Work machinery and valves for work machinery

Abstract

The objective is to provide a work machine and a valve for the work machine that suppress the generation of abnormal noises. [Solution] A working machine comprising an upper slewing body, a lower traveling body, an attachment including a boom and an arm, a boom cylinder, an arm cylinder, a boom directional control valve, an arm directional control valve, and a holding valve provided between the bottom-side oil chamber of the boom cylinder and the boom directional control valve, and / or between the rod-side oil chamber of the arm cylinder and the arm directional control valve, wherein the holding valve is provided with a cushion chamber.

Description

Technical Field

[0001] The present invention relates to a working machine and a valve for a working machine.

Background Art

[0002] Patent Document 1 discloses an excavator including a boom holding valve having a backflow prevention function in a hydraulic circuit connected to the bottom side oil chamber of a boom cylinder, and an arm holding valve having a backflow prevention function in a hydraulic circuit connected to the rod side oil chamber of an arm cylinder.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, when the holding valve is opened, there is a possibility that abnormal noise may occur due to the valve body colliding with the wall surface.

[0005] Therefore, in view of the above problems, an object is to provide a working machine and a valve for a working machine that suppress the generation of abnormal noise.

Means for Solving the Problems

[0006] To achieve the above object, according to one aspect, there is provided a working machine including an upper swing body, a lower traveling body, an attachment including a boom and an arm, a boom cylinder, an arm cylinder, a boom direction control valve, an arm direction control valve, and a holding valve provided between the bottom side oil chamber of the boom cylinder and the boom direction control valve and / or between the rod side oil chamber of the arm cylinder and the arm direction control valve, the holding valve being provided with a cushion chamber. [Effects of the Invention]

[0007] According to the above-described embodiment, it is possible to provide a work machine and a valve for the work machine that suppress the generation of abnormal noise. [Brief explanation of the drawing]

[0008] [Figure 1] This is a side view of the excavator according to this embodiment. [Figure 2] A block diagram showing an example of the configuration of a shovel according to this embodiment. [Figure 3] This figure shows an example of the configuration of the hydraulic system mounted on the excavator according to this embodiment. [Figure 4] This figure shows the closed position of the holding valve, which is located between the bottom oil chamber of the boom cylinder and the control valve. [Figure 5] This figure shows the state when the holding valve, located between the bottom oil chamber of the boom cylinder and the control valve, is open. [Figure 6] This figure shows the closed position of the holding valve, which is located between the rod-side oil chamber of the arm cylinder and the control valve. [Figure 7] This figure shows another example of a holding valve installed between the bottom oil chamber of a boom cylinder and the control valve. [Figure 8] This figure shows yet another example of a holding valve provided between the bottom oil chamber of a boom cylinder and the control valve. [Modes for carrying out the invention]

[0009] [Working machinery] First, with reference to Figure 1, a shovel 100 as an example of a work machine according to an embodiment of the present invention will be described. Figure 1 is a side view of the shovel 100 (an example of a work machine) according to this embodiment.

[0010] In this embodiment, the lower traveling body 1 of the shovel 100 includes crawlers. The crawlers are driven by a travel hydraulic motor 2M, which is a travel actuator mounted on the lower traveling body 1. Specifically, the crawlers include a left crawler and a right crawler. The left crawler is driven by a left travel hydraulic motor 2ML, and the right crawler is driven by a right travel hydraulic motor 2MR (see Figure 2, described later).

[0011] An upper rotating body 3 is mounted on the lower traveling body 1 via a rotating mechanism 2 so as to be able to rotate. The rotating mechanism 2 is driven by a rotating hydraulic motor 2A, which is mounted on the upper rotating body 3 as a rotating actuator. However, the rotating actuator may also be a rotating motor generator, which is an electric actuator.

[0012] A boom 4 is attached to the upper slewing body 3. An arm 5 is attached to the tip of the boom 4, and a bucket 6, which serves as an end attachment, is attached to the tip of the arm 5. The boom 4, arm 5, and bucket 6 constitute an attachment AT, which is an example of an attachment. The boom 4 is driven by a boom cylinder 7, the arm 5 is driven by an arm cylinder 8, and the bucket 6 is driven by a bucket cylinder 9. The boom cylinder 7, arm cylinder 8, and bucket cylinder 9 constitute an attachment actuator. In the example shown in Figure 1, the bucket 6 is an excavation bucket, but it may also be a skeleton bucket or a (gravel removal bucket). The bucket 6 may also be equipped with a bucket tilt mechanism.

[0013] The upper rotating body 3 is equipped with a cabin 10, which serves as the driver's cab, and is also fitted with a power source such as an engine 11. Inside the cabin 10 are an operating device 26 (see Figure 2, described later), a controller 30 (control device), and an operating mode switching device SD. The upper rotating body 3 is also fitted with a spatial recognition device 70. For convenience, in this document, the side of the upper rotating body 3 to which the attachment AT is attached is referred to as the front, and the side to which the counterweight is attached is referred to as the rear.

[0014] The spatial recognition device 70 is configured to recognize objects in the three-dimensional space surrounding the shovel 100. The spatial recognition device 70 may also be configured to calculate the distance from the spatial recognition device 70 or the shovel 100 to the recognized object. The spatial recognition device 70 includes, for example, an ultrasonic sensor, millimeter-wave radar, an imaging device, LIDAR, a distance image sensor, an infrared sensor, etc., or any combination thereof. The imaging device is, for example, a monocular camera or a stereo camera. In this embodiment, the spatial recognition device 70 includes a forward sensor 70F mounted on the front end of the upper surface of the cabin 10, a rear sensor 70B mounted on the rear end of the upper surface of the upper rotating body 3, a left sensor 70L mounted on the left end of the upper surface of the upper rotating body 3, and a right sensor (not shown) mounted on the right end of the upper surface of the upper rotating body 3. An upward sensor for recognizing objects in the space above the upper rotating body 3 may be mounted on the shovel 100.

[0015] The operating device 26 is a device used by the operator to operate the actuator. The operating device 26 includes, for example, an operating lever and an operating pedal. The actuator includes at least one of a hydraulic actuator and an electric actuator.

[0016] The operation mode switching device SD is configured to be able to switch the operation mode of the operation lever. For example, the operation mode switching device SD includes a push button switch provided on the right console in the cab 10, and is configured to be able to switch the operation mode of the operation lever between the first operation mode and the second operation mode each time the push button switch is pressed. For example, in the first operation mode, when the left operation lever 26L (see FIG. 3 described later) is tilted forward, the arm 5 is opened, when the left operation lever 26L is tilted backward, the arm 5 is closed, when the left operation lever 26L is tilted leftward, a left turn is executed, and when the left operation lever 26L is tilted rightward, a right turn is executed. Also, in the first operation mode, when the right operation lever 26R (see FIG. 3 described later) is tilted forward, the boom 4 is lowered, when the right operation lever 26R is tilted backward, the boom 4 is raised, when the right operation lever 26R is tilted leftward, the bucket 6 is closed, and when the right operation lever 26R is tilted rightward, the bucket 6 is opened. On the other hand, in the second operation mode, when the left operation lever 26L (see FIG. 3 described later) is tilted forward, a right turn is executed, when the left operation lever 26L is tilted backward, a left turn is executed, when the left operation lever 26L is tilted leftward, the arm 5 is opened, and when the left operation lever 26L is tilted rightward, the arm 5 is closed.

[0017] The operator of the excavator 100 may select the first operation mode, for example, when performing excavation work using an excavation bucket, and may select the second operation mode when performing gravel removal work using a skeleton bucket (gravel removal bucket).

[0018] The controller 30 is a control device for controlling the excavator 100. In the present embodiment, the controller 30 is composed of a computer including a CPU, a volatile memory device, a non-volatile memory device, and the like. Then, the controller 30 reads out a program corresponding to each function from the non-volatile memory device, loads it into the volatile memory device, and causes the CPU to execute the corresponding process. Each function includes, for example, a machine guidance function for guiding (guiding) the manual operation of the excavator 100 by an operator, and a machine control function for assisting the manual operation of the excavator 100 by the operator or operating the excavator 100 automatically or autonomously. The controller 30 may include a contact avoidance function for automatically or autonomously operating or stopping the excavator 100 in order to avoid contact between an object existing within the monitoring range around the excavator 100 and the excavator 100. The monitoring of the objects around the excavator 100 is performed not only within the monitoring range but also outside the monitoring range.

