JP4018208B2

JP4018208B2 - Pilot operated relief valve

Info

Publication number: JP4018208B2
Application number: JP27944997A
Authority: JP
Inventors: 優杉山; 昌廣藤坂
Original assignee: Toyooki Kogyo Co Ltd
Current assignee: Toyooki Kogyo Co Ltd
Priority date: 1997-09-25
Filing date: 1997-09-25
Publication date: 2007-12-05
Anticipated expiration: 2017-09-25
Also published as: JPH1194106A

Description

【０００１】
【発明の属する技術分野】
本発明は、液圧回路に設置するパイロット操作式リリーフ弁に関する。
【０００２】
【従来の技術】
このようなパイロット操作式リリーフ弁は、例えば実公昭５４−４３３８５号公報に記載されるようによく知られている。そして、このようなリリーフ弁は、これが接続される液圧回路での圧力が上昇しパイロット弁の開き圧力に達すると、パイロット弁が開いてパイロット通路からタンク側へ主弁の背圧室を通じさせ、これに応じ主弁が開かれて前記液圧回路の圧液をタンク側へ逃がす。このため液圧回路の圧力上昇がおさえられ、該液圧回路の最大圧力は、前記パイロット弁の開き圧力より若干高い程度の所定の圧力に制限される。
【０００３】
【発明が解決しようとする課題】
しかしながらこのようなリリーフ弁では、パイロット弁の入口部に、異物が詰まってパイロット弁が開かなくなる可能性がある。このようにパイロット弁が開かなくなると、主弁が開かないので液圧回路の圧力が安全限度を越えて上昇し、液圧回路におけるアクチュエータや配管部分などの破壊を招いたり、また、これに伴って人身事故を招くおそれがある。本発明は、パイロット弁が作動しない場合のこのような安全限度を越える圧力上昇を抑えるとともに、リリーフ弁が良好に作動しない異常状態が生じたことがわかるようになったパイロット操作式リリーフ弁を実現するものである。
【０００４】
【課題を解決するための手段】
このため、本発明では、主弁の背圧室をタンク側へ通じさせるパイロット通路に、主弁を開作動させるため所定の開き圧力で開作動するパイロット弁を設けたパイロット操作式リリーフ弁であって、パイロット弁を迂回して主弁の背圧室をタンク側へ通じさせる安全通路を設け、安全通路には当該通路を閉止するよう閉止栓を圧入して取り付け、閉止栓は主弁の背圧室側からの圧力作用に基づき押し動かされて安全通路を開通して設け、安全通路の開通がパイロット弁の開き圧力よりも高い圧力でなされるように閉止栓の安全通路への圧入条件を選定した。この場合、パイロット弁を迂回して主弁の背圧室をタンク側へ通じさせる安全通路を設け、安全通路には当該通路を閉止するよう閉止栓を設置し、閉止栓は主弁の背圧室側からの圧力作用に基づき破断されて安全通路を開通して設け、安全通路の開通がパイロット弁の開き圧力よりも高い圧力でなされるように閉止栓の破断個所の溝の深さを選定しても良い。
【０００５】
このような構成によると、パイロット弁が開かなくて主弁が開かない異常状態の際、圧力が上昇すると、閉止栓が押し動かされ又は破断されてパイロット弁を迂回する安全通路が開通し背圧室がタンク側へ通じられるので主弁が開く。このため閉止栓の押し動かし又は破断がパイロット弁の開き圧力よりは高いが、液圧回路の安全限度を越えない範囲の圧力で行われるよう閉止栓の安全通路への圧入条件又は閉止栓の形状を選定することにより、閉止栓は、パイロット弁が正常に作動するときには押し動かされず又は破断されず通常のリリーフ弁作動が行われ、パイロット弁が開かなくなった前記異常状態の際に圧力上昇に伴い押し動かされ又は破断されて主弁を開き、液圧回路でその安全限度を越えて圧力が上昇することを抑えることができる。
【０００６】
そして安全通路は閉止栓が一旦押し動かされ又は破断されると開通状態となるので、液圧回路の圧力が低下しても主弁は液圧回路から圧液を逃がすように開くことができて安全通路が開通した後は液圧回路の圧力が上がらず、このため、例えば液圧回路に接続されるアクチュエータが作動しなくなるなどで、異常な状態が生じたことが判る。
【０００７】
