shovel

Abstract

To provide a shovel capable of more adequately controlling regeneration flow rate or regenerative flow rate.SOLUTION: A shovel 100 comprises: a hydraulic control valve HV4 as a meter-in valve corresponding to a boom cylinder 7; a hydraulic control valve HV3 and a hydraulic control valve HV16 as meter-out valves corresponding to the boom cylinder 7; a hydraulic control valve HV5 as the meter-in valve corresponding to an arm cylinder 8; and a hydraulic control valve HV6 as the meter-in valve corresponding to the arm cylinder 8. A controller 30 is constituted so as to make at least a portion of hydraulic oil flowing out of a bottom side oil chamber of the boom cylinder 7 join the hydraulic oil discharged from a second hydraulic pump 14B by controlling the meter-out valves corresponding to the boom cylinder 7 when simultaneously operating the boom cylinder 7 and the arm cylinder 8.SELECTED DRAWING: Figure 5

Description

[Technical field]

[0001] The present disclosure relates to a shovel. [Background technology]

[0002] 2. Description of the Related Art Conventionally, a shovel has been known as an excavator for excavating the ground (see Patent Document 1).

[0003] This excavator is configured so that when the hydraulic actuator is operated, the opening area (meter-in opening area) of the first oil passage connecting the hydraulic pump and the hydraulic actuator and the opening area (meter-out opening area) of the second oil passage connecting the hydraulic actuator and the hydraulic oil tank can be controlled simultaneously by one spool valve. Also, this excavator is configured to include a regenerative control valve for supplying hydraulic oil flowing out from the bottom side oil chamber of the boom cylinder to the arm cylinder when the boom lowering operation and the arm closing operation are performed simultaneously. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent Publication No. 2017-106227 Summary of the Invention [Problem to be solved by the invention]

[0005] However, in the above-mentioned configuration, the correspondence relationship between the displacement of the spool valve and the opening areas of the first and second oil passages is uniquely determined by the physical shape of the spool valve, and therefore the above-mentioned configuration may not be able to appropriately control the flow rate (regenerative flow rate) of hydraulic oil flowing out of the bottom-side oil chamber of the boom cylinder and flowing into the bottom-side oil chamber of the arm cylinder.

[0006] It is therefore desirable to provide an excavator that can more appropriately control the flow rate (regenerative flow rate or regenerative flow rate) of hydraulic oil supplied from a specific hydraulic actuator to that specific hydraulic actuator or to other hydraulic actuators. [Means for solving the problem]

[0007] An excavator according to an embodiment of the present disclosure includes a hydraulic oil tank, a first hydraulic actuator, a second hydraulic actuator, a hydraulic pump capable of supplying hydraulic oil in the hydraulic oil tank to each of the first hydraulic actuator and the second hydraulic actuator, a meter-in valve corresponding to each of the first hydraulic actuator and the second hydraulic actuator, a meter-out valve corresponding to each of the first hydraulic actuator and the second hydraulic actuator, and a control device that controls each of the meter-in valve, the meter-out valve, and the hydraulic pump, wherein the meter-out valve is configured to be able to adjust a flow rate of hydraulic oil flowing toward the hydraulic oil tank and a flow rate of hydraulic oil flowing toward the hydraulic pump, and the control device is configured to control the meter-out valve corresponding to the first hydraulic actuator when the first hydraulic actuator and the second hydraulic actuator are operated simultaneously, thereby causing at least a portion of the hydraulic oil flowing out from the first hydraulic actuator to merge with the hydraulic oil discharged by the hydraulic pump. Effect of the Invention

[0008] The above-described shovel can better control the regenerative or regenerative flow rate. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a side view of a shovel according to an embodiment of the present disclosure. [Diagram 2] FIG. 2 is a diagram showing an example of the configuration of a hydraulic circuit mounted on a shovel. [Diagram 3] FIG. 2 is a diagram illustrating an example of the configuration of a hydraulic control valve. [Figure 4]FIG. 13 is a diagram showing an example of a control flow for operating a shovel. [Diagram 5] FIG. 3 is a schematic diagram of a portion of the hydraulic circuit shown in FIG. 2. [Figure 6] FIG. 11 is a diagram showing another example of the configuration of a hydraulic circuit mounted on a shovel. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] First, with reference to FIG. 1, an excavator (shovel 100) as a construction machine according to an embodiment of the present disclosure will be described. FIG. 1 is a side view of the excavator 100 according to an embodiment of the present disclosure. An upper rotating body 3 is rotatably mounted on a lower traveling body 1 of the excavator 100 shown in FIG. 1 via a rotating mechanism 2. A boom 4 is attached to the upper rotating 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 working elements constitute an excavation attachment, which is an example of an attachment. The boom 4 is driven by a boom cylinder 7, the arm 5 is driven by an arm cylinder 8, and the bucket 6 is driven by a bucket cylinder 9. A cabin 10 is provided on the upper rotating body 3, and a power source such as an engine 11 is mounted on the upper rotating body 3. The engine 11 is a drive source for the excavator 100, and is, for example, a diesel engine that operates to maintain a predetermined rotation speed. The drive source may be a hydrogen engine, an electric motor, or the like.

[0011] Next, a hydraulic circuit mounted on the excavator 100 will be described with reference to Fig. 2 and Fig. 3. Fig. 2 is a schematic diagram of the hydraulic circuit mounted on the excavator 100. The basic system of the excavator 100 mainly includes a hydraulic pump 14, a pilot pump 15, an operating device 26, a controller 30, hydraulic control valves HV, and pressure sensors S1 to S7. Fig. 3 is a diagram showing an example of the configuration of a hydraulic control valve HV1, which is one of the hydraulic control valves HV.

[0012] The hydraulic pump 14 is a hydraulic pump that supplies hydraulic oil to the hydraulic control valve HV via a hydraulic oil line. In the example shown in FIG. 2, the hydraulic pump 14 is a swash plate type variable displacement hydraulic pump that is driven by the engine 11, and the input shaft of the hydraulic pump 14 is connected to the output shaft of the engine 11. In the swash plate type variable displacement hydraulic pump, the stroke length of the piston that determines the displacement volume changes according to a change in the swash plate tilt angle, and the pump discharge amount per one rotation changes. The swash plate tilt angle is controlled by the regulator 13. The regulator 13 changes the swash plate tilt angle according to a change in the control current from the controller 30. For example, the regulator 13 is configured to increase the swash plate tilt angle according to an increase in the control current, thereby increasing the pump discharge amount of the hydraulic pump 14. Specifically, the hydraulic pump 14 includes a first hydraulic pump 14A and a second hydraulic pump 14B, and the regulator 13 includes a first regulator 13A and a second regulator 13B.

[0013] 2 and 3, the boom cylinder 7 and the arm cylinder 8 are driven by the hydraulic oil discharged by the first hydraulic pump 14A and the hydraulic oil discharged by the second hydraulic pump 14B. Furthermore, the bucket cylinder 9 is driven by the hydraulic oil discharged by the first hydraulic pump 14A and the hydraulic oil discharged by the second hydraulic pump 14B when contracting, but is driven only by the hydraulic oil discharged by the second hydraulic pump 14B when extending.

[0014] The pressure sensors S1 to S7 are devices for detecting the pressure of the hydraulic oil in each part of the hydraulic circuit.

