Boom control system for work machines

Abstract

To provide a boom control system of a work machine with a boom float function adjustable according to application.SOLUTION: A boom cylinder 10 drives a boom 6 and has a head side oil chamber 10h and a bottom side oil chamber 10b. A first valve 21 has a first opening 21c for discharging oil of the head side oil chamber 10h to an oil tank 25 and supplies oil from a hydraulic pump 20 to the head side oil chamber 10h. A second valve 22 has a second opening 22c for discharging the oil in the bottom side oil chamber 10b to the oil tank 25, and supplies the oil from the hydraulic pump 20 to the bottom side oil chamber 10b. A controller 30 controls an opening degree D1 of the first opening 21c and an opening degree D2 of the second opening 22c separately, in work including operation of the boom 6.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present disclosure relates to a boom control system for a work machine. [Background technology]

[0002] For example, Japanese Patent Laid-Open Publication No. 3-66838 (Patent Document 1) discloses a work machine such as a hydraulic excavator that is equipped with a boom float function. The boom float function is a function that enables the boom to swing freely by connecting the head side oil chamber and the bottom side oil chamber of the boom cylinder with an oil tank without discharging hydraulic oil from the hydraulic pump to the boom cylinder. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 3-66838 Summary of the Invention [Problem to be solved by the invention]

[0004] Work machines are used for a variety of purposes. For this reason, in recent years, there has been a demand for a boom float function that can be applied to a variety of purposes.

[0005] Therefore, an object of the present disclosure is to provide a boom control system for a work machine that is capable of adjusting a boom float function according to the application. [Means for solving the problem]

[0006] The boom control system for a work machine disclosed herein is a boom control system for a work machine including a boom, a boom cylinder, a hydraulic pump, an oil tank, a first valve, and a second valve. The boom cylinder drives the boom and has a head side oil chamber and a bottom side oil chamber. The first valve supplies oil from the hydraulic pump to the head side oil chamber and discharges it to the oil tank. The second valve supplies oil from the hydraulic pump to the bottom side oil chamber and discharges it to the oil tank. The first valve has a first opening that discharges oil from the head side oil chamber to the oil tank. The second valve has a second opening that discharges oil from the bottom side oil chamber to the oil tank. The boom control system for a work machine further includes a controller that individually controls the opening degree of the first opening and the opening degree of the second opening during work including operation of the boom. Effect of the Invention

[0007] According to the present disclosure, a work machine capable of adjusting a boom float function according to an application can be realized. [Brief description of the drawings]

[0008] [Figure 1] 1 is a perspective view showing a schematic configuration of a work machine according to an embodiment of the present disclosure; [Diagram 2] 2 is a diagram showing a configuration of a boom control system for the work machine shown in FIG. 1. [Diagram 3] FIG. 3 is a diagram showing an example of functional blocks of the boom control system shown in FIG. 2. [Figure 4] FIG. 4 is a flow chart showing an example of a boom control method for a work machine according to an embodiment of the present disclosure. [Diagram 5] FIG. 11 is a diagram showing the states of the first valve and the second valve in a cleaning mode. [Figure 6] FIG. 11 is a diagram showing the states of a first valve and a second valve in a breaker mode. [Figure 7] FIG. 11 is a diagram showing the states of the first valve and the second valve in an excavation assist mode. [Figure 8]11A is a diagram showing the relationship between the amount of boom lowering operation and the opening degree of the first valve in a clearing mode, and FIG. 11B is a diagram showing the relationship between the amount of boom lowering operation and the opening degree of the second valve in a clearing mode. [Figure 9] 11A is a diagram showing a relationship between the amount of boom lowering operation and the opening degree of the first valve in a breaker mode, and FIG. 11B is a diagram showing a relationship between the amount of boom lowering operation and the opening degree of the second valve in a breaker mode. [Figure 10] 11 is a diagram showing the relationship between the boom raising operation amount and the opening degree of the first valve (A) and the relationship between the boom raising operation amount and the opening degree of the second valve (B) in an excavation assist mode. FIG. [Figure 11] FIG. 1 is a side view showing a configuration of a work machine having a breaker as an attachment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, an embodiment of the present disclosure will be described with reference to the drawings.

[0010] In the specification and drawings, the same or corresponding components are denoted by the same reference numerals, and redundant explanations are not repeated. In addition, in the drawings, configurations may be omitted or simplified for convenience of explanation. In addition, at least a part of the embodiment and each modified example may be combined with each other in any desired manner.

