JP2008185182A - Hydraulic control system of working machine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To facilitate supply flow rate control to a hydraulic actuator when discharged oil from the hydraulic actuator is collected in an accumulator to be reused. <P>SOLUTION: The hydraulic control system is constituted so as to perform flow rate control of first and second main pumps 9 and 10 which are oil pressure supply sources of a boom cylinder 8 by load sensing flow rate control, and is provided with an accumulator 39 for accumulating the pressure of the discharged oil from a head side oil chamber 8a of the boom cylinder 8, and a hybrid pump 34 for supplying the pressure oil accumulated in the accumulator 39 to a delivery line 12 of the first and the second main pumps 9 and 10. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention belongs to the technical field of a hydraulic control system in a work machine that can recover and reuse the energy of oil discharged from a hydraulic actuator.

In general, a work machine such as a hydraulic excavator or a crane includes a working unit that can freely move up and down, and the working unit is configured to be lifted and lowered based on an expansion and contraction operation of a hydraulic cylinder supplied with pressure oil from a hydraulic pump. However, in this case, conventionally, the oil discharged from the hydraulic cylinder weight holding side oil chamber to the oil tank when the working unit is lowered is supplied to the hydraulic cylinder in order to prevent a sudden drop due to its own weight. Meter-out control is performed by a throttle provided in a control valve that performs discharge control. That is, the working unit located above the ground has potential energy, but the potential energy is converted into thermal energy when passing through the throttle of the control valve, and the thermal energy is further converted into an oil cooler. Will be discharged into the atmosphere, resulting in wasted energy loss.
Therefore, in order to recover and reuse the potential energy of the working unit, an auxiliary hydraulic cylinder (assist cylinder) is provided in addition to the normal hydraulic cylinder, and when the working unit is lowered, the auxiliary hydraulic cylinder is moved from the weight holding side oil chamber. A technique is disclosed in which the discharged oil is accumulated in an accumulator, and the pressure oil accumulated in the accumulator is supplied to the weight holding side of the auxiliary cylinder when the working unit is raised (see, for example, Patent Document 1). .)
Japanese Patent No. 2582310

  However, in the case of Patent Document 1, when the accumulator is accumulating when the working part is raised, the accumulator oil is supplied to the auxiliary hydraulic cylinder to support the raising of the working part, while the accumulator is sufficient. When the pressure is not accumulated in the engine, a part of the pressure oil supplied from the hydraulic pump to the normal hydraulic cylinder through the control valve is supplied to the auxiliary hydraulic cylinder and used for accumulator pressure accumulation. ing. For this reason, the amount of pressure oil supplied to the normal hydraulic cylinder changes depending on the pressure accumulation state of the accumulator, and the ascending speed of the working unit cannot be accurately controlled, resulting in poor workability. There is a problem to be solved by the present invention.

The present invention has been created in view of the above circumstances and has been created for the purpose of solving these problems. The invention of claim 1 includes a hydraulic actuator and a main pump serving as a hydraulic supply source of the hydraulic actuator. And a load sensing flow rate control means for controlling the discharge flow rate of the main pump in accordance with the load pressure of the hydraulic actuator, an accumulator for accumulating discharged oil from the hydraulic actuator, A hydraulic control system for a work machine, comprising: a hybrid pump that supplies pressure oil accumulated in an accumulator to a discharge line of the main pump.
In this way, the oil discharged from the hydraulic actuator can be effectively collected and reused using an accumulator and a hybrid pump. In this case, the discharge flow rate of the hybrid pump is the discharge rate of the main pump. The total flow rate of the main pump discharge flow rate and the hybrid pump discharge flow rate is higher than the load pressure of the hydraulic actuator by a predetermined differential pressure by the load sensing flow rate control means. Thus, the flow rate is controlled so as to become a flow rate required for the pressure, and the discharge flow rate of the main pump is automatically reduced by the discharge flow rate of the hybrid pump. Therefore, without providing a separate flow rate control means, the load sensing flow rate control can be used as it is, and the main pump discharge flow rate can be controlled to correspond to the increase or decrease of the hybrid pump discharge flow rate. The load sensing flow rate control can be easily implemented because it is a flow rate control that has been widely used in work machines.
According to a second aspect of the present invention, the hydraulic actuator is a hydraulic cylinder that raises and lowers a working unit provided in the work machine, and the hydraulic control system is discharged from the weight holding side oil chamber of the hydraulic cylinder when the working unit is lowered. The hydraulic control system for a work machine according to claim 1, further comprising a recovery oil passage that guides the pressure oil to an accumulator.
In this manner, the energy of the oil discharged from the weight holding side oil chamber of the hydraulic cylinder when the working unit is lowered can be accumulated in the accumulator via the recovery oil passage.
The invention according to claim 3 is characterized in that the recovered oil passage guides the pressure oil discharged from the weight holding side oil chamber of the hydraulic cylinder when the working unit is lowered to the accumulator and to the suction side of the hybrid pump. A hydraulic control system for a work machine according to claim 2.
In this manner, for example, when another hydraulic actuator is provided in the work machine, the high pressure oil discharged from the weight holding side oil chamber of the hydraulic cylinder when the working unit is lowered is hybridized. It can be reused for other hydraulic actuators via the pump.
The invention according to claim 4 is the hydraulic control system for a work machine according to claim 2 or 3, wherein a recovery valve for controlling a flow rate of the recovery oil passage is arranged in the recovery oil passage.
And by doing in this way, it is possible to control the discharge flow rate from the weight holding side oil chamber of the hydraulic cylinder by the recovery valve, and thus it is possible to accurately control the lowering speed of the working part, Good operability can be obtained.
According to a fifth aspect of the present invention, the hydraulic control system includes a regeneration oil passage that guides the pressure oil discharged from the weight holding side oil chamber of the hydraulic cylinder to the anti-weight holding side oil chamber of the hydraulic cylinder when the working unit is lowered. The hydraulic control system for a work machine according to any one of claims 2 to 4, characterized in that:
And by doing in this way, the high pressure oil discharged | emitted from the weight holding | maintenance side oil chamber of the hydraulic cylinder can be utilized as it is as the reclaimed oil to the anti-weight holding side oil chamber.
A sixth aspect of the present invention is the hydraulic control system for a work machine according to the fifth aspect, wherein a regeneration valve for controlling a flow rate of the regenerated oil passage is arranged in the regenerated oil passage.
And by doing in this way, it is possible to control the flow rate of the regenerated oil that is discharged from the weight holding side oil chamber of the hydraulic cylinder and supplied to the anti-weight holding side oil chamber by the recovery valve. Since the descent speed of the working unit can be controlled with high accuracy, good operability can be obtained.
According to a seventh aspect of the present invention, the hydraulic control system includes a control device that controls increase / decrease of the supply flow rate from the hybrid pump to the discharge line of the main pump according to the pressure accumulation amount of the accumulator. A hydraulic control system for a work machine according to any one of the above.
And by doing in this way, while being able to use the pressure accumulation oil of an accumulator reliably, for example, when it is set as the structure where the pressure oil supply from a hybrid pump is stopped suddenly when the accumulator becomes empty, for example Therefore, it is possible to contribute to improvement in operability without causing a sudden change in the circuit.
According to an eighth aspect of the present invention, the hydraulic control system includes an accumulator control valve that controls input / output of oil to the accumulator, and the hydraulic pressure in the working machine according to any one of claims 1 to 7 Control system.
And by doing in this way, the pressure accumulation oil of an accumulator can be utilized without waste when needed.
According to a ninth aspect of the present invention, in addition to the hydraulic actuator, the hydraulic control system includes another hydraulic actuator using a main pump as a pressure oil supply source. It is the hydraulic control system in the working machine.
And by doing in this way, the pressure accumulation oil of an accumulator can be utilized also for another hydraulic actuator.

