JP4167353B2

JP4167353B2 - Negative pressure booster

Info

Publication number: JP4167353B2
Application number: JP23888199A
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: 2008-10-15
Anticipated expiration: 2019-08-25
Also published as: JP2001063549A

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作動室を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倍力限界の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作動室を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，前記入力杆に，前記反力機構に連なる入力プランジャを連結し，この入力プランジャの外周に弁ピストンを，これが入力プランジャに対して軸方向に沿う後退位置及び前進位置間を移動し得るように嵌合すると共に，この弁ピストンを戻しばねにより前記後退位置側へ付勢し，この弁ピストンを前記制御弁に，この弁ピストンが前記前進位置まで前進したとき前記制御弁を前記作動室と大気との最大連通状態に切換えるように連結し，前記弁筒及び弁ピストンに，これらの軸方向相対移動に応じて互いに半径方向に重なりながら軸方向に相対移動する第１永久磁石及び第２永久磁石をそれぞれ付設し，これら第１及び第２永久磁石は，前記弁ピストンの入力プランジャに対する後退位置からの前進が所定距離に満たないときには，互いに同極を半径方向及び軸方向に対向させて前記弁ピストンを前記後退位置側へ付勢する反発力を発生して，前記弁ピストンを前記戻しばねと協働して前記後退位置側へ付勢し，前記弁ピストンの入力プランジャに対する後退位置からの前進が所定距離を超えたときには，互いに異極を半径方向及び軸方向に対向させて前記弁ピストンを前記前進位置まで移動させる吸引力を発生して，前記弁ピストンを前記戻しばねのセット荷重に抗して前記前進位置まで前進させることにより，前記制御弁を前記作動室と大気との最大連通状態にするように構成されることを第１の特徴とする。
【０００６】
この第１の特徴によれば，弁ピストンの弁筒に対する前進が所定距離未満となる通常ブレーキ時には，第１及び第２永久磁石は反発状態を維持し，それらの反発力が戻しばねの付勢力と協働して弁ピストンを後退方向へ付勢し続けるので，弁ピストンを後退位置側へ付勢する戻しばねのセット荷重を小さく設定することが可能となる。したがって，入力杆を急速に前進させる緊急ブレーキ時には，弁筒の作動遅れに伴い弁筒に対して弁ピストンが入力杆と共に前進して所定距離を超えることにより，第１及び第２永久磁石が反発状態から吸引状態に切換わるや否や，第１及び第２永久磁石相互の吸引力により，戻しばねの抵抗をあまり受けずに，弁ピストンを素早く前進させ，制御弁を作動室と大気との最大連通状態に切換える。その結果，作動室に大量の大気が一挙に導入され，作動室及び負圧室間の気圧差が最大となってブースタピストンの推力，即ち出力杆の出力を倍力限界点まで即座に増大させることができる。このような簡単な構成の採用により，緊急ブレーキに対応した強力なブレーキ力を発生することができる。
【０００７】
また本発明は，上記特徴に加えて，前記入力プランジャに前記入力杆の球状前端部を首振り可能にかしめ結合すると共に，そのかしめ結合部を前記弁ピストンで覆い，この弁ピストンの後端に形成した大気導入弁座と，この大気導入弁座を環状通路を挟んで囲繞するように前記弁筒に形成した負圧導入弁座と，前記弁筒に前後動可能に取付けられて前記負圧導入弁座及び大気導入弁座に前端の弁部を対向させる弁体と，この弁体の弁部を前記両弁座との着座方向へ付勢する弁ばねとから前記制御弁を構成すると共に，前記弁体の内側を大気に連通し，前記負圧導入弁座を前記負圧室に連通する第１ポートと，前記環状通路を前記作動室に連通する第２ポートとを前記弁筒に設け，前記弁ピストンの，前記環状通路に臨む外周面を後端に向かって小径となると共に第２ポートの内周面に連続するテーパ状に形成したことを第２の特徴とする。
【０００８】
この第２の特徴によれば，弁ピストンの外周面を，大気導入弁座に向かって小径となるテーパ状に形成したので，大気導入弁座の全開時には，大量の大気を弁ピストンのテーパ状外周面により作動室へスムーズに誘導して，ブースタピストンの応答性を向上に寄与することができ，しかも弁ピストンが入力杆及び入力プランジャのかしめ結合部を覆って，該かしめ部による風切り音の発生を抑えることができる。
【０００９】
【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。
【００１０】
図１は本発明の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部拡大図，図３は上記負圧ブースタの作用説明図，図４は上記負圧ブースタの倍力特性を示す線図である。
【００１１】
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Ｆ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。
【００１２】
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。
【００１３】
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。
【００１４】
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の後面に多数隆起させた突起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。
【００１５】
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有底のシリンダ孔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の後端面に，弁筒１０前部の中心部を摺動自在に貫通する入力プランジャ１８の前端が当接する。
【００１６】
入力プランジャ１８の後端部に形成された連結筒部１９には，弁筒１０の後端から挿入される入力杆２０の前端の球状部２０ａが嵌合されると共に，その抜け止めのために連結筒部１９の一部１９ａが内方へかしめる。こうして入力杆２０は入力プランジャ１８に首振り可能に連結される。
【００１７】
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には大径及び小径ピストン１５，１７に対向する偏平な弾性ピストン２２が充填される。
【００１８】
大径ピストン１５及び弾性ピストン２２の対向端面の一方（図示例では大径ピストン１５の前端には環状段部２３が凹設される。
【００１９】
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。
【００２０】
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。
【００２１】
弁筒１０には，前後部の負圧室２ａ，３ａ間を連通する第１連通路２８ａと，前後部の作動室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。また弁筒１０の前部内周面に円筒状の弁ピストン３３が摺動自在に嵌装され，この弁ピストン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。
【００２２】
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。
【００２３】
また上記環状通路３２を構成する弁ピストン３３の外周面３２ａは，大気導入弁座３１に向かって小径となると共に，第２ポート２９ｂの内周面に連続するテーパ状に形成される。
【００２４】
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。
【００２５】
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，それを通して大気導入弁座３１の内周は大気導入口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。
