Hydraulic control device for construction machinery and construction machinery equipped with the same

Abstract

To provide a hydraulic control device for a construction machine and the construction machine provided therewith capable of preventing jumping-up of a machine body upon striking operation without degrading operability upon operation other than the striking operation.SOLUTION: A hydraulic control device 100A is provided with: a hydraulic pump 11; a boom cylinder 7; a boom control device 20; a cut valve 52; and a control part 90. The cut valve 52 is capable of switching positions between a supply position where hydraulic oil to be discharged from the hydraulic pump 11 is allowed to be supplied to the boom cylinder 7 and a regulation position where the hydraulic oil is restricted from being supplied to the boom cylinder 7. The control part 90 determines whether or not downward operation corresponds to the striking operation striking a bucket 6 on the ground when the downward operation is input in the boom operation device 20 and sets the cut valve 52 at the regulation position when it corresponds to the striking operation.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a hydraulic control device that controls the drive of a boom cylinder and a construction machine equipped with the same. [Background technology]

[0002] Conventionally, construction machines having a machine body and a work attachment attached to the machine body have been known. Patent Document 1 discloses such a construction machine in which the work attachment includes a boom supported on the machine body so as to be able to be raised or lowered, an arm rotatably supported at the tip of the boom, and a bucket rotatably supported at the tip of the arm. The hydraulic excavator also has a mechanism for preventing the machine body from bouncing up during a pounding operation in which the back of the bucket is slammed into the ground to compact the ground. The machine body bouncing up is a phenomenon in which the machine body bounces up significantly due to a reaction force when the bucket is hit hard against the ground.

[0003] Specifically, in Patent Document 1, the hydraulic excavator has a work selector switch that can be switched between a normal work state and a striking work state. When the work selector switch is set to the normal work state and the operator commands the boom lowering operation, hydraulic oil is discharged from the head chamber of the boom cylinder and hydraulic oil is supplied from the hydraulic pump to the rod chamber, thereby accelerating the boom lowering speed. On the other hand, when the operator commands the boom lowering operation with the work selector switch set to the striking work state, hydraulic oil is discharged from the head chamber of the boom cylinder and some of the hydraulic oil supplied to the rod chamber is discharged from the bleed opening to a tank, thereby slowing the boom lowering speed and preventing the machine body from bouncing up. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 3115205 Summary of the Invention [Problem to be solved by the invention]

[0005] In the technology described in Patent Document 1, when the work selector switch is set to the striking work state, a portion of the hydraulic oil is always discharged from the bleed opening, which reduces the boom lowering speed even when no striking work is actually being performed, resulting in a problem in that the operator feels that the operability of the hydraulic excavator is poor.

[0006] The object of the present invention is to provide a hydraulic control device for a construction machine that can prevent the machine body from bouncing up during driving work without reducing operability when performing work other than driving work, and a construction machine equipped with the same. [Means for solving the problem]

[0007] The present invention provides a hydraulic control device for a construction machine including a boom and a work member attached to the boom. The hydraulic control device includes a hydraulic pump, a boom cylinder, a boom operation device, a switching valve, and a control unit. The boom cylinder operates to cause the boom to perform a boom-lowering operation and a boom-raising operation by receiving hydraulic oil from the hydraulic pump. The boom operation device accepts a lowering operation corresponding to the boom-lowering operation and a raising operation corresponding to the boom-raising operation, respectively. The switching valve is switchable between a supply position that allows hydraulic oil to be supplied from the hydraulic pump to the boom cylinder and a restricting position that reduces the maximum amount of hydraulic oil supplied to the boom cylinder compared to the supply position. When the lowering operation is input to the boom operation device, the control unit determines whether the lowering operation corresponds to a driving operation of driving the work member into the ground, and if the driving operation corresponds to the driving operation, sets the switching valve to the restricting position.

[0008] According to this configuration, when the lowering operation input to the boom operating device corresponds to a driving operation, the control unit sets the selector valve to the restricting position, thereby restricting the amount of hydraulic oil discharged from the hydraulic pump to the boom cylinder when the working member contacts the ground. As a result, the active supply of hydraulic oil to the boom cylinder does not press the working member against the ground with a large driving force, preventing the construction machine body from bouncing up due to the reaction and preventing the operator from feeling a large shock. Furthermore, because the control unit sets the selector valve to the restricting position when the input lowering operation corresponds to a driving operation, the control valve can set the selector valve to the supply position for other operations, such as lifting the machine body, allowing the working member to be used with a large driving force. Therefore, a decrease in operability for each operation can be prevented compared to when the selector valves are set to the restricting position simultaneously for both driving operations and the other operations.

[0009] In the above configuration, it is desirable that, in the restricting position, the switching valve prevents hydraulic oil discharged from the hydraulic pump from being supplied to the boom cylinder.

[0010] According to this configuration, when the lowering operation input to the boom operating device corresponds to a striking operation, the supply of hydraulic oil to the boom cylinder is blocked, further preventing the body of the construction machine from bouncing up and the operator from feeling a large impact.

[0011] In the above configuration, it is desirable that the control unit determines that the lowering operation corresponds to the striking work and sets the switching valve to the restricting position, and then, when the input of the lowering operation to the boom operating device is released, sets the switching valve to the supply position.

[0012] With this configuration, when a lowering operation is input and the selector valve is set to the restricting position, and then a raising operation is input, the control unit sets the selector valve to the supply position, so that the boom can be raised by supplying hydraulic oil to the boom cylinder. This makes it possible to raise and lower the boom while preventing the machine body from bouncing up, and enables the work member to repeatedly hit the ground.

[0013] In the above configuration, it is desirable that the device further includes a speed detection unit capable of detecting the speed of the boom, and that the control unit determines that the input lowering operation corresponds to the striking operation when the lowering operation is input to the boom operation device and the downward speed of the boom detected by the speed detection unit drops from a speed greater than a predetermined speed threshold to zero.

[0014] According to this configuration, the phenomenon of the work member being struck against the ground can be detected with high accuracy from changes in the speed of the boom, and it can be determined that the operator is performing striking work.

[0015] In the above configuration, it is desirable that the device further includes an acceleration detection unit capable of detecting the acceleration of the boom, and that the control unit determines that the input lowering operation corresponds to the striking work when the lowering operation is input to the boom operation device and at least the direction of the acceleration of the boom detected by the acceleration detection unit reverses from downward to upward.

[0016] According to this configuration, the phenomenon of the work member being struck against the ground can be detected with high accuracy based on the direction of the boom acceleration, and it can be determined that the operator is performing striking work.

[0017] In the above configuration, it is desirable that the control unit determines that the input lowering operation corresponds to the striking work when the acceleration of the boom is reversed and the magnitude of the upward acceleration of the boom detected by the acceleration detection unit is greater than a predetermined acceleration threshold value.