  Next, embodiments of the present invention will be described with reference to the drawings. In FIG. 1, reference numeral 1 denotes a hydraulic excavator that is an example of a work machine. The hydraulic excavator 1 includes a crawler-type lower traveling body 2 and an upper revolving body 3 that is rotatably supported above the lower traveling body 2. The working unit 4 is composed of various parts such as a working unit 4 mounted on the front of the upper swing body 3, and the working unit 4 further includes a boom 5 whose base end portion is supported by the upper swing body 3 so as to swing up and down, The arm 5 is supported at the front end of the boom 5 so as to be swingable back and forth, and the bucket 7 is attached to the front end of the arm 6.

  Reference numeral 8 denotes a pair of left and right boom cylinders (corresponding to the hydraulic actuator according to the present invention and a hydraulic cylinder for raising and lowering the working unit) that extend and contract to swing the boom 5 up and down. While holding the weight of the working part 4 by the pressure of the oil chamber 8a (corresponding to the weight holding side oil chamber of the present invention), the pressure oil supply to the head side oil chamber 8a and the rod side oil chamber 8b (of the present invention) The boom 5 is raised by the oil discharge from the oil chamber from the anti-weight holding side oil chamber), and the boom 5 is raised, and the oil is reduced by the pressure oil supply to the rod side oil chamber 8b and the oil discharge from the head side oil chamber 8a. The boom 5 is configured to be lowered. The working unit 4 as a whole moves up and down as the boom 5 moves up and down, and as the boom 5 moves up, the potential energy of the working unit 4 increases. It is collected and reused when descending.

Next, the hydraulic control system will be described based on the circuit diagram of FIG. 2, in which 9 and 10 are connected to the engine E mounted on the hydraulic excavator 1 via the pump drive gear portion G. These are the first and second main pumps, and the first and second main pumps 9 and 10 are configured to discharge the working oil sucked from the oil tank 11 to the discharge line 12.
Here, the first and second main pumps 9 and 10 include not only the boom cylinder 8 but also a plurality of other hydraulic actuators A (not shown in FIG. 2 as other hydraulic actuators A). Although a hydraulic actuator is shown, the hydraulic excavator 1 is a variable capacity type that serves as a hydraulic supply source of a plurality of hydraulic actuators A such as a swing motor, an arm cylinder, a bucket cylinder, and left and right traveling motors). It is a hydraulic pump, Comprising: These 1st, 2nd main pumps 9 and 10 are equivalent to the main pump of this invention.

  On the other hand, 13 is a control valve unit. The control valve unit 13 includes a boom control valve 14 for performing oil supply / discharge control for the boom cylinder 8, a boom pressure compensation valve 15, and an oil supply / discharge control for the hydraulic actuator A. Various valves such as a plurality of control valves 16 for the hydraulic actuator A, a pressure compensation valve 17 for the hydraulic actuator A, and a neutral flow bypass valve 18 to be described later are incorporated.

  The boom control valve 14 is constituted by a spool valve provided with an ascending pilot port 14a. When the pilot pressure is not input to the ascending pilot port 14a, the boom control valve 14 supplies and discharges oil to and from the boom cylinder 8. Although it is located in the neutral position N where it is not performed, the pilot pressure is input to the ascending pilot port 14a, so that the pressure oil supplied from the discharge line 12 is switched to the ascending position X to control the boom. While supplying to the head side oil chamber 8a of the boom cylinder 8 via the meter-in throttle 14b formed in the valve 14, the boom pressure compensation valve 15, and the cylinder head side oil passage 19, the rod side oil chamber 8b of the boom cylinder 8 is supplied. The oil discharged from the cylinder rod side oil passage 20 to the oil tank 11 is configured to flow. . The cylinder head side oil passage 19 is an oil passage connected to the head side oil chamber 8a to supply / discharge oil to / from the head side oil chamber 8a of the boom cylinder 8, and the cylinder rod side oil passage 20 is The oil passage is connected to the rod-side oil chamber 8b to supply and discharge oil to and from the rod-side oil chamber 8b of the boom cylinder 8.

  The control valve 16 for the hydraulic actuator A is constituted by a spool valve provided with pilot ports 16a and 16b. When no pilot pressure is input to both pilot ports 16a and 16b, the hydraulic actuator A However, when the pilot pressure is input to the pilot port 16a or 16b, the operation is switched to the first operation position X or the second operation position Y, so that the discharge line 12 Is supplied to the hydraulic actuator A via the meter-in throttle 16c or 16d formed in the control valve 16 for the hydraulic actuator A and the pressure compensation valve 17 for the hydraulic actuator A, while the hydraulic oil is supplied from the hydraulic actuator A. So that the drained oil flows into the oil tank 11 It has been made.

  On the other hand, 21 is an electromagnetic proportional pressure reducing valve for the boom, 22 is an electromagnetic proportional pressure reducing valve for the hydraulic actuator A, and the electromagnetic proportional pressure reducing valves 21 and 22 for the boom and hydraulic actuator A are for the boom operating lever and the hydraulic actuator. Based on the operation of the operation tool (none of which is shown, the hydraulic actuator operation tool is provided corresponding to each hydraulic actuator A), the ascending pilot port 14a of the boom control valve 14, the hydraulic actuator A Pilot pressure is output to the pilot ports 16a and 16b of the control valve 16, respectively. In the present embodiment, the boom operating lever and the hydraulic actuator A operating tool are constituted by electric levers, and the operation direction and operation amount thereof are input to the control device 23 described later, and the boom is operated from the control device 23. The control signal for pilot pressure output is output to the electromagnetic proportional pressure reducing valves 21 and 22 for the hydraulic actuator A, and is output from the electromagnetic proportional pressure reducing valves 21 and 22 for the boom and hydraulic actuator A. The pilot pressure increases or decreases corresponding to the operation amounts of the boom operation lever and the hydraulic actuator A operation tool, and the opening amount of the meter-in throttle 14b of the boom control valve 14 at the ascending position X, the first operation position. Open meter-in throttles 16c and 16d of control valve 16 for hydraulic actuator A at X or second operating position Y The amount is configured to increase or decrease in accordance with the input pilot pressure, so that meter-in control corresponding to the operation amounts of the boom operation lever and the hydraulic actuator A operation tool is performed. It is configured. In the figure, 24 is a pilot hydraulic pressure source.

  Further, the boom pressure compensation valve 15 and the hydraulic actuator A pressure compensation valve 17 receive the load signal pressure input to the pilot ports 15a and 17a from a load sensing signal circuit 25 described later, and the boom control valve 14 The hydraulic actuator A control valve 16 is configured to operate so as to maintain a constant differential pressure (differential pressure between the inlet side pressure and the outlet side pressure). The boom pressure compensation valve 15 and the hydraulic actuator A pressure compensation valve 17 hold the differential pressure across the front and rear so that the boom control valve 14 and the hydraulic actuator A control valve 16 are connected to the boom cylinder 8. The supply flow rate to the hydraulic actuator A can be controlled so as to be a flow rate corresponding to the opening amounts of the meter-in throttles 14a, 16c, and 16d regardless of the magnitude of the load.

