JP2009150462A - Hydraulic control system for working machine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To surely collect the positional energy of an elevating working part, and to reuse the collected energy in a state that the loss of the collected energy is reduced. <P>SOLUTION: This hydraulic control system for a working machine is provided with an accumulator 35 for accumulating oil discharged from a head side oil chamber 8a of a boom cylinder 8 when a boom is lowered and a pressure increasing cylinder 17 for increasing and outputting the oil pressure of a rod side oil chamber 17a by supplying the accumulated oil from the accumulator 35 to a head side oil chamber 17a, and constituted to supply the pressure oil increased in pressure by the pressure increasing cylinder 17 to the head side oil chamber 8a of the boom cylinder 8. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention belongs to the technical field of a hydraulic control system in a working machine that can recover and reuse the potential energy of the working part in a working machine that includes a working part that moves up and down.

In general, a work machine such as a hydraulic excavator or a crane includes a working unit that can be raised and lowered, and the working unit is configured to be lifted and lowered based on an expansion and contraction operation of a lifting hydraulic cylinder that is supplied with pressure oil from a hydraulic pump. However, in this case, the oil discharged from the weight holding side oil chamber of the lifting hydraulic cylinder to the oil tank when the working part is lowered is conventionally raised and lowered in order to prevent a sudden drop due to the weight of the working part. Meter-out control is performed by a throttle provided in a control valve that performs oil supply / discharge control of the hydraulic cylinder. 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 wasted into the atmosphere, resulting in wasted energy loss.
Therefore, in order to collect and reuse the potential energy of the working unit, an assist cylinder is provided in addition to the conventional lifting hydraulic cylinder, and when the working unit is lowered, it is discharged from the weight holding side oil chamber of the assist cylinder. A technique is disclosed in which oil to be accumulated is accumulated in an accumulator and pressure oil accumulated in the accumulator is supplied to the weight holding side oil chamber of the assist cylinder when the working unit is raised (for example, Patent Document 1). reference.).
Japanese Patent No. 2582310

However, in Patent Document 1, the oil discharged from the assist cylinder is accumulated in the accumulator when the working unit is lowered, but is discharged from the lifting hydraulic cylinder that has been conventionally provided to raise and lower the working unit. The oil is discharged to the oil tank via the control valve, and only a part of the potential energy possessed by the work implement is recovered. In addition, when the accumulator is not sufficiently accumulated when the working unit is raised, a part of the pressure oil supplied from the hydraulic pump to the lifting hydraulic cylinder via the control valve is supplied to the assist cylinder and the accumulator. Since it is configured to be used for accumulating pressure, there is a problem that the ascending speed of the working unit becomes slow and the working efficiency decreases.
On the other hand, without providing an assist cylinder, the oil discharged from the lifting hydraulic cylinder when the working part is lowered is accumulated in the accumulator, and the pressure oil accumulated in the accumulator is raised when the working part is raised. However, in this case, with the pressure of the accumulator's accumulated oil, the hydraulic cylinder for raising and lowering is used to raise the working part during high-load work. The pressure of the supplied pressure oil may be insufficient. Therefore, it is proposed that the accumulator pressure-accumulated oil is supplied to the lifting hydraulic cylinder at a high pressure by a dedicated pump driven by engine power, but in this case, the dedicated pump and the engine power for transmitting the engine power to the pump are proposed. Power transmission equipment (gear device, etc.) is required, which increases costs, and there are problems such as torque reduction in the power transmission equipment and loss of idling torque due to the inertial mass of the pump itself. There is a problem to be solved.

The present invention has been created in view of the above-described circumstances and has been created for the purpose of solving these problems. The invention of claim 1 includes a plurality of hydraulic pressures including a lifting hydraulic cylinder that lifts and lowers a working unit. In a hydraulic control system for a work machine including an actuator, a hydraulic pump that supplies hydraulic oil to these hydraulic actuators, and a control valve for each hydraulic actuator that controls a supply flow rate to each hydraulic actuator Accumulator for accumulating the oil discharged from the weight holding side oil chamber of the hydraulic cylinder, and the pressure increase by increasing the oil pressure of the output side oil chamber by supplying the accumulator oil of the accumulator to the input side oil chamber A pressure oil boosted by the pressure-increasing cylinder is supplied to at least one of the plurality of hydraulic actuators. A hydraulic control system in a working machine, characterized in that the structure to be used as the supply pressure oil to the hydraulic actuator.
According to a second aspect of the present invention, the hydraulic control system includes a pressure increasing cylinder output oil path that joins the pressure oil increased by the pressure increasing cylinder to the pressure oil supply oil path from the hydraulic pump to each hydraulic actuator control valve. The hydraulic control system for a work machine according to claim 1, comprising:
According to a third aspect of the present invention, in the work machine according to the second aspect, the merging valve for controlling the combined flow rate from the pressure increasing cylinder to the pressure oil supply oil path is arranged in the pressure increasing cylinder output oil path. It is a hydraulic control system.
The invention according to claim 4 is characterized in that the hydraulic control system has a pump flow rate reduction means for reducing the discharge flow rate of the hydraulic pump in accordance with the combined flow rate from the pressure increasing cylinder to the pressure oil supply oil passage. Or a hydraulic control system in the work machine according to 3.
According to a fifth aspect of the present invention, the hydraulic control system is configured so that the oil discharged from the weight holding side oil chamber of the lifting hydraulic cylinder when the working unit is lowered is supplied to the output side oil chamber of the accumulator and the pressure increasing cylinder. The hydraulic control system for a work machine according to any one of claims 1 to 4, wherein the hydraulic control system is provided.
6. The work machine according to claim 5, wherein a recovery valve for controlling a flow rate of oil discharged from a weight holding side oil chamber of the lifting hydraulic cylinder is arranged in the recovery oil passage. Is a hydraulic control system.
According to a seventh aspect of the present invention, the hydraulic control system controls the oil supply from the accumulator to the input side oil chamber of the pressure increasing cylinder and the oil supply from the recovery oil path to the output side oil chamber of the pressure increasing cylinder. The hydraulic control system for a work machine according to claim 5 or 6, further comprising a control valve.

