WO2016043206A1

WO2016043206A1 - Shovel

Info

Publication number: WO2016043206A1
Application number: PCT/JP2015/076233
Authority: WO
Inventors: 宏治川島
Original assignee: 住友重機械工業株式会社
Priority date: 2014-09-17
Filing date: 2015-09-16
Publication date: 2016-03-24
Also published as: JP2017201072A

Abstract

　A shovel according to an embodiment of the present invention has a main pump 14L for supplying working oil to hydraulic actuators 1A, 2A, 8, control valves 171L to 175L for controlling the flow of working oil between the main pump 14L and each of the hydraulic actuators 1A, 2A, 8, a reproducing oil channel 63c for enabling working oil to flow from a rod-side oil chamber of an arm cylinder 8 to a bottom-side oil chamber, a merging oil channel 24 in which working oil discharged by the main pump 14L and capable of flowing through a plurality of channels merges before reaching a working oil tank T when working oil passes through the reproducing oil channel 63c and flows from the rod-side oil chamber of the arm cylinder 8 to the bottom-side oil chamber, and an oil channel 25 capable of communicating the reproducing oil channel 63c with the merging oil channel 24.

Description

Excavator

The present invention relates to an excavator having a regeneration circuit that realizes a flow of hydraulic oil from a rod-side oil chamber to a bottom-side oil chamber of a hydraulic cylinder.

A hydraulic circuit for a construction machine is known in which hydraulic oil flowing out from one hydraulic cylinder can be used to drive another hydraulic cylinder (see Patent Document 1).

JP 2014-74433 A

However, Patent Document 1 does not mention a circuit for regenerating hydraulic oil flowing out from the rod side oil chamber of the hydraulic cylinder into the bottom side oil chamber of the same hydraulic cylinder.

In particular, when hydraulic oil flowing out from the rod side oil chamber of a hydraulic cylinder flows into the bottom oil chamber of the same hydraulic cylinder and the hydraulic cylinder is extended, the volume of the rod side oil chamber and the volume of the bottom side oil chamber Due to the difference, the flow rate of the hydraulic oil necessary to expand the bottom side oil chamber cannot be provided only by the flow rate of the hydraulic oil flowing out from the rod side oil chamber.

In view of the above, it is desired to provide an excavator that can efficiently perform a regenerating operation of flowing hydraulic oil flowing out from the rod side oil chamber of the hydraulic cylinder into the bottom side oil chamber.

An excavator according to an embodiment of the present invention controls a hydraulic pump that supplies hydraulic oil to a plurality of hydraulic actuators including a hydraulic cylinder, and a flow of hydraulic oil between each of the hydraulic pump and the plurality of hydraulic actuators. A plurality of control valves; a first oil passage that enables a flow of hydraulic oil from a rod-side oil chamber to a bottom-side oil chamber of the hydraulic cylinder; and the rod-side oil chamber through the first oil passage from the rod-side oil chamber. A second oil passage through which the hydraulic oil that can flow through a plurality of paths discharged from the hydraulic pump merges and flows before reaching the hydraulic oil tank when the hydraulic oil flows to the bottom-side oil chamber; and the first oil A third oil passage capable of communicating the passage and the second oil passage.

The above-described means provides an excavator that can efficiently execute a regeneration operation in which hydraulic oil flowing out from the rod-side oil chamber of the hydraulic cylinder flows into the bottom-side oil chamber.

It is a side view of the shovel which concerns on the Example of this invention. It is a block diagram which shows the structural example of the drive system of the shovel of FIG. It is the schematic which shows the structural example of the hydraulic circuit mounted in the shovel of FIG. It is a flowchart which shows the flow of an example of an arm reproduction | regeneration process. It is a figure which shows the state of the hydraulic circuit when arm closing operation is performed. It is a figure which shows the state of a hydraulic circuit when operating an arm reproduction circuit. It is a figure which shows the state of a hydraulic circuit when the regeneration replenishment flow rate is insufficient. It is a figure which shows the state of the hydraulic circuit when the regeneration replenishment flow rate is not insufficient. It is a flowchart which shows the flow of another example of an arm reproduction | regeneration process. It is the schematic which shows another structural example of the hydraulic circuit mounted in the shovel of FIG. It is the schematic which shows another structural example of the hydraulic circuit mounted in the shovel of FIG.

First, an excavator that is an example of a construction machine according to an embodiment of the present invention will be described with reference to FIG. FIG. 1 is a side view of the excavator. An upper swing body 3 is mounted on a lower traveling body 1 of the shovel shown in FIG. A boom 4 is attached to the upper swing body 3. An arm 5 is attached to the tip of the boom 4, and a bucket 6 is attached to the tip of the arm 5. The boom 4, the arm 5, and the bucket 6 are hydraulically driven by a boom cylinder 7, an arm cylinder 8, and a bucket cylinder 9, respectively. The upper swing body 3 is provided with a cabin 10 and a power source such as an engine 11 is mounted.

FIG. 2 is a block diagram showing a configuration example of the drive system of the excavator of FIG. 1, and the mechanical power system, the high-pressure hydraulic line, the pilot line, and the electric control system are represented by double lines, solid lines, broken lines, and dotted lines, respectively. Show.

The drive system of the shovel mainly includes an engine 11, a regulator 13, a main pump 14, a pilot pump 15, a control valve 17, an operating device 26, a pressure sensor 29, and a controller 30.

