JP4756600B2 - Hydraulic control system for work machines - Google Patents

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 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 wasted 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

  By the way, the thing of the said patent document 1 is a part of pressure oil supplied to a normal hydraulic cylinder from a hydraulic pump via a control valve, when the accumulator is not fully pressure-accumulated at the time of a raise of a working part. It is configured to be supplied to the cylinder and used for accumulator pressure accumulation. For this reason, if the accumulator pressure buildup is insufficient while the working part is moving up, the assist force from the auxiliary hydraulic cylinder cannot be received, or the supply flow rate to the normal hydraulic cylinder is distributed to the auxiliary hydraulic cylinder and accumulator pressure accumulation. As a result, the ascending speed of the working unit suddenly decreases. In other words, there is a problem that the ascending speed of the working unit is influenced by the pressure accumulation amount of the accumulator, and the work efficiency is lowered and the operability is inferior. .

The present invention was created in view of the above-described circumstances in order to solve these problems. The invention of claim 1 is directed to a hydraulic cylinder that raises and lowers the working part, and a hydraulic pressure when the working part is lowered. An accumulator for accumulating the oil discharged from the cylinder, a dedicated pump for sucking the pressure oil accumulated in the accumulator and supplying it to the hydraulic cylinder, a hydraulic pump for sucking oil from the oil tank and supplying it to the hydraulic cylinder, and the accumulator A pressure accumulation amount detecting means for detecting the pressure accumulation amount, and on the basis of the pressure accumulation amount of the accumulator detected by the pressure accumulation amount detecting means, the supply of pressure oil from the dedicated pump to the hydraulic cylinder when the working unit is raised and A hydraulic control system for a work machine, characterized in that a control device for controlling pressure oil supply from a hydraulic pump to a hydraulic cylinder is provided. It is a non.
And by doing in this way, the potential energy of the working unit that moves up and down can be effectively collected and reused using an accumulator, which can greatly contribute to energy saving. Even if the accumulated pressure of the hydraulic pump is insufficient and the supply of pressure oil from the dedicated pump to the hydraulic cylinder is insufficient, the hydraulic oil can be supplied from the hydraulic pump to the hydraulic cylinder and the accumulated pressure of the accumulator The pressure oil supply from the dedicated pump to the hydraulic cylinder and the pressure oil supply from the hydraulic pump to the hydraulic cylinder can be controlled according to the fluctuation, and therefore the operating speed of the working unit depends on the accumulated pressure of the accumulator. Can be avoided, it is excellent in operability and can contribute to the improvement of work efficiency.
According to a second aspect of the present invention, the control device supplies pressure oil from the dedicated pump to the hydraulic cylinder when the accumulated pressure amount of the accumulator is equal to or higher than a preset high accumulation amount when the working unit is raised. When the pressure oil supply from the hydraulic pump to the hydraulic cylinder is stopped and the accumulated pressure of the accumulator is less than the preset low accumulated pressure, the hydraulic oil is supplied from the hydraulic pump to the hydraulic cylinder, while the dedicated pump is connected to the hydraulic cylinder. When the pressure oil supply is stopped, and the accumulator pressure accumulation amount is between the high pressure accumulation amount and the low pressure accumulation amount, the supply flow rate from the dedicated pump to the hydraulic cylinder is reduced as the accumulator pressure accumulation amount decreases. In addition, control is performed to increase the supply flow rate from the hydraulic pump to the hydraulic cylinder, and the dedicated pump is used regardless of the accumulator pressure accumulation amount. The sum of the supply flow rate from the hydraulic pump to the hydraulic cylinder and the supply flow rate from the hydraulic pump to the hydraulic cylinder is controlled so as to be a flow rate required according to the operation amount of the hydraulic cylinder operating tool. 1 is a hydraulic control system for a work machine according to 1;
In this way, when the accumulator pressure accumulation amount is sufficient, the accumulator pressure accumulation oil can be utilized to the maximum, and even if the accumulator pressure accumulation amount decreases, it is always used for hydraulic cylinders. Since the flow rate corresponding to the operation amount of the operation tool can be supplied to the hydraulic cylinder, the working unit can be raised at a desired speed corresponding to the operation amount of the operation tool for the hydraulic cylinder. In addition, in this case, the supply flow rate from the dedicated pump to the hydraulic cylinder decreases as the accumulated pressure of the accumulator decreases, while the supply flow rate from the hydraulic pump to the hydraulic cylinder increases. And the supply flow rate from the hydraulic pump can always be supplied to the hydraulic cylinder in a well-balanced manner according to the accumulated pressure of the accumulator.For example, pressure oil is supplied only from the dedicated pump until the accumulator is empty when the working unit is raised, Smooth operation of the working unit is impaired when switching between pressure oil supply from the dedicated pump and pressure oil supply from the hydraulic pump, such as one configured to switch to pressure oil supply from the hydraulic pump when it becomes empty There is no problem that would be lost, and operability is excellent.
According to a third aspect of the present invention, the hydraulic control system includes a control valve for controlling a flow rate from the hydraulic pump to the hydraulic cylinder, and a control valve for controlling a flow rate from the dedicated pump to the hydraulic cylinder, while the control device includes an accumulator. The hydraulic control system for a work machine according to claim 1 or 2, further comprising a control valve control unit that controls each of the control valves based on the accumulated pressure amount.
In this way, the supply flow rate from the dedicated pump and the hydraulic pump to the hydraulic cylinder can be accurately controlled so as to correspond to the pressure accumulation amount of the accumulator.
According to a fourth aspect of the present invention, the control device has a dedicated pump control unit that controls the discharge flow rate of the dedicated pump based on the accumulated pressure amount of the accumulator. It is the hydraulic control system in the working machine.
In this way, the discharge flow rate of the dedicated pump can be supplied to the hydraulic cylinder without being wasted and insufficient, and the accumulator is not accumulated, that is, from the accumulator to the dedicated pump. In the state where oil is not supplied to the suction side, it is possible to reliably avoid a problem that the dedicated pump is driven to discharge the pressure oil and an excessive load is applied.
According to the fifth aspect of the invention, the control device calculates a share ratio of the dedicated pump and a share ratio of the hydraulic pump with respect to the flow rate supplied to the hydraulic cylinder when the working part is raised, based on the pressure accumulation amount of the accumulator. The hydraulic control system for a work machine according to any one of claims 1 to 4, wherein the hydraulic control system is provided.
In this way, the dedicated pump and hydraulic pump supply flow rate control and the dedicated pump corresponding to the accumulator pressure accumulation amount are used by using the dedicated pump sharing ratio and the hydraulic pump sharing ratio calculated by the sharing ratio calculation unit. The pump discharge amount can be controlled easily and accurately.
The invention according to claim 6 is the work machine according to any one of claims 1 to 5, wherein the hydraulic pump is a main pump serving as a hydraulic supply source of various hydraulic actuators provided in the work machine. It is a hydraulic control system.
In this way, the main pump generally installed in the work machine can be used as it is as a hydraulic pressure supply source of various hydraulic actuators, and a supply circuit from the main pump to the hydraulic cylinder can also be used. Thus, it is possible to contribute to the suppression of the increase in member devices and the complexity of the circuit.