【発明の実施の形態】
以下、本発明の一実施形態を図面により説明する。図１、図２において、１は主本体で、図示しない液圧回路に接続する入口通路２と、図示しないタンクに接続する逃がし通路３を有している。４は主弁５が着座する主弁座である。そして主弁５は、弁孔６に摺動自在に収容され、主弁座４に着座して入口通路２と逃がし通路３間を遮断し、主弁座４から離座して入口通路２と逃がし通路３間を通じさせるよう、軸方向移動により主弁座４を開閉する。７は、主本体１の上部に、その弁孔６の開口を閉じる如く、着脱可能に取り付けられたパイロット本体である。
【０００８】
主弁５とパイロット本体７の間には、主弁５のための背圧室８が形成されている。そして主弁５は、背圧室８に設置したばね９のばね力と絞り１０を経て入口通路２に通じた背圧室８の圧力の作用によって主弁座４への着座方向に押圧されるとともに、入口通路２の圧力の作用で主弁座４から離座する方向へ押圧されるようになっている。
【０００９】
１１はパイロット本体７に設けた弁孔で、その一端側は栓１２で閉じ、また中央には入口孔１４とそれに続いてパイロット弁座１５を形成した栓体１３が設置され、他端側にはばね受け１６が摺動自在に嵌合している。そして弁孔１１での栓体１３の一端側に導入室１７が、また、栓体１３の他端側に排出室１８が、それぞれ形成されている。１９は背圧室８と導入室１７を通じさせるようパイロット本体７に設けた通孔で、２０、２１は、排出室１８を逃がし通路３に通じさせるようパイロット本体７と主本体１にそれぞれ設けた通孔である。
【００１０】
２２はパイロット弁で、排出室１８側からパイロット弁座１５に着座するよう、ばね受け１６との間に設置した調圧ばね２３のばね力で押圧されている。このパイロット弁２２は、着座状態で入口孔１４を介する導入室１７と排出室１８の連通を断ち、入口孔１４を経て該弁２２に作用する導入室１７からの圧力が調圧ばね２３のばね力による開き圧力以上となって前記ばね力に打ち勝ちパイロット弁座１５から離座させられると入口孔１４を介し導入室１７と排出室１８を通じさせるように、該圧力に応じパイロット弁座１５を開閉する。そして、通孔１９、導入室１７、入口孔１４、排出室１８、通孔２０、２１は、このようなパイロット弁２２を介在させた、一連のパイロット通路２４を形成する。なお、２５は、回動調整によりばね受け１６を軸方向へ進退させて調圧ばね２３のばね力を変化させ、前記開き圧力を調整する調整ねじであり、２６はそのロックナットである。
【００１１】
２７は安全通路となる通孔で、２８は該通孔２７を閉止する閉止栓である。すなわち、図２を参照して、パイロット本体７には通孔２０に交差して設置孔２９が形成され、一端が通孔１９に通じた通孔２７の他端がこの設置孔２９の内端壁に開口している。閉止栓２８は、大径部２８Ａとその内側の小径部２８Ｂを備えている。そして閉止栓２８は、小径部２８Ｂ先端が前記内端壁に当接し通孔２７の開口を閉じるよう、大径部２８Ａを設置孔２９へ圧入して取り付けられている。閉止栓２８は通孔２７の圧力が先端に作用することで外方へと押圧されるが、この圧力が、パイロット弁２２の開き圧力より高く、かつ、液圧回路に接続される図示しないアクチュエータや配管など、液圧回路各部の破壊を招く安全限度を越えない範囲の所定の圧力に達するまでは、前記通孔２７の開口を閉じる取り付け状態が維持され、この圧力が、この所定の圧力に達すると、前記通孔２７の開口を閉じる取り付け状態が維持されなくなり閉止栓２８が外方へ押し動かされて通孔２７の開口の閉止作用が行われず通孔２７が開通するよう、大径部２８Ａの径や幅、設置孔２９の径などの圧入条件が選定されて取り付けられている。なお、３０は、設置孔を塞ぐ栓である。
【００１２】
この実施形態の作動を説明する。パイロット弁２２が正常に作動するときには、入口通路２が接続する液圧回路の圧力がパイロット弁２２の開き圧力を越えて上昇すると、パイロット弁２２が開き、これにより、背圧室８からパイロット通路２４を通って逃がし通路３への流出が生じ、背圧室８へは絞り１０を経て入口通路２からの流入があるが、絞り１０の抵抗を受けて背圧室８の圧力が入口通路２よりも低下し、この圧力差に基づく押圧力で主弁８は主弁座４から離座し、開作動して、入口通路２からの圧液を逃がし通路３へ逃がす。これにより、入口通路２が接続される液圧回路の圧力は、パイロット弁２２の開き圧力より若干高い圧力に制限される。そして、入口通路２が接続する液圧回路の圧力がパイロット弁２２の開き圧力より低下すると、パイロット弁２２が閉じて、前記パイロット通路２４への流出が止み、背圧室８と入口通路２との圧力差がなくなって主弁５は、ばね９により図示の着座状態に復帰する。このような作動によって、液圧回路の最大圧力は、パイロット弁２２の開き圧力より若干高い圧力に制限される。
