JP3999416B2

JP3999416B2 - Negative pressure booster

Info

Publication number: JP3999416B2
Application number: JP23888399A
Authority: JP
Inventors: 孝義篠原; 洋生川上
Original assignee: Nissin Kogyo Co Ltd
Current assignee: Nissin Kogyo Co Ltd
Priority date: 1999-08-25
Filing date: 1999-08-25
Publication date: 2007-10-31
Anticipated expiration: 2019-08-25
Also published as: JP2001063551A

Description

【０００１】
【発明の属する技術分野】
本発明は，自動車のブレーキマスタシリンダの倍力作動のために用いられる負圧ブースタに関し，特に，ブースタシェルに，その内部を負圧源に連なる前側の負圧室と後側の作動室とに区画するブースタピストンを収容し，このブースタピストンに，前記ブースタシェルの後壁に摺動自在に支承される弁筒を連設し，この弁筒内に，前後動可能の入力杆と，この入力杆の前後動に応じて前記作動室を前記負圧室と大気とに連通切換えする制御弁とを配設し，前記弁筒及び入力杆と，前記ブースタシェルに摺動可能に支持される出力杆との間に，入力杆に対する入力と，作動室及びを負圧室間の気圧差による前記ブースタピストンの推力との合力を該出力杆に伝達する反力機構を介裝したものゝ改良に関する。
【０００２】
【従来の技術】
従来，かゝる負圧ブースタにおいて，例えば特開平９−２２４６号公報に開示されているように，緊急ブレーキ時には，ソレノイド装置の励磁により制御弁の作動量を増加させ，作動室に大量の大気を素早く導入して出力杆に倍力限界の高出力を発揮させるようにしたものが知られている。
【０００３】
【発明が解決しようとする課題】
上記公報に開示された負圧ブースタでは，高価なソレノイド装置のみならず，緊急ブレーキ状態を検知するセンサを必要とするので，構成が複雑の上，コストが高くつく欠点がある。
【０００４】
本発明は，かゝる事情に鑑みてなされたもので，簡単で安価な構造を付加するだけで，緊急ブレーキ時には，作動室に大量の大気を素早く導入して出力杆に高出力を発揮させる得るようにした，前記負圧ブースタを提供することを目的とする。
【０００５】
【課題を解決するための手段】
上記目的を達成するために，本発明は，ブースタシェルに，その内部を負圧源に連なる前側の負圧室と後側の作動室とに区画するブースタピストンを収容し，このブースタピストンに，前記ブースタシェルの後壁に摺動自在に支承される弁筒を連設し，この弁筒内に，前後動可能の入力杆と，この入力杆の前後動に応じて前記作動室を前記負圧室と大気とに連通切換えする制御弁とを配設し，前記弁筒及び入力杆と，前記ブースタシェルに摺動可能に支持される出力杆との間に，入力杆に対する入力と，作動室及びを負圧室間の気圧差による前記ブースタピストンの推力との合力を該出力杆に伝達する反力機構を介裝した負圧ブースタにおいて，前記入力杆及び反力機構間を連結する入力ピストンに弁ピストンを，これが入力ピストンに対して軸方向に沿う後退位置及び前進位置間を摺動し得るように嵌合し，この弁ピストンの後端に形成される大気導入弁座と，前記弁筒に形成されてこの大気導入弁座を囲繞する負圧導入弁座と，これら大気導入弁座及び負圧導入弁座に着座可能に対置される共通の弁部を前端に有して前記弁筒の内周面に取付けられる筒状の弁体と，前記弁部を大気導入弁座及び負圧導入弁座との着座方向へ付勢する弁ばねとで前記制御弁を構成し，前記弁筒に，前記負圧室に連通して前記負圧導入弁座及び弁体間に開口する第１ポートと，前記作動室に連通して前記大気導入弁座及び負圧導入弁座間に開口する第２ポートとを設ける一方，前記弁体の内側を大気に連通し，前記弁ピストンを，戻しばねの，前記弁ばねより小さいセット荷重をもって前記後退位置側へ付勢すると共に，この弁ピストン及び入力ピストン間に，弁ピストンの前記戻しばねの付勢力による前進位置からの後退を遅延させる遅延手段を設けたことを第１の特徴とする。
【０００６】
この第１の特徴によれば，入力杆を急速前進させる緊急ブレーキ時には，弁ピストンは遅延手段の遅延作用を受けて，略前進位置を保ったまゝ入力ピストンと共に前進するため，弁ピストンの大気導入弁座が入力杆の前進と同時に弁体の弁部から大きく離れて最大に開放されることにより，作動室に大量の大気が導入され，ブースタピストンに負圧室及び作動室間の大なる気圧差による大なる前進推力を即座に与えて，出力杆の出力を素早く且つ大きく立ち上がらせ，緊急ブレーキに対応することができる。しかも，高価なソレノイド装置や緊急ブレーキセンサを必要としないので，コストの低減に寄与し得る。
【０００７】
一方，入力杆を普通の速度で前進させる通常ブレーキ時には，弁ピストンは遅延手段の遅延作用を受けることなく，入力杆と共に前進する入力ピストンに対して戻しばねの付勢力で後退位置まで移動してから，大気導入弁座を弁体の弁部から適度に離すので，作動室への大気導入量を適度に制限して，出力杆の出力を程よく増加させることができ，違和感を生じさせない。
【０００８】
また本発明は，上記特徴に加えて，前記遅延手段を，前記弁ピストン及び入力ピストンの一方の摺動嵌合面に装着されて他方の摺動嵌合面に密接するシール部材で構成したことを第２の特徴とする。
【０００９】
この第２の特徴によれば，弁ピストン及び入力ピストン間のシール部材が遅延手段を兼ねることになって，構成を一層簡素化し，コストを効果的に下げることができる。
【００１０】
【実施例の形態】
本発明の実施の形態を，添付図面に示す本発明の実施例に基づいて説明する。
【００１１】
図１は本発明の一実施例に係るタンデム型負圧ブースタの縦断面図，図２は図１の２部拡大断面図（休止状態），図３は上記負圧ブースタの通常ブレーキ時の作用説明図，図４は上記負圧ブースタの緊急ブレーキ時の作用説明図，図５は上記負圧ブースタの出力特性を示す線図，図６は上記負圧ブースタの要部の変形例を示す，図２に対応した断面図である。
【００１２】
先ず図１及び図２において，負圧ブースタＢのブースタシェル１は，対向端を相互に結合する前後一対のシェル半体１ａ，１ｂと，両シェル半体１ａ，１ｂ間に挟止されてブースタシェル１内部を前部シェル室２と後部シェル室３とに仕切る隔壁板１ｃとから構成され，その後部シェル半体１ｂが自動車の車室前壁Ｄにボルト８により固定して支持され，前部シェル半体１ａには，該ブースタＢにより作動されるブレーキマスタシリンダＭのシリンダボディＭａがボルト９により固着される。
【００１３】
前部シェル室２は，それに前後往復動可能に収容される前部ブースタピストン４と，その後面に重ねて結着されると共に前部シェル半体１ａと隔壁板１ｃ間に挟着される前部ダイヤフラム５とにより，前側の前部負圧室２ａと後側の前部作動室２ｂとに区画される。そして，前部負圧室２ａは，負圧導入管１４を介して負圧源Ｖ（例えば内燃機関の吸気マニホールド内部）と接続される。
【００１４】