[0015] The pressure sensor S1 is a device for detecting the pressure of hydraulic oil related to the operation of the left traveling hydraulic motor 1M. Specifically, the pressure sensor S1 includes a pressure sensor S1L and a pressure sensor S1R. The pressure sensor S1L detects the pressure of hydraulic oil in a first port (left port) of the left traveling hydraulic motor 1M. The pressure sensor S1R detects the pressure of hydraulic oil (right port pressure) in a second port (right port) of the left traveling hydraulic motor 1M.

[0016] The pressure sensor S2 is a device for detecting the pressure of hydraulic oil related to the operation of the right traveling hydraulic motor 2M. Specifically, the pressure sensor S2 includes a pressure sensor S2L and a pressure sensor S2R. The pressure sensor S2L detects the pressure of hydraulic oil at a first port (left port) of the right traveling hydraulic motor 2M. The pressure sensor S2R detects the pressure of hydraulic oil at a second port (right port) of the right traveling hydraulic motor 2M.

[0017] The pressure sensor S3 is a device for detecting the pressure of hydraulic oil related to the operation of the swing hydraulic motor 3M. Specifically, the pressure sensor S3 includes a pressure sensor S3L and a pressure sensor S3R. The pressure sensor S3L detects the pressure of hydraulic oil at a first port (left port) of the swing hydraulic motor 3M. The pressure sensor S3R detects the pressure of hydraulic oil at a second port (right port) of the swing hydraulic motor 3M.

[0018] The pressure sensor S4 is a device for detecting the pressure of hydraulic oil related to the operation of the boom 4. Specifically, the pressure sensor S4 includes a pressure sensor S4B and a pressure sensor S4R. The pressure sensor S4B detects the boom bottom pressure, which is the pressure of hydraulic oil in the bottom side oil chamber of the boom cylinder 7. The pressure sensor S4R detects the boom rod pressure, which is the pressure of hydraulic oil in the rod side oil chamber of the boom cylinder 7.

[0019] The pressure sensor S5 is a device for detecting the pressure of hydraulic oil related to the operation of the arm 5. Specifically, the pressure sensor S5 includes a pressure sensor S5B and a pressure sensor S5R. The pressure sensor S5B detects the arm bottom pressure which is the pressure of hydraulic oil in the bottom side oil chamber of the arm cylinder 8. The pressure sensor S5R detects the arm rod pressure which is the pressure of hydraulic oil in the rod side oil chamber of the arm cylinder 8.

[0020] The pressure sensor S6 is a device for detecting the pressure of hydraulic oil related to the operation of the bucket 6. Specifically, the pressure sensor S6 includes a pressure sensor S6B and a pressure sensor S6R. The pressure sensor S6B detects the bucket bottom pressure, which is the pressure of hydraulic oil in a bottom-side oil chamber of the bucket cylinder 9. The pressure sensor S6R detects the bucket rod pressure, which is the pressure of hydraulic oil in a rod-side oil chamber of the bucket cylinder 9.

[0021] The pressure sensor S7 is a device (discharge pressure sensor) for detecting the pump discharge pressure of the hydraulic pump 14. Specifically, the pressure sensor S7 includes a pressure sensor S7A and a pressure sensor S7B. The pressure sensor S7A detects the pump discharge pressure of the first hydraulic pump 14A. The pressure sensor S7B detects the pump discharge pressure of the second hydraulic pump 14B.

[0022] The hydraulic control valve HV is configured to be able to control the flow of hydraulic oil related to the hydraulic actuators. In this embodiment, the hydraulic control valve HV includes hydraulic control valves HV1 to HV20 of the same structure that are individually controlled by solenoid valves EV. The hydraulic control valve HV is configured to selectively supply hydraulic oil received from the hydraulic pump 14 through a hydraulic oil line to one or more hydraulic actuators in response to a change in pressure (pilot pressure) corresponding to the operation direction and operation amount of the operating device 26. The hydraulic actuators include, for example, a boom cylinder 7, an arm cylinder 8, a bucket cylinder 9, a left traveling hydraulic motor 1M, a right traveling hydraulic motor 2M, and a swing hydraulic motor 3M.

[0023] The hydraulic control valve HV1 is disposed in a pipeline connected to a first port (left port) of the swing hydraulic motor 3M, and is configured to selectively connect the first port (left port) of the swing hydraulic motor 3M to the first hydraulic pump 14A or the hydraulic oil tank T. The hydraulic control valve HV1 functions as a meter-in valve for the swing hydraulic motor 3M when the swing hydraulic motor 3M rotates in a first direction, and functions as a meter-out valve for the swing hydraulic motor 3M when the swing hydraulic motor 3M rotates in a second direction that is opposite to the first direction.

[0024] The hydraulic control valve HV2 arranged in the pipeline connected to the second port (right port) of the swing hydraulic motor 3M, the hydraulic control valve HV3 arranged in the pipeline connected to the bottom side oil chamber of the boom cylinder 7, the hydraulic control valve HV4 arranged in the pipeline connected to the rod side oil chamber of the boom cylinder 7, the hydraulic control valve HV5 arranged in the pipeline connected to the bottom side oil chamber of the arm cylinder 8, the hydraulic control valve HV6 arranged in the pipeline connected to the rod side oil chamber of the arm cylinder 8, the hydraulic control valve HV7 arranged in the pipeline connected to the first port (left port) of the left traveling hydraulic motor 1M, the hydraulic control valve HV8 arranged in the pipeline connected to the second port (right port) of the left traveling hydraulic motor 1M, the hydraulic control valve HV9 arranged in the pipeline connected to the rod side oil chamber of the bucket cylinder 9, the hydraulic control valve HV10 arranged in the pipeline connected to the oil chamber of the hydraulic actuator, the hydraulic control valve HV11 arranged in the pipeline connected to the rod side oil chamber of the bucket cylinder 9, The same is true for the hydraulic control valve HV11 arranged in the pipeline connected to the bottom oil chamber of the bucket cylinder 9, the hydraulic control valve HV12 arranged in the pipeline connected to the bottom oil chamber of the bucket cylinder 9, the hydraulic control valve HV13 arranged in the pipeline connected to the rod side oil chamber of the arm cylinder 8, the hydraulic control valve HV14 arranged in the pipeline connected to the bottom oil chamber of the arm cylinder 8, the hydraulic control valve HV15 arranged in the pipeline connected to the rod side oil chamber of the boom cylinder 7, the hydraulic control valve HV16 arranged in the pipeline connected to the bottom oil chamber of the boom cylinder 7, the hydraulic control valve HV17 arranged in the pipeline connected to the first port (left port) of the right traveling hydraulic motor 2M, the hydraulic control valve HV18 arranged in the pipeline connected to the second port (right port) of the right traveling hydraulic motor 2M, and the hydraulic control valve HV19 and the hydraulic control valve HV20 arranged in the pipelines connected to hydraulic actuators other than the above-mentioned hydraulic actuators.

[0025] The pilot pump 15 is a hydraulic pump for supplying hydraulic oil to various hydraulic control devices such as the operating device 26 via a pilot line. In the example shown in Fig. 3, the pilot pump 15 is a fixed displacement hydraulic pump that is driven by the engine 11, and an input shaft of the pilot pump 15 is connected to an output shaft of the engine 11. Note that the hydraulic pump 14 may be configured to supply hydraulic oil to various hydraulic control devices such as the operating device 26 via a pilot line after reducing the pressure of the discharged hydraulic oil by throttling or the like. In this case, the pilot pump 15 may be omitted.