[0011] The present disclosure is applicable to any work machine having a boom and a boom cylinder that drives the boom, other than a hydraulic excavator, and is applicable to work machines that perform boom operation, such as wheel loaders. In the following description, "up," "down," "front," "rear," "left," and "right" are directions based on the operator seated in the driver's seat 4S in the driver's cab 4 shown in FIG.

[0012] <Work machine configuration> First, the configuration of the work machine of this embodiment will be described with reference to FIG.

[0013] FIG. 1 is a perspective view showing a schematic configuration of a work machine according to an embodiment of the present disclosure. As shown in FIG. 1, a hydraulic excavator 100 has a main body 1 and a working implement 2 operated by hydraulic pressure. The main body 1 has a revolving body 3 and a running body 5. The running body 5 has a pair of tracks 5Cr and a traveling motor 5M. The hydraulic excavator 100 can travel by rotation of the tracks 5Cr. The traveling motor 5M is provided as a drive source for the running body 5. The traveling motor 5M is a hydraulic motor operated by hydraulic pressure. The running body 5 may have wheels (tires).

[0014] The rotating unit 3 is disposed on the running unit 5 and is supported by the running unit 5. The rotating unit 3 can rotate relative to the running unit 5 about a rotation axis RX. The rotating unit 3 has a driver's cab 4. A driver's seat 4S for an operator to sit in is provided inside the driver's cab 4. The operator (crew) can operate the work equipment 2 by getting into the driver's cab 4, can rotate the rotating unit 3 relative to the running unit 5, and can operate the hydraulic excavator 100 to travel using the running unit 5.

[0015] The rotating body 3 has an engine cover 9 and a counterweight provided at the rear of the rotating body 3. The engine cover 9 covers an engine room. An engine unit (engine, exhaust treatment structure, etc.) is disposed in the engine room.

[0016] The work machine 2 is supported by a rotating body 3. The work machine 2 has a boom 6, an arm 7, and a bucket 8. The work machine 2 further has a boom cylinder 10, an arm cylinder 11, and a bucket cylinder 12.

[0017] The boom 6 is rotatably connected to the main body 1 (the traveling body 5 and the rotating body 3). Specifically, a base end of the boom 6 is rotatably connected to the rotating body 3 with a boom foot pin 13 as a fulcrum.

[0018] The arm 7 is rotatably connected to the boom 6. Specifically, a base end of the arm 7 is rotatably connected to the tip of the boom 6 with a boom top pin 14 as a fulcrum. The bucket 8 is rotatably connected to the arm 7. Specifically, a base end of the bucket 8 is rotatably connected to the tip of the arm 7 with an arm top pin 15 as a fulcrum.

[0019] One end of the boom cylinder 10 is connected to the rotating body 3, and the other end is connected to the boom 6. The boom 6 can be driven relative to the main body 1 by the boom cylinder 10. By this drive, the boom 6 can be rotated in the vertical direction relative to the rotating body 3 with the boom foot pin 13 as a fulcrum.

[0020] One end of the arm cylinder 11 is connected to the boom 6, and the other end is connected to the arm 7. The arm 7 can be driven relative to the boom 6 by the arm cylinder 11. By this drive, the arm 7 can rotate up and down or back and forth relative to the boom 6 with the boom top pin 14 as a fulcrum.

[0021] One end of the bucket cylinder 12 is connected to the arm 7, and the other end is connected to a bucket link. The bucket 8 can be driven relative to the arm 7 by the bucket cylinder 12. By this drive, the bucket 8 can rotate up and down relative to the arm 7 with the arm top pin 15 as a fulcrum.

[0022] <Boom control system configuration> Next, the configuration of the boom control system of this embodiment will be described with reference to FIG.

[0023] Fig. 2 is a diagram showing the configuration of the boom control system of the work machine shown in Fig. 1. As shown in Fig. 2, the control system of the boom 6 in the work machine 100 has a boom cylinder 10, a hydraulic pump 20, a first valve 21, a second valve 22, check valves 23, 24, an oil tank 25, a controller (control unit) 30, operation devices 16a to 16c, a work mode setting unit 17, and a float switching unit 18.

[0024] The boom cylinder 10 has a head side oil chamber 10h and a bottom side oil chamber 10b. The hydraulic pump 20 supplies hydraulic oil to each of the head side oil chamber 10h and the bottom side oil chamber 10b of the boom cylinder 10.