The engine 11 is a drive source for the excavator. In this embodiment, the diesel engine is an internal combustion engine that operates to maintain a predetermined rotational speed. The output shaft of the engine 11 is connected to the input shafts of the main pump 14 and the pilot pump 15.

The main pump 14 is a device for supplying hydraulic oil to the control valve 17 through a high pressure hydraulic line. In this embodiment, the main pump 14 is a swash plate type variable displacement hydraulic pump.

The regulator 13 is a device for controlling the discharge amount of the main pump 14. In this embodiment, the regulator 13 controls the discharge amount of the main pump 14 by adjusting the swash plate tilt angle of the main pump 14 according to the discharge pressure of the main pump 14 or the control signal from the controller 30. To do.

The pilot pump 15 is a device for supplying hydraulic oil to various hydraulic control devices via a pilot line. In this embodiment, the pilot pump 15 is a fixed displacement hydraulic pump.

The control valve 17 is a hydraulic control device that controls a hydraulic system in the excavator. In the present embodiment, the control valve 17 is one or more of the boom cylinder 7, the arm cylinder 8, the bucket cylinder 9, the left traveling hydraulic motor 1A, the right traveling hydraulic motor 1B, and the turning hydraulic motor 2A. In contrast, hydraulic fluid discharged from the main pump 14 is selectively supplied. Hereinafter, the boom cylinder 7, the arm cylinder 8, the bucket cylinder 9, the left traveling hydraulic motor 1A, the right traveling hydraulic motor 1B, and the turning hydraulic motor 2A are collectively referred to as “hydraulic actuators”.

The operating device 26 is a device used by an operator for operating the hydraulic actuator. In this embodiment, the operating device 26 supplies the hydraulic oil discharged from the pilot pump 15 to the pilot port of the control valve in the control valve 17. Specifically, the operating device 26 supplies hydraulic oil discharged from the pilot pump 15 to the pilot port of the control valve corresponding to each of the hydraulic actuators. Note that the hydraulic oil pressure (pilot pressure) supplied to each pilot port is a pressure corresponding to the operation direction and operation amount of a lever or pedal (not shown) of the operation device 26 corresponding to each hydraulic actuator. It is.

The pressure sensor 29 is an example of an operation content detection unit for detecting the operation content of the operation device 26. In the present embodiment, the pressure sensor 29 detects the operation direction and the operation amount of the operation device 26 corresponding to each of the hydraulic actuators in the form of pressure, and outputs the detected value to the controller 30. Note that the operation content of the operation device 26 may be detected using a sensor other than the pressure sensor, such as an inclination sensor that detects the inclination of various operation levers. Specifically, the pressure sensor 29 is attached to each of the operation devices 26 such as a left travel lever, a right travel lever, an arm operation lever, a turning operation lever, a boom operation lever, and a bucket operation lever.

The controller 30 is a control device for controlling the excavator. In this embodiment, the controller 30 is composed of a computer having a CPU, RAM, ROM and the like. Further, the controller 30 reads programs corresponding to various functional elements from the ROM, loads them into the RAM, and causes the CPU to execute processes corresponding to the various functional elements.

Further, the controller 30 electrically detects each operation content (for example, presence / absence of lever operation, lever operation direction, lever operation amount, etc.) of the operation device 26 based on the output of the pressure sensor 29.

Next, a configuration example of a hydraulic circuit mounted on the excavator in FIG. 1 will be described with reference to FIG. FIG. 3 is a diagram illustrating a configuration example of a hydraulic circuit mounted on the shovel of FIG. 3 shows the high-pressure hydraulic line, the pilot line, and the electric control system by a solid line, a broken line, and a dotted line, respectively, as in FIG.

The

main pumps

14L and 14R are variable displacement hydraulic pumps driven by the engine 11 and correspond to the main pump 14 of FIG. In the present embodiment, the main pump 14L circulates the hydraulic oil to the hydraulic oil tank T through the center bypass oil passage 21L and the merged oil passage 24 that pass through each of the control valves 171L to 175L. The main pump 14L can supply hydraulic oil to each of the control valves 172L to 175L through a parallel oil passage 22L extending in parallel with the center bypass oil passage 21L. Similarly, the main pump 14R circulates the hydraulic oil to the hydraulic oil tank T through the center bypass oil passage 21R and the merging oil passage 24 that pass through each of the control valves 171R to 175R. The main pump 14R can supply hydraulic oil to each of the control valves 172R to 175R through a parallel oil passage 22R extending in parallel with the center bypass oil passage 21R. In the following, the main pump 14L and the main pump 14R may be collectively referred to as the “main pump 14”. The same applies to the other components configured by a pair of left and right.

The control valve 171L is a spool valve that switches the flow of hydraulic oil in order to supply the hydraulic oil discharged from the main pump 14L to the left-side traveling hydraulic motor 1A when a left-side traveling lever (not shown) is operated. is there.

The control valve 171R is a spool valve as a traveling straight valve. In this embodiment, the traveling straight valve 171R is a 4-port 2-position spool valve, and has a first valve position and a second valve position. Specifically, the first valve position has a flow path that connects the main pump 14L and the parallel oil path 22L, and a flow path that connects the main pump 14R and the control valve 172R. The second valve position has a flow path that connects the main pump 14R and the parallel oil path 22L, and a flow path that connects the main pump 14L and the control valve 172R.