【００２６】
入力プランジャ１８には，円筒状の弁ピストン３３の内周面にシール部材４３を介して摺動自在に嵌合する外向きフランジ１８ａが，また弁ピストン３３には，入力プランジャ１８の連結筒部１９の外周面に摺動自在に嵌合する内向きフランジ３３ａがそれぞれ一体に形成されており，これら両フランジ１８ａ，３３ａ間に，これらを前後に引き離す方向へ付勢する戻しばね４４が縮設されると共に，内向きフランジ３３ａの後端面を受けるストッパ環４５が連結筒部１９に係止される。また弁ピストン３３の内周面には，外向きフランジ１８ａの後端面に所定の間隙ｇを存して対向する当接段部４６が形成される。弁ピストン３３は，この間隙ｇの範囲内で，内向きフランジ３３ａをストッパ環４５に当接させる後退位置Ｒ（図２参照）と，当接段部４６を外向きフランジ１８ａに当接させる前進位置Ｆ（図３参照）との間を移動することができる。
【００２７】
尚，戻しばね４４のセット荷重は，前記弁ばね３６のそれより大きく設定される。したがって，入力杆２０による入力プランジャ１８の後退時には，戻しばね４４を圧縮させることなく弁ピストン３３により弁体３４の弁部３４ａを弁ばね３６のセット荷重に抗して後方へ変位させることができる。
【００２８】
弁ピストン３３において，外向きフランジ１８ａが嵌合する内周面の内径Ｄ１と，弁体３４が着座する大気導入弁座３１の有効径Ｄ２とは，互いに等しく設定される。こうすると，弁体３４が大気導入弁座３１に着座しているとき，負圧室２ａ，３ａの負圧が第１ポート２９ａから弁ピストン３３の前後に作用した場合でも，弁ピストン３３の前端部及び後端部に働く負圧による推力を互いに相殺させることができる。
【００２９】
弁筒１０には，外向きフランジ１８ａの前方で入力プランジャ１８を囲繞する円筒部５０が形成されており，この円筒部５０の外周に環状の第１永久磁石５１が係止環５３により固着され，この第１永久磁石５１に半径方向で重なりながら軸方向に相対移動し得る環状の第２永久磁石５２が弁ピストン３３の前端に接着等により固着される。これら第１及び第２永久磁石５１，５２は，軸方向両端に両極Ｎ，Ｓを有するが，第１及び第２永久磁石５１，５２のＮ，Ｓ極は，互いに向きが逆になっている。即ち，図示例では，第１永久磁石５１では前，後端にＳ，Ｎ極が配され，第２永久磁石５２では前，後端にＮ，Ｓ極が配される。しかも，第１及び第２永久磁石５１，５２は，弁ピストン３３の入力プランジャ１８に対する後退位置Ｒからの前進が所定距離ｓに満たないときには，互いに同極即ちＮ，Ｎ極を半径方向及び軸方向に対向させて弁ピストン３３を後退位置Ｒ側へ付勢する反発力を発生し，弁ピストン３３の入力プランジャ１８に対する後退位置Ｒからの前進が所定距離ｓを超えると，互いに異極即ちＳ，Ｎ極を半径方向及び軸方向に対向させて前記弁ピストン３３を前進位置Ｆまで移動させる吸引力を発生するように配置される。前記入力戻しばね４１のセット荷重は，両永久磁石５１，５２が吸引状態になったとき発生する吸引力より大きく設定される。
【００３０】
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に示すように，入力杆２０は後退限に位置し，制御弁３８は，弁体３４を大気導入弁座３１及び負圧導入弁座３０に着座させて前，後部両作動室２ｂ，３ｂを両負圧室２ａ，３ａ及び大気導入口３９のいずれとも不通にした中立状態にあり，このような制御弁３８により，両負圧室２ａ，３ａには，負圧導入管１４を通して供給される負圧源の負圧が蓄えられ，両作動室２ｂ，３ｂには，大気により適当に希釈された負圧が保持される。こうして前，後部ブースタピストン４，６には，前部の負圧室２ａと作動室２ｂ，後部の負圧室３ａと作動室３ｂの各間に生じる僅かな気圧差により小さな前進力が与えられるが，これらの前進力と弁筒戻しばね２７の力とが釣合って，両ブースタピストン４，６は後退限から僅かに前進したところで停止している。
［通常ブレーキ］
車両を制動すべくブレーキペダルＰを通常の速度で踏込み，入力杆２０，入力プランジャ１８及び弁ピストン３３を介して大気導入弁座３１を前進させれば，当初，両ブースタピストン４，６は不動であるから，大気導入弁座３１が弁体３４から直ちに離れて，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を通過し，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大きな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の力に抗して入力杆２０の動きに追従するように前進する。この両ブースタピストン４，６の前進推力は，大径ピストン１５から弾性ピストン２２に伝達して，カップ体２１，即ち出力杆２５を前方へ押動するので，ブレーキマスタシリンダＭをブレーキペダルＰの踏込みに遅れなく作動させ，車両に制動かけることができる。
【００３１】
ところで，このような制動中，弾性ピストン２２の後端面には，大径ピストン１５に加わる両ブースタピストン４，６の推力と，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，またその前端面には，出力杆２５の作動反力が作用し，これによって弾性ピストン２２は前後に圧縮される。その結果，出力杆２５の作動反力の一部が弾性ピストン２２を介して入力杆２０に伝達されることになり，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ことができる。
【００３２】
而して，出力杆２５の出力が倍力限界に達するまでは（図４の線ａ−ｂ参照），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。ところで，大径ピストン１５は，当初，環状段部２３を除く前端面を弾性ピストン２２に当接させているが，出力杆２５の出力が所定値を超えると，環状段部２３をも弾性ピストン２２に当接させるようになるため，大径ピストン１５及び小径ピストン１７の弾性ピストン２２に対する受圧面積比の変化により，図４に線ａ−ｂ−ｃで示すように倍力比が途中から増加する。
【００３３】
そして，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４の線ｃ−ｄ参照）。
【００３４】
上記のように，弁筒１０が入力杆２０の前進に殆ど遅れなく追従する場合には，弁筒１０の第１永久磁石５１と弁ピストン３３の第２永久磁石５２との相対変位は前記所定距離ｓを超えることがなく，両永久磁石５１，５２は互いに軸方向に反発し続けるので，弁ピストン３３は，図２に示すように，内向きフランジ３３ａを入力プランジャ１８のストッパ環４５に当接させる後退位置Ｒに保持される。このことは，弁ピストン３３を後退位置Ｒ側へ付勢する戻しばね４４のセット荷重を小さく設定することが可能となったことを意味する。
［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，弁筒１０の作動遅れに伴い，弁筒１０に対して弁ピストン３３が入力杆２０と共に前進して，第２永久磁石５２が第１永久磁石５１に対して所定距離ｓ以上前進すると，前述のように，第２永久磁石５２の前，後端端極（Ｓ，Ｎ極）が第１永久磁石５１の前，後端極（Ｎ，Ｓ極）に半径方向及び軸方向に対向するようになり，両永久磁石５１，５２は反発状態から吸引状態に切換わるので，それらの吸引力により，弁ピストン３３は，戻しばね４４のセット荷重に抗して，外向きフランジ１８ａに当接する前進位置Ｆ（図３の状態）まで前進して，大気導入弁座３１を弁体３４から最大に引き離し，全開状態とする。
【００３５】
こゝで，特に注目すべくき点は，戻しばね４４のセット荷重が，前述のように両永久磁石５１，５２が反発状態にあるときの反発力の利用により小さく設定してあるので，両永久磁石５１，５２が反発状態から吸引状態に切換わるや否や，戻しばね４４のセット荷重にあまり抵抗させずに，瞬間的に弁ピストン３３を急速に前進させ，大気導入弁座３１を即座に全開させることである。
【００３６】
その結果，大気導入口３９から両作動室２ｂ，３ｂに大量の大気が一挙に導入されることになるので，作動室２ｂ，３ｂ及び負圧室２ａ，３ａ間の気圧差によるブレーキピストン４，６推力，即ち出力杆２５の出力が倍力限界まで直ちに増大し，ブレーキマスタシリンダＭを急速且つ強力に作動させることができる。このような緊急ブレーキ操作は，図４にＰ１，Ｐ２，Ｐ３で示すように，ブレーキ開始と同時であろうと，通常ブレーキ時の途中であろうと，また通常ブレーキ時において倍力比が変化した後であろうと，これを行えば，常に，そのときから出力を倍力限界まで直ちに増大させることができる。