[0018] This configuration makes it possible to prevent the switching valve from being mistakenly set to the restricted position due to a reversal in the direction of the boom acceleration when the work member is gently pressed against the ground during lifting work on the machine body, for example.

[0019] In the above configuration, the boom cylinder has a cylinder body, and a piston rod that includes a partition that divides the cylinder body into a head chamber and a rod chamber and is movable relative to the cylinder body, and the piston rod is capable of extending relative to the cylinder body so as to receive hydraulic oil discharged by the hydraulic pump into the head chamber to cause the boom to perform the boom-up operation, while the piston rod is capable of contracting relative to the cylinder body so as to receive hydraulic oil discharged by the hydraulic pump into the rod chamber to cause the boom to perform the boom-down operation, and the boom cylinder further includes a pressure detection unit that can detect pressure in the rod chamber, and it is desirable that the control unit determines that the input lowering operation corresponds to the striking work when the lowering operation is input to the boom operation device and the pressure in the rod chamber detected by the pressure detection unit exceeds a predetermined pressure threshold.

[0020] According to this configuration, the phenomenon of the work member being struck against the ground can be detected with high accuracy from pressure changes in the rod chamber of the boom cylinder, and it can be determined that the operator is performing striking work.

[0021] In the above configuration, when the lowering operation is input to the boom operation device and then a deceleration operation for slowing down the boom speed during the boom lowering operation is input to the boom operation device, the control unit desirably determines that the lowering operation does not correspond to the striking work.

[0022] According to this configuration, if an operation to slow down the boom lowering speed is input after a lowering operation is input to the boom operation device, it is possible to quickly determine that the work the operator is attempting to perform is a work different from striking work.

[0023] In the above configuration, it is desirable to further provide an execution switch that can be switched between an on state for instructing the switching setting of the switching valve in accordance with the determination of the striking work, and an off state for preventing the switching setting of the switching valve.

[0024] According to this configuration, the hydraulic control device is equipped with an execution switch, so when an unskilled person operates the construction machine, they can perform the driving work while suppressing the machine body from bouncing up or shock by turning the execution switch on. Also, when an experienced person operates the construction machine, they can turn the execution switch off and perform the driving work by their own sense.

[0025] The present invention also provides a construction machine comprising a body, a boom supported on the body so that it can be raised and lowered, a working member attached to the boom, and the hydraulic control device for the construction machine described above.

[0026] According to this configuration, it is possible to prevent the machine body from bouncing up during driving work without reducing the operability of the construction machine when performing work other than driving work. [Effects of the Invention]

[0027] According to the present invention, it is possible to provide a hydraulic control device for a construction machine that can prevent the machine body from bouncing up during driving work without reducing operability when performing work other than driving work, and a construction machine equipped with the same. [Brief explanation of the drawings]

[0028] [Figure 1] 1 is a side view showing a construction machine equipped with a hydraulic control device according to an embodiment of the present invention. [Figure 2] 1 is a circuit diagram of a hydraulic control device according to an embodiment of the present invention. [Figure 3] 1 is a block diagram of a control unit of a hydraulic control device according to an embodiment of the present invention. [Figure 4] 3 is a flowchart showing the processing of a control unit in the hydraulic control device according to one embodiment of the present invention. [Figure 5] 4 is a graph showing the progress of the boom lowering speed in a construction machine equipped with a hydraulic control device according to one embodiment of the present invention. [Figure 6] 6 is a graph showing the transition of the rod pressure of a boom cylinder in a construction machine equipped with a hydraulic control device according to a first modified embodiment of the present invention. [Figure 7] 10 is a graph showing the transition of the acceleration of a boom cylinder in a construction machine equipped with a hydraulic control device according to a second modified embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0029] Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.

[0030] FIG. 1 shows a hydraulic excavator 100 (construction machinery) equipped with a hydraulic control device 100A according to one embodiment of the present invention. The hydraulic excavator 100 includes a crawler-type undercarriage 1 capable of traveling on a travel surface, an upper rotating body 2 (machine body) mounted on the undercarriage 1 so as to be rotatable about a central axis of rotation perpendicular to the travel surface, and a work attachment 3 mounted on the upper rotating body 2. The work attachment 3 includes a boom 4 supported on the upper rotating body 2 so as to be able to rise and fall, an arm 5 rotatably connected to the tip of the boom 4, and a bucket 6 (working member) rotatably connected to the tip of the arm 5. The upper rotating body 2 includes a rotating frame 2S and a cab 2A. The bucket 6 has a bottom surface 6S.

[0031] The hydraulic excavator 100 includes a boom cylinder 7 that operates to raise and lower the boom 4 relative to the upper rotating body 2, an arm cylinder 8 that operates to rotate the arm 5 relative to the boom 4, and a bucket cylinder 9 that operates to rotate the bucket 6 relative to the arm 5.

[0032] FIG. 2 is a circuit diagram of a hydraulic control device 100A according to this embodiment. As shown in FIG. 2, the hydraulic control device 100A includes a first hydraulic pump 11 (hydraulic pump), a second hydraulic pump 12, a tank T, a pilot pump (not shown), the boom cylinder 7, the arm cylinder 8, a boom control valve 40, an arm control valve 41, a confluence control valve 42, a boom operation device 20, an arm operation device 30, a cut valve 52, a meter-out valve 53, a supply valve 61, a check valve 62, multiple detectors, and a controller 90. Note that the bucket cylinder 9 is not shown in FIG. 2. The hydraulic control device 100A also includes a boom cylinder circuit L1, an arm cylinder circuit L2, a confluence circuit L3, a supply circuit L5, and a meter-out circuit L6.

[0033] The boom cylinder circuit L1 is an oil passage for supplying hydraulic oil discharged from the first hydraulic pump 11 to the boom cylinder 7. The boom cylinder circuit L1 connects the first hydraulic pump 11 and the boom cylinder 7.

[0034] The arm cylinder circuit L2 is an oil passage for supplying hydraulic oil discharged from the second hydraulic pump 12 to the arm cylinder 8. The arm cylinder circuit L2 connects the second hydraulic pump 12 and the arm cylinder 8.

[0035] The junction circuit L3 is an oil passage for merging the hydraulic oil discharged from the first hydraulic pump 11 into the arm cylinder 8. The junction circuit L3 connects the first hydraulic pump 11 and the arm cylinder 8. The junction circuit L3 branches off from the boom cylinder circuit L1 and is connected to the arm cylinder 8, but may also be connected to the arm cylinder circuit L2.

[0036] The supply circuit L5 is an oil passage for supplying hydraulic oil from the tank T to the rod chamber 7r of the boom cylinder 7 when negative pressure occurs in the rod chamber 7r of the boom cylinder 7. The supply circuit L5 connects the rod chamber 7r of the boom cylinder 7 and the tank T.

[0037] The meter-out circuit L6 is an oil passage for returning the hydraulic oil (discharged oil) discharged from the head chamber 7h of the boom cylinder 7 to the tank T. The meter-out circuit L6 connects the boom cylinder 7, the boom control valve 40, and the tank T.

