JP3807581B2 - Hydraulic drive circuit using swash plate type variable displacement pump - Google Patents

Hydraulic drive circuit using swash plate type variable displacement pump Download PDF

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Publication number
JP3807581B2
JP3807581B2 JP03951799A JP3951799A JP3807581B2 JP 3807581 B2 JP3807581 B2 JP 3807581B2 JP 03951799 A JP03951799 A JP 03951799A JP 3951799 A JP3951799 A JP 3951799A JP 3807581 B2 JP3807581 B2 JP 3807581B2
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Prior art keywords
pressure
variable displacement
displacement pump
swash plate
drive circuit
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Expired - Fee Related
Application number
JP03951799A
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Japanese (ja)
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JP2000240603A (en
Inventor
眞司 寺田
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Sumitomo Heavy Industries Ltd
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Sumitomo Heavy Industries Ltd
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Description

【０００１】
【発明の属する技術分野】
本発明は斜板式可変容量ポンプを用いた油圧駆動回路に関し、特に駆動されるアクチュエータの圧力制御特性の改善に関する。
【０００２】
【従来の技術】
斜板式可変容量ポンプ（以下、可変容量ポンプと呼ぶ）を用いた油圧駆動回路の一例として、例えば油圧式射出成形機における射出装置の油圧駆動回路について説明する。図２において、可変容量ポンプ１０は、被制御アクチュエータとしての射出シリンダ２０に作動油を供給するためのものである。可変容量ポンプ１０の吐出配管には、通常、流量検出用のフローセンサ１１、油圧検出用の圧力センサ１２、切換弁１３が接続されている。フローセンサ１１は、作動油の流れを絞って流量を計測するもので、抵抗弁として作用する。また、フローセンサに代えてシーケンス弁が抵抗弁として配置される場合もある。
【０００３】
可変容量ポンプ１０は、吐出圧あるいは吐出流量の設定値と検出圧力あるいは検出流量との偏差に基づいて斜板位置（角度）を可変調整する内部アクチュエータ１４に接続した２方弁型の制御弁１５を制御して吐出圧あるいは吐出流量を可変する。そして、射出工程においては、可変容量ポンプ１０からの作動油を切換弁１３を通して射出シリンダ２０に出し入れすることによりスクリュを進退駆動する。
【０００４】
【発明が解決しようとする課題】
上記のように、従来の射出装置の油圧駆動回路では、可変容量ポンプ単体での最低制御圧力を低くするために、可変容量ポンプ１０の吐出部とフローセンサ１１との間に配管を接続して制御弁１５のパイロットポートＰに接続し、フローセンサ１１のクラッキング圧力を利用して斜板の制御パイロット圧を確保するようにしている。この場合、圧抜き時に、フローセンサ１１のクラッキング圧力以下には圧力を下げることができないというデメリットがある。
【０００５】
すなわち、可変容量ポンプ１０の吐出圧を０（ｋｇｆ／ｃｍ2 ）まで圧抜きする場合、上記の油圧駆動回路では可変容量ポンプ１０の圧抜き動作時、制御弁１５が図示の位置になり、斜板を逆傾転方向へ動かす。この動作によって負荷側の油を吸い出し、圧力を下げる。しかし、上記の油圧駆動回路ではフローセンサ１１が閉弁してしまい、フローセンサ１１の２次側（出口側）部分の圧抜きがフローセンサ１１のクラッキング圧以下には下げられなくなる。これは、可変容量ポンプ１０の低圧制御性を改善する効果を持つフローセンサ１１があることによって、逆に圧抜きが不十分になってしまうことを意味する。
【０００６】
このような特性の改善のために、一般的には、制御弁１５内にドレンと連通するオリフィス状の小穴を設けて圧抜き時の最低制御圧力を下げることが知られている。しかし、間接的に可変容量ポンプ１０の吐出圧を下げるために圧抜き応答時間を長くし、可変容量ポンプ１０の圧力制御特性に外乱を与えない程度にしなければならない。このために、例えばスクリュの停止位置精度のバラツキ、射出−保圧工程の切換タイミングにショックが生じるなどの問題があり、高速かつ精度良く射出シリンダ２０を制御するためには十分にポンプ吐出圧が安定するまでラグタイムを設定せざるを得ない。これは、射出成形機のハイサイクル動作がラグタイムの影響を受けることを意味する。
【０００７】
そこで、本発明の課題は、斜板式可変容量ポンプ単体での圧力制御特性の改善を図り、被制御アクチュエータの位置制御特性を安定させることにある。
【０００８】
【課題を解決するための手段】
本発明によれば、斜板位置を制御するための制御弁を備え、抵抗弁を介して吐出油圧を被制御アクチュエータに供給するための斜板式可変容量ポンプにおいて、前記制御弁の１つのポートを圧抜きポートとして利用し、前記抵抗弁と前記被制御アクチュエータとの間の油圧配管と前記圧抜きポートとを接続する圧抜きドレン配管を設け、ポンプ圧抜き制御時に直接、前記制御弁から圧抜きを行うようにしたことを特徴とする斜板式可変容量ポンプを用いた油圧駆動回路が提供される。
【０００９】
【発明の実施の形態】
図１を参照して、本発明の実施の形態について説明する。本形態においても、図２と同様、油圧式射出成形機の射出装置に適用した場合について説明する。それゆえ、図２と同じ部分には同じ番号を付して詳細な説明は省略する。本形態においては、圧力（Ｐ），流量（Ｑ）指令によって斜板位置（角度）を制御するための制御弁として３方弁型、５方弁型等の多方弁型の制御弁（ここでは３方弁を図示）３０を用いて、その一つのポートを圧抜きポートＢとして利用する一方、可変容量ポンプ１０の吐出側に配設したフローセンサ１１の２次側と切換弁１３との間の油圧配管に圧抜きドレン配管３１を設け、この圧抜きドレン配管３１を圧抜きポートＢに接続したことを特徴とする。
【００１０】
この油圧駆動回路においては、可変容量ポンプ１０の吐出圧を０（ｋｇｆ／ｃｍ2 ）まで圧抜きする場合、圧抜きドレン配管３１を制御弁３０に図示の如く接続することで圧抜き時の最低圧力を０（ｋｇｆ／ｃｍ2 ）まで下げることができる。これによって、ラグタイムの縮小及び射出工程時におけるスクリュ位置の停止精度が向上する。以上の説明は、制御弁３０に３方弁型以外の多方弁型のものを用いた場合も同様である。
【００１１】
以上、本発明を油圧式射出成形機の射出装置に適用した場合について説明したが、本発明はこれに限らず、通常の開閉シリンダのような被制御アクチュエータにも適用可能である。この場合にも、開閉シリンダの位置制御の繰返し再現性が向上するという効果が得られる。
【００１２】
【発明の効果】
本発明においては、可変容量ポンプの斜板位置（角度）を制御するための制御弁に圧抜きポートとして利用できる３方弁型、５方弁型等の多方弁型を用い、この圧抜きポートに抵抗弁の２次側油圧配管と接続した圧抜きドレン配管を接続し、可変容量ポンプの圧抜き制御時に直接、制御弁から圧抜きを行なう。その結果、従来の間接的に圧抜きを行う方式とは異なり、極めて安定し、かつ応答性の高い０（ｋｇｆ／ｃｍ2 ）までの圧抜きが可能となり、可変容量ポンプ吐出側（負荷側）の残圧が減少し、被制御アクチュエータの制御性が向上する。
【図面の簡単な説明】
【図１】本発明による油圧駆動回路を油圧式射出成形機の射出装置に適用した場合の構成を示した図である。
【図２】従来の油圧駆動回路を、油圧式射出成形機の射出装置に適用して説明するための図である。
【符号の説明】
１０ 可変容量ポンプ
１１ フローセンサ
１２ 圧力センサ
１３ 切換弁
１４ 内部アクチュエータ
１５、３０ 制御弁
２０ 射出シリンダ
３１ 圧抜きドレン配管[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a hydraulic drive circuit using a swash plate type variable displacement pump, and more particularly to improvement of pressure control characteristics of a driven actuator.
