JP2004036663A

JP2004036663A - Hydraulic control valve

Info

Publication number: JP2004036663A
Application number: JP2002191427A
Authority: JP
Inventors: Akira Kahara; 花原　晃
Original assignee: Sumitomo Heavy Industries Construction Crane Co Ltd
Current assignee: Sumitomo Heavy Industries Construction Crane Co Ltd
Priority date: 2002-06-28
Filing date: 2002-06-28
Publication date: 2004-02-05
Anticipated expiration: 2022-06-28
Also published as: JP3838943B2

Abstract

<P>PROBLEM TO BE SOLVED: To provide a hydraulic control valve that accurately adjusts initial pressure of a pressure control valve, closes the maximum pressure to a theoretical value, and eliminates un-comfortableness of the operability by manufacturing error. <P>SOLUTION: A control spring 25 is set between a piston 29 of the hydraulic control valve 26 and a spool 28, and a shim 30 is interposed between the control spring 25 and the spool 28. The sleeve 32 is slidably engaged with the outside of the spool 28, and is energized by an adjusting spring 33 in the pressing direction of the piston 29. A shim 34 is disposed in the adjusting spring 33, and spring constant of the adjusting spring 33 and thickness of the shim 34 are changeable. The initial pressure is set by adjusting the spring force of the control spring 25 by changing the thickness of the shim 30 and by adjusting the spring force of the adjusting spring 33 by changing the thickness of the shim 34. Therefore, the maximum pressure can be easily and accurately adjusted regardless of the set initial pressure. <P>COPYRIGHT: (C)2004,JPO

Description

【０００１】
【発明の属する技術分野】
本発明は液圧制御弁に関するものであり、特に、油圧アクチュエータを用いた建設機械や産業機械に使用される液圧制御弁に関するものである。
【０００２】
【従来の技術】
図５は移動式クレーン１を示し、下部走行体２に上部旋回体３が旋回自在に載置されている。該移動式クレーン１にはブームの起伏装置４を始めとして、フックロープの巻き上げ下げ装置５、上部旋回体の旋回装置６、下部走行体の走行装置７等の各油圧装置が備えられている。
【０００３】
図６は前記旋回装置６の縦断面を示し、上部旋回体３側に設けた油圧モータ８の回転は、減速機構９により減速されてピニオンギヤ１０を回転させる。該ピニオンギヤ１０は下部走行体２側に固設したリングギヤ１１に噛合しており、該ピニオンギヤ１０が回転しながらリングギヤ１１の内周に沿って移動することにより、上部旋回体３が旋回する。
