JP5269754B2 - Pump controller for construction machinery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enhance energy efficiency by inhibiting pressure oil from a hydraulic pump from being wastefully consumed in the activation, turning acceleration, etc. of a revolving super structure. <P>SOLUTION: When a direction control valve 32 for turning is singly operated in a second control valve group 31, the second property is selected in place of the first property of controlling a relationship between the pressure and flow rate of discharge from the first and second pumps 14 and 15 so that horsepower of an engine 12 can become constant. In the case where the second property is selected, a pump capacity is controlled so that the flow rate of the discharge from the second pump 15 can gradually become lower than in the first property, when the pressure of the discharge from the second pump 15 exceeds relief set pressure Pb of relief valves 42A and 42B. Thus, the wasteful consumption of the pressure oil, discharged from the second pump 15, on the sides of the relief valves 42A and 42B can be reduced. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to a pump control device for a construction machine that is mounted on a construction machine such as a hydraulic excavator and is preferably used to variably control the discharge flow rate of pressure oil by a plurality of hydraulic pumps.

  In general, a construction machine such as a hydraulic excavator includes a plurality of variable displacement hydraulic pumps driven by a prime mover such as a diesel engine and a plurality of hydraulic actuators driven by pressure oil discharged from the respective hydraulic pumps (for example, , Hydraulic motor, hydraulic cylinder, etc.). Each variable displacement hydraulic pump can vary the discharge flow rate according to the discharge pressure so that the absorption horsepower of the pump does not exceed the output horsepower of the engine in order to effectively utilize the limited output horsepower of the engine. It is set as the structure to control (for example, refer patent document 1).

  By the way, when the upper swinging body is driven to turn on the lower traveling body by the hydraulic motor for turning, as a characteristic of the hydraulic motor, the rotation of the motor can be suppressed low by the action of the inertial force of the vehicle body at the time of turning start and turning acceleration. In many cases, the flow rate of the pressure oil supplied to the hydraulic motor (swing motor) is excessive compared to the required flow rate (for example, the required flow rate Qn shown in FIGS. 9 and 10). For this reason, the relief valve is opened by the excess (surplus) pressure oil on the turning hydraulic circuit side, and the excess oil at this time is returned to the tank, so that energy is wasted.

  Therefore, in the prior art disclosed in Patent Document 1, for example, a pressure sensor is provided at a position before and after the turning hydraulic motor, and a rotation sensor for detecting the rotation speed (turning speed) of the upper turning body is provided. When it is determined that the turning relief valve is open based on the detection signals from the sensors, the discharge flow rate of the hydraulic pump is reduced by the flow rate.

JP-A-9-195322

  However, in the prior art disclosed in Patent Document 1, the flow rate of excess pressure oil is calculated based on detection signals from the pressure sensors and the rotation sensors, and the discharge flow rate of the hydraulic pump is reduced by the flow rate according to the calculation result. It is the structure to make. For this reason, extra time is required for the arithmetic processing, time delay is likely to occur in actual pump control, and there is a problem that sufficient pump control cannot always be realized.

  Moreover, in the prior art according to Patent Document 1, since the pressure sensor and the rotation sensor are additionally provided, the overall configuration of the apparatus is complicated, the number of parts is increased, and workability during assembly is improved. There is a problem of lowering.

  The present invention has been made in view of the above-described problems of the prior art, and an object of the present invention is to suppress wasteful consumption of pressure oil from a hydraulic pump at the time of startup of a swing body, acceleration of a swing, and the like. An object of the present invention is to provide a construction machine pump control device capable of improving energy efficiency and the like.

  In order to solve the above-described problems, a pump control apparatus for a construction machine according to the invention of claim 1 is configured to be a traveling body, a revolving body provided on the traveling body so as to be able to swivel, and a revolving structure on the revolving body. A working device comprising a provided boom, arm and working tool, a plurality of hydraulic actuators for individually driving the traveling body, the turning body and the working device, and an engine for supplying pressure oil to each hydraulic actuator First and second hydraulic pumps comprising at least two variable displacement hydraulic pumps, and first and second capacities for variably controlling the discharge flow rate of pressure oil by the first and second hydraulic pumps A variable mechanism, first and second pressure detecting means for detecting discharge pressures of the first and second hydraulic pumps, a rotational speed detecting means for detecting the rotational speed of the engine, and the first hydraulic pump Discharged from Control valve group comprising a plurality of directional control valves for supplying pressure oil to be supplied to at least two hydraulic actuators among the plurality of hydraulic actuators, wherein the directional control valves are connected in a predetermined arrangement. And a plurality of directional control valves for supplying pressure oil discharged from the second hydraulic pump to at least two other hydraulic actuators among the plurality of hydraulic actuators. A second control valve group that is connected in an array, a plurality of operation means for individually switching each directional control valve constituting each of the first and second control valve groups, A plurality of operation detection means for individually detecting whether each operation means is operated, the detection results of the first and second pressure detection means, the rotation speed detection means, and the operation detection means Obedience Control means for variably controlling the discharge flow rates of the first and second hydraulic pumps by driving the first and second variable capacity mechanisms, and the discharge pressure by the first and second hydraulic pumps. A first characteristic storage means for storing the relationship between the engine flow and the discharge flow rate as a first characteristic so as to control the horsepower of the engine to be constant; and a control start point for controlling the horsepower of the engine to be constant; The discharge flow rate gradually decreases as the discharge pressure rises with respect to the first characteristic in a region where the discharge pressure exceeds a predetermined pressure based on the relief set pressure of the hydraulic actuator that drives the swing body to swing. As described above, there is provided a second characteristic storage means for storing the relationship between the discharge pressure and the discharge flow rate as the second characteristic.

  In the control means, the directional control valve for the swing body and the other directional control valve are combined and operated in the same control valve group of the first and second control valve groups. Are detected by the respective operation detection means, the first characteristic stored in the first characteristic storage means is selected to control the discharge flow rates of the first and second hydraulic pumps variably, and the same control valve When the plurality of operation detecting means detect that the directional control valve for the swivel body is operated alone in the group, the second characteristic stored in the second characteristic storage means is selected, and the first characteristic is selected. The discharge flow rate of one of the second hydraulic pumps is variably controlled.

  According to a second aspect of the present invention, the control means variably controls the discharge flow rates of the first and second hydraulic pumps according to the first characteristic when detecting the combined operation, and detects the single operation. Sometimes, the discharge flow rate of one of the first and second hydraulic pumps is variably controlled according to the second characteristic, and the discharge flow rate of the other hydraulic pump is variably controlled according to the first characteristic. It is configured.

  On the other hand, according to a third aspect of the present invention, the second characteristic storage means exceeds the control start point for controlling the engine horsepower to be constant, and the discharge pressure of the hydraulic actuator that drives the swivel to swivel. The relationship between the discharge pressure and the discharge flow rate is stored as the second characteristic so that the discharge flow rate gradually lowers than the first characteristic when the discharge pressure further increases in a region exceeding the relief set pressure. It is configured.

  According to a fourth aspect of the present invention, the second characteristic storage means exceeds a control start point for controlling the engine horsepower to a constant value, and the discharge pressure exceeds the pressure lower than the relief set pressure. In such a region, the relationship between the discharge pressure and the discharge flow rate is stored as the second characteristic so that the discharge flow rate gradually lowers than the first characteristic when the discharge pressure further increases.