  The neutral flow bypass valve 18 is disposed in a bypass oil passage 55 that unloads the pressure oil input from the discharge line 12 to the control valve unit 13 to the oil tank 11. The neutral flow bypass valve 18 is configured to switch from a closed position N for closing the bypass oil passage 55 to an open position X for opening the bypass oil passage 55 based on a control signal output from the control device 23. Yes.

  On the other hand, 26 and 27 are load pressure detection circuits into which the load pressures of the boom cylinder 8 and the hydraulic actuator A are respectively introduced. The load pressures introduced into these load pressure detection circuits 26 and 27 are a plurality of shuttle valves 28. Thus, the high pressure side is selected, and the highest pressure load pressure output from the final shuttle valve 28a is input to the load sensing signal circuit 25 as the load signal pressure. The load pressure detection circuits 26 and 27 do not introduce the load pressures of the boom cylinder 8 and the hydraulic actuator A when the boom control valve 14 and the hydraulic actuator control valve 16 are in the neutral position N. , Communicated with the oil tank 11.

  The load sensing signal circuit 25 includes the first and second load sensing regulators 29 and 30 of the first and second main pumps 9 and 10 and the boom pressure compensation valve 15 described above. , A circuit formed so as to reach the pilot ports 15 a and 17 a of the pressure compensation valve 17 for the hydraulic actuator A, and the load signal pressure is first and second load sensing via the load sensing signal circuit 25. Regulators 29 and 30, boom pressure compensation valve 15, and hydraulic actuator A pressure compensation valve 17 are input to pilot ports 15 a and 17 a.

  The first and second load sensing regulators 29 and 30 control the flow rate of the first and second main pumps 9 and 10 based on the load signal pressure input from the load sensing signal circuit 25 (load sensing flow rate control). The regulators included in the first and second main pumps 9 and 10 are configured so that the pressure of the discharge line 12 is loaded when the load signal pressure is input from the load sensing signal circuit 25. The flow rates of the first and second main pumps 9 and 10 are controlled so that the pressure Pp (Pp = PL + ΔP) is higher than the signal pressure PL by a predetermined differential pressure ΔP. The first and second load sensing regulators 29 and 30, the pressure compensation valves 15 and 16, the load pressure detection circuits 25 and 26, the shuttle valves 18 and 18a, the load sensing signal circuit 25, etc. Load sensing flow rate control means is configured.

  The first and second main pumps 9 and 10 are not only the first and second load sensing regulators 29 and 30 described above as regulators for controlling the flow rate, but also the first and second main pumps for performing constant horsepower control. Second power constant regulators 31 and 32 are provided. The first and second power constant regulators 31 and 32 receive the control signal pressure output from the main pump control electromagnetic proportional pressure reducing valve 33 in accordance with the engine speed, and output the pump at the time of full output. The flow rates of the first and second main pumps 9 and 10 are controlled so as to keep the pressure constant.

  On the other hand, reference numeral 34 denotes a hybrid pump, which is also a variable displacement pump connected to the engine E via a pump drive gear portion G. The hybrid pump 34 is supplied from a suction oil passage 35 to be described later. The oil is sucked and discharged to the discharge line 12. That is, the pressure oil discharged from the hybrid pump 12 merges with the discharge oil of the first and second main pumps 9 and 10 in the discharge line 12, but the discharge flow rate control of the hybrid pump 34 is controlled. It is configured to be performed by a hybrid regulator 36 that operates based on a control signal output from the device 23. In the drawing, reference numeral 63 denotes a check valve that allows oil flow from the hybrid pump 34 to the discharge line 12 but prevents reverse flow.

  Here, the suction oil passage 35 is an oil passage that guides the pressure oil supplied from an accumulator oil passage 37 and a recovery oil passage 38 described later to the suction side of the hybrid pump 34. Thus, as will be described later, the hybrid pump 34 collects the accumulated oil in the accumulator 39 supplied from the accumulator oil passage 37 or the discharged oil from the head side oil chamber 8a of the boom cylinder 8 supplied from the recovery oil passage 38. The air is sucked and discharged to the discharge line 12.

  The recovery oil passage 38 is an oil passage that is branched from the cylinder head-side oil passage 19 together with a later-described regeneration oil passage 40, and a recovery valve 41 is disposed in the recovery oil passage 38. The accumulator oil passage 37 and the suction oil passage 35 are connected downstream of the recovery valve 41. Further, the recovery oil passage 38 is provided with a check valve 42 that allows oil flow from the cylinder head side oil passage 19 to the accumulator oil passage 37 and the suction oil passage 35 but prevents reverse flow. . Thus, the oil discharged from the head side oil chamber 8 a of the boom cylinder 8 to the cylinder head side oil passage 19 can be supplied to the accumulator oil passage 37 and the suction oil passage 35 via the recovery oil passage 38. It can be done.

  The recovery valve 41 is an open / close valve in which the spool moves based on the operation of the recovery electro-oil conversion valve 43 to which a control signal from the control device 23 is input. In a state in which no oil is input, the recovery oil passage 38 is closed, but it is positioned at the closed position N. However, when a control signal is input to the recovery electric oil conversion valve 43, the spool moves, and the recovery oil passage 38 It is comprised so that it may switch to the open position X which opens.

  The movement stroke of the spool of the recovery valve 41 is controlled to increase or decrease by a control signal value input from the control device 23 to the recovery electro-oil conversion valve 43, and the increase or decrease of the movement stroke of the spool is controlled. By the control, increase / decrease control of the flow rate flowing from the head side oil chamber 8a of the boom cylinder 8 to the accumulator oil passage 37 and the suction oil passage 35 via the recovery oil passage 38 is performed.

  On the other hand, the accumulator oil passage 37 is an oil passage from the recovery oil passage 38 to the accumulator 39 via an accumulator check valve (corresponding to the control valve for accumulator of the present invention) 44. The maximum pressure is limited by a relief valve 45 connected to the accumulator oil passage 37. In the present embodiment, the accumulator 39 is an optimal bladder type for storing hydraulic energy, but is not limited thereto, and may be a piston type, for example.

  The accumulator check valve 44 is a valve that controls the input and output of oil to the accumulator 39, and is an accumulator that switches from the OFF position N to the ON position X based on the control signal output from the poppet valve 46 and the control device 23. A check valve electromagnetic switching valve 47 is used. The poppet valve 46 allows the oil flow from the recovery oil passage 38 to the accumulator 39 regardless of whether the accumulator check valve electromagnetic switching valve 47 is in the OFF position N or the ON position X. The flow of oil to the suction oil passage 35 is blocked when the accumulator check valve electromagnetic switching valve 47 is located at the OFF position N and allowed only when it is located at the ON position X. Yes. The flow of oil from the recovered oil passage 38 to the accumulator 39 is allowed regardless of whether the accumulator check valve electromagnetic switching valve 47 is in the OFF position N or the ON position X as described above. However, the accumulator check valve In the state where the electromagnetic switching valve 47 is located at the ON position X, the pressure in the accumulator oil passage 37 is not introduced into the spring chamber 46a of the poppet valve 46, and therefore the accumulator 39 is connected from the recovery oil passage 38 with almost no pressure loss. The oil can be made to flow.

  Reference numeral 48 denotes a discharge oil passage that is branched from the accumulator oil passage 37 and reaches the oil tank 11. A tank check valve 49 is disposed in the discharge oil passage 48.

