in the inoperative position is returned each by each of said spring mechanism, said first, supply fluid chamber opening of the relief passage of the second piston, respectively, the first, the second even in position overlaps the seal, said first, said provided in each of the second piston first, by the second safety hole, the first, the second pressure chamber said second The first and second liquid supply chambers are configured to communicate with each other.
[0016]
[Action]
In the master cylinder having such a configuration, the retreat limit of the piston changes, and the relief passage cannot return to the position where it communicates with the liquid supply chamber, and the liquid supply chamber opening of the relief passage overlaps with the seal and is blocked. If the piston had been since its has a retreating limit is restricted by the brake booster can not and also retracted child is pushed by the brake fluid pressure in the first pressure chamber. Therefore, in the conventional configuration, the brake fluid pressure in the pressure chamber becomes a residual pressure, and this residual pressure is held at a high pressure in the pressure chamber. However, according to the configuration of the present invention, the retreat limit of the piston changes, the relief passage cannot return to the position where it communicates with the liquid supply chamber, and the liquid supply chamber opening of the relief passage overlaps with the seal and is closed. even if had, since safety hole located behind the relief passage is communicated with the liquid supply chamber, the residual pressure is released to the liquid supply chamber through the safety hole.
[0017]
Also in the master cylinder of claim 2, wherein the first first piston relief passage for retreat limit is changed in the piston is not completely returned to the first fluid chamber, the liquid supply chamber opening of the relief passage When the first piston is closed due to overlapping with the seal, the backward movement limit of the first piston is regulated by the brake booster, so even if it is pressed by the brake fluid pressure in the first pressure chamber. It can not be the child retreat. Therefore, in the conventional configuration, the brake fluid pressure in the first pressure chamber becomes a residual pressure, and this residual pressure is held at a high pressure in the first pressure chamber. However, according to the configuration of the present invention, since the retracting limit of the first piston is changed , the relief passage of the first piston cannot return to the first liquid supply chamber, and the liquid supply chamber opening of the relief passage is not provided. even when sealing the overlapping got blocked, because safety hole located behind the relief passage communicating with the first liquid supply chamber, the residual pressure first fluid chamber through the safety hole To be released.
[0018]
Also, in the master cylinder of claim 3, since the retracting limits of the first and second pistons are changed , the relief passages of these first and second pistons are respectively connected to the first and second liquid supply chambers. not completely returned to the first liquid supply chamber opening in the respective relief passages, respectively, a second sealing and overlapping field had been closed by case, in the configuration of the past, the first, second pressure the brake fluid pressure in the chamber becomes residual pressure, residual pressure of these, the first, it would be retained in the second pressure chamber. However, according to the configuration of the present invention, since the retracting limits of the first and second pistons have changed, the respective relief passages cannot return to the first and second liquid supply chambers, and the supply of the respective relief holes. the liquid chamber openings each 1, even if had been closed overlaps the second seal, each of the first is the safety hole located behind the respective relief hole, communicating with the second fluid chamber since, the residual pressure of these first through the respective safety hole, is released into the second fluid chamber.
[0019]
DETAILED DESCRIPTION OF THE INVENTION
DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, exemplary embodiments of the invention will be described in detail with reference to the drawings. FIG. 1 is a longitudinal sectional view showing an embodiment of a master cylinder of the present invention, and FIGS. 2 and 3 are enlarged views of a portion A and a portion B in FIG. 1, respectively.
