JP7297401B2 - Excavator - Google Patents

Description

The present invention relates to a shovel with an attachment.

2. Description of the Related Art Conventionally, an excavator is known in which a regeneration circuit is mounted inside a spool valve that controls the flow of hydraulic oil in an arm cylinder (see Patent Document 1). The regenerative circuit is configured to allow hydraulic fluid flowing out of the rod-side oil chamber of the arm cylinder to flow into the bottom-side oil chamber of the arm cylinder.

JP 2013-130227 A

However, the above-described regeneration circuit is configured so that the hydraulic oil flowing from the hydraulic pump to the bottom side oil chamber of the arm cylinder joins the hydraulic oil flowing out from the rod side oil chamber of the arm cylinder, so the pressure loss increases. put away.

In view of the above, it is desirable to provide an excavator capable of reducing pressure loss when regenerating hydraulic oil from the contraction-side oil chamber of the hydraulic cylinder to the expansion-side oil chamber.

An excavator according to an embodiment of the present invention includes a lower traveling body, an upper revolving body rotatably attached to the lower traveling body, an attachment attached to the upper revolving body, a hydraulic cylinder for driving the attachment, and the a hydraulic pump mounted on an upper revolving structure; a hydraulic oil tank mounted on the upper revolving structure; a flow of hydraulic oil mounted on the upper revolving structure from the hydraulic pump to the hydraulic cylinder; a control valve that controls the flow of hydraulic fluid from the hydraulic cylinder to the hydraulic fluid tank; a first oil passage that connects the rod-side oil chamber of the hydraulic cylinder and the control valve; and a bottom-side oil chamber of the hydraulic cylinder. and the control valve, and the first oil passage and the second oil passage that connect the rod-side oil chamber of the hydraulic cylinder and the bottom-side oil chamber of the hydraulic cylinder to regenerate hydraulic oil. a third oil passage independent from, a valve that opens and closes the third oil passage, a rod pressure sensor that detects the pressure of hydraulic oil in the rod-side oil chamber of the hydraulic cylinder, and a bottom-side oil chamber of the hydraulic cylinder A bottom pressure sensor that detects the pressure of hydraulic oil and a controller that controls the valve , the valve controlling at least the discharge pressure of the hydraulic pump, the pressure of the bottom-side oil chamber, and the rod It is controlled according to the pressure in the side oil chamber.

The above means provide a shovel capable of reducing pressure loss when regenerating hydraulic oil from the contraction-side oil chamber of the hydraulic cylinder to the expansion-side oil chamber.

It is a side view of a shovel. It is a block diagram which shows the structural example of the drive system of an excavator. It is a schematic diagram showing a configuration example of part of a hydraulic system mounted on a shovel. It is a sectional view of an arm cylinder. It is a sectional view of an arm cylinder.

First, referring to FIG. 1, a shovel (excavator) 100 as a construction machine according to an embodiment of the present invention will be described. FIG. 1 is a side view of a shovel 100. FIG. An upper rotating body 3 is mounted on a lower running body 1 of the excavator 100 shown in FIG. 1 via a rotating mechanism 2 . A boom 4 is attached to the upper swing body 3 as a working element. An arm 5 as a working element is attached to the tip of the boom 4 , and a bucket 6 as a working element and an end attachment is attached to the tip of the arm 5 . The boom 4, arm 5, and bucket 6 constitute an excavation attachment, and 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 as an operator's cab, 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 100 of FIG. indicated by

A drive system of the excavator 100 mainly includes an engine 11, a regulator 13, a main pump 14, a pilot pump 15, a control valve 17, an operation device 26, a discharge pressure sensor 28, an operation pressure sensor 29, a controller 30, and the like.

The engine 11 is a drive source for the excavator 100 . In this embodiment, the engine 11 is, for example, a diesel engine as an internal combustion engine that operates to maintain a predetermined number of revolutions. Also, 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 via a high-pressure hydraulic line, and is, for example, 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 tilting angle of the swash plate of the main pump 14 according to the discharge pressure of the main pump 14, a command from the controller 30, and the like. .

The pilot pump 15 is a device that supplies working oil to various hydraulic control devices including the operating device 26 via a pilot line, and is, for example, a fixed displacement hydraulic pump.