[0025] The first valve 21 has openings 21a and 21b, and a first opening 21c. The opening 21a is a port connected to the hydraulic pump 20. The opening 21b is a port connected to the head side oil chamber 10h. The first opening 21c is a port connected to the oil tank 25 to discharge the hydraulic oil in the head side oil chamber 10h to the oil tank 25.

[0026] The second valve 22 has openings 22a, 22b and a second opening 22c. The opening 22a is a port connected to the hydraulic pump 20. The opening 22b is a port connected to the bottom-side oil chamber 10b. The second opening 22c is a port connected to the oil tank 25 to discharge the hydraulic oil in the bottom-side oil chamber 10b to the oil tank 25.

[0027] Each of the first valve 21 and the second valve 22 has a spool. The spool of the first valve 21 and the spool of the second valve 22 are designed to have the same dimensions.

[0028] A first valve 21 is connected between the head side oil chamber 10h and the hydraulic pump 20. This allows hydraulic oil to be supplied from the hydraulic pump 20 through the first valve 21 to the head side oil chamber 10h.

[0029] The head side oil chamber 10h is connected to an oil tank 25 through a first valve 21. This allows the hydraulic oil in the head side oil chamber 10h to be discharged to the oil tank 25 through the first valve 21.

[0030] The head side oil chamber 10h is connected to an oil tank 25 via a check valve 23. This allows oil in the oil tank 25 to be supplied through the check valve 23 into the head side oil chamber 10h.

[0031] A second valve 22 is connected between the bottom-side oil chamber 10b and the hydraulic pump 20. This allows hydraulic oil to be supplied from the hydraulic pump 20 through the second valve 22 to the bottom-side oil chamber 10b.

[0032] The bottom-side oil chamber 10b is connected to an oil tank 25 through a second valve 22. This allows the hydraulic oil in the bottom-side oil chamber 10b to be discharged to the oil tank 25 through the second valve 22.

[0033] The bottom-side oil chamber 10b is connected to an oil tank 25 via a check valve 24. This allows oil in the oil tank 25 to be supplied through the check valve 24 into the bottom-side oil chamber 10b.

[0034] The operation device 16a is, for example, an operation lever used by the operator to operate the operation of the boom 6. The operation device 16b is, for example, an operation lever used by the operator to operate the operation of the arm 7. The operation device 16c is, for example, an operation lever used by the operator to operate the operation of the bucket 8. The operation amount of each of the operation devices 16a to 16c is detected by, for example, a potentiometer, a Hall IC (Integrated Circuit), or the like, and input to the controller 30 as a control signal.

[0035] The work mode setting unit 17 is, for example, an input device operated by an operator. The work mode setting unit 17 may be, for example, a display device consisting of a touch panel. In this case, a plurality of work modes of the work machine 2 are displayed on the work mode setting unit 17. The work modes of the work machine 2 are, for example, a plowing mode, a breaker mode, an excavation assist mode, and the like. The operator selects and touches one of the plurality of work modes displayed on the work mode setting unit 17. A signal indicating the work mode selected by the operator is input to the controller 30 as a control signal.

[0036] Plowing is the process of removing the surface of the earth and leveling it. Breaker work is the process of breaking up rocks or hard layers of earth.

[0037] The float switching unit 18 is, for example, a changeover switch. An operator can selectively switch between execution and non-execution of the boom float function by operating the float switching unit 18. A switching signal for execution or non-execution selected by the operator is input to the controller 30 as a control signal.

[0038] The controller 30 receives control signals from the operation devices 16a to 16c, the work mode setting unit 17, and the float switching unit 18. During work including the operation of the boom 6, the controller 30 controls the operation of the spools of the first valve 21 and the second valve 22 individually based on the input control signals. As a result, during work including the operation of the boom 6, the opening degree of the first opening 21c and the opening degree of the second opening 22c are individually controlled by the controller 30. The controller 30 individually controls the opening degree of the first opening 21c and the second opening 22c based on the work mode selected by the work mode setting unit 17.

[0039] <Boom control system functional block configuration> Next, the configuration of functional blocks of the boom control system shown in FIG. 2 will be described with reference to FIG.

[0040] Fig. 3 is a diagram showing an example of functional blocks of the boom control system shown in Fig. 2. As shown in Fig. 3, the controller 30 has a work mode determination unit 31, a float switching determination unit 32, a float operation start determination unit 33, a first valve control unit 34, and a second valve control unit 35.

