WO2016056442A1 - ショベル - Google Patents
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- WO2016056442A1 WO2016056442A1 PCT/JP2015/077730 JP2015077730W WO2016056442A1 WO 2016056442 A1 WO2016056442 A1 WO 2016056442A1 JP 2015077730 W JP2015077730 W JP 2015077730W WO 2016056442 A1 WO2016056442 A1 WO 2016056442A1
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- WIPO (PCT)
- Prior art keywords
- pressure
- hydraulic
- hydraulic oil
- pump
- motor
- Prior art date
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- 239000010720 hydraulic oil Substances 0.000 claims abstract description 601
- 239000003921 oil Substances 0.000 claims description 245
- 238000006073 displacement reaction Methods 0.000 claims description 81
- 230000001133 acceleration Effects 0.000 claims description 80
- 239000012530 fluid Substances 0.000 claims description 60
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- 230000000903 blocking effect Effects 0.000 claims description 9
- 238000005336 cracking Methods 0.000 claims description 3
- 230000008929 regeneration Effects 0.000 abstract description 156
- 238000011069 regeneration method Methods 0.000 abstract description 156
- 238000009412 basement excavation Methods 0.000 description 73
- 238000009825 accumulation Methods 0.000 description 35
- 239000002689 soil Substances 0.000 description 30
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Images
Classifications
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- E—FIXED CONSTRUCTIONS
- E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
- E02F—DREDGING; SOIL-SHIFTING
- E02F9/00—Component parts of dredgers or soil-shifting machines, not restricted to one of the kinds covered by groups E02F3/00 - E02F7/00
- E02F9/20—Drives; Control devices
- E02F9/22—Hydraulic or pneumatic drives
- E02F9/2221—Control of flow rate; Load sensing arrangements
-
- E—FIXED CONSTRUCTIONS
- E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
- E02F—DREDGING; SOIL-SHIFTING
- E02F3/00—Dredgers; Soil-shifting machines
- E02F3/04—Dredgers; Soil-shifting machines mechanically-driven
- E02F3/28—Dredgers; Soil-shifting machines mechanically-driven with digging tools mounted on a dipper- or bucket-arm, i.e. there is either one arm or a pair of arms, e.g. dippers, buckets
- E02F3/30—Dredgers; Soil-shifting machines mechanically-driven with digging tools mounted on a dipper- or bucket-arm, i.e. there is either one arm or a pair of arms, e.g. dippers, buckets with a dipper-arm pivoted on a cantilever beam, i.e. boom
- E02F3/308—Dredgers; Soil-shifting machines mechanically-driven with digging tools mounted on a dipper- or bucket-arm, i.e. there is either one arm or a pair of arms, e.g. dippers, buckets with a dipper-arm pivoted on a cantilever beam, i.e. boom working outwardly
-
- E—FIXED CONSTRUCTIONS
- E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
- E02F—DREDGING; SOIL-SHIFTING
- E02F9/00—Component parts of dredgers or soil-shifting machines, not restricted to one of the kinds covered by groups E02F3/00 - E02F7/00
- E02F9/20—Drives; Control devices
-
- E—FIXED CONSTRUCTIONS
- E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
- E02F—DREDGING; SOIL-SHIFTING
- E02F9/00—Component parts of dredgers or soil-shifting machines, not restricted to one of the kinds covered by groups E02F3/00 - E02F7/00
- E02F9/20—Drives; Control devices
- E02F9/22—Hydraulic or pneumatic drives
-
- E—FIXED CONSTRUCTIONS
- E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
- E02F—DREDGING; SOIL-SHIFTING
- E02F9/00—Component parts of dredgers or soil-shifting machines, not restricted to one of the kinds covered by groups E02F3/00 - E02F7/00
- E02F9/20—Drives; Control devices
- E02F9/22—Hydraulic or pneumatic drives
- E02F9/2217—Hydraulic or pneumatic drives with energy recovery arrangements, e.g. using accumulators, flywheels
-
- E—FIXED CONSTRUCTIONS
- E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
- E02F—DREDGING; SOIL-SHIFTING
- E02F9/00—Component parts of dredgers or soil-shifting machines, not restricted to one of the kinds covered by groups E02F3/00 - E02F7/00
- E02F9/20—Drives; Control devices
- E02F9/22—Hydraulic or pneumatic drives
- E02F9/2221—Control of flow rate; Load sensing arrangements
- E02F9/2232—Control of flow rate; Load sensing arrangements using one or more variable displacement pumps
-
- E—FIXED CONSTRUCTIONS
- E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
- E02F—DREDGING; SOIL-SHIFTING
- E02F9/00—Component parts of dredgers or soil-shifting machines, not restricted to one of the kinds covered by groups E02F3/00 - E02F7/00
- E02F9/20—Drives; Control devices
- E02F9/22—Hydraulic or pneumatic drives
- E02F9/2264—Arrangements or adaptations of elements for hydraulic drives
- E02F9/2267—Valves or distributors
-
- E—FIXED CONSTRUCTIONS
- E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
- E02F—DREDGING; SOIL-SHIFTING
- E02F9/00—Component parts of dredgers or soil-shifting machines, not restricted to one of the kinds covered by groups E02F3/00 - E02F7/00
- E02F9/20—Drives; Control devices
- E02F9/22—Hydraulic or pneumatic drives
- E02F9/2278—Hydraulic circuits
- E02F9/2292—Systems with two or more pumps
-
- E—FIXED CONSTRUCTIONS
- E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
- E02F—DREDGING; SOIL-SHIFTING
- E02F9/00—Component parts of dredgers or soil-shifting machines, not restricted to one of the kinds covered by groups E02F3/00 - E02F7/00
- E02F9/20—Drives; Control devices
- E02F9/22—Hydraulic or pneumatic drives
- E02F9/2278—Hydraulic circuits
- E02F9/2296—Systems with a variable displacement pump
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
- F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
- F15B1/00—Installations or systems with accumulators; Supply reservoir or sump assemblies
- F15B1/02—Installations or systems with accumulators
- F15B1/027—Installations or systems with accumulators having accumulator charging devices
- F15B1/033—Installations or systems with accumulators having accumulator charging devices with electrical control means
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
- F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
- F15B11/00—Servomotor systems without provision for follow-up action; Circuits therefor
- F15B11/16—Servomotor systems without provision for follow-up action; Circuits therefor with two or more servomotors
- F15B11/17—Servomotor systems without provision for follow-up action; Circuits therefor with two or more servomotors using two or more pumps
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
- F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
- F15B21/00—Common features of fluid actuator systems; Fluid-pressure actuator systems or details thereof, not covered by any other group of this subclass
- F15B21/14—Energy-recuperation means
-
- E—FIXED CONSTRUCTIONS
- E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
- E02F—DREDGING; SOIL-SHIFTING
- E02F3/00—Dredgers; Soil-shifting machines
- E02F3/04—Dredgers; Soil-shifting machines mechanically-driven
- E02F3/28—Dredgers; Soil-shifting machines mechanically-driven with digging tools mounted on a dipper- or bucket-arm, i.e. there is either one arm or a pair of arms, e.g. dippers, buckets
- E02F3/36—Component parts
- E02F3/40—Dippers; Buckets ; Grab devices, e.g. manufacturing processes for buckets, form, geometry or material of buckets
- E02F3/401—Buckets or forks comprising, for example, shock absorbers, supports or load striking scrapers to prevent overload
-
- E—FIXED CONSTRUCTIONS
- E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
- E02F—DREDGING; SOIL-SHIFTING
- E02F9/00—Component parts of dredgers or soil-shifting machines, not restricted to one of the kinds covered by groups E02F3/00 - E02F7/00
- E02F9/20—Drives; Control devices
- E02F9/22—Hydraulic or pneumatic drives
- E02F9/2264—Arrangements or adaptations of elements for hydraulic drives
- E02F9/2271—Actuators and supports therefor and protection therefor
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
- F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
- F15B2201/00—Accumulators
- F15B2201/50—Monitoring, detection and testing means for accumulators
- F15B2201/51—Pressure detection
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
- F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
- F15B2211/00—Circuits for servomotor systems
- F15B2211/20—Fluid pressure source, e.g. accumulator or variable axial piston pump
- F15B2211/205—Systems with pumps
- F15B2211/20576—Systems with pumps with multiple pumps
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
- F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
- F15B2211/00—Circuits for servomotor systems
- F15B2211/20—Fluid pressure source, e.g. accumulator or variable axial piston pump
- F15B2211/21—Systems with pressure sources other than pumps, e.g. with a pyrotechnical charge
- F15B2211/212—Systems with pressure sources other than pumps, e.g. with a pyrotechnical charge the pressure sources being accumulators
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
- F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
- F15B2211/00—Circuits for servomotor systems
- F15B2211/40—Flow control
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
- F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
- F15B2211/00—Circuits for servomotor systems
- F15B2211/70—Output members, e.g. hydraulic motors or cylinders or control therefor
- F15B2211/705—Output members, e.g. hydraulic motors or cylinders or control therefor characterised by the type of output members or actuators
- F15B2211/7051—Linear output members
- F15B2211/7053—Double-acting output members
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
- F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
- F15B2211/00—Circuits for servomotor systems
- F15B2211/70—Output members, e.g. hydraulic motors or cylinders or control therefor
- F15B2211/705—Output members, e.g. hydraulic motors or cylinders or control therefor characterised by the type of output members or actuators
- F15B2211/7058—Rotary output members
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
- F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
- F15B2211/00—Circuits for servomotor systems
- F15B2211/70—Output members, e.g. hydraulic motors or cylinders or control therefor
- F15B2211/71—Multiple output members, e.g. multiple hydraulic motors or cylinders
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
- F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
- F15B2211/00—Circuits for servomotor systems
- F15B2211/80—Other types of control related to particular problems or conditions
- F15B2211/88—Control measures for saving energy
Definitions
- the present invention relates to an excavator equipped with a hydraulic circuit including a plurality of hydraulic pumps and at least one hydraulic device functioning as at least one of a hydraulic pump and a hydraulic motor.
- FIG. 2 It is a side view of an excavator. It is the schematic which shows the structural example of the hydraulic circuit mounted in the shovel of FIG. It is the schematic which shows another structural example of the hydraulic circuit mounted in the shovel of FIG.
- the state of the hydraulic circuit of FIG. 2 when excavation operation is performed is shown.
- the state of the hydraulic circuit of FIG. 2 when excavation operation is performed is shown.
- the state of the hydraulic circuit of FIG. 2 when excavation operation is performed is shown.
- the state of the hydraulic circuit of FIG. 3 in the case where excavation operation is performed is shown.
- the state of the hydraulic circuit of FIG. 2 in the case where excavation operation accompanied by engine assist by back pressure regeneration is performed is shown.
- the state of the hydraulic circuit of FIG. 3 in the case where excavation operation accompanied by engine assist by back pressure regeneration is performed is shown.
- FIG. 2 shows The state of the hydraulic circuit of FIG. 2 when excavation operation with accumulator assistance is performed.
- the state of the hydraulic circuit of FIG. 3 in the case where excavation operation with accumulator assistance is performed is shown.
- the state of the hydraulic circuit of FIG. 2 in the case where excavation operation with assistance of the hydraulic actuator by back pressure regeneration is performed is shown.
- the state of the hydraulic circuit of FIG. 3 in the case where excavation operation with assistance of the hydraulic actuator by back pressure regeneration is performed is shown.
- FIG. 3 shows the state of the hydraulic circuit in FIG. 2 when a soil removal operation accompanied by engine assist by back pressure regeneration is performed.
- the state of the hydraulic circuit of FIG. 3 in the case where the earth removal operation accompanied by the engine assist by back pressure regeneration is performed is shown.
- FIG. 3 when a boom lowering turning deceleration operation accompanied by accumulator pressure accumulation is performed.
- the state of the hydraulic circuit of FIG. 2 when the turning deceleration operation accompanied by the engine assist and the accumulator pressure accumulation is performed is shown.
- It is a control block diagram which shows the flow of control of a hydraulic system.
- It is a flowchart which shows the flow of a turning deceleration process.
- the state of the hydraulic circuit of FIG. 2 when the turning deceleration operation accompanied by the engine assist and the accumulator pressure accumulation is performed is shown.
- the state of the hydraulic circuit of FIG. 3 in the case where the turning deceleration operation accompanied by the engine assist and the accumulator pressure accumulation is performed is shown.
- FIG. 2 in the case where the turning acceleration operation with the engine assist and accumulator pressure accumulation is performed is shown. It is a flowchart which shows the flow of a turning acceleration process.
- the state of the hydraulic circuit of FIG. 3 in the case where the turning acceleration operation accompanied by the engine assist and the accumulator pressure accumulation is performed is shown.
- the state of the hydraulic circuit of FIG. 2 in the case where the turning acceleration operation with accumulator pressure accumulation is performed is shown.
- the state of the hydraulic circuit of FIG. 3 in the case where the turning acceleration operation with accumulator pressure accumulation is performed is shown.
- FIG. 1 is a side view showing an excavator to which the present invention is applied.
- An upper swing body 3 is mounted on the lower traveling body 1 of the excavator via a swing mechanism 2.
- a boom 4 is attached to the upper swing body 3.
- An arm 5 is attached to the tip of the boom 4, and a bucket 6 is attached to the tip of the arm 5.
- the boom 4, the arm 5, and the bucket 6 as work elements constitute a drilling attachment that is an example of an attachment, and are hydraulically driven by the boom cylinder 7, the arm cylinder 8, and the bucket cylinder 9, respectively.
- the upper swing body 3 is provided with a cabin 10 and is mounted with a power source such as the engine 11 and a controller 30.
- the controller 30 is a control device as a main control unit that performs drive control of the excavator.
- the controller 30 is constituted by an arithmetic processing unit including a CPU (Central Processing Unit) and an internal memory, and realizes various functions by causing the CPU to execute a drive control program stored in the internal memory.
- a CPU Central Processing Unit
- the turning hydraulic motor 21 is a hydraulic motor for turning the upper turning body 3, and ports 21L and 21R are connected to the hydraulic oil tank T via relief valves 22L and 22R, respectively, and a regeneration valve 22G via a shuttle valve 22S. And is connected to the hydraulic oil tank T via check valves 23L and 23R.
- the regeneration valve 22G is a valve that operates in response to a command from the controller 30 and switches communication / interruption of the regeneration oil passage between the turning hydraulic motor 21 (shuttle valve 22S) and the pump / motor 14A or the accumulator 80. .
- the regeneration valve 22G is an on-off valve whose opening degree can be adjusted.
- the controller 30 may control the pressure of the hydraulic oil flowing out from the turning hydraulic motor 21 by adjusting the opening of the regeneration valve 22G to adjust the flow passage area of the regeneration oil passage. This is because the braking torque for stopping the turning of the upper swing body 3 is adjusted.
- the check valve 23L opens when the pressure on the port 21L side becomes negative, and supplies hydraulic oil from the hydraulic oil tank T to the port 21L side.
- the check valve 23R opens when the pressure on the port 21R side becomes negative, and replenishes hydraulic oil from the hydraulic oil tank T to the port 21R side.
- the check valves 23L and 23R constitute a supply mechanism that supplies hydraulic oil to the suction side port when the swing hydraulic motor 21 is braked.
- the first pump 14L is a hydraulic pump that sucks and discharges hydraulic oil from the hydraulic oil tank T, and is a swash plate type variable displacement hydraulic pump in this embodiment.
- the first pump 14L is connected to a regulator.
- the regulator controls the discharge amount of the first pump 14L by changing the swash plate tilt angle of the first pump 14L in accordance with a command from the controller 30. The same applies to the second pump 14R.
- a relief valve 14aL is provided on the discharge side of the first pump 14L.
- the relief valve 14aL opens when the pressure on the discharge side of the first pump 14L reaches a predetermined relief pressure, and discharges the hydraulic oil on the discharge side to the hydraulic oil tank T.
- the pump motor 14A is a hydraulic device that functions as both a hydraulic pump (third pump) and a hydraulic motor.
- the pump motor 14A is a swash plate type variable displacement hydraulic pump / motor.
- the pump motor 14A is connected to a regulator in the same manner as the first pump 14L and the second pump 14R.
- the regulator changes the swash plate tilt angle of the pump / motor 14A in accordance with a command from the controller 30 to control the discharge amount of the pump / motor 14A.
- the pump / motor 14A may be a fixed displacement hydraulic pump / motor. Further, the pump / motor 14A may be connected to the engine 11 via a clutch mechanism so that the pump / motor 14A can idle as necessary when functioning as a hydraulic motor.
- a relief valve 70a is installed on the discharge side of the pump motor 14A.
- the relief valve 70a opens when the pressure on the discharge side of the pump / motor 14A reaches a predetermined relief pressure, and discharges the hydraulic oil on the discharge side to the hydraulic oil tank T.
- the first pump 14L, the second pump 14R, and the pump / motor 14A are mechanically coupled to their respective drive shafts.
- each drive shaft is connected to the output shaft of the engine 11 through the transmission 13 at a predetermined speed ratio. Therefore, if the engine speed is constant, each speed is also constant.
- the first pump 14L, the second pump 14R, and the pump motor 14A may be connected to the engine 11 via a continuously variable transmission or the like so that the rotation speed can be changed even if the engine rotation speed is constant. Good.
- the control valve 17 is a hydraulic control device that controls a hydraulic drive system in the excavator.
- the control valve 17 mainly includes variable load check valves 51 to 53, a merging valve 55, unified bleed-off valves 56L and 56R, switching valves 60 to 63, and flow control valves 170 to 173.
- the flow control valves 170 to 173 are valves that control the direction and flow rate of hydraulic oil flowing into and out of the hydraulic actuator.
- each of the flow control valves 170 to 173 is a 4-port 3-position operated by receiving a pilot pressure generated by an operating device (not shown) such as a corresponding operating lever at either the left or right pilot port. This is a spool valve.
- the operating device causes the pilot pressure generated according to the operation amount (operation angle) to act on the pilot port on the side corresponding to the operation direction.
- the flow control valve 170 is a spool valve that controls the direction and flow rate of the hydraulic oil flowing into and out of the turning hydraulic motor 21, and the flow control valve 171 is the hydraulic oil flowing into and out of the arm cylinder 8.
- the flow control valve 172 is a spool valve that controls the direction and flow rate of the hydraulic oil flowing into and out of the boom cylinder 7, and the flow control valve 173 controls the direction and flow rate of the hydraulic oil flowing into and out of the bucket cylinder 9. This is a spool valve.
