Excavator

Abstract

Provided is an excavator that suitably uses hydraulic fluid that flows out from a boom cylinder during excavation.　The excavator comprises a boom, an arm, a boom cylinder that drives the boom, and an arm cylinder that drives the arm and, during excavation, increases rod-side pressure in the boom cylinder and supplies same to the arm cylinder.

Description

[Technical field]

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

[0002] For example, Patent Document 1 discloses an excavator in which hydraulic oil flowing out from a bottom-side oil chamber of a boom cylinder when the boom is lowered is utilized by a regenerative hydraulic motor. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2013 / 0358153 Summary of the Invention [Problem to be solved by the invention]

[0004] However, the excavator disclosed in Patent Document 1 does not take into consideration regeneration by the hydraulic oil flowing out of the boom cylinder during excavation.

[0005] Therefore, an object of the present invention is to provide a shovel that makes suitable use of the hydraulic oil that flows out of the boom cylinder during excavation. [Means for solving the problem]

[0006] A shovel according to one aspect of an embodiment includes a boom, an arm, a boom cylinder that drives the boom, and an arm cylinder that drives the arm. A reaction force is received in the direction of extending the rod of the boom cylinder. During excavation, the rod side of the boom cylinder of hydraulic oil flowing out from Pressure With booster mechanism Increase pressure, Pressurized hydraulic oil The arm cylinder Bottom side of Supply to. Effect of the Invention

[0007] According to the present invention, it is possible to provide a shovel that makes suitable use of the hydraulic oil flowing out of the boom cylinder during excavation. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a side view of a shovel as an excavator according to a first embodiment. [Diagram 2] 4A to 4C are diagrams showing transitions in operational states of a shovel according to the first embodiment. [Diagram 3] FIG. 2 is a diagram illustrating an example of a configuration for hydraulically driving a boom cylinder and an arm cylinder in the excavator according to the first embodiment. [Figure 4] 5 is a flowchart showing oil regeneration control during an excavation operation of the shovel according to the first embodiment. [Diagram 5] FIG. 13 is a diagram illustrating an example of a configuration for hydraulically driving a boom cylinder and an arm cylinder in a shovel according to a second embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In each drawing, the same or corresponding components are denoted by the same or corresponding reference numerals, and the description thereof will be omitted.

[0010] First Embodiment First, an overview of a shovel 100 according to a first embodiment will be described with reference to Fig. 1. Fig. 1 is a side view of the shovel 100 as an excavator according to the first embodiment.

[0011] The excavator 100 according to the first embodiment comprises a lower running body 1, an upper rotating body 3 mounted on the lower running body 1 so as to be freely rotatable via a rotating mechanism 2, a boom 4, an arm 5, and a bucket 6 constituting an attachment (work machine), and a cabin 10.

[0012] The lower traveling body 1 has a pair of left and right crawlers that are hydraulically driven by traveling hydraulic motors (not shown), respectively, to travel the excavator 100. In other words, the pair of traveling hydraulic motors (an example of traveling motors) drive the lower traveling body 1 (crawlers) as a driven part.

[0013] The upper rotating body 3 is driven by a swing hydraulic motor (not shown) to swing relative to the lower traveling body 1. In other words, the swing hydraulic motor is a swing drive part that drives the upper rotating body 3 as a driven part, and can change the orientation of the upper rotating body 3.

[0014] The upper rotating body 3 may be electrically driven by an electric motor (hereinafter, "electric motor for rotation") instead of the hydraulic motor for rotation. In other words, the electric motor for rotation is a rotation drive part that drives the upper rotating body 3 as a non-driven part, similar to the hydraulic motor for rotation, and can change the orientation of the upper rotating body 3.

[0015] The boom 4 is pivotally attached to the front center of the upper rotating body 3 so as to be able to tilt up and down, an arm 5 is pivotally attached to the tip of the boom 4 so as to be able to rotate up and down, and a bucket 6 as an end attachment is pivotally attached to the tip of the arm 5 so as to be able to rotate up and down. The boom 4, arm 5, and bucket 6 are hydraulically driven by a boom cylinder 7, an arm cylinder 8, and a bucket cylinder 9, each of which serves as a hydraulic actuator.

