JP3938882B2

JP3938882B2 - Neutral / relief valve or neutral valve for hydraulic continuously variable transmission

Info

Publication number: JP3938882B2
Application number: JP2002110295A
Authority: JP
Inventors: 豪朗野崎
Original assignee: Yanmar Co Ltd
Current assignee: Yanmar Co Ltd
Priority date: 2002-04-12
Filing date: 2002-04-12
Publication date: 2007-06-27
Anticipated expiration: 2022-04-12
Also published as: JP2003301943A

Description

【０００１】
【発明の属する技術分野】
本発明は、油圧式無段変速機に設けられる、中立バルブの構成に関する。
【０００２】
【従来の技術】
従来から、可変容積型油圧ポンプと油圧モータより成る油圧式無段変速機（以下ＨＳＴ式変速機）においては、ＨＳＴ式変速機を中立（速度ゼロ）状態に操作した場合であっても、油圧ポンプの可動斜板の傾きを正確に中立位置に保持することは困難であったため、油路板に形成される一対のメイン回路にそれぞれ中立バルブを設けて、ＨＳＴ式変速機を中立状態に保持するようにしていた。また、ＨＳＴ式変速機に設けられるメイン回路のうちいずれか一方の作動油圧が、過剰に高圧となって設定されたリリーフ圧を超えると、低圧側のメイン回路に作動油を逃がすためのリリーフバルブが設けられている。このリリーフバルブは、一対のメイン回路の何れが高圧となった場合でも作動して、リリーフ機能を発揮することができるものである。
【０００３】
【発明が解決しようとする課題】
しかし、中立バルブと、リリーフバルブは一般に独立して設けられるものであり、また、中立バルブは各メイン回路に必要であり二個備えられるため、コストが嵩んでしまう。また、前述の二つのメイン回路に対し一個で機能する構造のリリーフバルブには、二つのメイン回路の圧が同時に作用するため、リリーフバルブの弁体に掛かるチャージ圧が高いほど実際のリリーフ圧は設定値に対し低下する傾向があり、設定通りのリリーフ圧が得られないという不具合がある。
【０００４】
【課題を解決するための手段】
本発明の解決しようとする課題は以上の如くであり、次にこの課題を解決するための手段を説明する。
【０００５】
請求項１においては、可変容積型油圧ポンプ（２１）と油圧モータ（２２）と油路板（３２）より成る油圧式無段変速機（１０）の中立状態を保持する中立・リリーフバルブ（３５Ａ）であって、該油路板（３２）には、油路板（３２）に形成されたメイン回路（３２ｍ・３２ｍ）間を連通する連通回路（３２ｄ）、及び該連通回路（３２ｄ）と片方のメイン回路（３２ｍ）の交差部を含むバルブ穴（５０）を形成し、該油路板（３２）の中央側部に位置するバルブ穴（５０）の奥部は、該連通回路（３２ｄ）と連通し、該奥部に弁座（４０）を形成し、該バルブ穴（５０）の該弁座（４０）近傍には環状溝（４３）を設け、該バルブ穴（５０）は、中途部でメイン回路（３２ｍ）と連通し、該バルブ穴（５０）には中立弁体（４６）を摺動可能に挿嵌し、該バルブ穴（５０）は油路板（３２）の外側から蓋体（４５）を挿入し閉塞し、前記中立弁体（４６）の頭面（４６ｆ）はバルブ穴（５０）の奥部に位置する弁座（４０）に当接可能とし、中立弁体（４６）の頭面（４６ｆ）が弁座（４０）に当接している状態で、前記中立弁体（４６）と蓋体（４５）とが離間するよう配置し、該中立弁体（４６）は、頭面（４６ｆ）が弁座（４０）に当接する位置から、尾面（４６ｎ）が蓋体（４５）に当接する位置までバルブ穴（５０）内を摺動可能とし、前記蓋体（４５）には、胴部（４５ｅ）から頭部（４５ｆ）へかけてメイン回路（３２ｍ）側が開口する穴を形成し、該穴をバネ室（４５ａ）とし、該バネ室（４５ａ）の奥部と、中立弁体（４６）内に嵌挿される安全弁体（４７）に一体的に設けられたバネ受け部（４７ｂ）との間に、安全弁体（４７）を連通回路（３２ｄ）側へ付勢するバネ（４２）を介装し、前記蓋体（４５）には、バネ室４５ａ内と外部のドレン回路とを連通する通路（４５ｃ）を形成し、前記中立弁体（４６）は、略円筒状の部材であり、内部に連通孔（４６ｈ）を形成し、該連通孔（４６ｈ）には尾面（４６ｎ）側から安全弁体（４７）を摺動可能に挿入し、該安全弁体（４７）の弁部（４７ａ）は、連通孔（４６ｈ）内部に形成されたリリーフバルブの弁座（４１）に着座し、前記バネ（４２）によって中立弁体（４６）が弁座（４０）に着座する方向に付勢し、前記中立弁体（４６）は、連通孔（４６ｈ）とメイン回路（３２ｍ）を連通するための通路（４６ｅ）を設け、リリーフバルブが開弁して、安全弁体（４７）の弁部（４７ａ）が弁座（４１）から離れたときには、該通路（４６ｅ）を通って連通回路（３２ｄ）からメイン回路（３２ｍ）へ、又はメイン回路（３２ｍ）から連通回路（３２ｄ）へ作動油をリリーフし、前記中立弁体（４６）の小径部（４６ｂ）端の頭面（４６ｆ）は、外周部と連通孔（４６ｈ）とを結ぶ溝（４６ｇ）を形成し、該溝（４６ｇ）によって、中立弁体（４６）の頭面（４６ｆ）が弁座（４１）に当接した状態でも、連通回路（３２ｄ）から溝（４６ｇ）を通って環状溝（４３）へ至る油路を確保し、該小径部（４６ｂ）の外周部は部分的に二面が切り欠かれた通路（４６ｃ・４６ｃ）を形成し、外周部がバルブ穴（５０）の内周に接していても、環状溝（４３）から通路（４６ｃ・４６ｃ）を介してメイン回路（３２ｍ）への油路を確保し、該通路（４６ｃ・４６ｃ）は頭面（４６ｆ）から離れた位置から形成し、前記油圧ポンプ（２１）の可動斜板（２１ｃ）が中立の時は、中立弁体（４６）が弁座（４０）に着座した状態で、連通回路（３２ｄ）とメイン回路（３２ｍ）間の油路が確保されているが、該可動斜板（２１ｃ）が中立の状態から傾動すると、連通回路（３２ｄ）側とメイン回路（３２ｍ）側との間で一定以上の差圧が生じ、連通回路（３２ｄ）側の油圧が大きいときには、連通回路（３２ｄ）とメイン回路（３２ｍ）間の油路を閉鎖し、該状態で、連通回路（３２ｄ）と連通する高圧側のメイン回路（３２ｍ）の油圧がリリーフ設定圧を超えたときには、安全弁体（４７）の弁部（４７ａ）に圧が掛かってバネ（４２）が収縮し、該弁部（４７ａ）と弁座（４１）が離れて、連通回路（３２ｄ）側から、中立弁体（４６）の連通孔（４６ｈ）と通路（４６ｅ）を通って低圧側のメイン回路（３２ｍ）に至る油路が形成され、高圧側のメイン回路（３２ｍ）から低圧側のメイン回路（３２ｍ）へ作動油を逃がすべく構成したものである。
【０００６】
請求項２においては、可変容積型油圧ポンプ（２１）と油圧モータ（２２）と油路板（３２）より成る油圧式無段変速機（１０）の中立状態を保持する中立・リリーフバルブ（３５Ｂ）であって、該油路板（３２）には、油路板（３２）に形成されたメイン回路（３２ｍ・３２ｍ）間を連通する連通回路（３２ｄ）、及び該連通回路（３２ｄ）と片方のメイン回路（３２ｍ）の交差部を含むバルブ穴（５０）を形成し、該油路板（３２）の中央側部に位置するバルブ穴（５０）の奥部は、該連通回路（３２ｄ）と連通し、該奥部に弁座（４０）を形成し、該バルブ穴（５０）の該弁座（４０）近傍には環状溝（４３）を設け、該バルブ穴（５０）は、中途部でメイン回路（３２ｍ）と連通し、該バルブ穴（５０）には中立弁体（５５）を摺動可能に挿嵌し、該バルブ穴（５０）は油路板（３２）の外側から蓋体（４５）を挿入し閉塞し、前記中立弁体（５５）の頭面（５５ｆ）はバルブ穴（５０）の奥部に位置する弁座（４０）に当接可能とし、中立弁体（５５）の頭面（５５ｆ）が弁座（４０）に当接している状態で、前記中立弁体（５５）と蓋体（４５）とが離間するよう配置し、該中立弁体（５５）は、頭面（５５ｆ）が弁座（４０）に当接する位置から、尾面（５５ｎ）が蓋体（４５）に当接する位置までバルブ穴（５０）内を摺動可能とし、前記蓋体（４５）には、胴部（４５ｅ）から頭部（４５ｆ）へかけてメイン回路（３２ｍ）側が開口する穴を形成し、該穴をバネ室（４５ａ）とし、該バネ室（４５ａ）の奥部と、中立弁体（５５）内に嵌挿される安全弁体（４７）に一体的に設けられたバネ受け部（４７ｂ）との間に、安全弁体（４７）を連通回路（３２ｄ）側へ付勢するバネ（４２）を介装し、前記蓋体（４５）には、バネ室４５ａ内と外部のドレン回路とを連通する通路（４５ｃ）を形成し、前記中立弁体（５５）は、略円筒状の部材であり、内部に連通孔（５５ｈ）を形成し、該連通孔（５５ｈ）には尾面（５５ｎ）側から安全弁体（４７）を摺動可能に挿入し、該安全弁体（４７）の弁部（４７ａ）は、連通孔（５５ｈ）内部に形成されたリリーフバルブの弁座（４１）に着座し、前記バネ（４２）によって中立弁体（５５）が弁座（４０）に着座する方向に付勢し、前記中立弁体（５５）は、連通孔（５５ｈ）とメイン回路（３２ｍ）を連通するための通路（５５ｅ）を設け、リリーフバルブが開弁して、安全弁体（４７）の弁部（４７ａ）が弁座（４１）から離れたときには、該通路（５５ｅ）を通って連通回路（３２ｄ）からメイン回路（３２ｍ）へ、又はメイン回路（３２ｍ）から連通回路（３２ｄ）へ作動油をリリーフし、該中立弁体（５５）は、尾面（５５ｎ）側に外周の二面を切り欠いた通路（５５ｋ・５５ｋ）が形成され、中立弁体（５５）の頭面（５５ｆ）が弁座４０に着座している状態、すなわち、可動斜板（２１ｃ）が中立となるよう操作されている状態では、メイン回路（３２ｍ）から、バルブ穴（５０）に形成した溝（４９）と、中立弁体（５５）の外径部に形成した通路（５５ｋ・５５ｋ）を通じて、バネ室（４５ａ）に連通する通路を形成し、バネ室（４５ａ）は、ドレン回路と連通し大気圧とし、該中立弁体（５５）の頭面（５５ｆ）が弁座（４０）に当接した状態において、メイン回路（３２ｍ）→バルブ穴（５０）に形成した溝（４９）→中立弁体（５５）の外径部に形成された通路（５５ｋ・５５ｋ）→バネ室（４５ａ）と連通し、前記油圧ポンプ（２１）の可動斜板（２１ｃ）が中立の時は、中立弁体（５５）が弁座（４０）に着座した状態で、連通回路（３２ｄ）とメイン回路（３２ｍ）間の油路が確保されているが、該可動斜板（２１ｃ）が中立の状態から傾動すると、連通回路（３２ｄ）側とメイン回路（３２ｍ）側との間で一定以上の差圧が生じ、連通回路（３２ｄ）側の油圧が大きいときには、連通回路（３２ｄ）とメイン回路（３２ｍ）間の油路を閉鎖し、該状態で、連通回路（３２ｄ）と連通する高圧側のメイン回路（３２ｍ）の油圧がリリーフ設定圧を超えたときには、安全弁体（４７）の弁部（４７ａ）に圧が掛かってバネ（４２）が収縮し、該弁部（４７ａ）と弁座（４１）が離れて、連通回路（３２ｄ）側から、中立弁体（５５）の連通孔（５５ｈ）と通路（５５ｅ）を通って低圧側のメイン回路（３２ｍ）に至る油路が形成され、高圧側のメイン回路（３２ｍ）から低圧側のメイン回路（３２ｍ）へ作動油を逃がすべく構成したものである。
【０００７】
請求項３においては、請求項１又は請求項２に記載の油圧式無段変速機の中立・リリーフバルブバルブにおいて、中立・リリーフバルブ（３５）の蓋体（４５）に通路（４５ｇ）を設け、該通路（４５ｇ）とチャージポンプ（５１）に接続されるチャージ回路（３２ｃ）とを接続し、該バネ室（４５ａ）の圧をチャージポンプ（５１）によって制御されるチャージ回路（３２ｃ）のチャージ圧と略等しくし、バネ室（４５ａ）をチャージ圧とすることで、中立弁体（４６・５５）が移動始める圧力を設定又は設定変更可能としたものである。
【０００８】
請求項４においては、可変容積型油圧ポンプ（２１）と油圧モータ（２２）と油路板（３２）より成る油圧式無段変速機（１０）の中立状態を保持する中立バルブ（３５Ｃ）であって、中立バルブ（３５Ｃ）は、前記油路板（３２）の連通回路（３２ｄ）とメイン回路（３２ｍ）が交わる部分に形成されたバルブ穴（５０）に挿嵌された中立弁体（５３）と、該バルブ穴（５０）に挿入して閉塞する蓋体（４５）とで構成し、前記蓋体（４５）の内部には、中立弁体（５３）側に開口する穴が形成されてバネ室（４５ａ）とし、前記中立弁体（５３）の頭面（５３ｆ）は連通回路（３２ｄ）に面し、該頭面（５３ｆ）がバルブ穴（５０）の奥部に形成された弁座（４０）と当接している状態で該中立弁体（５３）の尾面（５３ｎ）が蓋体（４５）の胴部（４５ｅ）と離間するよう構成し、該中立弁体（５３）の外周は、頭面（５３ｆ）から離れた位置から二面が切り欠かれて通路（５３ｃ・５３ｃ）を形成し、該頭面（５３ｆ）には、頭面（５３ｆ）が弁座（４０）に着座した状態でバルブ穴（５０）に形成された環状溝（４３）と連通回路（３２ｄ）とが連通するよう溝（５３ｇ）を形成し、前記中立弁体（５３）の頭面（５３ｆ）が弁座（４０）に着座した状態では、連通回路（３２ｄ）→頭面（５３ｆ）の溝（５３ｇ）→環状溝（４３）→小径部（５３ｂ）に形成された通路（５３ｃ）→メイン回路（３２ｍ）、又はメイン回路（３２ｍ）から連通回路（３２ｄ）への逆方向可能な油路を形成し、該中立弁体（５３）の外周はバルブ穴（５０）の内周に接して摺動可能とし、該外周端に位置する尾面（５３ｎ）に、バネ受け部（５３ｍ）を形成し、該バネ受け部（５３ｍ）と、蓋体（４５）に形成されたバネ室（４５ａ）の奥部との間にバネ（４２）を介装し、該バネ（４２）によって中立弁体（５３）を連通回路（３２ｄ）側へ付勢し、該中立バルブ（３５Ｃ）において、ＨＳＴ式変速機（１０）の油圧ポンプ（２１）の可動斜板（２１ｃ）が略中立位置にあるとき、中立弁体（５３）はバネ（４２）により付勢されて弁座（４０）に着座し、該状態で連通回路（３２ｄ）からメイン回路（３２ｍ）までの油路を確保し、該油路を通じて連通回路（３２ｄ）とメイン回路（３２ｍ）間で作動油が移動して差圧を解消し、ＨＳＴ式変速機（１０）を中立状態に保持する中立バルブとして作用し、前記可動斜板（２１ｃ）が傾倒して、連通回路（３２ｄ）とメイン回路（３２ｍ）間に差圧が生じ、連通回路（３２ｄ）側が高圧となれば、該中立弁体（５３）が蓋体（４５）側へ摺動し、該中立弁体（５３）が蓋体（４５）側へ移動する途中で、中立弁体（５３）の小径部（５３ｂ）の外周がバルブ穴（５０）の内周に接して連通回路（３２ｄ）とメイン回路（３２ｍ）間の油路を断つものである。
【０００９】
請求項５においては、請求項１・２又は４のいずれかに記載の油圧式無段変速機の中立・リリーフバルブ又は中立バルブの何れかにおいて、前記弁本体である中立弁体（４６・５３・５５）を、頭面（４６ｆ・・）側より小径部（４６ｂ・・）、中径部（４６ｄ・・）及び大径部（４６ａ・・）と、少なくとも大小二段の外径を有する筒状体として、小径部断面積と、大径部断面積と小径部断面積との差分面積とが略等しくなるように形成し、該小径部を一方のメイン回路に連通し、大径部と小径部との段差部を他方のメイン回路に連通したものである。