[0041] The work mode determination unit 31 receives a control signal indicating the work mode from the work mode setting unit 17. The work mode determination unit 31 determines the work mode selected by the operator based on the control signal input from the work mode setting unit 17.

[0042] The work modes include, for example, a plowing mode, a breaker mode, and an excavation assist mode. The plowing mode is a setting that puts the boom 6 into a floating state so that the bucket 8 moves along the unevenness of the ground during plowing work. The breaker mode is a setting that reduces vibration of the work machine caused by a breaker 8a when a breaker 8a is used as an attachment as shown in FIG. 11. The excavation assist mode is a setting that puts the boom 6 into a floating state so as to relieve the load on the bucket 8 during excavation.

[0043] The work mode determination unit 31 determines whether the work mode selected by the operator is, for example, a plowing mode, a breaker mode, or an excavation assist mode. The work mode determination unit 31 outputs a determination signal to the float switching determination unit 32.

[0044] The float switching determination unit 32 receives a switching signal for executing or not executing the boom float function from the float switching unit 18. When the float switching determination unit 32 receives a determination signal from the work mode determination unit 31, it determines whether execution or non-execution of the boom float function has been selected based on the switching signal input from the float switching unit 18. The float switching determination unit 32 outputs the determination signal to the float operation start determination unit 33.

[0045] The float operation start determination unit 33 determines whether or not to start boom float operation based on the operation of the operating device 16a by the operator. For example, when the work mode is the plowing mode or the breaker mode, the float operation start determination unit 33 determines whether or not to start boom float operation based on the operation signal for lowering the boom. Also, when the work mode is the excavation assist mode, the float operation start determination unit 33 determines whether or not to start boom float operation based on the operation signal for raising the boom.

[0046] When the float operation start determination unit 33 determines that the boom float operation should be started, it outputs a control signal based on the amount of operation of the operation device 16a to each of the first valve control unit 34 and the second valve control unit 35. As a result, the boom float operation is started with the operation signal input from the operation device 16a to the float operation start determination unit 33 as a trigger.

[0047] The first valve control section 34 controls the operation of the first valve 21 based on a control signal from the float operation start determination section 33. The second valve control section 35 controls the operation of the second valve 22 based on a control signal from the float operation start determination section 33.

[0048] <Boom control method> Next, a boom control method by the above boom control system will be described with reference to FIGS.

[0049] Fig. 4 is a flow diagram showing an example of a boom control method for a work machine in an embodiment of the present disclosure. Fig. 5, Fig. 6, and Fig. 7 are diagrams showing the states of the first valve and the second valve in the plowing mode, the breaker mode, and the excavation assist mode, respectively. Fig. 8, Fig. 9, and Fig. 10 are diagrams showing the relationship (A) between the boom operation amount and the opening degree of the first valve, and the relationship (B) between the boom operation amount and the opening degree of the second valve in the plowing mode, the breaker mode, and the excavation assist mode, respectively.

[0050] 3 and 4, the operator performs an input operation of the work mode in the work mode setting unit 17. At this time, the operator performs a touch operation on any one of the multiple work modes displayed on the work mode setting unit 17. As a result, one work mode is selected in the work mode setting unit 17.

[0051] As described above, the multiple work modes include, for example, the plowing mode, the breaker mode, and the excavation assist mode. By the above-mentioned input operation by the operator, for example, one of the plowing mode, the breaker mode, and the excavation assist mode is selected. A signal indicating the work mode selected by the operator is input as a control signal to the work mode determination unit 31 of the controller 30 (step S1: FIG. 4).

[0052] When the work mode determination unit 31 receives a control signal indicating the work mode from the work mode setting unit 17, it determines the work mode selected by the operator based on the control signal (step S2). For example, the work mode determination unit 31 determines whether the work mode selected by the operator is the plowing mode, the breaker mode, or the excavation assist mode.

[0053] (Sukitori mode) When the work mode determined by the work mode determination unit 31 is the plowing mode, the float switching determination unit 32 determines whether or not the boom float function is enabled based on the switching signal from the float switching unit 18 (step S3a: FIG. 4).

[0054] When the float switching determination unit 32 determines that the boom float function is disabled, normal control is performed (step S4a: FIG. 4). In normal control, the boom 6, the arm 7, and the bucket 8 (FIG. 1) are driven according to the amount of operation of the operation devices 16a to 16c (FIG. 2).