[0016] Incidentally, the bucket 6 is an example of an end attachment, and other end attachments, such as a slope bucket, a dredging bucket, a breaker, etc., may be attached to the tip of the arm 5 instead of the bucket 6 depending on the work content, etc.

[0017] The cabin 10 is a cab in which an operator sits, and is mounted on the front left side of the upper rotating body 3.

[0018] Next, an excavation and loading operation, which is one example of the operation of the shovel 100 according to the first embodiment, will be described with reference to Fig. 2. Fig. 2 is a diagram showing the transition of the operating state of the shovel 100 according to the first embodiment.

[0019] First, as shown in state CD1, the operator rotates the upper rotating body 3, and with the bucket 6 positioned above the excavation position, the arm 5 is open, and with the bucket 6 open, the operator lowers the boom 4 and lowers the bucket 6 so that the tip of the bucket 6 is at a desired height above the excavation target. Usually, when rotating the upper rotating body 3 and lowering the boom 4, the operator visually confirms the position of the bucket 6. Also, it is common for the upper rotating body 3 to rotate and the boom 4 to be lowered simultaneously. The above operation is referred to as the boom lowering rotation operation, and this operation section is referred to as the boom lowering rotation operation section.

[0020] When the operator determines that the tip of the bucket 6 has reached the desired height, he closes the arm 5 until it is approximately perpendicular to the ground, as shown in state CD2. This causes soil to be excavated to a predetermined depth, and the soil is raked up by the bucket 6 until the arm 5 is approximately perpendicular to the ground surface. Next, the operator further closes the arm 5 and the bucket 6, as shown in state CD3, and closes the bucket 6 until the bucket 6 is approximately perpendicular to the arm 5, as shown in state CD4. In other words, the bucket 6 is closed until the upper edge of the bucket 6 is approximately horizontal, and the raked up soil is stored in the bucket 6. The above operation is referred to as the excavation operation, and this operation section is referred to as the excavation operation section.

[0021] Here, during the excavation operation, for example, in the operation from state CD1 to state CD2, the arm 5 is operated in the closing direction, that is, the rod of the arm cylinder 8 is operated in the extending direction. As a result, the arm 5 rotates around the pin connecting the boom 4 and the arm 5 as a fulcrum, and the bucket 6 excavates the ground. At this time, a force acts in the direction of lifting the pin connecting the boom 4 and the arm 5 due to a reaction force from the ground. Therefore, the boom cylinder 7 receives a reaction force in the direction of extending the rod. Also, the operator slightly raises the boom at the same time as closing the arm. Therefore, hydraulic oil according to the amount of operation is supplied from the main pump 14A to the bottom side oil chamber of the boom cylinder 7.

[0022] Next, when the operator determines that the bucket 6 has been closed to a position substantially perpendicular to the arm 5, he raises the boom 4 with the bucket 6 closed until the bottom of the bucket 6 is at a desired height from the ground, as shown in state CD5. This operation is called the boom-raising operation, and this operation section is called the boom-raising operation section. Following or simultaneously with this operation, the operator rotates the upper rotating body 3, and rotates and moves the bucket 6 to the soil discharge position, as shown by arrow AR1. This operation including the boom-raising operation is called the boom-raising swing operation, and this operation section is called the boom-raising swing operation section.

[0023] The reason why the boom 4 is raised until the bottom of the bucket 6 reaches the desired height is that, for example, when discharging soil onto the bed of a dump truck, the bucket 6 must be raised higher than the height of the bed, otherwise the bucket 6 will hit the bed.

[0024] Next, when the operator determines that the boom raising and rotating operation is complete, as shown in state CD6, he opens the arm 5 and the bucket 6 while lowering the boom 4 or stopping the boom 4, and discharges the soil in the bucket 6. This operation is called the dump operation, and this operation section is called the dump operation section.

[0025] Next, when the operator determines that the dumping operation is complete, he rotates the upper rotating body 3 in the direction of the arrow AR2 as shown in state CD7, and moves the bucket 6 directly above the excavation position. At this time, the boom 4 is lowered simultaneously with the rotation, and the bucket 6 is lowered to a desired height from the excavation target. This operation is part of the boom lowering and rotating operation described in state CD1. Thereafter, the operator lowers the bucket 6 to a desired height as shown in state CD1, and resumes the excavation operation and subsequent operations.