[0019] FIG. 2 is a block diagram showing an example of the configuration of the excavator 100 according to the present embodiment.

[0020] In the figure, the mechanical power line is shown by a double line, the high-pressure hydraulic line is shown by a solid line, the pilot line is shown by a broken line, and the electric drive / control line is shown by a dotted line.

[0021] The hydraulic drive system for hydraulically driving the hydraulic actuators of the excavator 100 according to the present embodiment includes an engine 11, a regulator 13, a main pump 14, and a control valve unit 17. Further, the hydraulic drive system of the excavator 100 according to the present embodiment includes hydraulic actuators such as traveling hydraulic motors 2ML, 2MR, swing hydraulic motor 2A, boom cylinder 7, arm cylinder 8, and bucket cylinder 9 for hydraulically driving the lower traveling body 1, upper swing body 3, boom 4, arm 5, and bucket 6, respectively, as described above.

[0022] The engine 11 is the main power source in the hydraulic drive system and is mounted, for example, at the rear of the upper slewing body 3. Specifically, the engine 11 rotates at a constant speed at a preset target speed under direct or indirect control by the controller 30 (described later) and drives the main pump 14 and the pilot pump 15. The engine 11 is, for example, a diesel engine that uses light oil as fuel.

[0023] The regulator 13 controls the discharge rate of the main pump 14. For example, the regulator 13 adjusts the angle (tilt angle) of the swash plate of the main pump 14 in response to a control command from the controller 30.

[0024] The main pump 14 (an example of a hydraulic pump) is mounted at the rear of the upper slewing body 3, similar to the engine 11, and supplies hydraulic fluid to the control valve unit 17 through the high-pressure hydraulic line 16. The main pump 14 is driven by the engine 11, as described above. The main pump 14 is, for example, a variable displacement hydraulic pump, and as described above, under the control of the controller 30, the piston stroke length can be adjusted by adjusting the tilt angle of the swash plate by the regulator 13, thereby controlling the discharge flow rate (discharge pressure).

[0025] The control valve unit 17 is a hydraulic control device that controls the hydraulic system in the excavator 100. In this embodiment, the control valve unit 17 includes control valves 171 to 176. The control valve unit 17 is configured to selectively supply hydraulic fluid discharged by the main pump 14 to one or more hydraulic actuators through the control valves 171 to 176. The control valves 171 to 176 control, for example, the flow rate of hydraulic fluid flowing from the main pump 14 to the hydraulic actuators, and the flow rate of hydraulic fluid flowing from the hydraulic actuators to the hydraulic fluid tank. The hydraulic actuators include a boom cylinder 7, an arm cylinder 8, a bucket cylinder 9, travel hydraulic motors 2ML and 2MR, and a slewing hydraulic motor 2A. More specifically, control valve 171 corresponds to the left travel hydraulic motor 2ML, control valve 172 corresponds to the right travel hydraulic motor 2MR, and control valve 173 corresponds to the slewing hydraulic motor 2A. Furthermore, control valve 174 corresponds to bucket cylinder 9, control valve 175 corresponds to boom cylinder 7, and control valve 176 corresponds to arm cylinder 8.

[0026] The pilot pump 15 is an example of a pilot pressure generating device and is configured to supply hydraulic fluid to hydraulic control equipment via a pilot line. In this embodiment, the pilot pump 15 is a fixed-displacement hydraulic pump. However, the pilot pressure generating device may be implemented by the main pump 14. That is, the main pump 14 may have the function of supplying hydraulic fluid to the control valve unit 17 via a hydraulic fluid line, as well as the function of supplying hydraulic fluid to various hydraulic control equipment via a pilot line. In this case, the pilot pump 15 may be omitted.

[0027] The discharge pressure sensor 28 is configured to detect the discharge pressure of the main pump 14. In this embodiment, the discharge pressure sensor 28 outputs the detected value to the controller 30.

[0028] The operating device 26 is a device used by the operator to operate the actuator. The operating device 26 includes, for example, an operating lever and an operating pedal. The actuator includes at least one of a hydraulic actuator and an electric actuator.

[0029] The proportional valve 31, which functions as a control valve for machine control, is located in the pipeline connecting the pilot pump 15 and the pilot port of the control valve in the control valve unit 17, and is configured to change the flow area of ​​the pipeline. In this embodiment, the proportional valve 31 operates in response to control commands output by the controller 30. Therefore, the controller 30 can supply the hydraulic fluid discharged by the pilot pump 15 to the pilot port of the control valve in the control valve unit 17 via the proportional valve 31, independently of the operator's operation of the operating device 26.

[0030] This configuration allows the controller 30 to operate the hydraulic actuator corresponding to a specific operating device 26 even when no operation is being performed on that particular operating device 26.

[0031] The control system of the excavator 100 according to this embodiment includes a controller 30, a display device D1, an input device D2, and a communication device T1. The control system of the excavator 100 also includes, as a configuration related to the semi-automatic operation function, a proportional valve 31, a boom angle sensor S1, an arm angle sensor S2, a bucket angle sensor S3, a machine body tilt sensor S4, a slewing angle sensor S5, an imaging device S6, and a positioning device PS.

[0032] The operation sensor 29 is configured to detect the operator's actions using the operation device 26. In this embodiment, the operation sensor 29 detects the operating direction and amount of operation of the operation device 26 corresponding to each actuator and outputs the detected values ​​to the controller 30. In this embodiment, the controller 30 controls the opening area of ​​the proportional valve 31 according to the output of the operation sensor 29. The controller 30 then supplies the hydraulic fluid discharged by the pilot pump 15 to the pilot port of the corresponding control valve in the control valve unit 17. The pressure of the hydraulic fluid supplied to each pilot port (pilot pressure) is, in principle, the pressure corresponding to the operating direction and amount of operation of the operation device 26 corresponding to each hydraulic actuator. Thus, the operation device 26 is configured to supply the hydraulic fluid discharged by the pilot pump 15 to the pilot port of the corresponding control valve in the control valve unit 17.

[0033] The display device D1 is located in a place easily visible to a seated operator inside the cabin 10 and displays various information images under the control of the controller 30. The display device D1 may be connected to the controller 30 via an in-vehicle communication network such as CAN (Controller Area Network), or it may be connected to the controller 30 via a one-to-one dedicated line.

[0034] Furthermore, the display device D1 is not limited to a device pre-installed in the cabin 10, but may be a separate monitor. Moreover, the display device D1 can be any device capable of displaying information, and for example, a tablet terminal capable of communicating with the communication device T1 may be used.

[0035] The input device D2 is located within reach of a seated operator in the cabin 10 and receives various operation inputs from the operator, outputting signals corresponding to the operation inputs to the controller 30. The input device D2 includes a touch panel mounted on the display of a display device that shows various information images, a knob switch located at the tip of the lever device of the operation device 26, and button switches, levers, toggles, rotary dials, etc., installed around the display device D1. Signals corresponding to the operations performed on the input device D2 are received by the controller 30.

[0036] The controller 30 (an example of a control device) is installed, for example, inside the cabin 10 and controls the drive of the shovel 100. The functions of the controller 30 may be realized by any hardware, software, or a combination thereof. For example, the controller 30 is mainly composed of a microcomputer including a CPU (Central Processing Unit), ROM (Read Only Memory), RAM (Random Access Memory), a non-volatile auxiliary storage medium, and various input / output interfaces. The controller 30 realizes various functions by executing various programs stored in the ROM or non-volatile auxiliary storage medium on the CPU.

[0037] For example, the controller 30 sets a target rotational speed based on the actions of the operator, etc., and performs drive control to keep the engine 11 rotating at a constant speed.

[0038] Furthermore, for example, the controller 30 outputs control commands to the regulator 13 as needed, thereby changing the discharge rate of the main pump 14.

[0039] Furthermore, for example, the controller 30 controls the regulator 13 and adjusts the discharge amount of the main pump 14 based on detected pilot pressure values, etc., corresponding to the operating states of various operating elements (i.e., various hydraulic actuators) in the operating device 26, which are input from the operating sensor 29.