【００１３】
ところが、液圧回路の保守が良好でないなどの理由で作動液中の混入異物が多くて、この異物がパイロット弁２２における入口孔１４に詰まり、入口孔１４を塞いでしまうと、入口通路２が接続する液圧回路の圧力がパイロット弁２２の開き圧力を越えて上昇してもパイロット弁２２が開かず、主弁５も開作動しない。このため、液圧回路の圧力は、さらに上昇する。しかしこれが、前記所定の圧力に達すると、閉止栓２８が外方へと押し動かされて、通孔２７の、設置孔２９内端壁における開口が大きく開かれ、通孔２７が開通する。
【００１４】
このため、背圧室８からは通孔２７によりパイロット弁２２を迂回して通孔２０への流出が生じるので、前記同様に主弁５が開作動し、入口通路２から逃がし通路３へ圧液が逃がされて液圧回路の圧力は低下し、安全限度を越えて液圧回路の圧力が上昇することが抑えられ、液圧回路各部の破壊を招く事態は生じない。
【００１５】
そして、閉止栓２８は外方へ押し動かされた結果、正常時の小径部２８Ｂ先端で通孔２７の開口を閉止している取り付け状態が損壊され、通孔２７の開口は開いたままで通孔２７は開通したままとなる。従って、一旦閉止栓２８が外方へ押し動かされると、背圧室８からは通孔２７により常時通孔２０への流出が生じ、主弁５は入口通路２から逃がし通路３へ圧液を逃がすよう開作動できて液圧回路に高い圧力が生じなくなる。
【００１６】
このため、液圧回路に接続されたアクチュエータは作動しなくなり、異常な事態が生じたことが容易に判別できる。そして、このこのような閉止栓２８を用いる代わりに、パイロット弁２２に並列に、該弁２２より開き圧力を高くした別のパイロット弁を設置して、パイロット弁２２の入口孔１４が塞がれたとき、この他のパイロット弁に基づき、液圧回路の圧力を安全限度以内に制限することも考えられるが、この場合には、この別のパイロット弁も同様の作動不良を起こす可能性があり、また、たとえこのようなことがなかったとしても、パイロット弁２２が正常に開作動しないという異常な事態の発生を見過ごさせてしまう。例えば、パイロット弁２２の作動不良を招く程の作動液の汚染は、液圧回路に接続される他の機器にも、早晩故障を誘発するなどの悪影響を与えると見られるものであるが、このような事態が見過ごされるのである。これに対し本実施形態によると、一旦通孔２７が開かれると、液圧回路に高い圧力が生じなくなるので、異常な事態の発生が容易に判別でき、作動液の洗浄や交換、液圧回路における他の機器の洗浄、点検などの適正な保守作業を行うきっかけを得ることができる。
【００１７】
そして、このように損壊した閉止栓２８の取り替えは、パイロット本体７を、小径部２８Ｂ先端で通孔２７の開口を閉止した正規の取り付け状態にある閉止栓２８を有した別のパイロット本体と置き換えることによって行われる。
【００１８】
図３、図４は閉止栓のそれぞれ別の実施形態を示し、図１、図２のものと同じ部分には同符号を付して、図１、図２のものとの相違点を説明する。図３のものでは、閉止栓２８が板状である。そして、背圧室８に開口するようパイロット本体７に形成した内側が小径となる段付き状の孔３１と、この孔３１の小径部分を通孔２０に通じさせる通孔３２により安全通路が形成されている。閉止栓２８は、孔３１の開口側に螺着した押しリング３３により孔３１の段部３１Ａに当接して通孔２０側への流通を阻止するよう設置され、その両側の面には環状溝２８Ｃが形成されている。なお、この環状溝２８Ｃはどちらか一方の面に設けるのみでもよい。３４はシールリングである。そして、背圧室８側から前記所定の圧力が作用すると閉止栓２８は環状溝２８Ｃの位置で破断して損壊されるように、環状溝２８Ｃは、その深さが選定されている。
【００１９】
図４のものでは、背圧室８に開口するようパイロット本体７に形成した孔３１と、この孔３１の内端側を通孔２０に通じさせる通孔３２により安全通路が形成されており、つば２８Ｄを孔３１の開口側に有した閉止栓２８が孔３１に圧入されて通孔２０側への流通を阻止するように設置され、閉止栓２８の孔３１内端側は孔３１内周より径が小さい小径部２８Ｅとなっている。そして閉止栓２８にはその背圧室８側端面から小径部２８Ｅに達する深さの凹部２８Ｆが形成されており、さらに、小径部２８Ｅ外周には環状溝２８Ｃが形成され、前記所定の圧力が作用すると閉止栓２８は環状溝２８Ｃの位置で破断して損壊されるように、環状溝２８Ｃは、その深さが選定されている。