  The tank check valve 49 includes a poppet valve 50 and a tank check valve electromagnetic switching valve 51 that switches from the OFF position N to the ON position X based on a control signal output from the control device 23. . The poppet valve 50 permits the flow of oil from the accumulator oil passage 37 to the oil tank 11 only when the tank check valve electromagnetic switching valve 51 is located at the ON position X, and is located at the OFF position N. It is designed to stop when you are. Then, for example, when the excavator 1 is finished or maintained, the accumulator check valve electromagnetic switching valve 47 and the tank check valve electromagnetic switching valve 51 are both switched to the ON position X to accumulate pressure in the accumulator 39. The pressurized oil can be discharged to the oil tank 11.

  On the other hand, the regeneration oil passage 40 is an oil passage branched from the cylinder head side oil passage 19 together with the recovery oil passage 38 described above. The regeneration oil passage 40 is provided with a regeneration valve 52. The cylinder rod side oil passage 20 is connected to the downstream side of the regeneration valve 52. Furthermore, the regenerative oil passage 40 is provided with a check valve 53 that allows oil flow from the cylinder head side oil passage 19 to the cylinder rod side oil passage 20 but prevents reverse flow. Thus, the oil discharged from the head side oil chamber 8a of the boom cylinder 8 to the cylinder head side oil passage 19 is passed through the regeneration oil passage 40 to the rod side oil of the boom cylinder 8 from the cylinder rod side oil passage 20. It can supply to the chamber 8b.

  The regeneration valve 52 is an open / close valve in which the spool moves based on the operation of the regeneration electro-oil conversion valve 54 to which a control signal from the control device 23 is input. In a state in which no is input, the regeneration oil passage 40 is located at the closed position N, but when the control signal is input to the regeneration electric oil conversion valve 54, the spool is moved and the regeneration oil passage 40 is moved. It is comprised so that it may switch to the open position X which opens.

  The movement stroke of the spool of the regeneration valve 52 is increased / decreased controlled by a control signal value input from the control device 23 to the regeneration electric oil conversion valve 54, and the movement stroke of the spool is increased / decreased. By the control, increase / decrease control of the flow rate regenerated from the head side oil chamber 8a of the boom cylinder 8 to the rod side oil chamber 8b via the regenerative oil passage 40 is performed.

  On the other hand, the control device 23 is configured by using a microcomputer or the like, and as shown in the block diagram of FIG. 3, the boom operation detecting means 56 for detecting the operation direction and the operation amount of the boom operation lever. , Hydraulic actuator A operation detection means (provided corresponding to each hydraulic actuator A operation tool) 57 for detecting the operation direction and operation amount of the hydraulic actuator A operation tool, discharge for detecting the pressure of the discharge line 12 The line pressure sensor 58, the cylinder head side pressure sensor 59 connected to the cylinder head side oil passage 19 to detect the pressure of the head side oil chamber 8a of the boom cylinder 8, and the pressure of the rod side oil chamber 8b of the boom cylinder 8 are detected. A cylinder rod side pressure sensor 60 connected to the cylinder rod side oil passage 20 and an accumulator 39 A signal from an accumulator pressure sensor 61 or the like for detecting pressure is input, and based on these input signals, the neutral flow bypass valve 18, the boom electromagnetic proportional pressure reducing valve 21, the hydraulic actuator A electromagnetic proportional pressure reducing valve 22, Main pump control electromagnetic proportional pressure reducing valve 33, hybrid pump regulator 36, recovery electro-oil conversion valve 43, accumulator check valve electromagnetic switching valve 47, tank check valve electromagnetic switching valve 51, regeneration electro-oil conversion valve 54, etc. Output a control signal.

  Here, reference numeral 62 denotes a pressure accumulation amount calculation unit provided in the control device 23, and the pressure accumulation amount calculation unit 62 is based on the pressure of the accumulator 39 input from the accumulator pressure sensor 61. Calculate the amount (%). The accumulator amount (%) is set in advance, for example, as 0% if the pressure in the accumulator oil passage 37 is equal to the precharge pressure (accumulation start setting pressure) of the accumulator 39, and the accumulator 39 is sufficiently accumulated. If the pressure is equal to or higher than the set pressure, 100%, and if it is between the precharge pressure and the set pressure, the percentage increases as the pressure in the accumulator oil passage 37 increases. Depending on the temperature correction.

Next, the control of the control device 23 based on the operation on the raising and lowering sides of the boom operation lever and the operation of the operation tool for the hydraulic actuator A, and the load sensing flow control of the first and second main pumps 9 and 10 will be described. .
First, a description will be given of a case where the boom operation lever is operated to the ascending side. The control device 23 controls the boom operation lever to the ascending pilot port 14a of the boom control valve 14 with respect to the boom electromagnetic proportional pressure reducing valve 21. A control signal is output so as to output a pilot pressure corresponding to the operation amount. As a result, the boom control valve 14 is switched to the ascending position X, and the pressure oil input from the discharge line 12 to the control valve unit 13 passes through the boom control valve 14 and the cylinder head side oil passage 19. While being supplied to the head side oil chamber 8 a of the boom cylinder 8 via the oil, the oil discharged from the rod side oil chamber 8 b to the cylinder rod side oil passage 20 is supplied to the oil tank 11 via the boom control valve 14. In this case, the opening amount of the meter-in throttle 14b of the boom control valve 14 is controlled so as to correspond to the operation amount of the boom operation lever as described above.

  Further, when the boom control lever is operated to the ascending side, no control signal is output from the control device 23 to the recovery electro-oil conversion valve 43 and the regeneration electro-oil conversion valve 54. The valve 41 is located at a closed position N for closing the recovery oil passage 38, and the regeneration valve 52 is located at a closed position N for closing the regeneration oil passage 40. As a result, the pressure oil supplied to the cylinder head side oil passage 19 via the boom control valve 14 described above does not flow to the suction oil passage 35, the accumulator oil passage 37, or the cylinder rod side oil passage 20, It is supplied to the head side oil chamber 8 a of the boom cylinder 8. Further, no control signal is output from the control device 23 to the neutral flow bypass valve 18, and the neutral flow bypass valve 18 is located at the closed position N where the bypass oil passage 55 is closed. As a result, the pressure oil in the discharge line 12 input to the control valve unit 13 is not unloaded from the bypass oil passage 55 to the oil tank 11.

Further, when the boom operation lever is operated to the ascending side, the control device 23 determines that the discharge flow rate of the hybrid pump 34 is calculated by the pressure accumulation amount calculation unit 62 with respect to the hybrid pump regulator 36. The control command is output so that the flow rate corresponds to the amount and the operation amount of the boom operation lever.
Here, in the present embodiment, the hybrid pump 34 has a capacity approximately half the capacity of the first and second main pumps 9 and 10. In other words, when the first and second main pumps 9 and 10 each discharge a flow rate of one pump at a maximum (the flow rate of the first and second main pumps 9 and 10 combined is a maximum of two pumps), the hybrid The pump 34 can discharge a flow rate corresponding to a maximum of 0.5 pump. However, as shown by the solid line in FIG. 4, when the boom operation lever is fully operated, the hybrid pump 34 is almost accumulated in the accumulator 39. When the accumulator 39 is sufficiently accumulated (for example, when the accumulated pressure is 0% to 10%), the flow rate is zero, the flow rate increases as the accumulated pressure of the accumulator 39 increases (for example, When the pressure accumulation amount is 70% to 100%), the flow rate is controlled to be discharged by 0.5 pump. When the operation amount of the boom operation lever is smaller than the full operation, as shown by the broken line in FIG. 4, the discharge flow rate of the hybrid pump 34 decreases according to the operation amount, and the operation amount is zero (boom When the operation lever is not operated, the discharge flow rate is controlled to be zero.