[0026] The operation device 26 is a device used by an operator to operate the hydraulic actuator. The operation device 26 is, for example, an operation lever or an operation pedal. In the example shown in FIG. 3, the operation device 26 is an electric operation device, and outputs information on the operation direction and operation amount of the operation device 26 to the controller 30 as an electric signal (operation command value). The controller 30 can adjust the magnitude of the pilot pressure acting on the hydraulic control valve HV by adjusting the opening area of ​​the solenoid valve EV in response to the electric signal received from the operation device 26. The operation device 26 also includes a left operation lever for operating the swing hydraulic motor 3M and the arm cylinder 8, and a right operation lever for operating the boom cylinder 7 and the bucket cylinder 9. Hereinafter, for convenience, the left operation lever when operating the arm 5 is referred to as the arm operation lever, and the right operation lever when operating the boom 4 is referred to as the boom operation lever.

[0027] The controller 30 is a control device for controlling the shovel 100. In this embodiment, the controller 30 is configured with a computer including a CPU, a volatile storage medium, a nonvolatile storage medium, etc. The CPU of the controller 30 reads out programs corresponding to various functions from the nonvolatile storage medium, loads them into the volatile storage medium, and executes them to realize the functions corresponding to each of the programs.

[0028] For example, the controller 30 realizes a function of controlling the pump discharge amount of the hydraulic pump 14. Specifically, the controller 30 changes the magnitude of the control current to the regulator 13, and controls the pump discharge amount of the hydraulic pump 14 via the regulator 13.

[0029] Here, the hydraulic control valve HV will be described in detail with reference to Fig. 3. Note that the following description relates to the hydraulic control valve HV1, but is similarly applicable to each of the hydraulic control valves HV2 to HV20.

[0030] The hydraulic control valve HV1 is a 3-port, 3-position spool valve. In Fig. 3, (1) indicates the first position (first valve position), (2) indicates the second position (second valve position), and (3) indicates the third position (third valve position).

[0031] When the hydraulic control valve HV1 is positioned at the second position, which is the neutral position, it blocks communication between the left port of the swing hydraulic motor 3M and each of the first hydraulic pump 14A and the hydraulic oil tank T. In other words, when the hydraulic control valve HV1 is positioned at the second position, which is the neutral position, the opening area of ​​the first oil passage connecting the left port of the swing hydraulic motor 3M and the first hydraulic pump 14A and the opening area of ​​the second oil passage connecting the left port of the swing hydraulic motor 3M and the hydraulic oil tank are each minimized (zero).

[0032] Furthermore, when the hydraulic control valve HV1 is positioned at the first position, it communicates the left port of the swing hydraulic motor 3M with the first hydraulic pump 14A, and when the hydraulic control valve HV1 is positioned at the third position, it communicates the left port of the swing hydraulic motor 3M with the hydraulic oil tank T. That is, the hydraulic control valve HV1 is configured so that when the hydraulic control valve HV1 is positioned at the first position, the opening area of ​​the first oil passage is maximized, and when the hydraulic control valve HV1 is positioned at the third position, the opening area of ​​the second oil passage is maximized.

[0033] In addition, the hydraulic control valve HV1 is configured such that, in an intermediate position between the second position and the first position, the opening area of ​​the first oil passage becomes larger the further away from the neutral position, and, in an intermediate position between the second position and the third position, the opening area of ​​the second oil passage becomes larger the further away from the neutral position.

[0034] In addition, the hydraulic control valve HV1 is configured to move to the right when the pilot pressure at the left pilot port PL (left pilot pressure) becomes greater than the pilot pressure at the right pilot port PR (right pilot pressure), to move to the left when the left pilot pressure becomes smaller than the right pilot pressure, and to return to the neutral position when the left pilot pressure and the right pilot pressure become equal.

[0035] The left pilot pressure and the right pilot pressure are controlled by a solenoid valve EV. Specifically, the solenoid valve EV is a device for adjusting the pilot pressure, and is disposed between the hydraulic control valve HV1 and the pilot pump 15. In the example shown in FIG. 3, the solenoid valve EV operates in response to a current command from a controller 30. The solenoid valve EV is basically configured to operate the hydraulic control valve HV1 in response to the contents of an operation input to the operating device 26. Typically, the solenoid valve EV is configured to increase the amount of movement of the hydraulic control valve HV1 as the operation amount of the operating device 26 increases. In addition, the solenoid valve EV is configured to forcibly operate the hydraulic control valve HV1 regardless of the contents of the operation input to the operating device 26.

[0036] Specifically, the solenoid valve EV is a 4-port, 3-position spool valve. In Fig. 3, (1) indicates the first position (first valve position), (2) indicates the second position (second valve position), and (3) indicates the third position (third valve position).

[0037] When the solenoid valve EV is located at the second position, which is the neutral position, it connects the left pilot port PL and right pilot port PR of the hydraulic control valve HV1 to the hydraulic oil tank T, and blocks communication between the left pilot port PL and right pilot port PR and the pilot pump 15. At this time, the left pilot pressure and right pilot pressure acting on the hydraulic control valve HV1 become the hydraulic oil tank pressure (atmospheric pressure), so the hydraulic control valve HV1 returns to the neutral position.

[0038] Furthermore, when the solenoid valve EV is positioned at the first position, it communicates the left pilot port PL with the pilot pump 15, and also communicates the right pilot port PR with the hydraulic oil tank T. That is, when the solenoid valve EV is positioned at the first position, the opening area of ​​the first oil passage connecting the left pilot port PL with the pilot pump 15 is maximized, and the opening area of ​​the second oil passage connecting the right pilot port PR with the hydraulic oil tank T is maximized. At this time, the left pilot pressure acting on the hydraulic control valve HV1 becomes larger than the right pilot pressure, so the hydraulic control valve HV1 moves to the right.

[0039] Furthermore, when the solenoid valve EV is positioned at the third position, it communicates the left pilot port PL with the hydraulic oil tank T, and also communicates the right pilot port PR with the pilot pump 15. That is, when the solenoid valve EV is positioned at the third position, the opening area of ​​the third oil passage connecting the left pilot port PL with the hydraulic oil tank T is maximized, and the opening area of ​​the fourth oil passage connecting the right pilot port PR with the pilot pump 15 is maximized. At this time, the left pilot pressure acting on the hydraulic control valve HV1 becomes smaller than the right pilot pressure, so the hydraulic control valve HV1 moves to the left.

[0040] In addition, the solenoid valve EV is configured such that, in an intermediate position between the second position and the first position, the opening area of ​​the first oil passage and the second oil passage increases the further away from the neutral position, and, in an intermediate position between the second position and the third position, the opening area of ​​the third oil passage and the fourth oil passage increases the further away from the neutral position.

[0041] Next, an example of a control flow for operating the shovel 100 will be described with reference to FIG. 4. FIG. 4 is a diagram showing an example of a control flow for operating the shovel 100. This control is executed by the controller 30. In the example shown in FIG. 4, a control flow when a combined operation including a boom raising operation, an arm closing operation, and a bucket closing operation is performed is shown. In addition, in FIG. 4, the control flow executed by the controller 30 is represented by a plurality of functional blocks. In the example shown in FIG. 4, the functions represented by each functional block are realized by software. However, the functions represented by each functional block may be realized by hardware, or may be realized by a combination of software and hardware. In addition, in FIG. 4, for clarity, the meter-in valve is represented by an "MI valve" and the meter-out valve is represented by an "MO valve".