【００２０】
これら図３、図４のものにおいては、パイロット弁が開かず、主弁による逃がし作用が行われない結果液圧回路の圧力が上昇してこれが所定の圧力に達すると、閉止栓２８が環状溝２８Ｃの位置で破断する。これにより、孔３１が開通し、背圧室８から孔３１、通孔３２を経た通孔２０への流通が生じ主弁が開作動して、液圧回路の圧力は低下し、安全限度を越えて液圧回路の圧力が上昇することが抑えられるとともに、閉止栓２８が一旦破断により損壊すると通孔３１は開通状態を保ち、背圧室８から孔３１、通孔３２を経て通孔２０へ流通したままとなるので主弁は液圧回路からの圧液を逃がすよう開作動できて液圧回路に高い圧力が生じなくなり、異常な事態が生じたことが容易に判別できるなど、図１、図２のものと同様な効果が得られる。
【００２１】
なお、破断した閉止栓２８の取り替えは、図３のものでは、パイロット本体７での破断した閉止栓２８を、破断していない新たな閉止栓と交換することで行い、また、図４のものでは、パイロット本体７を、破断していない閉止栓が設置されているものと交換することで行う。
【００２２】
【発明の効果】
このように本発明によると、パイロット弁が開かなくなった異常状態の際に圧力上昇に伴い閉止栓が押し動かされ又は破断され安全通路が開通して主弁が開くので、液圧回路でその安全限度を越えて圧力が上昇することを抑えることができ、液圧回路各部の破壊やこれに伴う人身事故の発生を防止できる。そして閉止栓が一旦押し動かされ又は破断されると安全通路は開通したままとなるので主弁は液圧回路から圧液を逃がすように開くことができ閉止栓が押し動かされ又は破断された後は液圧回路の圧力が上がらず、このため、異常な状態が生じたことが判別でき、適正な保守作業を行うきっかけを与えることができる。
【図面の簡単な説明】
【図１】本発明の一実施形態を示した縦断面図。
【図２】図１の要部拡大図。
【図３】閉止栓の別実施形態を示す図２と同様な図。
【図４】閉止栓のさらに別実施形態を示す図２と同様な図。
【符号の説明】
５主弁
８背圧室
２２パイロット弁
２４パイロット通路
２８閉止栓
２７、３１、３２安全通路[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a pilot operated relief valve installed in a hydraulic circuit.
[0002]
[Prior art]
Such a pilot operated relief valve is well known as described in, for example, Japanese Utility Model Publication No. 54-43385. Such a relief valve, when the pressure in the hydraulic circuit to which it is connected rises and reaches the opening pressure of the pilot valve, the pilot valve opens and passes the back pressure chamber of the main valve from the pilot passage to the tank side. In response to this, the main valve is opened to release the hydraulic fluid from the hydraulic circuit to the tank side. For this reason, the pressure rise of the hydraulic circuit is suppressed, and the maximum pressure of the hydraulic circuit is limited to a predetermined pressure that is slightly higher than the opening pressure of the pilot valve.