[0026] The operator performs excavation and loading by repeating one cycle of the above-mentioned "boom lowering and swinging operation," "digging operation," "boom raising and swinging operation," and "dumping operation."

[0027] Fig. 3 is a diagram that shows an example of a configuration for hydraulically driving the boom cylinder 7 and the arm cylinder 8 in the excavator 100 according to the first embodiment. In Fig. 3, the control valves 175B, 175R, 176B, 176R and the regenerative valve 19 are shown in a state during regeneration, which will be described later. In Fig. 3 (and Fig. 5, which will be described later), the mechanical power system is shown by double lines, and the hydraulic oil lines are shown by solid lines. The moving direction of the rod during regeneration, which will be described later, is shown by an outlined arrow, and the flow of the hydraulic oil is shown by a filled arrow.

[0028] The drive system of the excavator 100 according to the first embodiment includes the engine 11, regulators 13A and 13B, main pumps 14A and 14B, and a control valve 17. As described above, the hydraulic drive system of the excavator 100 according to the first embodiment includes hydraulic actuators such as a traveling hydraulic motor (not shown), a swing hydraulic motor (not shown), a boom cylinder 7, an arm cylinder 8, and a bucket cylinder 9 that hydraulically drive the lower traveling body 1, the upper rotating body 3, the boom 4, the arm 5, and the bucket 6, respectively. Note that FIG. 3 shows the hydraulic drive system of the boom cylinder 7 and the arm cylinder 8, and does not show the hydraulic drive systems of the other hydraulic actuators (the traveling hydraulic motor (not shown), the swing hydraulic motor (not shown), the bucket cylinder 9, etc.).

[0029] The engine 11 is a main power source in the hydraulic drive system, and is mounted, for example, on the rear of the upper rotating body 3. Specifically, the engine 11 rotates at a constant speed at a preset target rotation speed under direct or indirect control by the controller 30, and drives the main pumps 14A, 14B. The engine 11 is, for example, a diesel engine that uses diesel as fuel.

[0030] The regulator 13A controls the discharge amount of the main pump 14A. For example, the regulator 13A adjusts the angle (tilt angle) of the swash plate of the main pump 14A in response to a control command from the controller 30. Similarly, the regulator 13B controls the discharge amount of the main pump 14B.

[0031] The main pumps 14A, 14B are mounted on the rear of the upper rotating body 3, for example, like the engine 11, and supply hydraulic oil to the control valve 17 through a high-pressure hydraulic line. The main pumps 14A, 14B are driven by the engine 11 as described above. The main pumps 14A, 14B are, for example, variable displacement hydraulic pumps, and as described above, under the control of the controller 30, the tilt angle of the swash plate is adjusted by the regulators 13A, 13B to adjust the stroke length of the pistons, thereby controlling the discharge flow rate (discharge pressure).

[0032] The control valve 17 is a hydraulic control device mounted, for example, at the center of the upper rotating body 3, and controls the hydraulic drive system in response to an operation of an operating device (not shown) by an operator. As described above, the control valve 17 is connected to the main pumps 14A, 14B via high-pressure hydraulic lines, and selectively supplies hydraulic oil supplied from the main pumps 14A, 14B to the hydraulic actuators (the traveling hydraulic motor, the swing hydraulic motor, the boom cylinder 7, the arm cylinder 8, and the bucket cylinder 9) in response to the operating state of the operating device (not shown).

[0033] Specifically, control valve 17 includes control valves 175B, 175R, 176B, and 176R that control the flow rate and flow direction of hydraulic oil supplied from main pumps 14A and 14B to boom cylinder 7 and arm cylinder 8, respectively. Note that control valves 175B and 175R correspond to boom cylinder 7, and control valves 176B and 176R correspond to arm cylinder 8.

[0034] The control valves 175B, 175R, 176B, and 176R may be, for example, electromagnetic solenoid spool valves that are driven by commands from the controller 30. The control valves 175B, 175R, 176B, and 176R have a pump side port, a tank side port, and an actuator side port.

[0035] A pump side port of the control valve 175B is connected to the main pump 14A via a hydraulic oil passage C1. A tank side port of the control valve 175B is connected to a hydraulic oil tank via a hydraulic oil passage C7. An actuator side port of the control valve 175B is connected to a bottom side oil chamber of the boom cylinder 7 via a hydraulic oil passage C2.