【００１０】
【発明の実施の形態】
次に、発明の実施の形態を説明する。図１は本発明の中立バルブが設けられるＨＳＴ式変速機を示す側面断面図、図２は同じくＨＳＴ式変速機の油路板を示す正面断面図である。図３は第一実施例に係る中立・リリーフバルブが開いている状態を示す断面図である。図４は中立弁体の図３におけるＶ矢視図、図５は中立弁体の図３におけるＸ−Ｘ矢視図、図６は中立バルブとして作用している中立・リリーフバルブが閉じている状態を示す断面図、図７は中立弁体の変位とメイン回路間の油路面積の変化を示す図、図８は第一実施例における中立弁体の別形態を示す断面図である。図９は第二実施例に係る中立・リリーフバルブが開いている状態を示す断面図、図１０は中立弁体の図９におけるＹ−Ｙ矢視図、図１１は第二実施例に係る中立・リリーフバルブが開いている状態を示す断面図、図１２は第二実施例に係る中立・リリーフバルブの別形態を示す図である。図１３は第三実施例に係る中立バルブが開いている状態を示す断面図、図１４は第三実施例に係る中立バルブが閉じている状態を示す断面図である。
【００１１】
まず、本発明の中立バルブ３５が設けられる油圧式無段変速機の概略構成について説明する。図１及び図２に示す如く、油圧式無段変速機（以降ＨＳＴ式変速機と記す）１０は油圧ポンプ２１及び油圧モータ２２により構成され、該油圧ポンプ２１及び油圧モータ２２はハウジング３１に内包されている。
【００１２】
油圧ポンプ２１は駆動軸２１ａ、シリンダブロック２１ｂ、プランジャ２１ｅ及び可動斜板２１ｃ等により、可変容量式油圧ポンプに構成されている。前記シリンダブロック２１ｂは、可動斜板２１ｃに当接するプランジャ２１ｅが摺動可能に挿嵌されるとともに、該シリンダブロック２１ｂに挿嵌された駆動軸２１ａと共に回動する。
【００１３】
また、前記可動斜板２１ｃはプランジャ２１ｅの摺動量を規制し、油圧ポンプ２１の作動油の吐出量を調節可能に構成されている。そして、油路板３２に設けられたメイン回路３２ｍを介して、作動油が油圧ポンプ２１より油圧モータ２２に供給される。
【００１４】
一方、前記油圧モータ２２は、出力軸２２ａ、シリンダブロック２２ｂ、プランジャ２２ｅ及び固定斜板２２ｃ等により構成されている。前記出力軸２２ａは、油路板３２に挿通され、シリンダブロック２２ｂに挿嵌され、その一端をハウジング３１により回動自在に支承されている。前記シリンダブッロク２２ｂは出力軸２２ａと共に回動し、該シリンダブッロク２２ｂにはプランジャ２２ｅが摺動自在に挿嵌されている。該プランジャ２２ｅはハウジング３１に固設された固定斜板２２ｃに当接している。
【００１５】
上記の構成により、駆動力が駆動軸２１ａに入力され、油圧ポンプ２１が駆動されると、該油圧ポンプ２１により吐出された作動油は油路板３２に形成されたメイン回路３２ｍ・３２ｍを介して油圧モータ２２に供給され、該作動油により油圧モータ２２が駆動されて、該駆動力が出力軸２２ａに伝達される。
【００１６】
また、前記油路板３２には、チャージ回路３２ｃが形成されており、該チャージ回路３２ｃと前記メイン回路３２ｍ・３２ｍとの間にはチェックバルブ３６・３６が介装されている。さらに、二つのメイン回路３２ｍ・３２ｍは連通回路３２ｄで連通されており、メイン回路３２ｍと連通回路３２ｄとの間に中立バルブ３５が介装されている。
【００１７】
ここで、本発明の第一実施例に係る中立バルブ３５（中立・リリーフバルブ３５Ａ）の構成について説明する。本第一実施例に係る中立バルブ３５は、リリーフバルブとしての機能を併せ持った、中立・リリーフバルブ３５Ａであり、油路板３２に形成されたバルブ穴５０に挿入されるリリーフバルブの弁本体としての中立弁体４６、調圧用バネ座としての蓋体４５及び安全弁体４７等で構成されている。すなわち、リリーフバルブとして、弁本体と調圧用バネ座が分離した構成としている。
【００１８】
ＨＳＴ式変速機１０の出力をゼロとする（即ち、出力軸２２ａの回転を停止させる）ためには、油圧ポンプ２１の可動斜板２１ｃの斜板角を中立位置に保持して、両メイン回路３２ｍ・３２ｍ間における作動油圧を等しくしなければならないが、実際には、該可動斜板２１ｃを正確に中立位置に保持しておくのは困難であり、二つのメイン回路３２ｍ・３２ｍ間で若干の差圧が生じてしまうことがある。そこで、中立バルブを設けて、二つのメイン回路３２ｍ・３２ｍ間で作動油に差圧が生じないようにして、ＨＳＴ式変速機１０の中立状態を保持するようにしている。また、リリーフバルブは、作動油の圧力が設定圧以上に高くなると開弁して高圧側のメイン回路３２ｍから低圧側のメイン回路３２ｍへ作動油を逃がし、メイン回路３２ｍ・３２ｍの油圧を設定圧以上とさせないために設けられている。
【００１９】
図２及び図３に示す如く、油路板３２には、該油路板３２に形成されたメイン回路３２ｍ・３２ｍ間を連通する連通回路３２ｄ、及び該連通回路３２ｄと片方のメイン回路３２ｍの交差部を含むバルブ穴５０が形成されている。そして、該バルブ穴５０の奥部（油路板３２の中央側部）は連通回路３２ｄと連通しており、該奥部に弁座４０が形成され、バルブ穴５０の該弁座４０近傍には環状溝４３が設けられている。また、該バルブ穴５０は、中途部でメイン回路３２ｍと連通している。
【００２０】
前記バルブ穴５０には中立弁体４６が摺動可能に挿嵌され、さらに、該バルブ穴５０は蓋体４５が挿入されて閉塞されている。前記中立弁体４６の頭面４６ｆはバルブ穴５０の奥部に位置する弁座４０に当接可能とし、中立弁体４６の頭面４６ｆが弁座４０に当接している状態で、中立弁体４６と蓋体４５とが離間するよう配置されている。従って、中立弁体４６は、頭面４６ｆが弁座４０に当接する位置から、尾面４６ｎが蓋体４５に当接する位置までバルブ穴５０内を摺動することができる。
【００２１】
前記蓋体４５は、頭部４５ｆと該頭部４５ｆより小径の胴部４５ｅとで構成され、胴部４５ｅがバルブ穴５０に螺挿されている。そして、蓋体４５内には、胴部４５ｅから頭部４５ｆへかけてメイン回路３２ｍ側が開口する穴が形成されており、該穴をバネ室４５ａとしている。該バネ室４５ａの奥部と、中立弁体４６内に嵌挿される安全弁体４７に一体的に設けられたバネ受け部４７ｂとの間に、安全弁体４７を連通回路３２ｄ側へ付勢するバネ４２が介装されており、バネ４２が圧縮されたときには安全弁体４７のバネ受け部４７ｂはバネ室４５ａ内を摺動することができる。
【００２２】
また、前記蓋体４５の胴部４５ｅには、バネ室４５ａ内と、バネ室４５ａ外部のドレン回路とを連通する通路４５ｃが形成されている。なお、ドレン回路は略大気圧とされているため、バネ室４５ａの内圧は略大気圧となっている。
【００２３】
一方、前記中立弁体４６は、略円筒状の部材であり、内部に連通孔４６ｈが形成され、該連通孔４６ｈには尾面４６ｎ側から安全弁体４７が摺動可能に挿入されている。安全弁体４７の弁部４７ａは、該安全弁体４７に一体的に設けられたバネ受け部４７ｂに当接し前記バネ室４５ａに内装されるバネ４２によって、連通孔４６ｈ内部に形成されたリリーフバルブの弁座４１に着座している。そして、該バネ４２によって付勢された安全弁体４７によって中立弁体４６が弁座４０に着座する方向に付勢されている。
【００２４】
前記中立弁体４６は、頭面４６ｆ側より小径部４６ｂ、中径部４６ｄ及び大径部４６ａとされている。中立弁体４６の中径部４６ｄに、連通孔４６ｈとメイン回路３２ｍを連通するための通路４６ｅが設けられており、リリーフバルブが開弁して、安全弁体４７の弁部４７ａが弁座４１から離れたときには、該通路４６ｅを通って連通回路３２ｄからメイン回路３２ｍへ、又はメイン回路３２ｍから連通回路３２ｄへ作動油がリリーフされる。また、前記中立弁体４６の大径部４６ａでは、内部に安全弁体４７を摺動可能に内挿し、また、その外周をバルブ穴５０に接して摺動するよう構成されている。
【００２５】
前記中立弁体４６の小径部４６ｂ端の頭面４６ｆは、図４にも示す如く、小径部４６ｂの外周部と連通孔４６ｈとを結ぶ溝４６ｇが形成されている。該溝４６ｇによって、中立弁体４６の頭面４６ｆが弁座４１に当接した状態であっても、連通回路３２ｄから溝４６ｇを通って環状溝４３へ至る油路が確保されている。また、図５に示す如く、小径部４６ｂの外周部は部分的に二面が切り欠かれて通路４６ｃ・４６ｃが形成されて、小径部４６ｂの外周がバルブ穴５０の内周に接していても、環状溝４３から通路４６ｃ・４６ｃを介してメイン回路３２ｍへの油路が確保されている。なお、通路４６ｃ・４６ｃは小径部４６ｂの頭面４６ｆから離れた位置から形成されている。このようにして、中立弁体４６の頭面４６ｆが弁座４０に当接した状態において、連通回路３２ｄ→溝４６ｇ→環状溝４３→通路４６ｃ→メイン回路３２ｍ（又は逆方向）という、連通回路３２ｄからメイン回路３２ｍ（又はメイン回路３２ｍから連通回路３２ｄ）へ通じる油路が形成されている。
【００２６】
なお、図８に示す如く、中立弁体４６の小径部４６ｂの外周に凹部４８を形成して、頭面４６ｆが弁座４０に当接している状態で、連通回路３２ｄ→溝４６ｇ→環状溝４３→凹部４８→メイン回路３２ｍ（又は逆方向）という油路を形成し、中立弁体４６が蓋体４５側へ摺動して凹部４８の壁面４８ａが環状溝４３の壁面４３ａと当接することによって該油路を断つように構成することもできる。
【００２７】
そして、図４に示す如く、前記中立弁体４６の連通回路３２ｄ側の受圧面積（Ａ）と、メイン回路３２ｍ側の受圧面積（Ｂ）とは略同一となるよう構成されている。すなわち、連通回路３２ｄ側の受圧面積（Ａ）は、頭面４ｆの面積（ａ１）と連通孔４６ｈの断面積（ａ２）の和であり、小径部４６ｂの半径Ｒ１を用いて表せば、「Ａ＝π（Ｒ１）2 」となる。また、メイン回路３２ｍ側の受圧面積（Ｂ）は、大径部４６ａの径を直径とする円の面積から中径部４６ｄの径を直径とする面積の差（ｂ２）と、中径部４６ｄの径を直径とする円の面積と小径部４６ｂの径を直径とする面積の差（ｂ１）との和であり、大径部４６ａの半径Ｒ２と小径部４６ｂの半径Ｒ１を用いて表せば、「Ｂ＝π（Ｒ２）2 −π（Ｒ１）2 」となる。そして、これらの間に、「Ａ≒Ｂ」という関係が成り立つように構成されているのである。
【００２８】
これは、連通回路３２ｄ側からの受圧面積と、メイン回路３２ｍ側からの受圧面積とを略等しくすることによって、連通回路３２ｄ側又はメイン回路３２ｍ側のいずれかの油圧が大きくなったときに中立バルブが作動するが、いずれの回路の油圧が大きくなった場合でも、略等しい差圧が生じたときに中立バルブを作動させるためである。
【００２９】
なお、例えば、ＨＳＴ式変速機１０を車両に備えて、前進時と後進時とで油圧ポンプ２１の可動斜板２１ｃの斜板角の中立比に差を設定するとき等には、連通回路３２ｄ側の受圧面積とメイン回路３２ｍ側の受圧面積とに差を設けるようにして、中立比の差を設定することもできる。
【００３０】
上述の如く構成した中立・リリーフバルブ３５Ａにおいて、可動斜板２１ｃが中立の状態から傾動する際に、連通回路３２ｄ側とメイン回路３２ｍ側との間で一定以上の差圧が生じ、連通回路３２ｄ側の油圧が大きいときには、中立弁体４６の頭面４６ｆに圧が掛かってバネ４２が圧縮され、安全弁体４７と中立弁体４６は一体となってバルブ穴５０を蓋体４５側へ摺動する。前述の如く、中立弁体４６が弁座４０に着座した状態では、連通回路３２ｄとメイン回路３２ｍ間の油路が確保されているが、中立弁体４６が摺動するに従って、その油路面積は減少し、環状溝４３と通路４６ｃ・４６ｃとの連通が断たれたときに油路面積はほぼゼロになり、連通回路３２ｄとメイン回路３２ｍ間の油路が断たれる。即ち、中立弁体４６の摺動位置により、溝４６ｇ、環状溝４３、及び通路４６ｃを通じて、一方のメイン回路３２ｍに連通する連通回路３２ｄと、他方のメイン回路３２ｍとの間が開閉される。なお、このあとも、図６に示す如く、中立弁体４６の尾面４６ｎが蓋体４５の胴部４５ｅに当接するまで該中立弁体４６が摺動する。
【００３１】
逆に、可動斜板２１ｃが中立の状態から傾動する際に、連通回路３２ｄ側とメイン回路３２ｍ側との間で一定以上の差圧が生じ、メイン回路３２ｍ側の油圧が大きいときには、中立弁体４６の大径部４６ａと中径部４６ｄの段差面に圧が掛かってバネ４２が圧縮され、安全弁体４７と中立弁体４６は一体となってバルブ穴５０を蓋体４５側へ摺動する。前述の如く、中立弁体４６が弁座４０に着座した状態では、連通回路３２ｄとメイン回路３２ｍ間の油路が確保されているが、中立弁体４６が摺動するに従って、その油路面積は減少し、環状溝４３と通路４６ｃ・４６ｃとの連通が断たれたときに油路面積はほぼゼロになり、連通回路３２ｄとメイン回路３２ｍ間の油路が断たれる。このあとも、中立弁体４６の尾面４６ｎが蓋体４５の胴部４５ｅに当接するまで該中立弁体４６が摺動する。
【００３２】
すなわち、図７に示す如く、可動斜板２１ｃが中立の状態から傾動する際に、連通回路３２ｄ側とメイン回路３２ｍ側との間で生じた差圧が一定圧力を超えたときに、中立弁体４６が移動し始めて、連通回路３２ｄとメイン回路３２ｍ間の油路面積が減少し始め、さらに、中立弁体４６が移動することによって該油路面積が略ゼロとなり、中立弁体４６の尾面４６ｎが蓋体４５に当接して中立弁体４６の移動が止まる。
【００３３】
上述の中立弁体４６の動作は、連通回路３２ｄ側又はメイン回路３２ｍ側のいずれの油圧が大きいときでも同様に動作し、連通回路３２ｄ側とメイン回路３２ｍ側との間で生じた差圧が一定圧力を超えるまで、すなわち、可動斜板２１ｃが中立位置に近い傾動位置にある状態では、連通回路３２ｄとメイン回路３２ｍ間の油路を通って作動油が移動し、連通回路３２ｄ側とメイン回路３２ｍ側との間の差圧を略ゼロとしてＨＳＴ式変速機１０の中立状態を保つようにする、中立バルブとして作用している。そして、可動斜板２１ｃの傾動角が大きくなって、連通回路３２ｄ側とメイン回路３２ｍ側との間で生じた差圧が一定圧力を超えた状態では、連通回路３２ｄとメイン回路３２ｍ間の油路が断たれて、個々のメイン回路３２ｍ・３２ｍが独立し、通常のＨＳＴ式変速機１０の動作に移行する。
【００３４】
一方、中立・リリーフバルブ３５Ａがリリーフバルブとして作用するとき、中立弁体４６の尾面４６ｎが蓋体４５に当接して、連通回路３２ｄとメイン回路３２ｍが断たれた状態で、連通回路３２ｄと連通する高圧側のメイン回路３２ｍの油圧がリリーフ設定圧を超えたときには、安全弁体４７の弁部４７ａに圧が掛かってバネ４２が収縮し、該弁部４７ａと弁座４１が離れて、連通回路３２ｄ側から、中立弁体４６の連通孔４６ｈと通路４６ｅを通って低圧側のメイン回路３２ｍに至る油路が形成され、高圧側のメイン回路３２ｍから低圧側のメイン回路３２ｍへ作動油を逃がす。
【００３５】