[0038] The first hydraulic pump 11 mainly discharges hydraulic oil for operating the boom cylinder 7. The second hydraulic pump 12 discharges hydraulic oil for operating the arm cylinder 8. The first and second hydraulic pumps 11, 12 and the pilot pump are driven by an engine (not shown).

[0039] The boom cylinder 7 is an actuator that operates to cause the boom 4 to perform a boom-lowering operation and a boom-raising operation by receiving a supply of hydraulic oil discharged by the first hydraulic pump 11. The boom cylinder 7 has a cylinder body 7A and a piston rod 7B that includes a partition portion 7c (piston portion) that divides the cylinder body 7A into a head chamber 7h and a rod chamber 7r, and that is movable relative to the cylinder body 7A. In the boom cylinder 7, the piston rod 7B can extend relative to the cylinder body 7A by receiving hydraulic oil discharged by the first hydraulic pump 11 into the head chamber 7h to cause the boom 4 to perform the boom-raising operation, and can contract relative to the cylinder body 7A by receiving hydraulic oil discharged by the first hydraulic pump 11 into the rod chamber 7r to cause the boom 4 to perform the boom-lowering operation.

[0040] The arm cylinder 8 is an actuator that operates to cause the arm 5 to perform an arm pushing operation and an arm pulling operation by receiving a supply of hydraulic oil discharged by the second hydraulic pump 12. The arm cylinder 8 also has a cylinder body, a partition portion (piston portion) that divides the cylinder body into a head chamber 8h and a rod chamber 8r, and a piston rod that is movable relative to the cylinder body.

[0041] The boom control valve 40 is interposed between the first hydraulic pump 11 and the boom cylinder 7, and opens and closes to change the flow rate of hydraulic oil supplied from the first hydraulic pump 11 to the boom cylinder 7. Specifically, the boom control valve 40 is a pilot-operated three-position directional control valve having a boom-lowering pilot port 40a and a boom-raising pilot port 40b, and is disposed in the boom cylinder circuit L1.

[0042] When no pilot pressure is input to either the boom-lowering or the boom-raising pilot ports 40a, 40b, the boom control valve 40 is maintained in a neutral position P1, and cuts off communication between the first hydraulic pump 11 and the boom cylinder 7. A relief valve (not shown) is arranged in the boom cylinder circuit L1 at a location between the first hydraulic pump 11 and the boom control valve 40 (specifically, at a location between the first hydraulic pump 11 and the cut valve 52).

[0043] When boom lowering pilot pressure is input to the boom lowering pilot port 40a, the boom control valve 40 is switched from the neutral position P1 to the boom lowering position P2 by a stroke corresponding to the magnitude of the boom lowering pilot pressure. This opens the valve to allow hydraulic oil to be supplied from the first hydraulic pump 11 to the rod chamber 7r of the boom cylinder 7 at a flow rate corresponding to the stroke, and to allow hydraulic oil to be discharged from the head chamber 7h of the boom cylinder 7. This drives the boom cylinder 7 in the boom lowering direction at a speed corresponding to the boom lowering pilot pressure.

[0044] When boom-raising pilot pressure is input to the boom-raising pilot port 40b, the boom control valve 40 is switched from the neutral position P1 to the boom-raising position P3 by a stroke corresponding to the magnitude of the boom-raising pilot pressure. This opens the valve to allow hydraulic oil to be supplied from the first hydraulic pump 11 to the head chamber 7h of the boom cylinder 7 at a flow rate corresponding to the stroke, and to allow hydraulic oil to be discharged from the rod chamber 7r of the boom cylinder 7. This drives the boom cylinder 7 in the boom-raising direction at a speed corresponding to the boom-raising pilot pressure.

[0045] The arm control valve 41 is interposed between the second hydraulic pump 12 and the arm cylinder 8, and opens and closes to change the flow rate of hydraulic oil supplied from the second hydraulic pump 12 to the arm cylinder 8. Specifically, the arm control valve 41 is made up of a pilot-operated three-position directional control valve having an arm-pushing pilot port 41a and an arm-pulling pilot port 41b, and is arranged in the arm cylinder circuit L2.

[0046] The junction control valve 42 is for supplying hydraulic oil from the first hydraulic pump 11 to the arm cylinder 8 in addition to hydraulic oil from the second hydraulic pump 12 during the arm pushing operation and the arm pulling operation. The junction control valve 42 is interposed between the first hydraulic pump 11 and the arm cylinder 8, and performs opening and closing operation to change the flow rate of hydraulic oil supplied from the first hydraulic pump 11 to the arm cylinder 8. Specifically, the junction control valve 42 is made up of a pilot-operated three-position directional control valve having an arm pushing pilot port 42a and an arm pulling pilot port 42b, and is arranged in the junction circuit L3.

[0047] The arm control valve 41 is maintained in a neutral position P1 when pilot pressure is not input to either of the arm push and arm pull pilot ports 41a, 41b, and blocks communication between the second hydraulic pump 12 and the arm cylinder 8. Similarly, the junction control valve 42 is maintained in a neutral position P1 when pilot pressure is not input to either of the arm push and arm pull pilot ports 42a, 42b, and blocks communication between the first hydraulic pump 11 and the arm cylinder 8. A relief valve (not shown) is disposed in the arm cylinder circuit L2 at a position between the second hydraulic pump 12 and the arm control valve 41.

[0048] When arm push pilot pressure is input to the arm push pilot port 41a, the arm control valve 41 is switched from the neutral position P1 to the arm push position P2 by a stroke corresponding to the magnitude of the arm push pilot pressure. This allows hydraulic oil to be supplied from the second hydraulic pump 12 to the rod chamber 8r of the arm cylinder 8 at a flow rate corresponding to the stroke, and opens to allow hydraulic oil to return from the head chamber 8h of the arm cylinder 8 to a tank. Similarly, when arm push pilot pressure is input to the arm push pilot port 42a, the junction control valve 42 is switched from the neutral position P1 to the arm push position P2 by a stroke corresponding to the magnitude of the arm push pilot pressure. This allows hydraulic oil to be supplied from the first hydraulic pump 11 to the rod chamber 8r of the arm cylinder 8 at a flow rate corresponding to the stroke, and opens to allow hydraulic oil to return from the head chamber 8h of the arm cylinder 8 to a tank. This drives the arm cylinder 8 in the arm push direction at a speed corresponding to the arm push pilot pressure.