[0002]
[Prior art]
As an example of a hydraulic drive circuit using a swash plate type variable displacement pump (hereinafter referred to as a variable displacement pump), for example, a hydraulic drive circuit of an injection device in a hydraulic injection molding machine will be described. In FIG. 2, a variable displacement pump 10 is for supplying hydraulic oil to an injection cylinder 20 as a controlled actuator. Normally, a flow sensor 11 for detecting a flow rate, a pressure sensor 12 for detecting hydraulic pressure, and a switching valve 13 are connected to a discharge pipe of the variable displacement pump 10. The flow sensor 11 measures the flow rate by restricting the flow of hydraulic oil, and acts as a resistance valve. Further, a sequence valve may be arranged as a resistance valve instead of the flow sensor.
[0003]
The variable displacement pump 10 is a two-way valve type control valve 15 connected to an internal actuator 14 that variably adjusts the swash plate position (angle) based on the deviation between the set value of the discharge pressure or discharge flow rate and the detected pressure or flow rate. To control the discharge pressure or the discharge flow rate. In the injection process, the screw is advanced and retracted by taking hydraulic oil from the variable displacement pump 10 into and out of the injection cylinder 20 through the switching valve 13.
[0004]
[Problems to be solved by the invention]
As described above, in the hydraulic drive circuit of the conventional injection device, a pipe is connected between the discharge portion of the variable displacement pump 10 and the flow sensor 11 in order to reduce the minimum control pressure of the variable displacement pump alone. The control port 15 is connected to the pilot port P of the control valve 15, and the control pilot pressure of the swash plate is secured using the cracking pressure of the flow sensor 11. In this case, there is a demerit that the pressure cannot be lowered below the cracking pressure of the flow sensor 11 at the time of pressure release.
[0005]
That is, when the discharge pressure of the variable displacement pump 10 is released to 0 (kgf / cm 2 ), in the above hydraulic drive circuit, the control valve 15 is in the illustrated position during the pressure release operation of the variable displacement pump 10, and Move the plate in the reverse direction. This action draws out oil on the load side and lowers the pressure. However, in the hydraulic drive circuit described above, the flow sensor 11 is closed, and the pressure relief on the secondary side (exit side) of the flow sensor 11 cannot be lowered below the cracking pressure of the flow sensor 11. This means that the presence of the flow sensor 11 having the effect of improving the low-pressure controllability of the variable displacement pump 10 makes the pressure relief insufficient.
[0006]
In order to improve such characteristics, it is generally known that an orifice-shaped small hole communicating with the drain is provided in the control valve 15 to lower the minimum control pressure at the time of depressurization. However, in order to indirectly reduce the discharge pressure of the variable displacement pump 10, it is necessary to lengthen the pressure release response time so that the pressure control characteristics of the variable displacement pump 10 are not disturbed. For this reason, for example, there are problems such as variations in the stop position accuracy of the screw and shocks at the switching timing of the injection-holding process, and the pump discharge pressure is sufficient to control the injection cylinder 20 at high speed and with high accuracy. The lag time must be set until it stabilizes. This means that the high cycle operation of the injection molding machine is affected by the lag time.
[0007]
Therefore, an object of the present invention is to improve the pressure control characteristic of a single swash plate type variable displacement pump and to stabilize the position control characteristic of the controlled actuator.
[0008]
[Means for Solving the Problems]
