JP3553651B2

JP3553651B2 - Displacement control device for variable displacement hydraulic pump

Info

Publication number: JP3553651B2
Application number: JP19248194A
Authority: JP
Inventors: 圭介高
Original assignee: Komatsu Ltd
Current assignee: Komatsu Ltd
Priority date: 1994-08-16
Filing date: 1994-08-16
Publication date: 2004-08-11
Anticipated expiration: 2019-08-11
Also published as: JPH0861303A

Description

【０００１】
【産業上の利用分野】
本発明は、油圧ショベル等の建設機械の油圧アクチュエータに圧油を供給する可変容量型油圧ポンプの容量を制御する装置に関する。
【０００２】
【従来の技術】
可変容量型油圧ポンプの吐出圧油を油圧アクチュエータに供給する油圧回路としては、例えば図１に示すものが知られている。
つまり、可変容量型油圧ポンプ１（以下可変油圧ポンプという）のポンプ吐出路２に方向制御弁３を設け、この方向制御弁３をパイロット弁４よりのパイロット圧で中立位置Ａから第１・第２位置Ｂ，Ｃに切換えて油圧アクチュエータ５に圧油を供給するようにしてある。
【０００３】
前述の方向制御弁３は中立位置Ａの時にポンプポート６を遮断するクローズドセンタ型式となり、可変油圧ポンプ１の吐出圧油が行き止まりとなって可変油圧ポンプ１を駆動するエンジン７の駆動馬力損失が大となる。
【０００４】
このために、可変油圧ポンプ１の容量をポンプ吐出圧と油圧アクチュエータ５の負荷圧（つまり、方向制御弁３の出力側圧力）により制御して方向制御弁３が中立位置Ａの時には可変油圧ポンプ１の容量を最小とする容量制御装置が知られている。
【０００５】
つまり、図１に示すように可変油圧ポンプ１の容量を変更する斜板８をシリンダ９のピストン１０に連結し、そのピストン１０をばね１１で縮め方向に付勢して斜板８を容量大方向に傾転し、その縮み室１２にポンプ吐出路２を接続し、伸び室１３を切換弁１４でタンク１５とポンプ吐出路２の一方に連通制御し、その切換弁１４をばね１６と第１受圧部１７の圧力でドレーン位置Ｄとし、第２受圧部１８の圧力で供給位置Ｅとなるようにすると共に、その第１受圧部１７を負荷圧検出路１９で方向制御弁３の負荷圧検出ポート２０に接続し、第２受圧部１８をポンプ吐出路２に接続してある。
【０００６】
かかる容量制御装置であれば、方向制御弁３が中立位置Ａの時には負荷圧検出ポート２０がタンク１５に連通するから、切換弁１４の第１受圧部１７の圧力はゼロで切換弁１４は第２受圧部１８に作用するポンプ吐出圧で供給位置Ｅとなり、ポンプ吐出圧油がシリンダ９の伸び室１３に供給されてピストン１０が伸長して斜板８が容量減方向に傾転する。
【０００７】
これにより、ポンプ吐出圧が低下するから、そのポンプ吐出圧がばね１６の取付荷重に見合う圧力以下となると切換弁１４はドレーン位置Ｄとなってピストン１０がばね１１で縮んで斜板８が容量大方向に傾転する。したがって、可変油圧ポンプ１の容量はばね１６の取付荷重に見合う容量となる。
【０００８】
方向制御弁３を第１位置Ｂ又は第２位置Ｃとすると油圧アクチュエータ５に負荷圧が発生し、その負荷圧が切換弁１４の第１受圧部１７に作用して切換弁１４をドレーン位置Ｄに押す。
これによりシリンダ９のピストン１０は縮んで斜板８は容量大方向に傾転して可変油圧ポンプ１の容量が増大するで、油圧アクチュエータ５に圧油を迅速に供給して作動できる。この時方向制御弁３の入口圧は負荷圧よりも若干高い圧力となる。つまり方向制御弁３の入口圧と負荷圧の差圧は常に一定となる。
【０００９】
【発明が解決しようとする課題】
かかる容量制御装置であると、ポンプ吐出圧が直接シリンダ９の縮み室１２と切換弁１４の第２受圧室１８に供給されるために斜板８が最小容量位置から最大容量位置に向けて傾転する速度は負荷圧によって決定される。つまり、負荷圧が急激に上昇すれば速く傾転し、ゆっくりと上昇すればゆっくりと傾転する。
【００１０】
このために、方向制御弁３を第１位置Ｂ又は第２位置Ｃに操作した時に油圧アクチュエータ５に作用する負荷が非常に軽い、若しくは油圧アクチュエータ５が重力方向に自重落下している場合、例えば方向制御弁３を第２位置Ｃとして油圧アクチュエータ５のボトム室５ａに圧油を供給する場合には負荷圧が著しく低くなり、方向制御弁３の負荷圧検出ポート２０の負荷圧も同じく低いため切換弁１４の第１受圧部１７の圧力も低く、切換弁１４は供給位置Ｅから切り換らない。