[0042] The boom required flow rate derivation unit F2 is configured to derive the boom required flow rate based on the boom operation amount and the boom thrust. The value of the boom operation amount is an example of an operation command value, and is the value of the operation amount of the operation device 26 for operating the boom 4. In the example shown in Fig. 4, the boom operation amount is a value corresponding to the tilt angle when the right operation lever is tilted in the forward / rearward direction.

[0043] Boom thrust is a thrust for moving the boom 4. Boom thrust is expressed, for example, by a value obtained by multiplying the pressure difference between the boom bottom pressure and the boom rod pressure by a pressure-receiving area. The pressure difference between the boom bottom pressure (meter-in pressure) and the boom rod pressure (meter-out pressure) is a value obtained by subtracting the meter-out pressure from the meter-in pressure, and is also called the "boom effective pressure", which is one of the "effective pressures". The pressure-receiving area is the pressure-receiving area of ​​the piston that constitutes the boom cylinder 7. In the example shown in FIG. 4, the pressure-receiving area in the rod-side oil chamber is smaller than the pressure-receiving area in the bottom-side oil chamber by the cross-sectional area of ​​the rod.

[0044] The boom required flow rate is a required flow rate of the boom cylinder 7. Specifically, the boom required flow rate is a target value for the amount of hydraulic oil flowing into the boom cylinder 7 per unit time.

[0045] The flow command generating unit F1 is configured to calculate a target value of the flow rate of the hydraulic oil to be supplied to each hydraulic actuator based on the required flow rate of each hydraulic actuator and the pump discharge pressure. In the example shown in Fig. 4, the flow command generating unit F1 is configured to output a command value corresponding to the target value.

[0046] 4, flow command generating unit F1 outputs a first boom inflow, which is an example of a flow command, to MI valve opening area calculating unit F5 and MO valve opening area calculating unit F6. The first boom inflow is a target value related to the flow rate of hydraulic oil supplied from the first hydraulic pump 14A through a first meter-in valve (in this example, hydraulic control valve HV3) to the boom cylinder 7. The first meter-in valve is one of two meter-in valves related to the boom cylinder 7.

[0047] The MI valve opening area calculation unit F5 is configured to control a first meter-in valve disposed between the first hydraulic pump 14A and the boom cylinder 7. For example, the MI valve opening area calculation unit F5 is configured to calculate the opening area of ​​the first meter-in valve. In the example shown in Fig. 4, the MI valve opening area calculation unit F5 calculates the opening area of ​​the hydraulic control valve HV3 that functions as the first meter-in valve during the boom raising operation.

[0048] Specifically, the MI valve opening area calculation unit F5 calculates the opening area of ​​the first meter-in valve (hydraulic control valve HV3) based on the first boom inflow volume, the first boom MI pressure, the pump discharge pressure of the first hydraulic pump 14A, and a predetermined calculation formula.

[0049] The first boom MI pressure is a detection value of the pressure sensor S4B, and the pump discharge pressure of the first hydraulic pump 14A is a detection value of the pressure sensor S7A.

[0050] The predetermined calculation formula is, for example, a flow rate calculation formula for an orifice shown in the following formula (1), where the first boom inflow amount is Qb, the pump discharge pressure of the first hydraulic pump 14A is Pa, the first boom MI pressure is Pb, and the opening area of ​​the first meter-in valve (hydraulic control valve HV3) is A1, then the opening area A1 of the first meter-in valve (hydraulic control valve HV3) is expressed by formula (2), where C is a flow coefficient and ρ is a fluid density.

[0051]

number

[0052] In this way, the MI valve opening area calculation unit F5 controls the opening area of ​​the first meter-in valve so that hydraulic oil can flow into the bottom side oil chamber of the boom cylinder 7 at a desired flow rate (first boom inflow amount Qb).

[0053] The flow rate command generating unit F1 is configured to similarly output flow rate commands to an MI valve opening area calculation unit F7 that controls the opening area of ​​the remaining one of the two meter-in valves related to the boom cylinder 7, an MO valve opening area calculation unit F6 and an MO valve opening area calculation unit F8 that control the opening areas of the two meter-out valves related to the boom cylinder 7, two MI valve opening area calculation units (not shown) that control the opening area of ​​the two meter-in valves related to the arm cylinder 8, two MO valve opening area calculation units (not shown) that control the opening area of ​​the two meter-out valves related to the arm cylinder 8, an MI opening area calculation unit (not shown) that controls the meter-in valve related to the bucket cylinder 9, and two MO valve opening area calculation units (not shown) that control the opening area of ​​the two meter-out valves related to the bucket cylinder 9.

[0054] Moreover, the flow command generating unit F1 is configured to output a command for determining the pump discharge rate of the hydraulic pump 14. Specifically, the flow command generating unit F1 outputs a pump discharge rate determination command to the maximum MI pressure selecting unit F9.

[0055] The maximum MI pressure selection unit F9 is configured to select the maximum value of one or more meter-in pressures as the maximum MI pressure. The meter-in pressure is the pressure of hydraulic oil downstream of the meter-in valve. Specifically, the meter-in pressure is the pressure of hydraulic oil in a pipe connecting the meter-in valve and the hydraulic actuator. In the example shown in FIG. 4 in which the boom raising operation is performed, the meter-in pressure includes the pressure of hydraulic oil in the pipe connecting the hydraulic control valve HV3 functioning as a meter-in valve and the bottom side oil chamber of the boom cylinder 7, i.e., the boom bottom pressure detected by the pressure sensor S4B.

[0056] When a combined operation consisting of a boom raising operation, an arm closing operation, and a bucket closing operation is performed, the maximum MI pressure selection unit F9 selects the maximum value among the boom bottom pressure, the arm bottom pressure, and the bucket bottom pressure as the maximum MI pressure.

[0057] 4, the maximum MI pressure selection unit F9 selects the maximum value of one or more meter-in pressures related to the first hydraulic pump 14A as the first maximum MI pressure, and selects the maximum value of one or more meter-in pressures related to the second hydraulic pump 14B as the second maximum MI pressure. The one or more meter-in pressures related to the first hydraulic pump 14A are the meter-in pressures related to one or more of the hydraulic control valves HV1 to HV10. The one or more meter-in pressures related to the second hydraulic pump 14B are the meter-in pressures related to one or more of the hydraulic control valves HV11 to HV20.

[0058] Then, the maximum MI pressure selection unit F9 outputs the selected maximum MI pressure to the pump discharge rate control unit F10.

[0059] The pump discharge rate control unit F10 is configured to control the pump discharge rate of the hydraulic pump 14. In the example shown in Fig. 4, the pump discharge rate control unit F10 calculates a command value to be output to the regulator 13 of the hydraulic pump 14 serving as a swash plate type variable displacement hydraulic pump, based on the maximum MI pressure output by the maximum MI pressure selection unit F9. In this case, the command value is, for example, the swash plate tilt angle.

[0060] Specifically, the pump discharge control unit F10 calculates the swash plate tilt angle to be output to the first regulator 13A of the first hydraulic pump 14A based on the first maximum MI pressure output by the maximum MI pressure selection unit F9. The pump discharge control unit F10 also calculates the swash plate tilt angle to be output to the second regulator 13B of the second hydraulic pump 14B based on the second maximum MI pressure output by the maximum MI pressure selection unit F9.