また後部シェル室３は，それに前後往復動可能に収容される後部ブースタピストン６と，その後面に重ねて結着され，且つ隔壁板１ｃと共に両シェル半体１ａ，１ｂ間に固着される後部ダイヤフラム７とにより，前側の後部負圧室３ａと後側の後部作動室３ｂとに区画される。
【００１５】
前，後部ブースタピストン４，６はそれぞれ鋼板により環状に成形されており，これらは中心部に固着される合成樹脂製の弁筒１０を介して一体に連結される。弁筒１０は，隔壁板１ｃにシール部材１１を介して，また後部シェル半体１ｂの中心部に形成された後方延長筒１２にシール部材１３を介して摺動自在に支承される。両ブースタピストン４，６の後退限は，後部ダイヤフラム７の後面に多数***させた突起７ａがブースタシェル１の後壁に当接することにより規定される。
【００１６】
弁筒１０には，その内周面に摺動自在に嵌合する入力ピストン１８，この入力ピストン１８に連結する入力杆２０，及びこの入力杆２０の前後動に応じて作動室２ｂ，３ｂを負圧室２ａ，３ａと大気とに連通切換えする制御弁３８とが配設される。入力ピストン１８は，弁筒１０の内周面に摺動自在に嵌合するピストン部１８ａと，このピストン部１８ａから後方へ突出する連結筒部１８ｂとより構成されており，その連結筒部１８ｂ内側に入力杆２０の球状前端部２０ａが嵌合されると共に，その抜け止めのために連結筒部１８ｂの一部１９がかしめられる。こうして入力杆２０は入力ピストン１８に首振り可能に連結される。入力杆２０の後端には，これを前進作動するブレーキペダルＰが連結される。
【００１７】
入力ピストン１８の連結筒部１８ｂ外周面には，円筒状の弁ピストン３３が摺動可能に嵌装される。この弁ピストン３３は，入力ピストン１８のピストン部１８ａに当接する前進位置Ｆ（図２参照）と，連結筒部１８ｂに係止されるストッパ環４５に当接する後退位置Ｒ（図３参照）との間を所定ストロークｓをもって摺動し得るもので，この弁ピストン３３と入力ピストン１８のピストン部１８ａとの間には，弁ピストン３３を後退位置Ｒに向かって付勢する戻しばね４４が縮設される。弁ピストン３３及び連結筒部１８ｂの一方の摺動嵌合面に形成された環状溝４６には，他方の摺動嵌合面に密接するシール部材としてのＯリング４７が装着される。上記環状溝４６は，図示例では，弁ピストン３３の内周面に設けたが，入力ピストン１８の外周面に設けることもできる。このＯリング４７は，弁ピストン３３及び入力ピストン１８の摺動嵌合部のシールを行うのみならず，戻しばね４４の付勢力による弁ピストン３３の前進位置Ｆからの後退を摩擦により遅延させる遅延手段を構成する。
【００１８】
尚，上記環状溝４６には，図６に示すように，上記Ｏリング４７に代えて断面方形のシール部材４７′を装着することもできる。
【００１９】
弁筒１０には，前後の負圧室２ａ，３ａ間を連通する第１連通路２８ａと，前後の作動室２ｂ，３ｂ間を連通する第２連通路２８ｂと，第１連通路２８ａに連なって弁筒１０内周面に開口する第１ポート２９ａと，第２連通路２８ｂに連なると共に，第１ポート２９ａより前方で弁筒１０内周面に開口する第２ポート２９ｂとが形成される。それら第１及び第２ポート２９ａ，２９ｂの前後方向中間部の弁筒１０内周面に環状の負圧導入弁座３０とが形成される。また前記弁ピストン３３の後端には，第２ポート２９ｂに連なる環状通路３２を挟んで負圧導入弁座３０に囲繞される環状の大気導入弁座３１が形成されており，負圧導入弁座３０及び大気導入弁座３１に対向する共通一個の弁体３４が弁筒１０内に配設される。この弁体３４は，負圧導入弁座３０及び大気導入弁座３１に着座可能に対向する環状の弁部３４ａを前端に，環状の取付けビード部３４ｂを後端に，その両部分３４ａ，３４ｂを軸方向相対変位可能に連結するダイヤフラム部３４ｃを中間部にそれぞれ形成してなるもので，取付けビード部３４ｂは，弁筒１０の後部内周面に嵌着される円筒状の弁ホルダ３５の前端部により，弁筒１０内周面に取付けられる。そして，その弁部３４ａを両弁座３０，３１との着座方向へ付勢する弁ばね３６が弁部３４ａと入力杆２０との間に縮設される。前記戻しばね４４のセット荷重は，この燃焼ばね３６のセット荷重のそれより小さく設定される。
【００２０】
以上において，上記両弁座３０，３１，弁体３４及び弁ばね３６は制御弁３８を構成する。
【００２１】
後方延長筒１２の後端には，中心部に大気導入口３９が開口する内向きフランジ１２ａが一体に形成されており，このフランジ１２ａの内側面に当接して入力杆２０の後退限を規定するストッパ板４０が入力杆２０に前後方向調節可能に固着され，その後退限に向かって入力杆２０は，弁ホルダ３５に支持される入力戻しばね４１により付勢される。
【００２２】
また弁筒１０の後端部内周には，エアフィルタ４２が装着され，それを通して弁体３４の内側は大気導入口３９と常時連通している。上記エアフィルタ４２は，入力杆２０の弁筒１０に対する前後動を妨げないように柔軟性を有する。
【００２３】
弁筒１０の前端部は大径ピストン１５に形成され，この大径ピストン１５の中心部に形成されて，その前面に開口するシリンダ孔１６に，大径ピストン１５より一定の割合で縮径した小径ピストン１７が摺動自在に嵌装され，この小径ピストン１７は，図示例の場合，前記弁ピストン３３の前端一体に連設される。大径ピストン１５の外周にはカップ体２１が摺動自在に嵌合され，このカップ体２１には，後端面を大径ピストン１５に当接させる偏平な弾性ピストン２２が充填される。前記小径ピストン１７は，通常，この弾性ピストン２２後端面に所定間隙ｇを存して対置されるもので，その所定間隙ｇは，弁ピストン３３の入力ピストン１８に対する前記摺動ストロークｓより大きく設定される。
【００２４】
以上において，大径ピストン１５，小径ピストン１７，弾性ピストン２２及びカップ体２１は，入力杆２０に対する入力とブースタピストン４，６の推力との合力を出力杆２５に伝達する反力機構２４を構成する。
【００２５】
カップ体２１の前面には出力杆２５が突設され，この出力杆２５は前記ブレーキマスタシリンダＭのピストンＭｂに連接される。またカップ体２１及び弁筒１０の前端面に当接するリテーナ２６が配設され，このリテーナ２６とブースタシェル１の前壁との間に弁筒戻しばね２７が縮設される。
【００２６】
次にこの実施例の作用について説明する。
［負圧ブースタの休止］
負圧ブースタＢの休止状態では，図１及び図２に示すように，入力杆２０がストッパ板４０を後方延長筒１２の内向きフランジ１２ａに当接させる後退限に位置すると共に，両ブースタピストン４，６が後部ダイヤフラム７の突起７ａをブースタシェル１の後壁に当接させる後退限に位置しており，制御弁３８は，弁体３４の弁部３４ａを大気導入弁座３１及び負圧導入弁座３０に着座させて両作動室２ｂ，３ｂを両負圧室２ａ，３ａ及び大気導入口３９の何れとも不通にした中立状態となっている。
【００２７】
この場合，弁ピストン３３を後退方向へ付勢する戻しばね４４のセット荷重が弁部３４ａを前方へ付勢する燃焼ばね３６のセット荷重より小さく設定されているから，入力戻しばね４１の付勢力により入力杆２０が後退限に保持されることに伴い，弁ピストン３３は，大気導入弁座３１を弁部３４ａに密着させつゝ戻しばね４４を圧縮させて，入力ピストン１８上の前進位置Ｆを占めている。
【００２８】
一方，弁ピストン３３及び入力ピストン１８の摺動嵌合面間のＯリング４７は，弁ピストン３３外周の負圧が弁ピストン３３及び入力ピストン１８間を通って弁体３４内側へリークするのを阻止している。
［通常ブレーキ］