【００１１】
しかし、ポンプ吐出圧は負荷圧分高くなるためシリンダ９のピストン１０は縮み側に動き斜板８が容量大方向に傾転し、ポンプ吐出流量はわずかに増加する。ポンプ吐出流量が増加するため負荷圧はわずかに上昇し、ポンプ吐出圧もわずかに増加する。よってシリンダ９のピストン１０は縮み側にその分動き、再びポンプ吐出流量が増加する。この繰り返しでそのうち切換弁１４がドレーン位置Ｄに切り換り必要流量が流れるが、方向制御弁３を操作してから油圧アクチュエータ５が作動するまでのタイムラグ（時間差）が大となる。
【００１２】
そこで、本発明は前述の課題を解決できるようにした可変容量型油圧ポンプの容量制御装置を提供することを目的とする。
【００１３】
【課題を解決するための手段】
本発明は、可変容量型油圧ポンプ１の吐出圧油を方向制御弁３によって油圧アクチュエータ５に供給する油圧回路において、
前記可変容量型油圧ポンプ１と方向制御弁３との間に所定の開弁圧で連通作動するシーケンス弁３０を設け、可変容量型油圧ポンプ１の吐出圧をシーケンス弁３０の開弁圧以上となるようにし、
前記可変容量型油圧ポンプ１の斜板８を、自己の吐出圧油で作動させ、前記油圧アクチュエータ５の負荷圧と前記シーケンス弁３０の出口側圧力の差圧により斜板８の方向を制御する機構を設けたことを特徴とする可変容量型油圧ポンプの容量制御装置である。
【００１４】
【作用】
本発明によれば、可変容量型油圧ポンプ１のポンプ吐出圧を油圧アクチュエータ５の負荷圧に関係なくシーケンス弁３０の開弁圧以上に補償し、油圧アクチュエータ５の負荷圧とシーケンス弁３０の出口側圧力の差により斜板８の方向を制御するから、油圧アクチュエータ５の負荷圧が著しく低圧の場合でも可変容量油圧ポンプ１の容量を迅速に増大できる。
したがって、油圧アクチェータ５の負荷圧が著しく低圧の場合でも方向制御弁３を操作すると同時に油圧アクチュエータ５に圧油を供給してタイムラグなく油圧アクチュエータを作動できる。
【００１５】
【実施例】
本発明の第１実施例を図２に基づいて説明する。なお従来と同一部材は符号を同一とする。
可変油圧ポンプ１のポンプ吐出路２の途中にシーケンス弁３０を設ける。このシーケンス弁３０は第１受圧室３１の入口側圧力で入口３２と出口３３を連通する方向に押され、第２受圧室３４の入口側圧力とばね３５で入口３２と出口３３を遮断する方向に押されるものであり、その第１受圧室３１の受圧面積は第２受圧室３４の受圧面積よりも大きくしてある。
【００１６】
このようであるから、シーケンス弁３０の入口側圧力は、（ばね３５の取付荷重）／（第１・第２受圧室３１，３４の受圧面積差）となり、可変油圧ポンプ１の最低吐出圧は第１・第２受圧室３１，３４の受圧面積差とばね３５の取付荷重による圧力に補償される。
【００１７】
シリンダ９の縮み室１２は第１回路３６でシーケンス弁３０の入口側に接続し、切換弁１４の第２受圧室１８は第２回路３７でシーケンス弁３０の出口側に接続してある。
【００１８】
次に作動を説明する。
シーケンス弁３０のばね３５の取付荷重は、切換弁１４のばね１６の取付荷重より大きく、シーケンス弁３０の開弁圧は切換弁１４の開弁圧より高くしてある。つまり、シーケンス弁３０の開口量とストロークとの関係は図５に示すようになっている。方向制御弁３が中立位置Ａの時、ポンプ吐出圧はシーケンス弁３０の開弁圧となっている。シーケンス弁３０の開口量は図５のａ付近にある。この時ポンプ吐出流量はごく微少のため、ポンプ駆動馬力の増加分は微少である。
【００１９】
方向制御弁３を第１位置Ｂに操作し、負荷圧がシーケンス弁３０の開弁圧より高くなるとシーケンス弁３０は全開する。シーケンス弁３０の開口量は図５のＣ付近となり、シーケンス弁３０を通過する際の損失馬力は微少となっている。よって可変油圧ポンプ１はシーケンス弁３０がない従来と同じ作動をする。
【００２０】
方向制御弁３を第２位置Ｃに操作すると油圧アクチュエータ５は自重落下方向へ動く。この時方向制御弁３のメータアウト絞りに対し、負荷圧が過大の場合、自重落下速度が速く、方向制御弁３の入口圧及びポンプ吐出圧は著しく低圧になろうとするが、ポンプ吐出圧がシーケンス弁３０の開弁圧より低くなるとシーケンス弁３０が開方向に動き、開弁圧を保持する。この時シーケンス弁３０の開口量は図５のｂ付近となる。よってポンプ吐出圧はシーケンス弁３０の開弁圧となり、シリンダ９のピストン１０は従来より縮み側に早く動き方向切換弁３を操作してから油圧アクチュエータ５が作動するまでのタイムラグを小とできる。