According to the first aspect of the present invention, when the working unit is lowered, the oil discharged from the weight holding side oil chamber of the elevating hydraulic cylinder is accumulated in the accumulator, while the pressure increasing cylinder has the accumulated oil in the accumulator. Pressure oil increased in pressure from the output-side oil chamber by being supplied to the input-side oil chamber is output, and the pressure oil increased by the pressure-increasing cylinder includes a plurality of hydraulic pressures including the lifting hydraulic cylinder. It will be used as supply pressure oil to at least one of the actuators. As a result, the potential energy recovered when the working unit is lowered can be reused, which can greatly contribute to energy saving, and can be used for high-load work by increasing the pressure with a pressure-increasing cylinder. Can be supplied to the hydraulic actuator. In addition, unlike the case where the pressure is increased using a pump driven by engine power, there is no loss of torque in the power transmission path from the engine to the pump or loss of idling torque due to the inertial mass of the pump itself, and the recovered energy can be used. It can be used in a state where the loss is as low as possible and is advantageous in terms of cost.
According to the second aspect of the present invention, the pressure oil increased by the pressure increasing cylinder is combined with the oil discharged from the hydraulic pump and supplied to the control valve for each hydraulic actuator. Regardless of the output flow rate from the cylinder, the supply flow rate to the hydraulic actuator can be controlled by each hydraulic actuator control valve, which contributes to simplification of the control.
By controlling the combined flow rate from the pressure-increasing cylinder to the pressure oil supply oil passage by the merging valve, the pressure oil increased by the pressure-increasing cylinder can be used efficiently without waste. Can do.
By setting it as invention of Claim 4, the discharge flow volume of a hydraulic pump can be reduced appropriately, and a low fuel consumption can be achieved efficiently.
According to the invention of claim 5, pressure oil is supplied to the output side oil chamber of the pressure increasing cylinder without separately providing pressure oil supplying means, and the weight holding side oil chamber of the lifting hydraulic cylinder is lowered when the working part is lowered. In addition to contributing to simplification of the system, the potential energy of the working unit can also be recovered here.
By controlling the discharge flow rate from the weight holding side oil chamber of the lifting hydraulic cylinder by means of the recovery valve, the lowering speed of the working part can be controlled by the recovery valve. Obtainable.
According to the seventh aspect of the present invention, the pressure oil can be appropriately supplied to the input side oil chamber and the output side oil chamber of the pressure increasing cylinder by the pressure increasing cylinder control valve.

  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 lifting hydraulic cylinder of the present invention) that extend and contract to swing the boom 5 up and down. The boom cylinder 8 includes a head-side oil chamber 8a (of the present invention). The weight of the working unit 4 is held by the pressure of the pressure holding oil chamber), and the boom 5 is extended by the pressure oil supply to the head oil chamber 8a and the oil discharge from the rod oil chamber 8b. Further, the boom 5 is lowered by reducing the pressure by supplying pressure oil to the rod side oil chamber 8b and discharging oil from the head side oil chamber 8a. The working unit 4 as a whole moves up and down as the boom 5 moves up and down, and the potential energy of the working unit 4 increases as the boom 5 moves up. The positional energy is lowered by the hydraulic control system described later. While sometimes recovered, the recovered energy is used when the boom 5 is raised.

  Next, the hydraulic control system will be described with reference to the circuit diagram of FIG. 2. In these drawings, 9 is a variable displacement main pump driven by the engine E mounted on the hydraulic excavator 1 (the hydraulic pressure of the present invention). 10 corresponds to a pump, and 11 is an oil tank. The main pump 9 includes not only the boom cylinder 8 but also a plurality of other hydraulic actuators (not shown, travel motor, swing motor, arm cylinder, bucket cylinder, etc.) provided in the hydraulic excavator 1. This is a hydraulic pump.

  Further, 12 is a regulator for controlling the discharge flow rate of the main pump 9, and the regulator 12 receives the control signal pressure from the electromagnetic proportional pressure reducing valve 14 for main pump output control, and controls the engine speed and the work load. While operating to obtain a corresponding pump output, constant horsepower control is performed in response to the discharge pressure of the main pump 9. Further, the regulator 12 performs flow control based on the negative control signal pressure Pn or the flow control signal pressure Pc, which will be described later.

  On the other hand, 15 is a pressure oil supply oil passage connected to the discharge side of the main pump 9, and the pressure oil supply oil passage 15 has a boom cylinder control valve (for controlling oil supply / discharge to the boom cylinder 8). 16) (corresponding to one of the control valves for the hydraulic actuator of the present invention) is connected. The pressure oil supply oil passage 15 is supplied with not only the oil discharged from the main pump 9 but also the pressure oil from the pressure increasing cylinder 17 as will be described later. The pressure oil supply oil passage 15 performs oil supply / discharge control for not only the boom cylinder control valve 16 but also a plurality of other hydraulic actuators (travel motor, swing motor, arm cylinder, bucket cylinder, etc.). A control valve for each hydraulic actuator is also connected, but is omitted in FIG.

  The boom cylinder control valve 16 is composed of a spool valve having ascending and descending pilot ports 16a and 16b, and in a state in which no pilot pressure is input to both the pilot ports 16a and 16b, Although it is located at the neutral position N where oil supply / discharge of oil to / from the cylinder 8 is not performed, when the pilot pressure is input to the ascending pilot port 16a, the spool moves and the pressure oil in the pressure oil supply oil passage 15 is supplied to the boom. An ascending side that supplies oil discharged from the rod side oil chamber 8b to the boom cylinder rod side oil passage 19 to the oil tank 11 while being supplied to the head side oil chamber 8a of the boom cylinder 8 via the cylinder head side oil passage 18. Switch to position X. Further, when the pilot pressure is input to the descending pilot port 16b, the spool moves to the side opposite to the ascending position X, and the pressure oil in the pressure oil supply oil passage 15 is supplied to the boom cylinder via the throttle 16c. A part of the oil supplied from the rod side oil passage 19 to the rod side oil chamber 8b and discharged from the head side oil chamber 8a to the boom cylinder head side oil passage 18 is supplied to the boom cylinder rod via the regeneration valve passage 16d. It is configured so as to switch to the descending position Y that is supplied from the side oil passage 19 to the rod side oil chamber 8b. The boom cylinder head side oil passage 18 is an oil passage connected to the head side oil chamber 8a to supply and discharge oil to the head side oil chamber 8a of the boom cylinder 8, and the boom cylinder rod side oil passage 19 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.