  Further, when the boom operation lever is operated to the upward side, the control device 23 outputs a control signal to the accumulator check valve electromagnetic switching valve 47 so as to switch to the ON position X. As a result, the accumulator check valve 44 is allowed to flow oil from the accumulator 39 to the suction oil passage 35. Thus, the pressure oil accumulated in the accumulator 39 is supplied to the suction side of the hybrid pump 34 via the suction oil passage 35.

On the other hand, when the boom operation lever is operated to the upward side, the load pressure of the boom cylinder 8 is first and second loads as the load signal pressure PL via the load pressure detection circuit 26 and the load sensing signal circuit 25. The first and second load sensing regulators 29 and 30 are input to the sensing regulators 29 and 30, respectively. As described above, the pressure of the discharge line 12 is a predetermined differential pressure ΔP from the load signal pressure PL. The flow rates of the first and second main pumps 9 and 10 are controlled so that the pressure Pp is high (Pp = PL + ΔP).
Incidentally, in the discharge line 12, the discharge flow rate Qm of the first and second main pumps 9 and 10 (the discharge flow rate Qm is the sum of the discharge flow rate of the first main pump 9 and the discharge flow rate of the second main pump 10). In addition to the flow rate (hereinafter the same), the discharge flow rate Qh of the hybrid pump 34 is also supplied. Thus, the discharge flow rate Qm of the first and second main pumps 9 and 10 is the sum of the discharge flow rate Qm of the first and second main pumps 9 and 10 and the discharge flow rate Qh of the hybrid pump 34. The discharge line 12 is controlled so as to have a flow rate Qr (Qr = Qm + Qh) required to make the pressure Pp higher than the load signal pressure PL by a predetermined differential pressure ΔP. That is, the discharge flow rate Qm of the first and second main pumps 9 and 10 is determined from the flow rate Qr required for making the pressure of the discharge line 12 higher than the load signal pressure PL by a predetermined differential pressure ΔP. Control is performed so that the flow rate (Qm = Qr−Qh) is obtained by subtracting the discharge flow rate Qh of the hybrid pump 34. When there is almost no pressure accumulation amount of the accumulator 39, the discharge flow rate Qh of the hybrid pump 34 is controlled to be zero as described above, so that the discharge flow rates Qm of the first and second main pumps 9 and 10 are controlled. Thus, the flow rate Qr necessary for making the pressure in the discharge line 12 higher than the load signal pressure PL by a predetermined differential pressure ΔP is supplied (Qr = Qm, where Qh = 0). When).

  Here, FIG. 5 shows the discharge flow rate Qm of the first and second main pumps 9 and 10, the discharge flow rate Qh of the hybrid pump 34, and the pressure of the discharge line 12 by a predetermined differential pressure ΔP than the load signal pressure PL. However, as shown in FIG. 5, when the required flow rate Qr is equal to 2 pumps, the discharge flow rate Qh of the hybrid pump 34 is Corresponding to the increase in the pressure accumulation amount of the accumulator 39, the maximum is 0.5 pump, while the discharge flow rate Qm of the first and second main pumps 9 and 10 is increased by the discharge flow rate Qh of the hybrid pump 34. In addition, the flow rate is controlled so that the total flow rate of the discharge flow rate Qm of the first and second main pumps 9 and 10 and the discharge flow rate Qh of the hybrid pump 34 becomes the required flow rate Qq.

  Thus, when the boom operation lever is operated to the upward side, the pressure oil in the discharge line 12 passes through the boom control valve 14 and the cylinder head side oil passage 19 in the head side oil chamber 8a of the boom cylinder 8. On the other hand, the oil discharged from the rod side hydraulic pressure 8b flows into the oil tank 11 via the cylinder rod side oil passage 20 and the boom control valve 14, and the boom 5 is thereby raised. When the hydraulic oil is accumulated in the accumulator 39 when the boom 5 is raised, the discharge flow rate of the first and second main pumps 9 and 10 and the discharge flow rate of the hybrid pump 34 are supplied to the discharge line 12. It will be supplied after joining. In this case, since the hybrid pump 34 sucks and discharges the high-pressure oil accumulated in the accumulator 39, the differential pressure between the suction side and the discharge side is small, and compared with the first and second main pumps 9 and 10. Pressure oil can be supplied with much less required power. Further, the first and second main pumps 9 and 10 are configured so that the hybrid pump 34 has a flow rate Qr required to make the pressure in the discharge line 12 higher than the load signal pressure PL by a predetermined differential pressure ΔP. Since the control is performed so that the flow Qm (Qm = Qr−Qh) obtained by reducing the discharge flow Qh is discharged, compared with the case where the hybrid pump 34 is not provided, the reduced discharge flow Qh of the hybrid pump 34. As a result, the discharge flow rate is reduced, and thus the required power of the first and second main pumps 9 and 10 can be reduced accordingly. On the other hand, when the pressure is not accumulated in the accumulator 39, the discharge flow rate Qh of the hybrid pump 34 becomes zero, but the discharge flow rate Qm of the first and second main pumps 9 and 10 is the load signal pressure PL. Therefore, even if the pressure is not accumulated in the accumulator 39, the boom cylinder 8 is supplied with pressure oil at the same flow rate, even if the pressure is not accumulated in the accumulator 39. Will be made.

  Further, in the case of a composite operation in which any of the operating tools for the hydraulic actuator A is operated simultaneously with the upward operation of the boom operation lever, the operation is performed from the control device 23 in addition to the control during the boom upward operation described above. A control command for pilot pressure output is output to the electromagnetic proportional pressure reducing valve 22 for the hydraulic actuator A, whereby the corresponding control valve 16 for the hydraulic actuator A is switched to the first operating position X or the second operating position Y. The pressure oil in the discharge line 12 is supplied to the hydraulic actuator A. In this case, the highest load pressure among the load pressures of the operated hydraulic actuators (the boom cylinder 8 and the hydraulic actuator A) is obtained. The load signal pressure PL is input to the first and second load sensing regulators 29 and 30. Then, the first and second load sensing regulators 29 and 30 have a total flow rate of the discharge flow rate Qm of the first and second main pumps 9 and 10 and the discharge flow rate Qh of the hybrid pump 34. The flow rates of the first and second main pumps 9 and 10 are controlled so that the pressure becomes a flow rate Qr necessary for making the pressure Pp higher than the load signal pressure PL by a predetermined differential pressure ΔP. Thus, when pressure is accumulated in the accumulator 39, the pressure-accumulated oil in the accumulator 39 can be used not only for the boom cylinder 8 but also for other hydraulic actuators A.

  Next, a case where the boom operation lever is operated to the lowering side will be described. In this case, when the boom operation lever is operated alone, another hydraulic pressure is applied simultaneously with the lowering operation of the boom operation lever. Since the control of the control device 23 is partly different from the case of the composite operation in which the actuator A operation tool is operated, first, a case where the boom operation lever is operated to be lowered alone will be described.

  When the boom operation lever is operated alone on the lower side, the control command for the pilot output is not output from the control device 23 to the boom electromagnetic proportional pressure reducing valve 21, and the boom control valve 14 is held at the neutral position N. The Thereby, oil supply / discharge of the boom cylinder 8 via the boom control valve 14 is not performed, and the load pressure of the boom cylinder 8 is not introduced into the load pressure detection circuit 26.