The control valve 172L is a spool valve that switches the flow of hydraulic oil in order to supply hydraulic oil discharged from the main pump 14 to an optional hydraulic actuator (not shown).

The control valve 172R is a spool valve that switches the flow of hydraulic oil in order to supply hydraulic oil discharged from the main pump 14 to the hydraulic motor 1B for right traveling when a right traveling lever (not shown) is operated. is there.

The control valve 173L is a spool valve that switches the flow of hydraulic oil in order to supply hydraulic oil discharged from the main pump 14 to the hydraulic hydraulic motor 2A when a turning operation lever (not shown) is operated. .

The control valve 173R is a spool valve that switches the flow of hydraulic oil to supply the hydraulic oil discharged from the main pump 14R to the bucket cylinder 9 when a bucket operation lever (not shown) is operated.

The

control valves

174L and 174R are spool valves that switch the flow of hydraulic oil to supply the hydraulic oil discharged from the main pump 14 to the boom cylinder 7 when a boom operation lever (not shown) is operated. . The control valve 174L additionally supplies hydraulic oil to the boom cylinder 7 when the boom operation lever is operated in the boom raising direction with a predetermined lever operation amount or more.

The

control valves

175L and 175R are spool valves that switch the flow of hydraulic oil to supply the hydraulic oil discharged from the main pump 14 to the arm cylinder 8 when an arm operation lever (not shown) is operated. . The control valve 175R additionally supplies hydraulic oil to the arm cylinder 8 when the arm operation lever is operated at a predetermined lever operation amount or more.

The hydraulic oil flowing out from each of the left traveling hydraulic motor 1A, the optional hydraulic actuator, the turning hydraulic motor 2A, and the arm cylinder 8 is discharged to the hydraulic oil tank T through the return oil path 23L and the merged oil path 24. . Similarly, the hydraulic oil flowing out from each of the right traveling hydraulic motor 1B, the bucket cylinder 9 and the boom cylinder 7 is discharged to the hydraulic oil tank T through the return oil path 23R and the merged oil path 24. In addition, part of the hydraulic oil flowing out from the arm cylinder 8 may be discharged to the hydraulic oil tank T through the return oil path 23R and the merged oil path 24.

The center

bypass oil passages

21L and 21R are respectively provided with negative control throttles 20L and 20R between the

control valves

175L and 175R on the most downstream side and the merge oil passage 24. Hereinafter, the negative control is abbreviated as “negative control”. The negative control throttles 20L and 20R generate a negative control pressure upstream of the negative control throttles 20L and 20R by limiting the flow of hydraulic oil discharged from the

main pumps

14L and 14R. The hydraulic oil discharged from the

main pumps

14L and 14R can reach the hydraulic oil tank T through a plurality of paths without passing through the hydraulic actuator that performs the regeneration operation among the hydraulic actuators. Specifically, the hydraulic oil flowing through each of the bleed oil passages, the center

bypass oil passages

21L and 21R, and the

return oil passages

23L and 23R formed by the control valves 171L to 175L and 171R to 175R is the combined oil passage 24. At the hydraulic oil tank T.

The pressure sensors S1L and S1R detect the negative control pressure generated upstream of the negative control throttles 20L and 20R, and output the detected value to the controller 30 as an electrical negative control pressure signal.

The pressure sensors S2L and S2R detect the discharge pressures of the

main pumps

14L and 14R, and output the detected values to the controller 30 as electrical discharge pressure signals.

The pressure sensor S3R detects the pressure in the rod side oil chamber of the arm cylinder 8 and outputs the detected value to the controller 30 as an electric arm rod pressure signal.

The pressure sensor S3B detects the pressure in the bottom side oil chamber of the arm cylinder 8, and outputs the detected value to the controller 30 as an electric arm bottom pressure signal.

Controller 30 receives the output of pressure sensor 29, S1L, S1R, S2L, S2R, S3R, S3B, etc., and causes the CPU to execute a program for operating arm regeneration circuit 60.

The arm regeneration circuit 60 is a circuit for regenerating the hydraulic oil flowing out from the rod side oil chamber of the arm cylinder 8 into the bottom side oil chamber. In this embodiment, the arm regeneration circuit 60 includes a pressure reducing valve 61, switching

valves

62, 63, 64, a variable throttle 65, a pressure reducing valve 66, a switching valve 67, and an accumulator 68.

The pressure reducing valve 61 is an electromagnetic valve used for simultaneously switching the switching

valves

62, 63, 64, and generates a predetermined secondary pressure using hydraulic fluid discharged from the pilot pump 15. Specifically, when the stop command is received from the controller 30, the secondary pressure is reduced and each of the switching

valves

62, 63, 64 is switched to the first valve position, and when the operation command is received from the controller 30, the secondary pressure is increased. Thus, each of the switching

valves

62, 63, 64 is switched to the second valve position.

Each of the switching valves 62 to 64 is a spool valve that is driven by the secondary pressure of the pressure reducing valve 61, and has a first valve position and a second valve position. The numbers in parentheses in the figure represent the valve position.

Specifically, the switching valve 62 blocks communication between the left side (arm closing side) pilot port of the control valve 175L and the hydraulic oil tank T at the first valve position, and the control valve 175L at the second valve position. The left side (arm closing side) pilot port and the hydraulic oil tank T are connected.