  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 cylinders of the present invention) that extend and contract to swing the boom 5 up and down. The boom cylinder 8 is operated by the pressure of the head side oil chamber 8a. And the boom 5 is lifted by the pressure oil supply to the head side oil chamber 8a and the oil discharge from the rod side oil chamber 8b, and the pressure oil supply to the rod side oil chamber 8b. Further, the boom 5 is lowered by being reduced by discharging the 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 diagrams of FIGS. 2 and 3. In these drawings, numerals 9 and 10 are connected to an engine E mounted on the hydraulic excavator 1 via a pump drive gear portion G. The first and second main pumps are configured such that the first and second main pumps 9 and 10 suck the hydraulic oil from the oil tank 11 and discharge it to the first and second pump oil passages 12 and 13. It is configured.
Here, the first and second main pumps 9 and 10 are not only the boom cylinder 8 but also various hydraulic actuators provided in the excavator 1 (not shown, travel motor, swing motor, arm cylinder, bucket cylinder, etc.) Of these first and second main pumps 9 and 10, the first main pump 9 corresponds to the hydraulic pump of the present invention. 2 and 3, circled numbers are connector symbols, and the corresponding circled numbers are connected to each other.

  Reference numerals 14 and 15 denote first and second regulators for controlling the discharge flow rates of the first and second main pumps 9 and 10, respectively. The first and second regulators 14 and 15 are controlled by a control device 16 to be described later. In response to the control signal pressure from the main pump control electromagnetic proportional pressure reducing valve 17, the pump is operated to produce a pump output corresponding to the engine speed and the work load, and the first and second main pumps 9 and 10 are discharged. Constant horsepower control is performed under pressure. Further, the first and second regulators 14 and 15 perform negative control flow rate control for increasing or decreasing the pump flow rate corresponding to the opening amounts of the center bypass valve passages 18f and 19b of the first and second control valves 18 and 19, as will be described later. Also configured to do.

  On the other hand, the first and second control valves 18 and 19 are direction switching valves respectively connected to the first and second pump oil passages 12 and 13, and the first and second control valves 18 and 19 The oil discharged from the first and second main pumps 9 and 10 is operated to be supplied to the boom cylinder 8. Since the first and second main pumps 9 and 10 serve as pressure oil supply sources for various hydraulic actuators provided in the hydraulic excavator 1 as described above, the first and second pump oil passages 12 and 13 Control valves for other hydraulic actuators are also connected, but these are omitted.

  The first control valve 18 (corresponding to the control valve for controlling the flow rate from the hydraulic pump to the hydraulic cylinder of the present invention) is composed of a spool valve having ascending and descending pilot ports 18a and 18b. When pilot pressure is not input to both pilot ports 18a and 18b, the pilot cylinder 18 is positioned at a neutral position N where oil is not supplied to or discharged from the boom cylinder 8, but pilot pressure is input to the ascending pilot port 18a. As a result, the spool moves to supply the pressure oil of the first main pump 9 to the head side oil chamber 8a of the boom cylinder 8 via the cylinder head side oil passage 20, while the rod side oil chamber 8b supplies the cylinder rod. The oil discharged to the side oil passage 21 is switched to the ascending position X that flows to the oil tank 11 via the return oil passage 22. The Further, when the pilot pressure is input to the descending pilot port 18b, the spool moves to the side opposite to the ascending position X, and the oil discharged from the head side oil chamber 8a to the cylinder head side oil passage 20 is discharged. Is switched to a descending position Y to be supplied from the cylinder rod side oil passage 21 to the rod side oil chamber 8b via the regeneration valve passage 18c. The cylinder head side oil passage 20 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 cylinder rod side oil passage 21 is a boom. This is an oil passage connected to the rod side oil chamber 8b to supply and discharge oil to the rod side oil chamber 8b of the cylinder 8.

  Here, the regeneration valve path 18c provided in the first control valve 18 at the descending position Y is a valve path that communicates the head side oil chamber 8a and the rod side oil chamber 8b of the boom cylinder 8, The regeneration valve path 18c is provided with a check valve 18d that restricts the flow of oil from the head-side oil chamber 8a to the rod-side oil chamber 8b but prevents the reverse flow, and a throttle 18e. Thus, as described above, when the first control valve 18 is at the lowering position Y, the oil discharged from the head side oil chamber 8a is supplied to the rod side oil chamber 8b via the regeneration valve path 18c. However, the flow rate depends on the opening characteristic of the throttle 18e arranged in the regeneration valve path 18c (the opening characteristic of the throttle 18e is set according to the spool movement stroke of the first control valve 18), and the head side It changes with the differential pressure | voltage of the oil chamber 8a and the rod side oil chamber 8b.

  On the other hand, the second control valve 19 is constituted by a spool valve provided with an ascending pilot port 19a, and when no pilot pressure is input to the ascending pilot port 19a, the oil supply / discharge of the boom cylinder 8 is performed. The spool is moved by the pilot pressure being input to the ascending-side pilot port 19a, and the pressure oil of the second main pump 10 passes through the cylinder head-side oil passage 20. The boom cylinder 8 is configured to switch to the ascending position X supplied to the head side oil chamber 8a.

  Reference numerals 23, 24, and 25 are first ascending side, first descending side, and second ascending side electromagnetic proportional pressure reducing valves. These electromagnetic proportional pressure reducing valves 23, 24, and 25 are control signals from the control device 16. Is operated to output a pilot pressure to the ascending pilot port 18a, the descending pilot port 18a of the first control valve 18 and the ascending pilot port 19a of the second control valve 19, respectively. The control signal is set so as to increase or decrease in accordance with the increase or decrease of the control signal value output from the control device 16. The first and second control valves 18, 19 correspond to the increase / decrease in the pilot pressure output from the first ascending side, first descending side, and second ascending electromagnetic proportional pressure reducing valves 23, 24, 25. The movement stroke of the spool is increased or decreased, and thereby, the increase / decrease control of the supply / discharge flow rate from the first and second control valves 18, 19 to the boom cylinder 8 is performed. 2 and 3, reference numeral 26 denotes a pilot pump serving as a pilot hydraulic pressure source.

  Further, the first and second control valves 18 and 19 have a center bypass for flowing the pressure oil of the first and second main pumps 9 and 10 to the oil tank 11 via the first and second negative control valves 27 and 28. Valve paths 18f and 19b are formed. The opening amount of the center bypass valve passages 18f and 19b is the largest when the first and second control valves 18 and 19 are in the neutral position N, and becomes smaller as the moving stroke of the spool switched to the rising side position X becomes larger. However, the center bypass valve path 18f of the first control valve 18 at the descending position Y has a characteristic of maintaining a large opening regardless of the movement stroke of the spool. The passage flow rate of the center bypass valve path 18f of the first control valve 18 at the position Y is set so as not to change from the passage flow rate at the neutral position N. The passage flow rate of the center bypass valve passages 18f and 19b is input to the first and second regulators 14 and 15 as a negative control control signal, and the first passage flow rate of the center bypass valve passages 18f and 19b decreases. The so-called negative control flow rate control in which the discharge flow rate of the second main pumps 9 and 10 is increased is performed. Here, as described above, the passage flow rate of the center bypass valve passage 18f of the first control valve 18 does not change from that at the neutral position N even when the first control valve 18 is switched to the descending position Y. The discharge flow rate of the first main pump 9 when the valve 18 is in the descending position Y is controlled to be minimized by negative control flow rate control.

