JP2011252511A

JP2011252511A - Hydraulic driving device of construction machine

Info

Publication number: JP2011252511A
Application number: JP2010124828A
Authority: JP
Inventors: Yasutaka Tsuriga; 靖貴釣賀; Kiwamu Takahashi; 究高橋; Keiji Takebayashi; 圭史竹林; Kazushige Mori; 和繁森
Original assignee: Hitachi Construction Machinery Co Ltd
Current assignee: Hitachi Construction Machinery Co Ltd
Priority date: 2010-05-31
Filing date: 2010-05-31
Publication date: 2011-12-15

Abstract

PROBLEM TO BE SOLVED: To provide a hydraulic driving device of a construction machine by which necessary actuator speed can be obtained by feeding the necessary maximum flow quantity as before in actuator operation other than running, the loss of energy can be reduced during running, and the efficiency of energy can be improved.SOLUTION: The hydraulic driving device has a running detecting circuit 33, a reduced torque control piston 35, and a reduced torque control release switch valve 36, control pilot pressure is generated in the first pilot oil passage 32 of the running detecting circuit 33 during running, and reduced torque control is carried out with driving pressure acting in the reduced torque control piston 35. Thereby the discharging flow rate of the hydraulic pump is reduced, the saturation state of an oil pump is generated, the target compensate pressure difference of a pressure compensate valve is lowered, the fore and aft pressure difference of a pressure compensate valve is also lowered, and the inner pressure loss of a flow rate control valve is reduced.

Description

本発明は油圧ショベル等の走行モータを備えた建設機械の油圧駆動装置に係わり、特に、油圧式ミニショベルの走行時のエネルギ効率を向上することができる建設機械の油圧駆動装置に関する。 The present invention relates to a hydraulic drive device for a construction machine including a travel motor such as a hydraulic excavator, and more particularly to a hydraulic drive device for a construction machine that can improve energy efficiency during travel of a hydraulic mini-excavator.

油圧ポンプ（メインポンプ）の吐出圧が複数のアクチュエータの最高負荷圧より目標差圧だけ高くなるよう油圧ポンプの吐出流量を制御する油圧駆動装置はロードセンシングシステムと呼ばれている。このロードセンシングシステムでは、複数の流量制御弁の前後差圧をそれぞれ圧力補償弁により所定差圧に保持し、複数のアクチュエータを同時に駆動する複合操作時に負荷圧の大小に係わらず流量制御弁の開口面積に応じた比率で圧油を供給できるようにしている。 A hydraulic drive device that controls the discharge flow rate of the hydraulic pump so that the discharge pressure of the hydraulic pump (main pump) is higher than the maximum load pressure of a plurality of actuators by a target differential pressure is called a load sensing system. In this load sensing system, the differential pressure across the flow control valves is held at a predetermined differential pressure by a pressure compensation valve, and the flow control valve is opened regardless of the load pressure during combined operation in which multiple actuators are driven simultaneously. Pressure oil can be supplied at a ratio according to the area.

このようなロードセンシングシステムでは、油圧ポンプの吐出圧と複数のアクチュエータの最高負荷圧との差圧（以下差圧ΔＰLSという）を圧力補償弁に導き、圧力補償弁のそれぞれの目標補償差圧を差圧ΔＰLSにより設定して、流量制御弁の前後差圧をその差圧ΔＰLSに保持するよう制御することが行われている（例えば特許文献１）。これにより複数のアクチュエータを同時に駆動する複合動作時に、油圧ポンプの吐出流量が不足するサチュレーション状態になったとき、サチュレーションの程度に応じて差圧ΔＰLSが低下し、圧力補償弁の目標補償差圧すなわち流量制御弁の前後差圧が小さくなるため、油圧ポンプの吐出流量をそれぞれのアクチュエータが要求する流量の比に再分配することができる。 In such a load sensing system, the differential pressure between the discharge pressure of the hydraulic pump and the maximum load pressure of a plurality of actuators (hereinafter referred to as differential pressure ΔPLS) is led to the pressure compensation valve, and the target compensation differential pressure of each pressure compensation valve is calculated. Control is performed by setting the differential pressure ΔPLS so that the differential pressure before and after the flow rate control valve is maintained at the differential pressure ΔPLS (for example, Patent Document 1). As a result, during a combined operation in which a plurality of actuators are driven simultaneously, when a saturation state occurs in which the discharge flow rate of the hydraulic pump is insufficient, the differential pressure ΔPLS decreases according to the degree of saturation, and the target compensation differential pressure of the pressure compensation valve, that is, Since the differential pressure across the flow control valve is reduced, the discharge flow rate of the hydraulic pump can be redistributed to the flow rate ratio required by each actuator.

特開２００１−１９３７０５号公報JP 2001-193705 A

上述した従来のロードセンシングシステムにおいては、定常走行時も油圧ポンプの吐出圧がアクチュエータの最高負荷圧よりも目標差圧だけ高くなるように油圧ポンプ吐出流量を制御するとともに、油圧ポンプの吐出圧と最高負荷圧との差圧ΔＰLSを圧力補償弁に導き、流量制御弁の前後差圧が同じ差圧ΔＰLSに保持されるように制御している。この流量制御弁の前後差圧ΔＰLSの保持は、複雑な複合操作時に、負荷圧の異なる各アクチュエータに流量制御弁の開口面積比に応じた流量を分配するために必要なものである。しかし、定常走行時は、その差圧ΔＰLSがエネルギのロスになってしまう。 In the conventional load sensing system described above, the hydraulic pump discharge flow rate is controlled so that the discharge pressure of the hydraulic pump is higher than the maximum load pressure of the actuator by the target differential pressure even during steady running, and the discharge pressure of the hydraulic pump A differential pressure ΔPLS with respect to the maximum load pressure is guided to the pressure compensation valve, and control is performed so that the differential pressure before and after the flow control valve is maintained at the same differential pressure ΔPLS. The holding of the front-rear differential pressure ΔPLS of the flow rate control valve is necessary for distributing the flow rate according to the opening area ratio of the flow rate control valve to the actuators having different load pressures during complex combined operation. However, during steady running, the differential pressure ΔPLS results in energy loss.

すなわち、走行モータが必要とする最大流量とブームシリンダ、アームシリンダ等の他のアクチュエータが必要とする最大流量を比べた場合、走行モータの方が他のアクチュエータよりも最大流量が少ないという関係にある。従来は、走行時においても流量制御弁の前後差圧を走行以外のアクチュエータ動作を行う場合と同じに制御していたため、走行モータが必要とする最大流量を他のアクチュエータが必要とする最大流量よりも少なくするために、走行用の流量制御弁の最大開口面積を他のアクチュエータの流量制御弁よりも小さく設定していた。この場合、走行以外のアクチュエータ動作では、流量制御弁の最大開口面積が大きいため、比較的少ない圧損でアクチュエータに必要な最大流量を供給し、必要なアクチュエータ速度を得ることができる。しかし、走行時は、流量制御弁の最大開口面積が他のアクチュエータのものよりも小さいため、流量制御弁を介して走行モータに圧油が供給されるとき、最大開口面積が小さくなった分、流量制御弁の内部圧損が増加し、エネルギロスが増加する。 That is, when the maximum flow rate required by the travel motor is compared with the maximum flow rate required by other actuators such as boom cylinders and arm cylinders, the travel motor has a smaller maximum flow rate than other actuators. . Conventionally, even during traveling, the differential pressure across the flow control valve was controlled in the same way as when actuator operations other than traveling were performed, so the maximum flow required by the traveling motor was greater than the maximum flow required by other actuators. Therefore, the maximum opening area of the flow control valve for traveling is set smaller than the flow control valves of other actuators. In this case, since the maximum opening area of the flow rate control valve is large in actuator operations other than traveling, the required maximum flow rate can be supplied to the actuator with a relatively small pressure loss, and the required actuator speed can be obtained. However, when traveling, because the maximum opening area of the flow control valve is smaller than that of other actuators, when pressure oil is supplied to the traveling motor via the flow control valve, the maximum opening area is reduced, The internal pressure loss of the flow control valve increases and the energy loss increases.

本発明の目的は、走行以外のアクチュエータ動作では、従来通り、必要な最大流量を供給して必要なアクチュエータ速度を得ることができるとともに、走行時はエネルギーのロスを低減し、エネルギ効率の向上を可能とする建設機械の油圧駆動装置を提供することである。 The object of the present invention is to provide the required maximum flow rate and obtain the required actuator speed as usual in actuator operations other than traveling, while reducing energy loss and improving energy efficiency during traveling. It is an object of the present invention to provide a hydraulic drive device for a construction machine that makes it possible.

（１）上記目的を達成するために、本発明は、エンジンと、このエンジンにより駆動される可変容量型の油圧ポンプと、この油圧ポンプから吐出された圧油により駆動される走行用の油圧モータを含む複数のアクチュエータと、前記油圧ポンプから前記複数のアクチュエータに供給される圧油の流量を制御する走行用の流量制御弁を含む複数の流量制御弁と、前記複数の流量制御弁の前後差圧をそれぞれ制御する複数の圧力補償弁と、前記油圧ポンプの吐出圧が上昇すると前記油圧ポンプの押しのけ容積を減らし、前記油圧ポンプの吸収トルクが予め設定した最大吸収トルクを超えないように制御するポンプトルク制御部及び前記油圧ポンプの吐出圧が前記複数のアクチュエータの最高負荷圧より目標差圧だけ高くなるよう前記油圧ポンプの押しのけ容積を制御するポンプ流量制御部を有するポンプ制御装置とを備え、前記複数の圧力補償弁は、前記流量制御弁の前後差圧が前記メインポンプの吐出圧と前記複数のアクチュエータの最高負荷圧との差圧に保持されるようにそれぞれの流量制御弁の前後差圧を制御する建設機械の油圧駆動装置において、前記エンジンにより駆動されるパイロットポンプと、このパイロットポンプの吐出油が供給される圧油供給油路に絞りを介して接続された第１パイロット油路を有し、前記走行用の油圧モータが駆動される走行時に前記第１パイロット油路に制御パイロット圧を発生させる走行検出回路と、前記第１パイロット油路に第２パイロット油路を介して接続され、前記第１パイロット油路に制御パイロット圧が発生したときにその制御パイロット圧が駆動圧力として導かれ、前記油圧ポンプの最大吸収トルクを減らす減トルク制御を行う減トルク制御ピストンと、前記第２パイロット油路に接続され、前記走行用の油圧モータの負荷圧が所定圧力を超えて上昇するときに前記第２パイロット油路をタンクに開放して、前記減トルク制御ピストンによる減トルク制御を解除する切替弁とを備えるものとする。 (1) In order to achieve the above object, the present invention provides an engine, a variable displacement hydraulic pump driven by the engine, and a traveling hydraulic motor driven by pressure oil discharged from the hydraulic pump. A plurality of flow control valves including a flow control valve for traveling that controls the flow rate of pressure oil supplied from the hydraulic pump to the plurality of actuators, and a difference between before and after the plurality of flow control valves A plurality of pressure compensating valves for controlling the pressure respectively, and when the discharge pressure of the hydraulic pump rises, the displacement of the hydraulic pump is reduced, and the absorption torque of the hydraulic pump is controlled so as not to exceed a preset maximum absorption torque The discharge pressure of the pump torque control unit and the hydraulic pump is adjusted so that the target differential pressure is higher than the maximum load pressure of the plurality of actuators. A pump control device having a pump flow rate control unit for controlling a displacement volume, wherein the plurality of pressure compensation valves have a differential pressure across the flow rate control valve that is a maximum of the discharge pressure of the main pump and the plurality of actuators. In a hydraulic drive device for a construction machine that controls the differential pressure across each flow control valve so as to be maintained at a differential pressure from a load pressure, a pilot pump driven by the engine and a discharge oil of the pilot pump are supplied A first pilot oil passage connected to the pressure oil supply oil passage through a throttle, and generating a control pilot pressure in the first pilot oil passage during traveling when the traveling hydraulic motor is driven A detection circuit is connected to the first pilot oil passage through a second pilot oil passage, and when a control pilot pressure is generated in the first pilot oil passage, A lot pressure is guided as a driving pressure, and a torque reduction control piston for performing torque reduction control for reducing the maximum absorption torque of the hydraulic pump, and a load pressure of the traveling hydraulic motor connected to the second pilot oil passage are predetermined. A switching valve is provided that opens the second pilot oil passage to the tank when the pressure exceeds the pressure and releases the torque reduction control by the torque reduction control piston.