  Here, the regeneration valve path 16d provided in the boom cylinder control valve 16 at the descending position Y is a valve path that connects the boom cylinder head side oil path 18 and the boom cylinder rod side oil path 19; The regeneration valve path 16d is provided with a check valve 16e and a throttle 16f that allow oil flow from the boom cylinder head side oil path 18 to the boom cylinder rod side oil path 19 but prevent reverse flow. ing. Thus, while the head-side oil chamber 8a is at a higher pressure than the rod-side oil chamber 8b, a part of the oil discharged from the head-side oil chamber 8a passes through the regeneration valve passage 16d and the rod-side oil chamber. 8b is supplied.

  Reference numerals 20 and 21 denote ascending and descending electromagnetic proportional pressure reducing valves. These electromagnetic proportional pressure reducing valves 20 and 21 are controlled by the boom cylinder control valve 16 on the basis of an excitation signal from the controller 13 described later. It operates to output pilot pressure to the ascending pilot port 16a and the descending pilot port 16b, respectively. The pilot pressure output from the ascending and descending electromagnetic proportional pressure reducing valves 20 and 21 is controlled so as to increase or decrease according to the operation amount of the boom operation lever (not shown), and the increase or decrease of the pilot pressure. The movement stroke of the spool of the boom cylinder control valve 16 is increased or decreased in response to the above, so that the increase / decrease control of the supply / discharge flow rate from the boom cylinder control valve 16 to the boom cylinder 8 is performed. It is configured.

  Further, the boom cylinder control valve 16 is formed with a center bypass valve passage 16g for allowing the pressure oil in the pressure oil supply oil passage 15 to flow to the oil tank 11 via the negative control valve 22. The passage flow rate of the center bypass valve passage 16g is the largest when the boom cylinder control valve 16 is in the neutral position N, and decreases as the spool movement stroke increases, that is, as the operation amount of the boom operation lever increases. Control is performed so that the flow rate through the center bypass valve passage 16g decreases, but the center bypass valve passage 16g of the control valve 16 at the descending position Y is opened via the throttle 16h even when the spool is at the maximum stroke. Then, the passage flow rate of the center bypass valve passage 16g is output to one input port 23a of the shuttle valve 23 described later as a negative control signal pressure Pn.

  On the other hand, 24 is a main pump flow control electromagnetic proportional pressure reducing valve that outputs a flow control signal pressure Pc based on an excitation signal from the controller 13, and the flow rate output from the main pump flow control electromagnetic proportional pressure reducing valve 24. The control signal pressure Pc is input to the other input port 23b of the shuttle valve 23.

  The shuttle valve 23 selects the high pressure side of the negative control signal pressure Pn and the flow rate control signal pressure Pc input from the input ports 23 a and 23 b and outputs the selected pressure to the regulator 12 of the main pump 9. The regulator 12 controls the flow rate of the main pump 9 such that the higher the input signal pressure, the lower the pump flow rate. That is, the signal pressure for reducing the discharge flow rate of the main pump 9 is selected by the shuttle valve 23 among the negative control signal pressure Pn and the flow rate control signal pressure Pc output from the electromagnetic proportional pressure reducing valve 24 for main pump flow rate control. When the negative control signal pressure Pn is input, the regulator 12 increases or decreases the pump flow rate corresponding to the increase or decrease of the operation amount of the boom operation lever. On the other hand, when the flow control signal pressure Pc is input, the flow control based on the flow control signal pressure Pc is performed. This flow control signal pressure Pc will be described later.

  Reference numeral 25 denotes a drift reduction valve disposed in the boom cylinder head side oil passage 18, and 26 denotes a drift reduction valve electromagnetic switching valve that switches from the OFF position N to the ON position X based on an excitation signal from the controller 13. The drift reduction valve 25 always allows the flow of oil from the boom cylinder control valve 16 to the head side oil chamber 8a of the boom cylinder 8, but the reverse flow is an electromagnetic switching valve for the drift reduction valve. It is configured to block when 26 is in the OFF position N and allow only when it is in the ON position X. Reference numeral 27 denotes a relief valve connected to the cylinder head side oil passage 18, and the maximum pressure of the boom cylinder head side oil passage 18 is limited by the relief valve 27.

  Reference numeral 28 denotes a recovery oil passage formed by branching from the boom cylinder head side oil passage 18 between the boom cylinder control valve 16 and the drift reduction valve 25. The recovery oil passage 28 includes a recovery valve 29. And is connected downstream of the recovery valve 29 to an accumulator oil passage 30 and a pressure increasing cylinder supply oil passage 31 which will be described later. Further, the recovery valve 29 allows a flow of oil from the boom cylinder head side oil passage 18 to the accumulator oil passage 30 and the pressure increasing cylinder supply oil passage 31, but prevents a reverse flow. Is built-in. Thus, the oil discharged from the head side oil chamber 8a of the boom cylinder 8 to the boom cylinder head side oil passage 18 is passed through the recovery oil passage 28, and the accumulator oil passage 30 and the pressure increasing cylinder supply oil passage 31. Can be supplied to.

  The recovery valve 29 is an open / close valve in which the spool moves based on the operation of the recovery valve electro-oil conversion valve 33 to which the excitation signal from the controller 13 is input, and the recovery valve electro-oil conversion valve 33 is not excited. In this state, it is located at the closed position N for closing the recovery oil passage 28, but when the excitation signal is input to the recovery valve electro-hydraulic conversion valve 33, the spool moves to open the recovery oil passage 28. It is configured to switch to position X.

  The movement stroke of the spool of the recovery valve 29 is controlled to increase / decrease by the signal value of the excitation signal input from the controller 13 to the electro-hydraulic conversion valve 33 for the recovery valve. By the increase / decrease control, the increase / decrease control of the flow rate of the oil discharged from the head side oil chamber 8a of the boom cylinder 8 to the accumulator oil passage 30 and the pressure increasing cylinder supply oil passage 31 via the recovery oil passage 28 is performed. It is configured.

  On the other hand, the accumulator oil passage 30 is an oil passage from the recovery oil passage 28 to the accumulator 35 via the accumulator check valve 34, and the maximum pressure of the accumulator oil passage 30 is connected to the accumulator oil passage 30. Limited by the relief valve 36. In the present embodiment, the accumulator 35 is an optimum bladder type for accumulating hydraulic energy, but is not limited thereto, and may be, for example, a piston type.