車両を制動すべくブレーキペダルＰを普通の速度で踏込み，入力杆２０，入力ピストン１８及び弁ピストン３３を前進させれば，この弁ピストン３３の普通の前進速度では，Ｏリング４７の遅延作用に殆ど影響されるとなく，弁ピストン３３は，図３に示すように，戻しばね４４の付勢力をもって入力ピストン１８上を後退位置Ｒに向かって相対的に摺動する。そして，弁ピストン３３が後退位置Ｒに達すると，入力杆２０，入力ピストン１８及び弁ピストン３３の三者が一体となって前進するが，当初，両ブースタピストン４，６は不動であるから，弁ピストン３３の大気導入弁座３１が弁体３４の弁部３４ａから適度に離れて，第２ポート２９ｂを環状通路３２を介して大気導入口３９に適度に連通させる。その結果，大気導入口３９から弁筒１０内に流入した大気は大気導入弁座３１及び弁部３４ａ間で適度に流量を制限されつゝ，第２ポート２９ｂを経て両作動室２ｂ，３ｂに素早く導入され，該室２ｂ，３ｂを両負圧室２ａ，３ａより高圧にするので，それらの気圧差に基づく前方推力を得て両ブースタピストン４，６は，弁筒１０及び大径ピストン１５を伴いながら弁筒戻しばね２７の力に抗して前進作動し，大径ピストン１５及び弾性ピストン２２を介してカップ体２１，即ち出力杆２５を前方へ押動する。
【００２９】
ところで，反力機構２４の弾性ピストン２２及び小径ピストン１７間には，当初，弁ピストン３３の入力ピストン１８に対する摺動ストロークｓより大きい所定間隙ｇが存在しているので，大気導入弁座３１が弁部３４ａから離れてから小径ピストン１７が弾性ピストン２２に当接するまでは，入力杆２０に若干の自由な前進ストロークが残っており，入力杆２０は，この前進ストロークを前進する間は反力機構２４から反力を受けないため，出力杆２５の出力は，図５の線ａ−ｂのように適度にジャンピングし，これによりブレーキマスタシリンダＭのピストンＭｂを適度に急速作動して，車輪ブレーキを素早く且つ違和感なく作動することができる。
【００３０】
その直後，小径ピストン１７が弾性ピストン２２に当接するようになると，弾性ピストン２２の後面には，大径ピストン１５に加わる両ブースタピストン４，６の推力の他に，入力杆２０から小径ピストン１７に加わる操縦者の踏力とが作用し，また弾性ピストン２２の前端面には出力杆２５の作動反力が作用しているので，弾性ピストン２２は圧縮されて，その一部をシリンダ孔１６に食み出させながら出力杆２５の作動反力の一部を入力杆２０に伝達することになり，操縦者は出力杆２５の出力，即ち制動力の大きさを感受するようになる。その結果，出力杆２５の出力は，倍力限界に達するまでは図５の線ｂ−ｃのように，入力杆２０の入力に比例して増加する。
【００３１】
その間，ブースタピストン４，６と一体の弁筒１０は，入力杆２０の前進量だけ前進するもので，入力杆２０が前進を止めると，弁筒１０と共に前進してきた弁体３４が大気導入弁座３１に再び着座して，作動室２ｂ，３ｂへの大気のそれ以上の導入を阻止するので，ブースタピストン４，６の前進も停止し，入力に対応した倍力出力が得られることになる。
【００３２】
出力杆２５の出力が倍力限界を超えると，ブースタピストン４，６の気圧差による推力が最大となり，大気導入弁座３１は弁体３４から離間したまゝとなるので，出力杆２５の出力は，ブースタピストン４，６の気圧差による最大推力と，ブレーキペダルＰへの踏力による入力杆２０の推力との和となる（図５の線ｃ−ｄ参照）。
［ブレーキ解除］
車両の制動状態を解除すべく，ブレーキペダルＰから踏力を解放すると，先ず入力杆２０及び入力ピストン１８が入力戻しばね４１の力をもって後退する。このとき，大気導入弁座３１が弁体３４の弁部３４ａに密着すると，弁ピストン３３は，戻しばね４４を圧縮させつゝ入力ピストン１８に対して相対的に前進位置Ｆへと移動し，その後は入力ピストン１８と共に後退して，弁部３４ａを負圧導入弁座３０から大きく離間させるので，両作動室２ｂ，３ｂが第２ポート２９ｂ，環状通路３２及び第１ポート２９ａを介して両負圧室２ａ，３ａと連通する。その結果，両作動室２ｂ，３ｂへの大気の導入が阻止される一方，両作動室２ｂ，３ｂの空気が両負圧室２ａ，３ａを経て負圧限Ｖに吸入され，それらの気圧差が無くなるため，ブースタピストン４，６も，弁筒戻しばね２７の力をもって後退し，マスタシリンダＭの作動を解除していく。
【００３３】
入力杆２０がストッパ板４０を後方延長筒１２の内向きフランジ１２ａに当接させる後退限まで後退すると，後部ブースタピストン６は，後部ダイヤフラム７の突起７ａをブースタシェル１の後壁に当接させる後退限まで戻り，負圧導入弁座３０をも弁部３４ａに密着させ，制御弁３８を当初の中立状態にする。
［緊急ブレーキ］
ブレーキペダルＰを急速に踏み込む緊急ブレーキ時には，図４に示すように，入力ピストン１８の前進速度が速いため，弁ピストン３３はＯリング４７の摩擦による遅延作用を受けて，略前進位置Ｆを保ったまゝ入力ピストン１８と共に前進する。したがって，弁ピストン３３の大気導入弁座３１は，入力杆２０の前進と同時に弁体３４の弁部３４ａから離れ，大気が作動室２ｂ，３ｂへ直ちに導入される。しかも，この場合は，大気導入弁座３１が弁部３４ａから離れてから小径ピストン１７が弾性ピストン２２に当接するまでの入力杆２０の自由な前進ストロークは，前述の通常ブレーキ時に比して大きいから，入力杆２０がこの大きな前進ストロークを前進する間に，大気導入弁座３１が最大に開放されて，作動室２ｂ，３ｂに大量の大気が導入されると共に，出力杆２５の出力が図５の線ａ−ｂ′のように大きくジャンピングする。かくして，高価なソレノイド装置及び緊急ブレーキセンサを用いることなく，出力杆２５の出力を素早く且つ大きく立ち上がらせ，緊急ブレーキに対応することができる。
【００３４】
大気導入弁座３１が最大に開放されてから一定時間が経過すると，弁ピストン３３は戻しばね４４の付勢力をもって後退位置Ｒまで戻り，通常ブレーキ状態となるので，出力杆２５の出力は図５の線ｂ′−ｃ−ｄを辿ることになる。
【００３５】
本発明は，上記実施例に限定されるものではなく，その要旨を逸脱しない範囲で種々の設計変更が可能である。例えば，負圧ブースタＢは，ブースタピストンを単一とするシングル型に構成することもできる。また反力機構２４の小径ピストン１７は，弁ピストン３３と別体に構成して，弁ピストン３３に当接配置することもできる。また負圧ブースタＢの休止状態では，制御弁３８において弁体３４の弁部３４ａを負圧導入弁座３０から離座させておくようにすることもできる。
【００３６】
【発明の効果】
以上のように本発明の第１の特徴によれば，入力杆及び反力機構間を連結する入力ピストンに弁ピストンを，これが入力ピストンに対して軸方向に沿う後退位置及び前進位置間を摺動し得るように嵌合し，この弁ピストンの後端に形成される大気導入弁座と，弁筒に形成されてこの大気導入弁座を囲繞する負圧導入弁座と，これら大気導入弁座及び負圧導入弁座に着座可能に対置される共通の弁部を前端に有して弁筒の内周面に取付けられる筒状の弁体と，弁部を大気導入弁座及び負圧導入弁座との着座方向へ付勢する弁ばねとで制御弁を構成し，弁筒に，負圧室に連通して負圧導入弁座及び弁体間に開口する第１ポートと，作動室に連通して大気導入弁座及び負圧導入弁座間に開口する第２ポートとを設ける一方，弁体の内側を大気に連通し，弁ピストンを，戻しばねの，弁ばねより小さいセット荷重をもって後退位置側へ付勢すると共に，この弁ピストン及び入力ピストン間に，弁ピストンの戻しばねの付勢力による前進位置からの後退を遅延させる遅延手段を設けたので，入力杆を急速前進させる緊急ブレーキ時には，弁ピストンの大気導入弁座が入力杆の前進と同時に弁体の弁部から大きく離れて最大に開放されることにより，作動室に大量の大気を導入し，ブースタピストンに気圧差による大なる前進推力を即座に与えて，出力杆の出力を素早く且つ大きく立ち上がらせ，緊急ブレーキに対応することができ，一方，入力杆を普通の速度で前進させる通常ブレーキ時には，大気導入弁座を弁体の弁部から適度に離して，作動室への大気導入量を適度に制限し，出力杆の出力を程よく増加させることができ，違和感を生じさせない。しかも，高価なソレノイド装置や緊急ブレーキセンサを必要としないので，コストの低減に寄与し得る。