[0020]
In FIG. 1, a body body 2 having an opening at one end, a cap 3 coupled to the opening of the body body 2, a cylinder 8 a is molded therein, and one end is fitted into the body body 2. The cylinder housing 1 is constituted by the sleeve 8 formed, and first and second pistons 4 and 5 are inserted in a cylinder 8a formed inside the sleeve 8 in series. The pistons 4 and 5 are sleeves. 8 is slidably disposed. The first piston 4 has a spherical shape so that one end of the first piston 4 protrudes outside the cylinder housing 1 and can be brought into contact with and engaged with an output portion (for example, a push rod) of the brake booster. A recess 4a is provided. The first and second pistons 4 and 5 and the cylinder housing 1 define a first pressure chamber 9, and the second piston 5 and the cylinder housing 1 define a second pressure chamber 10. The first and second pressure chambers 9 and 10 are connected to piping of a brake device through communication holes 1a and 1b provided in the cylinder housing 1, respectively. Further, first and second liquid supply chambers 21 and 22 are respectively defined between the outer circumferences of the first and second pistons 4 and 5 and the cylinder housing 1, and these first and second supply chambers are defined. The liquid chambers 21 and 22 are connected to the liquid reservoir 23 through communication holes 1c and 1d provided in the cylinder housing 1, respectively. The first liquid supply chamber 21 is sealed between the first pressure chamber 9 and the outside of the cylinder housing 1 by respective seals 24 and 25 provided on the cylinder housing 1. Similarly, the second liquid supply chamber 22 is sealed between the second pressure chamber 10 and the first pressure chamber 9 by respective seals 26 and 27 provided in the cylinder housing 1. Yes. The first and second pressure chambers 9 and 10 are respectively provided with spring mechanisms 11 and 12 for urging the first and second pistons 4 and 5 in the backward direction. The provided spring mechanism 11 is in contact with the rear end surface of the second piston 5 and is inserted into the retainer 17 through a substantially cylindrical spring retainer 17 guided by the protruding portion 5b of the rear end surface. A head 16a is engaged with the retainer 17 and is engaged with a recess bottom surface 4b formed on the front end side of the first piston 4, and between the spring retainer 17 and the guide pin engaging member 18. It consists of a return spring 15 which is retracted. Each of the spring mechanisms 11 and 12 is in a non-operating state in which the first piston 4 is moved to the second retreat limit regulated by the position of the output unit when the output unit of the brake booster has fully returned. The pistons 5 are respectively returned to the retreat limit regulated by the spring retainer 17, and the pistons 4 and 5 are held in the inoperative position. When the first and second pistons 4 and 5 are in the non-operating position, the first and second pressure chambers 9 and 10 are relief holes provided in each of the first and second pistons 4 and 5. 4c and 5c are configured to communicate with the first and second liquid supply chambers 21 and 22, respectively. As a result, the brake fluid pressure of the brake device is reduced to the communication holes 1a, 1b, the first and second pressure chambers 9, 10, the relief holes 4c, 5c, the first and second liquid supply chambers 21, 22 and the communication hole 1c. 1d is opened to the liquid reservoir 23 and the brake device is maintained in an inactive state. A radially projecting portion 17b is formed on the peripheral edge portion 17a of the spring retainer, and the sleeve 8 has an axially extending guide groove 20 into which the projecting portion 17b is inserted and engaged, and a position slightly beyond its retreat limit. The locking portion 20a with which the protruding portion 17b is brought into contact is molded so that the second piston 5 cannot be moved backward by the hydraulic pressure of the second pressure chamber 10 to be larger than its retracting limit. The piston 4 is configured so that it cannot be easily extracted to the outside.
[0021]
In the following, referring to FIG. 2, the first piston 4 passes through the first piston 4 and reaches the first pressure chamber 9 slightly behind the liquid supply chamber opening 4d of the relief hole 4c. A small-sized safety hole 4e provided in is opened. Here, even if the distance between the liquid supply chamber opening 4d of the relief hole 4c and the safety hole 4e is at a position where the liquid supply chamber opening 4d of the relief hole 4c overlaps the seal 24, the safety hole 4e. Is a distance that can still be communicated with the first liquid supply chamber 21, and the relief hole 4 c instantaneously moves the brake fluid between the first pressure chamber 9 and the first liquid supply chamber 21. In contrast to the relatively large passage area that can be obtained, the safety hole 4e allows the brake fluid to move between the first pressure chamber 9 and the first liquid supply chamber 21 over several seconds. As shown in the figure, it is a small-diameter hole. Note that the seal retainer 28 supports the seal 24 from behind in order to prevent the seal 24 from being deformed abnormally toward the first pressure chamber due to pressure. When the first piston 4 is returned to the retreat limit regulated by the position of the output part of the brake booster by the spring mechanism 11 and is in the non-operating position, the safety hole 4e is formed in the first liquid supply chamber 21 . communicating the first pressure chamber 9 is also configured to communicate with the first fluid chamber 21 by the safety hole 4e provided in the first piston 4.