【００３７】
また弁ピストン３３の，環状通路３２に臨む外周面３２ａは，第２ポート２９ｂの内周面に連続し，且つ大気導入弁座３１に向かって小径となるするテーパ面としてあるので，大気導入弁座３１の全開に伴い，大量の大気が環状通路３２から第２ポート２９ｂに流入するとき，その空気の流れが乱れることなくスムーズであり，弁ピストン３３が入力杆２０及び入力プランジャ１８のかしめ結合部１９ａを覆っていることゝ相俟って風切り音などの騒音の発生を抑えることができる。
【００３８】
このように，ブレーキペダルＰによる入力杆２０の急速前進時には，弁ピストン３３を弁筒１０及び弁ピストン３３にそれぞれ付設した第１及び第２永久磁石５１，５２間の吸引力により大気導入弁座３１を全開状態にさせるようにした簡単な構成を採用することにより，緊急ブレーキに対応し得る負圧ブースタＢを安価に提供することができる。
［緊急ブレーキの解除］
緊急ブレーキ状態を解除すべく，ブレーキペダルＰから踏力を解放すると，入力杆２０及び入力プランジャ１８が入力戻しばね４１の力をもって後退する。そのとき，入力戻しばね４１のセット荷重は両永久磁石５１，５２間の吸引力より大きく設定してあるから，入力プランジャ１８が上記吸引力に抗して弁ピストン３３を後退させることになり，その後退に伴い両永久磁石５１，５２が反発状態になれば，その反発力と戻しばね４４の力によって弁ピストン３３は，内向きフランジ３３ａを入力プランジャ１８のストッパ環４５に当接させる後退位置Ｒに直ちに戻ることができる。そして，弁ピストン３３は大気導入弁座３１を弁体３４に着座させると共に，その弁体３４を負圧導入弁座３０から大きく離間させるので，それ以後は通常ブレーキの解除時と同様に，両作動室２ｂ，３ｂは，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。
【００３９】
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，一旦，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，今度は負圧導入弁座３０を弁体３４に着座させると共に，弁体３４を大気導入弁座３１から離間させるので，再び両作動室２ｂ，３ｂに大気が導入されるが，それにより生ずる気圧差により両ブースタピストン４，６が僅かに前進すれば，負圧導入弁座３０にも弁体３４が着座し，制御弁３８を当初の中立状態にする。こうして両作動室２ｂ，３ｂには，大気に希釈された負圧が保持され，負圧ブースタＢは，図１及び図２の休止状態となる。
【００４０】
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，第１永久磁石５１では前後にＮ，Ｓ極を配する一方，第２永久磁石５２では前後にＳ，Ｎ極を配することもできる。また負圧ブースタ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。さらに入力杆２０のストッパ板４０及び後方延長筒１２の内向きフランジ１２ａを廃止し，負圧ブースタＢの休止時には，負圧導入弁座３０を開放したまゝにして，作動室２ｂ，３ｂを負圧室２ａ，３ａとの連通状態に保持するようにしてもよい。また環状段部２３を廃止して弾性ピストン２２の受圧面積を一定にし，倍力比を一定にしておくこともできる。
【００４１】
【発明の効果】
以上のように本発明の第１の特徴によれば，ブレーキペダルによる入力杆の急速前進時には，弁筒及び弁ピストンにそれぞれ付設した第１及び第２永久磁石の吸引力を利用して，大気導入弁座を全開状態にさせるようにした簡単な構成を採用することにより，緊急ブレーキに対応し得る負圧ブースタを安価に提供することができる。特に，弁ピストンの弁筒に対する前進が所定距離未満となる通常ブレーキ時には，第１及び第２永久磁石は反発状態を維持させ，それらの反発力により弁ピストンを後退方向へ戻しばねの付勢力と協働して付勢するようにしたので，弁ピストンを後退位置側へ付勢する戻しばねのセット荷重を小さく設定することが可能となり，その結果，緊急ブレーキ時，弁筒に対して弁ピストンが所定距離を超えて前進することにより，第１及び第２永久磁石が反発状態から吸引状態に切換わるや否や，第１及び第２永久磁石相互の吸引力により，戻しばねの抵抗をあまり受けずに，弁ピストンを素早く前進させ，制御弁を作動室と大気との最大連通状態に切換え，作動室に大量の大気を一挙に導入して，出力杆の出力を倍力限界点まで即座に増大させ，緊急ブレーキに的確に対応することができる。
【００４２】
また本発明の第２の特徴によれば，弁ピストンの，環状通路に臨む外周面を大気導入弁座に向かって小径となるテーパ状に形成したので，大気導入弁座の全開時には，大量の大気を弁ピストンのテーパ状外周面により作動室へスムーズに誘導して，ブースタピストンの応答性向上に寄与することができ，しかも，弁ピストンが入力杆及び入力プランジャのかしめ結合部を覆っているので，該かしめ部による風切り音の発生を抑えることができ，大気の作動室への流入がスムーズであることゝ相俟って全体の作動騒音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部拡大図。
【図３】上記負圧ブースタの作用説明図。
【図４】上記負圧ブースタの倍力特性を示す線図。
【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・・・・第１，第２永久磁石を反発状態から吸引状態に切換えるために弁ピストンが前進する所定距離
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・・・入力プランジャ
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
３２・・・環状通路
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
５１・・・第１永久磁石
５２・・・第２永久磁石[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 that switches the working chamber to a negative pressure chamber and the atmosphere according to the longitudinal movement of the rod, and the valve cylinder and the input rod; and an output rod that is slidably supported by the booster shell; During the operation, the input to the input Negative The present invention relates to an improvement of a bag through a reaction force mechanism that transmits a resultant force with a thrust of the booster piston due to a pressure difference between pressure chambers 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 increase the output limit to the output rod. An object of the present invention is to provide the negative pressure booster capable of exerting an output.