  In addition, 29 is a drift reduction valve disposed in the cylinder head side oil passage 20, and 30 is an electromagnetic switching valve for a drift reduction valve that switches from the OFF position N to the ON position X based on the ON signal from the control device 16. The drift reducing valve 29 always allows the flow of oil from the first and second control valves 18 and 19 and the third control valve 37, which will be described later, to the head side oil chamber 8a of the boom cylinder 8. The flow in the direction is configured to be blocked when the drift reducing valve electromagnetic switching valve 30 is in the OFF position N and allowed only when the drift reducing valve electromagnetic switching valve 30 is in the ON position X. Reference numeral 31 denotes a relief valve connected to the cylinder head side oil passage 20, and the maximum pressure of the cylinder head side oil passage 20 is limited by the relief valve 31.

  On the other hand, 32 is a dedicated pump, which is also a variable displacement pump connected to the engine E via the pump drive gear portion G. The dedicated pump 32 is oil supplied from the suction oil passage 33. And the discharge flow rate of the dedicated pump 32 is controlled by a dedicated pump regulator 35 that operates based on a control signal output from the control device 16. .

  Here, the suction oil passage 33 is supplied with pressure accumulation oil of the accumulator 36 or oil discharged from the head side oil chamber 8a of the boom cylinder 8, as will be described later. The pump 32 sucks the accumulated oil in the accumulator 36 or the discharged oil from the head side oil chamber 8 a of the boom cylinder 8 and discharges it to the dedicated pump oil passage 34.

  37 is a third control valve (corresponding to a control valve for controlling the flow rate from the dedicated pump of the present invention to the hydraulic cylinder) connected to the dedicated pump oil passage 34. The third control valve 37 is a control valve. Based on the control signal from the device 16, the pressure oil discharged from the dedicated pump 32 is operated to be supplied to the boom cylinder 8.

  The third control valve 37 will be described in detail. The third control valve 37 is used to operate the third ascending side and third descending electrooil conversion valves 38 and 39 to which a control signal from the control device 16 is input. When the control signal is not input to the two electro-hydraulic conversion valves 38 and 39, the spool is moved to the neutral position N where no oil is supplied to or discharged from the boom cylinder 8. However, when the control signal is input to the third ascending-side electro-oil conversion valve 38, the spool moves, and the discharge oil of the dedicated pump 32 passes through the cylinder head-side oil passage 20 to the head-side oil of the boom cylinder 8. While being supplied to the chamber 8 a, the oil discharged from the rod-side oil chamber 8 b to the cylinder rod-side oil passage 21 is switched to the ascending position X that flows into the oil tank 11 via the return oil passage 22. Further, when a control signal is input to the third descending electro-hydraulic conversion valve 39, the spool moves to the side opposite to the ascending position X, and the discharge oil of the dedicated pump 32 is supplied to the cylinder rod side oil passage 21. To the descending side position Y to be supplied to the rod side oil chamber 8b of the boom cylinder 8.

  The movement stroke of the spool of the third control valve 37 is controlled to increase or decrease by control signal values input from the control device 16 to the third ascending side and third descending electrooil conversion valves 38, 39. The supply / discharge flow rate from the third control valve 37 to the boom cylinder 8 is controlled to increase / decrease by the increase / decrease control of the movement stroke of the spool.

  Further, reference numeral 40 denotes a recovery oil passage branched from the cylinder head side oil passage 20, and a recovery valve 41 is arranged in the recovery oil passage 40, and a downstream side of the recovery valve 41. The accumulator oil passage 42 and the suction oil passage 33 are connected to each other. Further, the recovery oil passage 40 is provided with a check valve 43 that allows oil flow from the cylinder head side oil passage 20 to the accumulator oil passage 42 and the suction oil passage 33 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 20 can be supplied to the accumulator oil passage 42 and the suction oil passage 33 via the recovery oil passage 40. 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 44 to which a control signal from the control device 16 is input. In a state in which no oil is input, the recovery oil passage 40 is positioned at the closed position N. However, when the control signal is input to the recovery electro-oil conversion valve 44, the spool moves and the recovery oil passage 40 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 16 to the recovery electro-oil conversion valve 44, and the movement stroke of the spool is increased or decreased. 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 42 and the suction oil passage 33 via the recovery oil passage 40 is performed.

  On the other hand, the accumulator oil passage 42 is an oil passage from the recovery oil passage 40 to the accumulator 36 via the accumulator check valve 45, and the maximum pressure of the accumulator oil passage 42 is connected to the accumulator oil passage 42. Limited by the relief valve 46. In the present embodiment, the accumulator 36 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 45 is a valve for performing oil supply / discharge control with respect to the accumulator 36, and is an accumulator that switches from the OFF position N to the ON position X based on the poppet valve 47 and the ON signal output from the control device 16. The check valve electromagnetic switching valve 48 is used. The poppet valve 47 allows the flow of oil from the recovered oil passage 40 to the accumulator 36 regardless of whether the accumulator check valve electromagnetic switching valve 48 is in the OFF position N or the ON position X. The flow of oil to the suction oil passage 33 is blocked when the accumulator check valve electromagnetic switching valve 48 is located at the OFF position N and allowed only when it is located at the ON position X. Yes. Note that the flow of oil from the recovered oil passage 40 to the accumulator 36 is allowed regardless of whether the accumulator check valve electromagnetic switching valve 48 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 48 is in the ON position X, the pressure in the accumulator oil passage 42 is not introduced into the spring chamber 47a of the poppet valve 47, and therefore the accumulator oil is discharged from the recovery oil passage 40 with almost no pressure loss. Oil can flow through the passage 42.

  Further, 49 is a discharge oil passage that is branched from the suction oil passage 33 and reaches the oil tank 11, and a tank check valve 50 is disposed in the discharge oil passage 49.

  The tank check valve 50 includes a poppet valve 51 and a tank check valve electromagnetic switching valve 52 that switches from an OFF position N to an ON position X based on an ON signal output from the control device 16. . The poppet valve 51 allows oil flow from the suction oil passage 33 to the oil tank 11 only when the tank check valve electromagnetic switching valve 52 is located at the ON position X, and is located at the OFF position N. It is designed to stop when you are. For example, when the excavator 1 is finished or maintained, the accumulator check valve electromagnetic switching valve 48 and the tank check valve electromagnetic switching valve 52 are both switched to the ON position X to accumulate pressure in the accumulator 36. The pressurized oil can be discharged to the oil tank 11.

  On the other hand, the control device 16 is configured using a microcomputer or the like, and as shown in the block diagram of FIG. 4, a boom operation lever (not shown) (corresponding to the hydraulic cylinder operation tool of the present invention). Boom operation detecting means 53 for detecting the operation direction and the operation amount, the first discharge side pressure sensor 54 connected to the first pump oil passage 12 to detect the discharge pressure of the first main pump 9, and the second main pump 10 The second discharge side pressure sensor 55 connected to the second discharge side pump oil passage 13 to detect the discharge pressure of the second pump, and the third discharge side connected to the dedicated pump oil passage 34 to detect the discharge pressure of the dedicated pump 32 The pressure sensor 56, the suction side pressure sensor 57 connected to the suction oil passage 33 to detect the pressure on the suction side of the dedicated pump 32, and the pressure in the head side oil chamber 8a of the boom cylinder 8 are detected. The cylinder head side pressure sensor 58 connected to the cylinder head side oil passage 20 and the cylinder rod side pressure sensor 59 connected to the cylinder rod side oil passage 21 to detect the pressure in the rod side oil chamber 8b of the boom cylinder 8 Input signals from an accumulator pressure sensor 60 connected to the accumulator oil passage 42 to detect the pressure of the accumulator 36, an accumulator temperature sensor 61 to detect the temperature of the gas charged in the accumulator 36, and the like. The electromagnetic proportional pressure reducing valve 17 for main pump control, the first upward electromagnetic proportional pressure reducing valve 23, the first downward electromagnetic proportional pressure reducing valve 24, the second upward electromagnetic proportional pressure reducing valve 25, and the electromagnetic switching for the drift reducing valve. Valve 30, dedicated pump regulator 35, third ascending-side electro-oil conversion valve 38, third descending-side electro-oil conversion valve 9, recovery electro-hydraulic conversion valve 44, the electromagnetic switching valve 48 for accumulator check valve, and outputs a control signal to the electromagnetic switching valve 52 or the like for the tank check valve.