[0061] The regulator 13 changes the swash plate tilt angle of the hydraulic pump 14 in response to a command value from the pump discharge rate control unit F10 to change the pump discharge rate of the hydraulic pump 14. Specifically, the first regulator 13A changes the pump discharge rate of the first hydraulic pump 14A, and the second regulator 13B changes the pump discharge rate of the second hydraulic pump 14B.

[0062] In this way, the controller 30 can appropriately control the flow rate of hydraulic oil flowing into the hydraulic actuator, the flow rate of hydraulic oil flowing out of the hydraulic actuator, and the pump discharge rate of the hydraulic pump 14.

[0063] Next, referring to FIG. 5, an example of a process in which the controller 30 controls the movement of the hydraulic control valve HV through the solenoid valve EV will be described. FIG. 5 is a schematic diagram of a part of the hydraulic circuit shown in FIG. 2, and shows the flow of hydraulic oil when the boom cylinder 7 is contracted and the arm cylinder 8 is extended. That is, FIG. 5 is a schematic diagram of a hydraulic circuit including the hydraulic control valve HV3, the hydraulic control valve HV4, the hydraulic control valve HV13, the hydraulic control valve HV14, the hydraulic control valve HV16, the boom cylinder 7, the arm cylinder 8, the first hydraulic pump 14A, the second hydraulic pump 14B, and the hydraulic oil tank T, and shows the flow of hydraulic oil when a combined operation including a boom lowering operation and an arm closing operation is performed. In FIG. 5, for clarity, the flow of hydraulic oil toward each of the boom cylinder 7 and the arm cylinder 8 is represented by a thick solid arrow, and the flow of hydraulic oil from each of the boom cylinder 7 and the arm cylinder 8 toward the hydraulic oil tank T is represented by a thick dashed arrow. In addition, the boom cylinder 7 is actually composed of two hydraulic cylinders, but is represented below as one hydraulic cylinder for simplicity of explanation. In addition, the boom cylinder 7 and the arm cylinder 8 can actually each be operated using hydraulic oil discharged from the first hydraulic pump 14A and the second hydraulic pump 14B, respectively, but in the following, for simplicity of explanation, the boom cylinder 7 is represented as operating with hydraulic oil discharged from the first hydraulic pump 14A, and the arm cylinder 8 is represented as operating with hydraulic oil discharged from the second hydraulic pump 14B.

[0064] Also, in FIG. 5, the hydraulic control valve HV16 is configured to be able to utilize an intermediate position between the first position (see FIG. 3) and the third position (see FIG. 3). That is, the hydraulic control valve HV16 can cause a part of the hydraulic oil flowing out from the bottom-side oil chamber of the boom cylinder 7 to flow toward the hydraulic oil tank T, and cause the remaining part to flow toward the second hydraulic pump 14B. The same is true for the hydraulic control valve HV3, the hydraulic control valve HV4, the hydraulic control valve HV13, and the hydraulic control valve HV14. Therefore, in FIG. 5, for the sake of clarity, the hydraulic control valve HV3, the hydraulic control valve HV4, the hydraulic control valve HV13, the hydraulic control valve HV14, and the hydraulic control valve HV16 are illustrated as 3-port 2-position spool valves. Although not shown in FIG. 5, as shown in FIG. 2, the bottom side oil chamber of the arm cylinder 8 is connected to each of the first hydraulic pump 14A and the hydraulic oil tank T via a hydraulic control valve HV5, the rod side oil chamber of the arm cylinder 8 is connected to each of the first hydraulic pump 14A and the hydraulic oil tank T via a hydraulic control valve HV6, and the rod side oil chamber of the boom cylinder 7 is connected to each of the second hydraulic pump 14B and the hydraulic oil tank T via a hydraulic control valve HV15.

[0065] Specifically, Figure 5 shows the flow of hydraulic oil when a portion of the hydraulic oil flowing out from the bottom side oil chamber of the boom cylinder 7 is supplied (regenerated) to the rod side oil chamber of the boom cylinder 7, another portion of the hydraulic oil flowing out from the bottom side oil chamber of the boom cylinder 7 is supplied (regenerated) to the bottom side oil chamber of the arm cylinder 8, and the remaining portion of the hydraulic oil flowing out from the bottom side oil chamber of the boom cylinder 7 is discharged into the hydraulic oil tank T.

[0066] Fig. 5 also includes a cross-sectional view of the boom cylinder 7. Specifically, Fig. 5 includes a view of the cross section of the bottom-side oil chamber of the boom cylinder 7 viewed from below on an imaginary plane including the dashed-dotted line AA, and a view of the cross section of the rod-side oil chamber of the boom cylinder 7 viewed from above on an imaginary plane including the dashed-dotted line BB. "A11" represents the pressure-receiving area (surface area of ​​the area represented by the dot pattern) in the rod-side oil chamber of the piston 7S sliding inside the boom cylinder 7, and "A12" represents the pressure-receiving area (surface area of ​​the area represented by the dot pattern) in the bottom-side oil chamber of the piston 7S.

[0067] More specifically, the first pump discharge rate QS1 represents the flow rate of hydraulic oil discharged by the first hydraulic pump 14A, and the second pump discharge rate QS2 represents the flow rate of hydraulic oil discharged by the second hydraulic pump 14B. In the illustrated example, the first pump discharge rate QS1 is zero, and the second pump discharge rate QS2 is greater than zero. Furthermore, the first arm flow rate QA1 represents the flow rate of hydraulic oil flowing into the bottom side oil chamber of the arm cylinder 8, the second arm flow rate QA2 represents the flow rate of hydraulic oil flowing out of the rod side oil chamber of the arm cylinder 8, the first boom flow rate QB1 represents the flow rate of hydraulic oil flowing out of the bottom side oil chamber of the boom cylinder 7, and the second boom flow rate QB2 represents the flow rate of hydraulic oil flowing into the rod side oil chamber of the boom cylinder 7. Furthermore, the regeneration flow rate QRG1 represents the flow rate of hydraulic oil that is supplied (regenerated) to the rod side oil chamber of the boom cylinder 7 out of the first boom flow rate QB1, the regeneration flow rate QRG2 represents the flow rate of hydraulic oil that is supplied (regenerated) to the bottom side oil chamber of the arm cylinder 8 out of the first boom flow rate QB1, and the discharge flow rate QT represents the flow rate of hydraulic oil that is discharged to the hydraulic oil tank T out of the first boom flow rate QB1. In other words, the sum of the regeneration flow rate QRG1, the regeneration flow rate QRG2, and the discharge flow rate QT corresponds to the first boom flow rate QB1.

[0068] In the hydraulic circuit shown in FIG. 5, the regenerative flow rate QRG2 is determined based on the valve position of the hydraulic control valve HV16, the discharge flow rate QT is determined based on the valve position of the hydraulic control valve HV3, and the remaining flow rate (the flow rate obtained by subtracting the regenerative flow rate QRG2 and the discharge flow rate QT from the first boom flow rate QB1) is used as the regenerative flow rate QRG1.