[0040] Furthermore, for example, the controller 30 performs control related to a machine guidance function that guides the manual operation of the shovel 100 by the operator through the operating device 26. Also, the controller 30 performs control related to a machine control function that automatically assists the manual operation of the shovel 100 by the operator through the operating device 26.

[0041] Furthermore, some of the functions of controller 30 may be implemented by other controllers (control devices). That is, the functions of controller 30 may be implemented in a manner distributed among multiple controllers. For example, machine guidance functions and machine control functions may be implemented by dedicated controllers (control devices).

[0042] The proportional valve 31 is installed in the pilot line connecting the pilot pump 15 and the pilot ports of the control valves 171 to 176, and is configured to change its flow area (the cross-sectional area through which hydraulic fluid can flow). The proportional valve 31 operates in response to control commands input from the controller 30. As a result, even when the operating device 26 is not operated by the operator, the controller 30 can supply the hydraulic fluid discharged by the pilot pump 15 to the corresponding pilot port of the control valve in the control valve unit 17 via the proportional valve 31. The controller 30 can then apply the pilot pressure generated by the proportional valve 31 to the corresponding pilot port of the control valve.

[0043] This configuration allows the controller 30 to operate the hydraulic actuator corresponding to a specific operating device 26 even when no operation is being performed on that device. Furthermore, the controller 30 can forcibly stop the operation of the hydraulic actuator corresponding to a specific operating device 26 even when an operation is being performed on that device.

[0044] The boom angle sensor S1 is attached to the boom 4 and detects the elevation angle of the boom 4 relative to the upper slewing body 3 (hereinafter referred to as the "boom angle"), for example, the angle formed by the straight line connecting the pivot points at both ends of the boom 4 with respect to the slewing plane of the upper slewing body 3 in a side view. The boom angle sensor S1 may include, for example, a rotary encoder, an acceleration sensor, a 6-axis sensor, an IMU (Inertial Measurement Unit), etc. The boom angle sensor S1 may also include a potentiometer using a variable resistor, a cylinder stroke sensor that detects the stroke amount of the hydraulic cylinder (boom cylinder 7) corresponding to the boom angle, etc. The same applies to the arm angle sensor S2, bucket angle sensor S3, and machine tilt sensor S4. The detection signal corresponding to the boom angle from the boom angle sensor S1 is input to the controller 30.

[0045] The arm angle sensor S2 is attached to the arm 5 and detects the rotation angle of the arm 5 relative to the boom 4 (hereinafter referred to as "arm angle"). For example, in a side view, it detects the angle formed by the line connecting the pivot points at both ends of the arm 5 and the line connecting the pivot points at both ends of the boom 4. The detection signal corresponding to the arm angle from the arm angle sensor S2 is input to the controller 30.

[0046] The bucket angle sensor S3 is attached to the bucket 6 and detects the rotation angle of the bucket 6 relative to the arm 5 (hereinafter referred to as the "bucket angle"). For example, in a side view, it detects the angle formed by the line connecting the pivot point and the tip (cutting edge) of the bucket 6 with respect to the line connecting the pivot points at both ends of the arm 5. The detection signal corresponding to the bucket angle from the bucket angle sensor S3 is input to the controller 30.

[0047] The machine tilt sensor S4 detects the tilt state of the machine (upper rotating body 3 or lower traveling body 1) relative to the horizontal plane. The machine tilt sensor S4 is attached, for example, to the upper rotating body 3 and detects the tilt angle around two axes in the longitudinal and lateral directions of the shovel 100 (i.e., the upper rotating body 3) (hereinafter referred to as "longitudinal tilt angle" and "lateral tilt angle"). The detection signals corresponding to the tilt angles (longitudinal tilt angle and lateral tilt angle) detected by the machine tilt sensor S4 are input to the controller 30.

[0048] The rotation angle sensor S5 outputs detection information regarding the rotation state of the upper rotating body 3. The rotation angle sensor S5 detects, for example, the rotation angular velocity and rotation angle of the upper rotating body 3. The rotation angle sensor S5 includes, for example, a gyro sensor, a resolver, a rotary encoder, etc.

[0049] This embodiment describes an example using the rotation angle sensor S5, but this embodiment is not limited to the method using the rotation angle sensor S5. For example, an IMU (Inertial Measurement Unit) sensor may be used instead of the rotation angle sensor S5. Furthermore, instead of the rotation angle sensor S5, the orientation of the shovel 100 may be detected by a positioning device PS, which will be described later. Furthermore, instead of the rotation angle sensor S5, a geomagnetic sensor may be used.

[0050] The imaging device S6 is an example of a spatial recognition device 70 that images the area around the shovel 100. The imaging device S6 includes a camera that images the area in front of the shovel 100 (an example of a front sensor 70F), a camera that images the area to the left of the shovel 100 (an example of a left sensor 70L), a camera that images the area to the right of the shovel 100 (an example of a right sensor not shown), and a camera that images the area behind the shovel 100 (an example of a rear sensor 70B).

[0051] The positioning device PS is configured to acquire information regarding the position of the shovel 100. In this embodiment, the positioning device PS is configured to measure the position and orientation of the shovel 100. Specifically, the positioning device PS is a GNSS receiver incorporating an electronic compass, which measures the latitude, longitude, and altitude of the current position of the shovel 100, and also measures the orientation of the shovel 100.

[0052] The communication device T1 communicates with external devices through a predetermined network, including a mobile communication network with a base station as its endpoint, a satellite communication network, and the Internet network. The communication device T1 is, for example, a mobile communication module that supports mobile communication standards such as LTE (Long Term Evolution), 4G (4th Generation), and 5G (5th Generation), or a satellite communication module for connecting to a satellite communication network.

[0053] The shovel 100 operates actuators (e.g., hydraulic actuators) in response to the operation of the operator sitting in the cabin 10, driving the moving elements (hereinafter referred to as "driven elements") such as the lower traveling body 1, the upper slewing body 3, the boom 4, the arm 5, and the bucket 6.

[0054] Furthermore, instead of being configured to be operable by the operator in the cabin 10, or in addition to being configured to be operable by the operator in the cabin 10, the shovel 100 may also be configured to be remotely operated from outside the shovel 100. When the shovel 100 is remotely operated, the inside of the cabin 10 may be unoccupied.

[0055] Furthermore, the shovel 100 may automatically operate its actuators regardless of the operator's actions. As a result, the controller 30 of the shovel 100 has the function of automatically operating at least some of the multiple actuators that operate each of the driven elements such as the lower traveling body 1, the upper slewing body 3, the boom 4, the arm 5, and the bucket 6, that is, a so-called "automatic driving function" or "machine control function".

[0056] The automatic driving function may include a function that automatically operates driven elements (actuators) other than the target driven element (actuator) in response to the operator's operation of the control device 26 or remote control, that is, a so-called "semi-automatic driving function" or "operation-assist type machine control function". The automatic driving function may also include a function that automatically operates at least some of the multiple driven elements (hydraulic actuators) on the premise that there is no operation of the operator's control device 26 or remote control, that is, a so-called "fully automatic driving function" or "fully automatic machine control function". In the case of the excavator 100, when the fully automatic driving function is enabled, the interior of the cabin 10 may be unoccupied. Furthermore, the semi-automatic driving function and fully automatic driving function may include a mode in which the operation content of the driven elements (actuators) that are the target of automatic driving is automatically determined according to predetermined rules. Furthermore, semi-autonomous driving functions and fully autonomous driving functions may include a mode in which the shovel 100 autonomously makes various decisions, and the operation of the driven elements (hydraulic actuators) that are the target of autonomous driving is determined autonomously in accordance with the results of those decisions (so-called "autonomous driving function").

[0057] Specifically, when the arm 5 is operated by the operator via the operating device 26, the controller 30 may automatically operate at least one of the boom 4 and the bucket 6 so that the tip position of the bucket 6 coincides with a predetermined target construction surface. In addition, the controller 30 may also automatically operate the arm 5 regardless of the operating state of the operating device 26 that operates the arm 5. In other words, the controller 30 may trigger the attachment to perform predetermined actions based on the operator's operation of the operating device 26. Hereinafter, the function of the controller 30 that operates not only the arm 5 but also at least one of the boom 4 and the bucket 6 in response to the operation of the operating device 26 corresponding to the arm 5 will be referred to as the "semi-automatic operation function". The semi-automatic operation function may be executed, for example, by operating a predetermined switch (hereinafter referred to as the "MC (Machine Control) switch") located at the tip of any of the lever devices included in the operating device 26. In this embodiment, a paddle switch that executes a machine control function while pressed may be used as the MC switch.