[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 a working chamber that corresponds to the back and forth movement of the input rod. And a control valve for switching the communication to the atmosphere, and the input to the input rod, the working chamber and the input rod between the valve cylinder and the input rod and the output rod slidably supported by the booster shell. Negative In a negative pressure booster via a reaction force mechanism that transmits the resultant force with the booster piston thrust due to the pressure difference between the pressure chambers to the output rod, an input plunger connected to the reaction force mechanism is connected to the input rod. The valve piston is fitted to the outer periphery of the input plunger so that it can move between the retracted position and the advanced position along the axial direction with respect to the input plunger, and the valve piston is moved to the retracted position side by a return spring. The valve piston is connected to the control valve, and when the valve piston advances to the forward position, the control valve is connected so as to switch to the maximum communication state between the working chamber and the atmosphere. The piston is provided with a first permanent magnet and a second permanent magnet that move relative to each other in the axial direction while overlapping each other in the radial direction according to the relative movement in the axial direction. The second permanent magnet, when advancing from a retracted position with respect to the input plunger of the valve piston is less than the predetermined distance, the valve to face the same poles in the radial and axial directions piste The Generates a repulsive force that biases toward the retracted position And urging the valve piston toward the retracted position side in cooperation with the return spring, Advance of the valve piston from the retracted position with respect to the input plunger exceeds a predetermined distance. When , Generate a suction force that moves the valve piston to the forward position with the opposite polarities facing each other in the radial and axial directions The valve piston is advanced to the advance position against the set load of the return spring to bring the control valve into the maximum communication state between the working chamber and the atmosphere. The first feature is to be configured as described above.
[0006]
According to the first feature, at the time of normal braking in which the advancement of the valve piston with respect to the cylinder is less than a predetermined distance, the first and second permanent magnets maintain the repulsion state, and the repulsion force is In cooperation with the biasing force of the return spring Since the valve piston is continuously urged in the backward direction, the set load of the return spring that urges the valve piston toward the backward position side can be set small. Therefore, during emergency braking in which the input rod is rapidly advanced, the first and second permanent magnets are repelled by the valve piston moving forward with the input rod and exceeding a predetermined distance with the delay in operation of the valve tube. As soon as the state is switched from the suction state to the suction state, the suction force between the first and second permanent magnets causes the valve piston to move forward quickly without much resistance from the return spring, and the control valve is moved to the maximum between the working chamber and the atmosphere. Switch to the communication state. As a result, a large amount of air is introduced into the working chamber at once, and the pressure difference between the working chamber and the negative pressure chamber is maximized to immediately increase the thrust of the booster piston, that is, the output of the output rod to the boost limit point. be able to. By adopting such a simple configuration, it is possible to generate a strong braking force corresponding to emergency braking.