- variable load check valves 51 to 53 are valves that operate in response to a command from the controller 30.
- the variable load check valves 51 to 53 are two ports that can switch communication / blocking between each of the flow control valves 171 to 173 and at least one of the first pump 14L and the second pump 14R. This is a two-position solenoid valve.
- the variable load check valves 51 to 53 have a check valve for blocking the flow of hydraulic oil returning to the pump side at the first position. Specifically, when the variable load check valve 51 is in the first position, the flow control valve 171 communicates with at least one of the first pump 14L and the second pump 14R and is in the second position. In that case, the communication is cut off. The same applies to the variable load check valve 52 and the variable load check valve 53.
- the merging valve 55 is an example of a merging switching unit, and is a valve that operates in accordance with a command from the controller 30.
- the merging valve 55 is a hydraulic oil discharged from the first pump 14L (hereinafter referred to as “first hydraulic oil”) and a hydraulic oil discharged from the second pump 14R (hereinafter referred to as “second hydraulic oil”).
- first hydraulic oil a hydraulic oil discharged from the first pump 14L
- second hydraulic oil hereinafter referred to as “second hydraulic oil”.
- “).” Is a 2-port 2-position solenoid valve capable of switching whether or not to join. Specifically, the merging valve 55 merges the first hydraulic oil and the second hydraulic oil when in the first position, and merges the first hydraulic oil and the second hydraulic oil when in the second position. Do not let it.
- the unified bleed-off valves 56L and 56R are valves that operate in response to a command from the controller 30.
- the unified bleed-off valve 56L is a 2-port 2-position electromagnetic valve capable of controlling the discharge amount of the first hydraulic oil to the hydraulic oil tank T.
- the unified bleed-off valves 56L and 56R can reproduce the combined opening of the associated flow control valve among the flow control valves 170 to 173.
- the unified bleed-off valve 56L can reproduce the combined opening of the flow control valve 170 and the flow control valve 171
- the unified bleed-off valve 56R includes the flow control valve 172 and the flow control valve 172.
- the synthetic opening of the flow control valve 173 can be reproduced.
- the switching valves 60 to 63 are valves that operate according to a command from the controller 30.
- the switching valves 60 to 63 are three-port, two-position solenoid valves that can switch whether or not the hydraulic oil discharged from each of the hydraulic actuators flows to the upstream side (supply side) of the pump motor 14A. It is. Specifically, when the switching valve 60 is in the first position, the hydraulic oil discharged from the turning hydraulic motor 21 through the regeneration valve 22G flows to the supply side of the pump motor 14A and is in the second position. In addition, the hydraulic oil discharged from the turning hydraulic motor 21 through the regeneration valve 22G is caused to flow to the accumulator 80.
- the switching valve 61 when the switching valve 61 is in the first position, the hydraulic oil discharged from the arm cylinder 8 flows into the hydraulic oil tank T, and when it is in the second position, the hydraulic oil discharged from the arm cylinder 8 is allowed to flow. Flow to the supply side of the pump motor 14A. The same applies to the switching valve 62 and the switching valve 63.
- the accumulator 80 is a hydraulic device that accumulates pressurized hydraulic oil.
- the accumulator 80 is an accumulator using nitrogen gas, and the accumulation / release of hydraulic oil is controlled by the switching valve 81 and the switching valve 82.
- the switching valve 81 is a valve that operates in response to a command from the controller 30.
- the switching valve 81 is a two-port two-position electromagnetic valve that can switch communication / blocking between the first pump 14L, which is a supply source of pressurized hydraulic oil, and the accumulator 80.
- the switching valve 81 communicates between the first pump 14L and the accumulator 80 when in the first position, and blocks the communication when in the second position.
- the switching valve 81 has a check valve that blocks the flow of hydraulic oil that returns to the first pump 14L side in the first position.
- the switching valve 82 is a valve that operates in accordance with a command from the controller 30.
- the switching valve 82 is a 2-port 2-position electromagnetic valve that can switch communication / blocking between the supply side of the pump / motor 14A to which pressurized hydraulic oil is supplied and the accumulator 80. is there. Specifically, the switching valve 82 communicates between the pump motor 14A and the accumulator 80 when in the first position, and blocks the communication when in the second position. Note that the switching valve 82 has a check valve that blocks the flow of hydraulic oil that returns to the accumulator 80 side in the first position.
- the switching valve 90 is a valve that operates in response to a command from the controller 30.
- the switching valve 90 is a three-port, two-position electromagnetic valve capable of switching the supply destination of hydraulic oil discharged from the pump / motor 14A (hereinafter referred to as “third hydraulic oil”).
- third hydraulic oil capable of switching the supply destination of hydraulic oil discharged from the pump / motor 14A (hereinafter referred to as “third hydraulic oil”).
- the switching valve 90 allows the third hydraulic oil to flow toward the switching valve 91 when in the first position, and allows the third hydraulic oil to flow toward the hydraulic oil tank T when in the second position. .
- the switching valve 91 is a valve that operates in response to a command from the controller 30.
- the switching valve 91 is a four-port, three-position electromagnetic valve that can switch the supply destination of the third hydraulic oil. Specifically, the switching valve 91 directs the third hydraulic oil toward the arm cylinder 8 when in the first position, and directs the third hydraulic oil toward the turning hydraulic motor 21 when in the second position. When in position, the third hydraulic fluid is directed to the accumulator 80.
- the flow control valves 171A and 172B are valves that control the direction and flow rate of the hydraulic oil flowing into and out of the arm cylinder 8, and correspond to the flow control valve 171 in FIG. Specifically, the flow control valve 171 ⁇ / b> A supplies the first hydraulic oil to the arm cylinder 8, and the flow control valve 171 ⁇ / b> B supplies the second hydraulic oil to the arm cylinder 8. Therefore, the first hydraulic oil and the second hydraulic oil can flow into the arm cylinder 8 at the same time.
- the flow control valve 172A is a valve that controls the direction and flow rate of the hydraulic oil flowing into and out of the boom cylinder 7, and corresponds to the flow control valve 172 in FIG.
- the flow control valve 172B is a valve that allows the first hydraulic oil to flow into the bottom side oil chamber of the boom cylinder 7 when the boom raising operation is performed.
- the boom cylinder 7 The hydraulic oil flowing out from the bottom side oil chamber can be merged with the first hydraulic oil.
- the flow control valve 173 is a valve that controls the direction and flow rate of the hydraulic oil flowing into and out of the bucket cylinder 9 and corresponds to the flow control valve 173 in FIG. 3 includes a check valve for regenerating hydraulic oil flowing out from the rod side oil chamber of the bucket cylinder 9 into the bottom side oil chamber.
- variable load check valves 50, 51A, 51B, 52A, 52B, 53 are respectively flow rate control valves 170, 171A, 171B, 172A, 172B, 173 and at least one of the first pump 14L and the second pump 14R. It is a 2-port 2-position valve that can be switched between communication and blocking. These six variable load check valves operate in conjunction with each other, thereby functioning as a merging switching unit and realizing the function of the merging valve 55 of FIG. Therefore, the junction valve 55 of FIG. 2 is omitted in the hydraulic circuit of FIG. For the same reason, the switching valve 91 of FIG. 2 is omitted.
- the unified bleed-off valves 56L and 56R are 2-port 2-position valves capable of controlling the discharge amount of the first hydraulic oil to the hydraulic oil tank T, and correspond to the unified bleed-off valves 56L and 56R in FIG.
- each of the six flow control valves in FIG. 3 is a 6-port 3-position spool valve, and unlike the flow control valve in FIG. 2, has a center bypass port. Therefore, the unified bleed-off valve 56L in FIG. 3 is disposed downstream of the flow control valve 171A, and the unified bleed-off valve 56R is disposed downstream of the flow control valve 171B.
- the switching valve 61A is a 2-port 2-position valve capable of switching whether or not to let the hydraulic oil discharged from the rod-side oil chamber of the arm cylinder 8 flow to the upstream side (supply side) of the pump / motor 14A. Specifically, the switching valve 61A communicates between the rod-side oil chamber of the arm cylinder 8 and the pump / motor 14A when in the first position, and shuts off the communication when in the second position.
- the switching valve 62A is a 3-port 3-position valve capable of switching whether or not to let the hydraulic oil discharged from the boom cylinder 7 flow upstream (supply side) of the pump / motor 14A. Specifically, the switching valve 62A communicates between the bottom side oil chamber of the boom cylinder 7 and the pump motor 14A when in the first position, and the rod side of the boom cylinder 7 when in the second position. The oil chamber and the pump / motor 14A are communicated with each other, and the communication between the oil chamber and the pump / motor 14A is blocked when the oil chamber is in the third position (neutral position).
- the switching valve 62B is a 2-port 2-position variable relief valve capable of switching whether or not to discharge the hydraulic oil discharged from the rod side oil chamber of the boom cylinder 7 to the hydraulic oil tank T. Specifically, the switching valve 62B communicates between the rod-side oil chamber of the boom cylinder 7 and the hydraulic oil tank T when in the first position, and blocks communication when in the second position. The switching valve 62B has a check valve that blocks the flow of hydraulic oil from the hydraulic oil tank T in the first position.
- the switching valve 62C is a 2-port 2-position variable relief valve capable of switching whether or not the hydraulic oil discharged from the bottom side oil chamber of the boom cylinder 7 is discharged to the hydraulic oil tank T. Specifically, the switching valve 62C communicates between the bottom side oil chamber of the boom cylinder 7 and the hydraulic oil tank T when in the first position, and shuts off the communication when in the second position. Note that the switching valve 62C has a check valve that blocks the flow of hydraulic oil from the hydraulic oil tank T at the first position.
- the switching valve 90 is a 3-port 2-position electromagnetic valve capable of switching the supply destination of the third hydraulic oil discharged from the pump / motor 14A, and corresponds to the switching valve 90 of FIG. Specifically, the switching valve 90 allows the third hydraulic oil to flow toward the control valve 17 when in the first position, and causes the third hydraulic oil to flow toward the switching valve 92 when in the second position.
- the switching valve 92 is a four-port, three-position electromagnetic valve that can switch the supply destination of the third hydraulic oil. Specifically, when the switching valve 92 is in the first position, the third hydraulic oil is directed to the replenishment mechanism of the turning hydraulic motor 21, and when it is in the second position, the third hydraulic oil is directed to the accumulator 80, When in the third position, the third hydraulic oil is directed to the hydraulic oil tank T. [Drilling operation] Next, the state of the hydraulic circuit in FIG. 2 when the excavation operation is performed will be described with reference to FIGS. 4 to 6 show the state of the hydraulic circuit in FIG. 2 when the excavation operation is performed.
- the thick black solid line in FIGS. 4 to 6 represents the flow of hydraulic oil flowing into the hydraulic actuator, and the larger the solid line, the greater the flow rate.
- the controller 30 determines the operation content of the operator with respect to the shovel based on the output of an operation detection unit such as an operation pressure sensor (not shown) that detects the pilot pressure generated by the operation device.
- the controller 30 also includes a discharge pressure sensor (not shown) that detects the discharge pressure of each of the first pump 14L, the second pump 14R, and the pump / motor 14A, and a load pressure that detects each pressure of the hydraulic actuator. Based on the output of a load detector such as a sensor (not shown), the operation state of the shovel is determined.
- the load pressure sensor includes a cylinder pressure sensor that detects respective pressures of the bottom side oil chamber and the rod side oil chamber of the boom cylinder 7, the arm cylinder 8, and the bucket cylinder 9. Further, the controller 30 detects the pressure of hydraulic oil accumulated in the accumulator 80 (hereinafter referred to as “accumulator pressure”) based on the output of an accumulator pressure sensor (not shown).
- the merging valve 55 in the second position is moved in the direction of the first position in accordance with the operation amount of the arm operation lever, as shown in FIG. Then, the first hydraulic oil and the second hydraulic oil are merged, and the first hydraulic oil and the second hydraulic oil are supplied to the flow rate control valve 171.
- the flow control valve 171 receives the pilot pressure corresponding to the operation amount of the arm operation lever, moves to the right position in FIG. 4, and causes the first hydraulic oil and the second hydraulic oil to flow into the arm cylinder 8.
- the controller 30 determines whether the excavation operation or the floor excavation operation is performed based on the output of the load pressure sensor.
- the floor excavation operation is an operation of leveling the ground with the bucket 6, for example, and the pressure in the bottom side oil chamber of the arm cylinder 8 is lower than that during the excavation operation.
- the controller 30 When it is determined that the excavation operation is performed, the controller 30 responds to the operation amounts of the boom operation lever and the bucket operation lever based on pump discharge amount control such as negative control control, positive control control, load sensing control, and horsepower control. A discharge amount command value for the second pump 14R is determined. Then, the controller 30 controls the corresponding regulator so that the discharge amount of the second pump 14R becomes the command value.
- pump discharge amount control such as negative control control, positive control control, load sensing control, and horsepower control.
- a discharge amount command value for the second pump 14R is determined. Then, the controller 30 controls the corresponding regulator so that the discharge amount of the second pump 14R becomes the command value.
- the controller 30 uses the pump discharge amount control described above to flow between the discharge amount calculation value and the discharge amount command value in consideration of the operation amount of the arm operation lever in addition to the operation amount of the boom operation lever and the bucket operation lever.
- the difference is calculated, and the hydraulic oil having a flow rate corresponding to the flow rate difference is discharged to the pump motor 14A.
- the arm 5 is operated with a full lever (for example, an operation amount of 80% or more when the neutral state of the lever is 0% and the maximum operation state is 100%) as in the excavation operation.
- the maximum discharge amount of the second pump 14R is shown in FIG.
- the controller 30 operates the pump / motor 14A as a hydraulic pump, controls the corresponding regulator, and the discharge amount of the pump / motor 14A is a flow rate corresponding to the flow rate difference. Control to be. Then, the controller 30 directs the third hydraulic oil toward the switching valve 91 with the switching valve 90 in the first position, and directs the third hydraulic oil toward the arm cylinder 8 with the switching valve 91 in the first position.
- the controller 30 controls the opening area of the junction valve 55 based on the above-described flow rate difference, the discharge pressure of the first pump 14L, the discharge pressure of the second pump 14R, and the like. 4 to 6, the controller 30 refers to a previously registered opening map, determines the opening area of the merging valve 55, and outputs a command corresponding to the opening area to the merging valve 55.
- the controller 30 may determine the opening area of the merging valve 55 using a predetermined function instead of the opening map.
- the controller 30 sets the merging valve 55 to the second position as shown in FIG. The merge of the first hydraulic oil and the second hydraulic oil is shut off.
- the controller 30 closes the merging valve 55 as quickly as possible as long as the excavator movement does not become unstable, as shown in FIG. This is to improve the operability of the boom 4 and the bucket 6 by allowing only the second hydraulic oil to flow into the boom cylinder 7 and the bucket cylinder 9.
- the maximum discharge amount of the pump / motor 14A is smaller than the maximum discharge amount of the second pump 14R. Therefore, when the above-described flow rate difference exceeds the maximum discharge amount of the pump / motor 14A, the controller 30 operates the pump / motor 14A functioning as a hydraulic pump and the first pump 14L with the maximum discharge amount, 2 The discharge amount of the pump 14R is increased. Then, the difference between the maximum discharge amount of the second pump 14R and the actually increased discharge amount is set to be equal to or less than the maximum discharge amount of the pump / motor 14A. This is to prevent the operating speed of the arm 5 from falling below the operating speed of the arm 5 when the first hydraulic oil and the second hydraulic oil are used.
- the controller 30 closes the merging valve 55 during the excavation operation (second state) as shown in FIG. Position). This is because the operating speed of the arm 5 when the first hydraulic oil and the third hydraulic oil are used does not fall below the operating speed of the arm 5 when the first hydraulic oil and the second hydraulic oil are used. In this case, the controller 30 always causes only the first hydraulic oil and the third hydraulic oil to flow into the arm cylinder 8 and allows only the second hydraulic oil to flow into the boom cylinder 7 and the bucket cylinder 9 during the excavation operation. Therefore, the hydraulic oil for moving the arm 5 and the hydraulic oil for moving the boom 4 and the bucket 6 can be completely separated, and the operability of each can be improved.
- FIG. 7 shows the state of the hydraulic circuit in FIG. 3 when excavation is performed.
- the black and gray thick solid lines in FIG. 7 represent the flow of hydraulic oil flowing into the hydraulic actuator, and the larger the solid line thickness, the greater the flow rate.
- the gray solid line in FIG. 7 additionally indicates that the flow of hydraulic oil can be reduced or eliminated.
- the controller 30 determines the operation content of the operator with respect to the shovel based on the output of the operation detection unit, and determines the operation state of the shovel based on the output of the load detection unit.
- the flow control valve 171A receives the pilot pressure corresponding to the operation amount of the arm operation lever and moves to the left position in FIG. 7, and the flow control valve 171B corresponds to the operation amount of the arm operation lever. Under the pilot pressure, it moves to the right position in FIG.
- the controller 30 determines that the arm 5 has been operated, the controller 30 sets the variable load check valve 51A to the first position so that the first hydraulic oil reaches the flow control valve 171A through the variable load check valve 51A. Further, the variable load check valve 51B is set to the first position so that the second hydraulic oil reaches the flow control valve 171B through the variable load check valve 51B. The first hydraulic oil that has passed through the flow control valve 171A merges with the second hydraulic oil that has passed through the flow control valve 171B, and flows into the bottom side oil chamber of the arm cylinder 8.
- the controller 30 determines whether the excavation operation or the floor excavation operation is performed based on the output of the load pressure sensor. When it is determined that the excavation operation is performed, the controller 30 determines a discharge amount command value of the second pump 14R corresponding to the operation amounts of the boom operation lever and the bucket operation lever. Then, the controller 30 controls the corresponding regulator so that the discharge amount of the second pump 14R becomes the command value.
- the flow control valve 172A receives the pilot pressure corresponding to the operation amount of the boom operation lever and moves to the left position in FIG. Further, the flow control valve 173 receives the pilot pressure corresponding to the operation amount of the bucket operation lever and moves to the right position in FIG. Then, the controller 30 sets the variable load check valve 52A to the first position so that the second hydraulic oil reaches the flow control valve 172A through the variable load check valve 52A. Further, the variable load check valve 53 is set to the first position so that the second hydraulic oil reaches the flow control valve 173 through the variable load check valve 53. The second hydraulic oil that has passed through the flow control valve 172A flows into the bottom side oil chamber of the boom cylinder 7, and the second hydraulic oil that has passed through the flow control valve 173 flows into the bottom side oil chamber of the bucket cylinder 9. To do.