  Further, when the boom operation lever is operated alone on the lower side, the control device 23 outputs a control signal to the regeneration electro-oil conversion valve 54 so as to switch the regeneration valve 52 to the open position X. Thereby, the oil in the head side oil chamber 8a of the boom cylinder 8a is supplied to the rod side oil chamber 8b via the cylinder head side oil passage 19, the regeneration oil passage 40, and the cylinder rod side oil passage 20, The amount of reclaimed oil supplied from the head side oil chamber 8a to the rod side oil chamber 8b is the control signal value output from the control device 23 to the regenerating electro-oil conversion valve 54 based on the operation amount of the boom operation lever. Increase / decrease is controlled by.

  Further, when the boom operation lever is operated alone on the lower side, the control device 23 outputs a control signal to the recovery electro-hydraulic conversion valve 43 so as to switch the recovery valve 41 to the open position X. As a result, the oil in the head side oil chamber 8a of the boom cylinder 8a is supplied to the accumulator oil passage 37 via the cylinder head side oil passage 19 and the recovery oil passage 38 and accumulated in the accumulator 39, and the suction oil. The oil is supplied from the passage 35 to the suction side of the hybrid pump 34. The flow rate of the oil supplied to the accumulator 39 and the hybrid pump 34 via the recovery oil passage 38 is the amount of operation of the boom operation lever. Based on the control signal value output from the control device 23 to the recovery electro-oil conversion valve 43, the increase / decrease control is performed. Further, at this time, the control device 23 outputs a control signal to the accumulator check valve electromagnetic switching valve 47 so as to switch to the ON position X. As a result, oil can flow from the recovered oil passage 38 to the accumulator 39 with almost no pressure loss.

  By the way, when the boom 5 is lowered, the oil discharged from the head-side oil chamber 8a of the boom cylinder 8 is approximately twice the amount supplied to the rod-side oil chamber 8b due to the pressure receiving area acting on the piston 8c. In this embodiment, about half of the amount discharged from the head-side oil chamber 8a passes through the regenerated oil passage 40 and is supplied to the rod-side oil chamber 8b. Passes through the recovery oil passage 40, and about half of the passage amount of the recovery oil passage 40 is supplied to the suction side of the hybrid pump 34, and the remainder is accumulated in the accumulator 39. That is, for example, when the flow for two pumps is discharged from the head side oil chamber 8a, the flow for one pump is supplied to the rod side oil chamber 8b, while the flow for 0.5 pump is the hybrid pump. 34 is supplied to the suction side, and a flow rate corresponding to 0.5 pump is further accumulated in the accumulator 39.

  Further, when the boom operation lever is operated on the lower side alone, the control device 23 causes the hybrid pump regulator 36 to discharge the hybrid pump 34 at a flow rate corresponding to the operation amount of the boom operation lever. As such, the control command is output. Thus, the oil supplied from the head side oil chamber 8a of the boom cylinder 8 to the suction side of the hybrid pump 34 via the recovery oil passage 38 and the suction oil passage 35 is discharged from the hybrid pump 34 to the discharge line 12. The

  On the other hand, when the boom operation lever is operated alone on the lower side, the load pressure of the boom cylinder 8 is not introduced into the load detection circuit 26 as described above. The load signal pressure PL input to the regulators 29 and 30 has a minimum value, and thereby the first and second main pumps 9 and 10 are controlled to have a minimum flow rate. The minimum amount of pressure oil is discharged from the first and second main pumps 9 and 10 to the discharge line 12.

  Further, when the boom operating lever is operated alone on the lower side, the control device 23 outputs a control signal to the neutral flow bypass valve 18 so as to switch to the open position X. As a result, the bypass oil passage 55 is opened, and the oil discharged from the hybrid pump 34 and the first and second main pumps 9, 10 to the discharge line 12 is passed through the bypass oil passage 55 to the oil tank 11. To be unloaded.

  Next, a description will be given of a composite operation in which another operation tool for the hydraulic actuator A is operated simultaneously with the lowering operation of the boom operation lever. In this case, the electromagnetic proportional pressure reducing valve 21 for the boom, the regeneration electro-hydraulic conversion valve, and the like. 54, the control of the recovery electro-oil conversion valve 43, the accumulator check valve electromagnetic switching valve 47, and the hybrid pump regulator 36 is the same as the case where the boom operation lever described above is operated independently. The boom control valve 14 is held at the neutral position N, and the oil in the head-side oil chamber 8a of the boom cylinder 8 is regenerated to the rod-side oil chamber 8b via the reclaimed oil passage 40, while being recovered. The pressure is accumulated in the accumulator 39 via the oil passage 38, and supplied to the suction side of the hybrid pump 34. Further, the hybrid pump 4 through discharged into the discharge line 12.

Further, in the case of a composite operation in which another hydraulic actuator A operating tool is operated simultaneously with the lowering operation of the boom operating lever, the control device 23 controls the pilot proportional to the operated hydraulic actuator A electromagnetic proportional pressure reducing valve 22. Outputs a pressure output control command. As a result, the corresponding control valve 16 for the hydraulic actuator A is switched to the first operating position X or the second operating position Y, so that the pressure oil input from the discharge line 12 to the control valve unit 13 is used for the hydraulic actuator A. It is supplied to the hydraulic actuator A via the control valve 16.

  Further, in the case of a composite operation in which another operation tool for the hydraulic actuator A is operated simultaneously with the lowering operation of the boom operation lever, no control signal is output from the control device 23 to the neutral flow bypass valve 18, and the neutral flow bypass valve Reference numeral 18 denotes a closed position N that closes the bypass oil passage 55. As a result, the pressure oil in the discharge line 12 input to the control valve unit 13 is not unloaded from the bypass oil passage 55 to the oil tank 11.

  On the other hand, in the case of a composite operation in which another hydraulic actuator A operation tool is operated simultaneously with the lowering operation of the boom operation lever, the highest load pressure among the load pressures of the operated hydraulic actuator A is the load signal. The pressure PL is input to the first and second load sensing regulators 29 and 30. Then, the first and second load sensing regulators 29 and 30 have a total flow rate of the discharge flow rate Qm of the first and second main pumps 9 and 10 and the discharge flow rate Qh of the hybrid pump 34. The flow rates of the first and second main pumps 9 and 10 are controlled so that the pressure becomes a flow rate Qr necessary for making the pressure Pp higher than the load signal pressure PL by a predetermined differential pressure ΔP.

  Thus, when the boom operating lever is operated independently to the lowering side, or when the other operation tool for the hydraulic actuator A is operated simultaneously with the lowering operation of the boom operating lever, the boom cylinder 8 The oil discharged from the head side oil chamber 8a is at a high pressure due to the potential energy of the working unit 4, and the supply amount to the rod side oil chamber 8b due to the pressure receiving area acting on the piston 8c. The amount of oil discharged from the head-side oil chamber 8a is supplied to the rod-side oil chamber 8b via the reclaimed oil passage 40, while being discharged to the accumulator via the recovery oil passage 38. 39 is accumulated. Further, part of the discharged oil that passes through the recovered oil passage 38 is supplied to the suction side of the hybrid pump 34 and discharged from the hybrid pump 34 to the discharge line 12. The oil discharged from the hybrid pump 34 to the discharge line 12 is unloaded to the oil tank 11 via the bypass oil passage 55 when the boom operation lever is operated to the lower side alone. In the case of a composite operation in which another operation tool for the hydraulic actuator A is operated simultaneously with the lowering operation of the boom operation lever, the above operation is performed together with the oil discharged from the first and second main pumps 9 and 10. Thus, the potential energy of the working unit 4 can be recovered and reused without being wasted. Further, in the case of a composite operation in which another hydraulic actuator A operation tool is operated simultaneously with the lowering operation of the boom operation lever, the hybrid pump 34 sucks and discharges high-pressure discharged oil from the head-side oil chamber 8a. Therefore, the pressure oil can be supplied with much less required power than the first and second main pumps 9 and 10, and the discharge flow rate of the first and second main pumps 9 and 10 is the hybrid pump 34. Accordingly, the required power of the first and second main pumps 9 and 10 can be reduced accordingly.