[0069] The controller 30 as a control device can control the remaining one by controlling two of the three flow rates (regeneration flow rate QRG1, regeneration flow rate QRG2, and discharge flow rate QT) constituting the first boom flow rate QB1. In the illustrated example, the controller 30 controls the regeneration flow rate QRG1 by adjusting the valve position of the hydraulic control valve HV4, and controls the regeneration flow rate QRG2 by adjusting the valve position of the hydraulic control valve HV16. In this case, if the regeneration flow rate QRG1 and the regeneration flow rate QRG2 are controlled preferentially, the discharge flow rate QT is also controlled subordinately. The controller 30 may control the discharge flow rate QT by adjusting the valve position of the hydraulic control valve HV3, and control the regeneration flow rate QRG2 by adjusting the valve position of the hydraulic control valve HV16. In this case, if the discharge flow rate QT and the regeneration flow rate QRG2 are controlled preferentially, the regeneration flow rate QRG1 is also controlled subordinately. Alternatively, the controller 30 may control the discharge flow rate QT by adjusting the valve position of the hydraulic control valve HV3, and control the regeneration flow rate QRG1 by adjusting the valve position of the hydraulic control valve HV4. In this case, if the regeneration flow rate QRG1 and the discharge flow rate QT are controlled preferentially, the regeneration flow rate QRG2 is controlled subordinately.

[0070] In order to realize the state of the hydraulic circuit as shown in Fig. 5, the controller 30 calculates the first arm flow rate QA1 corresponding to the desired extension speed of the arm cylinder 8 based on the operation amount of the arm operating lever, and determines the regenerative flow rate QRG2 based on the first arm flow rate QA1. In the illustrated example, the controller 30 determines the regenerative flow rate QRG2 so that the first arm flow rate QA1 and the regenerative flow rate QRG2 are as close to each other as possible. This is to minimize the second pump discharge rate QS2, that is, to bring it as close to zero as possible.

[0071] Furthermore, the controller 30 calculates the second boom flow rate QB2 corresponding to the desired retraction speed of the boom cylinder 7 based on the operation amount of the boom operation lever, and determines the regeneration flow rate QRG1 based on the second boom flow rate QB2. In the illustrated example, the controller 30 determines the regeneration flow rate QRG1 so that the second boom flow rate QB2 and the regeneration flow rate QRG1 are as close to each other as possible. This is to minimize the first pump discharge rate QS1, i.e., to bring it as close to zero as possible.

[0072] Further, the controller 30 calculates the first boom flow rate QB1 based on the second boom flow rate QB2. Specifically, the controller 30 calculates the first boom flow rate QB1 (=(A11-A12) / A12×QB2) by multiplying the second boom flow rate QB2 by the ratio ((A11-A12) / A12) of the difference (A11-A12) between the pressure-receiving area A11 and the pressure-receiving area A12 in the rod-side oil chamber of the piston 7S of the boom cylinder 7.

[0073] Then, the controller 30 calculates the discharge flow rate QT by subtracting the regeneration flow rate QRG1 and the regeneration flow rate QRG2 from the first boom flow rate QB1.

[0074] The controller 30 may be configured to calculate the flow rate of the hydraulic oil passing through the hydraulic control valve HV based on the opening area of ​​the hydraulic control valve HV and the differential pressure before and after the hydraulic control valve HV. For example, the controller 30 may be configured to measure the first arm flow rate QA1 based on the opening area of ​​the PC port of the hydraulic control valve HV14 and the differential pressure before and after the hydraulic control valve HV14. The PC port of the hydraulic control valve HV14 is a port that connects the second hydraulic pump 14B and the bottom side oil chamber of the arm cylinder 8. Specifically, the controller 30 may calculate the opening area of ​​the PC port of the hydraulic control valve HV14 based on the output of a pilot pressure sensor that detects the pilot pressure of the hydraulic control valve HV14, and measure the first arm flow rate QA1 based on the opening area and the differential pressure before and after the hydraulic control valve HV14 calculated from the outputs of the pressure sensors S5B and S7A. Alternatively, the controller 30 may derive the opening area of ​​the PC port of the hydraulic control valve HV 14 from the value of the MI valve opening command. The same applies to the flow rates of the hydraulic oil passing through the other ports of the other hydraulic control valves HV.

[0075] In the above example, the controller 30 determines the regeneration flow rate QRG1 so that the first pump discharge rate QS1 of the first hydraulic pump 14A is the minimum amount (zero), i.e., so that the regeneration flow rate QRG1 is the maximum amount (second boom flow rate QB2). However, the controller 30 may determine the regeneration flow rate QRG1 so that the first pump discharge rate QS1 is a predetermined amount greater than the minimum amount (zero).

[0076] Furthermore, in the above example, the controller 30 determines the regenerative flow rate QRG2 so that the second pump discharge rate QS2 of the second hydraulic pump 14B is the minimum amount (zero), i.e., so that the regenerative flow rate QRG2 is the maximum amount (first arm flow rate QA1), but the controller 30 may determine the regenerative flow rate QRG2 so that the second pump discharge rate QS2 is a predetermined amount greater than the minimum amount (zero).

[0077] Furthermore, the controller 30 may control the hydraulic control valve HV so that the regeneration flow rate QRG1 becomes zero, or so that the regeneration flow rate QRG2 becomes zero, or so that both the regeneration flow rate QRG1 and the regeneration flow rate QRG2 become zero.

[0078] Furthermore, the hydraulic control valve HV may be an electromagnetic control valve. In this case, the electromagnetic valve EV may be omitted, because the controller 30 can directly control the electromagnetic control valve without the intervention of the electromagnetic valve EV.

[0079] With this configuration, the controller 30 can more appropriately control the regeneration flow rate QRG1 or the regeneration flow rate QRG2 compared to the flow rate control of the hydraulic oil using a conventional configuration in which the meter-in valve and the meter-out valve are not independent. Therefore, the controller 30 can suppress the execution of the regeneration function or the regeneration function from adversely affecting the operability of the hydraulic actuator. Specifically, the controller 30 can suppress the occurrence of a situation in which the extension speed of the arm cylinder 8 becomes excessively high when the regeneration flow rate QRG2 from the boom cylinder 7 is increased. Alternatively, the controller 30 can suppress the occurrence of a situation in which, when the extension speed of the arm cylinder 8 is limited, the retraction speed of the boom cylinder 7 is also limited in accordance with the limit. In other words, the controller 30 can suppress the movements of two hydraulic actuators operated simultaneously from interfering with each other in an undesirable manner.

[0080] Next, another example of the configuration of a hydraulic circuit mounted on the excavator 100 will be described with reference to Fig. 6. Fig. 6 is a schematic diagram of another example of the configuration of a hydraulic circuit mounted on the excavator 100, and corresponds to Fig. 5. Specifically, Fig. 6 shows the flow of hydraulic oil when a part of the hydraulic oil flowing out from the bottom-side oil chamber of the boom cylinder 7 is supplied (regenerated) to the rod-side oil chamber of the boom cylinder 7, and the remaining part of the hydraulic oil flowing out from the bottom-side oil chamber of the boom cylinder 7 is supplied (regenerated) to the bottom-side oil chamber of the arm cylinder 8.

[0081] The flow control of hydraulic oil using the hydraulic circuit shown in Fig. 6 differs from the flow control of hydraulic oil using the hydraulic circuit shown in Fig. 5 in that the hydraulic generator HG is used instead of the second hydraulic pump 14B when realizing the flow of hydraulic oil as described above, and in that the hydraulic control valve HV3 is not used, but in other respects it is the same as the flow control of hydraulic oil using the hydraulic circuit shown in Fig. 5. Therefore, in the following, a description of the common parts will be omitted, and the different parts will be described in detail. Also, the hydraulic control valve HV3 is not shown in Fig. 6.