Further, the switching valve 63 allows the control valve 175L to communicate with each of the rod-side oil chamber and the bottom-side oil chamber of the arm cylinder 8 at the first valve position, and the arm cylinder 8 through the regeneration oil passage 63c at the second valve position. The rod side oil chamber communicates with the bottom side oil chamber.

The regeneration oil passage 63c is an oil passage that connects the rod-side oil chamber and the bottom-side oil chamber of the arm cylinder 8, and includes a check valve. The check valve blocks the flow of hydraulic oil from the bottom side oil chamber of the arm cylinder 8 to the rod side oil chamber.

Further, the switching valve 64 blocks the oil passage 25 connecting the arm cylinder 8 and the merging oil passage 24 at the first valve position, and allows the oil passage 25 to communicate at the second valve position. The oil passage 25 includes a check valve that blocks the flow of hydraulic oil from the arm cylinder 8 to the merged oil passage 24.

The variable throttle 65 is placed on the merged oil path 24 downstream of the branch point between the merged oil path 24 and the oil path 25. In this embodiment, when the operation command is received from the controller 30, the throttle opening, that is, the flow passage area of the merge oil passage 24 is reduced, and when the stop command is received from the controller 30, the flow passage area of the merge oil passage 24 is increased.

The pressure reducing valve 66 is an electromagnetic valve used for switching the switching valve 67, and generates a predetermined secondary pressure using hydraulic oil discharged from the pilot pump 15. Specifically, when the stop command is received from the controller 30, the secondary pressure is reduced and the switching valve 67 is switched to the first valve position, and when the operation command is received from the controller 30, the secondary pressure is increased and the switching valve 67 is switched. Switch to the second valve position.

The switching valve 67 is a spool valve that is driven by the secondary pressure of the pressure reducing valve 66, and has a first valve position and a second valve position. Specifically, the switching valve 67 blocks communication between the oil passage 25 and the accumulator 68 at the first valve position, and connects the oil passage 25 and the accumulator 68 at the second valve position.

The accumulator 68 is a functional element that accumulates the hydraulic oil in the hydraulic system and releases the accumulated hydraulic oil as necessary. Specifically, the controller 30 outputs an operation command to the variable throttle 65 and the pressure reducing valve 66 when a predetermined condition is satisfied. Then, the throttle opening of the variable throttle 65 is reduced, and the switching valve 67 is switched to the second valve position so that the oil passage 25 and the accumulator 68 are communicated. Then, the controller 30 accumulates hydraulic oil flowing through the merged oil passage 24 in the accumulator 68. “When the predetermined condition is satisfied” is, for example, when the excavator is not operated or when the main pump 14 is under a low load. Further, the controller 30 passes through an oil passage (not shown) from hydraulic oil flowing out from the braking side (discharge side) of the turning hydraulic motor 2A during turning deceleration, or from the bottom side oil chamber of the boom cylinder 7 during boom lowering operation. The flowing hydraulic oil may be accumulated in the accumulator 68. For example, when the arm regeneration circuit 60 is operated, the controller 30 releases the hydraulic oil accumulated in the accumulator 68 to the oil passage 25.

Next, an example of a process in which the controller 30 operates the arm regeneration circuit 60 (hereinafter referred to as “arm regeneration process”) will be described with reference to FIGS. FIG. 4 is a flowchart showing an example of the arm regeneration process, and the controller 30 repeatedly executes the arm regeneration process at a predetermined control cycle. 5 to 8 are diagrams showing various states of the hydraulic circuit in FIG. 3, and the thick solid line arrow in the figure indicates the flow direction of the hydraulic oil, and the thicker the solid line is, the more the flow rate of the hydraulic oil is. Represents big.

First, the controller 30 determines whether or not an arm closing operation has been performed (step S1). In this embodiment, the controller 30 determines whether or not the arm operation lever has been operated in the closing direction based on the output of the pressure sensor 29.

FIG. 5 shows the state of the hydraulic circuit when the arm closing operation is performed. In FIG. 5, the control valve 175L receives the pilot pressure corresponding to the operation amount of the arm operation lever at the left side (arm closing side) pilot port and moves to the right side. As a result, the hydraulic oil discharged from the main pump 14L flows into the bottom oil chamber of the arm cylinder 8 through the control valve 175L. Depending on the operation amount of the arm operation lever, a part of the hydraulic oil discharged from the main pump 14L passes through the center bypass oil passage 21L and the merging oil passage 24 as a bleed flow rate passing through the bleed oil passage formed by the PT port of the control valve 175L. The oil is discharged to the hydraulic oil tank T. A part of the hydraulic oil flowing out from the rod side oil chamber of the arm cylinder 8 is regenerated to the bottom side oil chamber through a partially regenerated oil passage 175Lc formed in the control valve 175L, and the remaining part is returned oil. The oil is discharged to the hydraulic oil tank T through the passage 23L and the merging oil passage 24. The partially regenerated oil passage 175Lc may be omitted. Further, in FIG. 5, since only the arm closing operation is performed, the hydraulic oil discharged from the main pump 14R merges with the hydraulic oil that passes through the center bypass oil passage 21R and flows through the return oil passage 23L. The oil is discharged to the hydraulic oil tank T through the oil passage 24.