The control valve 17 is a hydraulic control device that controls the hydraulic system in the excavator 100 . Specifically, the control valve 17 includes a plurality of control valves that control the flow of hydraulic oil discharged by the main pump 14 . The control valve 17 selectively supplies hydraulic fluid discharged from the main pump 14 to one or more hydraulic actuators through these control valves. These control valves control the flow rate of hydraulic fluid flowing from the main pump 14 to the hydraulic actuator and the flow rate of hydraulic fluid flowing from the hydraulic actuator to the hydraulic fluid tank. In the example of FIG. 2, the hydraulic actuators include a boom cylinder 7, an arm cylinder 8, a bucket cylinder 9, a left travel hydraulic motor 1L, a right travel hydraulic motor 1R, and a turning hydraulic motor 2A. The turning hydraulic motor 2A is an example of a turning device for turning the upper turning body 3 with respect to the lower traveling body 1, and may be replaced with a turning electric motor as an electric actuator.

The operating device 26 is a device used by an operator to operate the hydraulic actuator. In this embodiment, the operating device 26 supplies the hydraulic fluid discharged by the pilot pump 15 to the pilot ports of the control valves corresponding to the hydraulic actuators through the pilot lines. The pressure of hydraulic fluid supplied to each of the pilot ports (hereinafter referred to as "pilot pressure") is a pressure corresponding to the direction and amount of operation of the lever or pedal of the operating device 26 corresponding to each hydraulic actuator. be.

The operation pressure sensor 29 is a sensor for detecting the content of the operator's operation using the operation device 26 . In this embodiment, the operating pressure sensor 29 detects, in the form of pressure, the operating direction and operating amount of the lever or pedal of the operating device 26 corresponding to each of the hydraulic actuators, and sends the detected value to the controller 30. Output. The operation content of the operating device 26 may be detected using a sensor other than the pressure sensor.

Controller 30 is a control device for controlling excavator 100 . In this embodiment, the controller 30 is configured by, for example, a computer including a CPU, RAM, NVRAM, ROM, and the like. The controller 30 reads programs corresponding to various functions from the ROM, loads them into the RAM, and causes the CPU to execute the corresponding processes. In the example of FIG. 3, the controller 30 has the function of controlling the reproduction circuit. The regeneration circuit is a circuit for regenerating hydraulic oil from the contraction-side oil chamber of the hydraulic cylinder to the expansion-side oil chamber.

The reproduction circuit will be described with reference to FIG. FIG. 3 is a schematic diagram showing a configuration example of part of the hydraulic system mounted on the excavator 100 of FIG. Specifically, a configuration example of a portion of the hydraulic system relating to the regeneration circuit 50 connected to the arm cylinder 8 is shown.

The regeneration circuit 50 regenerates hydraulic oil from the contraction side oil chamber of the arm cylinder 8 to the expansion side oil chamber. Typically, when the arm 5 is closed, hydraulic fluid that flows out from the rod-side oil chamber 8R of the arm cylinder 8 is caused to flow into the bottom-side oil chamber 8B. However, when the arm 5 is opened, the hydraulic oil that flows out from the bottom side oil chamber 8B of the arm cylinder 8 may flow into the rod side oil chamber 8R.

The arm cylinder 8 is a single-rod hydraulic cylinder having a rod 8X extending to one side of a piston 8P slidably disposed within a cylindrical cylinder body 8S. The arm cylinder 8 is connected to the main pump 14 via a control valve 170 arranged inside the control valve 17 . Specifically, the rod-side oil chamber 8R of the arm cylinder 8 is connected to the control valve 170 through the first oil passage C1, and the bottom-side oil chamber 8B of the arm cylinder 8 is connected through the second oil passage C2. It is connected to control valve 170 .

The control valve 170 operates according to the pilot pressure generated by the arm operating lever 26A, which is an example of the operating device 26. As shown in FIG. Arm operating lever 26A is connected to pilot pump 15 via pilot line PL1. Then, the pressure (primary pressure) of the hydraulic fluid discharged by the pilot pump 15 is used to generate the pilot pressure (secondary pressure). Specifically, when the arm operating lever 26A is operated in the arm opening direction, the pilot pressure in the pilot line PL2 is increased to move the control valve 170 rightward. Further, when the arm is operated in the closing direction, the pilot pressure in the pilot line PL3 is increased to move the control valve 170 leftward.