【００３７】
また本発明の第２の特徴によれば，遅延手段を，弁ピストン及び入力ピストンの一方の摺動嵌合面に装着されて他方の摺動嵌合面に密接するシール部材で構成したので，弁ピストン及び入力ピストン間のシール部材が遅延手段を兼ねることになって，構成を一層簡素化し，コストを効果的に下げることができる。
【図面の簡単な説明】
【図１】本発明の一実施例に係るタンデム型負圧ブースタの縦断面図。
【図２】図１の２部拡大断面図（休止状態）。
【図３】上記負圧ブースタの通常ブレーキ時の作用説明図。
【図４】上記負圧ブースタの緊急ブレーキ時の作用説明図。
【図５】上記負圧ブースタの出力特性を示す線図。
【図６】上記負圧ブースタの要部の変形例を示す，図２に対応した断面図。
【符号の説明】
Ｂ・・・・負圧ブースタ
Ｆ・・・・弁ピストンの前進位置
Ｒ・・・・弁ピストンの後退位置
Ｖ・・・・負圧源
ｓ・・・・弁ピストンの摺動ストローク
１・・・・ブースタシェル
２ａ・・・負圧室（前部負圧室）
３ａ・・・負圧室（後部負圧室）
２ｂ・・・作動室（前部作動室）
３ｂ・・・作動室（後部作動室）
４・・・・ブースタピストン（前部ブースタピストン）
６・・・・ブースタピストン（後部ブースタピストン）
１０・・・弁筒
１８・・・入力ピストン
２０・・・入力杆
２４・・・反力機構
２５・・・出力杆
２９ａ・・第１ポート
２９ｂ・・第２ポート
３０・・・負圧導入弁座
３１・・・大気導入弁座
３３・・・弁ピストン
３４・・・弁体
３４ａ・・弁部
３６・・・弁ばね
３８・・・制御弁
４４・・・戻しばね
４７・・・遅延手段（Ｏリング）
４７′・・遅延手段（シール部材）[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a negative pressure booster used for boosting operation of a brake master cylinder of an automobile, and more particularly, to a booster shell and a front negative pressure chamber connected to a negative pressure source and a rear working chamber. A compartmented booster piston is accommodated, and a valve cylinder that is slidably supported on the rear wall of the booster shell is connected to the booster piston. A control valve for switching the working chamber between the negative pressure chamber and the atmosphere according to the longitudinal movement of the rod, and an output supported slidably by the valve cylinder and the input rod and the booster shell It is related with the improvement of the thing which interposed the reaction force mechanism which transmits the resultant force of the input with respect to the input rod and the thrust of the booster piston by the pressure difference between the working chamber and the negative pressure chamber to the output rod. .
[0002]
[Prior art]
Conventionally, in such a negative pressure booster, as disclosed in, for example, Japanese Patent Laid-Open No. 9-2246, during emergency braking, the operation amount of the control valve is increased by excitation of the solenoid device, and a large amount of air is put in the operation chamber. It is known that the power is introduced quickly and the output power is made to show the high output of the boost limit.
[0003]
[Problems to be solved by the invention]
The negative pressure booster disclosed in the above publication requires not only an expensive solenoid device but also a sensor for detecting an emergency brake state, and thus has a drawback that the configuration is complicated and the cost is high.
[0004]
The present invention has been made in view of such circumstances, and by simply adding a simple and inexpensive structure, during emergency braking, a large amount of air is quickly introduced into the working chamber to cause the output rod to exhibit high output. An object of the present invention is to provide the negative pressure booster.