If it is determined that the arm closing operation has been performed (YES in step S1), the controller 30 determines whether or not the state of the arm 5 moving in the closing direction is suitable for the arm closing reproduction operation (step S2). . The arm closing regeneration operation is an operation in which all the hydraulic oil flowing out from the rod side oil chamber of the arm cylinder 8 flows into the bottom side oil chamber. The state suitable for the arm closing / reproducing operation includes the state of the arm 5 when the arm 5 is closed by its own weight, the state of the arm 5 when an external force is acting in the closing direction of the arm 5, and the like. In the present embodiment, the controller 30 determines whether or not the state of the arm 5 is suitable for the arm closing regeneration operation based on the outputs of the pressure sensors S3R and S3B. Specifically, the controller 30 multiplies the pressure of the hydraulic oil in the rod-side oil chamber output from the pressure sensor S3R by the rod-side pressure receiving area of the piston of the arm cylinder 8, and the rod that the hydraulic oil in the rod-side oil chamber exerts on the piston. Deriving side thrust. Similarly, the controller 30 multiplies the pressure of the hydraulic oil in the bottom side oil chamber output from the pressure sensor S3B by the bottom pressure receiving area of the piston of the arm cylinder 8 and the bottom side thrust exerted on the piston by the hydraulic oil in the bottom side oil chamber. To derive. When the controller 30 determines that the bottom thrust is smaller than the rod thrust even though the arm 5 moves in the closing direction, the controller 30 determines that the state of the arm 5 is suitable for the arm closing regeneration operation. To do.

When it is determined that the state of the arm 5 is a state suitable for the arm closing reproduction operation (YES in step S2), the controller 30 operates the arm reproduction circuit 60 (step S3). In this embodiment, the controller 30 outputs an operation command to the pressure reducing valve 61 and the variable throttle 65. As a result, each of the switching

valves

62, 63, 64 is switched to the second valve position, and the throttle opening of the variable throttle 65, that is, the flow passage area of the merging oil passage 24 is reduced. FIG. 6 shows a state of the hydraulic circuit when the arm regeneration circuit 60 is operated.

The switching valve 62 switched to the second valve position makes the left side (arm closing side) pilot port of the control valve 175L communicate with the hydraulic oil tank T and reduces the pilot pressure. As a result, the control valve 175L returns to the neutral position, and the hydraulic oil discharged from the main pump 14L reaches the merged oil passage 24 through the center bypass oil passage 21L.

Further, the switching valve 63 switched to the second valve position causes the rod-side oil chamber and the bottom-side oil chamber of the arm cylinder 8 to communicate with each other through the regeneration oil passage 63c. Therefore, all of the hydraulic oil flowing out from the rod side oil chamber flows into the bottom side oil chamber.

Further, the switching valve 64 switched to the second valve position causes the oil passage 25 connecting the arm cylinder 8 and the merging oil passage 24 to communicate with each other. Therefore, the hydraulic oil that travels through the oil passage 25 toward the arm cylinder 8 joins the hydraulic oil that flows from the rod-side oil chamber of the arm cylinder 8 to the bottom-side oil chamber.

Further, the variable throttle 65 with the throttle opening reduced reduces the hydraulic oil flowing through the merging oil passage 24 from being discharged to the hydraulic oil tank T, and the hydraulic oil flowing through the oil passage 25 to the arm cylinder 8 is reduced. Increase the flow rate. The throttle opening of the variable throttle 65 is at least one of the operation content of the arm operating lever for operating the arm cylinder 8, the pressure of the rod side oil chamber of the arm cylinder 8, and the pressure of the bottom side oil chamber of the arm cylinder 8. May be adjusted based on For example, the opening degree of the variable diaphragm 65 may be adjusted so as to decrease as the operation amount in the lowering direction of the arm operation lever increases. The throttle opening of the variable throttle 65 may be adjusted so as to decrease as the pressure in the rod-side oil chamber of the arm cylinder 8 increases, and decreases as the pressure in the bottom-side oil chamber of the arm cylinder 8 decreases. May be adjusted. This is because it is estimated that more hydraulic oil needs to flow into the arm cylinder 8.

Thus, the hydraulic oil flowing through the center bypass oil passage 21L discharged from the main pump 14L and the hydraulic oil flowing through the center bypass oil passage 21R discharged from the main pump 14R merge at the merge oil passage 24. The hydraulic oil merged in the merged oil passage 24 is suppressed from flowing to the hydraulic oil tank T by the variable throttle 65 and flows into the oil passage 25, and further from the rod side oil chamber of the arm cylinder 8 to the bottom side oil chamber. Joins the hydraulic fluid flowing through

For this reason, the insufficient regeneration flow rate, which is the difference between the hydraulic oil flow rate required for the expansion of the bottom side oil chamber and the hydraulic oil flow rate flowing out of the rod side oil chamber due to the contraction of the rod side oil chamber, And the replenishment replenishment flow rate which is the flow rate of the hydraulic oil flowing in through the switching valve 64. As a result, the arm cylinder 8 can be extended without generating cavitation in the bottom side oil chamber.

Thereafter, the controller 30 determines whether or not the regeneration replenishment flow rate is insufficient (step S4). In this embodiment, the controller 30 determines whether or not the regeneration replenishment flow rate is insufficient based on the pressure in the bottom side oil chamber of the arm cylinder 8 output from the pressure sensor S3B.