【０００４】
図７は前記旋回装置６の油圧モータ８を駆動する油圧回路を示し、操作レバー１２の基端部にカム１３が設けられ、該カム１３はカム戻しバネ１４により押されて前記操作レバー１２が中立位置へ復帰するように付勢されている。該カム１３の下方には制御バネ１５を介して左右の圧力制御弁１６Ｌ，１６Ｒを設けてあり、前記操作レバー１２の操作量に応じてスプールが移動して左側制御圧力Ｐ_ＣＬまたは右側制御圧力Ｐ_ＣＲを出力し、方向制御弁１７を切り替えて油圧モータ８の回転方向と回転速度を制御する。
【０００５】
図８及び図９に示すように、前記左右の圧力制御弁１６Ｌ，１６Ｒは中立位置を中心に若干の遊び域があり、そのときの制御圧力Ｐ_Ｃはタンク圧力Ｐ_Ｔである。遊び域を超えて調整域に入ると左右の制御圧力Ｐ_ＣＬ，Ｐ_ＣＲが発生し、制御圧力Ｐ_Ｃは初期圧力（クラッキング圧力）Ｐ_Ｓから最大圧力Ｐ_Ｍまで変化する。前記制御バネ１５のバネ定数が設計値より高いときは、実線で示した左側制御圧力Ｐ_ＣＬよりも、二点鎖線で示すように直線の傾きが急峻となる。一方、前記制御バネ１５のバネ定数が設計値より低いときは、実線で示した右側制御圧力Ｐ_ＣＲよりも、二点鎖線で示すように直線の傾きが緩やかとなる。
【０００６】
例えば、右側の圧力制御弁１６Ｒについて説明すれば、操作レバー１２を右側へ傾倒してカム１３を操作すれば、図９（ｂ）に示すように、初期圧力状態（Ｐ_ＣＲ＝Ｐ_Ｓ、Ｐ_ＣＬ＝Ｐ_Ｔ）ではスプール１８がポートＰとポートＰ_ＣＲの連通する位置までのストロークＬ_Ｓ１となり、カム１３の操作角がθ_Ｒとなる。操作レバー１２を更に右側へ傾倒してカム１３を操作すれば、図９（ｃ）に示すように、最大圧力状態（Ｐ_ＣＲ＝Ｐ_Ｍ、Ｐ_ＣＬ＝Ｐ_Ｔ）ではスプール１８とポートＰの位置は図９（ｂ）と変わらず、カム１３を操作角θ_ＲＭまで操作すれば制御バネ１５はＬ_Ｍ１分だけ圧縮されてＬ_Ｍ０となる。
【０００７】
【発明が解決しようとする課題】
図１０に示すように、例えば右側の圧力制御弁１６Ｒが中立状態であるときは、ピストン１９の押圧力Ｆ＝０、制御圧力Ｐ_Ｃ＝Ｐ_Ｔである。そして、制御バネ１５のセット荷重をＦ_Ｓ、スプール１８の投影面積をＡとすれば、前述した初期圧力Ｐ_Ｓは、ピストン１９を押圧力Ｆにて遊びの長さＬ_Ｓ１分だけ押し込んだときに次式で与えられる。
【０００８】
Ｐ_Ｓ＝Ｆ_Ｓ／Ａ　　（Ｆ_Ｓ≦Ｆとなるのが一般的）
Ｆ_Ｓは設計上の理論値であり、製造上の精度を全て加味するとＦ_Ｓはある範囲を有することになる。実際には制御バネ１５とともに介装するシム２０の厚さを調整することにより、Ｆ_Ｓの範囲を理論値に近づけている。
【０００９】
前述した最大圧力Ｐ_Ｍは、前記右側の圧力制御弁１６Ｒのピストン１９を押圧力Ｆにて更に強く押し込んだときに次式で与えられる。但し、Ｋは制御バネ１５のバネ定数である。
【００１０】
Ｐ_Ｍ＝（Ｆ_Ｓ＋Ｋ×Ｌ_Ｍ１）／Ａ　　（Ｆ_Ｓ≦Ｆとなるのが一般的）
制御バネ１５のセット荷重Ｆ_Ｓは性能上重要であり、制御バネ１５を加工してセット荷重Ｆ_Ｓを調整する。一方、バネ定数はバネの巻き径、線径、巻き数により決定されるため、制御バネ１５のセット荷重Ｆ_Ｓとバネ定数Ｋの双方を設計上の理論値にすることは製造上不可能に近い。また、既にシム２０の調整にて初期圧力Ｐ_Ｓを設定しているため、更にシム調整で最大圧力Ｐ_Ｍを調整することはできない。
【００１１】
図１１はある圧力制御弁の実測特性を示し、初期圧力は５．０を中心に（−０〜＋１．５）の範囲に入っていれば基準値以内とし、最大圧力は３５を中心に（−２〜＋４）の範囲に入っていれば基準値以内であるものとする。図示したように、初期圧力Ｐ_Ｓは左６．０、右５．５と略同一で基準値以内であるが、最大圧力Ｐ_Ｍが左３１．５、右２９．５と基準値に達せず低圧であるため、オペレータには力不足が感じられて使い難い。一方、図１２は他の圧力制御弁の実測特性を示し、初期圧力Ｐ_Ｓは左８．５、右６．５と左側が高すぎる。また、最大圧力Ｐ_Ｍが右３８．５と基準値以内で良好であるが左４１．５は基準値オーバーとなり、左右で最大圧力に大きな差があるため、オペレータには左右で操作の違和感があって使い難い
そこで、圧力制御弁の初期圧力を正確に調整するとともに、最大圧力をも理論値に近づけて、製作誤差による操作性の違和感を解消した液圧制御弁を提供するために解決すべき技術的課題が生じてくるのであり、本発明はこの課題を解決することを目的とする。