[0005]
[Means for Solving the Problems]
In order to achieve the above object, the present invention accommodates a booster piston that divides the inside thereof into a front negative pressure chamber and a rear working chamber connected to a negative pressure source. A valve cylinder that is slidably supported on the rear wall of the booster shell is connected, and an input rod that can be moved back and forth in the valve barrel, and the working chamber is moved in accordance with the longitudinal movement of the input rod. A control valve that switches between the pressure chamber and the atmosphere is disposed, and an input to the input rod and an operation between the valve cylinder and the input rod and an output rod that is slidably supported by the booster shell In the negative pressure booster through the reaction force mechanism that transmits the resultant force with the thrust of the booster piston due to the pressure difference between the chamber and the negative pressure chamber to the output rod, the input connecting the input rod and the reaction force mechanism The piston is a valve piston, which is Fitted so as to be slidable between the retracted position and the advanced position along the axial direction, and the atmosphere introduction valve seat formed at the rear end of the valve piston, and the atmosphere introduction valve seat formed on the valve cylinder A negative pressure introduction valve seat that surrounds, and a cylindrical valve that is attached to the inner peripheral surface of the valve cylinder having a common valve portion that is opposed to the atmospheric introduction valve seat and the negative pressure introduction valve seat at the front end. The control valve is constituted by a valve body and a valve spring that urges the valve portion in the seating direction of the atmospheric introduction valve seat and the negative pressure introduction valve seat, and communicates with the valve cylinder and the negative pressure chamber. A first port that opens between the negative pressure introduction valve seat and the valve body; and a second port that communicates with the working chamber and opens between the atmosphere introduction valve seat and the negative pressure introduction valve seat. The valve piston is moved to the retracted position with a set load smaller than that of the valve spring. While urging the side, between the valve piston and the input piston, a first feature in that a delay means for delaying the backward from the forward position by the biasing force of the return spring of the valve piston.
[0006]
According to the first feature, during emergency braking in which the input rod is rapidly advanced, the valve piston is subjected to the delay action of the delay means and moves forward with the input piston while maintaining the substantially forward position. As the valve seat moves away from the valve part of the valve body at the same time as the input rod advances, a large amount of air is introduced into the working chamber, and the booster piston has a large air pressure between the negative pressure chamber and the working chamber. A large forward thrust due to the difference can be applied immediately, and the output of the output rod can be raised quickly and greatly to cope with emergency braking. In addition, an expensive solenoid device or emergency brake sensor is not required, which can contribute to cost reduction.
[0007]
On the other hand, during normal braking in which the input rod is advanced at a normal speed, the valve piston does not receive the delay action of the delay means and moves to the reverse position by the biasing force of the return spring against the input piston that moves forward with the input rod. Therefore, since the air introduction valve seat is appropriately separated from the valve part of the valve body, the amount of air introduced into the working chamber can be appropriately limited, and the output of the output rod can be increased moderately, so that no uncomfortable feeling is caused.
[0008]
According to the present invention, in addition to the above features, the delay means is constituted by a seal member that is mounted on one sliding fitting surface of the valve piston and the input piston and is in close contact with the other sliding fitting surface. Is the second feature.
[0009]
According to the second feature, the seal member between the valve piston and the input piston also serves as the delay means, so that the configuration can be further simplified and the cost can be effectively reduced.
[0010]
[Embodiment]
Embodiments of the present invention will be described based on examples of the present invention shown in the accompanying drawings.
[0011]
FIG. 1 is a longitudinal sectional view of a tandem negative pressure booster according to an embodiment of the present invention, FIG. 2 is an enlarged sectional view of part 2 of FIG. 1 (resting state), and FIG. 3 is an operation of the negative pressure booster during normal braking. FIG. 4 is an explanatory diagram of the operation of the negative pressure booster during emergency braking, FIG. 5 is a diagram showing the output characteristics of the negative pressure booster, and FIG. 6 shows a modification of the main part of the negative pressure booster. FIG. 3 is a cross-sectional view corresponding to FIG. 2.
[0012]
1 and 2, the booster shell 1 of the negative pressure booster B is sandwiched between a pair of front and rear shell halves 1a and 1b and opposite shell halves 1a and 1b. A partition plate 1c that divides the inside of the shell 1 into a front shell chamber 2 and a rear shell chamber 3 is provided, and the rear shell half 1b is fixed and supported by a bolt 8 on the front wall D of the automobile. A cylinder body Ma of a brake master cylinder M operated by the booster B is fixed to the partial shell half 1 a by bolts 9.
[0013]
The front shell chamber 2 has a front booster piston 4 accommodated therein so as to be capable of reciprocating back and forth, and a front shell chamber 2 which is overlapped on the rear surface and is attached between the front shell half 1a and the partition plate 1c. The front diaphragm 5 is divided into a front front negative pressure chamber 2a and a rear front working chamber 2b. The front negative pressure chamber 2a is connected to a negative pressure source V (for example, inside the intake manifold of the internal combustion engine) via a negative pressure introduction pipe.
[0014]
The rear shell chamber 3 has a rear booster piston 6 accommodated therein so as to be capable of reciprocating back and forth, and a rear diaphragm which is bonded to the rear surface of the rear booster piston 6 and is fixed between the shell halves 1a and 1b together with the partition plate 1c. 7 is divided into a front rear negative pressure chamber 3a and a rear rear working chamber 3b.
[0015]
The front and rear booster pistons 4 and 6 are each formed in an annular shape from a steel plate, and these are integrally connected via a synthetic resin valve cylinder 10 fixed to the center. The valve cylinder 10 is slidably supported on the partition plate 1c via the seal member 11 and on the rear extension cylinder 12 formed at the center of the rear shell half 1b via the seal member 13. The retreat limit of the booster pistons 4 and 6 is defined by the protrusions 7 a that are raised on the rear surface of the rear diaphragm 7 abutting against the rear wall of the booster shell 1.
[0016]
The valve cylinder 10 is provided with an input piston 18 slidably fitted on the inner peripheral surface thereof, an input rod 20 connected to the input piston 18, and working chambers 2 b and 3 b according to the back-and-forth movement of the input rod 20. A control valve 38 that switches between the negative pressure chambers 2a and 3a and the atmosphere is disposed. The input piston 18 includes a piston portion 18a that is slidably fitted to the inner peripheral surface of the valve cylinder 10, and a connecting cylinder portion 18b that protrudes rearward from the piston portion 18a, and the connecting cylinder portion 18b. The spherical front end portion 20a of the input rod 20 is fitted inside, and a part 19 of the connecting tube portion 18b is caulked to prevent the input rod 20 from coming off. Thus, the input rod 20 is connected to the input piston 18 so as to be able to swing. A brake pedal P is connected to the rear end of the input rod 20 to move it forward.
[0017]
A cylindrical valve piston 33 is slidably fitted on the outer peripheral surface of the connecting cylinder portion 18 b of the input piston 18. The valve piston 33 includes a forward position F (see FIG. 2) that contacts the piston portion 18a of the input piston 18, and a reverse position R (see FIG. 3) that contacts the stopper ring 45 that is locked to the connecting cylinder portion 18b. Between the valve piston 33 and the piston portion 18a of the input piston 18, a return spring 44 that urges the valve piston 33 toward the retreat position R is compressed. Established. An O-ring 47 as a seal member that is in close contact with the other sliding fitting surface is attached to the annular groove 46 formed on one sliding fitting surface of the valve piston 33 and the connecting cylinder portion 18b. In the illustrated example, the annular groove 46 is provided on the inner peripheral surface of the valve piston 33, but may be provided on the outer peripheral surface of the input piston 18. The O-ring 47 not only seals the sliding fitting portion of the valve piston 33 and the input piston 18, but also delays the backward movement of the valve piston 33 from the forward position F due to the biasing force of the return spring 44 by friction. Configure the means.
[0018]
Incidentally, as shown in FIG. 6, a sealing member 47 ′ having a square cross section can be attached to the annular groove 46 in place of the O-ring 47.