When it is determined that the regeneration replenishment flow rate is insufficient (YES in step S4), the controller 30 releases hydraulic oil from the accumulator 68 (step S5). In the present embodiment, the controller 30 determines that the regeneration replenishment flow rate is insufficient when the pressure in the bottom side oil chamber falls below a predetermined pressure. Then, the controller 30 outputs an operation command to the pressure reducing valve 66. As a result, the switching valve 67 is switched to the second valve position, and the hydraulic oil accumulated in the accumulator 68 is discharged to the oil passage 25. As described above, the controller 30 feedback-controls the regeneration replenishment flow rate so that the regeneration insufficient flow rate becomes zero by adjusting the discharge amount of the accumulator 68 according to the output of the pressure sensor S3B. FIG. 7 shows the state of the hydraulic circuit when the controller 30 determines that the regeneration replenishment flow rate is insufficient.

The switching valve 67 switched to the second valve position causes the oil passage 25 and the accumulator 68 to communicate with each other. As a result, at least a part of the hydraulic oil discharged from the accumulator 68 flows toward the arm cylinder 8 and joins the hydraulic oil flowing from the rod side oil chamber of the arm cylinder 8 to the bottom side oil chamber.

Therefore, the regeneration insufficient flow rate is a regeneration flow rate that is a total flow rate of the hydraulic oil flowing in through the switching valve 64, that is, the hydraulic fluid flowing into the oil path 25 from the merged oil path 24 and the hydraulic oil discharged from the accumulator 68. Supplemented by replenishment flow. As a result, the arm cylinder 8 can be extended without generating cavitation in the bottom side oil chamber.

On the other hand, if it is determined that the regeneration replenishment flow rate is not insufficient (NO in step S4), the controller 30 continues the operation of the arm regeneration circuit 60 without releasing the hydraulic oil from the accumulator 68. In this embodiment, the controller 30 determines that the regeneration replenishment flow rate is not insufficient when the pressure in the bottom side oil chamber is equal to or higher than a predetermined pressure. Then, when the pressure reducing valve 66 is in the second valve position, the controller 30 outputs a stop command to the pressure reducing valve 66. As a result, the switching valve 67 is switched to the first valve position, and the release of the hydraulic oil from the accumulator 68 to the oil passage 25 is stopped. FIG. 8 shows the state of the hydraulic circuit when the controller 30 determines that the regeneration replenishment flow rate is not insufficient.

Specifically, FIG. 8 shows a state in which the boom raising operation is performed simultaneously with the arm closing operation, and the amount of hydraulic oil flowing into the merged oil passage 24 is larger than when the arm closing operation is performed alone. In this case, the flow rate of the hydraulic oil flowing into the merging oil passage 24 is the flow rate of the hydraulic oil flowing through the center bypass oil passage 21L discharged from the main pump 14L and the return oil passage 23R flowing out from the rod side oil chamber of the boom cylinder 7. And the flow rate of the hydraulic fluid flowing through the center bypass oil passage 21R through the PT port of the control valve 174R discharged from the main pump 14R (bleed flow rate).

Therefore, the insufficient regeneration flow rate is compensated by the regeneration replenishment flow rate constituted only by the flow rate of the hydraulic oil flowing from the merged oil passage 24 into the oil passage 25. As a result, the arm cylinder 8 can be extended without generating cavitation in the bottom side oil chamber without using the hydraulic oil discharged from the accumulator 68.

If it is determined that the arm closing operation has not been performed (NO in step S1), the controller 30 ends the current arm regeneration process without operating the arm regeneration circuit 60. Further, the controller 30 stops the arm regeneration circuit 60 when the arm regeneration circuit 60 is in an operating state. In this embodiment, the controller 30 outputs a stop command to the pressure reducing valve 61, the variable throttle 65, and the pressure reducing valve 66. As a result, each of the switching

valves

62, 63, 64, 67 is switched to the first valve position, and the throttle opening of the variable throttle 65, that is, the flow passage area of the merging oil passage 24 is increased.

Next, another example of the arm regeneration process will be described with reference to FIG. 9 and FIG. FIG. 9 is a flowchart showing the flow of another example of the arm regeneration process. FIG. 10 is a diagram showing a state of the hydraulic circuit in which the arm regeneration process of FIG. 9 is executed. The thick solid line arrow in the figure indicates the flow direction of the hydraulic oil, and the thicker the solid line, the greater the flow rate of the hydraulic oil. Is large.

The arm regeneration process in FIG. 9 increases the regeneration replenishment flow rate by increasing the discharge amount of the main pump 14 instead of increasing the regeneration replenishment flow rate using the hydraulic oil released by the accumulator when the regeneration replenishment flow rate is insufficient. This is different from the arm regeneration process in FIG. The hydraulic circuit of FIG. 10 is different from the hydraulic circuit of FIG. 3 in that the pressure reducing valve 66, the switching valve 67, and the accumulator 68 are omitted from the arm regeneration circuit 60, but is common in other points. Therefore, description of common parts is omitted, and different parts are described in detail.