  As described above, according to the first aspect of the present invention, the swivel direction control valve and the other direction control valve are combined and operated in the same control valve group of the first and second control valve groups. Is detected by each operation detecting means, the relationship between the discharge pressure and the discharge flow rate of the first and second hydraulic pumps is determined by selecting the first characteristic by the first characteristic storage means. The discharge flow rates of the first and second hydraulic pumps can be variably controlled so that the horsepower is controlled to be constant. Further, when the plurality of operation detecting means detect that the direction control valve for the swivel body is independently operated in the same control valve group, a second characteristic by the second characteristic storage means And the discharge flow rate of one of the first and second hydraulic pumps can be variably controlled, and the discharge pressure of the pump exceeds the pressure based on the relief set pressure. When the discharge pressure further increases, the discharge flow rate can be controlled to be gradually lower than the first characteristic. As a result, it is possible to suppress the excessive supply of pressure oil to the actuator (swing motor) for the swing body, and pressure oil (wasted wastefully via the relief valve at the time of swing start, swing acceleration, etc.) The amount of surplus oil) can be reduced.

  Moreover, since the discharge flow rate of each hydraulic pump is variably controlled in accordance with the first and second characteristics (discharge pressure-discharge flow rate characteristics) stored in advance by the first and second characteristic storage means, so-called feed-forward-like operation is performed. Flow rate control can be realized, and the occurrence of time delay in actual pump control can be suppressed to a small level. As a result, it is possible to reduce wasteful consumption of pressure oil via the relief valve at the time of turning activation or turning acceleration, and the energy efficiency can be improved, and the number of parts can be reduced to improve workability during assembly. Can be increased.

  According to the second aspect of the present invention, the discharge flow rates of the first and second hydraulic pumps can be variably controlled according to the first characteristic when detecting the composite operation, and when detecting the single operation, The discharge flow rate of one of the first and second hydraulic pumps can be variably controlled according to the second characteristic, and the discharge flow rate of the other hydraulic pump can be variably controlled according to the first characteristic. .

  On the other hand, according to the invention described in claim 3, the second characteristic by the second characteristic storage means is that the discharge pressure of the hydraulic pump exceeds the relief set pressure of the turning hydraulic actuator, and the discharge pressure further increases. The control characteristic can be such that the discharge flow rate gradually lowers than the first characteristic when rising.

  According to the fourth aspect of the present invention, the second characteristic by the second characteristic storage means is a pressure determined in advance as a pressure at which the discharge pressure of the hydraulic pump is lower than the relief set pressure of the hydraulic actuator for turning. When the discharge pressure further increases in a region exceeding the range, the control characteristic can be set such that the discharge flow rate gradually lowers than the first characteristic.

1 is an overall view showing a hydraulic excavator equipped with a pump control device for a construction machine according to an embodiment of the present invention. 1 is a hydraulic circuit diagram showing an overall configuration of a pump control apparatus according to an embodiment. It is the hydraulic circuit figure which expanded a part of pump control apparatus shown in FIG. FIG. 3 is an enlarged hydraulic circuit diagram of the remaining part of the pump control device shown in FIG. 2. FIG. 3 is a control block diagram of the pump control device shown in FIG. 2. It is a flowchart which shows the pump control processing by the controller in FIG. It is a characteristic diagram which shows the relationship between the discharge pressure and discharge flow volume by a 1st characteristic. It is a characteristic line figure which shows the relationship between the discharge pressure and discharge flow volume by a 2nd characteristic. It is a characteristic diagram which shows the relationship between the discharge flow rate at the time of turning start by the comparative example, and a required flow rate. It is a characteristic diagram which shows the relationship between the discharge flow rate at the time of turning acceleration by a comparative example, and a required flow rate. It is a characteristic diagram which shows the 2nd characteristic by the modification of this invention as a relationship between discharge pressure and discharge flow rate.

  Hereinafter, a construction machine pump control apparatus according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings, taking as an example a case where the construction machine pump control apparatus is mounted on a hydraulic excavator as a construction machine.

  1 to 8 show a construction machine pump control apparatus according to an embodiment of the present invention.

  In the figure, reference numeral 1 denotes a hydraulic excavator as a construction machine. The hydraulic excavator 1 is mounted on a crawler type lower traveling body 2 capable of self-propelling as shown in FIG. The upper revolving body 3 and a working device 8 to be described later are roughly configured. The lower traveling body 2 is provided with hydraulic motors 2A and 2B (hereinafter referred to as traveling motors 2A and 2B) that constitute a traveling hydraulic actuator, as illustrated in FIG.

  In this case, the upper swing body 3 of the hydraulic excavator 1 constitutes the vehicle body of the construction machine together with the lower traveling body 2. The upper turning body 3 has a turning frame 4 that is driven to turn on the lower traveling body 2. On the turning frame 4, a cab 5, a counterweight 6, a building cover 7, and the like, which will be described later, are provided. Yes. Further, a hydraulic motor 3A (hereinafter referred to as a swing motor 3A) constituting a swing hydraulic actuator is provided on the swing frame 4 of the upper swing body 3.

  Reference numeral 5 denotes a cab that constitutes a driver's cab disposed on the left side of the front portion of the revolving frame 4. The cab 5 has a driver's seat on which an operator sits or sits, an operation lever, and a travel lever (all not shown). ) Etc. are arranged.

  6 is a counterweight provided on the rear end side of the revolving frame 4. The counterweight 6 is detachably mounted on the rear end side of the revolving frame 4, and the entire upper revolving unit 3 with respect to the front working device 8. The weight balance is taken. In addition, a building cover 7 that houses an engine 12 and the like to be described later is provided on the front side of the counterweight 6.

  Reference numeral 7 denotes a building cover which is positioned between the cab 5 and the counterweight 6 and is erected on the revolving frame 4. The building cover 7 is formed by using a plurality of metal panels made of thin steel plates, for example. A machine room (not shown) for accommodating an engine 12 and the like to be described later is defined inside. In the building cover 7, hydraulic pumps 14 and 15 (see FIG. 2) described later that are driven to rotate by the engine 12 are provided. In the building cover 7, control valve groups 21, 31, which will be described later, are provided at positions close to the cab 5.

  8 is a working device provided at the front portion of the upper swing body 3 so as to be able to be lifted and lowered. The working device 8 includes a boom 9 whose base end is attached to the swing frame 4 so as to be able to be lifted and lowered, and a tip of the boom 9. The arm 10 is attached to the side so as to be able to move up and down, and a bucket 11 as a work tool rotatably provided on the distal end side of the arm 10 for performing excavation work such as earth and sand.

  The boom 9 of the working device 8 is lifted up and down with respect to the revolving frame 4 by the boom cylinder 9A, and the arm 10 is lifted up and down by the arm cylinder 10A on the tip side of the boom 9. . Further, the bucket 11 as the work tool is rotated up and down by the bucket cylinder 11A as the work tool cylinder on the distal end side of the arm 10. Here, the boom cylinder 9 </ b> A, the arm cylinder 10 </ b> A, and the bucket cylinder 11 </ b> A constitute a hydraulic actuator of the work device 8.

  Next, reference numeral 12 denotes a diesel engine (hereinafter referred to as an engine 12) that serves as a prime mover of the hydraulic excavator 1. The engine 12 is housed in a building cover 7 of the upper swing body 3 together with hydraulic pumps 14 and 15 described later. Yes. Further, the engine 12 is provided with an engine speed detector 13 as shown in FIG. 2, and the engine speed detector 13 outputs a detected signal (engine speed) to a controller 57 described later. is there.