[0003]
[Problems to be solved by the invention]
However, in such a relief valve, there is a possibility that the pilot valve cannot be opened due to clogging of foreign matter at the inlet of the pilot valve. If the pilot valve does not open in this way, the main valve will not open, and the pressure in the hydraulic circuit will rise beyond the safe limit, causing damage to the actuator and piping in the hydraulic circuit. May cause personal injury. The present invention realizes a pilot-operated relief valve that suppresses the pressure rise exceeding the safety limit when the pilot valve does not operate, and that an abnormal state in which the relief valve does not operate well has occurred. To do.
[0004]
[Means for Solving the Problems]
Therefore, the present invention provides a pilot operated relief valve in which a pilot valve that opens at a predetermined opening pressure is provided in a pilot passage that allows the back pressure chamber of the main valve to communicate with the tank. Thus, a safety passage that bypasses the pilot valve and connects the back pressure chamber of the main valve to the tank side is provided, and a stopper plug is press-fitted and attached to the safety passage so as to close the passage. It is pushed and moved based on the pressure action from the pressure chamber side to open the safety passage, and the conditions for press-fitting the stopcock into the safety passage are set so that the safety passage is opened at a pressure higher than the opening pressure of the pilot valve. Selected. In this case, a safety passage that bypasses the pilot valve and connects the back pressure chamber of the main valve to the tank side is provided, and a closing plug is installed in the safety passage to close the passage, and the closing plug is the back pressure of the main valve. The depth of the groove at the breakage point of the closure plug is selected so that the safety passage is opened by a pressure higher than the opening pressure of the pilot valve. You may do it.
[0005]
According to such a configuration, in the abnormal state where the pilot valve does not open and the main valve does not open, when the pressure rises, the safety plug that bypasses the pilot valve is opened by opening or closing the stopper plug, and the back pressure is opened. since the room is Ru are through to the tank side of the main valve is opened. For this reason , the conditions for press-fitting into the safety passage of the closing plug or the shape of the closing plug so that the pushing or breaking of the closing plug is higher than the opening pressure of the pilot valve but does not exceed the safety limit of the hydraulic circuit. When the pilot valve is normally operated, the closure plug is not pushed or broken , and the normal relief valve operation is performed. It can be pushed or broken to open the main valve, and the hydraulic circuit can prevent the pressure from rising beyond its safe limit.
[0006]
And since the safety passage becomes open state and a closed plug Ru is once pushed wheeled or breaking, is the main valve also decreases the pressure in the hydraulic circuit and can be opened from the hydraulic circuit so as to release the liquid After the safety passage is opened, the pressure in the hydraulic circuit does not increase, and therefore it can be seen that an abnormal condition has occurred, for example, the actuator connected to the hydraulic circuit stops operating.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to the drawings. 1 and 2, reference numeral 1 denotes a main body having an inlet passage 2 connected to a hydraulic circuit (not shown) and an escape passage 3 connected to a tank (not shown). Reference numeral 4 denotes a main valve seat on which the main valve 5 is seated. The main valve 5 is slidably accommodated in the valve hole 6 and is seated on the main valve seat 4 to block between the inlet passage 2 and the escape passage 3, and is separated from the main valve seat 4 to be separated from the inlet passage 2. The main valve seat 4 is opened and closed by axial movement so as to pass between the escape passages 3. A pilot body 7 is detachably attached to the upper part of the main body 1 so as to close the opening of the valve hole 6.
[0008]
A back pressure chamber 8 for the main valve 5 is formed between the main valve 5 and the pilot body 7. The main valve 5 is pressed in the seating direction on the main valve seat 4 by the action of the spring force of the spring 9 installed in the back pressure chamber 8 and the pressure of the back pressure chamber 8 that passes through the throttle 10 and the inlet passage 2. At the same time, the pressure of the inlet passage 2 is pressed in the direction away from the main valve seat 4.