[0007]
In addition to the above-described features, the present invention is configured such that the spherical front end portion of the input rod is caulked and coupled to the input plunger so as to be able to swing, and the caulking coupling portion is covered with the valve piston. A formed air introduction valve seat, a negative pressure introduction valve seat formed on the valve cylinder so as to surround the air introduction valve seat with an annular passage interposed therebetween, and the negative pressure mounted on the valve cylinder so as to be movable back and forth. The control valve is constituted by a valve body whose front end is opposed to the introduction valve seat and the atmospheric introduction valve seat, and a valve spring that urges the valve part of the valve body in the seating direction with the two valve seats. A first port that communicates the inside of the valve body to the atmosphere, communicates the negative pressure introduction valve seat to the negative pressure chamber, and a second port communicates the annular passage to the working chamber. The outer peripheral surface of the valve piston facing the annular passage faces the rear end. A smaller diameter Along with the inner peripheral surface of the second port The second feature is that the taper is formed.
[0008]
According to the second feature, the outer peripheral surface of the valve piston is formed in a taper shape having a small diameter toward the air introduction valve seat. Therefore, when the air introduction valve seat is fully opened, a large amount of air is passed through the valve piston taper shape. It can be smoothly guided to the working chamber by the outer peripheral surface to contribute to improving the responsiveness of the booster piston, and the valve piston covers the caulking joint portion of the input rod and the input plunger so that the wind noise generated by the caulking portion is not generated. Occurrence can be suppressed.
[0009]
[Embodiment]
Embodiments of the present invention will be described based on examples of the present invention shown in the accompanying drawings.
[0010]
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 view of part 2 of FIG. 1, FIG. 3 is an explanatory view of the operation of the negative pressure booster, and FIG. FIG.
[0011]
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 whose opposing ends are connected to each other, and both shell halves 1a and 1b. 1 is composed of a partition plate 1c that divides the interior into a front shell chamber 2 and a rear shell chamber 3, and a rear shell half 1b is fixed to and supported by a vehicle front wall F of a vehicle with bolts 8; A cylinder body Ma of a brake master cylinder M that is operated by the booster B is fixed to the shell half body 1 a by bolts 9.
[0012]
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.
[0013]
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.
[0014]
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.
[0015]
The front end portion of the valve cylinder 10 is formed in a large-diameter piston 15, formed in the center portion of the large-diameter piston 15, and in a bottomed cylinder hole 16 opened on the front surface thereof at a constant rate from the large-diameter piston 15. The reduced-diameter small-diameter piston 17 is slidably fitted, and the front end of the input plunger 18 that slidably penetrates the central portion of the front portion of the valve cylinder 10 contacts the rear end surface of the small-diameter piston 17.
[0016]
The connecting cylinder part 19 formed at the rear end part of the input plunger 18 is fitted with a spherical part 20a at the front end of the input rod 20 inserted from the rear end of the valve cylinder 10 and is used to prevent the disconnection. A part 19a of the connecting tube part 19 is caulked inward. Thus, the input rod 20 is connected to the input plunger 18 so as to be able to swing.
[0017]
A cup body 21 is slidably fitted on the outer periphery of the large-diameter piston 15, and the cup body 21 is filled with a flat elastic piston 22 facing the large-diameter and small-diameter pistons 15, 17.
[0018]
One of the opposed end surfaces of the large-diameter piston 15 and the elastic piston 22 (in the illustrated example, an annular step 23 is recessed at the front end of the large-diameter piston 15.
[0019]
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.
[0020]
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.
[0021]
The valve cylinder 10 has a first communication path 28a communicating between the front and rear negative pressure chambers 2a and 3a, a second communication path 28b communicating between the front and rear working chambers 2b and 3b, and a first communication path 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 formed in the second communication passage 28b are formed. Is done. An annular negative pressure introducing valve seat 30 is formed on the inner peripheral surface of the valve cylinder 10 in the middle in the front-rear direction of the first and second ports 29a, 29b. A cylindrical valve piston 33 is slidably fitted on the inner peripheral surface of the front portion of the valve cylinder 10, and negative pressure is introduced at the rear end of the valve piston 33 with an annular passage 32 connected to the second port 29b interposed therebetween. An annular atmosphere introduction valve seat 31 surrounded by the valve seat 30 is formed, and a common valve body 34 facing the negative pressure introduction valve seat 30 and the atmosphere introduction valve seat 31 is disposed in the valve cylinder 10. The 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.
[0022]
In the above, the valve seats 30 and 31, the valve body 34 and the valve spring 36 constitute a control valve 38.
[0023]
Further, the outer peripheral surface 32a of the valve piston 33 constituting the annular passage 32 has a small diameter toward the air introduction valve seat 31, and is formed in a tapered shape continuous with the inner peripheral surface of the second port 29b.
[0024]
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.
[0025]
An air filter 42 is attached to the inner periphery of the rear end of the valve cylinder 10, and the inner periphery of the atmosphere introduction valve seat 31 is always in communication with the atmosphere introduction port 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.
[0026]
The input plunger 18 has an outward flange 18a slidably fitted to the inner peripheral surface of a cylindrical valve piston 33 via a seal member 43, and the valve piston 33 has a connecting cylinder portion of the input plunger 18. Inward flanges 33a slidably fitted on the outer peripheral surface 19 are integrally formed, and a return spring 44 for urging the flanges 18a and 33a in the direction of pulling them back and forth is contracted between the flanges 18a and 33a. At the same time, the stopper ring 45 that receives the rear end surface of the inward flange 33 a is locked to the connecting cylinder portion 19. A contact step 46 is formed on the inner peripheral surface of the valve piston 33 so as to face the rear end surface of the outward flange 18a with a predetermined gap g. Within the range of the gap g, the valve piston 33 has a retracted position R (see FIG. 2) for bringing the inward flange 33a into contact with the stopper ring 45, and a forward movement for bringing the contact step 46 into contact with the outward flange 18a. It is possible to move between the positions F (see FIG. 3).
[0027]
The set load of the return spring 44 is set larger than that of the valve spring 36. Therefore, when the input plunger 18 is retracted by the input rod 20, the valve portion 34 a of the valve body 34 can be displaced rearward against the set load of the valve spring 36 by the valve piston 33 without compressing the return spring 44. .