[0049] When arm pull pilot pressure is input to the arm pull pilot port 41b, the arm control valve 41 is switched from the neutral position P1 to the arm pull position P3 by a stroke corresponding to the magnitude of the arm pull pilot pressure. This allows hydraulic oil to be supplied from the second hydraulic pump 12 to the head chamber 8h of the arm cylinder 8 at a flow rate corresponding to the stroke, and opens to allow hydraulic oil to return from the rod chamber 8r of the arm cylinder 8 to a tank. Similarly, when arm pull pilot pressure is input to the arm pull pilot port 42b, the junction control valve 42 is switched from the neutral position P1 to the arm pull position P3 by a stroke corresponding to the magnitude of the arm pull pilot pressure. This allows hydraulic oil to be supplied from the first hydraulic pump 11 to the head chamber 8h of the arm cylinder 8 at a flow rate corresponding to the stroke, and opens to allow hydraulic oil to return from the rod chamber 8r of the arm cylinder 8 to a tank. This drives the arm cylinder 8 in the arm pull direction at a speed corresponding to the arm pull pilot pressure.

[0050] The boom operation device 20 receives a boom lowering operation (lowering operation) and a boom raising operation (raising operation) for causing the boom 4 to perform the boom lowering operation and the boom raising operation, respectively, and operates to allow pilot pressure corresponding to the operations to be input from the pilot pump to the boom control valve 40. Specifically, the boom operation device 20 has a boom operation lever 21 and a boom pilot valve 22 (remote control valve).

[0051] The boom control lever 21 is a member that can rotate in response to the boom lowering operation and the boom raising operation by the operator. The boom lowering operation and the boom raising operation are operations that rotate the boom control lever 21 in mutually opposite directions.

[0052] The boom pilot valve 22 opens in conjunction with one of the boom-raising operation and the boom-lowering operation applied to the boom operation lever 21, thereby allowing pilot pressure of a magnitude corresponding to the amount of operation of one of the pilot ports 40a, 40b of the boom control valve 40 to be input from the pilot pump to the pilot port corresponding to the direction of the one of the operations.

[0053] The arm operating device 30 receives an arm pushing operation and an arm pulling operation for causing the arm 5 to perform the arm pushing operation and the arm pulling operation, respectively, and operates to allow pilot pressures corresponding to the operations to be input from the pilot pump to the arm control valve 41 and the junction control valve 42. Specifically, the arm operating device 30 has an arm operating lever 31 and an arm pilot valve 32 (remote control valve).

[0054] The arm operating lever 31 is a member that can rotate in response to the arm pushing operation and the arm pulling operation by the operator. The arm pushing operation and the arm pulling operation are operations that rotate the arm operating lever 31 in mutually opposite directions.

[0055] The arm pilot valve 32 opens in conjunction with one of the arm pushing operation and the arm pulling operation applied to the arm operating lever 31, thereby allowing a pilot pressure of a magnitude corresponding to the operation amount of one of the pilot ports 41a, 41b of the arm control valve 41 to be input from the pilot pump to the pilot port corresponding to the direction of one of the operations, and further allows a pilot pressure of a magnitude corresponding to the operation amount of one of the operations to be input from the pilot pump to the pilot port corresponding to the direction of one of the operations, of the pilot ports 42a, 42b of the junction control valve 42.

[0056] The cut valve 52 is configured to be capable of opening and closing (switchable) between a supply position P6 (supply position) that allows the hydraulic oil from the first hydraulic pump 11 to be supplied to the boom cylinder 7, more specifically, allows the hydraulic oil to be introduced into the supply-side port of the boom cylinder 7, and a cut-off position P7 (restriction position) that prevents the hydraulic oil from the first hydraulic pump 11 from being introduced into the supply-side port of the boom cylinder 7. The cut valve 52 is arranged in the boom cylinder circuit L1 between the first hydraulic pump 11 and the boom control valve 40.

[0057] In this embodiment, the cut valve 52 is an electromagnetic valve having a solenoid 52a. The cut valve 52 opens and closes between the supply position P6 and the shutoff position P7 based on an electrical signal B input from the control unit 90 to the solenoid 52a. The cut valve 52 may be a solenoid valve capable of on / off control for switching between the supply position P6 and the shutoff position P7, or may be an electromagnetic proportional valve capable of proportionally controlling the opening of the cut valve 52 between the supply position P6 and the shutoff position P7. The cut valve 52 may also have a pilot port and open and close between the supply position P6 and the shutoff position P7 in response to a pilot pressure input to the pilot port. In this case, a solenoid valve (not shown) may be disposed between the cut valve 52 and a pilot oil source, and the pilot pressure may be changed in response to a command signal input to the solenoid valve, thereby switching the position of the cut valve 52. In this case, the cut valve 52 and the solenoid valve constitute a switching valve of the present invention.

[0058] The meter-out valve 53 is configured to be capable of opening and closing between a permissive position P9 that allows the hydraulic oil discharged from the boom cylinder 7 to return to the tank T, and a shut-off position P8 that prevents the hydraulic oil discharged from the boom cylinder 7 from returning to the tank T. The meter-out valve 53 is disposed in the meter-out circuit L6.

[0059] In this embodiment, the meter-out valve 53 is configured as an electromagnetic valve having a solenoid 53a. The meter-out valve 53 opens and closes between the allowable position P9 and the shut-off position P8 based on an electrical signal input to the solenoid 53a from the control unit 90. The meter-out valve 53 may be a solenoid valve capable of performing on / off control to switch between the allowable position P9 and the shut-off position P8, or may be an electromagnetic proportional valve that can proportionally control the opening degree of the meter-out valve 53 between the allowable position P9 and the shut-off position P8.

[0060] The supply valve 61 is a check valve that allows hydraulic oil to flow from the tank T toward the boom cylinder 7 when negative pressure occurs in the rod chamber 7r of the boom cylinder 7, while restricting hydraulic oil from flowing in the opposite direction. The supply valve 61 is disposed in the supply circuit L5.

[0061] The check valve 62 is a check valve that allows the flow of hydraulic oil from the second hydraulic pump 12 toward the arm control valve 41, while restricting the flow of hydraulic oil in the opposite direction. The check valve 62 is disposed in the arm cylinder circuit L2.

[0062] The plurality of detectors include a boom operation detector 23, an arm operation detector 33, and a speed detector 26.

[0063] The boom operation detection unit 23 is configured to be able to detect that the boom operation device 20 has received the boom lowering operation. Specifically, the boom operation detection unit 23 is configured with a pressure sensor (boom pilot pressure sensor) that can detect the boom lowering pilot pressure output from the boom pilot valve 22 to the boom lowering pilot port 40a of the boom control valve 40. The boom operation detection unit 23 generates a pilot pressure detection signal A, which is an electrical signal corresponding to the boom lowering pilot pressure, and inputs the signal to the control unit 90.

[0064] The arm operation detection unit 33 is configured to be able to detect that the arm operating device 30 has received the arm pushing operation. Specifically, the arm operation detection unit 33 is configured with a pressure sensor (arm pilot pressure sensor) that can detect the arm pushing pilot pressure output from the arm pilot valve 32 toward the arm control valve 41 and the arm pushing pilot port 41a of the junction control valve 42. The arm operation detection unit 33 generates a pilot pressure detection signal C that is an electric signal corresponding to the arm pushing pilot pressure, and inputs the signal to the control unit 90.