【００２１】
これにより、負荷圧が低くゆっくりと昇圧する場合でも可変油圧ポンプ１の容量は方向制御弁３を操作すると直ちに増加するから、油圧アクチュエータ５をタイムラグなく迅速に作動できる。
【００２２】
図３は本発明の第２実施例を示し、方向制御弁３を手動レバー４０で操作するようにしてある。
なお、方向制御弁３はパイロット弁の代りに電磁比例制御弁よりパイロット圧を供給して操作するようにしても良い。
【００２３】
図４は本発明の第３実施例を示し、方向制御弁３は第１受圧部３ａに供給されるパイロット圧油で第１位置Ｂ、第２受圧部３ｂに供給されるパイロット圧油で第２位置Ｃに切換わるパイロット圧作動式となり、パイロット弁４は補助油圧ポンプ４０の吐出圧油を第１回路４１と第２回路４２にレバー４ａの操作ストロークに比例した圧力で出力するものとなり、その第１回路４１が第１受圧部３ａ、第２回路４２が第２受圧部３ｂにそれぞれ接続してある。
【００２４】
前記シーケンス弁３０は、第１受圧室３１の圧力で入口３２と出口３３を連通する方向に押され、第２受圧室３４の圧力と第３受圧室４３の圧力とばね３５によって入口３２と出口３３を遮断する方向に押されるものであり、その第２受圧室３４は入口側に接続し、第３受圧室４３は回路４４で前記第２回路４２に接続され、前記ばね３５の取付荷重は著しく小さく開弁圧は著しく低圧、例えばばね１６の取付荷重に見合う圧力よりも低圧としてある。
【００２５】
このようにすれば、パイロット弁４を操作しない時、つまり方向制御弁３が中立位置Ａの時にはシーケス弁３０の第３受圧室４３に圧力が供給されないので、シーケンス弁３０の開弁圧は著しく低圧となり、ポンプ吐出圧がごく低圧となりでエンジン７の駆動馬力損失を低減できる。
【００２６】
また、パイロット弁４を操作して第２回路４２にパイロット圧を出力して方向制御弁３を第２位置Ｃとし、油圧アクチュエータ５のボトム室５ａに圧油を供給する時には、第２回路４２のパイロット圧が回路３７よりシーケンス弁３０の第３受圧室４３に供給されてシーケンス弁３０を遮断方向に押す力が大となるので開弁圧が高圧となる。
【００２７】
これにより、シーケンス弁３０の出口側圧力が低くとも入口側圧力は高圧に補償されるので、油圧アクチュエータ５の負荷圧が著しく低圧であっても前述と同様に可変油圧ポンプ１の容量が迅速に増大するから、油圧アクチュエータをタイムラグなく作動できる。
【００２８】
つまり、方向制御弁３が第２位置Ｃとなると油圧アクチュエータ５のボトム室５ａに圧油が供給されるが、この時油圧アクチュエータは自重方向に自然落下してボトム室５ａ内の圧力は著しく低圧となり、シーケンス弁３０の出力側圧力も著しく低圧となるが、シーケンス弁３０の開弁圧が高くなってポンプ吐出圧は負荷圧よりも高い圧力（開弁圧）になるから、前述のように可変油圧ポンプ１の容量は迅速に増大する。
【００２９】
以上の実施例では、シーケンス弁３０の第３受圧室４３を第２回路４２に接続したが、これは油圧アクチュエータ５のボトム室５ａに圧油を供給する時に負荷圧が著しく低圧となるためであり、ロッド室５ｂに圧油を供給する時に負荷圧が著しく低圧となる場合には第１回路４１を第３受圧室４３に接続すれば良いし、ボトム室５ａ、ロッド室５ｂのどちらに圧油を供給する場合にも負荷圧が著しく低圧となるのであれば、シーケンス弁３０の第３受圧室４３をチェック弁を介して第１回路４１と第２回路４２にそれぞれ接続すれば良い。
【００３０】
また、方向制御弁３が電磁弁で切換え作動する電磁作動式の場合にはシーケンス弁３０の第３受圧室４３の代りに電磁弁を設け、方向制御弁３の電磁弁とシーケンス弁３０の電磁弁に同時に通電するようにすれば良い。
【００３１】
つまり、シーケンス弁３０を開弁圧を調節できるものとし、方向制御弁３を中立位置Ａから第１位置Ｂ、第２位置Ｃに切換作動する切換信号によってシーケンス弁３０の開弁圧を高くするようにすれば良い。
【００３９】
【発明の効果】
請求項１に係る発明によれば、可変容量型油圧ポンプ１のポンプ吐出圧を油圧アクチュエータ５の負荷圧に関係なくシーケンス弁３０の開弁圧以上に補償し、油圧アクチュエータ５の負荷圧とシーケンス弁３０の出口側圧力の差により斜板８の方向を制御するから、油圧アクチュエータ５の負荷圧が著しく低圧の場合でも可変容量油圧ポンプ１の容量を迅速に増大できる。
したがって、油圧アクチェータ５の負荷圧が著しく低圧の場合でも方向制御弁３を操作すると同時に油圧アクチュエータ５に圧油を供給してタイムラグなく油圧アクチュエータを作動できる。