According to the present invention, in the swash plate type variable displacement pump that includes the control valve for controlling the swash plate position and supplies the discharge hydraulic pressure to the controlled actuator via the resistance valve, one port of the control valve is provided. A pressure relief drain pipe that connects the pressure relief port and the hydraulic piping between the resistance valve and the controlled actuator is provided as a pressure relief port, and is directly released from the control valve during pump pressure relief control. A hydraulic drive circuit using a swash plate type variable displacement pump is provided.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
An embodiment of the present invention will be described with reference to FIG. Also in this embodiment, a case where the present invention is applied to an injection apparatus of a hydraulic injection molding machine will be described as in FIG. Therefore, the same parts as those in FIG. In this embodiment, a three-way valve type control valve (here, a three-way valve type or a five-way valve type) is used as a control valve for controlling the swash plate position (angle) by pressure (P) and flow rate (Q) commands. A three-way valve 30 is used, and one of its ports is used as a pressure relief port B, while the secondary side of the flow sensor 11 disposed on the discharge side of the variable displacement pump 10 and the switching valve 13. The pressure relief drain pipe 31 is provided in the hydraulic pipe, and the pressure relief drain pipe 31 is connected to the pressure relief port B.
[0010]
In this hydraulic drive circuit, when the discharge pressure of the variable displacement pump 10 is released to 0 (kgf / cm 2 ), the pressure release drain pipe 31 is connected to the control valve 30 as shown in the drawing to minimize the pressure at the time of pressure release. The pressure can be reduced to 0 (kgf / cm 2 ). As a result, the lag time is reduced and the stopping accuracy of the screw position during the injection process is improved. The above description is the same when the control valve 30 is a multi-way valve type other than the three-way valve type.
[0011]
As described above, the case where the present invention is applied to the injection device of the hydraulic injection molding machine has been described. However, the present invention is not limited to this and can be applied to a controlled actuator such as a normal opening / closing cylinder. Also in this case, the effect of improving the repeatability of the position control of the opening / closing cylinder can be obtained.
[0012]
【The invention's effect】
In the present invention, a multi-way valve type such as a three-way valve type or a five-way valve type that can be used as a pressure release port is used as a control valve for controlling the swash plate position (angle) of the variable displacement pump. A pressure relief drain pipe connected to the secondary side hydraulic pipe of the resistance valve is connected to the pressure valve, and the pressure relief is performed directly from the control valve during the pressure relief control of the variable displacement pump. As a result, unlike the conventional method of performing pressure relief indirectly, it is possible to perform pressure relief up to 0 (kgf / cm 2 ) which is extremely stable and highly responsive, and the variable displacement pump discharge side (load side) The residual pressure is reduced, and the controllability of the controlled actuator is improved.
[Brief description of the drawings]
FIG. 1 is a diagram showing a configuration when a hydraulic drive circuit according to the present invention is applied to an injection device of a hydraulic injection molding machine.
FIG. 2 is a diagram for explaining a conventional hydraulic drive circuit applied to an injection device of a hydraulic injection molding machine.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 Variable capacity pump 11 Flow sensor 12 Pressure sensor 13 Switching valve 14 Internal actuators 15 and 30 Control valve 20 Injection cylinder 31 Pressure release drain piping