また、中立・リリーフバルブ３５Ａがリリーフバルブとして作用するとき、中立弁体４６の尾面４６ｎが蓋体４５に当接して、連通回路３２ｄとメイン回路３２ｍが断たれた状態で、中立・リリーフバルブ３５Ａが挿嵌されたバルブ穴５０に連通するメイン回路３２ｍの油圧がリリーフ設定圧を超えたときには、中立弁体４６の中径部４６ｄに形成された通路４６ｅを通じて安全弁体４７の弁部４７ａに圧が掛かってバネ４２が収縮し、該弁部４７ａと弁座４１が離れて、メイン回路３２ｍ側から、中立弁体４６の通路４６ｅと連通孔４６ｈを通って連通回路３２ｄに至る油路が形成されて、高圧側のメイン回路３２ｍから連通回路３２ｄに繋がる低圧側のメイン回路３２ｍへ作動油を逃がす。
【００３６】
このように、いずれのメイン回路３２ｍが高圧側となっても中立・リリーフバルブ３５Ａはリリーフバルブとして作用することができる。なお、中立・リリーフバルブ３５Ａが中立バルブとして作用する差圧と、リリーフバルブとして作用する差圧との間には、十分な差がある。
【００３７】
上述の如く、中立・リリーフバルブ３５Ａは、可動斜板２１ｃが中立の状態で、連通回路３２ｄとメイン回路３２ｍ、すなわち、二つのメイン回路３２ｍ・３２ｍの差圧が一定圧以下のときには中立弁体４６が開弁し、可動斜板２１ｃが傾動して差圧が一定圧以上になると中立弁体４６が閉弁して、中立バルブとして作用する。また、中立・リリーフバルブ３５Ａは、可動斜板２１ｃが傾動している状態で、高圧側のメイン回路３２ｍが設定リリーフ圧以上となったときには安全弁体４７が開弁して、リリーフバルブとして作用する。
【００３８】
このように、一組の中立・リリーフバルブ３５Ａで、中立バルブとリリーフバルブの機能を併せ持つことができるため、従来のように、中立バルブとリリーフバルブとを別体のバルブとして構成するときと比較して、部品点数を低減させることができ、コストを削減することができる。また、従来中立バルブは、個々のメイン回路３２ｍ・３２ｍに必要であったが、一組のＨＳＴ式変速機１０に一つの中立バルブがあれば足り、部品点数を低減して、コストを削減することができる。
【００３９】
ここで、本発明の第二実施例に係る中立バルブ３５（中立・リリーフバルブ３５Ｂ）の構成について説明する。本第二実施例に係る中立バルブ３５（３５Ｂ）は、前記第一実施例で示した中立バルブ３５（３５Ａ）と同様に、リリーフバルブの機能を併せ持つ中立・リリーフバルブ３５Ｂであり、前記第一実施例と比較して、中立弁体５５の構造が異なり、また、ＨＳＴ式変速機１０の一方のメイン回路３２ｍに設ける形態のものである。本第二実施例においても、リリーフバルブと中立バルブを別体に構成するときと比較して、リリーフバルブと中立バルブを同一の部品とすることができるため、低コストに構成することができる。以下に、第一実施例と共通する蓋体４５及び安全弁体４７の構造に関する説明は省略し、中立弁体５５の構造に関して詳細に説明する。
【００４０】
図９に示す如く、油路板３２に形成されたバルブ穴５０に挿嵌された中立弁体５５は、連通回路３２ｄ側の頭面５５ｆを弁座４０に当接した状態で、その尾面５５ｎが蓋体４５の胴部４５ｅと離間するよう構成されている。該中立弁体５５は、頭面５５ｆ側から小径部５５ｂ、中径部５５ｄ及び大径部５５ａが設けられた円筒状の部材であり、内部に形成した連通孔５５ｈに尾面５５ｎ側から安全弁体４７を摺動可能に挿入し、該安全弁体４７を連通回路３２ｄ側へ付勢するバネ４２によって中立弁体５５が連通回路３２ｄ側へ付勢され、可動斜板２１ｃが中立状態であるとき、該中立弁体５５の頭面５５ｆが弁座４０に着座するよう構成されている。
【００４１】
前記中立弁体５５の中径部５５ｄには、安全弁体４７の弁部４７ａがリリーフバルブの弁座４１から離れたときに連通孔５５ｈとメイン回路３２ｍとを連通する通路５５ｅが形成されている。また、中立弁体５５の大径部５５ａは、図１０にも示す如く、尾面５５ｎ側に外周の二面を切り欠いた通路５５ｋ・５５ｋが形成されている。中立弁体５５の頭面５５ｆが弁座４０に着座している状態、すなわち、可動斜板２１ｃが中立となるよう操作されている状態では、メイン回路３２ｍから、バルブ穴５０に形成した溝４９と、中立弁体５５の外径部に形成された通路５５ｋ・５５ｋを通じて、バネ室４５ａに連通する通路が形成される。なお、バネ室４５ａは、図示せぬドレン回路と連通し、大気圧とされている
【００４２】
前述の如く、本実施例に係る中立・リリーフバルブ３５Ｂは、例えば、ＨＳＴ式変速機１が、一方のメイン回路３２ｍが主に高圧側となるように使用される場合に、一方のメイン回路３２ｍに設けられるものである。従って、可動斜板２１ｃが中立位置近傍に操作されている状態で、両メイン回路３２ｍ・３２ｍに差圧が生じた場合は、差圧分の作動油が中立・リリーフバルブ３５Ｂによってドレン回路側へ漏出されることで差圧が解消され、ＨＳＴ式変速機１を中立に保持することができる。
【００４３】
そして、可動斜板２１ｃの傾動角が大きくなって、中立・リリーフバルブ３５Ｂが設けられた側のメイン回路３２ｍの油圧が一定圧力以上となると、中立弁体５５の中径部５５ｄと大径部５５ａの段差面に圧が掛かって、中立弁体５５が蓋体４５側へ移動しバネ４２が圧縮される。図１１に示す如く、中立弁体５５は蓋体４５に当接するまで移動し、この状態では、中立弁体５５の大径部５５ａの外周がバルブ穴５０の内周に接してバネ室４５ａとメイン回路３２ｍ間の通路が断たれて、各メイン回路３２ｍ間に差圧が生じ得る状態となり、可動斜板２１ｃが傾倒可能な状態となる。
【００４４】
また、バネ室４５ａを大気圧とするのではなく、バネ室４５ａにチャージ圧を設定することもできる。図１２に示す如く、中立・リリーフバルブ３５Ｂの蓋体４５に通路４５ｇを設け、該通路４５ｇとチャージポンプ５１に接続されるチャージ回路３２ｃとを接続することで、チャージ回路３２ｃとバネ室４５ａとを連通して、バネ室４５ａの圧をチャージポンプ５１によって制御されるチャージ回路３２ｃのチャージ圧と略等しくしている。このように、バネ室４５ａをチャージ圧とすることで、中立弁体５５が移動始める圧力を容易に設定又は設定変更することができ、さらに、精密に設定することが可能となる。
【００４５】
また、バネ室４５ａをチャージ回路３２ｃに接続することで、リリーフバルブが開弁した際に、リリーフ油がドレン回路に流出しないため、チャージポンプ５１からチャージ回路３２ｃに送るチャージ流量を低く抑えることができる。そして、中立・リリーフバルブ３５Ｂがリリーフバルブとして作用するとき、連通回路３２ｄとメイン回路３２ｍのいずれの圧力にも対応し、左右両メイン回路３２ｍ・３２ｍ間の差圧が設定リリーフ圧になると開弁するよう作動する構成であるため、バネ室４５ａに圧を与えてチャージ圧とすることで、バネ室４５ａに内装されるバネ４２の強度を変化することなく、設定リリーフ圧を高圧に設定することができる。
【００４６】
次に、本発明の第三実施例に係る中立バルブ３５（３５Ｃ）について説明する。従来は各メイン回路３２ｍに設ける必要があるが、本第三実施例に係る中立バルブ３５ＣはＨＳＴ式変速機１０に一つ設ければ、両方向に対して機能を果たすことが可能である。
【００４７】
図１３に示す如く、中立バルブ３５Ｃは油路板３２の連通回路３２ｄとメイン回路３２ｍが交わる部分に形成されたバルブ穴５０に挿嵌された中立弁体５３と、該バルブ穴５０に挿入して閉塞する蓋体４５とで構成されている。
【００４８】
前記蓋体４５は、バルブ穴５０に挿入された胴部４５ｅと、該胴部４５ｅより大径の頭部４５ｆで構成されている。そして、蓋体４５の内部には、中立弁体５３側に開口する穴が形成されてバネ室４５ａとされている。前記中立弁体５３の頭面５３ｆは連通回路３２ｄに面し、該頭面５３ｆがバルブ穴５０の奥部に形成された弁座４０と当接している状態で該中立弁体５３の尾面５３ｎが蓋体４５の胴部４５ｅと離間するよう構成されている。
【００４９】
中立弁体５３は頭部４５ｆ側から小径部５３ｂ、中径部５３ｄ及び大径部５３ａで構成され、小径部５３ｂの外周は頭面５３ｆから離れた位置から二面が切り欠かれて通路５３ｃ・５３ｃが形成されている。また、頭面５３ｆには、頭面５３ｆが弁座４０に着座した状態でバルブ穴５０に形成された環状溝４３と連通回路３２ｄとが連通するよう溝５３ｇが形成されている。従って、中立弁体５３の頭面５３ｆが弁座４０に着座した状態では、連通回路３２ｄ→頭面５３ｆの溝５３ｇ→環状溝４３→小径部５３ｂに形成された通路５３ｃ→メイン回路３２ｍ（又は逆方向）の油路が形成されている。
【００５０】
中立弁体５３の大径部５３ａの外周はバルブ穴５０の内周に接して摺動可能とされ、また、該大径部５３ａ端に位置する尾面５３ｎにはバネ受け部５３ｍが形成されている。該バネ受け部５３ｍと、蓋体４５に形成されたバネ室４５ａの奥部との間にバネ４２が介装され、該バネ４２によって中立弁体５３が連通回路３２ｄ側へ付勢されている。
【００５１】
上述の如く構成した中立バルブ３５Ｃにおいて、ＨＳＴ式変速機１０の油圧ポンプ２１の可動斜板２１ｃが略中立位置にあるとき、中立弁体５３はバネ４２により付勢されて弁座４０に着座している。このとき、前述の如く、連通回路３２ｄからメイン回路３２ｍまでの油路が確保されており、該油路を通じて連通回路３２ｄとメイン回路３２ｍ間で作動油が移動して差圧を解消し、ＨＳＴ式変速機１０を中立状態に保持する。すなわち、中立バルブとして作用する。
【００５２】
そして、可動斜板２１ｃが傾倒して、連通回路３２ｄとメイン回路３２ｍ間に差圧が生じ、連通回路３２ｄ側が高圧となれば中立弁体５３の頭面５３ｆに、あるいは、メイン回路３２ｍ側が高圧となれば中立弁体５３の中径部５３ｄと大径部５３ａの段差面等に、圧が掛かって、図１４に示す如く、中立弁体５３が蓋体４５側へ摺動してバネ４２が圧縮される。中立弁体５３は尾面５３ｎが蓋体４５の胴部４５ｅに当接するまで移動する。
【００５３】
中立弁体５３が蓋体４５側へ移動する途中で、中立弁体５３の小径部５３ｂの外周がバルブ穴５０の内周に接して連通回路３２ｄとメイン回路３２ｍ間の油路が断たれて、連通回路３２ｄとメイン回路３２ｍが断絶される。すなわち、連通回路３２ｄに連通するメイン回路３２ｍとメイン回路３２ｍとが独立した状態となる。
【００５４】
上述の如く、ＨＳＴ式変速機１０に設けられた二つのメイン回路３２ｍ・３２ｍに設けた一つの中立バルブ３５Ｃによって、可動斜板２１ｃが中立状態にあるときに各メイン回路３２ｍ・３２ｍ間の差圧を解消することができる。従って、中立バルブを各メイン回路３２ｍに設ける従来の構成と比較して、部品点数を低減することができコストの削減に寄与している。
【００５５】
【発明の効果】
本発明は、以上のように構成したので、以下に示すような効果を奏する。
【００５６】
請求項１に示す如く、可変容積型油圧ポンプ（２１）と油圧モータ（２２）と油路板（３２）より成る油圧式無段変速機（１０）の中立状態を保持する中立・リリーフバルブ（３５Ａ）であって、該油路板（３２）には、油路板（３２）に形成されたメイン回路（３２ｍ・３２ｍ）間を連通する連通回路（３２ｄ）、及び該連通回路（３２ｄ）と片方のメイン回路（３２ｍ）の交差部を含むバルブ穴（５０）を形成し、該油路板（３２）の中央側部に位置するバルブ穴（５０）の奥部は、該連通回路（３２ｄ）と連通し、該奥部に弁座（４０）を形成し、該バルブ穴（５０）の該弁座（４０）近傍には環状溝（４３）を設け、該バルブ穴（５０）は、中途部でメイン回路（３２ｍ）と連通し、該バルブ穴（５０）には中立弁体（４６）を摺動可能に挿嵌し、該バルブ穴（５０）は油路板（３２）の外側から蓋体（４５）を挿入し閉塞し、前記中立弁体（４６）の頭面（４６ｆ）はバルブ穴（５０）の奥部に位置する弁座（４０）に当接可能とし、中立弁体（４６）の頭面（４６ｆ）が弁座（４０）に当接している状態で、前記中立弁体（４６）と蓋体（４５）とが離間するよう配置し、該中立弁体（４６）は、頭面（４６ｆ）が弁座（４０）に当接する位置から、尾面（４６ｎ）が蓋体（４５）に当接する位置までバルブ穴（５０）内を摺動可能とし、前記蓋体（４５）には、胴部（４５ｅ）から頭部（４５ｆ）へかけてメイン回路（３２ｍ）側が開口する穴を形成し、該穴をバネ室（４５ａ）とし、該バネ室（４５ａ）の奥部と、中立弁体（４６）内に嵌挿される安全弁体（４７）に一体的に設けられたバネ受け部（４７ｂ）との間に、安全弁体（４７）を連通回路（３２ｄ）側へ付勢するバネ（４２）を介装し、前記蓋体（４５）には、バネ室４５ａ内と外部のドレン回路とを連通する通路（４５ｃ）を形成し、前記中立弁体（４６）は、略円筒状の部材であり、内部に連通孔（４６ｈ）を形成し、該連通孔（４６ｈ）には尾面（４６ｎ）側から安全弁体（４７）を摺動可能に挿入し、該安全弁体（４７）の弁部（４７ａ）は、連通孔（４６ｈ）内部に形成されたリリーフバルブの弁座（４１）に着座し、前記バネ（４２）によって中立弁体（４６）が弁座（４０）に着座する方向に付勢し、前記中立弁体（４６）は、連通孔（４６ｈ）とメイン回路（３２ｍ）を連通するための通路（４６ｅ）を設け、リリーフバルブが開弁して、安全弁体（４７）の弁部（４７ａ）が弁座（４１）から離れたときには、該通路（４６ｅ）を通って連通回路（３２ｄ）からメイン回路（３２ｍ）へ、又はメイン回路（３２ｍ）から連通回路（３２ｄ）へ作動油をリリーフし、前記中立弁体（４６）の小径部（４６ｂ）端の頭面（４６ｆ）は、外周部と連通孔（４６ｈ）とを結ぶ溝（４６ｇ）を形成し、該溝（４６ｇ）によって、中立弁体（４６）の頭面（４６ｆ）が弁座（４１）に当接した状態でも、連通回路（３２ｄ）から溝（４６ｇ）を通って環状溝（４３）へ至る油路を確保し、該小径部（４６ｂ）の外周部は部分的に二面が切り欠かれた通路（４６ｃ・４６ｃ）を形成し、外周部がバルブ穴（５０）の内周に接していても、環状溝（４３）から通路（４６ｃ・４６ｃ）を介してメイン回路（３２ｍ）への油路を確保し、該通路（４６ｃ・４６ｃ）は頭面（４６ｆ）から離れた位置から形成し、前記油圧ポンプ（２１）の可動斜板（２１ｃ）が中立の時は、中立弁体（４６）が弁座（４０）に着座した状態で、連通回路（３２ｄ）とメイン回路（３２ｍ）間の油路が確保されているが、該可動斜板（２１ｃ）が中立の状態から傾動すると、連通回路（３２ｄ）側とメイン回路（３２ｍ）側との間で一定以上の差圧が生じ、連通回路（３２ｄ）側の油圧が大きいときには、連通回路（３２ｄ）とメイン回路（３２ｍ）間の油路を閉鎖し、該状態で、連通回路（３２ｄ）と連通する高圧側のメイン回路（３２ｍ）の油圧がリリーフ設定圧を超えたときには、安全弁体（４７）の弁部（４７ａ）に圧が掛かってバネ（４２）が収縮し、該弁部（４７ａ）と弁座（４１）が離れて、連通回路（３２ｄ）側から、中立弁体（４６）の連通孔（４６ｈ）と通路（４６ｅ）を通って低圧側のメイン回路（３２ｍ）に至る油路が形成され、高圧側のメイン回路（３２ｍ）から低圧側のメイン回路（３２ｍ）へ作動油を逃がすべく構成したので、中立バルブにリリーフバルブの機能を併せ持つことができ、また、複数のメイン回路に対し一個の中立バルブで機能を果たすため、部品点数を削減して安価に構成可能とすることができる。