[0065] The speed detection unit 26 is configured to be able to detect a speed index value that serves as an index of the speed of the boom lowering operation. Specifically, the speed detection unit 26 is configured, for example, by a stroke sensor or potentiometer provided on the boom cylinder 7. The stroke sensor or potentiometer can detect the retraction speed of the boom cylinder 7. Since the boom lowering operation is performed by retracting the boom cylinder 7, the retraction speed serves as an index of the speed of the boom lowering operation. The speed detection unit 26 generates a speed detection signal, which is an electrical signal that corresponds to the speed of the boom lowering operation, and inputs the signal to the control unit 90.

[0066] In this embodiment, the hydraulic control device 100A further includes a pressure sensor 24. The pressure sensor 24 is capable of detecting the pressure in the rod chamber 7r of the boom cylinder 7 (the rod pressure of the boom cylinder 7), and is disposed, for example, in a portion of the boom cylinder circuit L1 between the rod chamber 7r and the tank T. The pressure sensor 24 generates a pressure detection signal D, which is an electric signal corresponding to the pressure in the rod chamber 7r, and inputs the pressure detection signal D to the control unit 90.

[0067] FIG. 3 is a block diagram of the control unit 90 of the hydraulic control device 100A according to this embodiment.

[0068] The control unit 90 is composed of a CPU (Central Processing Unit), a ROM (Read Only Memory) that stores a control program, a RAM (Random Access Memory) used as a work area for the CPU, and the like. The control unit 90 functions to have functional units, such as a valve control unit 91, a calculation unit 92, a determination unit 93, and a storage unit 94, as a result of the CPU executing the control program stored in the ROM. These functional units do not have physical entities, but correspond to units of functions executed by the control program. Note that all or part of the control unit 90 is not limited to being provided within the hydraulic excavator 100, and may be located in a location different from the hydraulic excavator 100 when the hydraulic excavator 100 is remotely controlled. Furthermore, the control program may be transmitted from a remote server (management device) or cloud to the control unit 90 in the hydraulic excavator 100 and executed therein, or the control program may be executed on the server or cloud, and the generated command signal may be transmitted to the hydraulic excavator 100.

[0069] Valve control unit 91 inputs command signals to cut valve 52 and meter-out valve 53 to control the opening of each valve. In particular, when the boom lowering operation is input to at least boom operation device 20, valve control unit 91 determines whether the input boom lowering operation corresponds to a striking operation of striking bucket 6 against the ground, and if it determines that the operation corresponds to the striking operation, inputs the command signal to cut valve 52 to set cut valve 52 to shut-off position P7.

[0070] The calculation unit 92 executes calculation processes required for the various processes executed by the control unit 90. The determination unit 93 executes determination processes required for the various processes executed by the control unit 90. The storage unit 94 stores parameters and thresholds required for the various processes executed by the control unit 90.

[0071] The hydraulic excavator 100 also includes an input unit 35 and an angle sensor 36 (Fig. 3). The input unit 35 is located inside the cab 2A (Fig. 1) and receives various types of information for the operator to operate the hydraulic excavator 100. As an example, the input unit 35 has a switch function (execution switch) for executing the driving work assist process described below. The angle sensor 36 is provided on each rotation axis of the boom 4, arm 5, and bucket 6, and detects the rotation angle of each member. The detected angles are input to the control unit 90, and the attitude of the work attachment 3 is calculated by the calculation unit 92.

[0072] 4 is a flowchart showing a driving operation assist process executed by the control unit 90 in the hydraulic control device 100A according to this embodiment. Driving operation includes work (feather driving work) in which the bottom surface 6S (FIG. 1) of the bucket 6 is driven into the ground to compact and level the ground. Driving operation also includes work (pile driving work) in which the top end of a pile stuck in the ground is driven into the ground by the bottom surface 6S of the bucket 6. The control unit 90 executes the driving operation assist process during such driving operation to prevent the body of the hydraulic excavator 100 from bouncing up and improve workability.

[0073] When the operator switches on the execution switch included in the input unit 35 to instruct execution of the hammering operation assist process, the control unit 90 executes the flow of Fig. 4. The control unit 90 repeats the flow of Fig. 4 until the switch is turned off.

[0074] When the driving operation assist process is started, the determination unit 93 of the control unit 90 determines whether or not the operator has input a boom lowering operation via the boom operation lever 21 of the boom operation device 20 (step S1). At this time, the determination unit 93 makes the above determination based on the detection result of the boom operation detection unit 23. Note that if a boom lowering operation has not been input to the boom operation lever 21 (NO in step S1), the control unit 90 temporarily ends the flow in Fig. 4 (END) and starts again from step S1.

[0075] On the other hand, if a boom lowering operation has been input to the boom operation lever 21 in step S1 (YES in step S1), the determination unit 93 determines whether a boom lowering deceleration operation has been input (step S2). This boom lowering deceleration operation means inputting an operation to slow down the lowering speed of the boom 4, in other words, to return the boom operation lever 21 toward the neutral position, in response to the boom lowering operation confirmed in step S1. Typically, in earth-driving work, the boom lowering operation is not decelerated from the time the bottom surface 6S of the bucket 6 is positioned at a predetermined height from the ground until it hits the ground. Conversely, in work such as machine body lifting, when the bottom surface 6S of the bucket 6 is gently brought into contact with the ground and then the boom lowering operation is performed with a large driving force to lift the machine body, a boom lowering deceleration operation is often input in order to gently bring the bottom surface 6S of the bucket 6 into contact with the ground.

[0076] In this embodiment, from the above viewpoint, in addition to step S1, if a boom lowering deceleration operation is not input in step S2 (YES in step S2), the determination unit 93 proceeds to step S3.

[0077] In this case, the determination unit 93 determines whether the boom lowering speed is zero based on the detection result of the speed detection unit 26 (step S3). If the boom lowering speed is zero (YES in step S3), this means that the bottom surface 6S of the bucket 6 has been struck against the ground by the boom lowering operation. Therefore, the determination unit 93 determines whether the maximum value Vmax of the boom lowering speed V, which is continuously detected by the speed detection unit 26 and stored in the memory unit 94 during steps S1 to S3, is larger or smaller than a preset speed threshold Vlimit (step S4). The speed threshold Vlimit is set according to the specifications of the hydraulic excavator 100 and is stored in the memory unit 94. The speed threshold limit is set corresponding to the average maximum speed of the boom lowering operation when striking the bottom surface 6S of the bucket 6 against the ground for striking work.

[0078] In step S4, when Vlimit < Vmax (YES in step S4), the valve control unit 91 inputs a command signal to the cut-off valve 52 and switches the cut-off valve 52 to the shut-off position P7 (FIG. 2). Note that the meter-out valve 53 is set to the allowable position P9 when the boom lowering operation is input.