[0082] The hydraulic generator HG is a device that generates electricity by utilizing the hydraulic energy of the hydraulic oil flowing out from the hydraulic actuator. In the illustrated example, the hydraulic generator HG is composed of a third hydraulic pump 14C and a motor generator 14M. The motor generator 14M is a device configured to function as both an electric motor and a generator. Specifically, the hydraulic generator HG is configured to be controlled by an electric load sensing system. More specifically, when the controller 30 can supply a regenerative flow rate QRG2 larger than the first arm flow rate QA1, the controller 30 causes the third hydraulic pump 14C to function as a hydraulic motor and causes the motor generator 14M to function as a generator. In this case, a part of the hydraulic oil that constitutes the regenerative flow rate QRG2 flows into the bottom side oil chamber of the arm cylinder 8 as the first arm flow rate QA1, and the remaining part of the hydraulic oil that constitutes the regenerative flow rate QRG2 is used to rotate the third hydraulic pump 14C as a hydraulic motor. As a result, the hydraulic energy of the hydraulic oil that flows into the third hydraulic pump 14C is converted into electric energy by the motor generator 14M and is then used by an electric load mounted on the shovel 100, or is stored in a battery mounted on the shovel 100. In the example shown in FIG. 6, the first hydraulic pump 14A is driven by an electric motor, similar to the third hydraulic pump 14C. The same is true for the second hydraulic pump 14B (not shown). However, the first hydraulic pump 14A to the third hydraulic pump 14C may be driven by the engine 11.

[0083] On the other hand, when the controller 30 cannot supply a regenerative flow rate QRG2 larger than the first arm flow rate QA1, the controller 30 causes the third hydraulic pump 14C to function as a hydraulic pump and the motor generator 14M to function as an electric motor. In this case, the hydraulic oil constituting the regenerative flow rate QRG2 merges with the hydraulic oil discharged by the third hydraulic pump 14C, which is rotationally driven by the motor generator 14M and functions as a hydraulic pump, and flows into the bottom-side oil chamber of the arm cylinder 8. In this case, the controller 30 can determine the magnitude of the regenerative flow rate QRG2 so that the third pump discharge rate QS3 of the third hydraulic pump 14C is the minimum amount.

[0084] With this configuration, the controller 30 can utilize all of the hydraulic energy of the hydraulic oil that constitutes the first boom flow rate QB1 while appropriately controlling at least one of the regeneration flow rate QRG1 and the regeneration flow rate QRG2, similar to the case where the hydraulic circuit shown in Fig. 5 is employed. That is, the controller 30 can make the discharge flow rate QT in the first boom flow rate QB1 zero while appropriately controlling at least one of the regeneration flow rate QRG1 and the regeneration flow rate QRG2, similar to the case where the hydraulic circuit shown in Fig. 5 is employed.

[0085] As described above, as shown in Fig. 5, the excavator 100 according to the embodiment of the present disclosure includes a hydraulic oil tank T, a first hydraulic actuator (boom cylinder 7), a second hydraulic actuator (arm cylinder 8), a hydraulic pump 14 capable of supplying hydraulic oil in the hydraulic oil tank T to each of the first hydraulic actuator and the second hydraulic actuator, meter-in valves (hydraulic control valves HV4 and HV5) corresponding to each of the first hydraulic actuator and the second hydraulic actuator, meter-out valves (hydraulic control valves HV3, HV6, and HV16) corresponding to each of the first hydraulic actuator and the second hydraulic actuator, and a control device (controller 30) that controls each of the meter-in valves, the meter-out valves, and the hydraulic pump 14. The meter-out valves (hydraulic control valves HV3 and HV16) are configured to adjust the flow rate of hydraulic oil flowing toward the hydraulic oil tank T and the flow rate of hydraulic oil flowing toward the hydraulic pump 14 (second hydraulic pump 14B). The control device (controller 30) is configured, when the first hydraulic actuator (boom cylinder 7) and the second hydraulic actuator (arm cylinder 8) are operated simultaneously, to cause at least a portion of the hydraulic oil flowing out from the first hydraulic actuator (the bottom side oil chamber of the boom cylinder 7) to merge with the hydraulic oil discharged by the hydraulic pump 14 (second hydraulic pump 14B) by controlling the meter-out valve (hydraulic control valve HV3 and hydraulic control valve HV16) corresponding to the first hydraulic actuator.

[0086] In the example shown in FIG. 5, the simultaneous operation of the first hydraulic actuator and the second hydraulic actuator corresponds to a combined operation including a boom lowering operation and an arm closing operation, but may be a combined operation including a boom lowering operation and an arm opening operation, a combined operation including a boom lowering operation and a bucket closing operation, a combined operation including a boom lowering operation and a bucket opening operation, a combined operation including an arm opening operation and a bucket closing operation, a combined operation including an arm opening operation and a bucket opening operation, a combined operation including an arm closing operation and a bucket closing operation, or a combined operation including an arm closing operation and a bucket opening operation. In addition, in the example shown in FIG. 5, the simultaneous operation of the first hydraulic actuator and the second hydraulic actuator corresponds to a combined operation of the boom cylinder 7 and the arm cylinder 8, but may be a combined operation of the left traveling hydraulic motor 1M, the right traveling hydraulic motor 2M, or the swing hydraulic motor 3M and the boom cylinder 7, the arm cylinder 8, or the bucket cylinder 9. That is, the first hydraulic actuator may be not only a hydraulic cylinder but also a hydraulic motor. The same applies to the second hydraulic actuator.

[0087] With this configuration, the excavator 100 can more appropriately control at least one of the regeneration flow rate QRG1 and the regeneration flow rate QRG2, compared to a configuration in which the meter-in opening area and the meter-out opening area are simultaneously controlled by one spool valve. Therefore, this configuration brings about the effect that the hydraulic energy of the hydraulic oil flowing out of the first hydraulic actuator can be used more efficiently and without waste. In other words, this configuration can achieve both operability (accuracy of cylinder speed control) and energy saving (accuracy of regeneration flow rate control and regeneration flow rate control).

[0088] In addition, as shown in FIG. 5, when the first hydraulic actuator (boom cylinder 7) and the second hydraulic actuator (arm cylinder 8) are operated simultaneously, the control device (controller 30) may be configured to control the meter-out valves (hydraulic control valves HV3 and HV16) corresponding to the first hydraulic actuator so that at least a portion of the hydraulic oil flowing out from the first hydraulic actuator (the bottom-side oil chamber of the boom cylinder 7) merges with the hydraulic oil discharged by the hydraulic pump 14 (second hydraulic pump 14B) and flows into the second hydraulic actuator (the bottom-side oil chamber of the arm cylinder 8).

[0089] With this configuration, the excavator 100 can more appropriately control the regenerative flow rate QRG2 compared to a configuration in which the meter-in opening area and the meter-out opening area are simultaneously controlled by one spool valve. Therefore, this configuration brings about an effect that the hydraulic oil flowing out of the first hydraulic actuator can be more efficiently regenerated to the second hydraulic actuator.

[0090] 6, the excavator 100 may be provided with a hydraulic generator HG that generates electricity by utilizing hydraulic energy of hydraulic oil flowing out from a first hydraulic actuator (boom cylinder 7). In this case, the control device (controller 30) may be configured to control a meter-out valve (hydraulic control valve HV16) corresponding to the first hydraulic actuator when simultaneously operating the first hydraulic actuator (boom cylinder 7) and the second hydraulic actuator (arm cylinder 8) so that at least a part of the hydraulic oil flowing out from the first hydraulic actuator flows into the hydraulic generator HG.