  Here, 62 is a pressure accumulation amount calculation unit provided in the control device 16, and the pressure accumulation amount calculation unit 62 is a detection signal input from an accumulator pressure sensor (corresponding to pressure accumulation amount detection means of the present invention) 60. Based on the above, the current pressure accumulation amount of the accumulator 36 is calculated. In this embodiment, the accumulated pressure amount of the accumulator 36 calculated is the accumulated pressure ΔP accumulated in the accumulator 36 beyond the accumulated pressure start setting pressure, and the accumulated pressure ΔP is the current pressure of the accumulator 36. Calculated by subtracting the current accumulation start setting pressure (Po, pressure obtained by converting the precharge pressure at 20 degrees Celsius into the current temperature) from Pa (detected by the pressure sensor 60 for the accumulator). (ΔP = Pa−Po).

  Reference numeral 63 denotes a required pump capacity calculation unit. The request pump capacity calculation unit 63 inputs an operation signal for the boom operation lever output from the boom operation detection means 53 as shown in the block diagram of FIG. The required pump capacity DR is calculated by the gain control 64. The required pump capacity DR is a pump capacity required by the operation amount of the boom operation lever, and is set to increase as the operation amount of the boom operation lever increases, and is operated to the boom raising side. The value is set to be “positive” when it is operated, and is output as “negative” when operated to the boom lowering side.

  Reference numeral 65 denotes a sharing ratio calculation unit. The sharing ratio calculation unit 65 includes, as shown in FIG. 6, the accumulated pressure ΔP calculated by the accumulated pressure calculation unit 62 and the first main when the boom 5 is raised. There is an assist table 66 in which the relationship with the assist ratio α of the pump 9 (α = “0” to “1”, the assist ratio α corresponds to the share ratio of the hydraulic pump of the present invention) is set. The sharing ratio calculation unit 65 obtains the assist ratio α based on the assist table 66. In the present embodiment, the assist ratio α is obtained when the pressure accumulation ΔP is sufficient and the pressure accumulation amount of the accumulator 36 is sufficient. When the pressure reaches a preset high set pressure PH (the accumulated pressure of the accumulator when the accumulated pressure ΔP reaches the high set pressure PH corresponds to the high accumulated pressure of the present invention). “0”, when the accumulated pressure of the accumulator is almost equal to or lower than the low set pressure PL set in advance (the accumulated pressure of the accumulator when the accumulated pressure ΔP is less than or equal to the low set pressure PL) When the pressure is between “1” and the low set pressure PL, the assist ratio α is set to increase as the accumulated pressure ΔP decreases. Further, the share ratio calculation unit 65 subtracts the assist ratio α from “1”, so that the supply ratio β (β = 1−α, the supply ratio β of the dedicated pump 32 when the boom 5 is raised is (Corresponds to the share of the dedicated pump). The assist ratio α and the supply ratio β obtained based on these assist tables 66 are output from the sharing ratio calculation unit 65 when the boom operation lever is operated to the boom raising side, and will be described later. It is used for flow control of the first control valve 18 and third control valve 37 and discharge flow control of the dedicated pump 32. When the boom operating lever is operated to the boom lowering side, the assist ratio α and the supply ratio β output from the sharing ratio calculation unit 65 are always “1” regardless of the accumulated pressure ΔP of the accumulator 36. Is set to

  On the other hand, 67 is a first control valve control unit, and the first control valve control unit 67, as shown in the block diagram of FIG. The requested pump displacement DR output from the calculation unit 63 is input, and the assist ratio α and the requested pump displacement DR are multiplied by the multiplier 68 to obtain the requested requested pump displacement DRα. Further, the first control valve control unit 67 converts the requested pump capacity for assist DRα into a control signal value for the first ascending side and first descending electromagnetic proportional pressure reducing valves 23, 24. Based on the first valve table 69, control signal values for the first ascending side and first descending electromagnetic proportional pressure reducing valves 23, 24 are obtained. Then, the first control valve control unit 67 outputs the control signal value to the first ascending electromagnetic proportional pressure reducing valve 23 when the boom operating lever is operated to the boom raising side, and operates to the boom lowering side. In this case, the first descending electromagnetic proportional pressure reducing valve is set to output to the first lowering electromagnetic proportional pressure reducing valve. Control is performed so as to output a pilot pressure for changing the supply flow rate to the boom cylinder 8 to a flow rate obtained by multiplying the flow rate required according to the operation amount of the boom operation lever by the assist ratio α.

  Further, reference numeral 70 denotes a third control valve control unit. The first control valve control unit 70, as shown in the block diagram of FIG. 8, supplies the supply ratio β output from the share ratio calculation unit 65 and the requested pump capacity. The requested pump capacity DR output from the calculation unit 63 is input, and the supply ratio β and the requested pump capacity DR are multiplied by the multiplier 71 to obtain the requested pump capacity DRβ for supply. Further, the third control valve control unit 70 converts the above-mentioned requested pump capacity for supply DRβ into control signal values for the third ascending side, third descending side electro-hydraulic conversion valves 38, 39. Based on the third valve table 72, the control signal values for the third ascending side and third descending electrohydraulic conversion valves 38, 39 are obtained. The third control valve control unit 70 outputs the control signal value to the third ascending-side electro-hydraulic conversion valve 38 when the boom operating lever is operated to the boom ascending side, and operates the boom control side as the boom descending side. In this case, it is set to output to the third descending electro-oil conversion 39, but the third ascending-side electro-oil conversion valve 38 is controlled from the third control valve 37 when the boom is raised by the control signal value. The supply flow rate to the boom cylinder 8 is controlled to be a flow rate obtained by multiplying the flow rate required according to the operation amount of the boom operation lever by the supply ratio β.

Reference numeral 73 denotes a dedicated pump control unit. The dedicated pump control unit 73 calculates the supply ratio β output from the sharing ratio calculation unit 65 and the requested pump capacity DR output from the requested pump capacity calculation unit 63. Then, the supply ratio β and the required pump capacity DR are multiplied to obtain the required pump capacity DRβ for supply (DRβ = DR × β). The dedicated pump control unit 73 outputs a control signal to the dedicated pump regulator 35 in order to set the capacity of the dedicated pump 32 to the above-mentioned required pump capacity for supply DRβ. The flow rate is controlled to be a discharge flow rate obtained by multiplying the discharge flow rate required according to the operation amount of the boom operation lever by the supply ratio β.
The control device 16 includes various control units (not shown) for controlling the second control valve 19, the recovery valve 41, the drift reduction valve 29, the accumulator check valve 45, the tank check valve 50, and the like. However, the control in these control units will be described as the control of the control device 16 without being described individually.