  Reference numerals 14 and 15 denote first and second hydraulic pumps (hereinafter referred to as a first pump 14 and a second pump 15) that are rotationally driven by the engine 12. The first and second pumps 14 and 15 are variable displacement type. And a main hydraulic power source together with the tank 16. The first pump 14 discharges the hydraulic oil in the tank 16 as high pressure oil toward the center bypass pipe 17 and the like, and the second pump 15 sets the hydraulic oil in the tank 16 as high pressure oil in the center. It is discharged toward the bypass pipe 18 and the like.

  Further, the first and second pumps 14 and 15 have capacity variable portions 14A and 15A made of a swash plate or an oblique shaft, and the capacity variable portions 14A and 15A are tilt-driven by servo mechanisms 19 and 20 described later. Thus, the pump capacities of the first and second pumps 14 and 15 are changed, and the discharge flow rate of the pressure oil is increased or decreased according to the tilt angle.

  Reference numerals 19 and 20 denote first and second variable capacity mechanisms (hereinafter referred to as first and second capacity variable mechanisms) that variably control the discharge flow rate of the pressure oil by tilting the capacity variable portions 14A and 15A of the first and second pumps 14 and 15, , Referred to as a second servo mechanism). Here, the first and second servo mechanisms 19 and 20 are driven independently from each other in accordance with a control signal output from the controller 57 described later, and the capacity variable portions 14A and 15A are driven to tilt, thereby 1, the discharge flow rate of pressure oil by the second pumps 14 and 15 is increased or decreased.

  Reference numeral 21 denotes a first control valve group connected to the first pump 14 via a center bypass pipe line 17 or the like, and the first control valve group 21 is used for the left traveling described later as shown in FIG. The directional control valve 22 includes a directional control valve 24 for the bucket cylinder 11A, a directional control valve 26 for the boom cylinder 9A, and a directional control valve 28 for the arm cylinder 10A. The first control valve group 21 is configured to connect these directional control valves 22, 24, 26, 28 in series from the upstream side to the downstream side of the center bypass pipe line 17.

  Reference numeral 22 denotes a directional control valve for left travel disposed on the most upstream side of the center bypass pipe line 17 in the control valve group 21. The directional control valve 22 is, for example, a hydraulic pilot type directional control at 6 port 3 position. It comprises a valve, and a pair of hydraulic pilot portions 22A and 22B (see FIG. 3) are provided on both sides thereof. The direction control valve 22 has a pair of inflow / outflow ports connected to, for example, the left traveling motor 2A via the left traveling main conduits 23A and 23B.

  Here, the directional control valve 22 is switched from the neutral position (A) to the switching position (B) or (C) when pilot pressure is supplied by a lever device 43 described later. As a result, the left traveling motor 2A is supplied with the pressure oil from the first pump 14, and is thereby rotationally driven in the forward direction or the reverse direction.

  Reference numeral 24 denotes a directional control valve for the bucket cylinder 11 </ b> A that is located on the downstream side of the directional control valve 22 and is disposed in the middle of the center bypass pipe 17. The direction control valve 24 is constituted by, for example, a 7-port 3-position hydraulic pilot type direction control valve, and a pair of hydraulic pilot portions 24A and 24B are provided on both sides thereof. The directional control valve 24 has a pair of inlet / outlet ports connected to the bucket cylinder 11 </ b> A via bucket main lines 25 </ b> A and 25 </ b> B.

  Here, the directional control valve 24 is switched from the neutral position (A) to the switching position (B) or (C) when pilot pressure is supplied by a lever device 45 described later. Thus, the bucket cylinder 11A is driven in the extending or contracting direction by supplying and discharging the pressure oil from the first pump 14.

  Reference numeral 26 denotes a directional control valve for the boom cylinder 9 </ b> A that is located on the downstream side of the directional control valve 24 and is disposed in the middle of the center bypass pipe 17. This directional control valve 26 is constituted by, for example, a 7-port 3-position hydraulic pilot type directional control valve, and a pair of hydraulic pilot portions 26A and 26B are provided on both sides thereof. The direction control valve 26 has a pair of inflow / outflow ports connected to the boom cylinder 9A via boom main conduits 27A and 27B.

  Here, the directional control valve 26 is switched from the neutral position (A) to the switching position (B) or (C) when a pilot pressure is supplied by a lever device 46 described later. Thereby, the boom cylinder 9A is driven in the extending or contracting direction by supplying and discharging the pressure oil from the first pump 14.

  Reference numeral 28 denotes a directional control valve for the arm cylinder 10 </ b> A that is located on the downstream side of the directional control valve 26 and disposed in the middle of the center bypass pipe 17. The directional control valve 28 is constituted by, for example, a 6-port 3-position hydraulic pilot type directional control valve, and a pair of hydraulic pilot portions 28A and 28B are provided on both sides thereof. The directional control valve 28 has a pair of inflow / outflow ports connected to the arm cylinder 10A via arm main conduits 29A and 29B.

  Here, the directional control valve 28 is switched from the neutral position (A) to the switching position (B) or (C) when pilot pressure is supplied by a lever device 47 described later. As a result, the arm cylinder 10A is driven in the extending or contracting direction by the pressure oil from the first pump 14 being supplied and discharged.

  30 is a pressure oil supply line branched from the middle of the center bypass line 17, and the supply line 30 is connected to the center bypass line 17, one side of which is located between the directional control valves 22 and 24. The other side is connected to the middle part, and the other side is a plurality of branch pipe sections 30A, 30B, 30C. The supply pipeline 30 is connected in parallel to the direction control valves 24, 26, and 28 by these branch pipeline sections 30A, 30B, and 30C. Thereby, the direction control valves 24, 26, and 28 are connected in parallel to the pressure oil supplied from the first pump 14 via the center bypass pipe 17 and the supply pipe 30 to form a so-called parallel circuit. Is.

  Therefore, the first control valve group 21 including the directional control valves 22, 24, 26, and 28 connected to the first pump 14 via the center bypass pipe 17 and the like is positioned on the most upstream side. While the directional control valve 22 is held in the neutral position (A), pressure oil can be supplied to any of the directional control valves 24, 26, and 28 via the supply line 30. 24, 26, and 28 are supplied with pressure oil from the first pump 14 independently of each other.

  On the other hand, in the first control valve group 21, when the directional control valve 22 located on the most upstream side is switched from the neutral position (A) to any one of the switching positions (B) and (C), the downstream side thereof. The pressure oil supply to the side (supply line 30) is interrupted. For this reason, the supply of pressure oil to the direction control valves 24, 26, and 28 via the branch conduit portions 30A, 30B, and 30C of the supply conduit 30 is cut off. At this time, for example, the travel by the left travel motor 2A is performed. Operation is priority.

  Reference numeral 31 denotes a second control valve group connected to the second pump 15 via the center bypass pipe 18 and the like, and the second control valve group 31 is a direction for turning described later as shown in FIG. The control valve 32, the directional control valve 34 for the arm cylinder 10A, the directional control valve 35 for the boom cylinder 9A, the spare directional control valve 36, and the right traveling directional control valve 38 are configured. The second control valve group 31 is configured to connect these direction control valves 32, 34, 35, 36, 38 in series from the upstream side to the downstream side of the center bypass pipe 18.

  Reference numeral 32 denotes a turning direction control valve disposed on the most upstream side of the center bypass pipe 18 in the control valve group 31. The direction control valve 32 is, for example, a hydraulic pilot type direction control valve of 6 port 3 position. A pair of hydraulic pilot portions 32A and 32B (see FIG. 4) are provided on both sides thereof. The direction control valve 32 has a pair of inflow / outflow ports connected to the turning motor 3A via the turning main pipes 33A and 33B.