If it is determined that the regeneration replenishment flow rate is insufficient (YES in step S14), the controller 30 increases the discharge amount of the main pump 14L (step S15). In this embodiment, the controller 30 determines that the regeneration replenishment flow rate is insufficient when the pressure in the bottom oil chamber of the arm cylinder 8 falls below a predetermined pressure. Then, the controller 30 outputs a discharge amount increase command to the regulator 13L. In this manner, the controller 30 feedback-controls the regeneration replenishment flow rate so that the regeneration insufficient flow rate becomes zero by adjusting the discharge amount of the main pump 14L according to the output of the pressure sensor S3B. FIG. 10 shows the state of the hydraulic circuit when the controller 30 determines that the regeneration replenishment flow rate is insufficient.

The main pump 14L with the increased discharge amount joins the flow rate of the working oil flowing through the merging oil passage 24 and the oil passage 25, that is, the working oil regenerated from the rod side oil chamber of the arm cylinder 8 to the bottom side oil chamber. The regeneration replenishment flow rate that is the flow rate of the hydraulic oil is increased. Therefore, the insufficient regeneration flow rate is compensated by the regeneration replenishment flow rate. As a result, the arm cylinder 8 can be extended without generating cavitation in the bottom side oil chamber.

The controller 30 may increase the discharge amount of the main pump 14R instead of increasing the discharge amount of the main pump 14L, or may increase the discharge amounts of both the main pump 14L and the main pump 14R.

Further, the controller 30 may execute the arm regeneration process of FIG. 9 by the hydraulic circuit of FIG. For example, the controller 30 may increase the discharge amount of the main pump 14 when sufficient hydraulic oil is not accumulated in the accumulator 68. Alternatively, the controller 30 may increase the discharge amount of the main pump 14 simultaneously with the release of the hydraulic oil from the accumulator 68.

Next, still another example of the arm regeneration process will be described with reference to FIG. FIG. 11 is a diagram illustrating a state of the hydraulic circuit in which the arm regeneration process of FIG. 4 is executed. The thick solid arrow in the figure represents the flow direction of the hydraulic oil, and the thicker the solid line, the larger the flow rate of the hydraulic oil. Represents that.

The hydraulic circuit in FIG. 11 is different from the hydraulic circuit in FIG. 3 in that the hydraulic underflow rate can be reduced to zero using only the hydraulic oil that is discharged by the accumulator 68 when the under-regenerative flow rate is greater than zero. It is common in other points. Therefore, description of common parts is omitted, and different parts are described in detail.

The switching valve 64A is a spool valve that is disposed instead of the switching valve 64 of FIG. 3, and shuts off the oil passage 25 connecting the arm cylinder 8 and the merging oil passage 24 at the first valve position, and at the second valve position. The oil passage 25 is connected. The switching valve 64 is driven by the secondary pressure of the pressure reducing valve 61A.

The pressure reducing valve 61A is an electromagnetic valve used for switching the switching valve 64A, and generates a predetermined secondary pressure using hydraulic oil discharged from the pilot pump 15. Specifically, when the stop command is received from the controller 30, the secondary pressure is reduced and the switching valve 64A is switched to the first valve position, and when the operation command is received from the controller 30, the secondary pressure is increased and the switching valve 64A is switched. Switch to the second valve position. The pressure reducing valve 61A is controlled independently of the pressure reducing valve 61. Therefore, the switching valve 64A is switched regardless of the switching of the switching valve 62 and the switching valve 63.

When the arm closing operation is performed, the controller 30 determines that the insufficient regeneration flow is greater than zero when the pressure in the bottom oil chamber of the arm cylinder 8 output from the pressure sensor S3B falls below a predetermined pressure. Then, a stop command is output to the pressure reducing valve 61A, and an operation command is output to the pressure reducing valve 66. As a result, as shown in FIG. 11, the switching valve 64 </ b> A is switched to the first position, and the oil passage 25 connecting the arm cylinder 8 and the merged oil passage 24 is blocked. Further, the switching valve 67 is switched to the second valve position, and the hydraulic oil accumulated in the accumulator 68 is discharged to the oil passage 25. As described above, the controller 30 controls the discharge insufficient flow rate to be zero by adjusting the discharge amount of the accumulator 68 according to the output of the pressure sensor S3B. Therefore, the insufficient regeneration flow rate is compensated only by the hydraulic oil discharged from the accumulator 68. As a result, the arm cylinder 8 can be extended without generating cavitation in the bottom side oil chamber.

Further, when the arm opening operation is performed, the controller 30 may cause the hydraulic oil flowing out from the bottom side oil chamber of the arm cylinder 8 to flow into the rod side oil chamber of the arm cylinder 8 through the regeneration oil path 63c. Then, excess hydraulic oil that does not enter the rod-side oil chamber of the arm cylinder 8 may flow into the accumulator 68 through the oil passage 25.

With the above configuration, the controller 30 can cause all of the hydraulic oil flowing out from the rod side oil chamber of the arm cylinder 8 to flow into the bottom side oil chamber. Therefore, it is possible to more efficiently execute the arm closing regeneration operation in which the hydraulic oil flowing out from the rod side oil chamber of the arm cylinder 8 flows into the bottom side oil chamber.

Further, the controller 30 realizes a regeneration replenishment flow rate corresponding to the regeneration insufficient flow rate by discharging hydraulic oil from the accumulator 68 or increasing the discharge amount of the main pump 14. Therefore, the flow rate of the hydraulic oil discharged from the main pump 14 during the arm closing regeneration operation can be minimized.