【００１２】
【課題を解決するための手段】
本発明は上記目的を達成するために提案されたものであり、操作レバーの基端部に設けたカムによりピストンが押圧されてスプールが移動するように形成した圧力制御弁と、該圧力制御弁のスプールの外側にスリーブを設けるとともに、このスリーブを調整バネにてピストンの押圧方向へ付勢し、前記調整バネのバネ定数並びに調整バネに介装するシムの厚さを夫々変更可能に形成した圧力調整弁とを組み合わせて構成され、初期圧力と最大圧力とを個別に調整可能に形成した液圧制御弁、
及び、上記初期圧力から最大圧力に至る途中に圧力偏曲点を設けた液圧制御弁を提供するものである。
【００１３】
【発明の実施の形態】
以下、本発明の一実施の形態を図１乃至図４に従って詳述する。尚、説明の都合上、従来技術と同一構成部分には同一符号を付してその説明を省略する。図１は本発明の液圧制御弁２６の右側部分２６Ｒを示し、ピストン２９に下方が開放された筒状のカバー３１を固着し、該カバー３１内にカム戻しバネ２４を介装してカム１３を上方に押し戻すことにより、操作レバー１２が中立位置へ復帰するように付勢されている。また、ピストン２９とスプール２８との間に制御バネ２５をセットし、制御バネ２５とスプール２８との間にシム３０を介装してある。
【００１４】
ここで、図１（ａ）に示すように、本発明の液圧制御弁２６はスプール２８の外側にスリーブ３２をスライド自在に嵌合し、このスリーブ３２を調整バネ３３にてピストン２９の押圧方向へ付勢する。また、該調整バネ３３にはシム３４を介装し、後述するように、調整バネ３３のバネ定数とシム３４の厚さを夫々変更可能にしてある。即ち、前記スリーブ３２と調整バネ３３とシム３４とから、圧力制御弁の圧力変化を調整可能な圧力調整弁が構成される。
【００１５】
図１（ｂ）及び図２に示すように、操作レバー１２を右側へ傾倒してカム１３を操作すれば、初期圧力状態では（Ｐ_Ｃ＝Ｐ_Ｓ）ではスプール２８がポートＰとポートＰ_Ｃの連通する位置までのストロークＬ_Ｓ１となり、カム１３の操作角がθ_Ｒとなる。操作レバー１２を更に右側へ傾倒してカム１３を操作すれば、図１（ｃ）に示すように、圧力偏曲点（Ｐ_Ｃ＝Ｐ_ＳＨ）ではスプール２８とポートＰの位置は図１（ｂ）と変わらず、この時点までは前記制御バネ２５のバネ定数及びシム３０の厚さによって圧力Ｐ_Ｃが決定される。
【００１６】
この圧力偏曲点を過ぎて、更にカム１３を操作角θ_ＲＭまで操作すれば、図１（ｄ）に示すように、最大圧力状態（Ｐ_Ｃ＝Ｐ_Ｍ）となり、前記スリーブ３２が調整バネ３３を圧縮しながら図中上方へ移動し始める。従って、Ｐポート及びＴポートのスプール３２に対する位相がずれ、圧力変化が急峻となって最大圧力Ｐ_Ｍとなる。
【００１７】
図３に示すように、右側の圧力制御弁２６Ｒが中立状態であるときは、ピストン２９の押圧力Ｆ＝０、制御圧力Ｐ_Ｃ＝Ｐ_Ｔである。そして、制御バネ２５のセット荷重をＦ_Ｓ、スプール２８の投影面積をＡとすれば、従来技術で述べたように、初期圧力Ｐ_Ｓは、ピストン１９を押圧力Ｆにて遊びの長さＬ_Ｓ１分だけ押し込んだときに次式で与えられる。
【００１８】
Ｐ_Ｓ＝Ｆ_Ｓ／Ａ　　（Ｆ_Ｓ≦Ｆとなるのが一般的）
Ｆ_Ｓは設計上の理論値であり、製造上の精度を全て加味するとＦ_Ｓはある範囲を有することになる。実際には制御バネ２５とともに介装するシム３０の厚さを調整することにより、Ｆ_Ｓの範囲を理論値に近づけている。
【００１９】
ここで、調整バネ３３のセット荷重をＦ_Ｐ、スリーブ３２の外径投影面積をＡ_Ｐとすれば、前述した圧力偏曲点での圧力Ｐ_ＳＨは、カム１３が操作角θ_ＲＨだけ操作されてその分Ｐ_Ｃ圧力が上昇し、スリーブ３２がρ_Ｃ分動き出そうとする時点で、
Ｐ_ＳＨ＝Ｆ_Ｐ／（Ａ_Ｐ−Ａ）
そして、最大圧力Ｐ_Ｍは次式で与えられる。但し、Ｋ_Ｐは調整バネ３３のバネ定数である。
【００２０】
Ｐ_Ｍ＝［Ｆ_Ｓ＋｛Ｋ×（Ｌ_Ｍ１−ρ_Ｃ）｝］／Ａ
ρ_Ｃ＝｛Ｐ_Ｃ×（Ａ_Ｐ−Ａ）｝／Ｋ_Ｐ
この最大圧力Ｐ_Ｍが設計理論値よりも高いときは、シム３４を厚くしてバネ力を低下させる。これに対して、図２の点線で示すように、最大圧力Ｐ_Ｍが設計理論値よりも低いときは、シム３４を薄くしてバネ力を高くする。このように、初期圧力Ｐ_Ｓに関係なく、圧力偏曲点を設けたことにより最大圧力Ｐ_Ｍを調整することができる。
【００２１】