[0058] Next, with reference to Figure 3, an example of the configuration of the hydraulic system mounted on the excavator 100 according to this embodiment will be described. Figure 3 is a diagram showing an example of the configuration of the hydraulic system mounted on the excavator 100 according to this embodiment. In Figure 3, the mechanical power transmission system, hydraulic fluid line, pilot line, and electrical control system are shown by double lines, solid lines, dashed lines, and dotted lines, respectively.

[0059] The hydraulic system of the Shovel 100 mainly includes an engine 11, a regulator 13, a main pump 14, a pilot pump 15, a control valve unit 17, an operating device 26, a discharge pressure sensor 28, an operating sensor 29, and a controller 30, etc.

[0060] In Figure 3, the hydraulic system is configured to circulate hydraulic fluid from the main pump 14, driven by the engine 11, to the hydraulic fluid tank via the center bypass pipeline 40 or the parallel pipeline 42.

[0061] The engine 11 is the power source for the shovel 100. In this embodiment, the engine 11 is, for example, a diesel 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, respectively.

[0062] The main pump 14 is configured to supply hydraulic fluid to the control valve unit 17 via a hydraulic fluid line. In this embodiment, the main pump 14 is a swashplate type variable displacement hydraulic pump.

[0063] The regulator 13 is configured to control the discharge rate of the main pump 14. In this embodiment, the regulator 13 controls the discharge rate of the main pump 14 by adjusting the swash plate tilt angle of the main pump 14 in response to a control command from the controller 30.

[0064] The pilot pump 15 is an example of a pilot pressure generating device and is configured to supply hydraulic fluid to hydraulic control equipment via a pilot line. In this embodiment, the pilot pump 15 is a fixed-displacement hydraulic pump. However, the pilot pressure generating device may be implemented by the main pump 14. That is, the main pump 14 may have the function of supplying hydraulic fluid to the control valve unit 17 via a hydraulic fluid line, as well as the function of supplying hydraulic fluid to various hydraulic control equipment via a pilot line. In this case, the pilot pump 15 may be omitted.

[0065] The control valve unit 17 is a hydraulic control device that controls the hydraulic system in the excavator 100. In this embodiment, the control valve unit 17 includes control valves 171 to 176. Control valve 175 includes control valves 175L and 175R, and control valve 176 includes control valves 176L and 176R. The control valve unit 17 is configured to selectively supply hydraulic fluid discharged by the main pump 14 to one or more hydraulic actuators through the control valves 171 to 176. The control valves 171 to 176 control, for example, the flow rate of hydraulic fluid flowing from the main pump 14 to the hydraulic actuators, and the flow rate of hydraulic fluid flowing from the hydraulic actuators to the hydraulic fluid tank. The hydraulic actuators include a boom cylinder 7, an arm cylinder 8, a bucket cylinder 9, a left travel hydraulic motor 2ML, a right travel hydraulic motor 2MR, and a slewing hydraulic motor 2A.

[0066] The operating device 26 is configured to allow an operator to operate the actuator. In this embodiment, the operating device 26 includes a hydraulic actuator operating device configured to allow an operator to operate a hydraulic actuator. Specifically, the hydraulic actuator operating device is configured to supply hydraulic fluid discharged by the pilot pump 15 to the pilot port of the corresponding control valve in the control valve unit 17 via a pilot line. The pressure of the hydraulic fluid supplied to each pilot port (pilot pressure) is a pressure corresponding to the operating direction and amount of the operating device 26 corresponding to each hydraulic actuator.

[0067] The discharge pressure sensor 28 is configured to detect the discharge pressure of the main pump 14. In this embodiment, the discharge pressure sensor 28 outputs the detected value to the controller 30.

[0068] The operation sensor 29 is configured to detect the content of the operation of the operating device 26 by the operator. In this embodiment, the operation sensor 29 detects the operating direction and amount of operation of the operating device 26 corresponding to each actuator and outputs the detected values ​​to the controller 30.

[0069] The main pump 14 includes a left main pump 14L and a right main pump 14R. The left main pump 14L circulates the hydraulic fluid to the hydraulic fluid tank via the left center bypass pipeline 40L or the left parallel pipeline 42L, while the right main pump 14R circulates the hydraulic fluid to the hydraulic fluid tank via the right center bypass pipeline 40R or the right parallel pipeline 42R.

[0070] The left center bypass pipeline 40L is a hydraulic fluid line that passes through control valves 171, 173, 175L, and 176L located within the control valve unit 17. The right center bypass pipeline 40R is a hydraulic fluid line that passes through control valves 172, 174, 175R, and 176R located within the control valve unit 17.

[0071] The control valve 171 is a spool valve that switches the flow of hydraulic fluid to supply the hydraulic fluid discharged by the left main pump 14L to the left travel hydraulic motor 2ML, and to discharge the hydraulic fluid discharged by the left travel hydraulic motor 2ML to the hydraulic fluid tank.

[0072] The control valve 172 is a spool valve that supplies the hydraulic fluid discharged by the right main pump 14R to the right travel hydraulic motor 2MR, and switches the flow of hydraulic fluid to discharge the hydraulic fluid discharged by the right travel hydraulic motor 2MR to the hydraulic fluid tank.

[0073] The control valve 173 is a spool valve that supplies the hydraulic fluid discharged by the left main pump 14L to the swivel hydraulic motor 2A, and also switches the flow of hydraulic fluid to discharge the hydraulic fluid discharged by the swivel hydraulic motor 2A to the hydraulic fluid tank.

[0074] The control valve 174 is a spool valve that supplies the hydraulic fluid discharged by the right main pump 14R to the bucket cylinder 9 and switches the flow of the hydraulic fluid in order to discharge the hydraulic fluid in the bucket cylinder 9 to the hydraulic fluid tank.

[0075] Control valve 175L is a spool valve that switches the flow of hydraulic fluid to supply the hydraulic fluid discharged by the left main pump 14L to the boom cylinder 7. Control valve 175R is a spool valve that supplies the hydraulic fluid discharged by the right main pump 14R to the boom cylinder 7 and also switches the flow of hydraulic fluid to discharge the hydraulic fluid inside the boom cylinder 7 to the hydraulic fluid tank.

[0076] The control valve 176L is a spool valve that supplies the hydraulic fluid discharged by the left main pump 14L to the arm cylinder 8, and also switches the flow of the hydraulic fluid in order to discharge the hydraulic fluid in the arm cylinder 8 to the hydraulic fluid tank.

[0077] The control valve 176R is a spool valve that supplies the hydraulic fluid discharged by the right main pump 14R to the arm cylinder 8 and switches the flow of the hydraulic fluid in order to discharge the hydraulic fluid in the arm cylinder 8 to the hydraulic fluid tank.

[0078] The left parallel pipeline 42L is a hydraulic fluid line running parallel to the left center bypass pipeline 40L. The left parallel pipeline 42L can supply hydraulic fluid to a control valve further downstream if the flow of hydraulic fluid through the left center bypass pipeline 40L is restricted or blocked by any of the control valves 171, 173, and 175L. The right parallel pipeline 42R is a hydraulic fluid line running parallel to the right center bypass pipeline 40R. The right parallel pipeline 42R can supply hydraulic fluid to a control valve further downstream if the flow of hydraulic fluid through the right center bypass pipeline 40R is restricted or blocked by any of the control valves 172, 174, and 175R.

[0079] The regulator 13 includes a left regulator 13L and a right regulator 13R. The left regulator 13L controls the discharge volume of the left main pump 14L by adjusting the swash plate tilt angle of the left main pump 14L in accordance with the discharge pressure of the left main pump 14L. Specifically, the left regulator 13L reduces the discharge volume by adjusting the swash plate tilt angle of the left main pump 14L in accordance with an increase in the discharge pressure of the left main pump 14L. The same applies to the right regulator 13R. This is to ensure that the absorption power (absorption horsepower) of the main pump 14, which is expressed as the product of the discharge pressure and the discharge volume, does not exceed the output power (output horsepower) of the engine 11.