[0009]
11 is a valve hole provided in the pilot main body 7, one end of which is closed with a plug 12, and a plug body 13 having an inlet hole 14 followed by a pilot valve seat 15 is installed at the center, and the other end is provided with a plug body 13. The spring receiver 16 is slidably fitted. An introduction chamber 17 is formed on one end side of the plug body 13 in the valve hole 11, and a discharge chamber 18 is formed on the other end side of the plug body 13. 19 is a through hole provided in the pilot main body 7 so as to allow the back pressure chamber 8 and the introduction chamber 17 to pass, and 20 and 21 are provided in the pilot main body 7 and the main main body 1 so as to allow the discharge chamber 18 to escape and communicate with the passage 3. It is a through hole.
[0010]
A pilot valve 22 is pressed by a spring force of a pressure adjusting spring 23 provided between the spring receiver 16 and the pilot valve seat 15 so as to be seated on the pilot valve seat 15 from the discharge chamber 18 side. In the seated state, the pilot valve 22 cuts off the communication between the introduction chamber 17 and the discharge chamber 18 via the inlet hole 14, and the pressure from the introduction chamber 17 acting on the valve 22 via the inlet hole 14 is the spring of the pressure regulating spring 23. The pilot valve seat 15 is opened and closed according to the pressure so that when the spring force is overcome and the spring force is overcome and the pilot valve seat 15 is separated from the pilot valve seat 15, the inlet chamber 17 and the discharge chamber 18 are passed through the inlet hole 14. To do. The through hole 19, the introduction chamber 17, the inlet hole 14, the discharge chamber 18, and the through holes 20, 21 form a series of pilot passages 24 with the pilot valve 22 interposed therebetween. Reference numeral 25 denotes an adjusting screw that adjusts the opening pressure by moving the spring receiver 16 forward and backward in the axial direction by changing the rotation to change the spring force of the pressure adjusting spring 23, and 26 is a lock nut thereof.
[0011]
Reference numeral 27 denotes a through hole serving as a safety passage, and reference numeral 28 denotes a closing plug for closing the through hole 27. That is, referring to FIG. 2, an installation hole 29 is formed in the pilot body 7 so as to intersect the through hole 20, and the other end of the through hole 27 having one end communicating with the through hole 19 is the inner end of the installation hole 29. Open to the wall. The stopper plug 28 includes a large-diameter portion 28A and a small-diameter portion 28B inside thereof. The stopper plug 28 is attached by pressing the large-diameter portion 28A into the installation hole 29 so that the tip of the small-diameter portion 28B contacts the inner end wall and closes the opening of the through hole 27. The stopper plug 28 is pressed outward by the pressure of the through hole 27 acting on the tip. This pressure is higher than the opening pressure of the pilot valve 22 and is connected to a hydraulic circuit (not shown). Until the pressure reaches a predetermined pressure within a range that does not exceed the safety limit that causes destruction of each part of the hydraulic circuit such as pipes and pipes, the attachment state in which the opening of the through hole 27 is closed is maintained. When it reaches, the large diameter portion is such that the attachment state for closing the opening of the through hole 27 is not maintained and the closing plug 28 is pushed outward so that the opening of the through hole 27 is not closed and the through hole 27 is opened. The press-fitting conditions such as the diameter and width of 28A and the diameter of the installation hole 29 are selected and attached. Reference numeral 30 denotes a plug that closes the installation hole.
[0012]
The operation of this embodiment will be described. When the pilot valve 22 operates normally, when the pressure of the hydraulic circuit connected to the inlet passage 2 rises above the opening pressure of the pilot valve 22, the pilot valve 22 is opened. 24 flows out to the escape passage 3 and flows into the back pressure chamber 8 from the inlet passage 2 through the restrictor 10, but the pressure in the back pressure chamber 8 is reduced by the resistance of the restrictor 10. The main valve 8 is separated from the main valve seat 4 by the pressing force based on this pressure difference, and is opened to release the pressurized liquid from the inlet passage 2 to the passage 3. Thereby, the pressure of the hydraulic circuit to which the inlet passage 2 is connected is limited to a pressure slightly higher than the opening pressure of the pilot valve 22. When the pressure of the hydraulic circuit connected to the inlet passage 2 falls below the opening pressure of the pilot valve 22, the pilot valve 22 is closed and the outflow to the pilot passage 24 stops, and the back pressure chamber 8, the inlet passage 2, The main valve 5 returns to the illustrated seated state by the spring 9. By such an operation, the maximum pressure of the hydraulic circuit is limited to a pressure slightly higher than the opening pressure of the pilot valve 22.