[0055] When the float switching determination unit 32 determines that the boom float function is enabled, the float operation start determination unit 33 determines whether or not to start the float operation. The determination of whether or not to start the float operation is made based on whether or not the operator has performed a boom lowering operation (step S5a: FIG. 4). The float operation start determination unit 33 determines whether or not the operator has performed a boom lowering operation based on an operation signal input from the operating device 16a.

[0056] When the float operation start determination unit 33 determines that the boom lowering operation is not being performed, normal control is performed (step S4a: FIG. 4).

[0057] When the float operation start determination unit 33 determines that a boom lowering operation has been performed, the first valve control unit 34 controls the operation of the first valve 21, and the second valve control unit 35 controls the operation of the second valve 22. As a result, as shown in Fig. 5, the operations of the first valve 21 and the second valve 22 are controlled so that the first opening 21c of the first valve 21 and the second opening 22c of the second valve 22 are opened (step S6a: Fig. 4).

[0058] The first valve 21 has a spool 21s that controls the opening and closing of each of the openings 21a, 21b and the first opening 21c. The second valve 22 has a spool 22s that controls the opening and closing of each of the openings 22a, 22b and the second opening 22c. Each of the first valve 21 and the second valve 22 has, for example, a solenoid (not shown).

[0059] The controller 30 controls the drive of the spool 21s of the first valve 21 by inputting an electric signal to the solenoid of the first valve 21. This controls the operation of the spool 21s so that the opening 21b and the first opening 21c of the first valve 21 are each opened. This allows the hydraulic oil in the head side oil chamber 10h of the boom cylinder 10 to be discharged to the oil tank 25 through the opening 21b and the first opening 21c.

[0060] The controller 30 controls the drive of the spool 22s of the second valve 22 by inputting an electric signal to the solenoid of the second valve 22. This controls the operation of the spool 22s so that the opening 22b and the second opening 22c of the second valve 22 are each opened. This allows the hydraulic oil in the bottom-side oil chamber 10b of the boom cylinder 10 to be discharged to the oil tank 25 through the opening 22b and the second opening 22c.

[0061] 5, when the boom cylinder 10 extends in the clearing mode, the hydraulic oil in the head side oil chamber 10h is discharged to the oil tank 25 via the first valve 21, and the oil in the oil tank 25 is supplied to the bottom side oil chamber 10b via the check valve 24. When the boom cylinder 10 retracts in the clearing mode, the hydraulic oil in the bottom side oil chamber 10b is discharged to the oil tank 25 via the second valve 22, and the oil in the oil tank 25 is supplied to the head side oil chamber 10h via the check valve 23.

[0062] In the plowing mode, the opening degrees D1, D2 of the first opening 21c and the second opening 22c are controlled according to the amount of lowering operation of the boom 6 by the operating device 16a. Specifically, as shown in Fig. 8(A), the controller 30 controls the first valve 21 so that the opening degree D1 of the first opening 21c increases as the amount of lowering operation of the boom 6 by the operating device 16a increases. Also, as shown in Fig. 8(B), the controller 30 controls the second valve 22 so that the opening degree D2 of the second opening 22c increases as the amount of lowering operation of the boom 6 by the operating device 16a increases.

[0063] As shown in Figs. 8(A) and 8(B), the opening degree D1 of the first opening 21c and the opening degree D2 of the second opening 22c in response to the amount of boom lowering operation may be substantially the same.

[0064] (Breaker mode) 3 and 4, when the work mode determined by the work mode determination unit 31 is the breaker mode, the float switching determination unit 32 determines whether or not the boom float function is enabled (step S3b: FIG. 4). The float switching determination unit 32 determines whether or not the boom float function is enabled based on a switching signal from the float switching unit 18.

[0065] When the float switching determination unit 32 determines that the boom float function is disabled, normal control is performed (step S4b: FIG. 4).

[0066] When the float switching determination unit 32 determines that the boom float function is enabled, the float operation start determination unit 33 determines whether or not to start the float operation. The determination of whether or not to start the float operation is made based on whether or not the operator has performed a boom lowering operation (step S5b: FIG. 4). The float operation start determination unit 33 determines whether or not the operator has performed a boom lowering operation based on an operation signal input from the operating device 16a.