- the controller 30 calculates the flow rate difference between the maximum discharge amount of the second pump 14R and the discharge amount command value, and causes the pump motor 14A to discharge the hydraulic oil having a flow rate corresponding to the flow rate difference. Specifically, as shown in FIG. 7, the controller 30 operates the pump / motor 14A as a hydraulic pump, controls the corresponding regulator, and sets the discharge amount of the pump / motor 14A to a flow rate corresponding to the flow rate difference. Control to be. Then, the controller 30 sets the switching valve 90 to the first position and directs the third hydraulic oil to the control valve 17.
- the controller 30 controls the opening area of the variable load check valve 51B based on the above-described flow rate difference, the discharge pressure of the first pump 14L, the discharge pressure of the second pump 14R, and the like.
- the controller 30 determines the opening area of the variable load check valve 51B with reference to the opening map registered in advance, and outputs a command corresponding to the opening area to the variable load check valve 51B.
- the 2nd hydraulic fluid which flows into the bottom side oil chamber of the arm cylinder 8 reduces or lose
- the gray solid line in FIG. 7 indicates that the second hydraulic fluid flowing into the bottom side oil chamber of the arm cylinder 8 decreases or disappears as the flow rate of the third hydraulic fluid discharged from the pump / motor 14A increases. Represents what to do.
- the controller 30 operates the pump motor 14A as a hydraulic pump when excavation operations including raising the boom, closing the arm, and closing the bucket are performed. Then, the third hydraulic oil discharged from the pump / motor 14A is caused to flow into the hydraulic actuator (arm cylinder 8) having a high load pressure.
- the hydraulic actuator having a high load pressure can be operated at a desired speed using the first hydraulic oil and the third hydraulic oil, the merging valve 55 is closed (or the merging switching unit is functioned). The merge of the first hydraulic oil and the second hydraulic oil is blocked.
- the shovel according to the embodiment of the present invention operates the hydraulic actuator (arm cylinder 8) having a high load pressure with the first hydraulic oil, and the load hydraulic pressure with the second hydraulic oil having a lower pressure than the first hydraulic oil.
- Low hydraulic actuators boost cylinder 7 and bucket cylinder 9) can be operated. Specifically, it is not necessary to operate a hydraulic actuator having a low load pressure with the second hydraulic oil pressurized to the same pressure as the first hydraulic oil for merging with the first hydraulic oil. That is, it is not necessary to reduce the flow rate of the second hydraulic oil with a throttle so that the hydraulic actuator with a low load pressure is operated at a desired speed using the pressurized second hydraulic oil. As a result, it is possible to reduce or prevent pressure loss from occurring in the throttle, and to reduce or prevent energy loss.
- the controller 30 may increase the discharge amount of the first pump 14L by individual flow control instead of causing the pump / motor 14A to discharge the third hydraulic oil. Specifically, the flow rate of the second pump 14R is reduced after closing the merging valve 55 (or causing the merging switching unit to function) and blocking the merging of the first hydraulic oil and the second hydraulic oil. The maximum discharge amount (maximum swash plate tilt angle) of the first pump 14L may be increased. [Excavation with engine assist by back pressure regeneration] Next, the state of the hydraulic circuit in FIG. 2 when the excavation operation with the assist of the engine 11 by back pressure regeneration is performed will be described with reference to FIG. FIG. 8 shows a state of the hydraulic circuit of FIG.
- the black thick solid line in FIG. 8 represents the flow of hydraulic oil flowing into the hydraulic actuator, and the larger the solid line, the greater the flow rate.
- the black and gray thick dotted lines in FIG. 8 represent the flow of hydraulic oil flowing out from the hydraulic actuator.
- Back pressure regeneration is a process executed when a plurality of hydraulic actuators operate simultaneously and when the load pressures of the plurality of hydraulic actuators are different.
- the load pressure of the arm cylinder 8 (the pressure of the bottom oil chamber of the arm cylinder 8) is the load pressure of the boom cylinder 7 (the bottom of the boom cylinder 7). Higher than the pressure in the side oil chamber). This is because the bucket 6 is grounded during excavation, and the weights of the boom 4, the arm 5, and the bucket 6 are supported by the ground, and the excavation reaction force against the excavation operation (closing operation) of the arm 5 is caused by the boom 4.
- the controller 30 increases the system pressure of the hydraulic circuit (the discharge pressures of the first pump 14L and the second pump 14R) to cope with the relatively high load pressure of the arm cylinder 8.
- the controller 30 controls the flow rate of the hydraulic oil flowing into the bottom side oil chamber of the boom cylinder 7 in order to control the operating speed of the boom cylinder 7 that operates at a load pressure lower than the system pressure.
- a pressure loss energy loss
- the controller 30 realizes control of the operating speed of the boom cylinder 7 while increasing the pressure (back pressure) of the rod side oil chamber of the boom cylinder 7 while avoiding the occurrence of pressure loss in the flow control valve 172. To do. Further, in order to increase the pressure (back pressure) of the rod side oil chamber of the boom cylinder 7, the controller 30 supplies hydraulic oil flowing out from the rod side oil chamber to the pump motor 14A, and the pump motor 14A is hydraulically ( (Regenerative) function as a motor. Note that, when executing the back pressure regeneration, the controller 30 largely moves the flow control valve 172 to the right position in FIG. 8 regardless of the operation amount of the boom operation lever. This is because the opening area of the flow control valve 172 is maximized to minimize pressure loss. For example, the controller 30 assists the amount of movement of the flow control valve 172 by increasing the pilot pressure acting on the pilot port of the flow control valve 172 using a pressure reducing valve (not shown).
- the controller 30 determines the operation content of the operator for the shovel based on the output of the operation detection unit, and determines the operation state of the shovel based on the output of the load detection unit.
- the controller 30 determines that the pressure (load pressure) in the bottom side oil chamber of the boom cylinder 7 is the minimum, the controller 30 sets the switching valve 62 to the second position, as shown by the black thick dotted line, on the rod side of the boom cylinder 7.
- the hydraulic oil flowing out from the oil chamber is directed to the supply side of the pump / motor 14A.
- the controller 30 increases the pilot pressure acting on the pilot port on the right side of the flow control valve 172 by the pressure reducing valve regardless of the operation amount of the boom operation lever so that the flow control valve 172 is opened to the maximum, and the flow control valve Reduce pressure loss at 172.
- the controller 30 directs the hydraulic oil flowing out from the rod side oil chamber of the bucket cylinder 9 to the hydraulic oil tank T with the switching valve 63 in the first position.
- the controller 30 controls the amount of hydraulic oil absorbed (push-out volume) by the pump motor 14A as a hydraulic motor so that the operation speed of the boom cylinder 7 becomes a speed corresponding to the operation amount of the boom operation lever.
- the controller 30 controls the displacement volume by adjusting the swash plate tilt angle of the pump motor 14A with a regulator. For example, when the pump / motor 14A is rotated at a constant speed, the controller 30 can reduce the flow rate of hydraulic fluid flowing out from the rod side oil chamber of the boom cylinder 7 as the push-out volume is reduced. The pressure (back pressure) of the oil chamber can be increased. Using this relationship, the controller 30 can control the back pressure so that the back pressure becomes a pressure commensurate with a desired load pressure of the boom cylinder 7 (pressure in the bottom side oil chamber).
- the hydraulic oil flowing out from the rod side oil chamber of the boom cylinder 7 generates rotational torque by rotating the pump / motor 14A.
- This rotational torque is transmitted to the rotating shaft of the engine 11 via the transmission 13, and can be used as the driving force of the first pump 14L and the second pump 14R. That is, the rotational torque generated by the pump motor 14A is used to assist the rotation of the engine 11, and has an effect of suppressing the load on the engine 11 and thus the fuel injection amount.
- 8 indicates that the rotational torque is transmitted to the rotating shaft of the engine 11 via the transmission 13 and can be used as the driving force of the first pump 14L and the second pump 14R. Further, for the output control of the engine 11, it is desirable to use one that applies transient load control (torque base control).
- the controller 30 starts from the rod side oil chamber of the boom cylinder 7. At least a part of the flowing hydraulic oil is directed to the hydraulic oil tank T. Specifically, the controller 30 sets the switching valve 62 to an intermediate position between the first position and the second position, or completely switches the switching valve 62 to the first position, so that the rod side oil of the boom cylinder 7 is changed. At least part of the hydraulic oil flowing out of the chamber is discharged to the hydraulic oil tank T.
- the pressure (load pressure) in the bottom side oil chamber of the boom cylinder 7 is determined to be minimum.
- the pressure (load pressure) in the bottom side oil chamber of the bucket cylinder 9 is determined to be minimum.
- the controller 30 sets the switching valve 63 to the second position, and the controller 30 flows out from the rod side oil chamber of the bucket cylinder 9. Direct the oil to the supply side of the pump motor 14A.
- the controller 30 increases the pilot pressure acting on the pilot port on the right side of the flow control valve 173 by the pressure reducing valve regardless of the operation amount of the bucket operation lever, thereby setting the flow control valve 173 to the maximum opening. Reduce pressure loss at 173. Further, the controller 30 directs the hydraulic oil flowing out from the rod-side oil chambers of the arm cylinder 8 and the boom cylinder 7 to the hydraulic oil tank T with the switching valve 61 and the switching valve 62 set to the first positions, respectively. Further, the operation speed of the bucket cylinder 9 is controlled in the same manner as described above.
- the controller 30 determines that the pressure (load pressure) in the bottom side oil chamber of the arm cylinder 8 is the minimum, the controller 30 sets the switching valve 61 to the second position and pumps the hydraulic oil flowing out from the rod side oil chamber of the arm cylinder 8. ⁇ Direct toward the supply side of the motor 14A. Further, the controller 30 increases the pilot pressure acting on the pilot port on the right side of the flow control valve 171 by the pressure reducing valve regardless of the operation amount of the arm operation lever so that the flow control valve 171 is opened to the maximum. Reduce pressure loss at 171. Further, the controller 30 directs the hydraulic oil flowing out from the rod-side oil chambers of the boom cylinder 7 and the bucket cylinder 9 to the hydraulic oil tank T with the switching valve 62 and the switching valve 63 being in the first positions. Further, the operating speed of the arm cylinder 8 is also controlled in the same manner as described above.
- FIG. 9 shows the state of the hydraulic circuit of FIG. 3 when excavation operation accompanied by assist of the engine 11 by back pressure regeneration is performed.
- the black thick solid line of FIG. 9 represents the flow of the hydraulic fluid which flows into a hydraulic actuator, and represents that the flow volume is so large that the thickness of a solid line is thick.
- the black thick dotted line of FIG. 9 represents the flow of the hydraulic fluid which flows out from a hydraulic actuator.
- the controller 30 determines that the combined excavation operation by the boom raising operation, the arm closing operation, and the bucket closing operation is performed, the controller 30 sets the switching valve 62A to the second position, as indicated by a black thick dotted line.
- the hydraulic oil flowing out from the rod side oil chamber of the boom cylinder 7 is directed to the supply side of the pump / motor 14A.
- the controller 30 increases the pilot pressure acting on the pilot port on the left side of the flow control valve 172A by the pressure reducing valve regardless of the operation amount of the boom operation lever so that the flow control valve 172A is opened to the maximum, and the flow control valve Reduce pressure loss at 172A.
- the controller 30 causes the hydraulic oil tank T to discharge the hydraulic oil flowing out from the rod side oil chamber of the bucket cylinder 9 through the flow rate control valve 173.
- the controller 30 controls the amount of hydraulic oil absorbed (push-out volume) by the pump motor 14A as a hydraulic motor so that the operation speed of the boom cylinder 7 becomes a speed corresponding to the operation amount of the boom operation lever.
- the controller 30 may control the rod side oil chamber of the boom cylinder 7. At least a part of the hydraulic oil flowing out of the hydraulic oil is discharged to the hydraulic oil tank T. Specifically, the controller 30 sets the switching valve 62B to an intermediate position between the first position and the second position, or completely switches the switching valve 62B to the first position, so that the rod side oil of the boom cylinder 7 is changed. At least part of the hydraulic oil flowing out of the chamber is discharged to the hydraulic oil tank T.
- the controller 30 may block the communication between the rod-side oil chamber of the boom cylinder 7 and the pump / motor 14A by setting the switching valve 62A to the third position (neutral position) as necessary. 9 represents that the hydraulic oil flowing out from the rod side oil chamber of the boom cylinder 7 is discharged to the hydraulic oil tank T when the switching valve 62B is switched to the first position. .
- controller 30 additionally realizes the following effects in addition to the effects described in [Excavation Operation].
- the controller 30 when a boom raising operation is performed, the controller 30 generates a back pressure by rotating the pump motor 14A with hydraulic oil flowing out from the rod side oil chamber of the boom cylinder 7. Therefore, the excavator according to the embodiment of the present invention can use the rotational torque obtained when generating the back pressure for assisting the engine 11. As a result, it is possible to realize energy saving by reducing the engine output by the amount of the assist output, speeding up the operation and shortening the cycle time by adding the assist output to the engine output and increasing the output of the hydraulic pump. 9 indicates that the rotational torque is transmitted to the rotating shaft of the engine 11 via the transmission 13 and can be used as the driving force of the first pump 14L and the second pump 14R.
- FIG. 10 shows the state of the hydraulic circuit in FIG. 2 when excavation operation with accumulator assistance is performed. Also, the black thick solid line in FIG. 10 represents the flow of hydraulic oil flowing into the hydraulic actuator, and the larger the solid line, the greater the flow rate.
- the accumulator assist is a process of assisting the movement of the hydraulic actuator using the hydraulic oil accumulated in the accumulator 80, and includes a case where the hydraulic actuator is operated using only the hydraulic oil accumulated in the accumulator 80.
- the merging valve 55 at the second position is moved in the direction of the first position in accordance with the amount of operation of the arm operation lever, as shown in FIG. Move. Then, the first hydraulic oil and the second hydraulic oil are merged, and the first hydraulic oil and the second hydraulic oil are supplied to the flow rate control valve 171.
- the flow control valve 171 receives the pilot pressure corresponding to the operation amount of the arm operation lever, moves to the right position in FIG. 10, and causes the first hydraulic oil and the second hydraulic oil to flow into the arm cylinder 8.
- the controller 30 determines whether the excavation operation or the floor excavation operation is performed based on the output of the load pressure sensor.
- the controller 30 When it is determined that the excavation operation is performed, the controller 30 responds to the operation amounts of the boom operation lever and the bucket operation lever based on pump discharge amount control such as negative control control, positive control control, load sensing control, and horsepower control. A discharge amount command value for the second pump 14R is determined. Then, the controller 30 controls the corresponding regulator so that the discharge amount of the second pump 14R becomes the command value.
- pump discharge amount control such as negative control control, positive control control, load sensing control, and horsepower control.
- a discharge amount command value for the second pump 14R is determined. Then, the controller 30 controls the corresponding regulator so that the discharge amount of the second pump 14R becomes the command value.
- the controller 30 calculates the flow rate difference between the maximum discharge amount of the second pump 14R and the discharge amount command value, and causes the pump motor 14A to discharge the hydraulic oil having a flow rate corresponding to the flow rate difference. Specifically, the controller 30 places the switching valve 82 in the first position to allow communication between the accumulator 80 and the pump / motor 14A, and discharges hydraulic oil accumulated in the accumulator 80 toward the pump / motor 14A. .
- the controller 30 operates the pump / motor 14A as a hydraulic pump to reduce the pressure of the supply side hydraulic oil (accumulator pressure).
- the pressure is increased to the load pressure, and the corresponding regulator is controlled so that the discharge amount of the pump motor 14A becomes a flow rate corresponding to the flow rate difference.
- the pump motor 14A that operates as a hydraulic pump can discharge the hydraulic oil with a small pump load. As a result, energy saving can be realized by reducing the load on the engine 11.
- the controller 30 operates the pump motor 14A as a hydraulic motor to reduce the pressure of the supply side hydraulic oil (accumulator pressure).
- the pressure is reduced to the load pressure, and the corresponding regulator is controlled so that the discharge amount of the pump motor 14A becomes a flow rate corresponding to the flow rate difference.
- the pump motor 14A that operates as a hydraulic motor can assist the engine 11 and bear a part of the driving force for rotating the first pump 14L.
- the controller 30 can increase the absorption horsepower of the first pump 14L, or can suppress the load of the engine 11 and the fuel injection amount when the absorption horsepower is not increased.
- the black dashed-dotted arrow in FIG. 10 indicates that the rotational torque generated by the pump motor 14A operating as a hydraulic motor is transmitted to the rotating shaft of the engine 11 via the transmission 13, and the first pump 14L and the second pump It represents that it can be used as the driving force of the pump 14R.
- a gray dot-dash line arrow indicates that the pump motor 14 ⁇ / b> A operating as a hydraulic pump uses a part of the output of the engine 11.
- the controller 30 directs the third hydraulic oil toward the switching valve 91 with the switching valve 90 in the first position, and directs the third hydraulic oil toward the arm cylinder 8 with the switching valve 91 in the first position.
- the controller 30 controls the opening area of the junction valve 55 based on the above-described flow rate difference, the discharge pressure of the first pump 14L, the discharge pressure of the second pump 14R, and the like.
- the controller 30 determines the opening area of the merging valve 55 with reference to a previously registered opening map, and outputs a command corresponding to the opening area to the merging valve 55.
- the controller 30 may determine the opening area of the merging valve 55 using a predetermined function instead of the opening map.
- the controller 30 closes the merging valve 55 as quickly as possible unless the excavator movement becomes unstable. This is to improve the operability of the boom 4 and the bucket 6 by allowing only the second hydraulic oil to flow into the boom cylinder 7 and the bucket cylinder 9.
- the maximum discharge amount of the pump / motor 14A is smaller than the maximum discharge amount of the second pump 14R. Therefore, when the above-described flow rate difference exceeds the maximum discharge amount of the pump / motor 14A, the controller 30 operates the pump / motor 14A functioning as a hydraulic pump and the first pump 14L with the maximum discharge amount, 2 The discharge amount of the pump 14R is increased.