[0036] A pump side port of the control valve 175R is connected to the main pump 14A via a hydraulic oil passage C1. A tank side port of the control valve 175R is connected to a hydraulic oil tank via a hydraulic oil passage C7. An actuator side port of the control valve 175R is connected to a rod side oil chamber of the boom cylinder 7 via a hydraulic oil passage C3.

[0037] The pump side port of the control valve 176B is connected to the main pump 14B via a hydraulic oil passage C4. The tank side port of the control valve 176B is connected to the hydraulic oil tank via a hydraulic oil passage C7. The actuator side port of the control valve 176B is connected to the bottom side oil chamber of the arm cylinder 8 via a hydraulic oil passage C5.

[0038] The pump side port of the control valve 176R is connected to the main pump 14B via a hydraulic oil passage C4. The tank side port of the control valve 176R is connected to the hydraulic oil tank via a hydraulic oil passage C7. The actuator side port of the control valve 176R is connected to the rod side oil chamber of the arm cylinder 8 via a hydraulic oil passage C6.

[0039] The hydraulic oil passage C1 has one end connected to the main pump 14A, and the other branched end is connected to the pump side port of the control valve 175B and the pump side port of the control valve 175R. The hydraulic oil passage C2 has one end connected to the actuator side port of the control valve 175B, and the other branched end is connected to the bottom side oil chamber of the boom cylinder 7. The hydraulic oil passage C3 has one end connected to the actuator side port of the control valve 175R, and the other branched end is connected to the rod side oil chamber of the boom cylinder 7. The hydraulic oil passage C4 has one end connected to the main pump 14B, and the other branched end is connected to the pump side port of the control valve 176B and the pump side port of the control valve 176R. The hydraulic oil passage C5 has one end connected to the actuator side port of the control valve 176B, and the other end connected to the bottom side oil chamber of the arm cylinder 8. One end of the hydraulic oil passage C6 is connected to the actuator side port of the control valve 176R, and the other end is connected to the rod side oil chamber of the arm cylinder 8. One end of the hydraulic oil passage C7 is connected to a hydraulic oil tank, and the other branched end is connected to the tank side ports of the control valves 175B, 175R, 176B, and 176R.

[0040] Moreover, the excavator 100 according to the first embodiment has a regenerative device 41 that regenerates the pressure in the rod-side oil chambers of the boom cylinders 7A, 7B to the bottom-side oil chamber of the arm cylinder 8. The regenerative device 41 has hydraulic oil passages C8, C9, a pressure boosting mechanism 18, and a regenerative valve 19.

[0041] One end of the hydraulic oil passage C8 is connected to the hydraulic oil passage C3 (i.e., the rod-side oil chamber of the boom cylinder 7), and the other end is connected to the primary chamber of the booster mechanism 18. One end of the hydraulic oil passage C9 is connected to the secondary chamber of the booster mechanism 18, and the other end is connected to the hydraulic oil passage C5 (i.e., the bottom-side oil chamber of the arm cylinder 8).

[0042] The booster mechanism 18 is a device that boosts the pressure on the input side and outputs it from the output side, and for example, a booster piston can be used. The booster piston has a primary chamber on the input side, a secondary chamber on the output side, and a piston that separates the primary chamber and the secondary chamber, and boosts the pressure on the input side according to the pressure-receiving area ratio and outputs it from the output side. Note that the configuration of the booster mechanism 18 is not limited to this, and it may be a rotary booster mechanism.

[0043] The regenerative valve 19 is provided in the hydraulic oil passage C9 and is an on-off valve that opens and closes the hydraulic oil passage C9. The regenerative valve 19 may be, for example, a solenoid valve that is driven by a command from the controller 30.

[0044] The boom rod pressure sensor S7R detects the oil pressure in the rod side oil chamber of the boom cylinder 7. The boom bottom pressure sensor S7B detects the oil pressure in the bottom side oil chamber of the boom cylinder 7. The arm rod pressure sensor S8R detects the oil pressure in the rod side oil chamber of the arm cylinder 8. The arm bottom pressure sensor S8B detects the oil pressure in the bottom side oil chamber of the arm cylinder 8.