[0028]
In the valve piston 33, the inner diameter D1 of the inner peripheral surface with which the outward flange 18a is fitted and the effective diameter D2 of the atmospheric introduction valve seat 31 on which the valve body 34 is seated are set equal to each other. In this way, when the valve body 34 is seated on the air introduction valve seat 31, the front end of the valve piston 33 can be obtained even when the negative pressure in the negative pressure chambers 2a and 3a acts before and after the valve piston 33 from the first port 29a. The thrusts due to the negative pressure acting on the part and the rear end part can be canceled each other.
[0029]
The valve barrel 10 is formed with a cylindrical portion 50 surrounding the input plunger 18 in front of the outward flange 18 a, and an annular first permanent magnet 51 is fixed to the outer periphery of the cylindrical portion 50 by a locking ring 53. An annular second permanent magnet 52 that can move in the axial direction while overlapping the first permanent magnet 51 in the radial direction is fixed to the front end of the valve piston 33 by adhesion or the like. The first and second permanent magnets 51 and 52 have both poles N and S at both ends in the axial direction, but the N and S poles of the first and second permanent magnets 51 and 52 are opposite to each other. . That is, in the illustrated example, the first permanent magnet 51 has S and N poles arranged at the front and rear ends, and the second permanent magnet 52 has N and S poles arranged at the front and rear ends. In addition, the first and second permanent magnets 51 and 52 have the same polarity, ie, the N and N poles, in the radial direction and the axial direction when the valve piston 33 advances from the retracted position R with respect to the input plunger 18 to a predetermined distance s. When a repulsive force that urges the valve piston 33 to the reverse position R side is generated facing the direction, and the advance of the valve piston 33 from the reverse position R with respect to the input plunger 18 exceeds a predetermined distance s, they are different from each other, that is, S , N poles are opposed to each other in the radial direction and the axial direction so as to generate a suction force for moving the valve piston 33 to the forward position F. The set load of the input return spring 41 is set to be larger than the attractive force generated when the permanent magnets 51 and 52 are attracted.
[0030]
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 FIG. 1, the input rod 20 is positioned at the backward limit, and the control valve 38 seats the valve body 34 on the atmospheric introduction valve seat 31 and the negative pressure introduction valve seat 30. The front and rear working chambers 2b and 3b are in a neutral state where both the negative pressure chambers 2a and 3a and the air introduction port 39 are not in communication with each other. The negative pressure of the negative pressure source supplied through the negative pressure introduction pipe 14 is stored, and the negative pressure appropriately diluted with the atmosphere is held in both working chambers 2b and 3b. Thus, a small forward force is given to the front and rear booster pistons 4 and 6 by a slight pressure difference generated between the front negative pressure chamber 2a and the working chamber 2b and between the rear negative pressure chamber 3a and the working chamber 3b. However, the forward force and the force of the valve barrel return spring 27 are balanced, and the booster pistons 4 and 6 are stopped when they are slightly advanced from the retreat limit.
[Normal brake]
If the brake pedal P is depressed at a normal speed to brake the vehicle and the air introduction valve seat 31 is advanced through the input rod 20, the input plunger 18, and the valve piston 33, both the booster pistons 4 and 6 are initially stationary. Therefore, the air introduction valve seat 31 is immediately separated from the valve body 34, and the second port 29 b is communicated with the air 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 passes through the air introduction valve seat 31 and is quickly introduced into the working chambers 2b and 3b via the second port 29b. Since the negative pressure chambers 2a and 3a have a higher pressure than the negative pressure chambers 2a and 3a, the booster pistons 4 and 6 obtain a large forward thrust based on the pressure difference between them, Against this, it moves forward so as to follow the movement of the input rod 20. The forward thrust of the booster pistons 4 and 6 is transmitted from the large-diameter piston 15 to the elastic piston 22 and pushes the cup body 21, that is, the output rod 25 forward, so that the brake master cylinder M is moved to the brake pedal P. It can be operated without delay to depress and brake the vehicle.
[0031]
By the way, during such braking, the thrust of the booster pistons 4 and 6 applied to the large-diameter piston 15 and the pedaling force of the operator applied to the small-diameter piston 17 from the input rod 20 act on the rear end surface of the elastic piston 22. The operating reaction force of the output rod 25 acts on the front end surface of the front end surface, and the elastic piston 22 is thereby compressed back and forth. As a result, a part of the reaction force of the output rod 25 is transmitted to the input rod 20 via the elastic piston 22, and the driver senses the output of the output rod 25, that is, the magnitude of the braking force. Can do.
[0032]
Thus, until the output of the output rod 25 reaches the boost limit (see line ab in FIG. 4), the valve cylinder 10 integrated with the booster pistons 4 and 6 advances by the advance amount of the input rod 20. Therefore, when the input rod 20 stops moving forward, the valve element 34 that has moved forward together with the valve cylinder 10 is seated again on the atmosphere introduction valve seat 31 to prevent further introduction of the atmosphere into the working chambers 2b and 3b. Therefore, the forward movement of the booster pistons 4 and 6 is also stopped, and a boost output corresponding to the input can be obtained. By the way, the large-diameter piston 15 initially has the front end surface except the annular step portion 23 abutted against the elastic piston 22, but when the output of the output rod 25 exceeds a predetermined value, the annular step portion 23 is also moved to the elastic piston. Therefore, the boost ratio increases from the middle as shown by line abc in FIG. 4 due to the change in the pressure receiving area ratio of the large diameter piston 15 and the small diameter piston 17 to the elastic piston 22. To do.
[0033]
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 becomes maximum, 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. 4).