【００５７】
請求項２に示す如く、可変容積型油圧ポンプ（２１）と油圧モータ（２２）と油路板（３２）より成る油圧式無段変速機（１０）の中立状態を保持する中立・リリーフバルブ（３５Ｂ）であって、該油路板（３２）には、油路板（３２）に形成されたメイン回路（３２ｍ・３２ｍ）間を連通する連通回路（３２ｄ）、及び該連通回路（３２ｄ）と片方のメイン回路（３２ｍ）の交差部を含むバルブ穴（５０）を形成し、該油路板（３２）の中央側部に位置するバルブ穴（５０）の奥部は、該連通回路（３２ｄ）と連通し、該奥部に弁座（４０）を形成し、該バルブ穴（５０）の該弁座（４０）近傍には環状溝（４３）を設け、該バルブ穴（５０）は、中途部でメイン回路（３２ｍ）と連通し、該バルブ穴（５０）には中立弁体（５５）を摺動可能に挿嵌し、該バルブ穴（５０）は油路板（３２）の外側から蓋体（４５）を挿入し閉塞し、前記中立弁体（５５）の頭面（５５ｆ）はバルブ穴（５０）の奥部に位置する弁座（４０）に当接可能とし、中立弁体（５５）の頭面（５５ｆ）が弁座（４０）に当接している状態で、前記中立弁体（５５）と蓋体（４５）とが離間するよう配置し、該中立弁体（５５）は、頭面（５５ｆ）が弁座（４０）に当接する位置から、尾面（５５ｎ）が蓋体（４５）に当接する位置までバルブ穴（５０）内を摺動可能とし、前記蓋体（４５）には、胴部（４５ｅ）から頭部（４５ｆ）へかけてメイン回路（３２ｍ）側が開口する穴を形成し、該穴をバネ室（４５ａ）とし、該バネ室（４５ａ）の奥部と、中立弁体（５５）内に嵌挿される安全弁体（４７）に一体的に設けられたバネ受け部（４７ｂ）との間に、安全弁体（４７）を連通回路（３２ｄ）側へ付勢するバネ（４２）を介装し、前記蓋体（４５）には、バネ室４５ａ内と外部のドレン回路とを連通する通路（４５ｃ）を形成し、前記中立弁体（５５）は、略円筒状の部材であり、内部に連通孔（５５ｈ）を形成し、該連通孔（５５ｈ）には尾面（５５ｎ）側から安全弁体（４７）を摺動可能に挿入し、該安全弁体（４７）の弁部（４７ａ）は、連通孔（５５ｈ）内部に形成されたリリーフバルブの弁座（４１）に着座し、前記バネ（４２）によって中立弁体（５５）が弁座（４０）に着座する方向に付勢し、前記中立弁体（５５）は、連通孔（５５ｈ）とメイン回路（３２ｍ）を連通するための通路（５５ｅ）を設け、リリーフバルブが開弁して、安全弁体（４７）の弁部（４７ａ）が弁座（４１）から離れたときには、該通路（５５ｅ）を通って連通回路（３２ｄ）からメイン回路（３２ｍ）へ、又はメイン回路（３２ｍ）から連通回路（３２ｄ）へ作動油をリリーフし、該中立弁体（５５）は、尾面（５５ｎ）側に外周の二面を切り欠いた通路（５５ｋ・５５ｋ）が形成され、中立弁体（５５）の頭面（５５ｆ）が弁座４０に着座している状態、すなわち、可動斜板（２１ｃ）が中立となるよう操作されている状態では、メイン回路（３２ｍ）から、バルブ穴（５０）に形成した溝（４９）と、中立弁体（５５）の外径部に形成した通路（５５ｋ・５５ｋ）を通じて、バネ室（４５ａ）に連通する通路を形成し、バネ室（４５ａ）は、ドレン回路と連通し大気圧とし、該中立弁体（５５）の頭面（５５ｆ）が弁座（４０）に当接した状態において、メイン回路（３２ｍ）→バルブ穴（５０）に形成した溝（４９）→中立弁体（５５）の外径部に形成された通路（５５ｋ・５５ｋ）→バネ室（４５ａ）と連通し、前記油圧ポンプ（２１）の可動斜板（２１ｃ）が中立の時は、中立弁体（５５）が弁座（４０）に着座した状態で、連通回路（３２ｄ）とメイン回路（３２ｍ）間の油路が確保されているが、該可動斜板（２１ｃ）が中立の状態から傾動すると、連通回路（３２ｄ）側とメイン回路（３２ｍ）側との間で一定以上の差圧が生じ、連通回路（３２ｄ）側の油圧が大きいときには、連通回路（３２ｄ）とメイン回路（３２ｍ）間の油路を閉鎖し、該状態で、連通回路（３２ｄ）と連通する高圧側のメイン回路（３２ｍ）の油圧がリリーフ設定圧を超えたときには、安全弁体（４７）の弁部（４７ａ）に圧が掛かってバネ（４２）が収縮し、該弁部（４７ａ）と弁座（４１）が離れて、連通回路（３２ｄ）側から、中立弁体（５５）の連通孔（５５ｈ）と通路（５５ｅ）を通って低圧側のメイン回路（３２ｍ）に至る油路が形成され、高圧側のメイン回路（３２ｍ）から低圧側のメイン回路（３２ｍ）へ作動油を逃がすべく構成したので、中立バルブにリリーフバルブの機能を併せ持つことができ、部品点数を削減して安価に構成可能とすることができる。
【００５８】
請求項３に示す如く、請求項１又は請求項２に記載の油圧式無段変速機の中立・リリーフバルブバルブにおいて、中立・リリーフバルブ（３５）の蓋体（４５）に通路（４５ｇ）を設け、該通路（４５ｇ）とチャージポンプ（５１）に接続されるチャージ回路（３２ｃ）とを接続し、該バネ室（４５ａ）の圧をチャージポンプ（５１）によって制御されるチャージ回路（３２ｃ）のチャージ圧と略等しくし、バネ室（４５ａ）をチャージ圧とすることで、中立弁体（４６・５５）が移動始める圧力を設定又は設定変更可能としたので、中立バルブにリリーフバルブの機能を併せ持つことができ、部品点数を削減して安価に構成可能とすることができる。
また、リリーフバルブの開弁する圧力を、バネの圧力より大きく設定でき、さらに、リリーフ油がドレン回路に流れないため、チャージ流量を低く抑えることができる。
【００５９】
請求項４に示す如く、可変容積型油圧ポンプ（２１）と油圧モータ（２２）と油路板（３２）より成る油圧式無段変速機（１０）の中立状態を保持する中立バルブ（３５Ｃ）であって、中立バルブ（３５Ｃ）は、前記油路板（３２）の連通回路（３２ｄ）とメイン回路（３２ｍ）が交わる部分に形成されたバルブ穴（５０）に挿嵌された中立弁体（５３）と、該バルブ穴（５０）に挿入して閉塞する蓋体（４５）とで構成し、前記蓋体（４５）の内部には、中立弁体（５３）側に開口する穴が形成されてバネ室（４５ａ）とし、前記中立弁体（５３）の頭面（５３ｆ）は連通回路（３２ｄ）に面し、該頭面（５３ｆ）がバルブ穴（５０）の奥部に形成された弁座（４０）と当接している状態で該中立弁体（５３）の尾面（５３ｎ）が蓋体（４５）の胴部（４５ｅ）と離間するよう構成し、該中立弁体（５３）の外周は、頭面（５３ｆ）から離れた位置から二面が切り欠かれて通路（５３ｃ・５３ｃ）を形成し、該頭面（５３ｆ）には、頭面（５３ｆ）が弁座（４０）に着座した状態でバルブ穴（５０）に形成された環状溝（４３）と連通回路（３２ｄ）とが連通するよう溝（５３ｇ）を形成し、前記中立弁体（５３）の頭面（５３ｆ）が弁座（４０）に着座した状態では、連通回路（３２ｄ）→頭面（５３ｆ）の溝（５３ｇ）→環状溝（４３）→小径部（５３ｂ）に形成された通路（５３ｃ）→メイン回路（３２ｍ）、又はメイン回路（３２ｍ）から連通回路（３２ｄ）への逆方向可能な油路を形成し、該中立弁体（５３）の外周はバルブ穴（５０）の内周に接して摺動可能とし、該外周端に位置する尾面（５３ｎ）に、バネ受け部（５３ｍ）を形成し、該バネ受け部（５３ｍ）と、蓋体（４５）に形成されたバネ室（４５ａ）の奥部との間にバネ（４２）を介装し、該バネ（４２）によって中立弁体（５３）を連通回路（３２ｄ）側へ付勢し、該中立バルブ（３５Ｃ）において、ＨＳＴ式変速機（１０）の油圧ポンプ（２１）の可動斜板（２１ｃ）が略中立位置にあるとき、中立弁体（５３）はバネ（４２）により付勢されて弁座（４０）に着座し、該状態で連通回路（３２ｄ）からメイン回路（３２ｍ）までの油路を確保し、該油路を通じて連通回路（３２ｄ）とメイン回路（３２ｍ）間で作動油が移動して差圧を解消し、ＨＳＴ式変速機（１０）を中立状態に保持する中立バルブとして作用し、前記可動斜板（２１ｃ）が傾倒して、連通回路（３２ｄ）とメイン回路（３２ｍ）間に差圧が生じ、連通回路（３２ｄ）側が高圧となれば、該中立弁体（５３）が蓋体（４５）側へ摺動し、該中立弁体（５３）が蓋体（４５）側へ移動する途中で、中立弁体（５３）の小径部（５３ｂ）の外周がバルブ穴（５０）の内周に接して連通回路（３２ｄ）とメイン回路（３２ｍ）間の油路を断つので、複数のメイン回路に対し一個の中立バルブで機能を果たすため、部品点数を削減して安価に構成可能とすることができる。
【００６０】
請求項５に示す如く、請求項１・２又は４のいずれかに記載の油圧式無段変速機の中立・リリーフバルブ又は中立バルブの何れかにおいて、前記弁本体である中立弁体（４６・５３・５５）を、頭面（４６ｆ・・）側より小径部（４６ｂ・・）、中径部（４６ｄ・・）及び大径部（４６ａ・・）と、少なくとも大小二段の外径を有する筒状体として、小径部断面積と、大径部断面積と小径部断面積との差分面積とが略等しくなるように形成し、該小径部を一方のメイン回路に連通し、大径部と小径部との段差部を他方のメイン回路に連通したので、中立バルブの作動し始めるメイン回路間の差圧を両メイン回路で略等しくすることができる。
【図面の簡単な説明】
【図１】本発明の中立バルブが設けられるＨＳＴ式変速機を示す側面断面図。
【図２】同じくＨＳＴ式変速機の油路板を示す正面断面図。
【図３】第一実施例に係る中立・リリーフバルブが開いている状態を示す断面図。
【図４】中立弁体の図３におけるＶ矢視図。
【図５】中立弁体の図３におけるＸ−Ｘ矢視図。
【図６】中立バルブとして作用している中立・リリーフバルブが閉じている状態を示す断面図。
【図７】中立弁体の変位とメイン回路間の油路面積の変化を示す図。
【図８】第一実施例における中立弁体の別形態を示す断面図。
【図９】第二実施例に係る中立・リリーフバルブが開いている状態を示す断面図。
【図１０】中立弁体の図９におけるＹ−Ｙ矢視図。
【図１１】第二実施例に係る中立・リリーフバルブが開いている状態を示す断面図。
【図１２】第二実施例に係る中立・リリーフバルブの別形態を示す図。
【図１３】第三実施例に係る中立バルブが開いている状態を示す断面図。
【図１４】第三実施例に係る中立バルブが閉じている状態を示す断面図。
【符号の説明】
１０ＨＳＴ式変速機
２１油圧ポンプ
２２油圧モータ
３２ｃチャージ回路
３２ｄ連通回路
３２ｍメイン回路
３５（３５Ａ・３５Ｂ・３５Ｃ）中立バルブ
４０弁座
４１弁座
４５蓋体
４６・５３・５５中立弁体
４７安全弁体
５０バルブ穴[0001]
BACKGROUND OF THE INVENTION
  The present invention relates to a configuration of a neutral valve provided in a hydraulic continuously variable transmission.
[0002]
[Prior art]
  Conventionally, in a hydraulic continuously variable transmission (hereinafter referred to as HST transmission) composed of a variable displacement hydraulic pump and a hydraulic motor, even if the HST transmission is operated in a neutral (zero speed) state, Since it was difficult to accurately maintain the inclination of the movable swash plate of the pump at the neutral position, a neutral valve was provided in each of the pair of main circuits formed on the oil passage plate to hold the HST transmission in the neutral state. I was trying to do it. A relief valve for releasing hydraulic oil to the low-pressure main circuit when the hydraulic pressure of one of the main circuits provided in the HST transmission exceeds the relief pressure set to an excessively high pressure. Is provided. This relief valve operates even when any one of the pair of main circuits becomes high pressure, and can exert a relief function.
[0003]
[Problems to be solved by the invention]
  However, the neutral valve and the relief valve are generally provided independently, and two neutral valves are necessary for each main circuit, so that the cost increases. In addition, since the pressure of the two main circuits acts simultaneously on the relief valve having a structure that functions as a single unit for the two main circuits described above, the higher the charge pressure applied to the valve body of the relief valve, the higher the actual relief pressure is. There is a tendency to decrease with respect to the set value, and there is a problem that the relief pressure as set cannot be obtained.
[0004]
[Means for Solving the Problems]
  The problem to be solved by the present invention is as described above. Next, means for solving the problem will be described.