このように構成した本発明においては、走行以外のアクチュエータ動作では、第１パイロット油路に制御パイロット圧が発生せず、減トルク制御ピストンに駆動圧力は発生しないため、減トルク制御は行われず、ポンプ制御装置のポンプトルク制御部は、通常通り、油圧ポンプの吸収トルクが予め設定した最大吸収トルクを超えないように制御し、油圧駆動装置は通常通り動作する。これにより従来通り、必要な最大流量を供給して必要なアクチュエータ速度を得ることができる。 In the present invention configured as described above, in the actuator operation other than traveling, no control pilot pressure is generated in the first pilot oil passage, and no driving pressure is generated in the reduced torque control piston. Therefore, the reduced torque control is not performed. The pump torque control unit of the pump control device performs control so that the absorption torque of the hydraulic pump does not exceed a preset maximum absorption torque as usual, and the hydraulic drive device operates normally. As a result, the required maximum flow rate can be supplied and the required actuator speed can be obtained as usual.

定常走行等の走行時は、走行検出回路は第１パイロット油路に制御パイロット圧が発生し、減トルク制御ピストンに駆動圧力が作用して減トルク制御が行われる。この減トルク制御により油圧ポンプの最大吸収トルクが減少し、油圧ポンプの吐出流量が減少する。この油圧ポンプの吐出流量の減少により油圧ポンプのサチュレーション状態が発生し、油圧ポンプの吐出圧と最高負荷圧との差圧がポンプ流量制御部の目標差圧よりも小さくなり、圧力補償弁により制御される流量制御弁の前後差圧も同様に低下する。これにより流量制御弁の内部圧損が低減し、エネルギーのロスを低減し、エネルギ効率を向上することができる。 During travel such as steady travel, the travel detection circuit generates control pilot pressure in the first pilot oil passage, and drive torque acts on the torque reduction control piston to perform torque reduction control. By this torque reduction control, the maximum absorption torque of the hydraulic pump is reduced and the discharge flow rate of the hydraulic pump is reduced. Due to this decrease in the discharge flow rate of the hydraulic pump, a saturation state of the hydraulic pump occurs, and the differential pressure between the discharge pressure of the hydraulic pump and the maximum load pressure becomes smaller than the target differential pressure of the pump flow rate control unit and is controlled by the pressure compensation valve. Similarly, the differential pressure across the flow control valve is also reduced. Thereby, the internal pressure loss of the flow control valve can be reduced, energy loss can be reduced, and energy efficiency can be improved.

走行加速時、登坂時等、走行用の油圧モータの負荷圧が所定圧力を超えて上昇する走行時は、切替弁は第２パイロット油路をタンクに開放して、減トルク制御ピストンによる減トルク制御を解除する。これにより油圧ポンプの最大吸収トルクは本来の設定値（定格）へと戻り、走破性を確保することができる。 When traveling, such as during acceleration or climbing, when the load pressure of the traveling hydraulic motor rises above a predetermined pressure, the switching valve opens the second pilot oil passage to the tank and reduces torque by the torque reduction control piston. Release control. As a result, the maximum absorption torque of the hydraulic pump returns to the original set value (rated), and the running performance can be ensured.

（２）上記（１）において、好ましくは、前記走行検出回路は、前記第１パイロット油路から分岐した複数の分岐油路と、この複数の分岐油路とタンクＴとの間にそれぞれ配置され、前記複数の流量制御弁のそれぞれのメインスプールと連動して対応するメインスプールの動作を検出する複数の動作検出弁を有し、前記複数の動作検出弁は、前記走行用の油圧モータが駆動される走行時に前記第１パイロット油路とタンクとの連通を遮断することにより前記第１パイロット油路に前記制御パイロット圧を発生させる。 (2) In the above (1), preferably, the travel detection circuit is arranged between a plurality of branch oil passages branched from the first pilot oil passage and between the plurality of branch oil passages and the tank T. And a plurality of operation detection valves that detect the operation of the corresponding main spool in conjunction with the respective main spools of the plurality of flow control valves, and the plurality of operation detection valves are driven by the traveling hydraulic motor During the traveling, the control pilot pressure is generated in the first pilot oil passage by shutting off the communication between the first pilot oil passage and the tank.

これにより走行検出回路は複数の流量制御弁のそれぞれのメインスプールの動作を検出し、走行時に第１パイロット油路に制御パイロット圧を発生させることができる。 Thus, the travel detection circuit can detect the operation of the main spool of each of the plurality of flow control valves, and can generate a control pilot pressure in the first pilot oil passage during travel.

（３）また、上記（１）において、好ましくは、前記減トルク制御ピストンによる減トルク制御が行われないときの前記油圧ポンプの吐出圧と前記最高負荷圧との差圧をΔＰLS0、前記減トルク制御ピストンによる減トルク制御時における前記油圧ポンプの吐出圧と前記最高負荷圧との差圧をΔＰLSS、前記走行に必要な流量をＱｔ、前記走行用の流量制御弁の最大開口面積をＡａ、前記メインポンプの吐出圧と前記最高負荷圧との差圧がΔＰLS0にあるときに、前記走行用の油圧モータに流量Ｑｔを供給可能な流量制御弁の最大開口面積をＡｂとしたとき、前記最大開口面積Ａａは前記最大開口面積Ａｂの√（ΔＰLS0／ΔＰLSS）倍である。 (3) In the above (1), preferably, the differential pressure between the discharge pressure of the hydraulic pump and the maximum load pressure when the torque reduction control by the torque reduction control piston is not performed is ΔPLS0, the torque reduction At the time of torque reduction control by the control piston, the differential pressure between the discharge pressure of the hydraulic pump and the maximum load pressure is ΔPLS, the flow required for the travel is Qt, the maximum opening area of the flow control valve for travel is Aa, When the differential pressure between the discharge pressure of the main pump and the maximum load pressure is ΔPL S0, the maximum opening area of the flow rate control valve capable of supplying the flow rate Qt to the traveling hydraulic motor is Ab. The area Aa is √ (ΔPLS0 / ΔPLSS) times the maximum opening area Ab.

このように走行用の流量制御弁の最大開口面積を設定することにより、走行時に油圧ポンプのサチュレーション状態が発生して流量制御弁の前後差圧が減少しても、走行に必要な流量を確保することができる。 By setting the maximum opening area of the flow control valve for travel in this way, even if a hydraulic pump saturation condition occurs during travel and the differential pressure across the flow control valve decreases, the flow required for travel is secured. can do.

（４）また、上記（１）において、好ましくは、前記走行用の油圧モータの負荷圧が急上昇したときに前記減トルク制御解除用の切替弁による前記第１パイロット油路の制御パイロット圧の低下を徐々に行わせ、前記減トルク制御の解除を緩やかに行う圧力遅延回路を更に備える。 (4) In the above (1), preferably, when the load pressure of the traveling hydraulic motor suddenly rises, the control pilot pressure in the first pilot oil passage is lowered by the switching valve for releasing the torque reduction control. Is further provided, and a pressure delay circuit for gradually releasing the torque reduction control is further provided.

これにより例えば走行中に石などの抵抗物に乗り上げ、走行用の油圧モータの負荷圧が急上昇した場合は、減トルク制御が緩やかに解除されるため、油圧ポンプの最大吸収トルクが急上昇して油圧ポンプの吐出流量が急に増加し、走行の急加速が生じるという不具合を防止することができる。 As a result, for example, if the load pressure of a hydraulic motor for traveling suddenly rises on a resistor such as a stone while traveling, the torque reduction control is released gently, so the maximum absorption torque of the hydraulic pump suddenly increases and the hydraulic pressure It is possible to prevent a problem that the discharge flow rate of the pump suddenly increases and sudden acceleration of traveling occurs.

本発明によれば、走行以外のアクチュエータ動作では、従来通り、必要な最大流量を供給して必要なアクチュエータ速度を得ることができるとともに、走行時は減トルク制御によりエネルギーのロスを低減し、エネルギ効率を向上することができる。 According to the present invention, in actuator operation other than traveling, the required maximum flow rate can be supplied and the required actuator speed can be obtained as before, and energy loss can be reduced by reducing torque control during traveling. Efficiency can be improved.

また、走行加速時、登坂時等、走行用の油圧モータの負荷圧が所定圧力を超えて上昇する走行時は、減トルク制御が解除されるため、油圧ポンプの最大吸収トルクは本来の設定値（定格）へと戻り、走破性を確保することができる。 In addition, when the vehicle is running, when the load pressure of the hydraulic motor for traveling rises above a predetermined pressure, such as during traveling acceleration or when climbing, the reduced torque control is released, so the maximum absorption torque of the hydraulic pump is the original set value. Return to (Rating) and secure running performance.