  Here, the directional control valve 32 is switched from the neutral position (A) to the switching position (B) or (C) when pilot pressure is supplied by a lever device 48 described later. Thereby, the turning motor 3A is supplied with the pressure oil from the second pump 15 and is rotationally driven in the forward direction or the reverse direction, and causes the upper turning body 3 to turn on the lower traveling body 2.

  Reference numeral 34 denotes a directional control valve for the arm cylinder 10 </ b> A that is located on the downstream side of the directional control valve 32 and is disposed in the middle of the center bypass pipe 18. The directional control valve 34 is constituted by, for example, an 8-port 3-position hydraulic pilot type directional control valve, and a pair of hydraulic pilot portions 34A and 34B are provided on both sides thereof. The directional control valve 34 has a pair of inflow / outflow ports connected to the arm cylinder 10A via the arm main conduits 29A and 29B described above.

  In this case, the arm main pipelines 29A and 29B constitute a common main pipeline extending in parallel across the first control valve group 21 and the second control valve group 31, and the first control valve group 21 side. The direction control valve 28 and the direction control valve 34 on the second control valve group 31 side are connected together to the arm cylinder 10A. The direction control valve 34 is switched from the neutral position (A) to the switching position (B) or (C) together with the direction control valve 28 when pilot pressure is supplied by a lever device 47 described later. It is done. Thus, the arm cylinder 10A is driven in the extending or contracting direction by the pressure oil from the first and second pumps 14 and 15 being joined and discharged.

  Reference numeral 35 denotes a directional control valve for the boom cylinder 9 </ b> A that is located on the downstream side of the directional control valve 34 and is disposed in the middle of the center bypass pipe 18. The directional control valve 35 is constituted by, for example, a 6-port 3-position hydraulic pilot type directional control valve, and a pair of hydraulic pilot portions 35A and 35B are provided on both sides thereof. The direction control valve 35 is connected to the boom cylinder 9A via the boom main conduits 27A and 27B described above.

  In this case, the boom main pipelines 27A and 27B constitute a common main pipeline extending in parallel across the first control valve group 21 and the second control valve group 31, and are arranged on the first control valve group 21 side. The direction control valve 26 and the direction control valve 35 on the second control valve group 31 side are connected together to the boom cylinder 9A. The directional control valve 35 is switched from the neutral position (A) to the switching positions (B) and (C) together with the directional control valve 26 when pilot pressure is supplied by a lever device 46 described later. As a result, the boom cylinder 9A is driven in the extending or contracting direction by the pressure oil from the first and second pumps 14 and 15 being joined and discharged.

  Reference numeral 36 denotes a spare directional control valve which is located on the downstream side of the directional control valve 35 and is disposed in the middle of the center bypass pipe 18. The directional control valve 36 is constituted by, for example, a 6-port 3-position hydraulic pilot type directional control valve, and a pair of hydraulic pilot portions 36A and 36B are provided on both sides thereof. The direction control valve 36 has a pair of inflow / outflow ports connected to a spare actuator 50 (described later) via main pipes 37A and 37B.

  Here, the directional control valve 36 is switched from the neutral position (A) to the switching position (B) or (C) when pilot pressure is supplied by a lever device 49 described later. As a result, a pre-actuator 50 described later is driven with pressure oil supplied and discharged from the second pump 15.

  Reference numeral 38 denotes a right traveling direction control valve disposed on the most downstream side of the center bypass pipe line 18 in the second control valve group 31. The direction control valve 38 is, for example, a 6-port 3-position hydraulic pilot. It is comprised by a type | formula direction control valve, and a pair of hydraulic pilot parts 38A and 38B (refer FIG. 3) are provided in the both sides. The direction control valve 38 has a pair of inflow / outflow ports connected to, for example, the right traveling motor 2B via the left traveling main conduits 39A and 39B.

  Here, the directional control valve 38 is switched from the neutral position (A) to the switching position (B) or (C) when pilot pressure is supplied by a lever device 44 described later. As a result, the right traveling motor 2B is supplied with pressure oil from the second pump 15, and is thereby rotationally driven in the forward or reverse direction.

  Reference numeral 40 denotes a pressure oil supply line provided on the second control valve group 31 side. This supply line 40 is connected to the center bypass line 18 at a position where one side is upstream of the direction control valve 32. The other side is a plurality of branch pipe sections 40A, 40B, 40C, 40D, and 40E. The supply pipeline 40 is connected in parallel with the direction control valves 32, 34, 35, 36, and 38 by branch pipeline sections 40A, 40B, 40C, 40D, and 40E. Thus, the directional control valves 32, 34, 35, 36, and 38 are connected in parallel to the pressure oil supplied from the second pump 15 via the center bypass pipe 18 and the supply pipe 40, so-called parallel. It constitutes a circuit.

  Reference numeral 41 denotes a bypass pipe provided in addition to the main pipe 27B of the boom cylinder 9A. The bypass pipe 41 is located outside the first and second control valve groups 21 and 31 as shown in FIGS. Between the bottom oil chamber of the boom cylinder 9A and the directional control valves 26 and 35 so as to be in parallel with the main pipeline 27B. The detour pipe line 41 smoothes the flow of pressure oil supplied to and discharged from the bottom side oil chamber of the boom cylinder 9A through the main pipe line 27B.

  42A and 42B are a pair of overload relief valves (hereinafter referred to as turning relief valves 42A and 42B) provided in the turning main pipelines 33A and 33B. The turning relief valves 42A and 42B are shown in FIG. When the pressure in the main pipes 33A and 33B shown in FIG. 4 exceeds a predetermined relief setting pressure Pb (see FIG. 8), the excessive pressure is relieved to the tank 16 side by opening the valve. Thereby, the relief valves 42A and 42B prevent an overload from acting on the swing motor 3A.

  43 and 44 are left and right traveling lever devices as operation means for switching the direction control valves 22 and 38. The traveling lever devices 43 and 44 are constituted by, for example, pressure-reducing valve type pilot valves, respectively. The pump port and the tank port are connected to a pilot pump and a tank (both not shown).

  Here, the left travel lever device 43 is connected to the hydraulic pilot portions 22A and 22B of the direction control valve 22 via pilot pipes 43A and 43B as shown in FIG. The lever device 43 supplies the pilot pressure generated by the tilting operation of the operation lever 43C to the hydraulic pilot portions 22A and 22B of the direction control valve 22 via the pilot pipes 43A and 43B. Are switched from the neutral position (A) to the switching positions (B) and (C).

  Further, the lever device 43 is provided with a left traveling operation detector 43D (see FIG. 5) as an operation detecting means including a pressure sensor for detecting a pressure change in the pilot pipes 43A and 43B. The left travel operation detector 43D detects whether or not the operation lever 43C is tilted from the pressure change in the pilot pipes 43A and 43B, and outputs a detection signal to the controller 57 described later. .

  On the other hand, the right traveling lever device 44 is connected to the hydraulic pilot portions 38A and 38B of the direction control valve 38 via pilot pipes 44A and 44B. The lever device 44 supplies the pilot pressure generated by the tilting operation of the operation lever 44C to the hydraulic pilot portions 38A and 38B of the direction control valve 38 via the pilot pipes 44A and 44B. Are switched from the neutral position (A) to the switching positions (B) and (C).