[0080] The operating device 26 includes a left operating lever 26L, a right operating lever 26R, and a travel lever 26D. The travel lever 26D includes a left travel lever 26DL and a right travel lever 26DR.

[0081] The left operating lever 26L is used for slewing and operating the arm 5. When the left operating lever 26L is operated in the forward / backward direction, it uses the hydraulic fluid discharged by the pilot pump 15 to introduce a control pressure corresponding to the lever operation amount into the pilot port of the control valve 176. When it is operated in the left / right direction, it uses the hydraulic fluid discharged by the pilot pump 15 to introduce a control pressure corresponding to the lever operation amount into the pilot port of the control valve 173.

[0082] Specifically, when the left operating lever 26L is operated in the arm closing direction (the direction in which hydraulic fluid is supplied to the bottom oil chamber of the arm cylinder 8), hydraulic fluid is introduced into the right pilot port of the control valve 176L and into the left pilot port of the control valve 176R.

[0083] Furthermore, when the left operating lever 26L is operated in the arm opening direction (the direction in which hydraulic fluid is supplied to the rod-side oil chamber of the arm cylinder 8), hydraulic fluid is introduced into the left pilot port of the control valve 176L and into the right pilot port of the control valve 176R.

[0084] Furthermore, when the left operating lever 26L is operated in the left turning direction, it introduces hydraulic fluid into the left pilot port of the control valve 173, and when it is operated in the right turning direction, it introduces hydraulic fluid into the right pilot port of the control valve 173.

[0085] In the example shown in Figure 3, the left control lever 26L functions as an arm control lever when operated in the forward / backward direction and as a swivel control lever when operated in the left / right direction.

[0086] The right operating lever 26R is used to operate the boom 4 and the bucket 6. When the right operating lever 26R is operated in the forward / backward direction, it uses the hydraulic fluid discharged by the pilot pump 15 to introduce a control pressure corresponding to the lever operation amount into the pilot port of the control valve 175. When it is operated in the left / right direction, it uses the hydraulic fluid discharged by the pilot pump 15 to introduce a control pressure corresponding to the lever operation amount into the pilot port of the control valve 174.

[0087] Specifically, when the right operating lever 26R is operated in the boom lowering direction (the direction in which hydraulic fluid is supplied to the rod-side oil chamber of the boom cylinder 7), hydraulic fluid is introduced into the right pilot port of the control valve 175R.

[0088] Furthermore, when the right operating lever 26R is operated in the boom-raising direction (the direction in which hydraulic fluid is supplied to the bottom-side oil chamber of the boom cylinder 7), hydraulic fluid is introduced into the left pilot port of the control valve 175L and into the right pilot port of the control valve 175R.

[0089] Furthermore, when the right operating lever 26R is operated in the bucket closing direction, it introduces hydraulic fluid into the left pilot port of the control valve 174, and when it is operated in the bucket opening direction, it introduces hydraulic fluid into the right pilot port of the control valve 174.

[0090] In the example shown in Figure 3, the right operating lever 26R functions as a boom operating lever when operated in the forward / backward direction and as a bucket operating lever when operated in the left / right direction.

[0091] The travel lever 26D is used to operate the crawler. Specifically, the left travel lever 26DL is used to operate the left crawler. It may be configured to be linked with the left travel pedal. When the left travel lever 26DL is operated in the forward / backward direction, it uses the hydraulic fluid discharged by the pilot pump 15 to introduce a control pressure corresponding to the lever operation amount into the pilot port of the control valve 171. The right travel lever 26DR is used to operate the right crawler. It may be configured to be linked with the right travel pedal. When the right travel lever 26DR is operated in the forward / backward direction, it uses the hydraulic fluid discharged by the pilot pump 15 to introduce a control pressure corresponding to the lever operation amount into the pilot port of the control valve 172.

[0092] The discharge pressure sensor 28 includes discharge pressure sensors 28L and 28R. Discharge pressure sensor 28L detects the discharge pressure of the left main pump 14L and outputs the detected value to the controller 30. The same applies to discharge pressure sensor 28R.

[0093] The operation sensor 29 includes operation sensors 29LA, 29LB, 29RA, 29RB, 29DL, and 29DR. Operation sensor 29LA detects the operator's forward and backward movement of the left operation lever 26L and outputs the detected value to the controller 30. The operation details include, for example, the direction of lever operation and the amount of lever operation (lever operation angle).

[0094] Similarly, the operation sensor 29LB detects the operator's left-right operation of the left operation lever 26L and outputs the detected value to the controller 30. The operation sensor 29RA detects the operator's forward-backward operation of the right operation lever 26R and outputs the detected value to the controller 30. The operation sensor 29RB detects the operator's left-right operation of the right operation lever 26R and outputs the detected value to the controller 30. The operation sensor 29DL detects the operator's forward-backward operation of the left travel lever 26DL and outputs the detected value to the controller 30. The operation sensor 29DR detects the operator's forward-backward operation of the right travel lever 26DR and outputs the detected value to the controller 30.

[0095] The controller 30 receives the output of the operation sensor 29 and, if necessary, outputs a control command to the regulator 13 to change the discharge amount of the main pump 14. The controller 30 also receives the output of the control pressure sensor 19 located upstream of the throttle 18 and, if necessary, outputs a control command to the regulator 13 to change the discharge amount of the main pump 14. The throttle 18 includes a left throttle 18L and a right throttle 18R, and the control pressure sensor 19 includes a left control pressure sensor 19L and a right control pressure sensor 19R.

[0096] In the left center bypass pipeline 40L, a left throttle 18L is located between the control valve 176L, the downstreammost control valve, and the hydraulic fluid tank. Therefore, the flow of hydraulic fluid discharged by the left main pump 14L is restricted by the left throttle 18L. The left throttle 18L then generates a control pressure to control the left regulator 13L. The left control pressure sensor 19L is a sensor for detecting this control pressure and outputs the detected value to the controller 30. The controller 30 controls the discharge amount of the left main pump 14L by adjusting the swash plate tilt angle of the left main pump 14L in accordance with this control pressure. The controller 30 decreases the discharge amount of the left main pump 14L as the control pressure increases, and increases the discharge amount of the left main pump 14L as the control pressure decreases. The discharge amount of the right main pump 14R is controlled in the same way.

[0097] Specifically, as shown in Figure 3, when none of the hydraulic actuators in the shovel 100 are operated and the system is in standby mode, the hydraulic fluid discharged from the left main pump 14L passes through the left center bypass pipe 40L to the left constrictor 18L. The flow of hydraulic fluid discharged from the left main pump 14L increases the control pressure generated upstream of the left constrictor 18L. As a result, the controller 30 reduces the discharge volume of the left main pump 14L to the minimum allowable discharge volume, suppressing pressure loss (pumping loss) as the discharged hydraulic fluid passes through the left center bypass pipe 40L. On the other hand, when any of the hydraulic actuators are operated, the hydraulic fluid discharged from the left main pump 14L flows into the hydraulic actuator being operated via the control valve corresponding to that actuator. The flow of hydraulic fluid discharged from the left main pump 14L reduces or eliminates the amount reaching the left constrictor 18L, lowering the control pressure generated upstream of the left constrictor 18L. As a result, the controller 30 increases the discharge volume of the left main pump 14L, circulating sufficient hydraulic fluid to the hydraulic actuator being operated, and ensuring reliable operation of the hydraulic actuator. The controller 30 also controls the discharge volume of the right main pump 14R in the same manner.

[0098] With the configuration described above, the hydraulic system in Figure 3 can suppress unnecessary energy consumption in the main pump 14 when in standby mode. Unnecessary energy consumption includes pumping losses caused by the hydraulic fluid discharged by the main pump 14 in the center bypass pipeline 40. Furthermore, when operating a hydraulic actuator, the hydraulic system in Figure 3 can reliably supply the necessary and sufficient hydraulic fluid from the main pump 14 to the hydraulic actuator being operated.