[0045] Here, the operation of the hydraulic drive system under normal circumstances will be described. Under normal circumstances, the regenerative valve 19 is closed. During an operation to raise or lower the boom 4, the controller 30 controls the control valves 175B, 175R in response to an operation signal (lever operation) that commands the operation of the boom 4, thereby extending or retracting the boom cylinder 7, and thereby raising or lowering the boom 4. During an operation to close or open the arm 5, the controller 30 controls the control valves 176B, 176R in response to an operation signal (lever operation) that commands the operation of the arm 5, thereby extending or retracting the arm cylinder 8, and thereby closing or opening the arm 5.

[0046] <Operation of the First Embodiment> FIG. 4 is a flowchart showing oil regeneration control during excavation operation of the shovel 100 according to the first embodiment.

[0047] Here, the operator performs an operation to close the arm 5. That is, the controller 30 opens the control valves 176B and 176R in response to an operation signal (for example, a lever operation of an operation lever that operates the arm 5). The hydraulic oil discharged from the main pump 14B is supplied to the bottom side oil chamber of the arm cylinder 8 through the hydraulic oil passage C4, the control valve 176B, and the hydraulic oil passage C5. In addition, the hydraulic oil flowing out from the rod side oil chamber of the arm cylinder 8 flows into the hydraulic oil tank through the hydraulic oil passage C6, the control valve 176R, and the hydraulic oil passage C7. In addition, the operator performs an operation to slightly raise the boom 4 at the same time as the operation to close the arm 5. That is, the controller 30 opens the control valves 175B and 175R in response to an operation signal (for example, a lever operation of an operation lever that operates the boom 4). The hydraulic oil discharged from the main pump 14A is supplied to the bottom side oil chamber of the boom cylinders 7A and 7B through the hydraulic oil passage C1, the control valve 175B, and the hydraulic oil passage C2. Furthermore, the hydraulic oil flowing out from the rod-side oil chambers of boom cylinders 7A, 7B passes through hydraulic oil passage C3, control valve 175R, and hydraulic oil passage C7, and flows into the hydraulic oil tank.

[0048] In step S1, the controller 30 determines whether excavation has started. Here, the controller 30 determines whether excavation has started based on, for example, whether a reaction force is detected when the bucket 6 excavates the ground. For example, the controller 30 determines whether excavation has started based on the difference between the detected pressure of the boom rod pressure sensor S7R, which detects the hydraulic pressure of the rod side oil chamber of the boom cylinder 7, and the detected pressure of the arm bottom pressure sensor S8B, which detects the hydraulic pressure of the bottom side oil chamber of the arm cylinder 8. The controller 30 may also determine whether excavation has started based on, for example, an image captured by the front camera 60F. If it is determined that excavation has not started (S1·No), the controller 30 repeats the process of step S1. If it is determined that excavation has started (S1·Yes), the process of the controller 30 proceeds to step S2.

[0049] In step S2, the controller 30 determines whether the differential pressure ΔP is equal to or greater than a threshold value Pref1. Here, the pressure boost coefficient of the boosting mechanism 18 is C, the hydraulic pressure in the rod-side oil chamber of the boom cylinder 7 is Pbr, the hydraulic pressure in the bottom-side oil chamber of the arm cylinder 8 is Pab, and the differential pressure ΔP is given by the following formula (1). The threshold value Pref1 is a preset threshold value (offset value), and may be, for example, "Pref1=0".

[0050] ΔP = CPbr - Pab … (1)

[0051] If the pressure difference ΔP is not equal to or greater than the threshold Pref1 (S2·No), the controller 30 repeats the process of step S2. If the pressure difference ΔP is equal to or greater than the threshold Pref1 (S2·Yes), the process of the controller 30 proceeds to step S3.

[0052] In step S3, the controller 30 opens the regenerative valve 19. The controller 30 also closes the control valve 175R. The controller 30 opens the control valve 175B in response to an operation signal (for example, a lever operation of an operation lever that operates the boom 4). The controller 30 also opens the control valves 176B, 176R in response to an operation signal (for example, a lever operation of an operation lever that operates the arm 5). The hydraulic oil flowing out of the rod-side oil chambers of the boom cylinders 7A, 7B flows into the input side of the booster mechanism 18 through the hydraulic oil passage C8. As a result, the hydraulic pressure in the rod-side oil chamber of the boom cylinder 7 is boosted by the booster mechanism 18 and supplied to the bottom-side oil chamber of the arm cylinder 8.