- the difference between the maximum discharge amount of the second pump 14R and the actually increased discharge amount is set to be equal to or less than the maximum discharge amount of the pump motor 14A, and the operating speed of the arm 5 is the first hydraulic oil and the second operation. This is to prevent the operating speed of the arm 5 from being lowered when oil is used.
- the controller 30 can maintain the junction valve 55 in the closed state (second position) during the excavation operation. This is because the operating speed of the arm 5 when the first hydraulic oil and the third hydraulic oil are used does not fall below the operating speed of the arm 5 when the first hydraulic oil and the second hydraulic oil are used. In this case, the controller 30 always causes only the first hydraulic oil and the third hydraulic oil to flow into the arm cylinder 8 and allows only the second hydraulic oil to flow into the boom cylinder 7 and the bucket cylinder 9 during the excavation operation. Therefore, the hydraulic oil for moving the arm 5 and the hydraulic oil for moving the boom 4 and the bucket 6 can be completely separated, and the operability of each can be improved.
- FIG. 11 shows the state of the hydraulic circuit in FIG. 3 when excavation operation with accumulator assistance is performed.
- black and gray thick solid lines in FIG. 11 represent the flow of hydraulic oil flowing into the hydraulic actuator, and the larger the solid line thickness, the greater the flow rate.
- the gray solid line in FIG. 11 additionally indicates that the flow of hydraulic oil can be reduced or eliminated.
- the controller 30 determines the operation content of the operator for the shovel based on the output of the operation detection unit, and determines the operation state of the shovel based on the output of the load detection unit.
- the flow control valve 171A receives the pilot pressure corresponding to the operation amount of the arm operation lever and moves to the left position in FIG. 11, and the flow control valve 171B corresponds to the operation amount of the arm operation lever. It receives the pilot pressure and moves to the right position in FIG.
- the controller 30 determines that the arm 5 has been operated, the controller 30 sets the variable load check valve 51A to the first position so that the first hydraulic oil reaches the flow control valve 171A through the variable load check valve 51A. Further, the variable load check valve 51B is set to the first position so that the second hydraulic oil reaches the flow control valve 171B through the variable load check valve 51B. The first hydraulic oil that has passed through the flow control valve 171A merges with the second hydraulic oil that has passed through the flow control valve 171B, and flows into the bottom side oil chamber of the arm cylinder 8.
- the controller 30 determines whether the excavation operation or the floor excavation operation is performed based on the output of the load pressure sensor. When it is determined that the excavation operation is performed, the controller 30 determines a discharge amount command value of the second pump 14R corresponding to the operation amounts of the boom operation lever and the bucket operation lever. Then, the controller 30 controls the corresponding regulator so that the discharge amount of the second pump 14R becomes the command value.
- the flow control valve 172A receives the pilot pressure corresponding to the operation amount of the boom operation lever and moves to the left position in FIG. Further, the flow control valve 173 receives a pilot pressure corresponding to the operation amount of the bucket operation lever and moves to the right position in FIG. Then, the controller 30 sets the variable load check valve 52A to the first position so that the second hydraulic oil reaches the flow control valve 172A through the variable load check valve 52A. Further, the variable load check valve 53 is set to the first position so that the second hydraulic oil reaches the flow control valve 173 through the variable load check valve 53. The second hydraulic oil that has passed through the flow control valve 172A flows into the bottom side oil chamber of the boom cylinder 7, and the second hydraulic oil that has passed through the flow control valve 173 flows into the bottom side oil chamber of the bucket cylinder 9. To do.
- the controller 30 calculates the flow rate difference between the maximum discharge amount of the second pump 14R and the discharge amount command value, and causes the pump motor 14A to discharge the hydraulic oil having a flow rate corresponding to the flow rate difference. Specifically, the controller 30 places the switching valve 82 in the first position to allow communication between the accumulator 80 and the pump / motor 14A, and discharges hydraulic oil accumulated in the accumulator 80 toward the pump / motor 14A. .
- the controller 30 operates the pump / motor 14A as a hydraulic pump to reduce the pressure of the supply side hydraulic oil (accumulator pressure). Increase to load pressure. Then, the corresponding regulator is controlled so that the discharge amount of the pump motor 14A becomes a flow rate corresponding to the flow rate difference. Compared with the case where the hydraulic oil is sucked from the hydraulic oil tank T, the pump motor 14A that operates as a hydraulic pump can discharge the hydraulic oil with a small pump load. As a result, energy saving can be realized by reducing the load on the engine 11.
- the controller 30 operates the pump motor 14A as a hydraulic motor to reduce the pressure of the supply side hydraulic oil (accumulator pressure). Reduce to load pressure. Then, the corresponding regulator is controlled so that the discharge amount of the pump motor 14A becomes a flow rate corresponding to the flow rate difference.
- the pump motor 14A that operates as a hydraulic motor can assist the engine 11 and bear a part of the driving force for rotating the first pump 14L. As a result, the controller 30 can increase the absorption horsepower of the first pump 14L, or can suppress the load of the engine 11 and the fuel injection amount when the absorption horsepower is not increased.
- the controller 30 controls the opening area of the variable load check valve 51B based on the above-described flow rate difference, the discharge pressure of the first pump 14L, the discharge pressure of the second pump 14R, and the like.
- the controller 30 determines the opening area of the variable load check valve 51B with reference to the opening map registered in advance, and outputs a command corresponding to the opening area to the variable load check valve 51B.
- the 2nd hydraulic fluid which flows into the bottom side oil chamber of the arm cylinder 8 reduces or lose
- the gray solid line in FIG. 11 indicates that the second hydraulic oil flowing into the bottom side oil chamber of the arm cylinder 8 decreases or disappears as the flow rate of the third hydraulic oil discharged from the pump / motor 14A increases. Represents what to do.
- the controller 30 supplies hydraulic oil accumulated in the accumulator 80 to the pump motor 14A when an excavation operation is performed. Then, it is determined whether the pump / motor 14A is operated as a hydraulic pump or a hydraulic motor, and the displacement volume of the pump / motor 14A is controlled by controlling the displacement volume of the pump / motor 14A. Change the discharge pressure. Therefore, regardless of the magnitude relationship between the load pressure of the hydraulic actuator to which the third hydraulic oil is supplied and the accumulator pressure, the third hydraulic oil can flow into the hydraulic actuator. As a result, the flow rate balance between the first hydraulic oil and the third hydraulic oil can be flexibly controlled, and the hydraulic energy accumulated in the accumulator 80 can be efficiently reused.
- FIG. 12 shows the state of the hydraulic circuit in FIG. 2 when excavation operation with assist of the arm cylinder 8 by back pressure regeneration is performed.
- the black thick solid line of FIG. 12 represents the flow of the hydraulic fluid which flows into a hydraulic actuator, and represents that the flow volume is so large that the thickness of a solid line is thick.
- the black and gray thick dotted lines in FIG. 12 represent the flow of hydraulic oil flowing out from the hydraulic actuator.
- controller 30 increases the pilot pressure acting on the pilot port on the right side of the flow control valve 172 by the pressure reducing valve regardless of the operation amount of the boom operation lever so that the flow control valve 172 is opened to the maximum, and the flow control valve Reduce pressure loss at 172. Further, the controller 30 directs the hydraulic oil flowing out from the rod side oil chamber of the bucket cylinder 9 to the hydraulic oil tank T with the switching valve 63 in the first position.
- the pump motor 14A functioning as a hydraulic pump sucks in the hydraulic oil flowing out from the rod side oil chamber of the boom cylinder 7 so that the hydraulic oil can be operated with a smaller pump load than when the hydraulic oil is sucked in from the hydraulic oil tank T. Can be discharged. As a result, energy saving can be realized by reducing the load on the engine 11.
- the controller 30 starts from the rod side oil chamber of the boom cylinder 7. At least a part of the flowing hydraulic oil is directed to the hydraulic oil tank T. Specifically, the controller 30 sets the switching valve 62 to an intermediate position between the first position and the second position, or completely switches the switching valve 62 to the first position, so that the rod side oil of the boom cylinder 7 is changed. At least part of the hydraulic oil flowing out of the chamber is discharged to the hydraulic oil tank T.
- the controller 30 maintains the merging valve 55 in the second position so as not to merge the first hydraulic oil and the second hydraulic oil, and the movements of the arm cylinder 8 and the bucket cylinder 9 are operated separately. Be controlled independently with oil.
- the flow rate of the hydraulic oil flowing into the rod side oil chamber of the arm cylinder 8 can be directly controlled by the first pump 14L, and therefore does not need to be limited by the restriction in the flow rate control valve 171.
- the flow rate of the hydraulic oil flowing into the rod side oil chamber of the bucket cylinder 9 can be directly controlled by the second pump 14R, and therefore does not need to be limited by the restriction in the flow rate control valve 173.
- the controller 30 sets the switching valve 62A to the first position, and directs hydraulic oil flowing out from the bottom side oil chamber of the boom cylinder 7 toward the supply side of the pump / motor 14A. Further, the controller 30 reduces the pilot pressure acting on the pilot port on the right side of the flow control valve 172A by the pressure reducing valve regardless of the operation amount of the boom operation lever so that the flow control valve 172A is in the neutral position, and the boom cylinder 7 The flow of hydraulic oil from the bottom side oil chamber to the hydraulic oil tank T through the flow rate control valve 172A is cut off. In addition, the controller 30 places the variable load check valve 52A in the second position, and blocks communication between the second pump 14R and the flow control valve 172A.
- the controller 30 determines that the arm opening operation has been performed, the controller 30 sets the variable load check valve 51A to the first position, and communicates between the first pump 14L and the flow control valve 171A. Further, when the controller 30 determines that the bucket opening operation has been performed, the controller 30 sets the variable load check valve 53 to the first position, and communicates between the second pump 14R and the flow control valve 173.
- the controller 30 starts from the bottom side oil chamber of the boom cylinder 7. At least a part of the flowing hydraulic oil is directed to the hydraulic oil tank T. Specifically, the controller 30 sets the switching valve 62C to an intermediate position between the first position and the second position, or completely switches the switching valve 62C to the first position, so that the bottom side oil of the boom cylinder 7 is changed. At least part of the hydraulic oil flowing out of the chamber is discharged to the hydraulic oil tank T.
- controller 30 since the controller 30 generates the back pressure by rotating the pump / motor 14A, it is not necessary to restrict the flow of the hydraulic oil flowing out from the bottom side oil chamber of the boom cylinder 7 with the restriction, and the pressure loss is reduced with the restriction. It is not generated. Therefore, it can suppress or prevent that the positional energy of the boom 4 is consumed as heat energy, and can suppress or prevent energy loss.
- the flow control valve 172 receives the pilot pressure corresponding to the operation amount of the boom operation lever and moves to the left position in FIG.
- the flow control valve 171 receives a pilot pressure corresponding to the operation amount of the arm operation lever and moves to the left position in FIG. 16
- the flow control valve 173. 16 receives a pilot pressure corresponding to the operation amount of the bucket operation lever and moves to the left position in FIG.
- the controller 30 operates the pump motor 14A as a hydraulic motor to supply the hydraulic fluid on the supply side.
- the pressure pressure in the rod side oil chamber of the boom cylinder 7 is reduced to the load pressure.
- the controller 30 controls the displacement volume by adjusting the tilt angle of the swash plate of the pump motor 14A with a corresponding regulator so that the pressure in the bottom oil chamber of the boom cylinder 7 does not change suddenly.
- the controller 30 can reduce the flow rate of hydraulic fluid flowing out from the bottom side oil chamber of the boom cylinder 7 as the push-out volume is reduced.
- the pressure (back pressure) of the oil chamber can be increased.
- the controller 30 can set the pressure of the hydraulic fluid on the supply side of the pump / motor 14A so that the pressure of the hydraulic fluid on the discharge side of the pump / motor 14A becomes the load pressure of the arm cylinder 8.
- the pump motor 14 ⁇ / b> A can be controlled so as to have a back pressure of ⁇ .
- the controller 30 does not adjust the swash plate tilt angle and the rotational speed of the pump / motor 14A, but the pressure of the hydraulic oil on the discharge side of the pump / motor 14A is changed to the load of the arm cylinder 8 by the diversion control using the throttle
- the pressure of the hydraulic oil on the supply side of the pump / motor 14A may be a desired back pressure.
- the swash plate tilt angle of the pump motor 14A may be fixed.
- the controller 30 does not adjust the swash plate tilt angle and rotational speed of the pump motor 14A, but instead controls the discharge side and the supply side of the pump motor 14A by diversion control using a throttle.
- the pressure of each hydraulic oil may be a desired pressure.
- the controller 30 maintains the merging valve 55 in the second position so as not to merge the first hydraulic oil and the second hydraulic oil, and the movements of the arm cylinder 8 and the bucket cylinder 9 are operated separately. Be controlled independently with oil.
- the flow rate of the hydraulic oil flowing into the rod side oil chamber of the arm cylinder 8 can be directly controlled by the first pump 14L, and therefore does not need to be limited by the restriction in the flow rate control valve 171.
- the flow rate of the hydraulic oil flowing into the rod side oil chamber of the bucket cylinder 9 can be directly controlled by the second pump 14R, and therefore does not need to be limited by the restriction in the flow rate control valve 173.
- the controller 30 increases the pilot pressure acting on the pilot port on the left side of the flow control valves 171 and 173 by the pressure reducing valve, thereby controlling the flow control valves 171 and 173. May be the maximum opening, and the pressure loss at the flow control valves 171 and 173 may be reduced.
- FIG. 17 shows the state of the hydraulic circuit of FIG. 3 when a soil removal operation accompanied by the assist of the arm cylinder 8 by back pressure regeneration is performed.
- the black thick solid line of FIG. 17 represents the flow of the hydraulic fluid which flows into a hydraulic actuator, and represents that the flow volume is so large that the thickness of a solid line is thick.
- the black and gray thick dotted lines in FIG. 17 represent the flow of hydraulic oil flowing out from the hydraulic actuator.
- the flow control valve 171A receives the pilot pressure corresponding to the operation amount of the arm operation lever and moves to the right position in FIG.
- the flow control valve 173 receives the pilot pressure corresponding to the operation amount of the bucket operation lever and moves to the left position in FIG.
- the controller 30 determines that the arm opening operation has been performed, the controller 30 sets the variable load check valve 51A to the first position, and communicates between the first pump 14L and the flow control valve 171A. Further, when the controller 30 determines that the bucket opening operation has been performed, the controller 30 sets the variable load check valve 53 to the first position, and communicates between the second pump 14R and the flow control valve 173.
- the controller 30 operates the pump motor 14A as a hydraulic motor to supply the hydraulic fluid on the supply side.
- the pressure pressure in the rod side oil chamber of the boom cylinder 7 is reduced to the load pressure.
- the controller 30 controls the displacement volume by adjusting the tilt angle of the swash plate of the pump motor 14A with a corresponding regulator so that the pressure in the bottom oil chamber of the boom cylinder 7 does not change suddenly.
- the controller 30 can reduce the flow rate of hydraulic fluid flowing out from the bottom side oil chamber of the boom cylinder 7 as the push-out volume is reduced.
- the pressure (back pressure) of the oil chamber can be increased.
- the controller 30 can set the pressure of the hydraulic fluid on the supply side of the pump / motor 14A so that the pressure of the hydraulic fluid on the discharge side of the pump / motor 14A becomes the load pressure of the arm cylinder 8.
- the pump motor 14 ⁇ / b> A can be controlled so that the back pressure becomes equal to the above.
- the pump motor 14A that operates as a hydraulic pump can discharge hydraulic oil with a smaller pump load than when hydraulic oil is sucked from the hydraulic oil tank T. As a result, energy saving can be realized by reducing the load on the engine 11. Further, the controller 30 reduces the discharge amount of the first hydraulic oil discharged by the first pump 14L by the discharge amount of the third hydraulic oil discharged by the pump / motor 14A. As a result, energy saving can be realized by reducing the load on the engine 11 without changing the flow rate of the hydraulic oil flowing into the rod side oil chamber of the arm cylinder 8.
- the pump motor 14A operating as a hydraulic motor can assist the engine 11 and bear a part of the driving force for rotating the first pump 14L.
- the controller 30 can increase the absorption horsepower of the first pump 14L, or can suppress the load of the engine 11 and the fuel injection amount when the absorption horsepower is not increased.
- 17 indicates that the pump / motor 14A operating as a hydraulic pump uses a part of the output of the engine 11. 17 indicates that the pump motor 14A operating as a hydraulic motor assists the engine 11 and bears a part of the driving force of the first pump 14L.
- the controller 30 starts from the bottom side oil chamber of the boom cylinder 7. At least a part of the flowing hydraulic oil is directed to the hydraulic oil tank T. Specifically, the controller 30 sets the switching valve 62C to an intermediate position between the first position and the second position, or completely switches the switching valve 62C to the first position, so that the bottom side oil of the boom cylinder 7 is changed. At least part of the hydraulic oil flowing out of the chamber is discharged to the hydraulic oil tank T.
- the gray thick dotted line in FIG. 17 indicates that the hydraulic oil flowing out from the bottom side oil chamber of the boom cylinder 7 is discharged to the hydraulic oil tank T when the switching valve 62C is moved in the direction of the first position. And when the flow control valve 172B is moved to the left position, the hydraulic oil flowing out from the bottom side oil chamber of the boom cylinder 7 joins the first hydraulic oil at the flow control valve 172B.
- FIG. 18 shows the state of the hydraulic circuit in FIG. 2 when a soil removal operation involving accumulator pressure accumulation by back pressure regeneration is performed.
- the black thick solid line of FIG. 18 represents the flow of the hydraulic oil which flows into a hydraulic actuator, and represents that the flow volume is so large that the thickness of a solid line is thick.
- the black thick dotted line of FIG. 18 represents the flow of the hydraulic oil which flows out from a hydraulic actuator.
- the controller 30 sets the switching valve 62 to the second position, and directs the hydraulic oil flowing out from the bottom side oil chamber of the boom cylinder 7 toward the supply side of the pump / motor 14A, as indicated by a black thick dotted line. Further, the controller 30 increases the pilot pressure acting on the pilot port on the left side of the flow control valve 172 by the pressure reducing valve regardless of the operation amount of the boom operation lever so that the flow control valve 172 is opened to the maximum. Reduce pressure loss at 172. In addition, the controller 30 places the variable load check valve 52 in the second position, and blocks communication between the second pump 14R and the flow control valve 172.