  Further, the lever device 44 is provided with a left traveling operation detector 44D (see FIG. 5) as an operation detecting means including a pressure sensor for detecting a pressure change in the pilot pipes 44A and 44B. The left travel operation detector 44D detects whether or not the operation lever 44C has been tilted from the pressure change in the pilot pipes 44A and 44B, and outputs a detection signal to the controller 57 described later. .

  Reference numeral 45 denotes a bucket operating lever device as an operating means for switching the direction control valve 24. The lever device 45 is constituted by, for example, a pressure reducing valve type pilot valve or the like, and the direction control valve via pilot pipes 45A and 45B. 24 hydraulic pilot parts 24A and 24B are connected. Then, the lever device 45 supplies the pilot pressure generated by the tilting operation of the operation lever 45C to the direction control valve 24 via the pilot pipes 45A and 45B, whereby the direction control valve 24 is in the neutral position (A). Are switched to switching positions (B) and (C).

  Further, the lever device 45 is provided with a bucket operation detector 45D (see FIG. 5) as an operation detecting means including a pressure sensor for detecting a pressure change in the pilot pipes 45A and 45B. The bucket operation detector 45D detects whether or not the operation lever 45C has been tilted from the pressure change in the pilot pipes 45A and 45B, and outputs a detection signal to the controller 57 described later.

  Reference numeral 46 denotes a boom operating lever device as an operation means for switching the direction control valves 26 and 35. The lever device 46 is constituted by, for example, a pressure reducing valve type pilot valve or the like, and is directional through pilot pipes 46A and 46B. The hydraulic pilot portions 26A and 26B of the control valve 26 and the hydraulic pilot portions 35A and 35B of the direction control valve 35 are connected. The lever device 46 supplies the pilot pressure generated by the tilting operation of the operation lever 46C to the direction control valves 26 and 35 via the pilot pipes 46A and 46B. Switching from the neutral position (A) to the switching position (B) and (C).

  In addition, the lever device 46 is provided with a boom operation detector 46D (see FIG. 5) as an operation detecting means including a pressure sensor for detecting a pressure change in the pilot pipes 46A and 46B. The boom operation detector 46D detects whether or not the operation lever 46C is tilted from the pressure change in the pilot pipes 46A and 46B, and outputs a detection signal to the controller 57 described later.

  Reference numeral 47 denotes an arm operating lever device as an operating means for switching the direction control valves 28 and 34. The lever device 47 is constituted by, for example, a pressure reducing valve type pilot valve or the like, and is directional through the pilot pipes 47A and 47B. The hydraulic pilot portions 28A and 28B of the control valve 28 and the hydraulic pilot portions 34A and 34B of the direction control valve 34 are connected. The lever device 47 supplies the pilot pressure generated by the tilting operation of the operation lever 47C to the direction control valves 28 and 34 via the pilot pipes 47A and 47B, whereby the direction control valves 28 and 34 are Switching from the neutral position (A) to the switching position (B) and (C).

  In addition, the lever device 47 is provided with an arm operation detector 47D (see FIG. 5) as an operation detection means including a pressure sensor for detecting a pressure change in the pilot pipes 47A and 47B. The arm operation detector 47D detects whether or not the operation lever 47C is tilted from the pressure change in the pilot pipes 47A and 47B, and outputs a detection signal to the controller 57 described later.

  48 is a lever device for turning operation as an operation means for switching the direction control valve 32. The lever device 48 is constituted by, for example, a pressure reducing valve type pilot valve or the like, and the direction control valve via pilot pipes 48A and 48B. 32 hydraulic pilot portions 32A and 32B are connected. The lever device 48 supplies the pilot pressure generated by the tilting operation of the operation lever 48C to the direction control valve 32 via the pilot pipes 48A and 48B, so that the direction control valve 32 is in the neutral position (A). Are switched to switching positions (B) and (C).

  Further, the lever device 48 is provided with a turning operation detector 48D (see FIG. 5) as an operation detecting means including a pressure sensor for detecting a pressure change in the pilot pipes 48A and 48B. The turning operation detector 48D detects whether or not the operation lever 48C has been tilted from the pressure change in the pilot pipes 48A and 48B, and outputs a detection signal to the controller 57 described later.

  Reference numeral 49 is a lever device for preliminary operation as an operation means for switching the direction control valve 36. The lever device 49 is constituted by, for example, a pressure reducing valve type pilot valve or the like, and the direction control valve via pilot pipes 49A and 49B. It is connected to 36 hydraulic pilot parts 36A, 36B. The lever device 49 supplies the pilot pressure generated by the tilting operation of the operation lever 49C to the direction control valve 36 via the pilot pipes 49A and 49B, so that the direction control valve 36 is in the neutral position (A). Are switched to switching positions (B) and (C).

  In addition, the lever device 49 is provided with a spare operation detector 49D (see FIG. 5) as an operation detecting means including a pressure sensor for detecting a pressure change in the pilot pipes 49A and 49B. The spare operation detector 49D detects whether or not the operation lever 49C has been tilted from the pressure change in the pilot pipes 49A and 49B, and outputs a detection signal to the controller 57 described later.

  Reference numeral 50 denotes a reserve actuator that is driven and operated by a lever device 49. The reserve actuator 50 is constituted by, for example, a breaker (vibration device) used for crushing rocks or concrete. The spare actuator 50 is connected to the center bypass line 18 and the supply pipe from the second pump 15 when the direction control valve 36 is switched from the neutral position (A) to any one of the switching positions (B) and (C). It is driven by the pressure oil supplied via the branch pipe section 40D of the path 40.

  51 is a main relief valve for preventing an excessive pressure from acting on the first and second pumps 14 and 15, and the relief valve 51 is arranged on the first control valve group 21 side as shown in FIGS. Is connected to the center bypass conduit 17 via a check valve 52 at a position upstream of the direction control valve 22, and the pressure on the center bypass conduit 17 side is set to a relief set pressure Pc (FIG. 8). When the pressure is higher than the reference, the valve is opened to relieve the excess pressure to the tank 16 side.

  Further, the relief valve 51 is connected to the other side (downstream side) of the pressure oil supply line 40 via another check valve 53 on the second control valve group 31 side, and the center bypass line 18, When the pressure on the supply line 40 side becomes higher than the relief set pressure Pc (see FIG. 8), the excessive pressure is relieved to the tank 16 side by opening the valve. As a result, the main relief valve 51 prevents overload from acting on the first and second pumps 14 and 15.

  54 is a tank line connected to the tank 16, and this tank line 54 is connected to the most downstream side of the center bypass line 17 with respect to the first control valve group 21 side, and the second control valve The group 31 side is connected to the most downstream side of the center bypass pipe 18. The tank line 54 discharges the return oil (surplus oil) recirculated through the center bypass lines 17 and 18 out of the pressure oil discharged from the first and second pumps 14 and 15 to the tank 16. At the same time, when the relief valve 51 is opened, the excess pressure is circulated (relieved) to the tank 16 side.

  55 is a first pump discharge pressure sensor as a first pressure detecting means provided on the discharge side of the first pump 14, and this discharge pressure sensor 55 is the pressure of the pressure oil discharged from the first pump 14 ( Discharge pressure) and a detection signal is output to a controller 57 described later.

  56 is a second pump discharge pressure sensor provided as a second pressure detecting means provided on the discharge side of the second pump 15, and this discharge pressure sensor 56 is the pressure of the pressure oil discharged from the second pump 15 ( Discharge pressure) and a detection signal is output to a controller 57 described later.