[0053] In step S4, the controller 30 judges whether the differential pressure ΔP is less than the threshold value Pref2. Here, the threshold value Pref2 is a preset threshold value (offset value), and may be, for example, "Pref2=0". The threshold value Pref1 and the threshold value Pref2 may be the same or different. In order to prevent hunting in the control, it is preferable that "Pref1>Pref2". If the differential pressure ΔP is not less than the threshold value Pref2 (S4·No), the controller 30 repeats the process of step S4. If the differential pressure ΔP is less than the threshold value Pref2 (S4·Yes), the process of the controller 30 proceeds to step S5.

[0054] In step S5, the controller 30 closes the regenerative valve 19. The controller 30 also opens the control valves 175B, 175R in response to an operation signal (for example, lever operation of an operation lever that operates the boom 4). The controller 30 also opens the control valves 176B, 176R in response to an operation signal (for example, lever operation of an operation lever that operates the arm 5). This ends the regenerative supply of hydraulic pressure from the rod-side oil chamber of the boom cylinder 7 to the bottom-side oil chamber of the arm cylinder 8. The controller 30 then ends the processing shown in FIG.

[0055] As described above, according to the shovel 100 of the first embodiment, the reaction force generated in the boom cylinder 7 during excavation can be effectively utilized by the arm cylinder 8 that operates the arm 5 that performs excavation. This makes it possible to improve the operating speed of the shovel 100 during excavation and reduce energy consumption.

[0056] Furthermore, according to the excavator 100 of the first embodiment, by increasing the pressure using the pressure increasing mechanism 18, even when, for example, the reaction force is small and the pressure in the rod side oil chamber of the boom cylinder 7 is smaller than the pressure in the bottom side oil chamber of the arm cylinder 8, the pressure (reaction force) generated in the boom cylinder 7 can be utilized by the arm cylinder 8 that drives the excavation operation.

[0057] Second Embodiment Next, a shovel 100 according to a second embodiment will be described. Fig. 5 is a diagram that shows a schematic example of a configuration for hydraulically driving the boom cylinder 7 and the arm cylinder 8 in the shovel 100 according to the second embodiment. Note that in Fig. 5, the control valves 175B, 175R, 176B, 176R and the regenerative valves 20, 21 are shown in a regenerative state, which will be described later.

[0058] The shovel 100 according to the first embodiment has a regenerative device 41 shown in Fig. 3, whereas the shovel 100 according to the second embodiment has a regenerative device 42 as shown in Fig. 5, which is different. The other configurations are similar, and therefore repeated explanations will be omitted.

[0059] The hydraulic oil passage C3 has a hydraulic oil passage C11, a hydraulic oil passage C12, and a regenerative valve 20. One end of the hydraulic oil passage C11 is connected to a rod side oil chamber of the boom cylinder 7A, and the other end is connected to one port of the regenerative valve 20. One end of the hydraulic oil passage C12 is connected to an actuator side port of the control valve 175R, and the other branched end is connected to the other port of the regenerative valve 20 and the rod side oil chamber of the boom cylinder 7B.

[0060] The regenerative valve 20 is provided at a connection between the hydraulic oil passages C11 and C12, and is an on-off valve that opens and closes communication between the hydraulic oil passages C11 and C12. The regenerative valve 20 may be, for example, a solenoid valve that is driven by a command from the controller 30.

[0061] Moreover, the excavator 100 according to the second embodiment has a regenerative device 42 that regenerates the pressure in the rod-side oil chamber of the boom cylinder 7A to the bottom-side oil chamber of the arm cylinder 8. The regenerative device 42 has a hydraulic oil passage C13 and regenerative valves 20 and 21.

[0062] One end of the hydraulic oil passage C13 is connected to the hydraulic oil passage C11 (ie, the rod-side oil chamber of the boom cylinder 7A), and the other end is connected to the hydraulic oil passage C5 (ie, the bottom-side oil chamber of the arm cylinder 8).