[0005]
  In claim 1,A neutral / relief valve (35A) for maintaining a neutral state of a hydraulic continuously variable transmission (10) comprising a variable displacement hydraulic pump (21), a hydraulic motor (22), and an oil passage plate (32), The oil passage plate (32) includes a communication circuit (32d) communicating between the main circuits (32m and 32m) formed on the oil passage plate (32), and the communication circuit (32d) and one main circuit (32m). ), And the inner part of the valve hole (50) located at the center side of the oil passage plate (32) communicates with the communication circuit (32d). A valve seat (40) is formed at the back, an annular groove (43) is provided in the vicinity of the valve seat (40) of the valve hole (50), and the valve hole (50) is connected to the main circuit ( 32m), and a neutral valve body (46) is slidably inserted into the valve hole (50). The hole (50) is closed by inserting a lid (45) from the outside of the oil passage plate (32), and the head surface (46f) of the neutral valve body (46) is located at the back of the valve hole (50). The neutral valve body (46) and the lid body (45) can be brought into contact with the valve seat (40) and the head surface (46f) of the neutral valve body (46) is in contact with the valve seat (40). The neutral valve body (46) is positioned from the position where the head surface (46f) contacts the valve seat (40) to the position where the tail surface (46n) contacts the lid body (45). The inside of the valve hole (50) is slidable, and the lid (45) is formed with a hole that opens from the body (45e) to the head (45f) on the main circuit (32m) side. The spring chamber (45a) is provided integrally with the back of the spring chamber (45a) and the safety valve body (47) inserted into the neutral valve body (46). A spring (42) that urges the safety valve body (47) toward the communication circuit (32d) is interposed between the spring receiving portion (47b), and the lid (45) includes a spring chamber 45a, A passage (45c) communicating with an external drain circuit is formed, and the neutral valve body (46) is a substantially cylindrical member, and a communication hole (46h) is formed inside, and the communication hole (46h) A safety valve body (47) is slidably inserted from the tail surface (46n) side, and the valve portion (47a) of the safety valve body (47) is a valve of a relief valve formed inside the communication hole (46h). The neutral valve body (46) is urged by the spring (42) in the direction in which the neutral valve body (46) is seated on the valve seat (40), and the neutral valve body (46) is connected to the communication hole (46h). A passage (46e) for communicating the main circuit (32m) is provided, the relief valve is opened, and the safety valve body When the valve portion (47a) of (47) is separated from the valve seat (41), the communication circuit (32d) passes through the passage (46e) to the main circuit (32m) or from the main circuit (32m). The hydraulic oil is relieved to (32d), and the head surface (46f) at the end of the small diameter portion (46b) of the neutral valve body (46) forms a groove (46g) connecting the outer peripheral portion and the communication hole (46h). Even when the head surface (46f) of the neutral valve body (46) is in contact with the valve seat (41) by the groove (46g), the annular groove (43) passes through the groove (46g) from the communication circuit (32d). )What The outer diameter of the small-diameter portion (46b) forms a passage (46c, 46c) in which two surfaces are partially cut away, and the outer periphery contacts the inner periphery of the valve hole (50). Even so, an oil passage from the annular groove (43) to the main circuit (32m) through the passage (46c, 46c) is secured, and the passage (46c, 46c) is located away from the head surface (46f). When the movable swash plate (21c) of the hydraulic pump (21) is neutral, the neutral valve body (46) is seated on the valve seat (40), and the communication circuit (32d) and the main circuit (32m ) Is secured, but if the movable swash plate (21c) is tilted from the neutral state, a differential pressure of a certain level or more is generated between the communication circuit (32d) side and the main circuit (32m) side. When the hydraulic pressure on the communication circuit (32d) side is large, the communication circuit (32d) and the main circuit When the oil pressure in the high pressure side main circuit (32m) communicating with the communication circuit (32d) exceeds the relief set pressure in this state, the oil passage between the passages (32m) is closed and the valve of the safety valve body (47) The pressure is applied to the part (47a), the spring (42) contracts, the valve part (47a) and the valve seat (41) are separated, and the communication hole of the neutral valve body (46) from the communication circuit (32d) side. (46h) and a passage (46e) through which an oil passage leading to the low pressure side main circuit (32m) is formed, and hydraulic oil should be released from the high pressure side main circuit (32m) to the low pressure side main circuit (32m). ConfiguredIs.
[0006]
  In claim 2,A neutral / relief valve (35B) for maintaining a neutral state of a hydraulic continuously variable transmission (10) comprising a variable displacement hydraulic pump (21), a hydraulic motor (22), and an oil passage plate (32), The oil passage plate (32) includes a communication circuit (32d) communicating between the main circuits (32m and 32m) formed on the oil passage plate (32), and the communication circuit (32d) and one main circuit (32m). ), And the inner part of the valve hole (50) located at the center side of the oil passage plate (32) communicates with the communication circuit (32d). A valve seat (40) is formed at the back, an annular groove (43) is provided in the vicinity of the valve seat (40) of the valve hole (50), and the valve hole (50) is connected to the main circuit ( 32m), and a neutral valve body (55) is slidably inserted into the valve hole (50). The hole (50) is closed by inserting a lid (45) from the outside of the oil passage plate (32), and the head surface (55f) of the neutral valve body (55) is located at the back of the valve hole (50). The neutral valve body (55) and the lid body (45) can be brought into contact with the valve seat (40) and the head surface (55f) of the neutral valve body (55) is in contact with the valve seat (40). The neutral valve body (55) is positioned from the position where the head surface (55f) contacts the valve seat (40) to the position where the tail surface (55n) contacts the lid body (45). The inside of the valve hole (50) is slidable, and the lid (45) is formed with a hole that opens from the body (45e) to the head (45f) on the main circuit (32m) side. The spring chamber (45a) is provided integrally with the back of the spring chamber (45a) and the safety valve body (47) fitted into the neutral valve body (55). A spring (42) that urges the safety valve body (47) toward the communication circuit (32d) is interposed between the spring receiving portion (47b), and the lid (45) includes a spring chamber 45a, A passage (45c) communicating with an external drain circuit is formed, and the neutral valve body (55) is a substantially cylindrical member, and a communication hole (55h) is formed inside, and the communication hole (55h) A safety valve body (47) is slidably inserted from the tail surface (55n) side, and the valve portion (47a) of the safety valve body (47) is a valve of a relief valve formed inside the communication hole (55h). The neutral valve body (55) is urged by the spring (42) in the direction in which the neutral valve body (55) is seated on the valve seat (40), and the neutral valve body (55) is connected to the communication hole (55h). A passage (55e) for communicating the main circuit (32m) is provided, the relief valve is opened, and the safety valve body When the valve portion (47a) of (47) is separated from the valve seat (41), the communication circuit (32d) passes through the passage (55e) to the main circuit (32m) or from the main circuit (32m). The hydraulic oil is relieved to (32d), and the neutral valve body (55) is formed with a passage (55k, 55k) in which two outer peripheral surfaces are cut off on the tail surface (55n) side, and the neutral valve body (55) In a state where the head surface (55f) is seated on the valve seat 40, that is, in a state where the movable swash plate (21c) is operated to be neutral, the main circuit (32m) leads to the valve hole (50). A passage communicating with the spring chamber (45a) is formed through the formed groove (49) and a passage (55k, 55k) formed in the outer diameter portion of the neutral valve body (55), and the spring chamber (45a) The atmospheric pressure communicated with the circuit and the head of the neutral valve body (55) Abuts on (55f) is valve seat (40) In this state, the main circuit (32m) → the groove (49) formed in the valve hole (50) → the passage (55k / 55k) formed in the outer diameter portion of the neutral valve body (55) → the spring chamber (45a) When the movable swash plate (21c) of the hydraulic pump (21) is neutral, the neutral valve body (55) is seated on the valve seat (40), and the communication circuit (32d) and the main circuit (32m) ) Is secured, but if the movable swash plate (21c) is tilted from the neutral state, a differential pressure of a certain level or more is generated between the communication circuit (32d) side and the main circuit (32m) side. When the hydraulic pressure on the side of the communication circuit (32d) is large, the oil passage between the communication circuit (32d) and the main circuit (32m) is closed, and in this state, the high-pressure side main circuit communicating with the communication circuit (32d) When the hydraulic pressure of (32m) exceeds the relief set pressure, Pressure is applied to the valve parts (47a) of all the valve bodies (47), the springs (42) contract, and the valve parts (47a) and the valve seat (41) are separated from the communication circuit (32d) side, An oil passage is formed from the high pressure side main circuit (32m) to the low pressure side main circuit (32m) through the communication hole (55h) and the passage (55e) of the valve body (55). 32m) to release hydraulic oilIs.
[0007]
  In claim 3,The neutral / relief valve valve of the hydraulic continuously variable transmission according to claim 1 or 2, wherein a passage (45g) is provided in a lid (45) of the neutral / relief valve (35), and the passage (45g) And a charge circuit (32c) connected to the charge pump (51), and the pressure of the spring chamber (45a) is made substantially equal to the charge pressure of the charge circuit (32c) controlled by the charge pump (51). By setting the spring chamber (45a) as the charge pressure, the pressure at which the neutral valve body (46, 55) starts to move can be set or changed.Is.
[0008]
  In claim 4,A neutral valve (35C) for maintaining a neutral state of a hydraulic continuously variable transmission (10) comprising a variable displacement hydraulic pump (21), a hydraulic motor (22), and an oil passage plate (32), 35C) includes a neutral valve body (53) inserted into a valve hole (50) formed in a portion where the communication circuit (32d) and the main circuit (32m) of the oil passage plate (32) intersect, and the valve The lid (45) is inserted into the hole (50) and closed, and a hole opening toward the neutral valve body (53) is formed inside the lid (45) to form a spring chamber (45a). The valve seat (40) formed with the head surface (53f) of the neutral valve body (53) facing the communication circuit (32d) and the head surface (53f) formed at the back of the valve hole (50). The tail surface (53n) of the neutral valve body (53) is in contact with the body (45e) of the lid (45). The outer periphery of the neutral valve body (53) is cut away from the position away from the head surface (53f) to form a passage (53c, 53c), and the head surface (53f) The groove (53g) is formed so that the annular groove (43) formed in the valve hole (50) and the communication circuit (32d) communicate with each other with the head surface (53f) seated on the valve seat (40). When the head surface (53f) of the neutral valve body (53) is seated on the valve seat (40), the communication circuit (32d) → the groove (53g) of the head surface (53f) → the annular groove (43) → A passage (53c) formed in the small-diameter portion (53b) → the main circuit (32m), or an oil passage that can be reversed from the main circuit (32m) to the communication circuit (32d) is formed, and the neutral valve body (53 ) Is slidable in contact with the inner circumference of the valve hole (50), and the tail located at the outer circumference end (53n), a spring receiving portion (53m) is formed, and a spring (42) is provided between the spring receiving portion (53m) and the back of the spring chamber (45a) formed in the lid (45). The neutral valve body (53) is biased toward the communication circuit (32d) by the spring (42), and the neutral valve (35C) of the hydraulic pump (21) of the HST transmission (10) is energized. When the movable swash plate (21c) is in a substantially neutral position, the neutral valve body (53) is urged by the spring (42) and is seated on the valve seat (40), and in this state, the main circuit is connected from the communication circuit (32d). (32m) is secured, hydraulic oil moves between the communication circuit (32d) and the main circuit (32m) through the oil path to eliminate the differential pressure, and the HST transmission (10) is in a neutral state. The movable swash plate (21c) tilts and communicates as a neutral valve that holds the If a differential pressure is generated between the passage (32d) and the main circuit (32m) and the communication circuit (32d) side becomes high pressure, the neutral valve body (53) slides toward the lid body (45), and the neutral valve While the body (53) is moving toward the lid (45), the small diameter part (53b) of the neutral valve body (53) The outer circumference is in contact with the inner circumference of the valve hole (50), and the oil path between the communication circuit (32d) and the main circuit (32m) is cut off.Is.
[0009]
  In claim 5,5. The neutral / relief valve or neutral valve of the hydraulic continuously variable transmission according to claim 1, 2 or 4, wherein the neutral valve body (46, 53, 55), which is the valve body, is As a cylindrical body having a small diameter portion (46b...), A medium diameter portion (46d...), A large diameter portion (46a.. The cross-sectional area is formed so that the difference area between the cross-sectional area of the large-diameter part and the cross-sectional area of the large-diameter part and the small-diameter part is substantially equal, and the small-diameter part communicates with one main circuit, Communicated with the other main circuitIs.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
  Next, embodiments of the invention will be described. FIG. 1 is a side sectional view showing an HST transmission provided with a neutral valve of the present invention, and FIG. 2 is a front sectional view showing an oil passage plate of the HST transmission. FIG. 3 is a sectional view showing a state in which the neutral / relief valve according to the first embodiment is open. 4 is a view of the neutral valve body as viewed in the direction of arrow V in FIG. 3, FIG. 5 is a view of the neutral valve body in the direction of arrow XX in FIG. 3, and FIG. 6 is a view showing that the neutral / relief valve acting as a neutral valve is closed. FIG. 7 is a cross-sectional view showing the state, FIG. 7 is a view showing the displacement of the neutral valve body and the change in the oil passage area between the main circuits, and FIG. 8 is a cross-sectional view showing another embodiment of the neutral valve body in the first embodiment. 9 is a cross-sectional view showing a state in which the neutral / relief valve according to the second embodiment is open, FIG. 10 is a view of the neutral valve body taken along the line YY in FIG. 9, and FIG. 11 is a neutral view according to the second embodiment. FIG. 12 is a view showing another embodiment of the neutral / relief valve according to the second embodiment. FIG. 13 is a sectional view showing a state where the neutral valve according to the third embodiment is open, and FIG. 14 is a sectional view showing a state where the neutral valve according to the third embodiment is closed.
[0011]
  First, a schematic configuration of a hydraulic continuously variable transmission provided with the neutral valve 35 of the present invention will be described. As shown in FIGS. 1 and 2, a hydraulic continuously variable transmission (hereinafter referred to as “HST transmission”) 10 includes a hydraulic pump 21 and a hydraulic motor 22, and the hydraulic pump 21 and the hydraulic motor 22 are included in a housing 31. Has been.
[0012]
  The hydraulic pump 21 is configured as a variable displacement hydraulic pump by a drive shaft 21a, a cylinder block 21b, a plunger 21e, a movable swash plate 21c, and the like. The cylinder block 21b is slidably fitted with a plunger 21e that comes into contact with the movable swash plate 21c, and rotates together with a drive shaft 21a fitted into the cylinder block 21b.
[0013]
  The movable swash plate 21c is configured to regulate the sliding amount of the plunger 21e and to adjust the discharge amount of the hydraulic oil of the hydraulic pump 21. Then, hydraulic oil is supplied from the hydraulic pump 21 to the hydraulic motor 22 through a main circuit 32 m provided on the oil passage plate 32.
[0014]
  On the other hand, the hydraulic motor 22 includes an output shaft 22a, a cylinder block 22b, a plunger 22e, a fixed swash plate 22c, and the like. The output shaft 22a is inserted into the oil passage plate 32, is inserted into the cylinder block 22b, and one end of the output shaft 22a is rotatably supported by the housing 31. The cylinder block 22b rotates together with the output shaft 22a, and a plunger 22e is slidably inserted into the cylinder block 22b. The plunger 22e is in contact with a fixed swash plate 22c fixed to the housing 31.
[0015]
  With the above configuration, when the driving force is input to the drive shaft 21a and the hydraulic pump 21 is driven, the hydraulic oil discharged by the hydraulic pump 21 passes through the main circuits 32m and 32m formed in the oil passage plate 32. Then, the hydraulic motor 22 is driven by the hydraulic oil, and the driving force is transmitted to the output shaft 22a.
[0016]
  The oil passage plate 32 is formed with a charge circuit 32c, and check valves 36 and 36 are interposed between the charge circuit 32c and the main circuits 32m and 32m. Further, the two main circuits 32m and 32m are communicated by a communication circuit 32d, and a neutral valve 35 is interposed between the main circuit 32m and the communication circuit 32d.
[0017]
  Here, the configuration of the neutral valve 35 (neutral / relief valve 35A) according to the first embodiment of the present invention will be described. The neutral valve 35 according to the first embodiment is a neutral / relief valve 35A that also has a function as a relief valve, and is a valve body of a relief valve that is inserted into a valve hole 50 formed in the oil passage plate 32. A neutral valve body 46, a lid body 45 as a pressure adjusting spring seat, a safety valve body 47, and the like. That is, the relief valve has a structure in which the valve body and the pressure adjusting spring seat are separated.
[0018]
  In order to make the output of the HST transmission 10 zero (that is, stop the rotation of the output shaft 22a), the swash plate angle of the movable swash plate 21c of the hydraulic pump 21 is held at the neutral position, and both main circuits It is difficult to keep the movable swash plate 21c accurately in the neutral position, and the hydraulic pressure between the two main circuits 32m and 32m is slightly different. The differential pressure may occur. Therefore, a neutral valve is provided so that no differential pressure is generated in the hydraulic oil between the two main circuits 32m and 32m, so that the neutral state of the HST transmission 10 is maintained. The relief valve opens when the hydraulic oil pressure becomes higher than the set pressure and releases the hydraulic oil from the high-pressure side main circuit 32m to the low-pressure side main circuit 32m, and the hydraulic pressure of the main circuits 32m and 32m is set to the set pressure. It is provided to prevent the above.
[0019]
  As shown in FIGS. 2 and 3, the oil passage plate 32 includes a communication circuit 32d that communicates between the main circuits 32m and 32m formed on the oil passage plate 32, and a communication circuit 32d and one main circuit 32m. A valve hole 50 including an intersection is formed. The inner part of the valve hole 50 (the central side of the oil passage plate 32) communicates with the communication circuit 32d. A valve seat 40 is formed in the inner part of the valve hole 50 and in the vicinity of the valve seat 40 in the valve hole 50. Is provided with an annular groove 43. The valve hole 50 communicates with the main circuit 32m in the middle.