[0019]
The valve cylinder 10 is connected to a first communication passage 28a that communicates between the front and rear negative pressure chambers 2a and 3a, a second communication passage 28b that communicates between the front and rear working chambers 2b and 3b, and a first communication passage 28a. A first port 29a that opens to the inner peripheral surface of the valve cylinder 10 and a second port 29b that opens to the inner peripheral surface of the valve cylinder 10 in front of the first port 29a and that are continuous with the second communication passage 28b are formed. . An annular negative pressure introduction valve seat 30 is formed on the inner peripheral surface of the valve cylinder 10 at the intermediate portion in the front-rear direction of the first and second ports 29a, 29b. An annular atmosphere introduction valve seat 31 surrounded by a negative pressure introduction valve seat 30 is formed at the rear end of the valve piston 33 with an annular passage 32 connected to the second port 29b interposed therebetween. One common valve element 34 facing the seat 30 and the air introduction valve seat 31 is disposed in the valve cylinder 10. The valve body 34 has an annular valve portion 34a opposed to the negative pressure introduction valve seat 30 and the atmospheric introduction valve seat 31 at the front end, an annular mounting bead portion 34b at the rear end, and both portions 34a, 34b. In the middle part, a diaphragm part 34c is connected to each other so as to be axially displaceable. The mounting bead part 34b is formed by a cylindrical valve holder 35 fitted to the inner peripheral surface of the rear part of the valve cylinder 10. It is attached to the inner peripheral surface of the valve cylinder 10 by the front end. A valve spring 36 that urges the valve portion 34 a in the seating direction with both valve seats 30 and 31 is contracted between the valve portion 34 a and the input rod 20. The set load of the return spring 44 is set smaller than that of the combustion spring 36.
[0020]
In the above, the valve seats 30 and 31, the valve body 34 and the valve spring 36 constitute a control valve 38.
[0021]
An inward flange 12a having an air introduction port 39 opened at the center is integrally formed at the rear end of the rear extension cylinder 12, and the rearward limit of the input rod 20 is defined by contacting the inner surface of the flange 12a. The stopper plate 40 is fixed to the input rod 20 so as to be adjustable in the front-rear direction, and the input rod 20 is urged by an input return spring 41 supported by the valve holder 35 toward the retreat limit.
[0022]
An air filter 42 is attached to the inner periphery of the rear end portion of the valve cylinder 10, and the inside of the valve body 34 is always in communication with the atmospheric air inlet 39 through the air filter 42. The air filter 42 is flexible so as not to prevent the input rod 20 from moving back and forth with respect to the valve cylinder 10.
[0023]
The front end portion of the valve cylinder 10 is formed in a large-diameter piston 15, which is formed in the center portion of the large-diameter piston 15 and is reduced in diameter to a cylinder hole 16 opened on the front surface at a constant rate from the large-diameter piston 15. A small-diameter piston 17 is slidably fitted, and this small-diameter piston 17 is connected to the front end of the valve piston 33 in the illustrated example. A cup body 21 is slidably fitted to the outer periphery of the large-diameter piston 15, and the cup body 21 is filled with a flat elastic piston 22 whose rear end surface is in contact with the large-diameter piston 15. The small-diameter piston 17 is normally opposed to the elastic piston 22 at a rear end face with a predetermined gap g, and the predetermined gap g is set larger than the sliding stroke s of the valve piston 33 with respect to the input piston 18. Is done.
[0024]
In the above, the large-diameter piston 15, the small-diameter piston 17, the elastic piston 22, and the cup body 21 constitute a reaction force mechanism 24 that transmits the resultant force of the input to the input rod 20 and the thrust of the booster pistons 4, 6 to the output rod 25. To do.
[0025]
An output rod 25 projects from the front surface of the cup body 21, and this output rod 25 is connected to the piston Mb of the brake master cylinder M. A retainer 26 that contacts the cup body 21 and the front end surface of the valve cylinder 10 is disposed, and a valve cylinder return spring 27 is contracted between the retainer 26 and the front wall of the booster shell 1.
[0026]
Next, the operation of this embodiment will be described.
[Suspension of negative pressure booster]
In the resting state of the negative pressure booster B, as shown in FIGS. 1 and 2, the input rod 20 is positioned at the retreat limit where the stopper plate 40 is brought into contact with the inward flange 12a of the rear extension cylinder 12, and both booster pistons 4 and 6 are located in a retreat limit where the projection 7a of the rear diaphragm 7 is brought into contact with the rear wall of the booster shell 1, and the control valve 38 controls the valve portion 34a of the valve body 34 to the atmosphere introduction valve seat 31 and the negative pressure. It is in a neutral state in which both the working chambers 2 b and 3 b are not connected to both the negative pressure chambers 2 a and 3 a and the air introduction port 39 by being seated on the introduction valve seat 30.
[0027]
In this case, since the set load of the return spring 44 that biases the valve piston 33 in the backward direction is set smaller than the set load of the combustion spring 36 that biases the valve portion 34a forward, the biasing force of the input return spring 41 As the input rod 20 is held at the retreat limit by this, the valve piston 33 causes the atmosphere introduction valve seat 31 to be in close contact with the valve portion 34a and compresses the return spring 44, thereby moving the forward position F on the input piston 18 to F. Accounted for.
[0028]
On the other hand, the O-ring 47 between the sliding fitting surfaces of the valve piston 33 and the input piston 18 prevents the negative pressure around the valve piston 33 from leaking to the inside of the valve body 34 through the valve piston 33 and the input piston 18. Blocking.
[Normal brake]
If the brake pedal P is depressed at a normal speed to brake the vehicle and the input rod 20, the input piston 18 and the valve piston 33 are advanced, the normal advance speed of the valve piston 33 causes a delay action of the O-ring 47. As shown in FIG. 3, the valve piston 33 slides relatively on the input piston 18 toward the retracted position R with the urging force of the return spring 44, as shown in FIG. When the valve piston 33 reaches the reverse position R, the input rod 20, the input piston 18 and the valve piston 33 move forward together, but initially the booster pistons 4 and 6 are immobile. The air introduction valve seat 31 of the valve piston 33 is appropriately separated from the valve portion 34 a of the valve body 34, and the second port 29 b is appropriately communicated with the atmosphere introduction port 39 through the annular passage 32. As a result, the air flowing into the valve cylinder 10 from the air introduction port 39 is moderately limited in flow rate between the air introduction valve seat 31 and the valve portion 34a, and then enters the working chambers 2b and 3b via the second port 29b. Since the chambers 2b and 3b are introduced quickly and have a higher pressure than the negative pressure chambers 2a and 3a, the forward thrust based on the pressure difference between them is obtained so that the booster pistons 4 and 6 are connected to the valve cylinder 10 and the large-diameter piston 15. , The forward movement of the valve barrel return spring 27 is performed, and the cup body 21, that is, the output rod 25 is pushed forward via the large-diameter piston 15 and the elastic piston 22.
[0029]
Incidentally, a predetermined gap g larger than the sliding stroke s of the valve piston 33 with respect to the input piston 18 initially exists between the elastic piston 22 and the small-diameter piston 17 of the reaction force mechanism 24. Until the small-diameter piston 17 comes into contact with the elastic piston 22 after being separated from the valve portion 34a, a slight free forward stroke remains in the input rod 20, and the input rod 20 reacts while the forward stroke is advanced. Since the reaction force is not received from the mechanism 24, the output of the output rod 25 is appropriately jumped as shown by the line ab in FIG. 5, thereby causing the piston Mb of the brake master cylinder M to operate moderately and rapidly. The brake can be operated quickly and comfortably.