図４はある液圧制御弁の実測特性を示し、初期圧力Ｐ_Ｓは左６．２、右５．５と略同一で基準値以内である。図１１に示した従来例のものより左右の初期圧力にややバラツキがあるが、シム３４の厚さを変えて調整バネ３３のバネ力を調整し、スリーブ３２の動きを制御することにより圧力偏曲点以降での圧力変化を変更し、最大圧力Ｐ_Ｍが図１１の従来技術では左３１．５、右２９．５と基準値以下であったものが、図４では左３６．５、右３３．４と双方の圧力を基準値内に収めることができる。
【００２２】
尚、本発明は、本発明の精神を逸脱しない限り種々の改変を為すことができ、そして、本発明が該改変されたものに及ぶことは当然である。
【００２３】
【発明の効果】
本発明は上記一実施の形態に詳述したように、請求項１記載の発明は、圧力制御弁のスプールの外側にスリーブを設け、調整バネとシムとを変更可能にした圧力調整弁を構成したので、圧力制御弁のスプールの動きを調整して初期圧力を設定し、圧力調整弁のスリーブの動きを調整して最大圧力を設定する。即ち、初期圧力の調整に拘わらず最大圧力を調整可能として、左右の圧力差を可及的に減少させることにより、初期圧力を正確に調整するとともに、最大圧力をも理論値に近づけて、製作誤差による操作性の違和感を解消した液圧制御弁を提供することができる。
【００２４】
請求項２記載の発明は、上記初期圧力から最大圧力に至る途中に圧力偏曲点を設けたことにより、請求項１記載の発明の効果に加えて、最大圧力の調整が容易となって左右の圧力差を解消できる。
【図面の簡単な説明】
【図１】本発明の一実施の形態を示し、（ａ）乃至（ｄ）は液圧制御弁の作動状態の変化を示す縦断面図。
【図２】本発明の一実施の形態を示し、操作レバーのカム操作角と液圧制御弁の圧力変化の関係を示すグラフ。
【図３】本発明の一実施の形態を示し、液圧制御弁の圧力の関係を示す縦断面図。
【図４】本発明の一実施の形態を示し、ある液圧制御弁の実測特性を示すグラフ。
【図５】一般的な移動クレーンを示す側面図。
【図６】移動クレーンの旋回装置を示す縦断面図。
【図７】旋回装置の油圧回路図。
【図８】従来技術を示し、操作レバーのカム操作角と圧力制御弁の圧力変化の関係を示すグラフ。
【図９】従来技術を示し、（ａ）乃至（ｃ）は圧力制御弁の作動状態の変化を示す縦断面図。
【図１０】従来技術を示し、圧力制御弁の圧力の関係を示す縦断面図。
【図１１】従来技術を示し、ある圧力制御弁の実測特性を示すグラフ。
【図１２】従来技術を示し、他の圧力制御弁の実測特性を示すグラフ。
【符号の説明】
１２　　　　操作レバー
１３　　　　カム
２５　　　　制御バネ
２６　　　　液圧制御弁
２８　　　　スプール
２９　　　　ピストン
３０　　　　シム
３２　　　　スリーブ
３３　　　　調整バネ
３４　　　　シム[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a hydraulic pressure control valve, and more particularly to a hydraulic pressure control valve used for a construction machine or an industrial machine using a hydraulic actuator.
[0002]
[Prior art]
FIG. 5 shows a mobile crane 1 in which an upper rotating body 3 is mounted on a lower traveling body 2 so as to be freely rotatable. The mobile crane 1 includes hydraulic devices such as a boom hoisting / lowering device 4, a hook rope hoisting / lowering device 5, an upper revolving unit turning device 6, and a lower traveling unit traveling device 7.
[0003]