請求項３に係る発明によれば、方向制御弁３が中立位置Ａの時にはシーケンス弁３０の開弁圧が低圧で、第１位置Ｂ、第２位置Ｃの時にはシーケンス弁３０の開弁圧が高圧であるから、方向制御弁３が中立位置Ａの時にはポンプ吐出圧が低圧となってポンプ駆動馬力を無駄に消費することがない。
【図面の簡単な説明】
【図１】従来例の説明図である。
【図２】本発明の第１実施例を示す説明図である。
【図３】本発明の第２実施例を示す説明図である。
【図４】本発明の第３実施例を示す説明図である。
【図５】シーケンス弁のストロークと開口量の関係を示す図表である。
【符号の説明】
１…可変容量型油圧ポンプ、２…ポンプ吐出路、３…方向制御弁、５…油圧アクチュエータ、７…エンジン、８…斜板、９…シリンダ、１０…ピストン、１２…縮み室、１３…伸び室、１４…切換弁、１５…タンク、１６…ばね、１７…第１受圧部、１８…第２受圧部。[0001]
[Industrial applications]
The present invention relates to a device for controlling the capacity of a variable displacement hydraulic pump that supplies pressure oil to a hydraulic actuator of a construction machine such as a hydraulic shovel.
[0002]
[Prior art]
As a hydraulic circuit for supplying the discharge pressure oil of a variable displacement hydraulic pump to a hydraulic actuator, for example, the one shown in FIG. 1 is known.
That is, the directional control valve 3 is provided in the pump discharge path 2 of the variable displacement hydraulic pump 1 (hereinafter, referred to as a variable hydraulic pump), and the directional control valve 3 is moved from the neutral position A to the first and second positions by the pilot pressure from the pilot valve 4. The hydraulic oil is supplied to the hydraulic actuator 5 by switching between the two positions B and C.
[0003]
The above-described directional control valve 3 is of a closed center type that shuts off the pump port 6 when in the neutral position A, and the drive hydraulic power of the engine 7 that drives the variable hydraulic pump 1 is reduced due to the dead pressure of the discharge hydraulic oil of the variable hydraulic pump 1 stopping. It will be great.
[0004]
For this purpose, the capacity of the variable hydraulic pump 1 is controlled by the pump discharge pressure and the load pressure of the hydraulic actuator 5 (that is, the output side pressure of the directional control valve 3), and when the directional control valve 3 is at the neutral position A, the variable hydraulic pump 1 is controlled. A capacity control device that minimizes the capacity of one is known.