[0030]
Immediately after that, when the small-diameter piston 17 comes into contact with the elastic piston 22, on the rear surface of the elastic piston 22, in addition to the thrust of the booster pistons 4 and 6 applied to the large-diameter piston 15, the small-diameter piston 17 is input from the input rod 20. And the actuating reaction force of the output rod 25 is acting on the front end surface of the elastic piston 22, so that the elastic piston 22 is compressed and a part of the force is applied to the cylinder hole 16. A part of the reaction force of the output rod 25 is transmitted to the input rod 20 while protruding, and the operator can feel the output of the output rod 25, that is, the magnitude of the braking force. As a result, the output of the output rod 25 increases in proportion to the input of the input rod 20 as shown by the line bc in FIG. 5 until the boost limit is reached.
[0031]
Meanwhile, the valve cylinder 10 integrated with the booster pistons 4 and 6 moves forward by the advance amount of the input rod 20, and when the input rod 20 stops moving, the valve body 34 that has moved forward together with the valve barrel 10 is replaced with the air introduction valve. Since it is seated again on the seat 31 to prevent further introduction of the atmosphere into the working chambers 2b and 3b, the forward movement of the booster pistons 4 and 6 is also stopped, and a boost output corresponding to the input can be obtained. .
[0032]
When the output of the output rod 25 exceeds the boost limit, the thrust due to the pressure difference between the booster pistons 4 and 6 is maximized, and the atmosphere introduction valve seat 31 remains separated from the valve body 34. Is the sum of the maximum thrust due to the pressure difference between the booster pistons 4 and 6 and the thrust of the input rod 20 due to the depression force applied to the brake pedal P (see line cd in FIG. 5).
[Brake release]
When the pedaling force is released from the brake pedal P in order to release the braking state of the vehicle, first, the input rod 20 and the input piston 18 are moved backward by the force of the input return spring 41. At this time, when the air introduction valve seat 31 comes into close contact with the valve portion 34a of the valve body 34, the valve piston 33 moves to the forward position F relative to the input piston 18 while compressing the return spring 44, Thereafter, the valve portion 34a is moved backward together with the input piston 18 so as to be largely separated from the negative pressure introducing valve seat 30. It communicates with the negative pressure chambers 2a and 3a. As a result, the introduction of the atmosphere into both the working chambers 2b and 3b is prevented, while the air in both the working chambers 2b and 3b is sucked into the negative pressure limit V through both the negative pressure chambers 2a and 3a, and the pressure difference between them. Therefore, the booster pistons 4 and 6 are also moved backward by the force of the valve barrel return spring 27 to release the operation of the master cylinder M.
[0033]
When the input rod 20 is retracted to the retreat limit in which the stopper plate 40 is brought into contact with the inward flange 12a of the rear extension cylinder 12, the rear booster piston 6 makes the projection 7a of the rear diaphragm 7 contact the rear wall of the booster shell 1. Returning to the retreat limit, the negative pressure introducing valve seat 30 is also brought into close contact with the valve portion 34a, and the control valve 38 is brought into the initial neutral state.
[Emergency brake]
At the time of emergency braking in which the brake pedal P is depressed rapidly, the forward movement speed of the input piston 18 is fast as shown in FIG. 4, so that the valve piston 33 is maintained at the substantially forward position F due to the delay action caused by the friction of the O-ring 47. It moves forward together with the eggplant input piston 18. Accordingly, the atmosphere introduction valve seat 31 of the valve piston 33 is separated from the valve portion 34a of the valve body 34 simultaneously with the advancement of the input rod 20, and the atmosphere is immediately introduced into the working chambers 2b and 3b. In addition, in this case, the free forward stroke of the input rod 20 from when the air introduction valve seat 31 is separated from the valve portion 34a until the small-diameter piston 17 comes into contact with the elastic piston 22 is larger than that during the normal braking described above. Thus, while the input rod 20 advances this large forward stroke, the atmosphere introduction valve seat 31 is opened to the maximum, a large amount of atmosphere is introduced into the working chambers 2b and 3b, and the output of the output rod 25 is shown in FIG. As shown in FIG. Thus, without using an expensive solenoid device and emergency brake sensor, the output of the output rod 25 can be quickly and greatly raised to cope with emergency braking.
[0034]
When a certain period of time has elapsed since the atmosphere introduction valve seat 31 has been fully opened, the valve piston 33 returns to the reverse position R with the urging force of the return spring 44 and enters the normal braking state. The line b′-c-d is traced.
[0035]
The present invention is not limited to the above embodiment, and various design changes can be made without departing from the scope of the invention. For example, the negative pressure booster B can be configured as a single type having a single booster piston. Further, the small-diameter piston 17 of the reaction force mechanism 24 can be configured separately from the valve piston 33 and disposed in contact with the valve piston 33. Further, in the resting state of the negative pressure booster B, the valve portion 34 a of the valve body 34 can be separated from the negative pressure introducing valve seat 30 in the control valve 38.
[0036]
【The invention's effect】
As described above, according to the first feature of the present invention, the valve piston is connected to the input piston connecting the input rod and the reaction force mechanism, and this slides between the retracted position and the advanced position along the axial direction with respect to the input piston. An atmospheric introduction valve seat formed at the rear end of the valve piston, a negative pressure introduction valve seat formed on a valve cylinder surrounding the atmospheric introduction valve seat, and the atmospheric introduction valve A cylindrical valve body that is attached to the inner peripheral surface of the valve cylinder with a common valve part that is opposed to the seat and the negative pressure introduction valve seat at the front end, and the valve part is connected to the air introduction valve seat and the negative pressure A control valve is constituted by a valve spring that is urged in the seating direction with the introduction valve seat, and the valve cylinder communicates with the negative pressure chamber and opens between the negative pressure introduction valve seat and the valve body, and operates. A second port that opens between the air introduction valve seat and the negative pressure introduction valve seat is provided in communication with the chamber, while the inside of the valve body communicates with the atmosphere. The valve piston is urged toward the retreat position with a smaller set load of the return spring than the valve spring, and the retreat from the advance position by the urging force of the return spring of the valve piston is delayed between the valve piston and the input piston. In the event of an emergency brake that rapidly moves the input rod forward, the valve piston's air introduction valve seat moves away from the valve part of the valve body at the same time as the input rod moves forward, and is activated to the maximum. A large amount of air is introduced into the chamber, and a large forward thrust due to the pressure difference is immediately applied to the booster piston, so that the output of the output rod can be raised quickly and greatly, and it can respond to emergency braking. During normal braking at a normal speed, the air introduction valve seat is appropriately separated from the valve part of the valve body to limit the amount of air introduced into the working chamber to a moderate level and to produce output soot. It is possible to moderately increase, it does not cause discomfort. In addition, an expensive solenoid device or emergency brake sensor is not required, which can contribute to cost reduction.
[0037]
According to the second feature of the present invention, the delay means is constituted by a seal member that is mounted on one sliding fitting surface of the valve piston and the input piston and is in close contact with the other sliding fitting surface. Since the seal member between the valve piston and the input piston also serves as a delay means, the configuration can be further simplified and the cost can be effectively reduced.