[0067] When the float operation start determination unit 33 determines that the boom lowering operation is not being performed, normal control is performed (step S4b: FIG. 4).

[0068] Furthermore, when the float operation start determination unit 33 determines that a boom lowering operation has been performed, the first valve control unit 34 controls the operation of the first valve 21, and the second valve control unit 35 controls the operation of the second valve 22. As a result, as shown in Fig. 6, the operations of the first valve 21 and the second valve 22 are controlled so that the opening degree D1 of the first opening 21c in the first valve 21 is smaller than the opening degree D2 of the second opening 22c in the second valve 22 (step S6b: Fig. 4).

[0069] In the breaker mode, the spool 21s is controlled by the controller 30 so that the opening 21a is closed and the opening 21b and the first opening 21c are opened. This allows the hydraulic oil in the head side oil chamber 10h of the boom cylinder 10 to be discharged to the oil tank 25 through the opening 21b and the first opening 21c.

[0070] In the breaker mode, the spool 22s is controlled by the controller 30 so that the opening 22a is closed and the opening 22b and the second opening 22c are opened. This allows the hydraulic oil in the bottom-side oil chamber 10b of the boom cylinder 10 to be discharged to the oil tank 25 through the opening 22b and the second opening 22c.

[0071] Here, the controller 30 controls the opening degree D1 of the first opening 21c to be smaller than the opening degree D2 of the second opening 22c. Therefore, as shown in Figures 9(A) and 9(B), the opening degrees D1 and D2 both increase as the boom lowering operation amount increases, but the rate of increase in the opening degree D1 is smaller than the rate of increase in the opening degree D2.

[0072] In the breaker mode, the first opening 21c may be completely closed by the spool 21s.

[0073] 6, when the boom cylinder 10 extends in the breaker mode, the hydraulic oil in the head side oil chamber 10h is discharged to the oil tank 25 via the first valve 21, and the oil in the oil tank 25 is supplied to the bottom side oil chamber 10b via the check valve 24. When the boom cylinder 10 retracts in the breaker mode, the hydraulic oil in the bottom side oil chamber 10b is discharged to the oil tank 25 via the second valve 22, and the oil in the oil tank 25 is supplied to the head side oil chamber 10h via the check valve 23.

[0074] (Drilling Assist Mode) 3 and 4, when the work mode determined by the work mode determination unit 31 is the excavation assist mode, the float switching determination unit 32 determines whether or not the boom float function is enabled (step S3c: FIG. 4). The float switching determination unit 32 determines whether or not the boom float function is enabled based on a switching signal from the float switching unit 18.

[0075] When the float switching determination unit 32 determines that the boom float function is disabled, normal control is performed (step S4c: FIG. 4).

[0076] When the float switching determination unit 32 determines that the boom float function is enabled, the float operation start determination unit 33 determines whether or not to start the float operation. The determination of whether or not to start the float operation is made based on whether or not the operator has performed a boom raising operation (step S5c: FIG. 4). The float operation start determination unit 33 determines whether or not the operator has performed a boom raising operation based on an operation signal input from the operating device 16a.

[0077] When the float operation start determination unit 33 determines that the boom raising operation is not being performed, normal control is performed (step S4c: FIG. 4).

[0078] When the float operation start determination unit 33 determines that a boom-up operation has been performed, the first valve control unit 34 controls the operation of the first valve 21, and the second valve control unit 35 controls the operation of the second valve 22. As a result, as shown in Fig. 7, the opening degree D2 of the second opening 22c is controlled to be smaller than the opening degree D1 of the first opening 21c (step S6c: Fig. 4). At this time, the second opening 22c is, for example, closed.

[0079] In the excavation assist mode, the spool 21s is controlled by the controller 30 so that the opening 21b and the first opening 21c are opened. This allows the hydraulic oil in the head side oil chamber 10h of the boom cylinder 10 to be discharged to the oil tank 25 through the opening 21b and the first opening 21c.

[0080] In the excavation assist mode, the opening degree D2 of the second opening 22c is smaller than the opening degree D1 of the first opening 21c or is set to 0 (closed). Preferably, the second opening 22c is completely closed.