Next, the control of the control device 16 based on the operation on the raising side and the lowering side of the boom operation lever will be described.
First, the case where the boom operation lever is operated to the upward side will be described. The control device 16 outputs the pump outputs of the first and second main pumps 9 and 10 to the engine relative to the main pump control electromagnetic proportional pressure reducing valve 17. A control signal is output to correspond to the rotation speed and the work load.

  Further, when the boom operation lever is operated to the upward side, the control device 16 outputs a control signal value set according to the operation amount of the boom operation lever to the second upward electromagnetic proportional pressure reducing valve 25. To do. As a result, the pilot pressure is output from the second ascending electromagnetic proportional pressure reducing valve 25, the second control valve 19 is switched to the ascending position X, and the discharge oil of the second main pump 10 is thus increased. It flows into the cylinder head side oil passage 20 via the second control valve 19 at the position X, and is supplied to the head side oil chamber 8a of the boom cylinder 8, from the second control valve 19 to the head side oil chamber 8a. The supply flow rate is controlled to be a flow rate required according to the operation amount of the boom operation lever.

Further, when the boom operation lever is operated to the ascending side, the control device 16 controls the first ascending-side electromagnetic proportional pressure reducing valve 23 based on the control executed by the first control valve control unit 67. Output a signal. The supply flow rate from the first control valve 18 to the boom cylinder 8 according to the control signal value output to the first ascending electromagnetic proportional pressure reducing valve 23 is a flow rate required according to the operation amount of the boom operation lever. The flow rate is controlled to be multiplied by the assist ratio α.
That is, when the assist ratio α is “1”, the pilot pressure is output from the first ascending electromagnetic proportional pressure reducing valve 23 according to the control signal output from the control device 16, whereby the first control valve 18 is moved to the ascending position. Thus, the oil discharged from the first main pump 9 flows into the cylinder head side oil passage 20 via the first control valve 18 at the ascending side position X, and the head side oil of the boom cylinder 8 is switched to X. Although supplied to the chamber 8a, the supply flow rate from the first control valve 18 to the head side oil chamber 8a is controlled to be a flow rate required according to the operation amount of the boom operation lever.
When the assist ratio α is between “1” and “0” (however, “1” and “0” are not included), as in the case where the assist ratio α is “1”, the control device The pilot pressure is outputted from the first ascending electromagnetic proportional pressure reducing valve 23 by the control signal outputted from 16, whereby the first control valve 18 is switched to the ascending position X, and the discharged oil of the first main pump 9 is discharged. Although supplied to the head side oil chamber 8a of the boom cylinder 8, the supply flow rate from the first control valve 18 to the head side oil chamber 8a is an assist ratio to the flow rate required according to the operation amount of the boom operation lever. As the flow rate multiplied by α, that is, the assist ratio α decreases, the flow rate is controlled to be smaller than the flow rate required according to the operation amount of the boom operation lever.
Furthermore, when the assist ratio α is “0”, the control for reducing the supply flow rate from the first control valve 18 to the boom cylinder 8 from the control device 16 to the first ascending electromagnetic proportional pressure reducing valve 23 is zero. A signal is output. As a result, the first control valve 37 is held at the neutral position N. Thus, no pressure oil is supplied from the first main pump 9 to the head side oil chamber 8a of the boom cylinder 8, and the first control valve 37 is controlled by negative control flow rate control. The discharge flow rate of the main pump 9 is controlled to be a minimum.

  Further, when the boom operation lever is operated to the upward side, the control device 16 supplies the capacity of the dedicated pump 32 to the dedicated pump regulator 35 based on the control executed by the dedicated pump control unit 73. The control signal is output so that the required pump capacity DRβ is obtained. Thus, the dedicated pump 32 is controlled to have a discharge flow rate obtained by multiplying the discharge flow rate required according to the operation amount of the boom operation lever by the supply ratio β. Thus, when the supply ratio β is “1”, the dedicated pump 32 has a discharge flow rate required according to the operation amount of the boom operation lever, and the supply ratio β is “1” to “0”. (However, “1” and “0” are not included), the lower the supply ratio β, the smaller the discharge flow rate required by the operation amount of the boom operation lever. When the supply ratio β is “0”, the discharge flow rate becomes zero.

Further, when the boom operation lever is operated to the ascending side, the control device 16 controls the third ascending-side electro-oil conversion valve 38 based on the control executed by the third control valve control unit 70. Output a signal. The supply flow rate from the third control valve 37 to the boom cylinder 8 according to the control signal value output to the third ascending-side electro-oil conversion valve 38 is a flow rate required according to the operation amount of the boom operation lever. The flow rate is controlled to be multiplied by the supply ratio β.
That is, when the supply ratio β is “1”, the third control valve 37 is switched to the ascending side position X by the control signal output from the control device 16 to the third ascending side electro-hydraulic conversion valve 38. Then, the discharge oil of the dedicated pump 32 flows into the cylinder head side oil passage 20 via the third control valve 37 at the ascending position X, and is supplied to the head side oil chamber 8a of the boom cylinder 8. The supply flow rate from the third control valve 37 to the head side oil chamber 8a is controlled to be a flow rate required in accordance with the operation amount of the boom operation lever.
Further, when the supply ratio β is between “1” and “0” (however, “1” and “0” are not included), as in the case where the supply ratio β is “1”, the control device The third control valve 37 is switched to the ascending position X by a control signal output from 16 to the third ascending-side electro-oil conversion valve 38, and the discharge oil of the dedicated pump 32 is supplied to the head-side oil chamber 8a of the boom cylinder 8. However, the supply flow rate from the third control valve 19 to the head side oil chamber 8a is the flow rate obtained by multiplying the flow rate required according to the operation amount of the boom operation lever by the supply rate β, that is, the supply rate. As β decreases, the flow rate is controlled to be smaller than the flow rate required in accordance with the operation amount of the boom operation lever.
Further, when the supply ratio β is “0”, the control for reducing the supply flow rate from the third control valve 37 to the boom cylinder 8 from the control device 16 to the third ascending-side electro-hydraulic conversion valve 38 is zero. A signal is output. As a result, the third control valve 37 is held at the neutral position N, and pressure oil is not supplied from the dedicated pump 32 to the head side oil chamber 8a of the boom cylinder 8.

   Further, when the boom operation lever is operated to the ascending side, the control device 16 outputs an ON signal to the accumulator check valve electromagnetic switching valve 48 so as to be switched to the ON position X. As a result, the accumulator check valve 45 is in a state of allowing the oil flow from the accumulator oil passage 42 to the suction oil passage 33. Thus, the pressure oil accumulated in the accumulator 36 is supplied to the suction side of the dedicated pump 32 via the suction oil passage 33.

  When the boom operation lever is operated to the ascending side, no control signal is output from the control device 16 to the recovery electro-oil conversion valve 44, and the recovery valve 41 is in the closed position N where the recovery oil passage 40 is closed. positioned. As a result, the pressure oil supplied from the first, second, and third control valves 18, 19, and 37 described above does not flow into the accumulator oil passage 42 and the suction oil passage 33, and the head side oil chamber of the boom cylinder 8. 8a is supplied.

  Next, the pressure oil supply to the boom cylinder 8 that is executed based on the control of the control device 16 described above when the boom operation lever is operated to the boom raising side will be described for each pressure accumulation amount of the accumulator 36.