[0005]
That is, as shown in FIG. 1, a swash plate 8 for changing the capacity of the variable hydraulic pump 1 is connected to a piston 10 of a cylinder 9, and the piston 10 is urged in a contraction direction by a spring 11 to increase the capacity of the swash plate 8. The pump discharge path 2 is connected to the contraction chamber 12, and the expansion chamber 13 is controlled to communicate with the tank 15 and one of the pump discharge paths 2 by the switching valve 14, and the switching valve 14 is connected to the spring 16. The pressure of the first pressure receiving portion 17 is set to the drain position D, the pressure of the second pressure receiving portion 18 is set to the supply position E, and the first pressure receiving portion 17 is connected to the load pressure detection path 19 by the load pressure of the directional control valve 3. The second pressure receiving portion 18 is connected to the pump discharge passage 2 while being connected to the detection port 20.
[0006]
In such a capacity control device, when the directional control valve 3 is in the neutral position A, the load pressure detection port 20 communicates with the tank 15, so that the pressure of the first pressure receiving portion 17 of the switching valve 14 is zero and the switching valve 14 is 2 The pump discharge pressure acting on the pressure receiving portion 18 causes the pump discharge pressure to reach the supply position E, the pump discharge pressure oil being supplied to the extension chamber 13 of the cylinder 9, the piston 10 being extended, and the swash plate 8 tilting in the capacity decreasing direction.
[0007]
As a result, the pump discharge pressure is reduced. When the pump discharge pressure falls below a pressure corresponding to the mounting load of the spring 16, the switching valve 14 is in the drain position D, the piston 10 is contracted by the spring 11, and the swash plate 8 is displaced. Tilt in a large direction. Therefore, the capacity of the variable hydraulic pump 1 is a capacity corresponding to the mounting load of the spring 16.
[0008]
When the directional control valve 3 is set to the first position B or the second position C, a load pressure is generated in the hydraulic actuator 5 and the load pressure acts on the first pressure receiving portion 17 of the switching valve 14 to move the switching valve 14 to the drain position D. Press
As a result, the piston 10 of the cylinder 9 is contracted, and the swash plate 8 is tilted in the direction of large capacity to increase the capacity of the variable hydraulic pump 1. At this time, the inlet pressure of the direction control valve 3 is slightly higher than the load pressure. That is, the differential pressure between the inlet pressure of the directional control valve 3 and the load pressure is always constant.
[0009]
[Problems to be solved by the invention]
With such a displacement control device, the pump discharge pressure is directly supplied to the contraction chamber 12 of the cylinder 9 and the second pressure receiving chamber 18 of the switching valve 14, so that the swash plate 8 tilts from the minimum displacement position to the maximum displacement position. The speed of rotation is determined by the load pressure. In other words, if the load pressure rises sharply, it will tilt quickly, if it rises slowly, it will tilt slowly.
[0010]
For this reason, when the load acting on the hydraulic actuator 5 when the direction control valve 3 is operated to the first position B or the second position C is very light, or when the hydraulic actuator 5 is dropping its own weight in the direction of gravity, for example, When pressure oil is supplied to the bottom chamber 5a of the hydraulic actuator 5 with the directional control valve 3 in the second position C, the load pressure becomes extremely low, and the load pressure at the load pressure detection port 20 of the directional control valve 3 is also low. The pressure of the first pressure receiving portion 17 of the switching valve 14 is also low, and the switching valve 14 does not switch from the supply position E.
[0011]
However, since the pump discharge pressure becomes higher by the load pressure, the piston 10 of the cylinder 9 moves toward the contraction side, the swash plate 8 tilts in the direction of larger capacity, and the pump discharge flow rate slightly increases. Since the pump discharge flow rate increases, the load pressure slightly increases, and the pump discharge pressure also slightly increases. Therefore, the piston 10 of the cylinder 9 moves to the contraction side, and the pump discharge flow rate increases again. During this repetition, the switching valve 14 switches to the drain position D and the required flow rate flows, but the time lag (time difference) from when the directional control valve 3 is operated to when the hydraulic actuator 5 is operated becomes large.
[0012]
Therefore, an object of the present invention is to provide a displacement control device for a variable displacement hydraulic pump capable of solving the above-mentioned problems.