[0013]
However, if there is a large amount of foreign matter in the hydraulic fluid due to reasons such as poor maintenance of the hydraulic circuit, and this foreign matter clogs the inlet hole 14 in the pilot valve 22 and closes the inlet hole 14, the inlet passage 2 Even if the pressure of the connected hydraulic circuit rises above the opening pressure of the pilot valve 22, the pilot valve 22 does not open and the main valve 5 does not open. For this reason, the pressure of the hydraulic circuit further increases. However, when this reaches the predetermined pressure, the stopper plug 28 is pushed outward, the opening of the through hole 27 in the inner end wall of the installation hole 29 is opened widely, and the through hole 27 is opened.
[0014]
For this reason, the pilot valve 22 is bypassed by the through hole 27 from the back pressure chamber 8 and flows out to the through hole 20, so that the main valve 5 is opened and released from the inlet passage 2 to the escape passage 3 as described above. The liquid is released and the pressure of the hydraulic circuit is lowered, and the increase of the pressure of the hydraulic circuit beyond the safety limit is suppressed, and there is no situation in which each part of the hydraulic circuit is destroyed.
[0015]
Then, as a result of the closing plug 28 being pushed outward, the attachment state in which the opening of the through hole 27 is closed at the tip of the small diameter portion 28B in the normal state is damaged, and the opening of the through hole 27 remains open. 27 remains open. Accordingly, once the closing plug 28 is pushed outward, the back pressure chamber 8 always flows out to the through hole 20 through the through hole 27, and the main valve 5 escapes from the inlet passage 2 and supplies the pressure liquid to the passage 3. It can be opened so that it escapes, and no high pressure is generated in the hydraulic circuit.
[0016]
For this reason, the actuator connected to the hydraulic circuit stops operating, and it can be easily determined that an abnormal situation has occurred. Instead of using such a closing plug 28, another pilot valve having an opening pressure higher than that of the valve 22 is installed in parallel with the pilot valve 22, and the inlet hole 14 of the pilot valve 22 is blocked. In this case, it may be possible to limit the pressure of the hydraulic circuit within the safe limit based on this other pilot valve, but in this case, this other pilot valve may cause the same malfunction. Even if this does not happen, the occurrence of an abnormal situation in which the pilot valve 22 does not normally open is overlooked. For example, the contamination of the hydraulic fluid to the extent that the pilot valve 22 malfunctions is expected to have an adverse effect on other devices connected to the hydraulic circuit, such as inducing an early or late failure. Such a situation is overlooked. On the other hand, according to the present embodiment, once the through hole 27 is opened, no high pressure is generated in the hydraulic circuit, so that an abnormal situation can be easily determined, and the hydraulic fluid can be cleaned and replaced. You can get a chance to perform proper maintenance work such as cleaning and inspection of other equipment.
[0017]
Then, the replacement of the damaged stopper plug 28 in this way replaces the pilot body 7 with another pilot body having the stopper plug 28 in a properly attached state in which the opening of the through hole 27 is closed at the tip of the small diameter portion 28B. Is done by.
[0018]
3 and 4 show different embodiments of the stopper plugs, the same parts as those in FIGS. 1 and 2 are denoted by the same reference numerals, and differences from those in FIGS. 1 and 2 will be described. . In the thing of FIG. 3, the closing plug 28 is plate shape. Then, a safety passage is formed by a stepped hole 31 formed in the pilot main body 7 so as to open into the back pressure chamber 8 and having a small inside diameter and a through hole 32 through which the small diameter portion of the hole 31 is communicated with the hole 20. Has been. The stopper plug 28 is installed so as to abut against the step portion 31A of the hole 31 by a push ring 33 screwed to the opening side of the hole 31 so as to prevent the flow to the through hole 20 side. 28C is formed. The annular groove 28C may be provided only on one of the surfaces. Reference numeral 34 denotes a seal ring. The depth of the annular groove 28C is selected so that when the predetermined pressure is applied from the back pressure chamber 8 side, the closing plug 28 is broken and broken at the position of the annular groove 28C.