- the controller 30 controls the displacement volume by adjusting the tilt angle of the swash plate of the pump motor 14A with a corresponding regulator so that the pressure in the bottom oil chamber of the boom cylinder 7 does not change suddenly.
- the controller 30 can reduce the flow rate of hydraulic fluid flowing out from the bottom side oil chamber of the boom cylinder 7 as the push-out volume is reduced.
- the pressure (back pressure) of the oil chamber can be increased.
- the controller 30 ensures that the pressure of the hydraulic oil on the discharge side of the pump / motor 14A becomes the accumulator pressure, and the pressure of the hydraulic oil on the supply side of the pump / motor 14A becomes the desired back pressure.
- the pressure of the hydraulic oil can be controlled.
- the pump motor 14 ⁇ / b> A that operates as a hydraulic pump can accumulate the accumulator 80 with a small pump load, compared to the case where the hydraulic oil is sucked from the hydraulic oil tank T to accumulate the accumulator 80. As a result, energy saving can be realized by reducing the load on the engine 11. Further, the pump motor 14A operating as a hydraulic motor can assist the engine 11 and bear a part of the driving force for rotating the first pump 14L. As a result, the controller 30 can increase the absorption horsepower of the first pump 14L, or can suppress the load of the engine 11 and the fuel injection amount when the absorption horsepower is not increased. 18 indicates that the pump / motor 14A operating as a hydraulic pump uses a part of the output of the engine 11. 18 indicates that the pump motor 14A operating as a hydraulic motor assists the engine 11 and bears a part of the driving force of the first pump 14L.
- the controller 30 maintains the merging valve 55 in the second position so as not to merge the first hydraulic oil and the second hydraulic oil, and the movements of the arm cylinder 8 and the bucket cylinder 9 are operated separately. Be controlled independently with oil.
- the flow rate of the hydraulic oil flowing into the rod side oil chamber of the arm cylinder 8 can be directly controlled by the first pump 14L, and therefore does not need to be limited by the restriction in the flow rate control valve 171.
- the flow rate of the hydraulic oil flowing into the rod side oil chamber of the bucket cylinder 9 can be directly controlled by the second pump 14R, and therefore does not need to be limited by the restriction in the flow rate control valve 173.
- the controller 30 increases the pilot pressure acting on the pilot port on the left side of the flow control valves 171 and 173 by the pressure reducing valve, thereby controlling the flow control valves 171 and 173. May be the maximum opening, and the pressure loss at the flow control valves 171 and 173 may be reduced.
- the controller 30 starts from the bottom side oil chamber of the boom cylinder 7. At least a part of the flowing hydraulic oil is directed to the hydraulic oil tank T. Specifically, the controller 30 sets the switching valve 62 to an intermediate position between the first position and the second position, or completely switches the switching valve 62 to the first position, so that the bottom of the boom cylinder 7 is reached. At least a part of the hydraulic oil flowing out from the side oil chamber is discharged to the hydraulic oil tank T.
- FIG. 19 shows the state of the hydraulic circuit in FIG. 3 when a soil removal operation with the assist of the arm cylinder 8 by back pressure regeneration is performed.
- the black thick solid line of FIG. 19 represents the flow of the hydraulic fluid which flows into a hydraulic actuator, and represents that the flow volume is so large that the thickness of a solid line is thick.
- black and gray thick dotted lines in FIG. 19 represent the flow of hydraulic oil flowing out from the hydraulic actuator.
- the controller 30 determines that the boom lowering operation has been performed, the hydraulic oil flowing out from the bottom side oil chamber of the boom cylinder 7 with the opening of the regeneration valve 7 a being maximized is discharged to the rod side oil chamber of the boom cylinder 7. To flow into.
- the controller 30 sets the switching valve 62A to the first position, and directs hydraulic oil flowing out from the bottom side oil chamber of the boom cylinder 7 toward the supply side of the pump / motor 14A. Further, the controller 30 reduces the pilot pressure acting on the pilot port on the right side of the flow control valve 172A by the pressure reducing valve regardless of the operation amount of the boom operation lever so that the flow control valve 172A is in the neutral position, and the boom cylinder 7 The flow of hydraulic oil from the bottom side oil chamber to the hydraulic oil tank T through the flow rate control valve 172A is cut off. In addition, the controller 30 places the variable load check valve 52A in the second position, and blocks communication between the second pump 14R and the flow control valve 172A.
- the flow control valve 171A receives the pilot pressure corresponding to the operation amount of the arm operation lever and moves to the right position in FIG.
- the flow control valve 173 receives a pilot pressure corresponding to the operation amount of the bucket operation lever and moves to the left position in FIG.
- the controller 30 determines that the arm opening operation has been performed, the controller 30 sets the variable load check valve 51A to the first position, and communicates between the first pump 14L and the flow control valve 171A. Further, when the controller 30 determines that the bucket opening operation has been performed, the controller 30 sets the variable load check valve 53 to the first position, and communicates between the second pump 14R and the flow control valve 173.
- the controller 30 controls the discharge amount of the pump motor 14A according to the operation amount of the boom operation lever and the opening degree of the regeneration valve 7a. Specifically, when the accumulator pressure is higher than the desired back pressure (the pressure in the bottom side oil chamber) of the boom cylinder 7, the controller 30 operates the pump / motor 14A as a hydraulic pump to increase the pressure of the hydraulic fluid on the supply side. (The pressure in the bottom oil chamber of the boom cylinder 7) is increased to the accumulator pressure. Further, when the accumulator pressure is equal to or lower than the desired back pressure of the boom cylinder 7, the controller 30 operates the pump motor 14A as a hydraulic motor to supply the supply side hydraulic oil pressure (the pressure in the rod side oil chamber of the boom cylinder 7). ) To the accumulator pressure.
- the pump motor 14 ⁇ / b> A that operates as a hydraulic pump can accumulate the accumulator 80 with a small pump load as compared with the case where the accumulator 80 is accumulated by sucking the hydraulic oil from the hydraulic oil tank T. As a result, energy saving can be realized by reducing the load on the engine 11. Further, the pump motor 14A operating as a hydraulic motor can assist the engine 11 and bear a part of the driving force for rotating the first pump 14L. As a result, the controller 30 can increase the absorption horsepower of the first pump 14L, or can suppress the load of the engine 11 and the fuel injection amount when the absorption horsepower is not increased. 19 represents that the pump motor 14A that operates as a hydraulic pump uses a part of the output of the engine 11. 19 indicates that the pump motor 14A operating as a hydraulic motor assists the engine 11 and bears a part of the driving force of the first pump 14L.
- the controller 30 maintains the variable load check valve 51B in the second position so that the first hydraulic fluid and the second hydraulic fluid do not merge, and the movements of the arm cylinder 8 and the bucket cylinder 9 are different. Independently controlled by hydraulic fluid.
- the flow rate of the hydraulic oil flowing into the rod side oil chamber of the arm cylinder 8 can be directly controlled by the first pump 14L, it is not necessary to be limited by the restriction in the flow rate control valve 171A.
- the flow rate of the hydraulic oil flowing into the rod side oil chamber of the bucket cylinder 9 can be directly controlled by the second pump 14R, and therefore does not need to be limited by the restriction in the flow rate control valve 173.
- the controller 30 starts from the bottom side oil chamber of the boom cylinder 7. At least a part of the flowing hydraulic oil is directed to the hydraulic oil tank T. Specifically, the controller 30 sets the switching valve 62C to an intermediate position between the first position and the second position, or completely switches the switching valve 62C to the first position, so that the bottom side oil of the boom cylinder 7 is changed. At least part of the hydraulic oil flowing out of the chamber is discharged to the hydraulic oil tank T.
- controller 30 increases the pilot pressure acting on the pilot port on the left side of the flow control valve 172B by the pressure reducing valve regardless of the operation amount of the boom operation lever, so that the flow control valve 172B is set to the left position in FIG.
- the hydraulic oil flowing out from the bottom side oil chamber of the boom cylinder 7 may be merged with the first hydraulic oil.
- the gray thick dotted line in FIG. 19 indicates that the hydraulic oil flowing out from the bottom side oil chamber of the boom cylinder 7 is discharged to the hydraulic oil tank T when the switching valve 62C is moved in the direction of the first position. And when the flow control valve 172B is moved to the left position, the hydraulic oil flowing out from the bottom side oil chamber of the boom cylinder 7 joins the first hydraulic oil at the flow control valve 172B.
- the controller 30 has the following effects in addition to the effects described in [Soil discharging operation with assist of engine by back pressure regeneration] and [Soil discharging operation with assist of hydraulic actuator by back pressure regeneration]. Is realized additionally.
- the boom lowering turning deceleration operation is an operation including boom lowering and turning deceleration.
- the upper swing body 3 continues to rotate due to inertia, and the deceleration of the upper swing body 3 is controlled by adjusting the pressure of hydraulic oil on the discharge port side of the swing hydraulic motor 21. Specifically, the deceleration of the upper swing body 3 increases as the pressure of the hydraulic fluid on the discharge port side increases.
- the flow control valve 172 receives the pilot pressure corresponding to the operation amount of the boom operation lever and moves to the left position in FIG.
- the controller 30 sets the switching valve 62 to the second position, and directs the hydraulic oil flowing out from the bottom side oil chamber of the boom cylinder 7 toward the supply side of the pump / motor 14A, as indicated by a black thick dotted line. Further, the controller 30 increases the pilot pressure acting on the pilot port on the left side of the flow control valve 172 by the pressure reducing valve regardless of the operation amount of the boom operation lever so that the flow control valve 172 is opened to the maximum. Reduce pressure loss at 172. In addition, the controller 30 places the variable load check valve 52 in the second position, and blocks communication between the second pump 14R and the flow control valve 172.
- the controller 30 controls the discharge amount of the pump motor 14A according to the operation amount of the boom operation lever and the opening degree of the regeneration valve 7a. Specifically, the controller 30 operates the pump / motor 14A as a hydraulic motor and controls the corresponding regulator so that the pressure in the bottom side oil chamber of the boom cylinder 7 does not change suddenly. To control. Then, the controller 30 sets the switching valve 90 to the second position and causes the hydraulic oil tank T to discharge the third hydraulic oil discharged from the pump motor 14A.
- the controller 30 may direct the third hydraulic oil discharged from the pump / motor 14A to the accumulator 80 or the hydraulic actuator that is operating. Specifically, when the accumulator pressure is higher than the desired back pressure (the pressure in the bottom side oil chamber) of the boom cylinder 7, the controller 30 operates the pump / motor 14A as a hydraulic pump to increase the pressure of the hydraulic fluid on the supply side. (The pressure in the bottom oil chamber of the boom cylinder 7) is increased to the accumulator pressure. Further, when the accumulator pressure is equal to or lower than the desired back pressure of the boom cylinder 7, the controller 30 operates the pump motor 14A as a hydraulic motor to supply the supply side hydraulic oil pressure (the pressure in the rod side oil chamber of the boom cylinder 7). ) To the accumulator pressure.
- the controller 30 controls the displacement volume by adjusting the tilt angle of the swash plate of the pump motor 14A with a corresponding regulator so that the pressure in the bottom oil chamber of the boom cylinder 7 does not change suddenly. Further, the controller 30 sets the switching valve 90 to the first position to direct the third hydraulic oil discharged from the pump motor 14A to the switching valve 91, and sets the switching valve 91 to the third position to supply the third hydraulic oil to the accumulator. Turn to 80. In this way, the controller 30 ensures that the pressure of the hydraulic oil on the discharge side of the pump / motor 14A becomes the accumulator pressure, and the pressure of the hydraulic oil on the supply side of the pump / motor 14A becomes the desired back pressure. The pump motor 14A is controlled. The same applies to the case where the third hydraulic oil is directed to the operating hydraulic actuator.
- the pump motor 14A that operates as a hydraulic pump can discharge hydraulic oil with a smaller pump load than when hydraulic oil is sucked from the hydraulic oil tank T. As a result, energy saving can be realized by reducing the load on the engine 11. Further, the pump motor 14A operating as a hydraulic motor can generate a rotational torque to assist the engine 11 and bear a part of the driving force for rotating the first pump 14L. As a result, the controller 30 can increase the absorption horsepower of the first pump 14L, or can suppress the load of the engine 11 and the fuel injection amount when the absorption horsepower is not increased.
- the controller 30 when the pump / motor 14A is operated as a hydraulic motor and the third hydraulic oil is discharged to the hydraulic oil tank T, the controller 30 is driven by the rotational torque of the pump / motor 14A. Causes the first hydraulic oil discharged from the engine to flow into the accumulator 80.
- the controller 30 controls the displacement volume of the first pump 14L by a corresponding regulator so that the discharge pressure of the first pump 14L becomes the accumulator pressure.
- the controller 30 sets the switching valve 81 in the first position to allow communication between the first pump 14L and the accumulator 80.
- 20 indicates that the rotational torque of the pump motor 14A that operates as a hydraulic motor drives the first pump 14L.
- the gray solid line in FIG. 20 indicates that the pump motor 14A This represents that the first hydraulic oil of the first pump 14L driven by the rotational torque including the generated rotational torque flows into the accumulator 80.
- the controller 30 starts from the bottom side oil chamber of the boom cylinder 7. At least a part of the flowing hydraulic oil is directed to the hydraulic oil tank T. Specifically, the controller 30 sets the switching valve 62 to an intermediate position between the first position and the second position, or completely switches the switching valve 62 to the first position, so that the bottom side oil of the boom cylinder 7 is changed. At least part of the hydraulic oil flowing out of the chamber is discharged to the hydraulic oil tank T.
- the flow control valve 170 moves to the neutral position in FIG. 20 because the operation amount of the turning operation lever decreases and the pilot pressure decreases.
- the regeneration valve 22G is opened and the hydraulic oil on the discharge port 21L side of the turning hydraulic motor 21 is directed to the switching valve 60, as indicated by the thick black dotted line. And let it flow.
- the controller 30 sets the switching valve 60 to the second position, and causes the hydraulic oil flowing out from the turning hydraulic motor 21 to flow into the accumulator 80 as indicated by a black thick dotted line.
- the controller 30 adjusts the opening degree of the regeneration valve 22G or the opening degree of the switching valve 60 at the second position according to the pressure of the hydraulic oil on the discharge port 21L side of the turning hydraulic motor 21 and the accumulator pressure. . And the pressure of the hydraulic fluid by the side of the discharge port 21L is controlled so that the desired braking torque for stopping the turning of the upper turning body 3 can be generated.
- the controller 30 detects the pressure of hydraulic fluid on each side of the two ports 21L and 21R of the turning hydraulic motor 21 based on the output of the turning pressure sensor (not shown).
- the controller 30 may place the switching valve 60 in the first position and allow the hydraulic oil flowing out from the turning hydraulic motor 21 to flow into the supply side of the pump motor 14A.
- the controller 30 since the controller 30 generates the braking pressure by rotating the pump motor 14A, it is not necessary to throttle the flow of the hydraulic oil flowing out from the turning hydraulic motor 21, and the pressure loss is generated by the throttle. There is nothing. Therefore, it can suppress or prevent that the inertial energy of the upper revolving body 3 is consumed as heat energy, and can suppress or prevent energy loss.
- FIG. 21 shows the state of the hydraulic circuit of FIG. 3 when the boom lowering turning deceleration operation accompanied by accumulator 80 pressure accumulation is performed.
- 21 represents the flow of hydraulic oil flowing into the accumulator 80
- the black thick dotted line in FIG. 21 represents the flow of hydraulic oil flowing out from the hydraulic actuator.
- the controller 30 sets the switching valve 62A to the first position, and directs hydraulic oil flowing out from the bottom side oil chamber of the boom cylinder 7 toward the supply side of the pump / motor 14A. Further, the controller 30 reduces the pilot pressure acting on the pilot port on the right side of the flow control valve 172A by the pressure reducing valve regardless of the operation amount of the boom operation lever so that the flow control valve 172A is in the neutral position, and the boom cylinder 7 The flow of hydraulic oil from the bottom side oil chamber to the hydraulic oil tank T through the flow rate control valve 172A is cut off. In addition, the controller 30 places the variable load check valve 52A in the second position, and blocks communication between the second pump 14R and the flow control valve 172A.
- the controller 30 controls the discharge amount of the pump motor 14A according to the operation amount of the boom operation lever and the opening degree of the regeneration valve 7a. Specifically, the controller 30 operates the pump / motor 14A as a hydraulic motor and controls the corresponding regulator so that the pressure in the bottom side oil chamber of the boom cylinder 7 does not change suddenly. To control.
- the controller 30 turns the switching valve 90 to the second position and turns the switching valve 92 to the first position to direct the third hydraulic oil discharged from the pump motor 14 ⁇ / b> A to the replenishment mechanism of the turning hydraulic motor 21.
- the controller 30 may direct the third hydraulic oil discharged from the pump / motor 14A to the accumulator 80 or the hydraulic actuator that is operating. Specifically, when the accumulator pressure is higher than the desired back pressure (the pressure in the bottom side oil chamber) of the boom cylinder 7, the controller 30 operates the pump / motor 14A as a hydraulic pump to increase the pressure of the hydraulic fluid on the supply side. (The pressure in the bottom oil chamber of the boom cylinder 7) is increased to the accumulator pressure. Further, when the accumulator pressure is equal to or lower than the desired back pressure of the boom cylinder 7, the controller 30 operates the pump motor 14A as a hydraulic motor to supply the supply side hydraulic oil pressure (the pressure in the rod side oil chamber of the boom cylinder 7). ) To the accumulator pressure.
- the controller 30 controls the displacement volume by adjusting the tilt angle of the swash plate of the pump motor 14A with a corresponding regulator so that the pressure in the bottom oil chamber of the boom cylinder 7 does not change suddenly.
- the controller 30 sets the switching valve 90 to the first position and the switching valve 92 to the second position, and causes the third hydraulic oil discharged from the pump motor 14 ⁇ / b> A to flow into the accumulator 80.
- the controller 30 ensures that the pressure of the hydraulic oil on the discharge side of the pump / motor 14A becomes the accumulator pressure, and the pressure of the hydraulic oil on the supply side of the pump / motor 14A becomes the desired back pressure.
- the pump motor 14A is controlled. The same applies to the case where the third hydraulic oil is directed to the operating hydraulic actuator.