[0099] Furthermore, boom cylinder 7 is equipped with boom rod pressure sensor S7R and boom bottom pressure sensor S7B. Arm cylinder 8 is equipped with arm rod pressure sensor S8R and arm bottom pressure sensor S8B. Bucket cylinder 9 is equipped with bucket rod pressure sensor S9R and bucket bottom pressure sensor S9B. The boom rod pressure sensor S7R, boom bottom pressure sensor S7B, arm rod pressure sensor S8R, arm bottom pressure sensor S8B, bucket rod pressure sensor S9R, and bucket bottom pressure sensor S9B are collectively referred to as "cylinder pressure sensors". In addition, the swing hydraulic motor 2A is equipped with left swing pressure sensor S10L and right swing pressure sensor S10R.

[0100] The boom rod pressure sensor S7R detects the pressure in the rod-side oil chamber of the boom cylinder 7 (hereinafter referred to as "boom rod pressure"), and the boom bottom pressure sensor S7B detects the pressure in the bottom-side oil chamber of the boom cylinder 7 (hereinafter referred to as "boom bottom pressure"). The arm rod pressure sensor S8R detects the pressure in the rod-side oil chamber of the arm cylinder 8 (hereinafter referred to as "arm rod pressure"), and the arm bottom pressure sensor S8B detects the pressure in the bottom-side oil chamber of the arm cylinder 8 (hereinafter referred to as "arm bottom pressure"). The bucket rod pressure sensor S9R detects the pressure in the rod-side oil chamber of the bucket cylinder 9 (hereinafter referred to as "bucket rod pressure"), and the bucket bottom pressure sensor S9B detects the pressure in the bottom-side oil chamber of the bucket cylinder 9 (hereinafter referred to as "bucket bottom pressure"). The left slewing pressure sensor S10L detects the hydraulic fluid pressure at the left port of the slewing hydraulic motor 2A. The right slewing pressure sensor S10R detects the hydraulic fluid pressure at the right port of the slewing hydraulic motor 2A. The values ​​detected by each sensor are transmitted to the controller 30.

[0101] Furthermore, a holding valve 51 is provided between the bottom oil chamber of the boom cylinder 7 and the control valve 175. The holding valve 51 has a backflow prevention function, allowing hydraulic fluid to flow from the control valve 175 to the bottom oil chamber of the boom cylinder 7, and restricting the backflow of hydraulic fluid from the bottom oil chamber of the boom cylinder 7 to the control valve 175.

[0102] As a result, when the boom is raised, hydraulic fluid is supplied from the main pump 14 to the bottom oil chamber of the boom cylinder 7 via the control valves 175 (175L, 175R) and the holding valve 51.

[0103] Furthermore, when the boom is not being operated, the holding valve 51 is closed, preventing the hydraulic fluid from the bottom oil chamber of the boom cylinder 7 from leaking into the hydraulic fluid tank via the control valve 175. In other words, it prevents the boom 4 from lowering due to the weight of the attachment AT, etc.

[0104] Furthermore, when the boom is lowered, the pilot pressure supplied to the right pilot port of the control valve 175R opens the holding valve 51, and hydraulic fluid is discharged from the bottom oil chamber of the boom cylinder 7 to the hydraulic fluid tank via the holding valve 51 and the control valve 175R.

[0105] Furthermore, a holding valve 52 is provided between the rod-side oil chamber of the arm cylinder 8 and the control valve 176. The holding valve 52 has a backflow prevention function, allowing hydraulic fluid to flow from the control valve 176 to the rod-side oil chamber of the arm cylinder 8, and restricting the backflow of hydraulic fluid from the rod-side oil chamber of the arm cylinder 8 to the control valve 176.

[0106] As a result, when the arm is opened, hydraulic fluid is supplied from the main pump 14 to the rod-side oil chamber of the arm cylinder 8 via the control valve 176 (176L, 176R) and the holding valve 52.

[0107] Furthermore, when the arm is not being operated, the holding valve 52 is closed, preventing the hydraulic fluid from the rod-side oil chamber of the arm cylinder 8 from leaking into the hydraulic fluid tank via the control valve 176. In other words, it prevents the arm 5 from closing due to the weight of the attachment AT or the like.

[0108] Furthermore, when the arm is closed, the pilot pressure supplied to the right pilot port of control valve 176L (or the pilot pressure supplied to the left pilot port of control valve 176R) opens the holding valve 52, and hydraulic fluid is discharged from the rod-side oil chamber of the arm cylinder 8 to the hydraulic fluid tank via the holding valve 52 and control valves 176 (176L, 176R).

[0109] [Holding valves 51, 52] Next, the holding valve 51 will be explained using Figures 4 and 5. Figure 4 shows the holding valve 51, which is provided between the bottom oil chamber of the boom cylinder 7 and the control valve 175, in the closed position. Figure 5 shows the holding valve 51, which is provided between the bottom oil chamber of the boom cylinder 7 and the control valve 175, in the open position.

[0110] The holding valve 51 is provided between a passage 514 connected to the control valve 175 and a passage 515 connected to the bottom oil chamber side of the boom cylinder 7.

[0111] The holding valve 51 includes a poppet valve 511 and a switching valve 512.

[0112] The poppet valve 511 includes a valve body 511a, an elastic body 511b, a chamber 511c, a valve seat 511d, and a cushion chamber 511e.

[0113] The valve body 511a has a cylindrical shape with one end (the lower end in the example of Figures 4 and 5) closed and the other end (the upper end in the example of Figures 4 and 5) open. The cylindrical shape of the valve body 511a has an inner surface 511a1, an outer surface 511a2, and an end surface 511a3. The valve body 511a is positioned within the chamber 511c and is movable perpendicular to the valve seat 511d. The chamber 511c has a side surface 511c2 and a top surface 511c3. The valve body 511a is biased toward the valve seat 511d by an elastic body 511b. The holding valve 51 closes when the valve body 511a comes into contact with the valve seat 511d (see Figure 4), and opens when the valve body 511a separates from the valve seat 511d (see Figure 5).

[0114] The cushion chamber 511e communicates with chamber 511c, is provided separately from chamber 511c, and is located on the surface facing the valve seat 511d (in the example of Figures 4 and 5, the top surface 511c3 of chamber 511c). The cushion chamber 511e has an inner surface 511e1, an outer surface 511e2, and a top surface 511e3. The cushion chamber 511e reduces the noise caused by the end surface 511a3 of the valve body 511a contacting the top surface 511c3 of chamber 511c, or in other words, reduces the noise caused by the end surface 511a3 of the valve body 511a contacting the wall surface (top surface 511e3) of the cushion chamber 511e. As shown in Figure 5, the cushion chamber 511e is formed so that the upper end of the cylindrical portion of the valve body 511a can be inserted when the holding valve 51 is open. If the upper end portion of the valve body 511a has a cylindrical shape, the cushion chamber 511e is formed as an annular recess.

[0115] For example, the valve body 511a has a head portion that abuts against the valve seat 511d and a cylindrical portion. The cushion chamber 511e is formed as an annular recess that can be inserted into the cylindrical portion of the valve body 511a. The diameter of the radially outer side surface (outer surface 511e2) of the cushion chamber 511e is formed to be slightly larger than the diameter of the outer circumferential surface (outer cylindrical surface, outer surface 511a2) of the cylindrical portion of the valve body 511a, so that a clearance is provided when the cylindrical portion of the valve body 511a is inserted into the cushion chamber 511e (see Figure 5). The diameter of the radially outer side surface 511c2 of the cushion chamber 511e may be equal to the diameter of the outer surface 511e2 of the chamber 511c. The diameter of the radially inner side surface (inner surface 511e1) of the cushion chamber 511e is formed to be slightly smaller than the diameter of the inner circumferential surface (inner cylindrical surface, inner surface 511a1) of the cylindrical portion of the valve body 511a, so that a clearance is provided when the cylindrical portion of the valve body 511a is inserted into the cushion chamber 511e (see Figure 5). This allows the cylindrical portion of the valve body 511a to move upward (insert) and downward (separate) from the cushion chamber 511e, which is formed as an annular recess.