  The accumulator check valve 34 is a valve that controls the supply and discharge of oil to and from the accumulator 35. The accumulator check that switches from the OFF position N to the ON position X based on the poppet valve 37 and the excitation signal output from the controller 13 is performed. It is comprised using the solenoid valve 38 for valves. The poppet valve 37 allows the flow of oil from the recovered oil passage 28 to the accumulator 35 regardless of whether the accumulator check valve electromagnetic switching valve 38 is in the OFF position N or the ON position X. Oil flow to the pressure increasing cylinder supply oil passage 31 is prevented when the accumulator check valve electromagnetic switching valve 38 is located at the OFF position N and allowed only when it is located at the ON position X. It is configured. Note that the flow of oil from the recovered oil passage 28 to the accumulator 35 is allowed regardless of whether the accumulator check valve electromagnetic switching valve 38 is in the OFF position N or the ON position X as described above, but the accumulator check valve In the state where the electromagnetic switching valve 38 is in the ON position X, the pressure in the accumulator oil passage 30 is not introduced into the spring chamber 37a of the poppet valve 37, so that the accumulator oil is discharged from the recovery oil passage 28 with almost no pressure loss. Oil can flow through the passage 30.

  On the other hand, 39 is a pressure-increasing cylinder control valve connected to the pressure-increasing cylinder supply oil passage 31, and the pressure-increasing cylinder control valve 39 is based on a control signal from the controller 13. The pressure oil supplied from the passage 28 or the accumulator oil passage 30 to the pressure increase cylinder supply oil passage 31 is operated so as to be supplied to the pressure increase cylinder 17.

  The pressure-increasing cylinder control valve 39 will be described in detail. The pressure-increasing cylinder control valve 39 is based on the operation of the ascending and descending electro-hydraulic conversion valves 40 and 41 to which the excitation signal from the controller 13 is input. When the electro-hydraulic conversion valves 40 and 41 are in a non-excited state, the spool is moved in a neutral position N that closes the pressure-increasing cylinder supply oil passage 31 and is used for the pressure-increasing cylinder. The pressure oil in the supply oil passage 31 is not allowed to flow into the pressure increasing cylinder 17. On the other hand, when an excitation signal is input to the ascending-side electro-oil conversion valve 40, the spool moves and the pressure oil in the pressure-increasing cylinder supply oil passage 31 is supplied to the pressure-increasing cylinder via the pressure-increasing cylinder head side oil passage 42. 17 is switched to the ascending side position X supplied to the head side oil chamber 17a. Further, when an excitation signal is input to the descending-side electrooil conversion valve 41, the spool moves to the side opposite to the ascending-side position X, and the pressure oil in the booster cylinder supply oil passage 31 is supplied to the booster cylinder. It is configured to switch to a lower side position Y supplied to the rod side oil chamber 17b of the pressure increasing cylinder 17 via the rod side oil passage 43. The pressure-increasing cylinder head-side oil passage 42 is an oil passage connected to the head-side oil chamber 17a so as to supply and discharge oil to the head-side oil chamber 17a of the pressure-increasing cylinder 17. The passage 43 is an oil passage connected to the rod side oil chamber 17b so as to supply and discharge oil to the rod side oil chamber 17b of the pressure increasing cylinder 17.

  The movement stroke of the spool of the pressure increasing cylinder control valve 39 is controlled to increase or decrease by the signal value of the excitation signal input from the controller 13 to the ascending and descending electrooil conversion valves 40 and 41. The control is configured such that the supply flow rate to the pressure-increasing cylinder 17 is increased or decreased by increasing or decreasing the movement stroke of the spool.

  Here, the pressure increasing cylinder 17 is supplied with pressure oil to a head side oil chamber (corresponding to the input side oil chamber of the present invention) 17a, whereby a rod side oil chamber (corresponding to the output side oil chamber of the present invention). The hydraulic pressure of 17b is increased from the input pressure to the head side chamber 17a and output. The pressure increase ratio is equal to the ratio of the pressure receiving area of the rod side oil chamber 17b acting on the piston 17c and the pressure receiving area of the head side oil chamber 17a, but the output pressure from the rod side oil chamber 17b is high during high load work. Thus, the pressure oil output from the rod side oil chamber 17b can be merged with the discharge oil of the main pump 9, as will be described later. It is like that.

  On the other hand, reference numeral 44 denotes a pressure-increasing cylinder output oil passage that is branched from the pressure-increasing cylinder rod side oil passage 43 and is joined to the pressure oil supply oil passage 15. The merging valve 45 is arranged in the.

  The merging valve 45 is an open / close valve in which the spool moves based on the operation of the merging valve electro-oil conversion valve 46 to which the excitation signal from the controller 13 is input. In this state, the pressure increasing cylinder output oil passage 44 is located at the closed position N. However, when the excitation signal is input to the merging valve electro-hydraulic conversion valve 46, the spool is moved to increase the pressure increasing cylinder output. The oil passage 44 is configured to be switched to an open position X for opening. Further, the merging valve 45 incorporates a check valve 47 that allows oil flow from the pressure increasing cylinder rod side oil passage 43 to the pressure oil supply oil passage 15 but prevents reverse flow. Thus, when the merging valve 45 is switched to the open position X, the pressure oil in the rod side oil chamber 17b of the pressure increasing cylinder 17 is merged into the pressure oil supply oil path 15 via the pressure increasing cylinder output oil path 44. It can be made to.

  The movement stroke of the spool of the merging valve 45 is controlled to increase / decrease according to the signal value of the excitation signal input from the controller 13 to the electro-hydraulic conversion valve 46 for the merging valve. By the increase / decrease control, the increase / decrease control of the flow rate that joins the pressure oil supply oil passage 15 from the rod side oil chamber 17b of the pressure increase cylinder 17 via the pressure increase cylinder output oil passage 44 is performed.

  Further, a discharge oil passage 48 is branched from the pressure increasing cylinder head side oil passage 42 and reaches the oil tank 11, and an unload valve 49 is arranged in the discharge oil passage 48.

  The unload valve 49 includes a poppet valve 50 and an unload valve electromagnetic switching valve 51 that switches from the OFF position N to the ON position X based on the ON signal output from the controller 13. The poppet valve 50 permits the flow of oil from the pressure increasing cylinder head side oil passage 42 to the oil tank 11 only when the unloading valve electromagnetic switching valve 51 is located at the ON position X, and the OFF position N When it is located in, it will stop. Thus, by switching the unloading valve electromagnetic switching valve 51 to the ON position X, the pressure oil in the head side oil chamber 17a of the pressure increasing cylinder 17 is supplied to the pressure increasing cylinder head side oil passage 42 and the discharge oil passage 48. The oil tank 11 can be discharged via The electromagnetic switching valve 51 for the unloading valve 51 can be switched to the ON position X even when the pressure oil accumulated in the accumulator 35 is released to the oil tank 11 when the engine E of the excavator 1 is stopped. Will be described later.