本発明の第１の実施の形態における建設機械の油圧駆動装置の構成を示す油圧回路図である。1 is a hydraulic circuit diagram showing a configuration of a hydraulic drive device for a construction machine according to a first embodiment of the present invention. 走行用の流量制御弁の開口面積特性を示す図である。It is a figure which shows the opening area characteristic of the flow control valve for driving | running | working. 本発明が適用される建設機械の一例である油圧ショベルの外観を示す図である。It is a figure which shows the external appearance of the hydraulic shovel which is an example of the construction machine with which this invention is applied. 減トルク制御ピストンによるメインポンプの吸収トルクの変化を示すトルク線図である。It is a torque diagram which shows the change of the absorption torque of the main pump by a reduction torque control piston. 減トルク制御解除切替弁の作用によるメインポンプの吸収トルクの変化を示すトルク線図である。It is a torque diagram which shows the change of the absorption torque of the main pump by the effect | action of a reduction torque control cancellation | release switching valve. 減トルク制御解除切替弁に導かれる最高負荷圧（走行負荷圧）と同切替弁により調整される第１パイロット油路の制御パイロット圧との関係を示す図である。It is a figure which shows the relationship between the maximum load pressure (traveling load pressure) guide | induced to the reduced torque control cancellation | release switching valve, and the control pilot pressure of the 1st pilot oil path adjusted with the same switching valve. 減トルク制御解除切替弁により調整される第１パイロット油路の制御パイロット圧と減トルク制御ピストンにより調整されるメインポンプの最大吸収トルクとの関係を示す図である。It is a figure which shows the relationship between the control pilot pressure of the 1st pilot oil path adjusted with the reduction torque control cancellation | release switching valve, and the maximum absorption torque of the main pump adjusted with a reduction torque control piston. 本発明の第２の実施の形態における建設機械の油圧駆動装置の構成を示す油圧回路図である。It is a hydraulic circuit diagram which shows the structure of the hydraulic drive device of the construction machine in the 2nd Embodiment of this invention. 本発明の第３の実施の形態における建設機械の油圧駆動装置の構成を示す油圧回路図である。It is a hydraulic circuit diagram which shows the structure of the hydraulic drive device of the construction machine in the 3rd Embodiment of this invention.

以下、本発明の実施の形態を図面に従い説明する。
＜第１の実施の形態＞
図１に本発明の第１の実施の形態における建設機械の油圧駆動装置の構成を示す。 Hereinafter, embodiments of the present invention will be described with reference to the drawings.
<First Embodiment>
FIG. 1 shows a configuration of a hydraulic drive device for a construction machine according to a first embodiment of the present invention.

本実施例における油圧駆動装置は、エンジン１と、エンジン１によって駆動されるメインの油圧ポンプ（以下メインポンプという）２と、メインポンプ２と連動してエンジン１により駆動されるパイロットポンプ３と、コントロールバルブ４と、メインポンプ２から吐出された圧油がコントロールバルブ4を介して供給され、その圧油により駆動される複数のアクチュエータ６ａ，６ｂ，６ｃ，６ｄ，６ｅとを備えている。 The hydraulic drive apparatus in the present embodiment includes an engine 1, a main hydraulic pump (hereinafter referred to as a main pump) 2 driven by the engine 1, a pilot pump 3 driven by the engine 1 in conjunction with the main pump 2, The control valve 4 is provided with a plurality of actuators 6a, 6b, 6c, 6d, and 6e that are supplied with pressure oil discharged from the main pump 2 through the control valve 4 and are driven by the pressure oil.

本実施形態において建設機械は例えば油圧ショベルであり、アクチュエータ６ａ，６ｂは油圧ショベルの左右の走行モータであり、アクチュエータ６ｃ，６ｄ，６ｅはそれぞれ油圧ショベルのブームシリンダ、アームシリンダ、バケットシリンダである。油圧ショベルにはその他のアクチュエータも備えられているが、図１では図示の都合上、それらを省略している。 In this embodiment, the construction machine is, for example, a hydraulic excavator, the actuators 6a, 6b are left and right traveling motors of the hydraulic excavator, and the actuators 6c, 6d, 6e are a boom cylinder, an arm cylinder, and a bucket cylinder of the hydraulic excavator, respectively. Although other actuators are also provided in the hydraulic excavator, they are omitted in FIG. 1 for convenience of illustration.

コントロールバルブ４は、メインポンプ２の吐出油が供給される圧油供給油路２ａに接続され、メインポンプ２から各アクチュエータに供給される圧油の方向と流量をそれぞれ制御する複数のバルブセクション４ａ，４ｂ，４ｃ，４ｄ，４ｅと、複数のアクチュエータ６ａ〜６ｅの負荷圧のうち最も高い負荷圧（以下、最高負荷圧という)ＰLmaxを選択して信号油路２１に出力する最高負荷圧検出手段としての複数のシャトル弁２２ａ，２２ｂ，２２ｃ，２２ｄとを有している。また、図示はしないが、コントロールバルブ４は、メインポンプ２の圧油供給油路２ａに設けられ、メインポンプ２の最高吐出圧（最高ポンプ圧）を制限するメインリリーフ弁と、メインポンプ2の吐出圧Ｐdと最高負荷圧ＰLmaxとの差圧ΔＰLSがある一定値を超えたときにメインポンプ２の吐出流量の一部をタンクＴに戻し、差圧ΔＰLSをその一定値以下に保つアンロード弁とを有している。 The control valve 4 is connected to a pressure oil supply oil passage 2a to which discharge oil of the main pump 2 is supplied, and a plurality of valve sections 4a for controlling the direction and flow rate of the pressure oil supplied from the main pump 2 to each actuator. , 4b, 4c, 4d, 4e and the highest load pressure detection means for selecting the highest load pressure (hereinafter referred to as the maximum load pressure) PLmax among the load pressures of the plurality of actuators 6a-6e and outputting it to the signal oil passage 21 As a plurality of shuttle valves 22a, 22b, 22c, and 22d. Although not shown, the control valve 4 is provided in the pressure oil supply oil passage 2 a of the main pump 2, a main relief valve for limiting the maximum discharge pressure (maximum pump pressure) of the main pump 2, and the main pump 2 When the differential pressure ΔPLS between the discharge pressure Pd and the maximum load pressure PLmax exceeds a certain value, a part of the discharge flow rate of the main pump 2 is returned to the tank T, and the unload valve that keeps the differential pressure ΔPLS below the certain value. And have.

バルブセクション４ａは圧力補償弁７ａと流量制御弁（メインスプール）８ａとから構成され、バルブセクション４ｂは圧力補償弁７ｂと流量制御弁（メインスプール）８ｂとから構成され、バルブセクション４ｃは圧力補償弁７ｃと流量制御弁（メインスプール）８ｃとから構成され、バルブセクション４ｄは圧力補償弁７ｄと流量制御弁（メインスプール）８ｄとから構成され、バルブセクション４ｅは圧力補償弁７ｅと流量制御弁（メインスプール）８ｅとから構成されている。 The valve section 4a is composed of a pressure compensation valve 7a and a flow rate control valve (main spool) 8a, the valve section 4b is composed of a pressure compensation valve 7b and a flow rate control valve (main spool) 8b, and the valve section 4c is pressure compensated. The valve section 4d includes a pressure compensation valve 7d and a flow control valve (main spool) 8d, and the valve section 4e includes the pressure compensation valve 7e and the flow control valve. (Main spool) 8e.

流量制御弁８ａ〜８ｅは、メインポンプ２からそれぞれのアクチュエータ６ａ〜６ｅに供給される圧油の方向と流量をそれぞれ制御し、圧力補償弁７ａ〜７ｅは流量制御弁８ａ〜８ｅの前後差圧をそれぞれ設定値（目標補償差圧）に保持するよう制御する。 The flow rate control valves 8a to 8e control the direction and flow rate of the pressure oil supplied from the main pump 2 to the actuators 6a to 6e, respectively. The pressure compensation valves 7a to 7e are differential pressures before and after the flow rate control valves 8a to 8e. Are controlled to be kept at the set value (target compensation differential pressure).

圧力補償弁７ａ〜７ｅは目標差圧設定用の対向する受圧部２４ａ，２５ａ；２４ｂ，２５ｂ；２４ｃ，２５ｃ；２４ｄ，２５ｄ；２４ｅ，２５ｅを有し、受圧部２４ａ，２５ａ〜２４ｅ，２５ｅにはメインポンプ２の吐出圧（ポンプ圧）Ｐdと最高負荷圧ＰLmaxがそれぞれ導かれ、ポンプ圧Ｐdと最高負荷圧ＰLmaxとの差圧ΔＰLSにより目標補償差圧が設定されている。このような目標補償差圧の設定により、圧力補償弁７ａ〜７ｅは流量制御弁８ａ〜８ｅの前後差圧がポンプ圧Ｐdと最高負荷圧ＰLmaxとの差圧ΔＰLSに等しくなるように制御する。これにより複数のアクチュエータを同時に駆動する複合操作時は、アクチュエータ６ａ〜６ｅの負荷圧の大小に係わらず、流量制御弁８ａ〜８ｅの開口面積比に応じてメインポンプ２の吐出流量を分配し、複合操作性を確保することができる。また、メインポンプ２の吐出流量が要求流量に満たないサチュレーション状態になった場合は、差圧ΔＰLSはその供給不足の程度に応じて低下し、これに応じて圧力補償弁７ａ〜７ｅが制御する流量制御弁８ａ〜８ｅの前後差圧が同じ割合で低下して流量制御弁８ａ〜８ｅの通過流量が同じ割合で減少するため、この場合も流量制御弁８ａ〜８ｅの開口面積比に応じてメインポンプ２吐出流量を分配し、複合操作性を確保することができる。 The pressure compensation valves 7a to 7e have opposing pressure receiving portions 24a and 25a; 24b and 25b; 24c and 25c; 24d and 25d; 24e and 25e for setting a target differential pressure, and the pressure receiving portions 24a and 25a to 24e and 25e are provided. The discharge pressure (pump pressure) Pd and the maximum load pressure PLmax of the main pump 2 are respectively derived, and the target compensation differential pressure is set by the differential pressure ΔPLS between the pump pressure Pd and the maximum load pressure PLmax. By setting the target compensation differential pressure, the pressure compensation valves 7a to 7e are controlled so that the differential pressure across the flow control valves 8a to 8e is equal to the differential pressure ΔPLS between the pump pressure Pd and the maximum load pressure PLmax. As a result, during the combined operation of simultaneously driving a plurality of actuators, the discharge flow rate of the main pump 2 is distributed according to the opening area ratio of the flow rate control valves 8a to 8e regardless of the load pressure of the actuators 6a to 6e. Combined operability can be ensured. When the discharge flow rate of the main pump 2 is in a saturation state where the required flow rate is less than the required flow rate, the differential pressure ΔPLS decreases according to the degree of supply shortage, and the pressure compensation valves 7a to 7e control accordingly. Since the front-rear differential pressure of the flow control valves 8a to 8e decreases at the same rate and the passing flow rate of the flow control valves 8a to 8e decreases at the same rate, also in this case, depending on the opening area ratio of the flow control valves 8a to 8e. The discharge flow rate of the main pump 2 can be distributed to ensure composite operability.