First, when the pressure accumulation amount of the accumulator 36 is sufficient and the pressure accumulation pressure ΔP has reached the high set pressure PH, the supply ratio β is “1” and the assist ratio α is “0”. As described above, the discharge flow rate of the dedicated pump 32 is controlled to be a discharge flow rate required in accordance with the operation amount of the boom operation lever, and the third control valve 37 is operated with the operation amount of the boom operation lever. Accordingly, the flow rate required for one pump is controlled from the dedicated pump 32 (when the operation amount of the boom operation lever is maximum). It is supplied to the head side oil chamber 8a.
On the other hand, the first control valve 18 is held at the neutral position N, and therefore no pressure oil is supplied from the first main pump 9 to the head side oil chamber 8a.
Further, the second control valve 19 is controlled so as to supply the flow rate required according to the operation amount of the boom operation lever to the head side oil chamber 8a. The flow rate for one pump is supplied to the head side oil chamber 8a (when the operation amount of the boom operation lever is maximum).
The oil discharged from the rod side oil chamber 8b of the boom cylinder 8 flows into the oil tank 11 via the third control valve 37 at the ascending position X.

  Thus, when the accumulator 36 is operated to the boom raising side with a sufficient pressure accumulation amount, the head side oil chamber 8a of the boom cylinder 8 has a flow rate corresponding to the maximum one pump supplied from the second main pump 10. And the flow rate for one pump supplied from the dedicated pump 32 are combined and supplied, and even if the boom 5 is lifted against the heavy load of the working unit 4, The boom 5 can be raised at a desired speed corresponding to the operation amount. In this case, the dedicated pump 32 sucks and discharges the high-pressure oil accumulated in the accumulator 36, so that the suction side and the discharge side The differential pressure is small and the pressure oil can be supplied with less required power.

On the other hand, when there is almost no pressure accumulation amount of the accumulator 36 and the pressure accumulation pressure ΔP is equal to or lower than the low set pressure PL, the supply rate β is “0” and the assist rate α is “1”. In addition, the first control valve 18 is controlled so as to supply the flow rate required according to the operation amount of the boom operation lever to the head side oil chamber 8a. The flow rate for one pump is supplied to the head side oil chamber 8a (when the operation amount of the boom operation lever is maximum).
On the other hand, the dedicated pump 32 is controlled so that the discharge flow rate becomes zero, and the third control valve 37 is held at the neutral position N, and thus the pressure from the dedicated pump 32 to the head side oil chamber 8a. No oil supply is made.
The second control valve 19 is controlled so as to supply a flow rate required according to the operation amount of the boom operation lever to the head side oil chamber 8a. The flow rate for the pump is supplied to the head side oil chamber 8a.
The oil discharged from the rod side oil chamber 8b of the boom cylinder 8 flows to the oil tank 11 via the first control valve 18 at the ascending position X.

  Thus, when the accumulator 36 is operated to the boom ascending side with almost no pressure accumulation amount, pressure oil is supplied from the first main pump 9 instead of being supplied from the dedicated pump 32, so that the boom cylinder 8 The head-side oil chamber 8a is supplied with the flow rate for the maximum one pump supplied from the second main pump 10 and the flow rate for the maximum one pump supplied from the first main pump 9 combined. Therefore, even when the accumulator 36 is not accumulating pressure, the boom 5 can be raised at a desired speed corresponding to the operation amount of the boom operation lever, as in the case where the accumulator 36 is accumulating enough pressure. it can.

When the accumulated pressure ΔP of the accumulator 36 is between the high set pressure PH and the low set pressure PL, the supply ratio β and the assist ratio α are values between “1” and “0” (where β = α−1). In this case, as described above, the discharge flow rate of the dedicated pump 32 is requested in accordance with the operation amount of the boom operation lever as the supply ratio β decreases (that is, as the accumulated pressure ΔP decreases). The third control valve 37 is controlled so that the supply flow rate from the three control valves 37 to the head-side oil chamber 8a decreases as the supply ratio β decreases. The flow rate is controlled to be less than the required flow rate according to the operation amount.
On the other hand, in the first control valve 18, the amount of operation of the boom control lever is decreased as the assist rate α decreases (that is, the accumulated pressure ΔP increases) in the supply flow rate from the three control valves 18 to the head side oil chamber 8a. Accordingly, the discharge flow rate is controlled to be less than that required.
Here, the supply flow rate from the third control valve 37 to the head side oil chamber 8a is a flow rate obtained by multiplying the flow rate required according to the operation amount of the boom operation lever by the supply ratio β, The supply flow rate from the control valve 18 to the head side oil chamber 8a is a flow rate obtained by multiplying the flow rate required according to the operation amount of the boom operation lever by the assist rate α, and the assist rate α and the supply rate β. Since it is set to be “1” (α + β = 1) when added, the supply flow rate from the first control valve 18 increases as the supply flow rate from the third control valve 37 decreases, and the third control When the supply flow rate from the valve 37 and the supply flow rate from the first control valve 18 are added, the flow rate required according to the boom operating lever is obtained. Thus, the maximum flow rate (when the operation amount of the boom operation lever is maximum) added from the dedicated pump 32 and the first main pump 9 is supplied to the head-side oil chamber 8a.
The second control valve 19 is controlled so as to supply a flow rate required according to the operation amount of the boom operation lever to the head side oil chamber 8a. The flow rate for the pump is supplied to the head side oil chamber 8a.
The oil discharged from the rod side oil chamber 8b of the boom cylinder 8 flows into the oil tank 11 via the first control valve 18 at the ascending position X and the third control valve 37 at the ascending position X.

  Therefore, when the pressure accumulation pressure ΔP of the accumulator 36 is operated to the boom raising side when the pressure is between the high set pressure PH and the low set pressure PL, the second main pump is provided in the head side oil chamber 8a of the boom cylinder 8. 10 and the maximum flow rate of one pump supplied from the dedicated pump 32 and the first main pump 9 are combined and supplied, and accordingly, the accumulator 36 is supplied. Even if the pressure accumulation amount fluctuates, the boom 5 can be raised at a desired speed corresponding to the operation amount of the boom operation lever, as in the case where the accumulator 36 is sufficiently accumulated.

  Next, the control of the control device 16 when the boom operation lever is operated to the boom lowering side will be described. First, as described above, when the boom operating lever is operated to the boom lowering side, the output from the sharing ratio calculation unit 65 is performed. The assist ratio α and the supply ratio β to be set are always set to “1” regardless of the accumulated pressure ΔP of the accumulator 36. Thereby, when operated to the boom lowering side, the dedicated pump control unit 73 controls the discharge flow rate of the dedicated pump 32 to be the discharge flow rate required according to the operation amount of the boom operation lever. The third control control unit 70 controls the supply flow rate from the third control valve 37 to the boom cylinder 8 to be a flow rate required according to the operation amount of the boom operation lever.

  When the boom operation lever is operated to the boom lowering side, the control device 16 causes the main pump control electromagnetic proportional pressure reducing valve 17 to reduce the pump output of the first and second main pumps 9 and 10. Output a control signal.

Further, when the boom operation lever is operated to the lowering side, the control device 16 controls the first lowering electromagnetic proportional pressure reducing valve 24 based on the control executed by the first control valve control unit 67. Output a signal. As a result, the first control valve 18 is switched to the lowering position Y, and the oil discharged from the head side oil chamber 8a of the boom cylinder 8a passes through the regeneration valve path 18d at the lowering position Y. Although supplied to the rod-side oil chamber 8b, the flow rate is controlled to be a flow rate required according to the operation amount of the boom operation lever. Further, as described above, the discharge flow rate of the first main pump 9 when the first control valve 18 is at the lowering position Y is controlled to be minimized by the negative control flow rate control.
The second control valve 19 is held at the neutral position N when the boom 5 is lowered, and therefore does not supply and discharge oil to the boom cylinder 8, and the discharge flow rate of the second main pump 9 is also the negative control flow rate. It is controlled to be minimized by the control.