- the pump motor 14A that operates as a hydraulic pump can discharge hydraulic oil with a smaller pump load than when hydraulic oil is sucked from the hydraulic oil tank T. As a result, energy saving can be realized by reducing the load on the engine 11. Further, the pump motor 14A operating as a hydraulic motor can generate a rotational torque to assist the engine 11 and bear a part of the driving force for rotating the first pump 14L. As a result, the controller 30 can increase the absorption horsepower of the first pump 14L, or can suppress the load of the engine 11 and the fuel injection amount when the absorption horsepower is not increased.
- the controller 30 when the pump / motor 14A is operated as a hydraulic motor and the third hydraulic oil is discharged to the hydraulic oil tank T, the controller 30 is driven by the rotational torque of the pump / motor 14A. Causes the first hydraulic oil discharged from the engine to flow into the accumulator 80.
- the controller 30 controls the displacement volume of the first pump 14L by a corresponding regulator so that the discharge pressure of the first pump 14L becomes the accumulator pressure.
- the controller 30 sets the switching valve 81 in the first position to allow communication between the first pump 14L and the accumulator 80.
- 21 indicates that the rotational torque of the pump motor 14A that operates as a hydraulic motor drives the first pump 14L.
- the gray solid line in FIG. 21 indicates that the pump motor 14A This represents that the first hydraulic oil of the first pump 14L driven by the torque including the generated rotational torque flows into the accumulator 80.
- the controller 30 starts from the bottom side oil chamber of the boom cylinder 7. At least a part of the flowing hydraulic oil is directed to the hydraulic oil tank T. Specifically, the controller 30 sets the switching valve 62C to an intermediate position between the first position and the second position, or completely switches the switching valve 62C to the first position, so that the bottom side oil of the boom cylinder 7 is changed. At least part of the hydraulic oil flowing out of the chamber is discharged to the hydraulic oil tank T.
- the flow rate control valve 170 moves to the neutral position in FIG. 21 because the operation amount of the turning operation lever decreases and the pilot pressure decreases.
- controller 30 adjusts the opening degree of the regeneration valve 22G according to the hydraulic oil pressure and the accumulator pressure on the discharge port 21L side of the turning hydraulic motor 21. And the pressure of the hydraulic fluid by the side of the discharge port 21L is controlled so that the desired braking torque for stopping the turning of the upper turning body 3 can be generated.
- the controller 30 sets the switching valve 90 to the second position and the switching valve 92 to the first position so that the third hydraulic oil discharged from the pump motor 14A is directed to the replenishment mechanism of the turning hydraulic motor 21. Yes. Therefore, the check valve 23R can supply the third hydraulic oil discharged from the pump / motor 14A to the suction port 21R side, as indicated by a thick gray dotted line.
- the replenishment mechanism does not generate cavitation even when the amount of hydraulic oil in the hydraulic oil tank T decreases and it becomes difficult to suck hydraulic oil from the hydraulic oil tank T.
- the hydraulic oil can be supplied to the motor 21. Note that the amount of hydraulic fluid in the hydraulic fluid tank T decreases as the amount of hydraulic fluid accumulated in the accumulator 80 increases.
- the controller 30 performs the [soil discharging operation with the assist of the engine by the back pressure regeneration], [the soil discharging operation with the assist of the hydraulic actuator by the back pressure regeneration], and [accumulator pressure accumulation by the back pressure regeneration].
- the following effects are additionally realized.
- the controller 30 causes the hydraulic oil flowing out from the turning hydraulic motor 21 to flow into the accumulator 80 and to flow out from the bottom side oil chamber of the boom cylinder 7. Oil flows into the supply side of the pump motor 14A. Therefore, the excavator according to the present embodiment can store the hydraulic energy generated at the time of turning deceleration in the accumulator 80 and can use the hydraulic energy generated at the time of boom lowering for assisting the engine 11. Further, the first pump 14L is driven by assisting the engine 11 using hydraulic energy generated when the boom is lowered, and the first hydraulic oil discharged from the first pump 14L is caused to flow into the accumulator 80. The hydraulic energy generated when the boom is lowered can be stored in the accumulator 80.
- FIG. 22 shows the state of the hydraulic circuit of FIG. 2 when the turning deceleration operation accompanied by the assist of the engine 11 and the accumulator 80 is performed.
- FIG. 22 represents the flow of the hydraulic oil flowing out from the turning hydraulic motor 21, and the black dashed-dotted arrow indicates that the engine assist torque is transmitted to the rotating shaft of the engine 11 via the transmission 13. It shows how it is done.
- FIG. 22 shows, as an example, a case where the port 21L of the turning hydraulic motor 21 is a discharge port, but the following description is similarly applied to a case where the port 21R is a discharge port.
- the turning deceleration operation is an operation for reducing the turning speed of the upper turning body 3.
- the upper swing body 3 continues to rotate due to inertia even when the swing operation lever is returned to the neutral position.
- the deceleration of the upper swing body 3 is controlled by adjusting the pressure of hydraulic oil on the discharge port side of the swing hydraulic motor 21 (hereinafter referred to as “swing outflow pressure”). Specifically, the higher the turning outflow pressure, the greater the deceleration of the upper turning body 3.
- the flow rate control valve 170 moves to the neutral position as shown in FIG. 22 because the operation amount of the turning operation lever decreases and the pilot pressure decreases. As a result, the hydraulic oil flowing into the turning hydraulic motor 21 from at least one of the first pump 14L, the second pump 14R, and the pump motor 14A is blocked.
- the regeneration valve 22G is opened and the hydraulic oil on the discharge port 21L side of the turning hydraulic motor 21 is directed to the switching valve 60, as indicated by the thick black dotted line. And let it flow.
- the controller 30 sets the switching valve 60 to the second position, and causes the hydraulic oil flowing out from the turning hydraulic motor 21 to flow into the accumulator 80 as indicated by a black thick dotted line.
- the controller 30 places the switching valve 82 in the first position to allow communication between the accumulator 80 and the pump motor 14A, and pumps the hydraulic oil flowing out from the turning hydraulic motor 21 as indicated by a black thick dotted line. -Also flow into the motor 14A. As a result, the hydraulic oil flowing out from the turning hydraulic motor 21 flows into the accumulator 80 and the pump motor 14A at the same pressure.
- the controller 30 adjusts the opening degree of the regeneration valve 22G according to the turning outflow pressure that is the output of the turning pressure sensor and the accumulator pressure that is the output of the accumulator pressure sensor. Then, the turning outflow pressure is controlled so that a desired braking torque for stopping the turning of the upper turning body 3 can be generated.
- the controller 30 is arranged before and after the regeneration valve 22G so that the swing outflow pressure is slightly lower than the relief pressure or cracking pressure of the relief valve 22L (hereinafter referred to as “swing braking target pressure”).
- a differential pressure is generated by the difference between the turning braking target pressure and the accumulator pressure.
- the turning braking target pressure may be registered in advance in an internal memory or the like, and may be calculated each time based on the output of various sensors.
- the controller 30 decreases the opening of the regeneration valve 22G as the difference between the swing braking target pressure and the accumulator pressure increases, that is, as the accumulator pressure decreases, and the difference between the swing braking target pressure and the accumulator pressure decreases.
- the controller 30 may discharge the hydraulic oil on the port 21L side from the relief valve 22L to the hydraulic oil tank T by closing the regeneration valve 22G.
- the controller 30 calculates the engine assist torque generated by the pump motor 14A from the pushed-out volume of the pump motor 14A and the accumulator pressure.
- the displacement of the pump motor 14A is derived from, for example, the output of a swash plate tilt angle sensor (not shown). Then, the controller 30 adjusts the displacement of the pump motor 14A, that is, the swash plate tilt angle so that the engine assist torque becomes the assist torque target value.
- the assist torque target value may be registered in advance in an internal memory or the like, and may be calculated each time based on the outputs of various sensors.
- the controller 30 increases the swash plate tilt angle to increase the displacement volume. This is because the engine assist torque is brought close to the assist torque target value.
- the displacement volume is increased, the flow rate of the hydraulic oil flowing into the pump / motor 14A is increased, so that the flow rate of the hydraulic oil flowing into the accumulator 80 is decreased.
- the controller 30 reduces the swash plate tilt angle to reduce the displacement volume when the engine assist torque is larger than the assist torque target value. This is to keep the engine assist torque below the assist torque target value.
- the displacement volume is reduced, the flow rate of the hydraulic oil flowing into the pump / motor 14A is decreased, and the flow rate of the hydraulic oil flowing into the accumulator 80 is increased.
- the accumulator 80 increases the accumulator pressure as the volume of hydraulic oil accumulated inside increases, and decreases the difference between the turning braking target pressure and the accumulator pressure.
- the controller 30 increases the opening of the regeneration valve 22G so that the turning outflow pressure is maintained at the turning braking target pressure. This is to maintain a desired braking torque.
- the braking torque T B is represented by the following formula (1).
- D m represents the displacement volume (motor volume) of the turning hydraulic motor 21, and P m represents the turning outflow pressure.
- the flow rate of hydraulic oil flowing out from the turning hydraulic motor 21 (hereinafter referred to as “turning outflow flow rate”) Q m is expressed by the following equation (2).
- the turning outflow flow rate Q m is also the flow rate of the hydraulic oil flowing through the regeneration valve 22G, and therefore is expressed by the following equation (3).
- c ma is the flow coefficient
- P acc is the accumulator pressure
- [rho represents the density of the hydraulic fluid.
- the controller 30 may pivot outflow pressure P m to adjust the opening area A ma regeneration valve 22G so as to obtain a desired turning braking target pressure.
- this adjustment is referred to as “swing outflow pressure feedback control”.
- the flow rate Q P3 flowing to the pump motor 14A is expressed by the following equation using the ⁇ volume V P3 and the engine rotational speed omega e of the pump motor 14A (5).
- the controller 30 adjusts the displacement volume V P3 of the pump motor 14A so that the engine assist torque T P3 becomes a desired assist torque target value.
- this adjustment is referred to as “engine assist torque feedback control”.
- the controller 30 can control the turning outflow pressure and the engine assist torque to desired values by simultaneously and independently executing the turning outflow pressure feedback control and the engine assist torque feedback control.
- the allowable maximum value of the pump motor 14A can be generated engine assist torque T P3 is determined by the load of the engine 11 at that time. Therefore, the controller 30 may not be able to send all of the hydraulic oil flowing out from the turning hydraulic motor 21 to the pump motor 14A.
- the hydraulic oil that cannot be sent to the pump motor 14 ⁇ / b> A out of the hydraulic oil flowing out from the turning hydraulic motor 21 is accumulated in the accumulator 80.
- the accumulator pressure Pacc increases as the hydraulic oil is accumulated, and the differential pressure from the turning braking target pressure becomes smaller.
- the controller 30 increases the opening of the regeneration valve 22G according to the decrease in the differential pressure so that the pressure of the hydraulic oil flowing out from the turning hydraulic motor 21 is maintained at the turning braking target pressure.
- the controller 30 accumulates a part of the hydraulic oil flowing out from the turning hydraulic motor 21 during the turning deceleration in the accumulator 80 and directly stores the remaining part in the accumulator 80 without pumping the motor 14 ⁇ / b> A. Can be sent upstream. Then, a desired engine assist torque can be generated, for example, the drag torque of the engine 11 can be reduced to save energy. Further, the controller 30 can use the inertial energy of the upper swing body 3 more efficiently and promote energy saving compared to the case where the controller 30 temporarily accumulates in the accumulator 80 and then releases it to the upstream side of the pump motor 14A.
- FIG. 23 is a control block diagram showing a control flow of the hydraulic system, and a case where the turning hydraulic motor 21 is decelerated will be described as an example.
- FIG. 23 shows a state in which the flow rate Q acc1 , the flow rate Q cir , and the flow rate Q rf are subtracted from the swirl flow rate Q swg and the swirl flow rate Q m is derived in each of the calculation elements E1, E2, and E3. Represents. Also, showing the state of turning outflow rate Q m is converted to swirling outflow pressure P m through the calculation element E4 representing the compressed volume.
- K, D m , and s represent the bulk modulus, the displacement volume of the turning hydraulic motor 21, and the Laplace operator, respectively.
- FIG. 23 is a relief valve 22L, represents a state in which turning outflow pressure P m through the computing element E5 are converted to the flow rate Q rf representing the 22R, pivot outflow pressure P m through the computing element E6 ⁇ E10 is It shows how it is converted to flow rate Q cir .
- turning outflow pressure P m through the operation element E6 representing the pressure receiving area A SW of the turning hydraulic motor 21 is converted into torque T SW1, minus the resistance torque T R from the torque T SW1 in computing elements E7 braking torque T B Te is derived, furthermore, represents a state in which the braking torque T B via the computing elements E8 representing the inertia of the swing hydraulic motor 21 is converted into the angular velocity ⁇ of the swing hydraulic motor 21.
- J and s of the computation element E8 represent the moment of inertia and the Laplace operator, respectively.
- the angular velocity via the computing elements E9 representing the viscosity resistance B SW of the hydraulic oil in the swing hydraulic motor 21 omega is converted to the resistance torque T R
- computing element represents the pressure receiving area A SW of the turning hydraulic motor 21 E10 Represents the state in which the angular velocity ⁇ is converted to the flow rate Q cir via.
- the controller 30 reads out the swivel brake target pressure P Tgt which is previously set in the internal memory or the like, turning outflow pressure P m to adjust the opening degree of the regeneration valve 22G so as to pivot the brake target pressure P Tgt.
- Figure 23 is a deviation of the turning braking target pressure P Tgt the swivel outlet pressure P m is calculated in the calculation element E11, indicating how the deviation is input to the arithmetic element (PI controller) E12.
- the state where the turning outflow pressure P m is converted into the flow rate Q acc1 through the calculation elements E13 and E14 is shown.
- the flow rate Q acc1 corresponds to the flow rate that flows into the accumulator 80 when the flow rate Q P3 that flows into the pump motor 14A is zero.
- C ma , A ma , ⁇ P, and ⁇ in the calculation element E14 represent a flow coefficient, an opening area of the regeneration valve 22G, a differential pressure (P m ⁇ P acc ) before and after the regeneration valve 22G, and a fluid density, respectively.
- the controller 30 derives an assist torque target value T Tgt based on the outputs of various sensors. Then, the displacement volume V P3 of the pump / motor 14A is adjusted so that the engine assist torque T P3 generated by the pump / motor 14A becomes the assist torque target value T Tgt .
- FIG. 23 shows a state where the assist torque target value T Tgt is converted into the flow rate Q P3 via the calculation elements E15 and E16.
- the assist torque target value T Tgt is divided by the accumulator pressure P acc to derive the displacement volume V P3 of the pump motor 14A, and further represents the first order delay of the pump motor 14A.
- This shows how the displacement volume V P3 is converted into the flow rate Q P3 flowing into the pump motor 14A via the calculation element E16.
- K Q , T, and s in the calculation element E16 represent a proportional gain, a time constant, and a Laplace operator, respectively.
- the controller 30 may pivot outflow pressure P m to adjust the opening area A ma regeneration valve 22G to a desired pressure.
- FIG. 23 shows how the flow rate Q acc1 is converted into the accumulator pressure P acc via the calculation elements E17 to E21. Specifically, the flow rate Q acc is calculated by subtracting the flow rate Q P3 and the flow rate Q g from the flow rate Q acc1 in the calculation element E17. The flow rate Q g represents the flow rate caused by the volume change of the nitrogen gas in the accumulator 80.
- FIG. 23 shows a state in which the pressure change rate ⁇ P acc is converted into the flow rate Q g via the arithmetic element E19 representing the nitrogen gas in the accumulator 80.
- FIG. 23 shows a state in which the flow rate Q acc1 is integrated and converted into a volume V acc1 by the calculation element E20, and the volume V acc1 is used for adjusting each of the calculation elements E18 and E19.
- the accumulator pressure P acc is additionally used for adjusting the calculation element E19.
- FIG. 23 shows a state where the pressure change rate ⁇ P acc is integrated and converted into the accumulator pressure P acc by the calculation element E21.
- FIG. 24 is a flowchart showing the flow of the turning deceleration process, and the controller 30 repeatedly executes the turning deceleration process at a predetermined control cycle.
- the controller 30 determines whether or not the turning is being decelerated (step S1). In the present embodiment, the controller 30 determines whether or not the vehicle is decelerating based on the output of the operation pressure sensor corresponding to the turning operation lever.
- step S2 the controller 30 acquires the swing outflow pressure and the accumulator pressure (step S2).
- the controller 30 acquires the swing outflow pressure based on the output of the swing pressure sensor, and acquires the accumulator pressure based on the output of the accumulator pressure sensor.
- the controller 30 determines the opening degree of the regeneration valve 22G and the displacement volume of the pump / motor 14A (step S3).
- the controller 30 determines the opening degree of the regeneration valve 22G based on the differential pressure between the accumulator pressure and the turning braking target pressure so that the turning outflow pressure and the turning braking target pressure match.
- the controller 30 determines the displacement of the pump / motor 14A based on the accumulator pressure and the assist torque target value so that the engine assist torque generated by the pump / motor 14A matches the assist torque target value.
- the controller 30 increases the opening of the regeneration valve 22G when the turning outflow pressure, which is the output of the turning pressure sensor, exceeds the turning braking target pressure by the turning outflow pressure feedback control.
- the opening degree of the regeneration valve 22G is reduced.
- the controller 30 determines whether or not the engine assist torque has deviated from the assist torque target value (step S6). If it is determined that the engine assist torque has deviated from the assist torque target value (YES in step S6), the controller 30 adjusts the displacement of the pump / motor 14A (step S7).
- the controller 30 calculates the engine assist torque based on the accumulator pressure and the swash plate tilt angle of the pump motor 14A by engine assist torque feedback control.
- the displacement volume of the pump / motor 14A is reduced, and when the engine assist torque falls below the assist torque target value, the displacement volume of the pump / motor 14A is increased. To do.
- the controller 30 adjusts the opening of the regeneration valve 22G and the displacement of the pump motor 14A while monitoring the turning outflow pressure and the accumulator pressure, so that the desired braking torque and the desired engine assist are adjusted. Torque is maintained.
- controller 30 can prevent the engine 11 from being adversely affected by excessively increasing the engine assist torque by maintaining the desired engine assist torque.
- FIG. 25 shows another example of the state of the hydraulic circuit in FIG. 2 when the turning deceleration operation accompanied by the assist of the engine 11 and the accumulator 80 is performed.