When the control valve 170 moves rightward, the main pump 14 causes the hydraulic oil drawn from the hydraulic oil tank TK to flow into the rod-side oil chamber 8R of the arm cylinder 8, thereby expanding the rod-side oil chamber 8R. As a result, the rod 8X is retracted into the cylinder body 8S and the arm 5 is opened. When the control valve 170 moves leftward, the main pump 14 causes the hydraulic oil pumped from the hydraulic oil tank TK to flow into the bottom side oil chamber 8B of the arm cylinder 8 to expand the bottom side oil chamber 8B. As a result, the rod 8X is pushed out of the cylinder body 8S and the arm 5 is closed.

The regeneration circuit 50 mainly includes a switching valve 51, a switching valve 52, a switching valve 53, a third oil passage C3, and the like. The third oil passage C3 is an oil passage that connects the bottom side oil chamber 8B and the rod side oil chamber 8R of the arm cylinder 8, and is independent of the first oil passage C1 and the second oil passage C2.

The configuration in which the third oil passage C3 is independent from the first oil passage C1 and the second oil passage C2 is such that the hydraulic oil from the main pump 14 to the arm cylinder 8 via the control valve 170 and the arm cylinder 8 to the hydraulic oil tank TK via the control valve 170 does not pass through the third oil passage C3.

In the example of FIG. 3, the cylindrical cylinder body 8S of the arm cylinder 8 is formed with four openings H1 to H4. The opening H1 is connected to one end of the first oil passage C1, and the opening H2 is connected to one end of the second oil passage C2. The opening H3 is connected to one end of the third oil passage C3, and the opening H4 is connected to the other end of the third oil passage C3.

The switching valve 51 opens and closes the third oil passage C3. In the example of FIG. 3, the switching valve 51 switches communication/blocking between the rod-side oil chamber 8R and the bottom-side oil chamber 8B of the arm cylinder 8 according to the pilot pressure in the pilot line PL4. The opening area of the third oil passage C3 may be adjusted. Pilot line PL4 branches off from pilot line PL3 and reaches switching valve 51 . Pilot line PL<b>4 may be configured to branch from pilot line PL<b>1 and reach switching valve 51 .

Switching valve 52 controls the magnitude of the pilot pressure acting on switching valve 51 . In the example of FIG. 3, switching valve 52 is an electromagnetic valve that operates according to a command from controller 30, and is arranged on pilot line PL4.

The switching valve 51 may be an electromagnetic switching valve. In this case, switching valve 52 and pilot line PL4 may be omitted.

The rod pressure sensor 28R detects the pressure of hydraulic fluid in the rod-side oil chamber 8R of the arm cylinder 8 (hereinafter referred to as "rod pressure"). In the example of FIG. 3, it is arranged in the first oil passage C1. It may be attached to the rod side oil chamber 8R. The bottom pressure sensor 28B detects the pressure of hydraulic fluid in the bottom side oil chamber 8B of the arm cylinder 8 (hereinafter referred to as "bottom pressure"). In the example of FIG. 3, it is arranged in the second oil passage C2. It may be attached to the bottom side oil chamber 8B. The bottom pressure sensor 28B and the rod pressure sensor 28R output the detected values to the controller 30 .

The switching valve 53 opens and closes the oil passage CR that connects the control valve 170 and the hydraulic oil tank TK. In the example of FIG. 3 , the switching valve 53 is an electromagnetic valve that operates according to commands from the controller 30 . Similar to the combination of the switching valve 51 and the switching valve 52, it may be configured by a combination of a pilot type switching valve and an electromagnetic switching valve. The switching valve 53 adjusts the opening area of the oil passage CR, for example, in order to increase the rod pressure so that the working oil flows from the rod-side oil chamber 8R to the bottom-side oil chamber 8B during regeneration. The switching valve 53 can increase the rod pressure by, for example, reducing the opening area of the oil passage CR to limit the flow rate of hydraulic fluid flowing from the rod-side oil chamber 8R to the hydraulic fluid tank TK. After that, the switching valve 53 may increase the reduced opening area of the oil passage CR in order to suppress the regeneration amount. In this case, the switching valve 53 functions as a regeneration release valve.

The controller 30 controls the regeneration circuit 50 based on outputs from the discharge pressure sensor 28, the bottom pressure sensor 28B, the rod pressure sensor 28R, the operating pressure sensor 29, and the like. Specifically, the controller 30 controls the regeneration circuit 50 based on presence/absence of operation of the arm control lever, amount of operation, direction of operation, rod pressure, bottom pressure, discharge pressure of the main pump 14, and the like. For example, when the arm operating lever 26A is operated in the arm closing direction and the bottom pressure is less than a predetermined value, the controller 30 opens the switching valve 51 to communicate the third oil passage C3. Specifically, a command is output to the switching valve 52 to operate the switching valve 52 , and the pilot pressure acting on the switching valve 51 is adjusted. Then, the switching valve 51 is operated to adjust the degree of opening of the switching valve 51, that is, the opening area of the third oil passage C3.