[0013]
[Means for Solving the Problems]
The present invention relates to a hydraulic circuit for supplying discharge pressure oil of a variable displacement hydraulic pump 1 to a hydraulic actuator 5 by a directional control valve 3,
A sequence valve 30 is provided between the variable displacement hydraulic pump 1 and the directional control valve 3 so as to communicate with a predetermined valve opening pressure, and the discharge pressure of the variable displacement hydraulic pump 1 is set to be equal to or higher than the opening pressure of the sequence valve 30. So that
The swash plate 8 of the variable displacement hydraulic pump 1 is operated by its own discharge pressure oil, and the direction of the swash plate 8 is controlled by the differential pressure between the load pressure of the hydraulic actuator 5 and the outlet pressure of the sequence valve 30. A displacement control device for a variable displacement hydraulic pump, comprising a mechanism.
[0014]
[Operation]
According to the present invention, the pump discharge pressure of the variable displacement hydraulic pump 1 is compensated to be equal to or higher than the opening pressure of the sequence valve 30 regardless of the load pressure of the hydraulic actuator 5, and the load pressure of the hydraulic actuator 5 and the outlet of the sequence valve 30 are compensated. since that controls the direction of the swash plate 8 by the difference of the side pressure, the capacity of the variable displacement hydraulic pump 1 even when the load pressure is considerably low pressure hydraulic actuators 5 can be quickly increased.
Therefore, even if the load pressure of the hydraulic actuator 5 is extremely low, the hydraulic actuator can be operated without time lag by operating the direction control valve 3 and simultaneously supplying the hydraulic oil to the hydraulic actuator 5.
[0015]
【Example】
A first embodiment of the present invention will be described with reference to FIG. The same members as those in the related art have the same reference numerals.
A sequence valve 30 is provided in the middle of the pump discharge path 2 of the variable hydraulic pump 1. The sequence valve 30 is pushed by the inlet pressure of the first pressure receiving chamber 31 in the direction of communicating the inlet 32 and the outlet 33, and the inlet pressure of the second pressure receiving chamber 34 and the direction of shutting off the inlet 32 and the outlet 33 by the spring 35. The pressure receiving area of the first pressure receiving chamber 31 is larger than the pressure receiving area of the second pressure receiving chamber 34.
[0016]
Therefore, the pressure on the inlet side of the sequence valve 30 is (the mounting load of the spring 35) / (the pressure receiving area difference between the first and second pressure receiving chambers 31, 34), and the minimum discharge pressure of the variable hydraulic pump 1 is The pressure due to the pressure receiving area difference between the first and second pressure receiving chambers 31 and 34 and the pressure due to the mounting load of the spring 35 are compensated.
[0017]
The contraction chamber 12 of the cylinder 9 is connected to the inlet side of the sequence valve 30 by a first circuit 36, and the second pressure receiving chamber 18 of the switching valve 14 is connected to the outlet side of the sequence valve 30 by a second circuit 37.
[0018]
Next, the operation will be described.
The mounting load of the spring 35 of the sequence valve 30 is larger than the mounting load of the spring 16 of the switching valve 14, and the valve opening pressure of the sequence valve 30 is higher than the valve opening pressure of the switching valve 14. That is, the relationship between the opening amount of the sequence valve 30 and the stroke is as shown in FIG. When the direction control valve 3 is in the neutral position A, the pump discharge pressure is the valve opening pressure of the sequence valve 30. The opening amount of the sequence valve 30 is near a in FIG. At this time, since the pump discharge flow rate is very small, the increase in the pump driving horsepower is very small.
[0019]
When the direction control valve 3 is operated to the first position B and the load pressure becomes higher than the opening pressure of the sequence valve 30, the sequence valve 30 is fully opened. The opening amount of the sequence valve 30 is near C in FIG. 5, and the loss horsepower when passing through the sequence valve 30 is very small. Therefore, the variable hydraulic pump 1 operates in the same manner as in the related art without the sequence valve 30.
[0020]
When the directional control valve 3 is operated to the second position C, the hydraulic actuator 5 moves in the direction of its own weight drop. At this time, if the load pressure is excessive with respect to the meter-out throttle of the directional control valve 3, the own weight falling speed is high, and the inlet pressure of the directional control valve 3 and the pump discharge pressure tend to be extremely low. When the pressure becomes lower than the valve opening pressure of the sequence valve 30, the sequence valve 30 moves in the opening direction and maintains the valve opening pressure. At this time, the opening amount of the sequence valve 30 is near b in FIG. Accordingly, the pump discharge pressure becomes the valve opening pressure of the sequence valve 30, and the piston 10 of the cylinder 9 moves to the contraction side faster than before, and the time lag from when the direction switching valve 3 is operated to when the hydraulic actuator 5 is operated can be reduced.