  On the other hand, the controller 13 is configured by using a microcomputer or the like, and as shown in the block diagram of FIG. 3, a boom operation detecting means 52 for detecting the operation direction and the operation amount of the boom operation lever, the main A pump pressure sensor 53 for detecting the discharge pressure of the pump 9, a pressure increasing cylinder pressure sensor 54 for detecting the pressure in the rod side oil chamber 17 b of the pressure increasing cylinder 17, and an engine key operated to start and stop the engine E Signals from the switch 55 and the like are input, and based on these input signals, the above-described ascending electromagnetic proportional pressure reducing valve 20, descending electromagnetic proportional pressure reducing valve 21, main pump flow control electromagnetic proportional pressure reducing valve 24, and drift reducing valve use Electromagnetic switching valve 26, recovery valve electro-hydraulic conversion valve 33, accumulator check valve electromagnetic switching valve 38, ascending-side electro-oil conversion valve 40, Descending side electric oil conversion valve 41, the confluence valve for electro-hydraulic conversion valve 46, and outputs a control signal to the unloading valve electromagnetic switching valve 51 or the like.

Next, the control of the controller 13 based on the operation of the boom operation lever will be described.
First, when the boom control lever is not operated on either the lowering side or the rising side of the boom, the controller 13 controls the rising-side electromagnetic proportional pressure reducing valve 20, the lowering-side electromagnetic proportional pressure reducing valve 21, and the main pump flow control electromagnetic proportionality. Pressure reducing valve 24, drift reducing valve electromagnetic switching valve 26, recovery valve electro-hydraulic conversion valve 33, accumulator check valve electromagnetic switching valve 38, ascending-side electro-oil converting valve 40, descending-side electro-oil converting valve 41, and merging valve Control is performed so that all of the electro-hydraulic conversion valve 46 and the electromagnetic switching valve 51 for unloading valve are de-energized.

  On the other hand, when the boom operating lever is operated to the boom lowering side, that is, when the boom lowering operation detection signal is input from the boom operation detecting means 52, the controller 13 An excitation signal is output to the descending pilot port 16b of the boom cylinder control valve 16 so as to output a pilot pressure corresponding to the operation amount of the boom operation lever. As a result, the boom cylinder control valve 16 is switched to the lower position Y, and the pressure oil in the pressure oil supply oil passage 15 passes through the throttle 16c of the boom cylinder control valve 16 at the lower position Y. Is supplied to the rod side oil chamber 8b of the boom cylinder 8 and a part of the oil discharged from the head side oil chamber 8a is supplied to the rod side oil chamber 8b via the regeneration valve passage 16d. The flow rate is controlled to be a required flow rate according to the operation amount of the boom operation lever. As will be described later, when the boom operation lever is operated to the boom lowering side, only the discharge oil of the main pump 9 is supplied to the pressure oil supply oil 15.

  Furthermore, when operated to the boom lowering side, the controller 13 does not output an excitation signal to the electromagnetic proportional pressure reducing valve 24 for main pump flow rate control. As a result, the pressure inputted from the main pump flow rate control electromagnetic proportional pressure reducing valve 24 to the other port 23a of the shuttle valve 23 becomes the tank pressure, and thus the negative control signal pressure Pn is selected by the shuttle valve 23, Input to the regulator 12 of the main pump 9. As a result, the discharge flow rate of the main pump 9 is controlled by the negative control flow rate control in which the flow rate of the main pump 9 increases or decreases in response to the increase or decrease of the operation amount of the boom operation lever. The center bypass valve passage 16g of the boom cylinder control valve 16 is opened via the restrictor 16h when the spool is at the maximum stroke, so that the discharge flow rate of the main pump 9 can be achieved even when the operation amount of the boom operation lever is maximum. Is controlled to be less than the maximum flow rate.

  Further, when operated to the boom lowering side, the controller 13 outputs an excitation signal to the drift reducing valve electromagnetic switching valve 26 so as to be switched to the ON position X. As a result, the drift reduction valve 25 is allowed to discharge oil from the head side oil chamber 8a of the boom cylinder 8.

  Furthermore, when operated to the boom lowering side, the controller 13 outputs an excitation signal having a signal value corresponding to the operation amount of the boom operation lever to the recovery valve electro-hydraulic conversion valve 33. As a result, the recovery valve 29 is switched to the open position X where the recovery oil passage 28 is opened, so that the oil discharged from the head side oil chamber 8a of the boom cylinder 8 passes through the recovery oil passage 28 and the accumulator oil passage. 30 and the pressure-increasing cylinder supply oil passage 31, and the flow rate of the recovery oil passage 28 is controlled to be a flow rate required according to the operation amount of the boom operation lever. A part of the oil discharged from the head side oil chamber 8a is supplied to the rod side oil chamber 8b via the first control valve 16 at the descending position Y as described above.

  Further, at this time, the controller 13 outputs an excitation signal to the accumulator check valve electromagnetic switching valve 38 so as to switch to the ON position X. Thus, oil is supplied from the recovered oil passage 28 to the accumulator oil passage 30 with almost no pressure loss, and the oil supplied to the accumulator oil passage 30 is accumulated in the accumulator 35.

  Further, when operated to the boom lowering side, the controller 13 outputs an excitation signal having a signal value corresponding to the operation amount of the boom operation lever to the lowering electro-hydraulic conversion valve 41. As a result, the pressure-increasing cylinder control valve 39 is switched to the lowering position Y, so that the oil flowing from the recovery oil path 28 to the pressure-increasing cylinder supply oil path 31 is in the pressure-increasing cylinder at the lowering position Y. Is supplied to the rod side oil chamber 17 b of the pressure increasing cylinder 17 via the control valve 39.

  Further, at this time, the controller 13 outputs an excitation signal to the unloading valve electromagnetic switching valve 51 so as to switch to the ON position X. As a result, the unload valve 49 is allowed to flow oil from the head side oil chamber 17a of the pressure increasing cylinder 17 to the oil tank 11. As a result, the pressure in the head side oil chamber 17a decreases, and the oil supply to the rod side oil chamber 17b described above can be performed with almost no resistance.

  Furthermore, when operated to the boom lowering side, the controller 13 does not output an excitation signal to the electrovalve conversion valve 46 for the merging valve. As a result, the merging valve 45 is located at the closed position N that closes the pressure-increasing cylinder output oil passage 44, and pressure oil is supplied from the pressure-increasing cylinder output oil passage 44 to the pressure oil supply oil passage 15. Instead, only the oil discharged from the main pump 9 is supplied to the pressure oil supply oil passage 15.