また、本実施の形態の油圧駆動装置は、パイロットポンプ３の吐出油が供給される圧油供給油路３ａに接続され、圧油供給油路３ａの圧力を一定に保つパイロットリリーフ弁１１と、圧油供給油路３ａに接続された操作装置１２ａ，１２ｂ，１２ｃ，１２ｄとを備えている。操作装置１２ａ，１２ｂは走行用の流量制御弁８ａ，８ｂを操作するためのものであり、ペダルの踏み込み量に応じて圧油供給油路３ａの圧油に基づいて制御パイロット圧を生成するパイロットバルブ（減圧弁）備えている。操作装置１２ｃ，１２ｄは走行以外の流量制御弁８ｃ〜８ｅ等を操作するためのものであり、操作レバーの操作量に応じて圧油供給油路３ａの圧油に基づいて制御パイロット圧を生成するパイロットバルブ（減圧弁）備えている。 The hydraulic drive device of the present embodiment is connected to a pressure oil supply oil passage 3a to which the discharge oil of the pilot pump 3 is supplied, and a pilot relief valve 11 that keeps the pressure of the pressure oil supply oil passage 3a constant, Operation devices 12a, 12b, 12c, and 12d connected to the pressure oil supply oil passage 3a are provided. The operating devices 12a and 12b are for operating the flow control valves 8a and 8b for traveling, and pilots that generate control pilot pressure based on the pressure oil in the pressure oil supply oil passage 3a in accordance with the amount of depression of the pedal. A valve (pressure reducing valve) is provided. The operation devices 12c and 12d are for operating the flow control valves 8c to 8e other than traveling, and generate control pilot pressure based on the pressure oil in the pressure oil supply oil passage 3a according to the operation amount of the operation lever. A pilot valve (pressure reducing valve) is provided.

メインポンプ２は可変容量型の油圧ポンプであり、ポンプトルク制御部を構成するトルク制限制御ピストン１５と、ポンプ流量制御部を構成するＬＳ制御弁１６及びＬＳ制御傾転アクチュエータ１７を有している。 The main pump 2 is a variable displacement hydraulic pump, and has a torque limit control piston 15 constituting a pump torque control unit, an LS control valve 16 and an LS control tilt actuator 17 constituting a pump flow rate control unit. .

トルク制限制御ピストン１５はメインポンプ２の吐出圧が高くなるとメインポンプ２の傾転角を減らして、メインポンプ２の吸収トルクがバネ１５ａにより設定した値（最大トルク）を越えないように制限するものであり、これによりメインポンプ２の消費馬力を制限し、過負荷によるエンジン１の停止（エンジンストール）を防止する。 The torque limit control piston 15 reduces the tilt angle of the main pump 2 when the discharge pressure of the main pump 2 increases, and limits the absorption torque of the main pump 2 so as not to exceed the value (maximum torque) set by the spring 15a. This limits the horsepower consumed by the main pump 2 and prevents the engine 1 from being stopped (engine stall) due to overload.

ＬＳ制御弁１６は対向する受圧部１６ａ，１６ｂを有し、受圧部１６ａにはメインポンプ２の吐出圧が導かれ、受圧部１６ｂには信号油路２１の最高負荷圧ＰLmaxが導かれている。また、ＬＳ制御弁の受圧部１６ｂ側にはロードセンシング制御の目標差圧（目標ＬＳ差圧）を設定するためのバネ１６ｃが配置され、メインポンプ２の吐出圧が最高負荷圧ＰLmaxにバネ１６ｃの設定圧を加えた圧力よりも高くなると、圧油供給油路３ａの圧油をＬＳ制御傾転アクチュエータ１７に導いてメインポンプ２の傾転角を減らし、メインポンプ２の吐出圧が最高負荷圧ＰLmaxにバネ１６ｃの設定圧を加えた圧力よりも低くなると、ＬＳ制御傾転アクチュエータ１７をタンクＴに連通してメインポンプ２の傾転角を増やし、メインポンプ２の吐出圧Ｐdが最高負荷圧ＰLmaxよりもバネ１６ｃの設定値（目標ＬＳ差圧）だけ高くなるようにメインポンプ２の傾転量（押しのけ容積）を制御する。このようにＬＳ制御弁１６及びＬＳ制御傾転アクチュエータ１７は、メインポンプ２の吐出圧が複数のアクチユエータ６ａ〜６ｅの最高負荷圧ＰLmaxよりも目標ＬＳ差圧だけ高くなるようメインポンプ２の傾転を制御する。 The LS control valve 16 has pressure receiving portions 16a and 16b facing each other, the discharge pressure of the main pump 2 is led to the pressure receiving portion 16a, and the maximum load pressure PLmax of the signal oil passage 21 is led to the pressure receiving portion 16b. . Further, a spring 16c for setting a target differential pressure (target LS differential pressure) for load sensing control is arranged on the pressure receiving portion 16b side of the LS control valve, and the discharge pressure of the main pump 2 is set to the maximum load pressure PLmax and the spring 16c. When the pressure becomes higher than the set pressure, the pressure oil in the pressure oil supply oil passage 3a is led to the LS control tilt actuator 17 to reduce the tilt angle of the main pump 2, and the discharge pressure of the main pump 2 is the highest load. When the pressure PLmax is lower than the pressure set by the spring 16c, the LS control tilt actuator 17 is connected to the tank T to increase the tilt angle of the main pump 2, and the discharge pressure Pd of the main pump 2 is the highest load. The amount of displacement (displacement volume) of the main pump 2 is controlled so as to be higher than the pressure PLmax by a set value (target LS differential pressure) of the spring 16c. Thus, the LS control valve 16 and the LS control tilt actuator 17 tilt the main pump 2 so that the discharge pressure of the main pump 2 is higher than the maximum load pressure PLmax of the plurality of actuators 6a to 6e by the target LS differential pressure. To control.

また、前述したように、圧力補償弁７ａ〜７ｅの目標補償差圧はポンプ圧Ｐdと最高負荷圧ＰLmaxとの差圧ΔＰLSにより設定され、流量制御弁８ａ〜８ｅの前後差圧がその差圧ΔＰLSに等しくなるように制御されるため、メインポンプ２の吐出圧が最高負荷圧ＰLmaxよりもバネ１６ｃの設定圧（目標ＬＳ差圧）だけ高くなるように制御されるとき、圧力補償弁７ａ〜７ｅの目標補償差圧もバネ１６ｃの設定圧（目標ＬＳ差圧）に等しくなるように設定され、流量制御弁８ａ〜８ｅの前後差圧はそのバネ１６ｃの設定圧（目標ＬＳ差圧）に等しくなるように制御される。 As described above, the target compensation differential pressures of the pressure compensation valves 7a to 7e are set by the differential pressure ΔPLS between the pump pressure Pd and the maximum load pressure PLmax, and the differential pressures before and after the flow control valves 8a to 8e are the differential pressures. Since the discharge pressure of the main pump 2 is controlled so as to be higher than the maximum load pressure PLmax by the set pressure (target LS differential pressure) of the spring 16c, the pressure compensation valves 7a to 7 are controlled. The target compensation differential pressure of 7e is also set to be equal to the set pressure (target LS differential pressure) of the spring 16c, and the differential pressure before and after the flow control valves 8a to 8e becomes the set pressure of the spring 16c (target LS differential pressure). Controlled to be equal.

本実施の形態の油圧駆動装置は、更にその特徴的構成として、走行検出回路３３と減トルク制御ピストン３５と減トルク制御解除切替弁３６とを備えている。 The hydraulic drive apparatus according to the present embodiment further includes a travel detection circuit 33, a reduced torque control piston 35, and a reduced torque control release switching valve 36 as a characteristic configuration.

走行検出回路３３は、パイロットポンプ３の圧油供給油路３ａに固定絞り要素３１を介して接続された第１パイロット油路３２と、第１パイロット油路３２から分岐した分岐油路３２ａ〜３２ｅと、分岐油路３２ａ〜３２ｅとタンクＴとの間に配置され、流量制御弁８ａ〜８ｅのメインスプールとそれぞれ連動して対応するメインスプールの動作を検出する動作検出弁３７ａ〜３７ｅとを有し、左右の走行モータ６ａ，６ｂが同時に駆動される走行時に、動作検出弁３７ａ〜３７ｅが第１パイロット油路３２とタンクＴとの連通を遮断することにより第１パイロット油路３２に制御パイロット圧を発生させる。減トルク制御ピストン３５は、メインポンプ２に対してトルク制限制御ピストン１５と並列に設けられ、第１パイロット油路３２に制御パイロット圧が発生したときにその制御パイロット圧が第２パイロット油路３４を介して駆動圧力として導かれ、メインポンプ２の傾転を減らす方向に作用して、メインポンプ２の最大吸収トルクを減らす減トルク制御を行う。減トルク制御解除切替弁３６は、第２パイロット油路３４に接続され、走行モータ６ａ，６ｂの負荷圧が所定圧力を超えて上昇するときに第２パイロット油路３４をタンクＴに開放し、減トルク制御ピストン３５による減トルク制御を解除する。 The travel detection circuit 33 includes a first pilot oil passage 32 connected to the pressure oil supply oil passage 3a of the pilot pump 3 via a fixed throttle element 31, and branch oil passages 32a to 32e branched from the first pilot oil passage 32. And operation detection valves 37a to 37e that are arranged between the branch oil passages 32a to 32e and the tank T and detect the operation of the corresponding main spool in conjunction with the main spools of the flow control valves 8a to 8e. When the left and right traveling motors 6a and 6b are driven simultaneously, the operation detection valves 37a to 37e block the communication between the first pilot oil passage 32 and the tank T, so that the first pilot oil passage 32 is controlled by the pilot. Generate pressure. The reduced torque control piston 35 is provided in parallel with the torque limiting control piston 15 with respect to the main pump 2, and when the control pilot pressure is generated in the first pilot oil passage 32, the control pilot pressure is changed to the second pilot oil passage 34. As a driving pressure, the torque is controlled to reduce the maximum absorption torque of the main pump 2 by acting in a direction to reduce the tilt of the main pump 2. The reduced torque control release switching valve 36 is connected to the second pilot oil passage 34, and opens the second pilot oil passage 34 to the tank T when the load pressure of the travel motors 6a, 6b rises above a predetermined pressure. The torque reduction control by the torque reduction control piston 35 is released.