Claims (1)

斜板位置を制御するための制御弁を備え、抵抗弁を介して吐出油圧を被制御アクチュエータに供給するための斜板式可変容量ポンプにおいて、前記制御弁の１つのポートを圧抜きポートとして利用し、前記抵抗弁と前記被制御アクチュエータとの間の油圧配管と前記圧抜きポートとを接続する圧抜きドレン配管を設け、ポンプ圧抜き制御時に直接、前記制御弁から圧抜きを行うようにしたことを特徴とする斜板式可変容量ポンプを用いた油圧駆動回路。In a swash plate type variable displacement pump having a control valve for controlling the swash plate position and supplying discharge hydraulic pressure to a controlled actuator via a resistance valve, one port of the control valve is used as a pressure release port. In addition, a pressure relief drain pipe that connects the hydraulic pipe between the resistance valve and the controlled actuator and the pressure relief port is provided, and the pressure relief is performed directly from the control valve during pump pressure relief control. A hydraulic drive circuit using a swash plate type variable displacement pump.
JP03951799A 1999-02-18 1999-02-18 Hydraulic drive circuit using swash plate type variable displacement pump Expired - Fee Related JP3807581B2 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
JP03951799A JP3807581B2 (en) 1999-02-18 1999-02-18 Hydraulic drive circuit using swash plate type variable displacement pump

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
JP03951799A JP3807581B2 (en) 1999-02-18 1999-02-18 Hydraulic drive circuit using swash plate type variable displacement pump

Publications (2)

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JP2000240603A JP2000240603A (en) 2000-09-05
JP3807581B2 true JP3807581B2 (en) 2006-08-09

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Family Cites Families (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH021522Y2 (en) * 1986-05-14 1990-01-16
JP2964607B2 (en) * 1990-10-11 1999-10-18 日産自動車株式会社 Hydraulic supply device

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