  That is, when the boom 5 is lowered, the oil discharged from the head side oil chamber 8a of the boom cylinder 8 is at a high pressure due to the potential energy of the working unit 4, and the rod is determined from the relationship of the pressure receiving area acting on the piston 8c. The amount of oil discharged from the head side oil chamber 8a is about twice as large as the amount supplied to the side oil chamber 8b. The oil discharged from the head side oil chamber 8a passes through the recovery oil passage 28 and is used for the accumulator oil passage 30 and the pressure increasing cylinder. It flows into the supply oil passage 31. The pressure oil supplied to the accumulator oil passage 30 is accumulated in the accumulator 35, while the oil that has flowed to the pressure increase cylinder supply oil passage 31 is supplied to the rod side oil chamber 17 b of the pressure increase cylinder 17. become. A part of the oil discharged from the head side oil chamber 8a is supplied to the rod side oil chamber 8b via the regeneration valve path 16d of the boom cylinder control valve 16 as described above. Thus, the potential energy of the working unit 4 can be recovered and reused without being wasted.

  Next, the control of the controller 13 when the boom operating lever is operated to the boom raising side, that is, when the boom raising side operation detection signal is input from the boom operation detecting means 52 will be described.

  When operated to the boom raising side, the controller 13 does not output an excitation signal to the electromagnetic valve 26 for drift reduction valve. Thus, the drift reduction valve 25 is allowed to flow from the boom cylinder control valve 16 to the head side oil chamber 8a of the boom cylinder 8, but is prevented from flowing in the reverse direction.

  Further, when operated on the boom raising side, the controller 13 corresponds to the operation amount of the boom operation lever to the up / down pilot port 16a of the boom cylinder control valve 16 with respect to the ascending electromagnetic proportional pressure reducing valve 20. An excitation signal is output so as to output a pilot pressure. As a result, the boom cylinder control valve 16 is switched to the ascending position X, so that the pressure oil in the pressure oil supply oil passage 15 passes through the boom cylinder control valve 16 at the ascending position X. The oil discharged from the rod side oil chamber 8 b is discharged to the oil tank 11. As will be described later, when operated to the boom raising side, not only the oil discharged from the main pump 9 but also the pressure oil from the pressure increasing cylinder 17 is supplied to the pressure oil supply oil passage 15. ing.

  Furthermore, when operated to the boom raising side, the controller 13 does not output an excitation signal to the recovery valve electro-hydraulic conversion valve 33. As a result, the recovery valve 29 is located at the closed position N where the recovery oil passage 28 is closed. Thus, the recovery valve 29 passes through the boom cylinder control valve 16 at the ascending side position X to the boom cylinder head side oil passage 18. The supplied pressure oil is supplied to the head side oil chamber 8a of the boom cylinder 8 without flowing into the accumulator oil path 30 or the pressure increasing cylinder supply oil path 31 via the recovery oil path 28. It has become.

  Further, when operated to the boom raising side, the controller 13 outputs an excitation signal to the accumulator check valve electromagnetic switching valve 38 so as to switch to the ON position X. As a result, the accumulator check valve 34 is allowed to flow from the accumulator oil passage 30 to the pressure increasing cylinder supply oil passage 31. Thus, the pressure oil accumulated in the accumulator 35 is supplied to the pressure increasing cylinder supply oil passage 31.

  Furthermore, when operated to the boom raising side, the controller 13 outputs an excitation signal having a signal value corresponding to the operation amount of the boom operation lever to the ascending-side electro-hydraulic conversion valve 40. As a result, the pressure increasing cylinder control valve 39 is switched to the ascending side position X, and thus the pressure accumulating oil of the accumulator 35 supplied to the pressure increasing cylinder supplying oil passage 31 is changed to the pressure increasing cylinder at the ascending side position X. Is supplied to the head side oil chamber 17 a of the pressure increasing cylinder 17 via the control valve 39.

  Further, at this time, the controller 13 does not output an excitation signal to the unloading valve electromagnetic switching valve 51. As a result, the unload valve 49 is in a state of blocking the flow of oil from the head side oil chamber 17a of the pressure increasing cylinder 17 to the oil tank 11, and thus for the pressure increasing cylinder at the ascending side position X. The accumulated oil in the accumulator 35 via the control valve 39 is supplied to the head side oil chamber 17 a of the pressure increasing cylinder 17 without flowing into the oil tank 11.

  The pressure-increasing cylinder 17 increases the hydraulic pressure in the rod-side oil chamber 17b when the accumulated oil in the accumulator 35 is supplied to the head-side oil chamber 17a, and outputs it to the pressure-increasing cylinder output oil passage 44.

  Further, when operated to the boom raising side, the controller 13 outputs an excitation signal having a signal value corresponding to the operation amount of the boom operation lever to the electro-hydraulic conversion valve 46 for the merging valve. As a result, the merging valve 45 is switched to the open position X that opens the pressure-increasing cylinder output oil passage 44, and the pressure oil increased by the pressure-increasing cylinder 17 passes through the pressure-increasing cylinder output oil passage 44. It is supplied to the pressure oil supply oil passage 15. Then, the pressure oil from the pressure-increasing cylinder 17 supplied to the pressure oil supply oil passage 15 merges with the discharge oil of the main pump 9 and, as described above, the boom cylinder control valve 16 at the ascending side position X. Is supplied to the head side oil chamber 8a of the boom cylinder 8.

  Further, when operated to the boom raising side, the controller 13 outputs a control signal to the main pump flow rate control electromagnetic proportional pressure reducing valve 24 so as to output the flow rate control signal pressure Pc. In this case, the controller 13 determines the differential pressure between the discharge pressure of the main pump 9 input from the pump pressure sensor 53 and the pressure of the pressure increasing cylinder rod side oil chamber 17b input from the pressure increasing cylinder pressure sensor 54, and The combined flow rate from the pressure-increasing cylinder 17 to the pressure oil supply oil passage 15 is calculated based on the amount of opening of the merge valve 45 obtained from the control signal to the merge oil valve conversion oil 46. Then, the controller 13 controls the main pump 9 so that the discharge flow rate of the main pump 9 is a flow rate obtained by subtracting the combined flow rate from the pressure increasing cylinder 17 from the pump flow rate required by the operation amount of the boom operation lever. A flow control signal pressure Pc is output to the electromagnetic proportional pressure reducing valve 24.