[0079] FIG. 5 is a graph showing the transition of the boom lowering speed in the hydraulic excavator 100 equipped with the hydraulic control device 100A according to the present embodiment. In FIG. 5, after receiving the boom lowering operation and the boom lowering speed increases with time, when the bottom surface 6S of the bucket 6 contacts the ground, the boom lowering speed rapidly drops from Vmax to zero. In the present embodiment, when the change amount ΔV of the boom lowering speed is greater than the above-mentioned Vlimit, it is determined that the operator is trying to strike the bottom surface 6S of the bucket 6 against the ground at a predetermined speed, that is, trying to execute the striking operation.

[0080] As described above, when the cut-off valve 52 is closed, the hydraulic oil discharged from the first hydraulic pump 11 is prevented from flowing into the rod chamber 7r of the boom cylinder 7 through the boom control valve 40, while the hydraulic oil discharged from the head chamber 7h of the boom cylinder 7 flows into the tank T via the boom control valve 40 and the meter-out valve 53. Therefore, in response to the boom lowering operation for the striking operation, immediately after the bottom surface 6S of the bucket 6 is struck against the ground mainly by the weight of the work attachment 3, the boom 4 is not further lowered with a large driving force, and the body is prevented from bouncing up significantly due to the reaction.

[0081] When the cut-off valve 52 is closed in step S5, the determination unit 93 determines the presence or absence of the boom lowering operation from the detection result of the boom operation detection unit 23. Here, when the boom lowering operation is continuously input (NO in step S6), the control unit 90 repeats steps S5 and S6.

[0082] On the other hand, if there is no boom-lowering operation in step S6, in other words, if the boom operation lever 21 is returned to the neutral position, or if a boom-raising operation is received for the next striking operation, the valve control unit 91 switches the cut valve 52 to the supply position P6 and opens it (step S7). As a result, when a boom-raising operation is input, the hydraulic oil discharged from the first hydraulic pump 11 can flow into the head chamber 7h of the boom cylinder 7 via the boom control valve 40, as usual. That is, in this embodiment, the cut valve 52 is controlled to close in response to each striking operation during a striking operation using the bucket 6. Therefore, each time the bottom surface 6S of the bucket 6 strikes the ground, excessive hydraulic oil is prevented from flowing into the boom cylinder 7, and the reaction force that the machine body of the hydraulic excavator 100 receives can be suppressed.

[0083] Note that in each of the following cases: if a boom deceleration operation is input in step S2 (NO in step S2), if the boom lowering speed has not reached zero in step S3 (NO in step S3), or if Vlimit≧Vmax in step S4 (NO in step S4), the control unit 90 does not close the cut valve 52 in the current flow, and repeats the flow in FIG. 4 from step S1. This also includes a machine-lifting operation in which the operator gently brings the bottom surface 6S of the bucket 6 into contact with the ground and then inputs a large boom-lowering operation to lift the machine. In this case, because the cut valve 52 is open, the hydraulic oil discharged by the first hydraulic pump 11 actively flows into the rod chamber 7r of the boom cylinder 7, and the machine can be lifted with a large driving force using the work attachment 3 as a fulcrum.

[0084] As described above, in this embodiment, the control unit 90 determines whether the boom lowering operation input to the boom operating device 20 corresponds to a driving operation, and if the driving operation corresponds to a driving operation, the control unit 90 sets the cut valve 52 to the restricting position. This prevents hydraulic oil discharged from the first hydraulic pump 11 from being supplied to the boom cylinder 7 after the bottom surface 6S of the bucket 6 contacts the ground. As a result, the supply of hydraulic oil does not press the bucket 6 against the ground with a large driving force, preventing the machine body of the hydraulic excavator 100 from bouncing up due to the reaction and preventing the operator from feeling a large impact. Furthermore, because the cut valve 52 is set to the restricting position when the input boom lowering operation corresponds to a driving operation, hydraulic oil from the first hydraulic pump 11 can be supplied to the boom cylinder 7 as needed for other operations, such as lifting the machine body, allowing the operation to be performed with a large driving force. Therefore, a decrease in operability in each operation can be prevented compared to when the cut valve 52 is set to the restricting position collectively for both the driving operation and the other operations.

[0085] Furthermore, in this embodiment, the control unit 90 determines that the operation input to the boom operation device 20 corresponds to the striking work and sets the cut valve 52 to the shut-off position P7, and then, when the input of the boom lowering operation to the boom operation device 20 is released, inputs a command signal to the cut valve 52 to set the cut valve 52 to the supply position P6 (set to the supply position).

[0086] With this configuration, after a boom-lowering operation is input and cut valve 52 is set to shut-off position P7, when a boom-raising operation is input, cut valve 52 is set to supply position P6, so that the boom-raising operation can be stably performed by supplying hydraulic oil to boom cylinder 7. Therefore, even when bucket 6 repeatedly strikes the ground, boom 4 can be raised and lowered while preventing the machine body from bouncing up, etc.

[0087] Furthermore, in this embodiment, when a boom lowering operation is input to the boom operation device 20 and the downward speed of the boom 4 detected by the speed detection unit 26 drops from a speed greater than a preset speed threshold Vlimit to zero, the control unit 90 determines that the input boom lowering operation corresponds to a striking operation.

[0088] With this configuration, the phenomenon of the bucket 6 striking the ground can be accurately detected based on the speed of the boom 4, and it can be determined that the operator is performing striking work. Note that when the downward speed of the boom 4 is lower than the speed threshold Vlimit, the machine body is unlikely to bounce up even if the cut valve 52 remains open because the boom 4 lowering speed is slow. In other words, in this embodiment, by closing the cut valve 52 when the boom lowering speed is high, at which point the machine body is likely to bounce up, it is possible to adequately prevent the machine body from bouncing up.

[0089] In addition, in this embodiment, in addition to determining whether a boom lowering operation has been input, if a boom lowering deceleration operation for slowing down the speed of the boom 4 during the boom lowering operation is input to the boom operation device 20, the control unit determines that the boom lowering operation does not correspond to striking work.

[0090] With this configuration, if a boom lowering operation is input to the boom operating device 20 and then an operation to slow down the lowering speed of the boom 4 is input, it can be determined early on that the work the operator is attempting to perform is a work different from a striking work.

[0091] Furthermore, in this embodiment, as shown in Fig. 2, hydraulic oil can be supplied to the arm cylinder 8 from the first hydraulic pump 11 in addition to the second hydraulic pump 12. Meanwhile, the cut valve 52 is a so-called meter-in cut valve, and is arranged at a position closer to the boom control valve 40 than the branch point where the merged circuit L3 branches off from the boom cylinder circuit L1. Therefore, even when a combined operation of the boom 4 and the arm 5 is input, if the movement of the boom 4 corresponds to a driving operation, the cut valve 52 can be closed while hydraulic oil from the first hydraulic pump 11 is supplied to the arm cylinder 8. Therefore, even during the above-mentioned combined operation, it is possible to prevent the machine body from bouncing up due to the driving operation.