Further, the controller 30 controls the amount of regeneration by adjusting the opening of the switching valve 51 based on the discharge pressure, rod pressure and bottom pressure of the main pump 14 when the third oil passage C3 is communicated. good too. For example, the controller 30 may adjust the regeneration amount so as to reproduce the behavior of the arm 5 when the regeneration circuit is provided inside the control valve 170 as in the conventional art. In this case, the controller 30 may operate the switching valve 53 to adjust the opening area of the oil passage CR.

With this configuration, the excavator 100 can regenerate the hydraulic oil flowing out of the rod-side oil chamber 8R through the third oil passage C3 into the bottom-side oil chamber 8B. Therefore, the pressure loss that occurs during regeneration can be reduced. This is because there is no need to regenerate the hydraulic oil via the control valve 17 or the like, that is, via the first oil passage C1, the control valve 170 and the second oil passage C2. Specifically, this is because there is no need to merge the hydraulic fluid flowing out of the rod-side oil chamber 8R with the hydraulic fluid flowing from the main pump 14 to the bottom-side oil chamber 8B. Also, by using the third oil passage C3, the length of the oil passage through which the regenerated hydraulic oil flows can be shortened.

Also, the third oil passage C3 is completely independent of the first oil passage C1 and the second oil passage C2. Therefore, the flow of hydraulic oil from the main pump 14 to the arm cylinder 8 via the control valve 170 is not affected. Moreover, the flow of hydraulic oil from the arm cylinder 8 to the hydraulic oil tank TK through the control valve 170 is not affected. As a result, it is possible to prevent the operability of the arm 5 from being adversely affected by regeneration.

The regeneration circuit 50 may further have a fourth oil passage (not shown) connecting the third oil passage C3 and the hydraulic oil tank TK. The fourth oil passage is connected to the third oil passage C3 between the rod-side oil chamber 8R of the arm cylinder 8 and the switching valve 51, for example. A third oil passage C3 may be connected between the bottom side oil chamber 8B of the arm cylinder 8 and the switching valve 51 . An oil passage connected to the third oil passage C3 between the rod side oil chamber 8R and the switching valve 51, and a third oil passage C3 connected between the bottom side oil chamber 8B and the switching valve 51. It may consist of two oil passages.

A regeneration release valve is attached to the fourth oil passage. The regeneration release valve is a hydraulic device that opens and closes the fourth oil passage, and is composed of, for example, a combination of a pilot type switching valve and an electromagnetic switching valve, similar to the combination of the switching valves 51 and 52 . However, it may be composed only of an electromagnetic switching valve. The controller 30 cancels the regeneration, for example, when the bottom pressure exceeds a predetermined value while the third oil passage C3 is open. Specifically, the switching valve 51 is closed and the regeneration release valve is opened, and the rod-side oil chamber 8R is regenerated through the fourth oil passage connected to the third oil passage C3 between the rod-side oil chamber 8R and the switching valve 51. The hydraulic oil in is discharged to the hydraulic oil tank TK. The discharge amount may be controlled by adjusting the degree of opening of the regeneration release valve.

Controller 30 may use switching valve 51 to stabilize the posture of the attachment. For example, even if the boom-up operation is performed when the attachment is extended straight in the horizontal direction, the controller 30 can temporarily change the attitude of the attachment by opening and closing the switching valve 51. It can be suppressed or prevented from being lost. Specifically, it is possible to suppress or prevent the arm angle, which is the angle formed between the boom 4 and the arm 5, from temporarily decreasing. That is, it is possible to suppress or prevent the attachment from being unable to maintain its stretched state and being slightly bent.

More specifically, the acceleration (impact) of the raising operation of the boom 4 may excite the self-excited vibration of the arm 5 . That is, the arm 5 may vibrate due to the compressibility of the arm cylinder 8 and the inertia of the arm 5 itself. The controller 30 can suppress or prevent this vibration by opening and closing the switching valve 51 . This is because the rod pressure and the bottom pressure of the arm cylinder 8 are balanced when the switching valve 51 is opened. The controller 30 determines the timing of opening the switching valve 51 based on, for example, the pilot pressure generated by the boom operating lever during the boom raising operation, the rod pressure of the arm cylinder 8, the bottom pressure of the arm cylinder 8, and the like.