  Next, a case where the boom operating lever is not operated and at least one of the operating tools for the hydraulic actuator A is operated will be described. In this case, the control device 23 performs the electromagnetic proportional pressure reduction for the operated hydraulic actuator A. A control command for pilot pressure output is output to the valve 22. As a result, the corresponding control valve 16 for the hydraulic actuator A is switched to the first operating position X or the second operating position Y, so that the pressure oil input from the discharge line 12 to the control valve unit 13 is transferred to the hydraulic actuator A. Is supplied to the hydraulic actuator A via the control valve 16. The control signal is not output from the control device 23 to the boom electromagnetic proportional pressure reducing valve 21, and the boom control valve 14 is held at the neutral position N.

  Further, when the boom control lever is not operated and at least one of the hydraulic actuator A operating tools is operated, the control signal is not output from the control device 23 to the neutral flow bypass valve 18, and the neutral flow bypass valve 18. Is located at the closed position N for closing the bypass oil passage 55. As a result, the pressure oil in the discharge line 12 input to the control valve unit 13 is not unloaded from the bypass oil passage 55 to the oil tank 11. Further, no control signal is output from the control device 23 to the recovery electro-oil conversion valve 43 and the regeneration electro-oil conversion valve 54, and thus the recovery valve 41 is located at the closed position N where the recovery oil passage 38 is closed. Further, the regeneration valve 52 is located at the closed position N for closing the regeneration oil passage 40, and the oil in the head side oil chamber 8 a of the boom cylinder 8 flows out from the recovery oil passage 38 and the regeneration oil passage 40. There is no such thing.

  Further, when the boom operating lever is not operated and at least one of the hydraulic actuator A operating tools is operated, the control device 23 determines that the discharge flow rate of the hybrid pump 34 is the accumulated pressure with respect to the hybrid pump regulator 36. A control command is output so that the flow rate corresponds to the pressure accumulation amount of the accumulator 36 and the operation amount of the hydraulic actuator operation lever calculated by the amount calculation unit 62. In this case, the discharge flow rate of the hybrid pump 34 is controlled in the same manner as when the boom operation lever is operated to the upward side. Further, the control device 23 outputs a control signal to the accumulator check valve electromagnetic switching valve 47 so as to switch to the ON position X. As a result, the accumulator check valve 44 enters a state in which the flow of oil from the accumulator 39 to the suction oil passage 35 is allowed, and thus the pressure oil accumulated in the accumulator 39 passes through the suction oil passage 35, It is supplied to the suction side of the hybrid pump 34.

  On the other hand, when the boom operating lever is not operated and at least one of the operating tools for the hydraulic actuator A is operated, the highest load pressure among the load pressures of the operated hydraulic actuator A is the load signal. The pressure PL is input to the first and second load sensing regulators 29 and 30. Then, the first and second load sensing regulators 29 and 30 have a total flow rate of the discharge flow rate Qm of the first and second main pumps 9 and 10 and the discharge flow rate Qh of the hybrid pump 34. The flow rates of the first and second main pumps 9 and 10 are controlled so that the pressure becomes a flow rate Qr necessary for making the pressure Pp higher than the load signal pressure PL by a predetermined differential pressure ΔP.

  Thus, when the boom operating lever is not operated and at least one of the operating tools for the hydraulic actuator A is operated, pressure oil is supplied to the operated hydraulic actuator A from the discharge line 12. However, if pressure is accumulated in the accumulator 39 at this time, the discharge flow rate of the first and second main pumps 9 and 10 and the discharge flow rate of the hybrid pump 34 are combined and supplied to the discharge line 12. become. Thus, the accumulated oil in the accumulator 39 can also be used for the hydraulic actuator A. In this case, as described above, the hybrid pump 34 is compared with the first and second main pumps 9 and 10. Pressure oil can be supplied with significantly less required power, and the discharge flow rates of the first and second main pumps 9 and 10 are reduced by the discharge flow rate of the hybrid pump 34. The required power of the second main pumps 9 and 10 can be reduced. On the other hand, when pressure is not accumulated in the accumulator 39, the discharge flow rate Qm of the first and second main pumps 9 and 10 is a pressure Pp in which the pressure of the discharge line 12 is higher than the load signal pressure PL by a predetermined differential pressure ΔP. Therefore, even if the accumulator 39 is not accumulating pressure, the hydraulic actuator A is supplied with the same amount of pressure oil.

  In the present embodiment configured as described, the hydraulic control system of the excavator 1 includes a boom cylinder 8 and a hydraulic actuator A other than the boom cylinder 8 (a swing motor, an arm cylinder, a bucket cylinder, left and right traveling motors, etc.). And first and second main pumps 9 and 10 which are hydraulic pressure supply sources for the boom cylinder 8 and the other hydraulic actuators A, and the first and second main pumps 9 and 10 are load sensing devices. The first and second load sensing regulators 29 and 30 for controlling the discharge flow rates of the first and second main pumps 9 and 10 based on the load signal pressure input from the signal circuit 25 are provided. For example, an accumulator 39 for accumulating oil discharged from the head side oil chamber 8a of the boom cylinder 8 when the boom 5 is lowered. The pressure oil is accumulated in the accumulator 39 first, and the hybrid pump 34 is supplied to the discharge line 12 of the second main pumps 9 is provided.

  As a result, the potential energy of the working unit 4 can be effectively recovered and reused using the accumulator 39 and the hybrid pump 34. In this case, the discharge flow rate of the hybrid pump 34 is the first and second main pumps. 9 and 10, the first and second load sensing regulators 29 and 30 that perform load sensing flow rate control of the first and second main pumps 9 and 10, The total flow rate of the discharge flow rate of the first and second main pumps 9 and 10 and the discharge flow rate of the hybrid pump 34 is set so that the pressure of the discharge line 12 is higher than the load signal pressure PL by a predetermined differential pressure ΔP. Therefore, the flow rate is controlled so as to be a necessary flow rate, and therefore, the discharge flow rate of the hybrid pump 34, the first and second main pumps. , It can be supposed to discharge flow rate of 10 to automatically reduce, first, allowed to reliably reduce the required power of the second main pump 29 and 30. Moreover, since the hybrid pump 34 sucks and discharges the high pressure oil accumulated in the accumulator 39, it hardly needs the power of the engine E, and can greatly contribute to energy saving. In addition, since the discharge flow rate of the hybrid pump 34 can be used for other hydraulic actuators A using the first and second main pumps 9 and 10 as the pressure oil supply source, the range of use of the accumulated oil in the accumulator 39 can be reduced. Will spread.