  The flow control signal pressure Pc output from the main pump flow control electromagnetic proportional pressure reducing valve 24 is input to the other input port 23 b of the shuttle valve 23. On the other hand, the negative control signal pressure Pn is input to one input port 23a of the shuttle valve 23. In the state where the pressure oil from the pressure increasing cylinder 17 is joined to the pressure oil supply oil passage 15, the flow control signal is supplied. Since the pressure Pc is a signal pressure that reduces the pump flow rate than the negative control signal pressure Pn, that is, the flow control signal pressure Pc is higher than the negative control signal pressure Pn, the flow control signal pressure Pc is the shuttle. It is selected by the valve 23 and input to the regulator 12 of the main pump 9. Thus, the discharge flow rate of the main pump 9 is controlled to be a flow rate that is reduced by the combined flow rate from the pressure increasing cylinder 17, and thus the pump flow rate reducing means of the present invention is configured. Has been.

  That is, on the rising side of the boom 5, the accumulated oil in the accumulator 35 is supplied to the head side oil chamber 17 a of the pressure increasing cylinder 17, thereby increasing the pressure oil in the rod side oil chamber 17 b of the pressure increasing cylinder 17. . Then, the pressure oil increased by the pressure increasing cylinder 17 is supplied to the pressure oil supply oil path 15 via the pressure increasing cylinder output oil path 44 and merges with the discharge oil of the main pump 9 to be used for the boom cylinder. It is supplied to the head side chamber 8 a of the boom cylinder 8 through the control valve 16. Further, at this time, the discharge flow rate of the main pump 9 is controlled to be a flow rate reduced by the combined flow rate from the pressure increasing cylinder 17. Thus, the potential energy recovered in the accumulator 35 and the rod side oil chamber 17b of the pressure increasing cylinder 17 when the boom 5 is lowered can be reused when the boom 5 is raised, and the discharge flow rate of the main pump 9 is reduced accordingly. Be able to.

Next, accumulator discharge control performed by the controller 13 when the engine E is stopped will be described.
When the engine key switch 55 is switched from “ON” to “OFF”, the controller 13 controls the accumulator check valve electromagnetic switching valve 38, the rising-side electro-hydraulic conversion valve 40, and the unloading valve electromagnetic switching valve 51. An excitation signal is output for a predetermined time T. As a result, the accumulator check valve 34 is allowed to flow oil from the accumulator oil passage 30 to the pressure increasing cylinder supply oil passage 31. Further, the pressure increasing cylinder control valve 39 is switched to the ascending position X and allows the pressure oil in the pressure increasing cylinder supply oil path 31 to flow to the pressure increasing cylinder head side oil path 42. Further, the unload valve 49 is in a state of supplying the oil flow from the pressure increasing cylinder head side oil passage 42 to the oil tank 11. Thus, when the engine switch 55 is operated “OFF”, the accumulated oil in the accumulator 35 is transferred to the oil tank 11 via the accumulator check valve 34, the pressure-increasing cylinder control valve 39, and the unload valve 49. It is supposed to be discharged. The predetermined time T is a time set in advance as a time required for discharging the accumulated oil in the accumulator 35, and is appropriately set according to the capacity of the accumulator 35 and the like.

  When the engine key switch 55 is turned off at the end of the operation of the hydraulic excavator 1 by the accumulator discharge control, the accumulated oil in the accumulator 35 is automatically discharged to the oil tank 11 to be in a state suitable for long-term storage. Thus, even when the excavator 1 is not used for a long time, it is possible to reliably avoid a problem in which the amount of gas is reduced by leaving the oil accumulated in the accumulator 35 for a long period of time. It is like that.

  In the present embodiment configured as described, the hydraulic control system of the excavator 1 includes an accumulator 35 that accumulates oil discharged from the head-side oil chamber 8a of the boom cylinder 8 when the boom 5 is lowered, and the accumulator 35. A pressure-increasing cylinder 17 is provided to increase and output the oil pressure in the rod-side oil chamber 17b by supplying the pressure-accumulated oil to the head-side oil chamber 17a. The pressure increased by the pressure-increasing cylinder 17 is provided. The oil is supplied to the head side oil chamber 8a of the boom cylinder 8 when the boom 5 is raised.

  Thus, the oil discharged from the head side oil chamber 8a of the boom cylinder 8 when the boom 5 is lowered is increased in pressure due to the potential energy of the working unit 4, and this potential energy is used as pressure accumulation oil in the accumulator 35. While the pressure can be recovered, the pressure accumulated in the accumulator 35 is increased by the pressure increasing cylinder 17 and supplied to the head side oil chamber 8 a of the boom cylinder 8 when the boom 5 is raised. As a result, the potential energy recovered when the boom 5 is lowered can be reused when the boom 5 is raised, which can greatly contribute to energy saving. In this case, the pressure accumulated in the accumulator 35 is increased by the pressure increasing cylinder. Since the pressure is increased by 17, high-pressure oil that can cope with high-load work can be supplied to the head-side oil chamber 8 a of the boom cylinder 8. In addition, since the pressure is increased by using the pressure increasing cylinder 17, the torque is reduced in the power transmission path from the engine to the pump, or the inertia mass of the pump itself, as in the case of increasing the pressure by using a pump driven by engine power. There is no loss of idling torque, the recovered energy can be used with as little loss as possible, and it is advantageous in terms of cost. Furthermore, since the pressure accumulated in the accumulator 35 may be lower than the discharge pressure of the main pump 9, it is not necessary to use an expensive accumulator with high pressure specifications, which can contribute to cost reduction.

  Further, in this configuration, the pressure oil increased by the pressure increasing cylinder 17 passes through the pressure increasing cylinder output oil path 44 to the pressure oil supply oil path 15 from the main pump 9 to the boom cylinder control valve 16. Since it is configured to merge, the pressure oil increased by the pressure increasing cylinder 17 and the discharge oil of the main pump 9 merge and are supplied to the boom cylinder control valve 16. As a result, the supply flow rate to the boom cylinder 8 can be controlled by the boom cylinder control valve 16 without being influenced by the output flow rate from the booster cylinder 17, which can contribute to simplification of the control. As described above, the output pressure of the pressure-increasing cylinder 17 is set to be higher than the discharge pressure of the main pump 9 at the time of high load work. The pressure oil output from the pressure increasing cylinder 17 can be merged with the oil discharged from the main pump 9.