[0034]
As described above, when the valve cylinder 10 follows the forward movement of the input rod 20 almost without delay, the relative displacement between the first permanent magnet 51 of the valve cylinder 10 and the second permanent magnet 52 of the valve piston 33 is the predetermined value. Since the permanent magnets 51 and 52 continue to repel each other in the axial direction without exceeding the distance s, the valve piston 33 contacts the inward flange 33a against the stopper ring 45 of the input plunger 18 as shown in FIG. The retracted position R is held in contact. This means that the set load of the return spring 44 that biases the valve piston 33 toward the reverse position R can be set small.
[Emergency brake]
At the time of emergency braking in which the brake pedal P is rapidly depressed, the valve piston 33 moves forward together with the input rod 20 with respect to the valve cylinder 10 with the operation delay of the valve cylinder 10, and the second permanent magnet 52 becomes the first permanent magnet 51. On the other hand, when moving forward by a predetermined distance s or more, as described above, the front and rear end poles (S, N pole) of the second permanent magnet 52 are the front and rear end poles (N, S pole) of the first permanent magnet 51, as described above. Since the permanent magnets 51 and 52 are switched from the repulsion state to the attraction state, the valve piston 33 resists the set load of the return spring 44 by the attraction force. As a result, the valve moves forward to a forward position F (a state shown in FIG. 3) in contact with the outward flange 18a, and the air introduction valve seat 31 is pulled away from the valve body 34 to the maximum to be fully opened.
[0035]
Here, it should be noted that the set load of the return spring 44 is set to be small by using the repulsive force when the permanent magnets 51 and 52 are in the repulsive state as described above. As soon as the magnets 51 and 52 are switched from the repulsion state to the attraction state, the valve piston 33 is rapidly advanced without causing much resistance to the set load of the return spring 44, and the air introduction valve seat 31 is fully opened immediately. It is to let you.
[0036]
As a result, since a large amount of air is introduced into the working chambers 2b and 3b from the air introduction port 39 at once, the brake piston 4 due to the pressure difference between the working chambers 2b and 3b and the negative pressure chambers 2a and 3a. 6 thrusts, that is, the output of the output rod 25 immediately increases to the boost limit, and the brake master cylinder M can be operated rapidly and powerfully. Such an emergency brake operation, as indicated by P1, P2 and P3 in FIG. 4, is performed at the same time as the start of the brake, during the normal brake, or after the boost ratio changes during the normal brake. However, if you do this, you can always increase the output immediately to the boost limit.
[0037]
Further, the outer peripheral surface 32a of the valve piston 33 facing the annular passage 32 is a tapered surface that is continuous with the inner peripheral surface of the second port 29b and has a smaller diameter toward the atmospheric introduction valve seat 31. When a large amount of air flows into the second port 29b from the annular passage 32 as the seat 31 is fully opened, the air flow is smooth without being disturbed, and the valve piston 33 is joined by caulking between the input rod 20 and the input plunger 18. Covering the portion 19a can suppress the generation of noise such as wind noise.
[0038]
As described above, when the input rod 20 is rapidly advanced by the brake pedal P, the valve piston 33 is attached to the valve cylinder 10 and the valve piston 33 by the attractive force between the first and second permanent magnets 51 and 52, respectively. By adopting a simple configuration in which 31 is fully opened, the negative pressure booster B that can handle emergency braking can be provided at low cost.
[Release emergency brake]
When the pedal force is released from the brake pedal P to release the emergency brake state, the input rod 20 and the input plunger 18 are moved backward by the force of the input return spring 41. At that time, since the set load of the input return spring 41 is set to be larger than the attractive force between the permanent magnets 51 and 52, the input plunger 18 moves the valve piston 33 backward against the attractive force. When the permanent magnets 51 and 52 are in a repulsive state as they are retreated, the valve piston 33 is brought into a retreated position where the inward flange 33a abuts against the stopper ring 45 of the input plunger 18 by the repelling force and the force of the return spring 44. Return to R immediately. Then, the valve piston 33 seats the air introduction valve seat 31 on the valve body 34 and greatly separates the valve body 34 from the negative pressure introduction valve seat 30. The working chambers 2b and 3b communicate with the negative pressure chambers 2a and 3a through the second port 29b, the annular passage 32 and the first port 29a. 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.
[0039]
When the input rod 20 is retracted to the retreat limit where the stopper plate 40 is brought into contact with the inward flange 12a of the rear extension cylinder 12, the rear booster piston 6 once hits the projection 7a of the rear diaphragm 7 against the rear wall of the booster shell 1. Returning to the retreat limit, the negative pressure introduction valve seat 30 is seated on the valve body 34 and the valve body 34 is separated from the atmosphere introduction valve seat 31, so that the atmosphere is again introduced into the working chambers 2b and 3b. However, if the booster pistons 4 and 6 slightly move forward due to the pressure difference generated thereby, the valve body 34 is also seated on the negative pressure introduction valve seat 30 and the control valve 38 is brought into the initial neutral state. Thus, the negative pressure diluted to the atmosphere is maintained in both the working chambers 2b and 3b, and the negative pressure booster B enters the resting state shown in FIGS.
[0040]
The present invention is not limited to the above embodiments, and various design changes can be made without departing from the scope of the invention. For example, the first permanent magnet 51 may have N and S poles arranged at the front and rear, while the second permanent magnet 52 may have S and N poles arranged at the front and rear. The negative pressure booster B can also be configured as a single type with a single booster piston. Further, the stopper plate 40 of the input rod 20 and the inward flange 12a of the rear extension cylinder 12 are abolished, and when the negative pressure booster B is stopped, the negative pressure introduction valve seat 30 is opened and the working chambers 2b and 3b are opened. You may make it hold | maintain in the communication state with the negative pressure chambers 2a and 3a. Further, the annular stepped portion 23 can be eliminated, the pressure receiving area of the elastic piston 22 can be made constant, and the boost ratio can be made constant.