FIG. 6 shows a vertical section of the revolving device 6. The rotation of the hydraulic motor 8 provided on the upper revolving unit 3 is reduced by the reduction mechanism 9 to rotate the pinion gear 10. The pinion gear 10 meshes with a ring gear 11 fixedly provided on the lower traveling body 2 side. The pinion gear 10 moves along the inner periphery of the ring gear 11 while rotating, whereby the upper revolving body 3 turns.
[0004]
FIG. 7 shows a hydraulic circuit for driving the hydraulic motor 8 of the turning device 6. A cam 13 is provided at a base end of the operation lever 12, and the cam 13 is pushed by a cam return spring 14 to move the operation lever 12. It is urged to return to the neutral position. Right and left pressure control valves 16L and 16R are provided below the cam 13 via a control spring 15, and the spool moves according to the operation amount of the operation lever 12 to move the left control pressure _PCL or the right control pressure. It outputs the _PCR and switches the direction control valve 17 to control the rotation direction and rotation speed of the hydraulic motor 8.
[0005]
As shown in FIGS. 8 and 9, the right and left of the pressure control valve 16L, 16R has a slight play zone around the neutral position, the control pressure P _C at that time is the tank pressure P _T. Control pressure _P CL of the left and right beyond the play area into the adjusting _{zone, P CR} is generated, the control pressure _{P C} changes from the initial pressure (cracking pressure) _{P S} up to the maximum pressure _{P M.} When the spring constant of the control spring 15 is higher than the design value, than the left control pressure P _CL indicated by the solid line, the slope of the straight line becomes steep as shown by two-dot chain line. On the other hand, the spring constant of the control spring 15 when lower than the design value, than the right control pressure P _CR indicated by the solid line, the slope of the straight line is gentle, as shown by the two-dot chain line.