[0091] With this configuration, the excavator 100 can regenerate all of the hydraulic energy of the hydraulic oil flowing out from the first hydraulic actuator without discharging the hydraulic oil flowing out from the first hydraulic actuator into the hydraulic oil tank T. Specifically, the excavator 100 can hydraulically regenerate a portion of the hydraulic energy of the hydraulic oil flowing out from the first hydraulic actuator, and electrically regenerate the remaining portion of the hydraulic energy of the hydraulic oil flowing out from the first hydraulic actuator. Therefore, this configuration brings about the effect of being able to use the hydraulic oil flowing out from the first hydraulic actuator more efficiently and without waste, compared to a configuration that does not include a hydraulic generator HG.

[0092] 5 and 6, the control device (controller 30) may be configured to calculate a regeneration flow rate QRG1, which is the flow rate of hydraulic oil that flows out of the first hydraulic actuator (bottom-side oil chamber of the boom cylinder 7) and returns to the first hydraulic actuator (rod-side oil chamber of the boom cylinder 7) when the first hydraulic actuator (boom cylinder 7) and the second hydraulic actuator (arm cylinder 8) are simultaneously operated, and to calculate a regeneration flow rate QRG2, which is the flow rate of hydraulic oil that flows out of the first hydraulic actuator (bottom-side oil chamber of the boom cylinder 7) and is caused to flow into the second hydraulic actuator (bottom-side oil chamber of the arm cylinder 8) based on the calculated regeneration flow rate QRG1. That is, the control device (controller 30) may be configured to determine the regeneration flow rate QRG2 after determining the regeneration flow rate QRG1.

[0093] With this configuration, the first hydraulic actuator can be preferentially operated by the hydraulic oil flowing out from the first hydraulic actuator in the excavator 100. Therefore, in the example shown in Fig. 5, this configuration brings about an effect that the first pump discharge amount QS1, which is the flow rate of the hydraulic oil discharged by the first hydraulic pump 14A, can be set to zero.

[0094] However, the control device (controller 30) may be configured to determine the regeneration flow rate QRG1 after determining the regeneration flow rate QRG2. In this case, the excavator 100 can preferentially operate the second hydraulic actuator with the hydraulic oil flowing out of the first hydraulic actuator. Therefore, this configuration brings about an effect of increasing the probability that the second pump discharge rate QS2, which is the flow rate of the hydraulic oil discharged by the second hydraulic pump 14B, can be set to zero.

[0095] 5, the control device (controller 30) may be configured to calculate a discharge flow rate QT, which is a flow rate discharged to the hydraulic oil tank T, based on the calculated regeneration flow rate QRG1 and regeneration flow rate QRG2 when the first hydraulic actuator (boom cylinder 7) and the second hydraulic actuator (arm cylinder 8) are operated simultaneously. In other words, the control device (controller 30) may be configured to determine the discharge flow rate QT after determining the regeneration flow rate QRG1 and the regeneration flow rate QRG2.

[0096] With this configuration, the excavator 100 can preferentially operate the first hydraulic actuator and the second hydraulic actuator with the hydraulic oil flowing out from the first hydraulic actuator. Therefore, this configuration brings about an effect of increasing the probability that each of the first pump discharge rate QS1 and the second pump discharge rate QS2 can be set to zero.

[0097] The preferred embodiments of the present invention have been described above in detail. However, the present invention is not limited to the above-described embodiments, nor to the embodiments described below. Various modifications or substitutions may be applied to the above-described or following embodiments without departing from the scope of the present invention. Furthermore, features described separately may be combined unless technical contradictions arise. [Explanation of symbols]

[0098] 1···Lower traveling body 1M··Left traveling hydraulic motor 2···Slewing mechanism 2M··Right traveling hydraulic motor 3···Upper rotating body 3M··Slewing hydraulic motor 4···Boom 5··Arm 6··Bucket 7··Boom cylinder 7S··Piston 8···Arm cylinder 9··Bucket cylinder 10··Cabin 11··Engine 13··Regulator 13A··First regulator 13B··Second regulator 14··Hydraulic pump 14A··First hydraulic pump 14B··Second hydraulic pump 14C··Third hydraulic pump 14M··Motor generator 15··Pilot pump 26··Operating device 30··Controller 100··Excavator EV··Solenoid valve F1··Flow rate command generating section F2...Boom required flow rate derivation section F3...Arm required flow rate derivation section F4...Bucket required flow rate derivation section F5, F7...MI valve opening area calculation section F6, F8...MO valve opening area calculation section F9...Maximum MI pressure selection section F10...Pump discharge volume control section HG...Hydraulic generator HV, HV1 to HV20...Hydraulic control valve PL...Left pilot port PR...Right pilot port S1L, S1R, S2L, S2R, S3L, S3R, S4B, S4R, S5B, S5R, S6B, S6R, S7A, S7B...Pressure sensor T...Hydraulic oil tank

Claims

1. A hydraulic oil tank; A first hydraulic actuator; A second hydraulic actuator; a hydraulic pump capable of supplying hydraulic oil in the hydraulic oil tank to each of the first hydraulic actuator and the second hydraulic actuator; a meter-in valve corresponding to each of the first hydraulic actuator and the second hydraulic actuator; a meter-out valve corresponding to each of the first hydraulic actuator and the second hydraulic actuator; A control device that controls each of the meter-in valve, the meter-out valve, and the hydraulic pump, The meter-out valve is configured to adjust a flow rate of the hydraulic oil flowing toward the hydraulic oil tank and a flow rate of the hydraulic oil flowing toward the hydraulic pump, The control device is configured to control the meter-out valve corresponding to the first hydraulic actuator when the first hydraulic actuator and the second hydraulic actuator are operated simultaneously, so as to cause at least a portion of the hydraulic oil flowing out from the first hydraulic actuator to merge with the hydraulic oil discharged by the hydraulic pump. Shovel.

2. The control device is configured to control the meter-out valve corresponding to the first hydraulic actuator when the first hydraulic actuator and the second hydraulic actuator are operated simultaneously, so that at least a portion of the hydraulic oil flowing out from the first hydraulic actuator is merged with the hydraulic oil discharged by the hydraulic pump and flows into the second hydraulic actuator. The shovel according to claim 1.

3. a hydraulic generator that generates electricity by utilizing hydraulic energy of the hydraulic oil flowing out from the first hydraulic actuator, The control device is configured to control the meter-out valve corresponding to the first hydraulic actuator when the first hydraulic actuator and the second hydraulic actuator are operated simultaneously, thereby causing at least a portion of the hydraulic oil flowing out from the first hydraulic actuator to flow into the hydraulic generator. The shovel according to claim 1.

4. When the first hydraulic actuator and the second hydraulic actuator are operated simultaneously, the control device calculates a regeneration flow rate, which is a flow rate of hydraulic oil that returns to the first hydraulic actuator from among the hydraulic oil flowing out of the first hydraulic actuator, and calculates a regeneration flow rate, which is a flow rate of hydraulic oil that is caused to flow into the second hydraulic actuator from among the hydraulic oil flowing out of the first hydraulic actuator, based on the calculated regeneration flow rate. The shovel according to claim 1.

5. the control device calculates a discharge flow rate, which is a flow rate discharged to the hydraulic oil tank, based on the calculated regeneration flow rate and the calculated regeneration flow rate when the first hydraulic actuator and the second hydraulic actuator are operated simultaneously. The shovel according to claim 4.

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