動作検出弁３７ａ〜３７ｅは、走行用の流量制御弁８ａ，８ｂの両方が操作されたときにのみ第１パイロット油路３２とタンクＴとの連通を遮断して第１パイロット油路３２に制御パイロット圧を発生させる３位置切換弁である。これら動作検出弁３７ａ〜３７ｅのうち、走行に係わる動作検出弁３７ａ，３７ｂは走行用の流量制御弁８ａ，８ｂが中立位置（非操作位置）にあるときは開位置にあって、分岐油路３２ａ，３２ｂをタンクＴに連通させ、走行用の流量制御弁８ａ，８ｂが中立位置から操作されると閉位置に切り換えられて、分岐油路３２ａ，３２ｂとタンクＴとの連通を遮断する。走行以外のアクチュエータに係わる動作検出弁３７ｃ〜３７ｅは、対応する流量制御弁８ｃ〜８ｅが中立位置（非操作位置）にあるときは閉位置にあって、対応する分岐油路３２ｃ〜３２ｅとタンクＴとの連通を遮断し、対応する流量制御弁８ｃ〜８ｅが中立位置から操作されると開位置に切り換えられて、分岐油路３２ｃ〜３２ｅをタンクＴに連通させる。これにより走行用の流量制御弁８ａ，８ｂの一方のみが操作されたとき、或いは走行以外の流量制御弁８ｃ〜８ｅの少なくとも１つが操作されたときは、第１パイロット油路３２はタンクＴに連通し、走行用の流量制御弁８ａ，８ｂが同時に操作されたときにのみ第１パイロット油路３２とタンクＴとの連通を遮断し、第１パイロット油路３２に制御パイロット圧が発生するようになる。 The operation detection valves 37a to 37e control the first pilot oil passage 32 by cutting off the communication between the first pilot oil passage 32 and the tank T only when both the travel flow control valves 8a and 8b are operated. This is a three-position switching valve that generates pilot pressure. Among these operation detection valves 37a to 37e, the operation detection valves 37a and 37b related to traveling are in the open position when the flow control valves 8a and 8b for traveling are in the neutral position (non-operating position), and the branch oil passage 32a and 32b are communicated with the tank T, and when the travel flow control valves 8a and 8b are operated from the neutral position, they are switched to the closed position, and the communication between the branch oil passages 32a and 32b and the tank T is cut off. The operation detection valves 37c to 37e related to the actuators other than the traveling are in the closed position when the corresponding flow control valves 8c to 8e are in the neutral position (non-operation position), and the corresponding branch oil passages 32c to 32e and the tank The communication with T is cut off, and when the corresponding flow control valves 8c to 8e are operated from the neutral position, they are switched to the open position, and the branch oil passages 32c to 32e are communicated with the tank T. Accordingly, when only one of the flow control valves 8a and 8b for traveling is operated, or when at least one of the flow control valves 8c to 8e other than traveling is operated, the first pilot oil passage 32 is placed in the tank T. The communication between the first pilot oil passage 32 and the tank T is cut off only when the flow control valves 8a, 8b for communication are operated simultaneously, so that the control pilot pressure is generated in the first pilot oil passage 32. become.

減トルク制御解除切替弁３６は第２パイロット油路３４から分岐した油路３４ａとタンクＴとの間に配置された２位置切換弁であり、閉方向動作側に設けられた切換動作圧設定用のバネ３６ａと、開方向動作側に設けられた受圧部３６ｂとを有し、受圧部３６ｂは油路３９を介して信号油路２１に接続され、切替弁３６の動作はロードセンシング制御で使用する最高負荷圧ＰLmaxにより制御される。すなわち、最高負荷圧ＰLmaxが切替弁３６のバネ３６ａの設定値より低い場合は、切替弁３６は図示の閉位置に保たれ、第２パイロット油路３４の圧力は保持される。バネ３６ａの設定値より最高負荷圧ＰLmaxが高くなった場合は、切替弁３６は開位置に切り換えられ、第２パイロット油路３４の圧力はタンクＴに開放される。切替弁３６の開口面積特性は連続的であり、最高負荷圧ＰLmaxに応じて第２パイロット油路３４の圧力は連続的に変化する。 The torque reduction control release switching valve 36 is a two-position switching valve disposed between the oil passage 34a branched from the second pilot oil passage 34 and the tank T, and is used for setting the switching operation pressure provided on the closing direction operation side. Spring 36a and a pressure receiving portion 36b provided on the opening direction operation side. The pressure receiving portion 36b is connected to the signal oil passage 21 via an oil passage 39, and the operation of the switching valve 36 is used in load sensing control. The maximum load pressure PLmax is controlled. That is, when the maximum load pressure PLmax is lower than the set value of the spring 36a of the switching valve 36, the switching valve 36 is maintained in the illustrated closed position, and the pressure in the second pilot oil passage 34 is maintained. When the maximum load pressure PLmax is higher than the set value of the spring 36a, the switching valve 36 is switched to the open position, and the pressure in the second pilot oil passage 34 is released to the tank T. The opening area characteristic of the switching valve 36 is continuous, and the pressure of the second pilot oil passage 34 continuously changes according to the maximum load pressure PLmax.

図２に、走行用の流量制御弁８ａ，８ｂの開口面積特性を示す。図中、Ｍａが本実施の形態における流量制御弁８ａ，８ｂの開口面積特性であり、Ｍｂが従来の開口面積特性である。 FIG. 2 shows the opening area characteristics of the flow control valves 8a and 8b for traveling. In the figure, Ma is the opening area characteristic of the flow control valves 8a and 8b in the present embodiment, and Mb is the conventional opening area characteristic.

本実施の形態では、走行用の操作装置１２ａ，１２ｂを操作した走行時には、後述する如く、流量制御弁８ａ，８ｂの前後差圧が本来の設定値である圧力ΔＰLS0からΔＰLSSに低減し、そのままでは走行モータ６ａ，６ｂへ供給される圧油の流量が従来のものよりも減少してしまう。そこで、走行モータ６ａ，６ｂへ供給される圧油の流量を従来通りに確保するため、流量制御弁８ａ，８ｂの前後差圧が減少する分、流量制御弁８ａ，８ｂの開口面積を大きく設定している。 In the present embodiment, during traveling by operating the operating devices 12a and 12b for traveling, as will be described later, the differential pressure across the flow control valves 8a and 8b is reduced from the original set value pressure ΔPLS0 to ΔPLSS and remains as it is. Then, the flow rate of the pressure oil supplied to the traveling motors 6a and 6b is reduced as compared with the conventional one. Therefore, in order to ensure the flow rate of the pressure oil supplied to the traveling motors 6a and 6b as usual, the opening area of the flow rate control valves 8a and 8b is set to be large as the differential pressure across the flow rate control valves 8a and 8b decreases. is doing.

すなわち、本実施の形態における流量制御弁６ａ，６ｂの最大開口面積をＡａ、従来の流量制御弁の最大開口面積をＡｂ、走行に必要な流量をＱｔとすると、
Ｑｔ＝ｃＡａ√（２ΔＰLSS／ρ）＝ｃＡｂ√（２ΔＰLS0／ρ）
ｃ：流量係数
ρ：作動油の密度
の関係にあり、
Ａａ＝Ａｂ√（ΔＰLS0／ΔＰLSS）
の関係が得られる。よって、本実施の形態における流量制御弁６ａ，６ｂの最大開口面積Ａａは従来の流量制御弁の最大開口面積Ａｂの√（ΔＰLS0／ΔＰLSS）倍にする必要があり、流量制御弁６ａ，６ｂはそのような最大開口面積を持つ開口面積特性に設定されている。 That is, assuming that the maximum opening area of the flow rate control valves 6a and 6b in the present embodiment is Aa, the maximum opening area of the conventional flow rate control valve is Ab, and the flow rate required for traveling is Qt,
Qt = cAa√ (2ΔPLSS / ρ) = cAb√ (2ΔPLS0 / ρ)
c: Flow coefficient ρ: Hydraulic oil density,
Aa = Ab√ (ΔPLS0 / ΔPLSS)
The relationship is obtained. Therefore, the maximum opening area Aa of the flow control valves 6a and 6b in the present embodiment needs to be √ (ΔPLS0 / ΔPLSS) times the maximum opening area Ab of the conventional flow control valve, and the flow control valves 6a and 6b The opening area characteristic having such a maximum opening area is set.

なお、走行用の流量制御弁６ａ，６ｂの開口面積を増やす代わりに、従来の流量制御弁にパラレルに補助的な流量制御弁を配置し、合計の通過流量を従来の流量制御弁の通過流量と同じになるようにしてもよい。また、走行モータ６ａ，６ｂへ供給される圧油の流量を従来と同じにしなくてもよい場合は、必要とする流量が得られるよう走行用の流量制御弁６ａ，６ｂの開口面積を設定すればよい。 Instead of increasing the opening area of the flow control valves 6a and 6b for travel, an auxiliary flow control valve is arranged in parallel with the conventional flow control valve, and the total flow rate is set to the flow rate of the conventional flow control valve. May be the same. Further, when the flow rate of the pressure oil supplied to the traveling motors 6a and 6b does not have to be the same as the conventional flow rate, the opening area of the traveling flow control valves 6a and 6b should be set so that the required flow rate can be obtained. That's fine.

図３に油圧ショベルの外観を示す。 FIG. 3 shows the appearance of the hydraulic excavator.

図３において、油圧ショベルは、上部旋回体３００と、下部走行体３０１と、スイング式のフロント作業機３０２を備え、フロント作業機３０２は、ブーム３０６、アーム３０７、バケット３０８から構成されている。上部旋回体３００は下部走行体３０１を旋回モータ６ｆの回転によって旋回可能である。上部旋回体３００の前部にはスイングポスト３０３が取り付けられ、このスイングポスト３０３にフロント作業機３０２が上下動可能に取り付けられている。スイングポスト３０３はスイングシリンダ６ｇの伸縮により上部旋回体３００に対して水平方向に回動可能であり、フロント作業機３０２のブーム３０６、アーム３０７、バケット３０８はブームシリンダ６ｃ、アームシリンダ６ｄ、バケットシリンダ６ｅの伸縮により上下方向に回動可能である。下部走行体３０１は中央フレーム３０４を備え、この中央フレーム３０４にはブレードシリンダ６ｈの伸縮により上下動作を行うブレード３０５が取り付けられている。下部走行体３０１は、走行モータ６ａ，６ｂの回転により左右の履帯３１０，３１１を駆動することによって走行を行う。 In FIG. 3, the hydraulic excavator includes an upper swing body 300, a lower traveling body 301, and a swing-type front work machine 302, and the front work machine 302 includes a boom 306, an arm 307, and a bucket 308. The upper swing body 300 can swing the lower traveling body 301 by the rotation of the swing motor 6f. A swing post 303 is attached to the front portion of the upper swing body 300, and a front work machine 302 is attached to the swing post 303 so as to move up and down. The swing post 303 can be rotated in the horizontal direction with respect to the upper swing body 300 by expansion and contraction of the swing cylinder 6g. The boom 306, the arm 307, and the bucket 308 of the front work machine 302 are the boom cylinder 6c, the arm cylinder 6d, and the bucket cylinder. It can be rotated in the vertical direction by expansion and contraction of 6e. The lower traveling body 301 includes a central frame 304, and a blade 305 that moves up and down by expansion and contraction of the blade cylinder 6h is attached to the central frame 304. The lower traveling body 301 travels by driving the left and right crawler belts 310 and 311 by the rotation of the traveling motors 6a and 6b.