[0020]
  A neutral valve body 46 is slidably inserted into the valve hole 50, and the valve hole 50 is closed by inserting a lid body 45. The head surface 46f of the neutral valve body 46 can be brought into contact with the valve seat 40 located in the inner part of the valve hole 50, and the neutral valve body 46f is in contact with the valve seat 40 in the state where the head surface 46f of the neutral valve body 46 is in contact with the valve seat 40. The body 46 and the lid body 45 are arranged so as to be separated from each other. Therefore, the neutral valve body 46 can slide in the valve hole 50 from the position where the head surface 46 f contacts the valve seat 40 to the position where the tail surface 46 n contacts the lid body 45.
[0021]
  The lid body 45 includes a head portion 45f and a body portion 45e having a smaller diameter than the head portion 45f, and the body portion 45e is screwed into the valve hole 50. A hole is formed in the lid 45 from the body 45e to the head 45f so that the main circuit 32m side is open, and this hole serves as a spring chamber 45a. A spring that urges the safety valve body 47 toward the communication circuit 32d between the inner portion of the spring chamber 45a and a spring receiving portion 47b provided integrally with the safety valve body 47 that is inserted into the neutral valve body 46. 42 is interposed, and when the spring 42 is compressed, the spring receiving portion 47b of the safety valve body 47 can slide in the spring chamber 45a.
[0022]
  The body 45e of the lid body 45 is formed with a passage 45c that communicates the inside of the spring chamber 45a and the drain circuit outside the spring chamber 45a. In addition, since the drain circuit is set to approximately atmospheric pressure, the internal pressure of the spring chamber 45a is approximately atmospheric pressure.
[0023]
  On the other hand, the neutral valve body 46 is a substantially cylindrical member, and a communication hole 46h is formed therein, and a safety valve body 47 is slidably inserted into the communication hole 46h from the tail surface 46n side. The valve portion 47a of the safety valve body 47 is a relief valve formed inside the communication hole 46h by a spring 42 that is in contact with a spring receiving portion 47b provided integrally with the safety valve body 47 and is built in the spring chamber 45a. It is seated on the valve seat 41. The neutral valve body 46 is biased in a direction in which the neutral valve body 46 is seated on the valve seat 40 by the safety valve body 47 biased by the spring 42.
[0024]
  The neutral valve body 46 includes a small diameter portion 46b, a medium diameter portion 46d, and a large diameter portion 46a from the head surface 46f side. A passage 46e for communicating the communication hole 46h and the main circuit 32m is provided in the middle diameter portion 46d of the neutral valve body 46, the relief valve is opened, and the valve portion 47a of the safety valve body 47 is connected to the valve seat 41. When separated from the hydraulic fluid, the hydraulic fluid is relieved through the passage 46e from the communication circuit 32d to the main circuit 32m or from the main circuit 32m to the communication circuit 32d. Further, in the large diameter portion 46a of the neutral valve body 46, a safety valve body 47 is slidably inserted therein, and the outer periphery thereof is configured to slide in contact with the valve hole 50.
[0025]
  As shown in FIG. 4, the head surface 46f at the end of the small diameter portion 46b of the neutral valve body 46 is formed with a groove 46g connecting the outer peripheral portion of the small diameter portion 46b and the communication hole 46h. Even when the head surface 46f of the neutral valve body 46 is in contact with the valve seat 41, the oil passage is secured from the communication circuit 32d to the annular groove 43 through the groove 46g. Further, as shown in FIG. 5, the outer peripheral portion of the small diameter portion 46 b is partially cut away to form passages 46 c and 46 c, and the outer periphery of the small diameter portion 46 b is in contact with the inner periphery of the valve hole 50. In addition, an oil passage from the annular groove 43 to the main circuit 32m is secured through the passages 46c and 46c. The passages 46c and 46c are formed at positions away from the head surface 46f of the small diameter portion 46b. Thus, in a state where the head surface 46f of the neutral valve body 46 is in contact with the valve seat 40, the communication circuit 32d → the groove 46g → the annular groove 43 → the passage 46c → the main circuit 32m (or the reverse direction). An oil passage is formed from 32d to the main circuit 32m (or from the main circuit 32m to the communication circuit 32d).
[0026]
  As shown in FIG. 8, the communication circuit 32d → the groove 46g → the annular groove in a state where the recess 48 is formed on the outer periphery of the small diameter portion 46b of the neutral valve body 46 and the head surface 46f is in contact with the valve seat 40. An oil passage of 43 → concave 48 → main circuit 32m (or the reverse direction) is formed, and the neutral valve body 46 slides toward the lid body 45 so that the wall surface 48a of the recess 48 abuts against the wall surface 43a of the annular groove 43. It is also possible to configure so as to cut the oil passage.
[0027]
  As shown in FIG. 4, the pressure receiving area (A) on the communication circuit 32d side of the neutral valve body 46 and the pressure receiving area (B) on the main circuit 32m side are configured to be substantially the same. That is, the pressure receiving area (A) on the side of the communication circuit 32d is the sum of the area (a1) of the head surface 4f and the cross-sectional area (a2) of the communication hole 46h, and can be expressed using the radius R1 of the small diameter portion 46b. A = π (R1) 2 ". Further, the pressure receiving area (B) on the main circuit 32m side is the difference (b2) between the area of the circle having the diameter of the large diameter portion 46a as the diameter and the area having the diameter of the medium diameter portion 46d as the diameter (b2), and the medium diameter portion 46d. Is the sum of the area (b1) of the circle whose diameter is the diameter of the small diameter portion 46b and the area difference (b1) whose diameter is the diameter of the small diameter portion 46b, and is expressed using the radius R2 of the large diameter portion 46a and the radius R1 of the small diameter portion 46b. “B = π (R2) 2−π (R1) 2”. And between these, it is comprised so that the relationship of "A = B" may be materialized.
[0028]
  This is neutral when the pressure receiving area from the communication circuit 32d side is substantially equal to the pressure receiving area from the main circuit 32m side, so that the hydraulic pressure on either the communication circuit 32d side or the main circuit 32m side increases. This is because the valve operates, but the neutral valve is operated when a substantially equal differential pressure is generated regardless of the hydraulic pressure of any circuit.
[0029]
  For example, when the vehicle is equipped with the HST transmission 10 and the difference in the neutral ratio of the swash plate angle of the movable swash plate 21c of the hydraulic pump 21 is set between forward and reverse, the communication circuit 32d The difference in neutral ratio can be set by providing a difference between the pressure receiving area on the side and the pressure receiving area on the main circuit 32m side.
[0030]
  In the neutral / relief valve 35A configured as described above, when the movable swash plate 21c is tilted from the neutral state, a differential pressure of a certain level or more is generated between the communication circuit 32d side and the main circuit 32m side, and the communication circuit 32d. When the side hydraulic pressure is large, pressure is applied to the head surface 46f of the neutral valve body 46 and the spring 42 is compressed, and the safety valve body 47 and the neutral valve body 46 are integrally slid through the valve hole 50 toward the lid body 45. To do. As described above, in the state where the neutral valve body 46 is seated on the valve seat 40, an oil passage is secured between the communication circuit 32d and the main circuit 32m, but as the neutral valve body 46 slides, the oil passage area is increased. When the communication between the annular groove 43 and the passages 46c and 46c is cut off, the oil passage area becomes almost zero, and the oil passage between the communication circuit 32d and the main circuit 32m is cut off. That is, the sliding position of the neutral valve body 46 opens and closes the communication circuit 32d that communicates with one main circuit 32m and the other main circuit 32m through the groove 46g, the annular groove 43, and the passage 46c. After this, as shown in FIG. 6, the neutral valve body 46 slides until the tail surface 46 n of the neutral valve body 46 comes into contact with the body 45 e of the lid body 45.
[0031]
  Conversely, when the movable swash plate 21c tilts from the neutral state, a differential pressure of a certain level or more is generated between the communication circuit 32d side and the main circuit 32m side, and when the hydraulic pressure on the main circuit 32m side is large, the neutral valve Pressure is applied to the step surface of the large-diameter portion 46a and the medium-diameter portion 46d of the body 46 to compress the spring 42, and the safety valve body 47 and the neutral valve body 46 are integrally slid through the valve hole 50 toward the lid body 45. To do. As described above, in the state where the neutral valve body 46 is seated on the valve seat 40, an oil passage is secured between the communication circuit 32d and the main circuit 32m, but as the neutral valve body 46 slides, the oil passage area is increased. When the communication between the annular groove 43 and the passages 46c and 46c is cut off, the oil passage area becomes almost zero, and the oil passage between the communication circuit 32d and the main circuit 32m is cut off. Thereafter, the neutral valve body 46 slides until the tail surface 46n of the neutral valve body 46 abuts on the body 45e of the lid body 45.
[0032]
  That is, as shown in FIG. 7, when the movable swash plate 21c is tilted from the neutral state, when the differential pressure generated between the communication circuit 32d side and the main circuit 32m side exceeds a certain pressure, the neutral valve When the body 46 starts to move, the oil passage area between the communication circuit 32d and the main circuit 32m starts to decrease, and further, the movement of the neutral valve body 46 makes the oil passage area substantially zero, and the tail of the neutral valve body 46 The surface 46n comes into contact with the lid body 45, and the neutral valve body 46 stops moving.
[0033]
  The above-described operation of the neutral valve body 46 operates in the same way regardless of the hydraulic pressure on either the communication circuit 32d side or the main circuit 32m side, and the differential pressure generated between the communication circuit 32d side and the main circuit 32m side is the same. Until a certain pressure is exceeded, that is, when the movable swash plate 21c is in a tilted position close to the neutral position, the hydraulic oil moves through the oil passage between the communication circuit 32d and the main circuit 32m, and the communication circuit 32d side and the main It acts as a neutral valve that maintains the neutral state of the HST transmission 10 by setting the differential pressure between the circuit 32m and the circuit 32m to substantially zero. In the state where the tilt angle of the movable swash plate 21c is increased and the differential pressure generated between the communication circuit 32d side and the main circuit 32m side exceeds a certain pressure, the oil between the communication circuit 32d and the main circuit 32m The road is cut off, and the main circuits 32m and 32m become independent, and the operation of the normal HST type transmission 10 is started.
[0034]
  On the other hand, when the neutral / relief valve 35A acts as a relief valve, the tail surface 46n of the neutral valve body 46 comes into contact with the lid body 45, and the communication circuit 32d and the main circuit 32m are disconnected. When the hydraulic pressure of the communicating high-pressure main circuit 32m exceeds the relief set pressure, pressure is applied to the valve portion 47a of the safety valve body 47, the spring 42 contracts, and the valve portion 47a and the valve seat 41 are separated to communicate with each other. An oil path is formed from the circuit 32d side to the low pressure side main circuit 32m through the communication hole 46h and the passage 46e of the neutral valve body 46, and hydraulic fluid is supplied from the high pressure side main circuit 32m to the low pressure side main circuit 32m. Let it go.
[0035]
  Further, when the neutral / relief valve 35A acts as a relief valve, the neutral / relief valve is in a state where the tail surface 46n of the neutral valve body 46 is in contact with the lid 45 and the communication circuit 32d and the main circuit 32m are disconnected. When the hydraulic pressure of the main circuit 32m communicating with the valve hole 50 into which 35A is inserted exceeds the relief set pressure, the valve portion 47a of the safety valve body 47 is passed through the passage 46e formed in the intermediate diameter portion 46d of the neutral valve body 46. When the pressure is applied, the spring 42 contracts, the valve portion 47a and the valve seat 41 are separated from each other, and an oil passage from the main circuit 32m side to the communication circuit 32d through the passage 46e and the communication hole 46h of the neutral valve body 46 is formed. The hydraulic oil is released from the high-pressure side main circuit 32m to the low-pressure side main circuit 32m connected to the communication circuit 32d.
[0036]
  In this manner, the neutral / relief valve 35A can act as a relief valve regardless of which main circuit 32m is on the high pressure side. There is a sufficient difference between the differential pressure at which the neutral / relief valve 35A acts as a neutral valve and the differential pressure at which it acts as a relief valve.
[0037]
  As described above, the neutral / relief valve 35A is a neutral valve body when the movable swash plate 21c is in a neutral state and the differential pressure between the communication circuit 32d and the main circuit 32m, that is, the two main circuits 32m and 32m is equal to or less than a predetermined pressure. When the valve 46 is opened and the movable swash plate 21c is tilted and the differential pressure becomes equal to or higher than a certain pressure, the neutral valve body 46 is closed and acts as a neutral valve. Further, the neutral / relief valve 35A acts as a relief valve when the high pressure side main circuit 32m becomes equal to or higher than the set relief pressure in a state where the movable swash plate 21c is tilted, and the safety valve element 47 is opened. .
[0038]
  In this way, the neutral / relief valve 35A can function as both a neutral valve and a relief valve. Compared to the conventional configuration where the neutral valve and the relief valve are configured as separate valves. Thus, the number of parts can be reduced, and the cost can be reduced. Further, the conventional neutral valve is necessary for each of the main circuits 32m and 32m. However, one neutral valve is sufficient for one set of the HST transmission 10, and the number of parts is reduced to reduce the cost. be able to.
[0039]
  Here, the configuration of the neutral valve 35 (neutral / relief valve 35B) according to the second embodiment of the present invention will be described. Similar to the neutral valve 35 (35A) shown in the first embodiment, the neutral valve 35 (35B) according to the second embodiment is a neutral / relief valve 35B having a relief valve function. Compared to the embodiment, the structure of the neutral valve body 55 is different, and the neutral valve body 55 is provided in one main circuit 32m of the HST type transmission 10. Also in the second embodiment, the relief valve and the neutral valve can be made the same component as compared with the case where the relief valve and the neutral valve are configured separately, so that the cost can be reduced. Below, the description regarding the structure of the cover body 45 and the safety valve body 47 which is common in the first embodiment is omitted, and the structure of the neutral valve body 55 will be described in detail.
[0040]
  As shown in FIG. 9, the neutral valve body 55 inserted into the valve hole 50 formed in the oil passage plate 32 has its tail surface in a state where the head surface 55 f on the communication circuit 32 d side is in contact with the valve seat 40. 55 n is configured to be separated from the body 45 e of the lid 45. The neutral valve body 55 is a cylindrical member provided with a small-diameter portion 55b, a medium-diameter portion 55d, and a large-diameter portion 55a from the head surface 55f side, and is a safety valve from the tail surface 55n side to a communication hole 55h formed therein. When the body 47 is slidably inserted and the neutral valve body 55 is biased toward the communication circuit 32d by the spring 42 biasing the safety valve body 47 toward the communication circuit 32d, and the movable swash plate 21c is in the neutral state The head surface 55f of the neutral valve body 55 is configured to be seated on the valve seat 40.
[0041]
  A passage 55e that connects the communication hole 55h and the main circuit 32m when the valve portion 47a of the safety valve body 47 is separated from the valve seat 41 of the relief valve is formed in the intermediate diameter portion 55d of the neutral valve body 55. . Further, as shown in FIG. 10, the large-diameter portion 55a of the neutral valve body 55 is formed with passages 55k and 55k in which two outer peripheral surfaces are notched on the tail surface 55n side. In a state where the head surface 55f of the neutral valve body 55 is seated on the valve seat 40, that is, in a state where the movable swash plate 21c is operated to be neutral, a groove 49 formed in the valve hole 50 from the main circuit 32m. A passage communicating with the spring chamber 45a is formed through passages 55k and 55k formed in the outer diameter portion of the neutral valve body 55. The spring chamber 45a communicates with a drain circuit (not shown) and is at atmospheric pressure.
[0042]
  As described above, the neutral / relief valve 35B according to the present embodiment includes, for example, one main circuit 32m when the HST transmission 1 is used so that one main circuit 32m is mainly on the high pressure side. Is provided. Accordingly, when a differential pressure is generated in the main circuits 32m and 32m with the movable swash plate 21c being operated in the vicinity of the neutral position, hydraulic oil corresponding to the differential pressure is moved to the drain circuit side by the neutral / relief valve 35B. By leaking, the differential pressure is eliminated, and the HST transmission 1 can be held neutral.
[0043]
  When the tilt angle of the movable swash plate 21c is increased and the hydraulic pressure of the main circuit 32m on the side where the neutral / relief valve 35B is provided becomes equal to or higher than a predetermined pressure, the intermediate diameter portion 55d and the large diameter portion of the neutral valve body 55 are provided. Pressure is applied to the stepped surface of 55a, the neutral valve body 55 moves to the lid body 45 side, and the spring 42 is compressed. As shown in FIG. 11, the neutral valve body 55 moves until it comes into contact with the lid body 45. In this state, the outer periphery of the large diameter portion 55a of the neutral valve body 55 is in contact with the inner periphery of the valve hole 50 and the spring chamber 45a. The passage between the main circuits 32m is cut off, so that a differential pressure can be generated between the main circuits 32m, and the movable swash plate 21c can be tilted.