[0092] In this embodiment, the input unit 35 also includes an execution switch. The execution switch selectively receives information regarding the driving work assist process, i.e., whether or not switching of the cut valve 52 is necessary in accordance with the driving work determination process. In other words, the execution switch is switchable between an ON state for instructing the cut valve 52 to be switched in accordance with the driving work determination, and an OFF state for preventing the cut valve 52 from being switched. When the execution switch is ON, i.e., when information regarding the need to switch the cut valve 52 has been input to the execution switch, the control unit 90 executes the driving work assist process.

[0093] According to this configuration, the hydraulic control device 100A is provided with an execution switch, so when an unskilled person operates the hydraulic excavator 100, the execution switch is required to determine whether or not to perform the driving work, thereby enabling the driving work to be performed while preventing the machine body from bouncing up or causing shock. Also, when an experienced person operates the hydraulic excavator 100, the execution switch can be turned off and the driving work can be performed according to the skilled person's own sense.

[0094] In this embodiment, as described above, the control unit 90 can acquire posture information of the work attachment 3 based on the detection results of the angle sensor 36 (FIG. 3). Compared to when the arm 5 of the work attachment 3 is in the vertical posture shown in FIG. 1, when the arm 5 is in a posture in which it extends horizontally forward, the vehicle body is less likely to bounce up. Therefore, the control unit 90 may change the magnitude of the threshold value used to determine whether a striking operation is being performed, depending on the posture of the work attachment 3. For example, when the arm 5 is in a posture in which it extends horizontally forward, the aforementioned Vlimit may be increased to reduce the probability of closing the cut valve 52. In other words, when the vehicle body is in the vertical posture as shown in FIG. 1, it is more likely that the vehicle body will bounce up, so it is desirable to set Vlimit small (strictly). This also applies to the modified embodiment described below. Furthermore, posture information of the work attachment 3 may be acquired based on the detection results of stroke sensors that detect the strokes of the boom cylinder 7, arm cylinder 8, and bucket cylinder 9, respectively, instead of the angle sensor 36.

[0095] The hydraulic control device 100A according to the present invention and the hydraulic excavator 100 equipped with the same have been described above, but the present invention is not limited to this and can take on modified embodiments such as those described below.

[0096] (1) FIG. 6 is a graph showing changes in the rod pressure of the boom cylinder 7 in the hydraulic excavator 100 equipped with the hydraulic control device 100A according to the first modified embodiment of the present invention. In the previous embodiment, the boom lowering speed is used to determine whether the driving operation is being performed in steps S3 and S4 of FIG. 4. Alternatively, the driving operation may be determined based on the pressure in the rod chamber 7r of the boom cylinder 7. When the bottom surface 6S of the bucket 6 strikes the ground, the pressure in the rod chamber 7r increases instantaneously as shown in FIG. 6. Therefore, the determination unit 93 may determine that the boom lowering operation input via the boom operation lever 21 corresponds to driving operation when a boom lowering operation is input to the boom operation device 20 and the pressure in the rod chamber 7r detected by the pressure sensor 24 (pressure detection unit in FIG. 2) exceeds a preset pressure threshold Plimit.

[0097] With this configuration, the phenomenon of the bucket 6 striking the ground can be detected with high accuracy from pressure changes in the rod chamber 7r of the boom cylinder 7, and it can be determined that the operator is performing striking work.

[0098] (2) FIG. 7 is a graph showing the transition of acceleration of the boom cylinder 7 in a hydraulic excavator 100 equipped with a hydraulic control device 100A according to a second modified embodiment of the present invention. If the speed detection unit 26 shown in FIG. 3 is an acceleration sensor (acceleration detection unit), the boom lowering speed can be obtained by integrating the detection results. On the other hand, in this modified embodiment, striking operation is determined based on the boom acceleration detected by the acceleration sensor. Specifically, when the bottom surface 6S of the bucket 6 strikes the ground, the acceleration of the boom 4 instantaneously changes from the positive side (downward) to the negative side (upward) as shown in FIG. 6. Therefore, when a boom lowering operation is input to the boom operation device 20 and the direction of the acceleration of the boom 4 detected by at least the acceleration sensor reverses from downward to upward, the determination unit 93 can determine that the boom lowering operation input to the boom operation lever 21 corresponds to striking operation.

[0099] With this configuration, the phenomenon of the bucket 6 striking the ground can be detected with high accuracy based on the direction of acceleration of the boom 4, and it can be determined that the operator is performing striking work.

[0100] In addition, the determination unit 93 may determine that the boom lowering operation input to the boom operating lever 21 corresponds to a striking operation when, in addition to the acceleration of the boom 4 being reversed as described above, the magnitude (absolute value) of the upward acceleration of the boom 4 detected by the acceleration sensor after the reversal is greater than a predetermined acceleration threshold Alimit.

[0101] This configuration makes it possible to prevent the cut valve 52 from being erroneously set to the restricted position due to a reversal in the direction of acceleration of the boom 4 when the bucket 6 is gently pressed against the ground during lifting work of the machine body.

[0102] In the above modified embodiment, the driving operation is determined using the acceleration of the boom 4, but the jerk of the boom 4 (the derivative of the acceleration, the rate of change of acceleration per unit time) may be used instead of the acceleration. Furthermore, the driving operation may be determined more accurately by combining the speed, acceleration, jerk, rod pressure, etc., as described above.

[0103] (3) Furthermore, in each of the above embodiments, it has been described that the operation input to the boom operation lever 21 is determined to correspond to a striking operation on the condition that a boom lowering deceleration operation has not been input in step S2 of Figure 4. However, it is also possible to proceed to the next step, such as determining the boom lowering speed, only by inputting a boom lowering operation, without performing a determination process regarding the boom lowering deceleration operation.

[0104] (4) In the above embodiment, the hydraulic control device includes the first hydraulic pump 11 and the second hydraulic pump 12. However, the present invention is not limited to this, and one of the first hydraulic pump 11 and the second hydraulic pump 12 may be omitted. In such a case, the hydraulic oil discharged from the other hydraulic pump is supplied to the boom cylinder 7 and also to the arm cylinder 8.

[0105] Furthermore, in the above embodiment, the restricting position of cut valve 52 is described as completely blocking the supply of hydraulic oil to boom cylinder 7, but the maximum supply amount of hydraulic oil to boom cylinder 7 may also be set to be smaller than the supply position. In this case as well, when the boom lowering operation input to boom operating device 20 corresponds to a driving operation, control unit 90 sets cut valve 52 to the restricting position, and therefore the amount of hydraulic oil discharged from first hydraulic pump 11 and supplied to boom cylinder 7 after bucket 6 comes into contact with the ground is restricted. As a result, the bucket 6 is not pressed against the ground with a large driving force due to the active supply of hydraulic oil to boom cylinder 7, and therefore the body of hydraulic excavator 100 is prevented from jumping up due to the reaction and the operator is prevented from feeling a large impact.