[0081] In the excavation assist mode, the opening degree of each of the first opening 21c and the second opening 22c is controlled according to the amount of lifting operation of the boom 6 by the operating device 16a. Specifically, as shown in Fig. 10(A), the controller 30 controls the first valve 21 so that the opening degree D1 of the first opening 21c increases as the amount of lifting operation of the boom 6 by the operating device 16a increases. Also, as shown in Fig. 10(B), even if the amount of lifting operation of the boom 6 by the operating device 16a increases, the opening degree D2 of the second opening 22c hardly increases, or the second opening 22c remains closed.

[0082] As described above, in this embodiment, the controller 30 controls the opening degree D1 of the first opening 21c in the first valve 21 and the opening degree D2 of the second opening 22c in the second valve 22 separately.

[0083] Furthermore, the controller 30 individually controls the opening degrees D1, D2 based on the work mode of the work machine 2 (for example, plowing mode, breaker mode, excavation assist mode).

[0084] The controller 30 controls both the first opening 21c and the second opening 22c to be opened as shown in Fig. 5 and Fig. 8(A) and (B) based on the determination result that the work mode is the plowing mode. The controller 30 controls the opening degree D1 to be smaller than the opening degree D2 as shown in Fig. 6 and Fig. 9(A) and (B) based on the determination result that the work mode is the excavation assist mode. The controller 30 controls the opening degree D2 to be smaller than the opening degree D1 as shown in Fig. 7 and Fig. 10(A) and (B) based on the determination result that the work mode is the excavation assist mode.

[0085] <Effects> Next, the effects of this embodiment will be described.

[0086] 5 to 7, in this embodiment, the controller 30 individually controls the opening degree D1 of the first opening 21c in the first valve 21 and the opening degree D2 of the second opening 22c in the second valve 22. This makes it possible to individually control the discharge of the hydraulic oil from the head side oil chamber 10h and the bottom side oil chamber 10b of the boom cylinder 10 to the oil tank 25. This makes it possible to adjust the boom float function according to the application without providing an opening for the boom float in the spool and without preparing a valve for switching the boom float function separately from the main valve.

[0087] In this embodiment, the controller 30 controls the opening degrees D1, D2 individually based on the work mode (for example, plowing mode, breaker mode, excavation assist mode) of the work machine 2. This makes it possible to realize a work machine that can adjust the boom float function depending on the application, such as plowing mode, breaker mode, excavation assist mode, etc.

[0088] Also, in this embodiment, as shown in Figures 5 and 8(A) and (B), the controller 30 controls both the first opening 21c and the second opening 22c to be opened based on the determination result that the work mode is the plowing mode.

[0089] This allows the boom 6 to move freely up and down in response to external forces, making it easier for the bucket 8 to move along the unevenness of the ground during plowing work. Also, by executing the boom float function with the bucket 8 in the air, it becomes possible to lower the boom 6 by the weight of the work implement 2 until it touches the ground.

[0090] In addition, as shown in Fig. 11, when the breaker 8a is used as an attachment, if the chisel 8aa performs blank striking, the retainer pin, the chisel 8aa, etc., are likely to chip, and the chisel holder is likely to be damaged. For this reason, when the breaker 8a is operated, the tip of the chisel 8aa must be in contact with the object to be crushed.

[0091] In this embodiment, as shown in FIG. 6 and FIGS. 9(A) and (B), the controller 30 controls the opening degree D1 to be smaller than the opening degree D2 based on the determination result that the working mode is the breaker mode.

[0092] This makes it easier for the boom 6 to move downward (the side where the boom cylinder 10 retracts) but makes it harder for it to move upward (the side where the boom cylinder 10 extends). Therefore, in the breaker mode, the tip of the chisel 8aa is prevented from coming off the object to be crushed, and chipping of the retainer pin, the chisel 8aa, and damage to the chisel holder can be prevented.

[0093] Furthermore, in the case of demolition, hard objects may be crushed. In this case, if the load caused by the crushing is not released, the work machine 2 may be damaged.

[0094] In this embodiment, as shown in FIG. 7 and FIGS. 10(A) and (B), the controller 30 controls the opening degree D2 to be smaller than the opening degree D1 based on the determination result that the work mode is the excavation assist mode.

[0095] This makes it difficult for the boom 6 to move downward (the side where the boom cylinder 10 retracts) but makes it easier for it to move upward (the side where the boom cylinder 10 extends). Therefore, when excavating a hard object, the boom 6 moves to the upward side, so that the load caused by excavation can be relieved. This makes it possible to improve the durability of the work machine 2.