[0044]
  In addition, instead of setting the spring chamber 45a to atmospheric pressure, a charge pressure can be set in the spring chamber 45a. As shown in FIG. 12, the passage 45g is provided in the lid body 45 of the neutral / relief valve 35B, and the passage 45g and the charge circuit 32c connected to the charge pump 51 are connected, whereby the charge circuit 32c and the spring chamber 45a are connected. , And the pressure of the spring chamber 45a is made substantially equal to the charge pressure of the charge circuit 32c controlled by the charge pump 51. Thus, by setting the spring chamber 45a as the charge pressure, the pressure at which the neutral valve body 55 starts to move can be easily set or changed, and can be set more precisely.
[0045]
  Further, by connecting the spring chamber 45a to the charge circuit 32c, when the relief valve is opened, the relief oil does not flow out to the drain circuit, so that the charge flow rate sent from the charge pump 51 to the charge circuit 32c can be kept low. it can. When the neutral / relief valve 35B acts as a relief valve, it corresponds to any pressure in the communication circuit 32d and the main circuit 32m, and opens when the differential pressure between the left and right main circuits 32m and 32m reaches the set relief pressure. Since the pressure is applied to the spring chamber 45a to obtain a charge pressure, the set relief pressure is set to a high level without changing the strength of the spring 42 provided in the spring chamber 45a. Can do.
[0046]
  Next, the neutral valve 35 (35C) according to the third embodiment of the present invention will be described. Conventionally, it is necessary to provide each main circuit 32m. However, if one neutral valve 35C according to the third embodiment is provided in the HST transmission 10, it can function in both directions.
[0047]
  As shown in FIG. 13, the neutral valve 35 </ b> C is inserted into the valve hole 50, and the neutral valve body 53 inserted into the valve hole 50 formed in the portion where the communication circuit 32 d and the main circuit 32 m of the oil passage plate 32 intersect. The lid body 45 is closed.
[0048]
  The lid body 45 includes a body portion 45e inserted into the valve hole 50 and a head portion 45f having a larger diameter than the body portion 45e. A hole that opens to the neutral valve body 53 side is formed inside the lid body 45 to form a spring chamber 45a. The head surface 53f of the neutral valve body 53 faces the communication circuit 32d, and the tail surface of the neutral valve body 53 is in a state where the head surface 53f is in contact with the valve seat 40 formed at the back of the valve hole 50. 53 n is configured to be separated from the body 45 e of the lid 45.
[0049]
  The neutral valve body 53 includes a small-diameter portion 53b, a medium-diameter portion 53d, and a large-diameter portion 53a from the head 45f side, and the outer periphery of the small-diameter portion 53b is cut away from the position away from the head surface 53f, and a passage 53c. -53c is formed. Further, a groove 53g is formed in the head surface 53f so that the annular groove 43 formed in the valve hole 50 and the communication circuit 32d communicate with each other with the head surface 53f seated on the valve seat 40. Therefore, when the head surface 53f of the neutral valve body 53 is seated on the valve seat 40, the communication circuit 32d → the groove 53g of the head surface 53f → the annular groove 43 → the passage 53c formed in the small diameter portion 53b → the main circuit 32m (or An oil path in the reverse direction is formed.
[0050]
  The outer periphery of the large-diameter portion 53a of the neutral valve body 53 is slidable in contact with the inner periphery of the valve hole 50, and a spring receiving portion 53m is formed on the tail surface 53n located at the end of the large-diameter portion 53a. ing. A spring 42 is interposed between the spring receiving portion 53m and the back of the spring chamber 45a formed in the lid body 45, and the neutral valve body 53 is biased toward the communication circuit 32d by the spring 42. .
[0051]
  In the neutral valve 35C configured as described above, when the movable swash plate 21c of the hydraulic pump 21 of the HST transmission 10 is in a substantially neutral position, the neutral valve body 53 is urged by the spring 42 and is seated on the valve seat 40. ing. At this time, as described above, the oil passage from the communication circuit 32d to the main circuit 32m is secured, and the hydraulic oil moves between the communication circuit 32d and the main circuit 32m through the oil passage to eliminate the differential pressure. The transmission 10 is kept in a neutral state. That is, it acts as a neutral valve.
[0052]
  Then, the movable swash plate 21c is tilted to generate a differential pressure between the communication circuit 32d and the main circuit 32m. If the communication circuit 32d side becomes high pressure, the head valve 53f of the neutral valve body 53 or the main circuit 32m side has high pressure. Then, pressure is applied to the step surfaces of the intermediate diameter portion 53d and the large diameter portion 53a of the neutral valve body 53, and the neutral valve body 53 slides toward the lid body 45 as shown in FIG. Is compressed. The neutral valve body 53 moves until the tail surface 53n comes into contact with the body 45e of the lid body 45.
[0053]
  While the neutral valve body 53 moves to the lid body 45 side, the outer periphery of the small diameter portion 53b of the neutral valve body 53 is in contact with the inner periphery of the valve hole 50, and the oil path between the communication circuit 32d and the main circuit 32m is cut off. The communication circuit 32d and the main circuit 32m are disconnected. That is, the main circuit 32m and the main circuit 32m communicating with the communication circuit 32d are in an independent state.
[0054]
  As described above, the difference between the main circuits 32m and 32m when the movable swash plate 21c is in the neutral state by one neutral valve 35C provided in the two main circuits 32m and 32m provided in the HST transmission 10. Pressure can be released. Therefore, the number of parts can be reduced compared to the conventional configuration in which a neutral valve is provided in each main circuit 32m, which contributes to cost reduction.
[0055]
【The invention's effect】
  Since the present invention is configured as described above, the following effects can be obtained.
[0056]
  As shown in claim 1A neutral / relief valve (35A) for maintaining a neutral state of a hydraulic continuously variable transmission (10) comprising a variable displacement hydraulic pump (21), a hydraulic motor (22), and an oil passage plate (32), The oil passage plate (32) includes a communication circuit (32d) communicating between the main circuits (32m and 32m) formed on the oil passage plate (32), and the communication circuit (32d) and one main circuit (32m). ) To form a valve hole (50) including the intersection of the oil passage plate (32). The back part of the valve hole (50) located on the side part communicates with the communication circuit (32d), forms a valve seat (40) in the back part, and the valve seat (40) of the valve hole (50). ) An annular groove (43) is provided in the vicinity, the valve hole (50) communicates with the main circuit (32m) in the middle, and the neutral valve body (46) can slide in the valve hole (50). The valve hole (50) is closed by inserting the lid (45) from the outside of the oil passage plate (32), and the head surface (46f) of the neutral valve body (46) is closed by the valve hole (50). The neutral valve body (46) can be brought into contact with the valve seat (40) located at the back of the neutral valve body (46) and the head surface (46f) of the neutral valve body (46) is in contact with the valve seat (40). ) And the lid body (45) are separated from each other, and the neutral valve body (46) has a caudal surface (46n) from the position where the head surface (46f) contacts the valve seat (40). The valve hole (50) can be slid to the position where it abuts against (45), and the lid (45) opens from the body (45e) to the head (45f) on the main circuit (32m) side. The hole is formed as a spring chamber (45a), and is provided integrally with the back of the spring chamber (45a) and the safety valve body (47) inserted into the neutral valve body (46). A spring (42) that urges the safety valve body (47) toward the communication circuit (32d) is interposed between the spring receiving portion (47b), and the lid (45) includes a spring chamber 45a, A passage (45c) communicating with an external drain circuit is formed, and the neutral valve body (46) is a substantially cylindrical member, and a communication hole (46h) is formed inside, and the communication hole (46h) The safety valve body (47) is slidably inserted from the tail surface (46n) side into the valve portion (47) of the safety valve body (47). ) Is seated on the valve seat (41) of the relief valve formed inside the communication hole (46h), and is biased in the direction in which the neutral valve body (46) is seated on the valve seat (40) by the spring (42). The neutral valve body (46) is provided with a passage (46e) for communicating the communication hole (46h) with the main circuit (32m), the relief valve is opened, and the valve portion of the safety valve body (47) is provided. When (47a) moves away from the valve seat (41), hydraulic fluid passes through the passage (46e) from the communication circuit (32d) to the main circuit (32m) or from the main circuit (32m) to the communication circuit (32d). The head surface (46f) at the end of the small diameter portion (46b) of the neutral valve body (46) forms a groove (46g) connecting the outer peripheral portion and the communication hole (46h), and the groove (46g) By this, the head surface (46f) of the neutral valve body (46) is moved to the valve seat (41 ), The oil passage from the communication circuit (32d) through the groove (46g) to the annular groove (43) is secured, and the outer peripheral portion of the small diameter portion (46b) is partially two-sided. Even if the cut-out passages (46c, 46c) are formed and the outer peripheral portion is in contact with the inner periphery of the valve hole (50), the main circuit (32m) is formed from the annular groove (43) through the passages (46c, 46c). ), The passages (46c, 46c) are formed away from the head surface (46f), and when the movable swash plate (21c) of the hydraulic pump (21) is neutral, While the valve body (46) is seated on the valve seat (40), an oil passage is secured between the communication circuit (32d) and the main circuit (32m), but the movable swash plate (21c) is in a neutral state. When tilting from the main circuit (32m) side, the difference more than a certain level When the hydraulic pressure on the communication circuit (32d) side is large, the oil passage between the communication circuit (32d) and the main circuit (32m) is closed, and in this state, the high-pressure main that communicates with the communication circuit (32d) is closed. When the hydraulic pressure of the circuit (32m) exceeds the relief set pressure, pressure is applied to the valve portion (47a) of the safety valve body (47) and the spring (42) contracts, and the valve portion (47a) and the valve seat (41) ) Is separated and an oil passage is formed from the communication circuit (32d) side to the low pressure side main circuit (32m) through the communication hole (46h) and the passage (46e) of the neutral valve body (46). The hydraulic fluid is configured to escape from the main circuit (32m) on the side to the main circuit (32m) on the low pressure sideTherefore, the neutral valve can have the function of a relief valve, and the function can be achieved with one neutral valve for a plurality of main circuits. Therefore, the number of components can be reduced and the configuration can be made at low cost.
[0057]
  As shown in claim 2,A neutral / relief valve (35B) for maintaining a neutral state of a hydraulic continuously variable transmission (10) comprising a variable displacement hydraulic pump (21), a hydraulic motor (22), and an oil passage plate (32), The oil passage plate (32) includes a communication circuit (32d) communicating between the main circuits (32m and 32m) formed on the oil passage plate (32), and the communication circuit (32d) and one main circuit (32m). ), And the inner part of the valve hole (50) located at the center side of the oil passage plate (32) communicates with the communication circuit (32d). Valve at the back A seat (40) is formed, and an annular groove (43) is provided in the vicinity of the valve seat (40) of the valve hole (50). The valve hole (50) communicates with the main circuit (32m) in the middle. A neutral valve body (55) is slidably inserted into the valve hole (50), and the valve hole (50) is closed by inserting a lid (45) from the outside of the oil passage plate (32). The head surface (55f) of the neutral valve body (55) can be brought into contact with the valve seat (40) located at the back of the valve hole (50), and the head surface (55f) of the neutral valve body (55). The neutral valve body (55) and the lid body (45) are arranged so as to be separated from each other while the valve seat (40) is in contact with the valve seat (40), and the neutral valve body (55) has a head surface (55f). The inside of the valve hole (50) is slidable from the position where it abuts on the valve seat (40) to the position where the tail surface (55n) abuts on the lid (45). A hole is formed on the main circuit (32m) side from the body part (45e) to the head part (45f), and the hole is used as a spring chamber (45a). A spring that urges the safety valve body (47) toward the communication circuit (32d) between the safety receiving body (47b) provided integrally with the safety valve body (47) inserted into the valve body (55). (42) is interposed, and the lid (45) is formed with a passage (45c) communicating the inside of the spring chamber 45a with the external drain circuit, and the neutral valve body (55) is substantially cylindrical. A communication hole (55h) is formed inside, and a safety valve element (47) is slidably inserted into the communication hole (55h) from the tail surface (55n) side, and the safety valve element (47) The valve part (47a) is seated on the valve seat (41) of the relief valve formed inside the communication hole (55h) The neutral valve body (55) is urged by the spring (42) in the direction of seating on the valve seat (40), and the neutral valve body (55) communicates with the communication hole (55h) and the main circuit (32m). When the relief valve is opened and the valve part (47a) of the safety valve body (47) is separated from the valve seat (41), the communication circuit (32d) is passed through the passage (55e). ) From the main circuit (32m) to the main circuit (32m) or from the main circuit (32m) to the communication circuit (32d), the neutral valve body (55) cuts two outer surfaces on the tail surface (55n) side. The missing passage (55k, 55k) is formed, and the neutral valve body (55) is operated so that the head surface (55f) is seated on the valve seat 40, that is, the movable swash plate (21c) is neutral. In the state that is, from the main circuit (32m), the valve hole ( 50) and a passage communicating with the spring chamber (45a) through a groove (49) formed in the outer diameter portion of the neutral valve body (55) and a passage communicating with the spring chamber (45a) are formed, and the spring chamber (45a) Is formed in the main circuit (32 m) → valve hole (50) in a state where the pressure is communicated with the drain circuit and the atmospheric pressure is set, and the head surface (55f) of the neutral valve body (55) is in contact with the valve seat (40). The groove (49) → the passage (55k / 55k) formed in the outer diameter portion of the neutral valve body (55) → the spring chamber (45a) communicates with the movable swash plate (21c) of the hydraulic pump (21). In the neutral state, the oil passage between the communication circuit (32d) and the main circuit (32m) is secured with the neutral valve body (55) seated on the valve seat (40), but the movable swash plate ( 21c) tilts from the neutral state, the communication circuit (32d) side and the main circuit (32m) When a differential pressure of a certain level or more is generated between them and the hydraulic pressure on the side of the communication circuit (32d) is large, the oil passage between the communication circuit (32d) and the main circuit (32m) is closed, and in this state, the communication circuit ( When the hydraulic pressure of the main circuit (32m) on the high pressure side communicating with 32d) exceeds the relief set pressure, pressure is applied to the valve portion (47a) of the safety valve body (47) and the spring (42) contracts, The part (47a) and the valve seat (41) are separated from each other, and from the communication circuit (32d) side, through the communication hole (55h) and the passage (55e) of the neutral valve body (55), the main circuit (32m) on the low pressure side An oil path is formed to release hydraulic fluid from the high pressure side main circuit (32m) to the low pressure side main circuit (32m).Therefore, the function of the relief valve can be provided in addition to the neutral valve, and the number of parts can be reduced and the structure can be made inexpensively.
[0058]
  As shown in claim 3,The neutral / relief valve valve of the hydraulic continuously variable transmission according to claim 1 or 2, wherein a passage (45g) is provided in a lid (45) of the neutral / relief valve (35), and the passage (45g) And a charge circuit (32c) connected to the charge pump (51), and the pressure of the spring chamber (45a) is made substantially equal to the charge pressure of the charge circuit (32c) controlled by the charge pump (51). By setting the spring chamber (45a) as the charge pressure, the pressure at which the neutral valve body (46, 55) starts to move can be set or changed.Therefore, the function of the relief valve can be provided in addition to the neutral valve, and the number of parts can be reduced and the structure can be made inexpensively.
  Further, the pressure at which the relief valve is opened can be set larger than the pressure of the spring, and further, since the relief oil does not flow into the drain circuit, the charge flow rate can be kept low.