  Further, a merging valve 45 for controlling a combined flow rate from the pressure increasing cylinder 17 to the pressure oil supply oil path 15 is disposed in the pressure increasing cylinder output oil path 44. Thus, by controlling the combined flow rate by the merging valve 45, the pressure oil increased by the pressure increasing cylinder 17 can be used efficiently without waste.

  In addition, the discharge flow rate of the main pump 9 is increased from the pressure increasing cylinder 17 by the flow rate control signal pressure Pc output from the main pump flow rate control electromagnetic proportional pressure reducing valve 24 to the regulator 12 of the main pump 9 as described above. Control is performed so as to decrease in accordance with the combined flow rate to the supply circuit 15, and thus the discharge flow rate of the main pump 9 can be appropriately reduced, and low fuel consumption can be achieved efficiently.

  In this case, the oil discharged from the head side oil chamber 8a of the boom cylinder 8 when the boom 5 is lowered is accumulated in the accumulator 35 via the recovery oil passage 28, and at the rod side of the pressure increasing cylinder 17. The oil is supplied to the oil chamber 17b. As a result, pressure oil is supplied to the rod side oil chamber 17b, which is the output side oil chamber of the pressure increasing cylinder 17, without providing a separate pressure oil supply means, and the head side oil chamber 8a of the boom cylinder 8 is lowered when the boom 5 is lowered. In addition to contributing to simplification of the system, the potential energy of the working unit 4 can also be recovered here.

  In addition, a recovery valve 41 for controlling the flow rate of the oil discharged from the head side oil chamber 8a of the boom cylinder 8 is disposed in the recovery oil passage 28. Thus, the recovery valve 41 allows the head side oil chamber to be controlled. By controlling the discharge flow rate from 8a, the lowering speed of the boom 5 can be controlled to correspond to the operation amount of the boom operation lever, and good operability can be obtained.

  Further, in this case, for the pressure-increasing cylinder for controlling the oil supply from the accumulator 35 to the head-side oil chamber 17a of the pressure-increasing cylinder 17 and the oil supply from the recovery oil passage 28 to the rod-side oil chamber 17b of the pressure-increasing cylinder 17. Since the control valve 39 is provided, the pressure increasing cylinder control valve 39 supplies pressure oil to the head side oil chamber 17a and the rod side oil chamber 17b of the pressure increasing cylinder 17 when the boom is raised and lowered. , Each can be done appropriately.

Of course, the present invention is not limited to the above embodiment, and in the above embodiment, the pressure oil increased by the pressure increasing cylinder 17 is used as the head side oil of the boom cylinder 8 when the boom 5 is raised. Although it is the structure which supplies to the chamber 8a, it is not limited to this, The pressure oil pressure-intensified by the pressure-increasing cylinder is made into the some other hydraulic actuator (work machine is a hydraulic shovel of a hydraulic shovel) provided in a work machine. In such a case, it can be used as pressure oil supplied to a traveling motor, a turning motor, an arm cylinder, a bucket cylinder, or the like. In this case, the potential energy recovered when the working unit is lowered can be used for the operation of other hydraulic actuators.
Furthermore, the present invention can be implemented not only in a hydraulic excavator but also in a hydraulic control system for various work machines provided with a lifting hydraulic cylinder that lifts and lowers a working unit.
In the circuit diagram of FIG. 2, one main pump is shown as a hydraulic pump that supplies hydraulic oil to a plurality of hydraulic actuators. However, it is needless to say that two or more main pumps may be provided.

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 controller.

Explanation of symbols

4 Working Section 8 Boom Cylinder 8a Head Side Oil Chamber 9 Main Pump 13 Controller 15 Pressure Oil Supply Oil Path 16 Boom Cylinder Control Valve 17 Booster Cylinder 17a Head Side Oil Chamber 17b Rod Side Oil Chamber 23 Shuttle Valve 24 Main Pump Flow Control Solenoid proportional pressure reducing valve 28 Recovery oil path 29 Recovery valve 35 Accumulator 39 Booster cylinder control valve 44 Booster cylinder output oil path 45 Merge valve

Claims (7)

  A plurality of hydraulic actuators including a lifting hydraulic cylinder that lifts and lowers the working unit, a hydraulic pump that supplies pressure oil to these hydraulic actuators, and a control valve for each hydraulic actuator that controls the flow rate supplied to each hydraulic actuator In a working machine hydraulic control system, an accumulator that accumulates oil discharged from the weight holding side oil chamber of the lifting hydraulic cylinder when the working unit is lowered, and the accumulated oil of the accumulator is supplied to the input side oil chamber A pressure-increasing cylinder that increases and outputs the hydraulic pressure in the output-side oil chamber at the same time, and supplies the pressure oil increased by the pressure-increasing cylinder to at least one of the plurality of hydraulic actuators. A hydraulic control system for a working machine, characterized by being configured as oil.   The hydraulic control system has a pressure-increasing cylinder output oil path that joins the pressure oil increased by the pressure-increasing cylinder to a pressure oil supply oil path from the hydraulic pump to each hydraulic actuator control valve. Item 2. A hydraulic control system for a work machine according to Item 1.   The hydraulic control system for a work machine according to claim 2, wherein a confluence valve for controlling a combined flow rate from the pressure increasing cylinder to the pressure oil supply oil passage is arranged in the pressure increasing cylinder output oil passage.   4. The work machine according to claim 2, wherein the hydraulic control system includes a pump flow rate reduction unit that reduces a discharge flow rate of the hydraulic pump in accordance with a combined flow rate from the pressure increasing cylinder to the pressure oil supply oil passage. Hydraulic control system in.   The hydraulic control system includes a recovery oil passage that supplies oil discharged from the weight holding side oil chamber of the lifting hydraulic cylinder when the working unit is lowered to the output side oil chamber of the accumulator and the pressure increasing cylinder. The hydraulic control system in the working machine as described in any one of Claims 1 thru | or 4.   6. The hydraulic control system for a work machine according to claim 5, wherein a recovery valve for controlling a flow rate of oil discharged from a weight holding side oil chamber of the lifting hydraulic cylinder is arranged in the recovery oil passage.   The hydraulic control system has a pressure-increasing cylinder control valve that controls oil supply from the accumulator to the input-side oil chamber of the pressure-increasing cylinder and oil supply from the recovery oil passage to the output-side oil chamber of the pressure-increasing cylinder. The hydraulic control system for a work machine according to claim 5 or 6, characterized in that:

Images