[0116] The switching valve 512 is configured to switch between a first state (see Figure 4) in which the chamber 511c and the flow path 515 (the flow path on the bottom side of the boom cylinder 7's oil chamber) are connected, and a second state (see Figure 5) in which the chamber 511c and the hydraulic oil tank are connected. Normally, the switching valve 512 is in the first state (see Figure 4). The switching valve 512 enters the second state (see Figure 5) when pilot pressure is supplied. Specifically, the switching valve 512 has a first port that communicates with the chamber 511c from the top surface 511c3, a second port that communicates with the flow path 515, and a third port that communicates with the hydraulic oil tank via a throttle 513. In the first state of the switching valve 512 (see Figure 4), the first port and the second port are connected, and the third port is closed. In the second state of the switching valve 512 (see Figure 5), the first port and the third port are connected, and the second port is closed.

[0117] When the boom is not being operated, no pilot pressure is supplied to the switching valve 512, and the switching valve 512 is in the first state (see Figure 4). As a result, hydraulic fluid is supplied to the chamber 511c above the valve body 511a (the space opposite to the valve seat 511d) from the flow path 515 on the bottom side of the boom cylinder 7's oil chamber. In addition, the elastic body 511b biases the valve body 511a toward the valve seat 511d. Therefore, the holding valve 51 closes when the valve body 511a comes into contact with the valve seat 511d. Furthermore, the biasing force of the elastic body 511b suppresses chattering of the valve body 511a.

[0118] Furthermore, when the boom is raised, no pilot pressure is supplied to the switching valve 512, and the switching valve 512 is in the first state (see Figure 4). At this point, the valve body 511a is pushed up by the hydraulic fluid supplied from the main pump 14 via the control valve 175 (175L, 175R). Thus, hydraulic fluid is supplied from the main pump 14 to the bottom oil chamber of the boom cylinder 7 via the control valve 175 (175L, 175R) and the holding valve 51.

[0119] Furthermore, when the boom is lowered, pilot pressure is supplied to the switching valve 512, and the switching valve 512 is in the second state (see Figure 5). As a result, the hydraulic fluid in the chamber 511c above the valve body 511a (the space opposite to the valve seat 511d) is discharged to the hydraulic fluid tank via the switching valve 512 and throttle 513. Therefore, the holding valve 51 opens as the valve body 511a separates from the valve seat 511d.

[0120] Immediately after switching the switching valve 512 from the first state (see Figure 4) to the second state (see Figure 5), the valve body 511a is in contact with the valve seat 511d. Therefore, the pressure-receiving area on the upper side of the valve body 511a, where the pressure of the hydraulic fluid in the chamber 511c (intermediate pressure) acts, is the entire circular surface, while the pressure-receiving area on the lower side of the valve body 511a, where the pressure of the hydraulic fluid in the flow path 515 (bottom pressure of the boom cylinder 7) acts, is annular in shape. As a result, the hydraulic fluid in the chamber 511c above the valve body 511a (the space opposite to the valve seat 511d) is discharged to the hydraulic fluid tank via the throttle 513, and the intermediate pressure is reduced, causing the valve body 511a to separate from the valve seat 511d and the holding valve 51 to open.

[0121] Here, as the holding valve 51 repeatedly opens and closes, the valve body 511a reciprocates within the chamber 511c, causing wear on the outer surface (outer surface 511a2) of the valve body 511a and the inner surface (side surface 511c2) of the chamber 511c. This increases the gap between the outer surface (outer surface 511a2) of the valve body 511a and the inner surface (side surface 511c2) of the chamber 511c, increasing the leak flow rate. As this leak flow rate increases and approaches the flow rate at the throttle 513, the valve body 511a may not rise even when the switching valve 512 is set to the second state (see Figure 5), and the holding valve 51 may not open.

[0122] In other words, by increasing the throttling area of ​​the aperture 513, the valve body 511a can be reliably operated even if the outer surface (outer surface 511a2) of the valve body 511a and the inner surface (side surface 511c2) of the chamber 511c wear down, thereby extending the lifespan of the holding valve 51 and reducing the frequency of replacement.

[0123] On the other hand, by increasing the flow rate in the throttle 513, and when the boom is lowered, the hydraulic fluid in the chamber 511c above the valve body 511a (the space opposite to the valve seat 511d) is quickly discharged to the hydraulic fluid tank via the throttle 513. As a result, the valve body 511a rises at high speed, and there is a risk that the valve body 511a will come into contact with the wall of the chamber 511c (the top surface 511c3 if a cushion chamber 511e is not formed), generating abnormal noise. In addition, there is a risk that the valve body 511a may be damaged due to the impact of the valve body 511a coming into contact with the wall of the chamber 511c (the top surface 511c3 if a cushion chamber 511e is not formed).

[0124] In contrast, the holding valve 51 shown in Figures 4 and 5 has a cushion chamber 511e formed in the wall surface of the chamber 511c (top surface 511c3 in the example of Figures 4 and 5) where the valve body 511a is located. The cushion chamber 511e is a recess formed at the position where the upper end (end surface 511a3) of the valve body 511a abuts. The width of this cushion chamber 511e is formed to be slightly larger than the thickness of the valve body 511a.

[0125] As a result, the valve body 511a rises rapidly until its upper end (end face 511a3) reaches the cushion chamber 511e, causing the holding valve 51 to open. When the upper end portion of the valve body 511a is inserted into the cushion chamber 511e, the hydraulic fluid in the cushion chamber 511e is compressed by the upper end portion of the valve body 511a, slowing down the valve body 511a and suppressing its movement. Then, as the compressed hydraulic fluid leaks from the annular gap between the valve body 511a and the cushion chamber 511e, the valve body 511a rises slowly, and its upper end (end face 511a3) comes into contact with the wall surface (top surface 511e3) of the cushion chamber 511e. This suppresses the noise and impact that occur when the upper end (end face 511a3) of the valve body 511a comes into contact with the wall surface (top surface 511e3) of the cushion chamber 511e. Furthermore, the lifespan of the holding valve 51 can be extended. Also, since the flow rate at the throttle 513 can be set to a larger value, the responsiveness when opening the holding valve 51 can be improved. In other words, the responsiveness when starting to lower the boom can be improved.

[0126] Next, the holding valve 52 will be explained using Figure 6. Figure 6 shows the holding valve 52, which is provided between the rod-side oil chamber of the arm cylinder 8 and the control valve 176, in the closed position.

[0127] The holding valve 52 is provided between the flow path 524 connected to the control valve 176 and the flow path 525 connected to the rod-side oil chamber of the arm cylinder 8.

[0128] The holding valve 52 includes a poppet valve 521 and a switching valve 522. The poppet valve 521 includes a valve body 521a, an elastic body 521b, a chamber 521c, a valve seat 521d, and a cushion chamber 521e. The configuration of the poppet valve 521 is the same as that of the poppet valve 511 of the holding valve 51, so a redundant explanation will be omitted.

[0129] The switching valve 522 is configured to switch between a first state (see Figure 6) in which the chamber 521c is connected to the flow path 525 (the flow path on the rod side oil chamber of the arm cylinder 8), and a second state (not shown) in which the chamber 521c is connected to the hydraulic oil tank. Normally, the switching valve 522 is in the first state (see Figure 6). The switching valve 522 enters the second state (not shown) when pilot pressure is supplied.

[0130] When the arm is not being operated, no pilot pressure is supplied to the switching valve 522, and the switching valve 522 is in the first state (see Figure 6). As a result, hydraulic fluid is supplied to the chamber 521c above the valve body 521a (the space opposite to the valve seat 521d) from the passage 525 on the rod side of the arm cylinder 8. In addition, the elastic body 521b biases the valve body 521a toward the valve seat 521d. Therefore, the holding valve 52 closes when the valve body 521a comes into contact with the valve seat 521d.

[0131] Furthermore, when the arm is open, no pilot pressure is supplied to the switching valve 522, and the switching valve 522 is in the first state (see Figure 6). At this point, the valve body 521a is pushed up by the hydraulic fluid supplied from the main pump 14 via the control valve 176 (176L, 176R). Thus, hydraulic fluid is supplied from the main pump 14 to the rod-side oil chamber of the arm cylinder 8 via the control valve 176 (176L, 176R) and the holding valve 52.