[0006]
For example, as for the right pressure control valve 16R, if the operation lever 12 is tilted to the right and the cam 13 is operated, as shown in FIG. 9B, the initial pressure state (P _CR = P _S , P _{When CL} = P _T ), the spool 18 becomes the stroke L _S1 until the position where the port P communicates with the port P _CR , and the operation angle of the cam 13 becomes θ _R. By operating further cam 13 and tilted to the right operating lever 12, as shown in FIG. 9 (c), the maximum pressure conditions _{_{_{(P CR = P M, P}}} CL = P T) of the spool 18 and port P position unchanged 9 and (b), the control spring 15 by operating the cam 13 to the operating angle theta _RM becomes _{L M0} is compressed by _{L M1} minutes.
[0007]
[Problems to be solved by the invention]
As shown in FIG. 10, for example, when the right side of the pressure control valve 16R is neutral state, the pressing force F = 0 of the piston 19, a control pressure _{_P} C = _P _T. Assuming that the set load of the control spring 15 is F _S and the projected area of the spool 18 is A, the above-mentioned initial pressure P _S is obtained when the piston 19 is pushed by the pressing force F by the play length L _S1 . Is given by
[0008]
P _S = F _S / A (Generally, F _S ≦ F)
F _S is the theoretical value of the design, F _S when considering all the precision in manufacture will have a certain range. In fact by adjusting the thickness of the shim 20 is interposed along with the control spring 15, thus approximating a range of F _S to the theoretical value.
[0009]
Maximum pressure P _M that previously described is given by the following equation when pushed further strongly piston 19 of the right side of the pressure control valve 16R at the pressing force F. Here, K is a spring constant of the control spring 15.
[0010]
P _M = (F _S + K × L _M1 ) / A (Generally, F _S ≦ F)
Set load F _S of the control spring 15 is performance critical, to adjust the set load F _S by processing the control spring 15. On the other hand, the spring constant winding spring diameter, wire diameter, because it is determined by the number of turns, it is impossible manufacture to both the theoretical value of the design of the set load F _S and the spring constant K of the control spring 15 near. Moreover, because it is already set the initial pressure P _S in the adjustment shims 20 can not further adjust the maximum pressure P _M in shimming.
[0011]
FIG. 11 shows the measured characteristics of a certain pressure control valve. If the initial pressure is in the range of (−0 to +1.5) around 5.0, the initial pressure is within the reference value, and the maximum pressure is around 35 ( If the value falls within the range of −2 to +4), it is determined that the value is within the reference value. As shown, the initial pressure _{P S} is within the reference value substantially the same as the left 6.0, right 5.5, the maximum pressure _{P M} is left 31.5 not reach the right 29.5 and the reference value Since the pressure is low, the operator feels insufficient power and is difficult to use. On the other hand, FIG. 12 shows the measured characteristics of the other pressure control valve, the initial pressure P _S is left 8.5, right 6.5 and left too high. Further, the maximum pressure P _M is good within the right 38.5 and the reference value left 41.5 becomes a reference value over, since there is a large difference in the maximum pressure in the left and right, the discomfort of the operation in the right and left to the operator Therefore, the solution is to provide a hydraulic pressure control valve in which the initial pressure of the pressure control valve is accurately adjusted, and the maximum pressure is also close to the theoretical value, thereby eliminating the uncomfortable feeling of operability due to manufacturing errors. A technical problem to be solved arises, and an object of the present invention is to solve this problem.
[0012]
[Means for Solving the Problems]
The present invention has been proposed to achieve the above object, and a pressure control valve formed so that a piston is pressed by a cam provided at a base end of an operation lever to move a spool, and the pressure control valve A sleeve was provided on the outside of the spool, and the sleeve was urged in the pressing direction of the piston by an adjusting spring, so that the spring constant of the adjusting spring and the thickness of the shim interposed in the adjusting spring could be changed. A hydraulic pressure control valve configured in combination with a pressure adjustment valve, and formed so that the initial pressure and the maximum pressure can be individually adjusted;
It is another object of the present invention to provide a hydraulic pressure control valve having a pressure inflection point on the way from the initial pressure to the maximum pressure.