[0022]
In the following, referring to FIG. 3, the second piston 5 passes through the second piston 5 and reaches the second pressure chamber 10 slightly behind the liquid supply chamber opening 5 d of the relief hole 5 c. A small-sized safety hole 5e provided in is opened. Here, even if the distance between the liquid supply chamber opening 5d of the relief hole 5c and the safety hole 5e is at a position where the liquid supply chamber opening 5d of the relief hole 5c overlaps the seal 26, the safety hole 5e. Is a distance that can still be communicated with the second liquid supply chamber 22, and the relief hole 5 c instantaneously moves the brake fluid between the second pressure chamber 10 and the second liquid supply chamber 22. The safety hole 5e has a relatively large passage area so that the brake fluid moves between the second pressure chamber 10 and the second liquid supply chamber 22 over several seconds. As shown in the figure, it is a small-diameter hole. Note that a seal retainer 29 supports the seal 26 from behind to prevent the seal 26 from being deformed abnormally toward the first pressure chamber due to pressure. When the second piston 5 is returned to the retreat limit regulated by the spring retainer 17 disposed in the first pressure chamber 9 by the spring mechanism 12 and is in the non-operating position, the safety hole 5e is in the second position. communicated to the fluid chamber 22, the second pressure chamber 10 is also configured to communicate with the second fluid chamber 22 by the safety hole 5e provided on the second piston 5.
[0023]
If the relief holes 4c and 5c are initially assembled close to the seals 24 and 26 in order to shorten the invalid stroke, an unexpected change with time in the dimensions of the related parts causes the retraction limit of the pistons 4 and 5 to move forward. The pistons 4 and 5 cannot return to the normal non-operating position, and the liquid supply chamber openings 4d and 5d of the relief holes 4c and 5c overlap with the seals 24 and 26 and are blocked. . In this case, in the conventional master cylinder, the brake fluid pressure in the pressure chambers 9 and 10 cannot flow into the liquid supply chambers 21 and 22, but becomes a residual pressure. However, in the master cylinder of the present invention, the safety holes 4e, Since 5e is provided behind the relief holes 4c and 5c, the safety holes 4e and 5e are in the liquid supply chambers 9 and 10, respectively. Accordingly, this residual pressure is released into the liquid supply chambers 9 and 10 through the safety holes 4e and 5e even during traveling. The safety holes 4e and 5e are small-diameter holes so that the passage area is extremely small compared to the relief holes 4c and 5c so as not to increase the invalid stroke.
[0024]
The technique of the present invention is not limited to the technique in the above-described embodiment, and may be implemented by means of other modes that perform the same function, and the technique of the present invention may be variously modified within the scope of the above-described configuration. Can be added.
[0025]
【The invention's effect】
Conventionally, between the seal and the relief passage distance, in consideration of dimensional variations of the components related to this, piston of the seal when in inoperative normal position closes the relief passage absolutely It was necessary to make it a non-existent value, and when considering the dimensional change over time, a margin had to be added to this. Therefore, there is a limit in shortening the invalid stroke. However, according to the present invention, by providing a rear position of the small-diameter safety holes a relief passage, no longer necessary to provide a margin to the distance between the seal and the relief passage, correspondingly, reduce the ineffective stroke Is possible. Further, conventionally, setting the distance between the seal and the relief passage in consideration of dimensional variations and temporal dimensional change related parts, seals unexpected such abnormal changes going on components etc. It is possible to block the relief passage . However, according to the present invention, it is possible to avoid the brake fluid pressure from remaining in the pressure chamber by providing the small diameter safety hole at the rear position of the relief passage .
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional view showing an embodiment of a master cylinder of the present invention.
FIG. 2 is an enlarged view of part A in FIG.
FIG. 3 is an enlarged view of a portion B in FIG.