[0132] Furthermore, when the arm is closed, pilot pressure is supplied to the switching valve 522, and the switching valve 522 is in a second state (not shown). As a result, the hydraulic fluid in the chamber 521c above the valve body 521a (the space opposite to the valve seat 521d) is discharged to the hydraulic fluid tank via the switching valve 512 and throttle 523. Therefore, the holding valve 52 opens as the valve body 521a separates from the valve seat 521d.

[0133] Here, as the holding valve 52 repeatedly opens and closes, the valve body 521a reciprocates within the chamber 521c, causing wear on the outer surface of the valve body 521a and the inner surface of the chamber 521c. This increases the gap between the outer surface of the valve body 521a and the inner surface of the chamber 521c, increasing the leak flow rate. As this leak flow rate increases and approaches the flow rate at the throttle 523, the valve body 521a may not rise even when the switching valve 522 is set to the second state (not shown), and the holding valve 52 may not open.

[0134] In other words, by increasing the flow rate at the throttle 523, the valve body 521a can be operated even if the outer surface of the valve body 521a and the inner surface of the chamber 521c wear down, thereby extending the life of the holding valve 52 and reducing the frequency of replacement.

[0135] On the other hand, by increasing the flow rate in the throttle 523, and when the arm is closed, the hydraulic fluid in the chamber 521c above the valve body 521a (the space opposite to the valve seat 521d) is quickly discharged to the hydraulic fluid tank via the throttle 523. As a result, the valve body 521a rises at high speed, and there is a risk that the valve body 521a will come into contact with the wall surface of the chamber 521c (the top surface in the example of Figure 6), generating abnormal noise. In addition, there is a risk that the valve body 521a may be damaged due to the impact of contact between the valve body 521a and the wall surface of the chamber 521c (the top surface in the example of Figure 6).

[0136] In contrast, the holding valve 52 shown in Figure 6 has a cushion chamber 521e formed in the wall surface (top surface in the example of Figure 6) of the chamber 521c where the valve body 521a is located. The cushion chamber 521e is a recess formed at the position where the upper end of the valve body 521a abuts. The width of this cushion chamber 521e is formed to be slightly larger than the thickness of the valve body 521a.

[0137] As a result, the valve body 521a rises rapidly until its upper end reaches the cushion chamber 521e, causing the holding valve 52 to open. When the upper end of the valve body 521a is inserted into the cushion chamber 521e, the hydraulic fluid in the cushion chamber 521e is compressed by the upper end of the valve body 521a, slowing down the valve body 521a and suppressing the movement of the valve body 511a. Then, the compressed hydraulic fluid leaks from the annular gap between the valve body 521a and the cushion chamber 521e, causing the valve body 521a to rise slowly, and its upper end comes into contact with the wall (top) of the cushion chamber 521e. This suppresses abnormal noise and impact when the upper end of the valve body 521a comes into contact with the wall (top) of the cushion chamber 521e. It also extends the life of the holding valve 52. Furthermore, since the flow rate at the throttle 523 can be set to a larger value, the responsiveness when opening the holding valve 52 can be improved. In other words, the responsiveness when the arm starts to close can be improved.

[0138] In the holding valve 51 shown in Figures 4 and 5 (and the holding valve 52 shown in Figure 6), the compressed hydraulic fluid in the cushion chamber 511e is discharged into the chamber 511c through the annular gap between the valve body 511a and the cushion chamber 511e, and then discharged to the hydraulic fluid tank via the switching valve 512 and throttle 513. This is described as an example configuration, but the invention is not limited to this.

[0139] Figure 7 shows another example of a holding valve 51 provided between the bottom oil chamber of the boom cylinder 7 and the control valve 175. As shown in Figure 7, a throttle 511f may be provided to discharge hydraulic fluid from the cushion chamber 511e. This allows the compressed hydraulic fluid in the cushion chamber 511e to be discharged to the hydraulic fluid tank via the throttle 511f, switching valve 512, and throttle 513 when the cylindrical portion of the valve body 511a is inserted into the cushion chamber 511e. This reduces noise caused by the valve body 511a contacting the wall. In other words, the time until the valve body 511a contacts the wall can be extended without variation. Furthermore, the opening area of ​​the throttle 511f can be suitably controlled compared to the annular gap between the valve body 511a and the cushion chamber 511e (see Figures 4 and 5). This reduces variations due to machine differences in the time required from the valve body 511a contacting the wall until the holding valve 51 is fully open.

[0140] Figure 8 shows yet another example of a holding valve 51 provided between the bottom oil chamber of the boom cylinder 7 and the control valve 175. As shown in Figure 8, a notch 511g may be provided. This allows the compressed hydraulic fluid in the cushion chamber 511e to be discharged from the notch 511g into the chamber 511c when the cylindrical portion of the valve body 511a is inserted into the cushion chamber 511e, and then discharged to the hydraulic fluid tank via the switching valve 512 and throttle 513. This reduces the noise caused by the valve body 511a contacting the wall. In other words, the time until the valve body 511a contacts the wall can be extended without variation. In addition, the opening area of ​​the notch 511g can be suitably controlled compared to the annular gap between the valve body 511a and the cushion chamber 511e (see Figures 4 and 5). This reduces variations due to machine differences in the time required for the valve body 511a to contact the wall and for the holding valve 51 to fully open.

[0141] The above description uses the shovel 100 as an example of a work machine, but the configuration of a work machine is not limited to this. The description uses a work machine (shovel 100) in which the operator is seated in the cabin 10 and operates the control device 26 provided inside the cabin 10, but the configuration of the work machine (shovel 100) is not limited to this. The work machine (shovel 100) may also be configured to be remotely operated from the outside.

[0142] For example, the excavator system comprises a remote control room and a working machine (excavator 100). The remote control room includes a seat where the operator sits, an operating device operated by the operator seated in the seat, a display device, and a remote control room control unit. The remote control room control unit is communicatively connected to the controller 30 of the working machine (excavator 100). The display device shows, for example, an image captured by the imaging device S6 of the working machine (excavator 100). The operating device is configured to accept operator input, similar to the operating device 26. An operation sensor provided on the operating device inputs the operation amount to the remote control room control unit. The remote control room control unit transmits the operation amount to the controller 30 via a communication line and the excavator's communication device T1. The controller 30 controls the operation of each actuator of the excavator 100 based on the operation amount of the operating device transmitted from the remote control room control unit, instead of the detected value of the operating sensor 29. [Explanation of Symbols]

[0143] 100 Shovel 1. Lower running body 3. Upper rotating body 4 Boom 5 Arms 6 buckets 7 Boom Cylinder 8 Arm Cylinder 14. Main pump (hydraulic pump) 17 Control Valve Unit 171-176 Control valves (directional control valves) 51, 52 Holding valve 511 Poppet valve 511a Valve body 511b Elastic body Room 511c 511d Valve seat 511e Cushion Room 512 Switching valve 513 aperture 514 Channel 515 channel

Claims

1. Lower running body and An upper rotating body that can rotate relative to the lower traveling body, An attachment provided on the upper rotating body, including a boom and an arm, A boom cylinder for operating the aforementioned boom, An arm cylinder for operating the aforementioned arm, Boom directional control valve, Directional control valve for the arm, A holding valve is provided in at least one of the following locations: between the bottom-side oil chamber of the boom cylinder and the boom directional control valve, and between the rod-side oil chamber of the arm cylinder and the arm directional control valve. The holding valve is provided with a cushion chamber. A type of machinery used for industrial work.

2. The aforementioned holding valve is It comprises a valve body, a valve seat, and a chamber in which the valve body is arranged. The cushion chamber is in communication with the chamber and is provided separately from the chamber. The work machine according to claim 1.

3. The cushion chamber is provided on the wall surface of the chamber facing the valve seat, The working machine according to claim 2.

4. The cushion chamber reduces the sound caused by the valve body contacting the wall surface of the chamber. The working machine according to claim 2.

5. The cushion chamber is configured such that the movement of the valve body is suppressed when the hydraulic fluid inside the cushion chamber is compressed by the valve body. The working machine according to claim 2.

6. A valve for a work machine, provided between a hydraulic actuator and a directional control valve, Valve body and, The valve seat, The chamber in which the valve body is provided, The system comprises a cushion chamber that communicates with the aforementioned chamber, is provided separately from the aforementioned chamber, and is located on the wall surface of the aforementioned chamber facing the valve seat, Valves for industrial machinery.

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