[0021]
As a result, even when the load pressure is low and the pressure is slowly increased, the capacity of the variable hydraulic pump 1 is increased immediately when the directional control valve 3 is operated, so that the hydraulic actuator 5 can be quickly operated without a time lag.
[0022]
FIG. 3 shows a second embodiment of the present invention, in which the directional control valve 3 is operated by a manual lever 40.
The directional control valve 3 may be operated by supplying pilot pressure from an electromagnetic proportional control valve instead of the pilot valve.
[0023]
FIG. 4 shows a third embodiment of the present invention, in which a directional control valve 3 is provided with a pilot pressure oil supplied to a first pressure receiving portion 3a at a first position B and a pilot pressure oil supplied to a second pressure receiving portion 3b. The pilot pressure is switched to the 2 position C, and the pilot valve 4 outputs the discharge pressure oil of the auxiliary hydraulic pump 40 to the first circuit 41 and the second circuit 42 at a pressure proportional to the operation stroke of the lever 4a. The first circuit 41 is connected to the first pressure receiving section 3a, and the second circuit 42 is connected to the second pressure receiving section 3b.
[0024]
The sequence valve 30 is pushed by the pressure of the first pressure receiving chamber 31 in a direction to communicate the inlet 32 and the outlet 33, and the pressure of the second pressure receiving chamber 34, the pressure of the third pressure receiving chamber 43, and the spring 35 cause the inlet 32 and the outlet to be closed. The second pressure receiving chamber 34 is connected to the inlet side, the third pressure receiving chamber 43 is connected to the second circuit 42 by a circuit 44, and the mounting load of the spring 35 is The valve opening pressure is extremely small and is extremely low, for example, lower than the pressure corresponding to the mounting load of the spring 16.
[0025]
With this configuration, when the pilot valve 4 is not operated, that is, when the direction control valve 3 is in the neutral position A, no pressure is supplied to the third pressure receiving chamber 43 of the sequence valve 30, so that the valve opening pressure of the sequence valve 30 is significantly increased. The pressure becomes low, and the pump discharge pressure becomes extremely low, so that the driving horsepower loss of the engine 7 can be reduced.
[0026]
When the pilot valve 4 is operated to output pilot pressure to the second circuit 42 to set the direction control valve 3 to the second position C and supply pressure oil to the bottom chamber 5a of the hydraulic actuator 5, the second circuit 42 Is supplied from the circuit 37 to the third pressure receiving chamber 43 of the sequence valve 30 and the force for pushing the sequence valve 30 in the shutoff direction becomes large, so that the valve opening pressure becomes high.
[0027]
As a result, even if the pressure on the outlet side of the sequence valve 30 is low, the pressure on the inlet side is compensated for at a high pressure. Therefore, even if the load pressure of the hydraulic actuator 5 is extremely low, the capacity of the variable hydraulic pump 1 can be quickly increased as described above. Since it increases, the hydraulic actuator can be operated without a time lag.
[0028]
That is, when the directional control valve 3 is at the second position C, pressure oil is supplied to the bottom chamber 5a of the hydraulic actuator 5, but at this time, the hydraulic actuator drops naturally in the direction of its own weight, and the pressure in the bottom chamber 5a is extremely low. As a result, the output pressure of the sequence valve 30 becomes extremely low, but the valve opening pressure of the sequence valve 30 becomes high and the pump discharge pressure becomes higher than the load pressure (valve opening pressure). The capacity of the variable hydraulic pump 1 increases quickly.
[0029]
In the above embodiment, the third pressure receiving chamber 43 of the sequence valve 30 is connected to the second circuit 42, because the load pressure becomes extremely low when the pressurized oil is supplied to the bottom chamber 5a of the hydraulic actuator 5. If the load pressure becomes extremely low when the pressure oil is supplied to the rod chamber 5b, the first circuit 41 may be connected to the third pressure receiving chamber 43, and the pressure may be applied to either the bottom chamber 5a or the rod chamber 5b. If the load pressure becomes extremely low even when oil is supplied, the third pressure receiving chamber 43 of the sequence valve 30 may be connected to the first circuit 41 and the second circuit 42 via a check valve.