[0013]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an embodiment of the present invention will be described in detail with reference to FIGS. For convenience of explanation, the same components as those of the conventional art are denoted by the same reference numerals, and description thereof will be omitted. FIG. 1 shows a right side portion 26R of a hydraulic pressure control valve 26 according to the present invention, in which a cylindrical cover 31 whose lower part is opened is fixed to a piston 29, and a cam return spring 24 is interposed in the cover 31 to form a cam. By pushing back 13 upward, the operating lever 12 is urged to return to the neutral position. A control spring 25 is set between the piston 29 and the spool 28, and a shim 30 is interposed between the control spring 25 and the spool 28.
[0014]
Here, as shown in FIG. 1A, the hydraulic pressure control valve 26 of the present invention has a sleeve 32 slidably fitted to the outside of the spool 28, and the sleeve 32 is pressed by the adjustment spring 33 against the piston 29. Energize in the direction. Further, a shim 34 is interposed in the adjusting spring 33 so that the spring constant of the adjusting spring 33 and the thickness of the shim 34 can be changed as described later. That is, the sleeve 32, the adjusting spring 33, and the shim 34 constitute a pressure adjusting valve capable of adjusting a pressure change of the pressure control valve.
[0015]
As shown in FIGS. 1B and 2, if the operation lever 12 is tilted to the right to operate the cam 13, in the initial pressure state (P _C = P _S ), the spool 28 becomes the port P and the port P _C. The stroke L _S1 up to the position where the communication is established, and the operation angle of the cam 13 becomes θ _R. If the operation lever 12 is further tilted to the right to operate the cam 13, as shown in FIG. 1C, the position of the spool 28 and the port P at the pressure deflection point (P _C = P _SH ) is as shown in FIG. b) the unchanged, up to this point the pressure P _C is determined by the thickness of the spring constant and shim 30 of the control spring 25.
[0016]
When the cam 13 is further operated to the operation angle θ _RM after passing this pressure inflection point, as shown in FIG. 1D, a maximum pressure state (P _C = P _M ) is reached, and the sleeve 32 is adjusted. 33 starts to move upward in the figure while compressing it. Thus, phase shift with respect to the P port and T port of the spool 32, the pressure change is a maximum pressure P _M becomes steeper.
[0017]
As shown in FIG. 3, when the right side of the pressure control valve 26R is neutral state, the pressing force F = 0 of the piston 29, a control pressure _{_P} C = _P _T. Then, the set load F _S of the control spring _25, if the projected area of the spool 28 is A, as described in the prior art, initial pressure P _S is the length of the play of the piston 19 in the pressing force F L It is given by the following equation when the button is pushed in by _S1 .
[0018]
P _S = F _S / A (Generally, F _S ≦ F)
F _S is the theoretical value of the design, F _S when considering all the precision in manufacture will have a certain range. In fact by adjusting the thickness of the shim 30 which is interposed along with the control spring 25, thus approximating a range of F _S to the theoretical value.
[0019]
Here, assuming that the set load of the adjustment spring 33 is F _P and the projected area of the outer diameter of the sleeve 32 is A _P , the pressure P _SH at the pressure inflection point described above is such that the cam 13 is operated by the operation angle θ _RH. that amount P _C pressure is increased, when the sleeve 32 is going Ugokidaso [rho _C min Te,
_{_{_{P SH = F P / (A}}} P -A)
The maximum pressure P _M is given by the following equation. However, the spring constant of _{K P} is the adjustment spring 33.
[0020]
_{_{P M = [F S + {}} K × (L M1 -ρ C)}] / A
_{_{_{ρ C = {P C × (}}} A P -A)} / K P
The maximum time the pressure P _M is higher than the design theory reduces the spring force by thickening the shim 34. In contrast, as shown by the dotted line in FIG. 2, when the maximum pressure P _M is lower than the theoretical design value, to increase the spring force by reducing the shim 34. Thus, it related to the initial pressure P _S no, it is possible to adjust the maximum pressure P _M by providing the pressure inflection point.