[0106] (5) Furthermore, the tip attachment of the work attachment 3 is not limited to a bucket, but may be other tip attachments such as a grapple, crusher, breaker, fork, etc. Furthermore, the construction machine on which the hydraulic control device of the present invention is mounted is not limited to the hydraulic excavator, but may be other construction machine.

[0107] (6) In the previous embodiment, the machine body is a lower running body 1, but the machine body is not limited to a machine that can run like the lower running body 1, and may be a base that is installed in a specific location and supports the upper rotating body 2. [Explanation of symbols]

[0108] 1 Undercarriage 100 Hydraulic Excavator 100A Hydraulic Control Device 11 First hydraulic pump (hydraulic pump) 12 Second hydraulic pump 2 Upper rotating body (aircraft) 20 Boom operation device 21 Boom control lever 22 Boom pilot valve 23 Boom operation detector 24 Pressure sensor (pressure detection part) 26 Speed ​​detection unit (speed detection unit, acceleration detection unit) 2A Cab 2S Swivel Frame 3 Attachments 35 Input section (execution switch) 36 Angle Sensor 4. Boom 40 Boom control valve 41 Arm control valve 42 Confluence control valve 5 Arm 52 Cut valve (switching valve) 53 Meter-out valve 6 Bucket (working part) 6S bottom 7 Boom cylinder 8 Arm Cylinder 9 Bucket cylinder 90 Control Unit 91 Valve control section 92 Arithmetic section 93 Judgment section 94 Memory section T Tank

Claims

1. A hydraulic control device for a construction machine including a boom and a work member attached to the boom, A hydraulic pump, a boom cylinder that operates to cause the boom to perform a boom lowering operation and a boom raising operation by receiving hydraulic oil from the hydraulic pump; a boom operation device that accepts a lowering operation corresponding to the boom lowering operation and a raising operation corresponding to the boom raising operation; a switching valve switchable between a supply position that allows hydraulic oil to be supplied from the hydraulic pump to the boom cylinder and a restriction position that reduces the maximum amount of hydraulic oil supplied to the boom cylinder compared to the supply position; a control unit that, when the lowering operation is input to the boom operation device, determines whether the lowering operation corresponds to a striking operation of striking the work member against the ground, and sets the switching valve to the restricting position when it is determined that the lowering operation corresponds to the striking operation; a speed detection unit capable of detecting the speed of the boom, The control unit determines that the input lowering operation corresponds to the driving operation when the lowering operation is input to the boom operation device and the downward speed of the boom detected by the speed detection unit drops from a speed greater than a predetermined speed threshold to zero.

2. A hydraulic control device for a construction machine including a boom and a work member attached to the boom, A hydraulic pump, a boom cylinder that operates to cause the boom to perform a boom lowering operation and a boom raising operation by receiving hydraulic oil from the hydraulic pump; a boom operation device that accepts a lowering operation corresponding to the boom lowering operation and a raising operation corresponding to the boom raising operation; a switching valve switchable between a supply position that allows hydraulic oil to be supplied from the hydraulic pump to the boom cylinder and a restriction position that reduces the maximum amount of hydraulic oil supplied to the boom cylinder compared to the supply position; a control unit that, when the lowering operation is input to the boom operation device, determines whether the lowering operation corresponds to a striking operation of striking the work member against the ground, and sets the switching valve to the restricting position when it is determined that the lowering operation corresponds to the striking operation; an acceleration detection unit capable of detecting the acceleration of the boom, The control unit determines that the input lowering operation corresponds to the driving operation when the lowering operation is input to the boom operation device and the direction of the boom acceleration detected by at least the acceleration detection unit reverses from downward to upward.

3. A hydraulic control device for a construction machine as described in claim 2, wherein the control unit determines that the input lowering operation corresponds to the striking work when, in addition to the acceleration of the boom being reversed, the magnitude of the upward acceleration of the boom detected by the acceleration detection unit is greater than a predetermined acceleration threshold value.

4. A hydraulic control device for a construction machine including a boom and a work member attached to the boom, A hydraulic pump, a boom cylinder that operates to cause the boom to perform a boom lowering operation and a boom raising operation by receiving hydraulic oil from the hydraulic pump; a boom operation device that accepts a lowering operation corresponding to the boom lowering operation and a raising operation corresponding to the boom raising operation; a switching valve switchable between a supply position that allows hydraulic oil to be supplied from the hydraulic pump to the boom cylinder and a restriction position that reduces the maximum amount of hydraulic oil supplied to the boom cylinder compared to the supply position; a control unit that, when the lowering operation is input to the boom operation device, determines whether the lowering operation corresponds to a striking operation of striking the work member against the ground, and sets the switching valve to the restricting position when it is determined that the lowering operation corresponds to the striking operation, The boom cylinder has a cylinder body, and a piston rod that includes a partition that divides the cylinder body into a head chamber and a rod chamber and is movable relative to the cylinder body, and the piston rod is capable of extending relative to the cylinder body so as to cause the boom to perform the boom-up operation by receiving hydraulic oil discharged by the hydraulic pump into the head chamber, while the piston rod is capable of contracting relative to the cylinder body so as to cause the boom to perform the boom-down operation by receiving hydraulic oil discharged by the hydraulic pump into the rod chamber, Further, a pressure detection unit capable of detecting the pressure in the rod chamber is provided, The control unit is a hydraulic control device for a construction machine that determines that the input lowering operation corresponds to the driving work when the lowering operation is input to the boom operation device and the pressure in the rod chamber detected by the pressure detection unit exceeds a predetermined pressure threshold.

5. 5. The hydraulic control device for a construction machine according to claim 1, wherein the switching valve, in the restricting position, prevents hydraulic oil discharged from the hydraulic pump from being supplied to the boom cylinder.

6. 6. A hydraulic control device for a construction machine according to claim 1, wherein the control unit determines that the lowering operation corresponds to the driving operation and sets the switching valve to the restricting position, and then, when the input of the lowering operation to the boom operating device is released, sets the switching valve to the supply position.

7. 7. A hydraulic control device for a construction machine according to claim 1, wherein, when a deceleration operation for decelerating the boom speed during the boom lowering operation is input to the boom operation device after the lowering operation is input to the boom operation device, the control unit determines that the lowering operation does not correspond to the driving work.

8. A hydraulic control device for a construction machine as described in any one of claims 1 to 7, further comprising an execution switch that can be switched between an ON state that instructs the switching setting of the switching valve in accordance with the determination of the driving work, and an OFF state that prevents the switching setting of the switching valve.

9. The aircraft and a boom supported on the aircraft body so as to be able to be raised and lowered; a working member attached to the boom; A hydraulic control device for a construction machine according to any one of claims 1 to 8; Construction machinery equipped with

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