上部旋回体３００は運転室３１２を有し、運転室３１２内には走行用の操作装置１２ａ，１２ｂ（図３では片側のみ図示）、旋回用、ブーム用、アーム用、バケット用の操作装置１２ｃ，１２ｄ（図３では一部のみ図示）、ブレード用の操作装置（図示せず）、スイング用の操作装置（図示せず）等が設置されている。 The upper swing body 300 has a driver's cab 312, and operating devices 12 a and 12 b for traveling (only one side is shown in FIG. 3) in the driver's cab 312, operating devices 12 c for swing, boom, arm, and bucket. 12d (only part of which is shown in FIG. 3), a blade operation device (not shown), a swing operation device (not shown), and the like.

次に、本実施の形態の動作を図３及び図４を用いて説明する。 Next, the operation of this embodiment will be described with reference to FIGS.

図４は減トルク制御ピストン３５によるメインポンプ２の吸収トルクの変化を示すトルク線図であり、図５は減トルク制御解除切替弁３６の作用によるメインポンプ２の吸収トルクの変化を示すトルク線図である。 FIG. 4 is a torque diagram showing a change in the absorption torque of the main pump 2 by the reduced torque control piston 35, and FIG. 5 is a torque line showing a change in the absorption torque of the main pump 2 due to the action of the reduced torque control release switching valve 36. FIG.

図４において、横軸はメインポンプ２の吐出圧であり、縦軸はメインポンプ２の容量（押しのけ容積或いは傾転角）である。Ｔａはメインポンプ２の定格トルクＴrateの曲線であり、定格トルクＴrateはポンプトルク制御部のバネ１５ａによって設定されるメインポンプ２の最大吸収トルクである。 In FIG. 4, the horizontal axis represents the discharge pressure of the main pump 2, and the vertical axis represents the capacity of the main pump 2 (displacement volume or tilt angle). Ta is a curve of the rated torque Trate of the main pump 2, and the rated torque Trate is the maximum absorption torque of the main pump 2 set by the spring 15a of the pump torque control unit.

本実施の形態において、走行以外のアクチュエータ動作のとき（走行用の流量制御弁８ａ，８ｂの一方のみが操作されたとき、或いは走行以外の流量制御弁８ｃ〜８ｅの少なくとも１つが操作されたとき）は、第１パイロット油路３２に制御パイロット圧が発生せず、減トルク制御ピストン３５は機能しない。その結果、ポンプトルク制御部にはメインポンプ２の最大吸収トルクとして曲線Ｔａの定格トルクＴrateが設定され、メインポンプ２の吸収トルクはトルク制限制御ピストン１５により定格トルクＴrateを越えないように制御される。 In the present embodiment, when the actuator is operated other than traveling (when only one of the flow control valves 8a and 8b for traveling is operated, or when at least one of the flow control valves 8c to 8e other than traveling is operated) ), No control pilot pressure is generated in the first pilot oil passage 32, and the torque reduction control piston 35 does not function. As a result, the rated torque Trate of the curve Ta is set as the maximum absorption torque of the main pump 2 in the pump torque control unit, and the absorption torque of the main pump 2 is controlled by the torque limit control piston 15 so as not to exceed the rated torque Trate. The

減トルク制御ピストン３５を備えていない従来の油圧駆動装置では、走行時であるか否かに係わらずバネ１５ａによる定格トルクＴrateが設定され、メインポンプ２の吸収トルクは定格トルク曲線Ｔrateを越えないように制御される。 In the conventional hydraulic drive device that does not include the reduced torque control piston 35, the rated torque Trate by the spring 15a is set regardless of whether or not the vehicle is running, and the absorption torque of the main pump 2 does not exceed the rated torque curve Trate. To be controlled.

また、従来の油圧駆動装置では、走行直進時等、走行用の流量制御弁８ａ，８ｂが同時操作される走行時において、メインポンプ２は図３のＣ点で動作する。このときの走行モータ６ａ，６ｂの負荷圧（以下走行負荷圧という）はＰｔであり、メインポンプ２の吐出圧はＰｐｃである。このときメインポンプ２はＬＳ制御弁１６及びＬＳ制御傾転アクチュエータ１７によりメインポンプ２の吐出圧Ｐｄが最高負荷圧ＰLmaxよりΔＰLSだけ高くなるように制御されており、Ｐｐｃ−Ｐｔ＝ΔＰLSの関係にある。また、メインポンプ２の容量はｑｔであり、この容量ｑｔにメインポンプ２の回転数（エンジン回転数）を乗じた流量が走行に必要な流量として走行モータ６ａ，６ｂに供給される。 Further, in the conventional hydraulic drive device, the main pump 2 operates at a point C in FIG. 3 during traveling in which the flow control valves 8a and 8b for traveling are operated simultaneously, such as when traveling straight. At this time, the load pressure of the travel motors 6a and 6b (hereinafter referred to as travel load pressure) is Pt, and the discharge pressure of the main pump 2 is Ppc. At this time, the main pump 2 is controlled by the LS control valve 16 and the LS control tilt actuator 17 so that the discharge pressure Pd of the main pump 2 becomes higher than the maximum load pressure PLmax by ΔPLS, and the relationship of Ppc−Pt = ΔPLS is established. is there. The capacity of the main pump 2 is qt, and a flow rate obtained by multiplying the capacity qt by the rotational speed (engine speed) of the main pump 2 is supplied to the traveling motors 6a and 6b as a flow rate necessary for traveling.

ここで、走行時は、通常、メインポンプ２の吐出油の不足（サチュレーション）は生じておらず、メインポンプ２はロードセンシング制御によりポンプ吐出圧が最高負荷圧ＰLmaxよりもバネ１６ｃの設定圧（目標ＬＳ差圧）だけ高くなるように制御されているため、バネ１６ｃの設定圧（目標ＬＳ差圧）をΔＰLS0とすると、Ｐｐｃ−Ｐｔ＝ΔＰLS＝ΔＰLS0となる。 Here, during running, there is usually no shortage (saturation) of the discharge oil of the main pump 2, and the pump discharge pressure of the main pump 2 is higher than the maximum load pressure PLmax by load sensing control. Since it is controlled to increase by the target LS differential pressure), if the set pressure of the spring 16c (target LS differential pressure) is ΔPLS0, then Ppc−Pt = ΔPLS = ΔPLS0.

本実施の形態において、走行用の流量制御弁８ａ，８ｂが同時操作される走行時は、走行に係わる動作検出弁３７ａ，３７ｂが閉位置に切り換わり、第１パイロット油路３２に制御パイロット圧が発生する。その結果、減トルク制御ピストン３５が機能して、メインポンプ２の最大吸収トルクを減らす減トルク制御が行われる。 In the present embodiment, during travel in which the flow control valves 8a and 8b for travel are operated simultaneously, the motion detection valves 37a and 37b related to travel are switched to the closed position, and the control pilot pressure is applied to the first pilot oil passage 32. Will occur. As a result, the torque reduction control piston 35 functions and the torque reduction control for reducing the maximum absorption torque of the main pump 2 is performed.

図３において、Ｔｂは減トルク制御後のメインポンプ２の最大吸収トルクＴredを示す曲線である。このようにメインポンプ２の最大吸収トルクがＴrateからＴredに減少すると、メインポンプ２の動作点はＣ点からＩ点に遷移し、メインポンプ２の吐出圧は従来のＰpcよりも低いＰpiとなる。これは、メインポンプ２の吐出圧と最高負荷圧ＰLmaxとの差圧ΔＰLSが本来の設定圧であるΔＰLS0からΔＰLSSへと低下し、走行負荷圧Ｐｔに対して十分にＬＳ差圧が確保されていない状態（サチュレーショ状態）であることを意味する。また、この場合、圧力補償弁７ａ〜７ｅのの目標補償差圧はポンプ圧Ｐdと最高負荷圧ＰLmaxとの差圧ΔＰLSによって設定されているため、ロードセンシング差圧ΔＰLSの低下に応じて走行用の流量制御弁８ａ，８ｂの前後差圧もΔＰLS0からΔＰLSSへと低下する。 In FIG. 3, Tb is a curve showing the maximum absorption torque Tred of the main pump 2 after the torque reduction control. Thus, when the maximum absorption torque of the main pump 2 decreases from Trate to Tred, the operating point of the main pump 2 changes from the C point to the I point, and the discharge pressure of the main pump 2 becomes Ppi lower than the conventional Ppc. . This is because the differential pressure ΔPLS between the discharge pressure of the main pump 2 and the maximum load pressure PLmax is reduced from ΔPLS0, which is the original set pressure, to ΔPLSS, and a sufficient LS differential pressure is secured with respect to the traveling load pressure Pt. It means that there is no state (saturation state). In this case, the target compensation differential pressure of the pressure compensation valves 7a to 7e is set by the differential pressure ΔPLS between the pump pressure Pd and the maximum load pressure PLmax. The differential pressure across the flow control valves 8a and 8b also decreases from ΔPLS0 to ΔPLSS.

このように本実施の形態では、メインポンプ２のサチュレーション状態を意図的に発生することで、走行用の流量制御弁８ａ，８ｂの前後差圧を減らし、ポンプトルク負荷を低減することが可能となる。また、前述したように、走行用の流量制御弁８ａ，８ｂの前後差圧の減少を見越して流量制御弁８ａ，８ｂの開口面積を大きく設定しておくため、走行に必要な流量を確保することが可能となる。 Thus, in this embodiment, by intentionally generating the saturation state of the main pump 2, it is possible to reduce the differential pressure across the flow control valves 8a and 8b for traveling and reduce the pump torque load. Become. In addition, as described above, the opening area of the flow rate control valves 8a and 8b is set large in anticipation of a decrease in the differential pressure across the flow rate control valves 8a and 8b for travel, so that a flow rate necessary for travel is ensured. It becomes possible.