  57 is a controller as a control means constituted by a microcomputer or the like, and the controller 57 has an input side of the engine speed detector 13, the first pump discharge pressure sensor 55 and the first pump as shown in FIGS. As shown in FIG. 5, the left and right traveling operation detectors 43D and 44D, the bucket operation detector 45D, the boom operation detector 46D, the arm operation detector 47D, and the turning operation are connected to the two-pump discharge pressure sensor 56. The detector 48D and the spare operation detector 49D are connected.

  The output side of the controller 57 is connected to the first servo mechanism 19, the second servo mechanism 20, and the like. The controller 57 includes a storage unit 57A composed of a ROM, a RAM, and the like. In this storage unit 57A, a processing program (variably controlling the discharge capacity (discharge flow rate) of the first and second pumps 14 and 15). 6) and the like, and the first characteristic indicated by the characteristic line 58 indicated by a solid line in FIG. 7 and the second characteristic indicated by the characteristic line 59 indicated by a solid line in FIG. 8 are stored.

  That is, the storage unit 57A of the controller 57 has a first characteristic (a solid line in FIG. 7) so that the horsepower of the engine 12 is controlled to be constant with respect to the relationship between the discharge pressure and the discharge flow rate by the first and second pumps 14 and 15. The first characteristic storage means stored as a characteristic line 58) and a relief valve on the side of the swing motor 3A that exceeds the control start point Pa (see FIG. 8) for controlling the horsepower of the engine 12 to be constant. The relationship between the discharge pressure and the discharge flow rate is set to the second characteristic so that the discharge flow rate gradually decreases as the discharge pressure rises with respect to the first characteristic in the region exceeding the relief set pressure Pb by 42A and 42B. Second characteristic storage means stored as (characteristic line 59 shown by a solid line in FIG. 8).

  Here, when the controller 57 selects the first characteristic, the discharge flow rate of the pressure oil from the first and second pumps 14 and 15 is set to the characteristic line 58 (so-called P−) in FIG. Q characteristic) is controlled so as to satisfy the relationship, and the limited horsepower of the engine 12 is effectively utilized.

  When the second characteristic is selected, for example, when the discharge pressure by the second pump 15 exceeds the relief set pressure Pb shown in FIG. 8, the discharge flow rate of the second pump 15 follows the characteristic line portion 59A. In other words, the discharge flow rate is controlled to be lower than the first characteristic (characteristic line 58 indicated by a dotted line in FIG. 8) as the discharge pressure increases.

  Then, in the control of the discharge flow rate by the second characteristic, the second is performed until the discharge pressure exceeds the relief set pressure Pb by the relief valves 42A and 42B on the swing motor 3A side and reaches the relief set pressure Pc by the main relief valve 51. The discharge flow rate of the pump 15 is reduced in an oblique straight line along the characteristic line portion 59A. Note that the characteristic line portion 59A in this case is not necessarily limited to a straight line but may have a curved characteristic.

  The pump control device of the hydraulic excavator 1 according to the present embodiment has the above-described configuration. Next, the capacity control processing of the first and second pumps 14 and 15 by the controller 57 will be described.

  First, when an operator who has boarded the cab 5 of the hydraulic excavator 1 starts the engine 12, the first and second pumps 14 and 15 are rotationally driven together, and pressurized oil is directed toward the center bypass pipes 17 and 18. Is discharged. The discharge pressure at this time is detected by the first and second pump discharge pressure sensors 55 and 56, and the detection signal is output to the controller 57.

  Here, the controller 57 controls the capacities of the first and second pumps 14 and 15 according to the first characteristic described above, and the relationship between the discharge pressure and the discharge flow rate is the relationship along the characteristic line 58 shown in FIG. Thus, the limited horsepower of the engine 12 can be effectively utilized.

  By the way, for example, when a single swing operation is performed on the second control valve group 31 side and the upper swing body 3 is driven to swing on the lower traveling body 2 by the swing motor 3A, the characteristics of the swing motor 3A composed of a hydraulic motor are obtained. The rotation of the motor can be kept low by the action of the inertial force of the vehicle body when starting turning or accelerating turning. For this reason, as indicated by the hatched portion in FIGS. 9 and 10, the flow rate Qp of the pressure oil supplied to the turning motor 3A is often excessive compared to the required flow rate Qn. Then, on the hydraulic circuit side for the swing motor 3A, the relief valves 42A and 42B are opened by the excess (surplus) pressure oil, and the excess oil at this time is returned to the tank 16, so energy is wasted. Will be.

  Therefore, in the present embodiment, in addition to the first characteristic shown in FIG. 7 described above, the second characteristic shown in FIG. 8 is stored in advance in the storage unit 57A of the controller 57. For example, the second control valve When the single swing operation is performed on the group 31 side, the capacity of the second pump 15 is controlled so as to have a relationship between the discharge pressure and the discharge flow rate along the characteristic line 59 shown in FIG.

  That is, when the pump displacement control process by the controller 57 is started, from the engine speed detector 13, the first pump discharge pressure sensor 55, and the second pump discharge pressure sensor 56 in step 1 shown in FIG. The left and right traveling operation detectors 43D and 44D, the bucket operation detector 45D, the boom operation detector 46D, the arm operation detector 47D, the turning operation detector 48D and the spare operation detector shown in FIG. Each detection signal is also read from the operation detector 49D.

  Then, at the stage where the rotational speed of the engine 12 reaches the rated rotational speed, whether or not the turning operation is performed by the detection signal from the turning operation detector 48D in Step 2, that is, the operation lever 48C of the lever device 48 shown in FIG. It is determined whether or not the tilting operation has been performed from the neutral position, and while it is determined “NO” in step 2, it can be determined that the turning operation has not been performed.

  Therefore, in this case, the process proceeds to the next step 3 to read out the first characteristic shown in FIG. 7 from the storage unit 57A of the controller 57, and to control the capacity of the first and second pumps 14 and 15 in accordance with the first characteristic. I do. That is, the pump capacity is controlled so that the discharge pressure-discharge flow rate characteristics of the first and second pumps 14 and 15 are in a relationship along the characteristic line 58 shown in FIG. The horsepower can be used effectively.

  When it is determined as “YES” in step 2, a turning operation is performed, and the upper turning body 3 is driven to turn on the lower traveling body 2 by the turning motor 3A. Therefore, in the next step 4, whether the boom raising operation is performed by the detection signal from the boom operation detector 46D, that is, whether the operation lever 46C of the lever device 46 shown in FIG. 4 is tilted from the neutral position. Determine whether.

  During the determination of “YES” in step 4, at least the swing operation is performed in addition to the swing operation, and on the second control valve group 31 side, the direction control valve 32 for swing and the direction control valve for boom are used. 35 can be determined to be combined. Therefore, also in this case, the process proceeds to step 3 where the first pump 14 and the second pump 15 have the discharge pressure-discharge flow rate characteristic along the characteristic line 58 shown in FIG. 7 according to the first characteristic shown in FIG. The pump capacity is controlled so as to be related.

  When it is determined “NO” in step 4, it can be determined that the boom raising operation is not performed. Therefore, the process proceeds to the next step 5 where the arm operation is performed by the detection signal from the arm operation detector 47D, that is, whether the operation lever 47C of the lever device 47 shown in FIG. 4 is tilted from the neutral position. Determine whether.