FIG. 4 is a longitudinal sectional view showing a conventional master cylinder.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Cylinder housing 2 Body main body 3 Cap 4 1st piston 4b Recess bottom face 4c Relief hole 4d Safety hole 4d Safety hole 5 Second piston 5c Relief hole 5d Fluid supply room opening 5e Safety hole 8 Sleeve 8a Cylinder 9 First pressure chamber 10 Second pressure chamber 11 Spring mechanism 12 Spring mechanism 15 Return spring 16 Guide pin 16a Head 17 Spring retainer 17a Peripheral portion 17b Radius protrusion 20 Guide groove 20a Locking portion 21 First liquid supply Chamber 22 Second liquid supply chamber 24 Seal 25 Seal

Claims

Opening the cylinder to one end of the cylinder housing is provided with a piston fitted in the cylinder slidably, together defining a pressure chamber by said said piston cylinder housing, the cylinder housing and the outer periphery of the piston defining a fluid chamber between, and sealed by a seal between said liquid supply chamber and the pressure chamber, also arranged a spring mechanism for biasing the piston to the pressure chamber to the reverse direction In the master cylinder configured to communicate with the liquid supply chamber by a relief passage provided in the piston when the piston is returned from the spring mechanism and is in a non-operating position.
Wherein the piston, slightly rearward position of the liquid supply chamber opening of the relief passage provided in the piston, setting the opening of the small-diameter safety holes reaching said pressure chamber through said piston,
The opening of the safety hole, when the piston is in the inoperative position is returned by a spring mechanism which is disposed in the pressure chamber, the position of the liquid supply chamber opening of the relief passage is overlaps with the seal the even, depending on the safety hole provided in the piston, the master cylinder, characterized in that the pressure chamber is configured to communicate with said liquid supply chamber.

Opening the cylinder to one end of the cylinder housing, first, providing a second piston slidably, the first, the first pressure chamber and the second piston by the said cylinder housing to be fitted in the cylinder A second pressure chamber is defined by the second piston and the cylinder housing, and the first and second supply chambers are defined between the outer circumferences of the first and second pistons and the cylinder housing. A liquid chamber is respectively defined, and a first space between the first pressure chamber and the first liquid supply chamber, and a space between the second pressure chamber and the second liquid supply chamber, respectively. A spring mechanism for sealing the first and second pressure chambers in a retreating direction is disposed in the first and second pressure chambers, respectively, and the first and second pistons are sealed by a second seal. Returned by each of the spring mechanisms. When in the non-operating position, the first and second pressure chambers communicate with the first and second liquid supply chambers by relief passages provided in the first and second pistons, respectively. In the master cylinder configured as follows:
At least, wherein the first piston, slightly rearward position of the liquid supply chamber opening of the relief passage provided in the first piston, the first pressure chamber through said first piston setting the opening of the small-diameter safety hole reaching,
The opening of the safety hole, when said first piston is at the inoperative position is returned by the first disposed a spring mechanism to the pressure chamber, the liquid supply of the relief passage of said first piston even in a position where chamber opening overlaps with the first seal, said provided first piston by the safety hole, the first pressure chamber of the first fluid chamber A master cylinder characterized by being configured to communicate with a cylinder.

A cylinder housing is configured by a body body having an opening at one end, a cap coupled to the opening of the body body, a cylinder formed inside, and a sleeve fitted into the body body at one end The first and second pistons inserted into the cylinder are slidably provided, and the first pressure chamber is defined by the first and second pistons and the cylinder housing, and the second piston. A second pressure chamber is defined by the cylinder housing, and first and second liquid supply chambers are defined between the outer circumferences of the first and second pistons and the cylinder housing, And sealing between the first pressure chamber and the first liquid supply chamber and between the second pressure chamber and the second liquid supply chamber by first and second seals, respectively. The first and second A spring mechanism for urging the first and second pistons in the retracting direction is disposed in the force chamber, respectively, and the first and second pistons are returned by the spring mechanisms and are in the non-operating position. The first and second pressure chambers are configured to communicate with the first and second liquid supply chambers by a relief passage provided in each of the first and second pistons. In the master cylinder,
Wherein the first, the second piston, slightly rearward position of the liquid supply chamber opening of the relief passage provided in the piston of said 1,2, through said first, second piston the first small diameter provided so as to reach the first and second pressure chambers, respectively setting the opening of the second safety hole,
The first, opening of the second safety holes, respectively, the first, when the second piston is in the inoperative position is returned each by each of said spring mechanism, said first, second the liquid supply chamber opening of the relief passage of the piston, respectively, the first, even in a position overlaps the second seal, which is provided on each of said first, second piston first, by the second safety hole, said first, second pressure chamber is the first master cylinder, characterized in that each of the second fluid chamber is configured to communicate.