- FIG. 25 shows another example of the state of the hydraulic circuit in FIG. 2 when the turning deceleration operation accompanied by the assist of the engine 11 and the accumulator 80 is performed.
- the black thick dotted line in FIG. 25 represents the flow of hydraulic oil flowing out from the turning hydraulic motor 21, and the black dashed-dotted arrow indicates that the engine assist torque is transmitted to the rotating shaft of the engine 11 via the transmission 13. It shows how it is done.
- FIG. 25 shows, as an example, a case where the port 21L of the turning hydraulic motor 21 is a discharge port, but the following description is similarly applied to a case where the port 21R is a discharge port.
- the state of FIG. 25 is different from the state of FIG. 22 in that the switching valve 60 is in an intermediate position between the first position and the second position, and the switching valve 82 is in the second position. It is common in. Therefore, description of common parts is omitted, and different parts are described in detail.
- the controller 30 When determining that the turning deceleration operation has been performed, the controller 30 opens the regeneration valve 22G and causes the hydraulic oil on the discharge port 21L side of the turning hydraulic motor 21 to flow toward the switching valve 60, as indicated by the black thick dotted line. Let Further, the controller 30 places the switching valve 60 in an intermediate position, and as shown by a black thick dotted line, the controller 30 divides the hydraulic oil flowing out from the turning hydraulic motor 21 and applies the same pressure to each of the accumulator 80 and the pump motor 14A. Let it flow.
- controller 30 adjusts the opening degree of the regeneration valve 22G according to the turning outflow pressure that is the output of the turning pressure sensor and the accumulator pressure that is the output of the accumulator pressure sensor. Then, the turning outflow pressure is controlled so that a desired braking torque for stopping the turning of the upper turning body 3 can be generated.
- the controller 30 calculates the engine assist torque generated by the pump motor 14A from the pushed-out volume of the pump motor 14A and the accumulator pressure.
- the displacement of the pump motor 14A is derived from the output of a swash plate tilt angle sensor, for example. Then, the controller 30 adjusts the displacement of the pump motor 14A, that is, the swash plate tilt angle so that the engine assist torque becomes the assist torque target value.
- the controller 30 can realize the same effect as the case where the state of the hydraulic circuit shown in FIG. 22 is used by using the state of the hydraulic circuit shown in FIG.
- FIG. 26 shows the state of the hydraulic circuit in FIG. 3 when the turning deceleration operation accompanied by the assist of the engine 11 and the accumulator 80 is performed.
- 26 represents the flow of hydraulic oil flowing out from the turning hydraulic motor 21, and the black dashed-dotted arrow indicates that the engine assist torque is transmitted to the rotating shaft of the engine 11 via the transmission 13. It shows how it is done.
- FIG. 26 shows, as an example, a case where the port 21L of the turning hydraulic motor 21 is a discharge port, but the following description is similarly applied to a case where the port 21R is a discharge port.
- the flow rate control valve 170 moves to the neutral position as shown in FIG. 26 because the operation amount of the turning operation lever decreases and the pilot pressure decreases. As a result, hydraulic fluid flowing into the turning hydraulic motor 21 from at least one of the first pump 14L and the pump motor 14A is blocked.
- the regeneration valve 22G is opened and the hydraulic oil on the discharge port 21L side of the turning hydraulic motor 21 is directed toward the accumulator 80, as indicated by the black thick dotted line. Spill. Further, the controller 30 causes the switching valve 82 to be in the first position to allow communication between the accumulator 80 and the pump motor 14A, and pumps the hydraulic oil flowing out from the turning hydraulic motor 21 as indicated by a black thick dotted line. -Also flow into the motor 14A. As a result, the hydraulic oil flowing out from the turning hydraulic motor 21 flows into the accumulator 80 and the pump motor 14A at the same pressure.
- controller 30 adjusts the opening degree of the regeneration valve 22G according to the turning outflow pressure that is the output of the turning pressure sensor and the accumulator pressure that is the output of the accumulator pressure sensor. Then, the turning outflow pressure is controlled so that a desired braking torque for stopping the turning of the upper turning body 3 can be generated.
- the controller 30 calculates the engine assist torque generated by the pump motor 14A from the pushed-out volume of the pump motor 14A and the accumulator pressure.
- the displacement of the pump motor 14A is derived from the output of a swash plate tilt angle sensor, for example. Then, the controller 30 adjusts the displacement of the pump motor 14A, that is, the swash plate tilt angle so that the engine assist torque becomes the assist torque target value.
- the controller 30 can realize the same effect as the case where the state of the hydraulic circuit shown in FIG. 22 is used by using the state of the hydraulic circuit shown in FIG. [Turning acceleration operation with engine assist and accumulator pressure accumulation]
- FIG. 27 shows the state of the hydraulic circuit in FIG. 2 when the turning acceleration operation with the assist of the engine 11 and the accumulator 80 is performed.
- FIG. 27 represents the flow of hydraulic oil from the first pump 14L to the turning hydraulic motor 21, and the black thick dotted line represents the hydraulic oil flow from the branch point B1 to the accumulator 80 and the pump / motor 14A.
- a black dot-and-dash line arrow represents a state in which engine assist torque is transmitted to the rotation shaft of the engine 11 via the transmission 13.
- FIG. 27 shows, as an example, the case where the port 21R of the turning hydraulic motor 21 is a suction port, but the following description is similarly applied to the case where the port 21L is a suction port.
- the turning acceleration operation is an operation for increasing the turning speed of the upper turning body 3.
- the turning acceleration operation is executed, for example, when the turning operation lever is operated with a full lever.
- a part of the hydraulic oil discharged from the first pump 14L flows out from the relief valve 22R toward the hydraulic oil tank T, and the remaining part of the hydraulic oil discharged from the first pump 14L is used as the turning hydraulic pressure.
- the turning hydraulic motor 21 is rotated by flowing into the suction port 21R of the motor 21.
- the controller 30 accumulates the hydraulic oil that has flowed out from the relief valve 22R toward the hydraulic oil tank T in the accumulator 80 and / or supplies the hydraulic oil to the pump / motor 14A to effectively use the hydraulic energy. .
- the flow control valve 170 is switched to the right position as shown in FIG. As a result, the hydraulic oil discharged from the first pump 14L flows into the suction port 21R of the turning hydraulic motor 21.
- the regeneration valve 22G is opened and the hydraulic oil on the suction port 21R side of the turning hydraulic motor 21 is directed to the switching valve 60, as indicated by the thick black dotted line. And let it flow.
- the controller 30 sets the switching valve 60 to the second position, and causes the hydraulic oil flowing out from the regeneration valve 22G to flow into the accumulator 80, as indicated by a black thick dotted line.
- the controller 30 causes the switching valve 82 to be in the first position to allow communication between the accumulator 80 and the pump motor 14A, and the hydraulic oil flowing out from the regeneration valve 22G is pumped out from the regeneration motor 22G as indicated by a black thick dotted line. Also flow into 14A. As a result, the hydraulic oil flowing out of the regeneration valve 22G flows into the accumulator 80 and the pump motor 14A at the same pressure.
- the controller 30 adjusts the opening degree of the regeneration valve 22G according to the turning inflow pressure that is the output of the turning pressure sensor and the accumulator pressure that is the output of the accumulator pressure sensor. Then, the turning inflow pressure is controlled so that a desired acceleration torque for accelerating the turning of the upper turning body 3 can be generated.
- the controller 30 is arranged before and after the regeneration valve 22G so that the swing inflow pressure is slightly lower than the relief pressure or cracking pressure of the relief valve 22R (hereinafter referred to as “swing acceleration target pressure”).
- the differential pressure is generated by the difference between the turning acceleration target pressure and the accumulator pressure.
- the turning acceleration target pressure may be registered in advance in an internal memory or the like, and may be calculated each time based on the output of various sensors.
- the controller 30 decreases the opening of the regeneration valve 22G as the difference between the turning acceleration target pressure and the accumulator pressure increases, that is, as the accumulator pressure decreases, and the difference between the turning acceleration target pressure and the accumulator pressure becomes smaller.
- the controller 30 may discharge the hydraulic oil on the port 21R side from the relief valve 22R to the hydraulic oil tank T by closing the regeneration valve 22G.
- the controller 30 calculates the engine assist torque generated by the pump motor 14A from the pushed-out volume of the pump motor 14A and the accumulator pressure.
- the displacement of the pump motor 14A is derived from, for example, the output of a swash plate tilt angle sensor (not shown). Then, the controller 30 adjusts the displacement of the pump motor 14A, that is, the swash plate tilt angle so that the engine assist torque becomes the assist torque target value.
- the assist torque target value may be registered in advance in an internal memory or the like, and may be calculated each time based on the outputs of various sensors.
- the controller 30 increases the swash plate tilt angle to increase the displacement volume.
- the displacement volume is increased, the flow rate of the hydraulic oil flowing into the pump / motor 14A is increased, so that the flow rate of the hydraulic oil flowing into the accumulator 80 is decreased.
- the controller 30 reduces the swash plate tilt angle to reduce the displacement volume when the engine assist torque is larger than the assist torque target value.
- the displacement volume is reduced, the flow rate of the hydraulic oil flowing into the pump / motor 14A is decreased, and the flow rate of the hydraulic oil flowing into the accumulator 80 is increased.
- the accumulator 80 increases the accumulator pressure as the volume of hydraulic oil accumulated inside increases, and decreases the difference between the turning acceleration target pressure and the accumulator pressure.
- the controller 30 increases the opening of the regeneration valve 22G so that the turning inflow pressure is maintained at the turning acceleration target pressure. This is to maintain a desired acceleration torque.
- the acceleration torque T A is expressed by the following formula (7).
- D m represents the displacement volume (motor volume) of the turning hydraulic motor 21, and P m represents the turning inflow pressure.
- the flow rate Q m of the hydraulic oil flowing through the regeneration valve 22G is expressed by the following formula (8).
- Q P represents the discharge amount of the first pump 14L
- Q swg represents the swirl inflow rate.
- the flow rate Q m of the hydraulic oil flowing through the regeneration valve 22G is also expressed by the following equation (9).
- c ma is the flow coefficient
- P acc is the accumulator pressure
- [rho represents the density of the hydraulic fluid.
- the controller 30 the turning flows pressure P m to adjust the opening area A ma regeneration valve 22G so as to obtain a desired turning acceleration target pressure.
- this adjustment is referred to as “swing inflow pressure feedback control”.
- the switching valve 82 when the switching valve 82 is set to the first position and the accumulator 80 and the upstream side of the pump / motor 14A are communicated with each other, part or all of the hydraulic fluid flowing out from the turning hydraulic motor 21 is supplied to the pump / motor 14A. It flows upstream.
- the controller 30 adjusts the displacement volume V P3 of the pump motor 14A so that the engine assist torque T P3 becomes a desired assist torque target value.
- this adjustment is referred to as “engine assist torque feedback control”.
- the controller 30 can control the swing inflow pressure and the engine assist torque to desired values by executing the swing inflow pressure feedback control and the engine assist torque feedback control simultaneously and independently.
- the controller 30 accumulates a part of the hydraulic oil flowing out from the regeneration valve 22G during the turning acceleration in the accumulator 80 and directly accumulates the remaining part in the upstream of the pump motor 14A without accumulating in the accumulator 80. Can send. Then, a desired engine assist torque can be generated, and for example, the engine 11 can be assisted to save energy.
- the controller 30 can use the inertial energy of the upper swing body 3 more efficiently and save energy compared to the case where the hydraulic oil is once accumulated in the accumulator 80 and then discharged to the upstream side of the pump / motor 14A. Can promote.
- the control flow of the hydraulic system during the turning acceleration operation is the same as the control flow of the hydraulic system during the turning deceleration operation shown in FIG.
- FIG. 28 is a flowchart showing the flow of the turning acceleration process, and the controller 30 repeatedly executes the turning acceleration process at a predetermined control cycle.
- the controller 30 determines whether or not turning acceleration is being performed (step S11). In this embodiment, the controller 30 determines whether or not the turning acceleration is being performed based on the output of the operation pressure sensor corresponding to the turning operation lever.
- the controller 30 acquires the turning inflow pressure and the accumulator pressure (step S12).
- the controller 30 acquires the turning inflow pressure based on the output of the turning pressure sensor, and acquires the accumulator pressure based on the output of the accumulator pressure sensor.
- the controller 30 determines the opening degree of the regeneration valve 22G and the displacement volume of the pump / motor 14A (step S13).
- the controller 30 determines the opening degree of the regeneration valve 22G based on the differential pressure between the accumulator pressure and the turning acceleration target pressure so that the turning inflow pressure and the turning acceleration target pressure match. Further, the controller 30 determines the displacement of the pump / motor 14A based on the accumulator pressure and the assist torque target value so that the engine assist torque generated by the pump / motor 14A matches the assist torque target value.
- the controller 30 determines whether or not the turning inflow pressure has deviated from the turning acceleration target pressure (step S14). When it is determined that the turning inflow pressure has deviated from the turning acceleration target pressure (YES in step S14), the controller 30 adjusts the opening of the regeneration valve 22G (step S15).
- the controller 30 increases the opening of the regeneration valve 22G when the turning inflow pressure, which is the output of the turning pressure sensor, exceeds the turning acceleration target pressure by the turning inflow pressure feedback control. When the turning acceleration target pressure falls below, the opening of the regeneration valve 22G is reduced.
- the controller 30 determines whether or not the engine assist torque has deviated from the assist torque target value (step S16). When it is determined that the engine assist torque has deviated from the assist torque target value (YES in step S16), the controller 30 adjusts the displacement of the pump / motor 14A (step S17).
- the controller 30 calculates the engine assist torque based on the accumulator pressure and the swash plate tilt angle of the pump motor 14A by engine assist torque feedback control.
- the displacement volume of the pump / motor 14A is reduced, and when the engine assist torque falls below the assist torque target value, the displacement volume of the pump / motor 14A is increased. To do.
- the controller 30 adjusts the opening degree of the regeneration valve 22G and the displacement of the pump motor 14A while monitoring the swirling inflow pressure and the accumulator pressure, so that the desired acceleration torque and the desired engine assist are adjusted. Torque is maintained. Further, the controller 30 accumulates a part of the hydraulic oil discharged from the first pump 14L during turning acceleration in the accumulator 80 instead of discharging it through the relief valves 22L and 22R and / or supplies it to the pump motor 14A. be able to. As a result, the controller 30 can achieve effective use of hydraulic energy.
- FIG. 29 shows the state of the hydraulic circuit of FIG. 3 when the turning acceleration operation with the assist of the engine 11 and the accumulator 80 pressure accumulation is performed.
- 29 represents the flow of hydraulic oil from the first pump 14L to the turning hydraulic motor 21, and the black thick dotted line represents the flow of hydraulic oil from the branch point B1 to the accumulator 80 and the pump / motor 14A.
- a black dot-and-dash line arrow represents a state in which engine assist torque is transmitted to the rotation shaft of the engine 11 via the transmission 13.
- FIG. 29 shows, as an example, the case where the port 21R of the turning hydraulic motor 21 is a suction port, but the following description is similarly applied to the case where the port 21L is a suction port.
- variable load check valve 50 When the turning acceleration operation is performed, as shown in FIG. 29, the variable load check valve 50 is switched to the left position, and the flow control valve 170 is switched to the right position. As a result, the hydraulic oil discharged from the first pump 14L flows into the suction port 21R of the turning hydraulic motor 21.
- the regeneration valve 22G is opened and the hydraulic oil on the suction port 21R side of the turning hydraulic motor 21 is directed toward the accumulator 80, as indicated by the thick black dotted line. Spill. Further, the controller 30 causes the switching valve 82 to be in the first position so as to communicate between the accumulator 80 and the pump motor 14A, and the hydraulic oil flowing out from the regeneration valve 22G is pumped out from the regeneration motor 22G as indicated by a black thick dotted line. Also flow into 14A. As a result, the hydraulic oil flowing out of the regeneration valve 22G flows into the accumulator 80 and the pump motor 14A at the same pressure.
- controller 30 adjusts the opening degree of the regeneration valve 22G according to the turning inflow pressure that is the output of the turning pressure sensor and the accumulator pressure that is the output of the accumulator pressure sensor. Then, the turning inflow pressure is controlled so that a desired acceleration torque for accelerating the turning of the upper turning body 3 can be generated.
- the controller 30 calculates the engine assist torque generated by the pump motor 14A from the pushed-out volume of the pump motor 14A and the accumulator pressure.
- the displacement of the pump motor 14A is derived from the output of a swash plate tilt angle sensor, for example. Then, the controller 30 adjusts the displacement of the pump motor 14A, that is, the swash plate tilt angle so that the engine assist torque becomes the assist torque target value.
- FIG. 30 shows the state of the hydraulic circuit in FIG. 2 when a turning acceleration operation involving only accumulator 80 accumulation is performed.
- 30 represents the flow of hydraulic oil from the first pump 14L to the turning hydraulic motor 21, and the black thick dotted line represents the flow of hydraulic oil from the branch point B1 to the accumulator 80.
- 30 shows, as an example, the case where the port 21R of the turning hydraulic motor 21 is a suction port, but the following description is similarly applied to the case where the port 21L is a suction port.
- 30 is the same as the turning acceleration process shown in FIG. 28 except for the step of adjusting the displacement of the pump / motor 14A to generate a desired engine assist torque. It is.
- the control flow of the hydraulic system during the turning acceleration operation is the same as the control flow of the hydraulic system during the turning deceleration operation shown in FIG.
- the flow control valve 170 is switched to the right position as shown in FIG. As a result, the hydraulic oil discharged from the first pump 14L flows into the suction port 21R of the turning hydraulic motor 21.
- the regeneration valve 22G is opened and the hydraulic oil on the suction port 21R side of the turning hydraulic motor 21 is directed to the switching valve 60, as indicated by the thick black dotted line. And let it flow.
- the controller 30 sets the switching valve 60 to the second position, and causes the hydraulic oil flowing out from the regeneration valve 22G to flow into the accumulator 80, as indicated by a black thick dotted line.
- the controller 30 adjusts the opening degree of the regeneration valve 22G according to the turning inflow pressure that is the output of the turning pressure sensor and the accumulator pressure that is the output of the accumulator pressure sensor. Then, the turning inflow pressure is controlled so that a desired acceleration torque for accelerating the turning of the upper turning body 3 can be generated.