[0021]
Figure 4 shows the measured characteristics of a hydraulic pressure control valve, the initial pressure P _S left 6.2, it is within the reference value substantially the same as the right 5.5. Although the initial pressure on the left and right is slightly more variable than that of the conventional example shown in FIG. 11, the bias force is adjusted by adjusting the spring force of the adjusting spring 33 by changing the thickness of the shim 34 and controlling the movement of the sleeve 32. change the pressure changes at the inflection point after the maximum pressure left 31.5 in the prior art _{P M} is 11, what was less right 29.5 and the reference value, the left 36.5 in FIG. 4, right 33.4 and both pressures can be within reference values.
[0022]
The present invention can be variously modified without departing from the spirit of the present invention, and it goes without saying that the present invention extends to the modified ones.
[0023]
【The invention's effect】
As described in detail in the above embodiment, the invention according to claim 1 constitutes a pressure control valve in which a sleeve is provided outside the spool of the pressure control valve so that the adjustment spring and the shim can be changed. Therefore, the initial pressure is set by adjusting the movement of the spool of the pressure control valve, and the maximum pressure is set by adjusting the movement of the sleeve of the pressure control valve. In other words, the maximum pressure can be adjusted irrespective of the adjustment of the initial pressure, and the difference between the left and right pressures is reduced as much as possible, so that the initial pressure is accurately adjusted and the maximum pressure is also close to the theoretical value. It is possible to provide a hydraulic pressure control valve that eliminates an uncomfortable feeling of operability due to an error.
[0024]
According to the second aspect of the present invention, the pressure inflection point is provided on the way from the initial pressure to the maximum pressure. Pressure difference can be eliminated.
[Brief description of the drawings]
FIG. 1 shows an embodiment of the present invention, and (a) to (d) are longitudinal sectional views showing changes in the operating state of a hydraulic pressure control valve.
FIG. 2 is a graph showing an embodiment of the present invention and showing a relationship between a cam operation angle of an operation lever and a pressure change of a hydraulic pressure control valve.
FIG. 3 is a longitudinal sectional view showing an embodiment of the present invention and showing a relationship between pressures of a hydraulic pressure control valve.
FIG. 4 is a graph showing an embodiment of the present invention and showing measured characteristics of a certain hydraulic pressure control valve.
FIG. 5 is a side view showing a general mobile crane.
FIG. 6 is a longitudinal sectional view showing a turning device of the mobile crane.
FIG. 7 is a hydraulic circuit diagram of the turning device.
FIG. 8 is a graph showing a prior art, and showing a relationship between a cam operation angle of an operation lever and a pressure change of a pressure control valve.
FIGS. 9A to 9C are vertical cross-sectional views showing a conventional technique, and FIGS.
FIG. 10 is a longitudinal sectional view showing the prior art and showing the relationship between the pressures of the pressure control valves.
FIG. 11 is a graph showing a conventional technique and showing measured characteristics of a certain pressure control valve.
FIG. 12 is a graph showing a conventional technique, and showing measured characteristics of another pressure control valve.
[Explanation of symbols]
12 Operating lever 13 Cam 25 Control spring 26 Hydraulic pressure control valve 28 Spool 29 Piston 30 Shim 32 Sleeve 33 Adjustment spring 34 Shim

Claims

A pressure control valve formed so that a piston is pressed by a cam provided at a base end of an operation lever to move a spool, and a sleeve is provided outside the spool of the pressure control valve, and the sleeve is adjusted by an adjusting spring. It is constituted by combining a pressure adjusting valve formed to be capable of changing the spring constant of the adjusting spring and the thickness of the shim interposed in the adjusting spring, and urges the initial pressure and the maximum pressure. A hydraulic control valve characterized in that it is individually adjustable.

2. The hydraulic pressure control valve according to claim 1, wherein a pressure inflection point is provided on the way from the initial pressure to the maximum pressure.