  Further, when the boom operation lever is operated to the lower side, the control device 16 outputs a control signal to the dedicated pump regulator 35 based on the control executed by the dedicated pump control unit 73. As a result, the dedicated pump 32 is controlled so as to discharge the required discharge flow rate according to the operation amount of the boom operation lever.

  Further, when the boom operation lever is operated to the lowering side, the control device 16 controls the third lowering-side electro-oil conversion valve 39 based on the control executed by the third control valve control unit 70. Output a signal. As a result, the third control valve 37 is switched to the lower side position Y, and the discharge oil of the dedicated pump 32 is transferred to the cylinder rod side oil passage 21 via the third control valve 37 at the lower side position Y. It flows and is supplied to the rod side oil chamber 8b of the boom cylinder 8. The supply flow rate from the third control valve 37 to the rod side oil chamber 8b is a flow rate required according to the operation amount of the boom operation lever. It is controlled to become.

  Further, when the boom operation lever is operated to the lowering side, the control device 16 outputs an ON signal to the drift reducing valve electromagnetic proportional pressure reducing valve 30 so as to be switched to the ON position X. As a result, the drift reduction valve 29 is allowed to discharge oil from the head side oil chamber 8a of the boom cylinder 8.

  Further, when the boom control lever is operated to the lowering side, the control device 16 outputs a control signal to the recovery electro-oil conversion valve 44 so as to switch the recovery valve 41 to the open position X. As a result, the recovery valve 41 switches to the open position X where the recovery oil passage 40 is opened, and thus the oil discharged from the head side oil chamber 8a of the boom cylinder 8 passes through the recovery oil passage 40 and is stored in the accumulator. The oil flows into the oil passage 42 and the suction oil passage 33, is accumulated in the accumulator 36, and is supplied to the suction side of the dedicated pump 32. The flow rate of the recovery oil passage 40 is controlled by the boom operating lever. The flow rate is controlled according to the operation amount. Further, at this time, the control device 16 outputs an ON signal to the accumulator check valve electromagnetic switching valve 48 so as to switch to the ON position X. As a result, oil can flow from the recovery oil passage 40 to the accumulator oil passage 42 with almost no pressure loss.

  Thus, when the boom 5 is lowered, the pressure oil from the dedicated pump 32 via the third control valve 37 is supplied to the rod-side oil chamber 8b of the boom cylinder 8. In this case, the dedicated pump 32 sucks and discharges the high pressure oil discharged from the head side oil chamber 8a, so that the differential pressure between the suction side and the discharge side is small, and the required power is much less than that of the first main pump 9. Pressure oil can be supplied.

On the other hand, 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 in consideration of the pressure receiving area acting on the piston 8c. The amount of oil discharged from the head side oil chamber 8a is approximately twice as large as the amount supplied to the side oil chamber 8b, but the oil discharged from the head side oil chamber 8a passes through the recovery oil passage 40 and the suction oil passage 33 and the accumulator oil passage 42. Flowing into. The oil flowing in the suction oil passage 33 is supplied to the suction side of the dedicated pump 32 and supplied from the dedicated pump 32 to the rod-side oil chamber 8b, while the pressure oil supplied to the accumulator oil passage 42 is stored in the accumulator. As described above, the pressure is accumulated in 36 and supplied from the dedicated pump 32 to the head side oil chamber 8a when the boom 5 is raised. Thus, the potential energy of the working unit 4 can be recovered and reused without being wasted.
When the boom 5 is lowered, 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 18d of the first control valve 18.

  In the present embodiment configured as described above, the hydraulic control system of the excavator 1 includes an accumulator 36 that accumulates oil discharged from the boom cylinder 8 when the boom 5 is lowered, and pressure oil accumulated in the accumulator 36. A dedicated pump 32 that sucks in and supplies the boom cylinder 8 is provided. Thus, the potential energy of the working unit 4 can be effectively recovered and reused by using the accumulator 36, which greatly saves energy. In addition to this, there are a first main pump 9 that sucks oil from the oil tank 11 and supplies it to the boom cylinder 8, and an accumulator pressure sensor 60 for detecting the amount of accumulated pressure in the accumulator 36. To the boom cylinder 8 from the dedicated pump 32 when the boom 5 is raised A control device 16 is provided for controlling the pressure oil supply and the pressure oil supply from the first main pump 9 to the boom cylinder 8 based on the pressure accumulation amount of the accumulator 36 (in the present embodiment, the pressure accumulation pressure ΔP described above). ing.

  As a result, even if the pressure accumulation amount of the accumulator 36 is not sufficient and the pressure oil supply from the dedicated pump 32 to the boom cylinder 8 is insufficient, the pressure oil is supplied from the first main pump 9 to the boom cylinder 8. In addition, even if the pressure accumulation amount of the accumulator 36 fluctuates, the pressure oil supply from the dedicated pump 32 and the first main pump 9 to the boom cylinder 8 can be controlled in response to the fluctuation of the pressure accumulation amount. Thus, it is possible to avoid the problem that the ascending speed of the boom 5 is influenced by the pressure accumulation amount of the accumulator 36, which is excellent in operability and contributes to improvement in work efficiency.

  Moreover, in this case, when the boom 5 is raised, the control device 16 has a sufficient pressure accumulation amount of the accumulator 36 and the pressure accumulation pressure ΔP reaches the high set pressure PH (when the pressure accumulation amount is equal to or higher than the high pressure accumulation amount). Supplies the pressure oil from the dedicated pump 32 to the boom cylinder 8 while stopping the pressure oil supply from the first main pump 9 to the boom cylinder 8, and the accumulator 36 has almost no accumulated pressure, and the accumulated pressure ΔP is reduced. When the pressure is lower than the low set pressure PL (when the pressure accumulation amount is less than or equal to the low pressure accumulation amount), pressure oil is supplied from the first main pump 9 to the boom cylinder 8, while pressure oil is supplied from the dedicated pump 32 to the boom cylinder 8. Further, when the pressure accumulation ΔP of the accumulator 36 is between the high set pressure PH and the low set pressure PL (when the pressure accumulation amount is between the high pressure accumulation amount and the low pressure accumulation amount), the accumulator 3 As the pressure accumulation amount decreases, the supply flow rate from the dedicated pump 32 to the boom cylinder 8 is decreased, while the supply flow rate from the first main pump 9 to the boom cylinder 8 is controlled to increase, and the pressure accumulation amount of the accumulator 36 is increased. In any case, the sum of the supply flow rate from the dedicated pump 32 to the boom cylinder 8 and the supply flow rate from the first main pump 9 to the boom cylinder 8 depends on the operation amount of the boom operation lever. The flow rate will be controlled to the required level.