Next, another configuration example of the reproducing circuit 50 will be described with reference to FIG. 4 is a cross-sectional view of the arm cylinder 8. FIG. The regeneration circuit 50 of FIG. 4 differs from the regeneration circuit 50 of FIG. 3 in that the third oil passage C3 and the switching valve 51 are formed inside the cylinder body 8S, but they are common in other respects.

With this configuration, the regeneration circuit 50 of FIG. 4 can further reduce the pressure loss that occurs during regeneration. This is because the length of the third oil passage C3 through which the regenerated hydraulic oil flows can be further shortened.

Also in the example of FIG. 4, the regeneration circuit 50 may further have a fourth oil passage (not shown) connecting the third oil passage C3 and the hydraulic oil tank TK.

Next, still another configuration example of the reproducing circuit 50 will be described with reference to FIG. FIG. 5 is a cross-sectional view of the arm cylinder 8 and corresponds to FIG. The regeneration circuit 50 of FIG. 5 is shown in that the third oil passage C3 and the switching valve 51 are formed inside the piston 8P, and that only the two openings H1 and H2 are formed in the cylinder body 8S. 3, but has other points in common.

With this configuration, the regeneration circuit 50 of FIG. 5 can further reduce the pressure loss that occurs during regeneration. This is because the length of the third oil passage C3 through which the regenerated hydraulic oil flows can be further shortened.

As described above, the excavator 100 according to the embodiment of the present invention includes a lower traveling body 1, an upper revolving body 3 attached to the lower traveling body 1 so as to be able to turn, an attachment attached to the upper revolving body 3, and an attachment. a main pump 14 mounted on the upper revolving body 3; a hydraulic oil tank TK mounted on the upper revolving body 3; A control valve 170 that controls the flow of hydraulic fluid from the pump 14 to the arm cylinder 8 and the flow of hydraulic fluid from the arm cylinder 8 to the hydraulic fluid tank TK, the rod side oil chamber 8R of the arm cylinder 8, and the control valve 170 a second oil passage C2 connecting the bottom side oil chamber 8B of the arm cylinder 8 and the control valve 170; and a first oil passage C1 connecting the rod side oil chamber 8R and the bottom side oil chamber 8B. It has a third oil passage C3 independent of the oil passage C1 and the second oil passage C2, and a switching valve 51 that opens and closes the third oil passage C3. With this configuration, the excavator 100 can, for example, reduce pressure loss when regenerating hydraulic oil from the rod-side oil chamber 8R, which is the contraction-side oil chamber of the arm cylinder 8, to the bottom-side oil chamber 8B, which is the expansion-side oil chamber. . Further, the excavator 100 can reduce pressure loss when regenerating hydraulic oil from the bottom-side oil chamber 8B, which is the contraction-side oil chamber of the arm cylinder 8, to the rod-side oil chamber 8R, which is the expansion-side oil chamber, for example.

The cylinder body 8S of the arm cylinder 8 has an opening H1 connected to one end of the first oil passage C1, an opening H2 connected to one end of the second oil passage C2, an opening H3 connected to one end of the third oil passage C3, and a third oil passage C3. An opening H4 connected to the other end of the 3 oil passage C3 is formed. With this configuration, the excavator 100 can completely separate the working oil flowing through the third oil passage C3 from the working oil flowing through each of the first oil passage C1 and the second oil passage C2. Therefore, it is possible to eliminate the pressure loss associated with the merging of the hydraulic oil, and reduce the pressure loss when regenerating the hydraulic oil.

The excavator 100 may have a fourth oil passage connecting the third oil passage C3 and the hydraulic oil tank TK. With this configuration, the excavator 100 can discharge the hydraulic oil in the arm cylinder 8 directly, that is, without going through the control valve 170, to the hydraulic oil tank as needed.

The third oil passage C3 and the switching valve 51 may be formed inside the cylinder body 8S of the arm cylinder 8, or may be formed inside the piston 8P of the arm cylinder 8. With this configuration, the excavator 100 can further shorten the length of the third oil passage C3 through which the regenerated hydraulic oil flows. Therefore, it is possible to further reduce the pressure loss when regenerating the hydraulic oil.