  During the determination of “YES” in step 5, at least an arm operation is performed in addition to the turning operation, and on the second control valve group 31 side, a turning direction control valve 32 and an arm direction control valve 34. Can be determined to be combined. Therefore, also in this case, the process proceeds to step 3 so that the first pump 14 and the second pump 15 have the relationship of the discharge pressure-discharge flow rate characteristic along the characteristic line 58 according to the first characteristic shown in FIG. To control the pump capacity.

  Further, when it is determined as “NO” in Step 5, it can be determined that the arm operation is not performed. Therefore, the process proceeds to the next step 6 to determine whether or not the operation of the auxiliary actuator 50 is performed by the detection signal from the auxiliary operation detector 49D, that is, the operation lever 49C of the lever device 49 shown in FIG. 4 is tilted from the neutral position. It is determined whether or not a rolling operation is being performed.

  During the determination of “YES” in step 6, at least the turning operation is performed in addition to the turning operation, and the turning direction control valve 32 and the turning direction control are performed on the second control valve group 31 side. It can be determined that the valve 36 is operated in combination. Therefore, also in this case, the process proceeds to step 3 so that the first pump 14 and the second pump 15 have the relationship of the discharge pressure-discharge flow rate characteristic along the characteristic line 58 according to the first characteristic shown in FIG. To control the pump capacity.

  Next, when “NO” is determined in Step 6, it can be determined that the operation of the preliminary actuator 50 is not performed. Then, the process proceeds to the next step 7 and whether or not the right traveling operation is performed by the detection signal from the right traveling operation detector 44D, that is, the operation lever 44C of the lever device 44 shown in FIG. It is determined whether or not it has been done.

  During the determination of “YES” in step 7, at least the turning operation is performed in addition to the right traveling operation. On the second control valve group 31 side, the turning direction control valve 32 and the right traveling direction control are performed. It can be determined that the valve 38 is operated in combination. Therefore, also in this case, the process proceeds to step 3 so that the first pump 14 and the second pump 15 have the relationship of the discharge pressure-discharge flow rate characteristic along the characteristic line 58 according to the first characteristic shown in FIG. To control the pump capacity.

  On the other hand, when “NO” is determined in Step 7, the “boom raising operation”, “arm operation”, “preliminary operation”, and “right running operation” described above are not performed, and only the “turning operation” is performed alone. It can be determined that it is being operated. The turning single operation in this case is a case where the boom lowering operation is excluded, and even if the boom lowering operation is performed, it can be determined that the turning single operation is performed for the following reason.

  That is, as shown in FIG. 4, the directional control valves 26 and 35 for the boom cylinder 9A perform a boom lowering operation when switched from the neutral position (A) to the switching position (B). The cylinder 9 </ b> A is driven in the reduction direction when the pressure oil from the first pump 14 is supplied via the branch pipe part 30 </ b> B of the supply pipe 30, and swings (rotates) the boom 9 downward.

  In the second control valve group 31, when the direction control valve 35 is switched from the neutral position (A) to the switching position (B), the pressure oil (return oil) on the main line 27B side is transferred to the tank 16 side. For example, the pressure oil from the second pump 15 is not supplied via the branch pipe section 40C of the supply pipe 40 only by discharging. Therefore, during the boom lowering operation, the pressure oil discharged from the second pump 15 is not supplied to the boom cylinder 9A, and the flow rate control of the pressure oil discharged from the second pump 15 is controlled by the boom lowering. It is performed without being affected by the operation.

  Therefore, in step 8 shown in FIG. 6, when it is determined as “NO” in step 7 and it can be determined that the turning operation is performed alone, the second characteristic shown in FIG. The capacity of the pump 15 is controlled so as to satisfy the relationship of discharge pressure-discharge flow rate along the characteristic line 59. Thereby, the flow rate of the pressure oil discharged from the second pump 15 is similar to the characteristic line 58 (see FIG. 7) until the discharge pressure reaches the relief set pressure Pb of the relief valves 42A and 42B. Control is performed so that the relationship between the discharge pressure and the discharge flow rate is satisfied.

  However, when the discharge pressure of the second pump 15 exceeds the relief set pressure Pb, control is performed to reduce the discharge flow rate along the characteristic line portion 59A in FIG. 8, and the relief set pressure Pc by the main relief valve 51 is reached. Until, the capacity (discharge flow rate) of the second pump 15 is controlled so as to gradually decrease along the characteristic line portion 59A.

  Thus, when the direction control valve 32 for turning is operated independently on the second control valve group 31 side, the rotation of the turning motor 3A can be kept low by the action of the inertial force of the vehicle body when starting turning or turning acceleration. For this reason, even if the pressure oil flows to the swing motor 3A side in an excessive tendency, the pressure oil at this time can be prevented from being returned to the tank 16 side as excess oil, and energy is wasted. Can be reduced.

  That is, the pressure oil from the second pump 15 flows excessively toward the swing motor 3A during the swing operation alone, and is discharged from the second pump 15 when the pressure rises to the relief set pressure Pb of the relief valves 42A and 42B. 8 can be reduced along the characteristic line portion 59A in FIG. 8, so that the pressure oil at this time can be prevented from being wasted through the relief valves 42A and 42B, and energy efficiency can be reduced. Can be improved.

  Therefore, according to the present embodiment, when the turning direction control valve 32 is independently operated on the second control valve group 31 side, extra pressure oil from the second pump 15 is supplied to the turning motor 3A. The amount of pressure oil (surplus oil) consumed wastefully via the relief valves 42A and 42B at the time of turning activation or turning acceleration can be reduced.

  In addition, the discharge flow rates of the first and second pumps 14 and 15 are variable according to the first and second characteristics (discharge pressure-discharge flow rate characteristics shown in FIGS. 7 and 8) stored in advance in the storage unit 57A of the controller 57. Therefore, so-called feed-forward flow rate control can be realized, and time delay in actual pump control can be minimized.

  As a result, it is possible to reduce wasteful consumption of the pressure oil via the relief valves 42A and 42B at the time of turning activation or turning acceleration, and energy efficiency can be improved. And compared with the prior art by patent document 1, a number of parts can be reduced and, thereby, the workability | operativity at the time of an assembly can be improved.

  Further, at the time of the composite operation in which the directional control valve 32 for turning and any one of the other directional control valves 34, 35, 36, 38 are switched on the second control valve group 31 side, the first and second pumps 14, The discharge flow rate of 15 can be variably controlled according to the first characteristic (discharge pressure-discharge flow rate characteristic shown in FIG. 7). When detecting the single turning operation, the discharge flow rate of the second pump 15 can be variably controlled in accordance with the second characteristic (discharge pressure-discharge flow rate characteristic shown in FIG. 8). Can be variably controlled according to the first characteristic.

  In the above-described embodiment, the second characteristic of the characteristic line 59 shown in FIG. 8 is the same as that in the region where the discharge pressure of the second pump 15 exceeds the relief setting pressure Pb. The case where the characteristic gradually decreases has been described as an example. However, the present invention is not limited to this. For example, the characteristic of the modification shown in FIG. 11 may be adopted as the second characteristic.

  That is, in the modification shown in FIG. 11, the second characteristic is stored as the characteristic line 60 in the storage unit 57A (second characteristic storage means) of the controller 57. In this case, when the discharge pressure further increases in a region where the discharge pressure of the second pump 15 exceeds a pressure (set pressure Pd) determined in advance as a pressure lower than the relief set pressure Pb, the first pressure is increased. It is possible to achieve a control characteristic such that the discharge flow rate gradually lowers than the above characteristic. As a result, the discharge flow rate of the second pump 15 is reduced in a slanting straight line along the characteristic line portion 60A until the discharge pressure exceeds the set pressure Pd and reaches the pressure value Pe shown in FIG.