[0041]
【The invention's effect】
As described above, according to the first feature of the present invention, during the rapid advancement of the input rod by the brake pedal, the atmospheric force is obtained by using the attractive forces of the first and second permanent magnets attached to the valve cylinder and the valve piston, respectively. By adopting a simple configuration in which the introduction valve seat is fully opened, a negative pressure booster that can handle emergency braking can be provided at low cost. In particular, during normal braking in which the forward movement of the valve piston relative to the cylinder is less than a predetermined distance, the first and second permanent magnets maintain the repulsive state, and the repulsive force causes the valve piston to move backward. In cooperation with the biasing force of the return spring As a result, the set load of the return spring that urges the valve piston toward the retracted position can be set to a small value. As a result, the valve piston moves a predetermined distance from the cylinder during emergency braking. As soon as the first and second permanent magnets are switched from the repulsion state to the attraction state by moving forward, the valve is not subject to much resistance of the return spring due to the attraction force between the first and second permanent magnets. The piston is advanced quickly, the control valve is switched to the maximum communication state between the working chamber and the atmosphere, a large amount of air is introduced into the working chamber at once, and the output of the output rod is immediately increased to the boost limit point. It can deal with brakes accurately.
[0042]
According to the second feature of the present invention, the outer peripheral surface of the valve piston facing the annular passage is formed in a tapered shape having a small diameter toward the atmosphere introduction valve seat. Therefore, when the atmosphere introduction valve seat is fully opened, a large amount of The air can be smoothly guided to the working chamber by the tapered outer peripheral surface of the valve piston, contributing to improved response of the booster piston, and the valve piston covers the caulking joint of the input rod and input plunger. Therefore, it is possible to suppress the generation of wind noise due to the caulking portion, and it is possible to effectively reduce the entire operating noise due to the smooth inflow of the atmosphere into the working chamber.
[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.
FIG. 2 is an enlarged view of part 2 of FIG.
FIG. 3 is an operation explanatory view of the negative pressure booster.
FIG. 4 is a diagram showing a boost characteristic of the negative pressure booster.
[Explanation of symbols]
B ... Negative pressure booster
F ... Advance position of valve piston
R ... Retract position of valve piston
V ... Negative pressure source
s... a predetermined distance by which the valve piston moves forward to switch the first and second permanent magnets from the repulsive state to the attracting state
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 plunger
20 ... Input
24 ... Reaction force mechanism
25 ・・・ Output 杆
29a ..First port
29b ..Second port
30 ... Negative pressure introduction valve seat
31 ... Air introduction valve seat
32 ... Annular passage
33 ... Valve piston
34 ... Valve
34a ... Valve part
36 ... Valve spring
38 ... Control valve
44 ... Return spring
51 ... 1st permanent magnet
52 ... Second permanent magnet

Claims

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 (38) 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). Between the valve cylinder (10) and the input rod (20) and the output rod (25) slidably supported by the booster shell (1). inputs and, working chamber (2b, 3b)及beauty negative pressure chamber (2a, 3a) the by pressure differential between the booster piston (4 against, In the negative pressure booster which is Kai裝 the reaction force mechanism (24) for transmitting force to the output rod (25) and thrust),
An input plunger (18) connected to the reaction force mechanism (24) is connected to the input rod (20). A valve piston (33) is connected to the outer periphery of the input plunger (18), which is connected to the input plunger (18). The valve piston (33) is attached to the retracted position (R) side by a return spring (44) while being fitted so as to move between the retracted position (R) and the advanced position (F) along the axial direction. The valve piston (33) is moved to the control valve (38), and when the valve piston (33) is advanced to the forward position (F), the control valve (38) is moved to the working chamber (2b, 3b). The valve cylinder (10) and the valve piston (33) are connected so as to be switched to a maximum communication state between the valve and the atmosphere, and move relative to each other in the axial direction while overlapping each other in the radial direction according to the relative movement in the axial direction. 1 permanent magnet (51) and A second permanent magnet (52) is attached to each of the first and second permanent magnets (51, 52). The valve piston (33) has a predetermined advance from the retracted position (R) with respect to the input plunger (18). when less than the distance (s) is to generate a repulsive force that urges the same poles each other the valve piston to face the radial and axial direction (33) to said retracted position (R) side, the valve piston (33) is urged toward the retracted position (R) in cooperation with the return spring (44), and the valve piston (33) is advanced from the retracted position (R) with respect to the input plunger (18). When the distance (s) is exceeded , a suction force is generated to move the valve piston (33) to the forward position (F) with the opposite poles facing each other in the radial direction and the axial direction, and the valve piston (33 ) For the return spring (44) By advancing until said forward position (F) against the set load, the control valve (38) the working chamber (2b, 3b) and to be configured to maximize communication with the atmosphere Characteristic, negative pressure booster.

The negative pressure booster according to claim 1,
The spherical front end portion (20a) of the input rod (20) is caulked and coupled to the input plunger (18) in a swingable manner, and the caulking coupling portion (19a) is covered with the valve piston (33). (33) An atmospheric introduction valve seat (31) formed at the rear end and a negative pressure formed on the valve cylinder (10) so as to surround the atmospheric introduction valve seat (31) with the annular passage (32) interposed therebetween. The introduction valve seat (30) is attached to the valve cylinder (10) so as to be movable back and forth, and the front valve portion (34a) is opposed to the negative pressure introduction valve seat (30) and the atmospheric introduction valve seat (31). From the valve body (34) and the valve spring (36) for urging the valve portion (34a) of the valve body (34) in the seating direction with the valve seats (30, 31), the control valve (38). And the inside of the valve body (34) communicates with the atmosphere, and the negative pressure introduction valve A first port (29a) that communicates (30) with the negative pressure chamber (2a, 3a), and a second port (29b) that communicates the annular passage (32) with the working chamber (2b, 3b). An outer peripheral surface (32a) provided on the valve cylinder (10) and facing the annular passage (32) of the valve piston (33) has a smaller diameter toward the rear end and an inner periphery of the second port (29b). A negative pressure booster characterized by being formed into a taper shape continuous to the surface .