  Furthermore, as described above, the first and second load sensing regulators 29 and 30 allow the total flow rate of the discharge flow rates of the first and second main pumps 9 and 10 and the discharge flow rate of the hybrid pump 34 to be changed to the discharge line 12. Is controlled so as to have a flow rate required to increase the pressure of the accumulator 39 by a predetermined pressure difference ΔP higher than the load signal pressure PL. Even if the flow rate increases or decreases, the discharge flow rates of the first and second main pumps 9 and 10 automatically decrease correspondingly. Thus, the load sensing flow rate control is used as it is without providing a separate flow rate control means so that the discharge flow rates of the first and second main pumps 9 and 10 correspond to the increase and decrease of the discharge flow rate of the hybrid pump 34. Therefore, the load sensing flow rate control can be easily implemented because it is a flow rate control that has been widely used in work machines.

  In addition, in this configuration, since the discharge flow rate of the hybrid pump 34 is controlled to increase or decrease in accordance with the pressure accumulation amount of the accumulator 39, the accumulated oil of the accumulator 39 can be used reliably and, for example, the accumulator 39 is empty. When the pressure oil supply from the hybrid pump 34 is suddenly stopped at this point, it is possible to contribute to improvement in operability without causing a rapid change in the circuit as in the case where the configuration is such that the supply of pressure oil from the hybrid pump 34 is suddenly stopped.

  On the other hand, the oil discharged from the head-side oil chamber 8a of the boom cylinder 8 when the boom 5 is lowered is led to the accumulator 39 through the recovery oil passage 38 and accumulated, and the suction oil is accumulated. From the passage 35, it is guided to the suction side of the hybrid pump 34, so that when the other hydraulic actuator A is operated simultaneously with the lowering of the boom 5, from the head side oil chamber 8a of the boom cylinder 8. However, in this case, the hybrid pump 34 sucks and discharges high-pressure exhaust oil from the head-side oil chamber 8a. E power is not required, and the discharge flow rate of the first and second main pumps 9 and 10 is the hybrid pump 3 Supposed to decrease the discharge flow amount, first, it can be allowed to reliably reduce the required power of the second main pump 29 and 30.

  In addition, since the input / output of oil to the accumulator 39 is controlled by an accumulator check valve 44 disposed in the accumulator oil passage 37, the accumulated oil in the accumulator 39 can be used without waste when necessary. it can.

  Further, this is provided with a regenerative oil passage 40 for guiding the oil discharged from the head side oil chamber 8a of the boom cylinder 8 to the rod side oil chamber 8b when the boom 5 is lowered, and thus the head side oil chamber. The high-pressure oil discharged from 8a can be used as it is as regenerated oil for the rod-side oil chamber 8b. Moreover, the oil discharged from the head side oil chamber 8a of the boom cylinder 8 when the boom 5 is lowered is discharged about twice as much as the supply amount to the rod side oil chamber 8b due to the pressure receiving area acting on the piston 8c. However, about half of the discharged amount is led to the rod side oil chamber 8b through the regenerated oil passage 40, and the remaining half of the discharged amount is passed through the recovery oil passage 38 to the accumulator 39 and the hybrid. Since it is guided to the suction side of the pump 34, the accumulator 39 and the hybrid pump 34 can be downsized, the cost can be reduced, and the installation space can be easily secured.

  In addition, the recovery oil passage 38 and the regeneration oil passage 40 are provided with a recovery valve 41 and a regeneration valve 52 for controlling the flow rates of the recovery oil passage 38 and the regeneration oil passage 40, respectively. The discharge flow rate from the head-side oil chamber 8a and the supply flow rate to the rod-side oil chamber 8b can be controlled by the valve 41 and the regeneration valve 52. Therefore, the lowering speed of the boom 5 can be controlled by the operation amount of the boom operation lever. Therefore, it is possible to control with high accuracy so as to correspond to the above, and good operability can be obtained.

  Of course, the present invention is not limited to the above-described embodiment. In the above-described embodiment, the hydraulic control system of the hydraulic excavator has been described as an example. However, the present invention is not limited to a crane, a loader, or the like. It can be implemented in a hydraulic control system for work machines. Moreover, in the said embodiment, by accumulating the oil discharged | emitted from the weight holding | maintenance side oil chamber of the hydraulic cylinder which raises / lowers a working part to an accumulator, the potential energy which a working part has can be collect | recovered and reused effectively. However, for example, the present invention can be implemented even if the oil discharged from the hydraulic motor is accumulated in the accumulator.

It is a side view of a hydraulic excavator. It is a circuit diagram of a hydraulic control system. It is a block diagram which shows the input / output of a control apparatus. It is a graph which shows the relationship between the pressure accumulation amount of an accumulator, and the discharge flow volume of a hybrid pump. It is a graph which shows the relationship between the discharge flow rate of a hybrid pump, and the discharge flow rate of a 1st, 2nd main pump.

Explanation of symbols

4 Working Unit 8 Boom Cylinder 8a Head Side Oil Chamber 8b Rod Side Oil Chamber 9 First Main Pump 10 Second Main Pump 12 Discharge Line 23 Controller 25 Load Sensing Signal Circuit 29 First Load Sensing Regulator 30 Second Load Sensing Regulator 34 Hybrid pump 36 Hybrid pump regulator 38 Recovery oil path 39 Accumulator 40 Regeneration oil path 41 Recovery valve 44 Accumulator check valve 52 Regeneration valve A Other hydraulic actuators

Claims (9)

  In a hydraulic control system for a work machine comprising a hydraulic actuator, a main pump serving as a hydraulic supply source of the hydraulic actuator, and load sensing flow rate control means for controlling a discharge flow rate of the main pump according to a load pressure of the hydraulic actuator A hydraulic control system for a working machine, comprising: an accumulator for accumulating discharged oil from the hydraulic actuator; and a hybrid pump for supplying the pressure oil accumulated in the accumulator to a discharge line of the main pump.   The hydraulic actuator is a hydraulic cylinder that raises and lowers the working part equipped in the work machine, and the hydraulic control system collects the pressure oil discharged from the weight holding side oil chamber of the hydraulic cylinder to the accumulator when the working part is lowered. The hydraulic control system for a work machine according to claim 1, further comprising an oil passage.   3. The work according to claim 2, wherein the recovery oil passage guides the pressure oil discharged from the weight holding side oil chamber of the hydraulic cylinder when the working unit is lowered to the accumulator and to the suction side of the hybrid pump. Hydraulic control system for machines.   4. The hydraulic control system for a work machine according to claim 2, wherein a recovery valve for controlling a flow rate of the recovery oil passage is disposed in the recovery oil passage.   The hydraulic control system includes a regeneration oil passage that guides the pressure oil discharged from the weight holding side oil chamber of the hydraulic cylinder to the anti-weight holding side oil chamber of the hydraulic cylinder when the working unit is lowered. The hydraulic control system in the working machine as described in any one of thru | or 4.   6. The hydraulic control system for a work machine according to claim 5, wherein a regeneration valve for controlling a flow rate of the regeneration oil passage is disposed in the regeneration oil passage.   The hydraulic control system includes a control device that controls increase / decrease of the supply flow rate from the hybrid pump to the discharge line of the main pump according to the pressure accumulation amount of the accumulator. Hydraulic control system for work machines in Japan.   The hydraulic control system for a work machine according to any one of claims 1 to 7, wherein the hydraulic control system includes an accumulator control valve that controls input / output of oil to and from the accumulator.   The hydraulic control system for a work machine according to any one of claims 1 to 8, wherein the hydraulic control system includes, in addition to the hydraulic actuator, another hydraulic actuator using a main pump as a pressure oil supply source. .

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