Although the preferred embodiments of the present invention have been described in detail above, the present invention is not limited to the above-described embodiments, and various modifications and substitutions can be made to the above-described embodiments without departing from the scope of the present invention. Can be added.

For example, in the above-described embodiment, the regeneration oil passage 63c is formed in the switching valve 63 installed outside the control valve 175L, but the present invention is not limited to this configuration. For example, the switching valve 63 may be integrated with the control valve 175L. In this case, the control valve 175L may be configured with a 6-port 4-position spool valve instead of the 6-port 3-position spool valve, and a regenerated oil passage may be formed at the added valve position.

In the above-described embodiment, the oil passage 25 is connected to the oil passage connecting the rod-side oil chamber of the arm cylinder 8 and the switching valve 63, but the present invention is not limited to this configuration. For example, the oil passage 25 may be directly connected to the rod-side oil chamber, may be directly connected to the bottom-side oil chamber, or may be directly connected to the regenerated oil passage 63 c in the switching valve 63.

In the above-described embodiment, the present invention is applied to the arm regeneration circuit 60, but may be applied to other regeneration circuits such as a bucket regeneration circuit.

This application claims priority based on Japanese Patent Application No. 2014-189212 filed on September 17, 2014, the entire contents of which are incorporated herein by reference.

DESCRIPTION OF SYMBOLS 1 ... Lower traveling

body

1A, 1B ... Traveling hydraulic motor 2 ... Turning mechanism 2A ... Turning hydraulic motor 3 ... Upper turning body 4 ... Boom 5 ... Arm 6. -Bucket 7 ... Boom cylinder 8 ... Arm cylinder 9 ... Bucket cylinder 10 ... Cabin 11 ...

Engine

13, 13L, 13R ...

Regulators

14, 14L, 14R ... Main pump 15 ... Pilot pump 17 ...

Control valve

20L, 20R ...

Negative control throttle

21L, 21R ... Center

bypass oil passage

22L, 22R ...

Parallel oil passage

23L, 23R ... Return oil passage 24 ... Confluence oil passage 25 ... Oil passage 26 ... Operating device 29 ... Pressure sensor 30 ... Controller 60 ... Arm regeneration circuit 61 ... Pressure reducing valve 62-64 ... Switching valve 65 ... Variable throttle 66 ... Pressure reducing valve 67 ... Switching valve 68 ... Accumulator 171L-175L, 171R ~ 175R ... Control valve S1L, S2R, S2L, S2R, S3R, S3B ... Pressure sensor T ... Hydraulic oil tank

Claims

A hydraulic pump for supplying hydraulic oil to a plurality of hydraulic actuators including a hydraulic cylinder;
A plurality of control valves for controlling the flow of hydraulic oil between the hydraulic pump and each of the plurality of hydraulic actuators;
A first oil passage that allows a flow of hydraulic oil from a rod side oil chamber to a bottom side oil chamber of the hydraulic cylinder;
When hydraulic oil flows from the rod side oil chamber to the bottom side oil chamber through the first oil passage, before the hydraulic oil that can flow through a plurality of paths discharged by the hydraulic pump reaches the hydraulic oil tank. A second oil passage that flows into the
A third oil passage capable of communicating the first oil passage and the second oil passage;
Excavator with.
A variable throttle provided in the second oil passage;
The second oil passage is connected to the hydraulic oil tank downstream of the variable throttle, and is connected to the third oil passage at a branch point upstream of the variable throttle;
The variable throttle reduces the flow rate of hydraulic oil toward the hydraulic oil tank as the throttle opening is smaller, and increases the flow rate of hydraulic oil toward the first oil passage through the third oil passage.
The excavator according to claim 1.
The throttle opening of the variable throttle is adjusted based on at least one of the operation content of the operating device that operates the hydraulic cylinder, the pressure of the rod-side oil chamber, and the pressure of the bottom-side oil chamber.
The shovel according to claim 2.
An accumulator connected to the third oil passage;
The shovel according to claim 1 or 2.
When the hydraulic oil flows from the rod side oil chamber to the bottom side oil chamber through the first oil passage, the hydraulic oil discharged from the accumulator further flows to the bottom side oil chamber.
The excavator according to claim 4.
When the hydraulic oil flows from the bottom side oil chamber to the rod side oil chamber through the first oil passage, the hydraulic oil flowing out from the bottom side oil chamber flows to the accumulator.
The excavator according to claim 4 or 5.
When the hydraulic oil flowing through the second oil passage flows to the first oil passage through the third oil passage and the pressure in the bottom side oil chamber is less than a predetermined pressure, the hydraulic pump discharges Increase,
The shovel according to claim 1 or 2.
A switching valve for switching communication / blocking of the first oil passage;
A first control valve that controls a flow of hydraulic oil between the hydraulic pump and the hydraulic cylinder is one of the plurality of control valves;
The switching valve is provided separately from the first control valve,
The first control valve shuts off a flow of hydraulic oil between the hydraulic pump and the hydraulic cylinder when the switching valve communicates the first oil passage.
The shovel according to claim 1 or 2.
A switching valve for switching communication / blocking of the first oil passage;
A first control valve that controls a flow of hydraulic oil between the hydraulic pump and the hydraulic cylinder is one of the plurality of control valves;
The switching valve is integrated with the first control valve;
The shovel according to claim 1 or 2.