[0059]
  As shown in claim 4,A neutral valve (35C) for maintaining a neutral state of a hydraulic continuously variable transmission (10) comprising a variable displacement hydraulic pump (21), a hydraulic motor (22), and an oil passage plate (32), 35C) includes a neutral valve body (53) inserted into a valve hole (50) formed in a portion where the communication circuit (32d) and the main circuit (32m) of the oil passage plate (32) intersect, and the valve The lid (45) is inserted into the hole (50) and closed, and a hole opening toward the neutral valve body (53) is formed inside the lid (45) to form a spring chamber (45a). The valve seat (40) formed with the head surface (53f) of the neutral valve body (53) facing the communication circuit (32d) and the head surface (53f) formed at the back of the valve hole (50). The tail surface (53n) of the neutral valve body (53) is in contact with the body (45e) of the lid (45). The outer periphery of the neutral valve body (53) is cut away from the position away from the head surface (53f) to form a passage (53c, 53c), and the head surface (53f) The groove (53g) is formed so that the annular groove (43) formed in the valve hole (50) and the communication circuit (32d) communicate with each other with the head surface (53f) seated on the valve seat (40). When the head surface (53f) of the neutral valve body (53) is seated on the valve seat (40), the communication circuit (32d) → the groove (53g) of the head surface (53f) → the annular groove (43) → A passage (53c) formed in the small-diameter portion (53b) → the main circuit (32m), or an oil passage that can be reversed from the main circuit (32m) to the communication circuit (32d) is formed, and the neutral valve body (53 ) Is slidable in contact with the inner circumference of the valve hole (50), and the tail located at the outer circumference end (53n), a spring receiving portion (53m) is formed, and a spring (42) is provided between the spring receiving portion (53m) and the back of the spring chamber (45a) formed in the lid (45). The neutral valve body (53) is biased toward the communication circuit (32d) by the spring (42), and the neutral valve (35C) of the hydraulic pump (21) of the HST transmission (10) is energized. When the movable swash plate (21c) is in a substantially neutral position, the neutral valve body (53) is urged by the spring (42) and is seated on the valve seat (40), and in this state, the main circuit is connected from the communication circuit (32d). (32m) is secured, hydraulic oil moves between the communication circuit (32d) and the main circuit (32m) through the oil path to eliminate the differential pressure, and the HST transmission (10) is in a neutral state. The movable swash plate (21c) tilts and communicates as a neutral valve that holds the If a differential pressure is generated between the passage (32d) and the main circuit (32m) and the communication circuit (32d) side becomes high pressure, the neutral valve body (53) slides toward the lid body (45), and the neutral valve While the body (53) is moving toward the lid (45), the outer periphery of the small diameter portion (53b) of the neutral valve body (53) is in contact with the inner periphery of the valve hole (50) and the communication circuit (32d) is connected to the main body (53). Cut the oil path between the circuits (32m)Therefore, since the function is achieved with one neutral valve for a plurality of main circuits, the number of parts can be reduced and the structure can be made inexpensively.
[0060]
  As shown in claim 5,5. The neutral / relief valve or neutral valve of the hydraulic continuously variable transmission according to claim 1, 2 or 4, wherein the neutral valve body (46, 53, 55), which is the valve body, is As a cylindrical body having a small diameter portion (46b...), A medium diameter portion (46d...), A large diameter portion (46a.. The cross-sectional area is formed so that the difference area between the cross-sectional area of the large-diameter part and the cross-sectional area of the large-diameter part and the small-diameter part is substantially equal, and the small-diameter part communicates with one main circuit, Communicated with the other main circuitTherefore, the differential pressure between the main circuits where the neutral valve starts to operate can be made substantially equal in both main circuits.
[Brief description of the drawings]
FIG. 1 is a side sectional view showing an HST type transmission provided with a neutral valve of the present invention.
FIG. 2 is a front cross-sectional view showing an oil passage plate of the HST transmission.
FIG. 3 is a cross-sectional view showing a state in which a neutral / relief valve according to the first embodiment is open.
4 is a V arrow view of the neutral valve body in FIG. 3;
FIG. 5 is a view of the neutral valve body taken along line XX in FIG.
FIG. 6 is a cross-sectional view showing a state in which a neutral / relief valve acting as a neutral valve is closed.
FIG. 7 is a diagram showing the displacement of the neutral valve body and the change in the oil passage area between the main circuits.
FIG. 8 is a cross-sectional view showing another embodiment of the neutral valve body in the first embodiment.
FIG. 9 is a cross-sectional view showing a state in which a neutral / relief valve according to a second embodiment is open.
10 is a view of the neutral valve body as viewed in the direction of arrows YY in FIG. 9;
FIG. 11 is a cross-sectional view showing a state in which a neutral / relief valve according to a second embodiment is open.
FIG. 12 is a view showing another embodiment of the neutral / relief valve according to the second embodiment.
FIG. 13 is a cross-sectional view showing a state in which a neutral valve according to a third embodiment is open.
FIG. 14 is a cross-sectional view showing a state where a neutral valve according to a third embodiment is closed.
[Explanation of symbols]
  10 HST transmission
  21 Hydraulic pump
  22 Hydraulic motor
  32c charge circuit
  32d communication circuit
  32m main circuit
  35 (35A / 35B / 35C) Neutral valve
  40 Valve seat
  41 Valve seat
  45 lid
  46, 53, 55 Neutral disc
  47 Safety valve
  50 Valve hole

Claims

A neutral / relief valve (35A) for maintaining a neutral state of a hydraulic continuously variable transmission (10) comprising a variable displacement hydraulic pump (21), a hydraulic motor (22), and an oil passage plate (32), The oil passage plate (32) includes a communication circuit (32d) communicating between the main circuits (32m and 32m) formed on the oil passage plate (32), and the communication circuit (32d) and one main circuit (32m). ), And the inner part of the valve hole (50) located at the center side of the oil passage plate (32) communicates with the communication circuit (32d). A valve seat (40) is formed at the back, an annular groove (43) is provided in the vicinity of the valve seat (40) of the valve hole (50), and the valve hole (50) is connected to the main circuit ( 32m), and a neutral valve body (46) is slidably inserted into the valve hole (50). The hole (50) is closed by inserting a lid (45) from the outside of the oil passage plate (32), and the head surface (46f) of the neutral valve body (46) is located at the back of the valve hole (50). The neutral valve body (46) and the lid body (45) can be brought into contact with the valve seat (40) and the head surface (46f) of the neutral valve body (46) is in contact with the valve seat (40). The neutral valve body (46) is positioned from the position where the head surface (46f) contacts the valve seat (40) to the position where the tail surface (46n) contacts the lid body (45). The inside of the valve hole (50) is slidable, and the lid (45) is formed with a hole that opens from the body (45e) to the head (45f) on the main circuit (32m) side. The spring chamber (45a) is provided integrally with the back of the spring chamber (45a) and the safety valve body (47) inserted into the neutral valve body (46). A spring (42) that urges the safety valve body (47) toward the communication circuit (32d) is interposed between the spring receiving portion (47b), and the lid (45) includes a spring chamber 45a, A passage (45c) communicating with an external drain circuit is formed, and the neutral valve body (46) is a substantially cylindrical member, and a communication hole (46h) is formed inside, and the communication hole (46h) A safety valve body (47) is slidably inserted from the tail surface (46n) side, and the valve portion (47a) of the safety valve body (47) is a valve of a relief valve formed inside the communication hole (46h). The neutral valve body (46) is urged by the spring (42) in the direction in which the neutral valve body (46) is seated on the valve seat (40), and the neutral valve body (46) is connected to the communication hole (46h). A passage (46e) for communicating the main circuit (32m) is provided, the relief valve is opened, and the safety valve body When the valve portion (47a) of (47) is separated from the valve seat (41), the communication circuit (32d) passes through the passage (46e) to the main circuit (32m) or from the main circuit (32m). The hydraulic oil is relieved to (32d), and the head surface (46f) at the end of the small diameter portion (46b) of the neutral valve body (46) forms a groove (46g) connecting the outer peripheral portion and the communication hole (46h). Even when the head surface (46f) of the neutral valve body (46) is in contact with the valve seat (41) by the groove (46g), the annular groove (43) passes through the groove (46g) from the communication circuit (32d). ), And the outer peripheral portion of the small-diameter portion (46b) forms a passage (46c, 46c) in which two surfaces are partially cut away, and the outer peripheral portion is the inner periphery of the valve hole (50). Even if it is in contact with the main circuit via the annular groove (43) through the passage (46c, 46c) 32m), the passage (46c, 46c) is formed from a position away from the head surface (46f), and when the movable swash plate (21c) of the hydraulic pump (21) is neutral, With the neutral valve body (46) seated on the valve seat (40), an oil passage is secured between the communication circuit (32d) and the main circuit (32m), but the movable swash plate (21c) is neutral. When tilted from the state, a differential pressure of a certain level or more is generated between the communication circuit (32d) side and the main circuit (32m) side, and when the hydraulic pressure on the communication circuit (32d) side is large, the communication circuit (32d) and the main circuit When the oil pressure of the main circuit (32m) on the high pressure side communicating with the communication circuit (32d) exceeds the relief set pressure in this state, the oil passage between (32m) is closed and the valve portion of the safety valve body (47) (47a) is pressurized and the spring (42) contracts, The part (47a) and the valve seat (41) are separated from each other, and from the side of the communication circuit (32d), through the communication hole (46h) and the passage (46e) of the neutral valve body (46), the main circuit (32m) on the low pressure side A neutral / relief valve for a hydraulic continuously variable transmission, wherein an oil passage is formed to release hydraulic fluid from a high-pressure main circuit (32m) to a low-pressure main circuit (32m).

Variable displacement hydraulic pump (21), hydraulic motor (22) and oil passage plate (32 The hydraulic continuously variable transmission (10) is a neutral / relief valve (35B) for maintaining a neutral state. The oil passage plate (32) includes a main passage formed on the oil passage plate (32). A communication circuit (32d) communicating between the circuits (32m, 32m) and a valve hole (50) including an intersection of the communication circuit (32d) and one main circuit (32m) are formed, and the oil passage plate ( 32), the inner part of the valve hole (50) located at the center side communicates with the communication circuit (32d) to form a valve seat (40) at the inner part of the valve hole (50). An annular groove (43) is provided in the vicinity of the valve seat (40), the valve hole (50) communicates with the main circuit (32m) in the middle, and the neutral valve body (55) is connected to the valve hole (50). The valve hole (50) is closed by inserting a lid (45) from the outside of the oil passage plate (32). The head surface (55f) of the neutral valve body (55) can be brought into contact with the valve seat (40) located at the back of the valve hole (50), and the head surface (55f) of the neutral valve body (55) The neutral valve body (55) and the lid body (45) are arranged so as to be separated from each other in contact with the valve seat (40), and the neutral valve body (55) has a head surface (55f) as a valve. The inside of the valve hole (50) is slidable from the position in contact with the seat (40) to the position in which the tail surface (55n) contacts the lid (45). 45e) to the head (45f), a hole that opens on the main circuit (32m) side is formed. The hole is used as a spring chamber (45a), and the inner portion of the spring chamber (45a) and the neutral valve body (55 ) Between the safety valve body (47) and the spring receiving portion (47b) provided integrally with the safety valve body (47) inserted into the communication circuit (3 d) A spring (42) that biases toward the side is interposed, and a passage (45c) that connects the inside of the spring chamber 45a and an external drain circuit is formed in the lid (45), and the neutral valve body (55) is a substantially cylindrical member that has a communication hole (55h) formed therein, and a safety valve body (47) is slidably inserted into the communication hole (55h) from the tail surface (55n) side. The valve portion (47a) of the safety valve body (47) is seated on the valve seat (41) of the relief valve formed inside the communication hole (55h), and the neutral valve body (55) is formed by the spring (42). The neutral valve body (55) is provided with a passage (55e) for communicating the communication hole (55h) with the main circuit (32m). When the valve portion (47a) of the safety valve body (47) is separated from the valve seat (41) after opening the valve, The hydraulic oil is relieved through the passage (55e) from the communication circuit (32d) to the main circuit (32m) or from the main circuit (32m) to the communication circuit (32d), and the neutral valve body (55) On the (55n) side, a passage (55k, 55k) in which two outer peripheral surfaces are cut out is formed, and the head surface (55f) of the neutral valve body (55) is seated on the valve seat 40, that is, a movable slant In a state where the plate (21c) is operated to be neutral, it is formed from the main circuit (32m) to the groove (49) formed in the valve hole (50) and the outer diameter portion of the neutral valve body (55). A passage communicating with the spring chamber (45a) is formed through the passage (55k, 55k). The spring chamber (45a) communicates with the drain circuit and has an atmospheric pressure, and the head surface (55f) of the neutral valve body (55). Is in contact with the valve seat (40), the main circuit ( 2m) → the groove (49) formed in the valve hole (50) → the passage (55k / 55k) formed in the outer diameter portion of the neutral valve body (55) → the spring chamber (45a) communicated with the hydraulic pump ( 21) When the movable swash plate (21c) is neutral, an oil passage is secured between the communication circuit (32d) and the main circuit (32m) with the neutral valve body (55) seated on the valve seat (40). However, when the movable swash plate (21c) tilts from the neutral state, a differential pressure of a certain level or more is generated between the communication circuit (32d) side and the main circuit (32m) side, and the communication circuit (32d) When the side hydraulic pressure is high, the oil passage between the communication circuit (32d) and the main circuit (32m) is closed, and in this state, the hydraulic pressure of the high-pressure side main circuit (32m) communicating with the communication circuit (32d) is relieved. When the set pressure is exceeded, the valve part (47a of the safety valve body (47) The pressure is applied to the spring (42), the valve portion (47a) and the valve seat (41) are separated from the communication circuit (32d) side and the communication hole (55h) of the neutral valve body (55). An oil passage extending from the high pressure side main circuit (32m) to the low pressure side main circuit (32m) is formed through the passage (55e) to reach the low pressure side main circuit (32m). Neutral / relief valve featuring hydraulic continuously variable transmission.

The neutral / relief valve valve of the hydraulic continuously variable transmission according to claim 1 or 2, wherein a passage (45g) is provided in a lid (45) of the neutral / relief valve (35), and the passage (45g) And a charge circuit (32c) connected to the charge pump (51) , And the pressure of the spring chamber (45a) is made substantially equal to the charge pressure of the charge circuit (32c) controlled by the charge pump (51), and the spring chamber (45a) is used as the charge pressure. A neutral / relief valve for a hydraulic continuously variable transmission, wherein the pressure at which the valve body (46, 55) starts to move can be set or changed.

A neutral valve (35C) for maintaining a neutral state of a hydraulic continuously variable transmission (10) comprising a variable displacement hydraulic pump (21), a hydraulic motor (22), and an oil passage plate (32), 35C) includes a neutral valve body (53) inserted into a valve hole (50) formed in a portion where the communication circuit (32d) and the main circuit (32m) of the oil passage plate (32) intersect, and the valve The lid (45) is inserted into the hole (50) and closed, and a hole opening toward the neutral valve body (53) is formed inside the lid (45) to form a spring chamber (45a). The valve seat (40) formed with the head surface (53f) of the neutral valve body (53) facing the communication circuit (32d) and the head surface (53f) formed at the back of the valve hole (50). The tail surface (53n) of the neutral valve body (53) is in contact with the body (45e) of the lid (45). The outer periphery of the neutral valve body (53) is cut away from the position away from the head surface (53f) to form a passage (53c, 53c), and the head surface (53f) The groove (53g) is formed so that the annular groove (43) formed in the valve hole (50) and the communication circuit (32d) communicate with each other with the head surface (53f) seated on the valve seat (40). When the head surface (53f) of the neutral valve body (53) is seated on the valve seat (40), the communication circuit (32d) → the groove (53g) of the head surface (53f) → the annular groove (43) → A passage (53c) formed in the small-diameter portion (53b) → the main circuit (32m), or an oil passage capable of reversing from the main circuit (32m) to the communication circuit (32d) is formed, and the neutral valve body (53 ) Is slidable in contact with the inner circumference of the valve hole (50), and the tail located at the outer circumference end (53n), a spring receiving portion (53m) is formed, and a spring (42) is provided between the spring receiving portion (53m) and the back of the spring chamber (45a) formed in the lid (45). The neutral valve body (53) is biased toward the communication circuit (32d) by the spring (42), and the neutral valve (35C) of the hydraulic pump (21) of the HST transmission (10) is energized. When the movable swash plate (21c) is in a substantially neutral position, the neutral valve body (53) is urged by the spring (42) and is seated on the valve seat (40), and in this state, the main circuit is connected from the communication circuit (32d). (32m) is secured, hydraulic oil moves between the communication circuit (32d) and the main circuit (32m) through the oil path to eliminate the differential pressure, and the HST transmission (10) is in a neutral state. The movable swash plate (21c) tilts and communicates as a neutral valve that holds the If a differential pressure is generated between the passage (32d) and the main circuit (32m) and the communication circuit (32d) side becomes high pressure, the neutral valve body (53) slides toward the lid body (45), and the neutral valve While the body (53) is moving toward the lid (45), the outer periphery of the small diameter portion (53b) of the neutral valve body (53) is in contact with the inner periphery of the valve hole (50) and the communication circuit (32d) is connected to the main body (53). A neutral valve of a hydraulic continuously variable transmission, characterized in that an oil passage between circuits (32 m) is cut off.

5. The neutral / relief valve or neutral valve of the hydraulic continuously variable transmission according to claim 1, 2 or 4, wherein the neutral valve body (46, 53, 55), which is the valve body, is As a cylindrical body having a small diameter portion (46b...), A medium diameter portion (46d...), A large diameter portion (46a.. The cross-sectional area is formed so that the difference area between the cross-sectional area of the large-diameter part and the cross-sectional area of the large-diameter part and the small-diameter part is substantially equal, and the small-diameter part is communicated with one main circuit. A neutral / relief valve or neutral valve of the hydraulic continuously variable transmission, characterized in that the portion communicates with the other main circuit.