  As a result, when the amount of accumulated pressure in the accumulator 36 is sufficient, the accumulated oil in the accumulator 36 can be utilized to the maximum, and even if the amount of accumulated pressure in the accumulator 36 decreases, the operation lever for the boom is always operated. Since the flow according to the amount can be supplied to the boom cylinder 8, the boom 5 can be raised at a desired speed corresponding to the operation amount of the boom operation lever. Moreover, in this case, the supply flow rate from the dedicated pump 32 to the boom cylinder 8 decreases as the pressure accumulation amount of the accumulator 36 decreases, while the supply flow rate from the first main pump 9 to the boom cylinder 8 increases. Therefore, the supply flow rate from the dedicated pump 32 and the supply flow rate from the first main pump 9 can be always supplied to the boom cylinder 8 in a well-balanced manner according to the pressure accumulation amount of the accumulator 36. For example, when the boom 5 is raised, Pressure oil is supplied only from the dedicated pump 32 until it is emptied, and when it is emptied, it is switched to pressure oil supply from the first main pump 9. There is no problem that the smooth operation of the boom 5 is impaired at the time of switching to the pressure oil supply from the first main pump 9. Excellent operability.

  Further, in this case, a first control valve 18 for controlling the flow rate from the first main pump 9 to the boom cylinder 8 and a third control valve 37 for controlling the flow rate from the dedicated pump 32 to the boom cylinder 8 are provided. In addition, the control device 16 includes a first control valve control unit 67 and a third control valve control unit 70 that control the first control valve 18 and the third control valve 37, respectively, based on the pressure accumulation amount of the accumulator 36. Therefore, the supply flow rate from the dedicated pump 32 and the first main pump 9 to the boom cylinder 8 can be accurately controlled so as to correspond to the pressure accumulation amount of the accumulator 36.

  Further, since the control device 16 is provided with a dedicated pump control unit 73 that controls the discharge flow rate of the dedicated pump 32 based on the pressure accumulation amount of the accumulator 36, the discharge flow rate of the dedicated pump 32 is not wasted. And it can supply to the boom cylinder 8 without being insufficient. Further, when the pressure is not accumulated in the accumulator 36, that is, when the oil is not supplied from the accumulator 36 to the suction side of the dedicated pump 32, the dedicated pump 32 is driven to discharge the pressure oil, and an unreasonable load is applied. Problems can be avoided reliably.

  In addition, the control device 16 calculates the supply ratio β of the dedicated pump 32 and the assist ratio α of the first main pump 9 with respect to the supply flow rate to the boom cylinder 8 when the boom 5 is raised, based on the accumulated pressure amount of the accumulator 36. Therefore, the first control valve 18 and the second control valve 18 corresponding to the pressure accumulation amount of the accumulator 36 are used by using the supply ratio β and the assist ratio α calculated by the share ratio calculator 65. The flow control of the three control valves 37 and the discharge amount control of the dedicated pump 32 can be performed easily and accurately.

  In the present embodiment, the first main pump 9 is a hydraulic pump that serves as a hydraulic pressure supply source for various hydraulic actuators as well as the boom cylinder 8, and is generally used for a conventional hydraulic excavator that does not include the accumulator 36. Therefore, the hydraulic pump equipped in the conventional model can be used as it is, and the supply circuit from the first main pump 9 to the boom cylinder 8 can also be used. Can contribute to the suppression of complications.

Of course, the present invention is not limited to the above-described embodiment. In the above-described embodiment, the hydraulic control system for the boom cylinder of the hydraulic excavator has been described as an example. However, the present invention moves the working unit up and down. It can be implemented in a hydraulic control system for various hydraulic cylinders.
Further, in the above embodiment, as the pump for supplying pressure oil to the hydraulic cylinder, the second main pump is provided in addition to the dedicated pump and the first main pump. The pressure oil can be supplied at a flow rate of a minute, but the present invention can be implemented even when the second main pump is not provided.

It is a side view of a hydraulic excavator. It is a circuit diagram of a hydraulic control system. 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 block diagram which shows the control procedure of a request | requirement pump capacity | capacitance calculating part. It is a block diagram which shows the control procedure of a share ratio calculating part. It is a block diagram which shows the control procedure of a 1st control valve control part. It is a block diagram which shows the control procedure of a 2nd control valve control part.

Explanation of symbols

DESCRIPTION OF SYMBOLS 4 Working part 8 Boom cylinder 9 1st main pump 11 Oil tank 16 Control apparatus 18 1st control valve 32 Dedicated pump 36 Accumulator 37 3rd control valve 60 Pressure sensor for accumulator 65 Share ratio calculating part 67 1st control valve control part 70 Third control valve control unit 73 Dedicated pump control unit

Claims (6)

  A hydraulic cylinder that raises and lowers the working part, an accumulator that accumulates oil discharged from the hydraulic cylinder when the working part descends, a dedicated pump that sucks the pressure oil accumulated in the accumulator and supplies it to the hydraulic cylinder, and an oil from the oil tank A hydraulic pump that sucks in and supplies the pressure to the hydraulic cylinder, and a pressure accumulation amount detecting means for detecting the pressure accumulation amount of the accumulator, and the working unit based on the pressure accumulation amount of the accumulator detected by the pressure accumulation amount detection means A hydraulic control system for a work machine, comprising a control device for controlling the pressure oil supply from the dedicated pump to the hydraulic cylinder and the pressure oil supply from the hydraulic pump to the hydraulic cylinder at the time of rising.   The control device supplies pressure oil from the dedicated pump to the hydraulic cylinder when the accumulator pressure accumulation amount is higher than a preset high pressure accumulation amount when the working unit is raised, while pressure oil from the hydraulic pump to the hydraulic cylinder is supplied. When supply is stopped and the accumulator pressure accumulation amount is less than or equal to the preset low pressure accumulation amount, pressure oil is supplied from the hydraulic pump to the hydraulic cylinder, while pressure oil supply from the dedicated pump to the hydraulic cylinder is stopped, Also, when the accumulator pressure accumulation amount is between the high pressure accumulation amount and the low pressure accumulation amount, the supply flow rate from the dedicated pump to the hydraulic cylinder is reduced as the accumulator pressure accumulation amount decreases, while the hydraulic pump is transferred from the hydraulic pump to the hydraulic cylinder. The supply flow rate of the accumulator is controlled so as to increase, and the accumulator pressure can be increased in any case from the dedicated pump to the hydraulic cylinder. 2. The control according to claim 1, wherein the sum of the supply flow rate and the supply flow rate from the hydraulic pump to the hydraulic cylinder is controlled to be a flow rate required in accordance with an operation amount of the hydraulic cylinder operation tool. Hydraulic control system for work machines.   The hydraulic control system includes a control valve for controlling the flow rate from the hydraulic pump to the hydraulic cylinder and a control valve for controlling the flow rate from the dedicated pump to the hydraulic cylinder, while the control device is based on the accumulated pressure amount of the accumulator, The hydraulic control system for a work machine according to claim 1, further comprising a control valve control unit that controls each of the control valves.   4. The hydraulic control system for a work machine according to claim 1, wherein the control device has a dedicated pump control unit that controls a discharge flow rate of the dedicated pump based on a pressure accumulation amount of the accumulator. 5. .   The control device has a sharing ratio calculation unit that calculates a sharing ratio of the dedicated pump and a sharing ratio of the hydraulic pump with respect to the supply flow rate to the hydraulic cylinder when the working unit is raised based on the pressure accumulation amount of the accumulator. The hydraulic control system in the working machine as described in any one of Claims 1 thru | or 4.   The hydraulic control system for a work machine according to any one of claims 1 to 5, wherein the hydraulic pump is a main pump serving as a hydraulic supply source for various hydraulic actuators provided in the work machine.

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