[0019]
In FIG. 4, a safety passage is formed by a hole 31 formed in the pilot main body 7 so as to open to the back pressure chamber 8 and a through hole 32 communicating with the inner end side of the hole 31 to the through hole 20. A stopper plug 28 having a collar 28D on the opening side of the hole 31 is installed so as to be pressed into the hole 31 to prevent the flow to the through hole 20 side, and the inner end side of the hole 31 of the stopper plug 28 is the inner periphery of the hole 31. The smaller diameter portion 28E has a smaller diameter. A recess 28F having a depth reaching the small diameter portion 28E from the end surface on the back pressure chamber 8 side is formed in the closing plug 28. Further, an annular groove 28C is formed on the outer periphery of the small diameter portion 28E, and the predetermined pressure is applied. The depth of the annular groove 28C is selected so that the stopper plug 28 is broken and damaged at the position of the annular groove 28C when it is actuated.
[0020]
In these FIG. 3 and FIG. 4, when the pilot valve is not opened and the main valve is not released, the pressure of the hydraulic circuit rises and reaches a predetermined pressure. Break at 28C. As a result, the hole 31 is opened, the flow from the back pressure chamber 8 to the through hole 20 through the hole 31 and the through hole 32 is generated, the main valve is opened, the pressure of the hydraulic circuit is lowered, and the safety limit is reached. The pressure in the hydraulic circuit is prevented from rising and the closure plug 28 is damaged due to breakage, and the through hole 31 is kept open, and the through hole 20 passes from the back pressure chamber 8 through the hole 31 and the through hole 32. 1 so that the main valve can be opened to release the pressure fluid from the hydraulic circuit so that no high pressure is generated in the hydraulic circuit, and it is possible to easily determine that an abnormal situation has occurred. The same effect as that of FIG. 2 can be obtained.
[0021]
In FIG. 3, the broken stopper plug 28 is replaced by replacing the broken stopper plug 28 in the pilot body 7 with a new stopper plug that has not been broken. Then, the pilot main body 7 is replaced by replacing it with one that is not broken.
[0022]
【The invention's effect】
As described above, according to the present invention, in the abnormal state in which the pilot valve cannot be opened, the stopper plug is pushed or broken as the pressure rises, and the safety passage is opened and the main valve is opened. It is possible to suppress the pressure from rising beyond the limit, and it is possible to prevent the destruction of each part of the hydraulic circuit and the occurrence of personal injury associated therewith. Then after closing plug main valve which is moved push closure plug can be opened so as to release the liquid or breakage of the hydraulic circuit because once pressed wheeled or broken by Ru the safety passage and remains opened Since the pressure of the hydraulic circuit does not increase, it can be determined that an abnormal state has occurred, and an opportunity to perform appropriate maintenance work can be given.
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional view showing an embodiment of the present invention.
FIG. 2 is an enlarged view of a main part of FIG.
FIG. 3 is a view similar to FIG. 2 showing another embodiment of the closing plug.
FIG. 4 is a view similar to FIG. 2 showing still another embodiment of a closure plug.
[Explanation of symbols]
5 Main valve 8 Back pressure chamber 22 Pilot valve 24 Pilot passage 28 Closure stoppers 27, 31, 32 Safety passage

Claims

A pilot-operated relief valve that is provided with a pilot valve that opens at a specified opening pressure in order to open the main valve in the pilot passage that connects the back pressure chamber of the main valve to the tank side, bypassing the pilot valve A safety passage that connects the back pressure chamber of the main valve to the tank side is installed, and a stopper plug is press-fitted into the safety passage so that the passage is closed. A pilot operated relief valve that is pushed and moved to open the safety passage, and that the conditions for press-fitting the safety plug into the safety passage are selected so that the safety passage is opened at a pressure higher than the opening pressure of the pilot valve. .

A pilot-operated relief valve that is provided with a pilot valve that opens at a specified opening pressure in order to open the main valve in the pilot passage that connects the back pressure chamber of the main valve to the tank side, bypassing the pilot valve The safety valve is provided with a safety passage that allows the back pressure chamber of the main valve to communicate with the tank side, and a closing plug is installed in the safety passage to close the passage. A pilot-operated relief valve that is opened by opening a safety passage and selecting the depth of the groove at the breaking point of the closing plug so that the safety passage is opened at a pressure higher than the opening pressure of the pilot valve.