この減トルク制御は走行用の流量制御弁８ａ，８ｂが同時操作される走行時にのみ行われ、ターンを想定した左右どちらかの走行モータ６ａ，６ｂの単独の操作では減トルク制御は行われず、定格トルクＴrateにてメインポン２を動作させ、必要なトルクを確保することができる。 This torque reduction control is performed only during traveling in which the flow control valves 8a and 8b for traveling are operated simultaneously, and the torque reduction control is not performed in the single operation of either the left or right traveling motor 6a or 6b assuming a turn. The main pump 2 can be operated at the rated torque Trate to ensure the necessary torque.

更に、走行時でも、走行加速時、登坂時など、走行負荷圧が上昇した場合にも減トルク制御の効果を連続的に下げ、必要な走行トルクを確保できるようにしている。図４はこのときの動作を説明するための図であり、左上側のトルク線図の丸で囲った部分の拡大図が右下側に示されている。 Furthermore, even when the vehicle is traveling, even when traveling acceleration or climbing, such as when traveling load pressure increases, the effect of the reduced torque control is continuously reduced so that necessary traveling torque can be secured. FIG. 4 is a view for explaining the operation at this time, and an enlarged view of a circled portion of the upper left torque diagram is shown on the lower right side.

走行加速時、登坂時など、走行負荷圧ＰｔがＰｔ１，Ｐｔ２へと上昇すると、最高負荷圧（＝走行負荷圧）が上昇し、減トルク制御解除切替弁３６が開方向に連続的に切り換えられて、第１パイロット油路３２に発生した制御パイロット圧が連続的に低下し、減トルク制御ピストン３５の駆動圧が減少する。その結果、減トルク制御は解除され、定格トルク曲線Ｔａ上でメインポンプ２の吐出流量は減少する。 When the travel load pressure Pt increases to Pt1 and Pt2, such as during travel acceleration and climbing, the maximum load pressure (= travel load pressure) increases and the torque reduction control release switching valve 36 is continuously switched in the opening direction. Thus, the control pilot pressure generated in the first pilot oil passage 32 continuously decreases, and the drive pressure of the torque reduction control piston 35 decreases. As a result, the reduced torque control is released, and the discharge flow rate of the main pump 2 decreases on the rated torque curve Ta.

図６Ａは、切替弁３６に導かれる最高負荷圧（走行負荷圧）と切替弁３６により調整される第１パイロット油路３２の制御パイロット圧との関係を示す図であり、図６Ｂは、切替弁３６により調整される第１パイロット油路３２の制御パイロット圧と減トルク制御ピストン３５により調整されるメインポンプ２の最大吸収トルクとの関係を示す図である。最高負荷圧（走行負荷圧）がＰLa以下の走行状態では、切替弁３６は図示の閉位置を保ち、第１パイロット油路３２の制御パイロット圧はパイロットリリーフ弁１１で設定される値Ｐcmaxにある。最高負荷圧（走行負荷圧）がＰLaに達すると切替弁３６は開き始め、第１パイロット油路３２の制御パイロット圧は低下し始める。最高負荷圧（走行負荷圧）が更に上昇してＰLbｎ達すると切替弁３６は完全に開き、第１パイロット油路３２の制御パイロット圧はタンク圧となる。第１パイロット油路３２の制御パイロット圧がパイロットリリーフ弁１１の設定圧であるＰcmaxにある間は、減トルク制御ピストン３５による減トルク制御が機能し、メインポンプ２の最大吸収トルクは定格トルクＴrateからＴredに減少している。第１パイロット油路３２の制御パイロット圧がＰcmaxから低下すると、減トルク制御ピストン３５の駆動圧が低下し、メインポンプ２の最大吸収トルクはＴredから増加し、第１パイロット油路３２の制御パイロット圧がタンク圧になると、メインポンプ２の最大吸収トルクは定格トルクＴrateまで増大する。 6A is a diagram showing the relationship between the maximum load pressure (traveling load pressure) guided to the switching valve 36 and the control pilot pressure of the first pilot oil passage 32 adjusted by the switching valve 36, and FIG. FIG. 4 is a diagram showing the relationship between the control pilot pressure of the first pilot oil passage 32 adjusted by a valve 36 and the maximum absorption torque of the main pump 2 adjusted by a reduced torque control piston 35. In a traveling state where the maximum load pressure (traveling load pressure) is equal to or less than PLa, the switching valve 36 maintains the closed position shown in the figure, and the control pilot pressure of the first pilot oil passage 32 is at a value Pcmax set by the pilot relief valve 11. . When the maximum load pressure (traveling load pressure) reaches PLa, the switching valve 36 starts to open, and the control pilot pressure in the first pilot oil passage 32 starts to decrease. When the maximum load pressure (traveling load pressure) further increases and reaches PLbn, the switching valve 36 is completely opened, and the control pilot pressure of the first pilot oil passage 32 becomes the tank pressure. While the control pilot pressure of the first pilot oil passage 32 is at Pcmax which is the set pressure of the pilot relief valve 11, the torque reduction control by the torque reduction piston 35 functions, and the maximum absorption torque of the main pump 2 is the rated torque Trate. From Tred to Tred. When the control pilot pressure of the first pilot oil passage 32 decreases from Pcmax, the drive pressure of the torque reduction control piston 35 decreases, the maximum absorption torque of the main pump 2 increases from Tred, and the control pilot of the first pilot oil passage 32 When the pressure becomes the tank pressure, the maximum absorption torque of the main pump 2 increases to the rated torque Trate.

このような機能により、本来走行走破性が必要とされる走行加速時、登坂時などでは、メインポンプ２の吸収トルクを定格に切替え、エンジン１の出力を有効に利用し、走破性を確保することができる。 With such a function, when traveling acceleration or climbing that originally requires traveling performance, the absorption torque of the main pump 2 is switched to the rated value, and the output of the engine 1 is effectively used to ensure traveling performance. be able to.

以上のように本実施の形態によれば、走行以外のアクチュエータ動作では、従来通り、必要な最大流量を供給して必要なアクチュエータ速度を得ることができるとともに、走行時は減トルク制御によりエネルギーのロスを低減し、エネルギ効率を向上することができる。 As described above, according to the present embodiment, in actuator operations other than traveling, the required maximum flow rate can be supplied and the required actuator speed can be obtained as before, and energy can be reduced by reducing torque control during traveling. Loss can be reduced and energy efficiency can be improved.

また、走行加速時、登坂時等、走行用の油圧モータの負荷圧が所定圧力を超えて上昇する走行時は、減トルク制御が解除されるため、メインポンプ２の最大吸収トルクは本来の設定値（定格）へと戻り、走破性を確保することができる。
＜第２の実施の形態＞
本発明の第２の実施の形態を図７を用いて説明する。図中、図１に示す要素と同等の要素には同じ符号を付している。 In addition, when the vehicle is traveling, when the load pressure of the hydraulic motor for traveling increases beyond a predetermined pressure, such as during traveling acceleration or during climbing, the reduced torque control is released, so the maximum absorption torque of the main pump 2 is set to the original setting. It returns to the value (rated), and the running performance can be secured.
<Second Embodiment>
A second embodiment of the present invention will be described with reference to FIG. In the figure, elements equivalent to those shown in FIG.

図７において、本実施の形態の油圧駆動装置は、走行モータ６Ａ，６ｂの負荷圧が急上昇したときに減トルク制御解除切替弁３６による第１パイロット油路３２の制御パイロット圧の低下を徐々に行わせ、減トルク制御の解除を緩やかに行う圧力遅延回路４１を更に備えている。 In FIG. 7, the hydraulic drive apparatus according to the present embodiment gradually reduces the control pilot pressure of the first pilot oil passage 32 by the reduced torque control release switching valve 36 when the load pressure of the traveling motors 6A and 6b suddenly increases. The pressure delay circuit 41 is further provided for performing the release torque control gradually.

本実施の形態において、圧力遅延回路４１は、信号油路２１の最高負荷圧ＰLmaxを減トルク制御解除切替弁３６の受圧部３６ｂに導く油路３９に設けられており、圧力遅延回路４１は油路３９に設けられた固定絞り要素４１ａと、この固定絞り要素４１ａに並列に配置され、信号油路２１から切替弁３６の受圧部３６ｂへの圧力の伝達は阻止し、逆方向の圧力の伝達は許可するチェック弁４１ｂとを有している。最高負荷圧ＰLmaxの上昇時は、切替弁３６の受圧部３６ｂに固定絞り要素４１ａを介して圧力が伝達され、最高負荷圧ＰLmaxの低下時は、切替弁３６の受圧部３６ｂからチェック弁４１ｂを介して圧力が開放される。 In the present embodiment, the pressure delay circuit 41 is provided in the oil passage 39 that guides the maximum load pressure PLmax of the signal oil passage 21 to the pressure receiving portion 36b of the reduced torque control release switching valve 36. The fixed throttle element 41a provided in the passage 39 and the fixed throttle element 41a are arranged in parallel, and the transmission of pressure from the signal oil path 21 to the pressure receiving portion 36b of the switching valve 36 is blocked, and the pressure is transmitted in the reverse direction. Has a check valve 41b to allow. When the maximum load pressure PLmax increases, the pressure is transmitted to the pressure receiving portion 36b of the switching valve 36 via the fixed throttle element 41a. When the maximum load pressure PLmax decreases, the check valve 41b is moved from the pressure receiving portion 36b of the switching valve 36. The pressure is released.

その他の構成は第１の実施の形態と同じである。 Other configurations are the same as those of the first embodiment.

このように構成した本実施の形態では、例えば走行中に石などの抵抗物に乗り上げ、走行負荷圧が急上昇したとき、信号油路２１から油路３９を介して切替弁３６の受圧部３６ｂに伝わる最高負荷圧は、固定絞り要素の抵抗を受けて徐々に上昇するため、切替弁３６が急に開位置に切り換わって第１パイロット油路３２の制御パイロット圧が急低下することを防止し、第１パイロット油路３２の制御パイロット圧の急低下によりメインポンプ２の最大吸収トルクが急上昇してメインポンプ２の吐出流量が急に増加し、走行の急加速が生じるという不具合が防止される。
＜第３の実施の形態＞
本発明の第３の実施の形態を図８を用いて説明する。図中、図１に示す要素と同等の要素には同じ符号を付している。 In the present embodiment configured as described above, for example, when riding on a resistor such as a stone during traveling and the traveling load pressure suddenly increases, the signal receiving passage 36 from the signal oil passage 21 to the pressure receiving portion 36b of the switching valve 36 via the oil passage 39 is provided. Since the maximum load pressure transmitted gradually increases due to the resistance of the fixed throttle element, the switching valve 36 is suddenly switched to the open position to prevent the control pilot pressure in the first pilot oil passage 32 from rapidly decreasing. , The sudden decrease in the control pilot pressure in the first pilot oil passage 32 causes the maximum absorption torque of the main pump 2 to rapidly increase, the discharge flow rate of the main pump 2 increases rapidly, and a problem of sudden acceleration of traveling is prevented. .
<Third Embodiment>
A third embodiment of the present invention will be described with reference to FIG. In the figure, elements equivalent to those shown in FIG.