- the controller 30 generates a differential pressure by the difference between the turning acceleration target pressure and the accumulator pressure before and after the regeneration valve 22G so that the turning inflow pressure becomes the turning acceleration target pressure.
- the turning acceleration target pressure may be registered in advance in an internal memory or the like, and may be calculated each time based on the output of various sensors.
- the controller 30 decreases the opening of the regeneration valve 22G as the difference between the turning acceleration target pressure and the accumulator pressure increases, that is, as the accumulator pressure decreases, and the difference between the turning acceleration target pressure and the accumulator pressure becomes smaller.
- the controller 30 may discharge the hydraulic oil on the port 21R side from the relief valve 22R to the hydraulic oil tank T by closing the regeneration valve 22G.
- the accumulator 80 increases the accumulator pressure as the volume of hydraulic oil accumulated inside increases, and decreases the difference between the turning acceleration target pressure and the accumulator pressure.
- the controller 30 increases the opening of the regeneration valve 22G so that the turning inflow pressure is maintained at the turning acceleration target pressure. This is to maintain a desired acceleration torque.
- the controller 30 adjusts the opening of the regeneration valve 22G while monitoring the swirling inflow pressure and the accumulator pressure so that a desired acceleration torque is maintained. Further, the controller 30 can accumulate a part of the hydraulic oil discharged from the first pump 14L during the acceleration of turning in the accumulator 80 instead of discharging it through the relief valves 22L and 22R. As a result, the controller 30 can achieve effective use of hydraulic energy.
- FIG. 31 shows the state of the hydraulic circuit in FIG. 3 when a turning acceleration operation involving only accumulator 80 accumulation is performed.
- 31 represents the flow of hydraulic oil from the first pump 14L to the turning hydraulic motor 21, and the black thick dotted line represents the flow of hydraulic oil from the branch point B1 to the accumulator 80.
- FIG. 31 shows, as an example, the case where the port 21R of the turning hydraulic motor 21 is a suction port, but the following description is similarly applied to the case where the port 21L is a suction port.
- variable load check valve 50 When the turning acceleration operation is performed, as shown in FIG. 31, the variable load check valve 50 is switched to the left position, and the flow control valve 170 is switched to the right position. As a result, the hydraulic oil discharged from the first pump 14L flows into the suction port 21R of the turning hydraulic motor 21.
- the regeneration valve 22G is opened and the hydraulic oil on the suction port 21R side of the turning hydraulic motor 21 is directed toward the accumulator 80, as indicated by the thick black dotted line. Spill.
- controller 30 adjusts the opening degree of the regeneration valve 22G according to the turning inflow pressure that is the output of the turning pressure sensor and the accumulator pressure that is the output of the accumulator pressure sensor. Then, the turning inflow pressure is controlled so that a desired acceleration torque for accelerating the turning of the upper turning body 3 can be generated.
- the controller 30 can realize the same effect as the case where the state of the hydraulic circuit shown in FIG. 30 is used by using the state of the hydraulic circuit shown in FIG.
- the controller 30 determines that there is no need to generate back pressure in the rod side oil chamber of the boom cylinder 7 during excavation and that sufficient hydraulic fluid is accumulated in the accumulator 80, the accumulator assist An excavation operation involving the above may be performed.
- the controller 30 determines that it is necessary to generate a back pressure in the rod side oil chamber of the boom cylinder 7 during the excavation operation and the arm cylinder 8 needs to be operated quickly, the back pressure regeneration is performed.
- the excavation operation with the assistance of the hydraulic actuator may be performed.
- the controller 30 determines that it is necessary to generate a back pressure in the rod side oil chamber of the boom cylinder 7 during the excavation operation and it is not necessary to operate the arm cylinder 8 quickly, the back pressure regeneration is performed.
- the excavation operation with the assist of the engine may be performed.
- the controller 30 determines that it is necessary to generate a back pressure in the bottom oil chamber of the boom cylinder 7 during the soil discharging operation and the arm cylinder 8 needs to be operated quickly, the back pressure is determined.
- a soil removal operation accompanied by assist of the hydraulic actuator by regeneration may be performed.
- the controller 30 needs to generate a back pressure in the bottom oil chamber of the boom cylinder 7 during the soil discharging operation, and it is not necessary to operate the arm cylinder 8 quickly, and sufficient hydraulic oil is supplied to the accumulator 80.
- a soil discharging operation accompanied by engine assist by back pressure regeneration may be performed.
- the controller 30 needs to generate a back pressure in the bottom oil chamber of the boom cylinder 7 during the soil discharging operation, and it is not necessary to operate the arm cylinder 8 quickly, and sufficient hydraulic oil is supplied to the accumulator 80.
- a soil discharging operation accompanied by accumulator pressure accumulation by back pressure regeneration may be performed.
- the hydraulic actuator may include a left-side traveling hydraulic motor (not shown) and a right-side traveling hydraulic motor (not shown).
- the controller 30 may accumulate hydraulic energy at the time of traveling deceleration in the accumulator 80.
- the turning hydraulic motor 21 may be an electric motor.
- the excavator includes a motor generator (not shown) that assists the engine 11, a capacitor (not shown) that accumulates the power generated by the motor generator and supplies the motor generator with power. .), An inverter or the like for controlling the movement of the motor generator may be mounted.
- the pump motor 14A may be driven by a motor generator instead of being driven by the engine 11.
- the pump motor 14 ⁇ / b> A may operate the motor generator as a generator with the generated rotational torque to charge the accumulator with the generated power.
- the motor generator may operate as a motor using the electric power charged in the capacitor, and the pump / motor 14A may be operated as a hydraulic pump.
- Controller 50 51, 51A, 51B, 52, 52A 52B, 53 ...
- Variable load check valve 55 ... Junction valve 56L, 56R ... Unified bleed-off valve 60, 61, 61A, 62, 62A, 62B, 62C, 63, 81, 82, 90, 91, 92 ...
- Switching valve 70a Relief valve 80 ... Accumulator 170, 171, 171A, 171B, 172, 172A, 172B, 173 ...
- Flow control valve B1 ... Branch point T ... Hydraulic oil tank
Abstract
Description
旋回用油圧モータと、旋回加速中に前記旋回用油圧モータの吸入ポート側から流出する作動油、又は、旋回減速中に前記旋回用油圧モータの吐出ポート側から流出する作動油を蓄積可能なアキュムレータと、前記吸入ポート又は前記吐出ポートと前記アキュムレータとの間の連通・遮断を切り替える開度調整可能な開閉弁と、前記開閉弁を制御する制御装置と、を有し、前記制御装置は、前記開閉弁の開度を調整して前記流出する作動油の圧力を所定の目標圧とし、且つ、前記流出する作動油を前記アキュムレータに流入させる。
[掘削動作]
次に、図4~図6を参照し、掘削動作が行われる場合における図2の油圧回路の状態を説明する。なお、図4~図6は、掘削動作が行われる場合における図2の油圧回路の状態を示す。また、図4~図6の黒色の太実線は、油圧アクチュエータに流入する作動油の流れを表し、実線の太さが太いほど流量が大きいことを表す。
[背圧回生によるエンジンのアシストを伴う掘削動作]
次に、図8を参照し、背圧回生によるエンジン11のアシストを伴う掘削動作が行われる場合における図2の油圧回路の状態を説明する。なお、図8は、背圧回生によるエンジン11のアシストを伴う掘削動作が行われる場合における図2の油圧回路の状態を示す。また、図8の黒色の太実線は、油圧アクチュエータに流入する作動油の流れを表し、実線の太さが太いほど流量が大きいことを表す。また、図8の黒色及び灰色の太点線は、油圧アクチュエータから流出する作動油の流れを表す。
[アキュムレータアシストを伴う掘削動作]
次に、図10を参照し、アキュムレータアシストを伴う掘削動作が行われる場合における図2の油圧回路の状態を説明する。なお、図10は、アキュムレータアシストを伴う掘削動作が行われる場合における図2の油圧回路の状態を示す。また、図10の黒色の太実線は、油圧アクチュエータに流入する作動油の流れを表し、実線の太さが太いほど流量が大きいことを表す。
[背圧回生による油圧アクチュエータのアシストを伴う掘削動作]
次に、図12を参照し、背圧回生による油圧アクチュエータのアシストを伴う掘削動作が行われる場合における図2の油圧回路の状態を説明する。なお、図12は、背圧回生によるアームシリンダ8のアシストを伴う掘削動作が行われる場合における図2の油圧回路の状態を示す。また、図12の黒色の太実線は、油圧アクチュエータに流入する作動油の流れを表し、実線の太さが太いほど流量が大きいことを表す。また、図12の黒色及び灰色の太点線は、油圧アクチュエータから流出する作動油の流れを表す。
[背圧回生によるエンジンのアシストを伴う排土動作]
次に、図14を参照し、背圧回生によるエンジン11のアシストを伴う排土動作が行われる場合における図2の油圧回路の状態を説明する。なお、図14は、背圧回生によるエンジン11のアシストを伴う排土動作が行われる場合における図2の油圧回路の状態を示す。また、図14の黒色の太実線は、油圧アクチュエータに流入する作動油の流れを表し、実線の太さが太いほど流量が大きいことを表す。また、図14の黒色の太点線は、油圧アクチュエータから流出する作動油の流れを表す。
[背圧回生による油圧アクチュエータのアシストを伴う排土動作]
次に、図16を参照し、背圧回生による油圧アクチュエータのアシストを伴う排土動作が行われる場合における図2の油圧回路の状態を説明する。なお、図16は、背圧回生によるアームシリンダ8のアシストを伴う排土動作が行われる場合における図2の油圧回路の状態を示す。また、図16の黒色の太実線は、油圧アクチュエータに流入する作動油の流れを表し、実線の太さが太いほど流量が大きいことを表す。また、図16の黒色の太点線は、油圧アクチュエータから流出する作動油の流れを表す。
[背圧回生によるアキュムレータの蓄圧を伴う排土動作]
次に、図18を参照し、背圧回生によるアキュムレータ80の蓄圧を伴う排土動作が行われる場合における図2の油圧回路の状態を説明する。なお、図18は、背圧回生によるアキュムレータ80の蓄圧を伴う排土動作が行われる場合における図2の油圧回路の状態を示す。また、図18の黒色の太実線は、油圧アクチュエータに流入する作動油の流れを表し、実線の太さが太いほど流量が大きいことを表す。また、図18の黒色の太点線は、油圧アクチュエータから流出する作動油の流れを表す。
[アキュムレータの蓄圧を伴うブーム下げ旋回減速動作]
次に、図20を参照し、アキュムレータ80の蓄圧を伴うブーム下げ旋回減速動作が行われる場合における図2の油圧回路の状態を説明する。なお、図20は、アキュムレータ80の蓄圧を伴うブーム下げ旋回減速動作が行われる場合における図2の油圧回路の状態を示す。また、図20の灰色の太実線は、アキュムレータ80に流入する作動油の流れを表し、図20の黒色の太点線は、油圧アクチュエータから流出する作動油の流れを表す。
[エンジンのアシスト及びアキュムレータの蓄圧を伴う旋回減速動作]
次に、図22を参照し、エンジン11のアシスト及びアキュムレータ80の蓄圧を伴う旋回減速動作が行われる場合における図2の油圧回路の状態を説明する。なお、図22は、エンジン11のアシスト及びアキュムレータ80の蓄圧を伴う旋回減速動作が行われる場合における図2の油圧回路の状態を示す。また、図22の黒色の太点線は、旋回用油圧モータ21から流出する作動油の流れを表し、黒色の一点鎖線矢印は、エンジンアシストトルクが変速機13を介してエンジン11の回転軸に伝えられる様子を表す。また、図22は、旋回用油圧モータ21のポート21Lが吐出ポートとなる場合を一例として示すが、以下の説明は、ポート21Rが吐出ポートとなる場合についても同様に適用される。
[エンジンのアシスト及びアキュムレータの蓄圧を伴う旋回加速動作]
次に、図27を参照し、エンジン11のアシスト及びアキュムレータ80の蓄圧を伴う旋回加速動作が行われる場合における図2の油圧回路の状態を説明する。なお、図27は、エンジン11のアシスト及びアキュムレータ80の蓄圧を伴う旋回加速動作が行われる場合における図2の油圧回路の状態を示す。また、図27の黒色の太実線は第1ポンプ14Lから旋回用油圧モータ21への作動油の流れを表し、黒色の太点線は分岐点B1からアキュムレータ80及びポンプ・モータ14Aへの作動油の流れを表し、黒色の一点鎖線矢印はエンジンアシストトルクが変速機13を介してエンジン11の回転軸に伝えられる様子を表す。また、図27は、旋回用油圧モータ21のポート21Rが吸入ポートとなる場合を一例として示すが、以下の説明は、ポート21Lが吸入ポートとなる場合についても同様に適用される。
[アキュムレータの蓄圧のみを伴う旋回加速動作]
次に、図30を参照し、アキュムレータ80の蓄圧のみを伴う旋回加速動作が行われる場合における図2の油圧回路の状態を説明する。なお、図30は、アキュムレータ80の蓄圧のみを伴う旋回加速動作が行われる場合における図2の油圧回路の状態を示す。また、図30の黒色の太実線は第1ポンプ14Lから旋回用油圧モータ21への作動油の流れを表し、黒色の太点線は分岐点B1からアキュムレータ80への作動油の流れを表す。また、図30は、旋回用油圧モータ21のポート21Rが吸入ポートとなる場合を一例として示すが、以下の説明は、ポート21Lが吸入ポートとなる場合についても同様に適用される。また、図30の油圧回路で実行される旋回加速処理は、所望のエンジンアシストトルクを発生させるためにポンプ・モータ14Aの押退容積を調整する工程を除き、図28に示す旋回加速処理と同様である。また、旋回加速動作中の油圧システムの制御の流れは、図23に示す旋回減速動作中の油圧システムの制御の流れと同様である。
Claims (15)
- 複数の油圧ポンプを有するショベルであって、
旋回用油圧モータと、
旋回加速中に前記旋回用油圧モータの吸入ポート側から流出する作動油、又は、旋回減速中に前記旋回用油圧モータの吐出ポート側から流出する作動油を受けてエンジンアシストトルクを生成可能な油圧モータと、
前記流出する作動油を蓄積可能なアキュムレータと、
前記吸入ポート又は前記吐出ポートと前記油圧モータ及び前記アキュムレータとの間の連通・遮断を切り替える開度調整可能な開閉弁と、
前記開閉弁を制御する制御装置と、を有し、
前記制御装置は、前記開閉弁の開度を調整して前記流出する作動油の圧力を所定の目標圧とし、且つ、前記流出する作動油を同じ圧力で前記油圧モータ及び前記アキュムレータのそれぞれに流入させる、
ショベル。 - 前記流出する作動油を同じ圧力で前記油圧モータ及び前記アキュムレータのそれぞれに流入させる状態を選択的に実現する切替弁を有する、
請求項1に記載のショベル。 - 前記切替弁は、前記油圧モータと前記アキュムレータとの間に配置される、
請求項2に記載のショベル。 - 前記切替弁は、旋回減速中に、前記油圧モータと前記アキュムレータとの間を連通させ、前記開閉弁から流出する作動油を同じ圧力で前記油圧モータ及び前記アキュムレータのそれぞれに流入させる、
請求項3に記載のショベル。 - 前記切替弁は、前記吐出ポートと前記油圧モータ及び前記アキュムレータのそれぞれとの間に配置される、
請求項2に記載のショベル。 - 前記油圧モータは、可変容量型であり、前記エンジンアシストトルクが所定のアシストトルク目標値以下となるように押退容積が制御される、
請求項1に記載のショベル。 - 前記油圧モータの押退容積は、前記エンジンアシストトルクと前記アシストトルク目標値とが一致するように、前記アキュムレータに蓄積される作動油の圧力と前記アシストトルク目標値とに基づいて決定される、
請求項6に記載のショベル。 - 前記エンジンアシストトルクは、前記アキュムレータに蓄積される作動油の圧力と前記油圧モータの斜板傾転角とに基づいて算出される、
請求項6に記載のショベル。 - 前記目標圧は、前記旋回用油圧モータのリリーフ弁のリリーフ圧又はクラッキング圧よりも低い、
請求項1に記載のショベル。 - 前記制御装置は、旋回減速中に前記旋回用油圧モータの吐出ポート側から流出する作動油の圧力と前記目標圧とが一致するように、前記アキュムレータに蓄積される作動油の圧力と前記目標圧との差圧に基づいて前記開閉弁の開度を決定する、
請求項1に記載のショベル。 - 旋回減速中に前記旋回用油圧モータの吐出ポート側から流出する作動油の圧力は、旋回圧センサによって検出され、
前記アキュムレータに蓄積される作動油の圧力は、アキュムレータ圧センサによって検出される、
請求項10に記載のショベル。 - 前記制御装置は、旋回加速中に前記旋回用油圧モータの吸入ポート側から流出する作動油の圧力と前記目標圧とが一致するように、前記アキュムレータに蓄積される作動油の圧力と前記目標圧との差圧に基づいて前記開閉弁の開度を決定する、
請求項1に記載のショベル。 - 旋回加速中に前記旋回用油圧モータの吸入ポート側から流出する作動油の圧力は、旋回圧センサによって検出され、
前記アキュムレータに蓄積される作動油の圧力は、アキュムレータ圧センサによって検出される、
請求項12に記載のショベル。 - 前記制御装置は、前記アキュムレータに蓄積される作動油の圧力が前記目標圧より大きい場合、前記開閉弁を閉じて前記旋回用油圧モータの吸入ポート側の作動油をリリーフ弁から作動油タンクに排出する、
請求項1に記載のショベル。 - 複数の油圧ポンプを有するショベルであって、
旋回用油圧モータと、
旋回加速中に前記旋回用油圧モータの吸入ポート側から流出する作動油、又は、旋回減速中に前記旋回用油圧モータの吐出ポート側から流出する作動油を蓄積可能なアキュムレータと、
前記吸入ポート又は前記吐出ポートと前記アキュムレータとの間の連通・遮断を切り替える開度調整可能な開閉弁と、
前記開閉弁を制御する制御装置と、を有し、
前記制御装置は、前記開閉弁の開度を調整して前記流出する作動油の圧力を所定の目標圧とし、且つ、前記流出する作動油を前記アキュムレータに流入させる、
ショベル。
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