[0096] 2 and 3 in the above embodiment may be mounted on the work machine 100, or may be disposed remotely outside the work machine 100. When the controller 30 is disposed remotely outside the work machine 100, the controller 30 may be wirelessly connected to the work mode setting unit 17, the float switching unit 18, the operation devices 16a to 16c, the first valve 21, the second valve 22, etc. The controller 30 is, for example, a processor, and may be a CPU (Central Processing Unit).

[0097] The embodiments disclosed herein should be considered to be illustrative and not restrictive in all respects. The scope of the present invention is defined by the claims, not the above description, and is intended to include all modifications within the meaning and scope of the claims. [Explanation of symbols]

[0098] 1 main body, 2 working machine, 3 rotating body, 4 driver's cab, 4S driver's seat, 5 running body, 5Cr track, 5M running motor, 6 boom, 7 arm, 8 bucket, 8a breaker, 8aa chisel, 9 engine cover, 10 boom cylinder, 10b bottom side oil chamber, 10h head side oil chamber, 11 arm cylinder, 12 bucket cylinder, 13 boom foot pin, 14 boom top pin, 15 arm top pin, 16a, 16b, 16c operation device, 17 work mode setting unit, 18 float switching unit, 20 hydraulic pump, 21 first valve, 21a, 21b, 22a, 22b opening, 21c first opening, 21s, 22s spool, 22 second valve, 22c second opening, 23, 24 check valve, 25 oil tank, 30, 50 Controller, 31 work mode determination unit, 32 float switching determination unit, 33 float operation start determination unit, 34 first valve control unit, 35 second valve control unit, 50k memory unit, 100 hydraulic excavator, D1, D2 opening degree, RX rotation axis.

Claims

1. Boom and a boom cylinder that drives the boom and has a head side oil chamber and a bottom side oil chamber; A hydraulic pump; Oil tank and a first valve that supplies oil from the hydraulic pump to the head side oil chamber and discharges the oil to the oil tank; a second valve that supplies oil from the hydraulic pump to the bottom-side oil chamber and discharges oil to the oil tank, the first valve has a first opening through which oil in the head side oil chamber is discharged to the oil tank, the second valve has a second opening for discharging oil from the bottom oil chamber to the oil tank, A boom control system for a work machine, further comprising a controller that controls a boom float function by individually controlling the opening degree of the first opening and the opening degree of the second opening in accordance with a work mode selected from a plurality of work modes during work including operation of the boom.

2. 2. The boom control system for a work machine according to claim 1, wherein the controller individually controls the opening degree of the first opening and the opening degree of the second opening based on the work mode of a work machine having the boom and the boom cylinder.

3. 3. The boom control system for a work machine according to claim 1, wherein the controller controls to open both the first opening and the second opening based on a determination result that the work mode is a plowing mode.

4. 3. A boom control system for a work machine according to claim 1 or claim 2, wherein the controller controls the opening degree of the first opening to be smaller than the opening degree of the second opening based on a determination result that the work mode is a breaker mode.

5. 3. A boom control system for a work machine according to claim 1 or claim 2, wherein the controller controls the opening degree of the second opening to be smaller than the opening degree of the first opening based on a determination result that the work mode is an excavation assist mode.

6. A boom; a boom cylinder that drives the boom and has a head side oil chamber and a bottom side oil chamber; A hydraulic pump; Oil tank and a first valve that supplies oil from the hydraulic pump to the head side oil chamber and discharges the oil to the oil tank; a second valve that supplies oil from the hydraulic pump to the bottom-side oil chamber and discharges oil to the oil tank, the first valve has a first opening through which oil in the head side oil chamber is discharged to the oil tank, the second valve has a second opening for discharging oil from the bottom oil chamber to the oil tank, A boom control system for a work machine, further comprising a controller that, during work including operation of the boom, individually controls the degree of opening of the first opening and the degree of opening of the second opening based on a result of determining the type of work mode of a work machine having the boom and the boom cylinder.

7. A boom control system for a work machine as described in Claim 6, wherein the controller controls both the first opening and the second opening to be opened based on a determination result that the work mode is a plowing mode.

8. A boom control system for a work machine as described in Claim 6, wherein the controller controls the opening degree of the first opening to be smaller than the opening degree of the second opening based on the determination result that the work mode is a breaker mode.

9. A boom control system for a work machine as described in claim 6, wherein the controller controls the opening degree of the second opening to be smaller than the opening degree of the first opening based on the determination result that the work mode is an excavation assist mode.

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