図８において、本実施の形態の油圧駆動装置は、圧力遅延回路の他の例として、減トルク制御解除切替弁３６とタンクＴとを連絡する油路３４ｂに固定絞り要素４２を配置したものである。その他の構成は第１の実施の形態と同じである。 In FIG. 8, the hydraulic drive apparatus according to the present embodiment has a fixed throttle element 42 disposed in an oil passage 34 b that connects the reduced torque control release switching valve 36 and the tank T as another example of the pressure delay circuit. is there. Other configurations are the same as those of the first embodiment.

このように構成した本実施の形態においても、例えば走行中に石などの抵抗物に乗り上げ、走行負荷圧が急上昇し、この走行負荷圧が最高負荷圧として切替弁３６の受圧部３６ｂに導かれ、切替弁３６が急に開位置に切り換わったとしても、第１パイロット流路３２の制御パイロット圧は固定絞り要素４２の作用で徐々に低下するため、第１パイロット油路３２の制御パイロット圧の急低下によりメインポンプ２の最大吸収トルクが急上昇してメインポンプ２の吐出流量が急に増加し、走行の急加速が生じるという不具合を防止することができる。
＜その他の実施の形態＞
以上の実施の形態は本発明の精神の範囲内で種々の変更が可能である。例えば、上記実施の形態では、圧力補償弁７ａ〜７ｅの受圧部２４ａ，２５ａ〜２４ｅ，２５ｅにメインポンプ２の吐出圧と最高負荷圧を個別に導いて、ポンプ圧と最高負荷圧との差圧ΔＰLSを目標補償差圧として設定したが、特許文献１記載のようにメインポンプ２の吐出圧と最高負荷圧を絶対圧として出力する差圧減圧弁を設け、この差圧減圧弁の出力圧を圧力補償弁７ａ〜７ｅの開方向作動の受圧部に導いて目標補償差圧を設定してもよい。 Also in the present embodiment configured as described above, for example, the vehicle rides on a resistor such as a stone while traveling, the traveling load pressure rapidly increases, and this traveling load pressure is guided to the pressure receiving portion 36b of the switching valve 36 as the maximum load pressure. Even if the switching valve 36 is suddenly switched to the open position, the control pilot pressure in the first pilot fluid passage 32 gradually decreases due to the action of the fixed throttle element 42. As a result of the rapid decrease in the pressure, the maximum absorption torque of the main pump 2 suddenly rises, the discharge flow rate of the main pump 2 suddenly increases, and the problem of sudden acceleration of traveling can be prevented.
<Other embodiments>
Various modifications can be made to the above embodiment within the spirit of the present invention. For example, in the above embodiment, the discharge pressure and the maximum load pressure of the main pump 2 are individually guided to the pressure receiving parts 24a, 25a to 24e, 25e of the pressure compensation valves 7a to 7e, and the difference between the pump pressure and the maximum load pressure is obtained. Although the pressure ΔPLS is set as the target compensation differential pressure, a differential pressure reducing valve that outputs the discharge pressure of the main pump 2 and the maximum load pressure as absolute pressure is provided as described in Patent Document 1, and the output pressure of this differential pressure reducing valve is provided. May be guided to the pressure receiving portion of the pressure compensating valves 7a to 7e in the opening direction operation to set the target compensation differential pressure.

また、特許文献１記載のように、メインポンプ２を駆動するエンジン１の回転数に依存する圧力を絶対圧として出力する差圧減圧弁を設け、この差圧減圧弁の出力圧をＬＳ制御弁１６の開方向作動の受圧部に導き、ロードセンシング制御の目標差圧をエンジンの回転数に依存する可変値として設定してもよい。 Further, as described in Patent Document 1, a differential pressure reducing valve that outputs a pressure dependent on the number of revolutions of the engine 1 that drives the main pump 2 as an absolute pressure is provided, and the output pressure of the differential pressure reducing valve is set to an LS control valve. The target pressure difference of the load sensing control may be set as a variable value depending on the engine speed.

更に、上記実施の形態では、建設機械が油圧ショベルである場合について説明したが、走行モータを備えた建設機械であれば、油圧ショベル以外建設機械（例えば油圧クレーン、ホイール式ショベル等）に本発明を適用し、同様の効果を得ることができる。 Furthermore, although the case where the construction machine is a hydraulic excavator has been described in the above embodiment, the present invention is applicable to construction machines other than the hydraulic excavator (for example, a hydraulic crane, a wheeled excavator, etc.) as long as the construction machine includes a traveling motor. Can be applied to achieve the same effect.

１エンジン
２メインポンプ
３パイロットポンプ
４コントロールバルブ
６ａ，６ｂ走行モータ（走行用の油圧モータ）
６ｃ〜６ｅ他のアクチュエータ
４ａ〜４ｅバルブセクション
２２ａ〜２２ｄシャトル弁
７ａ〜７ｅ圧力補償弁
８ａ〜８ｅ流量制御弁
１１パイロットリリーフ弁
１２ａ〜１２ｄ操作装置
１５トルク制限制御ピストン
１５ａバネ
１６ＬＳ制御弁
１６ａ，１６ｂ受圧部
１６ｃバネ
１７ＬＳ制御傾転アクチュエータ
２４ａ，２５ａ〜２４ｅ，２５ｅ受圧部
３２第１パイロット油路
３２ａ〜３２ｅ分岐油路
３３走行検出回路
３４第２パイロット流路
３４ａ油路
３４ｂ油路
３５減トルク制御ピストン
３６減トルク制御解除切替弁
３６ａバネ
３６ｂ受圧部
３７ａ〜３７ｅ動作検出弁
４１圧力遅延回路
４１ａ固定絞り要素
４１ｂチェック弁
４２固定絞り要素
３００上部旋回体
３０１下部走行体
３０２フロント作業機
３０３スイングポスト
３０４中央フレーム
３０５ブレード
３０６ブーム
３０７アーム
３０８バケット 1 Engine 2 Main pump 3 Pilot pump 4 Control valves 6a, 6b Travel motor (hydraulic motor for travel)
6c to 6e Other actuators 4a to 4e Valve sections 22a to 22d Shuttle valves 7a to 7e Pressure compensation valves 8a to 8e Flow control valve 11 Pilot relief valves 12a to 12d Operating device 15 Torque limit control piston 15a Spring 16 LS control valve 16a, 16b Pressure receiving portion 16c Spring 17 LS control tilt actuators 24a, 25a to 24e, 25e Pressure receiving portion 32 First pilot oil passage 32a to 32e Branch oil passage 33 Travel detection circuit 34 Second pilot passage 34a Oil passage 34b Oil passage 35 Reduction Torque control piston 36 Decrease torque control release switching valve 36a Spring 36b Pressure receiving portions 37a to 37e Motion detection valve 41 Pressure delay circuit 41a Fixed throttle element 41b Check valve 42 Fixed throttle element 300 Upper swing body 301 Lower traveling body 302 Front work machine 303 Swing Pos 304 central frame 305 blade 306 boom 307 arm 308 bucket

Claims

Engine,
A variable displacement hydraulic pump driven by this engine;
A plurality of actuators including a traveling hydraulic motor driven by pressure oil discharged from the hydraulic pump;
A plurality of flow control valves including a flow control valve for traveling that controls the flow of pressure oil supplied from the hydraulic pump to the plurality of actuators;
A plurality of pressure compensating valves that respectively control the differential pressure across the plurality of flow control valves;
When the discharge pressure of the hydraulic pump rises, the displacement of the hydraulic pump is reduced, and the pump torque control unit for controlling the absorption torque of the hydraulic pump so as not to exceed the preset maximum absorption torque and the discharge pressure of the hydraulic pump are A pump control device having a pump flow rate control unit for controlling a displacement volume of the hydraulic pump so as to be higher by a target differential pressure than a maximum load pressure of the plurality of actuators,
The plurality of pressure compensation valves are configured so that the differential pressure between the flow control valves is maintained at the differential pressure between the discharge pressure of the main pump and the maximum load pressure of the actuators. In the hydraulic drive device of the construction machine that controls the pressure,
A pilot pump driven by the engine;
The first pilot oil passage has a first pilot oil passage connected to a pressure oil supply oil passage through which a discharge oil of the pilot pump is supplied via a throttle, and the travel hydraulic motor is driven during the travel. A travel detection circuit for generating a control pilot pressure in
The first pilot oil passage is connected to the first pilot oil passage through a second pilot oil passage, and when the control pilot pressure is generated in the first pilot oil passage, the control pilot pressure is guided as a driving pressure, and the maximum absorption of the hydraulic pump. A reduced torque control piston that performs reduced torque control to reduce torque; and
The second pilot oil passage is connected to the second pilot oil passage, and when the load pressure of the traveling hydraulic motor rises above a predetermined pressure, the second pilot oil passage is opened to the tank, and the torque is reduced by the torque reduction control piston. A hydraulic drive device for a construction machine, comprising: a switching valve for releasing control.

The hydraulic drive device for a construction machine according to claim 1,
The travel detection circuit is disposed between a plurality of branch oil passages branched from the first pilot oil passage and between the plurality of branch oil passages and the tank T, and each main spool of the plurality of flow control valves. A plurality of operation detection valves that detect the operation of the corresponding main spool in conjunction with the first pilot oil passage and the tank during traveling when the traveling hydraulic motor is driven. A hydraulic drive device for a construction machine, wherein the control pilot pressure is generated in the first pilot oil passage by blocking communication with the first pilot oil passage.

The hydraulic drive device for a construction machine according to claim 1,
ΔPL S0, a differential pressure between the discharge pressure of the hydraulic pump and the maximum load pressure when the torque reduction control by the torque reduction control piston is not performed.
ΔPLSS, a differential pressure between the discharge pressure of the hydraulic pump and the maximum load pressure during torque reduction control by the torque reduction piston.
Qt is a flow rate required for the traveling.
The maximum opening area of the flow control valve for traveling is Aa,
When the differential pressure between the discharge pressure of the main pump and the maximum load pressure is ΔPLS0, when the maximum opening area of the flow rate control valve capable of supplying the flow rate Qt to the traveling hydraulic motor is Ab,
The hydraulic drive device for a construction machine, wherein the maximum opening area Aa is √ (ΔPLS0 / ΔPLSS) times the maximum opening area Ab.

The hydraulic drive device for a construction machine according to claim 1,
When the load pressure of the hydraulic motor for traveling suddenly increases, the control pilot pressure of the first pilot oil passage is gradually reduced by the switching valve for canceling the torque reduction control, and the release of the torque reduction control is gradually performed. A hydraulic drive device for a construction machine, further comprising a pressure delay circuit.