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional view of a tandem negative pressure booster according to an embodiment of the present invention.
2 is an enlarged cross-sectional view of part 2 in FIG. 1 (resting state).
FIG. 3 is a diagram illustrating the operation of the negative pressure booster during normal braking.
FIG. 4 is a diagram illustrating the operation of the negative pressure booster during emergency braking.
FIG. 5 is a diagram showing output characteristics of the negative pressure booster.
6 is a cross-sectional view corresponding to FIG. 2, showing a modification of the main part of the negative pressure booster.
[Explanation of symbols]
B ... Negative pressure booster F ... Valve piston forward position R ... Valve piston reverse position V ... Negative pressure source s ... Valve piston sliding stroke 1 ... ..Booster shell 2a ... negative pressure chamber (front negative pressure chamber)
3a ... Negative pressure chamber (rear negative pressure chamber)
2b ... Working chamber (front working chamber)
3b ... Working chamber (rear working chamber)
4 .... Booster piston (front booster piston)
6. Booster piston (rear booster piston)
10 ... Valve 18 ... Input piston 20 ... Input rod 24 ... Reaction force mechanism 25 ... Output rod 29a ... First port 29b ... Second port 30 ... Negative pressure introduction Valve seat 31 ... Air introduction valve seat 33 ... Valve piston 34 ... Valve element 34a ... Valve part 36 ... Valve spring 38 ... Control valve 44 ... Return spring 47 ... Delay Means (O-ring)
47 '.. Delay means (seal member)

Claims

ブースタシェル（１）に，その内部を負圧源（Ｖ）に連なる前側の負圧室（２ａ，３ａ）と後側の作動室（２ｂ，３ｂ）とに区画するブースタピストン（４，６）を収容し，このブースタピストン（４，６）に，前記ブースタシェル（１）の後壁に摺動自在に支承される弁筒（１０）を連設し，この弁筒（１０）内に，前後動可能の入力杆（２０）と，この入力杆（２０）の前後動に応じて前記作動室（２ｂ，３ｂ）を前記負圧室（２ａ，３ａ）と大気とに連通切換えする制御弁（３８）とを配設し，前記弁筒（１０）及び入力杆（２０）と，前記ブースタシェル（１）に摺動可能に支持される出力杆（２５）との間に，入力杆（２０）に対する入力と，作動室（２ｂ，３ｂ）及びを負圧室（２ａ，３ａ）間の気圧差による前記ブースタピストン（４，６）の推力との合力を該出力杆（２５）に伝達する反力機構（２４）を介裝した負圧ブースタにおいて，
前記入力杆（２０）及び反力機構（２４）間を連結する入力ピストン（１８）に弁ピストン（３３）を，これが入力ピストン（１８）に対して軸方向に沿う後退位置（Ｒ）及び前進位置（Ｆ）間を摺動し得るように嵌合し，この弁ピストン（３３）の後端に形成される大気導入弁座（３１）と，前記弁筒（１０）に形成されてこの大気導入弁座（３１）を囲繞する負圧導入弁座（３０）と，これら大気導入弁座（３１）及び負圧導入弁座（３０）に着座可能に対置される共通の弁部（３４ａ）を前端に有して前記弁筒（１０）の内周面に取付けられる筒状の弁体（３４）と，前記弁部（３４ａ）を大気導入弁座（３１）及び負圧導入弁座（３０）との着座方向へ付勢する弁ばね（３６）とで前記制御弁（３８）を構成し，前記弁筒（１０）に，前記負圧室（２ａ，３ａ）に連通して前記負圧導入弁座（３０）及び弁体（３４）間に開口する第１ポート（２９ａ）と，前記作動室（２ｂ，３ｂ）に連通して前記大気導入弁座（３１）及び負圧導入弁座（３０）間に開口する第２ポート（２９ｂ）とを設ける一方，前記弁体（３４）の内側を大気に連通し，前記弁ピストン（３３）を，戻しばね（４４）の，前記弁ばね（３６）より小さいセット荷重をもって前記後退位置（Ｒ）側へ付勢すると共に，この弁ピストン（３３）及び入力ピストン（１８）間に，弁ピストン（３３）の前記戻しばね（４４）の付勢力による前進位置（Ｆ）からの後退を遅延させる遅延手段（４７，４７′）を設けたことを特徴とする，負圧ブースタ。A booster piston (4, 6) having a booster shell (1) divided into a front negative pressure chamber (2a, 3a) and a rear working chamber (2b, 3b) connected to the negative pressure source (V). The booster piston (4, 6) is connected to a valve cylinder (10) that is slidably supported on the rear wall of the booster shell (1). In the valve cylinder (10), An input rod (20) that can be moved back and forth, and a control valve that switches the working chamber (2b, 3b) between the negative pressure chamber (2a, 3a) and the atmosphere in response to the longitudinal movement of the input rod (20). (38), and an input rod (10) between the valve barrel (10) and the input rod (20) and an output rod (25) slidably supported by the booster shell (1). 20) and the booster pis due to the pressure difference between the working chamber (2b, 3b) and the negative pressure chamber (2a, 3a). In the negative pressure booster which is Kai裝 the reaction force mechanism (24) for transmitting the down (4, 6) output rod the resultant force of the thrust (25),
The valve piston (33) is connected to the input piston (18) that connects the input rod (20) and the reaction force mechanism (24), and the valve piston (33) moves backward with respect to the input piston (18) in the axial direction. Fitted so as to be slidable between positions (F), and formed in the atmosphere introduction valve seat (31) formed at the rear end of the valve piston (33) and the valve cylinder (10). A negative pressure introduction valve seat (30) surrounding the introduction valve seat (31), and a common valve portion (34a) opposed to the atmosphere introduction valve seat (31) and the negative pressure introduction valve seat (30) so as to be seated. A cylindrical valve body (34) attached to the inner peripheral surface of the valve cylinder (10) with the front end, and the valve portion (34a) comprising an air introduction valve seat (31) and a negative pressure introduction valve seat ( 30) and the valve spring (36) urging in the seating direction constitutes the control valve (38), and the valve cylinder (10) A first port (29a) that communicates with the negative pressure chamber (2a, 3a) and opens between the negative pressure introduction valve seat (30) and the valve body (34), and communicates with the working chamber (2b, 3b). A second port (29b) opened between the atmosphere introduction valve seat (31) and the negative pressure introduction valve seat (30), while the inside of the valve body (34) communicates with the atmosphere, The piston (33) is biased toward the retracted position (R) with a set load smaller than the valve spring (36) of the return spring (44), and between the valve piston (33) and the input piston (18). The negative pressure booster is provided with delay means (47, 47 ') for delaying the backward movement of the valve piston (33) from the forward position (F) by the urging force of the return spring (44).

請求項１記載の負圧ブースタにおいて，
前記遅延手段を，前記弁ピストン（３３）及び入力ピストン（１８）の一方の摺動嵌合面に装着されて他方の摺動嵌合面に密接するシール部材（４７，４７′）で構成したことを特徴とする，負圧ブースタ。The negative pressure booster according to claim 1,
The delay means is constituted by a seal member (47, 47 ') which is mounted on one sliding fitting surface of the valve piston (33) and the input piston (18) and is in close contact with the other sliding fitting surface. This is a negative pressure booster.