The switching valve 51 for opening and closing the third oil passage C3 is controlled according to at least the discharge pressure of the main pump 14, the pressure of the bottom side oil chamber 8B of the arm cylinder 8, and the pressure of the rod side oil chamber 8R of the arm cylinder 8. may be controlled. For example, control of the switching valve 51 includes control of the opening/closing timing of the switching valve 51, control of the opening area of the third oil passage C3, and the like. With this configuration, the excavator 100 can adjust the behavior of the attachment when the hydraulic fluid is regenerated. For example, by dynamically adjusting the opening area of the third oil passage C3, the behavior of the attachment when using a conventional regeneration circuit formed inside the control valve 170 can be reproduced. In addition, the excavator 100 dynamically connects and disconnects the rod-side oil chamber 8R and the bottom-side oil chamber 8B when the arm 5 is not in operation. You can maintain the posture of the state attachment stably.

The foregoing has been a detailed description of preferred embodiments of the present invention. However, the invention is not limited to the embodiments described above. Various modifications, substitutions, etc., may be applied to the above-described embodiments without departing from the scope of the present invention.

For example, in the above embodiment, the regeneration circuit 50 connected to the arm cylinder 8 was described, but the present invention is not limited to this configuration. The regeneration circuit 50 may be connected to, for example, the boom cylinder 7, the bucket cylinder 9, and the like.

REFERENCE SIGNS LIST 1 Lower traveling body 1L Left traveling hydraulic motor 1R Right 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 8B Bottom side oil chamber 8P Piston 8R Rod side oil chamber 8S Cylinder body 8X... Rod 9... Bucket cylinder 10... Cabin 11... Engine 13... Regulator 14... Main pump 15... Pilot pump 17... Control valve 26... Operating device 26A... Arm control lever 28... Discharge pressure sensor 28B... Bottom pressure sensor 28R... Rod pressure sensor 29... Operation pressure sensor 30... Controller 50... Regeneration circuit 51... Switching valve 52 Switching valve 53 Switching valve 170 Control valve C1 First oil passage C2 Second oil passage C3 Third oil passage CR Oil passage H1~H4・・・Opening PL1~PL4・・・Pilot line TK・・・Hydraulic oil tank

Claims (2)

a lower running body;
an upper rotating body rotatably attached to the lower traveling body;
an attachment attached to the upper revolving body;
a hydraulic cylinder that drives the attachment;
a hydraulic pump mounted on the upper rotating body;
a hydraulic oil tank mounted on the upper revolving body;
a control valve mounted on the upper slewing body for controlling the flow of hydraulic fluid from the hydraulic pump to the hydraulic cylinder and the flow of hydraulic fluid from the hydraulic cylinder to the hydraulic fluid tank;
a first oil passage connecting the rod-side oil chamber of the hydraulic cylinder and the control valve;
a second oil passage connecting the bottom-side oil chamber of the hydraulic cylinder and the control valve;
a third oil passage that connects the rod-side oil chamber of the hydraulic cylinder and the bottom-side oil chamber of the hydraulic cylinder to regenerate hydraulic oil, and is independent of the first oil passage and the second oil passage;
a valve that opens and closes the third oil passage;
a rod pressure sensor that detects the pressure of hydraulic fluid in the rod-side oil chamber of the hydraulic cylinder;
a bottom pressure sensor that detects the pressure of hydraulic oil in the bottom-side oil chamber of the hydraulic cylinder;
a controller that controls the valve ;
The valve is controlled according to at least the discharge pressure of the hydraulic pump, the pressure of the bottom side oil chamber, and the pressure of the rod side oil chamber,
Excavator. a lower running body;
an upper rotating body rotatably attached to the lower traveling body;
an attachment attached to the upper revolving body;
a hydraulic cylinder that drives the attachment;
a hydraulic pump mounted on the upper rotating body;
a hydraulic oil tank mounted on the upper revolving body;
a control valve mounted on the upper slewing body for controlling the flow of hydraulic fluid from the hydraulic pump to the hydraulic cylinder and the flow of hydraulic fluid from the hydraulic cylinder to the hydraulic fluid tank;
a first oil passage connecting the rod-side oil chamber of the hydraulic cylinder and the control valve;
a second oil passage connecting the bottom-side oil chamber of the hydraulic cylinder and the control valve;
a third oil passage that connects the rod-side oil chamber of the hydraulic cylinder and the bottom-side oil chamber of the hydraulic cylinder to regenerate hydraulic oil, and is independent of the first oil passage and the second oil passage;
a valve that opens and closes the third oil passage;
a switching valve disposed between the control valve and the hydraulic oil tank for adjusting the regeneration amount of the regenerated hydraulic oil;
Excavator with.

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