  The set pressure Pd in this case is set to, for example, a pressure of 75 to 85% (Pd = Pb × 0.75 to 0.85), preferably about 80% of the relief set pressure Pb. The pressure value Pe may be set to a pressure value (Pb <Pe <Pc) that is an intermediate value between the relief setting pressure Pb by the relief valves 42A and 42B and the relief setting pressure Pc by the main relief valve 51. Note that the characteristic line portion 60A in this case is not necessarily limited to a straight line, and may have a curved characteristic.

  And according to this modification, when the pressure of the pressure oil discharged from the second pump 15 rises to the set pressure Pd during the turning operation alone, the flow rate of the pressure oil discharged from the second pump 15 is shown in FIG. By reducing along the characteristic line portion 60A, even if the operability at the time of the single swing operation is slightly reduced, it is possible to prevent the pressure oil from being wastefully consumed via the relief valves 42A and 42B. Energy efficiency can be further improved.

  In the above embodiment, the left and right traveling operation detectors 43D and 44D, the bucket operation detector 45D, the boom operation detector 46D, the arm operation detector 47D, the turning operation detector 48D, and the spare operation detector 49D. In the above description, the pressure sensor is used as an example. However, the present invention is not limited to this. For example, the operation detection means may be configured by a position sensor or a stroke sensor that detects the tilting operation of the operation levers 43C, 44C, 45C, 46C, 47C, 48C, and 49C. It ’s good.

  On the other hand, in the above embodiment, the case where two variable displacement hydraulic pumps including the first and second pumps 14 and 15 are used has been described as an example. However, the present invention is not limited to this, and can be applied to a pump control apparatus using, for example, three or more variable displacement hydraulic pumps. Further, these variable displacement hydraulic pumps are not limited to swash plate type or oblique axis type hydraulic pumps, and may be configured to use, for example, a radial piston type variable displacement hydraulic pump.

  Further, in the above-described embodiment, the hydraulic excavator 1 has been described as a representative example of the construction machine. However, the present invention is not limited to this, and can be applied to various swivel construction machines such as a hydraulic crane including a traveling body and a swivel body.

1 Excavator (construction machine)
2 Lower traveling body 2A, 2B Traveling motor (hydraulic actuator)
3 Upper swing body 3A Swing motor (hydraulic actuator)
5 Cab (cab)
8 Working device 9 Boom 9A Boom cylinder (hydraulic actuator)
10 arm 10A arm cylinder (hydraulic actuator)
11 Bucket (work implement)
11A Bucket cylinder (hydraulic actuator)
12 engine 13 engine speed detector (speed detector)
14 First pump (first variable displacement hydraulic pump)
14A, 15A Variable displacement section 15 Second pump (second variable displacement hydraulic pump)
16 Tank 17, 18 Center bypass conduit 19 First servo mechanism (first capacity variable mechanism)
20 Second servo mechanism (second variable capacity mechanism)
21 First control valve group 22, 24, 26, 28 Direction control valve 31 Second control valve group 32, 34, 35, 36, 38 Direction control valve 42A, 42B Relief valves 43, 44, 45 for turning 46, 47, 48, 49 Lever device (operating means)
43D, 44D, 45D, 46D, 47D, 48D, 49D Operation detector (operation detection means)
50 Preliminary actuator 54 Tank line 55 Discharge pressure sensor for first pump (first pressure detecting means)
56 Discharge pressure sensor for second pump (second pressure detecting means)
57 Controller (control means)
58 Characteristic line (first characteristic)
59, 60 characteristic line (second characteristic)

Claims (4)

A traveling body,
A swivel body provided on the traveling body so as to be turnable;
A working device comprising a boom, an arm and a work implement provided on the swivel body so as to be able to be raised and lowered;
A plurality of hydraulic actuators for individually driving the traveling body, the swing body, and the working device;
First and second hydraulic pumps comprising at least two variable displacement hydraulic pumps driven by an engine to supply pressure oil to each of the hydraulic actuators;
First and second capacity variable mechanisms for variably controlling the discharge flow rate of the pressure oil by the first and second hydraulic pumps;
First and second pressure detecting means for detecting discharge pressures of the first and second hydraulic pumps;
A rotational speed detection means for detecting the rotational speed of the engine;
A plurality of directional control valves that supply pressure oil discharged from the first hydraulic pump to at least two of the plurality of hydraulic actuators are connected in a predetermined arrangement. A first control valve group comprising:
A plurality of directional control valves that supply pressure oil discharged from the second hydraulic pump to at least two other hydraulic actuators among the plurality of hydraulic actuators. The directional control valves are arranged in advance. A second control valve group connected by
A plurality of operation means for individually switching each directional control valve constituting each of the first and second control valve groups;
A plurality of operation detecting means for individually detecting whether or not each operating means is operated;
The first and second hydraulic pressure mechanisms are driven by driving the first and second variable capacity mechanisms according to the detection results of the first and second pressure detection means, the rotation speed detection means, and the operation detection means. Control means for variably controlling the discharge flow rate of the pump;
First characteristic storage means for storing the relationship between the discharge pressure and the discharge flow rate by the first and second hydraulic pumps as a first characteristic so as to control the horsepower of the engine to be constant;
In a region where the control pressure exceeds the control start point for controlling the horsepower of the engine to a constant level and the discharge pressure exceeds the pressure set in advance based on the relief setting pressure of the hydraulic actuator that drives the swing body to swing, the discharge pressure is Second characteristic storage means for storing the relationship between the discharge pressure and the discharge flow rate as a second characteristic so that the discharge flow rate gradually decreases with respect to the first characteristic as it rises;
The control means includes
The operation detecting means indicates that the directional control valve for the swing body and the other directional control valve are combined in the same control valve group of the first and second control valve groups. When detected, the first characteristic by the first characteristic storage means is selected to control the discharge flow rates of the first and second hydraulic pumps variably,
When the plurality of operation detecting means detect that the directional control valve for the swing body is operated alone in the same control valve group, the second characteristic is selected by the second characteristic storage means. A construction machine pump control device configured to variably control the discharge flow rate of one of the first and second hydraulic pumps.   The control means variably controls the discharge flow rates of the first and second hydraulic pumps according to the first characteristic when detecting the combined operation, and the first and second hydraulic pressures when detecting the single operation. The construction according to claim 1, wherein the discharge flow rate of one of the hydraulic pumps is variably controlled according to the second characteristic, and the discharge flow rate of the other hydraulic pump is variably controlled according to the first characteristic. Mechanical pump control device.   The second characteristic storage means discharges in a region where a control start point for controlling the horsepower of the engine to be constant and a discharge pressure exceeds a relief set pressure of the hydraulic actuator for driving the swing body to swing. 3. The configuration according to claim 1, wherein the relationship between the discharge pressure and the discharge flow rate is stored as the second characteristic so that the discharge flow rate gradually falls below the first characteristic when the pressure further increases. Pump controller for construction machinery.   The second characteristic storage means further increases the discharge pressure in a region exceeding a control start point for controlling the horsepower of the engine to be constant and exceeding the pressure where the discharge pressure is lower than the relief set pressure. The construction machine pump according to claim 1 or 2, wherein a relationship between a discharge pressure and a discharge flow rate is stored as the second characteristic so that the discharge flow rate is gradually lower than the first characteristic. Control device.

Images