[0063] The regenerative valve 21 is provided in the hydraulic oil passage C13 and is an on-off valve that opens and closes the hydraulic oil passage C13. The regenerative valve 19 may be, for example, a solenoid valve that is driven by a command from the controller 30.

[0064] Here, the operation of the hydraulic drive system under normal circumstances will be described. Under normal circumstances, the regenerative valve 20 is open and the regenerative valve 21 is closed. During an operation to raise or lower the boom 4, the controller 30 controls the control valves 175B, 175R in response to an operation signal (lever operation) that commands the operation of the boom 4, thereby extending or retracting the boom cylinder 7, and thereby raising or lowering the boom 4. During an operation to close or open the arm 5, the controller 30 controls the control valves 176B, 176R in response to an operation signal (lever operation) that commands the operation of the arm 5, thereby extending or retracting the arm cylinder 8, and thereby closing or opening the arm 5.

[0065] <Operation of the second embodiment> The shovel 100 of the second embodiment differs from the flowchart shown in FIG. 4 in the following respects.

[0066] Here, the operator performs an operation to close the arm 5. That is, the controller 30 opens the control valves 176B and 176R in response to an operation signal (for example, a lever operation of an operation lever that operates the arm 5). The hydraulic oil discharged from the main pump 14B is supplied to the bottom side oil chamber of the arm cylinder 8 through the hydraulic oil passage C4, the control valve 176B, and the hydraulic oil passage C5. In addition, the hydraulic oil flowing out from the rod side oil chamber of the arm cylinder 8 flows into the hydraulic oil tank through the hydraulic oil passage C6, the control valve 176R, and the hydraulic oil passage C7. In addition, the operator performs an operation to slightly raise the boom 4 at the same time as the operation to close the arm 5. That is, the controller 30 opens the control valves 175B and 175R in response to an operation signal (for example, a lever operation of an operation lever that operates the boom 4). The hydraulic oil discharged from the main pump 14A is supplied to the bottom side oil chamber of the boom cylinders 7A and 7B through the hydraulic oil passage C1, the control valve 175B, and the hydraulic oil passage C2. Furthermore, the hydraulic oil flowing out from the rod-side oil chambers of boom cylinders 7A, 7B passes through hydraulic oil passage C3, control valve 175R, and hydraulic oil passage C7, and flows into the hydraulic oil tank.

[0067] In step S3, the controller 30 opens the regenerative valve 21 and closes the regenerative valve 20. The controller 30 also opens the control valve 175R so that the hydraulic oil passage C3 (C12) and the hydraulic oil passage C7 communicate with each other. The controller 30 opens the control valve 175B in response to an operation signal (e.g., a lever operation of an operation lever for operating the boom 4). The controller 30 also opens the control valves 176B and 176R in response to an operation signal (e.g., a lever operation of an operation lever for operating the arm 5). The hydraulic oil flowing out of the rod-side oil chamber of the boom cylinder 7B flows into the hydraulic oil tank through the hydraulic oil passage C12, the control valve 175R, and the hydraulic oil passage C7. The hydraulic oil flowing out of the rod-side oil chamber of the boom cylinder 7A is supplied to the bottom-side oil chamber of the arm cylinder 8 through the hydraulic oil passage C13.

[0068] In step S5, the controller 30 opens the regenerative valve 21 and the regenerative valve 20. The controller 30 also opens the control valves 175B, 175R in response to an operation signal (for example, lever operation of an operation lever that operates the boom 4). The controller 30 also opens the control valves 176B, 176R in response to an operation signal (for example, lever operation of an operation lever that operates the arm 5). This ends the regenerative supply of hydraulic pressure from the rod-side oil chamber of the boom cylinder 7A to the bottom-side oil chamber of the arm cylinder 8.

[0069] The other processes are similar, and therefore a duplicated description will be omitted.

[0070] As described above, according to the shovel 100 of the second embodiment, the reaction force generated in the boom cylinder 7 during excavation can be effectively utilized by the arm cylinder 8 that operates the arm 5 that performs excavation. This makes it possible to improve the operating speed of the shovel 100 during excavation and reduce energy consumption.