[0030]
When the directional control valve 3 is of an electromagnetically operated type that is switched by an electromagnetic valve, an electromagnetic valve is provided in place of the third pressure receiving chamber 43 of the sequence valve 30, and the electromagnetic valve of the directional control valve 3 and the electromagnetic valve of the sequence valve 30 are connected. What is necessary is just to energize a valve simultaneously.
[0031]
That is, the sequence valve 30 can adjust the valve opening pressure, and the opening pressure of the sequence valve 30 is increased by a switching signal for switching the direction control valve 3 from the neutral position A to the first position B and the second position C. What should I do?
[0039]
【The invention's effect】
According to the invention of claim 1, the pump discharge pressure of the variable displacement hydraulic pump 1 is compensated to be equal to or higher than the valve opening pressure of the sequence valve 30 regardless of the load pressure of the hydraulic actuator 5, and the load pressure of the hydraulic actuator 5 and the sequence are compensated. since that controls the direction of the swash plate 8 by the difference in outlet pressure of the valve 30, the displacement of the variable displacement hydraulic pump 1 even when the load pressure is considerably low pressure hydraulic actuators 5 can be quickly increased.
Therefore, even if the load pressure of the hydraulic actuator 5 is extremely low, the hydraulic actuator can be operated without time lag by operating the direction control valve 3 and simultaneously supplying the hydraulic oil to the hydraulic actuator 5.
According to the third aspect of the invention, when the direction control valve 3 is in the neutral position A, the valve opening pressure of the sequence valve 30 is low, and when the direction control valve 3 is in the first position B and the second position C, the valve opening pressure of the sequence valve 30 is low. Since the pressure is high, when the directional control valve 3 is at the neutral position A, the pump discharge pressure becomes low and the pump driving horsepower is not wasted.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram of a conventional example.
FIG. 2 is an explanatory diagram showing a first embodiment of the present invention.
FIG. 3 is an explanatory view showing a second embodiment of the present invention.
FIG. 4 is an explanatory view showing a third embodiment of the present invention.
FIG. 5 is a table showing a relationship between a stroke of a sequence valve and an opening amount.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Variable displacement hydraulic pump, 2 ... Pump discharge path, 3 ... Direction control valve, 5 ... Hydraulic actuator, 7 ... Engine, 8 ... Swash plate, 9 ... Cylinder, 10 ... Piston, 12 ... Shrinkage chamber, 13 ... Extension Chamber, 14: switching valve, 15: tank, 16: spring, 17: first pressure receiving portion, 18: second pressure receiving portion.

Claims

In the hydraulic circuit for supplying the discharge pressure oil of the variable displacement hydraulic pump 1 to the hydraulic actuator 5 by the direction control valve 3,
A sequence valve 30 is provided between the variable displacement hydraulic pump 1 and the directional control valve 3 so as to communicate with a predetermined valve opening pressure, and the discharge pressure of the variable displacement hydraulic pump 1 is set to be equal to or higher than the opening pressure of the sequence valve 30. So that
The swash plate 8 of the variable displacement hydraulic pump 1 is operated by its own discharge pressure oil, and the direction of the swash plate 8 is controlled by the differential pressure between the load pressure of the hydraulic actuator 5 and the outlet pressure of the sequence valve 30. A displacement control device for a variable displacement hydraulic pump, comprising a mechanism.

The piston 10 of the cylinder 9 is connected to the swash plate 8 of the variable displacement hydraulic pump 1 so that the capacity is increased when the piston 10 is contracted and the capacity is decreased when the piston 10 is extended, and the contraction chamber 12 of the cylinder 9 is connected to a sequence valve. 30 connected to the entrance side,
A switching valve 14 is provided which can be switched between a drain position D communicating the extension chamber 13 of the cylinder 9 and the tank 15 and a communication position E communicating the extension chamber 13 and the output side of the sequence valve 30. 16 and the pressure of the first pressure receiving portion 17 so as to be in the drain position D, and the pressure of the second pressure receiving portion 18 to be in the communication position E. The load pressure is supplied to the first pressure receiving portion 17 and the second pressure receiving portion 18 is supplied with the load pressure. The displacement control device for a variable displacement hydraulic pump according to claim 1, wherein the output pressure of the sequence valve (30) is supplied.

Normally the valve opening pressure and low-pressure sequence valve 30, claim 1 as a first position B of the directional control valve 3 from the neutral position A, the valve opening pressure by switching signal is switched to the second position C becomes high Or a displacement control device for a variable displacement hydraulic pump according to 2 .