[0071] Moreover, according to the excavator 100 according to the second embodiment, of the two boom cylinders 7 (7A, 7B), one boom cylinder 7A is configured to support the reaction force. Therefore, compared to a case in which the reaction force during excavation is supported by two boom cylinders 7, by supporting the reaction force during excavation by one boom cylinder 7A, the pressure rise in the rod-side oil chamber of the boom cylinder 7A due to the reaction force increases. As a result, even if the reaction force is small, the pressure in the rod-side oil chamber of the boom cylinder 7A can be made higher than the pressure in the bottom-side oil chamber of the arm cylinder 8. Therefore, the pressure (reaction force) generated by the boom cylinder 7 can be utilized by the arm cylinder 8 that is driven during excavation operation.

[0072] The above describes the embodiments of the shovel 100, but the present invention is not limited to the above embodiments, and various modifications and improvements are possible within the scope of the gist of the present invention described in the claims.

[0073] This application claims priority based on Japanese Patent Application No. 2019-146180, filed on August 8, 2019, the entire contents of which are incorporated herein by reference. [Explanation of symbols]

[0074] 1 Undercarriage 2 Swivel mechanism 3. Upper rotating body 4. Boom 5 Arm 6 Bucket 7 Boom cylinder 8 Arm Cylinder 9 Bucket Cylinder 10 Cabin 11 Engine 14A, 14B Main pump 17 Control valve 175B, 175R, 176B, 176R Control valve 18 Pressure booster mechanism 19, 20, 21 Regenerative valve 30 Controller 41,42 Regenerative device 100 Shovel

Claims

1. Boom and An arm, A boom cylinder that drives the boom; an arm cylinder that drives the arm; During excavation, when a reaction force is applied in the direction of extending the rod of the boom cylinder, the pressure of the hydraulic oil flowing out from the rod side of the boom cylinder is increased by a boosting mechanism, and the pressurized hydraulic oil is supplied to the bottom side of the arm cylinder.

2. a regenerative hydraulic oil passage connecting a rod side of the boom cylinder and a bottom side of the arm cylinder; The pressure boosting mechanism provided in the regenerative hydraulic oil passage; An on-off valve for opening and closing the regenerative hydraulic oil passage is provided. The shovel according to claim 1.

3. Further comprising a control unit, The control unit is During the excavation, the on-off valve is opened. The shovel according to claim 2.

4. The pressure boosting mechanism A primary chamber connected to a rod side of the boom cylinder; A secondary chamber connected to a bottom side of the arm cylinder; a piston that separates the primary chamber from the secondary chamber; a pressure of the hydraulic oil in the secondary chamber is increased based on a pressure of the hydraulic oil flowing out from a rod side of the boom cylinder and flowing into the primary chamber in accordance with a pressure-receiving area ratio of the piston; The shovel according to any one of claims 1 to 3.

5. The boom cylinder for driving the boom includes two boom cylinders, During excavation, in which a reaction force is applied in a direction in which the rod of the boom cylinder is extended, the reaction force is supported by one of the boom cylinders, thereby increasing the pressure of the hydraulic oil flowing out from the rod side of one of the boom cylinders, and the increased pressure hydraulic oil is supplied to the bottom side of the arm cylinder. The shovel according to claim 1.

6. A regenerative hydraulic oil passage connecting a rod side of one of the boom cylinders and a bottom side of the arm cylinder; a regenerative on-off valve that opens and closes the regenerative hydraulic oil passage; a main on-off valve provided in a main hydraulic oil passage connecting a rod side of one of the boom cylinders and a control valve, and configured to open and close the main hydraulic oil passage; The shovel according to claim 5.

7. Further comprising a control unit, The control unit is During the excavation, the regenerative on-off valve is opened and the main on-off valve is closed. The shovel according to claim 6.

8. During the excavation, the hydraulic oil flowing out from the rod side of the other boom cylinder flows into the hydraulic oil tank via the control valve. The shovel according to claim 7.

9. During the excavation, hydraulic oil is supplied from the hydraulic oil pump to the bottom side of the arm cylinder. A shovel according to any one of claims 1 to 8.

10. An attachment is formed by the boom, the arm and the bucket, During the excavation, the arm is operated in a closing direction to excavate the excavation target with the bucket, and the reaction force is received in a direction to extend the rod of the boom cylinder. The shovel according to claim 9.

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